MAXIMIZING SYNGAS CARBON UTILIZATION AND CONVERSION TO BIOFUEL

Abstract

It is provided a process for optimizing syngas carbon utilisation and syngas purity from a varying scrubbed syngas source before feeding into a syngas conversion unit comprising the steps of feeding a scrubbed syngas into a purification unit comprising at least one absorption unit to remove CO.sub.2 from the scrubbed syngas. producing a clean CO+H.sub.2+CO.sub.2 syngas stream and a CO.sub.2 rich stream: and mixing the clean CO+H.sub.2+CO.sub.2 syngas stream with hydrogen producing a balanced syngas stream. wherein the balanced syngas stream meet the stoichiometric ratio and purity requirement of the syngas conversion unit.

Claims

1. A process for optimizing syngas carbon utilisation, syngas purity for subsequent syngas conversion into a downstream syngas conversion unit from a scrubbed syngas source comprising the steps of: a) feeding a scrubbed syngas into a purification unit comprising at least one absorption unit to partially remove CO.sub.2 from said scrubbed syngas, producing a clean syngas stream adjusted to optimal target carbon content and a CO.sub.2 rich stream, wherein the purification unit is an acid gas removal unit (AGR), wherein in said AGR, CO.sub.2 and sulfur species are absorbed from the scrubbed syngas in a absorption unit using said selective solvent, producing a loaded solvent and a clean syngas stream; the loaded solvent is withdrawn through at least one recirculation loop; the loaded solvent is pre-flashed at an intermediate pressure to recover absorbed H.sub.2 and CO, producing the CO.sub.2 rich stream rich in H.sub.2 and CO and a flashed solvent stream; the flashed solvent is flashed at lower pressure to recover CO.sub.2, generating a non-flammable CO.sub.2 rich stream and a second flashed solvent; and the second flashed solvent is stripped in a first stripping unit to remove the sulfur species, producing a rich sulfur species stream and a clean solvent which is recycled back into the absorption unit; b) mixing the clean syngas stream with hydrogen producing a balanced syngas stream, wherein the balanced syngas stream meet the stoichiometric ratio requirement of the syngas conversion unit; and c) feeding said balanced syngas stream in said syngas conversion unit.

2. The process of claim 1, wherein the at least one absorption unit further removes sulfur species and produces an additional sulfur species rich stream.

3. The process of claim 2, wherein the sulfur species is H.sub.2S, COS, CS.sub.2, or a combination thereof.

4. The process of claim 1, wherein the at least one absorption unit further removes nitrogen contaminant species and produces an additional nitrogen contaminant rich stream.

5. The process of claim 1, wherein the scrubbed syngas source comprises between 25 to 45 mol % of H.sub.2, 30 to 65 mol % of CO and 6 to 40 mol % of CO.sub.2 and/or wherein the clean syngas stream composition comprises 30% to 50 mol % H.sub.2, 40 to 68 mol % CO and 0 to 25 mol % CO.sub.2.

6. (canceled)

7. The process of claim 1, further comprising a step of recycling the CO.sub.2 rich stream for use as inerting gas, exporting said CO.sub.2 rich stream for Carbon Capture and Storage (CCS), and/or producing saleable merchant CO.sub.2 from said CO.sub.2 rich stream.

8. The process of claim 1, wherein a first portion of the loaded solvent is withdrawn through a first recirculation loop and a second portion of the loaded solvent is withdrawn through a second recirculation loop, and where, the first portion of the loaded solvent is pre-flashed at an intermediate pressure recovering the H.sub.2 and CO contained in the loaded solvent, producing a first CO.sub.2 stream rich in H.sub.2 and CO and a first flashed solvent, and the second portion of the loaded solvent is pre-flashed at an intermediate pressure recovering H.sub.2 and CO contained in the loaded solvent, producing a second CO.sub.2 stream rich in H.sub.2 and CO and a second flashed solvent; the first flashed solvent is flashed at lower pressure generating a non-flammable CO.sub.2 rich stream and a clean solvent which is recycled back into the absorption unit; the first and second CO.sub.2 streams rich in H.sub.2 and CO are recycled in the scrubbed syngas stream upstream of the absorption unit; and the second solvent is stripped in a first stripping unit to remove sulfur species, producing a rich sulfur species stream and a clean solvent which is recycled back into the absorption unit.

9. The process of claim 1, wherein the selective solvent of the purification unit further removes the sulfur species, and nitrogen species, producing a rich sulfur and nitrogen species stream.

10. The process of claim 9, wherein a first portion of the loaded solvent is withdrawn through a first recirculation loop, a second portion of loaded solvent is withdrawn through a second recirculation loop, and a third portion of loaded solvent is withdrawn through a third recirculation loop where; the first portion of the loaded solvent is pre-flashed at an intermediate pressure recovering the H.sub.2 and CO contained in the loaded solvent, producing a first CO.sub.2 stream rich in H.sub.2 and CO and a first flashed solvent; and the second portion of the loaded solvent is pre-flashed at an intermediate pressure recovering H.sub.2 and CO contained in the loaded solvent, producing a second CO.sub.2 stream rich in H.sub.2 and CO and a second flashed solvent; and, optionally, the third portion of the loaded solvent is pre-flashed at an intermediate pressure recovering the H.sub.2 and CO contained in the loaded solvent, producing a third CO.sub.2 stream rich in H.sub.2 and CO and a third flashed solvent; the first flashed solvent is flashed at lower pressure generating a non-flammable CO.sub.2 rich stream and a clean solvent which is recycled back into the absorption unit; the first, second and optional third CO.sub.2 streams rich in H.sub.2 and CO are recycled in the scrubbed syngas stream upstream of the absorption unit; and the second flashed and third flashed solvents, or unflashed solvents are stripped in a stripping unit to remove the sulfur species, and nitrogen species, producing a rich sulfur and nitrogen species stream and a clean solvent which is recycled back into the absorption unit.

11-19. (canceled)

20. The process of claim 1, wherein the non-flammable CO.sub.2 rich stream is further used as inerting gas, recovered for Carbon Capture and Storage (CCS) and/or to produce saleable merchant CO.sub.2.

