Ammonia desulfurization slurry waste heat utilization system

Abstract

The utility model discloses an ammonia process desulfurization slurry waste heat utilization system, which belongs to the technical field of flue gas desulfurization and comprises an absorption tower, a circulating heat exchange system and a slurry circulating system, wherein a water washing spraying layer and a concentration spraying layer are arranged in the absorption tower up and down, the circulating heat exchange system is connected with the water washing spraying layer, and the slurry circulating system is connected with the concentration spraying layer. Tower trays through which flue gas can pass but liquid cannot pass are arranged at the lower parts of the washing spraying layer and the concentrating spraying layer. According to the system, a circulating heat exchange system is arranged beside an absorption tower, namely, a bypass pipeline is additionally arranged at an outlet of a water circulating pump and enters a heat exchanger, and heat taken out from water circulating slurry and introduced demineralized water are subjected to heat exchange in the heat exchanger. Heat recovery is carried out in a mode of heating demineralized water by using heat of slurry, and water consumption of a desulfurization system is reduced. The system is used for heating desalted water, so that the steam consumption of the desalted water treatment system can be reduced; meanwhile, flue gas condensed water is used as make-up water of the desulfurization system, so that the make-up water amount can be reduced, and the heat efficiency of the unit is improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to flue gas desulfurization technical field especially relates to a kind of ammonia desulfurization slurry waste heat utilization system. BACKGROUND

[0002] Ammonia desulfurization is a kind of high efficiency, low energy consumption wet desulfurization mode, desulfurization process is gas-liquid phase reaction, reaction rate is fast, absorbent utilization rate is high, can keep desulfurization efficiency 95-99%.Ammonia desulfurization technology is based on the reaction of NH3 and SO2 in aqueous solution.NH3 in absorption section of flue gas desulfurization tower absorbs SO2 in boiler flue gas, and obtains ammonium sulfite or bisulfite solution.In the oxidation section of desulfurization tower, high-temperature oxidation air is blown into the oxidation section, ammonium sulfite is oxidized to generate ammonium sulfate solution, then the heat of boiler high-temperature flue gas is used to concentrate and crystallize ammonium sulfate solution, and the concentrated and crystallized ammonium sulfate solution is separated by cyclone and dewatered by centrifuge, and then dried to obtain ammonium sulfate product.Its biggest feature is that SO2 can be recycled and used as a high-value commercial product.The by-product ammonium sulfate is a nitrogen fertilizer with excellent performance and has good market prospects.

[0003] The flue gas at the outlet of boiler induced draft fan enters the absorption tower through the original flue gas inlet baffle door, first contacts the sprayed layer of oxidized concentrated ammonium sulfate slurry in countercurrent, fully utilizes the heat in flue gas to evaporate the moisture in oxidized ammonium sulfate solution, and the solution is supersaturated to precipitate ammonium sulfate crystals, and the cooled flue gas enters the absorption section and contacts the three-layer sprayed layer of absorption liquid from the circulating tank in countercurrent, and sulfur dioxide is fully absorbed.The flue gas temperature at the inlet of absorption tower with saturated crystals is usually not lower than 110 DEG C, and the flue gas exhaust temperature is 134 DEG C in some projects, which is relatively high, and in this case, the heat of flue gas is discharged to the atmosphere with clean flue gas after desulfurization, causing heat waste.Therefore, an ammonia desulfurization slurry waste heat utilization method is urgently needed to fully utilize the heat. CONTENT OF UTILITY MODEL

[0004] The utility model aims at providing a kind of ammonia desulfurization slurry waste heat utilization system, can simultaneously give consideration to the principle of saturation crystallization in tower and heat recovery full utilization, heat recovery is carried out by the way of slurry heat heating desalted water, and the water consumption of desulfurization system is reduced.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the utility model is:

[0006] A kind of ammonia desulfurization slurry waste heat utilization system, including the absorption tower that water washing spray layer and concentration spray layer are arranged inside up and down, circulating heat exchange system connected with water washing spray layer and slurry circulating system connected with concentration spray layer, the lower part of water washing spray layer and concentration spray layer is all provided with the tray that flue gas can pass through but liquid cannot pass through.

[0007] The further improvement of the technical scheme of the utility model lies in that the slurry circulating system comprises a slurry circulating tank and a slurry circulating pump arranged outside the absorption tower, the bottom of the slurry circulating tank is connected with the slurry circulating pump and the slurry circulating tank is used for conveying the slurry to the concentration section and the absorption section, and the slurry collected after the reaction of the absorption section is returned to the slurry circulating tank.

[0008] The further improvement of the technical scheme of the utility model lies in that the circulating heat exchange system comprises a water washing circulating pump and a heat exchanger, the heat exchanger is communicated with the external desalted water, the spraying water of the circulating heat exchange system enters the heat exchanger to exchange heat and then enters the absorption tower to spray, and the water sprayed is collected and recycled.

[0009] The further improvement of the technical scheme of the utility model lies in that the heat exchanger is a plate heat exchanger.

