A soot-resistant load bearing boiler

Abstract

The present application relates to a kind of anti-accumulation of dust load boiler, at least a part of the flue of the boiler is defined by multiple half-width horizontal smoke baffles, smoke film wall, boiler membrane wall, the smoke baffle is alternately extended from boiler rear membrane wall and smoke film wall from top to bottom respectively, and only cover the partial area between them, thereby forming serpentine flue gas path, wherein, heating surface is immediately adjacent to smoke film wall and has interval between boiler rear membrane wall, and the smoke baffle extended from boiler rear membrane wall is provided with openable and closable smoke door, and the smoke door is aligned up and down.Each smoke door can be selectively opened and closed according to load variation, thereby adjusting the length of heat exchange path, so as to adapt to load to avoid flue gas temperature too low dewing.In addition, in the preferred scheme, each smoke baffle transversely blocks 50%-70% of the full width of heating surface, so that flue gas can flow forward to flush the heating surface, thereby reducing dust accumulation.

Description

TECHNICAL FIELD

[0001] The present invention belongs to the field of heat exchange, and particularly relates to an anti-ash-deposition variable load boiler. BACKGROUND

[0002] Coal-fired boilers have requirements for carbon reduction, low-nitrogen, and low-dust emissions. To this end, first, the combustion should be efficient and complete to make full use of fuel heat energy; second, the heat exchange efficiency should be maximized to make full use of heat; and third, the initial and terminal emissions of harmful substances such as nitrogen, sulfur, and dust should be optimized.

[0003] In existing coal-fired boilers, the carbon in fly ash often cannot be completely burned, especially when burning low-quality coal, a large amount of "ash-coated carbon" in fly ash leads to unburned carbon being discharged with ash, resulting in energy waste.

[0004] In addition, the temperature of flue gas during denitrification is often not at the optimal temperature.

[0005] In addition, in terms of heat exchange, ash deposition is prone to occur on the heating surface, which leads to a decrease in heat exchange efficiency.

[0006] Finally, when the boiler is running at low load, condensation is prone to occur on the low-temperature section of the heating surface, which, together with ash deposition, forms acid corrosion and solidified ash that adheres, which worsens the heat transfer resistance and causes the heat exchange efficiency to decrease linearly, resulting in energy waste or even forced shutdown of the boiler due to blockage of the flue.

[0007] Therefore, there is a need in the art for improved technology. SUMMARY

[0008] The present invention aims to provide a boiler that can solve one of the above problems.

[0009] According to the present invention, in order to improve combustion efficiency, the present invention first proposes a slot-type separator in the flue to capture larger "ash-coated carbon" fly ash and return it to the furnace through a re-combustion ash fall opening. A water-cooled air pipe is provided below the re-combustion ash fall opening, which supplies air to the furnace to supplement oxygen, and this air supply can also supplement oxygen for the unburned gases H, CO2, CH4 in the reducing flue gas, which is usually burned at low temperature (to reduce NO X ) to achieve the purpose of complete combustion.

[0010] On the other hand, in order to improve combustion efficiency, the carbon-containing ash captured by the U-shaped turning inertia force of the descending high-temperature flue and the ascending high-temperature flue is also re-combusted and burned by being scattered on the "bottom fire" of the furnace bed through a re-combustion ash fall opening provided on the rear arch in an infinite ignition manner, thereby achieving the purpose of efficient combustion and carbon reduction.

[0011] According to the present application, in the aforementioned U-turn scheme, in order to achieve the optimal flue gas temperature for catalytic denitration, a temperature-adjusting flue door is further provided. Specifically, the temperature-adjusting flue door is arranged at the upper portion of the partition wall between the descending flue and the ascending flue, which defines the front side of the ascending flue, and can be referred to as the "first partition wall", and the rear side of the ascending flue further has a second partition wall, the upper portion of which is a light pipe portion, thereby providing an inlet for flue gas, through which the flue gas in the ascending flue moves downstream. When the flue gas temperature is too low due to the U-turn, which is not conducive to the downstream denitration process, the aforementioned temperature-adjusting flue door can be opened and the opening degree can be adjusted as needed, so that at least part of the flue gas does not pass through the U-shaped path but directly passes through the flue door into the inlet on the aforementioned second partition wall, thereby ensuring a higher flue gas temperature.

