CO2 Recycling in the Iron and Steel Industry via Power-to-Gas and Oxy-Fuel Combustion

Abstract

The iron and steel industry is the largest energy-consuming sector in the world. It is responsible for emitting 4–5% of the total anthropogenic CO2. As an energy-intensive industry, it is essential that the iron and steel sector accomplishes important carbon emission reduction. Carbon capture is one of the most promising alternatives to achieve this aim. Moreover, if carbon utilization via power-to-gas is integrated with carbon capture, there could be a significant increase in the interest of this alternative in the iron and steel sector. This paper presents several simulations to integrate oxy-fuel processes and power-to-gas in a steel plant, and compares gas productions (coke oven gas, blast furnace gas, and blast oxygen furnace gas), energy requirements, and carbon reduction with a base case in order to obtain the technical feasibility of the proposals. Two different power-to-gas technology implementations were selected, together with the oxy blast furnace and the top gas recycling technologies. These integrations are based on three strategies: (i) converting the blast furnace (BF) process into an oxy-fuel process, (ii) recirculating blast furnace gas (BFG) back to the BF itself, and (iii) using a methanation process to generate CH4 and also introduce it to the BF. Applying these improvements to the steel industry, we achieved reductions in CO2 emissions of up to 8%, and reductions in coal fuel consumption of 12.8%. On the basis of the results, we are able to conclude that the energy required to achieve the above emission savings could be as low as 4.9 MJ/kg CO2 for the second implementation. These values highlight the importance of carrying out future research in the implementation of carbon capture and power-to-gas in the industrial sector.

Revisiting the Rist diagram for predicting operating conditions in blast furnaces with multiple injections

“…Thus, in overall terms, the CO 2 is diminished by 71 kg CO2 /t HM with respect to the base case by using 1.93 GJ/t HM of electricity in the electrolyzer, so the energy penalty of the CO 2 avoidance is 27.1 MJ/kg CO2 . This value is line with the results of Perpiñán et al 8 for similar PtG integrations in the steel industry (he reported 34 MJ/kg CO2 ). Actually, since we have cut the coke consumption by 22.8 kg/t HM , which, in terms of electricity, is equivalent to a reduction of 0.24 GJ/t HM (assuming a coke heating value of 27.3 MJ/kg and a subcritical power plant net efficiency of 38% 31 ), and additionally we diminished the O 2 that has to be produced in the air separation unit by 77 kg O2 /t HM (we need inject 10 kg O2 /t HM more than in the base but we have 87 kg O2 /t HM available from electrolysis), which translates into a reduction of 0.05 MJ/t HM of electric consumption (assuming a typical ASU specific consumption of 0.61 MJ/kg O2 32 ), the net energy penalization of the CO 2 avoidance becomes 23.1 MJ/kg CO2 .…”

“…Since water electrolysis of the PtG process by-produces O 2 , it allows diminishing the electricity consumption of the air separation unit that feeds the OBF. A first approach to this OBF–PtG system was studied by Perpiñán et al 8 by using overall energy and mass balances. Assuming 430 MW electrolysis power capacity, they found a CO 2 emission reduction of 8% and specific electricity consumptions of 34 MJ/kg CO2 .…”

Valorizing Steelworks Gases by Coupling Novel Methane and Methanol Synthesis Reactors with an Economic Hybrid Model Predictive Controller

“…The main studies on methanation from steelworks POGs refer to use of COG [43,44], which, however, decreases the availability of the most suitable POG for internal heating and power production. Furthermore, only preliminary investigations can be found on the use of BFG and BOFG [45,46], including some works of the authors that were the basis of the investigation presented in this work [47,48].…”

Comparing different syngas for blast furnace ironmaking by using the extended operating line methodology

“…Because of the requirement of high-temperature heat (above 800-1200 • C) and the nature of the process itself (CO 2 release during reduction), the blast furnace ironmaking process cannot be decarbonized with electrification [8]. Within this framework, some authors have studied the utilization of syngas and renewable fuels in the blast furnace [8][9][10]. Syngas is a CO 2 -neutral fuel gas that is synthetically obtained and is commonly constituted of carbon monoxide, hydrogen and carbon dioxide (the CO 2 -neutrality extent will depend on the raw material used for the syngas production).…”