CN101629725A - Method for reducing ash fouling of air preheater of coal burning boiler and cyclone separator therefor - Google Patents

Abstract

The invention discloses a method for reducing ash blocking of an air preheater of a coal-fired boiler and a cyclone separator. A cyclone separator is installed between the outlet of the boiler tail flue economizer and the air preheater; the flue gas flowing out of the boiler tail flue economizer outlet first enters the cyclone separator for ash removal, and then passes through the cyclone separator for ash removal The treated flue gas enters the air preheater to heat the primary air and secondary air, and the flue gas flowing out of the air preheater enters the dust collector for further ash removal and is discharged. The bottom of the cyclone separator cylinder uses an electric air lock valve to collect fly ash particles and avoid secondary dust. The invention has strong operability and obvious effect, can reduce or control the dust blocking of the air preheater, reduce the cost of cleaning the dust blocking of the air preheater, reduce the exhaust gas temperature, and improve the efficiency of the boiler. The technical process of the invention is simple, less equipment and easy to implement. This method is applicable not only to the retrofit design of existing boiler systems, but also to the design of new systems.

Description

A method and cyclone separator for reducing ash blocking of air preheater of coal-fired boiler

technical field

The invention relates to a method for reducing ash blocking of an air preheater in a boiler system burning high ash coal, in particular to a method of using a cyclone separator to separate large particles of fly ash in flue gas to avoid ash blocking of the air preheater method.

Background technique

The air preheater is an important part of the modern boiler system. It is installed after the outlet of the boiler tail flue. The air preheater is a heat exchange device that uses the waste heat of the flue gas to heat the primary air and secondary air. The primary air is The air that carries pulverized coal into the boiler furnace, the secondary air is the air that directly enters the boiler furnace to support combustion, and the primary air and secondary air are heated by the flue gas through the air preheater before entering the boiler. The main functions are: (1) increase the temperature of the combustion air, strengthen the ignition and combustion process of pulverized coal, enhance the radiation heat transfer in the furnace, enhance the stability of combustion, and reduce the heat loss of incomplete combustion; The powder provides a drying medium, dries the coal powder entering the furnace, and strengthens the ignition of the coal powder; (3) reduces the exhaust gas temperature and reduces the heat loss of the exhaust gas.

However, due to the fact that the actual coal type used by the boiler deviates from the designed coal type, the high ash content, high sulfur content, etc., the fly ash content and sulfur content in the flue gas are large, which is easy to block and corrode the heat storage element of the air preheater. The primary and secondary air ducts are severely worn due to ash in the primary and secondary air ducts.

After the air preheater is blocked with dust, the current of the blower and induced draft fan will increase, the boiler exhaust gas temperature will increase, the hot air temperature will decrease, the resistance of the air-smoke system will increase, and the pressure on the positive pressure side of the primary air, secondary air and negative pressure side of the flue gas will increase. The difference increases, which increases the air leakage of the air preheater; causes the axial flow blower to surge, and the induced draft fan has no adjustment margin, which affects the use of the combustion automatic device. When the ash blockage is serious, it will seriously affect the output of the unit, that is, it cannot carry the full load.

Because the dust blocking and low-temperature corrosion of the air preheater are mutually promoted, the dust blocking of the air preheater can accelerate the condensation of sulfuric acid vapor in the flue gas and cause low-temperature corrosion of the air preheater, resulting in damage to the heat storage element of the air preheater. Increase equipment maintenance costs.

The traditional methods to solve the ash plugging of the air preheater generally include: using a new heat storage element waveform matched with the fuel composition; increasing the wall temperature of the low-temperature heating surface; adding a water washing system for the air preheater; strengthening combustion adjustment and reducing SO in flue gas ₃ content.

