Flue gas waste heat ammonia distillation system

Abstract

The utility model discloses a flue gas waste heat ammonia distillation system, and belongs to the technical field of ammonia distillation equipment. The device comprises an ammonia still, a reboiler, a hot water surge tank and a waste heat recovery device, a bottom waste liquid outlet of the ammonia still is connected with a bottom waste liquid inlet of the reboiler; a top outlet of the reboiler is connected with a bottom inlet of the distillation tower; and a water outlet of the reboiler is sequentially connected with a hot water surge tank, a waste heat recovery device and a water inlet of the reboiler. According to the utility model, firstly, circulating water and flue gas are subjected to heat exchange through the waste heat recovery device, and the circulating water subjected to heat exchange is conveyed to the reboiler beside the ammonia still, so that the pipe diameter is small, the construction cost is low, the heat loss of the circulating water in the conveying process is small, and the ammonia-containing waste liquid and the flue gas circulate in the two closed systems; and even if the heat exchange tube in the reboiler is damaged, the ammonia-containing waste liquid cannot enter the flue gas and drift away along with the flue gas to pollute the environment.

Description

Technical Field

[0001] The utility model belongs to the technical field of ammonia distillation equipment, and in particular relates to a flue gas waste heat ammonia distillation system. Background Art

[0002] Ammonia distillation technology in the coking industry can be divided into direct ammonia distillation process and indirect ammonia distillation process. The direct stripping ammonia distillation technology in the direct ammonia distillation process is commonly used in my country's coking industry. This technology is to separate the remaining ammonia water in the raw material tank by standing, and further remove impurities such as light and heavy tar in the ammonia water. The clarified raw ammonia water is pumped out by a water pump, and after flow control and adjustment, it is sent to the wastewater heat exchanger for heat exchange with the ammonia distillation wastewater. The raw ammonia water leaving the heat exchanger is heated to about 75℃-85℃, and enters the ammonia distillation tower from the top. At the same time, 0.4-0.6MPa low-pressure steam is introduced from the bottom of the tower as the heat source of the ammonia distillation tower for ammonia distillation. The top temperature of the tower is controlled between 102℃-103℃, and the evaporated ammonia gas is condensed to 98℃ by the fractionator at the top of the tower to obtain concentrated ammonia gas. This process is also the mainstream process in the domestic coking industry. However, the main problems of direct steam stripping ammonia distillation technology are high steam consumption, low ammonia content in the gas phase at the top of the tower, high oil content in the wastewater at the bottom of the tower, and easy blockage of the heat exchanger. In addition, steam is commonly used in China to directly evaporate the raw ammonia water, which consumes a lot of steam, increases the amount of ammonia evaporation wastewater, and also increases the cost of wastewater treatment. In addition, the heat of the flue gas directly discharged through the chimney after the desulfurization and denitrification devices of the coking large flue is not recovered at all.

[0003] Patent application CN102502703A discloses a method and equipment for ammonia distillation using waste heat of flue gas from a coke oven, which utilizes an evaporator to recover waste heat of flue gas, and vaporizes ammonia distillation wastewater flowing out of the outlet of ammonia distillation wastewater at the bottom of an ammonia distillation tower with an ammonia concentration of about 0.02%, thereby making full use of ammonia distillation wastewater and flue gas waste heat, reducing both sewage discharge and the use of soft water. However, in the process of directly exchanging heat between flue gas and ammonia-containing waste liquid in a heat exchanger, the wear of the heat exchange tube by flue gas and the corrosion of ammonia-containing waste liquid act on the heat exchange tube of the reboiler at the same time. Once the heat exchange tube is damaged, the ammonia-containing waste liquid enters the flue gas pipeline, and causes pollution to the environment with the flue gas, which will cause the ammonia distillation process to stop production; at the same time, in the process layout of coking, the ammonia distillation process and the large flue are hundreds of meters apart, and the long-distance transportation of flue gas not only has a large pipeline diameter and high engineering cost, but also has a large heat loss during the long transportation process of flue gas, which is not suitable for actual factory use. Utility Model Content

[0004] In view of the above problems, the utility model provides a flue gas waste heat ammonia distillation system, which can not only realize indirect ammonia distillation, but also avoid the shortcomings of the existing direct steam stripping ammonia distillation technology and the insufficiency of direct flue gas heat exchange ammonia distillation.

