A waste heat boiler system for waste incineration with flue gas reheating

Abstract

The present invention relates to a waste heat boiler system for waste incineration with flue gas reheating, characterized in that it comprises the first flue to the Nth flue arranged in sequence along the flue gas flow direction, the Nth flue is a horizontal flue surrounded by a superheater, a water-cooled evaporator screen, a first-stage superheater second, a third-stage superheater, a second-stage reheater, a second-stage superheater second, a second-stage superheater first, and a first-stage superheater first are arranged in sequence in the horizontal flue, the Nth flue is connected to the tail front flue, the tail front flue is connected in series with the tail rear flue, the tail front flue and the tail rear flue are composed of enclosures, and the first-stage reheater and the economizer are arranged in the tail front flue and the tail rear flue, respectively. The flue gas temperature in the area where the first-stage reheater is located is relatively low, and arranging it in the tail flue composed of enclosures can save floor space compared to the solution in which all convection heating surfaces are arranged in the horizontal flue.

Description

Technical Field

[0001] The invention relates to a waste heat boiler system for garbage incineration. Background Art

[0002] The waste fuel fluctuates greatly, and the combustion process, flue gas composition, flue gas volume and flue gas temperature fluctuate greatly; the flue gas composition of the incinerator is complex, containing chlorides, alkali metals and heavy metals, etc.; the content of low-melting-point solid substances in the flue gas dust is high. Due to the high concentration of chemical elements and high temperature, the hot surface tube bundle is prone to corrosion, so the steam parameters of the existing waste incinerator are kept relatively low.

[0003] Due to the complex flue gas atmosphere in the water-cooled wall area, the outer wall temperature of the fire-side tubes in the area with higher flue gas temperature is high, the main steam pressure increases, and the pressure of the steam drum and water-cooled wall increases accordingly, and the corresponding saturation temperature increases accordingly. The temperature of the steam-water mixing area in the water-cooled wall increases, causing the water-cooled wall temperature to rise and the corrosion risk to increase. Therefore, the selection of the main steam pressure of the waste heat boiler for waste incineration is mainly limited by the corrosion risk of the water-cooled wall.

[0004] The selection of main steam temperature is mainly limited by the fact that the corrosion risk of high-temperature heating surfaces will increase directly after the temperature is increased. At present, waste heat boilers for waste incineration are mainly medium-temperature medium-pressure (4MPa, 400℃) and medium-temperature sub-high-pressure (6.4MPa, 450℃). As the proportion of garbage subsidy income continues to decline, increasing power generation revenue is of great significance to waste incineration power plants. Summary of the invention

[0005] The purpose of the present invention is to improve the overall power generation efficiency and economic efficiency of the unit by studying the design scheme of a boiler with a reheat system.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the present invention is to provide a waste incineration waste heat boiler system with flue gas reheating, characterized in that it includes the first flue to the Nth flue arranged in sequence along the flue gas flow direction, the Nth flue is a horizontal flue surrounded by a superheater, a water-cooled evaporator screen, a first-stage superheater second, a third-stage superheater, a second-stage reheater, a second-stage superheater second, a second-stage superheater one, and a first-stage superheater one are arranged in sequence in the horizontal flue, the Nth flue is connected to the tail front flue, the tail front flue is connected in series with the tail rear flue, the tail front flue and the tail rear flue are composed of enclosures, and the first-stage reheater and the economizer are arranged in the tail front flue and the tail rear flue, respectively. The flue gas temperature in the area where the first-stage reheater is located is relatively low, and arranging it in the tail flue composed of enclosures can save floor space compared to the solution in which all convection heating surfaces are arranged in the horizontal flue.

[0007] Preferably, N=4, the first to third flues adopt a water-cooled wall structure, the fourth flue is a horizontal flue surrounded by a superheater, and the first to fourth flues are arranged in sequence along the flue gas flow direction, the flue gas flows from bottom to top along the first flue, flows from top to bottom along the second flue, and flows from bottom to top along the third flue, an ash hopper is arranged at the lower part of the second flue and the third flue, the first flue has a flue outlet smoke window, and the second flue has a flue outlet smoke window. The water-cooled wall heating surface of the first flue, the water-cooled wall heating surface of the second flue located above the flue outlet smoke window, and the water-cooled wall heating surface of the ash hopper at the lower part of the second and third flues are refractory cast; the water-cooled wall heating surface of the vertical section of the second flue and the water-cooled wall heating surface of the third flue are welded.

