A circulating fluidized bed boiler cold water up water system and method

Abstract

The application discloses a circulating fluidized bed boiler cold water up water system and method, including fixed exhaust header, water wall, denitration dilution water tank, economizer and cold water branch system; the first valve and the second valve are sequentially arranged on the water inlet pipeline of the denitration dilution water tank; the third valve, the fourth valve and the fifth valve are sequentially connected in series in the cold water branch system; one end of the cold water branch system is communicated between the first valve and the second valve, and the other end is communicated to the fixed exhaust header; the cold water branch system is configured to: in the cold furnace state, the second valve is closed, the first valve and the valves of the cold water branch system are opened, the desalted water enters the water wall and the economizer through the fixed exhaust header at the same time, a double-path up water channel is formed, and the boiler cold-state normal-temperature up water is realized.The application has the advantages that the core pipeline layout of the original process is not changed, the basic framework of the cold furnace cold water up water is built from the source, and the original valve is used to realize the flexible switching of the cold water up water path and the original desalted water path.

Description

Technical Field

[0001] This invention belongs to the field of boiler operation and energy-saving technology, specifically relating to a circulating fluidized bed boiler cold water supply system and method. Background Technology

[0002] The coal gasification operation unit's thermal power plant is equipped with multiple high-temperature, high-pressure circulating fluidized bed boilers, most commonly three high-temperature, high-pressure circulating fluidized bed boilers, operating in a two-on-one-standby mode. In existing technology, the water replenishment process during normal boiler operation and the water supply process when the boiler is shut down share the same hot water supply process. The specific operation method of this process is as follows: the demineralized water at room temperature is pressurized to a certain pressure value by the demineralized water pump and then preheated in three ways. One way is heated to above 100°C by the heat exchanger of the conversion device and directly enters the deaerator. The other two ways are first heated to a certain temperature by the steam turbine steam seal heater and the sampling cooling heat exchanger. Then, one way enters the denitrification dilution water tank, and the other way is further heated to about 80~90°C by the boiler slag cooler heat exchanger (the specific temperature is related to the circulating fluidized bed boiler model) and then merges into the deaerator. The demineralized water completes thermal deoxygenation in the deaerator. After the temperature rises to the saturation temperature under the corresponding working pressure of the deaerator and the deoxygenation is qualified, it is pressurized by the high-pressure boiler feed water pump and delivered to the boiler feed water platform, which is finally used to make up water for the boiler or to supply water to the shut-down boiler.

[0003] The existing hot water supply process described above, when supplying water to a normally operating hot boiler, ensures that the high-temperature feedwater matches the boiler's hot operating conditions and, after being heated by the economizer, can smoothly enter the boiler drum, meeting the needs of hot water supply. However, in practical applications, this process has significant shortcomings in adaptability to different boiler operating conditions. Especially when one or two boilers are operating normally, the deaerator is in operation, and water needs to be supplied to a shut-down cold boiler, continuing to use this hot water supply process will cause a series of serious problems. This severely restricts the safe, stable, and long-term operation of the boiler equipment, while also affecting production progress, increasing energy consumption, and raising equipment maintenance costs. Specific problems are as follows:

[0004] ① It is easy to cause water hammer and damage to equipment: When the demineralized water completes thermal deoxygenation in the deaerator, the water will be heated to more than 100°C. At this time, after the high temperature and high pressure feedwater enters the cold boiler economizer and supporting pipelines, the water vaporizes instantly due to the sudden temperature difference, forming a vapor-liquid two-phase flow, which causes a violent water hammer phenomenon. This has a strong impact on components such as economizer and pipeline welds, which greatly reduces the service life of the equipment.

[0005] ② High energy consumption of equipment operation, increasing operating costs: In the existing water supply process, the high-pressure boiler feed pump for pressurizing the water supply is equipped with a 10KV high-voltage motor. The equipment consumes a lot of electricity. The high-pressure feed pump is still used under cold boiler water supply conditions, resulting in ineffective energy consumption and increasing the electricity cost of production and operation.

[0006] ③ The temperature difference of the steam drum wall exceeds the standard, and there is a contradiction between the water supply efficiency and equipment protection: When the high-temperature feedwater is supplied to the cold boiler, if the water supply speed is too fast, it will cause a large temperature difference in the steam drum wall. In actual operation, the highest temperature difference is close to 50℃, which exceeds the temperature difference standard for safe operation of the boiler and seriously affects the service life of the steam drum. In order to control the temperature difference of the steam drum wall within the qualified range, it is necessary to use a small bypass for feedwater supply, which greatly slows down the water supply speed. Not only is the water supply efficiency extremely low, but it will also directly delay the start-up progress of the shut-down boiler, which will have an adverse impact on the production plan of the thermal power plant.

[0007] ④ Accelerates wear and tear on equipment components and increases maintenance costs: During the slow water supply process, the valve core of the water supply regulating valve is in a low flow regulation state for a long time. It is subjected to continuous water flow, which accelerates the wear and tear of components, leading to an increase in the frequency of equipment maintenance and further increasing the maintenance and operation costs of the equipment.

[0008] Based on the problems encountered in actual production and application, the existing hot water filling process requires several hours to complete the filling of a single boiler when the boiler is in a cold state, and is accompanied by problems such as water hammer, high energy consumption, and excessive temperature difference of the steam drum wall.

