Method of converting a low-density carbonaceous material into synthesis gas with thermal pre-treatment

Abstract

It is provided a method of converting a low-density carbonaceous material into synthesis gas comprising shredding and sorting a low-density carbonaceous material in a feed preparation unit; drying the sorted carbonaceous materials producing a dried material; treating said dried material at a temperature above 200ºC in a thermal pre-treatment unit (TPTU) producing a TPTU gas and carbon-densified solids; milling the carbon-densified solids in a first milling apparatus, producing milled carbon-densified solids; gasifying the milled carbon-densified solids at a temperature above 1000ºC, producing a scrubbed syngas and solid residues; and removing carbon dioxide (CO2) and hydrogen sulfide (H2S) from the scrubbed syngas, producing a sweet syngas.

Description

METHOD OF CONVERTING A LOW-DENSITY CARBONACEOUS MATERIAL INTO SYNTHESIS GAS WITH THERMAL PRETREATMENTCROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application is claiming priority from U.S. Provisional Application No. 63 / 749,200 filed January 24, 2025, the content of which is hereby incorporated by reference in their entirety.TECHNICAL FIELD

[0002] It is provided a method for converting a low-density carbonaceous material into synthesis gas.BACKGROUND

[0003] Synthesis gas, also called syngas, is a fuel gas or reactive mixture comprising primarily of carbon monoxide (CO), carbon dioxide (CO2) and hydrogen (H2). When it is a desired product, it may also be comprised of methane (CH4) by changing operating temperature.

[0004] Syngas can be produced from many sources, including biomass, or virtually any carbonaceous material, by reaction with steam (steam reforming), carbon dioxide (dry reforming), air (partial oxidation), oxygen (partial oxidation) or any mixture of the reactants listed. Syngas is a crucial intermediate resource for production of hydrogen, ammonia, and methanol for example. Utilization of syngas in internal combustion engines and as a renewable energy resource is ongoing extensive investigation.

[0005] Converting carbonaceous materials and waste into synthesis gas can be achieved with gasification techniques. The gasification provides a crude syngas which can include impurities such as ammonia (NH3), hydrogen cyanide (HCN), sulfur (as hydrogen sulfide (H2S) and carbonyl sulfide (COS), chlorine (as HCI), fine ashes (in the form of particles containing metals and metal salts) and volatile metals. At a temperature below 1000 °C and even below 1200 °C, the gasification also generates low molecular weight alkanes and alkenes, aromatic tars (NBTX; naphthalene, benzene, toluene and xylene), tars (including PAH), and char (solid particulates typically above 0.001 mm and containing metals, salts and mostly carbon). Such impurities, however, limit the ability ofthe syngas to be used as a fuel or to be employed in the synthesis of other useful materials without a cleaning process.

[0006] There are many types of gasifier apparatus that already exist and are used in various processes, including plasma assisted gasification, staged gasification and / or indirect gasification processes. Other examples include fixed bed, moving bed, fluidized bed, circulating fluidized bed and entrained-flow gasifiers (EFG). The entrained flow gasifier typically works at a higher outlet temperature than the other gasifiers. It produces a syngas with less residual char and tar than any other type of gasifier and melts the feedstock mineral material into a glass-like material. One drawback of the entrained-flow gasifier is the limitation in the solid material feeding preparation. Two forms of feed are generally employed in entrained-flow gasifiers; either very fine particle injection with a conveying gas (pneumatic conveying) or mechanical device, or injection of a liquid-solid slurry made of very fine solids. When installed downstream of another type of gasifier, the entrained flow gasifier acts as a thermal reformer.

[0007] Untreated waste and many untreated biomass materials require extensive grinding and / or pre-treatment to achieve a fine and homogeneous particle feed size. In addition, most types of waste, biomass, non-coal like carbonaceous solid materials and / or very low-density materials produce a fluffy feed instead of finely divided particles. It is accepted that waste and biomass can undergo a shredding and / or grinding process that produces coarse sized particles, many orders of magnitude bigger than those required for an entrained-flow gasifier.

[0008] One way to overcome the challenges associated with the feeding of waste and / or biomass in an entrained flow gasifier is to replace a fraction of an existing feed, slurry or coal, of an existing plant. This co-feeding approach has been demonstrated on a commercial scale (i.e. Nuon Power’s IGCC) where biomass was mixed up to 30% with coal to be dry-fed in a gasifier to produce syngas. This strategy still relies heavily on fossil fuel which is undesirable for the production of biofuel.

[0009] Contrary to coal feedstocks which have a relatively narrow range of particle density / size, biomass, waste and mixtures of both have a very broad range of particle diameter and bulk density. Entrained-flow gasifiers (or thermal reformer) can operate at high temperatures and handle melted mineral only when the particle size is small, in the micron range, and when the mass, particle size distribution, and residual mineral content is uniform.

[0010] In most types of gasifier apparatus, gasification is carried out at low to moderate pressure and even high pressure thus in almost all cases, pressurization of the feed is required. Inert gas, typically N2or CO2, is also injected to assist the feeding in the gasifier. The amount of gas required for the pressurization and feeding of the feed is a function of the feed density and gasification pressure. During the gasification process, N2and / or CO2entering with the feedstock must be heated to the reforming temperature which significantly reduces the efficiency of the gasifying process.

