Self-blowing ash anti-blocking system for a rotary air preheater of a coal-fired boiler

Abstract

The present invention discloses a self-blowing ash and anti-blocking system for a rotary air preheater of a coal-fired boiler. The primary air chamber of the air preheater includes a main primary air chamber and a sub-primary air chamber. A sub-primary air outlet duct is provided at the outlet of the sub-primary air chamber, and the sub-primary air outlet duct is connected to the secondary air outlet duct; the outlet of the main primary air chamber is connected to the primary air outlet duct, and the inlet of the secondary air outlet duct is also connected to the secondary air chamber. Under various operating loads of the boiler, the primary air entering the sub-primary air chamber of the air preheater is always maintained at a sufficient air volume, and its flow velocity is ≥ 15 m / s, which greatly strengthens the self-blowing ash effect of the primary air on the air preheater, and can ensure that the air volume entering the coal pulverizing system always exactly meets the requirements of the coal pulverizing system, which has very important practical significance for improving the safety and economy of the boiler.

Description

Technical Field

[0001] The invention is used for an air supply system of a coal-fired boiler air preheater, and specifically relates to a self-soot blowing system of a rotary air preheater of a coal-fired boiler. The system is suitable for rotary three-compartment and four-compartment air preheaters of all coal-fired boilers. Background Art

[0002] At present, due to the increase in sulfur content in coal, the widespread operation of SCR denitrification equipment, the decline in SCR catalyst performance and the increasingly low control of nitrogen oxide emission concentration, the low-temperature corrosion and ash blockage problems of air preheaters in power plant coal-fired boilers are becoming more and more serious. The result is not only a significant increase in the resistance of the air preheater air and smoke system, resulting in a reduction in the operating economy of the unit; more seriously, it will affect the safety and environmental protection of the boiler unit. In addition, the service life of the air preheater will also be significantly reduced, and the amount of air preheater maintenance will increase dramatically, resulting in a sharp increase in safety hazards and maintenance costs.

[0003] The current technology to prevent low-temperature corrosion and ash blockage of air preheaters is usually to increase the exhaust gas temperature or the inlet air temperature (such as using a heater or hot air recirculation system); in addition, there are various soot blowing technologies, such as various soot blowers, hydraulic flushing technology, etc. However, there is no report on the technology of self-soot blowing using the characteristics of the air preheater itself.

[0004] Although all air preheaters are equipped with soot blowers, the number of soot blows is very limited. Taking the common steam soot blower as an example, the blowing frequency of the boiler unit during normal operation is: 1 to 3 times in 24 hours, and 5 times at most. In other words, the shortest interval between each blowing is about 8 hours. During such a long interval, the ash particles and corrosion products adhering to the heat storage plate have solidified on the heat storage plate, and it is difficult to blow them away from the heat storage plate. Therefore, the soot blowing effect is greatly weakened, and the low-temperature corrosion and ash blockage problems of the air preheater cannot be solved.

[0005] From the above analysis, it can be seen that in order to better solve the low-temperature corrosion and ash blocking problems of the air preheater, the heat storage plate should be continuously blown before the ash particles solidify on the heat storage plate, which is something that various types of soot blowers currently cannot do. Therefore, it is necessary to develop a new technology that can continuously and powerfully blow ash on the heat storage plate of the air preheater.

[0006] When the rotary air preheater is working, the primary air flow, secondary air flow and flue gas actually blow soot to a certain extent on the heat storage plate of the air preheater (self-blowing ability). Under rated load, the blowing speed of the above-mentioned various airflows is above 10m / s, but under low load conditions, the blowing speed is greatly reduced. For example, at 30% rated load, due to the reduction of the primary air flow, secondary air flow (constrained by the pulverizing system and the oxygen content of the boiler operation) and flue gas flow entering the air preheater, the blowing speed of the above-mentioned various airflows is reduced to below 5m / s; on the other hand, the temperature of the flue gas discharged from the air preheater is also reduced. The former greatly reduces the self-blowing ability of the above-mentioned airflows in the air preheater smoke and wind system; the latter reduces the temperature of the heat storage plate in the low-temperature section of the air preheater. The combined effect of the two causes low-temperature corrosion and ash blockage to occur and intensify.

[0007] In fact, the ash blocking of the air preheater occurs in the low-load operation range of the boiler. It can be seen that the ash blocking of the air preheater is largely related to the reduction of the self-blowing ability of the air preheater under the low-load condition of the boiler. Therefore, it is necessary to take measures to strengthen the self-blowing ability of the air preheater, especially under the low-load operation condition of the boiler, so that when the boiler is running under any load condition, the air preheater has the blowing ability when the boiler is running under the rated load condition, or the blowing ability is stronger than that when it is running under the rated load condition. This is the key to solving the low-temperature corrosion and ash blocking problems of rotary air preheaters of coal-fired boilers in power plants, and it has great practical significance for improving the operating safety and economy of air preheaters and even boiler units.

