Water saving potential of coal-to-synthetic natural gas

High water consumption is confining the development of coal chemical industry in China. This work analyzed the details of water consumption and water-saving potential for coal-to-synthetic natural gas process. Results show that combined heat and power plant, shift, air separation and clean-up respectively take 23.4%, 21.9%, 18.8% and 14.4% of total water consumption in the production process. And 75% of water consumption is caused by the water loss in recirculating cooling water stations, around 90% of which is due to evaporation in the case analyzed. Thus, adopting combined dry and wet recirculating cooling water system can reduce 60% of water consumption in recirculating cooling water station. Cooling water distribution has been investigated as well, which will affect the amount of water withdrawal of the whole system. By upgrading recirculating cooling water technology, water consumption can be reduced to 3.50–4.93 t/kNm³ natural gas for coal-to-synthetic natural gas process. Besides, by taking water saving gasification technology, zero liquid discharge, integrating the water networks and improving other units, water consumption can be reduced to be lower than 3.50 t/kNm³.