[0011] A mechanical treatment such as pelletization can efficiently increase the drybulk density of the material, but the cost associated for this treatment can be significant. Moreover, a mechanical treatment also has little to no impact on the chemical properties and grindability of the carbonaceous material. The grindability of a material refers to the energy required to reduce the size of the material in a grinding or milling equipment.

[0012] A thermal pre-treatment can be successfully applied to biomass or plastics with existing technologies in order to produce a carbonized solid and / or oil with a higher density and / or heating value but its successful application to a mixture of biomass and plastics such as municipal solid waste (MSW) is still to be demonstrated. Moreover, many existing technologies for the thermal treatment of biomass or plastics operate in conditions where a lot of mass, including carbon and hydrogen, is lost in the waste gas and is burnt. The thermal pre-treatment’s main objective is to enable process improvements for the gasification step, which will result in higher gasification efficiency and higher syngas yield (i.e. H2and CO). In the production of biofuel (e.g. methanol or SAF), the carbon intensity (i.e. kilograms of CO2equivalent per Megajoules of product) of the overall process is critical. To improve the production cost and carbon intensity, it is very important for a biofuel project, to maximize the syngas yield (thus maximizing the amount of carbon ending up in the final product) and to minimize the utilization of fossil fuels or other energy sources that are greenhouse gas intensive. The thermal pretreatment of a low-density carbonaceous material also enables process improvements for a gasifying step comprising a bubbling bed gasifier coupled with a thermal reformer which will also result in higher syngas yield when the severity of the thermal pretreatment is low to moderate (mass loss below 40%).

[0013] In an embodiment, the end product or final product is Fischer Tropsch products, ethanol, or synthetic / substitute natural gas.

[0014] Considering the current available technologies, it is not possible to gasify low density carbonaceous materials with a carbon to syngas conversion as high or close to what is theoretically possible with an entrained flow gasifier.

[0015] There is still a need to be provided with alternative means and / or process for the gasification to improve the physical and chemical properties of low-density carbonaceous materials with a focus on the reduction of gasification inefficiencies while keeping a high conversion of carbon to syngas and especially high H2and CO yield.SUMMARY

[0016] It is provided a method of converting a low-density carbonaceous material into an optimized synthesis gas comprising shredding and sorting a low-density carbonaceous material in a feed preparation unit; drying the sorted carbonaceous materials producing a dried material; treating said dried material at a temperature above 200°C in a thermal pre-treatment unit (TPTU) producing a TPTU gas and carbon-densified solids; milling the carbon-densified solids in a first milling apparatus, producing milled carbon-densified solids or carbon-densified powder; gasifying the milled carbon-densified solids or carbon-densified powder at a temperature above 1000°C, producing a scrubbed syngas comprising H2, CO, CO2, and H2S, and solid residues; and removing carbon dioxide (CO2) and hydrogen sulfide (H2S) from the scrubbed syngas, producing the optimized synthesis gas or a sweet syngas.

[0017] In an embodiment, the drying step is conducted before the shredding and sorting step.

[0018] In another embodiment, the method further comprises feeding a biomass stream in the feed preparation unit.

[0019] In a further embodiment, the biomass stream and the low-density carbonaceous material are shredded and / or sorted together or separately in the feed preparation unit.

[0020] In another embodiment, the low-density carbonaceous material is a carbonaceous material with a dry-bulk density below 250 kg / m3.

[0021] In an embodiment, the dry-bulk density of the dried material is below 400

[0022] In a further embodiment, the method further comprises the steps of optionally removing metal and non-metal inert from the milled carbon-densified solids and; optionally grinding the milled carbon-densified solids in a second milling apparatus, producing a carbon-densified powder.

[0023] In another embodiment, the method further comprises the steps of shifting CO in a portion of the sweet syngas in a water gas shift unit and removing CO2in a CO2absorption unit producing a H2rich syngas and then mixing the H2rich syngas with the un-shifted portion of the sweet syngas, producing a balanced syngas and; converting said balanced syngas into methanol in a methanol synthesis unit, producing high purity methanol and water.

[0024] In a further embodiment, the TPTU comprises a contaminant removal unit and a burner, said contaminant removal unit removes gaseous contaminants upstream of the TPTU Burner.

[0025] In an embodiment, the gaseous contaminants are halogenic compounds and / or sulfur based compounds.

[0026] In another embodiment, the halogenic compounds are mainly HCI.

[0027] In an embodiment, the sulfur based compounds are mainly H2S.

[0028] In another embodiment, the TPTU Gas is burnt, producing heat which is recovered in an exchanger or indirectly in the TPTU reactor.

[0029] In a further embodiment, the recovered heat is used for the TPTU.

[0030] In another embodiment, the carbonaceous material is shredded to a particle size of 100 mm and less.

[0031] In an embodiment, the cooled carbon-densified solids are milled to a particle size of 10 mm and less.

[0032] In a further embodiment, the milled carbon-densified solids are grinded to a particle size of 1 mm and less.

