PRODUCTION OF SYNTHESIS GAS FROM GASIFYING AND REFORMING CARBONACEOUS MATERIAL

Abstract

It is provided a method of converting a carbonaceous material into syngas at a carbon conversion rate of at least 78% comprising gasifying the carbonaceous material in a fluidized bed reactor producing a crude syngas, classifying the crude syngas by particle size and density into a cut sizing device, introducing the classified particle crude syngas into a thermal reformer and reforming the classified crude syngas at a temperature above mineral melting point, producing the syngas.

Claims

1. A method of converting a carbonaceous material into synthesis gas comprising: a) gasifying the carbonaceous material in a fluidized bed, producing a crude syngas; b) classifying the crude syngas by particle aerodynamic velocity into a cut sizing device producing classified crude syngas comprising classified particles with a range of particle diameter and density; c) introducing said classified particle crude syngas into a thermal reformer; and d) reforming said classified crude syngas at a temperature above mineral melting point, producing the synthesis gas.

2. The method of claim 1, wherein the cut sizing device is a freeboard enlargement, a cyclone, a perforated shroud, a helical strakes, a longitudinal slats, a filter, a cascade impactor, an aerodynamic classifier or any combination thereof.

3. The method of claim 1, wherein the carbonaceous material is fed to the fluidized bed reactor by a feeding system.

4. (canceled)

5. The method of claim 1, wherein a fluidizing agent is used to heat up the fluidized bed reactor and feed oxygen to gasification of the carbonaceous material.

6. The method of claim 5, wherein the fluidizing agent is air, oxygen, carbon dioxide, nitrogen, steam or any combination thereof.

7. The method of claim 1, wherein the carbonaceous material is gasified at a temperature of about 450° C. to about 800° C.; or about 500° C. to about 700° C.

8. (canceled)

9. The method of claim 1, wherein the classified particle crude syngas is reformed in a thermal reformer.

10. The method of claim 1, wherein the reforming operating temperature is of about 1200° C. to about 2000° C.

11. The method of claim 10, wherein air, oxygen, carbon dioxide, nitrogen, steam or any combination in any proportion thereof is fed to the reformer to increase the temperature of said reformer.

12. The method of claim 1, wherein the classified crude syngas is reformed at a temperature of about 1200° C. to about 1800° C.

13. The method of claim 1, wherein the reformer comprises a cooling wall membrane.

14. The method of claim 13, wherein the cooling wall membrane is made of studded pipes.

15. The method of claim 1, wherein the carbonaceous material is converted into syngas with at least 78% of carbon conversion rate; at least 90% of carbon conversion rate; or at least 96% of carbon conversion rate.

16-17. (canceled)

18. The method of claim 1, wherein the carbonaceous material is a liquid, a solid and/or a gas containing carbon.

19. The method of claim 1, wherein the carbonaceous material is a biomass.

20. The method of claim 19, wherein the biomass is an homogeneous biomass, a non-homogenous biomass, a non-homogeneous biomass, a heterogeneous biomass, urban biomass, or a combination thereof.

21. The method of claim 20, wherein the homogenous biomass is from a coniferous tree, a deciduous tree, an agricultural material, a primary sludge, waste cooking oil, lychee fruit bark or stillage; or wherein the non-homogenous biomass is from mixed forest residues, or mixed tree residues.

22. (canceled)

23. The method of any one of claim 1, wherein the carbonaceous material comprises a plastic, a metal, an inorganic salt, an organic compound, industrial wastes, recycling facilities rejects, automobile fluff, municipal solid waste, ICI waste, C&D waste, refuse derived fuel (RDF), solid recovered fuel, sewage sludge, used wood utility poles, wood railroad ties, wood, tire, synthetic textile, carpet, synthetic rubber, materials of fossil fuel origin, expanded polystyrene, poly-film floc, construction wood material, or any combination thereof.

