【作者】 张巍；

【导师】 陈鸿伟；

【作者基本信息】 华北电力大学 ， 热能工程， 2020， 硕士

【摘要】 随着全球变暖趋势日益严峻,CO₂减排越来越得到重视,然而人类尚无法摆脱对化石燃料的依赖,化学链燃烧技术作为一种自带炭分离特性的燃烧方式受到广泛关注。其中,化学链燃烧分为气体燃料和固体燃料的化学链燃烧,结合我国富煤贫油少气的资源储备,煤炭等固体燃料的化学链燃烧尤为重要,但是无论是先气化再燃烧的间接燃烧还是直接进料燃烧均存在一定问题亟待解决,需要众多学者进一步研究。为避免固体燃料生成的灰分对载氧体活性的影响,本文设计了一种新型化学链燃烧装置,并搭建了冷态实验台进行了冷态实验研究。此装置采用三床串联结构,将固体燃料与载氧体隔离,同时利用载氧体余热对气化所用气体进行加热,既可以避免固体燃料灰分对载氧体的影响,同时减少额外的能量消耗。冷态实验中对空气反应器和循环流率控制阀对循环流率的控制效果和空气反应器和燃料反应器风速对实验系统运行状态的影响进行分析。结果表明,空气反应器与循环流率控制阀协同作用下可对固体循环流率进行较为精确的调整。分别调节两反应器风速,分析其对实验系统各部分的影响,单一反应器风速发生变化,另一反应器运行状态未发生显著变化,两反应器独立性较好。空气反应器风速增加会导致部分颗粒进入燃料反应器增加燃料反应器中整体压降;燃料反应器风速的增加会将燃烧室中部分颗粒送入气化室。空气反应器和燃料反应器风速的提升对固体循环流率均有促进作用,但是空气反应器表观风速对固体循环流率的影响明显强于燃料反应器。同时针对初步实验中遇到的气化室布风板部分区域堵塞故障现象采用CPFD方法进行数值模拟研究,分析其对床内颗粒流化特性的影响。模拟结果显示,布风板部分堵塞会导致床内存在高浓度区域,影响床内颗粒的混合。且高浓度区有向周边扩散的趋势,从风速、床料高度、堵塞面积三个方面对扩散的影响进行分析,发现随风速增加,扩散程度减弱,床料高度对其影响较小,堵塞面积的增大一定程度上加强其扩散程度。更多还原

【Abstract】 The global warming trend is becoming more and more serious,and CO₂ emission reduction is getting more and more attention.However,human beings are still unable to get rid of the dependence on fossil fuels.Chemical looping combustion technology has attracted extensive attention as a combustion method with its own carbon separation characteristics.Among them,chemical looping combustion is divided into chemical looping combustion of gaseous fuel and solid fuel.Combined with China’s rich coal-poor and low-gas resource reserves,chemical looping combustion of solid fuels such as coal is particularly important.But there are certain problems in combustion or direct feed combustion,which need to be solved by many scholars.In order to avoid the influence of ash generated by solid fuel on the activity of oxygen carrier,a new type of chemical looping combustion device was designed,and a cold model experimental system was built for cold model experiment.The device adopts a three-bed series structure to isolate the solid fuel from the oxygen carrier,simultaneously,the residual heat of the oxygen carrier was used to heat the gas for gasification,thereby avoiding the influence of the solid fuel ash on the oxygen carrier and reducing the additional energy consumption.In the cold model experiment,the effect of the air reactor and the circulating flow rate control valve on the circulation flow rate and the influence of the air reactor and the fuel reactor wind speed on the operating state of the experimental system were analyzed.The results show that the air reactor can be adjusted accurately with the circulating flow rate control valve.The wind velocity of the two reactors were adjusted separately,and the effects on the various parts of the experimental system were analyzed.The wind velocity of the single reactor changed,and the other reactors did not change significantly.The two reactors had good independence.An increase in the air reactor wind velocity causes some of the particles to enter the fuel reactor to increase the overall pressure drop in the fuel reactor;an increase in the fuel reactor wind speed will send some of the particles in the combustion chamber to the gasification chamber.The increase in wind velocity of the air reactor and the fuel reactor promotes the solids circulation rate,but the apparent wind velocity of the air reactor has more effect on the solids circulation rate than the fuel reactor’s.At the same time,the CPFD method was used to numerically simulate the blockage failure phenomenon in the gasification chamber of the gasification chamber encountered in the preliminary experiment,and its influence on the fluidization characteristics of the particles in the bed was analyzed.The simulation results show that partial blockage of the air distribution plate will result in a high concentration area in the bed,which will affect the mixing of particles in the bed.The high concentration zone has a tendency to diffuse to the periphery.The effects of wind speed,bed height and plugging area on the diffusion are analyzed.It is found that as the wind speed increases,the degree of diffusion decreases,and the bed height has less influence on it.The increase in area enhances the degree of diffusion to some extent.更多还原