*5.3. Integrated Steel Mills*

To assess the techno-economic and environmental impact of decarbonization applied to iron and steel production, the next plant concepts were used as illustrative examples:

Case 3.1—Conventional steel mill without decarbonization;

Case 3.2—Decarbonized steel mill based on reactive gas-liquid absorption (MDEA);

Case 3.3—Decarbonized steel mill based on reactive gas-solid system (CaL).

As presented in Table 1, a conventional integrated iron and steel plant was considered in the assessments with 4 Mt/y hot-rolled coil (HRC) production capacity [3]. All assessed decarbonized steel concepts are not considering any import of heat and power (steel mill off-gases are used for this purpose). In this respect, natural gas was used as additional fuel to cover the ancillary energy consumptions [36]. The decarbonized steel mill concepts capture CO2 from the most significant plant units, e.g., captive power plant, blast furnace hot stoves, and lime coke production units. The most important performances of evaluated steel plants are exhibited in Table 5.

**Table 5.** Integrated steel mills techno-economic and environmental performance indexes.


As shown in Table 5, the decarbonization of main CO2 emitters (captive heat and power plant, blast furnace, lime and coke production units) from an integrated iron and steel production plant cut the overall carbon footprint significantly (with a reduction of about 60 to 70%). Considering the significant amount of greenhouse gas emission of this important industrial sector, this reduction is very substantial [36]. The investigated looping cycle has some important advantages in comparison to the chemical scrubbing system, e.g., higher energy conversion yield and subsequent lower decarbonization energy and cost penalties, integration of spent calcium-based sorbent in the iron and steel production process with a positive impact on plant environmental performance [37]. As for the above-presented cases (combustion and gasification-based power generation), the decarbonization process reduces carbon footprint but increases other environmental indicators [36].

Decarbonization of iron and steel production process brings an economic penalty (6–13% increase of specific capital investment, 12–18% increase of steel production cost). The economic indicators show that the calcium looping option has slightly better economic performance than post-combustion capture in terms of specific capital investment (reduced by about 6%), steel production cost (reduced by about 5%), and CO2 avoided cost (reduced by about 6%).
