A flash desulfurization slurry waste heat recovery system and method

Abstract

The present invention provides a flash desulfurization slurry waste heat recovery system and method, belonging to the technical field of boiler flue gas energy saving, including a desulfurization tower and a negative pressure flash evaporation device, wherein a slurry area and a spray area are arranged in the desulfurization tower, and the slurry area and the spray area are connected through a slurry circulation pipeline, and a flash spray layer and a flash slurry layer are arranged in the negative pressure flash evaporation device, and the flash spray layer and the flash slurry layer are connected through a slurry pipeline and a slurry return pipeline and a slurry circulation pipeline respectively, and a first slurry regulating valve is arranged on the slurry pipeline, and a second slurry regulating valve is arranged on the slurry circulation pipeline, and the second slurry regulating valve is located between the slurry pipeline and the connection point between the slurry return pipeline and the slurry circulation pipeline. The present invention can control the load of the waste heat recovery system by adjusting the liquid inlet amount of the negative pressure flash evaporation device, and at the same time, disturb the slurry in the negative pressure flash evaporation device to prevent the desulfurization slurry from depositing and scaling.

Description

Technical Field

[0001] The invention belongs to the technical field of boiler flue gas energy saving, and in particular relates to a flash desulfurization slurry waste heat recovery system and method. Background Art

[0002] With the acceleration of urbanization, the demand for heating is gradually increasing. In industrial fields such as power plants, the desulfurization slurry in the wet desulfurization process contains a large amount of waste heat resources. If it is not utilized, it will not only cause energy waste, but also may cause secondary pollution to the environment. If these waste heat are recovered for heating, on the one hand, it can significantly save primary energy consumption and improve energy utilization. On the other hand, it can also recycle water resources and save water consumption.

[0003] However, due to the increasingly stringent environmental protection requirements of the country, the environmental protection indicators of coal-fired boilers are constantly improving. In order to meet these requirements, coal-fired boilers often need to undergo a series of modifications and upgrades. The upgrades to environmental protection facilities such as desulfurization, denitrification, and dust removal at the rear of the boiler take up a lot of space, leading to problems such as tight space behind the furnace and insufficient residual pressure of the induced draft fan.

[0004] In the prior art, slurry flash evaporation technology is usually used for waste heat recovery. On the one hand, it can solve the problem of system land occupation, while not affecting the original flue gas system of the boiler, not increasing the flue gas resistance, and not requiring the modification of the induced draft fan. On the other hand, slurry flash evaporation technology does not destroy the water balance of the original wet desulfurization absorption tower.

[0005] The waste heat recovery system currently using slurry flash evaporation technology often causes the waste heat recovery system to be overloaded due to the large amount of slurry that needs to be flashed, resulting in a decrease in the waste heat recovery effect. At the same time, the slurry will deposit and scale in the flash evaporation device, affecting the normal operation of the system. Summary of the invention

[0006] In view of the defects or shortcomings in the prior art, the present invention provides a flash desulfurization slurry waste heat recovery system and method, which can control the load of the waste heat recovery system by adjusting the liquid inlet amount of the negative pressure flash evaporation device, and at the same time disturb the slurry in the negative pressure flash evaporation device to prevent the desulfurization slurry from depositing and scaling.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] In the first aspect, an embodiment of the present invention provides a flash desulfurization slurry waste heat recovery system, comprising a desulfurization tower and a negative pressure flash device, wherein a slurry zone and a spray zone are arranged in the desulfurization tower, and the slurry zone and the spray zone are connected through a slurry circulation pipe, and a flash spray layer and a flash slurry layer are arranged in the negative pressure flash device, and the flash spray layer and the flash slurry layer are connected to the slurry circulation pipe through a slurry pipe and a slurry return pipe respectively, a first slurry regulating valve is arranged on the slurry pipe, and a second slurry regulating valve is arranged on the slurry circulation pipe, and the second slurry regulating valve is located between the slurry pipe and the connection point between the slurry return pipe and the slurry circulation pipe.

