Two-section type spraying flue gas water lifting and waste heat utilization system and use method of two-section type spraying flue gas water lifting and waste heat utilization system

Abstract

The invention discloses a two-section type spraying flue gas water lifting and waste heat utilization system, and relates to the technical field of wet desulphurization. The system comprises a spraying cooling tower, a plate heat exchanger, a condensation water lifting storage tank and a heat pump unit, a water pool, a first-stage spraying cooling area, a second-stage spraying cooling area and a third-stage ridge efficient demister are sequentially arranged in the spraying cooling tower from bottom to top, and a spraying cooling tower inlet is formed between the water pool and the first-stage spraying cooling area; and a liquid collecting tray is arranged between the first-stage spraying cooling area and the second-stage spraying cooling area. According to the invention, desulfurized low-temperature flue gas and low-temperature circulating spray liquid drops are in reverse contact for heat exchange, so that the temperature of the flue gas is further reduced, moisture carried in the flue gas is condensed and separated out, the white smoke phenomenon caused by direct discharge of the flue gas is reduced, meanwhile, condensed water is recycled, and the additional water supplementing amount of the desulfurization system is effectively reduced. The invention further discloses a using method of the two-section type spraying flue gas water lifting and waste heat utilization system.

Description

Technical Field

[0001] The present invention relates to the technical field of wet flue gas desulfurization, and more specifically, it is a two-stage spray flue gas water extraction and waste heat utilization system. The present invention also relates to a method for using such a two-stage spray flue gas water extraction and waste heat utilization system. Background Art

[0002] The wet flue gas desulfurization technology has been widely used in flue gas treatment due to its high desulfurization efficiency. However, the wet flue gas desulfurization technology also causes an increase in the water content of the flue gas. If the desulfurized flue gas is directly discharged into the atmosphere through the chimney, a large amount of saturated water vapor carried in the flue gas will float into the atmosphere with the flue gas, and the phenomenon of chimney rain is likely to occur. At the same time, the heat carried by the desulfurized flue gas is also wasted.

[0003] The water consumption of the wet flue gas desulfurization system accounts for more than 50% of the water consumption of the coal-fired power plant system, and the water loss of the desulfurized flue gas directly discharged outside accounts for more than 80% of the water consumption of the desulfurization system. In line with the principle of "saving water and reducing water consumption indicators", especially for water-scarce areas, developing flue gas water extraction technology to achieve less or even zero water replenishment in the desulfurization system is of great significance.

[0004] Currently, using the condensation method, whether it is indirect condensation by a heat exchanger or direct condensation by spraying, reducing the flue gas temperature below the water dew point to condense and recover the water vapor in the flue gas is a mainstream flue gas water extraction technology. However, for flue gas with a high dust content, how to achieve hierarchical utilization of the condensed water and increase the amount of high-quality condensed water is the focus of attention of power plants. In addition, for thermal power plants in cogeneration areas, how to further utilize the waste heat of the desulfurized flue gas to increase the heating capacity of the heat network on the premise of reducing the water consumption index of the desulfurization system is also an urgent problem to be solved.

[0005] Therefore, it is necessary to develop a two-stage spray flue gas water extraction and waste heat utilization system that can achieve hierarchical utilization of flue gas condensed water and improve the heating capacity of the heat network. Summary of the Invention

[0006] The first object of the present invention is to overcome the deficiencies of the above background art and provide a two-stage spray flue gas water extraction and waste heat utilization system.

[0007] The second object of the present invention is to provide a method for using such a two-stage spray flue gas water extraction and waste heat utilization system.

[0008] To achieve the above first objective, the technical solution of the present invention is as follows: A two-stage spray flue gas water extraction and waste heat utilization system, characterized in that it includes a spray cooling tower, a plate heat exchanger, a condensate water extraction storage tank, and a heat pump unit. Inside the spray cooling tower, from bottom to top, there are a water tank, a first-stage spray cooling area, a second-stage spray cooling area, and a third-stage ridge high-efficiency demister. There is an inlet of the spray cooling tower between the water tank and the first-stage spray cooling area, and a liquid collecting tray is arranged between the first-stage spray cooling area and the second-stage spray cooling area;

[0009] The bottom of the water tank is connected to the first-stage spray cooling area through a first-stage cooling circulation pump and a plate heat exchanger in sequence;

[0010] The liquid collecting tray is connected to the second-stage spray cooling area through a condensate water extraction storage tank, a second-stage cooling circulation pump, and a heat pump unit in sequence;

[0011] Packing layers are arranged below the first spray layer in the first-stage cooling area and the first spray layer in the second-stage cooling area.

[0012] The condensate water extraction storage tank is connected to the third-stage ridge high-efficiency demister and the process water tank through a demister flushing water pump;

[0013] The plate heat exchanger is connected to the heat pump unit through a plate heat exchanger cold source water supply pump, and the heat pump unit is connected to the heat network.

[0014] In the above technical solution, the first-stage spray cooling area includes a first spray layer in the first-stage cooling area and a second spray layer in the first-stage cooling area from bottom to top in sequence; the first-stage cooling circulation pump includes a first-stage cooling first circulation pump and a first-stage cooling second circulation pump;

[0015] The bottom of the water tank is connected to the first spray layer through the first-stage cooling first circulation pump, and the bottom is connected to the second spray layer in the first-stage cooling area through the first-stage cooling second circulation pump and the plate heat exchanger in sequence.

[0016] In the above technical solution, the heat pump unit includes a first-stage heat pump unit and a second-stage heat pump unit; the plate heat exchanger is connected to the first-stage heat pump unit, and the first-stage heat pump unit is connected to the heat network.

