INTEGRATION OF A HOT OXYGEN BURNER WITH PYROLYSIS PROCESSES

Description

FIELD OF THE INVENTION

The present invention relates to a method and system for optimizing pyrolysis processes in conjunction with gasification, to maximize the production of products that can be readily used in the marketplace. The method and system of the present invention optimizes the pyrolysis process to maximize the conversion of base feedstock into economically attractive saleable products (e.g., jet fuel, diesel, ethanol, methanol, renewable natural gas, green hydrogen, etc.). The integration of pyrolysis with gasification in the form of a hot oxygen burner (HOB) provides significant increases in net system performance, maximizing the yield of synthesis gas (i.e., syngas) that can be produced per mass of biomass fed into the integrated system.

BACKGROUND OF THE INVENTION

The primary goal of bio-oil producers via thermochemical processes is the conversion of the base feedstock into economically attractive saleable product. This means the producer must first optimize the pyrolysis process to maximize the production of liquid product. The producer must also make a product that can be readily used in the marketplace. One example is the production of pyrolysis oil from biomass, or other, feedstocks. The process is optimized to maximize production of liquids that can be shipped and sold. These liquid products may need to be purified prior to sale. For example, many industrial processes are unable to manage solids in the liquid. Therefore, the liquid products must be filtered prior to sale.

One potential industrial use of pyrolysis liquid is the production of syngas by partial oxidation. An example would be a hot oxygen-based gasification system where oxygen, a fuel gas, and the liquid feed are supplied such that the reactions take place in fuel rich (less oxygen than required for complete combustion of the feed and fuel) conditions. The resulting syngas is then cooled and used in a downstream syngas conversion process. The term “syngas” or “synthesis gas” is utilized interchangeably herein and it will be understood to mean primarily a mixture of carbon monoxide and hydrogen, with some water, carbon dioxide, methane and other small components produced from a wide range of carbonaceous feedstocks. Examples of the downstream syngas conversion processes include the production of liquid transportation fuels, reducing gas for iron/steel production, or the production of ‘green’ hydrogen.

Integrating the production of pyrolysis liquids with gasification, particularly hot oxygen gasification, can lead to significant increases in net system performance. In the present invention, the goal is to maximize the yield of syngas (defined as primarily CO+H₂) per mass of biomass fed to the integrated system. The goal is also to reduce the cost of resultant syngas. In some embodiments the integration would be enabled by only modifying pyrolyzer operation (allowing the pyrolysis unit and the gasifier to be decoupled). In others, the integration would include heat exchange between the gasifier and the pyrolysis unit, which by necessity requires the two units to be co-located.

For example, U.S. Pat. Nos. 5,792,340 and 8,105,482 B1 describe Ensyn Technologies' rapid thermal processing (RTP) method related to a converting biomass such as wood chips, bark, sawdust, and agricultural waste into a liquid fuel using a process called pyrolysis. In essence it is a method for rapidly heating the biomass and vaporizing it into a liquid bio-oil that can be collected and further processed.

Several other patents disclose the integrated pyrolysis and entrained flow gasification methods such as U.S. Pat. No. 9,874,142 where low rank fuels (i.e., fossil fuels and biomass-based materials) are pyrolyzed to produce pyrolysis gas and fixed carbon. The integrated gasification system receives the fixed carbon and produces a syngas stream. This document also discloses a system in which char produced from the pyrolysis unit can be mixed with water or other liquid to produce a slurry which can then be directed to the gasifier. They mention a hydrocarbon-rich syngas stream that can be conveyed to a removal system which includes a tar recovery unit.

In U.S. Patent Application No. 2023/0109160 A1 the integrated pyrolysis and gasification is performed using a convenient reactor configuration, such as fluidized coking reactor or a fluid catalytic cracking reactor configuration. In one aspect the biomass can be processed with a co-feed that is suitable for processing under fluidized coking conditions. Under the pyrolysis conditions the products produced comprise pyrolysis oil, char, coke, or a combination thereof, and a gas phase pyrolysis product, with at least a portion of the char, coke or combination thereof being deposited on the solid particles. It is a portion of the solid particles comprising deposited char, coke, or a combination thereof that are then passed from the pyrolysis reactor into a gasifier. The gasifier is run under partial oxidation conditions. One of the main drawbacks is that there is no mention of directing a pyrolysis vapor, liquid pyrolysis product or portions thereof to a gasification unit.