[0009] Patent No. CN115183230A discloses a cold-start water supply system for a circulating fluidized bed boiler in a power plant. This system introduces condensate from the condensate storage tank into a fixed-discharge collection tank via a condensate transfer pump, and then completes the cold-start boiler water supply through the boiler water-cooled wall drain pipes. This avoids direct connection between the water supply system and the high-pressure feedwater system, solving the problems of high maintenance workload and safety accidents caused by high-pressure feedwater leakage due to frequent disassembly and reassembly of detachable short pipes in traditional water supply methods. It achieves system safety improvements and simplified operation and maintenance for cold-start water supply. However, this invention only optimizes the system from the operational and maintenance perspective of cold-start boiler water supply. It still cannot solve the problems of water hammer, high energy consumption, and excessive temperature difference in the steam drum wall caused by high-temperature feedwater during cold boiler water supply, nor can it solve the hidden dangers of oxygen corrosion and high-pressure-to-low-pressure leakage caused by direct cold water supply.

[0010] Currently, the existing technology for water supply systems of circulating fluidized bed boilers still generally adopts a hot water supply process that combines cold and hot operating conditions, which cannot solve the technical problems such as water hammer, high energy consumption, and low efficiency caused by hot water supply to cold boilers. Summary of the Invention

[0011] This invention addresses the problems of high energy consumption and low efficiency in existing circulating fluidized bed boiler water supply systems.

[0012] The present invention solves the above-mentioned technical problems through the following technical means: A circulating fluidized bed boiler cold water supply system includes a fixed discharge manifold, water-cooled walls, a denitrification dilution water tank, a downcomer, an economizer, and a cold water branch system. The inlet pipe of the denitrification dilution water tank is sequentially equipped with a first valve and a second valve along the flow direction of the denitrified water. The cold water branch system includes a third valve, a fourth valve, and a fifth valve connected in series along the flow direction of the medium. One end of the cold water branch system is connected to the pipe section between the first and second valves, and the other end is connected to the fixed discharge manifold in the boiler's 0.00 layer process area. The fixed discharge manifold is connected to the water-cooled walls, the downcomer, and the economizer inlet pipe, and the economizer outlet is connected to the steam drum. The cold water branch system is configured such that, in a cold boiler state, the second valve is closed, and the first valve and all valves in the cold water branch system are opened, allowing ambient temperature denitrified water to simultaneously enter the water-cooled walls and the economizer through the fixed discharge manifold, forming a dual-parallel water supply channel to achieve cold-state low-pressure ambient temperature water supply to the boiler.

[0013] By retaining the original boiler's fixed-flow header and economizer, and through a minimally simplistic modification involving the addition of a cold water branch system, a cold water supply path for ambient temperature demineralized water bypassing the high-temperature deaerator was achieved. This approach did not alter the core pipeline layout of the original process, yet it established the basic framework for cold water supply to the cold boiler from the source. Simultaneously, the branch was connected between the two valves of the denitrification dilution water tank, allowing for flexible switching between the cold water supply path and the original demineralized water path using the existing valves. This system design is innovative, practical, and feasible, with low modification costs and strong pipeline adaptability.

[0014] Preferably, it also includes a hydrazine deoxygenation device, which is installed on the original sampling cooler inlet header of the circulating fluidized bed boiler.

[0015] The addition of a hydrazine deoxygenation device and its precise placement on the main water supply pipe of the sampling cooler effectively solves the oxygen corrosion problem of direct supply of demineralized water at room temperature, fills the equipment protection loopholes for cold water supply, eliminates the need for new independent deoxygenation pipelines, and achieves chemical deoxygenation solely through the existing main pipe, thus balancing protection and the simplicity of pipeline modification.

[0016] Preferably, the fixed discharge header is connected to the water-cooled wall and the economizer through the original boiler fixed discharge valve and economizer drain valve of the circulating fluidized bed boiler.

[0017] Preferably, the system is suitable for either a one-on-one standby circulating fluidized bed boiler operation mode or a multi-on-one standby circulating fluidized bed boiler operation mode.

[0018] Preferably, the newly added branch system includes multiple sets, with one set configured for each boiler.

[0019] Each boiler is equipped with a separate cold water branch system to achieve independent control of cold water supply for a single boiler. This system is compatible with the "one on, one on standby" or "multiple on, one on standby" operation modes of multiple boilers. When a single boiler is supplying water, it does not interfere with the normal operation of other boilers, greatly improving the system's operational flexibility and adaptability.

[0020] Preferably, the water supply to the cold water branch system comes from the inlet end of the original slag cooler of the circulating fluidized bed boiler.

[0021] Preferably, the newly added branch system further includes a discharge valve, which is installed between the fourth valve and the fifth valve.

[0022] Preferably, the fourth and fifth valves are high-pressure valves.

[0023] By setting the fourth and fifth valves as high-pressure valves, and combining them with the intermediate discharge valve, a double protective structure is formed to prevent high-pressure from entering low-pressure water supply pipes. This completely avoids the safety hazard of high-pressure media entering low-pressure demineralized water main pipes and ensures the pressure safety of the original demineralized water system and cold water supply system.