[0017] In the above technical solution, the second-stage spray cooling area includes a first spray layer in the second-stage cooling area and a second spray layer in the second-stage cooling area from bottom to top in sequence; both the first spray layer in the second-stage cooling area and the second spray layer in the second-stage cooling area are connected to the second-stage heat pump unit; the second-stage heat pump unit is connected to the heat network.

[0018] In the above technical solution, the bottom of the water tank is connected to the water usage point through a sewage pump.

[0019] In the above technical solution, it further includes an alkali solution tank; the alkali solution tank is connected to the connecting pipeline between the water tank and the first-stage cooling second circulation pump through a first alkali solution metering pump, and is connected to the connecting pipeline between the condensate water storage tank and the second-stage cooling circulation pump through a second alkali solution metering pump.

[0020] In the above technical solution, two sets of the second-stage cooling circulation pump, the demister flushing water pump, the plate heat exchanger cold source water supply pump, and the sewage pump are provided, one for use and one for standby.

[0021] In the above technical solution, a packing layer is provided below the first spray layer in the first-stage cooling zone and the first spray layer in the second-stage cooling zone.

[0022] In order to achieve the above second object, the technical solution of the present invention is: a use method of a two-stage spray flue gas water extraction and waste heat utilization system, which is characterized by including the following steps:

[0023] Step 1: The flue gas from the outlet flue of the absorption tower enters the first-stage spray cooling zone through the flue gas inlet of the spray cooling tower. The packing layer below the first spray layer in the first-stage cooling zone evenly distributes the flue gas while transferring heat and removing dust from the flue gas. After the spray liquid of the first spray layer in the first-stage cooling zone and the second spray layer in the first-stage cooling zone transfer heat and remove dust from the flue gas, the flue gas enters the second-stage spray cooling zone through the liquid collecting tray flue gas cap; the generated condensate water falls into the water tank; the temperature of the flue gas drops by 2-3°C in the first-stage spray cooling zone;

[0024] Step 2: The first-stage cooling first circulation pump extracts circulating spray water from the water tank and sends it to the first spray layer to cool the flue gas in a cycle;

[0025] The first-stage cooling second circulation pump extracts circulating spray water from the water tank and sends it to the plate heat exchanger. After the plate heat exchanger cools the circulating spray water, it sends the circulating spray water to the second spray layer in the first-stage cooling zone to cool the flue gas in a cycle;

[0026] Step 3: The heat exchange medium in the plate heat exchanger is sent from the cold source outlet to the first-stage heat pump unit through the plate heat exchanger cold source water supply pump. After being cooled by heat exchange in the evaporator of the first-stage heat pump unit, it is sent to the cold source inlet of the plate heat exchanger; the cold source inlet of the first-stage heat pump unit is connected to the return water of the heat network, and the cold source outlet is connected to the supply water of the heat network to heat the return water of the heat network; realizing the utilization of flue gas waste heat;

[0027] Step 4: The sewage pump sends the circulating spray water in the water tank to the water use points in the factory area;

[0028] Step 5: After the flue gas enters the secondary spray cooling zone, the packing layer below the first spray layer in the secondary cooling zone evenly distributes the flue gas while transferring heat to the flue gas. The spray liquid of the first spray layer in the secondary cooling zone and the second spray layer in the secondary cooling zone transfers heat to the flue gas. The three-stage roof high-efficiency demister removes mist droplets from the flue gas. The low-temperature clean flue gas is discharged from the top of the spray cooling tower and discharged into the atmosphere through the chimney. The generated condensed water is collected by the liquid collecting tray and flows into the condensed water storage tank, thereby realizing the recycling of the condensed water.

[0029] Step 6: The demister flushing water pump draws circulating spray water from the bottom of the condensate water storage tank and sends it to the three-stage roof ridge high-efficiency demister to flush the three-stage roof ridge high-efficiency demister; at the same time, the demister flushing water pump also sends the circulating spray water to the process water tank;

[0030] Step 7: The secondary cooling circulation pump draws circulating spray water from the bottom of the condensing water storage tank and sends it to the secondary heat pump unit. The circulating spray water is cooled by heat exchange in the evaporator of the secondary heat pump unit and sent to the first spray layer of the secondary cooling area and the second spray layer of the secondary cooling area to circulate and cool the flue gas. The cold source inlet of the secondary heat pump unit is connected to the return water of the heating network, and the cold source outlet is connected to the water supply of the heating network to heat the return water of the heating network, so as to realize the utilization of waste heat of flue gas.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1) The present invention uses reverse contact heat exchange between the low-temperature flue gas after desulfurization and the low-temperature circulating spray droplets to further reduce the flue gas temperature, condense and precipitate the water carried in the flue gas, and reduce the white smoke phenomenon caused by direct exhaust of the flue gas. At the same time, the condensed water is recycled, effectively reducing the additional water replenishment amount of the desulfurization system.

[0033] 2) The present invention adopts graded spray cooling. The first-level spray cooling zone cools the flue gas while washing away most of the dust. This zone controls the flue gas temperature to drop slightly, the amount of condensed water is small, the corresponding condensed water has a large solid content, and the water quality is poor, which is discharged to the corresponding water use point through a sewage pump; the second-level spray cooling zone mainly cools the flue gas. The flue gas temperature in this zone drops significantly, the amount of condensed water is large, and the solid content is extremely low. A large amount of high-quality condensed water recovery rate can be achieved, the application range of recovered water is increased, and the amount of water replenishment in the desulfurization system is reduced; the present invention effectively realizes graded control of the condensed water quality.

