Solid Fuel Combustion Apparatus and Method

Description

FIELD OF THE INVENTION

The present innovation relates to combustion apparatuses and processes for combusting a fuel that is a solid fuel (e.g. municipal waste, trash, biomass material, other solid fuel, etc.). Embodiments can be configured for combustion of solid fuel on a grate, for example.

BACKGROUND OF THE INVENTION

Combustion devices can combust a fuel. Some types of combustion devices include grate boilers and grate furnaces, which can utilize a grate to support fuel for combust a fuel on a grate. Examples of grate boilers and grate furnaces can be appreciated from U.S. Pat. Nos. 54,998, 645,131, 6,220,190, 8,939,093, and 9,260,675 and U.S. Pat. App. Pub. Nos. 2023/0392787, 2018/0180280, 2016/0209029 and 2014/0287470.

Combustion devices can also be provided for combusting municipal waste such as sewage or garbage. Examples of such devices can be appreciated from U.S. Pat. Nos. 4,928,606, 5,107,777, and 5,405,537.

SUMMARY OF THE INVENTION

We have determined that furnaces and boilers configured to utilize a grate for combustion of solid fuel (e.g., biomass, trash, municipal waste) can often have significant operational variability due to the irregular content of the solid fuel. This can be particularly true for solid fuel that includes wood chips, leaves, trash or municipal waste. For example, the water and volatile content of such material can vary greatly, which can affect the combustibility of the fuel. Also, there can be limited options for monitoring the content of such a solid fuel due to the way the solid fuel may be collected and/or stored for feeding to a furnace. These types of fuel composition challenges can often result in it being difficult to initiate ignition of a flame of such material for starting up of combustion.

Further, the fuel compositional changes that can occur during operation can result in a furnace experiencing substantial variability in combustion, which can result in prolonged downturn of operations or loss of combustion. For example, when a high moisture content solid fuel material is utilized as solid fuel, the combustion process may not be able to adapt to such a condition due to how the grate furnace is configured. This can result in the flame being lost or significantly degraded, which can drastically reduce the efficiency of the combustion process. In incinerator furnaces, such grate furnaces can be used to generate a partially combusted gaseous fuel or syngas from the solid fuel. The partially combusted gaseous fuel mixture is utilized or combusted in downstream burners in another process. In such furnaces, the impact on combustion process can impact the integrated incinerator and downstream process.

We have determined that a new combustion apparatus, burner and oxidant injection system, and combustion process can be utilized to help address such issues. Embodiments can provide improved operational flexibility as well as a more efficient approach for combustion of fuel. This can be particularly true for grate furnace and grate boiler devices that combust solid fuel material that can include trash (e.g. municipal waste, biomass, etc.). Embodiments can be utilized to provide a quicker and more efficient, reliable startup of combustion when a furnace may be cold. Embodiments can also help avoid downturns by reacting to high moisture content fuel inputs for avoiding significant decreases in heat or combustion. Embodiments can also be provided to help provide a quicker adaptation to a downturns situation (e.g. due to maintenance or an unexpected process condition), so that in the event a downturn may occur, combustion can be resumed at a higher rate within a pre-selected operational level so that a duration of a turndown can be reduced in situations where a turndown may not be able to be entirely avoided.

Some embodiments can also provide other advantages. For example, embodiments can permit a wider range of poor quality fuel to be burned as the solid fuel, or solid fuel material. Also, embodiments can be provided so that a startup of combustion or a response to a downturn condition does not require use of supplemental materials (easier to combust or has better combustion characteristics than the base fuel) being added to the furnace to mix with the fuel for facilitating combustion. Also, embodiments can permit combustion to be provided so that a smooth and reliable start-up of combustion can occur when utilizing high moisture content fuel and/or low volatile solid fuels. Embodiments can also be configured to avoid overheating a section of the furnace and/or avoid overheating of a grate on which the fuel is supported for the combustion of the fuel. Also, some embodiments can provide a more uniform and targeted oxygen (O2) distribution within the furnace, which can help contribute to improved uniform spread of combustion over the grate surface which can lead to enhanced furnace start-up and fuel efficiency, as well as a more flexible and adaptable operation of the furnace operation as the solid fuel composition varies.

We have found that embodiments can facilitate improved operational flexibility and efficiency while also reducing an amount of hardware (e.g. burners, etc.) that may be needed to provide a reliable start-up of the furnace, which can provide improved reliable performance and improved efficiencies in operations. For example, embodiments can utilize a lesser number of burners for a pre-selected level of operational efficiency and capacity, which can provide a reduction in capital cost for an installation and also provide a reduction in maintenance costs and maintenance operations that may be needed, which can provide enhanced operational flexibility and a more reliable operation.

In a first aspect, a process for combusting a solid fuel can be provided. Embodiments of the process can include combusting a solid fuel material on a grate within a combustion chamber of a furnace, monitoring the combustion of the solid fuel material to detect at least one pre-selected combustion parameter, in response to detection of the at least one pre-selected combustion parameter exceeding a pre-selected threshold, injecting oxidant within at least one intermediate zone of the combustion chamber via at least one oxidant injector positioned below the grate in the at least one intermediate zone of the combustion chamber, the injected oxidant having an oxygen content of between 30 mole percent (mol %) and 100 mol %; and in response to detecting that the at least one pre-selected combustion parameter being at or within the pre-selected threshold, deactivating the injection of the oxidant into the at least one intermediate zone of the combustion chamber to cease the injecting of the oxidant into the at least one intermediate zone of the combustion chamber.

In some embodiments, the solid fuel can include a biomass material. Examples of biomass material can include wood, leaves, yard debris, sewage or other types of municipal waste or trash. The solid fuel can also include other material (e.g. other types of biomass material, etc.).

In a second aspect, the combusting of the solid fuel material within the combustion chamber of the furnace can include feeding at least one fuel and at least one oxidant to at least one burner to generate at least one flame above the grate within the combustion chamber.

In a third aspect, the injected oxidant can be considered a second oxidant and the combusting of the solid fuel material within the combustion chamber of the furnace can also include feeding at least one fuel a first oxidant to at least one burner to generate at least one flame above the grate within the combustion chamber and feeding the first oxidant into the combustion chamber to output the first oxidant below the grate within the combustion chamber. The first oxidant can have an oxygen content of between 20.9 mol % and 30 mol %. The process can also include injecting the second oxidant within at least one intermediate zone of the combustion chamber to initiate combustion of the solid fuel material via the at least one oxidant injector positioned below the grate in the at least one intermediate zone of the combustion chamber. The injected second oxidant can have an oxygen content of between 80 mol % and 100 mol %.

In a fourth aspect, the at least one pre-selected combustion parameter can include one or more of: (i) a detected temperature of the combustion chamber being at or above a pre-selected temperature threshold such that the at least one-preselected threshold is exceeded when the detected temperature of the combustion chamber is below the pre-selected temperature threshold, (ii) a detected rate of temperature change of the combustion chamber being at or above a pre-selected temperature rate of change threshold such that the preselected temperature rate of change threshold is exceeded when the detected rate of temperature change of the combustion chamber is below the pre-selected temperature rate of change threshold, (iii) a concentration of carbon monoxide (CO) in flue gas output from the combustion chamber being at or above a pre-selected threshold; and/or (iv) a moisture concentration of the solid fuel material being above a pre-selected threshold.

In a fifth aspect, the combusting of the solid fuel material within the combustion chamber of the furnace can include feeding at least one fuel and at least one oxidant to at least one burner to generate multiple flames above the grate within the combustion chamber. In some embodiments, the multiple flames can be moveable via the at least one burner.

In a sixth aspect, the injectable oxidant can be considered a second oxidant and the combusting of the solid fuel material within the combustion chamber of the furnace can include feeding at least one fuel and at least one first oxidant to at least one burner to generate at least one flame above the grate within the combustion chamber; feeding the at least one first oxidant into the combustion chamber to output the first oxidant below the grate within the combustion chamber wherein the first oxidant has an oxygen content of between 20.9 mol % and 70 mol %; and injecting the second oxidant within the at least one intermediate zone of the combustion chamber to initiate combustion of the solid fuel material via the at least one oxidant injector positioned below the grate in the at least one intermediate zone of the combustion chamber. The injected second oxidant can have an oxygen content of between 80 mol % and 100 mol %. In some embodiments, the at least one flame that is generated can be multiple flames that are moveable within the combustion chamber via the at least one burner.

In a seventh aspect, the at least one intermediate zone can include a zone located in a position within the combustion chamber in which the solid fuel material undergoes oxidative pyrolysis after drying and/or devolatilization after drying.

In some embodiments, the at least one intermediate zone can include a zone located in a position within the combustion chamber in which the solid fuel material undergoes oxidative pyrolysis after drying and/or includes a zone in which burnout of carbon of the solid fuel material occurs.

In an eight aspect, the combustion chamber can have a first zone in which the solid fuel material undergoes drying and a fourth zone in which the solid fuel material is combusted to ash, and the at least one intermediate zone can include a second zone and a third zone wherein the second zone is positioned between the first zone and the third zone and the third zone is positioned between the second zone and the fourth zone.

In a ninth aspect, the process of the first aspect can include one or more features of the second aspect, third aspect, fourth aspect, fifth aspect, sixth aspect, seventh aspect, and/or eighth aspect. It should therefore be appreciated that other embodiments of the process can include other features or combinations of features. Examples of other embodiments can be appreciated from the discussion of exemplary embodiments of processed provided herein.