The patent application number is 200710017496.3, the publication number is CN 101050864A, and the patent name is "a control method for low-temperature corrosion and ash blocking of coal-fired boiler air preheater". The method of corrosion blocking ash, the idea is to install one or two sets of air bypass pipes of the air preheater in the air supply system of the boiler, and set a damper on the air bypass pipe, and the damper adjusts the flow into the bypass air pipe and the air preheater. The air volume of the heater, the bypass air volume or sent back to the air supply system after the air preheater; or directly sent into the furnace from the bottom of the cold ash hopper. In the case of constant air supply, the air volume entering the air preheater can be controlled by adjusting the bypass air, thereby controlling its heat absorption from the flue gas side, boiler exhaust gas temperature and low temperature of the air preheater Corrosion and clogging. The devices used in the method include pipelines, air doors, electric actuators, etc., all of which are arranged outside the furnace, and can be controlled by a dial, with good working conditions and high reliability. When the cleanliness of the heating surface of the boiler changes, it can be tracked and adjusted to avoid low exhaust gas temperature caused by the heating surface, and then solve the low-temperature corrosion and ash blocking problems of the air preheater.

However, the method proposed in this patent does not reduce the amount of ash that enters the air preheater flue gas. On the other hand, due to the partial bypass of the air, the heat absorption of the air is insufficient, which will affect the temperature of the primary and secondary air, which will not be conducive to the stable combustion of pulverized coal in the furnace. Because this patented technology does not change the total ash content of the flue gas entering the air preheater, it cannot fundamentally solve the problem of ash blocking in the air preheater.

It is precisely because the flue gas entering the air preheater contains a large amount of fly ash particles and sulfur oxides that the air preheater is blocked by dust, low-temperature corrosion, primary and secondary air duct wear and other damages. Therefore, if most of the fly ash particles are separated and removed before the flue gas enters the air preheater, it is possible to fundamentally solve the problem of ash blocking in the air preheater, and then solve the wear and tear of the primary and secondary air ducts and the air preheater. Low temperature corrosion problem.

Contents of the invention

Aiming at the ash clogging of the air preheater caused by the large amount of high-ash coal burned by the boiler, the existing solution to the ash clogging of the air preheater has the disadvantages of reducing the thermal efficiency of the boiler, increasing production costs, and making it difficult to clean the ash accumulation in the air preheater etc., the present invention proposes a method and a device used to fundamentally solve the dust blocking of the air preheater and the severe wear of the primary and secondary air pipes.

The method of the present invention to solve the ash blocking of the air preheater is that the flue gas flowing out of the outlet of the boiler tail flue economizer is firstly treated by the cyclone separator for dust removal and then enters the air preheater for heat exchange. Cyclone separator, also known as cyclone dust collector. The cyclone separator is generally composed of a dusty flue gas inlet, a flue gas discharge port, a cylinder body and an ash hopper. A cyclone separator is installed between the outlet of the boiler tail flue economizer and the flue gas inlet of the air preheater. The tangential direction enters the cylinder of the cyclone separator, and makes a spiral movement from top to bottom to form an external vortex flow, and gradually reaches the lower part of the cylinder. The fly ash particles in the airflow are thrown to the outer wall under the action of centrifugal force, and under the action of gravity and the drive of the downward airflow, the fly ash particles fall into the ash collecting hopper at the bottom. After the downward airflow reaches the lower part of the cylinder, it turns upward along the axis of the cyclone separator to form a rising inner vortex flow, and is discharged from the flue gas discharge port of the cyclone separator.

The content of fly ash particles in the flue gas after dust removal by the cyclone separator will be greatly reduced, and such flue gas will enter the air preheater for waste heat recovery and utilization. Although there will be a small amount of heat loss and increased flow resistance in the cyclone separator, since the amount of ash in the flue gas is greatly reduced and the rest is mostly small particles of fly ash, the fly ash particles attached to the heat storage element of the air preheater Reduce the heat transfer resistance of the heat storage element and improve the heat transfer efficiency of the air preheater, reduce the flow resistance of the flue gas, reduce the flow resistance and ash content of the primary air and secondary air, and make the air The possibility of dust blocking in the preheater is reduced; in addition, since the ash content in the flue gas flowing out of the air preheater is reduced, the power consumption of the dust collector downstream of the air preheater will also be reduced.