[0012] In one scheme of the present application, the flue downstream of the aforementioned inlet is formed by a smoke baffle and the surrounding boiler flue wall. The upstream end of the smoke baffle is airtightly connected to the lower end of the inlet of the second partition wall. Although a horizontal smoke baffle is also possible, in a preferred scheme, the smoke baffle sequentially includes an upwardly inclined segment, a vertically upwardly extending segment and a horizontally extending segment from the upstream end, thereby causing the flue gas to move vertically along the heat exchange tube bundle for a distance before moving horizontally. This vertical movement of the flue gas will help to remove the ash accumulated on the heat exchange tube bundle.

[0013] In the preferred scheme as above, the temperature-adjusting flue door can also be arranged in alignment with the upper portion of the inlet, thereby causing the flue gas entering the inlet via the temperature-adjusting flue door to not move vertically along the heat exchange tube bundle for heat exchange, thereby ensuring the temperature of the flue gas.

[0014] According to the present application, the flue downstream of the denitration chamber can also be specifically designed to facilitate the removal of ash and to adapt to different loads to avoid excessive low flue gas temperature causing condensation.

[0015] To this end, according to the present application, the flue downstream of the denitration chamber is defined by a plurality of half-width horizontal smoke baffles, the surrounding boiler flue wall (including the left, right and rear flue walls) and the second partition wall. By "half-width", it is meant that these smoke baffles do not extend to cover the entire area between the second partition wall and the rear flue wall, but only a part (not necessarily "half"). These half-width horizontal smoke baffles alternately extend from the rear flue wall and the second partition wall from top to bottom, thereby forming an S-shaped or serpentine flue gas path. The heat exchange tube bundle serving as a heating surface is spaced apart from the rear flue wall, and a flue door is provided on the smoke baffle extending from the rear flue wall, which is located in the spacing area. The spacing actually defines a "low-temperature flue", which is described in detail below.

[0016] When all the flue valves are closed, the flue gas flows back and forth through the heat exchange tube bundle along an S-shaped or serpentine flue gas path, thereby maximizing heat exchange. When the boiler is operating at low load, if the flue gas still undergoes maximum heat exchange along the aforementioned S-shaped or serpentine flue gas path, the downstream flue gas temperature will be too low, easily leading to condensation. In this case, the heat exchange path can be adjusted to suit the load by appropriately opening some flue valves, up to and including all of them. When all the flue valves are open, the flue gas flows vertically and directly through the area where the flue valves are located, without passing through the heat exchange tube bundle; therefore, the flue valves from top to bottom effectively define the aforementioned "low-temperature flue".

[0017] According to a particularly preferred embodiment of the present invention, the vertical spacing between each half-width horizontal smoke baffle is not constant, but gradually decreases from top to bottom, i.e. from the high temperature end to the low temperature end, thereby ensuring that the flue gas velocity in the low temperature heating surface section is not too low, thereby reducing ash accumulation and ensuring heat exchange efficiency. Attached Figure Description

[0018] Figure 1 A schematic front sectional view of the overall structure of a non-limiting embodiment of the inventive boiler is shown.

[0019] Figure 2 schematically shown Figure 1 Cross-sectional view of AA.

[0020] Figure 3 schematically shown Figure 1 BB stepped sectional view. Detailed Implementation

[0021] The accompanying drawings show a schematic diagram of a boiler according to a preferred embodiment of the present invention.

[0022] As shown in the figure, the boiler includes a front membrane wall 1, a rear membrane wall 2, and a left membrane wall 3 (see figure). Figure 2 The furnace wall consists of the right membrane wall 4 and the top membrane wall 5 of the boiler. As is well known, the membrane wall is composed of multiple parallel and spaced hot water exchange pipes and steel plates (also called ribs) that airtightly cover the gaps between the pipes.

[0023] According to the present invention, between the vertically extending front membrane wall 1 and the rear membrane wall 2 of the boiler, there are also generally vertically extending and spaced apart rear arch membrane wall 6, first smoke-proof membrane wall 9, and second smoke-proof membrane wall 10.

[0024] The rear arch membrane wall 6 is a membrane wall forming a rear arch 61. The lower part of the rear arch membrane wall 6 extends obliquely to form the rear arch 61 of the boiler combustion chamber. The middle part of the rear arch membrane wall 6 is a substantially vertical extension, which, together with the front membrane wall 1 and the left, right and top membrane walls of the boiler, forms the furnace. The rear arch membrane wall 6 forms an oblique extension extending obliquely upward toward the front membrane wall 1 of the boiler at a position close to the top membrane wall 5 of the boiler, and the oblique extension is connected to a slag pipe 62, which is in turn connected to the top membrane wall 5 of the boiler. The slag pipe is a prior art and will not be described in detail.

