Study On The Catalytic Effect And Mechanism Of Coal Combustion In Power Plant With Liquid Combustion Accelerant

The traditional energy saving method of thermal power plant is to increase the contact area of coal and oxygen to improve the combustion efficiency of coal.However,this method not only has complex operation process and high operation cost,but also has high requirements for coal quality and boiler operation stability.So how to effectively improve the efficient and clean utilization of coal in thermal power plants is very important for the implementation of energy saving policies in thermal power plants.This thesis is based on the efficient and clean utilization of coal for boiler in thermal power plants.Based on the synthesis of liquid accelerant,the liquid accelerant with the best catalytic effect was obtained by adjusting the concentration of Ni²⁺,Fe³⁺and p H value in the accelerant.It can effectively reduce the ignition point of coal into the furnace,make the combustion more full,can concentrate the release of more heat,improve the low-load stable combustion capacity of the boiler.To study catalytic combustion mechanism of combustion accelerant,and discuss the synergistic inhibition effect of different proportions of coal mixtures under the catalytic action of combustion accelerant,in order to improve the combustion efficiency of boiler coal in thermal power plants.The main results are as follows:（1）The performance of unmodified accelerant was characterized,and it was found that the best catalytic combustion effect could be achieved when the proportion of accelerant was 1 wt.‰in Datong coal.Compared with the combustion process of raw coal,the combustion characteristic values of coal samples with combustion accelerants were optimized in different degrees.In the process of accelerant modification,the burnout rate of coal sample could be kept stable,when the concentration of Ni²⁺in accelerant was adjusted to 500-2000 mg/L.When the concentration of Fe³⁺in the accelerant was adjusted to 1000-2000 mg/L,the volatiles in the coal can be precipitated and burned at a lower temperature,so that the coal sample could maintain good combustion characteristics.When the p H value of the accelerant was adjusted at 0.8-1.2,the coal sample could be burned more fully,the weight loss rate was higher,and the heat release of the coal sample could be promoted.The catalytic performance of the modified accelerant was significantly improved compared with that before modification.At this time,the p H value of the modified accelerant was 0.8,and the concentration of Ni²⁺and Fe³⁺was 1000 mg/L.（2）In the study of catalytic combustion mechanism of combustion accelerators,it was found that combustion accelerators could destroy the stability of the basic structural units of coal and the side chains and functional groups around it during the combustion process.In the combustion experiment,the addition of catalyst increased the yield of CO₂,and the amount of residual carbon in solid products decreased,indicating that the combustion of Datong coal could be more thorough.In the pyrolysis experiment,the main pyrolysis reaction stage of coal samples with accelerant was 137℃earlier than that of raw coal,and the number of weight loss peaks on DTG decreased,indicating that the pyrolysis reaction of coal samples was more concentrated and the pyrolysis reactivity of coal samples was enhanced.In the gas phase product analysis of pyrolysis,it was found that the addition of accelerant could advance the secondary pyrolysis reaction of coal samples,improved the output of CO₂ and CO in the pyrolysis process,promoted the decomposition of compounds.The results showed that the accelerant could destroy the molecular structure of coal and reduced the energy needed for coal reaction.（3）According to the study on the adaptability of the accelerant to a single coal,it was found that the accelerant could catalyze the combustion of Huangling coal and Jiafeng coal.When the amount of accelerant in Huangling coal was 1 wt.‰,the catalytic coal combustion effect was the best.When the additive amount of accelerant in Jiafeng coal was 5 wt.‰,the catalytic coal combustion effect was the best.According to the study on the adaptability of accelerant to mixed coal,it was found that the catalytic effect of accelerant on mixed coal combustion was related to the mass proportion of coal in mixed coal.When the proportion of Huangling coal was more than40%or less than 20%,the catalytic effect of the accelerant was poor.Because when the mass ratio of Huangling coal was too high,in the early stage of mixed coal combustion,the accelerant would reduce the ignition temperature point of Huangling coal.As a result,Huangling coal consumed a large amount of oxygen,which leaded to the combustion lag of Jiafeng coal and the pyrolysis process,thus increasing the burnout temperature.When the proportion of Huangling coal was too low,the accelerant made the volatiles of Huangling coal precipitate at a lower temperature.However,the volatile analysis output was not enough to ignite Jiafeng coal and reduced its ignition temperature point,so when the proportion of Huangling coal in the mixed coal was too low,the catalytic performance of the accelerant was poor.