Design and optimization of VOC control process for tail gas in Rectisol unit based on steady state and dynamic simulation

Rectisol wash process(RWP) is a common process in coal chemical purification unit. However, the CO₂ product gas and tail gas in the RWP carries volatile organic methanol, which must be controlled to meet the environmental protection requirements. This work develops a steady and dynamic model for the process of water washing tower(WWT) by Aspen Plus, which is used in Rectisol wash tail gas treatment. The effects of the theoretical stage number(TSN) and desalting water flow rate(FR_dw) of the washing tower on the methanol concentration in tail gas(c_MET) are studied through sensitivity analysis. The optimized TSN and FR_dw of WWT are 16 stages and 15 t/h, respectively. The c_MET is 4.1 mg/Nm³ under the optimal condition. The internal structure of WWT is optimized. The design of the WWT is verified by the hydraulic results and dynamic process simulation. The results help to efficiently and conveniently implement the control of volatile organic methanol from RWP.