Circulating fluidized bed boiler feed water optimization system and method

Abstract

The invention discloses a circulating fluidized bed boiler water supply optimization method and system, and belongs to the technical field of boiler energy conservation. The system mainly comprises a condensate water tank, a demineralized water tank, a slag cooler, a deoxygenization water tank, a condensate water pump, a demineralized water pump, a plate heat exchanger, a reverse osmosis membrane group, a demineralized water buffer tank and the like. The principle of'condensate water priority 'is adopted, the supply amount of condensate water is preferentially adjusted according to the liquid level of the deoxygenated water tank through the intelligent control unit, and the insufficient part is supplemented by demineralized water; the demineralized water subjected to heat exchange by the slag cooler is intelligently distributed to a demineralized water tank, a condensation water tank or a deoxygenization water tank according to the water outlet temperature; the plate heat exchanger can preheat reverse osmosis inlet water by adopting a desalting water mode or a steam mode; the demineralized water buffer tank effectively inhibits water impact. Dynamic balance and heat energy gradient utilization of steam condensate water and demineralized water are achieved, the problems of water tank overflow and energy waste are effectively solved, and the economical efficiency and stability of boiler operation are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of boiler energy-saving technology, specifically to a circulating fluidized bed boiler feedwater optimization system and method. Background Technology

[0002] Circulating fluidized bed boiler combustion technology is widely used in industrial enterprises due to its advantages such as wide fuel adaptability and low pollution emissions. Under the overall trend of energy conservation and consumption reduction, improving the thermal efficiency of boiler systems has become a continuous pursuit for those skilled in the art. Currently, a common energy-saving method is to return the condensate generated after the externally supplied steam is used to the boiler system for reuse as feedwater, in order to recover its moisture and contained heat.

[0003] In a typical circulating fluidized bed boiler feedwater system, the feedwater mainly comes from two sources: one part is the recycled steam condensate mentioned above, and the other part is demineralized water prepared by the boiler water treatment system to replenish system losses. In engineering practice, the usual practice is to first exchange heat with the high-temperature slag discharged from the slag cooler to absorb the residual heat in the slag before sending it to the boiler's deaerator tank; at the same time, the recycled steam condensate is pressurized by a condensate pump and directly sent to the deaerator tank.

[0004] However, the applicant discovered that the existing water supply system configuration and operation mode have obvious technical defects, mainly in the following aspects: The system faces a water balance challenge: the return volume of steam condensate depends on the steam usage of external users, resulting in fluctuating and unstable flow rates; while the flow rate of demineralized water after heat exchange in the slag cooler is related to the boiler ash discharge conditions. These two water flows converge at the deaerator tank, lacking an effective coordinated control mechanism. When the condensate return volume is large, if the demineralized water replenishment volume is not reduced accordingly, the deaerator tank level is prone to overflow, leading to a direct waste of high-quality condensate and heat. Conversely, when the condensate return volume is insufficient, if the demineralized water replenishment is not timely, it may threaten the safe operation of the boiler.

[0005] Insufficient energy utilization: Existing systems often directly send the demineralized water, heated to a higher temperature by the slag cooler, into the deoxygenated water tank. However, under certain operating conditions, its temperature may exceed the system's requirements, and this portion of heat energy is not further utilized in a cascade manner. Furthermore, to ensure the normal operation of the reverse osmosis membrane module under low-temperature conditions such as winter, additional self-generated steam is typically required to heat the feed water, increasing operating energy consumption and failing to achieve optimal integration of waste heat within the system.

[0006] Inflexible operation mode switching: When the cold slag machine needs to switch from parallel operation mode to series operation mode, or when the reverse osmosis membrane module produces water intermittently, it will generate a large flow or liquid level impact on the demineralized water system. The existing system lacks effective buffering and fine adjustment means, which can easily disrupt the stable balance of the entire water supply system.

