摘要
近年来,能源和环保问题成为制约世界各国发展的主要瓶颈。生物质能作为唯一可储存和运输的可再生能源,在人类未来的能源系统中将占有相当重要的地位。生物质颗粒燃料,不仅具有挥发分高、着火易、燃烧性能好、有害烟气低和排渣少等优良的热工及环保性能,而且能有效解决我国农村和城镇生产生活用能问题。
但当前我国对生物质颗粒燃料的研究还不够深入,在实际运行中,存在着玉米秸秆单质颗粒的结渣问题和木屑单质颗粒的价格问题等,这些都制约了生物质能的开发和利用。
为了解决上述问题,本文以玉米秸秆、木屑和稻壳为研究对象,通过结渣特性分析,分别获得了玉米秸秆与稻壳、木屑与稻壳的混合配比方案;利用正交化设计方法,讨论了混合颗粒的成型因素(即成型压力和成型温度)对成型指标(即成型密度和成型效果)的影响;对不同成型条件下的混合颗粒进行了热重分析,绘制出热重失重率(TG)和微商热重(DTG)曲线,分别获得了相关的热解特性参数和动力学参数。最终结论如下:混合颗粒与单质颗粒的燃烧特性基本一致;适当加入稻壳,可提高混合颗粒燃料的灰熔点,改善其结渣特性,且能解决实际燃烧过程的结渣问题。成型压力和升温速率提高,均可加快燃烧反应速度,延迟着火温度,而成型压力增大也使挥发分的燃烧特性更加明显;成型温度升高,使着火温度延迟,但反应速度减慢;稻壳含量减小,着火温度提前,加快反应速度。
以上试验研究和结论对设计生物质颗粒燃料成型机具有实用价值,对燃烧设备的设计也具有指导意义。
As the fourth-largest energy resources of world's primary energy consumption, Biomass energy is the only renewable energy that can be stored and transported. Biomass energy will occupy a very important role in mankind's future energy system. It's a form of solar energy which is stored in Biological bodies on basis of the chemical energy. With biomass as a carrier, it comes from plant photosynthesis directly or indirectly. It's renewable and stable. Compared with wind power, solar energy, it's rarely constrained by natural factors, and it also can be processed into conventional fuels of solid, liquid and gaseous.
Energy and environmental issues have become the focus of world attention when the human society entered the 21st century. Although coal, natural gas and oil are still the main sources of fuels, developing and utilizing of new clean renewable energy sources have become a very important and pressing issue with the increasing depletion of fossil energy and increasingly serious environmental problems. China is a large agricultural country and biomass resources are very rich. Utilization of biomass resources has still great developing potential. Therefore, adequate and reasonable developing and using biomass energy are of critical importance to ease the energy crisis of our country, preventing environmental degradation and enhancing national energy security and other aspects.
World powers began to research and utilize biomass energy as early as 30 years in the 20th century. In many developed countries such as Europe, America and Japan, molding and combustion equipment of biomass have realized industrialization. Although molding and combustion equipments of biomass in these countries have many advantages such as reasonable processing, high degree of specialization, good degree of automation, high thermal efficiency, low-smoke pollution and so on, it is not suitable for our country to import it in which they have many disadvantages such as high price, single variety of fuels, easy slagging, high power consumption and so on compared to my country.
We must also realize that the use and research of biomass energy are not deep enough in the current, and there is still a certain gap with developed countries. Especially, study of Biomass Briquette need to go a long way. Therefore, there is no available theory for practical application. Taking simple substance briquette of corn stalks as an example, there is a serious cinder problem in during of combustion, which makes higher requirements to molding and combustion equipment. Simple substance briquette of wood chips has been at high prices, and there is also a cinder problem in using, so it is difficult to promote the use of it in reality. Although ash melting point of simple substance briquette of rice husks is very high, there are problems of difficulties in forming and lower heat release in reality.
