Hearth system of circulating fluidized bed boiler
By installing preheating fuel nozzles and fuel pretreatment devices on the rear wall of the circulating fluidized bed boiler furnace, the problem of low flue gas temperature under low load conditions was solved, the SNCR denitrification efficiency and steam temperature were improved, and more efficient combustion and heat transfer effects were achieved.
Patent Information
- Application Number
- CN202423026795.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-09
- Publication Date
- 2025-10-21
- Estimated Expiration
- 2034-12-09
AI Technical Summary
Under low load conditions, the flue gas temperature at the furnace outlet of a circulating fluidized bed boiler is low, resulting in low SNCR denitrification efficiency, excessive nitrogen oxide emissions, high consumption of reducing agent, and insufficient boiler outlet steam temperature, which affects the unit's power generation capacity.
Multiple preheating fuel nozzles are installed on the rear wall of the furnace. The fuel is preheated by a fuel pretreatment device and then injected into the furnace to increase the furnace temperature. The preheated fuel combustion heats the lower part of the screen-type superheater and screen-type reheater, thereby enhancing the heat transfer effect.
It increased the flue gas temperature at the furnace outlet under low load conditions, enhanced the SNCR denitrification efficiency, reduced nitrogen oxide emissions, reduced reducing agent consumption, and increased the boiler outlet steam temperature.
Smart Images
Figure CN223460442U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to combustion equipment technical field especially a circulating fluidized bed boiler hearth system. BACKGROUND
[0002] With the adjustment of national energy structure, the proportion of new energy generation such as wind power and photovoltaic power is expanding continuously, in order to ensure the consumption of new energy generation and avoid the phenomenon of "abandoning wind and electricity", it has become an inevitable trend that thermal power units participate in deep peak regulation.
[0003] Circulating fluidized bed boilers have obvious advantages in thermal power unit peak regulation due to their strong fuel adaptability, low pollutant emission and wide load regulation range. In order to meet environmental protection requirements, usually, a SNCR denitration device (selective non-catalytic reduction) is configured at the furnace outlet of a circulating fluidized bed boiler to spray a reducing agent such as urea or ammonia water into flue gas to reduce nitrogen oxides in the flue gas into N2, achieving the purpose of flue gas denitration.
[0004] The nitrogen oxide removal efficiency of the SNCR process is greatly affected by the reaction temperature. If the flue gas temperature is too low, the reaction of NH3 is incomplete, the denitration efficiency is reduced, and problems such as excessive emission of nitrogen oxides, large consumption of reducing agent, increased ammonia escape, corrosion and blockage of downstream equipment, etc. may occur.
[0005] Under low load conditions (50% BMCR conditions), the flue gas temperature at the furnace outlet of a circulating fluidized bed boiler is low, deviating from the optimal temperature for SNCR denitration reaction, the denitration efficiency is low, and the emission of nitrogen oxides in the flue gas exceeds the standard, which seriously restricts the ability of circulating fluidized bed boiler units to deep peak regulation (low load operation).
[0006] The low flue gas temperature at the furnace outlet of a circulating fluidized bed boiler affects the heat exchange effect of each heating surface in the tail flue. In addition, the low flue gas temperature at the upper part of the furnace reduces the heat transfer temperature and pressure drop of the multiple screen superheaters and screen reheaters arranged at the upper part of the furnace, and reduces the heat absorption, ultimately resulting in a lower steam temperature at the boiler outlet than the steam inlet requirement of the steam turbine, affecting the power generation capacity of the unit.
[0007] Currently, some circulating fluidized bed boilers use flue gas recirculation technology under low load conditions. This technology introduces purified flue gas back into the furnace to maintain normal material fluidization in the furnace under the condition of maintaining a low air volume, meeting the basic requirements of boiler operation. However, this technology further reduces the flue gas temperature at the furnace outlet due to the introduction of flue gas into the furnace, which is more detrimental to the SNCR denitration efficiency at the furnace outlet. Moreover, due to the reduction of the furnace bed temperature, the heat transfer effect of the screen superheaters and screen reheaters at the upper part of the furnace is poor, and the temperature of the steam at the boiler outlet cannot meet the requirements of the steam turbine. SUMMARY
[0008] To solve at least one aspect of the above technical problems, the utility model provides a new type of circulating fluidized bed boiler.
