Biomass Power Plant Technology Options

Steam cycle with grate boilers

Grate or stoker boilers burn fuel on a moving or vibrating grate, raising steam for a turbine. They tolerate a wide range of particle sizes and moisture levels and are the most common choice for small and medium plants. Efficiency is moderate, and fuels with low ash melting points need careful design.

Fluidised bed boilers

Bubbling and circulating fluidised bed boilers burn fuel in a bed of hot sand-like material. They handle variable and low-grade fuels well, achieve good combustion and can reach larger sizes. They are more complex and costly, and need careful control of bed agglomeration with high-alkali fuels.

Organic Rankine cycle

Organic Rankine cycle units use a thermal oil loop and an organic working fluid instead of steam. They suit smaller plants, especially where heat is also used, and are simple to operate with low staffing needs. Electrical efficiency is lower than large steam cycles.

Gasification with engines

Gasifiers convert biomass into a combustible gas that can fuel engines. They can offer good electrical efficiency at small scale, but require clean, consistent fuel and careful gas cleaning to protect the engines. Tar handling is the main technical challenge.

Choosing between them

The fuel analysis, the required output, the use of heat and the skills available on site usually point clearly to one or two options.

Balance of plant

Whatever the conversion technology, the plant also needs fuel reception and storage, ash handling, water treatment, cooling, emissions control and electrical systems. These often account for a large share of capital cost and are where engineering experience matters most. USP&E engineers and builds balance of plant for power stations.