Flexible coal slime peak regulation device of circulating fluidized bed boiler and coal slime activating treatment method

Abstract

The invention relates to a circulating fluidized bed boiler system, comprising: a main circulating fluidized bed boiler comprising a main hearth, a main separator, a main return feeder and a flue; the activation and modification device comprises a coal slime inlet and a gas-solid fuel outlet, the coal slime is suitable for being at least partially gasified and combusted in the activation and modification device to form gas-solid fuel flowing out of the gas-solid fuel outlet, and the gas-solid fuel outlet is communicated with a fuel nozzle arranged in the main hearth. The invention further relates to a coal slime activating treatment method which comprises the following steps: at least part of coal slime is gasified and combusted in the activating and modifying device to generate gas-solid fuel; and gas-solid fuel is led to the middle lower part of the hearth of the circulating fluidized bed boiler. The scheme can be used for flexible peak regulation of the boiler.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the technical field of circulating fluidized bed boilers, and more particularly to a circulating fluidized bed boiler system and a coal slime activation treatment method. Background Art

[0002] With rising fuel costs, finding cost-effective and efficient fuel blending methods has become a research priority in the field of circulating fluidized bed boilers. Wet coal sludge, due to its low cost, offers significant cost advantages when blended in circulating fluidized bed boilers, making it a focus of attention for many power generation companies. However, the current blending method for wet coal sludge in circulating fluidized bed boilers has numerous drawbacks. Currently, the main method for combustion is pumping wet coal sludge from the top of the furnace. This method results in a very short residence time of the coal sludge in the furnace, resulting in a large amount of unburned coal sludge particles being discharged with the flue gas, resulting in a high carbon content in the fly ash and low combustion and boiler efficiency.

[0003] Wet coal slurry is pumped into the furnace from the top of the furnace, a method that is prone to fluctuations in the coal slurry supply. This unstable coal supply directly leads to large fluctuations in bed temperature, resulting in high and fluctuating NOx emissions. Furthermore, when wet coal slurry is fed into the furnace from the top, secondary air cannot effectively perform its classification function, making it difficult to control NOx emissions during the combustion process. These factors not only increase denitrification operating costs but also place significant pressure on the environment.

[0004] When a circulating fluidized bed boiler operates at different loads, the combustion characteristics of wet coal sludge present a series of problems. During high-load operation, the fine particle size of the wet coal sludge increases the amount of circulating ash, enhancing the water-cooled wall's evaporative heat absorption while reducing the heat absorption used for superheating and reheating. This ultimately leads to low main steam and reheat steam temperatures, affecting steam quality and power generation efficiency. During ultra-low load deep regulation, the low furnace bed temperature, combined with the high moisture content, high ash content, and low calorific value of the wet coal sludge, results in a slow coal sludge combustion reaction rate, difficulty in increasing load, and slow load regulation. This makes it impossible to quickly respond to the grid's load regulation requirements, making it difficult for the wet coal sludge to effectively participate in deep regulation at low loads. This severely restricts the circulating fluidized bed boiler's adaptability to grid load changes brought about by the rapid growth of renewable energy.

[0005] Specifically, the existing coal slime blending and combustion has the following technical defects:

[0006] 1) Coal slime has low cost, and co-firing in a circulating fluidized bed boiler is an effective way to reduce boiler costs. However, the current method of co-firing wet coal slime is mainly to inject it into the top of the furnace. However, this combustion method has the problems of short residence time of coal slime in the furnace, high carbon content of fly ash, and low combustion efficiency.

[0007] 2) Since the wet coal slurry is fed into the furnace for combustion by pumping from the furnace top, the coal feeding and bed temperature fluctuate greatly. At the same time, the wet coal slurry is fed into the furnace for combustion from the furnace top, and the secondary air has no classification effect. The above factors lead to high NOx emissions from coal slurry combustion.

