Flash ammonia distillation method and device for ammonia-containing wastewater

Abstract

The invention relates to an ammonia distillation method and device for ammonia-containing wastewater, in particular to an ammonia distillation method and device for ammonia-containing wastewater, which can reduce the load and energy consumption of an ammonia distillation tower in the industrial process of removing ammonia from the ammonia-containing wastewater. After raw ammonia-containing wastewater is heated, volatile ammonia contained in the raw ammonia-containing wastewater is rapidly separated, the separated ammonia gas is directly sent to a gas flow channel at the top of an ammonia still, and the wastewater from which the ammonia gas is rapidly separated is sent to the ammonia still for ammonia still, so that the load of the ammonia still is greatly reduced, and a foundation is laid for reducing ammonia still alkali consumption and heat source steam consumption; the flash separator is arranged in front of the ammonia-containing wastewater raw water inlet of the ammonia distillation tower, volatile ammonia is rapidly separated and directly sent to the gas flow channel at the top of the ammonia distillation tower, the purpose of reducing alkali consumption and heat source steam consumption for ammonia distillation is achieved with little equipment investment, and particularly, convenience is provided for transformation of existing process equipment.

Description

Technical Field

[0001] The present invention relates to a method and device for ammonia distillation of ammonia-containing wastewater, and in particular to a method and device for ammonia distillation of ammonia-containing wastewater that reduce the load and energy consumption of an ammonia distillation tower during the industrial process of removing ammonia from ammonia-containing wastewater, belonging to the fields of environmental protection and chemical engineering. Background Art

[0002] Generally, ammonia-containing wastewater is mostly refractory industrial wastewater with complex components, high toxicity, and poor biodegradability. The high-concentration ammonia nitrogen in it enters the biochemical treatment system, which will cause operating obstacles and seriously affect the treatment effect. Therefore, high-concentration ammonia-containing wastewater needs to be pretreated.

[0003] The ammonia distillation method is currently the most commonly used effective method for pretreating high-concentration ammonia-containing wastewater. During ammonia distillation, steam comes into full contact with the wastewater. According to the principle of stripping, heat and mass transfer occur between the steam and the wastewater, and ammonia escapes from the liquid phase (wastewater) into the gas phase (steam), so that the ammonia in the wastewater is separated and carried out by the steam, achieving the purpose of reducing the ammonia concentration in the wastewater. The most widely used ammonia distillation process so far is to preheat the ammonia-containing wastewater and add lye, then directly send it to the upper part of the ammonia distillation tower. Heat source is added at the bottom of the ammonia distillation tower to generate steam. Ammonia-containing gas is discharged from the top of the tower, and ammonia-distilled wastewater is discharged from the bottom of the tower. This process flow is simple and the equipment is few, but adding alkali to the ammonia-containing wastewater before entering the tower neutralizes the acidic substances in the original ammonia-containing wastewater, making it difficult to distill out, resulting in the inability to reduce the organic matter content in the ammonia-distilled wastewater discharged from the tower, high COD, and large alkali consumption. Both of these lead to an increase in the treatment cost of ammonia-containing wastewater.

[0004] To overcome the disadvantages of high alkali consumption and steam consumption of the above traditional ammonia distillation process, scientific and technological workers have respectively explored improved processes such as one-tower two-stage ammonia distillation and two-tower ammonia distillation. The basic process of one-tower two-stage ammonia distillation is to preheat the ammonia-containing wastewater and directly send it to the upper part of the ammonia distillation tower without adding alkali. Under low pH conditions, the acidic substances in the ammonia-containing wastewater are distilled out, and at the same time, part of the volatile ammonia is distilled out; alkali is added in the middle of the ammonia distillation tower to increase the pH value of the liquid phase, convert the fixed ammonia into volatile ammonia, and the ammonia is stripped and removed by the rising steam during the downward flow process, so that the ammonia concentration is reduced to the required value and then discharged from the bottom of the ammonia distillation tower. The ammonia-containing steam at the lower part of the ammonia distillation tower rises through the non-alkali-added volatile ammonia distillation section at the upper part of the ammonia distillation tower and is discharged from the top of the tower as ammonia-containing gas. Although this process improves the discharge effect of acidic substances in the ammonia-containing wastewater to a certain extent and reduces the alkali consumption. However, since the ammonia distilled out after adding alkali at the lower part of the ammonia distillation tower rises with the steam, it increases the ammonia partial pressure in the gas phase, reduces the driving force of ammonia transfer from the liquid phase to the gas phase at the upper part of the ammonia distillation tower, affects the ammonia distillation effect at the upper part, and the final result will be an increase in the number of trays required for the ammonia distillation tower. If the original ammonia distillation tower is transformed, there will be problems such as insufficient capacity of the original ammonia distillation tower and the inability of the ammonia-distilled wastewater to meet the effluent requirements, which also hinders the implementation of the transformation of the traditional process.

