秸秆成型燃料提质及清洁燃烧特性研究
发布时间：2019-05-23 20:20
【摘要】：生物质能是当今世界上仅次于煤炭、石油和天然气的第四大能源,占世界能源消费总量的14%;我国是农业大国,秸秆资源丰富。然而秸秆资源除了分布分散、能量密度低、运输成本高等缺点外,热转化及燃烧过程中碱金属和氯元素等引起等的颗粒物排放高、受热面积灰、结渣和腐蚀现象,以及燃料热值低等问题均限制其广泛应用。研究改善秸秆成型燃料品质及其清洁利用,对替代煤炭和发展可再生能源具有战略意义,是技术创新和行业可持续发展的基础。而成型加工、添加剂改性、热解提质等是解决此类弊端的有效手段。本文从改良秸秆原料角度出发,通过寻求合适的添加剂及成型热解工艺达到提高秸秆燃料品质及清洁燃烧的目的。采用实验、模拟分析、理论分析等方法研究添加剂对秸秆成型燃料燃烧中钾迁移及控制、氯和硫等污染物控制的作用规律,并在此基础上提出秸秆掺配添加剂—成型—热解提升成型炭品质的方法,系统研究热解温度和添加剂对成型炭理化、燃烧、灰熔融和污染物排放等特性的影响。本文开展的主要工作如下:选取NH_4H_2PO_4和Ca(H_2PO_4)_2作为磷基添加剂制备秸秆成型燃料,研究添加剂对灰熔融性及燃料燃烧成灰特性、钾转化的作用规律和机理。得出适宜的P/K掺配比为1.0～2.0,两种添加剂均可以明显提高成型燃料灰熔点,并明显改善成型燃料燃烧时熔融和结渣问题。添加剂在700～1100℃内均有效抑制钾析出,其中NH4H2PO4在1100℃时的固钾效果最佳,此时玉米秸秆(MS)和棉秆成型燃料(CS)的固钾率分别增长了 52.86%和64.89%。磷基添加剂与秸秆中的钾元素结合生成高熔点K-Ca-P化合物,从而提高了灰熔点、改善了烧结和熔融现象并控制钾析出,有利于秸秆成型燃料的清洁燃烧。选取BaCO_3、CaO和CaCO_3作为添加剂制备秸秆成型燃料,研究添加剂氯、硫等固定特性的影响。800℃后CaCl_2的分解反应开始明显,BaCl_2更稳定,且BaCO_3在800～1000℃之间固氯能力明显优于CaO和CaCO_3。适宜的Ba/Cl摩尔比为2.5,BaCO_3对CS在1000℃燃烧时固氯率增长了5.35倍。模拟KCl、NH_4H_2PO_4/Ca(H_2PO_4)_2和BaCO_3三种物质在500～1200℃反应产物,结果表明NH_4H_2PO_4和Ca(H_2PO_4)_2可以较好的将KCl转化为磷钾盐,但只增加1.5倍NH_4H_2PO_4添加量,950℃后KCl中接近75%的氯转化为气相HCl;只增加1.5倍BaCO_3添加量仅促进约1%的气相钾析出。结合实验结果,在添加NH_4H_2PO_4/Ca(H_2PO_4)_2的基础上掺配BaCO_3,适宜的Ba/K摩尔比为0.5～1,CS在1000℃燃烧时固氯率分别达到22.03%和26.20%。添加剂固硫能力由大到小依次为BaCO_3、CaCO_3、CaO。因此,通过掺配BaCO_3可显著降低氯、硫污染物排放,达到清洁燃烧的目的。针对秸秆热值低、炭产物难成型的问题,采用秸秆掺配添加剂—成型—热解技术制备成型炭,研究热解温度(250-650℃)和磷基添加剂对成型炭理化特性和燃烧特性的影响。所得成型炭具有理想的抗跌碎特性和抗吸水能力。随着热解温度的升高,MS中有机官断裂、聚合重组,芳香结构生成,添加剂不同程度上促进热解进程。热解中添加剂晶粒附着在纤维表面,和钾反应生成K-Ca-P化合物从而实现钾转化。所得成型炭热值明显提高,能量密度在10～15GJ/m3之间,优于原始生物质成型燃料或者粉状、颗粒状和纤维状燃料。热分析结果显示随着解热温度的升高,秸秆成型炭固定碳燃烧阶段增强。因此,掺配添加剂—成型—热解技术既有利于热解阶段钾转化和固定,又可以显著提高秸秆成型燃料的热值。研究了磷基添加剂和热解温度对成型炭灰熔融性、燃烧成灰特性、钾转化规律、氮氧化物和硫氧化物排放特性的影响。结果表明,实验热解温度下获得的秸秆成型炭具有严重结渣倾向,软化温度随热解温度的升高而降低;添加剂改良的成型炭软化温度显著提高,热解温度为650℃时NH_4H_2PO_4和Ca(H_2PO_4)_2分别将软化温度提高490℃和422℃。添加剂改良的成型炭燃烧时钾析出得到较好的控制,1000℃燃烧时最低固钾率仍高于60%,并未出现熔融现象。表征分析和模拟结果表明,两种磷基添加剂改善灰熔融性的作用原理不尽相同,尽管都具有将钾转化为高熔点K-Ca-P化合物的能力,NH_4H_2P0_4可更有效地抑制钾析出和硅酸钾盐生成,而Ca(H_2PO_4)_2转化为硅酸钙和钙磷化合物,从而改善灰熔融性。添加剂改良的成型炭SO_2和NO排放量均低于煤;获得相同热量的前提下,与生物质原样相比,磷基添加剂改良的成型炭具有低排放的优势。综上所述,磷基添加剂改良的秸秆成型炭具有热值高、熔点高、污染物低排放的优点,为秸秆成型燃料提质及清洁燃烧提供理论技术指导。
[Abstract]:Biomass energy is the fourth largest energy in the world after the coal, oil and natural gas, accounting for 14% of the total energy consumption of the world; China is an agricultural power, and the straw resources are abundant. However, in addition to the disadvantages of distributed dispersion, low energy density, high transportation cost, etc., the problems of high emission of particulate matter such as alkali metal and chlorine in the process of heat conversion and combustion, such as high heating area ash, slagging and corrosion, and low fuel heat value, all restrict its wide application. The research improves the quality of straw-forming fuel and its clean utilization, and is of strategic significance to replace coal and to develop renewable energy, and is the basis for technological innovation and sustainable development of the industry. And the forming and processing, the additive modification, the pyrolysis upgrading and the like are effective means for solving the defects. In this paper, the purpose of improving the quality of the straw fuel and the clean combustion is achieved by looking for suitable additives and forming the pyrolysis process from the viewpoint of improving the raw material of the straw. The