[0008] 3) During high-load operation, due to the fine particle size of the coal slurry, the large amount of circulating ash, the strong steam heat absorption, and the weak superheating and reheating heat absorption, the main steam temperature and the reheat steam temperature are low; during ultra-low load deep regulation, due to the low boiler furnace bed temperature, the high moisture content, high ash content and low calorific value of the wet coal slurry, the coal slurry combustion reaction rate is low, the load increase is difficult, the variable load regulation speed is slow, and it is impossible to quickly respond to the variable load regulation requirements of the power grid. Under low load, the wet coal slurry cannot participate in deep regulation, making it difficult to meet the rapidly growing demand for renewable energy.

[0009] In summary, the existing method of blending wet coal sludge in circulating fluidized bed boilers has obvious deficiencies in combustion efficiency, pollutant emissions and load regulation capability. A new technical means is urgently needed to solve these problems in order to improve the fuel flexibility and operation flexibility of circulating fluidized bed boilers. Summary of the Invention

[0010] In response to at least one aspect of the above problems, the present disclosure proposes the following technical solutions.

[0011] According to one aspect of an embodiment of the present disclosure, a circulating fluidized bed boiler system is provided, comprising:

[0012] The main circulating fluidized bed boiler includes the main furnace, main separator, main return device and flue;

[0013] The activation and modification device includes a coal slime inlet and a gas-solid fuel outlet. The coal slime is suitable for at least partial gasification and combustion in the activation and modification device to form gas-solid fuel flowing out of the gas-solid fuel outlet, wherein the gas-solid fuel outlet is connected to the fuel nozzle set in the main furnace.

[0014] Optionally, the fuel nozzle includes a fuel nozzle arranged in the lower middle portion of the main furnace.

[0015] Accordingly, according to another aspect of the embodiments of the present disclosure, a method for activating coal slime is proposed, comprising the steps of:

[0016] gasifying and burning at least part of the coal sludge in an activation and modification device to generate gas-solid fuel;

[0017] The gas-solid fuel is introduced into the lower middle part of the furnace of the circulating fluidized bed boiler. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The following description and accompanying drawings may better help understand these and other features and advantages of various embodiments disclosed in the present disclosure, wherein like reference numerals denote like components throughout the drawings, wherein:

[0019] Figure 1 It is a front view of a wet coal slime circulating fluidized bed boiler in the prior art;

[0020] Figure 2 is a front view of a circulating fluidized bed boiler system according to an exemplary embodiment of the present disclosure;

[0021] Figure 3 According to an exemplary embodiment of the present disclosure Figure 2 Top view of the circulating fluidized bed boiler system in Figure 1.

[0022] 1 - Furnace; 11 - Front wall; 12 - Rear wall; 13 - Right wall; 14 - Left wall; 15 - Heating surface; 16 - High-temperature fuel nozzle; 2 - Cyclone separator; 3 - Return feeder; 4 - Coal slurry pump; 5 - Coal slurry bin; 6 - Activation and modification unit; 61 - Partition or isolation wall. A0 - Furnace primary air; A1 - Activation and modification unit fluidizing air; C - Wet coal slurry. DETAILED DESCRIPTION

[0023] The technical solution of the present disclosure will be further specifically described below through examples and in conjunction with the accompanying drawings. The following description of the embodiments of the present disclosure with reference to the accompanying drawings is intended to explain the overall inventive concept of the present disclosure and should not be understood as a limitation of the present disclosure. These are some embodiments of the invention, not all embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field fall within the scope of protection of the present disclosure.

[0024] In response to the existing problems in the co-firing of wet coal slime in a circulating fluidized bed boiler, the present disclosure makes the following innovative improvements:

[0025] First, an activation and modification unit is added before the furnace. Within this unit, the wet coal slime undergoes a complex series of physical and chemical changes, including drying, activation, and partial gasification and combustion. During the drying phase, a heating system within the unit removes a significant amount of moisture from the wet coal slime, creating favorable conditions for subsequent reactions. The activation process alters the surface structure of the coal slime particles, increasing their specific surface area and significantly enhancing their reactivity. The large amount of moisture released during the drying process reacts with the carbon in the coal slime particles circulating in the activation and modification unit at high temperatures, generating large amounts of H₂ and CO₂, which further promote and accelerate the coal slime reactions.