[0033] In another embodiment, the gasifying process is a fluidized bed gasifier operating at a temperature below 1000°C, followed by a thermal reformer operating at a temperature above 1000°C, a quench, heat recovery exchangers and a water scrubber.

[0034] In another embodiment, the carbon-densified powder is fed directly in an entrained flow gasifier at a temperature above 1000°C.

[0035] In an embodiment, the CO2and H2S are removed from the syngas by absorption using a CO2selective solvent.

[0036] In an embodiment, the CO2selective solvent is methanol, ethanol, N-Methyl-2-pyrrolidone (NMP), amine, propylene carbonate, dimethyl ether of polyethylene glycol (DMPEG), methyl isopropyl ether of polyethylene glycol (MPEG), tributyl phosphate, or sulfolane.

[0037] In an embodiment, more than 50% of energy for the drying is recovered from the gasifying step.

[0038] In a further embodiment, wherein step of shifting CO in a portion of the sweet syngas in a water gas shift unit is replaced by the addition of green or blue hydrogen, producing the balanced syngas.

[0039] In a further embodiment, the balanced syngas has a molar ratio for H2, CO and CO2noted (H2-CO2) I (CO+CO2) is between 1.90 and 2.1.

[0040] In a further embodiment, the molar ratio (H2-CO2) I (CO+CO2) is between 2.0 and 2.05.

[0041] In another embodiment, the molar ratio (H2-CO2) I (CO+CO2) is equal to 2.03.

[0042] In another embodiment, the operating temperature of the TPTU is about 200°C to about 600°C.

[0043] In another embodiment, the carbonaceous material is converted into carbon-densified solids or carbon-densified powder with at least 80% of the carbon remaining in the carbon-densified solids or carbon-densified powder.

[0044] In a supplemental embodiment, the carbon-densified solids or carbon-densified powder is converted into CO and CO2in the syngas with at least 90% of carbon conversion rate.

[0045] In a supplemental embodiment, the carbon-densified solids or carbon-densified powder is converted into CO and CO2 in the syngas with at least 96% of carbon conversion rate.

[0046] In a supplemental embodiment, the carbonaceous material is a solid containing carbon.

[0047] In an embodiment, the carbonaceous material is a non-homogeneous biomass a heterogeneous biomass, urban biomass, or a combination thereof.

[0048] In an embodiment, the carbonaceous material is a homogeneous biomass from a coniferous tree, a deciduous tree, an agricultural material, a primary sludge, waste cooking oil, fruit bark, mixed forest residues, mixed tree residues or stillage.

[0049] In an embodiment, the carbonaceous material comprises plastics, 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, plastic film, construction wood material, or any combination thereof.

[0050] In a further embodiment, the end product is Fischer Tropsch products, ethanol, or synthetic / substitute natural gas.

[0051] In an embodiment, the balanced syngas has a molar ratio adjusted for the selected production.

[0052] In another embodiment, the carbonaceous material is pelletized before the dryer, or the dried material is pelletized before the TPTU or the carbon-densified solids are pelletized after the TPTU.

[0053] In an embodiment, the dried material is briquetted before the TPTU or the carbon-densified solids are briquetted after the TPTU.BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Reference will now be made to the accompanying drawings.

[0055] Fig. 1 illustrates a theoretical graph of syngas yield vs thermal pre-treatment severity (for an entrained flow gasifier).

[0056] Fig. 2 illustrates a block diagram view of the process provided herewith producing methanol in accordance to an embodiment.

[0057] Fig. 3 illustrates a block diagram of the feed preparation and drying of wet carbonaceous material with heat recovery from the gasifying unit as described herein.

[0058] Fig. 4 illustrates a block flow diagram of the thermal pre-treatment unit producing a carbon-densified powder as described and encompassed herein.

[0059] Fig. 5 illustrates a block flow diagram of the water gas shift unit.DETAILED DESCRIPTION

[0060] In accordance with the present description, there is provided a method of converting a low-density carbonaceous material into synthesis gas comprising shredding and sorting a low-density carbonaceous material in a feed preparation unit; drying the sorted carbonaceous materials producing a dried material; treating said dried material at a temperature above 200°C in a thermal pre-treatment unit (TPTU) producing a TPTU gas and carbon-densified solids; milling the carbon-densified solids in a first milling apparatus, producing milled carbon-densified solids; gasifying the milled carbon-densified solids at a temperature above 1000°C, producing a scrubbed syngas and coarse solid residues; and removing carbon dioxide (CO2) and hydrogen sulfide (H2S) from the scrubbed syngas, producing a sweet syngas.

[0061] As mentioned previously, to improve the production cost and carbon intensity, it is very important for a biofuel project, to maximize the amount of carbon ending up in the final product and to minimize the utilization of fossil fuels or other energy sources that are greenhouse gas intensive. Fig. 1 shows that a thermal pre-treatment, as described herein, coupled with an entrained flow gasifier can achieve a higher yield than a reference yield of a bubbling bed gasifier coupled with a thermal reformer (similar to an entrained flow gasifier) but when the severity of the thermal pre-treatment (expressed as mass lost) keeps increasing, the syngas yield of the thermal pre-treatment coupled with an entrained flow drops below the reference yield. Therefore, the operating conditions of the TPTU and its integration with the drying, milling and gasification steps are optimized to maximize the net syngas yield as shown in Fig 1. As encompassed herein, the operating temperature of the TPTU is e.g. of about 200°C to about 600°C. The thermal pre-treatment of a low-density carbonaceous material also enables process improvements for a gasifying step comprising a bubbling bed gasifier coupled with a thermal reformer which will also result in higher syngas yield when the severity of the thermal pre-treatment is low to moderate (mass loss below 40%).

