关键词: 生物质固体燃料, 热压成型, 温度场分布规律

Abstract:

Objective: The aim of this study was to study the distribution of the temperature field of the section of the molding block during the biomass hot compression molding,which was expected to provide a reference for the study of biomass hot forming technology. Method: This paper took the single plunger biomass molding machine independently developed by the School of Technology of Beijing Forestry University as the experimental equipment,and adopted the heating method of forming sleeve to study the waste pine sawdust used as the experimental materials. The orthogonal test was designed with heating temperature,raw material moisture content and motor frequency as experimental factors. The heating temperature was set as 155,170,185,200 and 215℃,the sawdust moisture content was adjusted to 10%,12%,14%,16% and 18%,and the motor frequency was set as 14,16,18,20 and 22 Hz,respectively. Using the variance analysis method to analyze the overall density of the molding block,the average temperature,the highest temperature and the center point temperature of the molding block section were affected by the experimental temperature,moisture content,and motor frequency. Experimental results showed that by establishing a multivariate regression model,the multiple regression equations could be obtained with the overall density of the molding block,the average temperature,the highest temperature,and the center point temperature of the molding block section as the dependent variables,with the experimental temperature,moisture content,and motor frequency as independent variables,and get a simplified multiple regression equation. Through the establishment of multiple regression models and comparative analysis,the best mathematical model relationships between the overall density of the forming block and the temperature field distribution of the biomass forming block were expected to be found. Result: For the center point temperature,the primary and secondary influencing factors are moisture content,motor frequency and temperature; for the average temperature,the primary influencing factors are temperature and moisture content,the secondary influencing factor is motor frequency; and for the highest temperature,the primary and secondary influencing factors are temperature,motor frequency and moisture content. Our results demonstrated that the error of each simplified multiple regression equation and the original multiple regression equation is less than 1.5%. The best multiple regression model and equations are obtained with the overall density of the biomass molding block as the dependent variable,and the average temperature,the highest temperature,and the center point temperature of the molding block section as the independent variables. Conclusion: In practical applications of biomass hot forming,the distribution of the temperature field of the section of the molding block has a profound effect on the quality of biomass molding. This paper explores the distribution of temperature field in biomass hot forming in actual experiments. Through analysis and modeling,it is found that there is a mathematical relationship between the overall density of the forming block and the distribution of the temperature field of the section of the molding block,which might broaden our ideas for subsequent biomass research.

Key words: biomass solid fuel, hot press forming, distribution of temperature field