Residual gas re-use in ammonia synthesis plant

摘要

Process is for the use of residual gases from the noble gas unit of an ammonia plant, in which hydrogen is produced by steam reforming a hydrocarbon contg. feedstock, the synthesis gas contains inert gases, sp. noble gases and methane, on entry into the synthesis circuit, the ammonia prod. is sepd. by partial condensation from the synthesis circuit gas, the circuit expansion gas is further processed in a subsequent hydrogen recovery unit and/or noble gas unit and one or more gas streams, at a higher pressure than that required in the reforming stage, are returned as feedstock to the reforming stage. The process involves (a) feeding the noble gas unit residual gas, which comprises components such as H2, N2, Ar and CH4 and which has a pressure below that of the reforming stage, to an ejector; (b) compressing the gas to the reforming stage pressure by means of one or more gas streams at higher pressure than the reforming stage pressure; and (c) introducing the resulting mixt. into the synthesis gas prodn. section upstream of the reforming stage.