[0008] Under the existing coal-fired boiler unit air and smoke system conditions, the primary air volume flowing through the primary air chamber is restricted by the pulverizing system, and the secondary air volume flowing through the secondary air chamber is restricted by the boiler operating oxygen volume, while the flue gas volume is proportional to the sum of the primary and secondary air volumes, and both decrease as the boiler load decreases. In other words, under this system and its characteristics, when the boiler is operating at medium and low loads, the self-blowing capacity of each chamber of the air preheater cannot reach the self-blowing capacity when the boiler is operating at rated load conditions.

[0009] The above phenomenon cannot be changed under the existing air and smoke system configuration conditions. Without major changes to the existing air and smoke system, the self-blowing capacity of the three chambers of the air preheater cannot be improved at the same time when the boiler is running at medium and low loads. Summary of the invention

[0010] Aiming at the low temperature corrosion and ash blocking problems of coal-fired boiler air preheater, the present invention aims to provide a self-soot blowing and anti-blocking system for the rotary air preheater of coal-fired boiler.

[0011] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0012] A self-soot blowing and anti-blocking system for a rotary air preheater of a coal-fired boiler, wherein the primary air chamber of the air preheater comprises a main primary air chamber and a sub-primary air chamber, a sub-primary air outlet duct is arranged at the outlet of the sub-primary air chamber, and the sub-primary air outlet duct is connected to the secondary air outlet duct; the outlet of the main primary air chamber is connected to the primary air outlet duct, and the inlet of the secondary air outlet duct is also connected to the secondary air chamber.

[0013] A further improvement of the present invention is that the cross section of the sub-primary air chamber is fan-shaped.

[0014] A further improvement of the present invention is that the central angle of the sector is 3.75°-15°.

[0015] A further improvement of the present invention is that a flow regulating door is provided on the outlet air duct of the sub-primary air chamber.

[0016] A further improvement of the present invention is that the primary wind speed flowing through the sub-primary air chamber is always ≧15 m / s.

[0017] A further improvement of the present invention is that the primary air outlet duct is connected to the powder making system.

[0018] A further improvement of the present invention is that the secondary air outlet duct is connected to the boiler body.

[0019] A further improvement of the present invention is that the secondary air chamber is connected to the secondary air inlet duct.

[0020] A further improvement of the present invention is that both the main primary air chamber and the sub-primary air chamber are connected to the primary air inlet duct. Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention divides the primary air chamber of the air preheater into a large and a small sub-mother-and-child chamber at the upper outlet of the primary air chamber of the air preheater, and configures two corresponding hot primary air ducts, one duct corresponds to and is connected to the sub-primary air chamber, and the other duct corresponds to and is connected to the main (mother) primary air chamber. The sub-primary air duct corresponding to the sub-primary air chamber directly leads to the hot secondary air duct, and is mixed with the secondary air and sent into the furnace as combustion-supporting air; the hot primary air duct corresponding to the main chamber is connected to the original hot primary air duct and sent to the powder making system to supply the hot primary air volume required for powder making. An adjusting damper is set on the sub-hot primary air duct, and the primary air volume introduced into the hot secondary air duct is controlled by the adjusting damper. Subject to the pressure of the air supply system, the differential pressure of the air flow inlet and outlet of the primary air chamber of the air preheater is 6 to 7 times that of the air flow inlet and outlet of the main chamber. Therefore, the primary air flow rate of the sub-primary air chamber can reach about 2.5 times the primary air flow rate of the main chamber. Under rated working conditions, it can reach about 25m / s; under low load conditions, such as 30% rated load conditions, the primary air velocity of the sub-primary air chamber can still reach about 15m / s, and the blowing capacity for the heat storage plate is still greater than the blowing capacity under rated load conditions. In operation, in order to avoid excessive flow rate (just enough to remove dust), the flow rate can be controlled by setting an adjustable door on the sub-heat primary air duct, so that the boiler can maintain sufficient primary air volume for self-blowing of the air preheater no matter what load it is running under, thereby solving or reducing the low-temperature corrosion and dust blockage problems of the air preheater without increasing the exhaust temperature.

[0022] The present invention utilizes the rotation characteristics of the air preheater rotor. When the air preheater rotor rotates one circle, each small compartment on the rotor will rotate through the primary wind sub-air chamber and experience a high-speed airflow purge, thereby completing a comprehensive soot blowing of the air preheater rotor. That is, a purge is completed in about 1 minute (the time required for the air preheater to rotate one circle), the soot blowing frequency reaches about 60 times per hour, and the soot blowing frequency for 24 hours is about 1440 times, thereby ensuring that the ash particles are blown away before they are firmly bonded. The present invention improves the purge capacity of a certain compartment of the primary wind chamber of the air preheater without affecting the safe operation of the powder making system, so that it can be ensured that when the air preheater rotor rotates one circle, a comprehensive purge of each compartment of the air preheater rotor is completed through the primary wind chamber.