24. The method of claim 1, further comprising the step of e) converting said synthesis gas into methanol in a methanol reactor, producing methanol.

25. The method of claim 24, further comprising the steps of: f) reacting the methanol with carbon monoxide (CO) in a carbonylation reactor to methyl acetate; and g) feeding said methyl acetate into an hydrogenolysis reactor and reacting said methyl acetate with hydrogen (H.sub.2) producing ethanol, methanol, ethyl acetate or a combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Reference will now be made to the accompanying drawings.

[0044] FIG. 1 illustrates a block diagram view of the process of producing syngas.

[0045] FIG. 2 illustrates a schematic view of the process of producing syngas in accordance to an embodiment.

[0046] FIG. 3 is an illustration of the studs on the surface of the cooling wall membrane of the reformer as described herein.

[0047] FIG. 4 present terminal velocity iso-curve of particles having different diameter and density.

[0048] FIG. 5 present, for a specific set of operating condition, residence time iso-curve needed to fully convert to syngas a char particle of different diameter and density.

[0049] FIG. 6 presents a superposition of FIG. 5 at different operation temperatures and residence times of 0.5, 2 and 5 sec over the FIG. 6.

[0050] FIG. 7 illustrates a histogram showing the increased conversion to syngas performance from reforming at 1050° C. versus 1300° C.

DETAILED DESCRIPTION

[0051] It is provided a method for preparing, treating and converting carbonaceous materials into suitable syngas with high carbon to syngas conversion rate. In order to achieve this objective, the method comprises gasifying carbonaceous materials to form crude syngas in a fluidized bed gasifier at a temperature low enough to avoid agglomeration problems. Crude syngas is the syngas created while gasifying at low temperature. It comprises syngas with the addition of char, bed material, mineral matter particle, tar and many gaseous, liquid and solid petroleum type products. Afterwards, the crude syngas is conveyed from the fluidized bed zone to a cut sizing device by fluidization entrainment.

[0052] As illustrated in FIG. 1, the carbonaceous material 10 is introduced in the fluidized bed gasifier 16 with the help of the feeding system 15. The gasifier 12 converts the carbonaceous material 10 into crude syngas using fluidizing agent 11. The crude syngas, which includes a broad range of particle diameter/density, is introduced into a cut sizing device 14 that sorts particles to suit the design of the crude syngas thermal reformer 20. The classified crude syngas and oxidizing agent 21 are introduced into the crude syngas thermal reformer 20 at high temperature to reform the crude syngas into a reformed syngas mainly composed of H.sub.2, CO, CO.sub.2, H.sub.2O and other compounds in small concentration. The reformed syngas undergoes a stage of water and/or chemical and/or physical scrubbing 24 to remove contaminants to produce a clean syngas for further use as fuel, power generation, alcohol synthesis (MeOH, DME, EtOH and others), hydrocarbon synthesis and others uses.

[0053] Also encompassed is the formation of other products from syngas as described herein, such as for example, Fischer-Tropsch fuel, Fischer-Tropsch to Olefins (FTO) synthesis.

[0054] In the embodiment, the carbonaceous material 10 is fed through a system consisting of three steps; pressurization 5, flow control 6 and feeding 7 to the gasifier 12. Each step can be performed from different equipment. As an example, typical types of equipment used are a lock-hopper, a conveyor and/or a screw.

[0055] The fluidized bed 16 comprises an appropriate fluidized bed material, such as for example, but not limited to, alumina, limestone, dolomite, sand, olivine, anthracite, desulfurized petroleum coke and any combination in any proportion thereof.

[0056] A fluidizing agent 11, composed of air, oxygen, carbon dioxide, nitrogen, steam or any combination in any proportion thereof is conveyed into the gasifier 12. Air is usually used for the start-up, to heat up the gasifier, and oxygen-steam are usually used during normal operation thereby minimizing the nitrogen content and syngas dilution effect for downstream catalytic conversion. The fluidizing agent can be preheated, such as for example to a temperature at or below bed temperature to minimize steam condensation and also to promote higher syngas yield in the gasifier 12. The final oxidant concentration is adjusted on temperature control to maintain the gasifier fluid bed temperature (e.g. between 450° C. and 800° C.).

