Pretreatment of biomass pellets by acid washing in order to reduce alkaline components
Due to the limited availability of wood, as the highest quality raw material for the production of biomass pellets, increasing attention is being paid to the production and use of pellets from low-quality materials such as different types of agricultural waste. However, the complex chemical composition of these types of biomass often leads to various problems during their combustion. One of the biggest problems when it comes to burning biomass pellets is related to the low melting temperature of the resulting ash and its tendency to sintering. By modifying the chemical composition of biomass, it is possible to influence the method of combustion and the characteristics of residual ash. Modification of biomass composition can be carried out by chemical pretreatment with acids, which reduces the concentration of alkali metals and alleviates ash adhesion and the tendency to form slag. Pellets made from wood biomass, soy straw and chamomile waste from the process of processing medicinal plants were used for the tests in this work. Chemical pretreatment, which consisted in washing the pellet samples with a diluted solution of hydrochloric acid, resulted in mass loss in all cases. The amount of ash, after treatment in hydrochloric acid solution, was reduced by 72.15% - 93.27%, depending on the concentration of acid and the type of biomass.