[0005] To achieve the above-mentioned purpose, the utility model provides a flue gas waste heat ammonia distillation system, including an ammonia distillation tower, a reboiler, a hot water pressure stabilizing tank and a waste heat recovery device;

[0006] The waste liquid outlet at the bottom of the ammonia distillation tower is connected to the waste liquid inlet at the bottom of the reboiler, and the top outlet of the reboiler is connected to the waste liquid inlet at the bottom of the distillation tower; the water outlet of the reboiler is connected to the hot water pressure regulating tank, the waste heat recovery device, and the water inlet of the reboiler in sequence.

[0007] As a further improvement of the utility model, the bottom outlet of the ammonia distillation tower is connected to the bottom inlet of the reboiler through a pipeline provided with a wastewater circulation pump.

[0008] As a further improvement of the utility model, the waste liquid inlet at the bottom of the reboiler is connected to the reboiler drain pipe, and a reboiler relief valve is arranged on the top of the reboiler.

[0009] As a further improvement of the utility model, the reboiler is a shell-and-tube heat exchanger, the waste liquid flows through the tube side, the heated hot water flows through the shell side, countercurrent heat exchange is adopted, the water outlet of the water-cooled wall tube of the reboiler is connected to the hot water pressure regulating tank, and the water inlet of the water-cooled wall tube is connected to the waste heat recovery device.

[0010] As a further improvement of the utility model, the hot water pressure stabilizing tank is connected to the waste heat recovery device through a pipeline provided with a hot water circulation pump.

[0011] As a further improvement of the utility model, the hot water pressure stabilizing tank is provided with a water supply pipeline, and a water supply valve is provided on the water supply pipeline.

[0012] As a further improvement of the utility model, a hot water pressure stabilizing tank drain pipe is arranged at the bottom of the hot water pressure stabilizing tank, and a hot water pressure stabilizing tank relief valve is arranged at the top.

[0013] As a further improvement of the utility model, the flue gas waste heat ammonia distillation system also includes a PLC control system. More preferably, the PLC control system is a programmable logic controller, which is respectively connected to the reboiler, the hot water pressure stabilizing tank and the waste heat recovery device to remotely monitor and control the reboiler, the hot water pressure stabilizing tank and the waste heat recovery device.

[0014] The PLC control system controls the drainage, release and water replenishment of the hot water pressure regulating tank, and interlocks the drainage and release of the hot water pressure regulating tank with the start and stop status of the hot water circulation pump to prevent the desalted water from vaporizing in the pipeline when the hot water circulation pump suddenly loses power, causing damage to equipment and pipelines; the PLC control system controls the water supply valve to enable the hot water pressure regulating tank to achieve automatic pressure stabilization and adjustment functions such as automatic release of overpressure or automatic water replenishment due to low liquid level.

[0015] The PLC control system collects the temperatures of the waste liquid and circulating hot water at the inlet and outlet of the reboiler, and adjusts the flow rate of circulating hot water entering the reboiler according to the temperature to ensure safe and stable operation of the system.

[0016] The beneficial effects of the utility model are as follows: the utility model first exchanges heat between circulating water and flue gas through a waste heat recovery device, and transports the circulating water after heat exchange to a reboiler next to an ammonia distillation tower. Not only is the pipe diameter small and the engineering cost low, the circulating water loses little heat during the transportation process, and the ammonia-containing waste liquid and flue gas circulate in two closed systems. Even if the heat exchange tube in the reboiler is damaged, the ammonia-containing waste liquid will not enter the flue gas and drift with the flue gas to cause environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the flue gas waste heat ammonia distillation system described in the utility model.