[0057] In an embodiment, the fluidized bed gasifier 12 is operated at about 650° C. and from 0.1 to 70 barg. In another embodiment, the gasifier 12 is operated at a temperature that does not exceed 750° C. and at a pressure that does not exceed 10 barg. In a non-limiting embodiment, the material 10 is gasified at a temperature which does not exceed 725° C. In another non-limiting embodiment, the material 10 is gasified at a temperature which does not exceed 700° C. In a non-limiting embodiment, the material 10 is gasified at a pressure which does not exceed 4 barg.

[0058] The temperature is set to avoid salt melting/agglomeration within the bed that occurs slightly above this point and to allow good thermal conversion and devolatilization of carbonaceous material into crude syngas. The overall reaction can be expressed as:

C.sub.nH.sub.m+n/2O.sub.2.fwdarw.nCO+m/2H.sub.2

[0059] Accordingly, this reaction represents the global exothermic reaction to produce CO and H.sub.2. Oxidation reactions are required to supply the heat for compensating endothermic reaction/transformation such as water evaporation and others. This means that some CO.sub.2 and H.sub.2O are also generated by oxidation reactions. Other minor reactions occur with other elements present in the material 10, such as chlorine that generates HCl and sulfur that produces H.sub.2S and COS. HCN, N.sub.2 and NH.sub.3 are also formed when nitrogen is present in the material 10.

[0060] The fluidized bed gasifier 12 as described herein and illustrated in FIG. 2 comprises a cut sizing device 14. The cut sizing device 14 consists of a freeboard zone of the gasifier 12. In an embodiment, the design of the freeboard zone shape is adjusted in such a manner that particles entrained from the bed zone 16 are classified by density, particle size and shape. The freeboard, driven by its enlarged diameter, will act as an aerodynamic particle cut sizing device. As encompassed herein, the cut sizing device can be a freeboard enlargement, a cyclone, a perforated shroud, a helical strakes, a longitudinal slats, a filter, a cascade impactor, an aerodynamic classifier or any combination thereof.

[0061] Big particles with low density having an aerodynamic terminal velocity smaller than the actual velocity of the cut sizing device will be entrained. Small particles with very high density having aerodynamic terminal velocity larger than the actual cut sizing device actual velocity will not be entrained and will drop back into the fluidized bed 16 for further gasification. For a specific particle shape, FIG. 4 presents the iso-curves of aerodynamic terminal velocity for different values of diameter and density, illustrating the separation effect of any aerodynamic cut sizing device. Separation is not based only on particle size or mass, it is a combination of the particle size, mass and shape. A bigger porous particle with low density may be entrained as a highly dense small particle could fall back in the fluidizing bed. This aerodynamic cut sizing device is adjusted to match the desired cut size/density/shape needed to maximize the carbon conversion efficiency of the subsequent steps.

[0062] For specific operating parameters and particle types, FIG. 5 presents time iso-curves needed to fully convert carbon containing particle to syngas within a crude syngas thermal reformer. In this graphic, for any iso-curve, any particle that would be located left and/or below the curve would be fully converted. As illustrated, the conversion time needed is not only proportional on particle diameter or density, but on a combination of diameter and density. This shows the need to condition the particle entrained with the crude syngas to achieve a cut classified crude syngas that increases the carbon conversion rate.

