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1.
Kinetics study on biomass pyrolysis for fuel gas production 总被引：1，自引：0，他引：1
INTRODUCTIONSincebiomassisanabundant,inexpensiveandrenewableresource ,itsconversiontosyn theticfuelsandchemicalproductsappearsat tractive.Amongallkindsofbiomassconversionroutes,pyrolysisisbeinggivenincreasingatten tionsincetheprocessissimpleandmaybeopti m… 相似文献
2.
By coupling the heat transfer equation with semi-global chemical reaction kinetic equations, a onedimensional, unsteady mathematical model is developed to describe the pyrolysis of single biomass pellet in the pyrolysis zone of downdraft gasifier. The simulation results in inert atmosphere and pyrolysis zone agree well with the published experimental results. The pyrolysis of biomass pellets in pyrolysis zone is investigated, and the results show that the estimated convective heat transfer coefficient and emissivity coefficient are suitable. The mean pyrolysis time is 15.22%, shorter than that in inert atmosphere, and the pellet pyrolysis process in pyrolysis zone belongs to fast pyrolysis. Among the pyrolysis products, tar yield is the most, gas the second, and char the least. During pyrolysis, the temperature change near the center is contrary to that near the surface. Pyrolysis gradually moves inwards layer by layer. With the increase of pyrolysis temperature and pellet diameter, the total pyrolysis time, tar yield, char yield and gas yield change in different ways. The height of pyrolysis zone is calculated to be 1.51—3.51 times of the characteristic pellet diameter. 相似文献
3.
Comparative study on the pyrolysis behaviors of corn stalk and pine sawdust using TG-MS 总被引：1，自引：0，他引：1
The pyrolysis behaviors of corn stalk（CS） and pine sawdust（PS） were investigated with thermogravimetry-mass spectroscopy（TG-MS）.The peak temperature of PS was higher and the main decomposition region shifted to higher temperature compared with CS,which implied that the hemicellulose and cellulose of PS were more thermally stable than those of CS.However,the hemicellulose and cellulose of PS were more easily decomposed into gaseous products than those of CS during pyrolysis.The pyrolysis process of biomass can be described by a two-step independent first-order kinetic model.This fundamental study provides a basic insight into the biomass pyrolysis,which is beneficial for understanding the pyrolysis mechanism of biomass and developing an advanced thermal process for effective utilization of biomass. 相似文献
4.
Based on a three-step kinetic mechanism, a one-dimensional, time dependent, numerical model is presented forthe smoldering propagation in a horizontally packed bed of cellulosic material. The kinetic processes include pyrolysis andoxidation degradation of fuel and oxidation of char. Heat transfer between solid and gas is taken into account, and the diffusioncoefficient varies with the temperature. Radiative heat transfer is included by using the diffusion approximation. The effectsof airflow velocity and oxygen concentration are simulated on the smoldering velocity and the averaged maximum temperatureof smoldering fuel. The results indicate that the spread rate varies linearly with increasing airflow velocity, and the inlet airvelocity has little effect on the maximum temperature. The evolutions of gas species and solid compositions are predicted.The effects of frequency factors (A1, A2 and A3) are analyzed. Simulations show that the smoldering spread rate increaseswith increasing A2 (fuel oxidation), but decreases with A1 (fuel pyrolysis) and A3 (char oxidation). 相似文献
5.
Fluidized-bed pyrolysis of waste bamboo 总被引：1，自引：0，他引：1
XIAO Gang NI Ming-jiang HUANG He CHI Yong XIAO Rui ZHONG Zhao-ping CEN Ke-fa 《浙江大学学报(A卷英文版)》2007,8(9):1495-1499
Bamboo was a popular material substituting for wood,especially for one-off commodity in China. In order to recover energy and materials from waste bamboo,the basic characteristics of bamboo pyrolysis were studied by a thermogravimetric analyzer. It implied that the reaction began at 190～210 °C,and the percentage of solid product deceased from about 25% to 17% when temperature ranged from 400 °C to 700 °C. A lab-scale fluidized-bed furnace was setup to research the detailed properties of gaseous,liquid and solid products respectively. When temperature increased from 400 °C to 700 °C,the mass percent of solid product decreased from 27% to 17% approximately,while that of syngas rose up from 19% to 35%. When temperature was about 500°C,the percentage of tar reached the top,about 31%. The mass balance of these experiments was about 93%～95%. It indicated that three reactions involved in the process: pyrolysis of exterior bamboo,pyrolysis of interior bamboo and secondary pyrolysis of heavy tar. 相似文献
6.
