Two-return flue gas cooling structure of integrated membrane wall boiler

Abstract

The utility model provides an integrated membrane wall boiler two-return-stroke smoke cooling structure which is characterized in that air inlets are formed in preset positions of four walls of a two-return stroke, and branch pipes of a backflow smoke air pipe are inserted into the air inlets; a sealing box is arranged at the air inlet. The flue gas temperature in the cavity of the two-return-stroke hearth can be effectively reduced, existence of solid particle molten soft cores in the flue gas is greatly reduced, attachment of ascending pipes of the two-return-stroke and three-return-stroke connecting sections can be reduced, the blockage phenomenon caused by dust accumulation is reduced, and the operation time of the boiler is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of boiler equipment, in particular to a two-return flue gas cooling structure of an integrated membrane wall boiler. BACKGROUND

[0002] Petrochemical devices produce various waste gas and waste liquid in the production process. The waste gas and waste liquid belong to hazardous waste and cannot be directly discharged. Therefore, waste gas and waste liquid incineration technology is produced. Through incineration + waste heat recovery + dust removal + denitration process, it is discharged again.

[0003] The integrated membrane wall boiler integrates the incinerator and the waste heat boiler in the waste gas and waste liquid incineration into one, and adopts a water-cooled wall structure. If the integrated membrane wall boiler is designed according to five returns, it generally has the following structure (see Figure 1 ):

[0004] The first return is a combustion oxidation section, the water-cooled wall is lined with refractory material on the fire surface, the burner is top-mounted, the waste liquid is sprayed into the furnace, the flue gas is incinerated at a temperature above 1100℃ for more than 2 seconds, the bottom pool temperature is controlled at about 1100℃, the falling ash is kept in a molten state, and the ash is discharged from the side of the boiler bottom; the second return is a cavity section without lining, mainly for flue gas cooling; the third return is also a cavity; the fourth return is an evaporator or a superheater; and the fifth return is an economizer.

[0005] Due to the structure of the boiler, there is a connecting channel between the second return and the third return, and an uptake is arranged at the interface of the two. The uptake has a boiler water flowing inside. In order to enable the flue gas to pass smoothly without dust accumulation, the number of uptakes is reduced and the spacing is expanded as much as possible. The original design calculates that the flue gas outlet temperature of the second return is about 800℃. In actual operation, the flue gas temperature decreases from 1100℃ at the bottom of the second return to about 850℃ at the upper outlet. At this time, the solid particles in the flue gas are still in a molten state, and when they encounter an uptake with a temperature of more than 200℃, they will rapidly cool and adhere to the wall of the uptake. As the accumulation increases, the outlet of the second return will gradually decrease, resulting in an increase in the resistance of the furnace, and large crystalline carbonate bodies will be produced, which will have a serious impact on the operation of the boiler.

[0006] In order to reduce the dust accumulation at the uptake, the flue gas temperature needs to be reduced to below 750℃. However, it is not practical to simply extend the length of the cavity, which will affect the overall structure and construction cost of the boiler, especially for devices that have been built and put into operation. Therefore, how to reduce the dust accumulation at the uptake while minimizing the modification of the existing structure has become a problem to be solved. CONTENT OF THE UTILITY MODEL

[0007] The present application provides a two-return flue gas cooling structure of an integrated membrane wall boiler, which can be used to solve the technical problem of dust accumulation at the uptake.

[0008] The application provides a two-pass flue gas cooling structure of an integrated membrane wall boiler, which comprises:

[0009] An air inlet is arranged at a preset position of the four walls of the two-pass flue, and a return flue gas duct branch is inserted into the air inlet; a sealing box is arranged at the air inlet.

[0010] Further, the preset position is 10 meters upward from the bottom of the two-pass flue.

[0011] Further, the angle between the inlet of the return flue gas duct branch and the water cooling wall is 45°.

[0012] Further, the return flue gas duct branch is connected with a main circulating flue gas pipeline branch line; the main circulating flue gas pipeline branch line extends to a front diameter contraction of the two-pass flue.

