COMMISSIONING OF A COGENERATION FACILITY IN THUNDER BAY TO MAXIMIZE ENERGY RECOVERY IN THE ABSENCE OF BIOGAS STORAGE

摘要

The City of Thunder Bay recently commissioned a gas engine cogeneration facility to maximizeonsite electrical power generation using biogas generated by biosolids treatment in the AtlanticAvenue Water Pollution Control Plant’s four anaerobic digesters as the principal fuel source. The600 kW Caterpillar G3512 engine-generator package includes a gas pretreatment system forremoval of hydrogen sulfide and siloxanes from the biogas. While the cogeneration system isdesigned to operate on biogas, natural gas, or an infinite variable blend of the two fuel gases, theprogram requirements of the electrical utility participating in the funding of the project, ThunderBay Hydro, necessitated that biogas be used as the principal fuel source for the cogenerationsystem and further that the use of natural gas be limited for servicing of the engine only. Inaddition to serving as a fuel source for the cogeneration system, the biogas is also available as afuel source for the plant’s hot water boiler system. Excess biogas is flared to prevent overpressurization of the digester gas system when biogas supply exceeds demand as there is nopressurized storage. Power generated onsite is tied into the plant’s onsite 4160 volt electricaldistribution system. Another requirement of Thunder Bay Hydro was that at no time was anypower to be exported from the plant’s system to the Thunder Bay Hydro grid. Heat recoveryfrom the cogeneration system was also required to reduce the costs of boiler operation usingnatural gas rather than biogas that was now being used to generate power. The challengespresented by these requirements, as well as the interaction of other systems in the normal day-todayand season-to-season operation of a municipal waste water treatment facility, are reviewed.