Co-combustion of liquid biofuels in PC boilers of 200 MW utility unit

The paper presents results obtained from the industrial-scale co-firing of bioliquid fuels. The co-firing of bioliquid is an interesting alternative to the co-firing of solid biomass. The chemical and physical properties of the most abundant biofuels to be co-combusted in PC boilers, i.e. crude glycerine, palm oil and rapeseed oil, were determined. Glycerine was found to be the most attractive fuel because of its properties, availability and price. Therefore glycerine was chosen for the test co-firing in PC boilers with a capacity of 100 MWth and 200 MWe installed in respectively CHP ROKITA and PS Kozienice. The primary objective of the research was to determine whether crude glycerine can be used as a co-firing fuel for industrial boilers in utility plants. Preliminary laboratory-scale co-firing tests were carried out. On the basis of the test results two burner designs were developed. One is a gas-dynamic burner with steam-biofuel (submicron-fine) atomization. This burner can burn any difficult liquid fuel at a rate of 1.5 t/h. The other design is a multi-jet burner with two-medium (steam and air) atomization, high outflow velocities and a capacity of 300-600 kg/h depending on the atomization medium and glycerine pressure at the burner head inlet. The two types of burners differ in the extent of the liquid fuel spray area. Tests of crude glycerine co-firing in two PC boilers: OP-130 and OP-650 were carried out. The tests focused on the effect of the liquid biomass-glycerine combination on the combustion behaviour. An analysis of the burnout from the co-firing was carried out. The operating boiler parameters in the two tests were compared, taking into account the emission of such pollutants as NOx and SO2. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.