Effect of oxygen content in boiler operation on boiler efficiency

Effect of oxygen content in boiler operation on boiler efficiency
Abstract: Due to the different oxygen content in the domestic waste incineration environment, the efficiency, flue gas composition and characteristics of the boiler will change in different degrees during the combustion process. According to the relevant investigation and research, if the operating oxygen content is properly increased, the exhaust gas temperature of the grate furnace will be increased, and the combustion efficiency of the boiler will also increase. Based on this, this paper will take the grate furnace as an example to quantitatively analyze the difference of the operating oxygen consumption of the boiler in the domestic waste incineration power plant, excavate the impact of the operating oxygen on the boiler efficiency, and finally propose effective measures to adjust the operating oxygen, so that the operating oxygen in the boiler can always be in the best state, so as to improve the combustion efficiency of the boiler.
       
Key words: oxygen content in boiler operation; Grate furnace; Domestic waste incineration; Boiler efficiency
       
Introduction: At this stage, some power plants operate in the way of domestic waste incineration power generation, which has strong safety and economy, and is in line with the energy conservation and environmental protection policies advocated by China, to minimize the emission of dust, sulfur dioxide and other pollutants and reduce the damage to the surrounding environment. In the selection of combustion equipment, grate furnace equipment is usually used. In the process of operation, it is found that there is a significant positive relationship between its operating oxygen content and boiler efficiency. Therefore, it is favored by more and more environmental protection energy enterprises, making the boiler efficiency further improved.
       
1. Quantitative analysis of operating oxygen consumption difference
       
1.1 Consumption difference analysis model
       
From the relevant investigation results, it can be seen that there are two main factors affecting the efficiency of grate furnace in the process of domestic waste incineration, one is smoke loss, the other is incomplete combustion loss of equipment. By constructing the counterbalance calculation model, it can be concluded that the operating oxygen content will have a decisive impact on the smoke loss and incomplete combustion loss. After calculating the incomplete combustion of the equipment, it is found that it is difficult to calculate the full combustion loss of the equipment simply by the carbon content in the fly ash. Therefore, it is far from enough to simply build a boiler efficiency model to study the relationship between the operating oxygen content and the boiler efficiency.
       
Through consulting relevant literature, explore the characteristics of domestic waste incineration and the operation characteristics of grate furnace, and establish an incomplete combustion loss assessment model based on the two, so as to comprehensively and systematically study the impact of operating oxygen on boiler efficiency. Therefore, in this study, the application of grate furnace in domestic waste incineration power generation will be taken as an example, and the various losses of the boiler in combustion will be analyzed with the help of the GBPTC counter-balance calculation model, and the change rule of the boiler efficiency will be obtained by observing various parameters, and the factors affecting the boiler efficiency will be explored. On this basis, a network model of the sum of the two losses will be constructed, Quantitative analysis of factors affecting boiler efficiency.
       
1.2 General calculation method
       
In the past, the traditional analysis methods mainly analyzed the impact of the operating oxygen content on the smoke exhaust, and then obtained the boiler efficiency, without considering the loss caused by the incomplete combustion of the equipment, or ignoring the impact of the oxygen content on the carbon content in the fly ash when the equipment is fully burned. In the process of changing boiler parameters, various consumption differences will inevitably occur. At this time, the traditional analysis method will be used to carefully divide the losses in the boiler, making it become a variety of boiler heat losses, and finally obtain a number of boiler loss parameters. Therefore, this traditional calculation method is applicable to the quantitative analysis of boiler efficiency which is small and not strictly required.
       
In this study, according to the GBPTC counterbalance calculation model and formula, the difference in consumption caused by the operating oxygen content of the grate furnace is calculated. The main parameters involved include: water vapor content in the flue gas, heat of the flue gas, oxygen content in the air, and so on. By substituting the measured operating oxygen content into the formula, the influence and correlation between the final oxygen content change and the boiler efficiency can be obtained.
       
2. Effect of operating oxygen on boiler efficiency
       
2.1 Impact on combustion characteristics
       
According to relevant investigation results, there is a certain relationship between boiler combustion characteristics and operating oxygen content. When the operating oxygen content exceeds 1000 cubic meters per hour, the exhaust temperature can reach 142 ℃, and the adiabatic combustion temperature is 1550 ℃; When the operating oxygen is continuously increased to 2000 cubic meters per hour, the exhaust temperature is 145 ℃, and the adiabatic combustion temperature is 1600 ℃; Until the operating oxygen reaches 4000 cubic meters per hour, the exhaust temperature is 152 ℃, and the adiabatic temperature is about 1640 ℃.
       
