Factors Favouring the Single-Pressure Process

The single-pressure process uses a higher ammonia conversion pressure. This higher pressure provides advantages in terms of equipment design, e.g. smaller converter dimensions and a single heat-exchanger-train layout. 

The higher temperature and the favourable pressure both increase the energy recovery from the process. The single-pressure process provides an extra 10% high-level recoverable heat energy as shown in Table C.3. 

Plant capital costs in the USA have been estimated at As8 million (USS5.1 million) for the single-pressure process and AS9.1 million (USS5.8 million) for the dual-pressure process. The AS1. I million higher cost of the dual-pressure process is accounted for by the larger vessels required at lower operating pressures. Estimates made for the two plants in European locations show a differential of AS0.8 million, also in favour of the single-pressure process. 

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