De Suphurisation Process

In the process the biogas is brought into intense contact with a circulating alkali liquid over an exchanger in a single stage counter current process (gas scrubber). The H2S in the gas is absorbed by the alkali liquid through several chemical reactions. Ultimately the hydrogen sulphide in the gas is almost totally converted into NaHS and sodium bicarbonate using sodium hydroxide. The process is controlled by a sophisticated H2S-detection and sampling system for very efficient operations and low chemical consumption.  Selective desulphurisation is possible due to the differences in the physical and chemical properties of H2S and CO2. The course of this chemical process is further determined by chemical concentrations, pH values and the temperature and pressure of the system. The following conditions should be taken into consideration:
• the lower the final concentration of H2S in the purified gas, the higher the specific lye demand;
• the higher the temperature and pressure of the system, the higher the specific lye demand;
• the higher the CO2 content in the raw gas, the higher the lye demand;
• The longer the gas remains in the scrubber, the higher the specific lye demand.

The following design data is required in order to design a gas desulphurisation plant:
• gas flow in Nm3/hour; maximum, minimum, average, current and future;
• gas temperature in degrees C. ;
• gas pressure in mbar or Pa;
• composition of gas ( CH4, CO2, H2S, other );
• Required efficiency; ppm H2S in the purified gas.


For optimal performance of the Sulfurex® process the following conditions need to be considered:
• fluctuations in gas flow preferably < 10 m3/hr per minute;
• system pressure preferably between - 250 and + 500 mmwg;
• Process temperature preferably between 2 and 50 degrees C.


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