21. The process of claim 1, further comprising treating the clean syngas stream with at least one solid adsorbent bed before or after mixing the clean syngas stream with hydrogen.

22-29. (canceled)

30. The process of claim 1, wherein H.sub.2S concentration in the clean syngas stream is adjusted to achieves a specific desired concentration, to meet the requirement of the downstream syngas conversion unit; while achieving low level of HCN and/or NH.sub.3 concentration.

31-32. (canceled)

33. The process of claim 1, wherein the hydrogen is imported from an external source.

34-35. (canceled)

36. The process of claim 1, wherein the purification unit comprises chilled methanol as a solvent.

37. The process of claim 1, wherein the balanced syngas stream meet the stoichiometric ratio requirement of the syngas conversion unit to produce fuel, a chemical, or a Fischer Tropsch product.

38-39. (canceled)

40. The process of claim 1, wherein the scrubbed syngas is from a gasification and/or reforming of a carbonaceous material.

41-44. (canceled)

45. The process of claim 1, further comprising admixing an external source of CO.sub.2 or CO.sub.2 input from another process effluent into the clean syngas stream along with the external source of hydrogen to produce a balanced syngas further boosted in carbon that meet the stoichiometric ratio of the desired end product, thus further increasing the production of the desired end product.

46-53. (canceled)

54. The process of claim 1, further comprising a reverse water gas shift (RWGS) unit to convert a portion of the CO.sub.2 along with a portion of the hydrogen to generate additional carbon monoxide prior to the syngas conversion unit.

55. (canceled)

56. The process of claim 1, wherein CO.sub.2 is recycled back to a carbonaceous feedstock gasification and/or reforming unit to reduce the scrubbed syngas source H.sub.2/CO ratio, increasing a total CO yield and production, and generating a boosted CO scrubbed syngas and a boosted CO clean syngas.

57. (canceled)

58. The process of claim 1, wherein the purification unit comprises a stripping unit including a split loading stripper column with at least a top and bottom mass transfer zone sections, where nitrogen species loaded methanol is fed at the top of the stripper column and above the top mass transfer zone, while the sulfur species loaded methanol is fed in the middle of the stripper column in between the top and bottom mass transfer zone sections.

59-60. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Reference will now be made to the accompanying drawings.

[0076] FIG. 1 illustrates a flow chart of the process described herein in accordance to an embodiment.

[0077] FIG. 2 illustrates a flow chart of the process described herein in accordance to an embodiment, including details of the purification unit.

[0078] FIG. 3 illustrates a flow chart of the process described herein in accordance to an embodiment, including details of the purification unit and the option to achieve high removal efficiency of HCN and/or NH.sub.3.

[0079] FIG. 4 illustrates a flow chart of the process described herein in accordance to an embodiment, including details of the purification unit and the option to achieve high removal efficiency of HCN and/or NH.sub.3 with a second stripping unit.

[0080] FIG. 5 illustrates a flow chart of the process described herein in accordance to an embodiment, including details of a CO.sub.2 recovery and purification unit and an option to recover additional ultra-clean high quality CO.sub.2 within the AGR. FIG. 5 is also showing a configuration where the fourth mass transfer zone for HCN/NH.sub.3 removal is installed in a separate column.

[0081] FIG. 6 illustrates a flow chart of the process described herein in accordance to an embodiment, including details of a split loading nitrogen and sulfur species stripping unit, and option to further improve the efficiency of the AGR.

DETAILED DESCRIPTION

[0082] In accordance with the present disclosure, it is provided a process for optimizing syngas carbon utilisation, syngas purity and subsequent syngas conversion into downstream syngas conversion unit.

[0083] It is provided a method for maximising yield of syngas derived product (e.g. methanol) from gasification and/or reforming of variable carbonaceous feedstock composition when an external source of hydrogen, preferably a green, renewable or low carbon intensity hydrogen, is available.

[0084] It has been disclosed that rather than shifting excess CO to H.sub.2 in a plant using carbonaceous feedstock, an external source of hydrogen could be imported into the plant and combined with the plant rich CO syngas to rebalance the overall plant H.sub.2/CO ratio to that required per the ratio derived from the stoichiometric reactions of the desired end product.

[0085] It is also known that some chemicals and fuel can be produced from the reaction of H.sub.2 and CO, but also from H.sub.2 and CO.sub.2. One such product is methanol, but also Fischer Tropsch using iron based catalyst and ethanol using micro-organism bio-catalyst.

[0086] In most existing syngas to methanol plant, methanol is produced in a catalytic reactor per the following chemical reactions.

##STR00002##

[0087] It is understood and required that a minimum amount of CO.sub.2 is needed in the syngas to the methanol reactor to obtain high methanol productivity and higher dry basis methanol purity (i.e. kg/hr Methanol per kg catalyst).

[0088] Typical modern syngas to methanol plant prepares a make-up syngas to be sent to a methanol reactor loop. In order to achieve high carbon efficiency (CO and CO.sub.2 conversion to methanol), the make-up syngas must be balanced., i.e. any large excess of CO, CO.sub.2 or H.sub.2 would results in losses of valuable molecules via the reactor loop purge gas stream, as inevitably some non-condensable gases that act as inert/diluent (usually N.sub.2, CH.sub.4, etc.) must be purged from the system.

[0089] A fully balanced syngas would have a stoichiometric ratio or number (SN) of 2.0, leading theoretically to full conversion of H.sub.2, CO and CO.sub.2 to methanol as per above three reactions. Typically, a slight excess of H.sub.2 is recommended, resulting in an SN slightly above 2.

[00001]$\begin{array}{cc}\mathrm{SN}=\frac{\left(H_2-{\mathrm{CO}}_2\right)}{\left(\mathrm{CO}+{\mathrm{CO}}_2\right)}& \left(5\right)\end{array}$

[0090] Since modern methanol reactor design and catalyst can also convert CO.sub.2 with H.sub.2 to methanol, carbonaceous rich feedstock gasification and/or reforming plants including an external source of hydrogen would benefit from a novel plant design as proposed herewith which would maximize carbonaceous feedstock derived CO and CO.sub.2 recovery to achieve higher methanol yield.

