A high-efficiency and energy-saving dual heat pump deammoniation method and device

Abstract

The present invention discloses a highly efficient and energy-saving dual heat pump deammoniation method, which includes the following aspects: A. The temperature of ammonia-containing wastewater rises, and the wastewater is sprayed into the deammoniation tower from the top to remove ammonia therein; B. The ammonia-containing steam discharged from the top of the tower is pressurized to form superheated gas as a heat source for the tower bottom, and enters the ammonia steam reboiler to heat the tower bottom liquid. After the heat of the ammonia-containing steam is removed, a part of it is converted into dilute ammonia water, and another part of the ammonia-containing steam that is not condensed is used to prepare ammonia water. A part of the dilute ammonia water is used as a spray liquid, and the other part enters the deammoniation tower for cyclic deammoniation; C. The deammoniation qualified wastewater discharged from the tower bottom uses a steam heat pump to evacuate and vaporize the high-temperature deammoniation wastewater under the action of fresh steam, and low-pressure steam is extracted. After mixing, secondary steam is generated to provide heat to the steam reboiler to heat the bottom liquid; the deammoniation wastewater is discharged from the system after heat exchange. The present invention uses two heat pumps in combination, which can greatly reduce the use of fresh steam and transportation insurance costs.

Description

Technical Field

[0001] The invention relates to a method for treating ammonia nitrogen wastewater, and in particular to a high-efficiency and energy-saving dual heat pump deammoniation method and device. Background Art

[0002] Steam stripping is widely used in industrial practice because of its mature technology, stable operation and strong adaptability to changes in ammonia nitrogen concentration. Steam stripping is to adjust the pH value of wastewater to alkaline, then introduce air or steam into the packed tower, and blow free ammonia in the wastewater into the atmosphere or steam through gas-liquid contact, so that ammonia nitrogen is transferred from the liquid phase to the gas phase. Steam stripping is suitable for treating low-concentration ammonia nitrogen wastewater at room temperature, and acid must be used to absorb the ammonia nitrogen transferred to the air to prevent secondary pollution of the atmosphere. At the same time, attention should be paid to the treatment of problems such as liquid carryover caused by large amounts of air discharge. Since the steam stripping method can increase the wastewater temperature and increase the proportion of ammonia stripped at a certain pH value, a higher ammonia nitrogen removal rate can be achieved. At the same time, the top product can be fully condensed, partially condensed, cooled and neutralized by acid liquid to obtain ammonia water, ammonia gas and ammonium salts as needed. Compared with the air stripping method, the steam stripping method is more widely used because of its strong adaptability to changes in ammonia nitrogen concentration in wastewater and high ammonia nitrogen removal rate. However, according to statistics, the traditional deamination method requires at least 125 kg of steam per cubic meter of wastewater, and the conventional pressurized deamination process consumes 120 to 160 kg / h of energy per ton of water. The steam requires high grade and the steam pressure is generally above 1 MPa, resulting in high costs for ammonia nitrogen wastewater treatment. Enterprises are unwilling or unable to bear the treatment costs. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art in the treatment of ammonia nitrogen wastewater, the present invention provides a highly efficient and energy-saving dual heat pump deammoniation method and device which is not only safe, stable and reliable in process, but also has low treatment and operation costs and reduces fresh steam consumption.

[0004] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0005] The present invention provides a highly efficient and energy-saving dual heat pump deammoniation method, which includes the following aspects:

[0006] A. The ammonia-containing wastewater from outside the boundary is preheated by condensate and tower bottom outlet water, and then sprayed into the deamination tower from the top, where it contacts with the rising steam in countercurrent to transfer mass and heat, and remove ammonia from the ammonia-containing wastewater;

[0007] B. The ammonia-containing steam discharged from the top of the tower is pressurized by the ammonia vapor compressor, and the electric energy is converted into internal energy. The steam temperature rises to form superheated gas. The superheated gas is saturated after being sprayed with condensate to increase humidity. As the heat source of the tower bottom, it enters the ammonia vapor reboiler to heat the tower bottom liquid. After the heat of the ammonia-containing steam is removed, a part of it is converted into dilute ammonia water, and the other part of the ammonia-containing steam that is not condensed enters the integrated reactor and the ammonia water storage tank to prepare ammonia water. The dilute ammonia water is discharged from the ammonia vapor reboiler and enters the condensate tank for buffering. After being pressurized by the condensate pump, a part of it is used as spray liquid, and the other part is mixed with the feed and enters the deammoniation tower for cyclic deammoniation;

[0008] C. The qualified deammoniation wastewater discharged from the bottom of the tower enters the heat pump evaporator through a pump. The high-temperature deammoniation wastewater is evacuated and vaporized by the steam heat pump under the action of fresh steam from outside the boundary, and low-pressure steam is extracted. After mixing, secondary steam is generated to provide heat to the steam reboiler to heat the kettle liquid; the deammoniation wastewater should be reduced in temperature due to flash vaporization, and then pressurized by a pump, heat exchanged with the feed heat exchanger to cool it down, and then discharged from the system through the deammoniation wastewater outlet.

