食用菌菌糠的热解特性及动力学分析

Pyrolysis characteristics and kinetic analysis of edible fungus chaff

为考察食用菌菌糠的热解特性和机理,该研究采用热重和热重-红外联用对香菇菌糠在氮气气氛下的热解特性进行研究,考察不同升温速率下菌糠的热重(TG)曲线和微分热重(DTG)曲线的变化规律,并对DTG曲线进行分峰分析,通过计算得到香菇菌糠热分解的反应活化能E、反应级数n及频率因子A,以及热解产物析出特性;在固定床上开展了香菇菌糠的定温热解试验,试验温度分别为500、550、600℃,并对三相产物产率和成分组成等进行了分析。结果表明:香菇菌糠热解可以分为3个阶段,水分析出段,热解段和炭化段,其中主要热解阶段为250~550℃,失质量率达到58%;升温速率对香菇菌糠热解影响不明显,但是随着升温速率的增大,试样的TG和DTG曲线向高温区移动;菌糠热解的表观活化能为66.33 kJ/mol,较低的表观活化能表明菌糠更容易发生热解。固定床定温热解结果表明菌糠热解气的主要成分为CO2、CO、CH4、H2,4种气体成分含量由高到低为:CO2、CO、CH4、H2;随着热解温度的升高,菌糠热解所得生物油成分以CxHyOz为主,表明菌糠热解生成的生物油具有一定的潜在利用价值;香菇菌糠热解半焦的主要成分是固定碳,相较于原料,挥发分的占比大幅度减少。

For investigating the pyrolytic characteristics and mechanism of spent mushroom substrate,this research studies the thermogravimetric(TG)curve and differential thermogravimetric(DTG)curves of spent mushroom substrate(SMS)of Shiitake mushroom at different heating rates,using the combination of thermogravimetry and thermogravimetry-infrared the pyrolysis in nitrogen atmosphere.A peak splitting technique was used to analyze the DTG curve,thereby to calculate the activation energy E,reaction order n,frequency factor A,further to obtain the precipitation characteristics of the pyrolysis products.A pyrolysis experiment at constant temperature for SMS of Shiitake mushroom was performed on a fixed bed,where the experimental temperatures were set at 500,550,and 600℃,thereby to analyze the yield and composition of three-phase products.Industrial analyzers were used to characterize and compare raw materials and pyrolysis semi-coke,where the FTIR was used to perform functional group analysis on semi-coke,the GC-MS was used to analyze pyrolysis tar,and a flue gas analyzer was selected to measure pyrolysis gas online.The results showed that the pyrolysis of SMS of Shiitake mushroom can be divided into three stages:the water precipitation,the pyrolysis,and the carbonization stage.The pyrolysis stage dominated during the entire process with the temperature range of 250-550℃,where the weight loss reached 58%.There was no obvious effect of heating rate on pyrolysis.Nevertheless,the TG and DTG curves of the sample shifted to the high temperature zone,as the heating rate increased.The apparent activation energy for the pyrolysis of SMS of Shiitake mushroom was 66.33 kJ/mol,easier for pyrolysis due to the low apparent activation energy.In the pyrolysis experiment performed on the fixed-bed at constant temperature,the main components of the pyrolysis gas of SMS of Shiitake mushroom were CO2,CO,CH4,H2,ranking in order:CO2,CO,CH4,H2,which was well consistent with the measured data from the TG-FTIR.At 600℃,the contents of CO and H2 increased significantly.The data of gas analysis showed that the overall gas yield of the reaction was well consistent under the experimental conditions,indicating that the pyrolysis reaction was fully completed.At 500℃,the liquid products of pyrolysis were mainly silicon-containing organics,showing that there was a certain amount of silicon in the raw material.The main component of the bio-oil from the pyrolysis of the mushroom residue was CxHyOz,as the pyrolysis temperature increased,indicating a promising potential application using the pyrolysis of mushroom residue to produce the bio-oil.In the semicoke from the slow pyrolysis of mushroom residue,the dominated component was fixed carbon,compared with the raw material,indicating the proportion of volatile contained in pyrolytic semicoke decreased significantly.There was no significant difference in the types of functional groups in the pyrolysis semicoke at the three temperatures,whereas,there were obvious characteristic peaks of alcohols,carboxylic acids,and aromatic groups.