This paper is exactly aimed at easy slagging of simple substance briquette, high prices and difficult molding problems on the basis of a large number of domestic and foreign documens. Reasonable mixed corn stalks, rice husks and wood chips as raw biomass materials through the scientific method. The author mainly focuses on the slagging characteristics, compression molding and combustion characteristics. The purpose of this paper is to get some more systematic and regular conclusions for biomass briquette applying to industrial production, which would provide some valuable guidance.
The main contents of this paper include:
1)Slagging characteristics research. In this paper, biomass materials of different components are made to mix and form. In order to product ash, the author used furnace to simulate the combustion process of biomass pellet fuel mixture in the boiler. By using Ash Fusion Tester to analyze the ash slag.Using whether softening temperature or the difficult degree of ash, simple substance briquette of corn stalks and wood chips slag severely, but rice husks doesn’t slag. Ash fusion temperature was higher than cinder temperature when evaluating with CRC(about 100-150℃). Experimental results show that there a marked increase of ash melting point with the increasing amount of rice husk. Slag can not be formed with 75% corn stalks - 25% rice husks and 80% wood chips -20% corn stalks. It means that mix of different kinds of simple substance briquette solves the slagging problem and this enable to meet the normal using requirements of the combustion equipment. Finally, the author provided two mixing ratios of biomass after comprehensive research and analysis. That is 75% corn stalks - 25% rice husks and 57% wood chips -43% corn stalks.
2)Design of Orthogonal Experiment. In this paper, the author uses corn stalks, rice husks and wood chips which were produced in northeast as the main object of study, and then thermoformed after mixing. The forming effect of biomass mixture is the basis of studying the fuel various aspects of characteristics of the fuel. The pressure and temperature of molding are two important factors in the forming tests. The author used Combination of binary quadratic regression orthogonal design method of Optimal Design and Analysis of Test to optimize the design of the test. Under the research and analysis of the molding experiment, the author obtains the orthogonal combination of the regression equation of forming density, heating temperature and molding pressure. And then he carries out the analysis of variance and significance test of the regression equation of the test indicators. The results show that the test is feasible.
3)Hot forming research. Forming pressure is the most basic conditions of the biomass mixture dense forming. Study shows that the relationship between forming pressure and forming density is similar to a quadratic function. If the pressure is too small, it will result in difficulties to form or forming density be very small. When the pressure reaches a certain value, the pressure increased while the increase of density is not obvious. The mixture of corn stalks and rice husk can achieve forming close, surface smooth and density moderate when the molding pressure values of the corn stalks and rice husk is within 16 to 48MPa, regression equation isρ= ?7. 63×10?7 (p?32)2+0.0012(p?32)+0.6817,and for Sawdust and rice husk mixture is within 24 to 48MPa, regression equation isρ= ?5 .08×10?7 (p?32)2+0.0011(p?32)+0.6291,Temperature and density of molding have a linear relationship. Comparing with the molding pressure, the impact of molding temperature to molding density is much smaller. The author sums up by experiment that we can get ideal result of the mixture 75% corn stalk and 25% rice hull when pressure values within 16 to 48MPa and molding temperature within the scope of 160 to 200 degrees, regression equation isρ= 0. 001T+0.991. While for mixture 57% sawdust and 43% rice husk, the pressure value is within 16 to 48MPa and molding temperature within above 180 degree, regression equation isρ= 0 .0017T+0.7782. The role of molding pressure to the molding density is greater than that of molding temperature within the scope of the test settings value.
4)Combustion characteristic test. The author carries out a TGA Test of programmed temperature method under the conditions of pure oxygen of the mixed sample, and then he finishes out the data of quality, temperature and time. Then he obtains the combustion characteristic parameters of mixed biomass particle by thermal gravimetric curves (TG) and derivative thermal gravimetric curves (DTG). Combustion process is divided into three phases based on the characteristic parameters: stage of Fuel desiccation, stage of precipitation and combustion of volatile constituents and stage of coke combustion. The second stage is the most important of all. We find that there are many advantages of mixed particles of biomass fuels by comparing combustion characteristic parameters of Biomass briquette and traditional coal. It can not only reduce the requirement of temperature of the boiler material, but also improve the efficiency of industrial boilers. This can reduce the operation and maintenance costs of dust desulphurization equipment.