[0091] Table 1 shows the range of CO.sub.2 concentration in the make-up gas for a constant stoichiometric number (SN) of 2.04, ranging from no CO.sub.2 (all methanol via equation 2) up to no CO (all methanol via net reaction 4). Accordingly, methanol can be produced from CO rich syngas to CO.sub.2 rich syngas, and in any proportion in between.

TABLE-US-00001 TABLE 1 CO.sub.2 Concentration in Methanol Reactor Make-up Gas at constant SN Syngas Composition (% v/v) - Main components % Non-condensable and others H.sub.2 CO CO.sub.2 (N.sub.2, CH.sub.4, etc.) SN 66.0% 32.3% 0.0% 1.8% 2.04 66.9% 28.3% 3.0% 1.8% 2.04 67.5% 25.7% 5.0% 1.8% 2.04 68.2% 23.0% 7.0% 1.8% 2.04 69.2% 19.0% 10.0% 1.8% 2.04 70.0% 15.7% 12.5% 1.8% 2.04 70.8% 12.4% 15.0% 1.8% 2.04 71.7% 9.1% 17.5% 1.8% 2.04 72.5% 5.7% 20.0% 1.8% 2.04 73.9% 0.0% 24.3% 1.8% 2.04

[0092] One of the challenges of waste, plastic rich waste, biomass and/or biomass rich gasification and/or reforming is the feedstock gasification/reforming composition variability overtime (weekly, monthly variations due to the variable nature of such feedstock), which impact the H.sub.2, CO, CO.sub.2 yield (flow rate) and contaminants concentration in the produced scrubbed syngas, i.e. the varying scrubbed syngas source. The downstream units design, especially the purification unit, must then have the ability to manage variable syngas composition while maximizing CO and CO.sub.2 recovery for maximum methanol or biofuel production while achieving target contaminants removal.

[0093] In an embodiment, the contaminants comprises, but are not limited to; sulfur species such as H.sub.2S, COS and/or CS.sub.2, nitrogen species such as HCN, NH.sub.3 and/or amine, water and aromatics such as benzene, toluene and xylene. Nitrogen (N.sub.2) is not a contaminant.

[0094] In a further embodiment, the purification unit is an acid gas removal unit (AGR) comprising a selective solvent for absorbing CO.sub.2, sulfur contaminants (ex. H.sub.2S, COS, and/or CS.sub.2, etc), and nitrogen contaminants (ex. HCN, NH.sub.3, and/or amine).

[0095] As described herein, the process provided for methanol production from a carbonaceous feedstock gasification and/or reforming also apply to other product which use methanol as intermediate and/or directly from syngas and/or other intermediate.

[0096] In an embodiment, the carbonaceous material/feedstock 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 electrical transmission pole, railroad ties, wood, tire, synthetic textile, carpet, synthetic rubber, materials of fossil fuel origin, expended polystyrene, poly-film floc, construction wood material, or any combination thereof. Accordingly, it is encompassed a process for methanol production from a carbonaceous feedstock gasification and/or reforming, such as e.g. a biomass, a biomass rich waste, a plastic rich waste and/or waste.

[0097] As depicted in FIG. 1, it is provided a process as described herein which involves maximizing the hydrogen, carbon monoxide and carbon dioxide recovery in the purification unit 11. Scrubbed syngas 10 is first feed to a purification unit 11 in order to optimize the CO.sub.2 recovery in the purification unit 11 to maximise the CO.sub.2 content in the clean syngas 40 leaving the purification unit 11. Imported hydrogen 42 is injected in the clean syngas 40 to prepare a balanced make-up syngas 44 to feed the catalytic syngas conversion unit 60 to produce the desired end product 61. A non-flammable CO.sub.2 rich stream 32 is generated, which can be used as inerting gas up-stream in the plant. In addition, in an embodiment, a high quality CO.sub.2 stream or ultraclean CO.sub.2 stream (88) can be generated to optionally be mixed with the clean syngas stream 40 along with the external source of hydrogen 42 to produce a balanced syngas 44 further boosted in carbon that meet the stoichiometric ratio target for the desired end product, thus further increasing the production of the desired end product (see FIG. 5). Furthermore, in another embodiment, the ultraclean CO.sub.2 can be sold off-site or send for storage (i.e. CCS) (stream 89). The process described herein allows removing the scrubbed syngas contaminants 29 in the purification unit 11.

[0098] Since the yield of H.sub.2+CO over CO.sub.2 in the varying scrubbed syngas source will vary over time, the AGR design and downstream syngas conversion unit must be designed to manage a range of syngas compositions, and must have the ability to adapt to such syngas yield variations while maximizing at all time the production within the plant and H.sub.2 import capacity.

[0099] The syngas yield refer to the quantity of H.sub.2, CO and CO.sub.2 produced by the gasification/reforming unit per input quantity of carbonaceous feedstock fed to the gasification/reforming unit. Syngas yield variations imply that total syngas flowrate and composition, and thus individual H.sub.2, CO and CO.sub.2 flowrate, will vary overtime (weekly, monthly variations due to the variable nature of such feedstock).

[0100] Furthermore, downstream of the gasifier/reformer there are often steps of hot syngas quench, heat recovery and wet scrubbing using water as scrubbing medium. The wet scrubbed syngas then feed the AGR with or without a compression step. A COS hydrolysis to H.sub.2S unit may also be included before the AGR, which also typically catalyse HCN hydrolysis to NH.sub.3.

