Heat exchange device, circulating system and method for efficiently recovering waste heat of desulfurization slurry

Abstract

The invention discloses a heat exchange device, a circulating system and a method for efficiently recovering waste heat of desulfurization slurry. The heat exchange device comprises an inlet end box body, an outlet end box body and a plurality of heat exchange pipes communicated with the inlet end box body and the outlet end box body. A slurry inlet is formed in the bottom of the inlet end box body, and a slurry outlet is formed in the top of the outlet end box body; a slope is arranged in the inlet end box body, so that the cross section of the inlet end box body is gradually reduced from bottom to top; and a slope is arranged in the outlet end box body, so that the cross section of the outlet end box body is gradually reduced from top to bottom. According to the invention, direct heat exchange between the desulfurization slurry and the boiler inlet air can be realized under the condition of no need of a heat medium, and the technological process of waste heat recovery of the desulfurization slurry is simplified.

Description

Technical Field

[0001] The present invention relates to the technical field of resource and environmental protection, and particularly to a heat exchange device, a circulation system and a method for efficiently recovering the waste heat of desulfurization slurry. Background Art

[0002] With the development of industry and the continuous progress of society, people's demand for energy is increasing continuously. Due to the high cost and large volatility of new energy, traditional energy has always occupied a dominant position in the domestic and foreign energy markets. However, the energy utilization rate of coal-fired power plants is only 30-40%, which means that more than half of the energy in the process of converting fossil fuels into electric energy is wasted. These wasted energies are discharged into the environment, which not only affects the efficiency of the power plants, but also causes thermal pollution.

[0003] At present, the high-temperature flue gas of thermal power plants is usually treated by the limestone-gypsum wet desulfurization process. The basic principle of wet desulfurization is that the high-temperature flue gas at 110-130°C enters the desulfurization tower and contacts reversely with the desulfurization slurry released from the spray layer. The sulfur-containing substances in the flue gas are removed, and the flue gas temperature is cooled to about 60°C and discharged into the atmosphere through the chimney. The heat loss in the desulfurization process and the smoke exhaust process is extremely large, accounting for about 10-15% of the boiler heat supply. If this part of energy is recovered, the efficiency of the power plant will be greatly improved.

[0004] In the desulfurization process, the lower the temperature of the desulfurization slurry, the better the desulfurization effect. The water vapor in the desulfurization flue gas is in a saturated state and has a high moisture content. During the discharge process, when the flue gas mixes and diffuses with the atmosphere, the temperature decreases, and the water in the flue gas condenses, resulting in the formation of a white plume that is difficult to diffuse around the chimney. Therefore, it is necessary to cool the desulfurization slurry by using cooling water and a heat exchanger to ensure the desulfurization efficiency and the elimination of white smoke in the flue gas.

[0005] However, the high-temperature flue gas volume is large, the demand for cooling water is large, the operating cost is high, and the waste heat recovery utilization rate is low. Therefore, the efficient recovery and full utilization of slurry waste heat have become a technical bottleneck for improving the energy utilization rate of coal-fired power plants.

[0006] In the actual application process, scientific and technological personnel have carried out various forms of exploration on the utilization of waste heat from desulfurization slurry. Waste heat utilization can be roughly divided into the following three methods: (1) Using heat exchange technology, the waste heat of slurry is extracted by heat exchange and transported to the demand side; (2) Using liquid-solid separation technology, the liquid phase waste heat is extracted by solid-liquid separation and transported to the demand side; (3) Using flash evaporation technology, the water in the slurry is quickly converted into steam by flash evaporation and transported to the demand side; However, these technologies are subject to many factors, resulting in unsatisfactory utilization efficiency of desulfurization slurry waste heat. The main limiting factors are as follows: (1) The desulfurization slurry contains non-homogeneous gypsum particles, which often cause problems such as blockage, wear and corrosion of the waste heat recovery system equipment; (2) The thermal balance problem of the desulfurization slurry waste heat recovery system; (3) The water balance problem of the desulfurization slurry system.