[0005] To solve the problems existing in the traditional single-tower ammonia distillation, scientific and technological workers have developed a two-tower staged ammonia distillation process, which is further divided into a gas series process in which the steam from the top of the second tower of ammonia-containing wastewater is sent to the bottom of the first tower, and a gas parallel process in which the steam of the second tower of ammonia-containing wastewater is not sent into the first tower but discharged after converging with the steam from the top of the first tower. The advantage of the gas series process is that it can utilize the steam generated by the heat source of the second tower, saving the heat source to a certain extent. However, there is also a problem that the ammonia distillation driving force in the first tower is reduced, resulting in insufficient mass transfer capacity. Only the problem is solved by increasing the number of trays during the construction of the two towers, and the result is an increase in equipment investment. The gas parallel process avoids the problems of the gas series process by directly discharging the ammonia-containing gas from the top of the second tower. However, the steam heat source in the second tower cannot be utilized either, and heat sources need to be added to both the first tower and the second tower, resulting in a significant decrease in energy utilization efficiency and an increase in energy consumption.

[0006] In summary, both the single-tower two-stage ammonia distillation and the two-tower ammonia distillation processes bring new problems, resulting in a serious weakening of their advantages compared with the traditional single-tower ammonia distillation process. In particular, it is difficult to implement the transformation of the existing process, so that the traditional single-tower ammonia distillation is still the mainstream process in industrial sites. It can be seen that the technical problem of improving the efficiency of ammonia distillation of ammonia-containing wastewater and reducing its cost lies in the root technical problems of poor investment economy with increased transformation costs and / or difficult reduction of operating costs in the existing process and equipment.

[0007] In view of the current situation of ammonia distillation technology and the problems existing in various processes, the present invention starts from the mechanism and process law of liquid-phase ammonia volatilization, and provides a method and device for flash distillation of ammonia-containing wastewater. After the raw water of ammonia-containing wastewater is heated, the saturated vapor pressure of liquid-phase ammonia increases significantly, and the ammonia is quickly separated and the separated ammonia gas is directly sent to the pipeline at the top of the ammonia distillation tower. The wastewater after quickly separating ammonia gas is sent into the ammonia distillation tower, and the ammonia concentration in the wastewater is reduced to below the required value by the rising steam, and the ammonia-containing wastewater discharged from the bottom of the ammonia distillation tower is flash-distilled. This provides an effective technical means for reducing the load of the ammonia distillation tower, reducing alkali consumption and heat source steam consumption. Summary of the Invention

[0008] The object of the present invention is to provide a method and device for reducing the alkali consumption and heat source steam consumption in the ammonia stripping of ammonia-containing wastewater. After the original ammonia-containing wastewater is heated, the volatile ammonia contained therein is quickly separated, and the separated ammonia gas is directly sent to the gas flow channel at the top of the ammonia stripper. The wastewater after quickly separating ammonia gas is sent into the ammonia stripper for ammonia stripping, greatly reducing the load of the ammonia stripper and laying a foundation for reducing the alkali consumption and heat source steam consumption in ammonia stripping; by setting a flash separator before the inlet of the original ammonia-containing wastewater in the ammonia stripper, the volatile ammonia is quickly separated and directly sent to the gas flow channel at the top of the ammonia stripper. The ammonia-containing wastewater after flash separation of the volatile ammonia is sent into the ammonia stripper for ammonia stripping, achieving the purpose of reducing the alkali consumption and heat source steam consumption in ammonia stripping with little equipment investment, especially providing convenience for the transformation of existing process equipment. Compared with the prior art, this method can reduce the amount of alkali used and heat source steam consumption, reduce the treatment cost of ammonia-containing wastewater. Especially for the transformation of existing ammonia strippers, the engineering quantity is small and the equipment investment is small, and the effects of improving the treatment efficiency, saving alkali and saving steam can be achieved.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows: A flash stripping ammonia method for ammonia-containing wastewater, characterized in that the ammonia stripping of ammonia-containing wastewater at least includes the following processes: (1) A raw water flash separation process in which the original ammonia-containing wastewater is heated to a temperature above 80 °C and then sent to a raw water flash separator with gas-liquid separation function to quickly separate volatile ammonia to obtain raw water flash gas and raw water flash wastewater; (2) A stripping tower ammonia stripping process in which the raw water flash wastewater obtained from the raw water flash separation process is sent into the ammonia stripper from the upper part of the ammonia stripper for ammonia stripping, or after adding alkali liquor to the raw water flash wastewater, it is sent into the ammonia stripper from the upper part of the ammonia stripper for ammonia stripping; The raw water flash gas separated in the raw water flash separation process is sent to the partial condenser at the top of the ammonia stripper or the gas flow channel after the partial condenser at the top of the ammonia stripper.

[0010] The method is characterized in that before the original ammonia-containing wastewater is sent to the raw water flash separator for the raw water flash separation process, alkali liquor is added to the original ammonia-containing wastewater and then the raw water flash separation process is carried out. The raw water flash gas separated in the raw water flash separation process is sent to the partial condenser at the top of the ammonia stripper or the gas flow channel after the partial condenser at the top of the ammonia stripper, and the obtained raw water flash wastewater is sent into the ammonia stripper from the upper part of the ammonia stripper for ammonia stripping.

[0011] The method is characterized in that the heating of the original ammonia-containing wastewater is that the original ammonia-containing wastewater is first heated by exchanging heat with the hot ammonia stripping wastewater discharged from the ammonia stripper and then further heated by exchanging heat with the hot heat source steam condensate discharged from the reboiler of the ammonia stripper.

