Study On Pyrolysis Characteristics Of Sweet Sorghum Stalk And Millet Stalk

In order to further explore the process and mechanism of the pyrolysis of sorghum stalks and millet stalks before and after pickling,the pyrolysis characteristic differences of sorghum stalks and millet stalks before and after pickling were compared and analyzed by thermal gravimetric analyzer?TGA?at 25(15,25,35,45,55,110,120,130,140,150,210,220,230,240,250,310,320,330,340,350,410,420,430,440,450?·min^-1)heating rates.Using Flynn-Wall-Ozawa?FWO?and Kissinger-Akahira-Sunose?KAS?methods,the activation energy values and their deviations of sweet sorghum stalks and millet stalks before and after pickling were calculated at 14?15%⁸0%?degrees of conversion.At the same time,different termination temperatures?150,250,450,950??were selected and Fourier transform infrared spectrometer?FTIR?was used to analyze the organic structure of residues of pyrolysis of sweet sorghum stalks and millet stalks before and after pickling.The pyrolysis process of sweet sorghum stalks and millet stalks before and after pickling can be divided into four stages,and the pyrolysis trends are similar at five low heating rates,with the increase of heating rate,thermal hysteresis occured.The higher the heating rate is,the more serious the thermal hysteresis is.However,when the heating rate reaches100?·min^-11 or more,the thermal hysteresis disappears.Arrangement has no regularity.After research,the overall trend of the TG curve is affected by many factors such as the chemical reaction rate,thermal hysteresis,and the uniqueness of the material.At high heating rates,the TG curve does not shift to high temperature in sequence,but the thermal hysteresis still exists.It is only affected by the relatively strong chemical reaction in the pyrolysis process and the non-uniform selection of each material.The final weight loss rate of sweet sorghum stalks and millet stalks after pickling was higher than that before pickling,and because of the different composition of their four components,the reaction peaks on the DTG curves were significantly different,and the pyrolysis characteristics were different.The FTIR spectra of the four samples were similar before and after the pyrolysis reaction.The infrared spectra of the biomass straws pyrolyzed at the same heating rate and different final temperatures for each sample showed the same overall trend.The position of the absorption peak did not change much,but the intensity of the absorption peak was significantly different.When the pyrolysis termination temperature was 950^°C,the infrared light was basically absorbed,leaving only a few absorption peaks and the absorption intensity was very low.The high-molecular polymers of sweet sorghum stalks and millet stalks have basically been decomposed into small molecules,and the pyrolysis reaction of biomass has basically ended.The heating rate has little effect on the pyrolysis products.At different heating rates,when the final temperature of pyrolysis is similar,the composition of each sample residue is similar,and the curves of the spectrum is also consistent.Although the high heating rate is not suitable for the study of the pyrolysis mechanism of biomass,it can still be used for the study of pyrolysis products.The KAS and FWO methods were used to calculate the activation energy values of sweet sorghum stalks and millet stalks before and after pickling.It was found that the activation values obtained by FWO method was slightly higher than that of KAS.The difference in the numerical value is because the approximate values selected in the calculation process are different.Although the accuracy of the two methods is different,the change trend of activation energy is consistent.After the pickling,the activation energy of the stalks is generally lower than before the pickling.The pickling will change the composition of the biomass,and the difference in the composition will cause a significant difference in the activation energy of the pyrolysis of the biomass.This study provides a theoretical basis for biomass high quality utilization and optimization design of pyrolysis reactor.