[0062] It is thus provided a method of converting a low-density carbonaceous material into synthesis gas comprising shredding and sorting the low-density carbonaceous material, thermally pre-treating the sorted carbonaceous material, reducing in size the densified solids, optionally grinding the milled carbon-densified solids, gasifying the carbon-densified solids or carbon-densified powder at a temperature above 1000°C, and scrubbing the syngas to obtain a scrubbed syngas.

[0063] As encompassed herein, carbonaceous material refers to any liquid, or combination thereof that contains the “carbon” atom. In most cases, these atoms may be originated from plants or animals and their derivatives, or from fossil fuel and its derivatives. Examples of carbonaceous materials include, but are not limited to, Municipal Solid Waste (MSW); Industrial, Commercial, and Institutional waste (IC&I); Construction and Demolition waste (C&D); any petroleum product; plastic; End of Life Tires (ELT); homogenous and / or non-homogeneous biomass.

[0064] Contrary to coal feedstocks which have a relatively narrow range of particle density / size, biomass, waste and mixtures of both have a very broad range of particle diameter and bulk density. As can be seen from Table 1, for a same mass, the particle size of different biomass, waste and aggregate can result into a particle apparent diameter ratio ranging from about 1 up to 800. If one would sieve such a broad range of material to a specific particle size diameter, particles having the same diameter would range in mass ratio from 1 to 800. Feeding such a range of feedstock density into an entrained-flow gasifier creates heterogeneity in the carbon to syngas efficiency. Thus, presently entrained-flow gasifiers (or thermal reformer) can operate at high temperatures and handle melted mineral only when the particle size is small, in the micron range, and when the mass, particle size distribution, and residual mineral content is uniform.Table 1: Average typical density of different material&

[0065] It has been demonstrated that thermally treating a carbonaceous or biomass material increases its calorific value (i.e., LHV or HHV) by losing proportionally more oxygen than carbon. The mass fraction of carbon also increases with increasing treatment temperature thus increasing the carbon density of the material. The thermal pre-treatment can also greatly increase the grindability of a carbonaceous or biomass material, enabling the size reduction to below 1mm with conventional milling apparatus.

[0066] In the case of low-density carbonaceous material, the thermal pre-treatment leads to a densification of the material as shown in Table 2. One can also see that a thermal pre-treatment can be adjusted to obtain a product, a stream of carbon-densified solids, with chemical and physical properties in a narrower range when compared to the low-density carbonaceous material, thus reducing the feed variability of the gasifying unit. Moreover, a more homogenous feed is expected to increase the availability and the predictability of the gasifying unit. A better availability can have a significant impact on the maintenance and production cost of the overall process.

[0067] Increasing the dry-bulk and carbon density of a feedstock also improves the gasification efficiency. Heat loss, fluidization steam and inert gas injection such as CO2all have a significant impact on the syngas yield of a gasifying unit comprising a fluidized bed gasifier followed by a thermal reformer. Densification of the feed to the gasifying unit enables an intensification of the process, meaning that heat loss and steam can be minimized by the use of a more compact gasifier and / or thermal reformer and inert gas injection can be minimized as the dry-bulk density of the feed increases.Table 2: Typical densities of material before and after thermal pre-treatment

[0068] It has been demonstrated by Rodrigues et al. (2016, Brazilian Journal of Chemical Engineering, 33: 401-414) that the higher heating value “HHV” of a feed to a gasifying unit operating at 1000°C has an impact on the gasification cold gas efficiency. Table 3 shows the reported results of that study. Thermally treating a carbonaceous or biomass material will lead to a loss of carbon, hydrogen and oxygen in the carbon-densified product which is not recovered in the gasifying unit. However, the increased HHV of the carbon-densified product has a positive impact on the gasification CGE, which can fully or partially compensate the loss of carbon and hydrogen in the thermal pre-treatment meaning that the syngas yield (i.e. H2and CO) of the gasifying unit fed with a carbon-densified product can surpass, be equivalent, or be slightly lower when compared to the yield for the equivalent carbonaceous material if fed to the gasifying unit in the same conditions (in this case, equivalent means the amount of dried carbonaceous material required to yield the carbon densified product).Table 3: Cold Gas Efficiency vs HHV for gasification @ 1000°C

[0069] As provided herein is a method of increasing the carbon density of a carbonaceous material and converting said low density carbonaceous material into synthesis gas comprising sorting the low density carbonaceous material in a feed preparation unit; drying the sorted carbonaceous material in a dryer using recovered energy from the gasifying process or from an external source; thermally pre-treating the dried carbonaceous material in a thermal pre-treatment unit “TPTU” producing a minimum of two streams, a TPTU Gas and a carbon-densified solids stream; milling the carbon-densified solids in a first milling step and; introducing the milled carbon-densified solids in a gasifying unit operating at a temperature above 1000°C and at a pressure below 14 barg, producing a scrubbed syngas; and purifying the scrubbed syngas in a CO2 / H2S absorption unit producing a sweet syngas.