In a tenth aspect, a process for combusting a fuel including solid fuel material can be provided. The process can include combusting a solid fuel material on a grate within a combustion chamber of a furnace. The combusting of the solid fuel material can include feeding at least one fuel to at least one burner positioned to generate at least one flame above the grate within the combustion chamber, feeding at least one first oxidant into the combustion chamber to output the first oxidant below the grate within the combustion chamber. The first oxidant can have an oxygen content of between 20.9 mol % and 70 mol %. A second oxidant can also be injected within at least one intermediate zone of the combustion chamber to initiate combustion of the solid fuel material via at least one oxidant injector positioned below the grate in the at least one intermediate zone of the combustion chamber. The injected second oxidant can have an oxygen content that is greater than the oxygen content of the first oxidant.

In some embodiments, the at least one intermediate zone can be located in a position within the combustion chamber between a first end of the grate and a second end of the grate in which the solid fuel material undergoes oxidative pyrolysis and/or devolatilization after drying of the solid fuel material has occurred.

In an eleventh aspect, the process can also include adjusting operation of the at least one burner and/or the injecting of the second oxidant in response to determining that the combusting of the solid fuel material has met a pre-selected combustion criteria. In some embodiments, the adjusting of the operation of the at least one burner and/or the injecting of the second oxidant can include (i) decreasing a rate at which the at least one fuel is fed to the at least one burner, (ii) decreasing a flow rate of the first oxidant fed to the at least one burner, (iii) ceasing the injecting of the second oxidant; and/or (iv) decreasing a rate at which the second oxidant is injected.

In a twelfth aspect, the process of the tenth aspect can include one or more features of the eleventh aspect and/or other features or elements. It should therefore be appreciated that other embodiments of the process can include other features or combinations of features. Examples of other embodiments can be appreciated from the discussion of exemplary embodiments of processed provided herein.

In a thirteenth aspect, an apparatus configured to combust a fuel that includes solid fuel material is provided. Embodiments of the apparatus can include a grate that is elongated between a first end of the grate and a second end of the grate. The grate can be positioned within a combustion chamber. An oxidant distribution system can be positioned to output a first oxidant via oxidant outlets located below the grate within the combustion chamber. The first oxidant can have an oxygen content of between 20.9 mole percent (mol %) and 70 mol %. At least one burner can be positioned in the combustion chamber. The at least one burner can include a first burner positioned above at least a portion of the grate to generate at least one flame within the combustion chamber. At least one oxidant injector can be positioned below the grate in at least one intermediate zone of the combustion chamber that is positioned between the first end of the grate and the second end of the grate. The at least one oxidant injector can include a first oxidant injector configured and positioned to inject a second oxidant into the combustion chamber below the grate so that the second oxidant is passable through the grate and the solid fuel material on the grate. The second oxidant can have an oxygen content that is greater than the oxygen content of the first oxidant. For example, the oxygen content of the second oxidant can be between 75 mol % and 100 mol % or be greater than or equal to 80 mol % and less than 100 mol %. Embodiments of the apparatus can be configured to implement an embodiment of the process.

In a fourteenth aspect, the first oxidant injector can be positioned coincident with the first burner, can be positioned upstream of the first burner, or can be positioned downstream of the first burner.

In a fifteenth aspect, the at least one burner can include a first burner and a second burner positioned adjacent opposite sides of the grate and the first oxidant injector can be positioned closer to the first end of the grate that the first burner and can also be positioned closer to the first end of the grate than the second burner. The first oxidant injector can be positioned in a location that is inward relative to first burner and the first oxidant injector can also be positioned in a location that is inward relative to the second burner.

In a sixteenth aspect, a source of the first oxidant can be fluidly connected to the oxidant outlets and a source of the second oxidant can be fluidly connected to the at least one oxidant injector. The apparatus can also include at least one sensor positioned to detect at least one parameter of combustion that is communicatively connected to a controller. The controller can be configured to receive data from the at least one sensor to monitor the combustion of the solid fuel material to selectively activate or deactivate the at least one oxidant injector based on at least one pre-selected combustion parameter. The controller can be a computer device that includes a processor connected to a non-transitory memory that is communicatively connectable to the sensor(s).

In a seventeenth aspect, the apparatus of the thirteenth aspect can include one or more features of the fourteenth aspect, fifteenth aspect, and/or sixteenth aspect. It should therefore be appreciated that other embodiments of the apparatus can include other features or combinations of features. Examples of other embodiments can be appreciated from the discussion of exemplary embodiments of processed provided herein.

Other details, objects, and advantages of a combustion apparatus, a burner and oxidant injection system, combustion process, and methods of making and using the same will become apparent as the following description of certain exemplary embodiments thereof proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of a combustion apparatus, a burner and oxidant injection system, combustion process, and methods of making and using the same are shown in the drawings included herewith. It should be understood that like reference characters used in the drawings may identify like components.

FIG. 1 is a schematic diagram of a first exemplary embodiment of an apparatus 1 configured to combustion a fuel that includes solid fuel material (e.g. trash, municipal waste, biomass, etc.).

FIG. 2 is a schematic diagram of an exemplary embodiment of a grate 7 that can be utilized in the first exemplary embodiment of the apparatus 1 configured to combust a fuel that includes solid fuel material.

FIG. 3 is a schematic diagram of a burner and oxidant injection system 9 that can be utilized in the first exemplary embodiment of an apparatus 1 configured to combustion a fuel that includes solid fuel material.

FIG. 4 is a schematic diagram of a burner and oxidant injection system 9 that can be utilized in the first exemplary embodiment of an apparatus 1 configured to combustion a fuel that includes solid fuel material.

FIG. 5 is a schematic diagram of a top view of a burner and oxidant injection system 9 that can be utilized in the first exemplary embodiment of an apparatus 1 configured to combustion a fuel that includes solid fuel material.

FIG. 6 is a schematic perspective view of a burner and oxidant injection system 9 that can be utilized in the first exemplary embodiment of an apparatus 1 configured to combustion a fuel that includes solid fuel material.

FIG. 7 is a graph illustrating a temperature profile of a top region above a grate 7 for a first exemplary embodiment of an apparatus 1 configured to combustion a fuel that includes solid fuel material when burners B are operational to combust fuel for combustion of solid fuel material positioned on the grate 7.

FIG. 8 is a graph illustrating an oxygen concentration profile of a region below the grate 7 of a first exemplary embodiment of an apparatus 1 configured to combustion a fuel that includes solid fuel material when burners B are operational to combust fuel for combustion of solid fuel material positioned on the grate 7.

FIG. 9 is a flow chart illustrating a first exemplary embodiment of a process for combustion of a fuel that includes solid fuel material.

FIG. 10 is a graph illustrating experimental results from conducted experimental work.

DETAILED DESCRIPTION

Referring to FIGS. 1-9, an apparatus 1 configured for combustion of a fuel that includes solid fuel material (e.g. trash, municipal waste, biomass, etc.) can include a burner and oxidant injection system 9 that can be configured to help facilitate improved start-up of combustion of the solid fuel that can provide enhanced operational flexibility, targeted and improved oxygen (O2) distribution within the furnace of the combustion apparatus 1 (e.g. below a grate in the furnace, etc.), reduced downturns, and enhanced efficient operation for the combustion of the fuel.

The furnace of the apparatus 1 can include a housing that encloses a combustion chamber 2 therein. The combustion chamber 2 can be enclosed by a floor 2f, walls that extend vertically from the floor 2f, and a ceiling that may be supported by the walls and/or positioned to enclose an upper region of the combustion chamber 2 in some configurations. At least one grate 7 can be positioned in the combustion chamber 2 adjacent to one or more burners B, which can be positioned above the grate. For example, a burner can be mounted to the ceiling, at least one wall of the housing that defines the combustion chamber 2, or on opposite walls of the combustion chamber 2. In some configurations, there can be burners B positioned on multiple walls (e.g. 2 walls, three walls, four walls) as well as at least one burner B that is mounted on a ceiling of the furnace. yet other embodiments, may only utilize a single burner B or only a few burners (e.g. less than or equal to four burners B, only two burners B, only three burners B, etc.).

Each of the one or more burners B can be conventional oxy-fuel burners, transient oxy-fuel burners, or other type of burner (e.g. air-oxy-fuel burners, air-fuel burners, etc.). Each burner B can be configured to generate at least one flame F in the combustion chamber 2 of the furnace. For example, each burner B can be configured to emit a fuel and/or oxidant to generate at least one flame F within the combustion chamber 2 above the grate 7 to provide heat for combusting the solid fuel on the grate(s) 7. In some embodiments, the burners B can include one or more transient burners B or moving flame burners B, which can assist to initiate ignition at multiple locations on the furnace grate bed by using a lower number of conventional burners. The solid fuel on the grate(s) 7 can include solid fuel material (e.g. biomass material, sewage, garbage, manure, cardboard, paper, plastic, cloth, paper pulp, wood stumps, yard waste, branches, food waste, straw, grass clippings, leaves, bark, and/or other carbon containing trash).