[0009] Furthermore, a multi-layer spray device is arranged in the spray area, and the slurry area is connected to the multi-layer spray device through a plurality of slurry circulation pipes respectively, the flash spray layer is connected to the slurry circulation pipe connected to the top spray device of the desulfurization tower through a slurry pipe, and the flash slurry layer is connected to the slurry circulation pipe connected to the top spray device of the desulfurization tower through a slurry return pipe.

[0010] Furthermore, a slurry return pipe connection point on the slurry circulation pipe is located above the slurry pipe connection point, and a slurry return pipe is provided with a slurry return pump and a slurry return valve.

[0011] Furthermore, a slurry disturbance pipeline is connected between the slurry pipeline and the flash slurry layer, and a slurry disturbance valve is arranged on the slurry disturbance pipeline.

[0012] Furthermore, the negative pressure flash evaporation device is connected to the dosing box through a dosing pipe, the connection port between the dosing pipe and the negative pressure flash evaporation device is located above the flash slurry layer, and a dosing pump is arranged on the dosing pipe.

[0013] Furthermore, the top of the negative pressure flash evaporation device is connected to the air inlet of the demister through a pipe, and the bottom of the demister is connected to the negative pressure flash evaporation device through a return pipe, and the connection point between the return pipe and the negative pressure flash evaporation device is located below the flash spray layer.

[0014] Furthermore, the air outlet of the demister is connected to an absorption heat pump through a pipeline, and the absorption heat pump is connected to a heat network.

[0015] Furthermore, a vacuum pump is provided on the outlet pipeline of the evaporator of the absorption heat pump, and the pressure of the negative pressure flash evaporation device is maintained to an absolute pressure of 4-6 kPa by the vacuum pump.

[0016] Furthermore, the absorption heat pump is provided with an exhaust steam condensate discharge device and a steam condensate discharge device, which are used to discharge exhaust steam condensate and steam condensate respectively.

[0017] In a second aspect, an embodiment of the present invention further provides a flash desulfurization slurry waste heat recovery method, using a flash desulfurization slurry waste heat recovery system as described above, comprising the following steps:

[0018] The spray slurry at the top of the desulfurization tower is taken for flash evaporation, and the low-temperature slurry after flash evaporation is returned to the desulfurization tower for spraying, and the first slurry regulating valve and the second slurry regulating valve are used to coordinately adjust and control the liquid inlet amount entering the negative pressure flash evaporation device, so as to control the load of the waste heat recovery system;

[0019] Open the slurry disturbance valve and use part of the slurry to disturb the flash slurry layer to prevent the desulfurization slurry from depositing and scaling. At the same time, open the dosing pump and regularly add scale inhibitors to the system to reduce scaling in the desulfurization system and ensure long-term stable operation of the system.

[0020] The exhaust steam flashed out by the negative pressure flash evaporation device first enters the demister for defogger, and the collected exhaust steam condensate returns to the negative pressure flash evaporation device through the reflux pipe. The flash exhaust steam enters the absorption heat pump evaporator after defogger, and the flash exhaust steam is converted into exhaust steam condensate after taking heat through the absorption heat pump evaporator. The exhaust steam condensate enters the exhaust steam condensate discharge device integrated in the absorption heat pump and is discharged, and the heat energy enters the heat network circulation.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention provides a first slurry regulating valve on the slurry pipeline, and provides a second slurry regulating valve on the slurry circulation pipeline between the slurry return pipeline and the slurry pipeline. The first slurry regulating valve and the second slurry regulating valve are used to collaboratively control the amount of liquid entering the negative pressure flash evaporation device, thereby ensuring that the negative pressure flash evaporation device is always in an efficient operating state, thereby controlling the load of the waste heat recovery system.

