Urea dissolving system, flushing method for dissolving pump thereof and application

Abstract

This invention discloses a urea dissolution system, its dissolution pump flushing method, and its application, solving the problems of wasted demineralized water and increased treatment burden caused by urea-containing wastewater in existing open flushing methods. The system includes a dissolution tank, a dissolution pump, a urea solution storage tank, a supply pipeline, a return pipeline, a delivery pipeline, and a controller. During flushing, the controller closes the delivery control valve and opens the return control valve, creating a closed-loop circulation path for the flushing solution between the dissolution tank, the dissolution pump, and the return pipeline. After flushing, the urea-containing flushing solution is retained in the dissolution tank as a pre-dissolution solution for the next dissolution cycle to dissolve solid urea. This invention achieves flushing solution recycling, eliminates the discharge of urea-containing wastewater, and shortens the unloading preparation time for the next dissolution cycle.

Description

Technical Field

[0001] This invention belongs to the technical field of urea dissolution systems for power plant denitrification, specifically relating to a urea dissolution system and its dissolution pump flushing method and application. Background Technology

[0002] Huaneng Shidongkou No. 1 Power Plant has two 650MW coal-fired steam turbine generator units. The denitrification system of the units uses urea as a reducing agent, and the urea-to-ammonia process adopts the hydrolysis method. Urea granules are transported to the plant by truck and then pneumatically conveyed to the urea dissolving storage tank. The granular urea is dissolved into a 40-50% mass concentration urea solution using demineralized water or steam dehydration, and then pumped to the urea solution storage tank via a urea dissolving pump.

[0003] After each urea preparation, the dissolving pump and its related pipelines need to be flushed to prevent urea from crystallizing and causing blockages in the pump chamber and its connecting pipelines. Current flushing methods are mainly open flushing: flushing fluid is introduced into the pump body and pipelines, and the flushing fluid, carrying residual urea solution, is directly discharged into the wastewater pit through the discharge pipeline, and finally enters the wastewater treatment system for external discharge. Since the flushing fluid is discharged directly after flushing the pump body and pipelines only once, it cannot be recycled, thus resulting in waste of the flushing fluid. Furthermore, a large amount of urea-containing wastewater enters the wastewater pit. Because urea contains a large amount of ammonia nitrogen, it requires post-treatment before discharge, thus increasing the burden on wastewater treatment and the pressure on discharge. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a urea dissolution system and its dissolution pump flushing method and application. By making the flushing liquid form a closed circulation path between the dissolution tank, the dissolution pump and the return pipeline, the flushing link is turned into a part of the production process, which completely changes the old model of flushing being wasteful.

[0005] To achieve the above objectives, the present invention employs the following technical solution: A first aspect of the present invention provides a urea dissolving system, comprising: A dissolving tank, wherein the dissolving tank is provided with a rinsing fluid replenishment port, a liquid inlet, a liquid outlet, and a discharge port; A dissolving pump, the inlet of which is connected to the outlet of the dissolving tank; A urea solution storage tank for storing urea solution from the dissolving pump; A liquid supply line, wherein the liquid supply line is connected to the inlet of the dissolving pump and the outlet of the dissolving tank; A reflux pipeline is provided, which connects the outlet of the dissolving pump and the inlet of the dissolving tank, and a reflux control valve is provided on the reflux pipeline. A delivery pipeline, connecting the outlet of the dissolving pump and the inlet of the urea solution storage tank, is equipped with a delivery control valve; and The controller controls the reflux control valve and the delivery control valve such that when flushing the dissolving pump, the delivery control valve is closed and the reflux control valve is opened, so that the flushing liquid forms a closed circulation path between the dissolving tank, the dissolving pump and the reflux pipeline.

[0006] By setting up a controller to uniformly control the opening and closing states of the reflux control valve and the delivery control valve, the delivery valve is closed and the reflux control valve is opened during flushing. This allows the flushing fluid to continuously circulate in a closed loop formed between the dissolving tank, the dissolving pump, and the reflux pipeline. The kinetic energy of the flushing fluid is used to continuously flush the inner wall of the dissolving pump chamber and the pipeline, thoroughly removing residual urea solution and preventing urea crystallization from clogging the pump body and pipeline. After flushing, all the flushing fluid is retained in the dissolving tank, and no urea-containing wastewater is discharged, achieving the recycling of the flushing fluid.