Each burner B can be fed an oxidant as well as a fuel for generation of the flame(s) F for heating the solid fuel material to combust the solid fuel material. For example, each burner B can be fed natural gas, propane gas, hydrogen gas, ammonia gas, or a combination thereof as a fuel source for combustion to form the flame(s) F. In some embodiments, the fuel fed to the burner(s) B for formation of the flame(s) F can be a low carbon intensity fuel (e.g. hydrogen gas, ammonia gas, etc.) to help maintain the carbon intensity of the operation of the furnace. The fuel fed to the burner(s) B can be provided with at least one flow of oxidant (e.g. air, oxygen enriched air, oxygen, etc.) to generate the flame(s) F for initiation of combustion.

Once the solid fuel material on the grate 7 is sufficiently heated via the flame(s) F to be ignited and begin to combust, the burner(s) may no longer be needed to supply the same level of heat via the flame(s) F to maintain combustion of the fuel on the grate 7. Once such a condition is detected, the burner(s) B can receive no more fuel or may receive a substantially reduced level of fuel to continue to maintain combustion of the solid fuel material on the grate 7 at a pre-selected steady state condition (e.g. operation in which the combustion of the fuel on the grate 7 occurs at greater than 50% of the designed for output capacity, high moisture content solid fuels, etc.).

For example, upon a start-up or a resumption after a downturn or process interruption that may have occurred, the burner(s) B may be fed fuel (e.g. natural gas, ammonia, hydrogen, propane, etc.) for formation of the flame(s) F so that the burner(s) B operate at an equivalence ratio that is about stoichiometric (e.g. 1, a value at which the fuel fed to the burner B is equal to the oxygen fed to the burner needed for stoichiometric combustion of that fuel for formation of the flame(s) F, or a value that provides a slightly fuel lean output from the burner B (e.g. an equivalence ratio of 0.9-0.99, 0.75-0.95, 0.5-0.9, etc.) or a value that provides fuel rich output from the burner B (e.g. an equivalence ratio of greater than 1 to 1.15, 1.05-1.15, etc.). After the solid fuel material on the grate 7 ignition starts and the solid fuel material begins to sufficiently combust, the equivalence ratio of the burner(s) B can be adjusted to use very little fuel, or no fuel. For instance, the burner(s) B can operate at an equivalence ratio that is very low that has a significant amount of excess oxidant (e.g. an equivalence ratio of 0.1 or between 0.1 and 0.3 or other fuel lean and oxygen rich condition). Alternatively, the burner(s) B may utilize the same flow rate of fuel, but may also be fed a higher rate of oxidant to reduce the equivalence ratio of the burner(s) B.

During steady-state operation in which the burner(s) B can operate at low equivalence ratios or operate in a condition in which only an oxidant is passed out of the burner(s) B, the flow rate of oxidant passed out of the burner(s) B can be varied to account for detected combustion conditions. For example, in the event a carbon monoxide (CO) concentration is detected that exceeds a pre-selected CO threshold, oxidant can be passed out of the burner(s) at a greater rate to mitigate CO formation. As another example, if poor solid fuel material quality is detected (e.g. a concentration of water is detected that exceeds a pre-selected threshold or a rate of temperature decrease exceeds a pre-selected threshold or a temperature decrease is detected that exceeds a pre-selected threshold), an increase in oxidant passed through the burner(s) B may be triggered to facilitate improved combustion to account for the poor quality solid fuel material and to also try and avoid use of fuel being fed to the burner(s) B so that the solid fuel material functions as the primary fuel for combustion. In situations in which the solid fuel has started to combust or has reached a pre-selected level of combustion in which additional heat from a flame of one or more burners B is no longer needed or desired, the cessation of feeding both fuel and oxidant can occur (e.g. valves controlling the flow of fuel and oxidant to the burner(s) B can be closed) and/or a cooling gas can be fed to the burner(s) B to keep the burner cool. When a cooling gas is fed to the burner(s) B, the cooling gas (e.g. (nitrogen, air, carbon dioxide gas, combinations thereof, etc.) can be passed through the burner B and output into the combustion chamber of the furnace to facilitate cooling of the burner(s) B.

The detection of one or more of these conditions can be provided by one or more sensors positioned in the combustion chamber 2 and/or downstream of the combustion chamber 2. The sensor(s) can include at least one temperature sensor, at least one analyzer, and/or other sensor(s) that may be communicatively connected to a controller that is configured to help monitor combustion processing for providing automated process control of the operation of the furnace. The controller can be a type of computer device that includes a processor connected to a non-transitory computer readable medium (e.g. non-transitory memory), for example.

The furnace can also include an oxidant distribution system 3 that is positioned below the grate 7 in the combustion chamber 2. The oxidant distribution system 3 can receive at least one feed of oxidant (e.g. air, oxygen enriched air, oxygen gas being at least 80 mole percent (mol %) oxygen, oxygen gas being between 80 mol % oxygen and 100 mol % oxygen, etc.) and pass that oxidant via a conduit arrangement so that the oxidant can be emitted below the grate 7 for passing through openings 70 of the grate 7 for mixing with the solid fuel material on the grate 7, passing through the solid fuel material on the grate 7, and passing into the atmosphere within the combustion chamber 2 above the grate 7 (e.g, the space above the grate 7 and below the ceiling of the combustion chamber 2) to facilitate combustion of the solid fuel material.

The oxidant feed can be provided via an oxidant feed system of the oxidant distribution system 3. The oxidant feed system can include a compressor, fan, or other device configured to drive air or oxygen enriched air into a first oxidant conduit arrangement of the oxidant distribution system 3 for being output via the oxidant outlets 30. The ambient air or oxygen enriched air can be a first source of oxidant for the oxidant feed distribution system 3 that has a first oxygen content level (e.g. an oxygen content of between 20.9 mole percent and 25 mole percent, an oxygen content of between 20.9 mole percent and 30 mole percent, an oxygen content of between 20.9 mole percent and 70 mole percent, etc.).

The oxidant feed system can also utilize a source of a second oxidant having a higher purity oxygen content as compared to the first oxidant that may be output via the oxidant outlets 30 (e.g. oxygen of over 50 mole percent (mol %) oxygen, oxygen content of between 80 mol % and 100 mol % oxygen, oxygen content of over 85 mol % oxygen and less than 100 mol % oxygen, etc.) for providing such a second oxidant to one or more oxidant injectors OI that can be positioned below the grate 7 in the combustion chamber 2. The oxidant distribution system 3 can include a second oxidant conduit arrangement that can fluidly connect the oxidant injector(s) OI that can be positioned under the grate 7 at pre-selected locations within the combustion chamber 2 to a source of the second oxidant (e.g. a second oxidant storage unit). For example, a tank of higher purity oxygen content oxidant that is at least 80 mol % oxygen can be fluidly connected to the oxidant injector(s) OI via a second oxidant conduit arrangement of the oxidant distribution system 3. Such a tank can include a single vessel or array of vessels that may store the higher purity oxygen as a gas or as a liquid for supplying to the oxidant injector(s) OI. In the event the second oxidant is stored in liquid form, it can be vaporized prior to being fed to the oxidant injector(s) OI via a vaporizer, which may use ambient air or other heating medium for vaporization of the liquid oxidant.

The solid fuel that is fed onto the grate 7 can be fed into the furnace via a fuel inlet of the furnace. The fuel inlet can pass the solid fuel material onto a first end 7a of the grate for being passed along the grate 7 in a solid fuel flow direction BMF as the solid fuel material is exposed to the heat in the furnace for being dried, undergoing pyrolysis (e.g. oxidative pyrolysis) or other degradation, and subsequently having the carbon of the heated material burned out to form ash. The ash that is formed can be output from the second end 7b of the grate 7, which may be an ash outputting end of the grate 7. An intermediate portion 7c of the grate 7 can be positioned between the first end 7a and second end 7b. The grate 7 can be inclined relative to horizontal such that the grate is tilted upwardly as it extends from its second end 7b to its first end 7a. For example, the first end 7a can be at a location that is higher than the second end 7b and the grate 7 can extend linearly between its second end and its first end along an angle AT that is an angle of inclination. This angle of inclination AT can be between greater than 0° and 60° in some embodiments. In other embodiments, the grate 7 can be horizontally positioned such that the first end 7a and second end 7b are at the same height and the grate extends linearly in a level manner (e.g. angle of inclination AT is at an angle of 0° such that there is no inclination or declination).

The grate 7 can be supported on a base that can include a plurality of feet 7s to help support the grate 7 above a floor 2f of the combustion chamber 2 in the furnace so that the grate 7 is positioned above a plurality of oxidant feed outlets 30 of the oxidant distribution system 3. As noted above, the oxidant feed outlets 30 of the oxidant distribution system 3 can output a first oxidant gas (e.g. air, oxygen enriched air, etc.) that it receives from at least one first oxidant source (e.g. ambient air, at least one oxidant storage vessel, etc.) for outputting the oxidant within the combustion chamber 2 below the grate 7 so that the oxidant can pass upwardly through openings 70 of the grate 7 and into the solid fuel material that includes the biomass material. The oxidant can pass through the solid fuel material to above the solid fuel material on the grate 7 as well to facilitate combustion of the fuel output from at least one burner B and/or the flame(s) F generated via the burner(s) B.

