MULTI-STEP PROCESS FOR CONVERSION OF CARBONACEOUS FEEDSTOCKS TO RENEWABLE LIQUID FUELS AND COMMODITY PRODUCTS

Abstract

A system and method of thermally processing carbonaceous materials, and especially sustainably cultivated woody biomass or cellulosic biomass sorted from municipal solid waste, to produce green fuel, such as diesel, sustainable aviation fuel and other beneficial by-products, including biochar. Synthesis gas is made by gasifying sustainably grown biomass, the thermal energy from which is used to create steam for treatment of biochar by-product to produce higher value activated carbon. Oxygen for the gasifier and hydrogen for a Fischer Tropsch (FT) or other catalytic synthesis stage of the process are generated by electrolysis of water using sustainably produced electricity. The gasification and electrolysis processes are operated to produce a 2:1 ratio of hydrogen to carbon monoxide needed for FT or other catalytic synthesis. The hydrocarbon product is distilled as required to produce either green alcohols or green diesel fuel and sustainable aviation fuel.

Claims

1. A method of thermally converting biomass to liquid fuels comprising the steps of: a. providing sustainable biomass comprising biomass, plastic, RFNBO qualified feedstock, or combinations thereof, for thermal conversion to synthesis gas; b. providing hydrogen; c. thermally converting the biomass to form synthesis gas; d. reforming the synthesis gas; e. cooling and cleaning the synthesis gas; f. combusting a portion of the reformed, cooled, and cleaned synthesis gas; g. recovering heat of the synthesis gas by transferring it into a synthesis gas generator; h. compressing the synthesis gas to a predetermined pressure and temperature prior to introducing the synthesis gas into a catalytic conversion process unit; i. blending the hydrogen with the synthesis gas to a 2:1 molar ratio of hydrogen to carbon monoxide; j. feeding the blended hydrogen and synthesis gas to the catalytic conversion process unit; and k. converting the synthesis gas to liquid fuel via a Fisher-Tropsch process.

2. The method of claim 1, further comprising the step of generating process steam using excess energy from the synthesis gas generated after the heat recovery step.

3. The method of claim 1, further comprising the step of cleaning the synthesis gas prior to exhausting it to the atmosphere.

4. The method of claim 1, further comprising the step of cooling and storing a solid product generated by gasification and/or pyrolytic generation of the synthesis gas.

5. The method of claim 1, wherein the hydrogen is provided electrolytically by an electrolyzer.

6. The method of claim 5, wherein the blending step is accomplished by controlling the parameters of a gasifier and the electrolyzer.

7. The method of claim 1 further comprising the step of reducing the particle size of the biomass by mechanical shredding, extrusion, washing, grinding, or combinations thereof.

8. The method of claim 1, wherein the hydrogen is provided from a natural source thereof.

9. The method of claim 1, wherein the biomass is a monofuel.

10. The method of claim 1, wherein the biomass comprises feedstock combined with plastic or other RFNBO qualified materials.

11. The method of claim 1, wherein the biomass is recovered from municipal solid waste.

12. The method of claim 1, wherein the synthesis gas is produced in an augured kiln.

13. The method of claim 1, wherein the synthesis gas is produced in a co-current rotary kiln.

14. The method of claim 1, wherein the synthesis gas is produced in a countercurrent rotary kiln.

15. The method of claim 1, wherein the synthesis gas is produced in a fluidized bed gasifier.

16. The method of claim 1, wherein the synthesis gas is produced in an entrained bed gasifier.

17. The method of claim 1, wherein the synthesis gas is reformed using steam plasma.

18. The method of claim 1, wherein the synthesis gas is reformed using cold plasma catalysis.

19. The method of claim 1, wherein the synthesis gas is reformed using hydrogen plasma.

20. The method of claim 1, wherein in step (b), oxygen is provided in addition to hydrogen.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0014] FIG. 1 illustrates the six process units or components of the present invention and their relationship to each other.

[0015] FIG. 2 illustrates the subsystem components of the multistage syngas generator and HRSG boiler and biochar generating section of the invention.

[0016] FIG. 3 illustrates the multistage pyrolizer gasifier multi-heat source augured kiln.

[0017] FIG. 4 depicts an alternative embodiment of the invention in which pyrolysis and gasification takes place in a fluidized bed.

[0018] FIG. 5 depicts an alternative embodiment of the invention in which pyrolysis and gasification takes place in an entrained bed gasifier and in which the synthesis gas and hydrocarbon gas emerging from the bed are reformed to a synthesis gas by use of a steam plasma.