[0023] 2. The present invention sets a slurry disturbance pipeline between the slurry pipeline and the flash slurry layer, and allows part of the slurry to enter the flash slurry layer through the slurry disturbance pipeline, thereby realizing self-disturbance of the desulfurization slurry, effectively preventing the desulfurization slurry from depositing and scaling in the negative pressure flash device, and ensuring the normal operation of the system.

[0024] 3. The present invention takes the spray slurry from the top layer of the desulfurization tower for flash evaporation, and the low-temperature slurry after flash evaporation is returned to the desulfurization tower for spraying, which has high heat exchange efficiency and improves the desulfurization efficiency to a certain extent.

[0025] 4. The present invention arranges the demister on the exhaust gas pipeline outside the negative pressure flash evaporation device. Compared with the traditional demister located in the negative pressure flash evaporation device, the size of the demister is not limited by the negative pressure flash evaporation device. By adjusting the size of the demister and reasonably setting the exhaust gas flow rate, the demisting efficiency is effectively improved.

[0026] 5. The present invention connects the dosing box to the negative pressure flash evaporation device through a dosing pipeline, and regularly injects descaling agent into the negative pressure flash evaporation device, which can effectively reduce the scaling phenomenon of the desulfurization system.

[0027] 6. The present invention integrates the exhaust condensate discharge device and the steam condensate discharge device into the absorption heat pump body, which can reduce the equipment footprint and on-site workload. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the overall structure of the waste heat recovery system in Embodiment 1 of the present invention;

[0029] Among them, 1. desulfurization tower; 101. slurry area; 102. spraying area; 103. slurry circulation pipeline; 104. slurry pump; 105. second slurry regulating valve; 2. negative pressure flash device; 201. flash spray layer; 202. flash slurry layer; 203. slurry pipeline; 204. first slurry regulating valve; 205. slurry reflux pipeline; 206. slurry reflux pump; 207. slurry reflux valve; 208. slurry disturbance pipeline; 209. slurry disturbance valve; 3. dosing box; 301. dosing pipeline; 302. dosing pump; 4. demister; 401. reflux pipeline; 5. absorption heat pump; 501. exhaust steam condensate discharge device; 502. vacuum pump; 503. steam condensate discharge device. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0031] Embodiment 1

[0032] A typical implementation of the present invention is as follows Figure 1 As shown, a flash desulfurization slurry waste heat recovery system includes a desulfurization tower 1 and a negative pressure flash device 2. A slurry area 101 and a spray area 102 are arranged in the desulfurization tower 1. The spray area 102 is located above the slurry area 101. A multi-layer spray device is arranged in the spray area 102. The slurry area 101 is connected to the multi-layer spray device through a plurality of slurry circulation pipes 103 respectively. A slurry pump 104 is arranged on the plurality of slurry circulation pipes 103. The slurry in the slurry area 101 is transported to the spray area 102 by the slurry pump 104 to spray the flue gas.

[0033] A flash spray layer 201 and a flash slurry layer 202 are provided in the negative pressure flash device 2. The flash spray layer 201 is located above the flash slurry layer 202. The flash spray layer 201 is connected to the slurry circulation pipeline 103 connected to the uppermost spray device of the desulfurization tower 1 through a slurry pipeline 203. A first slurry regulating valve 204 is provided on the slurry pipeline 203. A part of the slurry in the slurry area 101 of the desulfurization tower 1 enters the flash spray layer 201 of the negative pressure flash device 2 through the slurry pipeline 203 for flash evaporation.

[0034] The flash slurry layer 202 is connected to the slurry circulation pipe 103 connected to the uppermost spray device of the desulfurization tower 1 through the slurry return pipe 205. The connection point of the slurry return pipe 205 on the slurry circulation pipe 103 is located above the connection point of the slurry pipe 203. Since the temperature of the desulfurization slurry coming out of the negative pressure flash device 2 is lower than the temperature of the slurry in the slurry area 101 of the desulfurization tower 1, the slurry return pipe 205 is connected to the slurry circulation pipe 103 connected to the uppermost spray device of the desulfurization tower 1, and the connection point of the slurry return pipe 205 on the slurry circulation pipe 103 is located above the connection point of the slurry pipe 203. This can reduce the flue gas temperature in the desulfurization tower 1 to a lower level and recover the flue gas heat as much as possible.

