Schematic Acetic Acid Plant.





PROCESS. A process for acetic acid production by a continuous high pressure from methanol and carbon monoxide.

The conversion takes place at about 250°C and 650atm in liquid phase in the presence of water. The catalyst is dissolved cobaltous iodine.

The over all reaction is as follows :

Methanol   Carbon monoxide   Acetic Acid
2CH3OH + CO =====> CH3COOH

also, could be
Dimethyl ether   Water   Carbon monoxide   Acetic Acid
CH3OCH3 + H2O + 2CO =====> 2CH3COOH


In the Reactor

The reactor is continuously supplied with a feed containing methanol and carbon monoxide.

530 000kcal per ton of acetic acid produced is released during the reaction, which is absorbed (heat exchange) by the cold feed and gas.

A slight heat deficit is compensated by pre-heating the feed to 40-80°C. The crude acid and the unreacted gas are withdrawn at the top of the reactor and, afer cooling, expanded down to 10atm gage in the medium-pressure section.

In the Vent Gas Wash Column

Methyl iodine in unreacted gas is recovered by washing the vent gas with the feed methanol. The methanol is conbined with other components forming the feed without any further treatment, and the washed gas is used for fuel.

In the Separator 1

The acetic acid and the byproducts having a highter boiling point than acetic acid are separated from the crude acid and withdrawn. All the other components of the crude acid are mixed the methanol leaving the vent gas wash column. The mixture is supplied continuously to the reactor as feed.

In the Degasser-Separator 2-Catalizer Separator

The crude acid is degassed and freed from low-boilng components in a first distillation and then in the catalyst separation freed from cobaltous iodine that is removed from the column in aqueous acetic solution as bottoms.

In the Dehydrator

The catalyst-free crude acid is dehydrated and purified in the dehydrator column by means of azeotropic distillation.

The entrainer used is a steam volatile byproduct mixture which is formed in the reaction and which separates in the separator 2 as the upper phase.

In the Purifier

In the bottom of the dehydrator column acetic acid free of water and formic acid is recovered which is processed in the following two columns to pure acetic acid of over 99.8% purity, and a byproduct mixture that is free of acetic acid.

The synthesis and distillation sections are completely automated from a central control room and can be controlled by one operator.

For every 100Kg of acetic acid produced, 2 Kg of propionic acid and 2Kg of higher compounds are produced as byproducts


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