农业工程学报
農業工程學報
농업공정학보
2015年
3期
275-282
,共8页
生物质%热解%温度%玉米芯%质谱%升温速率%粒度%气体流速
生物質%熱解%溫度%玉米芯%質譜%升溫速率%粒度%氣體流速
생물질%열해%온도%옥미심%질보%승온속솔%립도%기체류속
biomass%pyrolysis%temperature%corn cob%mass spectrometry%heating rate%particle size%gas flow rate
为了全面掌握不同热解条件下玉米芯的热解特性及热解过程中气相产物随温度变化的释放规律，深刻理解玉米芯的热解行为及反应机理，该文采用热重-质谱联用技术对玉米芯进行了氮气气氛下的热解特性试验研究，对比研究了不同升温速率（5、10、20℃/min）、不同粒度（74、154、280、450μm）、不同气体流速（30、60、90 mL/min）等因素对玉米芯热解行为的影响，发现非等温失重过程可分为4个阶段：失水、预热解过渡、挥发分析出和炭化阶段。通过质谱分析研究了热解过程小分子气相产物（CO、CO2、CH4、O2、H2、H2O）的释放规律，并计算了挥发分释放指数。升温速率升高，热解反应越易进行；在粒度小于450μm范围内，试样热解的总失重率随粒度的增大而增加，而且颗粒越大，挥发分产物开始逸出的温度越低。粒度为＞154～450μm 的试样的热解过程主要受颗粒内部热传递影响，而粒度＜154μm的试样的热解主要受内在反应动力学速率控制；随着气体流速升高，试样热解的总失重率和初始温度增大，但增幅很小，最大失重速率对应的温度也有向高温段移动的趋势。利用Coats-Redfern方法计算出玉米芯的热解动力学参数，说明玉米芯热解的挥发分析出阶段可用单段一级反应描述。该研究对于优化以玉米芯为原料的热化学转化工艺参数和提高燃料产物的产量与品质等具有重要意义，对于设计和开发高效的生物质能转化设备也可提供参考。
為瞭全麵掌握不同熱解條件下玉米芯的熱解特性及熱解過程中氣相產物隨溫度變化的釋放規律，深刻理解玉米芯的熱解行為及反應機理，該文採用熱重-質譜聯用技術對玉米芯進行瞭氮氣氣氛下的熱解特性試驗研究，對比研究瞭不同升溫速率（5、10、20℃/min）、不同粒度（74、154、280、450μm）、不同氣體流速（30、60、90 mL/min）等因素對玉米芯熱解行為的影響，髮現非等溫失重過程可分為4箇階段：失水、預熱解過渡、揮髮分析齣和炭化階段。通過質譜分析研究瞭熱解過程小分子氣相產物（CO、CO2、CH4、O2、H2、H2O）的釋放規律，併計算瞭揮髮分釋放指數。升溫速率升高，熱解反應越易進行；在粒度小于450μm範圍內，試樣熱解的總失重率隨粒度的增大而增加，而且顆粒越大，揮髮分產物開始逸齣的溫度越低。粒度為＞154～450μm 的試樣的熱解過程主要受顆粒內部熱傳遞影響，而粒度＜154μm的試樣的熱解主要受內在反應動力學速率控製；隨著氣體流速升高，試樣熱解的總失重率和初始溫度增大，但增幅很小，最大失重速率對應的溫度也有嚮高溫段移動的趨勢。利用Coats-Redfern方法計算齣玉米芯的熱解動力學參數，說明玉米芯熱解的揮髮分析齣階段可用單段一級反應描述。該研究對于優化以玉米芯為原料的熱化學轉化工藝參數和提高燃料產物的產量與品質等具有重要意義，對于設計和開髮高效的生物質能轉化設備也可提供參攷。
위료전면장악불동열해조건하옥미심적열해특성급열해과정중기상산물수온도변화적석방규률，심각리해옥미심적열해행위급반응궤리，해문채용열중-질보련용기술대옥미심진행료담기기분하적열해특성시험연구，대비연구료불동승온속솔（5、10、20℃/min）、불동립도（74、154、280、450μm）、불동기체류속（30、60、90 mL/min）등인소대옥미심열해행위적영향，발현비등온실중과정가분위4개계단：실수、예열해과도、휘발분석출화탄화계단。통과질보분석연구료열해과정소분자기상산물（CO、CO2、CH4、O2、H2、H2O）적석방규률，병계산료휘발분석방지수。승온속솔승고，열해반응월역진행；재립도소우450μm범위내，시양열해적총실중솔수립도적증대이증가，이차과립월대，휘발분산물개시일출적온도월저。립도위＞154～450μm 적시양적열해과정주요수과립내부열전체영향，이립도＜154μm적시양적열해주요수내재반응동역학속솔공제；수착기체류속승고，시양열해적총실중솔화초시온도증대，단증폭흔소，최대실중속솔대응적온도야유향고온단이동적추세。이용Coats-Redfern방법계산출옥미심적열해동역학삼수，설명옥미심열해적휘발분석출계단가용단단일급반응묘술。해연구대우우화이옥미심위원료적열화학전화공예삼수화제고연료산물적산량여품질등구유중요의의，대우설계화개발고효적생물질능전화설비야가제공삼고。
Shortage of fossil fuels and environmental pollution become increasingly severe with the rapid economic development. As the only renewable energy which can be directly converted to gas, liquid and solid fuels, biomass has aroused growing attention all over the world. Corn is one of the main crops in China. Corn cob is the main agricultural waste produced in process of maize production, and the corn cob biomass contains a lot of biodegradable organic matter. Thermo-chemical conversion is an efficient means of biomass energy conversion. It can convert the organic matter of corn cob into many forms of energy, such as gas, liquid, solid, and other biomass products at high temperature. Pyrolysis is the most basic process of thermal chemical conversion. The characteristics of