Method for gasification of carbon-containing materials by thermal decomposition of methane and conversion of carbon dioxide
The present invention relates to a method for gasification of carbon-containing materials, and more specifically, to a method for gasification of carbon-containing materials which allows an increase in carbon efficiency and a reduction in carbon dioxide emission, comprising the steps of: gasification of carbon-containing materials to methane; thermal decomposition of CH 4 to C and H 2 ; and conversion of CO 2 to CO using the carbon produced during the decomposition. The method of the present invention greatly increases carbon efficiency and reduces the generation of carbon dioxide.
1. A method of gasifying a carbon-containing material, comprising:
i) reacting the carbon-containing material with steam in the presence of a catalyst comprising a hydroxide, an oxide or a salt of an alkali metal or an alkaline earth metal, or a mixture thereof, to produce a gas product including CO, CO 2 , CH 4 , H 2 O and H 2 , in which the ratio of steam to carbon is in a range of 1 to 2;
ii) thermally decomposing CH 4 generated in step i) into elemental carbon and H 2 , with at least a part of the elemental carbon generated being recirculated to step i); and
iii) converting CO 2 generated in step i) into (a) CO through a reverse water-gas shift reaction, a CO 2 reforming reaction, or a C—CO 2 gasification reaction, and/or (b) into —(CH 2 ) n — or CH 3 OH through a CO 2 hydrogenation reaction using the product of step i) or step ii);
wherein 30 to 70% of the total amount of H 2 and CO contained in the as product of step i) is recirculated back to step i).
2. The method of claim 1 , further comprising recirculating H 2 generated in step ii) back to step i).
3. The method of claim 2 , further comprising recirculating H 2 and CO generated in step iii) back to step i).
4. The method of claim 1 , further comprising recirculating H 2 and CO generated in step iii) back to step i).
5. The method of claim 1 , further comprising performing gas separation, after step i) which gasifies the carbon-containing material.
6. The method of claim 1 , further comprising performing a water-gas shift reaction, after step iii).
7. The method of claim 1 , wherein the carbon-containing material is coal, biomass, waste, heavy oil, or petroleum coke.
8. The method of claim 1 , wherein the gas product except for H 2 O generated in step i) comprises 20 to 25 vol. % of CH 4 , 20 to 25 vol. % of CO 2 and a remainder of H 2 and CO, the ratio of H 2 /CO being in a range of 1 to 4.
9. The method of claim 1 , wherein the carbon efficiency is in a range of 63 to 73%.
10. The method of claim 1 , wherein the amount of CO 2 generated is 0.4 mol CO 2 /mol C or less.