[0007] Therefore, the lack of linkage and optimized configuration between the steam condensate and demineralized water subsystems in existing technologies leads to waste of both water and heat, as well as system instability. There is an urgent need for a circulating fluidized bed boiler feedwater optimization method that can intelligently coordinate the two water sources, achieve on-demand heat distribution, and ensure long-term stable system operation. Summary of the Invention

[0008] The purpose of this invention is to provide a circulating fluidized bed boiler feedwater optimization system and method to solve the problem mentioned in the background art of the lack of a circulating fluidized bed boiler feedwater optimization method that can intelligently coordinate two water sources, realize on-demand heat distribution, and ensure long-term stable operation of the system.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A circulating fluidized bed boiler feedwater optimization system includes: The condensate tank unit is used to receive and store steam condensate returned from the outside; The demineralized water tank unit is used to store demineralized water prepared by the water treatment system. A deoxygenated water tank is used to receive and mix the makeup water from the condensate tank unit and the demineralized water tank unit. The slag cooler unit, comprising multiple slag coolers, is used to cool the hot slag discharged from the boiler using demineralized water. Plate heat exchangers and reverse osmosis membrane modules; plate heat exchangers are used to preheat the raw water entering the reverse osmosis membrane modules. The demineralized water buffer tank and demineralized water buffer pump are installed between the reverse osmosis membrane module and the demineralized water tank unit; The condensate delivery pipeline connects the condensate tank unit and the deoxygenated water tank, and a condensate pump is installed on the pipeline. The demineralized water delivery pipeline connects the demineralized water tank unit, the slag cooler unit, the plate heat exchanger, and the deoxygenated water tank. A demineralized water pump is installed on the pipeline. In addition, the control unit is interlocked with the level gauge, thermometer, pressure transmitter, flow meter, electric valve and water pump in the system to implement the "condensate priority" water supply strategy, dynamically adjust the water flow of each path and maintain the water balance of the system.

[0010] Furthermore, the outlet water pipes of the slag cooler unit are divided into at least three lines: The first reuse pipeline is connected to the demineralized water tank unit, which is equipped with a first electric switch valve. The second transfer pipeline is connected to the condensate tank unit and is equipped with an electric regulating valve; The third direct pipeline is connected to the deoxygenated water tank and is equipped with a second electric switch valve. The control unit is configured to control the opening and closing of the first electric switching valve and the electric regulating valve based on the reading of the thermometer installed at the outlet of the cold slag machine unit, so as to guide the demineralized water in different temperature ranges to different destinations.

[0011] Furthermore, multiple slag coolers in the slag cooler unit are configured through pipelines and valves, enabling them to switch between series and parallel modes; In series mode, multiple slag coolers are connected in sequence, and the demineralized water is heat-exchanged in stages. The control unit performs diversion control according to the final effluent temperature. In parallel mode, each slag cooler operates independently in parallel, and its effluent is directly sent to the deaerator water tank through the third direct delivery pipeline.

[0012] Furthermore, plate heat exchangers have two heating modes: Demineralized water heat exchange mode: The heat medium comes from the demineralized water in the demineralized water tank unit and is controlled by the fourth electric switch valve; Steam-assisted heating mode: The heat medium comes from the boiler's own steam and is controlled by a second electric regulating valve; The control unit is configured to switch or combine the two heating modes according to the season or raw water temperature requirements.

[0013] Furthermore, the demineralized water buffer tank is equipped with a level gauge, and the control unit is configured to control the start and stop of the reverse osmosis membrane module according to the signal from the level gauge; the demineralized water buffer pump runs continuously, and its outlet pipeline is equipped with an electric regulating valve interlocked with the control unit. The opening degree of the electric regulating valve is controlled by feedback from the level gauge on the demineralized water tank unit.

[0014] Furthermore, both the condensate tank unit and the demineralized water tank unit include at least two tanks connected in parallel via a bottom connecting valve, and each tank is independently equipped with a level gauge to enhance the system's redundancy and water storage regulation capabilities.

[0015] Furthermore, the condensate delivery pipeline is equipped with a third electric regulating valve for adjusting the flow rate and a flow meter for monitoring; the demineralized water tank unit is equipped with a thermometer, and the control unit triggers an alarm when the water temperature exceeds the set value.