[0012] The method is characterized in that before the raw ammonia-containing wastewater is heated to a temperature above 80°C and then sent to the raw water flash separator for the raw water flash separation process, the raw ammonia-containing wastewater is subjected to ultrasonic action, or an ultrasonic generator is built into the raw water flash separator to subject the raw ammonia-containing wastewater to ultrasonic action.

[0013] The device for implementing the method is characterized in that the device at least includes an ammonia stripping tower and a raw water flash separator; the top of the ammonia stripping tower is provided with an ammonia stripping ammonia gas outlet, the upper part is provided with a raw water flash separation wastewater inlet of the ammonia stripping tower, the bottom is provided with an ammonia stripping wastewater outlet of the ammonia stripping tower, the upper part of the raw water flash separator is provided with a raw ammonia-containing wastewater inlet of the raw water flash separator, the top is provided with a flash gas outlet of the raw water flash separator, and the bottom is provided with a raw water flash separation wastewater outlet of the raw water flash separator; the raw ammonia-containing wastewater inlet of the raw water flash separator is connected to the raw ammonia-containing wastewater side, the flash gas outlet of the raw water flash separator is connected to the ammonia stripping ammonia gas outlet side at the top of the ammonia stripping tower, and the raw water flash separation wastewater outlet of the raw water flash separator is connected to the raw water flash separation wastewater inlet of the ammonia stripping tower.

[0014] The device for implementing the method is characterized in that the heating of the raw ammonia-containing wastewater is achieved by arranging an ammonia stripping wastewater heat exchanger and a heat source steam condensate heat exchanger on the raw ammonia-containing wastewater flow path; the ammonia stripping wastewater heat exchanger has a raw ammonia-containing wastewater inlet of the ammonia stripping wastewater heat exchanger, a raw ammonia-containing wastewater outlet of the ammonia stripping wastewater heat exchanger, an ammonia stripping wastewater inlet of the ammonia stripping wastewater heat exchanger, and an ammonia stripping wastewater outlet of the ammonia stripping wastewater heat exchanger, and the heat source steam condensate heat exchanger has a raw ammonia-containing wastewater inlet of the heat source steam condensate heat exchanger, a raw ammonia-containing wastewater outlet of the heat source steam condensate heat exchanger, a heat source steam condensate inlet of the heat source steam condensate heat exchanger, and a heat source steam condensate outlet of the heat source steam condensate heat exchanger; the raw ammonia-containing wastewater inlet of the ammonia stripping wastewater heat exchanger is connected to the incoming raw ammonia-containing wastewater, the raw ammonia-containing wastewater outlet of the ammonia stripping wastewater heat exchanger is connected to the raw ammonia-containing wastewater inlet of the heat source steam condensate heat exchanger, the ammonia stripping wastewater inlet of the ammonia stripping wastewater heat exchanger is connected to the ammonia stripping wastewater outlet of the ammonia stripping tower, the ammonia stripping wastewater outlet of the ammonia stripping wastewater heat exchanger is connected to the ammonia stripping wastewater biochemical treatment system side, the raw ammonia-containing wastewater outlet of the heat source steam condensate heat exchanger is connected to the raw ammonia-containing wastewater inlet side of the raw water flash separator, the steam condensate inlet of the heat source steam condensate heat exchanger is connected to the heat source steam condensate outlet of the reboiler of the ammonia stripping tower, and the heat source steam condensate outlet of the heat source steam condensate heat exchanger is connected to the heat source steam condensate reuse system side.

[0015] The specific description is as follows: After heating the raw water of ammonia-containing wastewater to a temperature above 80°C, it is sent to a flash separator with gas-liquid separation function to quickly separate volatile ammonia, obtaining raw water flash gas and raw water flash wastewater. The obtained raw water flash wastewater is sent to the upper part of the ammonia stripping tower and flows downward, and the ammonia in the wastewater is stripped by the rising steam, reducing its concentration to below the required value, and discharged as ammonia stripping wastewater from the bottom of the ammonia stripping tower; the raw water flash gas separated during the raw water flash process is not mixed with the raw water flash wastewater but is separately sent to the partial condenser at the top of the ammonia stripping tower or the gas flow channel after the partial condenser. Thus, the load of the ammonia stripping tower can be significantly reduced, laying a foundation for reducing the alkali consumption and heat source steam consumption in ammonia stripping.

[0016] Before the raw water of ammonia-containing wastewater is sent to the flash separator for the raw water flash process, an alkali solution is added to the raw water of ammonia-containing wastewater and then the raw water flash is carried out. The raw water flash gas obtained by flash separation is not mixed with the raw water flash wastewater but is separately sent to the partial condenser at the top of the ammonia stripping tower or the gas flow channel after the partial condenser. The obtained raw water flash wastewater is sent to the upper part of the ammonia stripping tower for ammonia stripping. Although adding an alkali solution to the raw water of ammonia-containing wastewater before the raw water flash has no effect on reducing the alkali consumption, due to the rapid and large-scale separation of volatile ammonia, the ammonia stripping load of the ammonia stripping tower is significantly reduced, thus laying a foundation for reducing the amount of heat energy steam used in the ammonia stripping tower and achieving the purpose of saving heat source steam.

[0017] By setting a raw water flash separator in front of the raw water flash wastewater inlet of the ammonia stripping tower to quickly separate volatile ammonia and directly send it to the gas flow channel at the top of the ammonia stripping tower, the raw water flash wastewater after flash separation of volatile ammonia is sent to the ammonia stripping tower for ammonia stripping, achieving the purpose of ammonia stripping with the least equipment investment and reducing alkali consumption and heat source steam consumption, especially providing convenience for the transformation of existing process equipment.