[0024] Preferably, the present invention also provides a circulating fluidized bed boiler cooling water supply process using any of the above-described circulating fluidized bed boiler cooling water supply systems, comprising the following steps: S1. Confirm that the shut-down cold boiler is a boiler waiting to be filled with water, close the second valve of the electric valve of the denitrification dilution water tank, and open the first valve; S2. Simultaneously start the hydrazine deoxygenation device and add hydrazine deoxygenating agent to the demineralized water for chemical deoxygenation; S3. Sequentially open the third, fourth and fifth valves of the newly added branch system to allow the ambient temperature demineralized water in the demineralized water header to enter the fixed discharge manifold through the denitrification dilution water tank and the newly added branch system. S4. Open the boiler drain valve and economizer drain valve to allow the demineralized water to enter the boiler water-cooled wall and economizer simultaneously through the boiler drain header, thus completing the cold water supply operation.

[0025] Preferably, after the water supply operation is completed, the fifth valve, the fourth valve, the third valve, the boiler blowdown valve, the economizer drain valve, and the hydrazine deaerator are closed in sequence, and the second valve of the electric valve of the denitrification dilution water tank is restored to the open state, so that the boiler internal pipelines are restored to the original process flow direction.

[0026] The advantages of this invention are: (1) Increased equipment safety factor: The entire process is protected from both the source and the supporting design. The use of room temperature demineralized water to replace high temperature feedwater fundamentally eliminates water hammer and avoids damage to economizers, pipelines and other equipment. The addition of a hydrazine deoxygenation device solves the oxygen corrosion problem of direct cold water supply and ensures the service life of boiler tubes. The installation of high pressure valves and valve discharge valves forms a double protection against high pressure and low pressure, and avoids various process and equipment safety hazards in the process of cold water supply. (2) Low renovation cost: The boiler is modified in a very simple way based on the existing fixed-flow header, economizer, demineralized water pump and other equipment and pipelines. Only simple components such as cold water branch system and hydrazine deoxygenation device are added. No other equipment is needed. The water supply power can be directly reused from the original demineralized water pump. This not only greatly reduces the economic cost of equipment purchase and pipeline modification, but also avoids changes to the original core layout of the process. The construction period is short and the industrial implementation is easy. (3) High water supply efficiency and low energy consumption: Through the dual water supply design of connecting the water-cooled wall and the economizer with the fixed discharge header, the demineralized water can be supplied to the two core components at the same time, which greatly improves the water supply rate compared with the traditional single water supply. At the same time, the low-pressure demineralized water pump replaces the high-pressure boiler feed pump, which greatly reduces the water supply power consumption. This not only greatly shortens the water supply time of a single boiler, saving valuable time for emergency boiler start-up, but also achieves energy saving and consumption reduction, taking into account both production efficiency and operational economy. (4) Strong adaptability: The system is designed to be configured with an independent new branch for each boiler, which can realize independent control of water supply for a single boiler. It is also compatible with the mainstream operating modes of circulating fluidized bed boilers on the market, such as one-on-one standby and multiple-on-one standby. It can be adapted to circulating fluidized bed boilers of different scales and different steam requirements for coal gasification, thermal power, chemical industry, etc. The technical solution has strong versatility and wide application scenarios. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall process flow of the circulating fluidized bed boiler cooling water supply system before modification, according to the first embodiment of the present invention. Figure 2 This is a schematic diagram of the modification principle of the circulating fluidized bed boiler cooling water supply system according to the first embodiment of the present invention; Figure 3 This is a detailed schematic diagram of the overall principle of the modified circulating fluidized bed boiler cooling water supply system according to the first embodiment of the present invention. Figure 4 This is a detailed schematic diagram of boiler A after the modification of the circulating fluidized bed boiler cold water supply system according to the first embodiment of the present invention.

[0028] In the picture: 1. Desalination system; 11. Desalinated water tank; 12. Desalinated water pump; 2. Preheating system; 21. Shift converter heat exchanger; 22. Sampling cooler; 23. Steam seal heater; 24. Slag cooler; 3. Deoxygenation system; 4. High-pressure feed water delivery system; 41. High-pressure boiler feed water pump; 42. Boiler feed water platform; 43. Economizer; 5. Boiler system; 51. Boiler; 51A. Boiler A; 51B. Boiler B; 51C. Boiler C; 52. Downcomer, water wall lower header; 6. Denitration dilution water tank; 61. First valve; 62. Second valve; 7. Cold water branch system; 71. Third valve; 72. Fourth valve; 73. Fifth valve; 8. Hydrazine deoxygenation device; 9. Regular blowdown header; 10. Water wall. Specific implementation manners

[0029] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0030] Embodiment 1: Refer to Figure 1 , this embodiment is described by taking the most common 3 sets of 150t / h high-temperature and high-pressure circulating fluidized bed boilers on the market as an example.

[0031] For the 3×150t / h high-temperature and high-pressure circulating fluidized bed boilers supporting the thermoelectric device in the coal gasification operation department, the core operation mode of two running and one standby is adopted daily. Relying on a unified hot water feeding and water replenishing system to complete the water replenishing operation for the running boilers and the water feeding operation for the standby boilers out of service. The operation process of the whole system is centered around three core links: desalted water preheating, thermal deoxygenation, and high-pressure feed water delivery. To better understand the optimization solution of this application, the cold water feeding system of the traditional circulating fluidized bed boiler will be described first.