[0007] In some implementations, the dissolving tank is further equipped with a liquid level detection device, which sends the liquid level information of the dissolving tank to the controller in real time. The liquid level detection device feeds back the real-time liquid level information in the dissolving tank to the controller, enabling the controller to automatically determine whether the liquid level conditions required for the safe start-up of the dissolving pump and agitator are met, thereby realizing automatic monitoring and management of the liquid level.

[0008] In some embodiments, the urea dissolving system further includes a flushing fluid supply pipe connected to the flushing fluid replenishment port of the dissolving tank via a supply line. The supply line is equipped with a replenishment valve, wherein the controller controls the replenishment valve to open and replenish the dissolving tank when the liquid level in the dissolving tank is less than one meter.

[0009] The controller automatically controls the replenishment valve to replenish flushing fluid when the liquid level is below one meter, maintaining the liquid level above the minimum required for the safe start-up of the dissolving pump and agitator. This automates the replenishment process and avoids oversights caused by manual operation.

[0010] In some implementations, the dissolving pump includes a first dissolving pump and a second dissolving pump connected in parallel, and the liquid supply line includes a first liquid supply branch and a second liquid supply branch. The first dissolving pump is connected to the outlet of the dissolving tank through the first liquid supply branch, and the second dissolving pump is connected to the outlet of the dissolving tank through the second liquid supply branch.

[0011] The dual-pump parallel configuration enables one pump to be in use and the other to be on standby. When one dissolving pump is being used for closed-loop flushing, the other dissolving pump can be in standby mode, ensuring the continuity and reliability of the system operation.

[0012] In some implementations, the reflux line includes a first reflux branch, a second reflux branch, and a main reflux line. The first reflux branch connects the outlet of the first dissolving pump to the main reflux line, and the second reflux branch connects the outlet of the second dissolving pump to the main reflux line. A first reflux control valve is installed on the first reflux branch, and a second reflux control valve is installed on the second reflux branch.

[0013] The two return branches are merged into a main return pipeline and then connected to the inlet of the dissolving tank, which simplifies the pipeline layout, reduces the number of interfaces on the dissolving tank, and reduces the system complexity.

[0014] In some implementations, the first reflux control valve, the second reflux control valve, and the delivery control valve are all pneumatic valves. Pneumatic valves open and close by driving the actuator with a pneumatic source, and can be connected to a controller for remote automatic control. They are compatible with the controller's automated control logic and are suitable for highly automated urea dissolution systems in power plants.

[0015] In some embodiments, the urea dissolving system further includes a urea zone condensate tank, the dissolving tank further includes a condensate inlet, and the condensate supply pipeline connects the urea zone condensate tank and the condensate inlet to supply condensate from the urea zone condensate tank to the dissolving tank.

[0016] By connecting the urea zone condensate tank to the dissolving tank through the condensate supply pipeline, the condensate generated by the urea zone steam system can be recovered to the dissolving tank, realizing the recycling of condensate and further saving system water.

[0017] A second aspect of the present invention also provides a flushing method for a urea dissolving pump, comprising: Add rinsing fluid to the dissolving tank so that the liquid level in the dissolving tank is not less than one meter; Close the delivery control valve and open the return control valve to flush the dissolving pump, creating a closed-loop flow path for the flushing solution between the dissolving tank, the dissolving pump, and the return pipeline; and The urea-containing flushing solution is retained in the dissolving tank as a pre-dissolving solution for the next dissolving cycle to dissolve solid urea.

[0018] By controlling the liquid level above one meter, both the minimum suction level required for the safe start-up of the dissolving pump and the minimum liquid level required for the safe start-up of the mixer are met, achieving a functional coupling where a single replenishment satisfies the start-up conditions of both devices. After rinsing, the rinsing solution containing a small amount of dissolved urea is fully retained in the dissolving tank. When solid urea is subsequently unloaded into the dissolving tank, the mixer can be started directly because the liquid level already meets the start-up conditions, eliminating the need to wait for replenishment to the starting level. This eliminates the waiting time for replenishment after rinsing in existing technologies, shortens the unloading preparation time, and improves the overall dissolving efficiency.

[0019] In some embodiments, the rinsing solution is demineralized water. Demineralized water does not contain impurity ions and will not affect the quality of the urea solution in the dissolving tank, making it a preferred medium for the rinsing solution of this invention.

