Evaluation of wood and peat mixture biofuel characteristics

Abstract

As it may be seen from the obtained results, it is purposeful to prepare peat and wood chip mixtures since the ash quantity after burning the mixture is 45 % smaller than burning only peat. The recommended mixture composition is 50 % peat and 50 % wood chip. Wooden fuel is one of the most widely used fuel sorts in Lithuania. Peat resources in Lithuania make more than 500 million tons, but in the recent years, peat has not been widely used as fuel due to comparatively high emissions and the ash content (4-6 %). It is purposeful to expand the volumes of peat usage for fuel preparing mixtures of peat with wood chip. As the practice shows, when using the mixture of peat and wood chip, boilers do not wear out so quickly, their exploitation time increases since the burning process gets better quality. Many boilers for burning of chip wood may be effectively used for burning the mixture of peat and wood chip. The physical characteristics of peat, wood chip and their mixtures have been determined by experiments. Increasing the moisture of peat and wood chip from 20 to 40 %, their filled density increases accordingly 11-12 % and 14-15 %. Fall and natural pour angles of the mixture components (peat and wood chip) have been researched. The results of the experiments showed that moisture has bigger effect on the peat fall angle, which changed from 71.0 ± 0.6 to 90.3 ± 0.6 degrees, than on thewood chip angle, which changed from 84.0 ± 0.9 to 88.0 ± 0.8 degrees. The natural slope angle of wood chip changed from 39.3 ± 1.0 to 41.0 ± 1.0 degrees. Moisture of peat does not have big effect on the natural pour angle. Fractional composition of the components has been determined by the research. Based on the results, it may be stated that the biggest part of peat (about 50 %) is of 0-1 mm fraction. About 50 % of wood chip make fractional composition of 8 mm, the smallest fraction of wood chip is 0-1 mm. The calorific value of peat and wood chip is similar (18.7-20.1 MJ·kg-1); so, it may be supposed that when preparing mixtures, the quality of component mixing (evenness of mixture components) does not influence the fuel calorific value.