[0009] In one aspect, the arrangement of the device is provided, at least one aspect of the problem of low temperature of flue gas at the furnace outlet of the circulating fluidized bed boiler under low load condition, low denitration efficiency of SNCR device, excessive emission of nitrogen oxides in flue gas, and large consumption of reducing agent is solved.
[0010] In another aspect, the arrangement of the device is provided, the problem of low temperature of steam at the boiler outlet of the circulating fluidized bed boiler under low load condition is solved.
[0011] According to the embodiment of the utility model, a circulating fluidized bed boiler furnace system is provided, which comprises:
[0012] Fuel pretreatment device;
[0013] Boiler furnace, the upper part of the front wall of the furnace is provided with a screen type superheater and a screen type reheater, and the back wall of the furnace is provided with a furnace outlet;
[0014] SNCR nozzle, located at the furnace outlet, for injecting reducing agent into the flue gas at the furnace outlet,
[0015] The fuel pretreatment device comprises a plurality of preheated fuel nozzles arranged on the back wall of the furnace, the preheated fuel from the fuel pretreatment device is adapted to communicate with the plurality of preheated fuel nozzles, and the fuel flow from the preheated fuel nozzles is adapted to heat the screen type superheater and the screen type reheater.
[0016] Optionally, the lower part of the screen type superheater and the screen type reheater is provided with an anti-abrasion layer, and the height of the preheated fuel nozzle is arranged so that the flame from the preheated fuel nozzle is adapted to heat the lower part of the screen type superheater and the screen type reheater.
[0017] Optionally, the height of the preheated fuel nozzle is arranged to be flush with the lower part of the anti-abrasion layer of the longer one of the screen type superheater and the screen type reheater.
[0018] Optionally, the preheated fuel nozzle is arranged at the middle upper part of the back wall of the furnace, so that the flame from the preheated fuel nozzle is adapted to heat the lower part of the screen type superheater and the screen type reheater.
[0019] Optionally, the plurality of fuel pretreatment devices are arranged outside the middle upper portion of the back wall of the furnace, the preheated fuel outlets of the plurality of fuel pretreatment devices are connected with a preheated fuel header tank, and the preheated fuel header tank is located outside the middle upper portion of the back wall of the furnace, one end of the preheated fuel header tank is connected with the preheated fuel outlets of the plurality of fuel pretreatment devices, and the other end of the preheated fuel header tank is connected with the plurality of preheated fuel injection ports; or one fuel pretreatment device is arranged outside the middle upper portion of the back wall of the furnace, the preheated fuel outlet of the one fuel pretreatment device is connected with a preheated fuel header tank, and the preheated fuel header tank is located outside the middle upper portion of the back wall of the furnace, one end of the preheated fuel header tank is connected with the preheated fuel outlet of the one fuel pretreatment device, and the other end of the preheated fuel header tank is connected with the plurality of preheated fuel injection ports.
[0020] Optionally, the boiler furnace system further comprises a control device, which is configured to: when the boiler is operated at a load lower than 50% of the rated load of the boiler, fuel enters the fuel pretreatment device, the preheated fuel generated after pretreatment enters the preheated fuel header tank, and the preheated fuel is injected into the furnace from the preheated fuel injection ports; and simultaneously, coal feeding from the coal feeding port of the furnace into the furnace is reduced or stopped.
[0021] Optionally, the plurality of screen superheaters and the plurality of screen reheaters are arranged vertically to the front wall, and each is suspended in parallel and spaced apart in a direction parallel to the front wall.
[0022] Optionally, the plurality of preheated fuel injection ports are arranged staggered with the screen superheaters and the screen reheaters in a direction parallel to the front wall.
[0023] Optionally, the furnace outlet comprises at least two furnace outlets arranged on the back wall of the furnace; and in a plan view of the furnace, the plurality of preheated fuel injection ports are symmetrically arranged with the center line of the back wall of the furnace.
[0024] Optionally, the number of preheated fuel injection ports is the same as or different from the sum of the number of screen superheaters and the number of screen reheaters.
