Characteristics of heat pipe preheating boiler and its application in related glass industries. The operation of the waste heat boiler in the daily work process and related precautions.
The reuse of exhaust gas generated by the combustion of heavy oil (or other fuels) in glass kilns, as well as the so-called secondary use, have basically begun to be used in the glass and cement industries. Waste heat utilization can reduce business costs, and enterprises are willing to invest and improve waste heat utilization.
At present, the utilization of kiln costs is generally waste heat steam boiler or waste heat power generation boiler. Here only the application of waste heat steam boilers. In the utilization of waste heat, boilers can be briefly described as direct heat exchange boilers and indirect heat exchange boilers according to different heat exchange methods. The direct heat exchange type is similar to the smoke tube boiler according to the structure, and the direct heat exchange type is generally small capacity, low parameters, low water quality requirements, simple structure, and low heat exchange efficiency. Indirect heat exchange type refers to the heat pipe boiler, which is generally used in a relatively low temperature and corrosion-resistant environment, and its biggest feature is high heat exchange efficiency and low failure rate.
The basic principle of heat pipesThe working principle of heat pipe is briefly described as follows: the heat pipe absorbs heat from the flue gas, transfers the heat to the water in the steam drum through the medium in the heat pipe, and heats the water to vaporize.
The heat transfer of heat pipe is two wall heat exchange, and the cold and hot sides are separated by a partition, and the sealing between the heat pipe and the partition is good; Both cold and hot gases flow outside the heat pipe, and the heat transfer efficiency is high. Through thermal design, it can ensure that the temperature of the heat pipe wall is accurately higher than the temperature of the flue gas, which avoids corrosion, and at the same time makes the dust in the flue gas not easy to accumulate on the pipe wall and fins, so as to ensure the long-term stable operation of the equipment. Because of the indirect heat transfer, even one or two less heat pipes (damaged or aged) do not affect their use. Heat pipes have a large thermal conductivity, and it has the property of transferring a large heat flow at a small temperature difference. Under the condition of low temperature flue gas, the heat pipe waste heat boiler is used to make full use of the characteristics of the heat pipe, and in the case of a small temperature difference, it can increase the heat to more heat.
According to the working temperature in the heat pipe: low temperature heat pipe, room temperature heat pipe, medium temperature heat pipe, high temperature heat pipe, etc., according to the combination of tube shell and working liquid: copper-water heat pipe, carbon steel-water heat pipe, aluminum-acetone heat pipe, carbon steel-naphthalene heat pipe, stainless steel-sodium heat pipe, etc. The most commonly used in kiln flue gas is carbon steel-water heat pipe, which has a simple structure and relatively low cost, and meets the requirements of resisting corrosive gases in kiln exhaust gas. And the resistance is less, reducing the power of the system and saving the cost in operation.
Among the exhaust gases produced by the kiln, the most corrosive and damaging to the equipment is the small amount of fluoride contained in the flue gas with SO3 and SO2. Although the concentration of SO2 in the flue gas is much greater than that of SO3, the influence on the ** temperature is much less than that of SO3, because when approaching the ** temperature, SO3 is almost completely dissolved in water vapor, but SO2 is rarely dissolved in water vapor in the flue gas. Considering its best corrosion, in the flue gas waste heat boiler, its heat pipe boiler has obvious advantages, and its application has gradually expanded.
Due to the process or kiln structure, the exhaust gas temperature is generally 320-450, and the exhaust gas temperature can be reduced to 180-220, and the boiler can be based on the specific requirements of customers, such as steam consumption, use temperature, and the outlet temperature is not less than how many degrees, which can be adapted to local conditions.
In the process of using waste heat boilers, it is generally necessary to pay attention to the following aspects(1) Low temperature corrosion. In the standby furnace of waste heat boiler, if the boiler is not suitable for a long time, consider opening the boiler inlet or outlet ram a little to make the flue gas enter the boiler body, so that the heat pipe can maintain a certain temperature and prevent low-temperature corrosion.
2) Scaling effects. In the long-term use of the boiler or has been out of use, the boiler or the heat pipe heating sleeve will be rusted or scaled, this situation is generally to find a professional company for cleaning, in order to avoid such a situation, the boiler is required not to be shut down for too long, uninterrupted, and the frequency is higher.
3) Improper treatment of softened water causes boiler scaling or corrosion. In the use of waste heat boilers, it is carried out in strict accordance with the water quality standards of industrial boilers. Its feed water (low-pressure boiler) requirements: turbidity FTU 20, hardness 0030 mmol/l，8.0≤ph≤9.5. Dissolved oxygen 01 mg l, oil 20 mg l, total iron 03 mg/l。Unqualified water supply directly affects its efficiency, safety and life.
4) Continuous sewage discharge during the use of the boiler. There is a blowdown valve at the bottom of the boiler of the waste heat boiler, and the valve should be kept a certain opening during its use, and its opening can be adjusted according to the steam pressure, the size of the amount of steam used, etc., but the continuous blowdown should be opened during operation, because at the bottom of the boiler, the water of the boiler is concentrated here, and it is mainly some salts and sundries (produced in the feed water, or the cleaning and filtration is not thorough). It is necessary to continuously drain the higher concentration of the water in this boiler barrel to reduce the risk of the boiler structure.
5) In the process of boiler use, the cleaning of the boiler is also more important, the general boiler needs to be cleaned after about 10 days of operation, and the basis of the cleaning can be based on the number of days of boiler use, the resistance of the boiler inlet and outlet reaches the set value, the vibration of the boiler induced draft fan, and the change of the gas production of the boiler. When cleaning boilers, small boilers generally use steam or compressed air to purge and flush with water, and large boilers generally use ultrasonic or gas explosion cleaning. After the cleaning of the small boiler, it is necessary to maintain a certain temperature on the outer wall of the heat pipe to prevent accelerated corrosion.
The following aspects should be paid attention to in the daily boiler inspection1) The three major safety accessories of the boiler (thermometer, pressure gauge, safety valve) are indispensable, and the fault should be dealt with in time, and the pressure gauge and safety valve should be inspected regularly.
2) The choice of boiler feed pump, the horizontal (vertical) type single-stage (multi-stage) centrifugal pump can generally be selected, the mechanical seal should be considered when choosing the model, the packing seal is easy to leak, the maintenance is frequent, the water leakage is difficult to deal with, and the operating cost increases. The water supply mode can consider frequency conversion to reduce the impact on the boiler during operation, and also have a certain protective effect on the water pump. The arrangement and consideration of the standby pump should be spared, switchable, and directly operated on site.
3) The selection of the check valve used in the boiler feed water, the selection of the check valve in the steam boiler is more important, and the check valve is generally arranged horizontally in the inlet section, and the selection of the check valve is considered to be strictly sealed, and it is used for a long time, and it is not suitable for failure.
4) The layout of the pressure sensor in the inlet and outlet section of the boiler body, the installation position, if the installation is not suitable, the measurement is not accurate, not to mention, it is easy to block.
5) The selection of filters, softened water devices and deaerators used in boiler inlet water has a great impact on the boiler water quality.
6) The layout of the steam outlet pipeline and the trap of the cylinder, the selection and arrangement of the pipeline trap are also more important for the normal operation of the steam.