[0018] After the ammonia stripping wastewater heat exchanger for preheating the raw water of ammonia-containing wastewater in the traditional process, a heat source steam condensate heat exchanger is connected in series to further heat the raw water of ammonia-containing wastewater to increase the temperature, which can reduce the amount of heat source steam used and achieve energy saving in the ammonia stripping process.

[0019] Before heating the raw water of ammonia-containing wastewater to a temperature above 80°C and sending it to the raw water flash separator for the raw water flash process, ultrasonic treatment is carried out on the raw water of ammonia-containing wastewater, or an ultrasonic generator is installed in the raw water flash separator to carry out ultrasonic treatment on the raw water of ammonia-containing wastewater. Through the action of ultrasonic waves, the volatile ammonia in the raw water can quickly escape from the wastewater and transfer to the gas phase, realizing rapid gas-liquid separation.

[0020] In actual engineering, an air pump can be installed on the pipeline connecting the flash gas outlet of the raw water flash separator to the ammonia stripping ammonia gas outlet side at the top of the ammonia stripper, so as to suck the raw water flash gas from the raw water flash separator and send it into the partial condenser at the top of the ammonia stripper or the gas flow path after the partial condenser. By sucking with the air pump, the gas phase pressure in the raw water flash separator can be appropriately reduced, promoting the transfer of volatile ammonia from the liquid phase to the gas phase, increasing the conveying power, discharging more quickly from the raw water flash separator, and promoting the gas-liquid separation in the flash separator.

[0021] The volatile ammonia described in the present invention refers to ammonia with a high saturated vapor pressure in the liquid phase and is easily volatilized from the liquid phase to the gas phase. The hot ammonia stripping wastewater refers to the ammonia stripping wastewater discharged from the ammonia stripper without undergoing a cooling process, and the hot heat source steam condensate refers to the heat source steam condensate discharged from the reboiler of the ammonia stripper without undergoing a cooling process.

[0022] The beneficial effects of the present invention are as follows: after heating and raising the temperature of the raw water of the ammonia-containing wastewater, the volatile ammonia contained therein is quickly separated, and the separated ammonia gas is directly sent to the gas flow path at the top of the ammonia stripper. The raw water flash wastewater after quickly separating the volatile ammonia is sent into the ammonia stripper for ammonia stripping, greatly reducing the ammonia stripping load of the ammonia stripper, laying a foundation for reducing the ammonia stripping alkali consumption and heat source steam consumption; by installing a raw water flash separator in front of the raw water flash wastewater inlet of the ammonia stripper to quickly separate the volatile ammonia and directly send it to the gas flow path at the top of the ammonia stripper, the raw water flash wastewater after flash separation of the volatile ammonia is sent into the ammonia stripper for ammonia stripping, achieving the purpose of reducing alkali consumption and heat source steam consumption with the least equipment investment and reducing the treatment cost of ammonia-containing wastewater. Especially for the transformation of the existing ammonia stripper, the project volume is small and the equipment investment is small, providing convenience for the transformation of the existing ammonia stripping system; by connecting a heat source steam condensate heat exchanger in series after the ammonia stripping wastewater heat exchanger for preheating the raw water of the traditional ammonia-containing wastewater, further heating and raising the temperature of the raw water of the ammonia-containing wastewater, the amount of heat source steam used can be reduced, realizing energy conservation in the ammonia stripping process. The present invention provides an effective technical means for reducing the heat source steam consumption in the ammonia stripping process of ammonia-containing wastewater. Brief Description of the Drawings

[0023] Figure 1 : Schematic diagram of the ammonia stripping process flow of the raw water heating flash ammonia stripper for ammonia-containing wastewater; Figure 2 : Schematic diagram of the ammonia stripping process flow of the raw water heating flash and adding alkali ammonia stripper for ammonia-containing wastewater; Figure 3 : Schematic diagram of the ammonia stripping process flow of the raw water heating adding alkali flash ammonia stripper for ammonia-containing wastewater.

[0024] Wherein: 1 - raw ammonia-containing wastewater, 2 - inlet of raw ammonia-containing wastewater of the ammonia stripping wastewater heat exchanger, 3 - ammonia stripping wastewater heat exchanger, 4 - outlet of ammonia stripping wastewater of the ammonia stripping tower, 5 - hot ammonia stripping wastewater, 6 - inlet of ammonia stripping wastewater of the ammonia stripping wastewater heat exchanger, 7 - outlet of raw ammonia-containing wastewater of the ammonia stripping wastewater heat exchanger, 8 - inlet of raw ammonia-containing wastewater of the heat source steam condensate heat exchanger, 9 - heat source steam condensate heat exchanger, 10 - hot heat source steam condensate, 11 - heated raw ammonia-containing wastewater, 12 - outlet of raw ammonia-containing wastewater of the heat source steam condensate heat exchanger, 12 - outlet of ammonia stripping wastewater of the ammonia stripping wastewater heat exchanger, 13 - inlet of raw ammonia-containing wastewater of the raw water flash separator, 14 - raw water flash separator, 15 - flashed ammonia gas, 16 - outlet of flashed ammonia gas of the raw water flash separator, 17 - ammonia stripping tower, 18 - top condenser of the ammonia stripping tower, 19 - ammonia gas outlet of the ammonia stripping tower, 20 - raw water flash-separated wastewater, 21 - outlet of raw water flash-separated wastewater of the raw water flash separator, 22 - inlet of raw water flash-separated wastewater of the ammonia stripping tower, 23 - reboiler of the ammonia stripping tower, 24 - heat source steam for the reboiler of the ammonia stripping tower, 25 - outlet of ammonia stripping wastewater of the ammonia stripping wastewater heat exchanger, 26 - inlet of heat source steam condensate of the heat source steam condensate heat exchanger, 27 - outlet of heat source steam condensate of the heat source steam condensate heat exchanger, 28 - lye. Detailed implementation manners