[0034] 3) In the primary spray cooling zone, the temperature of the circulating spray water increases after heat exchange with the flue gas, but the water quality is poor. In order to keep the temperature of the circulating spray water stable and fully recycle the heat of the condensed water in this zone, the present invention adopts indirect heat exchange and configures a plate heat exchanger to cool the circulating spray water; the cold source water of the plate heat exchanger is heated in the plate heat exchanger, and is sent to the primary heat pump unit through the plate heat exchanger cold source water supply pump for further cooling, and then continues to be sent to the cold source inlet of the plate heat exchanger. The cold source water is closed and circulated at a constant temperature. The heat of the cold source water is absorbed by the primary heat pump unit and then heated to heat the heat network return water, thereby realizing the utilization of flue gas waste heat.

[0035] 4) In the secondary spray cooling zone, the temperature of the circulating spray water increases after heat exchange with the flue gas, and the water quality is good. The present invention directly uses a secondary heat pump unit to absorb the low-quality heat source of the condensate water and heat the return water of the heat network, realizing the utilization of the waste heat of the flue gas.

[0036] 5) The present invention is equipped with an alkali liquid tank. The alkali liquid is respectively sent into the inlet pipelines of the primary and secondary cooling circulation pumps through an alkali addition metering pump, and is fully mixed with the condensate water under the stirring action of the impeller of the condensate water circulation pump to ensure that the pH value of the system water quality is maintained between 6 and 7. Brief Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram of the present invention.

[0038] Among them, 100 - spray cooling tower, 110 - water pool, 120 - primary spray cooling zone, 121 - first spray layer in the primary cooling zone, 122 - second spray layer in the primary cooling zone, 130 - secondary spray cooling zone, 131 - first spray layer in the secondary cooling zone, 132 - second spray layer in the secondary cooling zone, 140 - three - level ridge high - efficiency demister, 150 - liquid collecting tray, 160 - packing layer, 200 - plate heat exchanger, 300 - condensate water extraction storage tank, 400 - heat pump unit, 410 - primary heat pump unit, 420 - secondary heat pump unit, 510 - primary cooling circulation pump, 511 - first circulation pump for primary cooling, 512 - second circulation pump for primary cooling, 520 - secondary cooling circulation pump, 530 - demister flushing water pump, 540 - cold source water supply pump for plate heat exchanger, 550 - sewage pump, 561 - first alkali liquid metering pump, 562 - second alkali liquid metering pump, 600 - alkali liquid tank. Detailed Embodiment

[0039] The following will describe in detail the implementation of the present invention in conjunction with the drawings. However, they do not constitute a limitation to the present invention and are only for illustration purposes. At the same time, the advantages of the present invention will become clearer and easier to understand through the description.

[0040] In order to solve the problems that the direct discharge of saturated low - temperature flue gas after desulfurization causes water loss, the desulfurization system has a large water consumption, which increases the system operation cost in water - scarce areas; for high - dust flue gas, the quality of the condensate water extracted by condensation is poor and the applicable range of the recovered water is small; and it is difficult to capture and utilize the waste heat of the flue gas after further cooling of the low - temperature flue gas, etc., the present invention proposes a two - stage spray flue gas water extraction and waste heat utilization system and its usage method, which realizes the further cooling and condensation of the flue gas after desulfurization and the recovery of the water carried in the flue gas, reducing the white smoke phenomenon generated by the direct discharge of the flue gas after desulfurization; the present invention adopts hierarchical spray cooling to achieve a high - quality condensate water recovery rate, increase the applicable range of the recovered water, and reduce the makeup water volume of the desulfurization system; at the same time, a heat pump is used to absorb the low - quality heat source of the condensate water and heat the return water of the heat network, realizing the utilization of the waste heat of the flue gas.

[0041] Referring to the accompanying drawings, it can be seen that: a two-stage spray flue gas water extraction and waste heat utilization system, characterized in that: it includes a spray cooling tower 100, a plate heat exchanger 200, a condensate water extraction storage tank 300, and a heat pump unit 400. Inside the spray cooling tower 100, from bottom to top, there are a water tank 110, a primary spray cooling zone 120, a secondary spray cooling zone 130, and a tertiary ridge high-efficiency demister 140. There is an inlet of the spray cooling tower 100 between the water tank 110 and the primary spray cooling zone 120, and a liquid collecting tray 150 is arranged between the primary spray cooling zone 120 and the secondary spray cooling zone 130;

[0042] The bottom of the water tank 110 is connected to the primary spray cooling zone 120 through a primary cooling circulation pump 510 and a plate heat exchanger 200 in sequence;

[0043] The liquid collecting tray 150 is connected to the secondary spray cooling zone 130 through a condensate water extraction storage tank 300, a secondary cooling circulation pump 520, and a heat pump unit 400 in sequence;

[0044] Packing layers 160 are arranged below the first spray layer 121 of the primary cooling zone and the first spray layer 131 of the secondary cooling zone.

[0045] The condensate water extraction storage tank 300 is connected to the tertiary ridge high-efficiency demister 140 and a process water tank through a demister flushing water pump 530;

[0046] The plate heat exchanger 200 is connected to the heat pump unit 400 through a plate heat exchanger cold source water supply pump 540, and the heat pump unit 400 is connected to a heat network.