[0009] The present invention also provides a device for realizing the described high-efficiency and energy-saving dual heat pump deammonification method, which comprises a make-up water inlet, an ammonia-containing wastewater inlet, a fresh steam inlet, a qualified ammonia water outlet, a condensed water outlet, a deammonification wastewater outlet, a deammonification tower, a tail gas absorption tower, a comprehensive reactor, and an ammonia water storage tank; the lower part of the deammonification tower is respectively connected to the steam reboiler inlet, the tower bottom pump, and the ammonia vapor reboiler circulation pump; the ammonia vapor reboiler circulation pump is connected to the ammonia vapor reboiler, the tower bottom pump is connected to the heat pump evaporator, the heat pump evaporator and the fresh steam inlet are respectively connected to the steam heat pump inlet, and the heat pump evaporator is connected to the deammonification wastewater outlet through a discharge pump and a feed heat exchanger; the steam heat pump outlet is connected to the steam reboiler, and the steam reboiler outlet is respectively connected to the deammonification tower middle inlet and the condensed water tank, which is connected to the condensed water outlet after passing through the waste heat exchanger through the condensate pump; the ammonia-containing wastewater inlet is sequentially connected to the raw water tank, the feed pump, the waste heat exchanger, the feed heat exchanger, the deammonification The upper inlet of the ammonia tower is connected; the top outlet of the deammonification tower is connected to the ammonia vapor compressor, the ammonia vapor compressor is connected to the upper inlet of the ammonia vapor reboiler, the upper outlet of the ammonia vapor reboiler is respectively connected to the middle inlet of the deammonification tower and the upper outlet of the condensate tank, the upper outlet of the condensate tank is connected to the integrated reactor, the lower outlet of the ammonia vapor reboiler is connected to the upper inlet of the condensate tank, and the lower outlet of the condensate tank is respectively connected to the outlet of the ammonia vapor compressor and the outlet of the feed heat exchanger through a condensate pump; the make-up water inlet is connected to the tail gas absorption tower, the lower part of the tail gas absorption tower is connected to the washing circulation tank, the lower outlet of the washing circulation tank is connected to the integrated reactor through a tail gas washing pump, the lower outlet of the integrated reactor is respectively connected to the ammonia water heat exchanger and the ammonia water storage tank through an ammonia water circulation pump, the ammonia water heat exchanger is connected to the integrated reactor, the upper outlets of the washing circulation tank, the integrated reactor and the ammonia water storage tank are all connected to the lower inlet of the tail gas absorption tower, and the lower outlet of the ammonia water storage tank is connected to the qualified ammonia water outlet through an ammonia water delivery pump.

[0010] The beneficial effects of the present invention are as follows: by making full use of the waste heat of the bottom liquid discharged from the deamination tower and using the two heat pumps, the MVR heat pump and the TVR heat pump, in combination, the use of fresh steam can be reduced to 30-42% of that in the conventional process; the electricity fee and the steam fee are uniformly converted into the operating fee, and compared with the conventional process, the overall operating fee is reduced to 55-75%. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the process structure of the present invention.

[0012] In the figure, 1, water replenishment inlet 2, deammonification tower 3, tail gas absorption tower 4, washing circulation tank 5, tail gas washing pump 6, ammonia water heat exchanger 7, qualified ammonia water outlet 8, ammonia water delivery pump 9, condensate water outlet 10, deammonification wastewater outlet 11, ammonia water storage tank 12, ammonia water circulation pump 13, integrated reactor 14, ammonia vapor compressor 15, condensate pump 16, feed heat exchanger 17, waste heat exchanger 18, condensate tank 19, ammonia vapor reboiler 20, ammonia vapor reboiler circulation pump 21, tower bottom pump 22, feed pump 23, condensate water pump 24, raw water tank 25, ammonia wastewater inlet 26, discharge pump 27, heat pump evaporation tank 28, condensate water tank 29, steam reboiler 30, steam heat pump 31, fresh steam inlet. DETAILED DESCRIPTION

[0013] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in combination with specific implementation modes according to the accompanying drawings.

