Boiler operation is of great significance in terms of energy saving and environmental protection.EPCB combines practical on-site operational experience with an in-depth discussion of the fundamentals of boiler thermal efficiency and related concepts, as well as a detailed analysis of the control factors that affect boiler thermal efficiency. In addition, strategies to reduce boiler heat loss and improve thermal efficiency will be carefully discussed, aiming to maximize the effective use of energy resources and promote sustainable economic development.

Relevant overview on thermal efficiency of boiler operation

1.Boiler thermal efficiency

The efficiency of the boiler is the percentage of the total heat from fuel combustion that is effectively utilized by the boiler. Generally use the principle of heat balance to analyze, comprehensively analyze the components of heat loss, heat loss is reduced, the effective use of heat is increased, the boiler thermal efficiency can be improved. Therefore, the effective way to enhance the thermal efficiency of the boiler is to reduce the heat loss of the boiler, only to take a variety of scientific methods to reduce the heat loss of the boiler, in order to promote the enhancement of the thermal efficiency of the boiler, to solve the current energy conflicts.

2. Heat loss

Boiler heat loss refers to the energy generated by fuel combustion is not effectively utilized by the boiler part of the heat. Causes of heat loss for more reasons, incomplete combustion of fuel, high-temperature flue gas to take away the heat, ash loss, boiler heat dissipation and other factors can lead to heat loss, which is incomplete combustion and high-temperature flue gas to take away the heat caused by the greatest impact, can reach about 30% of the total heat. Therefore, it is necessary to analyze the factors that cause heat loss in the boiler and take effective measures.

Reduce heat loss to improve boiler thermal efficiency control factors

1. Boiler heat loss

Boiler in the actual use of the process, unavoidable heat exchange with the external environment resulting in heat loss, the amount of heat dissipated by the boiler and the manufacture of boiler materials are closely related to the thermal insulation performance of different materials have a greater difference, only to the thermal insulation performance of different materials for in-depth analysis, in order to design a more reasonable boiler layout, reduce the heat loss of the boiler. Fuel combustion inside the boiler, so that the temperature inside the boiler is much higher than the temperature outside the boiler, the formation of heat conduction with the external environment, the use of poor thermal conductivity of the material on the boiler insulation or to improve the boiler's airtightness can effectively reduce the boiler heat dissipation.

2. Heat loss due to boiler emissions

In the operation of the boiler, the heat dissipated with the flue gas emission is also one of the causes of boiler heat loss, which must be controlled. Boiler emission control is also the main means to improve the thermal efficiency of the boiler, which should be based on the use of the boiler needs, choose a reasonable emission technology. With the heat emitted from the flue gas will cause changes in the internal pressure of the boiler, when the inside of the boiler is filled with pulverized coal or gas, heat is generated through the combustion of the fuel, and in addition to the heat of the effective work, a part of the heat will be retained in the flue gas or slag, but the continuous operation of the boiler needs to remove the flue gas and slag in a timely manner in order to guarantee that the pressure inside the boiler will be maintained at a safe value, which inevitably takes away a part of the heat, which should be attract the attention of technicians.

3. Heat loss due to inadequate fuel combustion

Fuel combustion is a complex chemical process, the effect of fuel combustion depends not only on the nature of the fuel itself, but also on the combustion conditions. When external conditions change, the combustion of fuel will also change greatly, the heat released has a big difference, the study of boiler heat loss, it is necessary to study the incomplete combustion of fuel this factor. Not fully combusted pulverized coal is discharged into the atmosphere with the flue gas, which will form a certain heat loss. Insufficient air supply in the boiler, poor fuel quality or uneven distribution of pulverized coal will also cause incomplete combustion, and these incomplete combustion fuels will be lost with the flue gas discharge or slag cleaning, which will reduce the thermal efficiency of the boiler.

Important measures to improve the thermal efficiency of boiler operation

Reduce the heat loss of the boiler in order to improve the thermal efficiency of the boiler, in line with the requirements of energy saving and emission reduction, the operation of the boiler must be analyzed to find measures to effectively improve the thermal efficiency of the boiler. In this process, we should actively seek theoretical support, start from the various factors affecting the efficiency of the boiler, and make targeted optimization, in order to truly improve the thermal efficiency of the boiler, and promote the application of the boiler in various production.

1. Reduction of heat loss from exhaust smoke

Exhaust heat loss is the main component of the boiler heat loss, in the actual operation of the boiler, reduce the exhaust heat loss is one of the ways to effectively enhance the thermal efficiency of the boiler, to take a variety of scientific means to reduce the exhaust heat loss is the preferred way to enhance the thermal efficiency of the boiler should be given high priority. Reduce the exhaust heat loss should start from the following three aspects.

(1) Control the exhaust temperature. Try to complete the heat exchange before the flue gas is discharged into the atmosphere, and it is strictly prohibited for users to privately remodel the boiler in actual use, so as not to cause the problem of declining boiler sealing. If the flue gas leakage due to poor boiler sealing is bound to enhance the heat loss, the problems in the exhaust system should be checked immediately and repaired in time.

(2) Improve the area of the heat exchange area and control the thermal conductivity of the heat exchange equipment. If the phenomenon of slagging inside the boiler is serious, it will greatly reduce the thermal conductivity of the heat exchange surface and increase the temperature of the exhaust smoke, which should be cleaned up in time so that the thermal conductivity of the heat exchange equipment is maintained within the excellent value. Therefore, in the actual operation of the boiler, the operational status of the boiler should be monitored, and the problems affecting heat exchange should be dealt with in a timely manner.

