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. 2021 Nov 29:1:141.
doi: 10.12688/openreseurope.14275.1. eCollection 2021.

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

Manuel Bailera  1   2 , Takao Nakagaki  3 , Ryoma Kataoka  4
Affiliations

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

Manuel Bailera et al. Open Res Eur. .

Abstract

Background: The Rist diagram is useful for predicting changes in blast furnaces when the operating conditions are modified. In this paper, we revisit this methodology to provide a general model with additions and corrections. The reason for this is to study a new concept proposal that combines oxygen blast furnaces with Power to Gas technology. The latter produces synthetic methane by using renewable electricity and CO 2 to partly replace the fossil input in the blast furnace. Carbon is thus continuously recycled in a closed loop and geological storage is avoided. Methods: The new model is validated with three data sets corresponding to (1) an air-blown blast furnace without auxiliary injections, (2) an air-blown blast furnace with pulverized coal injection and (3) an oxygen blast furnace with top gas recycling and pulverized coal injection. The error is below 8% in all cases. Results: Assuming a 280 t HM/h oxygen blast furnace that produces 1154 kg CO2/t HM, we can reduce the CO 2 emissions between 6.1% and 7.4% by coupling a 150 MW Power to Gas plant. This produces 21.8 kg/t HM of synthetic methane that replaces 22.8 kg/t HM of coke or 30.2 kg/t HM of coal. The gross energy penalization of the CO 2 avoidance is 27.1 MJ/kg CO2 when coke is replaced and 22.4 MJ/kg CO2 when coal is replaced. Considering the energy content of the saved fossil fuel, and the electricity no longer consumed in the air separation unit thanks to the O 2 coming from the electrolyzer, the net energy penalizations are 23.1 MJ/kg CO2 and 17.9 MJ/kg CO2, respectively. Discussion: The proposed integration has energy penalizations greater than conventional amine carbon capture (typically 3.7 - 4.8 MJ/kg CO2), but in return it could reduce the economic costs thanks to diminishing the coke/coal consumption, reducing the electricity consumption in the air separation unit, and eliminating the requirement of geological storage.

Keywords: Blast furnace; CO2; Carbon capture; Oxyfuel combustion; Power to Gas; Rist diagram; ironmaking; operating diagram.

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Conflict of interest statement

No competing interests were disclosed.

Figures

Figure 1.
Figure 1.. Schematic diagram of a blast furnace and its typical temperature profile.
Figure 2.
Figure 2.. Rist diagram.
Figure 3.
Figure 3.. Equilibrium of the Fe-O-C and Fe-O-H systems.
The variable ω stands for n CO2/(n CO+n CO2) in the case of ω WC and ω MC , and for n H2O/(n H2+n H2O) in the case of ω WH and ω MH .
Figure 4.
Figure 4.. Conceptual diagram of a blast furnace, indicating the input and output data of the model.
Figure 5.
Figure 5.. Operating lines obtained from the Data sets 1, 2 and 3 ( Table 3 and Table 4).
Figure 6.
Figure 6.. Conceptual schemes summarizing the mass flows and relative errors obtained during the validation of the model for Data set 1, 2 and 3 (the complete data sets are presented in Table 3 and Table 4).
Figure 7.
Figure 7.. Conceptual schemes summarizing the mass flows obtained for Data sets 4, 5 and 6 (see Table 4).
Figure 8.
Figure 8.. Operating lines of oxygen blast furnaces, obtained from Data sets 4, 5 and 6 ( Table 4).
See this image and copyright information in PMC

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