Study On Compositions And Combustion Characteristics Of Typical Crop Straws

As a typical biomass energy,crop straw had a huge amount in China.However,due to some subjective and objective factors,there are still some straws that have not been effectively utilized in China,which has caused a series of environmental problems.Therefore,it is of great theoretical and practical significance to study the composition and combustion characteristics of crop straw and provide important data and theoretical support for the comprehensive utilization of straw.In this study,three typical straws（wheat straw,rice straw and maize straw）were selected,and their components（industrial analysis,element analysis,fiber composition）were analyzed.The combustion kinetics of straw direct combustion was studied by the method of DTA,and the emission characteristics were studied in the laboratory.The results are as follows:（1）Among the three kinds of straws,rice straw had the highest ash and holocellulose content,wheat straw had the highest S and Hg content,and other characteristics（moisture,volatile,fixed carbon）and element（C,H,O,N）composition had no significant difference.The three kinds of straw have the characteristics of high volatile matter,low ash content（except rice straw）and low sulfur content.（2）The overall trend of TG and DTG curves of three kinds of straws is similar at different heating rates.The two distinct weightlessness peaks correspond to the stage of volatile matter precipitation and combustion and the stage of fixed carbon combustion respectively,and the weightlessness rate of the former is much higher than that of the latter.At the same heating rate,the maximum weightlessness rate of the three kinds of straws in the low temperature combustion zone（volatile analysis and combustion）is wheat in turn from high to low.Straw>Rice straw>Maize straw,while the maximum weight loss rate of maize and rice straw in high temperature combustion zone（fixed carbon combustion）was not significantly different,higher than that of wheat straw.The two-component staged reaction model can scientifically describe the combustion kinetics of crop straw.（3）The results of the direct combustion simulation experimentsshowed that Under two stacking modes,CO and SO₂emission factors gradually increased with the increase of moisture content,while NO_Xemission factors decreased with the increase of moisture content.When wheat straw is laid flat,it is obvious;when stacking burns,it is smoldering.When wheat straw is laid flat,the open-flame burning is main,while when straw is stacked,the smoldering is main.