[0101] It is thus provided a novel AGR design for processing the scrubbed syngas through an acid gas removal unit specially designed to manage variable scrubbed syngas yield and split it into different gas streams: [0102] (i) a clean syngas stream with low sulfur contaminants concentration (H.sub.2S, COS, and/or CS.sub.2, but not limited to), and optionally low nitrogen contaminants concentration (HCN and/or NH.sub.3, but not limited to). [0103] (ii) rich syngas contaminants loaded gas streams (with sulfur species and/or HCN/NH.sub.3); [0104] (iii) low quality CO.sub.2 stream(s) rich in H.sub.2 and CO (recycled back to the syngas inlet of the AGR absorption column); [0105] (iv) a non-flammable rich CO.sub.2 stream (medium quality CO.sub.2); and [0106] (v) optionally a high quality and/or ultra clean CO.sub.2 stream.

[0107] The novel AGR design has operating handles that allow to maximise H.sub.2 and CO recovery while adjusting the CO.sub.2 recovery with variable inlet scrubbed syngas compositions to maximise methanol production.

[0108] As illustrated in FIG. 2, the scrubbed syngas 10 is first feed to an absorption column 12 using a solvent selective for CO.sub.2 and H.sub.2S and other sulfur species. Such solvent can be for example but not limited to, chilled methanol.

[0109] The absorption column 12 has at least 3 mass transfer zone sections (example, but not limited to, trays, random packing and/or structured packing, namely the top 18, middle 16 and bottom section 14). The 3 mass transfer zone sections can be installed in one single column 12 with 3 sections or in 2 or 3 separate columns.

[0110] The loaded solvent still containing H.sub.2 and CO passes through at least 2 recirculation loops around the absorber, the first loop 20 and the second loop 22. The second loop 22 is taken from the bottom section 14 and the first loop 20 is taken from the middle section 16 of the absorption column 12.

[0111] Both loops that withdraw solvent from the absorber sections, are pre-flashed (21, 23) at intermediate pressure to recover the valuable H.sub.2 and CO absorbed in the solvent, thus producing two CO.sub.2 streams rich in H.sub.2 and COone 26 for the second loop 22 and one for the first loop 20 which are then combined and recycle up-stream of the absorption column 12, in the syngas feed 10. The recovered valuable H.sub.2 and CO have another chance to pass through and leave the absorption column as part of the clean syngas 40 sent to the downstream catalytic reactor unit (60). Such pre-flash and recycle allow for more than 99% H.sub.2+CO recovery in the overall AGR unit (i.e. Recovery=Quantity of H.sub.2 and CO in stream 40 divided by the quantity of H.sub.2 and CO in the inlet scrubbed syngas stream 10).

[0112] As a second step, the first loop solvent 20 is then further flashed 30 at lower pressure to generate a non-flammable CO.sub.2 rich stream 32, which can be used as inerting gas up-stream in the plant. Alternatively, this CO.sub.2 rich stream can be recovered for Carbon Capture and Storage (CCS) and/or to produce saleable merchant CO.sub.2, with or without additional processing. The clean solvent is recycled back 33 into the absorption column 12.

[0113] As a second step, the pre-flashed second loop solvent 24 is then fed for regeneration to a thermal stripping unit 25 to remove the absorbed sulfur contaminants, thus producing a rich sulfur contaminants gas stream 29 and a clean regenerated solvent stream which is recycled back 27 at the top section 18 of the adsorber 12. The thermal stripping unit 25 can be a column with trays or packing equipped with either or both a reboiler and a condenser.

[0114] As illustrated in FIG. 3, when required the purification unit can be fitted with a third recirculation loop (46) to increase NH.sub.3 and HCN removal efficiency. The fourth mass transfer zone section 45 can be added in the main absorption column 12 (FIG. 3.) or installed in a separate column (FIG. 5). The third loop solvent 46 is pre-flashed at intermediate pressure 53 to recover the valuable H.sub.2 and CO absorbed in the solvent, thus producing a CO.sub.2 stream rich in H.sub.2 and CO 47 which is then combined and recycle up-stream of the absorption column 12, in the syngas feed 10.

[0115] The pre-flashed third loop solvent 48 is then fed for regeneration to the thermal stripping unit 25 to remove the absorbed nitrogen contaminants, thus producing a rich sulfur species, NH.sub.3 and HCN gas stream 29.

[0116] Alternatively, as illustrated in FIG. 4, the pre-flashed third loop solvent 48 can be fed to a separate thermal stripping unit 52 to remove absorbed nitrogen contaminants, thus producing a rich NH.sub.3 and HCN gas stream 51 and a clean solvent 49.

[0117] Alternatively, the solvent fed to the fourth mass transfer zone section 45 can be supplied partially or entirely from a slip stream 54 from the first solvent loop 20, as shown on FIGS. 3 and 4. In this configuration, the second solvent loop 22 can thus be either a total or partial liquid draw from the third mass transfer zone 14. When the fourth mass transfer zone section 45 is installed in a separated column, as in FIG. 5, [0118] the scrubbed syngas 10 is fed at the bottom of mass transfer zone section (53); [0119] solvent stream 54 taken from the first recirculation loop 20 is fed at the top of the fourth mass transfer zone section 45, and [0120] the pretreated gas 41 leaving the top of the fourth mass transfer zone section 45 is fed at the bottom of the absorber column 12 (bottom of the third mass transfer 14).

[0121] When low level of nitrogen species contaminants are present in the scrubbed syngas and thus requiring a lower third loop flowrate, the recoverable H.sub.2+CO and CO.sub.2 in the pre-flash step 53 will also be lower. As such, the extra project CAPEX to install step 53 may not be justified. In such a cases, the absorbed H.sub.2+CO and CO.sub.2 in third solvent loop 46 would be lost in the stripper vent stream 29 (FIG. 3) or 51 (FIG. 4).

[0122] The clean regenerated solvent 49 and 27 are taken respectively from stripping unit 52 (FIG. 4) and/or stripping unit 25 (FIGS. 2 and 3) and then cooled prior to be fed at the top section 18 of the adsorber 12 thus removing the final traces of sulfur and/or nitrogen contaminant from the syngas and thus producing a clean syngas stream 40 with low sulfur contaminants concentration (FIGS. 2, 3 and 4) and/or very low nitrogen contaminants concentration (FIGS. 3 and 4).