[0025] Based on the above technical solutions, the technical solutions of the present application can solve the problems of low furnace outlet flue gas temperature, low SNCR denitration efficiency, excessive nitrogen oxide emission in flue gas, and large consumption of reducing agent in the low load condition of a circulating fluidized bed boiler, and can also solve the problem of low boiler outlet steam temperature in the low load condition of a circulating fluidized bed boiler. BRIEF DESCRIPTION OF DRAWINGS
[0026] The following description and drawings can better help understand these and other features and advantages of the various embodiments disclosed by the present application, in which the same reference signs always represent the same components, and in which:
[0027] Figure 1Fig. 1 is a front view of a furnace of a circulating fluidized bed boiler furnace system according to an exemplary embodiment of the present application;
[0028] Figure 2 Fig. 2 is a top view of the furnace of the circulating fluidized bed boiler furnace system according to the exemplary embodiment of the present application.
[0029] Reference signs:
[0030] 1 - furnace, 11 - platen superheater, 111 - superheater platen wear protection layer, 12 - platen reheater, 121 - reheater platen wear protection layer, 13 - furnace front wall, 14 - furnace rear wall, 15 - furnace outlet, 16 - coal feed port, 17 - air chamber, 21 - fuel pretreater, 22 - preheated fuel header, 30 - SNCR injection port, 23 - preheated fuel injection port DETAILED DESCRIPTION
[0031] The technical solution of the present application will be further described below by way of examples and with reference to the accompanying drawings. In the description, identical or similar reference signs indicate identical or similar parts. The following description of the embodiments of the present application with reference to the accompanying drawings is intended to explain the general inventive concept of the present application and should not be construed as limiting the present application in any way.
[0032] The present application provides a circulating fluidized bed boiler furnace system, comprising:
[0033] a fuel pretreatment device;
[0034] a boiler furnace, a platen superheater and a platen reheater are arranged at an upper portion of a furnace front wall of the boiler furnace, and a furnace outlet is arranged at a furnace rear wall of the boiler furnace; and
[0035] a SNCR injection port arranged at the furnace outlet and configured to inject a reducing agent into flue gas at the furnace outlet;
[0036] The fuel pretreatment device comprises a plurality of preheated fuel injection ports arranged at the furnace rear wall, preheated fuel from the fuel pretreatment device is adapted to communicate with the plurality of preheated fuel injection ports, and fuel flow from the preheated fuel injection ports is adapted to heat the platen superheater and the platen reheater.
[0037] Reference will now be made to Figure 1 and Figure 2 to illustrate the technical solution of the present application. Figure 1 Fig. 1 is a front view of a furnace of a circulating fluidized bed boiler furnace system according to an exemplary embodiment of the present application;
[0038] Figure 2 Fig. 2 is a top view of the furnace of the circulating fluidized bed boiler furnace system according to the exemplary embodiment of the present application.
[0039] Based on the above embodiment, the utility model provides a kind of circulating fluidized bed boiler furnace system, including the furnace 1 of circulating fluidized bed boiler and fuel pretreatment device 2.
[0040] The lower part of the front wall 13 of the furnace 1 is uniformly arranged with multiple coal feeding ports 16; the bottom of the furnace 1 is provided with an air chamber 17, and the primary air enters the furnace 1 through the air chamber; the upper part of the front wall 13 of the furnace 1 is suspended with multiple screen superheaters 11 and screen reheaters 12 which are perpendicular to the front wall of the furnace along a direction parallel to the front wall 13; the back wall 14 of the furnace 1 is arranged with multiple furnace outlets 15, and multiple SNCR nozzles 30 are arranged on the sidewalls of each furnace outlet 15 to inject a reducing agent into the flue gas of the furnace outlet to reduce nitrogen oxides in the flue gas.
[0041] Optionally, the number of furnace outlets 15 is two, which are arranged on the two sides of the back wall of the furnace, and optionally, the two furnace outlets are symmetrically arranged with the center line of the back wall of the furnace as a mirror line.
[0042] When the number of furnace outlets 15 is three, one of the furnace outlets is located in the middle of the back wall of the furnace; when the number of furnace outlets 15 is four, two of the furnace outlets are symmetrically arranged on the two sides of the center line of the back wall of the furnace. According to the scheme of the utility model, the number of furnace outlets is adaptively adjusted according to the size of the furnace of the boiler.