[0016] A method for optimizing feedwater in a circulating fluidized bed boiler, characterized by comprising the following steps: Step S1: Prioritize sending steam condensate to the deoxygenated water tank via a condensate pump; Step S2: Divide the demineralized water into two parts: one part is sent to the slag cooler unit to cool the hot slag, and the other part is sent to the plate heat exchanger to preheat the feed water of the reverse osmosis membrane module. Step S3: Monitor the outlet water temperature of the slag cooler unit, and dynamically distribute the demineralized water after heat exchange to the demineralized water tank, condensate tank or deoxygenated water tank according to the temperature value. Step S4: Water is smoothly replenished to the demineralized water tank unit through the demineralized water buffer tank and buffer pump, and the operation of the reverse osmosis membrane module is controlled by the liquid level interlock.

[0017] Furthermore, in winter or low-temperature conditions, when the demineralized water heat exchange mode cannot meet the feed water temperature requirements of the reverse osmosis membrane module, it will automatically start or switch to steam-assisted heating mode to ensure the stability of preheating.

[0018] The "condensate priority" principle is implemented through the following control logic: The target liquid level of the deoxygenated water tank (4) is set as follows: The real-time liquid level is L; the control unit calculates the real-time water replenishment amount of the deoxygenated water tank. The calculation formula is as follows:

[0019] in, The proportional coefficient is used; the control unit prioritizes adjusting the flow rate of the condensate pump (5). To meet The demand, that is ; When the condensate pump reaches its maximum output And there is still a need for water replenishment (i.e.) > ), control unit according to difference To adjust the amount of desalinated water replenished.

[0020] Compared with the prior art, the beneficial effects of the present invention are: (1) Significantly improve economic efficiency and achieve energy saving and consumption reduction: This invention adheres to the principle of "condensate priority" and uses high-quality steam condensate as the primary source of boiler feedwater, maximizing the recovery of its moisture and waste heat, and directly reducing the self-use steam consumption required for reheating the feedwater in the deaerator tank. At the same time, through system optimization, it achieves efficient recovery and cascade utilization of heat from the slag cooler, and innovatively adopts dual-mode preheating to ensure low-temperature operation of the reverse osmosis unit, reducing external energy input from multiple dimensions and significantly improving the overall economic efficiency of boiler operation; (2) Intelligent balanced water supply system to eliminate resource waste: By introducing intelligent control logic based on feedback from multiple parameters such as liquid level, temperature, and flow rate, this invention dynamically and accurately adjusts the replenishment ratio and flow direction of the steam condensate and demineralized water sources. This system can effectively cope with fluctuations in condensate return water volume and changes in the operating mode of the slag cooler, fundamentally solving the problem of overflow of the deaerator tank or forced discharge of steam condensate caused by water volume mismatch, realizing the full utilization of water resources and ensuring stable system operation; (3) Enhance system robustness and ensure stable operation: By setting up a demineralized water buffer tank and matching pump set between the reverse osmosis membrane module and the demineralized water tank, the flow and level shocks caused by the intermittent water production of the reverse osmosis unit to the main feedwater system are effectively mitigated. This design, combined with the redundant arrangement of the water tank unit and the flexible pipeline switching capability, gives the system stronger anti-interference capability and adaptability, and can cope with abnormal operating conditions such as equipment failure, thereby ensuring the long-term, continuous and stable operation of the circulating fluidized bed boiler feedwater system. Attached Figure Description

[0021] Figure 1 This is an overall architecture diagram of a circulating fluidized bed boiler feedwater optimization system according to the present invention; Explanation of reference numerals in the attached figures: First condensate tank 11; Second condensate tank 12; Demineralized water tank 2; First slag cooler 31; Second slag cooler 32; Third slag cooler 33; Deoxygenated water tank 4; First condensate pump 51; Second condensate pump 52; First demineralized water pump 61; Second demineralized water pump 62; Plate heat exchanger 7; Reverse osmosis membrane module 8; First thermometer 91; Second thermometer 92; Third thermometer 93; Fourth thermometer 94; First magnetic level gauge 101; Second magnetic level gauge 102; First electric regulating valve 111; Second electric regulating valve 112; Third electric regulating valve 113; Fourth electric regulating valve 114; First electric switch valve 121; Second electric switch valve 122; Third electric switch valve 123; Fourth electric switch valve 124; Fifth electric switch valve 125; Sixth electric switch valve 126; First flow meter 131; Second flow meter 132; Third flow meter 133; Fourth flow meter 134; First check valve 141; Second check valve 142; Third check valve 143; Fourth check valve 144; Fifth check valve 145; Sixth check valve 146; Seventh check valve 147; Eighth check valve 148; Gate valve 15; Demineralized water buffer tank 16; First pressure transmitter 171; Second pressure transmitter 172; Third pressure transmitter 173; Fourth pressure transmitter 174; Demineralized water buffer pump 18. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings. This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operation processes, but the scope of protection of the present invention is not limited to the following embodiments.