[0007] In order to solve the above problems, CN202211209726 discloses a desulfurization slurry waste heat recovery system, which uses a supplementary heat device to supplement heat and adjust the flow of the heat medium flowing between the slurry heat exchanger and the heater, solving the problems of slurry blockage, low heat transfer efficiency, poor flexibility, etc. in the desulfurization slurry waste heat recovery system. However, there are still some technical problems that need to be improved in this patent: (1) The desulfurization slurry waste heat recovery system recovers waste heat through a heat medium, which requires the purchase of a heat medium and related equipment and devices, which is expensive and cumbersome; (2) The heat supply end and the demand end cannot exchange heat directly, and must perform two-stage energy conversion through a heat medium, which inevitably loses some heat, resulting in a relatively low waste heat recovery rate.

[0008] Therefore, how to further optimize the technical route of the desulfurization slurry waste heat recovery system, which can not only simplify the process flow and reduce investment costs, but also efficiently utilize the slurry waste heat and improve the return on investment, is still a key issue that needs to be urgently solved in this field. Summary of the invention

[0009] The present invention provides a heat exchange device, a circulation system and a method for efficiently recovering waste heat of desulfurized slurry, which can realize direct heat exchange between desulfurized slurry and boiler inlet air without the need for a heat medium, thereby simplifying the process of recovering waste heat of desulfurized slurry.

[0010] The technical solution of the present invention is as follows:

[0011] A heat exchange device for efficiently recovering waste heat of desulfurized slurry, comprising an inlet end box, an outlet end box, and a plurality of heat exchange pipes connecting the inlet end box and the outlet end box;

[0012] The bottom of the inlet end box is provided with a slurry inlet, and the top of the outlet end box is provided with a slurry outlet;

[0013] The inlet end box body is provided with a slope, so that the cross-section of the inlet end box body gradually decreases from the bottom to the top; the outlet end box body is provided with a slope, so that the cross-section of the outlet end box body gradually decreases from the top to the bottom.

[0014] The inlet end box body and the outlet end box body are respectively provided with a slope structure for adjusting the flow rate of the slurry in the heat exchange tubes, so that the slurry flow rates in each heat exchange pipeline are the same, ensuring sufficient heat exchange and preventing the slurry from depositing and blocking the heat exchange tubes.

[0015] Preferably, the inclination angle of the slope in the inlet end box body is 4.5 - 7°; the inclination angle of the slope in the outlet end box body is 4.5 - 7°.

[0016] The inclination angle of the slope being 4.5 - 7° means that the included angle between the inclined side wall of the box body and the opposite side wall of the box body is 4.5 - 7°.

[0017] Preferably, the inner diameter of the heat exchange tube is 15 - 35 mm.

[0018] Preferably, the heat exchange device for efficiently recovering the waste heat of the desulfurized slurry is further provided with an induced draft fan, and the heat exchange tubes are arranged at the air inlet of the induced draft fan.

[0019] The induced draft fan accelerates the air flow around the heat exchange tubes, making the heat exchange efficiency between the slurry and the air higher.

[0020] The present invention also provides a circulation system for efficiently recovering the waste heat of the desulfurized slurry, including a desulfurization tower, a filtering device, a circulation pump, a heat exchange device, a boiler induced draft fan, and a backwashing water tank;

[0021] The bottom of the desulfurization tower is a slurry pool, a spray layer and a packing layer are arranged above the slurry pool, a smoke inlet is arranged on the side wall between the packing layer and the slurry pool, and a smoke outlet is arranged at the top of the desulfurization tower; a slurry circulation outlet is arranged on the side wall of the slurry pool, and a slurry circulation inlet is arranged on the spray layer;

[0022] The slurry circulation outlet is connected in sequence through pipelines to the filtering device, the circulation pump, the heat exchange device, and the slurry circulation inlet; the heat exchange device exchanges heat with the boiler inlet air;

[0023] The filtering device includes at least two filters arranged in parallel;

[0024] The backwashing water tank is communicated with the pipeline between the circulation pump and the heat exchange device and is used for backwashing the blocked filters.