The technical scheme of the method for reducing the ash blocking of the air preheater in the boiler system of the present invention is as follows:

Step 1, the flue gas flowing out from the outlet of the boiler tail flue economizer enters the cyclone separator under the action of the fan for ash removal;

Step 2, the flue gas after the ash removal treatment by the cyclone separator enters the air preheater to heat the primary air and secondary air;

Step 3, the flue gas flowing out of the air preheater enters the dust collector for further ash removal and then is discharged from the chimney;

Step 4, the fly ash particles separated by the dust collector fall into the dust hopper of the dust collector, and are collected and cleaned by the dust removal system;

Step 5, the fly ash particles separated by the cyclone separator are collected and cleaned by the ash removal system.

If multiple air preheaters are used to heat the primary air and secondary air, a cyclone separator is installed in front of each air preheater, and the flue gas flows out from the outlet of each economizer and first enters the cyclone separator for ash removal , and then enter the air preheater for heat exchange.

The cyclone separator used in the method for reducing the ash blocking of the air preheater in the boiler system of the present invention is composed of a flue gas inlet, a flue gas discharge port, a cyclone separator cylinder, an ash collecting bucket and an electric air lock valve. The flue gas inlet is connected to the outlet of the boiler tail flue economizer, and the flue gas discharge port of the cyclone separator is connected to the flue gas inlet of the air preheater.

The bottom of the cylinder of the cyclone separator adopts an electric air lock valve to collect fly ash particles and prevent the flue gas from going downward, so as to avoid the phenomenon of "secondary dust" caused by the flue gas passing through the cyclone separator taking the ash particles away again.

The bottom of the cylinder body of the cyclone separator can be equipped with an ash collecting hopper, or no ash collecting hopper can be installed. When there is no ash collecting hopper, an electric air lock valve is installed at the bottom outlet of the cyclone separator cylinder; An electric air lock valve can be installed between the outlet at the bottom of the separator cylinder and the ash collection hopper, or no electric air lock valve can be installed, and an electric air lock valve must be installed at the outlet of the ash collection hopper. The outlet of the electric air lock valve can be connected with the outlet of the inertial gravity sedimentation separator at the bottom of the economizer, or connected with the outlet of the ash hopper of the dust collector to realize continuous ash removal.

In order to reduce the heat loss when the flue gas passes through the cyclone separator, the outer surface of the cylinder of the cyclone separator is covered with an insulation layer, and the material of the insulation layer covered on the outer surface is glass wool felt or foamed asbestos.

The beneficial effects of the present invention: effectively reduce the ash content of the flue gas entering the air preheater, reduce the erosion and wear of the fly ash particles on the heat storage element of the air preheater, and reduce the flue gas in the air preheater The flow resistance and the heat transfer resistance between the flue gas and the heat storage element improve the heat transfer efficiency of the air preheater; due to the improved heat transfer efficiency, the exhaust gas temperature decreases and the boiler efficiency increases; the occurrence of dust blocking in the air preheater is reduced frequency, and even avoid the phenomenon of dust blocking; reduce the inlet resistance and ash content of the primary air and secondary air to avoid or reduce the wear of the primary and secondary air pipes; reduce the dust removal of the downstream equipment of the air preheater - the dust collector load to reduce power consumption. The invention has strong operability and obvious effect, and can reduce or thoroughly control the dust blocking of the air preheater, further reduce or avoid low-temperature corrosion of the air preheater, and reduce the cost of cleaning the dust blocking of the air preheater. The technological process of the present invention is simple, less equipment, easy to implement. This method is applicable not only to the retrofit design of equipment that has been put into operation, but also to the system design of new equipment.

Description of drawings

Fig. 1 is a schematic diagram of the method for reducing dust blocking of an air preheater according to the present invention.

Figure 2 is a schematic diagram of the three-dimensional structure of the cyclone separator.