In the doctoral theses entitled Gasification of Bio-oil and Bio-oil/Char Slurry of Masakazu Sakaguchi at University of British Columbia, 2010, the investigation of fast pyrolysis bio-oil and bio-oil/char slurry is a fluidized bed reactor is provided. The research included the use of a reforming catalyst and a comparison of stream versus partial oxidation gasification. However, all the work is done on fluidized bed reactor. In a similar vein in the article entitled Methanol Production from Pyrolysis Oil Gasification—Model Development and Impacts of Operating Conditions to Zhihai Zhang et al. and published in Applied Sciences in 2020 a simulation model to produce methanol from the pyrolysis of pyrolysis oil is provided. However, this document does not contemplate the integration of a pyrolysis system with the gasification system, let alone the one of the present invention, which is described in detail below.

In order to address the drawbacks of the related art in the field of pyrolysis and gasification, the present invention provides an integration of these systems for increased yield of saleable products. By designing the pyrolysis process to produce pyrolytic liquid, biochar, and biogas and integrating it with the gasification reactor, the yield of syngas per biomass feed can be increased significantly. The HOB based gasification system of the present invention enables the use of lower quality or unacceptable feedstocks to be utilized in solid, liquid or gaseous state. The HOB gasification system is tolerant of contaminants that might be present in lower quality biomass feedstocks, such as agricultural waste containing chemical elements like potassium chloride or sulfur, enabling the use of otherwise unacceptable feedstocks.

The proposed system of the invention provides economic advantages by optimizing the production of byproducts, such as biochar and biogas, which can be fed into the gasifier to increase the yield of syngas per mass of biomass feed into the system. By intentionally degrading product quality or selecting feedstocks to reduce liquid yield and increase the conversion of syngas per mass of feedstock, overall conversion efficiency can be increased, leading to improved performance and profitability of the system. Moreover, tailored liquids can be produced which tend to have a lower yield from the input feedstock. However, the overall economics can be improved as the increased yield of byproducts, char and biogas can be directed to the HOB gasifier to produce syngas.

In addition, the proposed system of this invention offers a solution to the issue of fines in the pyrolysis feed, which can hamper efficient conversion to liquid fuels. By bypassing fines and feeding them directly to the gasifier, the yield of syngas can be increased with little or no increase in oxygen required. Finally, the proposed system offers environmental advantages by enabling the conversion of biomass into saleable products, reducing greenhouse gas emissions associated with traditional fossil fuels and improving environmental sustainability.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the present invention, a method for optimizing the conversion of biomass into a saleable product derived from pyrolytic liquid and syngas is provided. The method includes: a) pyrolyzing a biomass feedstock in a pyrolysis reactor to produce liquid products, and byproducts including biochar, and biogas; b) gasifying the biochar and biogas along with the liquid products in a hot oxygen-based gasification system employing a hot oxygen burner to produce syngas; c) cooling the resulting syngas; and d) utilizing the syngas in a downstream syngas conversion process; wherein the pyrolysis process is optimized to increase the conversion efficiency of the biomass feedstock into byproducts and reduce the liquid yield such that the yield of syngas per mass of biomass fed into the integrated system is increased.

In another aspect of the invention, a system for optimizing the conversion of biomass into saleable product derived from pyrolytic liquid and syngas is provided. The system includes: a) a pyrolysis reactor for converting a biomass feedstock into liquid products, biochar, and biogas; b) a hot oxygen-based gasification system comprising a hot oxygen burner for gasifying the biochar and biogas along with the liquid products to produce syngas; c) a cooling system for cooling the resulting syngas; and d) a downstream syngas conversion process utilizing the cooled syngas; wherein the pyrolysis reactor and the gasification system are optimized to increase the yield of syngas per mass of biomass fed into the integrated system, and to handle contaminants present in lower quality biomass feedstocks.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts the block flow diagram of a system for optimizing pyrolysis processes in conjunction with gasification in an HOB partial oxidation reactor.

DETAILED DESCRIPTION OF THE INVENTION

The present invention optimizes the pyrolysis process to maximize the conversion of base feedstock into economically attractive saleable products. The integration of pyrolysis with gasification provides significant increases in net system performance, maximizing the yield of syngas that can be produced per mass of biomass fed into the integrated system.