[0020] The third aspect of the invention also provides the application of the urea dissolution system described in the first aspect of the invention in a power plant SCR denitrification system.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention controls the opening and closing of the reflux control valve and the delivery control valve by the controller, changing the open flushing to closed circulation flushing. The flushing liquid continuously circulates in the closed loop to flush the pump chamber and pipe wall. After the flushing is completed, the liquid is completely retained in the dissolving tank, which fundamentally eliminates the problem of urea-containing flushing wastewater being discharged into the wastewater pit. The amount of wastewater generated is reduced to zero, which significantly reduces the burden of wastewater collection and treatment.

[0022] (2) The liquid level in the dissolving tank is monitored in real time by the liquid level detection device and fed back to the controller. When the liquid level is less than one meter, the controller automatically opens the liquid replenishment valve to replenish the liquid and maintain the liquid level above the minimum liquid level required for the safe start of the dissolving pump and the agitator. After rinsing, the liquid level in the dissolving tank meets the start-up conditions of the agitator. After unloading in the next dissolving cycle, the agitator can be started directly without waiting for the liquid to be replenished to the start-up liquid level. This eliminates the liquid replenishment waiting time after rinsing in the prior art, shortens the unloading preparation time, and improves the overall dissolving efficiency.

[0023] (3) The rinsing fluid is recycled in a closed loop and is no longer discharged all at once. The demineralized water used for each rinsing is completely recovered, saving the consumption of demineralized water. At the same time, the small amount of dissolved urea carried in the rinsing fluid is directly retained in the dissolving tank and converted into the pre-dissolving mother liquor for the next dissolving cycle. This realizes the fluid reuse connection between the rinsing and dissolving processes and improves the utilization rate of raw materials.

[0024] (4) Closed-loop flushing uses the power of the dissolving pump to drive the flushing liquid to circulate. The flushing path is completely consistent with the normal production process. The flushing liquid acts directly on the inner wall of the pump chamber and the pipe wall. There are no dead corners in the flushing. The flushing effect is reliable. There is no need to add additional flushing equipment, and the modification cost is low. Attached Figure Description

[0025] Figure 1 A schematic diagram of a urea dissolving system according to a first embodiment of the present invention is shown.

[0026] Figure 2 A schematic diagram of a urea dissolving system according to a second embodiment of the present invention is shown.

[0027] Explanation of reference numerals in the attached figures: 10: Dissolving tank; 11: Stirrer; 12: Heater; 13: Feed inlet; 14: Rinse solution replenishment inlet; 15: Liquid inlet; 16: Drainage inlet; 17: Liquid outlet; 18: Discharge port; 20: Dissolving pump; 20-1: First dissolving pump; 20-2: Second dissolving pump; 30: Liquid supply line; 30-1: Main liquid supply line; 30-2: First liquid supply branch; 30-3: Second liquid supply branch; 40: Return line; 40-1: Main return line; 40-2: First return branch; 40-3: Second return branch; 41: Return control valve; 41-1: First return line Control valve; 41-2: Second reflux control valve; 50: Delivery pipeline; 50-1: Main delivery pipeline; 50-2: First delivery branch; 50-3: Second delivery branch; 51: Delivery control valve; 51-1: First delivery control valve; 51-2: Second delivery control valve; 60: Liquid replenishment pipeline; 70: Urea solution storage tank; 80: Urea area condensate tank; 90: Drain flushing pipeline; 90-1: Main condensate flushing pipeline; 90-2: First condensate flushing branch; 90-3: Second condensate flushing branch; TI: Thermometer; TE: Temperature detection device; LT: Liquid level detection device. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0030] The present invention will now be described in further detail with reference to the accompanying drawings. Figure 1 This is a schematic diagram of the urea dissolution system according to the first embodiment of the present invention. See also... Figure 1 The urea dissolving system includes a dissolving tank 10, a dissolving pump 20, a supply pipeline 30, a return pipeline 40, a delivery pipeline 50, a replenishment pipeline 60, a urea solution storage tank 70, a urea area drainage tank 80, and a controller.