According to the above data, it can be seen that the change of the operating oxygen content will drive the bidirectional change of the adiabatic combustion temperature and the exhaust gas temperature, and the temperature change inside the boiler can also be reflected through the combustion temperature. If the theoretical combustion temperature in the furnace is higher, the actual internal temperature will also be higher, and the effect of radiation heat transfer and heat transfer in the furnace will also be improved. If the operating oxygen content in the grate furnace is increased, the emission of flue gas will also be increased, and the heat transfer system will be reduced, which will affect the actual temperature of flue gas. Generally, there is not much oxygen in the flue gas, so the concentration of flue gas will generally be around 1.6%.
       
2.2 Impact on boiler efficiency
       
The change of operating oxygen will also lead to the change of boiler efficiency. For example, in an energy and environmental protection limited company powered by waste incineration in a certain place, when analyzing the impact of operating oxygen and boiler efficiency, the following data are obtained: when the operating oxygen is 0 square meters per hour, the boiler thermal efficiency is 90%; When the oxygen content is 1000 cubic meters per hour, the boiler thermal efficiency is 90.5%; If the oxygen content is increased to 4000 cubic meters per hour, the thermal efficiency is about 92%. From the above experimental results, it can be seen that there is a positive proportional relationship between the operating oxygen content and the actual combustion efficiency of the boiler. In addition, from the above data, it can also be concluded that there is a close relationship between the operating oxygen content and the thermal efficiency of the boiler, that is, the oxygen content in the boiler is gradually increasing, which increases the oxygen content of the combustion aids, thus making the combustion of domestic waste more sufficient, reducing the amount of unburned waste, and avoiding the heat loss caused by the unburned or incomplete combustion of some waste. It can be seen that the calculation of the operating oxygen content should be combined with the actual demand to minimize energy waste, heat loss and other conditions, so as to further improve the combustion efficiency of the boiler.
       
3. Analysis of regulation mode of operating oxygen
       
3.1 Reduce heat loss of smoke exhaust
       
It can be seen from the above research that there is a great relationship between the operating oxygen content and the boiler efficiency. Therefore, in the process of domestic waste incineration, in order to improve the combustion efficiency of the boiler and generate more electric energy, it is necessary to control the operating oxygen content scientifically and reasonably. When the grate furnace is operating at high load, the temperature in the furnace is high and the combustion condition is good. At this time, the combustion stability is relatively high, but it is easy to produce heat loss of exhaust gas. In order to further improve the combustion efficiency of the boiler, it is necessary to take correct measures to reduce the heat loss of exhaust gas, and reduce the speed of exhaust gas while ensuring the increase of the internal temperature of the boiler, so as to extend the time of flue gas staying in the boiler, reduce the loss of incomplete combustion to a large extent, and enable domestic garbage to be fully burned to the maximum extent. At this time, it is necessary to ensure the sealing degree of the grate furnace, prevent air leakage, and keep the temperature in the furnace at the best state, so as to improve the operation efficiency of the boiler.
       
3.2 Change the boiler air supply
       
On the premise of optimizing and changing the air supply volume of the boiler, adjust the operating oxygen content of the boiler to make the amount of excess air within a reasonable range. If the amount of excess air is too large, the thermal efficiency of the boiler will be reduced, and the flow rate of flue gas in the boiler will be increased, so that many garbage that is not easy to burn can not be fully burned, resulting in heat loss. In addition, the excessive amount of excess air will lead to an increase in the oxygen content in the furnace, which will be discharged out of the furnace together with the flue gas, resulting in a large amount of waste of resources and increasing the input cost of the enterprise. To sum up, during the operation of the grate furnace, it is necessary to ensure the correctness of the operating oxygen content, give full play to the role of the forced draft fan, effectively regulate the oxygen content, and make the oxygen content in the flue gas as a reference standard for adjustment, so that the operating oxygen content is always kept in the most ideal state, so that domestic waste can be fully burned in the grate furnace, and reduce the combustion loss caused by incomplete combustion, Thus, the operating efficiency of the boiler is significantly improved.
       
Conclusion: To sum up, it can be seen from the research in this paper that there is a great correlation between the oxygen content in boiler operation and the operating efficiency and combustion characteristics. Therefore, in the process of practical application, the oxygen content in the boiler should be strictly controlled to minimize the heat loss of exhaust gas, inadequate combustion loss and heat dissipation loss, so as to further improve the combustion efficiency of the boiler. In addition, attention should be paid to the control of operating oxygen when using grate furnace for waste incineration, so that energy and environmental protection enterprises can achieve win-win economic and ecological benefits, and promote the healthy and harmonious development of society.