[0026] In addition, a partition wall is provided at the top of the activation and modification device. The wet coal slime enters the activation and modification device from the top, away from the outlet of the activation and modification device. During the falling process, the wet coal slime undergoes agglomeration, heating and drying, crushing, and a series of reaction modifications. Then, under the action of the fluidizing air at the bottom of the activation and modification device, it leaves the activation and modification device from the outlet of the activation and modification device, enters the cyclone separator and the return material device for multiple cycles, and then leaves the activation and modification device to enter the furnace for combustion. The top partition wall of the activation and modification device effectively extends the residence time of the wet coal slime in the activation and modification device, thereby enhancing the activation and modification effect of the wet coal slime. At the same time, the circulation system of the activation and modification device can fully break up the agglomerated wet coal slime, ensuring that the coal slime particles entering the furnace for combustion are evenly dispersed, thereby greatly improving the combustion efficiency of the wet coal slime. This method of fundamentally changing the combustion characteristics of wet coal slime effectively solves the problem of low coal slime combustion efficiency under the traditional furnace top pumping method.

[0027] Secondly, the atmosphere in the activation and modification device is precisely controlled. The activation and modification device is set to a strong reducing atmosphere, so that the wet coal sludge air equivalent ratio is strictly controlled within the range of 0.2-0.6. In this strong reducing atmosphere, the fuel nitrogen in the coal sludge can be directly reduced to N2, suppressing NO from the source of the reaction. x The generation of NO during coal slime combustion is greatly reduced. x Original emission concentration, this improvement measure not only solves the problem of NO x It solves the problem of difficult-to-control high emissions and reduces the denitrification operating costs of boilers under a wide load range, with significant environmental and economic benefits.

[0028] Furthermore, the activation and modification unit's air equivalence ratio precisely controls the temperature of the activation and modification unit at 800-1000°C. In this high-temperature, strongly reducing atmosphere, the large amount of water in the wet coal sludge reacts with the carbon in the sludge to form a water-gas reaction, producing large quantities of H2 and CO combustible gases. After activation and modification, the wet coal sludge is converted into high-temperature gas-solid fuel before entering the furnace for combustion, successfully overcoming the difficulty of directly co-firing wet coal sludge at low loads. High-temperature gas-solid fuel has higher reactivity and reaction speed, significantly improving the operational flexibility of wet coal sludge boiler units and enabling them to better adapt to combustion requirements under varying loads.

[0029] Finally, in response to the problem of low main steam temperature and reheat steam temperature of wet coal sludge boiler unit under low load, the present invention evenly arranges multiple high-temperature gas-solid fuel nozzles along the width of the furnace below the screen superheater and screen reheater in the middle and lower part of the furnace rear wall. This arrangement effectively reduces the evaporation heat absorption of the water-cooled wall in the lower part of the furnace, so that more heat can be used to enhance the superheat heat absorption of the superheated steam and reheated steam in the upper part of the furnace, thereby improving the steam temperature characteristics of the boiler unit under deep regulation and low load, and ensuring that the main steam temperature and reheat steam temperature can be maintained at a reasonable level during low load operation.

[0030] In summary, the present disclosure effectively solves the problems of existing wet coal slime blending technology in combustion efficiency, pollutant emissions, load regulation, etc. by activating and modifying wet coal slime before combustion and optimizing the internal structure of the furnace, thereby improving the overall performance of the circulating fluidized bed boiler.

[0031] The present invention mainly provides a circulating fluidized bed boiler wet coal slime high-temperature activation modification flexible combustion and rapid peak regulation device to solve the problems of low combustion efficiency, high NOx emissions and difficulty in deep adjustment of boilers in the existing wet coal slime blending process.