[0123] If required, to protect the downstream syngas conversion catalyst, the clean syngas stream 40 is further treated in a solid adsorbent bed 36 (before or after H.sub.2 import addition 42), including a single or multiple adsorbent beds, in one or more parallel or/and in series vessel(s). Adsorbent may include alumina based adsorbent for removal of HCl and halogen, ZnO based adsorbent for removal of HCl, halogen and H.sub.2S, a Cu based adsorbent for removing COS, CS.sub.2 and Arsine, an adsorbent for carbonyl (Fe or Ni, or other) removal and/or adsorbent for HCN and/or NH.sub.3 removal.

[0124] The clean syngas stream 40 is mixed with an external source of hydrogen 42 to produce a balanced syngas that meet the stoichiometric ratio requirement of the syngas conversion unit, thus producing an optimised carbon recovery balanced syngas 44.

[0125] The improved process of the present disclosure allow to produce an optimised carbon recovery balanced syngas which in turn allow to increase overall carbon scrubbed syngas and carbon feedstock conversion into the final desired product by more then 65% (as compared with the traditional approach of shifting the excess CO with water gas shift WGS and removing the excess CO.sub.2), and even more then 140% depending on the initial scrubbed syngas composition (see Tables 2 and 3).

TABLE-US-00002 TABLE 2 Example composition of scrubbed syngas (10) and resulting improved process clean syngas composition (40) Improved Process Scrubbed Syngas (10) Clean Syngas (40) Scrubbed Syngas Case (10) #1 #2 #3 #4 #1 #2 #3 #4 Concentration\Configuration B B B B H2 mol % 27% 31% 43% 32% 33% 38% 47% 33% CO mol % 40% 41% 43% 62% 49% 49% 47% 65% CO2 mol % 31% 26% 14% 6% 16% 10% 5% 1% N2 mol % 1% 1% 1% 0% 2% 2% 1% 1%

TABLE-US-00003 TABLE 3 Improved process scrubbed syngas carbon recovery with H.sub.2 import compared to traditional approach with WGS. Scrubbed Syngas (10) Traditional Approach with Improved Process with H2 (Total 100 kmol/h basis) WGS - Balanced Syngas import - Balanced Syngas (44) Scrubbed Syngas Case (10) #1 #2 #3 #4 #1 #2 #3 #4 #1 #2 #3 #4 Component flow\Configuration A A A A B B B B (Note 1) (Note 1) (Note 1) (Note 1) H2 kmol/h 27 31 43 32 47 50 60 66 119 107 100 127 CO kmol/h 40 41 43 62 20 21 25 28 40 40 42 62 CO2 kmol/h 31 26 14 6 2 2 3 3 13 8 5 0.5 N2 kmol/h 1 1 1 0 1 1 1 0 1 1 1 0.5 S.N. = (H2 0.06 0.08 0.51 0.38 2.04 2.04 2.04 2.04 2.04 2.04 2.04 2.04 CO2)/(CO + CO2) Carbon Syngas % Ref. Ref. Ref. Ref. 31% 35% 49% 45% 73% 73% 83% 92% Recovery % Increase % Ref. Ref. Ref. Ref. 138% 105% 69% 102% Carbon Syngas Recovery (Note 1) Configuration B without the third recirculation loop (46), and thus without also the fourth mass transfer zone section 45 and flash steps 53

[0126] For methanol production, the balanced syngas would have an optimal stoichiometric ratio (SN) slightly above 2, as explain before. Although, it can also operate at lower or higher stoichiometric ratio. Other syngas conversion units or technology to obtain different end products may have different target stoichiometric ratio equations and/or values.

[0127] In an embodiment, the imported/external source of hydrogen 42 is from a renewable source and/or a source of low carbon intensity.

[0128] In an additional embodiment, the imported source of hydrogen 42 is from a water electrolysis with renewable power or low carbon intensity (CI) power, a biogas reforming or steam reforming, a low carbon intensity (CI) hydrogen source, or a low CI waste H.sub.2 source.

[0129] Finally, the optimised carbon recovery balanced syngas 44 is feed to a syngas conversion unit 60 (syngas conversion reaction system), thus producing an optimised carbon content fuel and/or chemical as desired end product (61).

[0130] Considering that the downstream syngas conversion unit 60 will be designed with a maximum capacity and/or that the H.sub.2 import 42 will also have a maximum supply capacity, to maximize plant profitability with varying scrubbed syngas composition and yield, design and operating handles have to be provided to maximize at all time the biofuel production and profitability.

[0131] At lower H.sub.2+CO yield in the scrubbed syngas, higher AGR CO.sub.2 recovery will be required to maintain the plant at is maximum methanol capacity and up to the availability of import hydrogen, since per reaction 3 more H.sub.2 is required for conversion to methanol from CO.sub.2.

[0132] At higher H.sub.2+CO yield in the scrubbed syngas, lower AGR CO.sub.2 recovery will be required to maintain the plant at is maximum methanol capacity, while minimizing H.sub.2 import and thus variable operating costs.

[0133] In the provided AGR design, the AGR include the following design and operation handles to optimize the CO.sub.2 recovery to maintain the plant at its maximum methanol capacity and optimal hydrogen usage.

[0134] The first 20 and second loops 22 flow rates and/or temperature are adjusted to achieve the target CO.sub.2 content and low reduced sulfur content in the final clean syngas stream (40), and/or,

[0135] The pre-flash pressures of the first and/or second loops (21 and 23 respectively) are further optimised and the generated CO.sub.2 streams (28 and 26 respectively) are recycle up-stream of the AGR to maximise CO.sub.2 recovery in the final clean syngas stream (40).

[0136] The pressure of the first loop 20 low pressure flash 30 can be adjusted to optimize CO.sub.2 recovery to achieve the exact required quantity of non-flammable rich CO.sub.2 stream 32, and thus keeping the balance of the CO.sub.2 in the clean syngas 40 leaving the AGR 12.