[0025] When the circulation system of the present invention is working, large particulate solids are filtered out by the filtering device, and almost 100% of the slurry is all transported to the heat exchange device to exchange heat with the boiler inlet air, and there is almost no loss of the heat of the slurry before heat exchange. At least two filters are arranged in parallel. When the working filter is blocked, it can be switched to another conveying pipeline to ensure the normal operation of the circulation system; when the filter is blocked, a water pipe is introduced behind the slurry circulation pump to convey the standby water in the backwashing water tank to backwash the filter and solve the blockage problem.

[0026] In the desulfurization tower described, in the tower body above the spray layer, a demister, a condenser, and a liquid accumulation tank are sequentially arranged from top to bottom.

[0027] The filter described is a wire mesh filter; the filter aperture is 0.4 - 0.65 mm.

[0028] The present invention also provides a method for efficiently recovering the waste heat of the desulfurization slurry based on the above-mentioned circulation system, including the following steps:

[0029] (1) The desulfurization slurry in the slurry pool is transported to the filtering device by a circulation pump to filter out large solid particles in the slurry and prevent blockage and wear of the pipeline and the heat exchange device;

[0030] (2) The slurry after filtration enters the heat exchange device to exchange heat and cool down with the boiler inlet air;

[0031] (3) The slurry after heat exchange is sent back to the spray layer of the desulfurization tower to carry out desulfurization reaction and heat exchange with the high-temperature flue gas, removing sulfur components in the flue gas and cooling the flue gas temperature at the same time;

[0032] (4) The slurry after the desulfurization reaction returns to the slurry pool for a new round of slurry circulation heat exchange;

[0033] The high-temperature flue gas entering the desulfurization tower from the flue gas inlet passes through the liquid accumulation tank, the condenser, and the demister in sequence after the desulfurization reaction, is further cooled and deeply desulfurized, and finally discharged through the flue gas outlet.

[0034] Preferably, in step (2), the temperature of the slurry in the heat exchange device is 55 - 60 °C, and the temperature of the boiler inlet air outside the heat exchange device is -20 - -30 °C; after heat exchange, the slurry temperature drops to 10 - 30 °C, and the boiler inlet air temperature rises to 0 - 10 °C.

[0035] Preferably, the flue gas inlet temperature of the flue gas inlet is 110 - 130 °C, and the temperature of the flue gas after the desulfurization reaction is 50 - 60 °C.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] The high-efficiency recycling circulation system for the waste heat of desulfurization slurry of the present invention enables the desulfurization slurry to directly exchange heat with the demand side (boiler inlet air) without a heat transfer medium, reducing the energy loss of heat energy between the desulfurization slurry, the heat transfer medium, and the boiler inlet air, maximizing the utilization of the waste heat of the desulfurization slurry, and efficiently recovering and utilizing the waste heat of the slurry. Since the desulfurization slurry directly exchanges heat with the boiler inlet air, the heating effect of the boiler inlet air is excellent, the temperature reduction efficiency of the desulfurization slurry is high, and the cooling and desulfurization effects on the high-temperature flue gas are better. The reduction in the flue gas temperature causes the flue gas velocity to slow down, passing more slowly through the upper structure of the desulfurization tower, fully condensing and demisting, thereby improving the purification efficiency of the flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic connection diagram of the desulfurization slurry waste heat circulation system shown in the embodiment of the present invention. In the figure: desulfurization tower 1, slurry filter 2, standby slurry filter 3, slurry circulation pump 4, backwashing standby water tank 5, slurry heat exchange device 6, induced draft fan 7; flue gas outlet 11, demister layer 12, condenser 13, liquid accumulation tank 14, spray layer 15, packing layer 16, slurry pool 17, flue gas inlet 18, first valve 31, second valve 32, water stop valve 51, third valve 52;

[0039] Figure 2 It is a schematic diagram of the slurry heat exchange device shown in the embodiment of the present invention. In the figure: slurry inlet 61, left header speed regulation ramp 62, left header 63, slurry heat exchange tube 64, right header 65, left header speed regulation ramp 66, slurry outlet 67. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The present invention will be further described in detail below in conjunction with the drawings and embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention and do not impose any limitations on it.

[0041] As Figure 1 shown, the high-efficiency recycling circulation system for the waste heat of desulfurization slurry of the present invention includes a desulfurization tower 1, a slurry filter 2, a standby slurry filter 3, a slurry circulation pump 4, a backwashing water tank 5, a slurry heat exchange device 6, and an induced draft fan 7.

