The purpose of purificating natural gas is to get rid of H2S、CO2、H2O and other impurity in the gas, so that the gas meets related standards, and to recover sulphur in the gas, so that emission meets environment protection requirement.
Processes of natural gas purification include desulfurization, dehydration, sulphur recovery and emission disposal.
Coal Gas
Major components of cola gas varies with difference of method how coal is gasified, and components and percentage of impuity also differs. But normally, there are H2, CO, CO2, CH4, N2, dust, sulfide, coal tar, halide, alkali metal compounds, arsenic compounds, NH3 and HCN.
Coal gas purification includes cleaning out solid particles and gas impuity purification. Generally there are two steps: preliminary purification and purification.
Specifically:
1. Dust is cleaned out by separation of mechanical forces, electrostatic precipitation, filtration and washing.
2. Coal tar, halide, alkali metal compounds, arsenic compounds, NH3 and HCN is cleaned out by wet washing, using the same equipment as dust washing.
3. Desulfurization normally adopts dry or wet process, in which physical method, chemical method and physical-chemical method are used.
4. Clean up of CO normally adopts water-gas shift reaction, making CO and H2O react to generate CO2 and H2, thus change CO to CO2, which is easy to clean, and also get the same volume of H2.
5. CO2 is cleaned by rectisol, NHD and MDEA. At the same time, sulfide can also be cleaned.
Coke Oven Gas(COG)
COG has many posionous impuity, and must be cleaned out. After purification, impurities like hydrogen sulfide, hydrogen cyanide, ammonia, tar, and naphthalene is cleaned to make COG meeting relative standart for industry or civil usage. Meanwhile, chemical by-products are recovered.
COG purification technologies include: cooling and discharging of coke oven gas, separation of tar and ammonia, removal of tar, naphthalene, hydrogen sulfide, hydrogen cyanide, ammonia and other impurities, and crude benzol recovery.
Major COG purification equipment are condensing blower unit, desulfurization and cyanide removal device, ammonia recovery unit and benzol recovery device.