Process for catalytic gasification of carbonaceous feedstock

Patent metadata

Field	Value
Publication number	US-10208262-B2
Application number	US-201314765575-A
Country	US
Kind code	B2
Filing date	Dec 18, 2013
Priority date	Feb 5, 2013
Publication date	Feb 19, 2019
Grant date	Feb 19, 2019

Abstract

An improved process for the catalytic gasification of a carbonaceous feedstock in a dual fluidized bed reactor for producing synthesis gas is disclosed. The disclosure uses γ-alumina as a catalyst support i and heat carrier in the gasification zone ( 102 ). The gasification zone ( 102 ) is operated at 700-750° C. to prevent substantial conversion of γ-alumina to α-alumina, which would manifest in the enablement of high catalyst loading and high recyclability. The catalyst is an alkali metal, preferably K 2 CO 3 , so that conversion proportional to total K 2 CO 3 to solid carbon ratio is achieved with as high K 2 CO 3 loading as 50 wt % on the solid support. The combustion zone ( 140 ) is operated at 800°-840° C., to prevent any conversion of the γ-alumina to α-alumina, so that catalyst recyclability of up to 98% is achieved between two successive cycles.

First claim

The invention claimed is:

1. A process for catalytic gasification of solid carbonaceous feedstock to synthesis gas in a dual fluidized bed, said process comprising the following steps:
i. gasifying a primary portion of said solid carbonaceous feedstock in a fluidized gasification zone ( 102 , 202 ) at a temperature between 600-800° C. with steam and in the presence of a catalyst consisting of an alkali metal compound impregnated on a solid particulate carrier selected from γ-alumina, silica, ZSM-5, fluid catalytic cracking (FCC) spent catalyst, and mixtures thereof, to produce synthesis gas; wherein heat for endothermic gasification reaction is supplied by said heated catalyst provided in said fluidized gasification zone at a catalyst to feedstock ratio of 2:1 to 50:1, wherein, the alkali metal compound is impregnated on the solid particulate carrier in an amount between, 1:1 to 1:5, wherein, a molar ratio of the solid carbonaceous feedstock to the steam varies between 1:1.5 to 1:3, and wherein, the conversion of said solid carbonaceous feedstock to the synthesis gas per pass is at least 90 wt %;
wherein the synthesis gas comprises hydrogen in the range of 55 to 60 mole %, carbon monoxide in the range of 23 to 35 mole %, carbon dioxide in the range of 9 to 16 mole % and methane in the range of 0.3 to 0.6 mole %;

ii. discharging heat-extracted catalyst from an operative top of the fluidized gasification zone ( 102 , 202 ) to a fluidized combustion zone ( 140 , 240 ); and
iii. combusting a secondary portion of said solid carbonaceous feedstock and unreacted carbon from said fluidized gasification zone ( 102 , 202 ) in a fluidized combustion zone ( 140 , 240 ) at a temperature between 800-840° C. with air, wherein heat generated during the exothermic combustion reaction is transferred to said heat-extracted catalyst to provide said heated catalyst which is re-circulated to said fluidized gasification zone ( 102 , 202 ), so that said heated catalyst remains within the dual fluidized bed and said heated catalyst is used in the next preparation of the synthesis gas; wherein the fluidized gasification zone ( 102 , 202 ) and fluidized combustion zone ( 140 , 240 ) are provided in two fluidized beds.

2. The process as claimed in claim 1 , wherein the catalyst in an amount of 98% w/w per pass is recycled between two successive operations of the catalytic gasification.

3. The process as claimed in claim 1 , wherein the fluidized gasification zone ( 102 , 202 ) operates under pressure varying between 1 to 5 bars (g) and with a weight hourly space velocity varying between 0.2 to 50 hr −1 .

4. The process as claimed in claim 1 , wherein the fluidized combustion zone operates under pressure varying between 2-6 bars, with a weight hourly space velocity varying between 0.2-30 hr −1 , and with a bed superficial velocity varying between 0.5 to 1 m/s.

5. The process as claimed in claim 1 , wherein said alkali metal compound is at least one selected from the group consisting of oxides, hydroxides, nitrate, carbonate, and chlorides of Li, Na, K, Rb, and Cs.

6. The process as claimed in claim 5 , wherein the alkali metal compound is selected from the group consisting of potassium carbonate (K 2 CO 3 ), potassium hydroxide (KOH), and potassium nitrate (KNO 3 ).

7. The process as claimed in claim 1 , wherein said solid carbonaceous feedstock is selected from petroleum coke, coal, biomass, wood, other solid carbon-containing materials, and mixtures thereof.

8. The process as claimed in claim 1 , wherein the temperature difference between said fluidized combustion zone and said fluidized gasification zone is at least 50° C.

9. The process as claimed in claim 1 , wherein carbon dioxide is used as a secondary gasifying agent.

10. The process as claimed in claim 1 , wherein oxygen or enriched air is fed to said gasification zone to aid the endothermic heat requirement.

11. The process as claimed in claim 1 , wherein said fluidized gasification zone and said fluidized combustion zone are operated in a fluidization regime selected from dense bed, bubbling bed, turbulent bed, fast fluidization bed, pneumatic transport, and entrained bed.

12. The process as claimed in claim 1 , wherein the flow pattern of said solid carbonaceous feedstock and said catalyst in said fluidized gasification zone and said fluidized combustion zone is selected from counter-current and co-current.

13. The process as claimed in claim 1 , wherein the catalyst and the unreacted carbon are separated from the synthesis gas in a cyclone separator, which are subsequently recycled to said fluidized gasification zone.

14. The process as claimed in claim 1 , wherein heat from the synthesis gas is extracted by exchanging heat with water to obtain steam.

15. The process as claimed in claim 1 , wherein heat from a flue gas generated in said fluidized combustion zone is extracted by exchanging heat with water to generate steam.

16. The process as claimed in claim 1 , wherein said synthesis gas in a weight proportion varying between 10 wt % to 50 wt %, with respect to the total weight of the synthesis gas is recycled to the fluidized gasification zone to alter the synthesis gas composition.

17. The process as claimed in claim 1 , wherein the synthesis gas comprises combustible gas in an amount of at least 70 wt %, said combustion gas is a mixture of hydrogen and carbon monoxide in a molar ratio of 3:1 to 1.5:1.

Assignees

• Reliance Industries Ltd

Inventors

• Daggupati Sateesh
• Mandal Sukumar
• Das Asit Kumar
• Sapre Ajit Vishwanath

Classifications

• B01J23/04 Primary

  Alkali metals · CPC title

• B01J27/25

  Nitrates · CPC title

• C10J2300/1807

  Recycle loops, e.g. gas, solids, heating medium, water · CPC title

• B01J29/40

  of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively · CPC title

• B01J29/084

  Y-type faujasite · CPC title