[0032] The overall operation mode of the traditional circulating fluidized bed boiler cold water feeding system is as follows: Refer to Figure 1 , the normal-temperature desalted water is the water source of the system. The water source in the desalted water tank 11 is pressurized to 1 MPa by the desalted water pump 12 and then divided into three paths to enter the preheating system 2. After completing the gradient temperature rise, they converge and enter the deoxygenation system 3 (i.e., the deaerator). After thermal deoxygenation, it is pressurized and delivered to the boiler feed water platform 42 by the high-pressure boiler feed water pump 41, and then after passing through the economizer 43, it provides high-temperature water replenishment for two running boilers 51. The water feeding operation for the standby boilers out of service also follows this whole process. The specific pipeline routing and operation logic are as follows: ① Demineralized water waste heat preheating stage: The waste heat preheating process for demineralized water includes three branches. The first branch: the demineralized water is heated to 110°C by the heat exchanger 21 of the shift converter and directly enters the deoxygenation system 3. The second and third branches: the demineralized water is heated to 50°C by the steam seal heater 23 and the sampling cooler 22, respectively, and then the branches are combined and then split. One of the branches enters the denitrification dilution water tank 6. Figure 1 In the diagram, only the inlet path of the denitrification dilution water tank is shown, not the outlet path. This is a standard simplified representation of the process system diagram. The outlet water of the denitrification dilution water tank is mainly connected to the denitrification system for reducing agent dilution. Its outlet path belongs to the denitrification process system and is unrelated to the boiler feedwater and cold furnace water supply process. Therefore, it is not shown in the boiler feedwater system diagram. Another path is heated to 80~90℃ by the boiler slag cooler 24 and finally flows into the deaeration system 3.

[0033] ② Thermal deoxygenation stage: After being preheated through multiple paths, the demineralized water undergoes high-pressure thermal deoxygenation in the deoxygenation system 3. Once the temperature reaches 158°C and the deoxygenation is qualified, it is stored in the deaerator in preparation for boiler feedwater. ③ High-pressure water supply stage: The deoxygenated, high-temperature demineralized water is pressurized to 13-14 MPa by the high-pressure boiler feedwater pump 41 and transported to the boiler feedwater platform 42. After passing through the economizer 43, it enters the boiler drum and finally supplies water to the core heating surfaces such as the furnace water-cooled walls, completing the normal boiler makeup water process. This completes the water supply process.

[0034] When the boiler is shut down and needs to be filled with water, no pipeline adjustment is required. The hot water at 158℃ and 13~14MPa is directly transported to the standby boiler through the boiler feedwater platform 42 via the above-mentioned high temperature and high pressure water supply process, and the water supply is completed along the economizer → steam drum → water-cooled wall.

[0035] When the entire system was initially started up (all three boilers were shut down and the deaerator was not in operation), the demineralized water was directly fed into the system at room temperature via the aforementioned path due to the lack of preheating and the deaerator not being operational, and no operational problems were initially observed. However, during the normal operating condition of two boilers running and one boiler on standby, the cold-state water supply to the shut-down standby boiler still reused the high-temperature and high-pressure feedwater process, which caused numerous problems in actual use, including: ① Water hammer occurred in the economizer and pipelines, causing equipment leakage and damage: When the high-temperature and high-pressure hot water at 158℃ enters the economizer 43 and its supporting pipelines in the cold standby state, the water vaporizes instantly due to the drastic temperature difference between the cold equipment and the high-temperature feedwater, forming a vapor-liquid two-phase flow, which causes a strong water hammer phenomenon in the pipeline and economizer 43. The impact force generated by the water hammer continuously impacts the pipeline welds and economizer heat exchange tubes, significantly reducing the service life of the equipment.

[0036] ② The high power consumption of the high-pressure water pump increases operating costs: In this embodiment, the high-pressure boiler feed pump 41 is equipped with a 10KV high-voltage motor. Its original design purpose is to meet the pressure requirements of high-temperature and high-pressure water replenishment of the operating boiler. However, when the boiler is cold, the high-pressure boiler feed pump 41 still needs to be turned on throughout the process. Compared with the actual pressure requirements of the boiler when it is cold, there is a serious mismatch, resulting in ineffective consumption of electrical energy and significantly increasing the operating cost of the boiler water supply process.

[0037] ③ The temperature difference of the steam drum wall exceeds the standard, and there is a contradiction between water supply efficiency and equipment protection: When high-temperature hot water enters the cold steam drum, the temperature difference between the inner and outer walls of the steam drum reaches nearly 50°C, far exceeding the temperature difference standard for safe boiler operation, which directly affects the service life of the steam drum. In order to control the wall temperature difference within the acceptable range, in actual use, only a small bypass of the feedwater can be used to reduce the water flow rate to 5~15t / h. This results in a water supply time of 3~4 hours for a single cold boiler, with extremely low water supply efficiency, which seriously delays the boiler start-up progress and adversely affects the production continuity of the unit in the two-operation-one-standby mode.

[0038] ④ The continuous flushing of the water supply regulating valve core accelerates the wear and tear of equipment components. When the boiler is filled with water, the water supply regulating valve is kept in a small opening state for a long time to control the flow and temperature. The high temperature and high pressure water flow continuously washes the valve core at a high velocity, which greatly accelerates the wear rate of the valve core. This not only increases the frequency of inspection and maintenance of the regulating valve and the maintenance cost, but also easily causes pipeline leakage due to the decline in the sealing performance of the valve core, further increasing the safety hazards of system operation.

