Prodn. of ammonia synthesis gas from brown coal - by gasification without predrying, washing and partial combustion

摘要

Prodn. of ammonia synthesis gas from undried brown coal by (a) breaking to below 6 mm. and gasifying at up to 1150 degrees C in an externally-heated tube furnace, (b) cooling the raw gas to below the dew point, washing with its own circulating condensate, de-sulphurising and washing to remove CO2, (c) separating a H2 fraction by cooling to low temps., (d) burning part of the desulphurised gas or H2 fraction in sufficient air to provide ann the N2 required, (e) cooling the gas to below the dew point to remove water, and removing any traces of O2 or CO2, and (e) mixing the N2 obtd. with the H2 fraction. Elimination of predrying of the brown coal which usually contains 50-60 wt.% water, reduces prodn. costs. No free O2 or external steam are required. The coal does not have to be finely ground or sieved. No gas conversion plant is required. Energy requirements are reduces from 14.5x106 to 11x106 kcal/t. NH3. In an example, 195 t/h brown col contg. 59 vol. % is gasified at 800 degrees C under 40 bar, the gas treated as above, and fractionated at -200 degrees C to give 101415 Nm3/h pure H2. of this, 15540 Nm3/h is burnt with 37000 Nm3/h air to give a N2/H2 mixt., which is combined with the remaining H2 to give 114500 Nm3/h ammonia synthesis gas.