[0024] like Figure 1 As shown in the figure, the circulating fluidized bed boiler feedwater optimization system provided in this embodiment mainly includes a first condensate tank 11, a second condensate tank 12, a demineralized water tank 2, a first slag cooler 31, a second slag cooler 32, a third slag cooler 33, a deoxygenated water tank 4, a first condensate pump 51, a second condensate pump 52, a first demineralized water pump 61, a second demineralized water pump 62, a plate heat exchanger 7, a reverse osmosis membrane module 8, a demineralized water buffer tank 16, and a demineralized water buffer pump 18.

[0025] The bottoms of the first condensate tank 11 and the second condensate tank 12 are connected by a gate valve 15, forming a condensate tank unit. A first magnetic level gauge 101 is installed on the first condensate tank 11, and a second magnetic level gauge 102 is installed on the second condensate tank 12. Externally returned steam condensate enters the condensate tank unit through a pipe equipped with a first electric switch valve 121.

[0026] The demineralized water tank 2 is equipped with a third magnetic level gauge 103 and a first thermometer 91. A first electric regulating valve 111 is installed on the inlet pipe of the demineralized water tank 2 for receiving demineralized water from the demineralized water buffer pump 18.

[0027] The inlets of both the first condensate pump 51 and the second condensate pump 52 are connected to the condensate tank unit via gate valve 15, and their outlets are connected to the condensate delivery main pipe via gate valve 15 and check valves (the outlet of the first condensate pump 51 is the fourth check valve 144, and the outlet of the second condensate pump 52 is the fifth check valve 145). A first pressure transmitter 171, a third electric regulating valve 113, and a third flow meter 133 are sequentially installed on this main pipe, which ultimately connects to the deoxygenated water tank 4. The deoxygenated water tank 4 is equipped with a fourth magnetic level gauge 104 and a fifth magnetic level gauge 105.

[0028] The inlets of both the first demineralized water pump 61 and the second demineralized water pump 62 are connected to the demineralized water tank 2 via gate valve 15, and their outlets are connected to the demineralized water delivery main pipe via gate valve 15 and check valves (the outlet of the first demineralized water pump 61 is the second check valve 142, and the outlet of the second demineralized water pump 62 is the third check valve 143). A second pressure transmitter 172 is installed on this main pipe, which then splits into two paths: One branch flows to plate heat exchanger 7: This branch is equipped with a fourth electric switch valve 124 and a gate valve 15. After the demineralized water exchanges heat with the raw water in the plate heat exchanger 7, it returns to the demineralized water tank 2.

[0029] Another path flows to the slag cooler unit: this branch first passes through a gate valve 15, and then through the sixth electric switching valve 126 to achieve series / parallel mode switching.

[0030] Specific working principle: Series operation mode of slag coolers: Close the inlet and outlet gate valves 15 of the first slag cooler 31, the second slag cooler 32, and the third slag cooler 33, and open the sixth electric switch valve 126. Demineralized water flows sequentially through the first slag cooler 31, the second slag cooler 32, and the third slag cooler 33 for series heat exchange. A third pressure transmitter 173 and a third thermometer 93 are installed on the outlet main pipe of the third slag cooler 33.

[0031] When the temperature detected by the third thermometer 93 is below 60℃, the second electric switch valve 122 is opened, and the demineralized water after heat exchange returns to the demineralized water tank 2 for reuse via the second flow meter 132 and the first check valve 141.