[0032] The technical solution of this disclosure is described in detail as follows:

[0033] This invention relates to a circulating fluidized bed boiler wet coal slime high temperature activation modification flexible combustion and rapid peak regulation device. The existing circulating fluidized bed boiler wet coal slime mixing combustion method is as follows Figure 1 As shown, the specific device of the first embodiment of the present disclosure is shown in Figure 2 and Figure 3 As shown, the circulating fluidized bed boiler consists of a furnace 1, a cyclone separator 2, a return feeder 3, an activation and modification device 6, a coal slurry pump 4, a coal slurry bin 5, etc. The furnace 1 is composed of a front wall 11, a rear wall 12, a right wall 13, a left wall 14, a screen heating surface 15 in the furnace and a high-temperature fuel nozzle 16. The outlet of the coal slurry pump 4 is connected to the inlet of the coal slurry bin 5, the outlet of the coal slurry bin 5 is connected to the left side of the top of the activation and modification device 6, the upper outlet of the activation and modification device 6 is connected to the high-temperature fuel nozzle 16 on the rear wall of the furnace, the bottom of the activation and modification device 6 is arranged with fluidizing air A1, the top of the activation and modification device 6 is arranged with a partition wall 61, the bottom of the furnace is arranged with primary air A0, and four high-temperature fuel nozzles are evenly distributed on the rear wall of the furnace along the width of the furnace. The high-temperature fuel nozzles are arranged on the straight section of the rear wall of the furnace after the transition between the dense phase zone and the dilute phase zone of the furnace below the screen superheater and the screen reheater. On the one hand, this ensures the uniformity of heat load distribution and temperature distribution along the width of the furnace, and on the other hand, it improves the steam temperature of the main steam and reheated steam under low load.

[0034] The wet coal slime C is first sent into the coal slime bin 5 through the coal slime pump 4, and then sent into the activation modification device from the top of the activation modification device 6 through the coal slime bin 5. In the activation modification device, it undergoes the processes of drying, activation, partial gasification and combustion in sequence. After the activation modification is completed, it becomes a high-temperature gas-solid fuel. In this process, the agglomerated wet coal slime is crushed by the activation modification circulation system, and the modification effect is ensured by atmosphere control and temperature control. The high-temperature gas-solid fuel is sent into the four high-temperature fuel nozzles on the rear wall of the furnace through a conveying pipeline and evenly sprayed into the furnace for combustion. During the combustion process, according to the boiler load and steam temperature, the fuel flow rate of the nozzle and the operating parameters of the activation modification device are adjusted to achieve efficient combustion of the wet coal slime and low NO xEmissions and rapid peak regulation ensure stable operation of the boiler under different loads.

[0035] The wet coal slime high temperature fuel nozzles 16 can also be evenly distributed along the rear wall of the furnace below the platen superheater and platen reheater, with two nozzles, or evenly distributed on the left and right side walls of the furnace, or evenly distributed on the front wall of the furnace with 1-4 nozzles. The specific number and position of the nozzles are determined according to the actual situation of the boiler site.

[0036] In the present disclosure, the extension length of the isolation wall or partition 61 in the height direction of the activation and modification furnace is 5% to 15% of the height of the activation and modification furnace; and / or the isolation wall or partition 61 is located in the middle position of the activation and modification furnace in the direction perpendicular to the front and rear walls of the activation and modification furnace.

[0037] In the present disclosure, the moisture content of the coal slime is within the range of 15% to 40%, the ash content is within the range of 15% to 45%, and the calorific value is within the range of 800 to 4000 kcal / kg.

[0038] In the present disclosure, unless expressly stated otherwise, each numerical range includes the endpoints and may be the median, one-third, or two-thirds of the numerical range.

[0039] Based on the above technical solution, at least one of the following technical effects can be achieved:

[0040] 1) In terms of improving combustion efficiency, after the wet coal slime is activated and modified by the activation and modification device, it enters the furnace from multiple nozzles in the lower middle part of the rear wall of the furnace for combustion. In addition, a partition wall is set at the top of the activation and modification device to effectively extend the residence time of the wet coal slime in the activation and modification device to enhance the activation and modification effect of the wet coal slime. On the one hand, the activation and modification increases the temperature of the fuel coal slime, increases the specific surface area of the coal slime, and enhances the reaction activity. This series of changes significantly accelerates the combustion reaction rate. On the other hand, the position where the wet coal slime is fed into the furnace is changed from the top of the furnace to the lower middle part of the furnace, which greatly extends the residence time of the coal slime in the furnace. The synergistic effect of these two aspects significantly reduces the carbon content of the fly ash from the combustion of wet coal slime. The reduction in the carbon content of the fly ash means that more coal slime is fully burned and energy is used more efficiently, thereby significantly improving the efficiency of the boiler.