Vacuum pyrolysis was employed to dispose scrap brominated epoxy printed circuit boards (PCBs). Pyrolysis characteristics of waste PCBs under normal pressure and vacuum were investigated in this paper. A detailed study on the analysis of the elemental composition of PCBs and the pyrolysis products was performed. The thermal decomposition kinetics was measured by a thermogravimetric (TG) analyzer. The activation energy of pyrolysis under nitrogen atmosphere and vacuum were 193 kJ/mol to 206 kJ/mol and 145 kJ/mol to 165 kJ/mol, respectively. The composition of materials was analyzed by elemental analyzer. The pyrolysis products were analyzed by GC (gas chromatograph), GC-MS (chromatography and mass spectrometry) and FT-IR (Fourier transform infrared spectroscopy). Vacuum helped to increase the yield of pyrolysis oil. The liquid yield of PCBs pyrolysis at 15 kPa and normal pressure were 31.3? and 23.5?, respectively. The main components in pyrolysis oils were phenol, isopropyl-phenol, and their brominated substitution. 相似文献
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Based on a systemic survey, the pyrolysis characteristics and apparent kinetics of the municipal solid waste （ MSW） under different conditions were researched using a special pyrolysis reactor, which could overcome the disadvantage of thermo-gravimetric analyzer. The thermal decomposition behaviour of MSW was investigated using thermo-gravimetric （ TG ） analysis at rates of 4.8,6.6,8.4, 12.0 and 13. 2 K/min. The pyrolysis characteristics of MSW were also studied in different function districts. The pyrolysis of MSW is a complex reaction process and three main stages are found according to the results. The first stage represents the degradation of cellulose and hemicellulose, with the maximum degradation rate occuring at 150℃ -200 ℃： the second stage represents dehydrochlorination and depolymerization of intermediate products and the differential thermogravimetric （ DTG ） curves have shoulder peaks at about 300℃： the third stage is the decomposition of the residual big molecular organic substance and lignin at 400 ℃- 600 ℃. Within the range of given experimental conditions, the results of non-linear fitting algorithm and experiment are in agreement with each other and the correlation coefficients are over0. 99. The kinetic characteristics are concerned with the material component and heating rate. The activation energy of reaction decreases with the increase of heating rate. 相似文献
8.
The coal tar was qualitative and quantitative anMyzed by gas chromatography （GC） method. 74 components were identified exactly by gas chromatographY-mass spectrometry （GC-MS）. 31 components （37%） were quantitatively analyzed by gas chromatography-flame ionization detector （GC-FID）. The linearity, accuracy, precision, limit of detection （LOD） and limit of quantitative （LOQ） determination were inspected. The scope of quantitative analysis by CC was discussed. The experimental results of thermogravimetric analysis （TGA） proved that GC quantitative analysis of the coal tar was reliable. 相似文献
9.