[0042] The bottom of the desulfurization tower is a slurry pool 17. Above the slurry pool 17, from top to bottom, there are a demister 12, a condenser 13, a liquid accumulation tank 14, a spray layer 15, and a packing layer 16; on the left side and the top of the tower body, there are a flue gas inlet 17 and a flue gas outlet 11 respectively; on the side wall of the slurry pool 17, there is a slurry circulation outlet, and on the spray layer 16, there is a slurry circulation inlet; the slurry circulation outlet is connected to the inlet of the slurry filter 2 through a pipeline, the outlet of the slurry filter 2 is connected to the inlet of the slurry circulation pump 4 through a pipeline, the outlet of the slurry circulation pump 4 is connected to the inlet of the slurry heat exchange device 6 through a pipeline, and the outlet of the slurry heat exchange device 6 is connected to the slurry circulation inlet of the spray layer through a pipeline.

[0043] As shown Figure 2 in the figure, the slurry heat exchange device 6 includes a slurry inlet 61, a left header 63, a left header speed regulation ramp 62, slurry heat exchange tubes 64, a right header 65, a right header speed regulation ramp 66, and a slurry outlet 67. The left side wall of the slurry heat exchange device 6 is provided with the slurry inlet 61, which is communicated with the left header 63; the slurry heat exchange tubes 64 are respectively communicated with the two headers; the right header 65 is communicated with the slurry outlet 67.

[0044] The left header 63 and the right header 65 are respectively provided with a ramp structure, and the ramp inclination angle is 4.5 - 7°, which is used to adjust the slurry flow rate, so that the slurry flow rate in each slurry heat exchange tube 64 is consistent, fully exchange heat and prevent slurry deposition and blockage.

[0045] The desulfurized slurry flowing in the slurry heat exchange tube 64 exchanges heat with the boiler inlet air flowing outside the tube. After heat exchange, the desulfurized slurry flows into the right header 65 and finally flows out from the slurry outlet 67.

[0046] The slurry temperature in the slurry heat exchange tube 64 of the slurry heat exchange device 6 is 55 - 60°C, and the boiler inlet air temperature outside the tube is -20 - -30°C; after heat exchange, the slurry temperature drops to 20°C, and the inlet air temperature rises to 0 - 10°C.

[0047] The inlet flue gas temperature of the desulfurization tower 1 is 110 - 130°C. After the high-temperature flue gas undergoes a desulfurization reaction with the desulfurized slurry, the flue gas temperature is also cooled to 60°C.

[0048] The slurry filter 2 and the standby slurry filter 3 are arranged in parallel. When blocked, it can be switched to another slurry conveying pipeline to ensure the normal operation of the circulation system.

[0049] The circulating system for efficiently recovering the waste heat of the desulfurized slurry of the present invention is provided with an anti-flushing device. When the slurry filter is blocked, a water pipe is introduced behind the slurry circulation pump to convey the water in the anti-flushing water tank 5 to flush it and solve the blockage problem.

[0050] The method for preheating recovery based on the circulating system for efficiently recovering the waste heat of the desulfurized slurry of the present invention includes the following steps:

[0051] S1: The desulfurized slurry in the slurry pond 17 is transported to the slurry filter 2 through the slurry circulation pump 4 to filter out the large solid particles in the slurry, preventing blockage and wear of the pipeline and the slurry heat exchanger 6;

[0052] S2: The slurry after filtration enters the slurry heat exchanger 6 and exchanges heat with the boiler inlet air to cool down;

[0053] S3: The slurry after heat exchange is returned to the spray layer 15 of the desulfurization tower 1, where it undergoes desulfurization and heat exchange reactions with the high-temperature flue gas, removing sulfur from the flue gas while cooling the flue gas temperature.

[0054] S4: The slurry that has completed the desulfurization reaction finally returns to the slurry pond 17 for a new round of slurry circulation and heat exchange.