[0008] Preferably, due to the increase in flue gas reheating and the improvement in parameters, the heat absorption ratio of the convection heating surface is greatly increased, and the flue gas temperature at the inlet of the convection heating surface is correspondingly increased. In order to reduce the flue gas temperature at the convection heating surface as much as possible, the ceiling and side wall coverings of the horizontal flue are both equipped with superheating structures to increase the heat absorption of the superheating system and reduce the flue gas temperature at the inlet of the convection heating surface, so as to achieve the purpose of controlling the corrosion rate of the convection heating surface in the high smoke temperature area.

[0009] Preferably, the control of flue gas temperature is essentially the control of the temperature of the heating surface tube wall and the flue gas contact surface. In order to avoid the superposition of high flue gas temperature and high steam temperature to increase the risk of corrosion, the first-stage superheater 2 is placed in front (the first-stage superheater 2 is the first-stage superheater in the flue gas process), and the first-stage superheater 2 is arranged downstream along the steam flow direction. The steam temperature and tube wall temperature of the first-stage superheater 2 are relatively low to effectively reduce the risk of high-temperature corrosion.

[0010] Preferably, a desuperheater is arranged at the inlet of the first-stage reheater, and a portion of the steam at the inlet of the first-stage reheater is bypassed to the outlet of the first-stage reheater, so as to achieve the purpose of adjusting the temperature of the reheated steam.

[0011] The present invention has the following advantages:

[0012] 1) The present invention avoids serious high-temperature corrosion through reasonable heating surface arrangement and material selection.

[0013] 2) The four flues of the waste incineration waste heat boiler conventionally use water-cooled membrane walls, but for the ceiling heating surface, as the pressure increases, the steam-water density difference of the water cooling system becomes smaller, the water circulation characteristics of the water-cooled ceiling deteriorate, and the heat transfer deterioration phenomenon such as steam-water stratification is prone to occur. The ceiling and side wall coverings of the fourth flue of the present invention are all superheated, and the saturated steam coming out of the steam drum in the steam-water process first passes through the ceiling and side walls. Changing the heat exchange medium of the superheated ceiling to a single-phase medium does not result in heat transfer deterioration, and is relatively safe and reliable. At the same time, the superheated ceiling and covering can bear part of the heat, and the superheated steam absorbs heat to avoid excessively high flue gas temperatures entering the convection heating surface.

[0014] 3) The present invention considers that the flue gas temperature range of the primary reheater is less than 400°C, and arranges the primary reheater in a vertical flue composed of enclosures, which can effectively shorten the length of the horizontal flue and reduce the floor space.

[0015] 4) The present invention places part of the first-stage superheater in front (the second-stage superheater is used as the first-stage superheater in the flue gas process), which can effectively avoid the superposition of high flue gas temperature and high steam temperature. The second-stage superheater is used as the first-stage superheater in the flue gas process, and the inlet flue gas temperature of the third-stage superheater is controlled at the conventional 580℃-600℃, which can effectively avoid corrosion of the high-temperature heating surface. The low-temperature superheater is placed in front of the low-temperature reheater.

[0016] 5) Superheated steam has a relatively large specific heat capacity, and the temperature deviation of the heating surface tube wall is easier to control. When placed in an area where the smoke temperature is higher than 600°C, the wall temperature will not rise sharply.

[0017] 6) The steam temperature at the inlet of the first-stage reheater is 285℃, which is lower than the steam temperature of 346℃ at the inlet of the first-stage superheater. The heat exchange of the flue gas temperature range after the first stage can be fully utilized, and the heat energy utilization after the first stage reheater is more reasonable.

[0018] 7) Aiming at increasing the primary steam pressure of the reheat system, the present invention re-formulates the refractory material laying plan of the water cooling system on the basis of considering the safety of the water cooling system.