The proposed system offers several advantages over conventional pyrolysis systems. For example, modifying the pyrolysis process to increase the char loading in oil and/or by skipping the filtration of the char can lead to an increase in the yield of syngas per mass of biomass fed into the system. Similarly, by reducing liquid yield, the overall conversion efficiency of syngas per mass of biomass feed can be increased. Additionally, bypassing small or fine-sized biomass feed can increase the yield of syngas with little to no increase in oxygen required, while the integration of pyrolysis with gasification can enable the use of lower quality feedstocks to produce saleable syngas.

With reference to FIG. 1, the proposed system includes a pyrolysis reactor (102), a gasification reactor (104) (e.g., a hot oxygen-based gasification system such as a partial oxidation reactor (with an associated air separation unit (109) which provides oxygen), and a downstream syngas conversion process (e.g., production of liquid transportation fuels, reducing gas for iron/steel production, or the production of ‘green’ H2) (not shown). The pyrolysis reactor (102) converts the feedstock, typically received from a feedstock conditioning unit (101) into pyrolytic liquid products (pyoil) (107), biochar (105), and biogas (108). The biochar and biogas are then sent to the gasification reactor (104), where they are gasified along with the liquid products. As explained below, the biochar stream (105) and feedstock fines (106) are routed to a storage and blending tank to make a slurry which is routed to the HOB gasification reactor (104) to convert to a syngas. The resulting syngas is then cooled and used in the downstream syngas conversion process.

Although the pyrolysis reactor is preferably integrated with the gasification reactor, it is contemplated that these could be decoupled in order to carry out the pyrolysis at one location and the resulting product transported and gasified at a different location. The integration of the Ensyn RTP pyrolysis process of U.S. Pat. Nos. 5,792,340 and 8,105,482 B1, which are incorporated herein by reference, with the hot oxygen burner gasification which is able to handle or process liquids, solids or gaseous feedstocks, whether at a single or multiple locations maximizes the production of liquid products. The gasification reactor includes the hot oxygen burner which is a specially designed burner that produces a high temperature, high momentum jet containing oxygen. The jet is produced by combusting a small amount of fuel 10 with a large amount of oxygen 20 in a combustion chamber of the burner 100. The resulting gas mixture has an oxygen concentration ranging from 65-90% (along with some H₂O and/or CO₂ depending on the fuel being used) at temperatures ranging from 1000-2500° C. The “hot oxygen” mixture is then accelerated through a nozzle 30 to velocities ranging from 500-800 m/s. The overall effect is a highly reactive jet 40 with exceptional mixing and shearing capability. For example, the jet is capable of atomizing liquids while simultaneously entraining surrounding gases. The high O₂ content and high temperature make the jet very reactive, forcing all liquids, gases and solids drawn into the jet to rapidly react to produce the desired effect on the process. The specifics of this HOB burner gasification reactor is further explained in Applicants U.S. Patent Application Ser. No. 63/574,322 filed on Apr. 4, 2024, which is incorporated by reference in its entirety.

The high velocity, reactive, jet to drive atomization and mixing of various feedstocks without needing to resort to a complex burner design as shown in the prior art. Specifically, the mixing power of the jet is high enough that even after mixing/atomizing a first feedstock stream there is adequate mixing power to mix a second, or more, feedstock stream of different types. A secondary aspect of the HOB is the ability to independently change the mixing power of the jet depending on the mixture of feedstocks in use at any given time. The use of this type of HOB is a way to achieve excellent atomization and combustion for liquids, viscous liquids, slurries and sludges. Naturally, the HOB can be associated with a reactor in which the entrainment and gasification of the gas/liquid/solid feedstock combination can occur to form the syngas. Thus, the integration of the RTP pyrolysis process with this type of HOB gasification reactor maximized the production of finished products downstream.

More specifically, the pyrolysis process is modified to increase the char loading in oil and/or omitting the filtration of the liquid. By intentionally degrading the product quality exiting the pyrolysis process, higher energy content products can be obtained from the feedstock, and yield of syngas per mass of biomass fed into the system can be increased. Similarly, the pyrolysis plant operation can be modified to reduce liquid yield and increase the production of byproducts, which can be fed into the HOB gasifier together with liquid hydrocarbons, thereby increasing the syngas yield.