[0025] Example 1

[0026] This example is an example of heating, flash separation and ammonia stripping of raw ammonia-containing wastewater, and the process flow is as Figure 1As shown in the figure. The raw ammonia-containing wastewater 1 from industries such as coal gasification or coking is fed into the ammonia-containing wastewater heat exchanger 3 through the ammonia-containing wastewater raw water inlet 2 of the ammonia-containing wastewater heat exchanger. After being heated and raised in temperature by the hot ammonia-containing wastewater 5 fed from the ammonia-containing wastewater heat exchanger ammonia-containing wastewater inlet 6 discharged from the ammonia stripping tower ammonia-containing wastewater outlet 4, it is fed into the heat source steam condensate heat exchanger 9 through the ammonia-containing wastewater raw water inlet 8 connected to the ammonia-containing wastewater raw water outlet 7 of the ammonia-containing wastewater heat exchanger. After being further heated and raised in temperature to above 90 °C by the hot heat source steam condensate 10 generated by the condensation of the heat source steam 24 of the ammonia stripping tower reboiler and fed from the heat source steam condensate heat exchanger heat source steam condensate inlet 26, it is discharged as the temperature-raised ammonia-containing wastewater 11 from the ammonia-containing wastewater raw water outlet 12 of the heat source steam condensate heat exchanger. The temperature-raised ammonia-containing wastewater raw water 11 after preheating and temperature raising is fed into the raw water flash separator 14 through the ammonia-containing wastewater raw water inlet 13 of the raw water flash separator. The flashed ammonia gas 15 obtained through rapid gas-liquid separation is fed into the ammonia gas flow path behind the top condenser 18 of the ammonia stripping tower 17 through the flashed ammonia gas outlet 16 of the raw water flash separator, and converges with the ammonia gas generated by the ammonia stripping tower (not marked in the figure), and is sent to the next process through the ammonia gas outlet 19 of the ammonia stripping tower; the flashed raw water flash wastewater 20 is discharged from the raw water flash wastewater outlet 21 of the raw water flash separator, and is fed into the ammonia stripping tower 17 through the ammonia stripping tower raw water flash wastewater inlet 22. During the downward flow, it contacts the rising steam (not marked in the figure) generated by heating with the heat source steam 24 of the ammonia stripping tower reboiler in the ammonia stripping tower reboiler 23, evaporates the ammonia in the liquid phase into the gas phase, and rises to the top condenser 18 of the ammonia stripping tower for condensation and is discharged from the ammonia gas outlet 19 of the ammonia stripping tower to the next process; the wastewater liquid flows downward and is mixed with the lye at an appropriate position (not marked in the figure), converts the fixed ammonia into volatile ammonia, transfers it to the gas phase and is distilled out. After the ammonia concentration in the liquid phase reaches below the required value of the ammonia stripping wastewater, it is discharged from the ammonia stripping wastewater outlet 4 of the ammonia stripping tower, completing the ammonia stripping. The ammonia stripping wastewater that is cooled by heat exchange in the ammonia stripping wastewater heat exchanger is discharged from the ammonia stripping wastewater heat exchanger ammonia stripping wastewater outlet 25 and sent to the ammonia stripping wastewater biochemical treatment system, and the heat source steam condensate that is cooled by heat exchange is discharged from the heat source steam condensate heat exchanger heat source steam condensate outlet 27 and sent to the steam condensate reuse system.

[0027] After heating the raw water of ammonia-containing wastewater, the volatile ammonia contained in the raw water is quickly separated, and the separated ammonia gas is directly sent to the gas flow channel at the top of the ammonia distillation tower, greatly reducing the ammonia distillation load of the ammonia distillation tower and laying a foundation for reducing the alkali consumption and heat source steam consumption in ammonia distillation; by setting a raw water flash separator before the raw water flash separation wastewater inlet of the ammonia distillation tower to quickly separate the volatile ammonia and directly send it to the gas flow channel at the top of the ammonia distillation tower, the raw water flash separation wastewater after flash separation of the volatile ammonia is sent to the ammonia distillation tower for ammonia distillation, achieving the purpose of ammonia distillation with low alkali consumption and low heat source steam consumption with little equipment investment, thereby reducing the treatment cost of ammonia-containing wastewater. Especially for the transformation of the existing ammonia distillation tower, the project volume is small and the equipment investment is small, and the effects of improving the treatment efficiency, saving alkali and saving steam can be achieved; by connecting a heat source steam condensate heat exchanger in series after the ammonia distillation wastewater heat exchanger for preheating the raw water of traditional ammonia-containing wastewater, further heating the raw water of ammonia-containing wastewater to increase the temperature, the amount of heat source steam used can be reduced, and energy conservation in the ammonia distillation process can be realized.