The grate 7 can be configured to move to help drive a flow of the solid fuel that includes the solid fuel material along the grate 7 in a solid fuel flow direction BMF so that the fuel can travel from the first end 7a to the second end 7b as it is exposed to heat for being combusted ultimately into ash. For example, a vibration mechanism or other movement mechanism can be operatively connected to the grate 7 to cause the grate 7 to vibrate or otherwise move to help the fuel move as it is exposed to heat via the flame(s) F and is combusted. In some embodiments, the grate 7 can be configured to periodically be vibrated to facilitate the movement of the solid fuel material, for example.

A flow of flue gas FG formed via combustion of the solid fuel material and/or formation of the flame(s) F can pass through the combustion chamber 2 in a flow direction that is countercurrent to the solid fuel flow direction BMF. FIGS. 2, 3, 4, and 5 may best illustrate this countercurrent flow relationship between the flow of the flue gas FG passing through the combustion chamber 2 toward the flue gas distribution element 4 and the flow of the solid fuel material moving along the grate 7 toward the second end 7b of the grate 7.

In some embodiments, the grate 7 can also include cooling water cooling conduits that are arranged in different sections of the grate 7 within the combustion chamber 2. The water cooling conduits of the grate 7 can be positioned and configured to utilize a flow of water through the conduits to facilitate conductive cooling of the grate 7 via the outer wall of the conduit through which the cooling water passes to help prevent overheating of the grate 7 during operation.

The flue gas formed via combustion of the solid fuel that includes solid fuel material and combustion of fuel output from the burner(s) B for forming the flame(s) F can be passed out of the combustion chamber 2 and into a flue gas distribution element 4 of the apparatus 1. The flue gas distribution element 4 can be a convention section of the furnace or a stack of a furnace that is in fluid communication with the combustion chamber 2 in some configurations. The flue gas distribution element 4 can be positioned above the grate 7 and adjacent to the first end of the grate 7 in some embodiments so that formed flue gas (e.g. combustion products from formation of the flame(s) F and combustion of the solid fuel material (e.g. solid fuel material that includes biomass), partially combusted solid fuel flue gas, syngas (e.g. mixture of carbon monoxide, hydrogen gas (H2), and unburnt hydrocarbons, etc.) can be output from the combustion chamber 2 of the furnace for subsequent use and output from a flue gas outlet 5 of the furnace.

In some embodiments, there can be at least one heat exchanger conduit (not shown) that can include a fluid (e.g. water, other fluid) that can be heated via the flue gas passed into the flue gas distribution element 4 for use of the heat of the flue gas as a heating medium to heat that fluid. The cooled flue gas can be output from the flue gas outlet 5 for emission into atmosphere or for being passed to another process unit for treatment and/or use (e.g. a scrubber, a stripper, a bag filter, a filter house, a filter element, a carbon capture unit, and/or other processing element). In some embodiments, after the flue gas has been utilized as a heating medium, it may be optionally treated for subsequent emission and then emitted to atmosphere. In other configurations, the flue gas output from the outlet 5 can be fed to a downstream unit (not shown) for use in other operations of an industrial facility (e.g. used to form a syngas, used as a fuel in burner systems in another downstream process, etc.).

The fluid within one or more heat exchanger conduits (not shown), which can be positioned in the flue gas distribution element 4, can include water in some configurations so that the water can be boiled and the steam formed via the boiled water can be utilized in operations of an industrial facility of a plant having the apparatus 1 configured for combustion. For example, the steam can be utilized in steam methane reformer operations, reformer operations, syngas generation operations, or other operations. As another example, the steam that may be formed can be utilized in a turbine for generation of power or as a heating medium in another industrial plant process.

In other configurations, the fluid within one or more heat exchanger conduits (not shown), which can be positioned in the flue gas distribution element 4, can include another fluid (e.g. liquid water for being heated to a desired temperature, a heating medium fluid, a process fluid to be pre-heated for use in another process element of a plant, etc.). The heat from the flue gas can be provided to facilitate heating or pre-heating for an industrial process fluid so that the fluid can be utilized in another process downstream of the flue gas distribution element 4 of the furnace.

As may best be appreciated from FIGS. 1, 2, and 5, the combustion chamber 2 of the furnace can include multiple zones of combustion. The zones of combustion in the combustion chamber 2 can include a first zone Z1, a second zone Z2, a third zone Z3, and a fourth zone Z4. The first zone Z1 can be adjacent the solid fuel inlet and/or the first end 7a of the grate. The second zone Z2 can be positioned between the first zone Z1 and the third zone Z3. The second zone Z2 and the third zone Z3 can be closer to the second end 7b of the grate 7 than the first zone Z1. The first zone Z1 can be closer to the first end 7a of the grate than the second and third zones Z2 and Z3. The second zone Z2 can be closer to the first end 7a of the grate 7 than the third zone Z3 and the third zone Z3 can be closer to the second end 7b of the grate 7 than the second zone Z2.

The third zone Z3 can be positioned between the second zone Z2 and the fourth zone Z4. The third zone Z3 and the fourth zone Z4 can be closer to the second end 7b of the grate 7 than the second zone Z2. The second zone Z2 can be closer to the first end 7a of the grate than the third and fourth zones Z3 and Z4. The third zone Z3 can be closer to the first end 7a of the grate 7 than the fourth zone Z4 and the fourth zone Z4 can be closer to the second end 7b of the grate 7 than the third zone Z3.

Some embodiments of the furnace can be configured so that the combustion chamber 2 has four zones of combustion in which the fourth zone Z4 may be a final zone that is at the second end 7b of the grate 7. Other embodiments may include additional zones or less than 4 zones (e.g. only first, second, and third zones, etc.). For example, in some embodiments, a fifth zone Z5 can be utilized (indicated via broken line reference line in FIGS. 1, 2 and 5). In embodiments that may utilize a fifth zone Z5, the fourth zone Z4 can be positioned between the third zone Z3 and the fifth zone Z5. The fourth zone Z4 and the fifth zone Z5 can be closer to the second end 7b of the grate 7 than the third zone Z3. The third zone Z3 can be closer to the first end 7a of the grate than the fourth and fifth zones Z4 and Z5. The fourth zone Z4 can be closer to the first end 7a of the grate 7 than the fifth zone Z5 and the fifth zone Z5 can be closer to the second end 7b of the grate 7 than the fourth zone Z4. In embodiments where only five zones of combustion are provided, the fifth zone Z5 may be the final zone of combustion at the second end 7b of the grate 7.

In a first zone Z1 of combustion, the heat from combustion of the solid fuel material on the grate 7 and/or the flame(s) F can facilitate drying of the solid fuel fed to the grate 7 via the fuel inlet adjacent the first end 7a of the grate 7. The dried fuel can subsequently move along the grate 7 to the second zone Z2 in the combustion chamber in which the fuel that includes solid fuel material can undergo oxidative pyrolysis. Then, the fuel including the solid fuel material can continue to move along the grate to the third zone Z3 of combustion in which the carbon of the fuel can be burned out. The fuel may then be passed to the fourth zone Z4 of combustion adjacent the second end 7b of the grate to be finally combusted into ash for subsequent output and disposal of the ash.

In embodiments that may utilize a fifth zone Z5, the oxidative pyrolysis and carbon burnout may occur as the fuel is passed from the second zone Z2 of combustion to the fourth zone Z4 of combustion wherein the oxidative pyrolysis can occur upstream of the carbon burnout as the fuel moves along the grate from the first end 7a to the second end 7b. In such a configuration, the fifth zone Z5 of combustion may be the zone in which ash is formed or combusted.

In yet other embodiments that utilize other zones of combustion, an initial set of one or more upstream zones can be zones in which drying of the solid fuel immaterial (e.g. biomass material, etc.) occurs adjacent a first end 7a of the grate 7. An intermediate set of zones between these drying zones and a final set of ash formation zone(s) adjacent the second end 7b of the grate 7 can be positioned to facilitate oxidative pyrolysis after drying and then burnout of carbon after the oxidative pyrolysis has occurred in an intermediate portion 7c of the grate 7 that can be located between the first end 7a and the second end 7b of the grate 7. The final set of one or more zones of combustion in the combustion chamber 2 can then be provided as the ash formation zone(s) adjacent the second end 7b of the grate.

The oxidant distribution system 3 can include an array of oxidant feed outlets 30 for outputting a first oxidant under the grate 7 at various different locations along the grate 7 between the first end 7a of the grate 7 and the second end 7b of the grate 7. The oxidant distribution system 3 can also include oxidant injectors OI positioned below the grate 7 to help facilitate a feeding of a second oxidant into the combustion chamber 2 below the grate for being passed through the grate and solid fuel material on the grate 7 and passing subsequently above the solid fuel material for being passed into an upper region of the combustion chamber 2 near at least one flame F generated via at least one burner B. The one or more oxidant injectors OI can be one or more lances or other type of injector that can be selectively activated for supplying additional oxidant into one or more pre-selected zones of the combustion chamber (e.g, the first zone Z1, second zone Z2, and/or third zone Z3, only the second zone Z2, etc.).

In some embodiments, the oxidant injector(s) OI can have a slot shaped aperture (e.g. oval shaped, other slot shape) to facilitate the output of oxidant from the oxidant injector OI for providing a more uniform distribution of the oxidant. In some embodiments, the oxygen injectors OI can be incorporated within the first oxidant feed outlets (e.g. concentric nozzles wherein an oxidant injector OI is inside a nozzle and oxidant feed outlet is an outer nozzle that encircles the inner oxidant injector nozzle OI). This type of configuration can enable more uniform mixing of second oxidant with the first oxidant.