[0031] The dissolving tank 10 is used to dissolve urea. The dissolving tank 10 includes a stirrer 11, a heater 12, a thermometer 11, a temperature sensing device TE, and a liquid level detection device LT. The heater heats the dissolving tank 10 with steam from the auxiliary steam header in the urea area. The steam after heat exchange condenses into condensate and is transported to the urea area condensate tank 80 via pipeline. The top of the dissolving tank 10 is provided with a feed inlet 13, a flushing fluid replenishment inlet 14, and a liquid inlet 15. The bottom of the dissolving tank 10 is provided with a liquid outlet 17 and a discharge outlet 18. The liquid level detection device LT monitors the liquid level in the dissolving tank 10 in real time and sends the liquid level information to the controller so that the controller can determine whether the liquid level meets the minimum liquid level requirements for the safe start-up of the dissolving pump 20 and the stirrer 11.

[0032] The liquid supply line 30 connects the inlet of the dissolving pump 20 to the outlet 17 of the dissolving tank 10. After the dissolving pump 20 is started, the liquid in the dissolving tank 10 flows into the dissolving pump 20 through the outlet 17 along the liquid supply line 30, and is pressurized by the dissolving pump 20 and output from the outlet of the dissolving pump 20.

[0033] The return pipeline 40 connects the outlet of the dissolving pump 20 to the inlet 15 of the dissolving tank 10, and a return control valve 41 is installed on the return pipeline 40. The delivery pipeline 50 connects the outlet of the dissolving pump 20 to the inlet of the urea solution storage tank 70, and a delivery control valve 51 is installed on the delivery pipeline 50. The outlet of the dissolving pump 20 is connected to both the return pipeline 40 and the delivery pipeline 50. The controller switches between the "production delivery" and "closed-loop flushing" working states by controlling the opening and closing states of the return control valve 41 and the delivery control valve 51.

[0034] The flushing fluid supply pipe is connected to the flushing fluid inlet 14 of the dissolving tank 10 via a replenishment pipe 60, and a replenishment valve is installed on the replenishment pipe 60. The controller controls the replenishment valve: when the controller receives liquid level information from the liquid level detection device LT indicating that the liquid level in the dissolving tank 10 is less than one meter, the controller opens the replenishment valve to replenish the dissolving tank 10 with flushing fluid until the liquid level reaches more than one meter, then closes the replenishment valve to stop replenishing the fluid.

[0035] Under normal production and conveying conditions, the controller opens the conveying control valve 51 and closes the return control valve 41. The dissolving pump 20 conveys the urea solution in the dissolving tank 10 to the urea solution storage tank 70 via the supply pipeline 30, the dissolving pump 20, and the conveying pipeline 50. Under closed-loop flushing conditions, the controller closes the conveying control valve 51 and opens the return control valve 41. The flushing liquid flows into the supply pipeline 30 through the outlet 17, is pressurized by the dissolving pump 20, and then enters the return pipeline 40. Finally, it returns to the dissolving tank 10 through the inlet 15, forming a closed loop between the dissolving tank 10, the dissolving pump 20, and the return pipeline 40.

[0036] As the flushing fluid continuously circulates within the closed loop, its kinetic energy continuously washes away the residual urea solution on the inner wall of the dissolving pump 20 and the wall of the return pipeline 40, causing the residual urea solution to be carried by the flushing fluid and evenly distributed in the closed loop, thereby preventing urea crystals from adhering to the inner wall of the pump chamber and the pipe wall.

[0037] In some examples, the dissolving tank 10 is also equipped with a condensate inlet 16. A condensate supply pipeline connects the urea zone condensate tank 80 and the condensate inlet 16 to supply condensate from the urea zone condensate tank 80 to the dissolving tank 10, and to recover condensate generated by the urea zone steam system to the dissolving tank 10, thus achieving condensate recycling and further saving system water. Furthermore, the condensate from the urea zone condensate tank 80 can also be used to flush the dissolving pump 20. For example, a condensate flushing pipeline 90 connecting the urea zone condensate tank 80 and the dissolving pump 20 can be provided to supply condensate to the dissolving pump 20 for flushing.

[0038] In some instances, the flushing method for the urea dissolving system described above is performed according to the following steps.

[0039] First, after one urea preparation cycle is completed, the controller receives liquid level information from the liquid level detection device LT. When the liquid level in the dissolving tank 10 is below one meter, the controller automatically opens the replenishment valve and replenishes demineralized water into the dissolving tank 10 through the replenishment pipeline 60. Once the reading of the liquid level detection device LT rises to at least one meter, the controller closes the replenishment valve and stops replenishing the liquid.