[0063] For specific operating parameters and particle types, FIG. 6 presents a concatenation of FIG. 5 over FIG. 4. The wide grey stripe represents crude syngas thermal reformer conversion time of 0.5, 2 and 5 seconds (s) for a range of high temperature operating setpoint and for different particle diameter and density. The iso-curve represents the aerodynamic terminal velocity for different diameter and density. As illustrated, both conversion curve in seconds and aerodynamic terminal velocity in m/s closely match for any given diameter and density. As an example, a design of reformer having a residence time of 0.5 seconds would have a higher conversion to reformed syngas when an aerodynamic cut sizing device is added to retain in the fluidizing bed particles with an aerodynamic terminal velocity higher than 0.5 m/s. This allows a particle with 0.4 mm in diameter and 500 kg/m.sup.3 to be fully converted as well as a particle of 0.2 mm in diameter and 1500 kg/m.sup.3. A particle of 0.4 mm in diameter and 1500 kg/m.sup.3 falls back in the bed, preventing a too large/dense particle from entering the crude syngas thermal reformer and thus not being fully converted.

[0064] The classified crude syngas is then introduced into a syngas thermal reformer 20. The syngas thermal reformer 20 is designed to operate at high temperature above the inert and salt softening point, to handle melted mineral and to discharge this melted mineral into a cooling zone for its extraction.

[0065] The classified crude syngas then flows to the syngas thermal reformer 20 where pure oxygen 21 is fed in the upper part of the reformer 20, thereby increasing the temperature above mineral melting point, usually >1200° C., and enhancing thermal conversion of the heavy tars, char, aromatics and methane and alike into additional CO and H.sub.2. In an embodiment, air, oxygen, carbon dioxide, nitrogen, steam or any combination in any proportion thereof is fed to the reformer to increase the temperature of the reformer.

[0066] The entrained solids melt at the reformer's 20 operating temperatures and they are entrained as fine droplets in the syngas and accumulated on the wall by creating a film of molten materials slowly flowing on an external layer of solidified materials. As illustrated in FIG. 3, in an embodiment, the reformer 20 described herein comprises a cooling wall membrane made of studded cooling pipes 22. At this stage, both the hot syngas mixture and the molten solids are corrosive, and the mentioned formation of a solid layer on the wall of the reformer acts as a protective barrier. In an embodiment, the layer is maintained by means of circulating high-pressure boiler water in the cooling wall membrane 22, thus providing sufficient cooling to the first layer to keep it in the solid form.

[0067] At this point, the total carbon conversion to syngas reaches 90 to >99% conversion. The final syngas composition could vary depending on the operating temperature and feedstock/material 10 composition. It is thus provided a means to substantially increase the rate of conversion of the total carbon into syngas as illustrated in FIG. 7, wherein the rates of desired species CO, CO.sub.2 and H.sub.2 are substantially increased following the process described herein compared to the flow rate obtained of such species when the reforming is conducted for example at 1050° C. In addition, undesired species such as CH.sub.4 are minimized.

[0068] The resulting syngas produced by the process described herein has low char, tar, HAP, phenol and other petroleum like by-products. The process provided has a high carbon conversion efficiency 90 to >99%, can handle coarse fluffy, fine fluffy or course to finely ground materials. Additionally, said process can handle molten minerals, optimizes the size/density of the feedstock preparation for the high temperature gasification zone and minimizes particle size/density range to optimize conversion and molten mineral flowability.

[0069] The carbonaceous materials encompassed herein can be biomass-rich materials which may be gasified in accordance with an embodiment, and include, but are not limited to, homogeneous biomass-rich materials, non-homogeneous biomass-rich materials, heterogeneous biomass-rich materials, and urban biomass. The carbonaceous material can also be plastic rich residues or any waste/product/gas/liquid/solid that include carbon. It may also be any type of coal and derivative such as pet coke, petroleum product & by-product, waste oil, oily fuel, hydrocarbon and tar.

[0070] Homogeneous biomass-rich materials are biomass-rich materials which come from a single source. Such materials include, but are not limited to, materials from coniferous trees or deciduous trees of a single species, agricultural materials from a plant of a single species, such as hay, corn, or wheat, or for example, primary sludge from wood pulp, and wood chips. It may also be materials from refined single source like waste cooking oil, lychee fruit bark or stillage from corn to methanol by-product.