[0019] 8) In addition to using conventional desuperheating water to adjust the reheat steam temperature, the reheat system of the present invention also adopts a temperature adjustment scheme of bypassing part of the low-temperature reheater inlet steam to the low-temperature reheater outlet, thereby increasing the temperature adjustment means of the reheat system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a waste incineration waste heat boiler system with flue gas reheating disclosed in an embodiment. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0022] like Figure 1 As shown, the waste incineration waste heat boiler disclosed in this embodiment adopts a ∏-type arrangement as a whole. It should be noted that the technical solution disclosed in this application is not only applicable to waste incineration waste heat boilers with a ∏-type arrangement, but also applicable to waste incineration waste heat boilers with other arrangements. Although this embodiment takes the ∏-type arrangement as an example, it does not exclude waste incineration waste heat boilers with other arrangements.

[0023] In this embodiment, the first three flues (i.e., the first to third flues) are vertical channels composed of membrane water-cooled heating surfaces, and the fourth flue is a horizontal flue surrounded by a superheater. For waste incineration waste heat boilers with medium temperature, sub-high pressure and lower parameters, the water-cooled wall casting range is below the flue 1 outlet smoke window of the first flue (the area corresponding to Ⅰ in the figure). For waste incineration waste heat boilers with reheat, due to the increase in the pressure of the primary steam system, the heat absorption ratio of the latent heat of gasification is reduced, and the saturation temperature of the water-cooled wall is increased. In order to ensure the safety of the water-cooled wall, the refractory casting range is increased to the flue 1 smoke window and the flue 2 smoke window ( Figure 1 The second flue straight section and the third flue (the area corresponding to Ⅳ and Ⅵ in the figure) are all welded.

[0024] For high-temperature convection heating surfaces, controlling the inlet flue gas temperature is an important measure to avoid high-temperature corrosion. Compared with systems without reheating, the convection heating surface needs to complete the superheater and reheater heat absorption, and the inlet flue gas temperature of the convection heating surface is increased.

[0025] The water-cooled evaporator screen, the first-stage superheater 215, the third-stage superheater 25, the second-stage reheater 38, the second-stage superheater 21, the second-stage superheater 120, and the first-stage superheater 11 are arranged in the horizontal flue in sequence. The first-stage reheater (including the first-stage reheater A31, the first-stage reheater B32, and the first-stage reheater C33) and the economizer are arranged in the tail front flue and the tail rear flue respectively. The tail front flue and the tail rear flue are connected in series and consist of a coaming.

[0026] The saturated steam at the outlet of the drum 1 is introduced into the horizontal flue furnace top inlet header 3 through the connecting pipe 2. The horizontal flue furnace top inlet header 3 is connected to the horizontal flue furnace top superheater 4, and enters the horizontal flue furnace top superheater outlet header 5 after absorbing heat through the horizontal flue furnace top superheater 4. The horizontal flue furnace top superheater outlet header 5 is connected to the header 6 on the side package wall of the rear half of the horizontal flue, and the header 6 on the side package wall of the rear half of the horizontal flue is connected to the side package wall of the rear half of the horizontal flue. The superheated steam after absorbing heat through the side package wall of the rear half of the horizontal flue is introduced into the lower header 7 of the horizontal flue side package wall, and enters the side package wall of the front half of the horizontal flue through the lower header 7 of the horizontal flue side package wall. After absorbing heat in the side package wall of the front half of the horizontal flue, the steam is collected in the header 8 on the side package wall of the front half of the horizontal flue, and then led out to the inlet header 10 of the first superheater 11 through the connecting pipe 9.

[0027] The steam at the outlet of the furnace top and the sheathing superheater enters the first-stage superheater 11 through the inlet header 10 of the first-stage superheater 11 and absorbs heat, and then is collected in the outlet header 12 of the first-stage superheater 11. The outlet header 12 is connected to the inlet header 14 of the first-stage superheater 15 through the connecting pipe 13. The steam absorbs heat through the first-stage superheater 15 and is collected in the outlet header 16 of the first-stage superheater 15. The outlet header 16 is connected to the inlet header 19 of the second-stage superheater 20 through the connecting pipe 17 and the desuperheater 18. The inlet header 19 absorbs heat through the second-stage superheater 20 and the second-stage superheater 21, and then is collected in the outlet header 22 of the second-stage superheater 21. The outlet header 22 is connected to the inlet header 24 of the third-stage superheater 25 through the connecting pipe 22 and the desuperheater 23. After absorbing heat in the third-stage superheater 25, the steam is collected in the outlet header 26 of the third-stage superheater 25, and finally sent to the high-pressure cylinder of the steam turbine through the superheater outlet connecting pipe 27 to perform work.