[0047] The primary spray cooling zone 120 includes a first spray layer 121 of the primary cooling zone and a second spray layer 122 of the primary cooling zone from bottom to top in sequence; the primary cooling circulation pump 510 includes a first primary cooling circulation pump 511 and a second primary cooling circulation pump 512;

[0048] The bottom of the water tank 110 is connected to the first spray layer 121 through the first primary cooling circulation pump 511, and the bottom is connected to the second spray layer 122 of the primary cooling zone through the second primary cooling circulation pump 512 and the plate heat exchanger 200 in sequence.

[0049] The heat pump unit 400 includes a first-stage heat pump unit 410 and a second-stage heat pump unit 420; the plate heat exchanger 200 is connected to the first-stage heat pump unit 410, and the first-stage heat pump unit 410 is connected to a heat network.

[0050] The secondary spray cooling zone 130 sequentially includes a first spray layer 131 and a second spray layer 132 of the secondary cooling zone from bottom to top; both the first spray layer 131 and the second spray layer 132 of the secondary cooling zone are connected to the secondary heat pump unit 420; the secondary heat pump unit 420 is connected to the heat network.

[0051] The bottom of the water tank 110 is connected to the water use point through a sewage pump 550; the condensate water of the water tank 110 is sent to the water use point in the factory area to maintain the liquid level balance of the water tank 110.

[0052] It further includes an alkali liquid tank 600; the alkali liquid tank 600 is connected to the connecting pipeline between the water tank 110 and the first-stage cooling second circulation pump 512 through a first alkali liquid metering pump 561, and is connected to the connecting pipeline between the condensate water lifting storage tank 300 and the second-stage cooling circulation pump 520 through a second alkali liquid metering pump 562.

[0053] Two sets of the second-stage cooling circulation pump 520, the demister flushing water pump 530, the plate heat exchanger cold source water supply pump 540, and the sewage pump 550 are provided, one for use and one for standby.

[0054] Packing layers 160 are provided below both the first spray layer 121 of the first-stage cooling zone and the first spray layer 131 of the second-stage cooling zone.

[0055] A method for using a two-stage spray flue gas water extraction and waste heat utilization system, characterized by including the following steps:

[0056] Step 1: The flue gas from the outlet flue of the absorption tower enters the first-stage spray cooling zone 120 through the flue gas inlet of the spray cooling tower 100. The packing layer 160 below the first spray layer 121 of the first-stage cooling zone evenly distributes the flue gas and transfers heat and removes dust from the flue gas. After the spray liquid of the first spray layer 121 and the second spray layer 122 of the first-stage cooling zone transfer heat and remove dust from the flue gas, the flue gas enters the second-stage spray cooling zone 130 through the flue gas cap of the liquid collecting tray 150; the generated condensate water falls into the water tank 110; the temperature of the flue gas drops by 2 - 3 °C in the first-stage spray cooling zone 120.

[0057] Step 2: The first-stage cooling first circulation pump 511 extracts circulating spray water from the water tank 110 and sends it to the first spray layer 121 to cool the flue gas in a cycle.

[0058] The first-stage cooling second circulation pump 512 extracts circulating spray water from the water tank 110 and sends it to the plate heat exchanger 200. After the plate heat exchanger 200 cools the circulating spray water, it sends the circulating spray water to the second spray layer 122 of the first-stage cooling zone to cool the flue gas in a cycle.

[0059] Step 3: The heat exchange medium in the plate heat exchanger 200 is sent from the cold source outlet to the first-stage heat pump unit 410 through the plate heat exchanger cold source water supply pump 540, and after being cooled by heat exchange in the evaporator of the first-stage heat pump unit 410, it is sent to the cold source inlet of the plate heat exchanger 200; the cold source inlet of the first-stage heat pump unit 410 is connected to the return water of the heat network, and the cold source outlet is connected to the supply water of the heat network to heat the return water of the heat network; realizing the utilization of flue gas waste heat;

[0060] Step 4: The sewage pump 550 sends the circulating spray water in the water tank 110 to the water use points in the factory area;

[0061] Step 5: After the flue gas enters the secondary spray cooling zone 130, the packing layer 160 below the first spray layer 131 in the secondary cooling zone evenly distributes the flue gas and transfers heat to the flue gas at the same time. The spray liquid of the first spray layer 131 and the second spray layer 132 in the secondary cooling zone transfers heat to the flue gas. The three-stage ridge high-efficiency demister 140 removes the droplets from the flue gas, and the low-temperature clean flue gas is discharged from the top of the spray cooling tower 100 and discharged into the atmosphere through the chimney; the generated condensed water is collected by the liquid collecting tray 150 and flows into the condensed water extraction storage tank 300; realizing the recovery and utilization of condensed water;

[0062] Step 6: The demister flushing water pump 530 extracts the circulating spray water from the bottom of the condensed water extraction storage tank 300 and sends it to the three-stage ridge high-efficiency demister 140 to flush the three-stage ridge high-efficiency demister 140; at the same time, the demister flushing water pump 530 also sends the circulating spray water to the process water tank as needed;

[0063] Step 7: Since the quality of the condensed water generated in the secondary spray cooling zone 130 is relatively high, the secondary cooling circulation pump 520 extracts the circulating spray water from the bottom of the condensed water extraction storage tank 300 and directly sends it to the second-stage heat pump unit 420. The circulating spray water is cooled by heat exchange in the evaporator of the second-stage heat pump unit 420 and then sent to the first spray layer 131 and the second spray layer 132 in the secondary cooling zone to cool the flue gas in a cycle; the cold source inlet of the second-stage heat pump unit 420 is connected to the return water of the heat network, and the cold source outlet is connected to the supply water of the heat network to heat the return water of the heat network; realizing the utilization of flue gas waste heat.

