Abstract
Carbon dioxide capture technology using ceramic absorbent (lithium silicate) has been developed by Toshiba Corporation and Toshiba Mitsubishi-Electric Industrial Systems Corporation to reduce CO2 emissions and help alleviate global warming. A system containing a steam reforming catalyst and a CO2 absorbing ceramic is being considered for application to an industrial-scale boiler system. The following reactions take place in this system.
Reforming reaction : CH4 + H2O = CO + 3H2 - 209 kJ
Steam shift reaction: CO + H2O = CO2 + H2 + 44 kJ
Absorption reaction : CO2 + Li4SiO4 = Li2CO3 + Li2SiO3
The carbon from the fuel (natural gas) is removed in the initial step and hydrogen-rich gas is fed back to the boiler system as fuel. This system has the following 3 advantages: (1) the CO2 removal efficiency is higher than in a post-combustion capture system, because the CO2 concentration is higher than flue gas, (2) the reforming reaction can be carried out efficiently at a lower temperature because the reforming reaction equilibrium shifts to the right side as a result of CO2 absorption and (3) the energy consumption is lower because part of the energy required for the endothermic reforming reaction is obtained from the energy released by the exothermic CO2 absorption reaction. To demonstrate the feasibility of this CO2 removal system, the reaction efficiency of a packed-bed reactor containing a reforming catalyst and absorbing ceramic was studied.
