A commercial-scale gasification plant using mixed feedstock of biomass and coal has been demonstrated at the 253 MWe Nuon Power Plant in Buggenum, the Netherlands [6]. The plant was built in 1993, and it uses biomass to reduce CO2 emissions based on dry feed Shell gasification technology. The Shell gasifier is an oxygen-blown continuous slagging, entrained flow reactor. The plant is capable of using different types of coal and contains several advanced design features that are different from U. S. IGCC plants. The air separation unit and gas turbine are very closely coupled, with the gas tur­bine compressor supplying all the air to the ASU. Although this improves efficiency, it makes the plant more complex and harder to start.

Pulverized coal is fed into the gasifier with transport gas via dense phase conveying. Either product gas or nitrogen can be used as a carrier gas. The reactor is operated at 1,500-1,600°C and pressure ranging from 350 to 650 psig to produce syngas principally composed of H2 and CO and very little CO2. Operation at the elevated temperatures eliminates the production of hydrocarbon gases and liquids in the product gas. The molten slag at high temperature runs down the refractory-lined water wall of the gasifier into a water bath, where it is solidified and is removed through a lock hopper as slurry in the water. The hot gas leaving the reactor is first cooled by the recy­cling product gas and then by a waste heat recovery (syngas cooler) unit. The syngas is further cooled before particle removal in a wet scrubber. The syn­gas is then treated to remove carbonyl sulfide and hydrogen sulfide before going to a gas turbine.

The plant processed mixed feedstock of coal and biomass first from 2001­2004 with about 18% by weight of pure and mixed biomass. More recently, biomass concentration has increased up to 30 wt%. In addition to gasifica­tion of demolition wood, tests were also conducted with chicken litter and sewage sludge. The test program evaluated the effects of biomass on product gas and ash quality. The NUON/IGCC plant uses the coal and biomass com­position shown in Table 7.10. As shown, the plant takes about 30% by weight biomass, most of which is waste wood to provide about 17% of energy input to the gasifier.