煤粉加压富氧燃烧特性及系统能耗分析

发布时间：2018-03-12 06:57

本文选题：加压富氧燃烧　切入点：加压TGA　出处：《北京交通大学》2017年博士论文　论文类型：学位论文

【摘要】：煤粉富氧燃烧在CO_2分离和固定领域中具有明显的优势,但由于空分系统和CO_2净化压缩系统能耗巨大,造成系统的经济性较差,加压富氧燃烧技术是在富氧燃烧技术的基础上提出来的,基于加压富氧燃烧技术的发电系统具有更高的发电效率,本文对0.1～5 MPa条件下煤粉的燃烧特性和加压富氧燃烧系统的能耗进行了分析。本文构建了加压富氧近零排放发电系统,空分制氧、煤粉燃烧、烟气中CO_2分离压缩过程均在高压下进行,利用高压烟气冷凝器回收锅炉排烟中水蒸气的气化潜热,提高了发电系统效率;同时,用多级压缩加中冷的方法液化回收烟气中的 CO_2。在加压气氛下,煤粉的燃烧特性与常压气氛下存在很大的差别。本文应用高压TGA 设备,研究了不同压力(0.1 MPa,1 MPa,2 MPa,3 MPa,4 MPa、5 MPa等6种压力条件)、不同氧气和二氧化碳比例(21%02/79%CO_2、30%02/70%CO_2、40%02/60%CO_2等3种体积比)、不同煤种(烟煤、褐煤)条件下煤粉的燃烧和燃尽特性,获得了燃烧动力学参数。结果显示:相对于常压富氧气氛,加压富氧气氛下煤粉的着火温度更低,综合燃烧性能更好;在相同O2/CO_2比例条件下,随着压力的逐渐增大,煤粉的着火温度先逐渐降低再逐渐增大,3 MPa时着火点最低,综合燃烧性能最好;在同一压力条件下,随着氧气浓度的提高,煤粉的失重提前,氧气浓度越高,反应越剧烈;烟煤和褐煤TG曲线和DTG曲线随压力变化的规律是一致的,但由于两个煤种挥发分含量的差异,在相同压力条件下,褐煤燃烧反应速度更快;指数为1的随机成核和随后生长函数可以较好地表征加压富氧条件下煤粉燃烧的动力学过程。煤粉燃烧的烟气成分在不同的压力条件下存在一定的区别,本文利用搭建的加压富氧固定床试验台分析了不同压力条件下煤粉燃烧烟气成分的变化情况。结果表明:在加压富氧条件下,煤粉的着火时间均小于常压气氛,燃尽时间普遍高于常压气氛;对于褐煤和烟煤而言,煤粉燃烧的平均温度均高于常压气氛,这说明提升压力,可以提高煤粉的燃烧强度;不论烟煤还是褐煤,各个压力条件下氧气浓度随时间变化的规律是一致的,烟煤由于挥发分含量较低,初始阶段不同压力条件下O2浓度变化不明显;适当提高反应压力(2 MPa),烟气中的CH4含量会提高,当压力进一步提高,CH4的生成量会降低;烟气中CO和CO_2的生成规律正好相反,在低压条件下,由于烟气流速较快,不利于煤粉颗粒和氧气混合燃烧,造成低压条件下烟气中CO的浓度较高,高压条件下,由于烟气流速较慢,有利于煤粉完全燃烧,CO_2浓度较高,实验条件下CO_2的最高体积浓度接近90%。以某300 MW燃煤锅炉为研究对象,利用ASPEN PLUS软件建立了加压条件下煤粉富氧燃烧发电系统模型,研究了不同压力条件下系统的能耗。随着压力的上升,空分制氧能耗逐渐增大,当压力从0.1 MPa到5 MPa,制氧能耗从64.862 MW上升到115.025 MW,单位制氧能耗也从0.309kWh/m3上升到0.548 kWh/m3;烟气压缩系统的能耗随着压力的升高而逐渐降低,0.1 MPa时,烟气压缩系统能耗最大,为41.325 MW;随着压力的升高,可以从烟气中回收水蒸气的气化潜热,部分补偿了空分系统能耗;加压富氧燃烧系统相对于常压富氧燃烧系统,电厂净效率更高。当压力从0.1 MPa提升到2 MPa时,发电系统的净效率从27.73%提高到29.28%,2 MPa条件下电厂净效率最高。
[Abstract]:CO_2 has obvious advantages in separation and fixed in the field of pulverized coal oxygen enriched combustion, but because of the air separation system and purification CO_2 compression system of huge energy consumption, caused by poor economic system, pressurized oxygen enriched combustion technology is put forward based on oxygen enriched combustion technology, power generation system based on pressurized oxygen enriched combustion technology with higher generation efficiency in this paper, the energy consumption of 0.1 ~ 5 MPa in the condition of combustion characteristics of pulverized coal and pressurized oxygen enriched combustion system is analyzed. This paper constructs the pressurized oxygen enriched near zero emission power generation system, air separation, coal combustion, flue gas CO_2 separation and compression process is carried out under high pressure, the use of high pressure gas latent heat recovery boiler flue gas condenser water vapor, improve the power generation efficiency of the system; at the same time, with the method of multi-stage compression and cold recycling CO_2. in flue gas in pressurized atmosphere, the combustion of pulverized coal. There is a big difference with the normal atmosphere. The application of high voltage TGA devices of different pressure (0.1 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa and 6 pressure conditions), different proportion of oxygen and carbon dioxide (21%02/79%CO_2,30%02/70%CO_2,40%02/60%CO_2 3 volume ratio, different kinds of coal (bituminous coal)), lignite combustion and burnout characteristic of coal under the condition of the combustion kinetic parameters. The results showed that: compared with atmospheric oxygen atmosphere, pressurized oxygen enriched atmosphere pulverized coal ignition temperature lower, combustion performance is better; in the same proportion under the condition of O2 /CO_2, with the increasing of pressure, the ignition temperature of pulverized coal decreased gradually increase