pyrolysis are important tool which can express the influence of pyrolysis parameters on raw material conversion rate. In order to fully grasp the pyrolysis characteristics of corn cob and the release law of gas-phase products with temperature change in the thermal decomposition process in different working conditions, and to deeply understand the pyrolysis behavior of corn cob and its reaction mechanism, simultaneous thermogravimetry-mass spectrometry (TG-MS) was used to investigate the pyrolysis behavior and kinetics of corn cob under nitrogen atmosphere. The pyrolysis behavior of corn cob was comparatively studied at different heating rates (5, 10, 20℃/min), different particle sizes (74, 154, 280, 450μm) and different carrier gas flow rates (30, 60, 90 mL/min). It was found that the non-isothermal weight loss process of the samples was composed of dehydration, preheating pyrolysis, volatile matter separation and carbonization. The temperature interval of 210-405℃ was the main floating zone. There were two obvious peaks in corn cob’s weight loss rate curves. The release laws of small molecule gas products (CO, CO2, CH4, O2, H2and H2O) were studied by mass spectrometry analysis. The pyrolysis characteristics index was calculated as well, showing that the higher the heating rate, the quicker the pyrolysis reaction. The maximum pyrolysis rate and the index increased with the rise of heating rate. The peak corresponding to the maximum pyrolysis rate moved to higher temperature. The peak temperature of maximum pyrolysis rate varied along with the change of particle size weakly. But the relationship between the maximum weight loss rate and particle size was not obvious. Within the scope of particle size less than 450μm, the total pyrolytic weight loss of sample increased with the rise of particle size. The process of pyrolysis was mainly affected by particle internal heat and the mass transfer for the sample of 154-450μm. Over 500℃, it showed a strong exothermic reaction. The heat release increased with the rise of particle size. But the pyrolysis was mainly controlled by the rate of intrinsic reaction kinetics for the sample with particle size less than 154μm. The effect of carrier gas flow rate on the pyrolysis was negligible especially for the pyrolysis reaction rate. The kinetic parameters were calculated by the Coats-Redfern method, indicating that the volatile matter separation stage of corn cob pyrolysis could be described in the single first-order reaction. This research has guiding significance for the optimization of the parameter of thermal chemical conversion process and for improving the yield and quality of fuel products. Moreover, it can also be used to provide reference for designing and developing some efficient biomass energy conversion devices.