[0064] During actual use, since the solid content of the condensed water generated in the first spray cooling zone 120 is relatively large, it is difficult to meet the water quality requirements of the first-stage heat pump unit 410 for the low-temperature heat source. To maintain the stability of the overall circulating water temperature in the cooling section of the first cooling zone 120, a plate heat exchanger 200 is configured in the pipeline of the second spray layer 122 in the first cooling zone to cool the circulating spray water; the cold source water of the plate heat exchanger 200 is heated in the plate heat exchanger 200, and after being sent to the evaporator of the first-stage heat pump unit 410 through the plate heat exchanger cold source water supply pump 540 for further heat exchange and cooling, it is continuously sent to the cold source inlet of the plate heat exchanger 200, and the cold source water of the plate heat exchanger 200 circulates in a closed loop at a constant temperature.

[0065] The demister flushing water pump 530 also functions as a flue gas condensate extraction pump, diverting a portion of the flue gas condensate from the secondary spray cooling zone 130 through the demister flushing water pump 530 into the process water tank.

[0066] While cooling the flue gas, the circulating spray water also absorbs some acidic gases in the flue gas, so the circulating spray water is acidic. Therefore, the present invention is equipped with an alkali tank 600. The alkali liquid is sent into the inlet pipeline of the first-stage cooling second circulation pump 512 through the first alkali liquid metering pump 561 and into the secondary cooling circulation pump 520 through the second alkali liquid metering pump 562. Through the impeller agitation of the first-stage cooling second circulation pump 512 and the secondary cooling circulation pump 520, it is fully mixed with the condensate to ensure that the pH value of the system water quality is maintained between 6 and 7. Although the content of SO2 in the flue gas after desulfurization is very low, a part of SO2 can still be absorbed through spraying in the spray cooling tower 100. Cumulative operation will cause the condensate in the tower to be acidic. Acidic liquids will corrode pipelines and flow-through equipment (pumps, heat exchangers, heat pumps, etc.). To avoid this hidden danger, if acid-resistant metal materials are selected, the costs of pipelines, equipment, etc. will increase. Therefore, the present invention is equipped with an alkali tank 600 to neutralize the acidic liquid by adding alkali and maintain it within a neutral range with a pH value between 6 and 7.

[0067] The first spray layer 121 in the first-stage cooling zone, the second spray layer 122 in the first-stage cooling zone, the first spray layer 131 in the secondary cooling zone, and the second spray layer 132 in the secondary cooling zone all use two-way nozzles, which can not only improve the atomization effect of a single nozzle, but also significantly obtain a dense secondary atomization effect, uniform distribution of the flue gas, and optimal flue gas cooling and condensation effect under the condition of optimizing the combination of the layout of different function nozzles. Thus, while improving the cooling and condensation effect, the condensate water circulation volume can be saved, the number of spray layers can be reduced, and the purpose of energy conservation and consumption reduction can be achieved.

[0068] The present invention adopts a two-stage water extraction idea. Among them, the first-stage spray cooling zone 120 removes the dust in the flue gas while cooling the flue gas, and the secondary spray cooling zone 130 cools and condenses the flue gas to precipitate the water in the flue gas, which can effectively achieve hierarchical control of the condensate water quality.

[0069] By reducing the flue gas temperature drop in the first-stage spray cooling zone 120 (controlling the temperature drop at 2 - 3 °C), the amount of condensate water in this zone will be less, and the heat loss discharged through the sewage pump 550 will be less. And the heat released by the flue gas temperature drop in this zone is transferred to the first-stage circulating spray water in the first-stage spray cooling zone 120. The first-stage circulating spray water transfers the heat to the return water of the heat network through the plate heat exchanger 200 and the first-stage heat pump unit 410, realizing that most of the heat released by the flue gas temperature drop in the first-stage spray cooling zone 120 is recovered by the first-stage heat pump unit 410 to heat the return water of the heat network.

[0070] Under the condition of the same overall flue gas temperature drop, the present invention reduces the flue gas temperature drop in the first-stage spray cooling zone 120, so that the flue gas temperature drop in the second-stage spray cooling zone 130 increases.

[0071] Since most of the dust in the flue gas has been removed in the first-stage spray cooling zone 120, the amount of condensed water in the second-stage spray cooling zone 130 is large and the water quality is clean. The heat released by the flue gas temperature drop in the second-stage spray cooling zone 130 is transferred to the secondary circulating spray water in the second-stage spray cooling zone 130, and the low-quality heat of the circulating spray water is recovered and used to heat the return water of the heat network through the secondary heat pump unit 420.

[0072] Compared with the prior art, on the premise of meeting the water quality requirements of the cooling circulating water for the heat pump unit 400, the present invention effectively reduces the intermediate heat exchange link, reduces the configuration of heat exchange equipment, and maximally recovers and utilizes the heat released by the flue gas cooling through the heat pump unit 400.

[0073] Embodiment 1

[0074] The present invention will be further described below in conjunction with actual parameters, but the present invention is not limited to the scope of the embodiments described herein.