[0041] 2) In terms of environmental protection benefits, the fuel volatile nitrogen in the wet coal slime is directly converted into nitrogen under the strong reducing atmosphere of the activation and modification device. This process greatly reduces the NO x Original emission concentration. Compared with the traditional wet coal slime furnace top combustion method, it significantly reduces NO x The original emission concentration effectively solved the difficult problem of high NOx emission from wet coal slime furnace top combustion, and the lower NO xEmissions not only reduce pollution to the atmospheric environment and help improve air quality, but also reduce the denitrification operating costs of the boiler under a wide load.

[0042] 3) In terms of load regulation flexibility, the wet coal sludge is activated and modified by an activation and modification device before entering the furnace for combustion, transforming the fuel properties from room-temperature solid fuel to high-temperature gas-solid fuel. Furthermore, the moisture in the wet coal sludge participates in the water-gas reaction in the high-temperature reducing atmosphere, producing large amounts of combustible gases H2 and CO. After the high-temperature gas-solid fuel is sprayed into the furnace, it undergoes a rapid combustion reaction upon encountering air. This rapid reaction characteristic significantly enhances the reactivity and flexibility of the coal sludge, allowing the boiler to respond more quickly to the load regulation needs of the power grid. Whether it is the need to quickly increase output at high loads or the need for stable combustion and rapid load adjustment at low loads, this device enables the boiler to quickly adapt to changes, effectively enhancing the boiler's variable load capacity, ensuring the stability and reliability of power supply, and meeting the needs of frequent changes in power grid load brought about by the rapid growth of renewable energy.

[0043] 4) To increase steam temperature at low loads, multiple high-temperature gas-solid fuel nozzles are evenly arranged along the width of the furnace, below the platen superheater and platen reheater in the lower middle section of the furnace rear wall. This successfully addresses the problem of low main steam and reheat steam temperatures during deep regulation and low load. During low-load operation, the high-temperature fuel nozzles absorb heat from the platen superheater and platen reheater, replenishing the heat within the furnace and optimizing heat distribution within the furnace. Stable main steam and reheat steam temperatures ensure steam quality, promote stable operation of equipment such as the steam turbine, extend equipment service life, reduce equipment failures and maintenance costs caused by abnormal steam temperatures, and further enhance the reliability and economy of the entire power generation system.

[0044] In summary, the present disclosure improves the performance of circulating fluidized bed boilers when using wet coal sludge for combustion from multiple key aspects, achieving multiple goals of efficient combustion, environmental protection and emission reduction, and flexible peak regulation, providing strong support for the power industry in comprehensive energy utilization and responding to the challenges of renewable energy development.

[0045] It should be noted that, in the present disclosure, although the activation and modification device is described by taking a circulating fluidized bed as a specific example, the activation and modification device is not limited thereto, as long as it can achieve activation and modification of coal slime.

[0046] It should be pointed out that, in the present disclosure, the top of the activation and modification furnace includes the furnace roof, and may also include the top position of the furnace side wall, all of which are within the protection scope of the present disclosure.

[0047] In the present disclosure, the isolation wall serves to prolong the residence time of the coal slime in the activation and modification device. More specifically, the extension length of the isolation wall in the height direction of the activation and modification furnace is 5% to 15% of the height of the activation and modification furnace; and / or the isolation wall is located in the middle position of the activation and modification furnace in the direction perpendicular to the front and rear walls of the activation and modification furnace.

[0048] In the present disclosure, the coal slurry has a moisture content of 15% to 40%, an ash content of 15% to 45%, and a calorific value of 800 to 4000 kcal / kg. It should also be noted that any fuel that is suitable for co-firing, including coal slurry, is within the aforementioned ranges, regardless of the coal slurry content.