[0028] Example 2: This example is an example of ammonia distillation treatment of ammonia-containing wastewater by the ammonia distillation process of heating and flash separation of the raw water of ammonia-containing wastewater and adding alkali. The process flow is as Figure 2As shown in the figure. The raw ammonia-containing wastewater 1 from industries such as coal gasification or coking is fed into the ammonia-containing wastewater heat exchanger 3 through the ammonia-containing wastewater raw water inlet 2 of the ammonia distillation wastewater heat exchanger. After being heated and raised in temperature by the hot ammonia distillation wastewater 5 fed from the ammonia distillation wastewater outlet 4 of the ammonia distillation tower through the ammonia distillation wastewater inlet 6 of the ammonia-containing wastewater heat exchanger, it is fed into the heat source steam condensate heat exchanger 9 through the ammonia-containing wastewater raw water inlet 8 connected to the ammonia-containing wastewater raw water outlet 7 of the ammonia distillation wastewater heat exchanger. After being further heated and raised in temperature to above 90 °C by the hot heat source steam condensate 10 discharged from the reboiler 23 of the ammonia distillation tower and fed into the heat source steam condensate heat exchanger through the heat source steam condensate inlet 26, it is discharged as the heated ammonia-containing wastewater 11 from the ammonia-containing wastewater raw water outlet 12 of the heat source steam condensate heat exchanger. The preheated and heated ammonia-containing wastewater raw water 11 is fed into the raw water flash separator 14 through the ammonia-containing wastewater raw water inlet 13 of the raw water flash separator. The flashed ammonia gas 15 obtained through rapid gas-liquid separation is fed into the ammonia gas flow channel after the top condenser 18 of the ammonia distillation tower of the ammonia distillation tower 17 through the flashed ammonia gas outlet 16 of the raw water flash separator, and converges with the ammonia gas generated by the ammonia distillation tower (not marked in the figure), and is sent to the next process through the ammonia gas outlet 19 of the ammonia distillation tower; the raw water flash wastewater 20 obtained by flashing is discharged from the raw water flash wastewater outlet 21 of the raw water flash separator and mixed with the lye 28, and then fed into the ammonia distillation tower 17 through the raw water flash wastewater inlet 22 of the ammonia distillation tower. During the downward flow, it contacts the rising steam (not marked in the figure) generated by heating the reboiler 23 of the ammonia distillation tower with the heat source steam 24 of the reboiler of the ammonia distillation tower, evaporates the ammonia in the liquid phase into the gas phase, and rises to the top condenser 18 of the ammonia distillation tower for condensation and is discharged from the ammonia gas outlet 19 of the ammonia distillation tower and sent to the next process; the wastewater liquid flows downward, the ammonia contained therein is transferred to the gas phase and evaporated, and after the ammonia concentration in the liquid phase reaches below the required value of the ammonia distillation wastewater, it is discharged from the ammonia distillation wastewater outlet 4 of the ammonia distillation tower, completing the ammonia distillation. The ammonia distillation wastewater cooled by heat exchange in the ammonia distillation wastewater heat exchanger is discharged from the ammonia distillation wastewater outlet 25 of the ammonia distillation wastewater heat exchanger and sent to the ammonia distillation wastewater biochemical treatment system, and the heat source steam condensate cooled by heat exchange is discharged from the heat source steam condensate outlet 27 of the heat source steam condensate heat exchanger and sent to the steam condensate reuse system.

[0029] By this process, the flashed ammonia gas is directly sent to the gas flow channel at the top of the ammonia distillation tower, greatly reducing the ammonia distillation load of the ammonia distillation tower, achieving the purpose of reducing the alkali consumption and heat source steam consumption in ammonia distillation, reducing the treatment cost of ammonia-containing wastewater. Especially for the transformation of the existing ammonia distillation tower, the engineering volume is small and the equipment investment is small, and the effect of improving the treatment efficiency, saving alkali and saving steam can be achieved. Example 3