Figure 3 is a schematic plan view of the cyclone separator.

Fig. 4 is a schematic structural diagram of a cyclone separator equipped with an ash collecting hopper and an air lock valve.

Fig. 5 is a schematic structural diagram of a cyclone separator without a dust collecting hopper and provided with an air lock valve.

Figure 6 is a schematic diagram of the arrangement of the device for reducing ash blocking at the outlet of a flue after the economizer.

Figure 7 is a schematic diagram of the arrangement of the device for reducing ash plugging at the outlets of the two flues behind the economizer.

Figure 8 is a schematic diagram of the arrangement of the device for reducing ash plugging at the outlets of the three flues behind the economizer.

Figure 9 is a schematic diagram of the layout of the device for reducing ash plugging at the outlets of the four flues behind the economizer.

In the figure: the dust-containing flue gas inlet 1 of the cyclone separator, the flue gas discharge port 2 of the cyclone separator, the cylinder body of the cyclone separator 3, the upper electric air lock valve 4, the ash collecting bucket 5, the lower electric air lock valve 6, Economizer 11, inertia gravity sedimentation separator 12, cyclone separator 13, air preheater 14, dust collector 15.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

The flow chart of the method for reducing ash plugging in the air preheater of the present invention is shown in Figure 1. A cyclone separator is installed between the outlet of the boiler economizer and the inlet of the air preheater, and the dust-rich flue gas containing fly ash particles first passes through After the cyclone separator separates most of the dust particles, the flue gas containing less fly ash particles enters the air preheater to preheat the primary and secondary air, and the low-temperature flue gas flowing out of the air preheater enters the dust collector for further Discharge after ash removal; according to the specific conditions of the equipment, the outlet of the fly ash particles of the cyclone separator can be connected with the outlet of the inertial gravity sedimentation separator at the bottom of the economizer, or connected with the ash hopper of the dust collector. The basic equipment for realizing this method includes the traditional cyclone Separators, connecting pipes and electric air lock valves, for different boilers, other auxiliary equipment or electric control systems can be added on the basis of basic equipment.

The structure of the cyclone separator adopted in the present invention is shown in Fig. 2 and Fig. 3 . The main components of the cyclone separator are dust-laden flue gas inlet 1, flue gas discharge port 2, cyclone separator cylinder 3, upper electric air lock valve 4, ash collecting bucket 5, lower electric air lock valve 6; cyclone separator The flue gas inlet 1 is connected to the outlet of the boiler tail flue economizer, and the flue gas discharge port 2 of the cyclone separator is connected to the flue gas inlet of the air preheater.

The bottom of the cylinder body of the cyclone separator can be provided with an ash collecting hopper 5, as shown in Figure 3 and Figure 4; or no ash collecting hopper can be provided, as shown in Figure 5. When there is no ash collecting hopper, an electric air lock valve is installed at the bottom outlet of each cyclone separator; when there is an ash collecting hopper, an electric air lock valve 4 is installed at the bottom outlet of each cyclone separator to ensure The electric air lock valve 6 is installed at the bottom of the bucket, or only the electric air lock valve is installed at the dust collecting hopper outlet.

