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生物油煤浆的制备及其气化特性研究
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学位类型博士
导师宋文立
2016-07
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业化学工程
关键词生物油煤浆 流变特性 雾化特性 气化特性 气流床
摘要

生物质作为自然界唯一的含碳可再生能源,用以替代化石燃料,可以降低二氧化碳等温室气体的排放。鉴于生物质原料存在分散性广、能量密度低及不适宜长时间存储等缺点,生物质的利用宜采用“分散制油,集中制气”的手段,提高对原料的收集效率并降低运输成本。即先在较小范围内将生物质热解成为生物质热解油(生物油),再将分散制备的生物油运输至中心工厂。而生物质热解制备的生物油具有酸性高、含水含氧量高、热值低及不稳定等缺点,直接利用较为困难。因此,将生物油与煤制备成为生物油煤浆,并利用气化技术产生合成气,为生物油的利用提供了一种新途径。而且,与生物油相比,生物油煤浆热值更高,适用性更广;另外,由于利用了生物油中的碳,生物油煤浆又被归为部分绿色能源。因此,本论文从煤浆利用的工艺出发,对生物油煤浆的流变特性、雾化特性及其气化特性进行了系统的研究,主要研究内容和结果如下:首先,生物油煤浆作为一种新型燃料,需要对其流变特性进行研究以确定适用于工业应用的煤浆组成和操作条件。论文研究了不同煤阶煤样制备的生物油煤浆的流变特性,指出影响其流变特性的最主要煤质因素为煤的空气干燥基水份和羧基官能团含量,并明确了适宜制浆的煤种为烟煤和无烟煤。对于神木烟煤,其最大成浆浓度约为45 wt. %,该部分的研究为生物油煤浆的雾化和气化过程做了良好的铺垫。雾化过程是浆态燃料进入反应器反应的第一个步骤,也是实现工业应用的关键步骤之一。论文选用双流体喷嘴较好地实现了生物油煤浆的雾化,并利用CCD耦合图像数字处理技术对煤浆雾化液滴的粒径和速度分布进行了测量和分析。弥补了生物油煤浆雾化数据的空白,获得了合适的雾化工艺条件。同时丰富了双流体喷嘴雾化液滴的粒径和速度分布研究,为生物油煤浆在气流床反应器中进行试验奠定了基础。生物油煤浆的气化特性研究为其工业应用提供了有效的参考数据。论文研究了生物油煤浆在常压气流床反应器内1200 oC-1400 oC范围内的气化特性,并与水煤浆的气化特性进行对比。实验表明,生物油煤浆的碳转化率达95%以上,明显高于水煤浆。在工艺流程计算中,生物油煤浆的气化效率比水煤浆高出3个百分点,比氧耗比水煤浆降低约18%,证明了生物油煤浆在气流床中气化制备合成气的可行性。生物油煤浆气化所得固体产物的研究作为对生物油煤浆气流床气化特性研究的补充,以增进对生物油煤浆气化过程的了解。气化固体产物的分析与表征结果表明,生物油煤浆气化所得飞灰的反应性高于水煤浆飞灰,并且生物油煤浆的过滤器飞灰比旋风分离器飞灰有更高的气化反应性,生物油中含有的可溶性K盐是气化反应性较高的主要原因。

其他摘要

Biomass is the only renewable and carbon neutral energy resource in nature, and its utilization would help the reduction of CO2 emission as an alternative fuel. Due to the wide distribution, low energy density and danger of spontaneous-ignition for long time storage, the concept of a regional flash-pyrolysis and a central gasification and synthesis is more suitable for biomass utilization, because this would minimize the transportation cost. The first step of this concept is flash-pyrolysis of biomass and its main products are pyrolysis liquids (or bio-oil), char and gas. The bio-oil is then sent to central plant for syngas production. Bio-oil exhibits high oxygen content, high water content, strong acidity and instability, and all this makes it difficult for direct utilization. One of the effective applications of bio-oil is to make slurries with coal for the preparation of coal/bio-oil slurry. With coal added into bio-oil, the suspensions have much higher calorific value than bio-oil, and the bio-oil in turn contributes much more heat to coal/bio-oil slurry than coal/water slurry with the same coal concentration. Thus coal/bio-oil slurry could also be considered as a partial green fuel. This research focuses on the process of coal/bio-oil utilization which involves the rheology, atomization and gasification of the slurry. Firstly the rheology of coal/bio-oil slurry was studied to select the proper slurry composition. The influence of coal rank, solid concentration, particle size distribution and temperature on apparent viscosity of slurries were investigated. Based on grey relational analysis, moisture and carboxyl groups in coal are determined as main factors affecting the apparent viscosity of coal/bio-oil slurries. Slurries prepared by bituminous coal and anthracite presents lower apparent viscosity. The maximum solid concentration can reach 45% for Shenmu bituminous coal.Atomization of slurry is the first step before feeding into gasifiers, it is also a key process in industry. Atomization performance of pilot-scale atomizers for feeding of coal/bio-oil slurry in an entrained flow gasifier was studied. Advanced techniques were applied to measure the size of slurry droplets with a high speed infrared camera followed by digitalization of a series pictures automatically. The effects of coal concentration in slurry, gas flow and slurry flow on average size of the droplets and velocity of the droplets were investigated. The profiles of droplet size and droplet velocity were also provided to determine the development of the spray. The selection of nozzle and operating conditions are applicable in the slurry-fed entrained flow reactor in Technicial University of Denmark. .Gasification of coal/bio-oil slurry was carried out in an entrained flow reactor with the temperature range of 1200-1400 oC, which provides a feasibility for coal/bio-oil slurry gasification in industry. Its gasification performance was compared with that of coal/water slurry. Results show that the carbon conversion of coal/bio-oil slurry reached 95% and it was much higher than coal/water slurry in experiments. Gasification of coal/bio-oil slurry and coal/water slurry based on industrial parameters were calculated using Aspen Plus, and the cold gas efficiency of coal/bio-oil slurry is 3% higher than that of coal/water slurry.The characterization of the solid products from coal/bio-oil slurry gasification was a supplementary to get a deeper understanding of this process. Results show that fly ash obtained from coal/bio-oil slurry gasification presents higher gasification reactivity than those from coal/water slurry. Fly ash collected in filter from coal/bio-oil slurry gasification has higher gasification reactivity than those collected in cyclone. AAEMs in bio-oil especially K plays an important roal in enhancing gasification reactivity. 

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/22908
专题研究所(批量导入)
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封萍. 生物油煤浆的制备及其气化特性研究[D]. 北京. 中国科学院研究生院,2016.
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