Increasing the Calorific Value of Rye Straw Pellets with Biogenous and Fossil Fuel Additives

Abstract

Pelletizing biomass, especially straw and stalky materials, require a product-specific size reduction and liberation. This paper characterizes the cereal straw rye and specifies the necessities for production of energy pellets. The product-specific size reduction was achieved with the help of an impact mill. Further, the moisture content and the particle size distribution play an important role in the pelletization process and also with respect to the energy characteristics. Rye straw pellets have a lower heating value of 17.2 MJ/kg. The objective of this work is to increase the heating value from 17.2 MJ/kg to a value in between 18 and 18.5 MJ/kg. The pellets are prepared with increasing water contents and with the biogenous and fossil additives. The biogenous and fossil additives are chosen such that they ensure the necessary binding and simultaneously increase the heating value. Besides the heating value, the main pellet quality parameters such as mechanical stability, abrasion resistance, and combustion technical characteristics have been tested according to the existing norms (DIN51731, ÖNORM-M7135, DINplus, Agro+, and Agro). The particle size characteristics indicate an ideal distribution of the particles for the combustion in furnaces. The durability and mechanical stability of the pellets were in acceptance with the existing norms. Particle size characteristics, abrasion values, and strength characteristics showed a good correlation and displayed optimal combustion characteristics.