[0071] Non-homogeneous biomass-rich materials in general are materials which are obtained from plants of more than one species. Such materials include, but are not limited to, forest residues from mixed species, and tree residues from mixed species obtained from debarking operations or sawmill operations.

[0072] Heterogeneous biomass-rich materials in general are materials that include biomass and non-biomass materials such as plastics, metals, and/or contaminants such as sulfur, halogens, or non-biomass nitrogen contained in compounds such as inorganic salts or organic compounds. Examples of such heterogeneous biomass-rich materials include, but are not limited to, industrial wastes, recycling facilities rejects, automobile fluff and waste, urban biomass such as municipal solid waste, such as refuse derived fuel (RDF), solid recovered fuel, sewage sludge, tire, synthetic textile, carpet, synthetic rubber, expended polystyrene, poly-film floc, etc. of fossil or vegetal origin, used wood utility poles and wood railroad ties, which may be treated with creosote, pentachlorophenol, or copper chromium arsenate, and wood from construction and demolition operations which may contain one of the above chemicals as well as paints and resins.

[0073] In an embodiment, carbonaceous materials can be fed as low density fluff RDF by a feeding system, lowering the costs of the pre-treatment of the feedstock by only partially pre-treating the RDF fluff. In another embodiment, carbonaceous materials can be a mixture of low density fluff having a particle size ranging from a few millimeters to many centimeters. In a non-limiting embodiment, carbonaceous materials can be in high density pelletized form with or without low density fluff. In another non-limiting embodiment, carbonaceous materials can be a solid, liquid, gas or any composition in any proportion thereof that contain the carbon atom.

[0074] In an embodiment, as encompassed herein, the reforming operating temperature is of about 1200° C. to about 2000° C. Accordingly, the thermal reforming temperature is above mineral melting point, such as for example of about 1200-1800° C., which increases syngas and ultimately alcohol yield. At 1300-1500° C., the thermal reforming as described herein provides virtual complete conversion of carbonaceous species to CO, H.sub.2, CO.sub.2 and H.sub.2O, wherein the final syngas composition is driven by a Water Gas Shift (WGS) equilibrium.

[0075] While using a fluidized gasifier and cut sizing device as described and encompassed herein, the thermal reforming, as described herein at temperature above 1200° C. allows syngas conversion and yield to increase, with virtual complete conversion of methane, tar and aromatic tars (NBTX; naphthalene, benzene, toluene and xylene), wherein residual char/unconverted carbon is reduced.

[0076] Compared to a gasification as described in U.S. Pat. No. 8,137,655, wherein reforming is performed to at most 1200° C., mainly at about 1000° C., the process described herein allows decreasing substantially the amount of residual char as reported in FIG. 7.

[0077] The process described herein allows achievement of a high carbon to syngas conversion rate of at least 78% to 96%.

[0078] The syngas at the outlet of the thermal reformer 20 contains H.sub.2, CO, CO.sub.2 and H.sub.2O. After additional processing as described below, the resulting clean syngas produced by the process described herein can then be subjected to further processing and conversion into other useful products such as a chemical. Particularly, it is encompassed that the process described herein produces for example fuel, preferably liquid fuel as well as a number of renewable chemicals. Examples of chemicals encompassed herein include methanol (MeOH), ethanol (EtOH), methyl acetate (MeOAc) and ethyl acetate (EtOAc), as described for example in WO 2013/188949 and WO 2013/091067, the content of which are incorporated herein by reference.

[0079] Typically the cleaning stages 24 of the reformed syngas process to produce clean syngas consists of sulfur removal, ammonia removal, chlorine removal, particle removal, carbon dioxide removal and other low trace catalyst poison removal steps. Typical process steps encompassed herein are for example wet water scrubbers, acid gas scrubbers and solid phase guard beds.