As noted above, the oxidant fed to the oxidant injector(s) can be a second oxidant that has a significantly higher oxygen concentration as compared to the oxygen content of first oxidant output from the oxidant outlets 30 of the oxidant distribution system 3. For example, the first oxidant that may be output from the oxidant outlets can be air or oxygen enriched air having an oxygen content of between 20.9 mol % oxygen and 25 mol % oxygen and the second oxidant output from the oxidant injector(s) OI can be at least 80 mol % oxygen (e.g. between 80 mol % oxygen and 100 mol % oxygen, between 80 mol % oxygen and 90 mol % oxygen, etc.).

In some embodiments, one or more oxidant injectors OI can be positioned below at least one burner B in a zone of the combustion chamber 2 in which pyrolysis (e.g. oxidative pyrolysis) of the solid fuel material may occur while it is being periodically moved along the grate 7 (e.g. moved toward the second end 7b of the grate 7). Also, the one or more oxidant injectors OI can be positioned in a zone of the combustion chamber 2 adjacent to where the solid fuel material may be combusted and downstream of where the solid fuel material may be dried and/or devolatized (e.g. in a zone or zones in which pyrolysis may occur) to provide makeup oxygen to account for oxygen levels being reduced near such a location due to the use of the oxygen that occurs from combustion of the solid fuel material. The oxygen output from the oxidant injectors OI can form oxygen enhanced air in zones or regions where solid fuel starts to devolatize and the increased oxygen enrichment can assist in improving combustion characteristics of the solid fuel.

This location for the one or more oxidant injectors OI can be in the second zone Z2, at an interface of between the first zone Z1 and the second zone Z2, between the second zone Z2 and the third zone Z3, and/or at another location in which pyrolysis of the solid fuel material is expected to occur or adjacent to and/or upstream of the location at which the solid fuel material combusts in the combustion chamber 2 (e.g. in the pyrolysis zone(s)). The location of the one or more oxidant injectors OI can be coincident with a location of at least one burner B that can be located above the grate 7 (e.g. wall mounted above the grate 7, ceiling mounted above the grate 7, etc.). In some configurations, the oxidant injectors OI can be located in zones where carbon burnout occurs (e.g. in the third zone Z3), which may help in clearing blockages that may form on the grate during combustion.

In some such configurations, the burners B can be wall mounted and there can be a pair of burners B on opposite sidewalls of the combustion chamber 2. Such a configuration may best be seen from FIGS. 5 and 6. In other configurations, there may be a single burner B that is wall mounted or ceiling mounted. In yet other configurations, there may be more than two burners (B) with some being wall mounted and at least one being ceiling mounted.

For example, as may best be appreciated from FIGS. 3-4, a first oxidant injector OI can be positioned coincident with a burner B that is positioned above the grate 7 such that the center region of the oxidant injector OI is aligned with a center region of the burner B. The grate 7 can have a length L1 that is a linear length between the first end 7a and second end 7b of the grate (e.g. a horizontally extending length between the first and second ends 7a and 7b). The burner B can be positioned a horizontally extending linear distance L2 from the first end 7a of the grate 7. The oxidant injector OI can be located a horizontally extending linear distance L3 from the first end 7a of the grate in a position that is below the grate 7. This distance L3 can be the same as distance L2 in some embodiments. In other embodiments, the distance L3 can be within 10% or 20% of the distance L2. The oxidant injector(s) OI can be positioned so that a ratio of L3 to L1 (e.g. L3/L1) is between 0.2 and 0.6 in some embodiments. The burner(s) B to which the oxidant injector(s) OI are coincident (and below) can be positioned so that there is a ratio of L2 to L1 (L2/L1) of between 0.2 and 0.6 as well.

The ceiling of the combustion chamber 2 can have a pre-selected height H. The burner(s) B can be positioned at a pre-selected height H4 above the grate 7, the oxidant injector(s) OI can be positioned a pre-selected distance below the grate 7 (e.g, the grate 7 can be a pre-selected height H3 above the oxidant injector(s) OI), and a pre-selected height H2 above the floor 2f of the combustion chamber. Such positioning can be in the second zone Z2 of combustion within the combustion chamber 2, or other zone or interface of zones at which pyrolysis of the solid fuel material may occur in some embodiments. The height H4 at which the burner(s) can be above the grate 7 can be a distance of between 1 foot and 5 feet (e.g. between 0.3 m and 1.53 m). This distance or height can assist in flame development and allow to spread the flame over a larger surface area of the grate.

The oxidant injector(s) OI can be positioned so that the grate 7 is a pre-selected height H3 above the oxidant injector(s) OI. These distances or heights can assist in development of the jets and facilitate production of oxygen enriched air regions that can spread over a larger surface area below the grate 7. The exit velocities from the oxidant output from the oxidant injectors OI can be in the range of 30 m/s to 92 m/s or other suitable velocity (e.g. up to sonic velocity, between 100 ft/s and 300 ft/s, etc.) that can allow the secondary oxidant to entrain surrounding air and lower oxygen concentration of the jets before they are located below the grate surface. This pre-selected height H3 can be a distance of between 1 foot and 5 feet (e.g. between 0.3 m and 1.53 m). In some configurations, the pre-selected height H3 can be the same as the pre-selected height H4, for example.

The pre-selected height H1 of the ceiling can be any suitable height. The pre-selected height at which the oxidant injector(s) OI are positioned above the floor 2f of the combustion chamber 2 below the grate 7 can be any suitable height as well for accommodating the desired pre-selected height H3 at which the grate 7 is above the oxidant injector(s) OI.

The burner(s) B can be configured to emit at least one flame F at an angle relative to horizontal and/or emit the flame F horizontally (e.g. tilted at an angle of between greater than 0° and 15° relative to horizontal, tilted at an angle of between 1° and 15° relative to horizontal, etc.). Such an angle of outputting of the flame(s) F via the burner(s) B can be referred to as an angle beta.

The oxidant injector(s) OI can also be configured to emit the oxidant horizontally or at an angle relative to horizontal (e.g. tilted at an angle of between greater than 0° and 15° relative to horizontal downwards toward the grate 7, tilted at an angle of between 1° and 15° relative to horizontal downwards toward the grate 7, etc.) such that the output oxidant gas subsequently moves along an oxidant flow path Ox in which the oxidant can rise above the oxidant injector(s) OI, pass through the grate 7 and solid fuel material on the grate 7, and above the solid fuel material on the grate 7. In some embodiments, this oxidant flow angle is angled upwards towards the grate 7 or angled towards the grate 7. In some embodiments, the angle at which the flame(s) F is output via the burner(s) B can be the same as the angle at which the oxidant is output form the oxidant injector(s) OI. Such an angle of outputting of the oxidant via the oxidant injector(s) OI can be referred to as an angle theta.

Oxidant injector(s) OI can also (as shown in broken line in FIG. 3) be positioned upstream and/or downstream of the burner(s) B under the grate 7 (wherein the upstream and downstream positioning is relative to the solid fuel flow direction at which the solid fuel material moves along the grate 7 from the first end 7a to the second end 7b of the grate). Such oxidant injector(s) OI (shown in broken line in FIG. 3) can have different positioning along the length of the grate 7 such that one or more oxidant injectors OI can be closer to the first end 7a of the grate upstream of the burner B and/or one or more oxidant injectors OI can be closer to the second end 7b of the grate downstream of the burner B. In such embodiments, the upstream oxidant injector(s) can be positioned a pre-selected upstream distance L4U upstream of the burner(s) B under the grate 7 and/or the downstream oxidant injector(s) can be positioned a pre-selected downstream distance L4D downstream of the burner(s) B under the grate 7.

The distance L4U can be a horizontally extending distance from a location under the grate 7 that is coincident with the burner(s) B to a center of the oxidant injector OI. The pre-selected downstream distance L4D can also be a horizontally extending distance from a location under the grate 7 that is coincident with the burner(s) B to a center of the downstream oxidant injector(s) OI. These pre-selected upstream and downstream distances L4U, L4D can be pre-selected to be relative to an overall length L1 of the grate 7 in situations where the burner(s) are positioned in a center of the grate 7 or in another region of the grate that may coincide with a pre-selected zone of combustion (e.g. second zone Z2, third zone Z3, a zone of combustion in which pyrolysis of the solid fuel material may occur, etc.). In some embodiments, a ratio of the downstream distance L4D to the overall length L1 of the grate (e.g. L4D/L1) can be between 0.05 and 0.3 and/or a ratio of the upstream distance L4U to the overall length L1 of the grate (e.g. L4U/L1) can be between 0.05 and 0.3.

In embodiments that may utilize one or more upstream oxidant injectors OI and one or more downstream oxidant injectors OI, the oxidant injectors OI can each be positioned a same or similar height H2 above the floor 2f of the combustion chamber. Such positioning may result in different oxidant injectors being positioned different distances below the grate 7. In other configurations, the oxidant injectors OI may be at different heights above the floor 2f of the combustion chamber 2 and be similar distances below the grate 7 (e.g. a same distance below the grate at different locations along the length of the grate, a similar distance that is within 10% or 5% of being the same distance at different locations along the length of the grate, etc.).