[0137] When high HCN and/or NH.sub.3 removal level are required with FIG. 3 or 4 configurations, the AGR design further include the following design and operation handles to optimize the CO.sub.2 recovery: [0138] a third recirculation loop 46 flow rates and/or temperature are adjusted to achieve the target CO.sub.2 content and low reduced nitrogen species content in the final clean syngas stream (40), and/or, [0139] the pre-flash pressures of third loop (53) is further optimised and the generated CO.sub.2 stream (47) is recycled up-stream of the AGR to maximise CO.sub.2 recovery in the final clean syngas stream (40).

[0140] As exemplified herein, syngas production for methanol production have been used as an example. However, it can be applied with any syngas conversion process to chemical and fuel, that can be produced from H.sub.2 and CO.sub.2 in addition to H.sub.2 and CO, i.e. Fischer Tropsch using iron based catalyst and ethanol using micro-organism bio-catalyst, etc. but not limited to. Desired Fischer Tropsch products, include fuels such as diesel, kerosene/jet fuel and/or naphtha following crude Fischer Tropsch products refining or upgrading, but also waxes, base oil, etc.

[0141] Methanol can also be used as an intermediate product. When first produced, it can be further converted to olefins (propylene and ethylene), formaldehyde, gasoline, naphtha, kerosene, aviation fuel, and/or diesel. Ethanol can be used as a fuel or as intermediate product, for example for ethylene production via dehydration.

[0142] In addition, the objective of maximizing syngas derived product yield with syngas CO.sub.2 recovery and an external H.sub.2 import from biomass rich feedstock, is also applicable to any carbonaceous feedstock with the objective to either maximise yield and production and/or reduce CO.sub.2 green house gases (GHG) emissions. For example, plastic rich waste, waste rubber and tire, etc. chemical recycle via gasification process would also benefit of this novel AGR design by maximizing the total feedstock carbon conversion to the desired final product, thus minimizing the plant CO.sub.2 GHG emission. More specifically, olefins production from methanol or ethanol can be used for plastic production, thus closing the circular loop when using plastic rich waste as gasification feedstock.

[0143] In an embodiment, the clean syngas stream 40 at the outlet of the AGR absorber achieves less than 100 ppbv, less than 10 ppbv, or alternatively less than 5 ppbv HCN and NH.sub.3.

[0144] In another embodiment, the clean syngas stream 40 at the outlet of the AGR absorber achieves less than 10 ppmv, less than 5 ppmv, less than 1 ppmv, or alternatively less than 0.1 ppmv of combined sulfur species.

[0145] In another embodiment, the clean syngas stream at the outlet of the solid adsorbent bed 36 achieves less than 10 ppbv, or alternatively less than 5 ppbv of sulfur species, of halogen species (ex. HCl, HF, HBr, etc.), of arsine, and/or of metal (ex. Ni and/or Fe) carbonyl.

[0146] In another embodiment, the H.sub.2S concentration in the clean syngas stream 40 at the outlet of the AGR absorber can be adjusted to achieves a specific higher desired concentration to meet the requirement of the downstream syngas conversion unit; while achieving low level of HCN and/or NH.sub.3. This functionality is of special interest when using micro-organism syngas conversion technology (60) for which some H.sub.2S is required to maintain the micro-organism activities, while HCN is a well-known poison. In such case, the H.sub.2S concentration in the clean syngas stream 40 at the outlet of the AGR absorber can be maintained below 200 ppmv, alternatively below 100 ppmv, while achieving low level of HCN and/or NH.sub.3. Reducing the H.sub.2S removal requirement, allow to reduce the flowrate and/or stripping unit (25) duty of the second recirculation loop 22, reduce the inherent loss of CO.sub.2 with the rich sulfur contaminants gas stream 29, thus increase the CO.sub.2 recovery and concentration in the clean syngas 40 and producing a further optimised carbon content fuel and/or chemical as desired end product (61).

[0147] In another embodiment, this novel AGR design can also be used to fully removed the CO.sub.2 from the scrubbed syngas 10 to produce an ultra-low CO.sub.2 concentration clean syngas 40 or to achieve a specific lower CO.sub.2 concentration in the clean syngas 40. With such objective, the recirculation loops pre-flash pressure are optimised to reduce CO.sub.2 flash (and recycle back to the absorber), while still achieving the targe H.sub.2 and CO recovery. The recirculation loops flow rate are increased to achieve higher CO.sub.2 removal. Such flexible design is especially of interest for plant design when H.sub.2 import is not available, and/or for syngas conversion technology that cannot make the desired end-product with CO.sub.2+H.sub.2.

[0148] In another embodiment, an external source of CO.sub.2 or CO.sub.2 input from another process effluent can be mixed with the clean syngas stream 40 along with the external source of hydrogen 42 to produce a balanced syngas 44 further boosted in carbon that meet the stoichiometric ratio target for the desired end product, thus further increasing the production of the desired end product. The flow of the external source of hydrogen (42) must be increased accordingly. Alternatively, if this additional CO.sub.2 sources require cleaning, it could be fed to the AGR inlet.

[0149] Such CO.sub.2 sources from another part of the process can be the unrecovered CO.sub.2 lost in the rich sulfur stream (29) and/or nitrogen species rich stream (51). As such, to recover the CO.sub.2 from this waste stream for catalytic synthesis, additional treatment units would be required to reduce contaminants down to ultra-low level. Such additional treatment units includes, but not limited to, additional absorption/stripping technology, solid adsorbent technologies, etc.

[0150] In another embodiment, additional ultra-clean high quality CO.sub.2 can be recovered by adding a CO.sub.2 recovery and purification unit (99) within the AGR as shown in FIG. 5.

[0151] In such configuration, the CO.sub.2 loaded methanol (33), rather than being recycled to the AGR absorber (12), a portion (35) is sent to the top of a primary CO.sub.2 column (70), which include at least one mass transfer zone. In addition, the CO.sub.2 and sulfur species loaded methanol (24) is sent to the bottom of the primary CO.sub.2 column (70). In the primary CO.sub.2 column, the low sulfur CO.sub.2 loaded methanol 35 acts as a scrubbing medium to keep the sulfur species down the column, while recovering a 2.sup.nd medium quality CO.sub.2 (71) from both loaded methanol streams. The primary CO.sub.2 columns also remove additional non-condensable gas (ex. CO and H.sub.2) from the bottom of the column, which further contributes to achieve ultra-low CO specifications in high quality CO.sub.2 (stream 80).