Embodiment one

As shown in Figure 6, this embodiment is aimed at the high ash coal-fired boiler unit with only one air preheater, and a cyclone separator system is set up, correspondingly arranged at the flue gas outlet of the boiler economizer 11 and the air preheater 14 between imports. One cyclone separator system is not limited to one cyclone separator, but can be composed of multiple cyclone separators, the specific number depends on the flue gas volume and installation space. After adding the cyclone separator 13 at the outlet of the boiler economizer 11, the dust-rich flue gas rich in fly ash particles at the outlet of the economizer passes through the flue gas inlet 1 of the cyclone separator and enters the cylinder body 3 of the cyclone separator, where the fly ash Particle separation and dust removal treatment, the dust-poor flue gas after dust removal leaves the cyclone separator through the flue gas discharge port 2 and enters the air preheater 14 to heat the primary and secondary air, and then the flue gas enters the dust collector 15 for further dust removal and is discharged from the chimney. About 80% of the larger fly ash particles in the flue gas are separated by the cyclone separator. The fly ash particles enter the ash collecting hopper 5 through the upper electric air lock valve 4 and are discharged through the outlet of the lower electric air lock valve 6 . The electric air lock valve is driven by the electric deceleration mechanism. There is a sealing structure between the rotating blade and the electric air lock valve shell, which is enough to prevent air leakage. When the blade rotates, it can not only discharge the ash smoothly, but also prevent air leakage without secondary dust. The outlet of the lower electric air lock valve at the bottom of the ash collecting hopper of the cyclone separator can be connected with the outlet of the inertial gravity sedimentation separator 12 at the bottom of the economizer, or connected with the ash hopper of the dust collector, so as to realize the connection with the existing ash removal system and realize continuous Ash removal. In order to reduce the heat loss when the flue gas passes through the cyclone separator, the outer surface of the cylinder of the cyclone separator and the outer surface of the flue gas inlet are covered with a glass wool felt insulation layer. The whole system is running well, the air preheater has very slight dust accumulation, the primary and secondary air pipes have very slight wear, the resistance of the smoke and air system has not increased significantly, the exhaust gas temperature has decreased, and the hot air temperature has increased.

Embodiment two

As shown in Figure 7, this embodiment is aimed at the high ash coal-fired boiler unit with two air preheaters, setting up two cyclone separator systems, corresponding to the two flue gas outlets arranged at the outlet of the boiler economizer 11 , Between the inlets of two air preheaters 14 . Each cyclone separator system is not limited to one cyclone separator, but can be composed of multiple cyclone separators, and the specific number depends on the flue gas volume and installation space. After adding the cyclone separator 13 at the outlet of the boiler economizer 11, the dust-rich flue gas rich in fly ash particles at the economizer outlet enters the cyclone separator cylinder 3 through the dust-laden flue gas inlet 1 of the cyclone separator, where the Separation and dedusting of fly ash particles. After dedusting, the dust-poor flue gas leaves the cyclone separator through the flue gas discharge port 2 and enters the air preheater 14 to heat the primary and secondary air. Then the flue gas enters the dust collector 15 for further dust removal and is discharged from the chimney. . About 80% of the larger fly ash particles in the flue gas are separated by the cyclone separator. The fly ash particles enter the ash collecting hopper 5 along the lower cone surface of the cyclone separator cylinder, and are discharged through the outlet of the lower electric air lock valve 6 . The electric air lock valve is driven by the electric deceleration mechanism. There is a sealing structure between the rotating blade and the electric air lock valve shell, which is enough to prevent air leakage. When the blade rotates, it can not only discharge the ash smoothly, but also prevent air leakage without secondary dust. The outlet of the lower electric air lock valve at the bottom of the ash collecting hopper of the cyclone separator can be connected with the outlet of the inertial gravity sedimentation separator 12 at the bottom of the economizer, or connected with the ash hopper of the dust collector, so as to realize the connection with the existing ash removal system and realize continuous Ash removal. In order to reduce the heat loss when the flue gas passes through the cyclone separator, the outer surface of the flue gas inlet of the cylinder of the cyclone separator is covered with a foamed asbestos insulation layer. The whole system is running well, the air preheater has very slight dust accumulation, the primary and secondary air ducts have very slight wear, the resistance of the flue gas system has not increased significantly, the exhaust gas temperature has decreased, and the hot air temperature has increased.

As shown in Fig. 8, for the high ash coal-fired boiler unit with three air preheaters, a three-way cyclone separator system is set up, corresponding to the three-way flue gas outlet arranged at the outlet of the boiler economizer, and three air preheaters. between heater inlets.

As shown in Figure 9, for the high ash coal-fired boiler unit with four air preheaters, a four-way cyclone separator system is set up, corresponding to the four-way flue gas outlets arranged at the outlet of the boiler economizer, four air between the preheater inlets.