In another embodiment, the syngas yield is increased by bypassing small or fine-sized biomass feed and feeding it to the gasifier to be converted into syngas, without affecting the integrated system performance. Moreover, the integration of pyrolysis with gasification can enable the use of lower quality feedstocks to produce saleable syngas. By selecting the feedstock that maximizes pyoil conversion efficiency, the integration of pyrolysis with gasification can increase syngas production using cheaper, lower quality feeds, thereby reducing the overall cost of production. By leveraging the properties of the HOB gasification system to tolerate contaminants that might be present in lower quality biomass feedstocks, such as agricultural waste containing chemical elements like potassium, chlorine or sulfur, the proposed system can be used to produce saleable biofuels and other industrial products.

Many industrial combustion systems, including those using liquid hydrocarbons as fuel, are not designed for solid particulate in either the fuel or the flue gas. The presence of solid char in the liquid can also hamper or degrade catalytic upgrading of the liquids to higher value products. Consequently, the thermochemically produced liquid product is normally filtered or purified before being offered for sale.

In another exemplary embodiment, the pyrolysis operation is modified to reduce or preferentially select the pyrolytic liquid that is directed to saleable applications such as, but not limited to, heating fuel applications, refinery processes, chemical applications, carbon black, graphite processes, anode applications, road paving applications, and resins. The pyrolytic liquid that is not directed to saleable applications can be sent to the HOB gasification system for the purpose producing synthesis gas. Typically, a commercial pyrolysis process is optimized to maximize the production of pyrolytic liquids which are the main source of revenue for the operator. However, when the pyrolysis process is integrated with a gasification process it may be better to optimize the plant such that liquid production is reduced or preferentially selected.

In an exemplary embodiment of the present invention, the pyrolysis process and the gasification process are integrated such that removal of the solid carbon is not only not required, it is not desirable. With reference to Table 1, below, the effect of either omitting filtration of the liquid product or returning a portion of the solid carbon to the liquid product is illustrated. A fixed amount of feedstock is assumed to be fed to a pyrolysis system. The resulting liquid product is then filtered to capture the biochar. A portion of the biochar is returned to the liquid product while the remainder is used for heat generation in the pyrolysis process.

In Example 1 a partial oxidation reactor based on the hot oxygen technology (HOT) is used to gasify bioliquids. The HOT design allows cofeed of liquids, solids, and gaseous feeds. In the ‘baseline’ configuration the bioliquid fed to the reactor is essentially free of solid char since that is the typical composition of a commercial bioliquid product. Examples 1a through 1c illustrate the effect of varying the amount of biochar returned to and shipped with the liquid product is shown as less than 13%, 26% and 40%, respectively and more specifically 12.8%, 25.6%, and 38.5%, respectively. The solid-containing liquid product is used as feed to a hot oxygen-based gasification system. Natural gas is used as the fuel for the hot oxygen burner. The performance of the system was then modeled using conventional methods. Replacement heat for the pyrolysis system (that would have been provided by combustion of the char) is assumed to be available either by modifications of the pyrolysis system or by thermal integration with the gasification system. Thus, as can be seen in this instance where the feed to the gasification system of a degraded product (i.e., including both liquid bio-oil and biochar) by eliminating the purification step, the syngas yield per pound of biofeed to the pyrolysis reactor increases from 5.6% to 10.8% and 16.3%, respectively, while also reducing the oxygen consumption.

In another exemplary embodiment, the pyrolysis operation is modified to reduce the liquid yield in order to increase the syngas production per mass of biomass feed. Typically, a commercial pyrolysis process is optimized to maximize the production of pyrolytic liquids which are the main source of revenue for the operator. However, when the pyrolysis process is integrated with a gasification process it may be better to optimize the plant such that liquid production is reduced. With reference to Table 2, below, two examples are provided where the conventional pyrolysis plant is optimized for liquid production such that byproduct yields are increased.

In these Examples 2a and 2b it is assumed that the pyrolytic liquid and the byproduct char and gas are fed to the gasifier simultaneously. The energy that would normally have been provided to the pyrolysis process by combustion of the byproduct feeds is provided by thermal integration with the gasifier and/or the syngas consumption process. An example of the appropriate gasifier is the hot oxygen gasifier where multi component feeds have been disclosed in Applicants U.S. Patent Application Ser. No. 63/574,322. In Example 2a the pyrolizer operation is modified such that more of the initial biomass ends up as byproducts (i.e., biochar and biogas) by as much as 27%. When feeding these streams to the HOT gasification unit as described as the baseline for in Example 1 the syngas yield (scf/lb biomass feed) increases by over 20% while the oxygen required (lb/sch syngas) is reduced by 3%. Example 2b illustrates that the integration may offer additional optimization potentials. Changing the operating conditions still further from Example 2a so that more biogas and less biochar is produced leads to a lower syngas yield (yet still higher than the original baseline). Thus, clearly reducing the liquid yield from the pyrolysis process when integrated with the HOB gasification unit which handles byproducts in any one of liquid/solid/gaseous state yields an overall higher conversion of syngas per pound of raw biomass feedstock in the pyrolysis process.