[0040] By controlling the liquid level to above one meter, the minimum liquid level requirement for the safe start-up of the dissolving pump 20 can be met, preventing cavitation during startup. At the same time, the minimum liquid level requirement for the safe start-up of the mixer can also be met, achieving functional coupling that satisfies the startup conditions of two devices with a single liquid replenishment.

[0041] Next, the controller closes the delivery control valve 51, opens the return control valve 41, and starts the dissolving pump 20. The demineralized water in the dissolving tank 10 enters the dissolving pump 20 through the outlet 17 along the supply pipeline 30. After being pressurized by the dissolving pump 20, it flows from the outlet of the dissolving pump 20 into the return pipeline 40. After passing through the return control valve 41, it returns to the dissolving tank 10 through the inlet 15, forming a closed-loop flow path between the dissolving tank 10, the dissolving pump 20, and the return pipeline 40, circulating and flushing the inner walls of the dissolving pump 20 and the return pipeline 40. Because the flushing liquid always flows within the closed loop and is not discharged externally, the demineralized water is recycled, and no urea-containing wastewater enters the wastewater pit.

[0042] After rinsing is completed, the controller stops the dissolving pump 20 and closes the reflux control valve 41, retaining the rinsing liquid in the dissolving tank 10 without discharge. At this time, the liquid retained in the dissolving tank 10 contains a small amount of urea dissolved during the circulating rinsing process, and the liquid level is maintained at no less than one meter, meeting the liquid level requirements for starting the agitator.

[0043] Subsequently, after the rinsing solution is retained in the dissolving tank 10, when solid urea is discharged into the dissolving tank 10 again through the feed inlet 13, the liquid level in the dissolving tank 10 already meets the start-up conditions of the agitator 11, so the agitator 11 can be started directly without waiting for replenishment to reach the start-up liquid level of the agitator 11. After the agitator 11 is started, the rinsing solution containing a small amount of dissolved urea retained in the dissolving tank 10 comes into contact with the newly added solid urea particles, and the urea already dissolved in the rinsing solution enters the dissolving process together with the newly added solid urea.

[0044] Since the liquid level has met the start-up conditions of the agitator 11, the agitator 11 can be started immediately after the next dissolution cycle is unloaded, eliminating the waiting time required for the liquid level to rise to the start-up conditions of the agitator after rinsing in the prior art, and shortening the unloading preparation time.

[0045] In some implementations, both the reflux control valve 41 and the delivery control valve 51 are pneumatic valves. Pneumatic valves open and close by driving the actuator with an air source, and can be connected to a controller for remote automatic control. They are compatible with the controller's automated control logic and are suitable for highly automated urea dissolution systems in power plants.

[0046] Figure 2 This is a schematic diagram of a urea dissolution system according to a second embodiment of the present invention. The following description will refer to... Figure 2 The main focus is on describing and Figure 1 The difference from the first embodiment.

[0047] refer to Figure 2 The urea dissolving system according to the second embodiment may include a dissolving tank 10, a replenishment pipeline 60, a urea solution storage tank 70, a urea zone hydrophobic tank 80, and a controller. The structure and features of these components are similar to their counterparts in the first embodiment. The following will focus on describing the parts that are different from the first embodiment.

[0048] In the second embodiment, the dissolving pump includes a first dissolving pump 20-1 and a second dissolving pump 20-2 connected in parallel. The supply pipeline consists of a main supply pipeline 30-1, a first supply branch 30-2, and a second supply branch 30-3. The outlet 17 of the dissolving tank 10 is connected to the main supply pipeline 30-1, which branches upstream of the first dissolving pump 20-1 and the second dissolving pump 20-2 into a first supply branch 30-2 and a second supply branch 30-3. The first dissolving pump 20-1 is connected to the main supply pipeline 30-1 via the first supply branch 30-2, thereby further communicating with the outlet 17 of the dissolving tank 10. The second dissolving pump 20-2 is connected to the main supply pipeline 30-1 via the second supply branch 30-3, thereby further communicating with the outlet 17 of the dissolving tank 10.