of 3 MPa. The lowest comprehensive combustion performance is best; in conditions under the same pressure, with the increase of oxygen concentration, mass loss of coal in advance, the oxygen concentration is higher, the violent reaction of bituminous coal and lignite; TG curve Is the consistent line and DTG curve changes with the pressure, but because of the difference of two kinds of volatile content, under the same pressure, lignite combustion reaction faster; index of 1 random nucleation and subsequent growth function can characterize the pressurized coal powder under the condition of oxygen enrichment combustion kinetics. Some differences between the composition of flue gas of pulverized coal combustion under different pressure conditions, this paper using the pressurized reactor fixed bed test rig is analyzed under different pressure conditions of pulverized coal combustion flue gas composition changes. The results show that the pressure in the oxygen rich conditions, ignition time of pulverized coal is less than atmospheric pressure atmosphere, combustion time is generally higher than the atmosphere pressure; for lignite and bituminous coal, the average temperature of pulverized coal combustion is higher than that of normal atmosphere, indicating that the lifting pressure can increase the intensity of combustion of pulverized coal; bituminous coal is also no lignite, respectively Is a concentration of oxygen under pressure varies with time, because the coal volatile content is low, the initial stage under different pressure conditions O2 concentration did not change significantly; increase the reaction pressure (2 MPa), CH4 content in the flue gas will increase further when the pressure increases, the amount of CH4 will decrease; the formation of CO and CO_2 in flue gas on the contrary, under the condition of low pressure, the gas flow rate is fast, is not conducive to the pulverized coal and oxygen mixed combustion, resulting in higher concentration of flue gas under low pressure in CO, under the condition of high pressure, the flue gas flow rate is slow, is conducive to the pulverized coal complete combustion, the concentration of CO_2, the highest volume concentration under the experimental conditions of CO_2 close to 90%. with a 300 MW coal-fired boiler as the research object, a pressurized power system model under the condition of oxygen enriched combustion using ASPEN PLUS software, studied under different pressure system The consumption of energy. As the pressure rises gradually increases energy consumption of air separation, when the pressure from 0.1 MPa to 5 MPa, oxygen consumption increased from 64.862 MW to 115.025 MW, the energy consumption per unit of oxygen also increased from 0.309kWh/m3 to 0.548 kWh/m3; energy consumption of flue gas compression system decreases with the increase of pressure 0.1 MPa, compressed gas the energy consumption of the system is 41.325 MW; the largest, with the increase of pressure, water vapor latent heat of vaporization can be recovered from the flue gas, partly compensates for the air separation system of energy consumption; pressurized oxygen enriched combustion system relative to atmospheric oxygen enriched combustion system, power plant net efficiency higher. When the pressure increased from 0.1 MPa to 2 MPa, the net efficiency of power system from 27.73% to 29.28%, under the condition of 2 MPa power plant net efficiency is highest.

【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X773;TM621.2

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