Abstract
Abstract: China is a large agricultural nation with abundant straw, and the straw is regarded as a kind of precious biology resource. However, the resource of straw is seriously burned, or not utilized, which causes severe pollution to the environment. Thus, in order to make full use of the straw, a technique and machine used for the extrusion and molding is needed. By the extrusion of a molding machine, the straw can be compressed into briquetting with higher density and calorific value, and can be used as one type of effective fuel in an oven. So as to mold the briquetting with superior combustion characteristic, relevant research about the calorific value of rice straw briquetting was conducted. For the establishment of the predicted model of the calorific value of the rice straw briquetting and in order to provide a theoretical basis for the extrusion molding of the high quality fuel briquetting, the rice straw briquettings were used as the research object and the test samples, produced from a ring molding machine of the type of 9JYK-2000A, and the density, moisture content, and fugitive constituent were taken as the influencing factors. The low calorific value and the high calorific value of briquetting were used as the test index in the experimental study. Before the experiment, various physical properties demanded of rice straw briquettings were prepared with the aid of the experimental apparatus, such as the grinder, dryer, muffle, and so on, and then the briquettings were classified and bagged. The experiment was designed as a quadratic regression orthogonal of three factors and five levels, and by using the regression analysis method and response surface analysis of the software of Design-Expert 8.0.6, the mathematical model concerning the three factors' impact on the calorific value was set up and analyzed, and the experimental verification of the mathematical model was also conducted. Compared with the experimental result, it turned out that the range of error was less than 5%, which meant that the model established was useful and could be used for predicting and optimizing. By an analysis of the test result, it was shown that the sequence of the contributed value of the factors' influence on low calorific value was: density > moisture content > fugitive constituent, and the sequence of the contributed value of the influence on the high calorific value was: density > fugitive constituent > moisture content. When the density was 1.39 g/cm3, the moisture content was 13.68%, and the fugitive constituent was 0.76, the lower calorific value could reach the best result, which was 2 848.45 kcal. The indicators of the best model of the higher calorific value was a density of 0.92 g/cm3, a moisture content of 23.21%, and a fugitive constituent of 0.75, which could reach the best higher calorific value of 4 313.54 calories. The best model of the integrated calorific value was as follows: density was 1.18 g/cm3, moisture content was 11.78%, fugitive constituent was 0.78, the lower calorific value was 2 830.48 kcal, and the higher calorific value was 4 488.051 kcal. Or the model, whose density was 1.43 g/cm3, had a moisture content of 1.84%, a fugitive constituent of 0.80, a lower calorific value of 2 851.08 kcal, and a higher calorific value of 4 480.91 kcal.
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