[0039] The above problems are all caused by the inherent defects of sharing a single water supply system for both hot and cold conditions under the traditional operating mode, which has become the core issue restricting the safe, stable, and long-term operation of the 3×150t / h circulating fluidized bed boiler.

[0040] See Figure 2, in this application, for a 3×150t / h high-temperature and high-pressure circulating fluidized bed boiler operating in the "two running and one standby" mode (it can also be a high-temperature and high-pressure circulating fluidized bed boiler of other models or operating modes with one running and one standby or multiple running and one standby), the traditional high-temperature and high-pressure feed water system shared by cold and hot working conditions leads to technical problems such as water hammer, high energy consumption, and excessive temperature difference of the steam drum wall during cold furnace water filling. Based on the above problems, this embodiment provides a cold water filling system for a circulating fluidized bed boiler. The core of it is: taking the demineralized water main pipe at the inlet of the slag cooler 24 as the water source connection point for cold water filling, and leading a branch from this connection point and introducing it into the downcomer and the lower header 52 of the water wall. This connection point is the front-end node where demineralized water enters the deaeration system 3. The demineralized water remains at normal temperature (about 50°C), and with the help of the original demineralized water pump 11, a stable pressure of 1MPa is achieved, which not only ensures the water temperature requirement for cold water filling but also realizes the efficient reuse of the original equipment and pipelines. By using this set of cold water filling system, the entire process system of the original demineralized water preheating, high-pressure thermal deaeration, and high-pressure feed water delivery can be completely retained.

[0041] Specifically, referring to Figure 3 , the cold water filling system for a circulating fluidized bed boiler specifically includes a denitration dilution water tank 6, a cold water branch system 7, a regular blowdown header 9, and an economizer 43. Among them, the cold water branch system 7 includes three sets (the actual number of sets matches the number of boilers), which are adapted to each boiler and have the same configuration method. For the convenience of description, in this embodiment, boiler A is used as the description object.

[0042] Specifically, referring to Figure 4 , the denitration dilution water tank 6 is an original equipment of the denitration system supporting a 3×l50t / h high-temperature and high-pressure circulating fluidized bed boiler. It is an atmospheric-pressure closed water storage equipment supporting the denitration system. Its original function is to store demineralized water, provide a stable water source for denitration reductant dilution, and buffer the pressure fluctuation of the demineralized water main pipe. It includes a first valve 61 and a second valve 62. In this application, its body structure and original function are not changed. Only through pipeline connection and valve switching, it is used as a path switching node for cold water filling to realize the function reuse of the original equipment, providing normal-temperature and low-pressure demineralized water for cold water filling and flexible pipeline switching guarantee.

[0043] Referring to Figure 2 and Figure 4 , in this embodiment, the inlet section of the slag cooler 24 is used as the connection point, and a water filling branch is led from this section and connected to the inlet pipeline of the denitration dilution water tank 6, and two control valves, namely the first valve 61 and the second valve 62, are connected in series. After the branch is led, it does not affect the normal water supply of the main pipe to other process units, realizing the dual reuse of the original conveying function and the cold water filling water source function.

[0044] Specifically, referring to Figure 4, the cold water branch system 7 is an independent controllable pipeline system newly added on the basis of the original process pipeline in this application to realize the special cold water feeding for the cold boiler. The input end of the cold water branch system 7 is connected to the water inlet pipeline of the denitration dilution water tank 6, at the pipe section between the first valve 61 and the second valve 62; the output end is directly connected to the boiler regular blowdown header 9, forming a completely independent cold water dedicated conveying channel from the traditional high-temperature and high-pressure feed water system. The main body of the cold water branch system 7 is successively connected in series with a third valve 71, a fourth valve 72, and a fifth valve 73. Through the opening and closing cooperation of each valve, the on-off and shutdown control of the branch are realized. The cold water branch system 7 can be independently configured for each boiler, and the newly added branches of each boiler do not interfere with each other. The water feeding operation is only for the corresponding standby boiler that is out of service, without affecting the normal heating of the operating boiler and the original process flow of the whole plant's demineralized water and denitration system, truly realizing the system separation and independent operation of cold furnace cold water feeding and hot state high-temperature water replenishment.

[0045] Specifically, refer to Figure 4 , the regular blowdown header 9 is the core component of the original regular blowdown system supporting a 3×150t / h high-temperature and high-pressure circulating fluidized bed boiler. This application does not make any changes to its body structure, and only incorporates it into the cold water feeding process by adding a new cold water branch system 7, enabling it to have both the original regular blowdown and the new cold furnace cold water feeding functions. The regular blowdown header 9 as a whole includes the regular blowdown header body, the original connecting pipeline, and the supporting valves. Among them, the regular blowdown header body is the original pressure-bearing metal header of the boiler, arranged in the process area of the 0.00 layer at the bottom of the boiler. Each boiler corresponds to an independent regular blowdown header 9, and the regular blowdown headers 9 of each boiler are independent of each other, enabling separate operations of single-boiler blowdown and water feeding, without interfering with the normal operation of other boilers, meeting the requirements of independent water feeding for each single cold standby boiler in this application.