[0025] A water-cooled air pipe 67 is arranged at the junction of the substantially vertical extension and the oblique extension of the rear arch membrane wall 6. One end of a slot-type separator 63 is connected to the water-cooled air pipe 67, and the other end is connected to the top membrane wall 5 of the boiler. The slot-type separator is also a prior art and, as shown in Figure 2 , includes a plurality of spaced water-cooled pipes, each of which is provided with fins, thereby blocking and capturing larger carbon-containing dust particles.

[0026] The slot-type separator 63, together with the oblique extension of the rear arch membrane wall 6 and the slag pipe 62, encloses a dust collection area. The bottom end of the dust collection area corresponds to the lower end of the oblique extension of the rear arch membrane wall 6. In this area, the rear arch membrane wall 6 is a bare tube, i.e. only the heat exchange water pipe is provided without inter-tube steel plate fins, thereby providing a dust falling port communicating with the furnace. A dust falling door 64 is provided corresponding to the dust falling port. When the dust falling door 64 is opened, the dust particles in the dust collection area fall into the furnace, thereby reigniting. The dust falling door 64 can generally be of a rotary plate structure (as shown in Figure 3 , which includes a rotary shaft 65 and a rotary plate 66 carried by the rotary shaft 65) or a gate structure (not shown, which is a translational structure, and the gate can be moved in translation to block or open the dust falling port).

[0027] According to an important feature of the present application, the slot-type separator 63 is not arranged vertically, but the upper end is arranged forwardly with respect to the direction of travel of the flue gas, so that the dust can fall more advantageously.

[0028] In addition, the water-cooled air pipe 67 is a pipe-in-pipe structure composed of an inner pipe and an outer pipe. The inner pipe is ventilated, water is circulated between the outer pipe and the inner pipe, and a blast nozzle is formed on the inner pipe extending to the outside of the water-cooled air pipe. The blast nozzle extends into the furnace through the rib of the rear arch membrane wall 6 to blow air into the furnace to supplement oxygen, thereby not only facilitating the reignition and burning of the dust particles falling into the furnace in the high-temperature furnace, but also increasing the oxygen content above the furnace, which is beneficial to full combustion.

[0029] According to the present application, in order to further reduce the particulate matters in the flue gas and thus reduce the ash deposit on the heat receiving surface, the flue gas will be subjected to a U-shaped path after passing through the slot-type separator, i.e. the flue gas will first go down and then go up. In this way, at the bottom of the U-shaped path, the particulate matters in the flue gas will be trapped due to inertia, and thus a drop ash port is provided at this position so as to send the particulate matters to the combustion chamber for secondary combustion.

[0030] Specifically, as shown in Figure 1 , the U-shaped path is formed by the rear arch membrane wall 6, the first smoke partition membrane wall 9 and the second smoke partition membrane wall 10 which are adjacent to and spaced apart from each other, wherein the rear arch membrane wall 6 and the first smoke partition membrane wall 9 define the down flue 7, and the first smoke partition membrane wall 9 and the second smoke partition membrane wall 10 define the up flue 8.

[0031] The lower region of the first smoke partition membrane wall 9 close to the rear arch is a light tube structure without fins, thereby providing a lower inlet smoke port 11 through which the flue gas of the down flue 7 can flow to the up flue.

[0032] The upper region of the second smoke partition membrane wall 10 is a light tube portion, thereby providing an upper inlet smoke port 12 through which the flue gas of the up flue 8 moves downstream. The lower region of the second smoke partition membrane wall 10 is airtightly connected to the rear arch membrane wall 6.

[0033] As mentioned above, when the flue gas is subjected to the U-shaped turn, the particulate matters in the flue gas will be trapped at the bottom of the U-shaped path due to inertia, i.e. at the concave portion formed by the connection of the second smoke partition membrane wall 10 and the rear arch membrane wall 6. Therefore, in the present application, the portion of the rear arch membrane wall 6 adjacent to the second smoke partition membrane wall 10 is a light tube structure, thereby providing a drop ash port 13, and thus a drop ash door is provided. The drop ash door can have a similar structure as the aforementioned drop ash door 64. In this way, the drop ash door can be opened as needed so that the particulate matters fall on the hearth 23 for secondary combustion, thereby achieving the purpose of efficient combustion and carbon reduction.