[0013] The medium in the return flue gas duct branch is hot flue gas at about 150 DEG C, which is extracted from the main circulating flue gas pipeline branch line before the device enters the chimney, and a draft fan provides a power source; the draft amount is 10-15% of the total flue gas amount.

[0014] Further, the furnace walls of the two-pass flue are all water cooling wall structures, and the water cooling wall is formed by integrally welding φ60*5mm boiler pipes and 40*5mm flat steel; at the opening, the boiler pipes are bent to leave a hole, and the shape of the air inlet is formed.

[0015] Further, sealing castable is arranged in the sealing box, so that the air inlet is attached to the four walls of the two-pass flue.

[0016] The design of the two-pass flue temperature of the integrated membrane wall boiler is reduced, and the flue gas temperature of the two-pass flue cavity is reduced to below 750 DEG C.

[0017] Since the two-pass flue temperature needs to be reduced from 1100 DEG C to below 750 DEG C, the heat exchange area of the water cooling wall of the two-pass flue cavity needs to be increased. There are two methods to increase the heat exchange area, one is to extend the length of the two-pass flue, and the other is to increase the cross-sectional area of the two-pass flue. Both methods have a great influence on the overall structure and manufacturing cost of the boiler, especially for the devices that have been built and put into operation. Therefore, it is more appropriate to adopt a simple and practical measure.

[0018] In order to reduce the flue gas temperature of the two-pass furnace cavity, about 150 DEG C clean hot flue gas before the exhaust chimney of the waste liquid incineration device is pressurized by a draft fan and sent to the lower part of the two-pass flue, and the draft amount is 10-15% of the total flue gas amount. Four air inlets are arranged on the water cooling wall of the two-pass flue, and a circulating cooling flue gas pipeline is arranged. Figure 3The device PFD) is connected, and the cooling flue gas is sprayed into the furnace cavity in a circular arrangement on four sides. The flue gas is uniformly mixed, so that the temperature of the flue gas in the two-pass furnace cavity is reduced to below 750°C. The device has operational flexibility, and the normal operating condition processing capacity is usually 120%, so that the increased backflow flue gas does not affect the normal operation of the device. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is an integrated boiler profile diagram;

[0020] Figure 2 is a boiler top view provided by the embodiment of the present application;

[0021] Figure 3 is a device flow process schematic diagram of the two-pass circulating flue gas reconstruction provided by the embodiment of the present application;

[0022] Figure 4 is a flow field simulation schematic diagram of the two-pass circulating flue gas arranged in a circular arrangement at the furnace inlet provided by the embodiment of the present application;

[0023] Figure 5 is a schematic diagram of the distribution spacing of the riser at the two-pass inlet provided by the embodiment of the present application;

[0024] Figure 6 is a schematic diagram of the opening height of the circulating flue gas provided by the embodiment of the present application;

[0025] Figure 7 is a schematic diagram of the cross section of the circulating flue gas inlet position at a height of 10m of the two-pass provided by the embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application more clear, the embodiments of the present application will be further described in detail below in combination with the drawings.

[0027] Firstly, the embodiments of the present application will be introduced below in combination with the drawings.

[0028] Taking the integrated waste liquid incinerator of the Zhenhai Refining and Chemical Co., Ltd. POSM device as an example, the boiler is a five-pass integrated waste liquid incinerator, as shown in Figure 1 is a boiler profile diagram.

[0029] The first pass is a combustion section; the second pass and the third pass are cavities, mainly for reducing the temperature of the flue gas; the fourth pass is a superheating section; and the fifth pass is a economizer section.

[0030] As shown in Figure 2As shown in the boiler overhead view, the cross section of each pass of the boiler is rectangular, the first pass, the second pass, the third pass and the fourth pass wall are all water cooled wall structure, the water cooled wall is welded by φ60*5mm boiler tube and 40*5mm flat steel; the connecting channel between each pass is also rectangular, which is composed of water cooled wall. Due to the structure of the boiler, the boiler water in the water cooled wall needs to flow smoothly up and down, and is not allowed to be disconnected, so there will still be water cooled wall pipes at the interface channel of the second and third passes, but in order to ensure the flow of flue gas, the spacing of the water cooled wall pipes cannot be equal to the spacing of the pipes of the furnace wall, and should be expanded as much as possible, such as Figure 5 As shown, on the basis of ensuring flow, the water cooled wall pipes converge into 8 φ108 pipes with a spacing of 800mm and a position of Figure 1 the water cooled wall rising pipe at the outlet of the second pass of the middle.