[0018] In the figure: 1. Ammonia distillation tower, 2. Reboiler vent valve, 3. Reboiler, 4. Hot water pressure regulating tank vent valve, 5. Hot water circulation pump, 6. Waste heat recovery device, 7. Hot water pressure regulating tank drain pipe, 8. Hot water pressure regulating tank, 9. Reboiler drain pipe, 10. Waste water circulation pump. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the described embodiments are only part of the embodiments of the utility model, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0020] Example 1

[0021] like Figure 1 As shown, this embodiment adds a reboiler, a hot water pressure regulating tank and a waste heat recovery device on the basis of the original coking equipment. The waste heat recovery device adopts a flue gas waste heat recovery device commonly used in the art. The flue gas waste heat recovery device is installed after the coking large flue desulfurization and denitrification device, and uses the flue gas as the heat source of the flue gas waste heat recovery device to heat the circulating water of the flue gas waste heat recovery device.

[0022] Therefore, in this embodiment, a flue gas waste heat ammonia distillation system includes an ammonia distillation tower 1, a reboiler 3, a hot water pressure stabilizing tank 8, and a waste heat recovery device 6.

[0023] The waste liquid outlet at the bottom of the ammonia distillation tower 1 is connected to the waste liquid inlet at the bottom of the reboiler 3 through a pipeline provided with a wastewater circulation pump 10 , and the waste liquid outlet at the top of the reboiler 3 is connected to the waste liquid inlet at the bottom of the distillation tower 1 .

[0024] The top outlet of the ammonia evaporation tower 1 is connected to the ammonia collecting device, and the ammonia-containing waste liquid in the ammonia evaporation tower 1 releases ammonia gas in the ammonia evaporation tower 1, and goes out from the top outlet of the ammonia evaporation tower 1 and enters the ammonia collecting device.

[0025] A drain pipe 9 is provided on the lowest pipe before the waste liquid inlet at the bottom of the reboiler 3 and is equipped with steam cleaning; a reboiler relief valve 2 is provided on the upper part of the reboiler 3.

[0026] The water outlet of the reboiler 3 is connected to the hot water pressure stabilizing tank 8, the hot water circulation pump 5, the waste heat recovery device 6, and the water inlet of the reboiler 3 in sequence to form a water circulation system. The circulating water that obtains heat from the flue gas by the waste heat recovery device 6 enters the reboiler 3 and performs heat exchange with the ammonia-containing waste liquid in the reboiler 3. The heated ammonia-containing waste liquid expands or even vaporizes due to the heat, and then the ammonia-containing waste liquid enters the ammonia distillation tower 1 for ammonia distillation. The circulating water after the heat exchange enters the hot water pressure stabilizing tank 8, which has the functions of sewage discharge and water replenishment.

[0027] The hot water pressure stabilizing tank 8 is provided with a water supply pipeline, a hot water pressure stabilizing tank relief valve 4 and a hot water pressure stabilizing tank sewage pipe 7, and a water supply valve is provided on the water supply pipeline.

[0028] The flue gas waste heat ammonia distillation system also includes a programmable logic controller, which is connected to the reboiler 3, the hot water pressure stabilizing tank 8 and the waste heat recovery device 6 respectively to remotely monitor and control the reboiler 3, the hot water pressure stabilizing tank 8 and the waste heat recovery device 6.

[0029] The programmable logic controller controls the water replenishment and sewage discharge of the hot water pressure regulating tank 8 through the water supply valve, the hot water pressure regulating tank release valve 4 and the hot water pressure regulating tank sewage pipe 7. The water pressure regulating tank release valve 4 and the hot water pressure regulating tank sewage pipe 7 of the hot water pressure regulating tank are interlocked with the start and stop states of the hot water circulation pump to prevent the desalted water from vaporizing in the pipeline when the hot water circulation pump suddenly loses power, causing damage to equipment and pipelines; the PLC control system controls the water supply valve to enable the hot water pressure regulating tank to realize automatic pressure stabilization and adjustment functions such as automatic discharge of overpressure or automatic water replenishment at low liquid level.

[0030] The PLC control system collects the temperatures of the waste liquid and circulating hot water at the inlet and outlet of the reboiler 3, and adjusts the flow rate of the circulating hot water entering the reboiler 3 according to the temperature to ensure the safe and stable operation of the system. At the same time, the PLC control system controls the discharge of sewage in the reboiler 3 through the reboiler sewage pipe 9.

