Fuel gas blending systems for boilers and generators are designed to accurately blend biogas with natural gas, with preference given to the biogas to reduce natural gas consumption. Perfect for facilities that have their own source of digester gas, landfill gas, or other manufactured fuel gas, and want to minimize natural gas consumption and expense.
Boiler or generator owners who have invested in a source of biogas (typically digester gas or landfill gas) want to burn as much of their “free gas” as possible. Preferred’s gas blending stations monitor the availability and flow of biogas. During low load situations, the Preferred blending station discharges as much biogas as available. If the boiler or generator load exceeds the available supply of biogas, additional natural gas is blended into the mixed gas stream to meet the load. This blending action is carefully balanced against the fuel quality and variability constraints of the connected boilers or generators. Variable Btu fuels, gas engine applications, and cold start considerations are factored into the control strategies.
- Supply Pressure Transmitters - Pressure transmitters at the inlet of the biogas train and natural gas train are used to confirm the availability of gas. They may also be used to pressure compensate the gas flow meters.
- Gas Flow Meters - Pressure and temperature compensated flow meters are the primary input to the control system.
- Flow Control Valves - Electric or pneumatic flow control valves are used to modulate the flows of both biogas and natural gas to achieve the desired gas mixture.
- Discharge Pressure Transmitter - Sometimes used to maintain discharge blended gas pressure within acceptable limits.
- Wobbe Index Analyzer - Certain combinations of biogas fuels and fired devices will require a Wobbe Index analyzer or Btu analyzer to determine the heating value of the fuel.
- Controls - A Preferred PWC or third-party PLC provides the brain of the Preferred gas blending system. Color touchscreens provide the interface for operators and service technicians.
- Materials of Construction
- Natural gas trains are usually made from carbon steel valves and and steel pipe. Biogas trains are made from 304 or 316 steel depending on the composition of the biogas. Electrical enclosures are NEMA 4, NEMA 4X, or NEMA 7 depending on the local area requirement.
Preferred gas blending systems are custom engineered for each application. A successful project depends upon gathering good jobsite information before the blending system is designed, built, and programmed. The worksheet below indicates the information needed for Preferred to provide a gas blending station proposal.