[0034] In the embodiment shown in Figure 1 , the side of the second smoke partition membrane wall 10 opposite to the first smoke partition membrane wall 9 is immediately adjacent to the heat receiving surface 14. At this time, according to a particularly preferred scheme of the present application, the position of the upper inlet smoke port 12 of the second smoke partition membrane wall 10 is also particularly set, i.e. although the majority of the downstream flue section adjacent to the upper inlet smoke port 12 is a horizontal extension section 15, the upper inlet smoke port 12 is not horizontally aligned with this horizontal flue section 15 as usual, but is offset downward by a certain distance, as shown in Figure 1 . Correspondingly, the smoke partition plate 16 for defining the flue downstream of the upper inlet smoke port 12 is not simply horizontally configured, but also includes an inclined extension section 162 extending obliquely upward from the lower end of the upper inlet smoke port 12 in addition to the horizontal extension section 161. In a further preferred embodiment, as shown inFigure 1 There is also a vertical extension 163 between the inclined extension and the horizontal extension. It is noted that the vertical extension 163 is not necessary.

[0035] The benefit of the above arrangement is that the flue gas entering the upper flue gas inlet 12 will, before moving horizontally, move vertically along the heat exchange tube bundle (i.e. the heating surface 14) for a distance due to the presence of the inclined extension 162 and optionally the vertical extension 163. This vertical movement of the flue gas will help to reduce the ash deposition on the heat exchange tube bundle. In this regard, it is known to those skilled in the art that when flue gas flows across the heat exchange tube, the leeward side of the heat exchange tube is prone to ash deposition, which can be avoided when the flue gas flows along the axis of the heat exchange tube as in the present application.

[0036] In a further preferred aspect of the present application, the U-shaped turn of the flue gas extends the heat exchange path, which can cause excessive heat exchange between the flue gas and the membrane wall, and in turn, cause the flue gas to be too low in temperature to facilitate the subsequent denitration reaction. The present application further provides a temperature adjustment flue gas door 20 at the upper portion of the first smoke partitioning membrane wall 9, and correspondingly, the first smoke partitioning membrane wall 9 is in a light tube structure at this region. The temperature adjustment flue gas door 20 can have a similar structure as the ash falling door 64, i.e. it can be a rotating plate type (see Figure 2 ), or a gate type. The temperature adjustment flue gas door 20 on the first smoke partitioning membrane wall 9 is generally horizontally aligned with the upper flue gas inlet 12 on the second smoke partitioning membrane wall 10. When the flue gas door 20 is opened, it provides a "shortcut" for the flue gas, so that the upstream flue gas can pass straight through the first smoke partitioning membrane wall 9 without flowing through the U-shaped turn path. In this way, the temperature adjustment flue gas door 20 can send "high temperature" flue gas to the upper flue gas inlet 12 to ensure that the downstream flue gas has sufficient temperature to perform catalytic denitration.

[0037] The opening of the flue gas door 20 is adjustable to adjust the proportion of "high temperature" flue gas as required.

[0038] In order to minimize the amount of "high temperature" flue gas supplemented via the flue gas door 20, so that most of the flue gas can still be turned back along the U-shaped path to remove particulate matter, the temperature adjustment flue gas door 20 is arranged to align with the upper portion of the upper flue gas inlet 12. Compared to being arranged at other positions, the above arrangement can minimize the heat exchange path of the newly supplemented "high temperature" flue gas, which is beneficial to ensure the temperature of the downstream flue gas.

[0039] The flue gas passing through the upper flue gas inlet 12 to the downstream can be introduced to a denitration chamber 21 outside the flue gas duct for denitration, and then be re-introduced into the flue gas duct. One aspect of the present application also relates to the improvement of the flue gas duct downstream of the denitration chamber, which is described in detail below.

[0040] As Figure 1As shown, at least a portion of the flue downstream of the denitration chamber 21 is defined by a plurality of half-width horizontal damper plates 17, 18, the second damper membrane wall 10, the boiler rear membrane wall 2, and the boiler left and right membrane walls. By "half-width", it is meant that these damper plates do not extend to cover the entire area between the second damper membrane wall 10 and the boiler rear membrane wall 2, but only a portion thereof (see Figure 3 the reference numeral 18, but not necessarily "half").

[0041] These half-width horizontal damper plates 17, 18 extend alternately from the boiler rear membrane wall 2 and the second damper membrane wall 10 from top to bottom, thereby forming an S-shaped or serpentine flue gas path. The heat exchange tube bundle serving as the heating surface 14 is disposed between the second damper membrane wall 10 and the boiler rear membrane wall 2, in close proximity to the second damper membrane wall 10, but with a spacing from the boiler rear membrane wall 2. The damper plate 17 extending from the boiler rear membrane wall is provided with flue gas doors 19 located in the spacing area between the heating surface 14 and the boiler rear membrane wall 2, and aligned vertically.