[0035] A slurry reflux pump 206 and a slurry reflux valve 207 are provided on the slurry reflux pipeline 205 to control the flow rate of the slurry reflux. The slurry after flash evaporation is pumped into the slurry circulation pipeline 103 through the slurry reflux pump 206, and enters the uppermost spray device of the desulfurization tower 1 through the slurry circulation pipeline 103 for spraying, thereby reducing the flue gas temperature to below 35°C. The slurry reflux pump 206 adopts frequency conversion regulation, and the slurry liquid level in the negative pressure flash evaporation device 2 is controlled by adjusting the frequency of the slurry reflux pump 206 to ensure the stability of the slurry liquid level in the negative pressure flash evaporation device 2, and avoid excessive fluctuations in the slurry liquid level in the negative pressure flash evaporation device 2, resulting in unstable negative pressure, thereby affecting the flash evaporation effect.

[0036] A second slurry regulating valve 105 is also provided on the slurry circulation pipeline 103, and the second slurry regulating valve 105 is located between the connection point of the slurry return pipeline 205 and the connection point of the slurry pipeline 203. The first slurry regulating valve 204 and the second slurry regulating valve 105 cooperate to control the liquid inlet amount entering the negative pressure flash evaporation device 2, and adjust the liquid inlet amount of the negative pressure flash evaporation device 2 to always be at a set value. On the other hand, when the boiler operating load fluctuates, the first slurry regulating valve 204 and the second slurry regulating valve 105 can be used to timely adjust the liquid inlet amount of the negative pressure flash evaporation device 2 to ensure that the negative pressure flash evaporation device 2 is not affected by the fluctuation of the boiler operating load and is always in high-efficiency operation, thereby controlling the load of the waste heat recovery system.

[0037] A slurry disturbance pipeline 208 is also connected between the slurry pipeline 203 and the flash slurry layer 202. A slurry disturbance valve 209 is arranged on the slurry disturbance pipeline 208. The slurry disturbance valve 209 is opened during the normal operation of the system. At this time, part of the slurry enters the flash slurry layer 202 to disturb the slurry, thereby preventing the desulfurization slurry from depositing and scaling, causing blockage in the pipeline and the negative pressure flash device 2, and affecting the stability of the system. By setting a slurry disturbance pipeline 208 in the flash slurry layer 202 of the negative pressure flash device 2, the slurry enters the negative pressure flash device 2 through the slurry disturbance pipeline 208, and stirs the slurry inside the negative pressure flash device 2, thereby playing the role of a stirrer, so that the particles in the slurry are in a suspended state, avoiding the deposition of particles, and ensuring the normal operation of the system.

[0038] The negative pressure flash device 2 is connected to the dosing box 3 through the dosing pipe 301. The connection port between the dosing pipe 301 and the negative pressure flash device 2 is located above the flash slurry layer 202. A dosing pump 302 is provided on the dosing pipe 301. When the system is normally put into operation, the dosing pump 302 is started regularly to inject scale inhibitor into the system, which can effectively reduce the scaling phenomenon of the desulfurization system and ensure the long-term stable operation of the system.

[0039] The top of the negative pressure flash device 2 is connected to the air inlet of the demister 4 through a pipeline, and the bottom of the demister 4 is connected to the negative pressure flash device 2 through a return pipe 401. The connection point of the return pipe 401 and the negative pressure flash device 2 is located below the flash spray layer 201. The exhaust steam flashed out by the negative pressure flash device 2 first enters the demister 4 for defogger, and the collected exhaust steam condensate returns to the negative pressure flash device 2 through the return pipe 401. By setting the return pipe 401, the collected exhaust gas condensate is discharged into the negative pressure flash device 2 in time. On the one hand, it can avoid that more and more water accumulates in the demister 4, resulting in a reduction in the defogger area and affecting the defogger effect. On the other hand, it can avoid that the exhaust gas condensate enters the absorption heat pump 5 and affects the stable operation of the absorption heat pump 5.