[0070] In an embodiment, the milled carbon densified solids can be further ground into a carbon-densified powder, further increasing the dry-bulk density and carbon density and enabling the operation of the gasifying unit at high pressure and comprising the steps of; optionally removing metal and non-metal inert from the milled carbon-densified solids; grinding the milled carbon-densified solids in a second milling step to produce a carbon-densified powder; introducing the carbon-densified powder in a gasifying unit operating at a temperature above 1000°C and a pressure above 14 barg, producing a scrubbed syngas and; purifying the scrubbed syngas in a CO2 / H2S absorption unit producing a sweet syngas. In another embodiment, the first and second milling steps are combined, directly producing a carbon-densified powder in a single milling step.

[0071] In an alternate embodiment, it is further provided shifting the sweet syngas in a water gas shift (WGS) unit or alternatively adding imported H2to produce a balanced syngas and; introducing the balanced syngas in a methanol production unit to produce high purity methanol.

[0072] As encompassed herein, balanced syngas has a molar ratio for H2, CO and CO2noted (H2-CO2) I (CO+CO2) is between 1.90 and 2.1.

[0073] It is provided a method for preparing, treating and converting low density carbonaceous materials into an optimized synthesis gas or sweet syngas with high carbon to syngas conversion rate, maximized production of H2and CO and minimal impurities. In order to achieve this objective, the method comprises shredding, sorting, drying and thermally-pre-treating a low-density carbonaceous material to form carbon-densified solids or carbon-densified powder. As encompassed herein, the carbonaceous material is converted into carbon-densified solids or carbon-densified powder with at least 80% of the carbon remaining in the carbon-densified solids or carbon-densified powder. Afterwards, the carbon-densified solids or carbon-densified powder are conveyed from the TPTU to a gasifying unit to form a scrubbed syngas. The gasifying unit comprises a high temperature gasifier, quench, heat recovery exchangers and scrubbing column. Afterwards, CO2, H2S and other contaminants are removed from the scrubbed syngas by absorption using a selective solvent, thus forming a sweet syngas (e.g. methanol, ethanol, N-Methyl-2-pyrrolidone (NMP), amine, propylene carbonate, dimethyl ether of polyethylene glycol (DMPEG), methyl isopropyl ether of polyethylene glycol (MPEG), tributyl phosphate, or sulfolane).

[0074] As illustrated in Fig. 2, the low-density carbonaceous material 001 and optionally a biomass stream 002 are introduced in a feed preparation unit 100 where they are shredded and sorted to remove metal inerts 102 such as iron, copper or aluminum and non-metallic inerts 103 such as rock, glass or ceramics. The sorted carbonaceous material 101 is introduced in a drying unit 200 to reduce the moisture between 6 and 14 wt%. The dried material 201 is then introduced in a TPTU 300 where it is exposed to moderate temperature in the absence of oxygen or almost no oxygen and where chemical and physical changes occur. The products of the TPTU are milled carbon-densified solids or carbon-densified powder 301 and a TPTU gas 319. The TPTU gas 319 is combusted in a gas burner and the heat is recovered from the hot flue gas 320. The cold flue gas 322 is then treated in a gas treatment unit to remove contaminants before its release to the atmosphere as clean flue gas 333. The milled carbon-densified solids or carbon-densified powder 301 is introduced in the gasifying unit 400 where it is converted to a scrubbed syngas 401 mainly composed of H2, CO, CO2and other compounds in small concentration. The scrubbed syngas 401 is then introduced in a H2S & CO2absorption unit 500 where it is purified to produce a sweet syngas for further use as fuel, power generation, alcohol synthesis (MeOH, DME, EtOH and others), hydrocarbon synthesis and other uses. The H2S and CO2absorption unit also produces a residual gas 505 containing mainly CO2and H2S. Fig. 2 illustrates the example of methanol synthesis and, the stoichiometry of the sweet syngas (H2vs CO and CO2) must be adjusted as it is the case for other chemical synthesis. To adjust the stoichiometry, a portion of the sweet syngas 501 is introduced in a water gas shift unit “WGS” where CO and H2O are converted to CO2and H2over a catalyst and where the produced CO2is removed by absorption with a selective solvent. The gas leaving the WGS unit is mixedwith the un-shifted portion of the sweet syngas 501 to form a balanced syngas 601 which is introduced in a methanol synthesis 700 to produce high purity methanol 701. The methanol synthesis unit 700 comprises a methanol reaction loop operating at high pressure and distillation columns operating near atmospheric pressure or below atmospheric pressure or both to remove water 703 and contaminants. The liquid contaminants 702 are recycled with waste liquid 504 from the CO2 / H2S Absorption unit 500 to the gasifying unit 400 where they are converted back to syngas.

[0075] 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.

[0076] In an embodiment, the low-density carbonaceous material and biomass stream are shredded to a size below 50-100 cm.