[0055] S5: The flue gas that enters the desulfurization tower from the flue gas inlet, after completing the desulfurization reaction, successively passes through the liquid accumulation tank, condenser, and demister, for further cooling and deep desulfurization, and finally is discharged through the flue gas outlet.

[0056] The above-described embodiments have detailed the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements, equivalent replacements, etc. made within the scope of the principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A heat exchange device for efficiently recovering waste heat from desulfurized slurry, characterized in that: It includes an inlet end box, an outlet end box, and a plurality of heat exchange tubes connecting the inlet end box and the outlet end box; The bottom of the inlet end box is provided with a slurry inlet, and the top of the outlet end box is provided with a slurry outlet; The inlet box body is provided with a slope so that the cross section of the inlet box body gradually decreases from the bottom to the top; the outlet box body is provided with a slope so that the cross section of the outlet box body gradually decreases from the top to the bottom.

2. The heat exchange device for efficiently recovering waste heat from desulfurized slurry according to claim 1 is characterized in that: The inclination angle of the slope in the box at the inlet end is 4.5-7°; the inclination angle of the slope in the box at the outlet end is 4.5-7°.

3. The heat exchange device for efficiently recovering waste heat from desulfurized slurry according to claim 1 is characterized in that: The heat exchange device for efficiently recovering waste heat from desulfurized slurry is also provided with an induced draft fan, and the heat exchange pipe is arranged at the air inlet of the induced draft fan.

4. A circulation system for efficiently recovering waste heat from desulfurized slurry, characterized in that: It includes a desulfurization tower, a filtering device, a circulating pump, a heat exchange device according to any one of claims 1 to 3, a boiler induced draft fan, and a backwash water tank; The bottom of the desulfurization tower is a slurry pool, a spray layer and a packing layer are arranged above the slurry pool, a smoke inlet is arranged on the side wall between the packing layer and the slurry pool, and a smoke outlet is arranged on the top of the desulfurization tower; a slurry circulation outlet is arranged on the side wall of the slurry pool, and a slurry circulation inlet is arranged on the spray layer; The slurry circulation outlet is connected to the filter device, the circulation pump, the heat exchange device, and the slurry circulation inlet in sequence through a pipeline; the heat exchange device exchanges heat with the boiler inlet air; The filtering device comprises at least two filters arranged in parallel; The backwash water tank is connected to the pipeline between the circulation pump and the heat exchange device and is used for backwashing the clogged filter.

5. The circulation system for efficiently recovering waste heat from desulfurized slurry according to claim 4 is characterized in that: In the desulfurization tower, a demister, a condenser and a liquid storage tank are arranged in sequence from top to bottom in the tower body above the spray layer.

6. A method for efficiently recovering waste heat from desulfurized slurry based on the circulation system according to claim 4 or 5, characterized in that: The following steps are involved: (1) The desulfurized slurry in the slurry pool is transported to the filtering device through a circulating pump to filter out large solid particles in the slurry to prevent clogging and wear of pipelines and heat exchange devices; (2) The filtered slurry enters the heat exchange device and exchanges heat with the boiler inlet air for cooling; (3) After the heat exchange, the slurry is returned to the spray layer of the desulfurization tower to react with the high-temperature flue gas for desulfurization and heat exchange, removing the sulfur in the flue gas while cooling the flue gas temperature; (4) The slurry that has completed the desulfurization reaction returns to the slurry pool for a new round of slurry circulation heat exchange; The high-temperature flue gas entering the desulfurization tower from the smoke inlet completes the desulfurization reaction and then passes through the liquid accumulation tank, condenser, and demister in sequence for further cooling and deep desulfurization, and is finally discharged through the smoke outlet.

7. The method for efficiently recovering waste heat from desulfurized slurry according to claim 6, characterized in that: In step (2), the slurry temperature in the heat exchange device is 55 to 60°C, and the boiler inlet air temperature outside the heat exchange device is -20 to -30°C; after heat exchange, the slurry temperature drops to 10 to 30°C, and the boiler inlet air temperature rises to 0 to 10°C.

8. The method for efficiently recovering waste heat from desulfurized slurry according to claim 6, characterized in that: The smoke inlet temperature is 110-130°C, and the smoke temperature after the desulfurization reaction is completed is 50-60°C.

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