(60b) Plant-Wide Simulation of Ethanol Oxidation Process for Acetic Acid Production

Acetic acid is an important chemicals that is widely used in manufacturing for many products, such as medicine, photographic film, synthetic fiber, food additives, and paint. The annual global demand of acetic acid is about 6.5 million tons.  There are three major processes for acetic acid productions: i) low-pressure carbonylation of methanol synthesis process, which employs methanol and carbon monoxide reaction to produce acetic. It is currently most popular method for acetic acid production. ii) Ethylene oxidation process, where ethylene is oxidized to acetaldehyde first, and then further oxidized to acetic acid. iii) Ethanol oxidation process, where acetaldehyde is prepared by ethanol oxidation, and then acetaldehyde is oxidized to acetic.

In this study, a plant-wide model for ethanol oxidation process to produce acetic acid is developed by using Aspen Hysys.  The modeled process is divide into two main sections: the ethanol oxidization to acetaldehyde process and the acetaldehyde oxidization to acetic acid process.  In the first section, the raw feeds of ethanol and water is mixed, evaporated, and directed to a reactor for oxidation.  Besides the major product of acetaldehyde, there are some byproducts of CO,CO₂, methane, tr-Crotonal, small quantity of acetic acid  as well as unreacted materials.  After the reaction, the outflow goes to an absorber system to separate the insoluble gases from the liquid.  Next, the liquid effluent enter two distillation columns to separate unreacted ethanol for recycle and the byproduct of formaldehyde, as well as obtain the high-purity acetaldehyde.  In second manufacturing section, the enriched acetaldehyde, air, and the catalyst of manganese acetate are sent into a distillation column for oxidation reaction and separation. then the bottom outflow goes to a distillation column to get the product of acetic acid, while the light component goes to another two distillations to separate oxidation byproduct of lipid and recycle unreacted acetaldehyde.  The recycled acetaldehyde goes back to the oxidation column.  We simulate the entire plant with these both process in steady-state model first, and obtain the simulation results agreeing well with real plant data. Then some critical sections are further examined by dynamic models to examine the process control ability.  Some valuable process and control knowledge have been disclosed by our simulations, which can provide more technical support for plant future manufacturing.