| In order to explore the effect of straw materials and carbonization conditions on thermal chemical characteristics of straw biochar samples,analyze the correlation between element composition and industrial composition and calorific value,discusses the feasibility of rapid deter mination for thermal chemical characteristics in straw biochar samples with FT-MIR,5 kinds of straw,including cotton straw,wheat straw,corn straw,rape straw,rice straw,straw biochar samples had been collected,175 biochar samples were collected by carbonization processing.Element composition and industrial composition and calorific value were measure-ed by standard methods.Then infrared spectrum were collected by the VERTEX type 70 Fourier infrared spectrometer.According to correlation and collinearity analysis,a prediction model of gross calorific value and net calorific value of straw biochar was builded;TQ Analyst 8.3 was used to preprocess the spectra,the PLS model was established to predict the thermal chemical charac-teristics index of straw biochar samples.The results of the study were as follows:?1?The results of caloric value showed that the caloric value of the crop straw was increased after carbonization.The results of element composition showed that C element content was the highest and N element content was the lowest.The results of industrial composition showed that ash and fixed carbon content were increased,volatile matter was reduced in contrast.The CV of moisture content was the largest and there is no obvious trend.?2?The thermal chemical properties under different carbonization conditions were compared.The results showed that the thermal chemical properties were influenced by straw materials,the holding time and the heating rate have little effect on the thermochemical properties.With the increase of temperature:N element,H element and O element content were reduced,C element content was increased in contrast.Ash and volatile matter content were reduced,fixed carbon content was increased in contrast.Among the five kinds of crops,Rice straw biochar samples has the minimum calorific value and C element content,the largest content of Ash.?3?A prediction model of gross calorific value and net calorific value of straw biochar was builded based on element composition.The results indicated that the principal component regression?PCR?is the best method.The deter mination coefficient,the predicted standard deviation and the relative standard deviation of the prediction model of gross calorific value were 0.75?1255.72 J·g-1?5.32%;the deter mination coefficient,the predicted standard deviation,the relative standard deviation of the prediction model of net calorific value were 0.75?1274.88 J·g-1?5.32%.The results of external validation indicated that the relative standard deviation of the prediction model of the gross calorific value and the net calorific value were 5.32%?5.32%.The results show that the calorific value model can only be used for the general estimate,the accuracy needs to be improved.?4?A prediction model of gross calorific value and net calorific value of straw biochar was builded based on industrial composition.The results indicated that the principal component regression?PCR?is the best method.The deter mination coefficient,the predicted standard deviation and the relative standard deviation of the prediction model of gross calorific value were 0.86?1126.79 J·g-1?4.79%;the deter mination coefficient,the predicted standard deviation,the relative standard deviation of the prediction model of net calorific value were 0.83?1167.25 J·g-1?4.93%.The results of external validation indicated that the relative standard deviation of the prediction model of the gross calorific value and the net calorific value were 4.41%?4.91%.The results show that the calorific value model can be used to predict the calorific value of straw biochar.?5?A the PLS model for gross calorific value and net calorific value of straw biochar was builded by FT-MIR.Take the independent verification set to validate the model and the results showed that the correlation coefficient Rp is 0.91,and the RMSEP is 614 J·g-1,and the predicted standard deviation RSD is 2.61%of gross calorific value,the correlation coefficient Rp is 0.87,and the RMSEP is 707 J·g-1,and the predicted standard deviation RSD is 3.12%of net calorific value.The results show that using FT-MIR to predict calorific value of straw biochar is a feasible method.?6?A the PLS model for C,N,O,H element content of straw biochar was builded by FT-MIR.Take the independent verification set to validate the model and the results showed that the correlation coefficient RP is 0.90,and the RMSEP is 2.44%,and the predicted standard deviation RSD is 4.07%of C element content,the correlation coefficient RP is 0.75,and the RMSEP is 0.31%,and the predicted standard deviation RSD is 22.46%of N element content,the correlation coefficient RP is 0.92,and the RMSEP is 1.35%,and the predicted standard deviation RSD is 9.74%of O element content,the correlation coefficient RP is 0.81,and the RMSEP is 0.81%,and the predicted standard deviation RSD is 13.6%of H element content.The results show that C element and O element PLS model can be used in the actual prediction;the accuracy H element PLS model needs to be improved;N element PLS model can not be used in the actual forecast.?7?A the PLS model for ash,volatile matter,fixed carbon content of straw biochar was builded by FT-MIR.Take the independent verification set to validate the model and the results showed that the correlation coefficient RP is 0.97,and the RMSEP is1.59%,and the predicted standard deviation RSD is 9.64%of ash,the correlation coefficient RP is0.89,and the RMSEP is 4.17%,and the predicted standard deviation RSD is 14.35%of volatile matter,the correlation coefficient RP is 0.86,and the RMSEP is 4.79%,and the predicted standard deviation RSD is 9.21%of fixed carbon.The results show that ash PLS model can be used in the actual prediction;the accuracy volatile matter and fixed carbon PLS model needs to be improved. |
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