[0023] The present invention utilizes the differential pressure of the hot primary and secondary air ducts at the outlet of the boiler air preheater to introduce the primary air in the hot primary air chamber into the secondary hot air. The system does not involve any power equipment and has no impact on the original operation mode of the boiler air and smoke system and the powder making system.

[0024] After the present invention is put into operation, the primary air flow rate flowing through the sub-primary air chamber can be equal to or greater than the primary air flow rate under rated load conditions. The larger the flow rate, the better the soot blowing effect, but the economic loss will also increase slightly; from the perspective of economy, the minimum flow rate, i.e., the flow rate, is based on the requirement of being able to achieve the purpose of blowing, and the minimum flow rate can be determined through a special adjustment test after the system transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a system schematic diagram of the present invention;

[0026] In the figure, 1 is the primary air inlet duct, 2 is the secondary air inlet duct, 3 is the mother primary air chamber, 4 is the secondary air chamber, 5 is the primary air outlet duct, 6 is the secondary air outlet duct, 7 is the sub-primary air chamber, 8 is the sub-primary air chamber outlet duct, and 9 is the regulating damper. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0028] The present invention divides the original air preheater primary air chamber into a large and a small sub-mother-and-child chamber, and sets two corresponding hot primary air ducts at the outlet, one duct corresponds to and is connected to the sub-primary air chamber, and the other duct corresponds to and is connected to the main (mother) chamber. The sub-primary air duct corresponding to the sub-primary air chamber is directly connected to the original hot secondary air duct of the boiler, and is sent into the furnace together with the secondary air as combustion-supporting air; the hot primary air duct corresponding to the main chamber is directly connected to the original hot primary air duct, and is sent into the powder making system to supply the hot primary air volume required for powder making. An adjusting damper is set in the sub-primary air duct, and the air volume of the primary air introduced into the hot secondary air duct is controlled by the adjusting damper.

[0029] Regardless of the operating load of the boiler, the primary air flow through the sub-primary air chamber of the air preheater can always be maintained above the design air volume under the rated load condition (maintained above the minimum flow that can effectively blow soot, the specific flow is determined based on the test after commissioning), so that when the air preheater rotates one circle, the high-speed primary air flow through the sub-primary air chamber completes a high-speed soot blowing on the air preheater rotor. Under this system, the hot primary air volume introduced into the secondary air is limited, which will not affect the air volume entering the pulverizing system, and can fully ensure the safe operation of the pulverizing system.

[0030] The basic equipment of the present invention includes a communication pipeline and an adjustable damper, which can be adjusted manually or electrically (the latter is not shown in the figure).

[0031] The following are examples.

[0032] Example 1

[0033] See also Figure 1This embodiment has a 1-way air preheater self-blowing system, corresponding to a single series of air and smoke system boilers (see Figure 1 ). In the primary air system, the primary air enters the main primary air chamber 3 and the sub-primary air chamber 7 through the primary air inlet duct 1. The cross-section of the sub-primary air chamber 7 is fan-shaped, and the central angle of the fan is 3.75°~15°. At the outlet of the air preheater, the primary air is separated into two hot primary air by the main primary air chamber 3 and the sub-primary air chamber 7. One is sent to the powder making system through the original primary air outlet duct 5; the other is introduced into the secondary air outlet duct 6 through the sub-primary air chamber outlet duct 8, and is sent to the furnace of the boiler body after mixing with the secondary air. An adjusting damper 9 is provided in the sub-primary air chamber outlet duct 8 to control the amount of sub-primary air introduced into the secondary air outlet duct 6. In the secondary air system, the secondary air enters the original secondary air chamber 4 through the secondary air inlet duct 2. At the outlet of the air preheater, the secondary air is mixed with the sub-primary air introduced into the secondary air and is sent to the furnace. In this operating mode, under various unit loads, the primary air volume entering the air preheater sub-primary air chamber 7 always maintains a sufficient air volume, so that its primary air speed is always ≧15m / s, so as to strengthen its soot blowing effect on the air preheater heat storage plate, and the secondary air volume entering the air preheater secondary air chamber 4 is reduced accordingly, and the reduction amount is approximately equal to the hot primary air volume entering the secondary air, so that the total hot primary and secondary air volumes entering the boiler remain unchanged.

