The present invention relates to the conversion of biomass to useful hydrocarbon, aqueous, and biochar products. More specifically, the present invention relates to the multi-stage conversion of biomass from pruning of sustainably cultivated arbor, as well as cellulosic biomass and plastics recovered from municipal, commercial, or industrial solid waste, to enable broad control and optimization of quantities and qualities of the resulting products.
A majority of nations in the world now support the shift from use of fossil derived hydrocarbon fuels to “green” fuels generated from renewable and sustainable sources, including renewable fuels of non-biological origin (RFNBO) in certain jurisdictions. The definition of renewable or “green” energy feedstocks or products, as applied to municipal solid waste components, varies by jurisdiction. In the USA, for example, a full lifecycle analysis must be done to certify a published USEPA “pathway” (feedstock, process, product) for sustainable fuel production. Waste plastics, for example, do not qualify as sustainable feedstocks in the US. Under the RED III policy in the EU and in Canada, however, non-recyclable plastic components of municipal solid waste can be a renewable energy feedstock.
These are in a class designated as Renewable Fuels of Non-Biological Origin (RFNBO). RFNBOs are fuels the energy content of which is derived from renewable sources other than biomass.
The adjective “green” in the context of the present invention refers to renewable energy sources, either fully sustainable as in the US, or of reduced fossil carbon content, including RFNBO fuels as in the EU and Canada. The definition of green, therefore, depends on the jurisdiction in which the fuels are produced.
This shift away from the use of fossil fuels results in reduced fossil carbon emission to the atmosphere and oceans, mitigating global warming and harmful ocean acidification. One of commercially available paths to produce fully sustainable or RFNBO green fuels is the production of synthesis gas via gasification of biomass, or biomass and non-recyclable plastics, including such materials recovered from municipal solid waste. After cleaning and adjustment of the composition, the synthesis gas, or syngas (comprised mainly of carbon monoxide and hydrogen), may be used as a feedstock for Fisher-Tropsch or other catalytic methods of synthesis of clean, high-quality hydrocarbon or alcohol fuel products. These fuel products can be further refined by settling, filtration, or further separation or purification by distillation as required.
While systems based upon prior state of the art and inventions can produce quality liquid fuels and other products, they fall short of optimal carbon utilization, discharging significant amounts of carbon dioxide to the atmosphere unless additional hydrogen is provided. This outcome results from the need to shift the hydrogen to carbon monoxide ratio in the synthesis gas from that obtained from gasification or pyrolytic conversion of biomass or RFNBO by processes utilizing water gas shift reactions.
The method disclosed herein comprises utilizing green hydrogen produced by electrolysis of water using renewable power or hydrogen extracted from geological sources. Fully sustainable electrical power may be generated from sources such as solar or wind to achieve the optimal hydrogen to carbon monoxide feed mixture ratio for Fisher-Tropsch or other catalytic synthesis of hydrocarbon fuels with subsequent separation and refining. One option is the generation of green hydrogen via electrolysis, which also produces oxygen. Use of this sustainably produced oxygen in the gasification and or pyrolytic conversion of biomass, plastic or other carbonaceous feedstock, can provide flexibility in controlling a fully sustainable thermal conversion process. Such enhanced control results in sustainably produced materials that offer both environmental and economic advantages and are widely sought in the hydrocarbon market. Alternatively, use of hydrogen and especially geologic or other sustainably sourced hydrogen, can greatly reduce carbon dioxide emissions from processes converting biomass or biomass and plastics to liquid fuels, whether the feedstock source be arbor, agricultural or sorted fractions of municipal solid waste.
The present invention is an integrated system and method for the optimal conversion of biomass and non-recyclable plastic, including sustainably cultivated and harvested biomass, to useful fuel products. Resultant fuel products may include liquid fuels and or blend stocks, alcohols, and ultra-low sulfur middle distillate fuels such as sustainable diesel and aviation fuel (SAF). The invention provides for the conversion of biomass using a combination of process units that enables control and optimization of the yield and quality of the resulting products.