[0075] A method for using a two-stage spray flue gas water extraction and waste heat utilization system includes the following steps:

[0076] Step 1: The clean flue gas (about 1,290,000 Nm 3 / h, 51 °C, dust content about 30 mg / Nm 3 ) from the outlet flue of the absorption tower enters the first-stage spray cooling zone 120 at the inlet of the spray cooling tower 100. The packing layer 160 below the first spray layer 121 in the first cooling zone distributes the flue gas evenly while transferring heat and removing dust from the flue gas. After the spray liquid of the first spray layer 121 and the second spray layer 122 in the first cooling zone transfer heat and remove dust from the flue gas, the flue gas enters the second-stage spray cooling zone 130 through the chimney cap of the liquid collecting tray 150;

[0077] In the first-stage spray cooling zone 120, the flue gas temperature drops from 51 °C to 49 °C, generating 10.7 t / h of condensed water, and the condensed water falls into the water tank 110; the dust removal efficiency of the first-stage spray cooling zone 120 is about 70%, and the dust content in the flue gas drops from 30 mg / Nm 3 to 9 mg / Nm 3 .

[0078] Step 2: The first-stage cooling first circulation pump 511 and the first-stage cooling second circulation pump 512 are unit systems; the first-stage cooling first circulation pump 511 extracts 1500 m 3 / h of circulating spray water from the water tank 110 and sends it to the first spray layer 121 to cool the flue gas in a cycle;

[0079] To maintain the stable temperature of the overall circulating water in the first-stage spray cooling zone 120's cooling section, the first-stage cooling second circulation pump 512 pumps 1400 m 3 / h of circulating spray water from the water tank 110 to the plate heat exchanger 200. The plate heat exchanger 200 cools the temperature of 1400 m 3 / h of circulating spray water from 52 °C to 47 °C. The cold source water (800 m 3 / h) of the plate heat exchanger 200 increases in temperature from 22 °C to 30.6 °C; the cooled circulating spray water is sent to the second spray layer 122 of the first-stage cooling zone to cool the flue gas by circulation;

[0080] Step 3: 800 m 3 / h, 30.6 °C water at the cold source outlet of the plate heat exchanger 200 is sent to the first-stage heat pump unit 410 by the plate heat exchanger cold source water supply pump 540. After heat exchange in the evaporator of the first-stage heat pump unit 410, the temperature is reduced to 22 °C and then sent to the cold source inlet of the plate heat exchanger 200; the cold source inlet of the first-stage heat pump unit 410 is connected to the return water of the heat network, and the cold source outlet is connected to the supply water of the heat network to heat the return water of the heat network; realizing the utilization of flue gas waste heat;

[0081] Step 4: The sewage pump 550 sends the circulating spray water in the water tank 110 to the water use points in the factory area; the condensate water in the water tank 110 is sent to the water use points in the factory area to maintain the liquid level balance of the water tank 110.

[0082] Step 5: The flue gas (about 1290000 Nm 3 / h, 49 °C, dust content about 9 mg / Nm 3 ) enters the second-stage spray cooling zone 130. The packing layer 160 below the first spray layer 131 of the second-stage cooling zone distributes the flue gas evenly while transferring heat to the flue gas. The spray liquid of the first spray layer 131 and the second spray layer 132 of the second-stage cooling zone transfer heat to the flue gas. The three-stage roof high-efficiency demister 140 removes the droplets from the flue gas. The low-temperature clean flue gas with a droplet content lower than 20 mg / Nm 3 is discharged from the top of the spray cooling tower 100 and connected to the inlet flue of the wet electrostatic demister after entering the absorption tower, and finally discharged into the atmosphere through the chimney; in the second-stage spray cooling zone 130, the flue gas is cooled from 49 °C to 34 °C, and the generated condensate water volume of 69.3 t / h is collected by the liquid collecting tray 150 and flows into the condensate water extraction storage tank 300; realizing the recycling of condensate water;

[0083] By measures such as increasing the contact area and drainage capacity, reasonably selecting the blade type and spacing, optimizing the flushing system, and strictly following the clear space design to ensure the uniformity of the flow field before and after the demister, the liquid droplets at the outlet of the three-stage roof high-efficiency demister 140 are stably not more than 20 mg / Nm 3 .

[0084] Step 6: Two demister flushing water pumps 530 are provided, one in use and one in standby. The demister flushing water pumps 530 draw 150 m 3 / h of circulating spray water from the bottom of the condensate pumping storage tank 300 and send it to the three-stage roof high-efficiency demister 140 for flushing the three-stage roof high-efficiency demister 140. At the same time, the demister flushing water pumps 530 also serve as flue gas condensate pumping pumps, and a part of the flue gas condensate water in the secondary spray cooling zone 130 is sent to the process water tank through the demister flushing water pumps 530.

[0085] Step 7: Two secondary cooling circulating pumps 520 are provided, with a header pipe system, one in use and one in standby. Since the quality of the condensate water generated in the secondary spray cooling zone 130 is relatively high, 4300 m 3 / h of circulating spray water at 43°C is directly drawn from the bottom of the condensate pumping storage tank 300 by the secondary cooling circulating pumps 520 and sent to the secondary heat pump unit 420. After the circulating spray water is cooled to 32°C through heat exchange in the evaporator of the secondary heat pump unit 420, it is sent to the first spray layer 131 in the secondary cooling zone and the second spray layer 132 in the secondary cooling zone to cool the flue gas in a cycle. The cold source inlet of the secondary heat pump unit 420 is connected to the return water of the heat network, and the cold source outlet is connected to the supply water of the heat network to heat the return water of the heat network, realizing the utilization of flue gas waste heat.

[0086] The specific data is shown in the following table:

[0087]

[0088]

[0089] Example 2

[0090] The difference between this example and Example 1 is that in Step 1, in the primary spray cooling zone 120, the flue gas temperature drops from 51°C to 46°C.