[0046] The regular blowdown header body is connected to the core heating surface of the boiler and the end equipment of the blowdown through the original fixed pipelines. This application directly reuses this part of the pipelines as the conveying path for cold water feeding, without adding any boiler body pipelines. Specifically, the regular blowdown header is directly connected to the lower header of the boiler water wall through the original pipeline, which is the core medium connection point for the regular blowdown of the water wall 10 and the water feeding path for normal-temperature demineralized water to enter the water wall 10 in this application; the regular blowdown header 9 is also connected to the economizer water inlet valve through the original pipeline, and then connected to the economizer inlet through this valve, forming a pipeline connection with the economizer 43, which becomes the water feeding path for normal-temperature demineralized water to enter the economizer 43 in this application; the regular blowdown header 9 is also connected to the boiler regular blowdown flash tank through the original blowdown pipeline, and this path is in a closed state during the cold water feeding process and does not participate in the water feeding process.

[0047] The supporting valves of the regular blowdown header system include the boiler regular blowdown valve, which is installed on the original pipeline between the regular blowdown header 9 and the lower header of the water wall. This valve is opened during the cold water filling of this application to enable the delivery of normal-temperature demineralized water from the regular blowdown header 9 to the water wall 10. It also includes the economizer downcomer valve, which is installed on the original pipeline between the regular blowdown header 9 and the inlet of the economizer 43. This valve is opened during the cold water filling of this application to enable the delivery of normal-temperature demineralized water from the regular blowdown header 9 to the economizer 43. It further includes the total blowdown valve, which is installed on the original pipeline between the regular blowdown header 9 and the regular blowdown flash tank. It is the original regular blowdown master control valve. This valve is closed during the cold water filling of this application to block the flow of cold water to the blowdown flash tank and ensure that all cold water enters the boiler heating surface. When not using cold water filling, the valves of the newly added cold water branch system 7 are in the closed state, and the regular blowdown header 9 resumes its original function. By opening the boiler regular blowdown valve, the economizer downcomer valve, and the total blowdown valve, the boiler water in the water wall and the economizer is regularly discharged to reduce the salt content of the boiler water and remove impurities in the furnace, ensuring the quality of the boiler steam-water. The blowdown medium finally enters the regular blowdown flash tank for flash evaporation treatment. When it is necessary to fill water into the standby boiler, when the valves of the newly added cold water branch system 7 are in the open state, the total blowdown valve is closed, and the boiler regular blowdown valve and the economizer downcomer valve are opened. After the normal-temperature demineralized water of the newly added cold water branch system 7 enters the regular blowdown header 9, it is delivered to the water wall 10 and the economizer 43 simultaneously through the boiler regular blowdown valve and the economizer downcomer valve via the original pipeline, achieving dual-path synchronous water filling. Finally, the two paths of cold water converge and enter the boiler steam drum to complete the cold boiler water filling process.

[0048] Embodiment 2: Based on Embodiment 1, this embodiment only optimizes the newly added branch system, and no changes are made to other components.

[0049] To enhance the operation safety, a drain valve 74 is installed between the fourth valve 72 and the fifth valve 73. The use of the drain valve can drain the accumulated water and residual pressure in the branch of the cold water branch system 7 during shutdown or maintenance, avoiding pipe pressure buildup or liquid corrosion. At the same time, the fourth valve 72 and the fifth valve 73 adopt high-pressure grade valves, which can effectively prevent the high-pressure medium on the boiler body side from reversely flowing into the low-pressure demineralized water header pipe, ensuring the safe and stable operation of the original demineralized water system.

[0050] Embodiment 3: This embodiment adds a chemical deoxygenation device, specifically a hydrazine deoxygenation device 8, based on Embodiment 1. The hydrazine deoxygenation device 8 is a chemical deoxygenation equipment added in this application to prevent oxygen corrosion during cold boiler water filling. It is installed on the inlet water header of the sampling cooler 22 and connected to the demineralized water header, without occupying additional space or affecting the original pipeline layout. The device mainly includes a reagent storage unit, a metering and dosing unit, and a control unit, internally storing hydrazine deoxygenating agent. During cold boiler water filling, the device can automatically or manually add a measured amount of hydrazine agent according to the water flow rate, ensuring thorough mixing with the demineralized water. The hydrazine reacts chemically with dissolved oxygen in the water, reducing and removing the dissolved oxygen, thereby lowering the oxygen concentration of the demineralized water. This prevents oxygen corrosion of pressure-bearing metal components such as the water-cooled wall 10, economizer 43, and steam drum from directly entering the boiler at room temperature, ensuring the structural safety and service life of the boiler equipment during cold water filling and subsequent operation.

[0051] Example 4: Based on Embodiments 1, 2, and 3, this embodiment will clearly demonstrate the method of using this application, including the following steps: S1. Confirm that the shut-down cold boiler is a boiler waiting to be filled with water, close the second valve of the electric valve of the denitrification dilution water tank, and open the first valve; S2. Simultaneously start the hydrazine deoxygenation device and add hydrazine deoxygenating agent to the demineralized water for chemical deoxygenation; S3. Sequentially open the third, fourth and fifth valves of the newly added branch system to allow the ambient temperature demineralized water in the demineralized water header to enter the fixed discharge manifold through the denitrification dilution water tank and the newly added branch system. S4. Open the boiler drain valve and economizer drain valve to allow the demineralized water to enter the boiler water-cooled wall and economizer simultaneously through the boiler drain header, thus completing the cold water supply operation.

[0052] See Figure 3 and Figure 4 This embodiment describes the process using boiler A as a standby boiler and boilers B and C as boilers in normal use. If boiler B or boiler C is a standby boiler, the operating method is exactly the same.

