低阶碎煤流化床两段气化技术基础研究

发布时间：2018-05-21 17:12

本文选题：低阶碎煤 + 流化床两段气化　；参考：《中国科学院大学(中国科学院过程工程研究所)》2017年硕士论文

【摘要】：我国对煤制工业燃气需求量巨大,全年产量可达7560亿m3。现阶段,国内煤制工业燃气技术主要以单段和两段固定床煤气发生炉为主,其技术局限性在于使用优质块煤,对碎煤适应性差,原料成本高;生产规模小,放大困难;燃气中焦油含量高,后期燃气净化处理阶段易产生含酚废水造成二次污染。气流床气化工艺由于操作条件较为苛刻,生产成本高,不适合工业燃气生产的应用。以鼓泡流化床和循环流化床为代表的流化床气化技术具有热质传递效果好、处理强度大、放大容易、适合处理小粒径原料等特点,但仍面临着生成气体中焦油含量高、气体热值较低、转化率不高等挑战。中国科学院过程工程研究所提出了流化床热解耦合输送床气化的新型低焦油两段气化技术,采用低阶碎煤清洁生产工业燃气。流化床两段气化技术将煤炭气化过程解耦为煤热解和半焦气化两个子过程,并分别在流化床热解器和输送床气化炉内进行。原料首先在流化床热解器中发生干燥、热解和部分气化反应,生成的全部产物(热解气、半焦和焦油)进入到气化炉中,进行半焦气化,同时利用输送床气化炉内的高温有氧环境和半焦对焦油的催化重整作用脱除焦油,生产洁净工业燃气。利用实验室流化床装置和两段气化中试实验平台,本文对关键性反应参数和工艺可行性进行了系统研究和验证。主要的研究内容和结果整理归纳如下:(1)在实验室射流预氧化流化床反应装置上研究了小龙潭褐煤的热解行为,重点考察了反应温度、外部水蒸气气氛、物料含水量、含氧气氛等对煤样热解行为的影响,分别对热解产物分布、半焦气化活性、气体和焦油组成变化进行了分析。惰性气氛下随着反应温度的提高,气体收率逐渐增大,半焦和焦油的收率降低;半焦比表面积增大,气化活性提高,但过高的反应温度,如在900℃下,会引起半焦的晶格结构有序化程度增大,气化活性反而降低。活性气氛(氧、水蒸气)下能够进一步提高气体收率和半焦的气化活性;外部水蒸汽条件能够促使焦油轻质化,同时降低焦油整体收率;煤中固有含水一定程度上能够提高焦油中轻质组分的含量,但也会引起挥发分析出不完全,进而造成物料热解程度降低,因此物料的含水量需控制在一定的范围内;在同等水煤比条件下,外部通水蒸气较物料内部含水对气体收率的提高程度更大。氧气气氛下焦油中重质组分含量提高,焦油整体收率降低;综合考虑基础实验结果,流化床两段气化工艺上段流化床热解反应器内最佳的反应条件为:反应温度800℃、外部通水蒸汽情况下水煤质量为0.11、原料含水量水煤比小于0.11、过量空气系数为0.14。(2)基于100kg/h的自热式流化床两段气化中试实验平台,在典型操作条件下开展了内蒙胜利褐煤流化床两段气化实验,运行结果显示,随着热解器和气化炉操作温度的提高,热解气和气化气的有效气体组分提高,气体中的焦油含量明显降低。当热解器和气化炉的温度分别为840℃和1000℃时,气化炉出口处气体的热值达到1100kcal/Nm3,气化气中的焦油含量为365 mg/Nm3;热解气所含焦油组分中重质组分较高,经过气化炉内高温裂解和半焦床层催化裂解作用后,产品气中所含重质组分和焦油总量减少,轻质组分增多,有利于其进一步脱除;中试实验结果充分说明了流化床两段气化的工艺可行性和技术特点,为工艺进一步放大提供了良好的技术支撑。
[Abstract]:In China, the demand for coal industrial gas is huge, the annual output can reach 756 billion m3. stage. Domestic coal industrial gas technology mainly consists of single section and two fixed bed gas generator. Its technical limitations lie in the use of high quality lump coal, poor adaptability to coal, high cost of raw materials, small production scale, difficult amplification and tar content in gas. It is easy to produce two times of pollution in the stage of gas purification treatment. The air entrained flow gasification process is not suitable for industrial gas production because of its harsh operating conditions and high production cost. The fluidized bed gasification technology, represented by bubbling fluidized bed and circulating fluidized bed, has good heat and mass transfer effect, large treatment strength and magnification. It is easy to deal with the characteristics of small particle size material, but it still faces the challenge of high tar content, low calorific value and low conversion rate in generating gas. The Institute of process engineering of China Academy of Sciences has proposed a new two stage gasification technology of low coke oil with fluidized bed pyrolysis coupled conveying bed gasification, and a clean production of industrial gas with low rank coal. The gasification process of two stages of fluidized bed gasification is used to decouple the coal gasification process into two sub processes of coal pyrolysis and semi coke gasification, which are carried out in a fluidized bed pyrogener and a conveyer bed gasifier respectively. The raw materials are first dried, pyrolysis and partial gasification in a fluidized bed pyrolysis reactor, and all the products (thermal, semi coke and tar) are formed into the gasifier. At the same time, the semi coke gasification is carried out, and the high temperature aerobic environment and the semi coke are used to remove the tar from the catalytic reforming of the tar in the conveyer bed gasifier, and the clean industrial gas is produced. Using the laboratory fluidized bed device and the two stage gasification