[0030] This example is an example of ammonia distillation treatment of ammonia-containing wastewater using the ammonia distillation process of heating and adding alkali to the raw ammonia-containing wastewater and flashing in the ammonia distillation tower. The process flow is as Figure 3As shown in the figure. The raw water 1 of ammonia-containing wastewater from industries such as coal gasification or coking is fed into the ammonia-containing wastewater heat exchanger 3 through the ammonia-containing wastewater raw water inlet 2 of the ammonia distillation wastewater heat exchanger. After being heated and raised in temperature by the hot ammonia distillation wastewater 5 discharged from the ammonia distillation wastewater outlet 4 of the ammonia distillation tower and fed into the ammonia-containing wastewater raw water inlet 6 of the ammonia distillation wastewater heat exchanger, it is fed into the heat source steam condensate heat exchanger 9 through the ammonia-containing wastewater raw water outlet 7 of the ammonia distillation wastewater heat exchanger and the ammonia-containing wastewater raw water inlet 8 of the heat source steam condensate heat exchanger. It is further heated and raised in temperature to above 90°C by the hot heat source steam condensate 10 discharged from the heat source steam condensate heat exchanger heat source steam condensate inlet 26 and generated by the condensation of the heat source steam 24 of the ammonia distillation tower reboiler 23, and then discharged as the heated ammonia-containing wastewater 11 from the ammonia-containing wastewater raw water outlet 12 of the heat source steam condensate heat exchanger. After the preheated and heated ammonia-containing wastewater raw water 11 is mixed with the lye 28, it is fed into the raw water flash separator 14 through the ammonia-containing wastewater raw water inlet 13 of the raw water flash separator. The flashed ammonia gas 15 obtained through rapid gas-liquid separation is fed into the ammonia gas flow path after the top condenser 18 of the ammonia distillation tower of the ammonia distillation tower 17, converges with the ammonia gas generated by the ammonia distillation tower (not marked in the figure), and is sent to the next process through the ammonia gas outlet 19 of the ammonia distillation tower; the flashed raw water flash wastewater 20 is discharged from the raw water flash wastewater outlet 21 of the raw water flash separator and fed into the ammonia distillation tower 17 through the raw water flash wastewater inlet 22 of the ammonia distillation tower. During the downward flow, it contacts the rising steam (not marked in the figure) generated by the heating of the ammonia distillation tower reboiler 23 by the heat source steam 24 of the ammonia distillation tower reboiler, evaporates the ammonia in the liquid phase into the gas phase, and rises to the top condenser 18 of the ammonia distillation tower for condensation and then is discharged through the ammonia gas outlet 19 of the ammonia distillation tower to the next process; the wastewater liquid flows downward, the ammonia contained in it is transferred to the gas phase and evaporated, and after the ammonia concentration in the liquid phase reaches below the required value of the ammonia distillation wastewater, it is discharged from the ammonia distillation wastewater outlet 4 of the ammonia distillation tower, completing the ammonia distillation. The ammonia distillation wastewater cooled by heat exchange in the ammonia distillation wastewater heat exchanger is discharged from the ammonia distillation wastewater outlet 25 of the ammonia distillation wastewater heat exchanger and sent to the ammonia distillation wastewater biochemical treatment system, and the heat source steam condensate cooled by heat exchange is discharged from the heat source steam condensate heat exchanger heat source steam condensate outlet 27 and sent to the steam condensate reuse system.

[0031] By directly sending the ammonia gas obtained by flashing to the top flow path of the ammonia distillation tower through this process, the load of the ammonia distillation tower is significantly reduced, the purpose of reducing the alkali consumption and heat source steam consumption of ammonia distillation is achieved, the treatment cost of ammonia-containing wastewater is reduced. Especially for the transformation of the existing ammonia distillation tower, the project volume is small and the equipment investment is small, and the effect of improving the treatment efficiency, saving alkali and saving steam can be achieved. Example 4

[0032] The basic process is the same as that of Example 1. The difference is that the raw water 1 of ammonia-containing wastewater is heated and raised in temperature to above 80°C by the hot ammonia distillation wastewater 5 discharged from the ammonia distillation tower in the ammonia distillation wastewater heat exchanger 3, and then fed into the raw water flash separator 14 through the ammonia-containing wastewater raw water inlet 13 of the raw water flash separator for flash separation. Example 5

[0033] The basic process is the same as that of Example 1. The difference is that the raw ammonia-containing wastewater 1 is heated and raised in temperature by the hot ammonia-distilled wastewater 5 discharged from the ammonia distillation tower in the ammonia-distilled wastewater heat exchanger 3, and then is fed into the heat source steam condensate heat exchanger 9 from the raw ammonia-containing wastewater inlet 8 of the heat source steam condensate heat exchanger, and is further heated and raised in temperature to above 90 °C by the hot heat source steam condensate 10 discharged from the reboiler of the ammonia distillation tower to be the temperature-raised ammonia-containing wastewater 11, and is fed into the ammonia distillation tower 17 through the raw water flash-separation wastewater inlet 22 of the ammonia distillation tower for ammonia distillation. Example 6

[0034] The basic process is the same as that of Example 1. The difference is that the raw ammonia-containing wastewater 1 is heated and raised in temperature by the hot ammonia-distilled wastewater 5 discharged from the ammonia distillation tower in the ammonia-distilled wastewater heat exchanger 3, and then is fed into the heat source steam condensate heat exchanger 9 from the raw ammonia-containing wastewater inlet 8 of the heat source steam condensate heat exchanger, and is further heated and raised in temperature to above 90 °C by the hot heat source steam condensate 10 discharged from the reboiler of the ammonia distillation tower to be the temperature-raised ammonia-containing wastewater 11, and after being subjected to the ultrasonic action of the ultrasonic actuator, is fed into the raw water flash separator 14 for rapid gas-liquid separation of volatile ammonia and wastewater. Example 7

[0035] The basic process is the same as that of Example 1. The difference is that an ultrasonic generator is installed inside the raw water flash separator 14, and the temperature-raised ammonia-containing wastewater 11 heated and raised to above 90 °C is simultaneously subjected to ultrasonic action inside the raw water flash separator for rapid gas-liquid separation of volatile ammonia and wastewater; and an air pump can be installed on the pipeline connecting the flash-separated gas outlet of the raw water flash separator and the ammonia-distilled ammonia gas outlet side at the top of the ammonia distillation tower to suck the raw water flash-separated gas from the raw water flash separator and feed it into the partial condenser at the top of the ammonia distillation tower or the gas flow path after the partial condenser.

