Many processing plants produce large amounts of waste water, causing plant owners to rethink their energy use strategy. In 2013, a mid-western US food plant found a way to use its own waste water as an alternative energy source.
When the city of Janesville, WI began constructing an anaerobic digestion system at its waste water treatment facility, the city created a contract to sell conditioned biogas back to the food plant.
Using its own conditioned biogas, the food plant unlocked the ability to burn self-produced alternative fuel. But in order for the project to be a success, the plant needed a combustion system capable of handling such a unique demand. Based on prior success with a similar plant., the plant owner’s turned to Preferred Utilities and a team consisting of Leidos Engineering, LLC and American Boiler.
Preferred Utilities designed and supplied a complete combustion system, including an API-800 Burner, a bio/natural gas mixture piping train, and a proprietary burner management/combustion control system.
The system was designed to burn either natural gas alone, or a mixture of preferential biogas and supplemental natural gas. Because digester gas contains sulfur and water, Preferred fashioned 316 stainless steel for all burner and piping components to resist corrosion. The combustion system’s startup and operation procedure is governed by a BurnerMate TS burner management/combustion control system.
The system consists of Preferred Instruments DCS-III digital controllers and a GNE 5004-M-85 Flame Safeguard module. The plant now employs a full metering combustion control strategy with FD fan, VFD control, and oxygen trim. The combustion air demand is determined based on the sum of the combustion air requirements established by the inputs of both the natural gas and biogas flow rates.
The combustion system now fires a natural gas/biogas mixture, with priority given to biogas based on availability established by supply pressure, thus maximizing fuel cost savings for the food processing plant.