In some embodiments (and as also noted above), the oxidant passed to and output from the oxygen injector(s) OI can be a second oxidant that has a significantly higher oxygen concentration as compared to the oxygen content of oxidant output from the oxidant outlets 30 of the oxidant distribution system 3. For example, the first oxidant that may be output from the oxidant outlets can be air or oxygen enriched air having an oxygen content of between 20.9 mol % oxygen and 25 mol % oxygen or between 20.9 mol % oxygen and 30 mol % oxygen and the second oxidant output from the oxidant injector(s) OI can be at least 80 mol % oxygen (e.g. between 80 mol % oxygen and 100 mol % oxygen, between 80 mol % oxygen and 90 mol % oxygen, etc.).

We have found that utilization of the oxidant injector(s) OI can be selectively utilized at oxidant injector locations OL below the grate 7 to account for pre-selected operational conditions. For example, the oxidant injector(s) OI can be utilized during startup, during a downturn, or during a time in which combustion is detected as being below a pre-selected rate of consumption of the solid fuel material to provide selective improvement in combustion conditions for the solid fuel material in a quick and efficient manner that provides enhanced operational flexibility, faster combustion corrective performance, while also providing a reduction in capital costs, a reduction in maintenance, and a reduction in operational downtime.

We have also found that one or more burners B can include transient heating burners that may provide multiple flames F (as indicated as an option via broken line flames F in FIGS. 3 and 4). The utilization of such burners B can help provide flames F that can cover a larger portion of the length of the grate 7. This multiple set of flames or use of multiple moveable flames can initiate solid fuel (e.g. biomass) ignition at multiple locations on the grate 7 as compared to conventional stationary burner system or single flame burner systems to help provide a more uniform combustion of the solid fuel material (e.g. biomass material, etc.) on the grate. In some embodiments, the utilization of such burners can permit a lower number of burners to be utilized in the combustion chamber 2. The lower number of burners B can help reduce the hardware cost of burners B and associated skids or control systems. The use of transient burners B that move a flame F or have multiple flames F or multiple moveable flames can help avoid over-heating a section of the furnace. These transient burners B can also help generate fuel rich flames that are lower temperature flames F as compared to a stoichiometric oxy-fuel combustion flame. The lower temperature of the flame(s) F can help avoid formation of a hot spot in the furnace.

Additionally, we have found that utilization of a transient oxy-fuel heating burner in some embodiments can help create cyclical fuel rich and fuel lean surfaces on the grate surface (e.g. the grate surface can be cycled between a fuel rich condition and a fuel lean condition repeatedly). This can allow the solid fuel to be first ignited and then excess oxidant from the fuel lean condition can subsequently create local oxygen enrichment that can allow the combustion to spread and sustain the flame F during the start-up in a cold furnace.

The transient burners or other burners B that may be utilized can also facilitate generation of moveable flame(s) in the combustion chamber. Each burner can output one or more flames F such that the flames can be adjusted in length and/or direction to provide a desired flame within the combustion chamber 2 for heating the solid fuel material for facilitating combustion of the solid fuel material on the grate 7.

A process for combustion of a fuel that includes solid fuel material can be utilized to control operation of the apparatus 1 as well as the selective utilization of the oxidant injectors OI. An example of such a process is shown in FIG. 5.

FIGS. 7 and 8 illustrate graphs to provide exemplary illustrations of an exemplary temperature profile (FIG. 7) that can be provided above the grate 7 for facilitating combustion of the solid fuel material on the grate. This type of temperature profile can be provided via multiple burners positioned at an end wall adjacent to an ash discharge end of the grate (e.g. a lower end of the grate) operating in conjunction with multiple oxidant injectors OI positioned on a wall opposite the end wall on which the burners are located adjacent to an upper region of the grate within the second zone Z2 and/or a transition interface between the second zone Z2 and the third zone Z3, and/or a transition interface between the first zone Z1 and the second zone Z2 of the combustion chamber to facilitate pyrolysis of the solid fuel material. FIG. 8 illustrates an oxygen concentration profile of the combustion chamber 2 below the grate 7 for this operational arrangement as well.

As may be appreciated from the exemplary temperature and oxygen concentration profiles of FIGS. 7 and 8, the temperature within the combustion chamber can be hottest near the burner locations BL of the burners where flames F are output from the burners. The oxygen concentration can be highest between these burner locations BL and upstream of the burners B (e.g. closer to a solid fuel material inlet end of the grate 7). A higher oxygen concentration under the grate 7 can be provide in a middle region of the grate between the burners B to help facilitate combustion of the solid fuel material as the oxidant passes through the grate and into the solid material for combustion of the solid fuel material. As can best be seen in FIG. 8, the oxygen concentration is lowest in regions adjacent to the flames F output from the burners B and can be highest in locations along the grate 7 between the flames F. We have found that the higher oxygen concentrations that can be provided can facilitate initial ignition of the solid fuel material more quickly and assist in spread of combustion from the burner locations BL towards the center and upper part of grate (towards the first zone Z1 or location at which solid fuel is fed onto the grate). This can be particularly true for arrangements in which the oxidant injectors OI are in oxidant injector locations OL that are upstream of the burners B in intermediate zones (e.g. second zone Z2) and are between the burners B at burner locations BL adjacent an end wall at an ash discharge end of the grate 7. For example, the oxidant injector locations OL can be inward relative to a burner location BL of a first burner B and a burner location BL of a second burner B that are positioned adjacent opposite sides of the grate 7.

During initial start-up of the process, the location of burners BL and oxidant injectors OI can assist to spread the heated gases along the grate surface towards the feed zone by buoyancy effect. This can assist to initiate ignition of the solid fuel in upper regions of the grate 7. The oxidant injector locations OL can also be closer to a first end of the grate 7 (e.g, the solid fuel material feed end of the grate and/or at an interface between the first zone Z1 and the second zone Z2) than the burner locations BL of the burners B. This type of spacing of the oxidant injector locations OL and burner locations BL can provide greater oxygen at regions of the grate 7 within the combustion chamber 2 in which solid fuel material can undergo pyrolysis to help facilitate improved combustion to facilitate ignition and combustion of the solid fuel material (e.g. high moisture content or low volatile content solid fuel). Additionally, FIG. 8 shows that the peak concentration of oxygen below the grate 7 can be close to 25% by volume (25 vol %). This can help ensure that the compatibility of the grate material is not impacted due to enriched oxygen atmosphere.

FIG. 9 illustrates an exemplary process, or method, which can utilize an embodiment of the apparatus 1. In a first step S1, solid fuel or solid fuel material (e.g. biomass, etc.) on a grate 7 can be combusted within a furnace (e.g. within combustion chamber 2). The solid fuel combustion can be initiated via operation of at least one burner B as noted above, which can receive fuel and oxidant for generation of at least one flame F to heat the solid fuel material for combusting that material. During a startup of the combustion process (e.g, where the combustion chamber is cold), oxidant having a high oxygen content can be injected using oxidant injectors OI into the second zone Z2, at an interface between the first zone Z1 and the second zone Z2, and/or at an interface between the second zone Z3 and the third zone Z3 below the burner as noted above to help facilitate combustion of the solid fuel material.

The combustion of the solid fuel material may then occur and the combustion of the solid fuel material may stabilize such that the combustion can be at a steady state condition, or a condition in which the solid fuel material can be combusted on the grate 7 due to the heat in the combustion chamber 2 at a pre-selected designed rate of consumption of solid fuel material without need of a substantial flame F and/or supplemental fuel for the flame(s) F via the burner. At this point, the equivalence ratio of the burner(s) B can be adjusted to a lower setting so that less fuel (e.g. propane, ammonia, hydrogen, natural gas, combinations thereof, etc.) is fed to the burner(s) B and/or more oxidant is fed to the burner(s) B. At some point after processing reaches steady-state or the solid fuel combustion has initiated well, first the fuel to burner B is ceased, and after some time oxidant to the burner(s) B is ceased, or the fuel and oxidant supply to the burner(s) B can be ceased. Also outputting of high oxygen content oxidant from the oxidant injector(s) OI can be ceased so that only a lower oxygen content oxidant from oxidant outlets 30 is provided via the oxidant distribution system 3.

In a second step S2, the combustion of the solid fuel material can be monitored via one or more sensors to detect at least one pre-selected combustion parameter. Such a combustion parameter can include, for example, temperature of the combustion chamber in one or more zones, temperature of the flue gas in one or more regions of the flue gas distribution element 4, temperature of the flue gas output from the flue gas distribution element 4 via the flue gas outlet 5, a concentration of CO in the flue gas, a concentration of another flue gas constituent in the flue gas or within the combustion chamber 2. The combustion parameter may also include, or may also be, a rate of temperature change or an absolute temperature change exceeding a pre-selected threshold. For example, a first temperature sensor T1 in the combustion chamber 2, or a second temperature sensor T2 in the flue gas distribution element 4, or a third temperature sensor T3 in the flue gas distribution element 4 at a location that is downstream of the second temperature sensor T2 may be utilized to detect a temperature or monitor temperature for monitoring combustion of the solid fuel material. The sensor data from such sensors or other sensors (e.g. CO analyzer data of a CO analyzer, other content analyzer or temperature sensor, etc.) can be communicated to a controller to collect and evaluate that data to monitor the one or more pre-selected combustion parameters. In some embodiments, the sensor data can include camera data from a camera positioned to detect the flame and/or a thermal camera positioned to detect a two-dimensional temperature above the grate 7.

