Gasification

Gasification is the conversion of non-homogenous matter into homogenous matter. At Babcock & Wilcox Vølund, we gasify wood chips that are converted into a combustible gas. For example, this gas can be utilized in a gas engine for the production of electricity and heat. This makes it possible to achieve very high efficiencies and optimize the use of biomass resources. The plants can with great advantage be placed locally in small communities where steam or heat is needed.

The fuel comes directly from the woods where it is chopped. No further treatment (such as drying or sorting of fractions) is necessary. The biomass is CO2 neutral and thus helps reduce the greenhouse effect when used to replace fossil fuels.

Gasification plants from us are fully automatic and require minimal monitoring. This means that the operating and maintenance costs can be kept at an acceptable level. Our demo plant at Harboøre, Denmark, is in unmanned operation evenings, nights, and weekends. So far, the gas engines have been in operation for 70,000 hours, which is quite outstanding!

Updraft gasification

Gasification of biomass may be carried out according to several different schemes. Back in 1989, we decided to base future work on updraft gasification. Here’s why we make this important choice:

• Updraft gasification is well proven technology (for peat and coal) and some information on design and operation was available from various sources.
• For updraft gasifiers a wide fuel mix and moisture content range is considered possible
• The updraft gasifier features a high carbon conversion and high cold-gas efficiency (a measure for transforming chemical energy from solid fuel into gas).
• High modulation range and fast modulation capability were reported as inherent in the technology.
• Information on “up-scalability” indicated that gasifiers based on this concept might be built in unit sizes up to about 20 MW fuel input.

Advantages of the gasification process

The advantage of the gasification process is that the inhomogeneous biomass was converted into a homogenous gas with a considerably higher level of applicability:

• The product gas may, without any cleaning, be used for gas-fired steam boilers combined with steam turbines or for increased steam superheating (and consequently higher power efficiency) at e.g. municipal solid waste energy plants.
• The product gas may, after a modest clean-up, be burned using low NOx gas burner technology in connection with indirectly fired power technologies such as indirectly fired gas turbines, ORC and Stirling engines.
• After adequate clean-up the product gas may even be used for direct firing of gas engines with a potential efficiency exceeding 38% in a combined cycle configuration.

Today, our biomass installations are among the most efficient in the world. More importantly, they use renewable materials which can be produced locally. As such, using this biomass in a proactive and environmentally safe manner represents a huge benefit to our environment.