[0043] The fuel pretreatment device 2 is used for preheating fuel, and the fuel pretreatment device 2 comprises a fuel pretreater 21, a preheated fuel header 22, and a preheated fuel nozzle 23.
[0044] In a specific example:
[0045] Multiple fuel pretreaters 21 are arranged on the outer side of the upper part of the back wall 14 of the furnace; the preheated fuel outlet of the fuel pretreater 21 is connected to the preheated fuel header 22;
[0046] The preheated fuel header 22 is located on the outer side of the upper part of the back wall 14 of the furnace, one end of which is connected to the preheated fuel outlet of the multiple fuel pretreaters 21, and the other end of which is connected to the multiple preheated fuel nozzles 23;
[0047] The preheated fuel nozzle 23 is arranged on the upper part of the back wall 14 of the furnace and is symmetrically arranged with the horizontal center line of the back wall 14 (or the center line of the back wall in the plan view of the furnace) as a mirror line. One end of the preheated fuel nozzle 23 is located on the back wall 14 of the furnace, and the other end is connected to the preheated fuel header 22;
[0048] The number of the preheating fuel injection ports 23 is the same as or different from the sum of the number of the screen superheaters 11 and the number of the screen reheaters 12. Alternatively, when the number of the preheating fuel injection ports 23 is different from the sum of the number of the screen superheaters 11 and the number of the screen reheaters 12, the difference is within 3.
[0049] The preheating fuel injection ports 23 are arranged at the positions of the furnace back wall 14 in an interlaced manner with the screen superheaters 11 and the screen reheaters 12, so as to prevent the flame of the preheating fuel from directly impacting the screen heating surface and causing local overheating of the heating surface.
[0050] The height of the preheating fuel injection ports 23 is leveled with the lower part of the anti-abrasion layer 111 or the anti-abrasion layer 121 of the longer one between the screen superheater 11 and the screen reheater 12, so as to avoid the flame of the preheating fuel from directly impacting the metal tube at the upper part of the screen and causing overheating of the metal tube.
[0051] In addition, when the boiler is operated at a lower load (such as 50% BMCR and below), the fuel enters the multiple fuel pre-processors 21, and after being preheated, becomes high-temperature gas-solid mixed fuel with good activity. The mixed fuel is collected from the outlets of the multiple fuel pre-processors 21 into the preheating fuel collecting tank 22, and then is injected into the furnace 1 from the preheating fuel injection ports 23. At this time, the coal feeding port 16 of the furnace 1 can be fed with a small amount of coal or stopped from feeding coal, and the heat in the furnace is partially or entirely from the heat generated by the combustion of the fuel provided by the fuel pre-processing device.
[0052] In the scheme of the utility model, the preheating fuel has good activity, and after being injected into the furnace 1, the preheating fuel quickly reacts with air at the upper part of the furnace 1, thereby increasing the flue gas temperature at the upper part of the furnace 1 and making the flue gas temperature at the furnace outlet 15 reach the temperature of the SNCR denitration reaction, improving the denitration efficiency, and reducing the emission amount of nitrogen oxides in the flue gas.
[0053] In the scheme of the utility model, the flue gas temperature at the furnace outlet 15 is increased, the convection heat exchange effect in the tail flue is enhanced, and the main steam temperature and the reheated steam temperature are both improved. In addition, the preheating fuel injection ports 23 are located at the middle and upper part of the furnace back wall 14, and the height thereof is close to the region (anti-abrasion layer) of the furnace back wall 14 where the refractory material is laid at the lower part of the screen superheater 11 and the screen reheater 12. The flame of the preheating fuel can directly heat the lower part of the screen superheater 11 and the screen reheater 12, so that the main steam temperature in the screen superheater 11 and the reheated steam temperature in the screen reheater 12 are both improved.
[0054] The furnace system of the circulating fluidized bed boiler of the utility model can obtain at least one of the following technical effects:
[0055] 1. The flue gas temperature at the furnace outlet under a low load condition is increased, the SNCR denitration efficiency at the furnace outlet is improved, the emission amount of nitrogen oxides is reduced, and the consumption of the reducing agent is reduced.