Claims

1. A method for flash distillation of ammonia from ammonia-containing wastewater, characterized in that The ammonia stripping of ammonia-containing wastewater at least includes the following processes: (1) Heating the raw ammonia-containing wastewater to a temperature above 80°C and then feeding it into a raw water flash separator with gas-liquid separation function to quickly separate volatile ammonia, obtaining a raw water flash gas and a raw water flash wastewater in the raw water flash process; (2) Feeding the raw water flash wastewater obtained from the raw water flash process into the ammonia stripper from the upper part of the ammonia stripper for ammonia stripping, or adding alkali liquor to the raw water flash wastewater and then feeding it into the ammonia stripper from the upper part of the ammonia stripper for ammonia stripping in the ammonia stripper ammonia stripping process; The raw water flash gas separated in the raw water flash process is fed into the top condenser of the ammonia stripper or the gas flow channel after the top condenser of the ammonia stripper.

2. The method according to claim 1, characterized in that Before the raw ammonia-containing wastewater is fed into the raw water flash separator for the raw water flash process, alkali liquor is added to the raw ammonia-containing wastewater and then the raw water flash process is carried out. The raw water flash gas separated in the raw water flash process is fed into the top condenser of the ammonia stripper or the gas flow channel after the top condenser of the ammonia stripper, and the obtained raw water flash wastewater is fed into the ammonia stripper from the upper part of the ammonia stripper for ammonia stripping.

3. The method according to claim 1, characterized in that Heating the raw ammonia-containing wastewater is that the raw ammonia-containing wastewater first exchanges heat with the hot ammonia stripping wastewater discharged from the ammonia stripper to increase the temperature, and then exchanges heat with the hot heat source steam condensate discharged from the reboiler of the ammonia stripper to be further heated and the temperature is increased.

4. The method according to claim 1, wherein Before heating the raw ammonia-containing wastewater to a temperature above 80°C and then feeding it into the raw water flash separator for the raw water flash process, ultrasonic treatment is carried out on the raw ammonia-containing wastewater, or an ultrasonic generator is installed in the raw water flash separator to carry out ultrasonic treatment on the raw ammonia-containing wastewater.

5. Apparatus for implementing the method for flash distillation of ammonia-containing wastewater according to claim 1, characterized in that The device at least includes an ammonia stripper and a raw water flash separator; the top of the ammonia stripper is provided with an ammonia stripping ammonia outlet, the upper part is provided with an ammonia stripper raw water flash wastewater inlet, the bottom is provided with an ammonia stripper ammonia stripping wastewater outlet, the upper part of the raw water flash separator is provided with a raw water flash separator raw ammonia-containing wastewater inlet, the top is provided with a raw water flash separator flash gas outlet, and the bottom is provided with a raw water flash separator raw water flash wastewater outlet; the raw water flash separator raw ammonia-containing wastewater inlet is connected to the raw ammonia-containing wastewater side, the raw water flash separator flash gas outlet is connected to the ammonia stripping ammonia outlet side at the top of the ammonia stripper, and the raw water flash separator raw water flash wastewater outlet is connected to the ammonia stripper raw water flash wastewater inlet.

6. The device for implementing the flash distillation ammonia separation method for ammonia-containing wastewater described in claim 1, characterized in that The heating of the raw ammonia-containing wastewater is to set an ammonia stripping wastewater heat exchanger and a heat source steam condensate heat exchanger on the flow path of the raw ammonia-containing wastewater; the ammonia stripping wastewater heat exchanger has an ammonia-containing wastewater raw water inlet, an ammonia-containing wastewater raw water outlet, an ammonia stripping wastewater inlet, and an ammonia stripping wastewater outlet of the ammonia stripping wastewater heat exchanger, and the heat source steam condensate heat exchanger has a heat source steam condensate heat exchanger ammonia-containing wastewater raw water inlet, a heat source steam condensate heat exchanger ammonia-containing wastewater raw water outlet, a heat source steam condensate inlet of the heat source steam condensate heat exchanger, and a heat source steam condensate outlet of the heat source steam condensate heat exchanger; the ammonia-containing wastewater raw water inlet of the ammonia stripping wastewater heat exchanger is connected to the incoming water of the raw ammonia-containing wastewater, the ammonia-containing wastewater raw water outlet of the ammonia stripping wastewater heat exchanger is connected to the ammonia-containing wastewater raw water inlet of the heat source steam condensate heat exchanger, the ammonia stripping wastewater inlet of the ammonia stripping wastewater heat exchanger is connected to the ammonia stripping wastewater outlet of the ammonia stripping tower, the ammonia stripping wastewater outlet of the ammonia stripping wastewater heat exchanger is connected to the ammonia stripping wastewater biochemical treatment system side, the ammonia-containing wastewater raw water outlet of the heat source steam condensate heat exchanger is connected to the ammonia-containing wastewater raw water inlet side of the raw water flash separator, the steam condensate inlet of the heat source steam condensate heat exchanger is connected to the heat source steam condensate outlet of the reboiler of the ammonia stripping tower, and the heat source steam condensate outlet of the heat source steam condensate heat exchanger is connected to the heat source steam condensate reuse system side.

Images