(3) Heat exchanger tube scaling should be cleaned in time. There are many factors that lead to heat exchanger tube scaling, the pH value of the circulating water in the boiler is not appropriate, the water contains too many metal ions can accelerate the heat exchanger tube scaling, so we should regularly clean up the heat exchanger tube fouling, to maintain the heat exchange efficiency of the heat exchanger tube in a certain value, so that the flue gas in the boiler can be fully exchanged for heat. Management of the temperature in the furnace, air supply unreasonable will affect the combustion of the boiler, flue leakage can also affect the combustion of the boiler, we must regularly check the air supply system and flue whether there are problems, to realize the monitoring of the combustion state of the boiler, to ensure that the furnace is always in a highly efficient combustion state.

2. Avoidance of heat loss due to incomplete fuel combustion

Incomplete combustion of fuel is one of the main causes of heat loss, incomplete combustion of fuel will produce more slag and soot, not only increase the pollution of the environment, but also make the combustion environment in the furnace chamber worse. 

To avoid the phenomenon of incomplete fuel combustion, we must effectively control the furnace temperature. General furnace outlet temperature should reach more than 800 ℃, and in the combustion process need to add a certain amount of water, in order to effectively promote combustion, so that fuel combustion is more complete. Improve the mixing degree of fuel and air can also effectively improve the fuel combustion rate.

In the actual operation of the boiler, more scientific furnace structure should be used to promote fuel combustion, and scientific monitoring of the combustion state, so that the amount of air supply, the amount of coal blowing, slagging speed of the three indicators to adapt to each other, once the indicators are not well matched will cause fuel combustion incomplete.

3. Reduction of heat loss from incomplete gas combustion

Incomplete combustion of the gas will not release all the heat, reducing the thermal efficiency of the boiler. When optimizing the design to improve the thermal efficiency of the boiler, the combustion rate of the gas must be considered, and active means must be taken to improve the degree of combustion of the gas:

① Regulate the air volume to optimize the mixing state of fuel and air, and adopt stratified combustion to make the combustion in the furnace chamber more complete;

② Take effective measures to extend the residence time of the flue gas so that the gas has enough time to complete combustion;

③ Conduct all-round monitoring of the combustion state in the furnace, accurately measure the heat dissipation and water temperature of the boiler, and take effective heat preservation measures in the outer layer of the boiler, so as to enhance the thermal efficiency of the boiler in all aspects.

Example analysis

1. Absorption heat pump design parameters

A project requires that the exhaust temperature exceeds 60 ℃, its actual exhaust temperature up to 70 ℃, the exhaust velocity in line with the design requirements, basically in line with the conditions of use of lithium bromide absorption heat pumps, and therefore can be used in this way to design the boiler's heat recovery device, and ultimately determine the design indicators for: heat 4000 kW, the final temperature of the flue gas 28 ℃, the overall cooling capacity of more than 144 ℃.

2. Heat exchanger and heat transfer rate

Heat conversion efficiency is the main performance indicator of the heat pump, but also the heat pump inspection index. In order to achieve the required conversion rate, it is necessary to calculate the total amount of heat exchange between the boiler and the heat exchange of each sub-agency, where the total amount of heat exchange refers to the heat pump's final effective conversion of heat.

Different fluids are added on both sides of the heat pump to realize the exchange of heat in the shell and tube heat exchanger. Heat is transferred from the flue gas high temperature measurement to the low temperature measurement of the exchange medium in order to realize the recovery of heat. Eventually, the condenser returns the recovered heat to the boiler water, realizing the complete cycle of heat.

The water temperature on one side of the evaporator is considerably higher than the temperature of the cooling medium on the other side of the tube shell, thus inducing them to transfer heat at a faster rate and realizing the purpose of heat exchange. The heat of the circulating water is absorbed by the cooling medium and transferred to the heat pump which carries out the heat circulation. The situation inside the condenser is similar, the coolant outside the tube shell flows through the heat exchanger absorbs the heat of the boiler water, so that the heat given off by the water vapor produces a phase change, and the boiler water absorbs this heat, forming a complete cycle of heat.

Conclusion

Boiler heat loss contains many factors, only from the factors affecting the thermal efficiency of the boiler, take targeted measures to effectively improve the thermal efficiency of the boiler. Boiler thermal efficiency depends not only on the degree of fuel combustion, but also depends on the operating conditions of the boiler.

Therefore, when improving the thermal efficiency of the boiler, it is necessary to optimize the structure and equipment of the boiler and improve the management level of the boiler in order to maximize the thermal efficiency of the boiler and meet the requirements of energy saving and emission reduction by reducing the heat loss of exhaust smoke, avoiding the heat loss caused by incomplete combustion of fuels, and reducing the heat loss of incomplete combustion of gases in order to improve the thermal efficiency of the boiler and meet the requirements of energy saving and emission reduction.

In the coming period of time, the relevant enterprises should follow the principle of heat balance, from the actual situation of boiler operation, targeted measures to reduce the heat loss of the boiler, the operation of the boiler for a full range of control, in order to truly enhance the level of boiler operation, to achieve the goal of energy saving and emission reduction.