[0040] The demister is arranged on the exhaust gas pipeline outside the negative pressure flash evaporation device. Compared with the traditional demister located inside the negative pressure flash evaporation device, the size of the demister is not limited by the negative pressure flash evaporation device. The exhaust gas flow rate can be reasonably set by adjusting the size of the demister, thereby effectively improving the demisting efficiency.

[0041] The air outlet of the demister 4 is connected to the absorption heat pump 5 through a pipeline, and the absorption heat pump 5 is connected to the heat network. The flash exhaust steam enters the evaporator of the absorption heat pump 5 after defogger, and the flash exhaust steam is converted into exhaust steam condensate after taking heat through the evaporator of the absorption heat pump 5. The exhaust steam condensate enters the exhaust steam condensate discharge device 501 integrated in the absorption heat pump 5 and is discharged, and the heat energy enters the heat network circulation.

[0042] A vacuum pump 502 is provided on the outlet pipeline of the evaporator of the absorption heat pump 5, and the pressure of the negative pressure flash evaporation device 2 is maintained to an absolute pressure of 4-6 kPa by the vacuum pump 502.

[0043] The absorption heat pump 5 in this embodiment is a common absorption heat pump on the market. It uses a small amount of high-temperature steam as driving steam to generate a large amount of medium-temperature useful thermal energy. The driving steam enters the generator of the absorption heat pump 5 to do work, and the steam condenses into steam condensate discharge device 503 for discharge.

[0044] The exhaust steam condensate discharge device 501 and the steam condensate discharge device 503 are both integrated in the absorption heat pump body, which can reduce the equipment footprint and on-site workload.

[0045] Embodiment 2

[0046] This embodiment provides a flash desulfurization slurry waste heat recovery method, using a flash desulfurization slurry waste heat recovery system as described in Example 1, including the following steps:

[0047] The spray slurry at the top of the desulfurization tower 1 is taken for flash evaporation, and the low-temperature slurry after flash evaporation is returned to the desulfurization tower 1 for spraying. The first slurry regulating valve 204 and the second slurry regulating valve 105 are used to coordinately adjust and control the amount of liquid entering the negative pressure flash evaporation device 2, so as to control the load of the waste heat recovery system;

[0048] Open the slurry disturbance valve 209, use part of the slurry to disturb the flash slurry layer 202 to prevent the desulfurization slurry from depositing and scaling. At the same time, open the dosing pump 302 to regularly add scale inhibitors into the system to reduce scaling in the desulfurization system and ensure long-term stable operation of the system.

[0049] The exhaust steam flashed out by the negative pressure flash evaporation device 2 first enters the demister 4 for defogger, and the collected exhaust steam condensate returns to the negative pressure flash evaporation device 2 through the reflux pipe 401. The flash exhaust steam enters the evaporator of the absorption heat pump 5 after defogger, and the flash exhaust steam is converted into exhaust steam condensate after taking heat from the evaporator of the absorption heat pump 5. The exhaust steam condensate enters the exhaust steam condensate discharge device 501 integrated in the absorption heat pump 5 and is discharged, and the heat energy enters the heat network circulation.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A flash desulfurization slurry waste heat recovery system, characterized in that: It includes a desulfurization tower and a negative pressure flash device, wherein a slurry zone and a spray zone are arranged in the desulfurization tower, and the slurry zone and the spray zone are connected through a slurry circulation pipeline; a flash spray layer and a flash slurry layer are arranged in the negative pressure flash device, and the flash spray layer and the flash slurry layer are connected to the slurry circulation pipeline through a slurry pipeline and a slurry return pipeline respectively; a first slurry regulating valve is arranged on the slurry pipeline, and a second slurry regulating valve is arranged on the slurry circulation pipeline, and the second slurry regulating valve is located between the slurry pipeline and the connection point between the slurry return pipeline and the slurry circulation pipeline.