[0056] 2. Increase the main steam and reheat steam temperature at low load conditions.
[0057] While embodiments of the present application have been shown and described, it is to be understood that the embodiments described are merely divergences of the present application, and that many modifications can be made by those skilled in the art without departing from the spirit and scope of the present application, which is defined by the following claims and their equivalents.
Claims
1. A circulating fluidized bed boiler furnace system, comprising: a fuel pretreatment device; and a boiler furnace, an upper portion of a front wall of the boiler furnace is provided with a screen superheater and a screen reheater, a back wall of the boiler furnace is provided with a furnace outlet; an SNCR nozzle located at the furnace outlet for injecting a reducing agent into flue gas at the furnace outlet, characterized in that: the fuel pretreatment device comprises a plurality of preheated fuel nozzles provided at the back wall of the furnace, preheated fuel from the fuel pretreatment device is adapted to communicate with the plurality of preheated fuel nozzles, and a fuel flow from the preheated fuel nozzles is adapted to heat the screen superheater and the screen reheater.
2. The boiler furnace system according to claim 1, characterized in that: a lower portion of the screen superheater and the screen reheater is provided with a wear-resistant layer, and a height of the preheated fuel nozzles is arranged such that a flame from the preheated fuel nozzles is adapted to heat the lower portion of the screen superheater and the screen reheater.
3. The boiler furnace system according to claim 2, characterized in that: a position height of the preheated fuel nozzles is arranged to be level with a lower portion of the wear-resistant layer of a longer one of the screen superheater and the screen reheater.
4. The boiler furnace system according to claim 1, characterized in that: the preheated fuel nozzles are arranged at a middle upper portion of the back wall of the furnace, such that a flame from the preheated fuel nozzles is adapted to heat a lower portion of the screen superheater and the screen reheater.
5. The boiler furnace system according to claim 1, characterized in that: a plurality of fuel pretreatment devices are arranged at an outer side of the middle upper portion of the back wall of the furnace, preheated fuel outlets of the plurality of fuel pretreatment devices are connected with a preheated fuel header, and the preheated fuel header is located at the outer side of the middle upper portion of the back wall of the furnace, one end of the preheated fuel header is connected with the preheated fuel outlets of the plurality of fuel pretreatment devices, and the other end of the preheated fuel header is connected with the plurality of preheated fuel nozzles; or one fuel pretreatment device is arranged at the outer side of the middle upper portion of the back wall of the furnace, a preheated fuel outlet of the one fuel pretreatment device is connected with a preheated fuel header, and the preheated fuel header is located at the outer side of the middle upper portion of the back wall of the furnace, one end of the preheated fuel header is connected with the preheated fuel outlet of the one fuel pretreatment device, and the other end of the preheated fuel header is connected with the plurality of preheated fuel nozzles.
6. The boiler furnace system according to claim 5, characterized in that: the boiler furnace system further comprises a control device, and the control device is arranged such that when the boiler is operated at a load lower than 50% of a rated load of the boiler, fuel enters the fuel pretreatment device, preheated fuel generated after being pretreated enters the preheated fuel header, and the preheated fuel is injected into the furnace from the preheated fuel nozzles; and at the same time, coal feeding into the furnace from a coal feeding port of the furnace is reduced or stopped.
7. The boiler furnace system according to any one of claims 1-6, characterized in that: the plurality of screen superheaters and the plurality of screen reheaters are arranged vertically to the front wall, and each of the plurality of screen superheaters and the plurality of screen reheaters is suspended in parallel and spaced apart in a direction parallel to the front wall.
8. The boiler furnace system according to claim 7, characterized in that: the plurality of preheated fuel nozzles are arranged staggered with the screen superheaters and the screen reheaters in a direction parallel to the front wall at the back wall of the furnace.
9. The boiler furnace system of claim 7, wherein: the furnace outlet includes at least two furnace outlets disposed on the back wall of the furnace; and the plurality of preheated fuel injection ports are disposed symmetrically about a centerline of the back wall of the furnace in a plan view of the furnace.
10. The boiler furnace system of claim 7, wherein: the number of preheated fuel injection ports is the same as or different from the sum of the number of platen superheaters and the number of platen reheaters.