The controller can be a computer device having a processor connected to a non-transitory computer readable medium having code stored thereon that can be executed by the processor. The processor of the controller can also be communicatively connected to at least one transceiver for communications with the sensor(s) and other process control elements. A user device can also be communicatively connected to the controller to provide input to the controller or receive output from the controller. The user device may be, for example, a laptop computer, smart phone, tablet, or other computer device that an operator may utilize to visually see a graphical user interface to monitor data collected by the controller and to adjust setpoints or other control parameters the controller may utilize. The user may utilize at least one input device and/or at least one output device of the user device (e.g. a pointer device, a keyboard, a touch screen, a printer, etc.) to facilitate communication of input to the controller or receipt of data from the controller for being displayed or otherwise output to the user via the user's device.

In a third step S3, at least one pre-selected combustion parameter can be detected as exceeding a pre-selected threshold. Such a parameter can be associated with a poor quality solid fuel material for detection of combustion of high moisture content and/or poor quality solid fuel material. Such a parameter can also, or alternatively, be associated with another problem that may be detrimental to stable combustion of the solid fuel material on the grate 7. In response to detection of such a condition, oxidant can be injected into an intermediate zone(s) of the combustion chamber via at least one oxidant injector OI that is under the grate 7 and also adjacent to and below at least one burner B (e.g. coincident with the burner B and below it, upstream of the burner B and below it, and/or downstream of the burner B and below it). The oxidant that is injected can be a second oxidant that has a higher oxygen content as compared to a first oxidant fed to the combustion chamber via the oxidant outlets 30 of the oxidant distribution system 3 as noted above.

The supplying of additional oxidant can be provided in the third step S3 in a zone or zones of the combustion chamber 2 in which pyrolysis (e.g. oxidative pyrolysis) of the solid fuel material may occur while it is being periodically moved along the grate 7 toward the second end 7b of the grate 7. Also, (or alternatively), the injection of the oxidant via at least one oxidant injector OI in step S3 can occur in at least one zone of the combustion chamber 2 adjacent to where the solid fuel material may be combusted and downstream of where the solid fuel material may be dried and/or devolatized (e.g. in a zone or zones in which pyrolysis can occur) to provide makeup oxygen to account for oxygen levels being reduced near such a location due to the use of the oxygen that occurs from combustion of the solid fuel material. In some embodiments, this location for the injection of oxidant via one or more oxidant injectors OI can be in the second zone Z2, at an interface of between the first zone Z1 and the second zone Z2, in the third zone Z3, between the second zone Z2 and the third zone Z3, or at another location in which pyrolysis of the solid fuel material is expected to occur or adjacent to and/or upstream of the location at which the solid fuel material combusts in the combustion chamber 2 (e.g. in the pyrolysis zone(s)).

As noted above, the injection of oxidant can occur in the combustion chamber below the grate 7 at a location of the one or more oxidant injectors OI that can be coincident with a location of at least one burner B that can be located above the grate 7 (e.g. wall mounted above the grate 7, ceiling mounted above the grate 7, etc.). The injection of oxidant via the oxidant injector(s) OI can alternatively occur via oxidant injectors positioned below the grate 7 that are upstream and/or downstream of the burner(s) B as noted above. The injection of oxidant via the oxidant injector(s) OI can alternatively occur via oxidant injectors in which at least one oxidant injector OI is positioned below the grate 7 at a location that can be coincident with a location of at least one burner B as well as via at least one oxidant injector OI that can be positioned below the grate 7 that is upstream and/or downstream of the burner(s) B as noted above (e.g. there can be upstream oxidant injector(s), downstream oxidant injector(s) and a burner coincident oxidant injector(s), etc.).

The monitoring of the combustion of the solid fuel material may continue during the third step S3 and/or after such a step. In response to detecting that the one or more pre-selected combustion parameters are at or under the pre-selected threshold(s) for the parameter(s), the combustion of the solid fuel material can be considered to have stabilized sufficiently that the oxidant via the oxidant injector(s) OI is no longer necessary. In response to such a detection, the injection of the oxidant via the oxidant injector(s) OI can be deactivated so that only oxidant from the oxidant outlets 30 is provided to facilitate combustion. The process of combustion can then proceed back to the second step S2 for continued monitoring of the combustion of the solid fuel material.

In the event another detection of at least one pre-selected combustion parameter being at or exceeding a pre-selected threshold, the third step S3 may again be performed to help stabilize combustion. Then the deactivation can again occur and the process can again return to the second step S2. The cycling between the second, third, and fourth steps S2-S4 may occur numerous times during operation of the apparatus 1.

Embodiments of the process can also utilize other steps or features. For example, based on a detected level of oxygen, more or less oxidant can be fed to the burner to facilitate reduced CO creation and/or higher oxygen concentration with the flue gas as noted above. As another example, the grate 7 may be periodically vibrated to help facilitate motion of the solid fuel material along the grate 7 during operations as noted above.

As another example, in some embodiments the feeding of oxidant via the oxidant outlets 30 and the oxidant injector(s) OI can also be provided to control an oxygen content in the flue gas for use in downstream processing. For example, in embodiments where the flue gas output from the furnace may be used for creating syngas, the oxidant feed provided via the burner(s) B, oxidant outlets 30 and oxidant injector(s) OI can be adjusting to provide a desired oxygen concentration in the flue gas and/or achieve partial combustion of solid fuel to achieve desired composition of the flue gas.

As yet another example, embodiments of a grate furnace or a grate boiler can have oxidant injectors OI installed under a grate 7 and a second oxidant supply connected to the oxidant injectors OI to retrofit a furnace to include the oxidant injectors, utilize a second oxidant supply, and be able to perform an embodiment of the process for combustion a fuel that includes solid fuel material. Such a retrofitting operation can also include installation of sensors and/or a controller to facilitate monitoring and operation of the combustion process as well.

Some embodiments of the process can also only include the first step S1. In such an embodiment, the solid fuel material can be ignited and/or combusted via operation of at least one burner B as noted above, which can receive fuel for generation of at least one flame F to heat the solid fuel material for combusting that material. During a startup of the combustion process (e.g. where the combustion chamber is cold), oxidant having a high oxygen content can be injected into at least one intermediate zone (e.g, the second zone Z2, third zone Z3, a transition zone at an interface between the second zone Z2 and the first zone Z1 and/or a transition zone at an interface between the second zone Z2 and the third zone Z3) below the burner and also below the grate 7 as noted above to help facilitate combustion of the solid fuel material.

The combustion of the solid fuel material may then occur and the combustion of the solid fuel material may stabilize such that the combustion can be at a steady state condition, or a condition in which the solid fuel material can be combusted on the grate 7 due to the heat in the combustion chamber 2 at a pre-selected designed rate of consumption of solid fuel material without need of a substantial flame F and/or supplemental fuel for the flame(s) F via the burner. At this point, the equivalence ratio of the burner(s) B can be adjusted to a lower setting so that less fuel (e.g. propane, ammonia, hydrogen, natural gas, combinations thereof, etc.) is fed to the burner(s) B and/or more oxidant is fed to the burner(s) B. Also outputting of high oxygen content oxidant from the oxidant injector(s) OI can be ceased so that only a lower oxygen content oxidant from oxidant outlets 30 is fed into the combustion chamber 2 via the oxidant distribution system 3 to provide oxidant for the combustion of the solid fuel material. Also, the fuel and oxidant to burner(s) B can be ceased as noted above and, optionally, a cooling gas can be passed through the burner(s) B as noted above.

Embodiments of our process and apparatus can be provided to provide smooth, repeatable, and reliable start-up of a grate furnace for combustion of solid fuel material that may have a high moisture content and/or be a low volatile solid fuel. Embodiments can facilitate improved ignition characteristics of such a poor quality solid fuel (high moisture or low volatiles). Embodiments can also be provided so supplemental ignition materials are not needed for initiation of combustion of the solid fuel material.

Some embodiments may utilize one or more transient heating burners or one or more moving flame burners, which can help facilitate ignition of solid fuel at multiple areas over the grate by use of a lesser number of burners and also lower the peak temperature over the grate (as compared to stationary or conventional oxy-fuel burners) due to fuel staged operation of the transient heating burner(s) or moving flame burner(s). The peak temperature of fuel rich flames can be lower as compared to stoichiometric flame for such embodiments.

Embodiments can also provide a more effective and efficient use of oxygen, thereby injecting oxidant from oxidant injectors OI in grate regions where combustion initiates that includes the devolatilization zone, and/or the fuel pyrolysis zone (which can have a local lower oxygen content). Embodiments can include the oxidant injectors OI to assist and/or improve the ignition or combustion characteristics of the solid fuel (low volatiles or high moisture for example) in an enriched-oxygen environment in the grate zones where solid fuel starts to devolatilize and/or pyrolyze. Embodiments can also provide a higher carbon conversion rate for solid fuel materials, or oxidant from oxidant injectors OI can be used to facilitate carbon burnout in local regions when needed. Embodiments can be configured to utilize the oxidant injectors OI to assist in the increase of a production rate of current furnace (e.g. via a retrofitting of the furnace to include the oxidant injectors OI for outputting oxidant below the grate at pre-selected zones or transition zones as noted above).

