【作者】 吕东慧；

【导师】 王德成； Lope G.Tabil；

【作者基本信息】 中国农业大学 ， 农业机械化工程， 2014， 博士

【摘要】 农作秸秆是一种丰富廉价的能源来源,其能源化转化是目前世界上发展可再生能源的一种趋势。针对目前持续增长的秸秆能源化转化的需求与低效的麦秸制粒生产机械化技术的矛盾,研究了麦秸能源化成型颗粒的制粒技术,同时兼顾麦秸制粒系统对环境的影响,提出了采用添加剂的方式优化麦秸能源化成型制粒工艺技术的优化方案,最终提升了麦秸制粒过程和颗粒产品的强度和品质。进行了秸秆压缩的影响因素分析,讨论了压缩力、温度、秸秆粒度、含水率和化学组分对压缩制粒的影响,设计并搭建了麦秸能源颗粒试制的单颗粒制粒试验台和颗粒抗张强度测试试验台。基于麦秸单颗粒试制试验台,开展添加剂对麦秸制粒的影响试验研究。采用粗甘油、膨润土、木质素磺酸盐、未处理锯木屑和微波碱溶液处理的锯木屑进行麦秸能源化颗粒的试制。研究表明：添加剂的添加可以提高麦秸颗粒的强度,降低麦秸颗粒制粒的能耗,提高麦秸颗粒密度,以及麦秸颗粒的高位热值；通过采用添加剂,颗粒的抗张强度从0.84MPa提高到(1.13-1.63)MPa；当采用粗甘油、未处理锯木屑和预处理锯木屑作为添加剂时,颗粒的高位热值显著增加,达到(17.98-18.77)MJ/kg;添加剂功能综合分析表明,预处理锯木屑、未处理锯木屑和膨润土的性能更好；不同添加剂能从增加强度、致密、降低能耗、提高高位热值等角度优化麦秸制粒过程,提高颗粒品质。研究总结不同预处理技术的麦秸颗粒生产系统的工艺及关键技术参数,采用生命周期评估(LCA)方法对目前的麦秸制粒系统进行环境影响比较分析。结果表明：采用蒸汽爆碎预处理方式的制粒系统对环境影响较大；采用添加剂的方式能降低麦秸制粒系统对环境的影响；添加未处理锯木屑和烘焙预处理方式的麦秸制粒系统总体上对环境影响较低；添加剂的添加可以降低不可再生能源的消耗。添加剂的优化试验结果表明：抗张强度、比能耗、颗粒密度模型预测精度高,模型的平方确定系数(R2)分别为0.78、0.93和0.94;压缩载荷的增加使抗张强度、颗粒密度和比能耗增加；粗甘油添加量的增加使比能耗、抗张强度降低；未处理锯木屑和膨润土添加量的增加使制粒比能耗降低。以抗张强度、比能耗和颗粒密度的优化为目标,兼顾考虑高位热值、灰分和原料成本,得出六种优化方案,优化方案的中试规模的生产试验结果表明：添加未处理锯木屑30%,膨润土0.57%,粗甘油3.80%(方案三)时麦秸制粒能耗低,颗粒耐久性等颗粒品质较优：添加未处理锯木屑20.16%,膨润土1.62%,粗甘油2.60%(方案一)时颗粒的堆积密度最大,达到744.04kg/m3；六种方案的LCA比较研究表明方案三对环境的冲击相对较小。采用添加剂能提高麦秸颗粒机械化制备技术水平,降低有害物质排放,是一种可持续机械化生产方式。更多还原

【Abstract】 Agricultural residue is an aboundance source of sustainable energy to substitute for fossil fuel. Pelletization of agricultural straw is a way to improve the efficiency of utilizing biomass as fuel especially for long distance transportation. While straw pellets are often dusty and easy to break during handling and transportation process. In order to manufacture strong wheat straw fuel pellets and research on the effect of binders on the quality of wheat straw fuel pellets, a single pellet unit was set up. Crude Glycerol, Bentonite, Lignosulfonate and wood waste were selected as binders for wheat straw pelletization. Microwave alkaline treated wood waste was also considered to be a binder. The results showed that the tensile strength of wheat straw pellets was significantly increased by adding these binders. The specific energy consumption was decresed and the pellet density was increased as well. The pellet with the addition of crude glycerol achieved the highest heating value. The heating value of the pellets can achieve as high as17.98-18.77MJ/kg with the addition of appropriate binders.The sustainable of wheat straw pelleting system was evaluated by the method of Life Cycle Accessment. The environmental impact of five pretreatment methods (steam explosion, microwave alkaline, binder addition, radiofrequency alkaline, and torrefaction) were evaluated in terms of global warming potential, acidification, eutrophication, human toxicity, marine aquatic ecotoxicity, ozone layer depletion, abiotic depletion, fresh water aquatic ecotoxicity, photochemical oxidation, terrestrial ecotoxidation, and non-renewable energy use. The results revealed that the environmental impact of wheat straw pelletization system can be reduced by using binders. Wood waste as binder and torrefaction method were the best pretreatment method that can help to decrease the environment impact of wheat straw pelleting.The optimization of biners and the compression load experimental trials were conducted. The responses of specific energy consumption, tensile strength and pellet density models were derived verified. The tensile strength and the pellet density increased as the increase of compression load. The specific energy consumption increased due to the increase of the compression load as well. The addition of cruede glycerol can reduce the specific energy consumption, but at the same time it decresed the tensile strength. The optimized solutions of making quality wheat straw fuel pellets were derived both by using the models and considering the heating value, ash content and the cost of the raw matetials.The pilot scale experiments were conducted based on the6optimized options. By analyzing the output rate, energy consumption and the quality of pellets, option3was considered to be better than other options which was wheat straw with the addition of30%wood waste, bentonite and3.80%crude glycerol. The environmental impact of6options was derived by using LC A method. In general, option3had a minimum impact on environment compared to other options.In conclusion, binder addition method could be a good way to increase the technology level of manufacturing wheat straw pellets, both efficiently and sustainably.更多还原