[0053] Step S1 involves the following steps: First, confirm that the boiler currently awaiting water supply (i.e., boiler A) is a shut-down, cold-state boiler, while other boilers (i.e., boilers B and C) are in normal operation, ensuring the overall system meets the cold-state water supply requirements. Then, switch the state of the inlet valve of the denitrification dilution water tank 6: close the second valve 62 of the denitrification dilution water tank and simultaneously open the first valve 61. This operation prevents the ambient temperature denitrified water from the demineralized water main branch from entering the denitrification dilution water tank 6, instead trapping it in the pipe section between the first valve 61 and the second valve 62, thus preparing the path for subsequent flow into the newly added cold water branch system 7 and the cold water supply to the boiler manifold 9. The entire process does not affect the normal operation of the denitrification system, nor does it interfere with the demineralized water main's water supply to other process units.

[0054] The specific process of step S2 includes: while opening the cold water delivery branch, simultaneously starting the hydrazine deoxygenation device 8 installed on the inlet water header of the sampling cooler to perform online chemical deoxygenation treatment on the room temperature demineralized water in the pipeline. By adding hydrazine deoxygenating agent, the dissolved oxygen content in the demineralized water is reduced, avoiding oxygen corrosion of metal components such as the water-cooled wall 10, economizer 43, and steam drum after the room temperature demineralized water directly enters the boiler heating surface, ensuring the structural safety of the boiler body during cold water filling and subsequent heating process, and extending the service life of the equipment.

[0055] The specific process of step S3 includes: after completing the path switching and starting the hydrazine deaerator 8, the third valve 71, the fourth valve 72, and the fifth valve 73 in the newly added cold water branch system 7 are opened in sequence, allowing the ambient temperature demineralized water remaining between the first valve 61 and the second valve 62 to enter the boiler blowdown header 9 along the newly added cold water branch system 7. At this time, the demineralized water is continuously and stably transported under the pressure provided by the original demineralized water pump, and the entire branch forms a smooth dedicated cold water channel, providing a stable water source and pressure guarantee for the subsequent dual-line water supply to the water-cooled wall 10 and the economizer 43.

[0056] The specific process of step S4 includes: after the ambient temperature demineralized water is stably transported to the fixed discharge manifold 9 via the newly added cold water branch system 7, the boiler fixed discharge valve and economizer drain valve of the boiler fixed discharge manifold 9 are opened simultaneously, and the main drain valve of the fixed discharge manifold 9 leading to the fixed discharge expansion tank is closed to block the flow of cold water to the drain end. At this time, the ambient temperature demineralized water entering the fixed discharge manifold 9 achieves dual-path synchronous water supply through the original connecting pipeline between the fixed discharge manifold 9 and the boiler body: one path enters the water-cooled wall 10 through the boiler fixed discharge valve, and the other path enters the economizer 43 through the economizer drain valve. The two cold water paths flow along their respective original pipelines and finally merge into the steam drum, completing the medium distribution and transportation of cold boiler water supply. During the water supply process, the flow rate of cold water can be controlled by adjusting the valve opening of the newly added cold water branch system 7, ensuring uniform and stable water supply and avoiding excessive temperature difference of the steam drum wall due to excessive flow. At the same time, the high-pressure feed water pump does not need to be used throughout the process, balancing water supply efficiency and equipment safety, and without interfering with the normal operation of other boilers.

[0057] Once the boiler drum water level reaches the set cold boiler water supply level, the cold water supply operation is complete, followed by system reset and operational restoration. First, valves 73 (fifth), 72 (fourth), and 71 (third) in the newly added cold water branch system 7 are closed sequentially, cutting off the flow of demineralized water to the blowdown manifold 9. Then, the boiler blowdown valves and economizer drain valves are closed, restoring the blowdown manifold 9 to its normal standby state. Simultaneously, the hydrazine deoxygenation unit 8 is stopped, ending the chemical deoxygenation dosing operation. Finally, valve 62 in the inlet pipe of the denitrification dilution water tank 6 is opened, restoring valves 61 and 62 to their fully open state, allowing the demineralized water main to resume normal water supply to the denitrification dilution water tank 6, and the entire demineralized water system returns to its original process flow. At this point, the dedicated cold boiler water supply branch is completely decommissioned, the boiler remains in a full, static state, and can be switched to ignition and heating or standby maintenance at any time. The entire process does not affect the normal operation of other operating boilers and the denitrification and demineralized water systems within the unit.

[0058] The system has proven effective in practical use. Specifically, the entire process of filling a traditional boiler with cold water takes approximately 3-4 hours and consumes no less than 2000 kWh of electricity, with water hammer occurring during the process. However, with the system described in this application, the entire process of filling a boiler of the same specifications with cold water takes approximately 1.5-2 hours and consumes approximately 100 kWh of electricity, with no water hammer occurring.

