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To solve the unreasonable energy distribution and excessive energy waste in the steam system of iron and steel (I&S) industry, a mixed integer linear programming model based on the theory of exergy and energy level is developed in this study to optimize the steam system. After optimization, the utilization potential of waste energy is found. Then, several waste energy recovery technologies are compared according to their application results. The results show that the exergy efficiency of steam system is 74.065%. After optimization, the exergy efficiency of steam system is increased by 10.568%, the energy input of the I&S enterprise is reduced by 84.30 MJ t−1‐CS−1, and waste energy potential is found at hot rolling, sintering, and converter. Herein, flue gas waste heat from hot rolling and sintering is recovered using series two‐stage Organic Rankine Cycle with cyclopentane as the working fluid, and steam waste energy from converter is recovered using saturated steam power generation. These waste energy technologies increase the electricity generation of I&S enterprise by 15.25 kWh t−1‐CS−1. Overall, combining the optimization model with the use of waste energy recovery technologies is necessary and effective for I&S enterprise to increase their energy efficiency. [ABSTRACT FROM AUTHOR]

Due to high material density, high energy consumption density and CO 2 emission density, it is not only difficult but significant to clarify the relationship between energy consumption, the CO 2 emission and the production cost in different conditions. However, the previous researches rarely refer how to balance the energy consumption, the CO 2 emission and the production cost after the fluctuation of material, energy and carbon price as well as what will happen to them if production structure changes. Therefore, based on the conservation law of mass and energy, to study iron and steel manufacturing process (ISMP), this paper, taking carbon price into consideration, establishes a muti-optimization model of energy consumption, CO 2 emission and cost. After optimization with different objectives, the production cost per tonne of crude steel is reduced by 192.03 CNY (7.71%), the CO 2 emission per tonne of crude steel is reduced by 224.22 kg (13.37%), and the energy consumption per tonne of steel is reduced by 51.20 kgce (9.10%). Moreover, based on the optimization results under different objectives, it is ironmaking process (coal ratio and ore ratio) and steelmaking process (amount of scrap steel) that has more impact on three above as well as ore blending and coal blending have a great influence on production cost but little effect on energy consumption and CO 2 emission. • The muti-objective optimization model of iron and steel industry is established. • The carbon price is considered during model establishment and analyzing. • The objective with energy consumption, CO 2 emissions and cost are optimized. • The factors affecting cost, energy consumption and CO 2 emission are discussed. [ABSTRACT FROM AUTHOR]

Towards the target of carbon neutrality, the need for deep decarbonization in iron and steel industry is increasingly recognized. Existing studies rarely mention the effects of collaboration with its source industries for carbon emission reduction in ISI. Furthermore, the fundamental laws of CO 2 emission reduction capacity with cost change of source substitutions for various steel production routes under market economics are unclear. To avoid the blind substitution of clean sources for meeting the urgent requirements for decarbonization in China's steel industry, which may result in increased carbon emissions and uneconomical carbon reduction from a lifecycle perspective. This paper integrates the production and utilization processes of source resources into the steel production process, establishes coupling models of carbon and value flows for four main types of steel production routes, and aims to quantitatively analyze the specific CO 2 emission reduction potential and costs. Three economic market development scenarios from 2021 to 2060 are set, and the marginal carbon prices of various source substitutions are determined. Subsequently, decarbonization pathways with the goal of minimizing production costs are developed. Finally. The future resource demand and the carbon emission reduction contributions of source industries collaborated are predicted. The results show that (1) about 81.7–89.9 % of CO 2 emissions could be reduced in the scenarios; (2) the demands of electric power and hydrogen energy will reach 54.48–511.90 BkWh and 7.47–10.31 Gt in 2060, respectively; and (3) collaboration with source industries could make 18.3–18.3% of CO 2 emission reduction contributions. All in all, this study could provide scientific support for the low-carbon transformation of China's steel industry. • Carbon and value flows of BF-BOF, Scrap-EAF, DRI-EAF, MOE-EAF routes are analyzed. • CO 2 emission reduction potential with marginal carbon price is determined. • Decarbonization paths during 2021–2060 for China's steel industry are developed. • Quantify the contribution of collaborative carbon reduction with source industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Exergy loss of enterprise is optimized by building mathematical programming model. • Influences of 9 key factors on system's total exergy loss and cost are discussed. • Recovery and utilization of waste heat are optimized by detailed technical models. • Waste heat potential and heating capacity of enterprise are evaluated. • Interface loss between upstream & downstream processes is quantified by exergy. A substantial quantity of waste heat resources generated in iron and steel manufacturing process (ISMP) can fulfill certain demand for urban heating. However, the waste heat utilization level of different iron and steel enterprises varies a lot and few studies have combined the upstream enterprise's production with downstream waste heat utilization for discussion. By establishing an optimization model based on material balance, thermodynamic laws and reaction mechanism of the ISMP, this study firstly obtain the minimum exergy loss and the corresponding production cost ＆ exergy efficiency. The total exergy loss of ISMP is reduced from 8413.19 MJ/t-MS to 7669.27 MJ/t-MS. The exergy efficiency of the whole process is increased from 63.75 % to 65.46 % and the total waste heat potential reaches 1471.25 MJ/t-MS. It is found that coke ratio, air leakage rate, scrap steel ratio, etc. have great impact on exergy loss of ISMP. Then, the optimization and evaluation of the waste heat utilization are carried out by establishing models with taking urban heating into consideration. The available external heat supply is 813.15 to 853.55 MJ/t-MS and the enterprise's heating load can reach 229.23–251.47 MW, which allow to supply heat for an area of 5.46–5.93 million m2. Finally, the problem of waste heat instability in the heating process is briefly discussed and some solution strategies are proposed to overcome this defect. [ABSTRACT FROM AUTHOR]