Coal Conversion of the District Heating Power Station in Vasteraas, Sweden

Vasteraas District Heating Power Station was before 1980 to 100 percent dependent on oil supply from abroad, and all the district heating was based on oil. It was then decided to convert three of the four boilers into solid fuel firing, pulverized coal. In summer 1981 two boilers were commissioned on coal-firing. The third boiler will be commissioned in summer 1983. The experiences from the first conversion tell us that it is possible to convert a boiler without derating it. The slagging problems of these boilers can be handled with good steam sootblowing. Also the unburnt and the excess air levels can be kept at an acceptable level. The stack gas temperatures raise and have to be lowered in some way. Also the tightness of the airsystem before the boiler has to be modified, especially in the air heater and the windbox. The cost to convert is significantly lower than building a new boiler, and we figure that the investment will be repaid in 4 - 5 years.