[0091] The specific data is shown in the following table:

[0092]

[0093]

[0094] Example 3

[0095] The difference between this example and Example 1 is that in Step 1, in the primary spray cooling zone 120, the flue gas temperature drops from 51°C to 43°C.

[0096] The specific data is shown in the following table:

[0097] Number Comparison item Unit Example 3 Flue gas volume at the inlet of the spray cooling tower 100 Nm3 / h ～12900 Flue gas temperature at the inlet of the spray cooling tower 100 ℃ ～51 Flue gas temperature at the outlet of the primary spray cooling zone 120 ℃ ～43 Flue gas temperature at the outlet of the secondary spray cooling zone 130 ℃ ～34 Total released heat of flue gas condensation MW 61 Condensate water volume generated in the primary spray cooling zone 120 m3 / h 45.3 Cooling water volume of the primary circulating spray water m3 / h 2700 Water temperature of the primary circulating spray water ℃ ～41 Water temperature of the water tank 110 ℃ ～52 Condensate water volume generated in the secondary spray cooling zone 130 m3 / h 34.7 Cooling water volume of the secondary circulating spray water m3 / h 2000 Water temperature of the condensate water lifting storage tank 300 ℃ ～43 Heat carried by the external drainage of the primary spray cooling zone 120 kJ / h ～9894 Heat carried by the external drainage of the secondary spray cooling zone 130 kJ / h ～6267 Total heat carried by the external drainage kJ / h 16161 Input low-temperature heat source of the heat pump (ignoring heat loss during transportation) kJ / h 203439 Coefficient of performance of the heat pump COP 1.7 Heat of the return water of the heat supply network kJ / h 494066

[0098] According to Embodiments 1-3, it can be known that in the present invention, when the temperature drop of the flue gas in the primary spray cooling zone 120 is 2°C, the total heat carried by the external drainage is the least, and the heat of the return water of the heat supply network is the highest; Embodiment 1 is the preferred embodiment.

[0099] In summary, the present invention adopts hierarchical spray cooling. While the primary spray cooling zone 120 cools the flue gas, most of the dust is washed away. The temperature drop of the flue gas in this zone is controlled to be 2-3°C. The condensate water volume is small, and the corresponding solid content in the condensate water is relatively large, and the water quality is poor. It is discharged by the sewage pump 550 to the corresponding water use point; the secondary spray cooling zone 130 mainly cools the flue gas. The temperature drop of the flue gas in this zone is large, the condensate water volume is large, and the solid content is extremely low. A large amount of high-quality condensate water recovery rate can be achieved, the applicable range of the recovered water is increased, and the makeup water volume of the desulfurization system is reduced; the present invention effectively realizes the hierarchical control of the condensate water quality.

[0100] In the primary spray cooling zone 120, the present invention adopts indirect heat exchange. The heat released by the temperature drop of the flue gas in this zone is transferred to the primary circulating spray water in the primary spray cooling zone 120. The primary circulating spray water transfers the heat to the return water of the heat supply network through the plate heat exchanger 200 and the primary heat pump unit 410, realizing that most of the heat released by the temperature drop of the flue gas in the primary spray cooling zone 120 is recovered and heated by the primary heat pump unit 410 for the return water of the heat supply network; in the secondary spray cooling zone, the condensate water volume in the secondary spray cooling zone 130 is large and the water quality is clean. The heat released by the temperature drop of the flue gas in the secondary spray cooling zone 130 is transferred to the secondary circulating spray water in the secondary spray cooling zone 130, and the low-quality heat of the circulating spray water is recovered and heated for the return water of the heat supply network through the secondary heat pump unit 420; on the premise of meeting the water quality requirements of the heat pump unit 400 for the cooling circulating water, the intermediate heat exchange link is effectively reduced, and the configuration of heat exchange equipment is also reduced. The heat released by the flue gas cooling is recovered and utilized by the heat pump unit 400 to the greatest extent.

[0101] Other parts not described are all prior art.

Claims

1. A two-stage spray flue gas water extraction and waste heat utilization system, characterized in that: It includes a spray cooling tower (100), a plate heat exchanger (200), a condensate water storage tank (300), and a heat pump unit (400). Inside the spray cooling tower (100), there are a water tank (110), a first-stage spray cooling area (120), a second-stage spray cooling area (130), and a third-stage ridge high-efficiency demister (140) from bottom to top. There is an inlet of the spray cooling tower (100) between the water tank (110) and the first-stage spray cooling area (120), and a liquid collecting tray (150) is arranged between the first-stage spray cooling area (120) and the second-stage spray cooling area (130). The bottom of the water tank (110) is connected to the first-stage spray cooling area (120) through a first-stage cooling circulation pump (510) and a plate heat exchanger (200) in sequence. The liquid collecting tray (150) is connected to the second-stage spray cooling area (130) through a condensate water storage tank (300), a second-stage cooling circulation pump (520), and a heat pump unit (400) in sequence. Packing layers (160) are arranged below the first spray layer (121) of the first-stage cooling area and the first spray layer (131) of the second-stage cooling area. The condensate water storage tank (300) is connected to the third-stage ridge high-efficiency demister (140) and a process water tank through a demister flushing water pump (530). The plate heat exchanger (200) is connected to the heat pump unit (400) through a plate heat exchanger cold source water supply pump (540), and the heat pump unit (400) is connected to a heat network.