effects of additives on the control of potassium migration and control, chlorine and sulfur in the combustion of straw-shaped fuel were studied by means of experiment, simulation analysis and theoretical analysis. The effects of pyrolysis temperature and additives on the physical and chemical, combustion, ash fusion and pollutant discharge of the formed carbon were investigated. The main work in this paper is to select NH _ 4H _ 2PO _ 4 and Ca (H _ 2PO _ 4) _ 2 as the phosphorus-based additive to prepare the straw-forming fuel, and to study the effect and mechanism of the additive on the ash-melting property and the ash-forming property and the potassium transformation of the fuel. The proper P/ K ratio is 1.0-2.0, the melting point of the fuel ash can be obviously improved by the two additives, and the problem of melting and slagging in the combustion of the formed fuel is obviously improved. The effect of the additive on the precipitation of potassium was inhibited in 700-1100 鈩，
本文编号：2484197
[Abstract]:Biomass energy is the fourth largest energy in the world after the coal, oil and natural gas, accounting for 14% of the total energy consumption of the world; China is an agricultural power, and the straw resources are abundant. However, in addition to the disadvantages of distributed dispersion, low energy density, high transportation cost, etc., the problems of high emission of particulate matter such as alkali metal and chlorine in the process of heat conversion and combustion, such as high heating area ash, slagging and corrosion, and low fuel heat value, all restrict its wide application. The research improves the quality of straw-forming fuel and its clean utilization, and is of strategic significance to replace coal and to develop renewable energy, and is the basis for technological innovation and sustainable development of the industry. And the forming and processing, the additive modification, the pyrolysis upgrading and the like are effective means for solving the defects. In this paper, the purpose of improving the quality of the straw fuel and the clean combustion is achieved by looking for suitable additives and forming the pyrolysis process from the viewpoint of improving the raw material of the straw. The effects of additives on the control of potassium migration and control, chlorine and sulfur in the combustion of straw-shaped fuel were studied by means of experiment, simulation analysis and theoretical analysis. The effects of pyrolysis temperature and additives on the physical and chemical, combustion, ash fusion and pollutant discharge of the formed carbon were investigated. The main work in this paper is to select NH _ 4H _ 2PO _ 4 and Ca (H _ 2PO _ 4) _ 2 as the phosphorus-based additive to prepare the straw-forming fuel, and to study the effect and mechanism of the additive on the ash-melting property and the ash-forming property and the potassium transformation of the fuel. The proper P/ K ratio is 1.0-2.0, the melting point of the fuel ash can be obviously improved by the two additives, and the problem of melting and slagging in the combustion of the formed fuel is obviously improved. The effect of the additive on the precipitation of potassium was inhibited in 700-1100 鈩，
本文编号：2484197
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