A fuel gas dehumidifier or gas drier is an ancillary system to a gas engine that is used to remove moisture from the fuel gas for the cogeneration system (dessication). The removal of water from the fuel gas helps to optimise the combustion process in the engine, prevents condensation and helps protect the engine from the acid.
The drying of the gas is achieved by cooling the raw incoming gas to a temperature below the dew point temperature in two heat exchangers. This causes the moisture to be removed as condensate prior to reheating the gas as it leaves the dehumidifier. The added benefit of this system is that some sulphur is removed from the gas in the condensate, helping improve the overall gas quality.
System Benefits
- Protects engine
- Removes moisture from fuel gas
- Reduces in sulphur from fuel gas
- Reduces engine maintenance requirements
- Improves oil life
Factors to consider
Fuel gas dehumidifiers are specified based upon the following key factors:
- Gas type
- Gas flow rate
- Gas methane concentration
- Raw gas temperature
- Gas contaminants
- Permissible pressure loss
Different gas dehumidifiers may be supplied depending upon which type of fuel gas is being dried (e.g. is it biogas, landfill gas or other). The gas flow rate and gas methane concentration will determine how much gas the dehumidifier must be able to process. The raw gas temperature at the inlet to the dehumidifier will determine how large the cooling capacity of the dehumidifier will be. Contaminants in the fuel gas may produce undesirable effects for the unit and should be checked that they are within acceptable limits. Finally, permissible levels of pressure loss must be considered as gas holders usually exist at low pressures and there is also a loss in pressure across the dehumidifer. It is undesirable to suck gas through pipes under negative pressure.
Fuel Gas Quality
There are specific requirements for the fuel quality for Jenbacher gas engines laid of in the Jenbacher technical instruction document (please contact your local Clarke Energy office to receive a copy). Moisture levels in the gas must be kept to a minimum in order to protect the engine and to optimise combustion. High moisture is a particular characteristic of biologically derived gases and coal gas.
Supply
Clarke Energy are able to supply high-quality gas dehumidifiers within a turn-key scope of supply, or free issue with the generator. We do not supply dehumidifiers outside of the scope of a Jenbacher gas engine or combined heat and power installation.
Please contact your local Clarke Energy office to find out more information.