[0077] In an embodiment, a portion or all of the heat for the dryer is provided from process recovered heat which is transferred with a transfer fluid 410 and 411. The heat can also be recovered from the TPTU 300. In another embodiment, the temperature of the TPTU is between 200°C and 550°C.

[0078] In an embodiment, the gasifying unit comprises a fluidized bed gasifier operating at a temperature between 500 and 1000°C, followed by a thermal reformer operating at a temperature above 1000°C, a quench, heat recovery exchangers and a water scrubber. For reference, such gasifying method is described in W02020206538, the content of which is incorporated herein by reference. In another embodiment, the carbon-densified powder 301 is fed directly in the thermal reformer, thus removing the fluidized be reformer. The thermal reformer is thus now used as an entrained flow gasifier.

[0079] As illustrated in Fig. 3, the low-density carbonaceous material 001 and biomass stream 002 are treated in separate conditioning lines 106 and 107 where they are shredded and sorted. The sorted carbonaceous material 104 and sorted biomass 105 are stored in a wet storage 108. The sorted material is then introduced in the feed dryer 206 which uses hot air 204 to remove moisture from the material in the dryer. The air 203 is heated in heat exchangers 208 and the heat is provided by a heat transfer fluid 410. A short-term storage 207 provides a buffer capacity and it is fed with the dried material 202 from the dryer 206. The dried material 201 leaves the drying unit 200 witha moisture content preferably below 14 wt% and most preferably below 10 wt%. Hot humid air 205 also leaves the drying unit to be eventually released to the atmosphere.

[0080] In an embodiment, the low-density carbonaceous material 001 and biomass stream 002 are shredded and / or sorted in the same conditioning line 106.

[0081] In an embodiment, the dry-bulk density and carbon density of the milled carbon-densified solids are increased by a factor of 2 to 4.5 when compared to low-density carbonaceous material with a dry-bulk density such as for example of 75 kg / m3. The grinding of the milled carbon-densified solids to a carbon-densified powder further increases the carbon density by a factor of 2.5 to 5 when compared to the low-density carbonaceous material with a dry-bulk density of 75 kg / m3.

[0082] In an embodiment, the low-density carbonaceous material is a carbonaceous material with a dry-bulk density below 250 kg / m3.

[0083] In another embodiment, the dry-bulk density of the dried material is below 400 kg / m3.

[0084] In an embodiment, the low-density carbonaceous material is pelletized in the feed preparation unit. In another embodiment, the dried material is pelletized or briquetted after the drying unit. In another embodiment, the carbon-densified solids are pelletized or briquetted after the TPTU.

[0085] As illustrated in Fig. 4 the dried material is introduced in a feeding device 302 that minimizes the amount of air entering the thermal pre-treatment reactor 305. The feeding device also prevents gas from leaving the thermal pre-treatment reactor. The dried material is exposed to a temperature between 200 and 600°C inside the thermal pre-treatment reactor. In this temperature range, the dried material undergoes physical and chemical changes which produces two streams, a TPTU Gas 324 and carbon-densified solids 326. The TPTU gas leaves the TPTU reactor and, in an option illustrated in Fig. 4, the TPTU gas is heated in a heat recovery exchanger 315 with the hot TPTU flue gas 320 from the TPTU burner 312. A portion 317 of the heated TPTU gas 319 is recirculated in the TPTU reactor 305 to provide heat for the thermal pre-treatment. A smaller portion of the heated TPTU gas is vented to the TPTU burner, producing the hot TPTU flue gas. The cooled TPTU flue gas 334 leaving the heat recovery exchanger 315 is treated in a flue gas treatment unit 313 in order to comply with applicable regulations. In an alternative option (dashed lines), the TPTU Gas 324 is burnt in the TPTU burner312 and the hot TPTU flue gas is providing heat indirectly to the TPTU reactor 305. The cooled TPTU flue gas 322 leaving the TPTU reactor 305 flue is treated in the flue gas treatment unit similarto the previous option. On the solid side, the carbon-densified solids 326 fall into a cooling apparatus 306 to reduce the temperature below 150°C. The cooled carbon-densified solids 327 may be more or less agglomerated depending on the composition of the dried material 201 and the operating temperature of the TPTU. The cooled carbon-densified solids 327 are then introduced in a first milling apparatus 307, producing milled carbon-densified solids 328 with a particle size of 10 mm or less. The milled carbon-densified solids 328 can be the final product of the TPTU 300 but it can optionally be sorted in a second sorting apparatus 308 removing metal (331) and non-metal inert (332). The thermal pre-treatment combined with milling below 10 mm can enable the sorting of metal and non-metal inert that are not accessible (e.g., imbedded in plastic) in the feed preparation unit. To produce a powder, the milled carbon-densified solids 328 or the sorted milled carbon-densified solids 329 are introduced in a second milling apparatus 309, producing a carbon-densified powder 301 with a particle size of 1 mm or less.Table 4: Typical densities of material before and after thermal pre-treatment

[0086] In an embodiment, the TPTU reactor 305 is heated with a heat transfer fluid such as thermal fluid or molten salts which is heated with recovered heat from the TPTU unit 300 and / or from and external heat source. In another embodiment, the TPTU reactor is heated with electricity directly or indirectly, for example by resistive heating or plasma arc.

