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

Abstract

Manufacturing units, which use biomass for combustion and cofiring, are obliged to increase the amount of biomass from agricultural sources gradually 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 aims. A huge variety of plants, that give biomass useful in the power industry, is connected with a big diversity of physical characteristics (hardness, specific gravity, moisture content, porosity) and chemical composition. It significantly affects not only the biomass calorific value 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 that we used for the analysis were: boilers slagging, the tendency of fuel to form impurities, sintering and agglomeration. There was shown a significant variation in the content of alkalies, 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 as Virginia mallow or Jerusalem artichoke may cause pollution deposition and reduce the efficiency of boilers to the greatest degree. Because of the fact that biomass of different plant species show the diversity of energy parameters and tendencies to foul boilers there is a need to select the material to the combustion carefully and also 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.

Keywords

• combustion
• biomass
• fouling
• slagging