[0059] The circulating fluidized bed boiler cooling water supply system and method provided in this application have the following beneficial effects: (1) Increased equipment safety factor: The entire process is protected from both the source and the supporting design. The use of room temperature demineralized water to replace high temperature feedwater fundamentally eliminates water hammer and avoids damage to economizer 43, pipelines and other equipment. The addition of hydrazine deoxygenation device 8 solves the oxygen corrosion problem of direct cold water supply and ensures the service life of boiler tubes. The installation of high pressure valves and valve discharge valves forms a double protection against high pressure and low pressure, and avoids various process and equipment safety hazards in the process of cold water supply. (2) Low renovation cost: The boiler is modified in a very simple way based on the existing fixed-flow header 9, economizer 43, demineralized water pump 12 and other equipment and pipelines. Only simple components such as the newly added cold water branch system 7 and hydrazine deoxygenation device 8 are added. No other equipment is needed. The water supply power can be directly reused from the original demineralized water pump 12. This not only greatly reduces the economic cost of equipment procurement and pipeline modification, but also avoids changes to the original core process layout. The construction period is short and the industrial implementation is easy. (3) High water supply efficiency and low energy consumption: Through the dual water supply design of the fixed discharge header 9 connecting the water-cooled wall 10 and the economizer 43, the demineralized water can be supplied to the two core components at the same time, which greatly improves the water supply rate compared with the traditional single water supply. At the same time, relying on the low-pressure demineralized water pump 12 to replace the high-pressure boiler feed pump 41, the power consumption of water supply is greatly reduced. This not only greatly shortens the water supply time of a single boiler, but also saves valuable time for emergency boiler start-up, and achieves energy saving and consumption reduction, taking into account both production efficiency and operational economy. (4) Strong adaptability: The system is designed to configure an independent new cold water branch system 7 for each boiler 51, which can realize independent control of water supply for a single boiler. It is also compatible with the mainstream operating modes of circulating fluidized bed boilers on the market, such as one-on-one standby and multiple-on-one standby. It can be adapted to circulating fluidized bed boilers of different scales and steam requirements for coal gasification, thermal power, chemical industry, etc. The technical solution has strong versatility and wide application scenarios.

[0060] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Terms such as "upper," "lower," "left," "right," "front," and "rear" used in the invention are merely for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A circulating fluidized bed boiler cold water up water system comprising a fixed header, a downcomer, a water wall, a denitration dilution water tank and an economizer, characterized in that, It also includes a cold water branch system; the inlet pipe of the denitrification dilution water tank is equipped with a first valve and a second valve in sequence along the flow direction of the denitrified water; the cold water branch system includes a third valve, a fourth valve and a fifth valve connected in series along the flow direction of the medium; one end of the cold water branch system is connected to the pipe section between the first valve and the second valve, and the other end is connected to the fixed discharge header of the boiler's 0.00 layer process area; the fixed discharge header is connected to the water-cooled wall, the downcomer and the economizer inlet pipe respectively, and the economizer outlet is connected to the steam drum; the cold water branch system is configured such that, in the cold boiler state, the second valve is closed and the first valve and all valves of the cold water branch system are opened, so that the ambient temperature denitrified water enters the water-cooled wall and the economizer simultaneously through the fixed discharge header, forming a dual parallel water supply channel to realize cold low-pressure ambient temperature water supply to the boiler.

2. The circulating fluidized bed boiler cooling water supply system according to claim 1, characterized in that, It also includes a hydrazine deoxygenation device, which is installed on the original sampling cooler inlet header of the circulating fluidized bed boiler.

3. The circulating fluidized bed boiler cooling water supply system according to claim 1, characterized in that, The fixed discharge header is connected to the water-cooled wall and the economizer through the original boiler fixed discharge valve and economizer drain valve of the circulating fluidized bed boiler.

4. A cold water up water system for a circulating fluidized bed boiler according to claim 1, characterized in that, The system is suitable for either a one-on-one standby circulating fluidized bed boiler operation mode or a multi-on-one standby circulating fluidized bed boiler operation mode.

5. A cold water up water system for a circulating fluidized bed boiler as defined in claim 1, characterized in that The cold water branch system comprises multiple sets, with one set configured for each boiler.

6. A cold water up water system for a circulating fluidized bed boiler according to claim 5, characterized in that The water supply to the cold water branch system comes from the inlet of the original slag cooler of the circulating fluidized bed boiler.

7. A cold water up water system for a circulating fluidized bed boiler according to claim 5, characterized in that The cold water branch system also includes a drain valve, which is installed between the fourth valve and the fifth valve.

8. A circulating fluidized bed boiler cooling water supply system according to claim 7, characterized in that, The fourth and fifth valves are high-pressure valves.

9. A circulating fluidized bed boiler cooling water supply process based on the circulating fluidized bed boiler cooling water supply system according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Confirm that the shut-down cold boiler is a boiler waiting to be filled with water, close the second valve of the electric valve of the denitrification dilution water tank, and open the first valve; S2. Simultaneously start the hydrazine deoxygenation device and add hydrazine deoxygenating agent to the demineralized water for chemical deoxygenation; S3. Sequentially open the third, fourth and fifth valves of the newly added branch system to allow the ambient temperature demineralized water in the demineralized water header to enter the fixed discharge manifold through the denitrification dilution water tank and the newly added branch system. S4. Open the boiler drain valve and economizer drain valve to allow the demineralized water to enter the boiler water-cooled wall and economizer simultaneously through the boiler drain header, thus completing the cold water supply operation.

10. A cold water up water process for a circulating fluidized bed boiler according to claim 9, characterized in that, After the water filling operation is completed, close the fifth valve, fourth valve, third valve, boiler blowdown valve, economizer drain valve and hydrazine deaerator in sequence, and restore the second valve of the electric valve of the denitrification dilution water tank to the open state, so that the boiler pipeline can be restored to the original process flow direction.

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