[0087] In an embodiment, the cooling device 306 also includes a discharge device which, similarly to the feeding device 302, minimizes air leaks inside the thermal pretreatment reactor 305 as well as gas leaks outside of the thermal pre-treatment reactor.

[0088] In an embodiment, the cooling device 306 uses water injection to reduce the temperature of the carbon-densified solids by evaporation. In this case, the generatedwater vapor circulates back in the thermal pre-treatment reactor and mixes, partially or completely, with the TPTU gas leaving the reactor.

[0089] In an embodiment, the cooled TPTU flue gas 334 or 322 is treated in the flue gas treatment unit of the gasifying process.

[0090] In an embodiment, natural gas 336 or another combustible gas or liquid is added in the TPTU burner 312 to stabilize the operation or to provide additional heat.

[0091] In an embodiment, the TPTU comprises a contaminant removal unit and a burner, said contaminant removal unit removes gaseous contaminants upstream of the TPTU Burner.

[0092] In the example of methanol production illustrated in Fig. 2, it is necessary to adjust the stoichiometry of the syngas entering the methanol synthesis unit. Hydrogen 710 can be added (e.g. green or blue hydrogen) in the syngas to get the preferred ratio of H2over CO and CO2(SN = 2.03). When hydrogen is not available, a WGS unit is generally used to produce more hydrogen from the reaction of CO with H2O (reaction 1). As illustrated in Fig. 5, the sweet syngas 501 is separated into two fractions in the WGS unit 600. The first syngas fraction 502 is heated in the WGS feed effluent exchanger 610 and Steam 606 is added to the heated syngas fraction 607. The mixture of steam and syngas is introduced in the WGS reactor 604 where the reaction occurs. The product from the WGS reactor is a hot shifted syngas 609 with more hydrogen, less CO, more CO2and un-reacted H2O. The energy in the hot shifted syngas 609 is recovered in the WGS feed / effluent exchanger 610 after which the gas is cooled in a condenser 615, generally using water or air as a utility fluid. The shifted syngas is further cooled in a second feed / effluent exchanger 616 to condense the un-reacted H2O. A cooled shifted syngas 611 is then introduced in a CO2absorption unit 605 producing a cold H2rich syngas 612 and where CO2603 and H2O 614 are extracted in separate streams. The CO2absorption unit may also produce a low pressure H2rich gas 613 that is recycled upstream of the H2S and CO2absorption unit 500. The second syngas fraction 503 is mixed with the cold H2rich syngas 612 before the second feed / effluent exchanger 616 where the gas is heated. At this point, the resulting syngas is a balanced syngas 601, also called makeup gas, with the preferred stoichiometry for the production of Methanol.CO + H2O CO2+ H2(1)SN =h-CO(CO + CO2) (2)

[0093] As provided, in an embodiment, more than 50% of energy for the drying in step is recovered from the gasifying step.

[0094] Accordingly, the method provided herewith provides a mean to reduce variability in physical and chemical properties of the feedstock. The thermally treated material can be fed directly in an EFG, avoiding co-feeding with a fossil fuel (e.g., coal or liquid hydrocarbon). The process provided herewith increases reliability of the gasification process as any “black swan event” will happen at the pre-treatment stage. The pre-treatment step encompassed herein can enable the removal of imbedded inert material (e.g., insulated metal wire) before the gasification step. It increases the overall gasification efficiency when compared to direct gasification of waste or biomass. The process described herein provides that the carbon-densified solids or carbon-densified powder is converted into CO and CO2in the syngas with at least 90%-96% of carbon conversion rate.

[0095] The greenhouse gas (GHG) reduction of the overall process (waste to syngas) has been demonstrated as:-more H2+CO production per ton of feedstock;-less electricity needed;-less O2input to the gasifying process; and-less H2import needed when it is the selected line-up.

[0096] 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 and 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.

Claims

WHAT IS CLAIMED IS:

1. A method of converting a low-density carbonaceous material into an optimized synthesis gas comprising:a) shredding and sorting a low-density carbonaceous material in a feed preparation unit;b) drying the sorted carbonaceous materials producing a dried material;c) treating said dried material at a temperature above 200°C in a thermal pretreatment unit (TPTU) producing a TPTU gas and carbon-densified solids; d) milling the carbon-densified solids in a first milling apparatus, producing milled carbon-densified solids or carbon-densified powder;e) gasifying the milled carbon-densified solids or carbon-densified powder at a temperature above 1000°C, producing a scrubbed syngas comprising H2, CO, CO2, and H2S, and solid residues; andf) removing carbon dioxide (CO2) and hydrogen sulfide (H2S) from the scrubbed syngas, producing the optimized synthesis gas or sweet syngas,or wherein the drying step is conducted before the shredding and sorting step.

2. The method of claim 1, further comprising feeding a biomass stream in the feed preparation unit.

3. The method of claim 2, wherein the biomass stream and the low-density carbonaceous material are shredded and / or sorted together or separately in the feed preparation unit.

4. The method of any one of claims 1-3, wherein the low-density carbonaceous material is a carbonaceous material with a dry-bulk density below 250 kg / m3.