[0010] Thanks to the above technical scheme, the utility model has the following technical progress:

[0011] The application discloses an ammonia desulfurization slurry waste heat utilization system, a circulating heat exchange system is arranged beside the absorption tower, that is, a bypass pipeline is added at the outlet of the water circulating pump and enters the heat exchanger, and the heat in the water circulating slurry is exchanged with the introduced desalted water in the heat exchanger. The heat is recovered by heating the desalted water with the heat of the slurry, and the water consumption of the desulfurization system is reduced. The system can heat the desalted water, so that the steam consumption of the desalted water treatment system is reduced; meanwhile, the flue gas condensate water is used as the make-up water of the desulfurization system, so that the make-up water consumption is reduced; the process reduces the exhaust gas temperature and improves the thermal efficiency of the unit. The system can be applied to different capacity coal-fired units. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a schematic view of the ammonia desulfurization slurry waste heat utilization system of the utility model;

[0013] In the drawings, 1 is an absorption tower, 2 is a plate heat exchanger, 3 is a slurry circulating tank, 4 is a slurry circulating pump, 5 is a water washing circulating pump, and 6 is a tower tray. DETAILED DESCRIPTION

[0014] The utility model will be further described in detail in combination with the embodiments as follows:

[0015] As shown in the drawings, Figure 1 A kind of ammonia desulfurization slurry waste heat utilization system, including absorption tower 1 that is arranged inside up and down water washing spray layer and concentration spray layer, with the circulating heat exchange system of water washing spray layer connection and with the slurry circulating system of concentration spray layer connection, the lower portion of water washing spray layer and concentration spray layer is all provided with tower tray 6, and flue gas can pass through but liquid cannot pass through.The circulating heat exchange system and the slurry circulating system are arranged outside absorption tower 1.

[0016] A water washing section is arranged in the ammonia desulfurization system, that is, a certain flow of water is sent into the water washing spray layer of the absorption tower to further wash the ammonia, hyponitrite and sulfamate entrained in the flue gas, recover the ammonia in the flue gas, and further wash the particulate matters in the flue gas. The circulating heat exchange system is arranged in the water washing section and includes a water washing circulating pump 5 and a heat exchanger 2. The spray water of the circulating heat exchange system enters the heat exchanger 2 to be heat exchanged after passing through the water washing circulating pump 5, and then enters the absorption tower 1 to be sprayed, and the water after being sprayed is collected to be recycled again. Meanwhile, the spray water of the circulating heat exchange system heats the external desalted water.

[0017] The slurry circulating system includes a slurry circulating tank 3 arranged outside the absorption tower 1 and a slurry circulating pump 4. The slurry circulating tank 3 is connected with the slurry circulating pump 4 at the bottom and delivers the slurry to the concentration section and the absorption section, and meanwhile, the slurry collected after the reaction of the absorption section is returned to the slurry circulating tank 3.

[0018] The heat exchanger 2 is a plate heat exchanger. The material directly contacting with the slurry is 2205, which meets the anticorrosion requirement.

[0019] An application example:

[0020] After the slurry of the water washing spray layer is heat exchanged by the flue gas by using the ammonia desulfurization slurry waste heat utilization system, the temperature can reach 55-60℃. A bypass pipeline is added at the outlet of the water washing circulating pump 5 to enter the heat exchanger 2. The heat in the water circulating slurry is exchanged with the introduced desalted water in the heat exchanger 2. For example, in a certain project, the desalted water is increased from 20℃ to 39℃ in winter, and the desalted water is heated from 30℃ to 39℃ in summer. Meanwhile, the slurry with reduced temperature is returned to the absorption tower 1 to continue the reaction with the flue gas and reduce the flue gas temperature, and the heat in the flue gas is taken away. The condensate water amount is 10.3t / h, and the condensed water is used as the make-up water of the desulfurization system.

[0021] Recovery heat calculation: The flue gas temperature is reduced by 3℃.

[0022] Unit hour heat recovery data table

[0023] Season Flow (t / h) Inlet water (°C) Return water (°C) Heat (GJ) Winter 330 20 39 26.33 Summer 330 30 39 12.47

[0024] Condensate water amount calculation: 10.3t / h, and the condensed water is used as the make-up water of the desulfurization system. The annual saved water is about 10.3x8000=8.24 million tons per year.

[0025] The annual recovered heat is about 16.4 million GJ (single set).

Claims

1. An ammonia desulfurization slurry waste heat utilization system, characterized in that: The absorption tower (1) comprises a water washing spray layer and a concentration spray layer arranged on the inside up and down, a circulating heat exchange system connected with the water washing spray layer, and a slurry circulating system connected with the concentration spray layer, and the lower part of the water washing spray layer and the concentration spray layer is provided with a tower tray (6) through which flue gas can pass but liquid cannot pass.

2. The system according to claim 1, characterized in that: The slurry circulating system comprises a slurry circulating tank (3) and a slurry circulating pump (4) arranged outside the absorption tower (1), the bottom of the slurry circulating tank (3) is connected with the slurry circulating pump (4) and delivers slurry to the concentration section and the absorption section, and the slurry collected after the reaction of the absorption section is returned to the slurry circulating tank (3).

3. The system according to claim 1, characterized in that: The circulating heat exchange system comprises a water washing circulating pump (5) and a heat exchanger (2), the heat exchanger (2) is connected with external desalted water, the spray water of the circulating heat exchange system enters the heat exchanger (2) to be heat exchanged and then enters the absorption tower (1) to be sprayed, and the collected sprayed water is circulated again.

4. The system according to claim 3, characterized in that: The heat exchanger (2) is a plate heat exchanger.

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