Ammonia Production from Coal

The process under analysis comprises three major sections: (1) Coal Gasification; (2) Raw Syngas Purification; and (3) Ammonia Synthesis.

Coal Gasification. Initially, coal and limestone are received from the storage area, prepared, metered, mixed and conveyed to the gasifier. As coal is fed to the gasifier, it dries due to the vaporization of water and undergoes pyrolysis, producing coke. Steam and oxygen are fed to the gasifier and react with the char, producing mainly carbon monoxide and carbon dioxide. The gasification reactions are carried out at high temperatures (700°C) and medium pressures (3 – 4 MPa), with gaseous reaction products ascending countercurrent to the coal introduced in the gasifier.

Raw Syngas Purification. The outlet from the gasification is fed to a two-stage high and low temperature reactors, where the bulk of the carbon monoxide is converted into carbon dioxide and hydrogen. The shifted gas is then cooled through a series of heat exchangers, in such a way that water present in the gas condenses and is removed. Mercury and other contaminants still present in the gas stream are removed by means of a carbon bed adsorption system. The gas stream is sent to the CO2 Absorption for the removal of CO2 and H2S. A Claus plant is used for recovering Sulfur from the stream rich in H2S. The gas stream free from CO2 is heated and fed to the Methanator, where residual carbon oxides are converted to methane in the presence of catalysts.

Ammonia Synthesis. After a nitrogen wash that removes remaining carbon monoxide and methane, the resulting gas is compressed and directed to the Ammonia Reactor, an intercooled horizontal converter, where hydrogen and nitrogen reacts at the correct stoichiometric ratio yielding Ammonia.