[0049] The reflux pipeline consists of a main reflux pipeline 40-1, a first reflux branch 40-2, and a second reflux branch 40-3. The first reflux branch 40-2 connects the outlet of the first dissolving pump 20-1 to the main reflux pipeline 40-1, and the second reflux branch 40-3 connects the outlet of the second dissolving pump 20-2 to the main reflux pipeline 40-1. The main reflux pipeline 40-1 is connected to the inlet 15 of the dissolving tank 10. Therefore, the flushing solution from the first dissolving pump 20-1 and the second dissolving pump 20-2 can be refluxed back to the dissolving tank 10 for circulation. To facilitate the control of the first and second dissolving pumps 20-1 and 20-2, a first reflux control valve 41-1 can be installed on the first reflux branch 40-2, and a second reflux control valve 41-2 can be installed on the second reflux branch 40-3.

[0050] The delivery pipeline consists of a main delivery pipeline 50-1, a first delivery branch 50-2, and a second delivery branch 50-3. The outlet of the first dissolving pump 20-1 is connected to the main delivery pipeline 50-1 via the first delivery branch 50-2, and the outlet of the second dissolving pump 20-2 is connected to the main delivery pipeline 50-1 via the second delivery branch 50-3. The main delivery pipeline 50-1 is connected to the inlet of the urea solution storage tank 70. Therefore, the outlets of the first dissolving pump 20-1 and the second dissolving pump 20-2 are connected to the inlet of the urea solution storage tank 70 through the delivery pipeline. For ease of control, a first delivery control valve 51-1 can be installed on the first delivery branch 50-2, and a second delivery control valve 51-2 can be installed on the second delivery branch 50-3.

[0051] Therefore, the outlets of the first dissolving pump 20-1 and the second dissolving pump 20-2 are simultaneously connected to the return pipeline and the delivery pipeline. The controller switches between the two working states of "production delivery" and "closed-loop flushing" by controlling the opening and closing states of the first return control valve 41-1, the second return control valve 41-2, the first delivery control valve 51-1 and the second delivery control valve 51-2.

[0052] Furthermore, to make reasonable use of the condensate from the urea zone, condensate can be supplied to the first dissolving pump 20-1 and the second dissolving pump 20-2 through a condensate flushing pipeline, thereby flushing the first dissolving pump 20-1 and the second dissolving pump 20-2. Specifically, the condensate flushing pipeline consists of a main condensate flushing pipeline 90-1, a first condensate flushing branch 90-2, and a second condensate flushing branch 90-3. The first dissolving pump 20-1 is connected to the main condensate flushing pipeline 90-1 through the first condensate flushing branch 90-2, and the second dissolving pump 20-2 is connected to the main condensate flushing pipeline 90-1 through the second condensate flushing branch 90-3. Therefore, the condensate from the urea zone condensate tank 80 can flush the first dissolving pump 20-1 and the second dissolving pump 20-2.

[0053] Therefore, the parallel configuration of two pumps can achieve one in use and one in standby. When one dissolving pump is used for closed-loop flushing, the other dissolving pump can be in standby mode, ensuring the continuity and reliability of system operation.

[0054] In addition, the two return branches are merged into a main return pipeline 40-1 and then connected to the inlet 15 of the dissolving tank 10, which simplifies the pipeline layout, reduces the number of interfaces on the dissolving tank 10, and reduces the system complexity.

[0055] When flushing the first dissolving pump 20-1, the controller closes the first delivery control valve 51-1, opens the first return control valve 41-1, and starts the first dissolving pump 20-1. The flushing solution is pressurized by the first dissolving pump 20-1 and enters the first return branch 40-2, then returns to the dissolving tank 10 via the main return pipeline 40-1, forming a closed loop. The flushing operation for the second dissolving pump 20-2 is the same.

[0056] As an example, the first reflux control valve 41-1, the second reflux control valve 41-2, the first delivery control valve 51-1, and the second delivery control valve 51-2 are all pneumatic valves. The controller can send control signals to each pneumatic valve to achieve independent control of the dual-pump flushing operation.

[0057] It is understood that, without altering the core structural mechanism of the aforementioned closed-loop rinsing, the rinsing solution is not limited to demineralized water; it can also be other clean water free of impurity ions and that does not affect the quality of the urea solution, as long as it can form a closed-loop flow path between the dissolving tank 10, the dissolving pump 20, and the return pipeline 40, and flush the pump chamber and pipe walls. Where there is no conflict, more than two dissolving pumps can also be provided, and the technical features of the aforementioned embodiments can be combined with each other.