使用粉煤灰作为催化剂,对聚丙烯进行热解处理,并用程序升温的热重法(TG)和恒温法两种模型方法对热解反应进行研究。结果表明,这两种方法都适用于聚丙烯的催化降解,且粉煤灰含量为2%时,恒温模型计算得到的反应活化能为196kJ/mol,TG模型计算的结果是233kJ/mol(反应级数为1)。从两种模型计算的计算结果与实验结果的拟合情况来看,恒温法得到的结果与实验结果更加吻合。 相似文献
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研究了用电子自旋顺磁共振(ESR)法对香烟烟气中的自由基进行分析的样品处理方法及ESR检测方法.对四种英国产香烟样品中的粒相及气相自由基进行了分析检测并对检测结果进行了讨论.结论:大多数英国产的检测样品香烟中,含有1.5～3倍于国产对照香烟样品的气相自由基;而国产对照样品香烟的粒相自由基的含量水平则处于较高水平.实验结果还显示:同品牌的Sobranie香烟中,不同型号样品中粒相自由基含量与焦油含量具有负相关性,但不同品牌则不同;对于检测样品而言,气相自由基的含量与焦油含量有正相关性. 相似文献
11.
高天秀 《淮南职业技术学院学报》2014,(3):10-14
煤沥青是煤炭经高温热分解后的副产物煤焦油经进一步蒸馏加工后的产物,煤沥青组成极为复杂,具有稳定的性能,以煤沥青为原料,经过进一步加工后可获得一系列重要的高附加值衍生产品;综述了煤沥青用作煤沥青涂料、筑路沥青、炭素工业浸渍剂和粘结剂以及中间相煤沥青等方面的应用原理和进展。 相似文献
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Carcinogenic and mutagenic polycyclic aromatic hydrocarbons (PAHs) generated in coal combustion have caused great environmental health concern. Seventeen PAHs (16 high priority PAHs recommended by USEPA plus Benzo[e]pyrene) present in five raw bituminous coals and released during bituminous coal combustion were studied. The effects of combustion temperature, gas atmosphere, and chlorine content of raw coal on PAHs formation were investigated. Two additives (copper and cupric oxide) were added when the coal was burned. The results indicated that significant quantities of PAHs were produced from incomplete combustion of coal pyrolysis products at high temperature, and that temperature is an important causative factor of PAHs formation. PAHs concentrations decrease with the increase of chlorine content in oxygen or in nitrogen atmosphere. Copper and cupric oxide additives can promote PAHs formation (especially the multi-ring PAHs) during coal combustion. 相似文献
14.
Carcinogenic and mutagenic polycyclic aromatic hydrocarbons (PAHs) generated in coal combustion have caused great environmental health concern. Seventeen PAHs (16 high priority PAHs recommended by USEPA plus Benzo[e]pyrene) present in five raw bituminous coals and released during bituminous coal combustion were studied. The effects of combustion temperature, gas atmosphere, and chlorine content of raw coal on PAHs formation were investigated. Two additives (copper and cupric oxide) were added when the coal was burned. The results indicated that significant quantities of PAHs were produced from incomplete combustion of coal pyrolysis products at high temperature, and that temperature is an important causative factor of PAHs formation. PAHs concentrations decrease with the increase of chlorine content in oxygen or in nitrogen atmosphere. Copper and cupric oxide additives can promote PAHs formation (especially the multi-ring PAHs) during coal combustion. 相似文献
15.
Reputation-based linear cooperation for spectrum sensing in cognitive radio networks 总被引：1，自引：0，他引：1
We propose a reputation-based cooperative spectrum sensing scheme in cognitive radio （CR） networks to solve the uncertainty resulting from the multipath fading and shadowing effect. In the proposed scheme, each cooperative CR user has a reputation degree that is initialized and adjusted by the central controller, and used to weight the sensing result from the corre- sponding CR user in the linear fusion process at the central controller. A simple method for adjusting the reputation degree of CR users is also presented. We analyzed and evaluated the detection performance of the reputation-based cooperative spectrum sensing scheme. Simulation results showed that our proposed scheme alleviates the problem of corrupted detection resulting from destructive channel conditions between the primary transmitter and the CR user. The performance of our proposed scheme was improved compared to the average-based linear cooperation scheme, and was similar to that of the optimal linear cooperation scheme with feasible computational complexity. Moreover, our proposed scheme does not require knowledge of channel statistics. 相似文献
16.
