COAL-BASED AMMONIA PLANT OPERATION.

This report describes an ammonia plant whch was brought on stream in 1974 in South Africa. This 1,100 ton/day coal-based plant is based on the Koppers-Totzek low-pressure, high-temperature, coal gasification process. In this system, oxygen for the gasifiers is supplied from a single-stream air separation unit. Coal dust, produced in two large ring and ball mills, is gasified in six gasifiers. The gas is compressed and desulfurized by washing with methanol at minus 36 degree F at a pressure of about 30 atmospheres. Desulfurized gas containing about 58% CO is reacted with steam over conventional iron high temperature shift catalyst to produce hydrogen. Carbon dioxide is removed from the gas by washing with methanol at minus 72 degree F at a pressure of about 51 atmospheres. Among the problems encountered during startup were valve and joint failures, a dust bunker explosion, and erosion from ash particles impinging on boiler tubes. These problems as well as toxic gas hazards and environmental impact are detailed.