[0049] Based on the above, the present disclosure proposes the following technical solutions:

[0050] 1. A circulating fluidized bed boiler system, comprising:

[0051] The main circulating fluidized bed boiler includes the main furnace, main separator, main return device and flue;

[0052] The activation and modification device includes a coal slime inlet and a gas-solid fuel outlet. The coal slime is suitable for at least partial gasification and combustion in the activation and modification device to form gas-solid fuel flowing out of the gas-solid fuel outlet, wherein the gas-solid fuel outlet is connected to the fuel nozzle set in the main furnace.

[0053] 2. The circulating fluidized bed boiler system according to item 1, wherein:

[0054] The fuel nozzles include fuel nozzles arranged in the middle and lower part of the main furnace.

[0055] 3. The circulating fluidized bed boiler system according to item 1, wherein:

[0056] A platen heat exchanger is provided on the front wall of the main furnace, and the fuel nozzles include rear wall fuel nozzles provided on the rear wall of the main furnace below the platen heat exchanger.

[0057] 4. The circulating fluidized bed boiler system according to item 3, wherein:

[0058] The rear wall fuel nozzle is arranged at the straight section after the transition between the dense phase area and the dilute phase area of the furnace below the platen heat exchanger.

[0059] 5. The circulating fluidized bed boiler system according to item 1, wherein:

[0060] The fuel nozzles include a plurality of rear wall fuel nozzles evenly arranged on the rear wall of the main furnace; and / or

[0061] The fuel nozzle includes a side wall fuel nozzle or a plurality of side wall fuel nozzles arranged evenly on the left and right side walls of the main furnace; and / or

[0062] The fuel nozzles include one front wall fuel nozzle provided on the front wall of the main furnace or a plurality of front wall fuel nozzles arranged evenly.

[0063] 6. The circulating fluidized bed boiler system according to any one of 1 to 5, wherein:

[0064] The activation and modification device is a circulating fluidized bed activation and modification device, comprising an activation and modification furnace, a preheating separator and a preheating return device, wherein the gas-solid outlet of the preheating separator constitutes the gas-solid fuel outlet;

[0065] The bottom of the activation and modification furnace is provided with fluidizing air, and the top of the activation and modification furnace is provided with the coal slime inlet on a side away from the preheating separator.

[0066] 7. The circulating fluidized bed boiler system according to item 6, wherein:

[0067] The top of the activation and modification furnace is provided with an isolation wall extending from the top to the bottom of the furnace to divide the top of the activation and modification furnace into front and back sides, wherein the coal slime inlet is provided on the front side, and the rear side is communicated with the inlet of the preheating separator.

[0068] 8. The circulating fluidized bed boiler system according to item 7, wherein:

[0069] The extension length of the isolation wall in the height direction of the activation and modification furnace is 5% to 15% of the height of the activation and modification furnace; and / or

[0070] The separation wall is located in the middle of the activation and modification furnace in a direction perpendicular to the front and rear walls of the activation and modification furnace.

[0071] 9. The circulating fluidized bed boiler system according to item 6, wherein:

[0072] The activation and modification device is configured to: control the coal slime-air equivalence ratio in the activation and modification furnace within the range of 0.2-0.6; and / or control the temperature in the activation and modification furnace within the range of 800-1000°C.

[0073] 10. The circulating fluidized bed boiler system according to item 1, wherein:

[0074] The moisture content of the coal slime is within the range of 15% to 40%, the ash content is within the range of 15% to 45%, and the calorific value is within the range of 800 to 4000 kcal / kg.

[0075] 11. A method for activating coal slime, comprising the steps of:

[0076] gasifying and burning at least part of the coal sludge in an activation and modification device to generate gas-solid fuel;

[0077] The gas-solid fuel is introduced into the lower middle part of the furnace of the circulating fluidized bed boiler.

[0078] 12. The method according to 11, comprising the steps of:

[0079] Gasifying and burning at least part of the coal slurry in an activation and modification device to generate a gas-solid fuel at a temperature in the range of 800-1000° C.; and / or

[0080] The coal slime-air equivalent ratio in the activation and modification device is controlled within the range of 0.2-0.6.