[0032] When the value detected by the third thermometer 93 is higher than 60℃, the second electric switch valve 122 is closed and the second electric regulating valve 112 is opened. The high-temperature demineralized water is sent to the first condensate tank 11 and / or the second condensate tank 12 via the first flow meter 131.

[0033] When the condensate system malfunctions, the second electric switch valve 122 and the second electric regulating valve 112 are closed, and the third electric switch valve 123 is opened. The heated demineralized water then enters the deoxygenated water tank 4 directly through the seventh check valve 147.

[0034] Parallel operation mode of slag coolers: Close the sixth electric switch valve 126 and open the inlet and outlet gate valves 15 of the first slag cooler 31, the second slag cooler 32, and the third slag cooler 33. Demineralized water flows into the three slag coolers in parallel, and after heat exchange, it merges and is directly sent to the deaerator water tank 4 via the fourth pressure transmitter 174, the fourth thermometer 94, the gate valve 15, and the sixth check valve 146 on the parallel outlet main pipe.

[0035] Reverse osmosis water production and buffering system: After the initial heat treatment, the water enters the reverse osmosis membrane module 8, and the resulting demineralized water is sent to the demineralized water buffer tank 16. The demineralized water buffer tank 16 is equipped with a sixth magnetic level gauge 106. Its effluent is pumped by the demineralized water buffer pump 18, passes through the gate valve 15 and the eighth check valve 148, and then enters the demineralized water tank 2 via the first electric regulating valve 111. The demineralized water buffer pump 18 operates continuously, and the opening of the first electric regulating valve 111 is controlled by feedback from the third magnetic level gauge 103 to maintain a stable water level in the demineralized water tank 2.

[0036] Plate heat exchanger with steam-assisted heating: A steam auxiliary pipeline from the boiler's own steam is also provided on the heat source side of the plate heat exchanger 7. A gate valve 15 and a fourth electric regulating valve 114 are installed on this pipeline. When the first thermometer 91 shows that the demineralized water temperature is insufficient in winter, the fourth electric regulating valve 114 can be opened to supplement the heating of the raw water with steam.

[0037] The control logic of the system described in this invention includes the acquisition of signals from various level gauges, thermometers, pressure transmitters, and flow meters, as well as the linkage control of various electric regulating valves, electric switching valves, and water pumps. All of these are executed by the control unit (not shown in the figure) in the system, thereby realizing the automatic optimization management of "condensate priority" and system water balance.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A circulating fluidized bed boiler feedwater optimization system, characterized in that, include: Condensate tank unit (1) is used to receive and store steam condensate returned from outside; Demineralized water tank unit (2) is used to store demineralized water prepared by the water treatment system; Deoxygenated water tank (4) is used to receive and mix the makeup water from the condensate tank unit and the demineralized water tank unit; The slag cooler unit (3) includes multiple slag coolers for using demineralized water to cool the hot slag discharged from the boiler. Plate heat exchanger (7) and reverse osmosis membrane module (8), wherein the plate heat exchanger is used to preheat the raw water entering the reverse osmosis membrane module; A demineralized water buffer tank (16) and a demineralized water buffer pump (18) are disposed between the reverse osmosis membrane assembly (8) and the demineralized water tank unit (2); A condensate delivery pipeline connects the condensate tank unit (1) and the deoxygenated water tank (4), and a condensate pump (5) is installed on the pipeline. The demineralized water conveying pipeline connects the demineralized water tank unit (2), the slag cooler unit (3), the plate heat exchanger (7), and the deoxygenated water tank (4), and a demineralized water pump (6) is installed on the pipeline. In addition, the control unit is interlocked with the level gauge, thermometer, pressure transmitter, flow meter, electric valve and water pump in the system to implement the "condensate priority" water supply strategy, dynamically adjust the water flow of each path and maintain the water balance of the system.

2. The system according to claim 1, characterized in that, The outlet water pipe of the slag cooler unit (3) is divided into at least three lines: The first reuse pipeline is connected to the demineralized water tank unit (2), which is equipped with a first electric switch valve (121). The second transfer pipeline is connected to the condensate tank unit (1), and a second electric regulating valve (112) is provided on it. The third direct pipeline is connected to the deoxygenated water tank (4), and a fourth electric regulating valve (114) is provided on it. The control unit is configured to control the opening and closing of the first electric switching valve (121) and the electric regulating valve (112) based on the reading of the thermometer (93) installed at the outlet of the slag cooler unit (3) so as to guide the demineralized water in different temperature ranges to different destinations.

