Cofiring Biomass at a Steam Turbine Gas Power Plant, Is It Possible?

 Cofiring technology is divided into several types, namely direct cofiring, indirect cofiring, and parallel cofiring. The choice of using the cofiring type is mainly related to the type of fuel and combustion technology used. In general, based on its form, fuel is divided into three namely solid, liquid and gas fuels. The form of the fuel affects the combustion technology used. Liquid fuel which is a fluid, then combustion with a burner. Whereas fuel for combustion technology with fixed bed, fluidized bed and pulverized combustion. Mixing solid fuels such as biomass especially PKS / palmkernel shells, wood pellets and wood chips with coal is usually done in the direct cofiring type and this is the most common cofiring type. Then how about cofiring biomass with biomass fuels that are solid form with fossil fuels that are liquid or gas?

Steam Turbine

Fossil fuels such as diesel oil and gas such as natural gas usually used to fuel power plants in internal combustion engines (IC engines) whose output is mechanical energy to drive generators. Gas engine is an IC engine that is commonly used for the production of electricity from gas fuels such as natural gas. But if diesel oil or natural gas is used on external combustion engines (EC engines) such as furnaces and boilers that produce steam. Steam will then drive the turbine that is connected to the generator. In the EC engine cofiring mechanism can be done namely parallel cofiring type. In this mechanism, biomass as will be used to produce steam for additional steam from the fossil fueled EC engine.

Avedore Power Plant, Denmark

An example of a biomass cofiring with a gas power plant is the Avedore Unit 2 power plant, which is located in Denmark near Copenhagen. The power plant operates at ultra-supercritical with a capacity of 430 MW using steam turbine with natural gas fuel and is also equipped with 2 gas turbines with a capacity of 51 MW each. The gas turbine is used to provide electricity at peak load and boiler feed water via the exhaust heat recovery unit. Whereas a biomass boiler with a capacity of around 50 MW is used to provide additional steam to the system. The biomass boiler burns straw at a consumption of 150 thousand tons per year and produces 40 kg / second of steam at 583 C and pressures up to 310 bar.