In yet another exemplary embodiment, in the integrated plant, the syngas yield is increased through the bypassing of small size (fines) biomass feed to the HOB gasifier. Typically, in the commercial pyrolysis process the incoming bio feedstock is ground to a relatively fine size, typically on the order of 6 mm or less, before being fed to the pyrolysis reactors. During this grinding process a small amount of the feed is inevitably ground to a finer than desired size (i.e., “fines”). Since it is undesirable to ‘waste’ any of the feedstock these fines are used as part of the process. However, the fines can actually degrade the process for liquid make such that less liquid is produced per mass of biomass delivered to the plant. In contrast, the integration of the pyrolysis facility with a HOB gasifier of the present invention provides a unique opportunity be allowing the ‘fines’ to be bypassed and sent to the gasifier to be converted, along with any other feeds from the gasifier to syngas. For example, if the same facility described in Example 1 (and the subsequent examples) is modified such that fines are simply bypassed around the process and fed into the gasifier along with the liquid products. The syngas yield (scf/lb biomass feedstock) is increased with little or no increase in oxygen required (lb/scf syngas) by the HOB gasifier. With reference to Table 3, below, in each of the Examples 3a and 3b the gasifier and the pyrolysis systems can actually be integrated without being co-located as the fines can be simply mixed with the liquid products at the pyrolysis facility and delivered to the gasifier.

In the case of co-located pyrolysis plant and gasifier the fines can also be delivered and fed as a solid or slurry. The co-located plant can further increase the degree of integration (and syngas efficiency) by thermally integrating the gasifier and the pyrolysis unit. For example, if the facilities are thermally integrated the byproducts (biochar and biogas) that are normally used for energy production can be fed directly to the gasifier along with the normal liquid products and, in this example, the fines. Example 3b (Table 3) demonstrates that thermally integrating the pyrolysis plant and the gasifier while keeping everything else the same can significantly increase the syngas yield per lb of biomass feed.

In another exemplary embodiment, lower quality feedstocks may be used by the integration of the RTP Pyrolysis process with the HOB gasifier. For instance, lower cost biomass residuals such as softwood bark, hardwood bark, higher ash content wood, energy cane, corn stover, wheat straw and other agricultural-based feedstocks typically have lower product yields and quality than higher priced, cleaner feedstocks such as lumber mill byproducts making the former unappealing for processing. However, through the inventive integration of pyrolysis with HOB gasification overcomes these limitations by simultaneously converting any lower quality liquid fractions and the byproducts into useable syngas. In fact, the net efficiency of syngas production can be increased. This is illustrated for representative alternate feeds in Table 4.

As be seen from the table the use of the processing of alternate biomass in the pyrolysis process, and with the added flexibility of HOB gasification which allows the processing of liquids as well as byproducts (i.e., char, and bio-gases (e.g., CH4, CO)) increases the syngas production per pound of bio feed and requires less oxygen to produce the syngas. Coupled with the lower initial cost of the alternate feeds, yields a reduction in the cost produce quality syngas, and ultimately saleable products such as transportation fuels, heating oil, and jet fuel.

In a further embodiment, low-cost biomass feedstocks, such as palm residuals, may yield a fast pyrolysis bio-oil that contains components that are unacceptable for use in certain applications comprising transportation fuel production, heating fuel, chemical isolation, etc. Examples of such undesirable components include chlorine, potassium and calcium. Due to the nature of the operation of the HOT system, it is tolerant of these contaminants, enabling the use of otherwise unacceptable, low-cost, feedstocks in both distributed and integrated with the RTP pyrolysis process and the HOT gasifier.

While the invention has been described in detail with reference to specific embodiments thereof, it will become apparent to one skilled in the art that various changes and modifications can be made, and equivalents employed, without departing from the scope of the appended claims.