Life cycle assessment of coke production based on real plant and model-optimised data

Abstract Purpose Coke production is essential for the iron and steel industry, but this process can release several pollutants into the air, soil, and water, which cannot be ignored. Moreover, coke oven gas purification requires additional energy and auxiliary materials, resulting in significant indirect emissions. The purpose of this study to assess the environmental impact of coke production based on the data of a real coking plant and compare four different operation scenarios using model optimised data. Method The “cradle to gate” life cycle assessment of the investigated coking plant were conducted by subdivision method. The functional unit was determined as the production of 1 ton of coke. Four scenarios were compared in this research work. The first one assumed normal operating conditions (scenario 1), the second one assumed environmentally optimised conditions as defined by the steady-state model of the gas purification technology (scenario 2), the third one assumed energetically optimised conditions as also defined by the model (scenario 3), and the fourth one assumed no gas purification technology at all (scenario 4). The study was performed using Sphera’s Life cycle assessment software (formerly known as GaBi) based on ISO 14040 and ISO 14044 standards, and nine environmental impact categories were considered. Results and discussion Besides coke production, transportation and gas purification had the most highest relative impact in most categories, with an average of 32%, 20%, and 12%, respectively. Among the input auxiliary materials, electricity contributed the most to the investigated categories (avg. 62%), followed by steam (avg. 26%) and process water (avg. 11%). The comparative analysis revealed that, compared to the base scenario, the energetically optimised scenario had the lowest environmental impact in the most considered categories (e.g. GWP decreased from 546.54 to 544.15 kg CO 2 eq). The optimisation reduces the energy demand of the plant, while the pollutant emissions do not exceed the standards; therefore, the direct emissions do not lead to a significant increase in environmental impact. The sensitivity analysis shows that a 10% reduction in electricity consumption significantly decreases the environmental impact of all the sub-processes. Conclusions This is the first study to perform a coke production life cycle assessment using optimised data calculated by a process simulator alongside real plant data. Through this, the intention was to provide valuable insights into the environmental significance of coke oven gas cleaning technology.