In some embodiments the method includes: (a) providing a biomass, sustainably produced biomass, or plastic feedstock for thermal conversion to synthesis gas, (b) producing and distributing green electrical power, (c) electrolytically producing molecular hydrogen and oxygen from water, and or use of geologic hydrogen, (d) thermally converting the biomass to form a synthesis gas including light hydrocarbon components, (e) reforming of the synthesis gas, (f) cooling and cleaning the synthesis gas, and recycling the purge carbon dioxide stream (g) combusting a portion of the cleaned synthesis gas, (h) recovering the heat in the flue gas by transfer into the synthesis gas generator, (i) utilizing some or all of the green oxygen generated electrolytically in converting the biomass to synthesis gas, (j) compressing the synthesis gas to optimal inlet pressure and temperature for Fisher-Tropsch or other catalytic conversion, (k) blending of the green hydrogen, produced electrolytically or from geologic formations, with the cleaned reformed synthesis so as to achieve the optimal hydrogen to carbon monoxide ratio of feed to the Fisher-Tropsch process, (l) converting, via Fisher-Tropsch or other catalytic synthesis processes, to liquid fuel and other products, (m) generating process steam using the sensible energy in the flue gas generated after it exits the heat recovery portion of the biomass conversion to synthesis gas system, (n) cleaning the flue gas, including capturing carbon dioxide from the flue gas prior to exhaust to the atmosphere and recycling it to extinction or net complete conversion, and (o) cooling and storing the residual solids product of the gasification and or pyrolytic generation of the synthesis gas.
The process also includes utility support systems, depending on feedstock characteristics and desired product suite. These support or auxiliary systems include: (a) a high- and low-pressure hydrocarbon vent gas collection system, which delivers gas either for process heating or in an exhaust thermal oxidizer, (b) an air pollution control system with flue gas recycling for use in combustion emissions control, (c) a water management system for recycling, generation of boiler feed make-up water and for wastewater effluent discharge treatment, and (d) a dry coolant system.
The components and utility support systems described herein, along with other incidental but essential subsystems common to commercial facilities, such as process monitoring and control systems, achieve biomass conversion to fully sustainable or RFNBO products at higher carbon utilization efficiencies and higher liquid fuel yields than currently available processes.
The advantages compared to the current standard for biomass conversion through synthesis gas generation and Fisher-Tropsch or other catalytic synthesis include: (a) higher yields of green liquid fuels, (b) reduced carbon dioxide emission in such processes, and (c) greater control of both the synthesis gas generation process used and the Fisher-Tropsch or other catalytic process used.
It will be recognized that some, or all, of the Figures are schematic representations for purposes of illustration and do not necessarily depict the actual relative sizes or locations of the elements shown. The Figures are provided for the purpose of illustrating one or more embodiments of the invention with the explicit understanding that they will not be used to limit the scope or the meaning of the claims.
In the following description, for the purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the invention of the present invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without some of these specific elements. Throughout this description, the embodiments and examples shown should be considered as exemplars, rather than as limitations on the invention. That is, the following description provides examples, and the accompanying drawings show various examples for the purposes of illustration. However, these examples should not be construed in a limiting sense as they are merely intended to provide examples of the invention rather than to provide an exhaustive list of all possible implementations of the invention.
In the Figures included herein both mechanical elements are designated by number. Process streams common to the views and embodiments shown are designated by encircled letters. These letters refer to those same process streams and points in the process common among the views and embodiments illustrated in the Figures. “A” designates feedstock, “AA” is the gas phase product from thermal treatment of the feedstock, “AB” is the char product from the feedstock, “AR” is the syngas recycled from the Fischer-Tropsch reactor, “F” is the hot flue gas from the LoNOx burner. “FF” is the cooler flue gas prior to entry into the air pollution control unit (APCU). “St” designates steam from the heat recovery steam generator, “O2” and “H2” designate oxygen and hydrogen from an electrolyzer, respectively. “O2” may designate oxygen from a pressure swing absorption system and “H2” may designate geologic hydrogen.
Referring now to
Boiler feed make-up water is produced in the water treatment plant 102. Water leaving the plant has been treated to boiler feed water specifications for total dissolved solids content and pH meets specification for electrolytic dissociation in the electrolytic hydrogen and oxygen generator 105. The electrolytic generator 105 provides hydrogen and oxygen gas streams for use in the conversion process as described below. Electrical energy for the electrolytic generator 105 may be from a solar panel or other sustainable energy source such as wind. Steam produced by the RFNBO fuel fired HRSG may also be used to generate renewable electrical power 103 or for process control or production of activated carbon for biochar residue.
