Abstract
A novel configuration of the Ca–Cu looping process is proposed for the production of a H2-enriched fuel gas by means of the sorption enhanced water gas shift (SEWGS) of blast furnace gas (BFG) in steel mills. CO2 is simultaneously removed from the gas using a CaO-based sorbent. A Cu/CuO chemical loop supplies the energy required for the regeneration of the sorbent via the exothermic reduction of CuO with coke oven gas (GOG). The process is carried out in an arrangement of interconnected fluidized-bed reactors operating at atmospheric pressure, which allows for a solids' segregation step to be introduced that will reduce significantly the solid circulation between reactors A reference case study is presented, where the SEWGS is operated at 600 °C and the regeneration of the sorbent at 870 °C. About 27% of the BFG can be decarbonized in the SEWGS reactor producing 110 Nm3 of H2 per tonne of steel. A CO2 capture ratio of 31% with respect to the total carbon emissions in the steel mill can be achieved. More than 60% of the thermal input can be recovered as high-temperature heat, which could be efficiently recovered for producing electricity.
Highlights
A drastic reduction in anthropogenic CO2 emissions is needed before 2050 in order to achieve the climate change mitigation targets [1] that have been set as long term objectives after COP21
Apart from the H2 produced, more than 60% of the thermal input of the Ca-Cu process ends as high temperature heat generated in the sorption enhanced water gas shift (SEWGS) reactor and as sensible heat in the exhaust gases that could be efficiently recovered by producing high pressure steam to generate electricity in the steel mill power plant
The assumed SEWGS operating temperature of 600°C and S/C=1 must be reasonably close to an economic optimum because they allow CO2 capture efficiency from the blast furnace gas (BFG) of about 95% with moderate steam consumption and at a temperature where both WGS and CaO carbonation are known to be sufficiently fast [13, 86, 95]
Summary
A drastic reduction in anthropogenic CO2 emissions is needed before 2050 in order to achieve the climate change mitigation targets [1] that have been set as long term objectives after COP21. The process is carried out in an arrangement of fluidized-bed reactors, in which a solids segregation step is introduced in order to obtain separately the CaO required for the ironmaking process and to improve the performance of the process since the copper-based particles would act as thermal ballast in the SEWGS stage, as explained below This novel configuration has been envisaged to reach a substantial reduction of carbon emissions in the steelmaking process if the rich streams of CO2 generated in the process are purified and safely stored. A sensitivity analysis of the main operating parameters has been carried out to demonstrate the theoretical viability of the process and to determine the operational window that will ensure optimal performance in terms of energy and CO2 capture efficiency
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