Research in science education has recognized the importance of history and philosophy of science. Given this perspective, the study was designed to develop a framework for examining the way in which chemistry textbooks describe the kinetic theory and related issues. The framework was developed by a rational reconstruction of the kinetic molecular theory of gases based primarily on the interpretations of Maxwell and Boltzmann, by historians and philosophers of science. Another aspect of the framework was based on an analysis of freshman chemistry students' performance on gas problems that required the use of algorithms or conceptual understanding. Subsequently, 22 textbooks were evaluated using a framework consisting of six criteria. Results obtained showed that most textbooks lacked a history and philosophy of science framework and did not deal adequately with the following aspects: (1) Postulates of the kinetic theory were speculative and played the role of simplifying assumptions, considered to be the rule in science rather than being the exceptions; (2) Based on these simplifying assumptions, the theorists built a series of tentative models that progressively incorporated the behavior of real gases; (3) Similar to other research programs in the history of science, Maxwell's was based on inconsistent foundations; (4) Development of the kinetic theory had to compete with chemical thermodynamics, a rival research program; (5) Maxwell and Boltzmann facilitated our understanding of gas behavior beyond the observable hydrodynamical laws, by explaining the internal properties (e.g., molecular collisions). 相似文献
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ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｍｏｄｅｌｉｎｇｍｅｔｈｏｄｓｏｆｇａｓ ｓｏｌｉｄｆｌｏｗａｒｅｋｎｏｗｎｔｏｉｎｃｌｕｄｅｔｈｅＥｕｌｅｒｉａｎ/ＥｕｌｅｒｉａｎａｐｐｒｏａｃｈａｎｄｔｈｅＥｕｌｅｒｉａｎ/Ｌａｇｒａｎｇｉａｎｏｎｅ.ＴｈｅＥｕｌｅｒｉａｎ/Ｅｕｌｅｒｉａｎａｐｐｒｏａｃｈｔｒｅａｔｓｂｏｔｈｐｈａｓｅｓａｓｓｅｐａｒａｔｅｉｎｔｅｒｐｅｎｅｔｒａｔｉｎｇｃｏｎｔｉｎｕｕｍ ,ｗｈｉｌｅｔｈｅＥｕｌｅｒｉａｎ/Ｌａｇｒａｎｇｉａｎａｐｐｒｏａｃｈｔｒｅａｔｓｔｈｅｇａｓｐｈａｓｅａｓ… 相似文献
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在场致发射器件中 ,发射电流通常会随着工作时间的增加而跌落 .发射电流跌落的机理较为复杂 .本文模拟分析了一次电子从场致发射发射体表面的发射情况 .根据一次电子的电流密度分布和运动轨迹 ,研究残余气体分子的电离 .然后计算正离子在电场中的运动轨迹 ,利用半经验模型分析不同能量的正离子对发射体表面的损伤情况 ,最后估计出在不同残余气压和一次电流下发射电流的衰减 相似文献
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Based on the Bhatnagar-Gross-Krook distillation for two components in the presence equation, a new scheme of wiped-film molecular of inert gas is developed. The equations in the scheme are solved numerically by the method of finite difference and iteration. The new scheme is used to simulate the molecular distillation of dibutyl phthalate and dibutyl sebacate （ DBP-DBS ） mixture. The effects of the inert gas pressure, the distance between the evaporation surface and condensation surface, the rotation rate of blade, and the number of blades on the distillation rate and separation factor are discussed. 相似文献
20.
ZHOU Jie YANG Yong-rong REN Xiao-hong STAPF Siegfried 《浙江大学学报(A卷英文版)》2006,7(8):1440-1446
INTRODUCTION Waste tires cannot degrade in the short term; they may cause accidental fire and emit poisonous gases rich in dioxins. How to recycle and utilize them effectively, and prevent secondary pollution to the environment has become a new issue that the reuse of resources is faced with. Pyrolysis is an environ-ment-friendly process for recycling of used tires. Three products are typically obtained from the pyrolysis of waste tires: gas, oil and char (Gonzalez etal., 2001). Pyrolyt… 相似文献