[0152] The 1.sup.st recovered medium quality CO.sub.2 stream is in fact stream 32 as described earlier. Both medium quality CO.sub.2 streams (32 and 71) are combined into stream 82, which meet the non-flammable quality criteria as described earlier. Optionally, they are compressed in a compressor (83) for use as inert gas in the plant front end feed system or other uses, as described earlier.

[0153] The bottom CO.sub.2 and sulfur species loaded methanol (72) is fed to the secondary CO.sub.2 column (73) in between its 2 mass transfer zones (74 and 75). The balance of the CO.sub.2 loaded methanol (34), is fed to the top of the column and acts as a scrubbing medium to keep the sulfur species and other contaminants down the secondary CO.sub.2 column (73), while recovering a high quality CO.sub.2 stream (80) from both CO.sub.2 and sulfur species loaded methanol (72) and the balance of the CO.sub.2 loaded methanol (34). At the bottom of the secondary CO.sub.2 column (73) the enriched sulfur species loaded methanol (76) is sent to a CO.sub.2 flash unit (77) to maximize CO.sub.2 recovery from the bottom enriched sulfur species loaded methanol (76).

[0154] The CO.sub.2 flash unit (77) include a combination of low pressure flash with flash gas recompression and/or thermal heating assisted pressurized flash. The flash CO.sub.2 rich streams (78) are returned at the bottom of the secondary CO.sub.2 column (73).

[0155] The enriched sulfur species loaded methanol (79) is taken from the CO.sub.2 flash unit (77) and then sent to the AGR stripping unit (25). The nitrogen species loaded methanol (48) is either sent directly to the AGR stripping unit (25) or could be incorporated into the CO.sub.2 recovery and purification unit 99 to recover its small CO.sub.2 content. The AGR stripping unit 25 regenerate both loaded methanol into a lean methanol (27), which is recycled at the top of the AGR absorber (12) section (18), as described earlier. The resulting AGR sulfur and/or nitrogen species waste gas stream (29) is thus further enriched in sulfur and nitrogen species, and thus results in lower loss of carbon (as CO.sub.2) out of the process.

[0156] The recovered high quality CO.sub.2 stream (80), is then, if required, compressed to higher pressure in a compressor (81). Depending on the required high quality CO.sub.2 target specification it can then be treated in a solid phase absorbent unit (90) to remove remaining contaminants down to ultra-low ppm or ppb level as described before for the clean syngas guard beds (36). The produced ultraclean CO.sub.2 stream (87, 88) can then be mixed with the clean syngas stream 40 along with the external source of hydrogen 42 to produce a balanced syngas 44 further boosted in carbon that meet the stoichiometric ratio target for the desired end product, thus further increasing the production of the desired end product. The flow of the external source of hydrogen (42) must be increased accordingly, as described earlier.

[0157] Table 4 below show that additional CO.sub.2 recovery and yield increase with this additional functionality to the AGR.

TABLE-US-00004 TABLE 4 Improved process scrubbed syngas carbon recovery with CO2 Recovery and Purification unit and with H.sub.2 import compared to traditional approach with WGS. Scrubbed Traditional Improved Process Syngas (10) Approach Improved Process with CO2 Recovery and (Total 100 with WGS - with H2 Import - Purification Unit (99) - kmol/h basis) Balanced Syngas Balanced Syngas (44) Balanced Syngas (44) Scrubbed Syngas Case (10) #1 #2 #1 #2 #1 #2 #1 #2 Component flow\Configuration. A A B B C C (Note 1) (Note 1) (Note 1, 2) (Note 1, 2) H2 kmol/h 27 31 47 50 119 107 147 128 CO kmol/h 40 41 20 21 40 40 40 40 CO2 kmol/h 31 26 2 2 13 8 22 15 N2 kmol/h 1 1 1 1 1 1 1 1 S.N. = (H2 0.06 0.08 2.04 2.04 2.04 2.04 2.04 2.04 CO2)/(CO + CO2) Carbon Syngas % Ref. Ref. 31% 35% 73% 73% 86% 83% Recovery % Increase % Ref. Ref. 138% 105% 178% 134% Carbon Syngas Recovery (Note 1) Configuration B and C without the third recirculation loop (46), and thus without also the fourth mass transfer zone section 45 and flash steps 53 (Note 2) Configuration C without optional first solvent circulation loop flash steps 30

[0158] For sure, such additional CO.sub.2 recovery and desired product yield increase require availability for additional imported hydrogen (42). For different reasons, a specific project and plant location may have limited access to imported hydrogen. As such, one of the important feature of this invention is that each project can decide to include all or only part of the described features herein to achieve the specific requirements of the project and minimize the project profitability and/or environmental foot print.

[0159] If lower quality CO.sub.2 are required, the flash step 30 can be omitted, and thus first loop 31 would be split in 2 (34 and 35), rather than stream 33, to feed the primary (70) and secondary (73) CO.sub.2 columns. In that configuration, all the medium CO.sub.2 quality would be supplied from the primary CO.sub.2 column via stream 71. Alternatively, the primary CO.sub.2 column could be omitted if lower CO.sub.2 quality is required. In that configuration, the CO.sub.2 loaded methanol (33) is fed directly at the top of the secondary CO.sub.2 columns (73), and the CO.sub.2 and sulfur species loaded methanol (24) is fed directly to the secondary CO.sub.2 column (73) in between its 2 mass transfer zones (74 and 75).

[0160] In another embodiment, if limited hydrogen supply is available, or the desired end product synthesis catalyst and unit (60) cannot convert the recovered ultraclean CO.sub.2 (87) into additional desired product, the ultraclean CO.sub.2 can be sold off-site or send for storage (i.e. CCS) (stream 89).