[0031] Since the start of operation, in actual operation, due to the high temperature of the flue gas at the outlet of the second pass, the flue gas temperature decreases from 1100℃ at the bottom of the second pass to about 850℃ at the upper outlet, at this time the solid particles in the flue gas are still in a molten state, when passing through the connecting channel of the second and third passes, they will quickly cool and adhere to the pipe wall after encountering the water cooled wall rising pipe at the outlet of the second pass with a temperature of more than 200℃, as the accumulation becomes more and more, the 800mm spacing outlet of the rising pipe at the outlet of the second pass will gradually decrease, resulting in an increase in the resistance drop in the furnace, at the same time, large crystalline bodies of carbonate will be produced, which will have a serious impact on the operation of the boiler. Therefore, the flue gas passing through the second pass needs to be cooled.

[0032] The second pass of the present project has a cross section of 3800*7200mm, and four inlet holes with a diameter of DN100 are designed on the side wall of the furnace 10m above the bottom of the second pass, the distance from the edge of the water cooled wall of the second pass (i.e. the side wall of the second pass) is 672.5mm and 2672.5mm, and the angle between the inlet and the water cooled wall is 45° (see Figure 7 ). The outer wall of the water cooled wall has a sealing box pouring sealing castable to seal the opening of the water cooled wall, and a flange is connected with the branch line of the main circulating flue gas pipe, the diameter of the main circulating flue gas pipe is 600mm, and the diameter is reduced before entering the furnace (i.e. the second pass) to accelerate the flow rate of the flue gas and enter the furnace in a jet shape. The medium in the circulating flue gas pipe is hot flue gas at about 150℃, which is extracted from the flue gas pipe before the device enters the chimney by providing a power source through a draught fan.

[0033] The basic parameters of the draught fan of the present project are as follows:

[0034] The centrifugal cantilever supported fan has a flow rate of about 18000m3 / h and a total pressure of 4000Pa. In order to facilitate real-time adjustment of the flue gas volume, the fan uses a 4P-55KW frequency conversion motor.

[0035] Through the above structure improvement, the original two-pass outlet temperature is reduced to below 750 DEG C, greatly reducing the existence of solid particles in the flue gas in the molten state, which can reduce the attachment of the two-three-pass connecting section riser, reduce the phenomenon of blockage due to dust accumulation, and prolong the boiler operation time.

[0036] The above-described embodiments of the present application do not constitute a limitation of the protection scope of the present application.

Claims

1. An integrated membrane wall boiler two-pass flue gas cooling structure, characterized in that, The structure comprises: The air inlet (3) is arranged at the preset position of the four walls of the double return, and the return flue gas duct branch (1) is inserted into the air inlet (3); the sealing box (2) is arranged at the air inlet (3).

2. The structure of claim 1, wherein The preset position is 10 meters upward from the bottom of the double return.

3. The structure of claim 1, wherein The angle between the inlet of the return flue gas duct branch (1) and the water cooling wall is 45 degrees.

4. The structure of claim 1, wherein The return flue gas duct branch (1) is connected with the main circulating flue gas pipeline branch line; the main circulating flue gas pipeline branch line extends to the front diameter contraction of the double return; The medium in the return flue gas duct branch (1) is hot flue gas at about 150 DEG C, which is extracted from the main circulating flue gas pipeline branch line before the device enters the chimney, and a draft fan provides a power source; the draft amount is 10-15% of the total flue gas amount.

5. The structure of claim 1, wherein The furnace walls of the double return are all water cooling wall structures, and the water cooling wall is formed by welding a φ60*5mm boiler pipe and a 40*5mm flat steel in an integral row; at the opening, the boiler pipe is bent to leave a hole, forming the shape of the air inlet.

6. The structure of claim 1, wherein The sealing box (2) is filled with sealing castable, so that the air inlet (3) is attached to the four walls of the double return.

Images