A METHOD FOR THE REDUCTION OF METHANOL EMISSION FROM AN AMMONIA PLANT

Abstract

In a method for the reduction of methanol emission from an ammonia plant, a chilled methanol-containing feed gas is fed to a methanol absorber, carbon dioxide is separated from the gas phase leaving the methanol absorber, the methanol-containing gas is fed to a final separator, and the chilled, methanol-free process condensate from the final separator is used to wash out the methanol in a scrubbing column. By cooling the streams to the column and inserting a number of individual wash trays in the column, a practically quantitative removal of methanol is possible.

Claims

1. A method for the reduction of methanol emission from an ammonia plant, wherein the methanol-containing feed gas is cooled and fed into a methanol absorber, a cooled, methanol-free aqueous stream is used to absorb the methanol in the feed stream, the methanol-lean gas is leaving the methanol absorber in the top and routed to downstream processing, preferably a CO.sub.2 removal, and the methanol-rich aqueous stream is leaving the methanol absorber in the bottom and routed to further processing elsewhere in the plant.

2. Method according to claim 1, wherein the CO.sub.2-free gas from the CO.sub.2 removal is passed through a final separator to obtain a methanol-free process condensate.

3. Method according to claim 2, wherein the methanol-free process condensate is cooled and then used to wash out the methanol in the methanol absorber.

4. Method according to claim 3, wherein a small amount of a cooled, regenerated process condensate is added to the cooled, methanol-free process condensate from the final separator before washing out the methanol.

5. Method according to claim 1, wherein the streams are cooled down to a suitable low temperature for the absorption of methanol and a number of wash trays are inserted in the methanol absorber.

Description

[0022] The attached FIGURE shows a possible equipment design for the reduction of methanol emission from an ammonia plant by the method of the invention, said design comprising a feed gas chiller (1), which provides the necessary cooling of the methanol-containing feed gas. The cooled gas is passed to a methanol absorber (2), where methanol is separated off. Then the gas phase from the methanol absorber is fed to a carbon dioxide removal section (3), and the CO.sub.2-free gas is passed to a final separator (4), thereby obtaining a methanol-free process condensate. This process condensate is mixed with a stripped process condensate (5) and passed to the methanol absorber (2) via a wash water chiller (6).

[0023] Calculations have shown that, even in the worst case, a practically quantitative removal of methanol is possible if the streams to the column are cooled down to around 5 C. and ten wash trays are inserted in the column. If a catalyst with an ability to inhibit by-product formation is used and/or the environmental restrictions are less strict, the number of wash trays in the column can be reduced.