2. A flash desulfurization slurry waste heat recovery system according to claim 1, characterized in that: A multi-layer spray device is arranged in the spray area, and the slurry area is connected to the multi-layer spray device through a plurality of slurry circulation pipes respectively. The flash spray layer is connected to the slurry circulation pipe connected to the top spray device of the desulfurization tower through a slurry pipe, and the flash slurry layer is connected to the slurry circulation pipe connected to the top spray device of the desulfurization tower through a slurry return pipe.

3. A flash desulfurization slurry waste heat recovery system according to claim 1, characterized in that: The slurry return pipe connection point on the slurry circulation pipe is located above the slurry pipe connection point, and the slurry return pipe is provided with a slurry return pump and a slurry return valve.

4. A flash desulfurization slurry waste heat recovery system according to claim 1, characterized in that: A slurry disturbance pipeline is also connected between the slurry pipeline and the flash slurry layer, and a slurry disturbance valve is arranged on the slurry disturbance pipeline.

5. A flash desulfurization slurry waste heat recovery system according to claim 1, characterized in that: The negative pressure flash evaporation device is connected to the drug-dosing box through a drug-dosing pipeline. The connection port between the drug-dosing pipeline and the negative pressure flash evaporation device is located above the flash slurry layer. A drug-dosing pump is arranged on the drug-dosing pipeline.

6. A flash desulfurization slurry waste heat recovery system according to claim 1, characterized in that: The top of the negative pressure flash evaporation device is connected to the air inlet of the demister through a pipeline, and the bottom of the demister is connected to the negative pressure flash evaporation device through a return pipeline. The connection point between the return pipeline and the negative pressure flash evaporation device is located below the flash spray layer.

7. A flash desulfurization slurry waste heat recovery system according to claim 6, characterized in that: The air outlet of the demister is connected to an absorption heat pump through a pipeline, and the absorption heat pump is connected to a heat network.

8. A flash desulfurization slurry waste heat recovery system according to claim 7, characterized in that: A vacuum pump is provided on the outlet pipeline of the evaporator of the absorption heat pump, and the pressure of the negative pressure flash evaporation device is maintained to an absolute pressure of 4-6 kPa by the vacuum pump.

9. A flash desulfurization slurry waste heat recovery system according to claim 7, characterized in that: The absorption heat pump is provided with an exhaust steam condensate discharge device and a steam condensate discharge device, which are used for discharging exhaust steam condensate and steam condensate respectively.

10. A flash desulfurization slurry waste heat recovery method, using a flash desulfurization slurry waste heat recovery system according to any one of claims 1 to 9, characterized in that: The following steps are involved: The spray slurry at the top of the desulfurization tower is taken for flash evaporation, and the low-temperature slurry after flash evaporation is returned to the desulfurization tower for spraying, and the first slurry regulating valve and the second slurry regulating valve are used to coordinately adjust and control the liquid inlet amount entering the negative pressure flash evaporation device, so as to control the load of the waste heat recovery system; Open the slurry disturbance valve and use part of the slurry to disturb the flash slurry layer to prevent the desulfurization slurry from depositing and scaling. At the same time, open the dosing pump and regularly add scale inhibitors to the system to reduce scaling in the desulfurization system and ensure long-term stable operation of the system. The exhaust steam flashed out by the negative pressure flash evaporation device first enters the demister for defogger, and the collected exhaust steam condensate returns to the negative pressure flash evaporation device through the reflux pipe. The flash exhaust steam enters the absorption heat pump evaporator after defogger, and the flash exhaust steam is converted into exhaust steam condensate after taking heat through the absorption heat pump evaporator. The exhaust steam condensate enters the exhaust steam condensate discharge device integrated in the absorption heat pump and is discharged, and the heat energy enters the heat network circulation.

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