[0042] When the boiler is operated at high load, the flue gas doors 19 are all closed, and the flue gas passes back and forth through the heating surface 14 along the S-shaped or serpentine flue gas path, thereby performing maximum heat exchange. When the boiler is operated at low load, if the flue gas still performs maximum heat exchange along the above-mentioned S-shaped or serpentine flue gas path, the downstream flue gas temperature will be too low and easily lead to condensation. Therefore, at this time, a number of flue gas doors 19 (even all of them) can be properly opened to adjust the length of the heat exchange path, thereby adapting to the load. In particular, when all the flue gas doors 19 are opened, the flue gas passes vertically and directly through the spacing area between the heating surface 14 and the boiler rear membrane wall 2, without passing through the heating surface 14, so that the spacing area between the heating surface 14 and the boiler rear membrane wall 2 actually defines a "low-temperature flue 22".

[0043] According to a particularly preferred scheme of the present application, the vertical spacing between each half-width horizontal damper plate is not constant, but gradually decreases from top to bottom (i.e. from the high-temperature end to the low-temperature end), thereby ensuring that the flue gas flow rate of the low-temperature heating surface section is not too low, thereby reducing ash deposition.

[0044] In addition, in a particularly preferred scheme, as shown in Figure 1As shown, the half-width horizontal damper 17 extending from the rear membrane wall 2 of the boiler comprises a lower first horizontal section 171 connected to the rear membrane wall 2 of the boiler, a higher second horizontal section 172 extending into the region of the heating surface 14, and an inclined section 173 connecting the first horizontal section and the second horizontal section, wherein the smoke door 19 is arranged in the lower first horizontal section 171. In this way, the first horizontal section 171, together with the inclined section 173 and the rear membrane wall 2 of the boiler, forms a recess in which particles in the flue gas tend to accumulate due to inertia when the flue gas is turned in a serpentine path close to the side of the rear membrane wall 2 of the boiler. In this way, the ash can be cleaned by periodically opening the smoke door 19. Therefore, the smoke door 19 also functions as an ash door in this sense.

[0045] In a further preferred embodiment, the half-width horizontal damper 18 extending from the second damper membrane wall 10 comprises an inclined section 181 extending obliquely downward from the second damper membrane wall 10 and a horizontal section 182 connected to the inclined section. In this way, compared to the case without the inclined section 181, the corner of the half-width horizontal damper extending from the second damper membrane wall 10 is less likely to accumulate ash when the flue gas is turned in a serpentine path at the second damper membrane wall 10.

[0046] In a preferred embodiment, the damper 17, 18 blocks 50%-70% of the full width of the heating surface in the transverse direction, and the remaining 50%-30% is the heating surface that is washed by the flue gas in the forward direction (i.e. the flue gas flows substantially in the length direction of the heating surface tube bundle), thereby reducing the accumulation of ash.

[0047] It should be noted again that, Figure 1 The embodiments are merely preferred embodiments which include all the improvements of the present application over the prior art. However, those skilled in the art should understand that any scheme containing the improvements of any aspect of the present application should be within the scope of the present application.

Claims

1. A boiler, characterized in that At least a part of the flue of the boiler is defined by a plurality of half-width horizontal smoke baffles, smoke membrane walls, a rear membrane wall of the boiler, and left and right membrane walls of the boiler, the half-width horizontal smoke baffles extending alternately from the rear membrane wall and the smoke membrane walls from top to bottom and covering only a partial area between the smoke membrane walls and the rear membrane wall of the boiler, thereby forming an S-shaped or serpentine flue gas path, wherein the heating surface is arranged between the smoke membrane walls and the rear membrane wall of the boiler, adjacent to the smoke membrane walls and spaced apart from the rear membrane wall of the boiler, a smoke door is arranged on the smoke baffle extending from the rear membrane wall of the boiler, the smoke door being located in the spaced apart area between the heating surface and the rear membrane wall of the boiler and vertically aligned with the heating surface; wherein the half-width horizontal smoke baffle extending from the rear membrane wall of the boiler comprises a lower first horizontal section connected to the rear membrane wall of the boiler, a higher second horizontal section extending into the area of the heating surface, and an inclined section connecting the first horizontal section and the second horizontal section, and the smoke door is arranged in the first horizontal section.

2. A boiler as claimed in claim 1, characterised in that The vertical spacing between the half-width horizontal smoke baffles gradually decreases from top to bottom.

3. The boiler of claim 1, wherein The half-width horizontal smoke baffle extending from the smoke membrane wall comprises an inclined section extending obliquely downward from the smoke membrane wall and a horizontal section connected to the inclined section.

4. The boiler of claim 1, wherein Each smoke baffle laterally blocks 50%-70% of the full width of the heating surface.

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