5. The method of any one of claims 1-4, wherein the dry-bulk density of the dried material is below 400 kg / m3.

6. The method of claims 1-5, further comprising the steps of:d’) optionally removing metal and non-metal inert from the milled carbon-densified solids and;d”) optionally grinding the milled carbon-densified solids in a second milling apparatus, producing a carbon-densified powder.

7. The method of any one of claims 1-6, further comprising the steps of:g) shifting CO in a portion of the sweet syngas in a water gas shift unit and removing CO2in a CO2absorption unit producing a H2rich syngas and then mixing the H2rich syngas with the un-shifted portion of the sweet syngas, producing a balanced syngas;h) converting said balanced syngas into methanol in a methanol synthesis unit, producing high purity methanol and water.

8. The method of any one of claims 1-7, wherein the TPTU comprises a contaminant removal unit and a burner, said contaminant removal unit removes gaseous contaminants upstream of the TPTU Burner.

9. The method of claim 8, wherein the gaseous contaminants are halogenic compounds and / or sulfur based compounds.

10. The method of claim 8 or 9, wherein the halogenic compounds are mainly HCI.

11. The method of any one of claims 8-10, wherein the sulfur based compounds are mainly H2S.

12. The method of any one of claims 1-11, wherein the TPTU Gas is burnt, producing heat which is recovered in an exchanger or indirectly in the TPTU reactor.

13. The method of claim 12, wherein the recovered heat is used for the TPTU.

14. The method of any one of claims 1-13, wherein in step a) the carbonaceous material is shredded to a particle size of 100 mm and less.

15. The method of any one of claims 1-14, wherein in step d) the cooled carbon-densified solids are milled to a particle size of 10 mm and less.

16. The method of any one of claims 1-15, wherein the milled carbon-densified solids are grinded to a particle size of 1 mm and less.

17. The method of any one of claims 1-16, wherein the gasifying process is a fluidized bed gasifier operating at a temperature below 1000°C, followed by a thermal reformer operating at a temperature above 1000°C, a quench, heat recovery exchangers and a water scrubber.

18. The method of claims 1 or 6, wherein the carbon-densified powder is fed directly in an entrained flow gasifier at a temperature above 1000°C.

19. The method of any one of claims 1-18, wherein the CO2and H2S are removed from the syngas by absorption using a CO2selective solvent.

20. The process of claim 19, wherein the CO2selective solvent is methanol, ethanol, N-Methyl-2-pyrrolidone (NMP), amine, propylene carbonate, dimethyl ether of polyethylene glycol (DMPEG), methyl isopropyl ether of polyethylene glycol (MPEG), tributyl phosphate, or sulfolane.

21. The method of claim 1 , wherein more than 50% of energy for the drying in step b) is recovered from the gasifying step e).

22. The method of claim 7, wherein step g) is replaced by the addition of green or blue hydrogen, producing the balanced syngas.

23. The method of claim 7 or 22, wherein the balanced syngas has a molar ratio for H2, CO and CO2noted (H2-CO2) I (CO+CO2) is between 1.90 and 2.1.

24. The method of any one of claims 7, 22 and 23, wherein the molar ratio (H2-CO2) I (CO+CO2) is between 2.0 and 2.05.

25. The method of any one of claims 7 and 22-24, wherein the molar ratio (H2-CO2) I (CO+CO2) is equal to 2.03.

26. The method of any one of claims 1-25, wherein the operating temperature of the TPTU is about 200°C to about 600°C.

27. The method of any one of claims 1-6, wherein the carbonaceous material is converted into carbon-densified solids or carbon-densified powder with at least 80% of the carbon remaining in the carbon-densified solids or carbon-densified powder.

28. The method of any one of claims 1 -6, wherein the carbon-densified solids or carbon-densified powder is converted into CO and CO2in the syngas with at least 90% of carbon conversion rate.

29. The method of any one of claims 1-6 and 28, wherein the carbon-densified solids or carbon-densified powder is converted into CO and CO2 in the syngas with at least 96% of carbon conversion rate.

30. The method of any one of claims 1-29, wherein the carbonaceous material is a solid containing carbon.

31. The method of any one of claims 1-30, wherein the carbonaceous material is a non-homogeneous biomass a heterogeneous biomass, urban biomass, or a combination thereof.

32. The method of claim 1-31, wherein the carbonaceous material is a homogeneous biomass from a coniferous tree, a deciduous tree, an agricultural material, a primary sludge, waste cooking oil, fruit bark, mixed forest residues, mixed tree residues or stillage.

33. The method of any one of claims 1 -30, wherein the carbonaceous material comprises plastics, 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 floe, construction wood material, or any combination thereof.

34. The method of claim 7, wherein in step h), producing an end product consisting of Fischer Tropsch products, ethanol, or synthetic / substitute natural gas.

35. The method of claim 34, wherein the balanced syngas has a molar ratio adjusted for the selected production.

36. The method of any one of claims 1 -6, wherein the carbonaceous material is pelletized before the dryer, or the dried material is pelletized before the TPTU or the carbon-densified solids are pelletized after the TPTU.

37. The method of any one of claims 1-6, wherein the dried material is briquetted before the TPTU or the carbon-densified solids are briquetted after the TPTU.

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