In some embodiments of the process, the process can include initiating the start-up of combustion in the combustion chamber. This can include feeding solid fuel material onto the grate and initiating the feeding of a first oxidant (e.g. air, oxygen-enriched air, etc.) via oxygen outlets 30. One or more of the burners B can be started up as well by initiating the feeding of fuel and oxidant to the burner(s) B to generate at least one flame F in the combustion chamber 2. The one or more oxidant injectors OI for injection of a second oxidant having a higher oxygen concentration can also be initiated (e.g. injection of oxidant that is 80 mol %-100 mol % oxygen can be initiated for outputting of such second oxidant via oxidant injectors OI located under the grate in the second zone Z2 and/or third zone Z3, etc.). These actions can occur in conjunction with the combustion of solid fuel material (e.g. biomass, etc.) on the grate 7 within the combustion chamber 2 in a first step S1 of the process.

The process can also include monitoring combustion parameters to determine when combustion of the solid state fuel has sufficiently occurred. For example, temperature can be monitored via one or more temperature sensors as noted above to determine when a steady-state or relatively steady-state condition has occur. This monitoring can be performed in the second step S2. The monitoring that is performed can be performed to determine whether the solid material fuel has begun combusting sufficiently via sensor data or other data indicating that the combustion of the solid material fuel has met a pre-selected combustion criteria.

In a third step S3 of the process, at least one pre-selected combustion parameter can be detected as exceeding a pre-selected threshold or other type of pre-selected criteria. In response to such a detected condition (e.g. via a controller or via sensors as noted above), oxidant injection and/or burner operation can be adjusted. For example, if a pre-selected criteria for a steady-state condition has been detected, the fuel and/or oxidant fed to the burner(s) B can be reduced or ceased. Also, or alternatively, second oxidant fed to the oxidant injectors OI can be ceased or reduced in flow rate. As yet another example, cooling gas can be fed to the burner(s) B to facilitate cooling of the burner(s) in a situation where the burner(s) are no longer fed oxidant and fuel.

For example, as indicated in a fourth step S4 of FIG. 9, the injection of oxidant via oxidant injectors OI can be ceased. The process can also return to the monitoring so that other adjustments may be subsequently made. For example, oxidant injection via the oxidant injectors OI can be reactivated or otherwise changed, burner operation can be adjusted further (e.g. burner(s) B can be reactivated via feeding of fuel and/or oxidant for forming of at least one flame F, etc.). The adjustments can be made via sensor feedback and pre-selected process control criteria.

Embodiments can provide enhanced operational flexibility by providing flexibility to use of poor quality solid fuel material or account for variation in the solid fuel type while minimizing process offsets. Some embodiments can provide a more stable combustion process in which the combustion of solid fuel material may occur more often in a steady state condition or with a pre-selected desired operational rate to provide enhanced boiler operations for boiling of water via the flue gas distribution element 4 and/or improve the availability of steady-state supply of syngas or partially combusted fuel.

The improvement in solid fuel (e.g. biomass material, etc.) processing can also be provided in a way that utilizes less burners, less equipment (e.g. number of skids, etc.) and reduced maintenance. The reduction in maintenance can also reduce operational downtime.

We also performed evaluation work to help evaluate the effectiveness of exemplary embodiments of our apparatus 1 and process. FIG. 10 shows temperature data from a laboratory experiment that was performed in a test furnace. The solid fuel used was wood chip biomass that had ˜51 weight percent (wt %) moisture level. Table 1 below shows the elemental composition of the solid fuel. The estimated higher heating value (HHV) values in Table 1 were determined from the elemental CHNSO (CHNOS) analysis for determination of carbon, hydrogen, nitrogen, sulfur and oxygen content data using the equation:

HHV = 0 . 3 ⁢ 3 ⁢ 5 ⁢ C + 1.423 H - 0 . 1 ⁢ 54 ⁢ O - 0. 1 ⁢ 4 ⁢ 5 ⁢ N

TABLE 1
CHNOS analysis for combustion of wood chips

	Carbon	Hydrogen	Nitrogen	Oxygen	Sulfur	HHV
Fuel	(wt %)	(wt %)	(wt %)	(wt %)	(wt %)	(MJ/kg)
Wood	23.91%	8.96%	0.25%	14.06%	<0.1%	18.558
chips

An oxy-fuel burner was used for the experiment to initiate the combustion of the solid fuel (wood chips). The bed height of material (solid fuel) above the grate was about 5 in. to 6 in high. The test furnace had capability to have either air as the under-grate oxidizer or add a secondary oxidant ((>95% by vol. purity oxygen) to the under-grate air to generate oxygen-enriched under-grate air. FIG. 10 shows the temperature from four thermocouples positioned in the test furnace: one measured the furnace gas temperature, and the other three measured gas temperature in the grate having the solid fuel (e.g. wood chips). The thermocouples were at three different heights above the grate. FIG. 10 shows comparison of data (gas temp and temp at 0.5″ height) from two experiments: case A: when oxy fuel burner was used and no under-grate air oxygen enrichment was used and case B: when combination of oxyfuel burner and oxygen enriched under-grate air was used. The plot of FIG. 10 shows that oxy-fuel burner was able to initiate the combustion of the solid fuel biomass within about 3 minutes from the point the oxy-fuel burner ignited. This is visible as the bed temp at 4″ above the grate surface starts to see ramp in temperature as shown in FIG. 10.

In case B, At about 10 mins, the oxygen enrichment of under-grate air was started at 24.5% oxygen enrichment. As a result, we observed the bed temperature (4″ height location) for the solid fuel on the grate to rise from about 700° C. to 850-900° C. This happened as the oxygen enrichment improved the combustion characteristics of the solid fuel (e.g. wood chips in the experiment). Simultaneously, the firing rate of the oxy-fuel burner was reduced by 95%. After reduction of the firing rate, the solid fuel bed continued to sustain combustion as can be noticed from the temperature plots of FIG. 10. At about 10 minutes, combustion progressed up to 2″ above the grate surface and at about 12 minutes, the combustion had progressed up to 0.5″ above the grate surface. For oxy-fuel burner in case B, fuel flow rate was reduced to zero at 13 mins.

However in case A, similar to case B, oxy-fuel burner initiates the ignition of the biomass. However, when the oxy-fuel burner firing rate was reduced and closed at 10 mins-13:00 mins in case A, the temperature drops inside the furnace and sustaining biomass combustion is a challenge (indicated by the drop in temperature of furnace gas and bed thermocouple at 0.5″). This showcases how the idea for experiment B, a combination of oxy-fuel burner and under-grate oxygen enrichment provides improved results where the biomass combustion initiates and sustains after the oxy-fuel burner fuel supply is closed. This allows to reduce the time of use of oxy-fuel burner and optimize on the cost of secondary fuels.

In the conducted testing in case B, more room temperature biomass was loaded in the test furnace at 13 minutes and 15 minutes. The temperature plots of FIG. 10 shows that temporarily the temperature drops in the bed as new cold biomass was loaded in the furnace. However, the bed combustion continued to sustain and the temperature re-ramped to the bed temperature before the room temperature solid fuel was dropped into the furnace. The temperature started to reduce after 16 minutes as the biomass on the grate was towards the end of being consumed.

This conducted experiment shows how use of combination of oxy-fuel burner with under-grate oxidant enrichment helped initiate the combustion of high moisture content biomass fuel and sustained the combustion of the solid fuel on the grate. This is true especially during the test furnace start-up from a cold furnace (21° C.). This experiment needed no second fuel to be added to the solid fuel for ignition or combustion of the fuel. The heat generated from the combustion of the solid fuel and the under-grate oxygen enrichment was able to initiate and sustain the combustion of the newly loaded high moisture solid fuel as well. The newly loaded high moisture solid fuel was able to sustain combustion without the need of energy from the oxy-fuel burner. The experimental results from the conducted experiment further corroborated the significant improvement that embodiments can provide for the combustion of solid fuel.

Embodiments can also utilize other modifications. It should therefore be appreciated that other modifications can also be made to meet a particular set of criteria for different embodiments of the apparatus 1 or process. For instance, the positioning of the oxidant injectors OI, type of oxidant injectors OI (e.g. lances, other type of oxidant injector, etc.), and type of burner B (e.g. transient heating burner, conventional oxy-fuel burner, etc.) for the burner and oxidant injection system 9 can be any of a number of suitable types and configurations. As another example, the grate configuration and angle of inclination (or horizontal orientation for the grate) can be any of a number of suitable configurations that permit oxidant to pass from below the grate through solid fuel material on the grate, and into the atmosphere within a furnace above the solid fuel material on the grate within the furnace.

As yet another example, embodiments of the combustion apparatus, process for combustion, and/or burner and oxidant injection system, can be configured to include process control elements positioned and configured to monitor and control operations (e.g., temperature and/or pressure sensors, flow sensors, an automated process control system having at least one work station that includes a processor, non-transitory memory and at least one transceiver for communications with the sensor elements, valves, and controllers for providing a user interface for an automated process control system that may be run at the work station and/or another computer device of the plant, etc.). It should be appreciated that embodiments can be configured to utilize a distributed control system (DCS) for implementation of one or more processes and/or controlling operations of an apparatus or process as well.

As another example, it is contemplated that a particular feature described, either individually or as part of an embodiment, can be combined with other individually described features, or parts of other embodiments. The elements and acts of the various embodiments described herein can therefore be combined to provide further embodiments. Thus, while certain exemplary embodiments of the apparatus, process, and system, and methods of making and using the same have been shown and described above, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.