Process to Produce a Methane Rich Gas Mixture From Gasification Derived Sulphur Containing Synthesis Gases

Abstract

A method for converting a raw gas into a methane-rich and/or hydrogen-rich gas includes the following steps: a) providing the raw gas stemming from a coal and/or biomass gasification process, thereby the raw gas comprising beside a methane and hydrogen content carbon monoxide, carbon dioxide, alkanes, alkenes, alkynes, tar, especially benzole and naphthalene, COS, hydrogen sulfide and organic sulfur compounds, especially thiophenes; thereby the ratio of hydrogen to carbon monoxide ranges from 0.3 to 4; b) bringing this raw gas into contact with a catalyst in a fluidized bed reactor at temperatures above 200° C. and at pressures equal or greater than 1 bar in order to convert the raw gas into a first product gas, thereby simultaneously converting organic sulfur components into hydrogen sulfide, reform tars, generate water/gas shift reaction and generate methane from the hydrogen/carbon monoxide content; c) bringing the first product gas into a sulfur absorption process to generate a second product gas, thereby reducing the content of hydrogen sulfur and COS from 100 to 1000 ppm down to 1000 ppb or less; d) optionally bringing the second product gas into a carbon dioxide removal process to generate a third product gas at least almost free of carbon dioxide; e) bringing the third product gas into a second methanation process to generate a fourth product gas having a methane content above 5 vol %; f) optionally bringing the fourth product gas into a carbon dioxide removal process to generate a fifth product gas at least almost free of carbon dioxide g) bringing the fifth product gas into an hydrogen separation process in order to separate a hydrogen rich gas from a remaining methane-rich gas, called substitute natural gas.

1 - 15 . (canceled) 
     
     
         16 . A process for producing a methane-rich gas mixture for further application in high temperature fuel cells or for manufacturing synthetic natural gas (SNG) from gasification-derived synthesis gas mixtures that contain at least some compounds problematic to conventional methanation units, the process which comprises.
 at least one unit allowing for methanation, water gas shift reaction, and for converting most or parts of the problematic compounds to less problematic compounds by one or more of the following.
 hydrodesulphurization of organic sulfur species; 
 hydrodenitrogenation of organic nitrogen species; 
 hydrogenation or reformation of alkanes, alkenes, and alkynes; and 
 hydrogenation, reforming or cracking of hydrocarbons; 
   the unit being operated at temperatures between 200° C. and 900° C. and at pressures between 0.8 bara and 70 bara; and   the unit including a catalyst containing metals forming an active phase selected from the group consisting of molybdenum, cobalt, ruthenium, nickel, tungsten or sulfides thereof, and the active phase metals being supported on materials containing one or more materials selected from the group consisting of aluminum, silicon, titanium, zirconium, cerium, gadolinium, manganese, vanadium, lanthanum, chromium, or oxides thereof.   
     
     
         17 . The process according to  claim 16 , wherein the problematic compounds are compounds selected from the group consisting of organic sulfur or nitrogen compounds, alkanes, alkenes, alkynes, aromatic hydrocarbons or non-aromatic hydrocarbons 
     
     
         18 . The process according to  claim 17 , wherein the aromatic hydrocarbons are selected from the group consisting of naphthalene, toluene, benzene, and phenols. 
     
     
         19 . The process according to  claim 16 , which comprises carrying out the process in a fluidized bed reactor with catalyst particles having a size in a range from 20 to 2000 μm. 
     
     
         20 . The process according to  claim 19 , which comprises controlling a temperature with heat transfer means. 
     
     
         21 . The process according to  claim 19 , which comprises controlling a temperature of the process with heat transfer means in the fluidized bed reactor. 
     
     
         22 . The process according to  claim 16 , which comprises feeding additional hydrogen into the process. 
     
     
         23 . The process according to  claim 22 , which comprises feeding the additional hydrogen from a recycle stream at the top of the reactor, at the bottom of the reactor, and/or in between. 
     
     
         24 . The process according to  claim 22 , which comprises feeding the additional hydrogen into the process as secondary injection into a fluidized bed. 
     
     
         25 . The process according to  claim 16 , which comprises feeding additional steam into the process, by feeding at the top of the reactor, at the bottom of the reactor, and/or in between. 
     
     
         26 . The process according to  claim 25 , which comprises feeding the additional steam into the process as secondary injection into a fluidized bed. 
     
     
         27 . The process according to  claim 16 , which comprises processing in an additional bed of active carbon, ZnO, or other metal oxides for removing undesired species including H 2 S and COS. 
     
     
         28 . The process according to  claim 27 , which comprises effecting a water removal process prior to the bed of active carbon, ZnO or other metal oxides to enhance a separation efficiency (e.g., by means of a membrane). 
     
     
         29 . The process according to  claim 16 , which comprises additionally removing carbon dioxide. 
     
     
         30 . The process according to  claim 16 , which comprises additionally feeding in steam, followed by a second methanation step. 
     
     
         31 . The process according to  claim 16 , which comprises additionally feeding in steam, followed by a second methanation step carried out in a fluidized bed reactor. 
     
     
         32 . The process according to  claim 30 , which comprises additionally removing carbon dioxide. 
     
     
         33 . The process according to  claim 16 , which comprises additionally removing water. 
     
     
         34 . The process according to  claim 16 , which comprises additionally removing hydrogen. 
     
     
         35 . The process according to  claim 34 , which comprises returning the hydrogen removed in the additional removal step in a recycle stream fed into the first methanation unit. 
     
     
         36 . A method for converting a raw gas into a methane-rich and/or hydrogen-rich gas, which comprises the following steps.
 a) providing raw gas originating from a coal and/or biomass gasification process, the raw gas including a content of methane and hydrogen and a content of carbon monoxide, carbon dioxide, alkanes, alkenes, alkynes, tar, COS, hydrogen sulfide, and organic sulfur compounds; wherein a ratio of hydrogen to carbon monoxide ranges from 0.2 to 5;   b) bringing the raw gas into contact with a catalyst arranged as a fluidized bed reactor at temperatures above 200° C. and at pressures equal or larger than 1 bar in order to convert the raw gas into a first product gas, thereby simultaneously converting organic sulfur components into hydrogen sulfide, reform tars, generating water/gas shift reaction, and generating methane from the hydrogen/carbon monoxide content;   c) introducing the first product gas into a sulfur absorption process to generate a second product gas, thereby reducing a content of hydrogen sulfur and COS from 100 to 1000 ppm down to 1000 ppb or less;   d) optionally bringing the second product gas into a carbon dioxide removal process to generate a third product gas substantially or completely free of carbon dioxide;   e) introducing the third product gas into a second methanation process to generate a fourth product gas having a methane content above 5 vol %;   f) optionally bringing the fourth product gas into a carbon dioxide removal process to generate a fifth product gas substantially or completely free of carbon dioxide; and   g) introducing the fifth product gas into an hydrogen separation process in order to separate a hydrogen rich gas from a remaining methane-rich gas (substitute natural gas).   
     
     
         37 . The method according to  claim 36 , wherein the raw gas contains at least one of benzole, naphthalene, and thiophenes.