Alternatively, hydrogen required to provide sufficient conversion of all carbon dioxide generated in either the thermal or catalytic synthesis portion of the conversion process may come from geologic hydrogen. Oxygen from the electrolytic generator 105 is used as the oxidant for the gasifier in the multistage syngas generator 104. Syngas comprised of mainly carbon monoxide and hydrogen from the multistage syngas generator 104 is combined with hydrogen from the electrolytic generator 105 as a feedstock for the Fischer Tropsch (FT) or other catalytic synthesis reactor and product separation section 107 of the invention. Syngas not used in the FT system (process stream AR) is recycled to the syngas generator in 104.
Syngas from the multistage gasifier pyrolizer 204 is reformed by a cold plasma 205. The reformed syngas is then quenched, cleaned, and compressed 207 and conveyed to the green hydrogen addition “tee” junction, after which the hydrogen to carbon monoxide molar ratio is adjusted to 2:1. Hot flue gas from the gasifier is directed to the HRSG boiler 201 where it generates steam that can be used for generation of green power, process control and for activation of biochar to make activated carbon 202. Organic volatiles from the activated carbon generation are cooled and cleaned 206 and added to the fuel gas stream for the low NOx fuel gas burner. Activated carbon made by high treatment of biochar with steam from the HRSG boiler 201 is cooled and packaged for storage and sale 203.
This oxygen can also be injected into the kiln as means of heating. The combined “St” and “O2” designations indicate that the steam and oxygen can be mixed in various proportions prior to injection into the kiln bed. The positions for gas mixing and injection indicated in the drawing are illustrative only and do not indicate the actual number type of positions of gas injection into the stationary kiln body. Alternatively, hydrogen can be used as a means of achieving proper energy balance through exothermic hydrogenation reactions, especially in the case of feedstocks with high oxygen to carbon ratios such as biomass.
Turning now to the mechanical elements of the multistage pyrolizer gasifier multi-heat source augured kiln, 301 is the outer casing of the kiln unit. The kiln case is preferably lined with insulation to retain heat within the volume of the case. The case is preferably hinged at a level just above the auger axle 302 and can be opened to allow access to the kiln body 303. This hinged lid also allows access to electrical heating wiring 306 and mechanical elements (not shown) for rotation of the auger 302. The auger blades or flights 305 move the feedstock material along the kiln from left to right in the illustration.
The pitch of the auger flights 305 may be altered such that the process material moves forward at different rates along the length of the auger. A heating control unit 304 controls current in the heating coils 306. The heating can be programmed to provide a temperature gradient along the length of the kiln body. The principal reactions, drying and devolatilization and steam cracking and gasification, and the areas that they take place along the length of the kiln, are designated by the labels along the top of the kiln casing in
The embodiment shown in
The feed bin (not shown) and biomass feed auger 601 are designed to minimize the amount of air that is introduced into the kiln with the biomass or other carbonaceous material feed. Feedstock is charged into the kiln preferably by an auger screw 601. An auger 603 also discharges the char material and syngas at the opposite end of the rotary kiln.
Char and syngas exiting the rotary kiln are separated in the gas/char separator 604 with the syngas and light hydrocarbons directed to process stream AA (See
As in the co-current embodiment, the rotary kiln can be heated by introduction of hot flue gas 705, process stream F into the rotary kiln case 702 which is lined with insulation to retain heat. As in
The embodiment shown in
The syngas and hydrocarbon product are extracted from the rotary kiln through an annular passage with the biomass feed auger 801 by means of an induction fan 811 as in
Specific embodiments of the invention will now be further described by the following, nonlimiting examples which will serve to illustrate various features. The examples are intended merely to facilitate an understanding of ways in which the invention may be practiced and to further enable those of skill in the art to practice the invention. Accordingly, the examples should not be construed as limiting the scope of the invention. In addition, reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
One skilled in the art will appreciate that the present invention can be practiced by other than the above-described embodiments, which are presented in this description for purposes of illustration and not of limitation. The specification and drawings are not intended to limit the exclusionary scope of this patent document. It is noted that various equivalents for the particular embodiments discussed in this description may practice the invention as well. That is, while the present invention has been described in conjunction with specific embodiments, it is evident that any alternatives, modifications, permutations, and variations will become apparent to those of ordinary skill in the art in light of the foregoing description. Accordingly, it is intended that the present invention embrace all such alternatives, modifications and variations as fall within the scope of the appended claims. The fact that a product, process. or method exhibits differences from one or more of the above-described exemplary embodiments does not mean that the product or process is outside the scope (literal scope and/or other legally recognized scope) of the following claims.
This application claims the benefit of U.S. Provisional Application No. 63/488,876 filed on Mar. 7, 2023.
Number | Date | Country | |
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63488876 | Mar 2023 | US |