[0014] The present invention provides a highly efficient and energy-saving dual heat pump deammoniation method, which includes the following aspects:

[0015] A. The ammonia-containing wastewater from outside the boundary is preheated by condensate and tower bottom outlet water to raise its temperature (heated to 70~90℃), and then sprayed into the deamination tower from the top, where it contacts with the rising steam in countercurrent to transfer mass and heat, and remove ammonia from the ammonia-containing wastewater;

[0016] B. The ammonia-containing steam (temperature of 85-100℃, concentration of 10-30%) discharged from the top of the tower is pressurized by the ammonia vapor compressor, and the electric energy is converted into internal energy. The steam temperature rises to form superheated gas. After the superheated gas is sprayed and humidified by the condensate, it reaches saturation and enters the ammonia vapor reboiler as the heat source of the tower bottom to heat the tower bottom liquid. After the heat of the ammonia-containing steam is removed, a part of it is converted into 2-6% dilute ammonia water, and the other part of the uncondensed 25-35% ammonia-containing steam enters the comprehensive reactor and the ammonia water storage tank to prepare ammonia water. The dilute ammonia water is discharged from the ammonia vapor reboiler and enters the condensate tank buffer. After being pressurized by the condensate pump, a part of it is used as spray liquid, and the other part is mixed with the feed and enters the deammonification tower for cyclic deammonification. This process is the working process of the MVR heat pump. Due to the input of electric energy, the input of steam is reduced. According to the ammonia nitrogen concentration of the feed ammonia-containing wastewater, the steam input can be saved by about 40-60%;

[0017] C. The qualified deammoniation wastewater discharged from the tower kettle enters the heat pump evaporator through a pump. The steam heat pump is used to evacuate and vaporize the high-temperature deammoniation wastewater under the action of fresh steam from outside the boundary, and low-pressure steam is extracted. After mixing, secondary steam is generated to provide heat to the steam reboiler to heat the kettle liquid; the deammoniation wastewater should be reduced in temperature due to flash vaporization, and then pressurized by the pump and cooled by heat exchange with the feed heat exchanger, and then discharged from the system through the deammoniation wastewater outlet. This process is the TVR heat pump working project. The amount of steam extracted is different according to the pressure of the raw steam. Taking 0.30-0.80MPa steam as the benchmark, it can reduce the raw steam input by 8-25%. .

[0018] The device of the dual heat pump deammonification method of the present invention is a highly efficient and energy-saving device, which includes a water inlet 1, an ammonia-containing wastewater inlet 25, a fresh steam inlet 31, a qualified ammonia water outlet 7, a condensed water outlet 9, a deammonification wastewater outlet 10, a deammonification tower 2, a tail gas absorption tower 3, a comprehensive reactor 13, and an ammonia water storage tank 11; the lower part of the deammonification tower is respectively connected to the steam reboiler 29 inlet, the tower bottom pump 21, and the ammonia steam reboiler circulation pump 20; the ammonia steam reboiler circulation pump 20 is connected to the ammonia steam reboiler 19, and the tower bottom pump is connected to the heat pump steam The steam inlet of the steam heat pump 30 is connected to the inlet of the steam heat pump 30 respectively, and the heat pump evaporator is connected to the outlet 10 of the deammoniation wastewater through the discharge pump 26 and the feed heat exchanger 16; the outlet of the steam heat pump 30 is connected to the steam reboiler 29, and the outlet of the steam reboiler is connected to the middle inlet of the deammoniation tower 2 and the condensate tank 28 respectively, and the condensate tank 28 is connected to the condensate outlet 9 after passing through the waste heat exchanger 17 through the condensate pump 23; the ammonia-containing wastewater inlet 25 is connected to the raw water tank 24, the feed pump 22, the waste heat exchanger 16 in sequence. 17, the feed heat exchanger 16 is connected to the upper inlet of the deamination tower 2; the top outlet of the deamination tower is connected to the ammonia vapor compressor 14, the ammonia vapor compressor is connected to the upper inlet of the ammonia vapor reboiler 19, the upper outlet of the ammonia vapor reboiler is respectively connected to the middle inlet of the deamination tower 2 and the upper outlet of the condensate tank 18, the upper outlet of the condensate tank is connected to the integrated reactor 13, the lower outlet of the ammonia vapor reboiler is connected to the upper inlet of the condensate tank, and the lower outlet of the condensate tank is respectively connected to the outlet of the ammonia vapor compressor and the outlet of the feed heat exchanger through the condensate pump 15; the water inlet 1 is connected to the tail gas absorption tower 3, the lower part of the tail gas absorption tower is connected to the washing circulation tank 4, the lower outlet of the washing circulation tank is connected to the integrated reactor through the tail gas washing pump 5, the lower outlet of the integrated reactor is connected to the ammonia water heat exchanger 6 and the ammonia water storage tank 11 respectively through the ammonia water circulation pump 12, the ammonia water heat exchanger is connected to the integrated reactor, the upper outlets of the washing circulation tank 4, the integrated reactor 13 and the ammonia water storage tank 11 are all connected to the lower inlet of the tail gas absorption tower 3, and the lower outlet of the ammonia water storage tank is connected to the qualified ammonia water outlet 7 through the ammonia water delivery pump 8.

