Waste Heat Recovery from Synthesis Gas Compressor

The heat that is recovered from the synthesis gas compressor with the use of a heat exchanger is frequently discarded into cooling water. There is a potential to recover this heat and use it to preheat the methanator feed gas, however, this has shown to hinder the temperature control of the LTS converter and shorten the catalyst life. In order to effectively use the heat exchanger, the boiler feed water can be injected into the process gas allowing for better temperature control (ECCJ, 1999 p. 153).

Typical temperatures in the LTS converter, using a copper oxide/zinc oxide catalyst are about 200-220oC (IPTS/EC, 2007 p.41). When the heat is exchanged with the compressor exit gas, the inlet temperature of the LTS converter increases from 214°C to 238°C. By injecting the boiler feed water at 130°C into the process gas, the sensible heat is changed into latent heat. In this way, the heating value increases without raising the temperature, which is maintained at the set level of 214°C. The use of boiler feed water increases the supply rate of latent heat to the process reboiler of the CO2 regenerator. As a result, the load of feed steam to the steam reboiler can be decreased (ECCJ, 1999 p. 153).

This measure maximizes recovery of the synthesis gas compressor heat exchanger, reducing the amount of heat rejected in cooling water. 

Development Status Products

Waste Heat Recovery from Synthesis Gas Compressor Costs & Benefits

Parent Process: Ammonia Synthesis
Energy Savings Potential
CO2 Emission Reduction Potential

The investment cost is estimated at 60 million Yen, and the payback period is about 2 years [1999 values] (ECCJ, 1999 p.153). 

Waste Heat Recovery from Synthesis Gas Compressor Publications

Directory of Energy Conservation Technology in Japan - Section 3: Chemical Industry

Prepared by New Energy and Industrial Technology Development Organization and the Energy Conservation Center, Japan, this extensive directory covers an extensive list of energy saving measures applicable to diverse range of industries. Section 3 concentrates on measures applicable to chemical industry, including ammonia production.

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