5)Combustion Kinetics. The author carries out the combustion dynamics analysis and the corresponding kinetic model of combustion. Through the combustion kinetics of the formula, draw the curve of. The combustion process is divided into two stages through Curve equation. And then calculate the specific values of initiation and termination combustion temperature, activation energy and frequency factor of every stage. Under different experimental conditions, the result shows that the combustion process of biomass includes the volatile combustion stage and the coke burning stage. Increasing molding pressure can improve the reaction rate, but delay the ignition point temperature, so that the combustion characteristic of volatile components is more obvious. Increasing heating rate of speed can also improve the reaction rate, but delay the ignition point temperature . Rising molding temperature can increase the ignition temperature, but the combustion reaction slow down. Reduction of rice husk mixed content, ignition temperature of the mixed grains becomes lower and the reaction becomes faster. The combustion characteristic of Volatile constituents is very obvious. The relationship of model parameters and combustion characteristics value made activation energy reflects the rate of combustion reaction clearly. When the activation energy and frequency factor are reduced, the combustion reaction and the combustion temperature accelerate. On the contrary, no exception
This paper further study the slagging properties, hot forming and combustion characteristics of biomass fuels, and provided a theoretical basis for the future development of molding equipment. At the same time, it also has a guiding significance of biomass fuel boiler designing optimization and industrialization.
引文
[1]魏学锋,张小云,罗婕,等.生物质燃料的开发利用现状与展望[J].节能,2004,1(8):14-18.
[2]Johansson L S,ullin C ,Leckner B,etal.Particle emissions from biomass Combustion in small combustors[J].Biomass and Bioenergy,2003,25(4):435-446.
[3]田贺忠,郝吉明,陆永琪,等.中国生物质燃烧排放、量的估算[J].环境科学学报,2002,22(2):204-208.
[4]朱清时,阎立峰,郭庆祥,等.生物质洁净能源[M].北京:化学工业出版社,2002.
[5]高先声.生物质的能源利用和生物质气化[J].太阳能.2002,(1):5-7.
[6]蒋剑春.生物质能源应用研究现状与发展前景[J].林产化学与工业,2002,(2):75-80.
[7]LEUNG DENN IS Y C,CHANG J,WU C Z,etal.A review on the energy production consumption and prospect of renewable energy in China[J].Renewable and Sustainable Energy Re2 views,2003,7(5):453-468.
[8]张永廉.稻壳使用特性及其能源利用[J].能源研究与利用,1991,(2):23-25.
[9]骆仲泱,周劲松,王树荣,等.中国生物质能利用技术评价[J].中国能源,2004,26(9):39-42.
[10]顾树华.开发利用生物质能是我国农林业发展的重要领域[J].研究与探讨,2006,28(9):11-15.
[11]PAR IKKA.Global biomass fuel resources[J].Biomass and Bioenergy,2004,27(6): 613-620.
[12]温从科,乔旭,张进平.生物质高压液化技术研究进展[J].生物质化学工程,2006,40(1):32-34.
[13]王庆一.中国可在生能源现状障碍与对策一开发利用现状[J].中国能源,2002,(7):39-44.
[14]梁宝芬.美国生物质能等可在再能源发电考查报告[J].新能源,1994,16(10):1-7.
[15]肃林湘.多种方式开发利用生物质能源[J].中国林业,2006,(11).
[16]王海滨.国外生物质能转化技术与应用[J].新能源,2001,(6):15-16.
[17]莫非.生物质液体燃料的制取[J].新能源,2000,22(10):18-20.
