Experimental study on optimization of directional regulation process on straw biochar

Abstract: China is rich in crop straw resources, but straw burning is serious and resource utilization is not high. To solved the ecological pollution and resource waste caused by straw burning, and let straw carbonization equipment market promotion. The orthogonal experiment of carbonization process was designed according to the literature and the results of preliminary experiment. The straw biochar produced by process test was analyzed. The thermal characteristic parameters and combustion characteristic parameters were calculated. Straw biochar yield, fuel ratio, hydrocarbon atomic ratio, alkalinity index, high calorific value and dimensionless comprehensive combustion index Z were used as quality evaluation indexes for high quality straw biochar. Grey correlation analysis method and comprehensive quality score method were used to analyze the evaluation indexes and influencing factors, and the response surface method designed by CCD experiment was used to optimize the production process of straw biochar directional regulation. The experiment provides a theoretical basis for improving the energy utilization rate of straw and provides a large number of data support for the popularization and application of continuous straw carbonization equipment. The results showed that temperature was the primary factor affecting the quality of straw biochar. The five evaluation indexes of straw biochar quality except the yield of straw biochar were ranked as follows: Z > H/C >FR >AI >HHV, the quality of straw biochar produced by the equipment is stable and close to the burning quality of bituminous coal. In the orthogonal experiment, the experiment in group 16 and group 12 obtained a higher comprehensive score, and the optimal process parameter combination was A3B4C1. CCD test results after response surface optimization, in the balance of the two response values to meet the maximum, the predicted optimal process parameters are: cut after the corn straw, after 600 ℃ thermal carbonization for 50 min, the production of straw biochar output is 53.05%, its combustion index Z is 0.726 6. The empirical test showed that the difference between the experimental value and the predicted value was less than 0.2%, the fitting model and the response surface optimization method were accurate and feasible, and the combustion quality of straw biochar produced by the optimal carbonization process was greatly improved. The C content and H/C of straw biochar produced under the best technological conditions are increased by nearly 2 times, which is closed to the combustion quality of bituminous coal and anthracite, and far better than the barbecue biochar purchased in the market. Through the carbonization process in this study, the utilization quality of straw biochar can be controlled directionally, forming a reproducible and generalized quasi-directional regulation method of high quality fuelized straw biochar. The analysis methods greatly reduce the experiment times, choose the appropriate fuel straw biochar quality evaluation index, and on the premise of saving the cost of raw materials and energy, quick understanding of high quality energy straw biochar production process parameters, facilitate continuous piecewise uniform crop straw carbonization market-oriented all-round production system of rapid popularization and application.In addition, the experimental design and data analysis method in this paper can also provide data support for the production of straw carbonization process using straw as raw material for adsorption and fertilizer carbon.