[0080] Acid gases produced at the end of the process described hereinabove mainly consist of carbon dioxide and hydrogen sulfide (H.sub.2S). The syngas needs to be cleaned of those acid gases to protect the downstream catalysts from sulfur poisoning and to meet the optimal CO.sub.2 purity for reuse in the process. The acid gas removal can be achieved using an acid gas removal (AGR) loop consisting of a countercurrent absorption using a regenerative methanol solvent in an absorption column. Alternatively, other systems can by used for acid gas removal, such as amine scrubbers, Selexol process, Purisol process, propylene carbonate solvent, etc.

[0081] As described herein, the AGR allows the removal of H.sub.2S and CO.sub.2 from the syngas, in addition to other traces of sulfurous and nitrogenous compounds, i.e. carbonyl sulfide, carbon disulfide, etc. At the outlet of the absorption column, syngas is composed mainly of CO, H.sub.2, with some of CO.sub.2, and traces of sulfur compounds and it is sent to a syngas guard bed to remove the remaining sulfur compounds, as well as carbonyls and arsine, which are poisonous to synthesis catalysts and can reduce their active life significantly.

[0082] As described hereinabove, the process described herein can be subjected to further processing and encompassed is the conversion of syngas into chemicals. In an embodiment, the clean syngas may be reacted in the presence of a catalyst to produce methanol.

[0083] The clean syngas is then fed into a methanol reactor. Typically, a methanol reactor comprises a catalyst, such as for example a copper oxide (CuO) catalyst and/or a zinc oxide (ZnO) catalyst, where hydrogen, carbon monoxide and carbon dioxide combine at the surface of the catalyst and are transformed into methanol, as per the following main reactions:

CO+2H.sub.2.Math.CH.sub.3OH

CO.sub.2+H.sub.2.Math.CO±H.sub.2O

CO.sub.2+3H.sub.2.Math.CH.sub.3OH+H.sub.2O

[0084] Typically, the syngas enters the methanol reactor at 200° C. to 230° C. In an embodiment, the hydrogen, carbon monoxide and carbon dioxide are reacted at a temperature from about 100° C. to about 300° C. Hydrogen and carbon monoxide from the syngas are reacted at a pressure from about 250 to about 2 000 psi.

[0085] As an example, in ethanol production processes, the methanol produced from the methanol reactor can be further reacted with carbon monoxide in a carbonylation reactor to produce methyl acetate as per the following reaction:

CH.sub.3OH+CO.Math.CH.sub.3OOH (carbonylation reaction)

CH.sub.3OOH+CH.sub.3OH.Math.CH.sub.3COOCH.sub.3+H.sub.2O (esterification reaction)

[0086] Depending on the carbonylation reactor integration, excess acetic acid (CH.sub.3COOH) can be esterified in a separate reaction zone.

[0087] The methyl acetate produced is then fed into an hydrogenolysis reactor wherein the methyl acetate and hydrogen react to form ethanol and methanol as per the following reaction:

CH.sub.3COOCH.sub.3+2H.sub.2.Math.CH.sub.3CH.sub.2OH+CH.sub.3OH

[0088] Particularly, carbon monoxide and hydrogen for the carbonylation and hydrogenolysis reactors above are obtained from a syngas separation step to generate a CO rich stream and an H.sub.2 rich stream which can be used in their respective reactors. Such syngas separation step includes, for example known, membrane separation technology and/or cryogenic CO separation, etc.

[0089] As described herein, the generated syngas can be used for further processing into methanol and/or ethanol production. Alternatively, the generated syngas can be used for power and/or heat generation, hydrocarbon or drop-in fuel production (ex. using known Fischer-Tropsch process), higher alcohol and/or chemicals production.

[0090] While the present disclosure has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations, including such departures from the present disclosure as come within known or customary practice within the art and as may be applied to the essential features hereinbefore set forth, and as follows in the scope of the appended claims.