[18]李海滨,吴创之.我国垃圾处理的技术出路[J].中国科技成果,2002,(15):19-20.
[19]朱锡锋.生物质液化制备合成气的研究[J].可在生能源,2003,(1):11-1.
[20]李改莲,王远红,杨继涛等.中国生物质能的利用状况及展望[J].河南农业大学学报,2004,38(1).
[21]张百良.农村能源工程学[M].北京:中国农业出版社,1999.
[22]赵廷林,舒伟,邓大军,等.生物质致密成型技术研究现状与发展[J].特别关注,2007,12(4):29-33.
[23]陈军,陶占良.能源化学[M].北京:化学工业出版社,2004.
[24]Lingdley J A.VossoughiM.Physical Properties of Biomass Briquettes[J].Transactions of the ASAE,1989,32(2):361-366.
[25]Husain Z,Zainac Z,Abdullah Z.Briquetting of palm fibre and shell from the processing of palm nuts to palm oil[J].Biomass and Bioenergy,2002,20:505-509.
[26]李美华,俞国胜.生物质燃料成型技术研究现状[J].木材加工机械,2005,16(2):36-40.
[27]张百良.农村能源工程[M].北京:中国农业出版社,1999,第一版.
[28]P D Grover,S K Mishra.Proceedings of the international workshop on biomass briquetting[C].New Delhi,India,1996.
[29]P D Grover,S K Vtishra . Biomass briquetting[J] . technology practices,Reginal New De1hi,India,1996.
[30]Naidu B S K.biomass briquetting-An Indian Perspective[C]. Proceedings of the international workshop on biomass briquetting.New Delhi,India,1995.
[31]苏俊林.生物质气化燃烧锅炉技术报告[C].长春鸿鑫热能有限公司,2008,3.
[32]刘宇刚.关于利用生物质能技术的思考[J].佳木斯大学学报,2005,2.
[33]中国大百科全书出版社编辑部.能源百科全书[M].北京:中国大百科全书出版社,2002.
[34]马孝琴.生物质成型燃料燃烧动力学特性及液压秸秆成型机改进设计[D].河南农业大学博士论文,2002,6.
[35]王作安.缠绕压缩式牧草压饼机的研制[J].粮油加工与食品机械,1990(4).
[36]盛奎川,蒋成球.生物质压缩成型燃料技术研究综述[J].能源工程,1996(3):8-11.
[37]罗小金.生物质颗粒燃料燃烧的试验研究[D].吉林大学硕士论文,2007,6.
[38]刘圣勇.国内外生物质致密成型燃料及燃烧设备研究与开发现状[J].可再生能源,2002(4):14-15.
[39]Margaret K M,ParnelaL S.Life cycle Assessment of a Biomass Gasifieation Combined-Cyele Power system[M].戴林,王革华,占增安译.贡光禹校.中国环境科学出版社,2000,5.
[40]China-European Union Renewable Energy Technology Conference[C].Beijing China,1999,9.
[41]Federov M.F.Study of the process of Compression of Straw[J].Traktory Iselkhoz-mashing,1972.5:21-24.
[42]Osobov V I,Theoretical Principles of Compressing Fibrous Plant Materials[J].Thudy Viskhom,1967,55:221-265.
[43]Bellinger P L,Mccolly H H.Energy requirements for Forming Hay Pellets[J].Agricultural Engineering,1961.42(5):244-247.
[44]Neale M A.Research and Development for on-Farm Straw Packaging Machines[J].Straw:A Valuable Material,Proeeedings of Intemational Conferenee,Cambridge England,October,1987.
[45]日本能源学会编,史仲平,华兆哲译.生物质和生物能源手册[M].北京:化学工业出版社,2006.
[46]戴文仪.生物质颗粒燃料燃烧特性及燃烧动力学实验研究[D].硕士论文,吉林大学,2007,6.