[0028] Most of the high-exhaust steam from the turbine is introduced into the inlet header 30 of the primary reheater A31 through the connecting pipe 28 and the desuperheater 29, and after absorbing heat in the primary reheater A31, the primary reheater B32 and the primary reheater C33, it is collected in the outlet header 34 of the primary reheater C33. A small part of the high-exhaust steam from the turbine participates in regulating the reheat steam temperature. This small part of the high-exhaust steam from the turbine is combined with the reheat steam after heat exchange in the primary reheater A31, the primary reheater B32 and the primary reheater C33 through the connecting pipe 35, and then introduced into the inlet header 37 of the secondary reheater 38 through the connecting pipe 36. After heat exchange in the secondary reheater 38, the steam is collected in the outlet header 39 of the secondary reheater 38, and finally sent to the intermediate pressure cylinder of the turbine through the connecting pipe 40 to perform work.

[0029] The waste heat boiler for garbage incineration adopts a ∏-type layout as a whole. The flue gas passes through the first three vertical empty flues (the first flue, the second flue, and the third flue), the horizontal flue, the front flue at the rear (arranged with a first-stage reheater A31, a first-stage reheater B32, and a first-stage reheater C33), and the rear flue at the rear (arranged with an economizer). The first-stage evaporation screen, the first-stage superheater 215, the third-stage superheater 25, the second-stage reheater 38, the second-stage superheater 21, the second-stage superheater 120, and the first-stage superheater 11 are arranged in sequence in the horizontal flue.

Claims

1. A waste incineration waste heat boiler system with flue gas reheating, characterized in that: It includes the 1st to Nth flues arranged in sequence along the flue gas flow direction, the Nth flue is a horizontal flue surrounded by superheater covering, the water-cooled evaporator screen, the first-stage superheater 2, the third-stage superheater, the second-stage reheater, the second-stage superheater 2, the second-stage superheater 1, and the first-stage superheater 1 are arranged in sequence in the horizontal flue, the first-stage superheater 2 is placed in front and arranged downstream along the steam flow direction, the first-stage superheater 2 is used as the first-stage superheater in the flue gas flow process, and the inlet flue gas temperature of the third-stage superheater is controlled at 580℃-600℃, the ceiling and side wall coverings of the horizontal flue are all covered with superheating structure, the Nth flue is connected with the tail front flue, the tail front flue is connected in series with the tail rear flue, the tail front flue and the tail rear flue are composed of enclosures, the first-stage reheater and the economizer are arranged in the tail front flue and the tail rear flue respectively, and the first-stage reheater is arranged in the vertical flue composed of enclosures.

2. A waste incineration waste heat boiler system with flue gas reheating as claimed in claim 1, characterized in that: N=4, the first to third flues adopt water-cooled wall structure, the fourth flue is a horizontal flue surrounded by a superheater, and the first to fourth flues are arranged in sequence along the flue gas flow direction, the flue gas flows from bottom to top along the first flue, flows from top to bottom along the second flue, and flows from bottom to top along the third flue, the second flue and the third flue are connected with the ash hopper, the first flue has a flue outlet smoke window, and the second flue has a flue outlet smoke window, the water-cooled heating surface of the water-cooled wall structure of the first flue, the water-cooled heating surface of the water-cooled wall structure of the second flue located above the flue outlet smoke window, and the water-cooled heating surface of the water-cooled wall structure of the ash hopper are cast with refractory; the water-cooled heating surface of the water-cooled wall structure of the vertical section of the second flue and the water-cooled heating surface of the water-cooled wall structure of the third flue are welded.

3. A waste incineration waste heat boiler system with flue gas reheating as claimed in claim 1, characterized in that: A desuperheater is arranged at the inlet of the first-stage reheater, and a portion of the steam at the inlet of the first-stage reheater is bypassed to the outlet of the first-stage reheater, so as to achieve the purpose of adjusting the temperature of the reheated steam.

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