Research Of Slow Pyrolysis Of Rice Husk And Corn Stalk In Auger Reactor

China is rich in agricultural biomass resources.By using pyrolysis technology,these agricultural biomass resources can be converted to pyrolysis char,pyrolysis liquid and pyrolysis gas.However,most researches on the pyrolysis of agricultural biomass reported in literature focused on the pyrolysis in fluidized bed reactors.And several researches on biomass pyrolysis in auger reactors focused on the effect of various reaction conditions to the yield and characterization of pyrolysis liquid.Therefore,the main aim of this paper is to investigate the slow pyrolysis of corn stalk and rice husk in auger reactor.This thesis focuses on the effect of temperature on pyrolysis gas and pyrolysis char,and the combustion kinetics of pyrolysis char.The slow pyrolysis of corn stalk and rice husk?two main types of lignocellulosic agricultural biomasses in China?was studied in an auger reactor with 350 g h^-11 feeding ability.The product yields and the properties of the pyrolysis products were characterized under six different pyrolysis temperatures of 350,400,450,500,550 and 600°C with the feeding speed of 2.22 g min^-1 The results shows that:?1?the pyrolysis liquid and char yields in the auger reactor are comparable to those reported for the same feedstocks in fluidized bed reactors;?2?the pyrolysis temperature significantly affects the mass yields of the pyrolysis products;?3?rice husk produces more char at the same pyrolysis temperature than corn stalk;?4?with the increase of the pyrolysis temperature?from 350 to 600°C?,the char yield decreases while the gas yield increases;?5?The maximum pyrolysis liquid yield is obtained at the pyrolysis temperature of 500°C for both feedstocks?51 wt.%of rice husk and 54 wt.%of corn stalk?.The proximate analysis results of chars from the pyrolysis rice husk and corn stalk show a decrease in volatile matter and an increase in ash content with the increase of the temperature.Both atom H:C and O:C ratios of char decreases with the increase of the pyrolysis temperature?from 350to 600°C?for both feedstocks.The higher heating values?HHVs?of rice husk char increases from 17.2 MJ kg^-1 to 21.3 MJ kg^-1 while that of corn stalk char increases from 19.89 MJ kg^-1 to 26.05 MJ kg^-1 as the pyrolysis temperature increases from 350 to 600°C.Both corn stalk and rice husk pyrolysis liquid shows relatively strong acidity,but rice husk pyrolysis liquid show more acidic than corn stalk pyrolysis liquid.The pH values of pyrolysis liquid increase from 3.06 to 4.83for corn stalk pyrolysis liquid and from 2.79 to 3.64 for rice husk with the increase of pyrolysis temperature.Compared with the water contents?around 35wt.%?of bio-oil from other pyrolysis reactors,the average water content of pyrolysis liquid obtained in this work are higher and reaches50%⁶0%.The gases from the pyrolysis of rice husk and corn stalk show a similar tendency:the molar fractions of combustible gas including CO,CH₄ and other light hydrocarbons increase gradually while the molar fraction of CO₂decreases with the increase of the pyrolysis temperature?from 350 to600°C?.H₂ is detectable at 500°C and 550°C for the pyrolysis of rice husk and corn stalk,respectively.When the pyrolysis temperature is high enough,the molar fraction of H2 increases sharply with the increase of the pyrolysis temperature for the pyrolysis of both feedstocks.The HHV of gas increases with the increase of the pyrolysis temperature for both feedstocks.To study the combustion performance of pyrolysis char,the combustion kinetics of pyrolysis char were studied.The combustion kinetic data should be preprocessed before further kinetic isoconversional analysis.The preprocessing of combustion kinetic data mainly includes the numerical differentiation and data smoothing.The combustion kinetics of corn stalk biochar was studied by using thermogravimetric analysis?TGA?technique at three heating rates of 5,10 and 20 K min^-1.The experimental?–T data has some errors and the corresponding d?/dT–T curves have many fluctuations.The Robust Locally Weighted Scatterplot Smoothing?robust LOESS?method coupled with the Corrected Akaike's Information Criterion?corrected AIC?smoothing parameter selection method was used for the smoothing of the noisy data.The following conclusions can be drawn.?1?The strategy of firstly smoothing?–T data and then differentiating smoothed?–T data for obtaining the smooth d?/dT–T data is not effective.?2?The strategy of firstly differentiating?–T data and then smoothing d?/dT–T data is effective.?3?With the corrected AIC method,the optimal smoothing parameters for the smoothing of the d?/dT–T curves were 0.05,0.03,and 0.04 for the data at 5,10,and 20 K min^-1,respectively.?4?The smoothed d?/dT–T curves of biochar combustion were processed by using the Friedman isoconversional method and the effective activation energies were obtained.The results shows that as the conversion degree increased from 0.05 to 0.95,the effective activation energies of biochar combustion increase from about 150 kJ mol^-1 and reach the maximum value of about 250kJ mol^-1 at the conversion degree of 0.3,then decrease to about 150 kJ mol^-1.