The embodiment shown in Fig. 8 and Fig. 9 is also that the dust-rich flue gas containing fly ash particles first passes through the cyclone separator to separate most of the fly ash particles, and then the dust-poor flue gas containing less fly ash particles enters the air again. The preheater preheats the primary and secondary air, thereby achieving the effect of reducing the dust blocking of the air preheater and the wear of the primary and secondary air pipes.

A cyclone separator is installed between the flue gas outlet of the boiler economizer and the inlet of the air preheater. The specific number of cyclone separators is determined by the number of air preheaters or the number of flue gas outlets of the boiler tail flue economizer.

The upper and lower electric air lock valves used in the present invention are commercially available products, and the upper and lower electric air lock valves can adopt the same model and specification.

Claims (10)

1. one kind is reduced the stifled grey method of air preheater in the steam generator system:

Step 1, the flue gas that comes out from the boiler back end ductwork economizer exit flows through wind of air preheater heating, secondary wind air;

Step 2, the flue gas that is flowed out by air preheater enters deduster and is handled by ash disposal, and the flue gas after the ash disposal is discharged;

Step 3, the dust that deduster is collected is cleared up by ash disposal system;

It is characterized in that flue gas enters air preheater again wind, a secondary wind air are heated after being come out to be introduced into cyclone separator and handled by ash disposal by the boiler back end ductwork economizer exit.

2. the method for the stifled ash of air preheater is characterized in that in the minimizing steam generator system according to claim 1, collects cleaning by the isolated fly ash granule of cyclone separator by ash disposal system.

3. the method for the stifled ash of air preheater in the minimizing steam generator system according to claim 1, it is characterized in that, when the boiler back end ductwork economizer exit is a plurality of, the flue gas that flows out from each economizer exit is introduced into the cyclone separator that connects separately to carry out ash disposal and handles, and enters the air preheater that connects separately again and carries out heat exchange.

4. one kind is used for the described cyclone separator that is used to reduce the method for the stifled ash of steam generator system air preheater of claim 1, comprise gas approach (1), fume emission mouth (2), cylindrical shell (3), flue-dust retainer (5), it is characterized in that the gas approach of cyclone separator (1) is connected with the boiler back end ductwork economizer exit, the fume emission mouth (2) of cyclone separator is connected with the air preheater smoke inlet.

5. the cyclone separator that is used for reducing the stifled ash of steam generator system air preheater according to claim 4, it is characterized in that, install electric lock air valve (4) between the bottom of described cyclone separator cylindrical shell (3) and the flue-dust retainer (5), electric lock air valve (6) is down installed in the flue-dust retainer bottom.

6. the cyclone separator that is used for reducing the stifled ash of steam generator system air preheater according to claim 4 is characterized in that, described cyclone separator cylindrical shell (3) bottom directly is connected with flue-dust retainer (5), and electric lock air valve (6) is down installed in the flue-dust retainer bottom.

7. the cyclone separator that is used for reducing the stifled ash of steam generator system air preheater according to claim 4 is characterized in that, electric lock air valve (6) is down installed in described cyclone separator cylindrical shell (3) bottom.

8. according to claim 5 or the 6 or 7 described cyclone separators that are used for reducing the stifled ash of steam generator system air preheater, it is characterized in that, the outlet of described electric lock air valve (6) down is connected with the inertia-gravity settlement separator outlet of economizer bottom, or is connected with the dust collector ash hopper outlet.

9. the cyclone separator that is used for reducing the stifled ash of steam generator system air preheater according to claim 4 is characterized in that the cylindrical shell of described cyclone separator (3) outer surface covering and heat insulating layer.

10. the cyclone separator that is used for reducing the stifled ash of steam generator system air preheater according to claim 9 is characterized in that the heat-insulation layer material that described cyclone separator cylindrical shell (3) outer surface covers is blanket of glass wool or litaflex.

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