[0161] Alternatively, when the desired end product synthesis catalyst and unit (60) cannot convert the recovered ultraclean CO.sub.2 (87) into additional desired product, the ultraclean CO.sub.2 could be sent (stream 89) to a methanol reactor along with additional imported hydrogen to co-produce methanol in the plant. Alternative to methanol co-production are any technology that can convert CO.sub.2+H.sub.2 to a desired end product, as described before.

[0162] In another embodiment, any excess (85) of medium quality CO.sub.2 (84) could be mixed with the high quality CO.sub.2 (86), to further maximize desired end-product yield and production.

[0163] When a CO.sub.2 recovery and purification unit (99) is included in the AGR configurations, the AGR design further include the following design and operation handles to optimize the CO.sub.2 recovery from the variable scrubbed syngas source: [0164] The first 20 and second loops 22 flow rates and/or temperature are adjusted to achieve the target CO.sub.2 content and low sulfur content in the final clean syngas stream (40), and/or, the target recovery of high purity CO.sub.2 (87). [0165] The pre-flash pressures of the first and/or second loops (21 and 23 respectively) are further optimised and the generated CO.sub.2 streams (28 and 26 respectively) are recycle up-stream of the AGR to balance the desired CO.sub.2 recovery in the final clean syngas stream (40) versus the recovery of high purity and/or ultraclean CO.sub.2 (87). [0166] The pressure of the first loop 20 and low pressure flash 30 can be used to reduce the CO content in the high quality CO.sub.2 (80). [0167] The CO.sub.2 flash unit (77) pressure and/or temperature can be adjusted to achieve the desired high purity CO.sub.2 (87).

[0168] In another embodiment, the AGR stripping unit (25) is a split loading nitrogen and sulfur species stripping unit design, rather than a standard configuration stripper where the combined contaminants loaded solvents are sent at the top of the stripper to be stripped off their contaminants as the solvents flow down to the bottom of the stripper to generate a regenerated solvent at the bottom of the stripper.

[0169] The split loading design option (FIG. 6) of the AGR stripping unit (25) allow to further improve the overall energy efficiency of the overall AGR unit as shown in Table 5 below.

TABLE-US-00005 TABLE 5 AGR efficiency improvement with split loading stripper design compared to standard configuration stripper Standard Split Loading Unit/ Stripper (25) Stripper (100) Case #1 (Note 1) #2 (Note 1) Nb of Theoritical Stages (single Nb 18 mass transfer zone) Nb of Theoritical Stages - Bottom Nb 6 mass transfer zone (101) Nb of Theoritical Stages - Bottom Nb 12 mass transfer zone (102) Total Nb of Theoritical Stages Nb 18 18 in stripper Heat Duty (25) kW 2471 Heat Duty (52) kW Heat Duty (100) kW 2471 Total Heat duty kW 2471 2471 AGR H2S removal efficiency % >99.9 >99.9 AGR HCN removal efficiency % 98.5 >99.9 (Note 1): Both cases include the third recirculation loop (46), and thus also the fourth mass transfer zone section 45 and flash steps 53

[0170] In the split loading design option, the stripper column (100) has at least 2 mass transfer zone sections (101 and 102). The nitrogen species loaded methanol (48) is fed at the top of the stripper column and above the top mass transfer zone (102), while the sulfur species loaded methanol (79) is fed in the middle of the stripper column (100) in between the top (102) and bottom (101) mass transfer zone sections. Thermal energy (114) is supplied to the stripper column (100) via the stripper reboiler (112), which evaporate a portion (111) of the column bottom product (110) to generate the vapor boil-up (113), which is returned to the bottom of the stripper column (100). The stripper column (100) is also equipped with a condenser (104) which cool and condense the methanol vapor in the column overhead vapor (103). At the outlet of the condenser (104) stream 105 contains the condensed methanol and non-condensable vent gases, which are separated in the reflux drum (106) into the liquid reflux (109) required for the column operation, and the sulfur and/or nitrogen species vent gases (29). The regenerated solvent (27) at the bottom of the stripper column (100) is then recycled, as described earlier, back to the absorber column (12) top mass transfer zone section (18).

[0171] In an embodiment, when the scrubbed syngas (10) contain significant concentration of aromatic such as benzene and toluene, a liquid purge (108) may be extracted from the reflux steam (109) to minimise build-up to these aromatic compound in the AGR loops.

[0172] In an embodiment, this novel AGR design, can also be integrated with processes incorporating reverse water gas shift (RWGS) unit to convert the recovered CO.sub.2 along with the imported H.sub.2 to generate additional carbon monoxide prior to the syngas conversion unit, as described in patent application U.S. 63/185,482, the content of which is incorporated herein in its entirety. The additional CO production being mixed with the balance of the clean syngas to generate a boosted CO clean syngas.

[0173] In another embodiment, as described in patent application U.S. 63/185,482, the recovered CO.sub.2 of this novel AGR design can be recycled back to the carbonaceous feedstock gasification and/or reforming unit to reduce the reformed syngas H.sub.2/CO ratio, increase the total CO yield and production, and thus generating a boosted CO scrubbed syngas and a boosted CO clean syngas at the outlet of the AGR.

[0174] In both cases, the boosted CO clean syngas is mixed with hydrogen producing a balanced syngas stream, wherein the balanced syngas stream meet the stoichiometric ratio requirement of the syngas conversion unit. Such option being advantageous when the syngas conversion unit can only convert in-situ H.sub.2+CO and not H.sub.2+CO.sub.2 into desired product, for example but not limited to Fischer Tropsch unit or technology using Cobalt based catalyst, or ethanol production technology using the methanol carbonylation pathway

[0175] While the disclosure has been described with particular reference to the illustrated embodiment, it will be understood that numerous modifications thereto will appear to those skilled in the art. Accordingly, the above description and accompanying drawings should be taken as illustrative and not in a limiting sense. For simplification purpose, several secondary details were omitted, such as pump, heat exchangers, some compressors, etc.

[0176] While the 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 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.