Synthesis gas, for example a mixture of hydrogen and nitrogen, is an important preliminary product for ammonia production and thus subsequent fertiliser production. Synthesis gas is obtained from the catalytic conversion of natural gas with water vapour and air in the catalyst at very high temperatures. This produces a gas mixture of hydrogen and nitrogen at a ratio of 3:1. Most synthesis gas production processes involve relatively elaborate and complex purification and treatment of the synthesis gas mixture downstream of the reactor. This is basically the CO₂ separation in the gas scrubber, where the carbon dioxide is removed from the mixture by an alkali scrubber, e.g. using amine.

KROHNE offers high-precision ultrasonic flowmeters for this, which reliably measure the flow of process gases in the measuring tube without moving parts. They do not cause any pressure loss, are low-maintenance and highly durable. Level transmitters with guided radar are available for monitoring CO₂ gas scrubbing. There are also industrial resistance thermometers with interchangeable measuring inserts for measuring the temperature of the circulating scrubbing agent.