[0081] 13. The method for activating coal slime according to item 11 or 12, wherein:

[0082] The coal slime activation treatment method treats coal slime in a circulating fluidized bed boiler system according to any one of 1-10.

[0083] While embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A circulating fluidized bed boiler system, comprising: The main circulating fluidized bed boiler includes the main furnace, main separator, main return device and flue; The activation and modification device includes a coal slime inlet and a gas-solid fuel outlet. The coal slime is suitable for at least partial gasification and combustion in the activation and modification device to form gas-solid fuel flowing out of the gas-solid fuel outlet, wherein the gas-solid fuel outlet is connected to the fuel nozzle set in the main furnace.

2. The circulating fluidized bed boiler system according to claim 1, wherein: The fuel nozzles include fuel nozzles arranged in the middle and lower part of the main furnace.

3. The circulating fluidized bed boiler system according to claim 1, wherein: A platen heat exchanger is provided on the front wall of the main furnace, and the fuel nozzles include rear wall fuel nozzles provided on the rear wall of the main furnace below the platen heat exchanger.

4. The circulating fluidized bed boiler system according to claim 3, wherein: The rear wall fuel nozzle is arranged at the straight section after the transition between the dense phase area and the dilute phase area of the furnace below the platen heat exchanger.

5. The circulating fluidized bed boiler system according to claim 1, wherein: The fuel nozzles include a plurality of rear wall fuel nozzles evenly arranged on the rear wall of the main furnace; and / or The fuel nozzle includes a side wall fuel nozzle or a plurality of side wall fuel nozzles arranged evenly on the left and right side walls of the main furnace; and / or The fuel nozzles include one front wall fuel nozzle provided on the front wall of the main furnace or a plurality of front wall fuel nozzles arranged evenly.

6. The circulating fluidized bed boiler system according to any one of claims 1 to 5, wherein: The activation and modification device is a circulating fluidized bed activation and modification device, comprising an activation and modification furnace, an activation and modification separator, and an activation and modification return device, wherein the gas-solid outlet of the activation and modification separator constitutes the gas-solid fuel outlet; The bottom of the activation and modification furnace is provided with fluidizing air, and the coal slime inlet is provided on the side of the top of the activation and modification furnace away from the activation and modification separator.

7. The circulating fluidized bed boiler system according to claim 6, wherein: The top of the activation and modification furnace is provided with an isolation wall extending from the top to the bottom of the furnace to divide the top of the activation and modification furnace into front and back sides, wherein the coal slime inlet is provided on the front side, and the rear side is communicated with the inlet of the preheating separator.

8. The circulating fluidized bed boiler system according to claim 7, wherein: The extension length of the isolation wall in the height direction of the activation and modification furnace is 5% to 15% of the height of the activation and modification furnace; and / or The separation wall is located in the middle of the activation and modification furnace in a direction perpendicular to the front and rear walls of the activation and modification furnace.

9. The circulating fluidized bed boiler system according to claim 6, wherein: The activation and modification device is configured to: control the coal slime-air equivalence ratio in the activation and modification furnace within the range of 0.2-0.6; and / or control the temperature in the activation and modification furnace within the range of 800-1000°C.

10. The circulating fluidized bed boiler system according to claim 1, wherein: The moisture content of the coal slime is within the range of 15% to 40%, the ash content is within the range of 15% to 45%, and the calorific value is within the range of 800 to 4000 kcal / kg.

11. A method for activating coal slime, comprising the steps of: gasifying and burning at least part of the coal sludge in an activation and modification device to generate gas-solid fuel; The gas-solid fuel is introduced into the lower middle part of the furnace of the circulating fluidized bed boiler.

12. The method according to claim 11, comprising the steps of: At least partially gasifying and burning the coal sludge in an activation and modification device to generate a gas-solid fuel having a temperature in the range of 800-1000° C.; and / or The coal slime-air equivalent ratio in the activation and modification device is controlled within the range of 0.2 to 0.

6.

13. The method for activating coal slime according to claim 11 or 12, wherein: The coal slime activation treatment method is used to treat coal slime in a circulating fluidized bed boiler system according to any one of claims 1 to 10.

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