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Carbon monoxide production using a steel mill gas in a combined chemical looping process

2021; Elsevier BV; Volume: 68; Linguagem: Inglês

10.1016/j.jechem.2021.12.042

2096-885X

Varun Singh, Lukas C. Buelens, Hilde Poelman, Mark Saeys, Guy Marin, Vladimir Galvita,

Carbon Dioxide Capture Technologies

Up to 9% of the global CO2 emissions come from the iron and steel industry. Here, a combined chemical looping process to produce CO, a building block for the chemical industry, from the CO2-rich blast furnace gas of a steel mill is proposed. This cyclic process can make use of abundant Fe3O4 and CaO as solid oxygen and CO2 carriers at atmospheric pressure. A proof of concept was obtained in a laboratory-scale fixed bed reactor with synthetic blast furnace gas and Fe3O4/CaO = 0.6 kg/kg. CO production from the proposed process was investigated at both isothermal conditions (1023 K) and upon imposing a temperature program from 1023 to 1148 K. The experimental results were compared using performance indicators such as CO yield, CO space time yield, carbon recovery of the process, fuel utilisation, and solids’ utilisation. The temperature-programmed CO production resulted in a CO yield of 0.056 ± 0.002 mol per mol of synthetic blast furnace gas at an average CO space time yield of 7.6 mmol kgFe−1 s−1 over 10 cycles, carbon recovery of 48% ± 1%, fuel utilisation of 23% ± 2%, and an average calcium oxide and iron oxide utilisation of 22% ± 1% and 11% ± 1%. These experimental performance indicators for the temperature-programmed CO production were consistently better than those of the isothermal implementation mode by 20% to 35%. Over 10 consecutive process cycles, no significant losses in CO yield were observed in either implementation mode. Process simulation was carried out for 1 million metric tonnes per year of equivalent CO2 emissions from the blast furnace gas of a steel mill to analyse the exergy losses in both modes of operation. Comparison of the exergy efficiency of the temperature-programmed process to the isothermal process showed that the former is more efficient because of the higher CO concentration achievable, despite 20% higher exergy losses caused by heat transfer required to change temperature.