Control of an ammonia synthesis loop at partial load

A process for synthesis of ammonia, the process comprising:

• producing an ammonia make-up synthesis gas in a front-end;
• raising the pressure of said make-up gas in a first compressor;
• feeding high-pressure make-up synthesis gas delivered by said first compressor to an ammonia synthesis loop;
• wherein said ammonia synthesis loop includes at least:
• a converter where ammonia is synthesized catalytically;
• a circulator, which is a compressor configured to maintain circulation in the loop and to deliver a feed gas, which includes the make-up synthesis gas, to said converter;
• a converter feed line from the circulator to the converter;
• a condensation section arranged downstream from the ammonia synthesis loop to receive an ammonia-containing gaseous product;
• and
• a separation section wherein a condensate produced in said condensation section is separated into an ammonia liquid product and a gaseous recycle stream;
• a recycle line from the separation section to a suction of the circulator;
• wherein the ammonia synthesis loop has a full load condition corresponding to the processing of a nominal flow rate of make-up gas transferred from the front end to the ammonia synthesis loop;
• and
• controlling the loop at a partial load condition, wherein the flow rate of make-up gas transferred from the front end to the loop is smaller than said nominal flow rate, by the following steps:
• the pressure at which ammonia is synthesized is lowered to a reduced ammonia synthesis pressure, which is less than a nominal synthesis pressure at said full load condition of the ammonia synthesis loop;
• and
• the synthesis pressure is maintained within a target range which includes said reduced synthesis pressure, by controlling a flow rate of feed gas bypassing the converter.