[0019] FIG. 6 shows an embodiment of the present invention based on an externally heated rotary kiln operating in the co-current mode.

[0020] FIG. 7 shows an embodiment of the present invention based on an externally heated rotary kiln operating in the counter current mode.

[0021] FIG. 8 shows an embodiment based on a rotary kiln heated by fuel gas burners.

[0022] 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.

DETAILED DESCRIPTION OF THE INVENTION

[0023] 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.

[0024] 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, O.sub.2 and H.sub.2 designate oxygen and hydrogen from an electrolyzer, respectively. O.sub.2 may designate oxygen from a pressure swing absorption system and H.sub.2 may designate geologic hydrogen.

[0025] Referring now to FIG. 1, carbonaceous feedstock, preferably biomass feedstock, such as sustainably produced biomass feedstock, is transferred to the augured kiln pyrolizer gasifier component of the multi-stage syngas generator and heat recovery steam generator (HRSG) boiler section 104. Further detail of syngas generator 104 is shown in FIGS. 2 through 8. Flue gas leaving the HRSG component of syngas generator 104 is conveyed to an APCU 101, that removes particulate and other criteria pollutants prior to release of the flue gas to the atmosphere. A portion of the flue gas exiting the APCU is recycled to the LoNOx burner 106 where it is mixed with combustion air. The recycle flue gas and air is mixed with the fuel gas and injected into the burner in a manner to minimize peak flame temperature and thermal NOx formation from a combination of reduced oxygen partial pressure and the average flame temperature in the burner.

[0026] 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.

[0027] 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.

[0028] FIG. 2 shows details of multistage syngas generator 104 including the HRSG boiler and biochar treatment section shown in FIG. 1. Section 204 includes a multi-stage augured kiln that serves as a gasifier and pyrolizer. Other embodiments wherein the kiln is a rotary kiln and wherein fluid bed and entrained bed gasifiers are used, are illustrated in FIGS. 4 through 8. In FIG. 2, the augured kiln can be externally heated by fuel gas or electricity or both. Heat energy may also be provided auto-thermally by pyrolysis or gasification via hydrogenation through use of hydrogen. Sustainably produced oxygen may be provided to the augured kiln from the electrolysis of water as shown in FIG. 1. Using oxygen as the oxidant for the gasification process increases the yield of syngas and minimizes nitrogen content. Sustainably produced oxygen may also be provided by a pressure swing absorption apparatus powered by renewable electrical energy.

[0029] 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.

[0030] FIG. 3 shows additional detail of the multistage pyrolizer gasifier multi-heat source augured kiln, element 204 in FIG. 2. The letter designations for the process streams shown in FIG. 3 are as follows: A is biomass, plastic, or another carbonaceous feedstock. AA is raw synthesis gas resulting from pyrolysis and gasification of the feedstock. F is hot flue gas used to heat the augured kiln from outside the main kiln body within the case 301 and from inside the hollow axle of the auger 302. FF is the exhaust of the flue gas that is sent to the air pollution clean-up system as shown in FIG. 1 and FIG. 2. AB is biochar comprised of the solid-state material exiting the end of the kiln. E designates points in the electrical circuit that provides controlled electrical current to the heating coils affixed to the outer body of the augured kiln. St designates steam that can be injected into the process material bed at a multiplicity of points along the stationary body of the augured kiln, O.sub.2 designates oxygen from the electrolytic generator 105 in FIG. 1.

[0031] This oxygen can also be injected into the kiln as means of heating. The combined St and O.sub.2 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.

[0032] 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.

[0033] 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 FIG. 3. As in FIG. 3, the letters used in FIG. 4 and FIG. 5 designate process streams that are also shown in other Figures that illustrate different components, aspects or embodiments of the invention.

[0034] FIG. 4 shows an embodiment of the present invention wherein the feedstock is introduced into a fluidized bed gasifier. The synthesis gas and light hydrocarbon gas emerging from the fluid bed gasifier 401 are directed to a steam, or a hydrogen, plasma reformer 402. Steam is then injected to reform the light hydrocarbon gas components into synthesis gas. As depicted in FIG. 1, the reformer product synthesis gas is used as a feedstock for the Fischer Tropsch synthesis reactor 107.