3. The system according to claim 2, characterized in that, The multiple cold slag machines in the cold slag machine unit (3) are configured through pipelines and valves and can switch between series mode and parallel mode; In series mode, multiple slag coolers are connected in sequence, and the demineralized water is heat-exchanged in stages. The control unit executes the diversion control as described in claim 2 according to the final effluent temperature. In parallel mode, each slag cooler operates independently in parallel, and its effluent is directly sent to the deaerator water tank (4) through the third direct delivery pipeline.

4. The system according to claim 1, characterized in that, The plate heat exchanger (7) has two heating modes: Demineralized water heat exchange mode: The heat medium comes from the demineralized water in the demineralized water tank unit (2) and is controlled by the fourth electric switch valve (124); Steam-assisted heating mode: The heat medium comes from the boiler's own steam and is controlled by the second electric regulating valve (122); The control unit is configured to switch or combine the two heating modes according to the season or raw water temperature requirements.

5. The system according to claim 1, characterized in that, The demineralized water buffer tank (16) is equipped with a level gauge (107), and the control unit is configured to control the start and stop of the reverse osmosis membrane module (8) according to the signal of the level gauge (107); the demineralized water buffer pump (18) runs continuously, and its outlet pipeline is equipped with an electric regulating valve (111) interlocked with the control unit. The opening degree of the electric regulating valve (111) is controlled by the level gauge on the demineralized water tank unit (2).

6. The system according to claim 1, characterized in that, The condensate tank unit (1) and the demineralized water tank unit (2) each include at least two water tanks connected in parallel via bottom connecting valves. Each water tank is independently equipped with a level gauge to enhance the redundancy and water storage regulation capability of the system.

7. The system according to claim 1, characterized in that, The condensate delivery pipeline is equipped with a third electric regulating valve (113) for adjusting the flow rate and a flow meter (133) for monitoring; the demineralized water tank unit (2) is equipped with a thermometer, and the control unit triggers an alarm when the water temperature exceeds the set value.

8. A method for optimizing feedwater in a circulating fluidized bed boiler using the system described in any one of claims 1-7, characterized in that, Includes the following steps: Step S1: Prioritize sending steam condensate to deaerator water tank (4) via condensate pump (5); Step S2: Divide the demineralized water into two parts. One part is sent to the slag cooler unit (3) to cool the hot slag, and the other part is sent to the plate heat exchanger (7) to preheat the reverse osmosis membrane module (8) feed water. Step S3: Monitor the outlet water temperature of the cold slag machine unit (3), and dynamically distribute the demineralized water after heat exchange to the demineralized water tank (2), condensate tank (1) or deoxygenated water tank (4) according to the temperature value. Step S4: The flow shock caused by the intermittent water production of the reverse osmosis membrane module (8) is suppressed by the demineralized water buffer tank (16) and the buffer pump (18), so as to achieve stable water replenishment to the demineralized water tank unit (2), and the start and stop of the reverse osmosis membrane module (8) is controlled by the liquid level interlocking logic.

9. The method according to claim 8, characterized in that, In winter or under low temperature conditions, when the demineralized water heat exchange mode cannot meet the inlet water temperature requirements of the reverse osmosis membrane module (8), it will automatically start or switch to steam-assisted heating mode to ensure the stability of preheating.

10. The method according to claim 8 or 9, characterized in that, The "condensate priority" principle is implemented through the following control logic: The target liquid level of the deoxygenated water tank (4) is set as follows: The real-time liquid level is L; the control unit calculates the real-time water replenishment amount of the deoxygenated water tank. The calculation formula is as follows: in, The proportional coefficient is used; the control unit prioritizes adjusting the flow rate of the condensate pump (5). To meet The demand, that is ; When the condensate pump reaches its maximum output And when there is still a need for water replenishment, (i.e.) > ), control unit according to difference To adjust the amount of desalinated water replenished.

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