Energy, safety, and absorption efficiency evaluation of a pilot-scale H2S abatement process using MDEA solution in a coke-oven gas

Abstract

This study models an H2S removal unit for steel-manufacturing coke-oven gas and suggests optimal operating conditions and safety analysis for absorption and regeneration columns. Sensitivity analysis was performed on H2S removal to identify the minimum methyldiethanolamine (MDEA) solution flow rate using 99% H2S removal as a constraint and minimal heat duty. The optimized L/G ratio and regeneration column pressure were investigated accordance with change in H2S emission limit or desulfurization efficiency (99-99.9%), to reflect the different usage of COG. For the absorption column, the MDEA solution and heating duty were expected to be reduced in optimal conditions by 35% and 23% respectively when absorbent to gas mass ratio was decreased from 2.0 to 1.3, respectively. The most effective operating pressure for the distillation column was 2.5 bar (Basis pressure: 1.2 bar) based on a trade-off between reboiler energy and the H2S remaining in the recycle stream. According to optimization result with variation in efficiency, the higher optimized L/G ratio, higher reboiler duty, higher intermediate heat exchanger duty, and lower optimized regenerator pressure were required to maintain higher efficiency with different COG utilization. To ensure safe operating conditions, chemical reactivity tests were conducted for mixture of chemicals. Additionally, Gas dispersion analysis predicted the concentration and distance of gas spread to ensure safety from gas leak accident.