[0035] FIG. 5 shows an embodiment of the present invention wherein biomass feedstock is introduced into a pyrolysis chamber 502 connected to an entrained bed gasifier 501 by means of a standpipe. Steam and oxygen injected into the entrained bed gasifier to serve to gasify the char in the entrained bed, that is transported into the pyrolysis chamber while producing a water gas. Recycle syngas (AR) is introduced to the pyrolysis unit. The circulation rate of heat and solids between the zones is controlled by a slide valve in the standpipe which regulates the height that the gasifier solids bed rises into the conical freeboard and the associated entrainment rate from the top of the bed. The resulting syngas and light hydrocarbon gas is sent to a steam or geologic hydrogen plasma reformer 503 the syngas is fined before use in a Fischer-Tropsch synthesis reactor.

[0036] The embodiment shown in FIG. 6 is based on an indirectly heated rotary kiln operating in the co-current mode in which the gas flow and solid material flow are in the same direction. Specifically, steam and or hydrogen is injected axially with the feedstock charging auger in one end of the kiln body. Solid phase char and gas phase products exit the kiln at the opposite end. The drive mechanism for rotation of the kiln is not shown in FIG. 6. The kiln is mounted in a housing 608 that is lined with high temperature insulation to retain heat. Heating is provided by circulating hot flue gas 605 around the rotating body of the kiln or by electrical heating elements 606 or by both. Flue gas introduced into the case for heating the kiln body is extracted from the case 611, process stream FF and conveyed to the air pollution cleanup unit, which includes carbon dioxide capture, as shown in FIG. 1. A controller 602 for the electrical heating elements allows control of the temperature along the length of the kiln body. Angled metal flights 607 affixed to the interior of the kiln body 609 are oriented to as to move the feedstock material from the charge end 601 of the rotary kiln to the discharge end 603 of the kiln body as it rotates.

[0037] 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.

[0038] 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 FIG. 1 and FIG. 2). Char exiting element 604 is directed to the char process stream as shown in FIG. 1 and FIG. 2. Steam and or geologic hydrogen can be injected into the kiln axially through a passage 610 annular to the biomass feed auger 601.

[0039] FIG. 7 shows a counter-current rotary kiln embodiment of invention wherein the gas phase hydrocarbon and syngas products are extracted from the same end of the rotary kiln from which the biomass or carbonaceous feed is charged into the rotary kiln body. As in the co-current embodiment shown in FIG. 6, biomass is charged into the rotary kiln by an auger screw 701 and extracted at the opposite end by an auger 708. In the countercurrent embodiment, steam and or hydrogen is injected into the kiln body 703 through a passage 706 annular to the extraction auger 708 at the extraction end of the kiln. Syngas and light hydrocarbon gas phase products are extracted using an induction fan 712 from the biomass feed end of the kiln through a passage 711 annular to the biomass feed auger 701 tube. Any gas phase products leaving the rotary kiln via the char discharge auger 708 are separated from the char in the gas/char separator 707 with the gas phase product being directed to the AA process stream of the invention as shown in FIG. 1 and FIG. 2.

[0040] 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 FIG. 6, flue gas circulated to heat the rotary kiln body is extracted from the case and sent to the air pollution clean-up unit (process stream FF as shown in FIG. 1) The rotary kiln body 703 can also be heated with electrical heating coils 704 controlled by the heating control unit 710. As with the co-current embodiment flights 709 are affixed to the interior of the rotary kiln body 703 so as to convey the solid feedstock material from the charge end to the discharge end of the rotary kiln as it rotates.

[0041] The embodiment shown in FIG. 8 is based on a rotary kiln operating in counter current mode as shown FIG. 7. In this embodiment, kiln heating is provided by electrical coils 805 and a controller 809 and a multiplicity of fuel gas burners 804 mounted inside the case 802. A gas distribution line 806 mounted outside the case 802 provides fuel gas to each burner. The burners 804 are mounted on the floor of the case in an array such that the flame for any given burner does not impinge directly on any other burner. Elements in common with the countercurrent embodiment in FIG. 7 are as follows: 801 is the feed auger, 802 is the rotary kiln case, 803 is the rotary kiln body, 805 are electrical heating coils, 807 is the char extraction auger, 808 is the char gas separator, 809, is the heating control unit and 810 is the burner exhaust extraction port for process stream FF.

[0042] 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 FIG. 7. As in the embodiment in FIG. 7, steam and or geologic hydrogen may be injected into the kiln (803) through a passage annular to the char extraction auger 807.

[0043] 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.

[0044] 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.