Construction of a New Gas Purification Plant at the Bülk Sewage Treatment Plant

Cause

The state capital Kiel operates a sewage treatment plant with a capacity of 375,000 PE at the Strande, Bülker Huk site. The operator's strategic goal is to modernize the existing gas utilization plant, which has been in operation since 1994. A combined heat and power plant consisting of four modules is currently available to utilize the digester gas as an energy source and is now due for renewal due to its service life and the need to adapt to the changed quantities of digester gas. The gas purification plant is to go into operation as an early measure in order to fulfil the requirements of the licensing authority with regard to TA-Luft and the formaldehyde value in the exhaust gas.

Process

Gas drying takes place according to the condensation drying principle via water-cooled tube bundle heat exchangers. By cooling the gas flow, the moisture contained in the gas condenses and is removed from the gas via condensate separators.

Gas reheating is used to increase the temperature of the digester gas from 5 °C to approx. 25 °C in order to prevent further condensation at low outside temperatures within the downstream filters. The gas is heated by means of a tube bundle heat exchanger; the necessary heat output is supplied by an electric water heater.

The activated carbon filter is used to separate hydrogen sulphide and siloxane from the sewage gas for subsequent utilisation in the CHP unit. It is designed for the complete removal of hydrogen sulphide and siloxanes with an acceptable service life of the filter material. The activated carbon filter unit is designed as an upright double-chamber adsorber and is installed directly downstream of the gas reheater. The double-chamber adsorber consists of two separate chambers with activated carbon, through which the gas flows one after the other. Gas samples for gas analyses can be taken through the measuring connections. If the permissible limit value is reached in the gas flow, the activated carbon must be replaced.