[0034] Example 2

[0035] See also Figure 1 This embodiment has a 1-way air preheater self-blowing system, corresponding to the double series air and smoke system boiler, Figure 1 Only one side is given, the other side is Figure 1Exactly the same. In the primary air system, the primary air enters the main primary air chamber 3 and the sub-primary air chamber 7 through the primary air inlet duct 1. At the outlet of the air preheater, the primary air is separated into two hot primary air by the main primary air chamber 3 and the sub-primary air chamber 7. One is sent to the powder making system through the original primary air outlet duct 5; the other is introduced into the secondary air outlet duct 6 through the sub-primary air chamber outlet duct 8, and is sent to the furnace after mixing with the secondary air. An adjusting damper 9 is provided in the sub-primary air chamber outlet duct 8 to control the amount of sub-primary air introduced into the secondary air outlet duct 6. In the secondary air system, the secondary air enters the original secondary air chamber 4 through the secondary air inlet duct 2. At the outlet of the air preheater, the secondary air is mixed with the sub-primary air introduced into the secondary air and is sent to the furnace. In this operating mode, under various unit loads, the primary air volume entering the air preheater sub-primary air chamber 7 always maintains sufficient air volume, so that its primary air speed is always ≧15m / s, so as to strengthen its soot blowing effect on the air preheater heat storage plate, and the secondary air volume entering the air preheater secondary air chamber 4) is reduced accordingly, and the reduction amount is approximately equal to the hot primary air volume entering the secondary air, so that the total hot primary and secondary air volumes entering the boiler remain unchanged.

[0036] The working principle of the present invention is as follows:

[0037] The air preheater self-blowing anti-blocking technology of the present invention divides the original air preheater primary air chamber into a large and a small mother-and-child chamber, and sets two corresponding hot primary air ducts at its outlet, one duct corresponds to and is connected to the sub-primary air chamber, and the other duct corresponds to and is connected to the main (mother) chamber. The sub-primary air duct corresponding to the sub-primary air chamber is directly connected to the original hot secondary air duct of the boiler, and is sent into the furnace together with the secondary air as combustion-supporting air; the hot primary air duct corresponding to the main chamber is connected to the original hot primary air duct, and is sent into the powder making system to supply the hot primary air volume required for powder making. An adjusting damper is set in the sub-primary air duct, and the air volume of the primary air introduced into the hot secondary air duct is controlled by the adjusting damper.

[0038] After adopting the present invention, under various operating load conditions, the primary air velocity through the sub-primary air chamber is always ≧15m / s, which greatly improves the self-blowing force. Compared with the steam soot blower blowing 1 to 5 times in 24 hours, the blowing times in 24 hours are close to 1500 times, which is more than 300 times of the latter.

[0039] The system is very simple, requires little investment, and is very easy to implement. It is not only suitable for the transformation of existing boilers, but also for newly built boilers. For existing boilers, the construction is very simple, and the original air duct of the boiler does not need to be changed; and no power equipment needs to be added. It only needs to separate the primary air chamber of the air preheater into a large and a small mother-and-child chamber, and configure the corresponding primary air duct and damper, etc., which is very easy to implement. It is even easier to implement for newly built boilers.

[0040] The air preheater self-soot blowing and anti-blocking technology of the present invention is suitable for three-compartment and four-compartment rotary air preheaters used in coal-fired boilers of various capacities and various combustion modes.

Claims

1. Self-blowing ash and anti-blocking system for a rotary air preheater of a coal-fired boiler Characterized in that The primary air chamber of the air preheater includes a main primary air chamber (3) and a sub-primary air chamber (7). A sub-primary air outlet duct (8) is provided at the outlet of the sub-primary air chamber (7), and the sub-primary air outlet duct (8) is connected to the secondary air outlet duct (6); the outlet of the main primary air chamber (3) is connected to the primary air outlet duct, and the inlet of the secondary air outlet duct (6) is also connected to the secondary air chamber (4); A flow regulating valve (9) is provided on the outlet duct (8) of the sub-primary air chamber The cross-section of the sub-primary air chamber (7) is fan-shaped The central angle of the fan is 3.75° - 15° The primary air velocity flowing through the sub-primary air chamber (7) is always ≥ 15 m / s The primary air outlet duct is connected to the coal pulverizing system The secondary air outlet duct is connected to the boiler body Utilizing the rotation characteristics of the air preheater rotor, when the air preheater rotor rotates one week, each small compartment on the rotor rotates through the primary air sub-primary air chamber once, experiencing a purge of high-speed air flow, thereby completing a comprehensive ash blowing of the air preheater rotor 2. The self-blowing ash and anti-blocking system for a rotary air preheater of a coal-fired boiler according to claim 1 Characterized in that The secondary air chamber (4) is connected to the secondary air inlet duct (2) 3. The self-blowing ash and anti-blocking system for a rotary air preheater of a coal-fired boiler according to claim 1 Characterized in that Both the main primary air chamber (3) and the sub-primary air chamber (7) are connected to the primary air inlet duct (1)

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