The Influence of the Ash from the Biomass on the Power Boiler Pollution

Manufacturing units, which use biomass for combustion and co-firing, are obliged to gradually increase the amount of biomass from agricultural sources in place of timber biomass from forests. Many different species of trees that grow on arable land, bushes, grasses or perennials can be used for energy purposes. A huge variety of plants that give biomass useful in the power industry, is connected with a large diversity of physical characteristics (hardness, specific gravity, moisture content, porosity) and chemical composition. It significantly affects not only the calorific value of biomass but also the condition of the boilers in which it is burnt. This paper presents the results of the research concerning the influence of the process of combustion biomass from seven plant species on the boilers fouling on the basis of ash chemical composition. The indicators used for the analysis were as follows: boilers slagging, the tendency of fuel to form impurities, sintering and agglomeration. A significant variation in the content of alkalies was shown that cause the formation of sediment on the boilers heating surfaces. The smallest risk of heating boilers fouling is associated with perennial grasses incineration, especially the ones from the Miscanthus species that contain significant quantities of silicon monoxide, which is responsible for the heating surfaces erosion. The usage of polycarpic plants, such as Virginia mallow or Jerusalem artichoke, may cause pollution deposition and reduce the efficiency of boilers to the greatest degree. Because the biomass of different plant species exhibits the diversity of energy parameters and tendencies to foul boilers, there is a need to select the material to the combustion carefully. Moreover, blends of biomass raw materials (or biomass with coal) should be composed so that they are adapted to the boiler parameters and to the conditions of the combustion process.