[47]段菁春,肖军,王杰林,等.生物质与煤共燃研究[J].电站系统工程,2004,20(1):1-4.
[48]樊峰鸣,张百良,李保谦,等.大粒径生物质成型燃料物理特性的研究[J].农业环境科学报,2005,24(2):398-402
[49]《京都议定书》联合国气候变化框架公约秘书处,1997,12.
[50]袁艳文,林聪,赵立欣.生物质固体成型燃料抗结渣研究进展[J].可再生能源,2009,27(5):48-51.
[51]别如山,杨励丹,张子栋,等.SHL20型锅炉结渣分析及改造措施[J].节能技术,1994,(4):1-3.
[52]A.Williams,M Pourkashanian,J M jones.Combustion of Pulverized Coal and Biomass[J].Progress in Energy and Combustion Science,2001(27):587-610.
[53]宋宏伟,郭民臣,王欣.生物质燃烧过程中的积灰结渣特性[J].节能与环保,2003,12(9):29-31.
[54]T R Miles,L L Baxter,R W Bryers.Alkali Deposits found in Biomass Power Plants[J].Apreliminary Investigation of the Irextent and nature,National Renewable Energy Laboratory,Golden,CO,1995.
[55]Easterly J L,Burnham M.Overview of Biomass and Waster Fuel Resources for Power Production[J].Biomass and Bioenergy,1996:79-92.
[56]B M Jenkins,L L Baxter,T R. Miles.Combustion Properties of Biomass[J].Fuel Processing technology,1998(54):17-46.
[57]刘春焱,谢玉珑.浅谈煤灰熔融性测定的重要性及方法[J].热电技术,2002(4):52-55.
[58]任露泉.试验优化设计与分析[M].吉林科学技术出版社,2001,5.
[59]矫振伟.燃料燃烧热重试验台的研制[M].吉林大学,2006,9.
[60]陈华艳.生物质型煤优化配比及燃烧特性研究[D].吉林大学硕士论文,2006,6.
[61]高名旺,董玉平.生物质热压成型温度场数值模拟[J].可再生能源,2004,114(2):23-25.
[62]O Dogherty M J.A review of the mechanical behavior of straw when compressed to high densities[J].J Agric Engng Res,1989,44:241-265.
[63]Lindley J A,Vossoughi M.Physical properties of biomass briquettes[J].Transactions of the ASAE,1989,32(2):361-366.
[64]李美华.生物质燃料致密成型参数的研究[D].北京林业大学硕士论文,2005,6.
[65]乐园,李龙生.秸秆类生物质燃烧特性的研究[J].能源工艺,2006(4):30-33.
[66]Demirabas A.Combustion characteristics of different biomass fuels[J].Progress in Energy and Combustion Science,2004,30:219-230.
[67]Fenkins BM,BaxterL L,Miles JrTR,etal.Combustion properties of biomass[J].Fuel Processing Technology,1998,54:17-46.
[68]闵凡飞,张明旭.生物质与不同变质程度煤混合燃烧特性的研究[J].中国矿业大学学报,2005,34(2):236-241.
[69]于伯龄,姜胶东.实用热分析[M].纺织工业出版社,1990,3(1):11-38.
[70]虞继舜.煤化学[M].冶金工业出版社,2000,8,177-184.
[71]赵智海.无粘结剂冷压成型工艺生产工业型煤[J].煤炭加工与综合利用,1996(4):83-84.
[72]李水娥,金会心,吴复忠.生物质型煤的制备及燃烧性能研究[J].贵州工业大学学报(自然科学版),2004,33(6):5-8.
[73]胡荣祖,史启祯.热分析动力学[M].科学出版社,2001,8.
[74]傅维镳,张永康,王清安.燃烧学[M].高等教育出版社,1989,4(1).
[75]张全国,马孝琴.金属化合物对煤矿石燃烧动力学特性的影响[J].环境科学学报,1999,19(1):72-76.