Method for the control of pressure in a loop for the preparation of ammonia or methanol

A system for controlling pressure in a loop for the synthesis of ammonia or methanol, comprising:

• a make-up gas compressor configured to pressurize a make-up synthesis gas,
• a synthesis loop configured to receive a pressurized make-up synthesis gas from the make-up gas compressor, the synthesis loop comprising a synthesis reactor, a synthesis loop cooler, a loop recirculation compressor, a synthesis loop heater, and a pressure monitor;
• the synthesis reactor arranged to receive a heated loop recirculation gas from the synthesis loop heater and configured to provide an at least partially synthesized gas to the synthesis loop cooler;
• the synthesis loop cooler configured to cool the at least partially synthesized gas and separate into a product stream and a loop recirculation gas;
• the loop recirculation compressor arranged to receive the loop recirculation gas and configured to pressurize and provide a pressurized loop recirculation gas to the synthesis loop heater;
• wherein the loop recirculation compressor comprises an anti-surge valve and/or a compressor flow regulation valve in communication with the pressure monitor, the anti-surge valve and/or a compressor flow regulation valve being configured to control the flow of the loop recirculation gas through the anti-surge valve and/or a compressor flow regulation valve to obtain a substantially constant pressure in the ammonia or methanol synthesis loop.