[0031] The working principle of the flue gas waste heat ammonia distillation system is as follows:

[0032] The waste heat recovery device 6 is installed after the desulfurization and denitration device of the coking flue. The flue gas is used as the heat source of the waste heat recovery device to heat the circulating water in the waste heat recovery device 6. The circulating hot water after heat exchange is used as the heat source of the reboiler 3 and enters the reboiler 3. At the same time, the bottom of the ammonia still 1 is opened, and the waste liquid at the bottom of the ammonia still 1 is pressurized by the waste water circulation pump 10 and then connected to the reboiler 3. Heat is exchanged with the circulating hot water inside the reboiler 3. The circulating water after heat exchange is sent to the flue gas waste heat recovery device 6 through the hot water pressure stabilizing tank 8 and the hot water circulation pump 5. The recovery device 6 continues to circulate, and the programmed logic controller controls the water supply valve, the hot water pressure regulating tank release valve 4 and the hot water pressure regulating tank sewage pipe 7 of the hot water pressure regulating tank 8 to replenish water, release and discharge sewage. The sewage discharge and release of the hot water pressure regulating tank 8 are interlocked with the start and stop state of the hot water circulation pump 5 to prevent the desalted water from vaporizing in the pipeline when the hot water circulation pump 5 suddenly loses power, causing damage to the equipment and pipelines; the PLC control system controls the water supply valve to enable the hot water pressure regulating tank 8 to realize automatic pressure regulation functions such as automatic release of overpressure or automatic water replenishment at low liquid level. The PLC control system collects the temperature of the waste liquid and circulating hot water in the inlet and outlet of the reboiler 3, and adjusts the flow of circulating hot water entering the reboiler 3 according to the temperature to ensure safe and stable operation of the system.

[0033] The ammonia-containing waste liquid in the reboiler 3 heated by the circulating hot water returns to the bottom of the ammonia evaporation tower 1 through the pipeline, and releases ammonia gas in the ammonia evaporation tower 1, thereby achieving the purpose of ammonia evaporation. A sewage and oil discharge pipeline is set on the lowest pipeline before the waste liquid inlet of the reboiler 3, and is equipped with steam cleaning. The reboiler vent valve 2 and the reboiler blowdown pipe 9 set on the reboiler 3 control the venting and blowdown in the reboiler 3.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit the protection scope of the utility model. Although the utility model is described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the utility model.

Claims

1. A flue gas waste heat ammonia distillation system, characterized by: It includes an ammonia still, a reboiler, a hot water pressure regulating tank and a waste heat recovery device; The waste liquid outlet at the bottom of the ammonia distillation tower is connected to the waste liquid inlet at the bottom of the reboiler, and the top outlet of the reboiler is connected to the waste liquid inlet at the bottom of the distillation tower; the water outlet of the reboiler is connected to the hot water pressure regulating tank, the waste heat recovery device, and the water inlet of the reboiler in sequence.

2. The flue gas waste heat ammonia distillation system according to claim 1, characterized in that: The bottom outlet of the ammonia distillation tower is connected to the bottom inlet of the reboiler through a pipeline provided with a wastewater circulation pump.

3. The flue gas waste heat ammonia distillation system according to claim 1, characterized in that: The waste liquid inlet at the bottom of the reboiler is connected to the reboiler drain pipe, and a reboiler relief valve is arranged on the top of the reboiler.

4. The flue gas waste heat ammonia distillation system according to claim 1, characterized in that: The hot water pressure stabilizing tank is connected to the waste heat recovery device through a pipeline provided with a hot water circulation pump.

5. The flue gas waste heat ammonia distillation system according to claim 1, characterized in that: The hot water pressure stabilizing tank is provided with a water supply pipeline, and a water supply valve is provided on the water supply pipeline.

6. The flue gas waste heat ammonia distillation system according to claim 1, characterized in that: A hot water pressure stabilizing tank sewage pipe is arranged at the bottom of the hot water pressure stabilizing tank, and a hot water pressure stabilizing tank relief valve is arranged at the top.

7. The flue gas waste heat ammonia distillation system according to claim 1, characterized in that: The flue gas waste heat ammonia distillation system also includes a PLC control system; the PLC control system is respectively connected to the reboiler, the hot water pressure regulating tank and the waste heat recovery device to remotely monitor and control the reboiler, the hot water pressure regulating tank and the waste heat recovery device.

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