Claims

1. A highly efficient and energy-saving dual heat pump deammoniation method, characterized in that: The method includes the following aspects: A. The ammonia-containing wastewater from outside the boundary is preheated by condensate and tower bottom outlet water, and then sprayed into the deamination tower from the top, where it contacts with the rising steam in countercurrent to transfer mass and heat, and remove ammonia from the ammonia-containing wastewater; B. The ammonia-containing steam discharged from the top of the tower is pressurized by the ammonia vapor compressor, and the electric energy is converted into internal energy. The steam temperature rises to form superheated gas. The superheated gas is saturated after being sprayed and humidified by the condensate. As the heat source of the tower bottom, it enters the ammonia vapor reboiler to heat the tower bottom liquid. After the heat of the ammonia-containing steam is removed, a part of it is converted into dilute ammonia water, and the other part of the ammonia-containing steam that is not condensed enters the integrated reactor and the ammonia water storage tank to prepare ammonia water. The dilute ammonia water is discharged from the ammonia vapor reboiler and enters the condensate tank for buffering. After being pressurized by the condensate pump, a part of it is used as spray liquid, and the other part is mixed with the feed and enters the deammoniation tower for cyclic deammoniation; C. The qualified deammoniation wastewater discharged from the bottom of the tower enters the heat pump evaporator through a pump, and the high-temperature deammoniation wastewater is evacuated and vaporized by a steam heat pump under the action of fresh steam from outside the boundary, and low-pressure steam is extracted. After mixing, secondary steam is generated to provide heat to the steam reboiler to heat the bottom liquid; the deammoniation wastewater is reduced in temperature through flash vaporization, and then pressurized by a pump and cooled by heat exchange with the feed heat exchanger, and then discharged from the system through the deammoniation wastewater outlet; the above method is implemented by using the following device, which includes a water supply inlet (1), an ammonia-containing wastewater inlet (25), a fresh steam inlet (31), a qualified ammonia water outlet (7), a condensate outlet (9), a deammoniation wastewater outlet (10), and a deammoniation tower (2). , tail gas absorption tower (3), integrated reactor (13), ammonia water storage tank (11); the lower part of the deamination tower is respectively connected to the steam reboiler (29) inlet, the tower bottom pump (21), and the ammonia vapor reboiler circulation pump (20); the ammonia vapor reboiler circulation pump (20) is connected to the ammonia vapor reboiler (19), the tower bottom pump is connected to the heat pump evaporator (27), the heat pump evaporator and the fresh steam inlet are respectively connected to the steam heat pump (30) inlet, the heat pump evaporator is connected to the deamination wastewater outlet (10) through the discharge pump (26) and the feed heat exchanger (16); the steam heat pump (30) outlet is connected to the steam reboiler (29), and the steam reboiler outlet is respectively connected to the deamination tower middle inlet, the condenser The condensate tank is connected to the condensate outlet (9) after passing through the waste heat exchanger (17) via the condensate pump (23); the ammonia-containing wastewater inlet (25) is connected to the raw water tank (24), the feed pump (22), the waste heat exchanger (17), the feed heat exchanger (16), and the upper inlet of the deammonification tower in sequence; the top outlet of the deammonification tower is connected to the ammonia vapor compressor (14), the ammonia vapor compressor is connected to the upper inlet of the ammonia vapor reboiler (19), the upper outlet of the ammonia vapor reboiler is respectively connected to the middle inlet of the deammonification tower and the upper outlet of the condensate tank (18), the upper outlet of the condensate tank is connected to the integrated reactor (13), the lower outlet of the ammonia vapor reboiler is connected to the upper inlet of the condensate tank, and the condensate tank is connected to the integrated reactor (13). The lower outlet of the liquid tank is connected to the outlet of the ammonia gas compressor and the outlet of the feed heat exchanger respectively through a condensate pump (15); the water replenishment inlet is connected to the tail gas absorption tower (3); the lower part of the tail gas absorption tower is connected to the washing circulation tank (4); the lower outlet of the washing circulation tank is connected to the integrated reactor (13) through a tail gas washing pump (5); the lower outlet of the integrated reactor is connected to the ammonia heat exchanger (6) and the ammonia storage tank (11) respectively through an ammonia circulation pump (12); the ammonia heat exchanger is connected to the integrated reactor; the upper outlets of the washing circulation tank, the integrated reactor and the ammonia storage tank are all connected to the lower inlet of the tail gas absorption tower; the lower outlet of the ammonia storage tank is connected to the qualified ammonia outlet (7) through an ammonia delivery pump (8).

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