[0058] This invention completely eliminates the discharge of flushing wastewater, preventing it from entering wastewater pits and reducing wastewater generation at the source. This alleviates the pressure on wastewater collection and treatment, significantly lowering environmental operating costs. Furthermore, the flushing water is fully recycled, saving a significant amount of demineralized water with each flush. Simultaneously, the heat carried by this water is retained within the system, reducing heating energy consumption in subsequent dissolution processes. Therefore, the urea dissolution system of this invention is highly suitable for integration into power plant SCR denitrification systems.

[0059] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A urea dissolving system, characterized in that, include: A dissolving tank, wherein the dissolving tank is provided with a rinsing fluid replenishment port, a liquid inlet, a liquid outlet, and a discharge port; A dissolving pump, the inlet of which is connected to the outlet of the dissolving tank; A urea solution storage tank for storing urea solution from the dissolving pump; A liquid supply line, wherein the liquid supply line is connected to the inlet of the dissolving pump and the outlet of the dissolving tank; A reflux pipeline is provided, which connects the outlet of the dissolving pump and the inlet of the dissolving tank, and a reflux control valve is provided on the reflux pipeline. A delivery pipeline, connecting the outlet of the dissolving pump and the inlet of the urea solution storage tank, is equipped with a delivery control valve; and The controller controls the reflux control valve and the delivery control valve such that when flushing the dissolving pump, the delivery control valve is closed and the reflux control valve is opened, so that the flushing liquid forms a closed circulation path between the dissolving tank, the dissolving pump and the reflux pipeline.

2. The urea dissolving system according to claim 1, characterized in that, The dissolving tank is also equipped with a liquid level detection device, and the liquid level detection device sends the liquid level information of the dissolving tank to the controller in real time.

3. The urea dissolving system according to claim 2, characterized in that, The urea dissolving system also includes a flushing fluid supply pipe, which is connected to the flushing fluid replenishment port of the dissolving tank via a supply line. A replenishment valve is installed on the supply line. The controller controls the replenishment valve so that when the liquid level in the dissolving tank is less than one meter, the replenishment valve is opened and the dissolving tank is replenished.

4. The urea dissolving system according to claim 1, characterized in that, The dissolving pump includes a first dissolving pump and a second dissolving pump connected in parallel. The liquid supply pipeline includes a first liquid supply branch and a second liquid supply branch. The first dissolving pump is connected to the outlet of the dissolving tank through the first liquid supply branch, and the second dissolving pump is connected to the outlet of the dissolving tank through the second liquid supply branch.

5. The urea dissolving system according to claim 4, characterized in that, The reflux pipeline includes a first reflux branch, a second reflux branch, and a main reflux pipeline. The first reflux branch connects the outlet of the first dissolving pump to the main reflux pipeline, and the second reflux branch connects the outlet of the second dissolving pump to the main reflux pipeline. A first reflux control valve is installed on the first reflux branch, and a second reflux control valve is installed on the second reflux branch.

6. The urea dissolving system according to claim 5, characterized in that, The first reflux control valve, the second reflux control valve, and the delivery control valve are all pneumatic valves.

7. The urea dissolving system according to claim 1, characterized in that, The urea dissolving system also includes a urea zone condensate tank, and the dissolving tank also includes a condensate inlet. The condensate supply pipeline connects the urea zone condensate tank and the condensate inlet to supply condensate from the urea zone condensate tank to the dissolving tank.

8. A flushing method for a urea dissolving pump, characterized in that, The flushing method is applicable to the urea dissolving system according to any one of claims 1 to 7, comprising: Add rinsing fluid to the dissolving tank so that the liquid level in the dissolving tank is not less than one meter; Close the delivery control valve and open the return control valve to flush the dissolving pump, creating a closed-loop flow path for the flushing solution between the dissolving tank, the dissolving pump, and the return pipeline; and After rinsing, the urea-containing rinsing solution is retained in the dissolving tank as a pre-dissolving solution for the next dissolving cycle to dissolve solid urea.

9. The rinsing method according to claim 8, characterized in that, The rinsing solution is demineralized water.

10. The application of the urea dissolution system according to any one of claims 1 to 6 in the SCR denitrification system of a power plant.

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