Multi-objective optimization of water consumption for a methanol synthesis process

Methanol is an important product in chemical industries, having many applications: solvent, fuel and mainly being a feedstock for a large number of industrial processes. As the search for a more sustainable synthesis process grows, the methanol synthesis loop from synthesis gas was studied. In this work, an optimization based on an environmental objective function was developed to reduce the total water consumption of the plant. The methanol synthesis plant and the utility plants of a cooling water system and steam generation cycle were modeled and simulated. A multi-objective optimization study was performed to obtain the optimal trade-off between the economic performance and the reduced water usage. Two distinct scenarios were considered: the integrated use of the steam produced in the reactor cooling and its exporting for profits. The results show that the optimized green design can reduce up to 18% of the water consumed by the process. The exported steam case study provided more economic benefits, while the integrated steam case attained a smaller water consumption indicator.