2. The two-stage spray flue gas water extraction and waste heat utilization system according to claim 1, wherein: The first-stage spray cooling area (120) includes a first spray layer (121) and a second spray layer (122) of the first-stage cooling area from bottom to top; the first-stage cooling circulation pump (510) includes a first-stage cooling first circulation pump (511) and a first-stage cooling second circulation pump (512). The bottom of the water tank (110) is connected to the first spray layer (121) through the first-stage cooling first circulation pump (511), and is connected to the second spray layer (122) of the first-stage cooling area through the first-stage cooling second circulation pump (512) and a plate heat exchanger (200) in sequence at the bottom.

3. The two-stage spray flue gas water extraction and waste heat utilization system according to claim 2, wherein: The heat pump unit (400) includes a first-stage heat pump unit (410) and a second-stage heat pump unit (420); the plate heat exchanger (200) is connected to the first-stage heat pump unit (410), and the first-stage heat pump unit (410) is connected to a heat network.

4. A two-stage spray flue gas water extraction and waste heat utilization system according to claim 3, characterized in that: The second-stage spray cooling area (130) includes a first spray layer (131) and a second spray layer (132) of the second-stage cooling area from bottom to top; both the first spray layer (131) and the second spray layer (132) of the second-stage cooling area are connected to the second-stage heat pump unit (420); the second-stage heat pump unit (420) is connected to a heat network.

5. A two-stage spray flue gas water extraction and waste heat utilization system according to claim 4, characterized in that: The bottom of the water tank (110) is connected to a water-using point through a sewage pump (550).

6. A two-stage spray flue gas water extraction and waste heat utilization system according to claim 5, characterized in that: It also includes an alkali solution tank (600); the alkali solution tank (600) is connected to the connecting pipeline between the water tank (110) and the first-stage cooling second circulation pump (512) through a first alkali solution metering pump (561), and is connected to the connecting pipeline between the condensate water extraction storage tank (300) and the second-stage cooling circulation pump (520) through a second alkali solution metering pump (562).

7. A two-stage spray flue gas water extraction and waste heat utilization system according to claim 6, characterized in that: Two of each of the second-stage cooling circulation pump (520), the demister flushing water pump (530), the plate heat exchanger cold source water supply pump (540), and the sewage pump (550) are provided, one in use and one in reserve.

8. A method for using the two-stage spray flue gas water extraction and waste heat utilization system according to claim 7, characterized in that, It includes the following steps: Step 1: The flue gas from the outlet flue of the absorption tower enters the first-stage spray cooling zone (120) through the flue gas inlet of the spray cooling tower (100). The packing layer (160) below the first spray layer (121) in the first-stage cooling zone evenly distributes the flue gas while transferring heat and removing dust from the flue gas. After the spray liquid of the first spray layer (121) and the second spray layer (122) in the first-stage cooling zone transfer heat and remove dust from the flue gas, the flue gas enters the second-stage spray cooling zone (130) through the flue gas cap of the liquid collecting tray (150); the generated condensate water falls into the water tank (110); the temperature of the flue gas drops by 2 - 3 °C in the first-stage spray cooling zone (120). Step 2: The first-stage cooling first circulation pump (511) extracts circulating spray water from the water tank (110) and sends it to the first spray layer (121) to cool the flue gas in a cycle. The first-stage cooling second circulation pump (512) extracts circulating spray water from the water tank (110) and sends it to the plate heat exchanger (200). After the plate heat exchanger (200) cools the circulating spray water, it sends the circulating spray water to the second spray layer (122) in the first-stage cooling zone to cool the flue gas in a cycle. Step 3: The heat exchange medium in the plate heat exchanger (200) is sent from the cold source outlet to the first-stage heat pump unit (410) through the plate heat exchanger cold source water supply pump (540). After being cooled by heat exchange in the evaporator of the first-stage heat pump unit (410), it is sent to the cold source inlet of the plate heat exchanger (200); the cold source inlet of the first-stage heat pump unit (410) is connected to the return water of the heat network, and the cold source outlet is connected to the supply water of the heat network to heat the return water of the heat network; realizing the utilization of flue gas waste heat. Step 4: The sewage pump (550) sends the circulating spray water in the water tank (110) to the water use points in the factory area. Step 5: After the flue gas enters the second-stage spray cooling zone (130), the packing layer (160) below the first spray layer (131) in the second-stage cooling zone evenly distributes the flue gas while transferring heat to the flue gas. The spray liquid of the first spray layer (131) and the second spray layer (132) in the second-stage cooling zone transfer heat to the flue gas, and the three-stage ridge high-efficiency demister (140) removes the droplets from the flue gas. The low-temperature clean flue gas is discharged from the top of the spray cooling tower (100) and is discharged into the atmosphere through the chimney; the generated condensate water is collected by the liquid collecting tray (150) and flows into the condensate water extraction storage tank (300); realizing the recovery and utilization of condensate water. Step 6: The demister flushing water pump (530) extracts circulating spray water from the bottom of the condensate water extraction storage tank (300) and sends it to the three-stage ridge high-efficiency demister (140) for flushing the three-stage ridge high-efficiency demister (140); meanwhile, the demister flushing water pump (530) also sends the circulating spray water to the process water tank as a side task; Step 7: The secondary cooling circulation pump (520) extracts circulating spray water from the bottom of the condensate water extraction storage tank (300) and sends it to the secondary heat pump unit (420). After the circulating spray water is cooled by heat exchange in the evaporator of the secondary heat pump unit (420), it is sent to the first spray layer (131) and the second spray layer (132) in the secondary cooling area to cool the flue gas in a circulating manner; the cold source inlet of the secondary heat pump unit (420) is connected to the return water of the heat network, and the cold source outlet is connected to the supply water of the heat network to heat the return water of the heat network; realizing the utilization of the waste heat of the flue gas.

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