pilot test platform, the key reaction parameters and technological feasibility are systematically studied and verified in this paper. The main research contents and results are summarized as follows: (1) the pyrolysis behavior of Xiaolong Tan lignite was studied on the fluidized bed reactor in the laboratory. The influence of reaction temperature, external vapor atmosphere, material moisture content, oxygen atmosphere on the pyrolysis behavior of coal samples was investigated, and the distribution of pyrolysis products and the gasification of semi coke were carried out respectively. The gas and tar composition changes are analyzed. With the increase of the reaction temperature, the gas yield increases with the increase of the reaction temperature, the yield of the semi coke and tar is reduced, the surface area of the semi coke ratio increases and the gasification activity increases, but the high reaction temperature, if at 900, will increase the degree of ordering of the lattice structure of the semi coke, and the gasification activity is reversed. While the active atmosphere (oxygen, water vapor) can further improve the gas yield and the gasification activity of the semi coke, the external steam conditions can promote the light quality of the tar and reduce the overall yield of tar, and the natural water content in the coal can increase the content of the light components in the tar, but it will also cause the incomplete volatilization analysis. The water content of the material should be controlled in a certain range. Under the same ratio of coal water to coal, the external water vapor has a greater increase in the gas yield than the water content inside the material. The heavy component content in the tar in the oxygen atmosphere and the overall yield of coke oil are reduced. The results of the basic experiment are considered synthetically. The best reaction conditions in the fluidized bed two stage gasification process fluidized bed pyrolysis reactor are as follows: the reaction temperature is 800, the water coal quality is 0.11, the water and coal ratio of raw materials are less than 0.11, the excess air coefficient is 0.14. (2) 100kg/h based autothermal fluidized bed two stage gasification pilot test platform, and the typical operating strip is in the typical operating strip. The two stage gasification experiment of Inner Mongolia Shengli lignite fluidized bed was carried out. The operation results showed that with the increase of the operating temperature of the pyrolysator and gasifier, the effective gas components of thermal Degas and gasification gas were improved and the tar content in the gas was obviously reduced. When the temperature of the pyrogenator and the gasifier was 840 and 1000 C, the gas at the outlet of the gasifier was at the outlet. The calorific value of the body is up to 1100kcal/Nm3, the tar content in the gasification gas is 365 mg/Nm3, the heavy component in the tar component of the thermal gas is higher. After the pyrolysis of the gasifier and the catalytic cracking of the semi coke bed, the heavy components and tar content in the gas are reduced and the light and mass components are increased, which is beneficial to the further removal of the gas. The results fully illustrate the feasibility and technical characteristics of two stage gasification in fluidized beds, providing good technical support for further enlargement of the process.
【学位授予单位】：中国科学院大学(中国科学院过程工程研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ546

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