Concentrated ammonia purification device

Abstract

The utility model discloses a kind of concentrated ammonia water purification devices, it is related to coking chemical product recovery field, including raw material feed pipe, the raw material feed pipe is connected with raw material heat exchanger and raw material evaporator, the outlet pipeline of raw material evaporator is connected with the feed pipe mouth of molecular sieve membrane module;Molecular sieve membrane module is arranged in the molecular sieve membrane tube of tubular structure arrangement, each molecular sieve membrane tube is equipped with protective sleeve, the discharge pipe mouth of molecular sieve membrane module is connected with product condensing cooler by raw material heat exchanger, the outlet pipeline of this product condensing cooler is connected with the import of product tank, the top of product tank is provided with incondensable gas pipeline, the incondensable gas pipeline is connected with vacuum pump, compared with prior art, the utility model sets raw material heat exchanger, preheats using purified ammonia water as raw material, save the steam required for raw material preheating, reduce energy consumption;Molecular sieve membrane tube is provided with protective sleeve, prolong the service life of membrane tube, the device is simple to operate, and the land space is small.

Description

Technical Field

[0001] This utility model relates to the field of coking chemical product recovery technology, and in particular to a concentrated ammonia water purification device. Background Technology

[0002] Coking wastewater is a type of recalcitrant industrial wastewater generated during the coking process. It primarily originates from coking oven gas cooling, gas purification, and the refining of chemical products such as benzene, naphthalene, and tar. This type of wastewater is extremely complex, containing not only high concentrations of ammonia nitrogen, phenols, cyanides, and oily substances, but also recalcitrant organic pollutants such as polycyclic aromatic hydrocarbons and heterocyclic compounds. It is characterized by high pollution concentrations, strong biological toxicity, and poor biodegradability. In existing processes, the recovery of ammonia resources from the remaining ammonia water relies on a distillation process using an ammonia stripping tower. After the remaining ammonia water is fed into the ammonia stripping tower, it undergoes distillation separation by introducing high-temperature steam. The ammonia gas distilled from the top of the tower is mainly used in two ways, depending on subsequent product planning: one is to react with sulfuric acid in a saturator to prepare ammonium sulfate crystals; the other is to be directly introduced into an ammonia decomposition furnace to decompose into nitrogen and hydrogen before being discharged or recovered. However, this process has inherent defects: during the ammonia stripping process, the tar, naphthalene and other impurities remaining in the wastewater have boiling points close to those of ammonia gas, and are easy to form aerosols that escape with the ammonia gas. This results in the final concentrated ammonia water containing a large amount of organic impurities. Depending on the concentrated ammonia water production process, the oil content of the concentrated ammonia water is usually between 500 mg / L and 5000 mg / L, and the content of acidic gases (H2S, CO2) is about 1000 to 20000 mg / L, which is difficult to meet the needs of high-end applications.

[0003] To optimize ammonia recovery, some companies have improved the process by using phosphoric acid washing. In this process, ammonia vapor from the top of the ammonia stripping tower first enters the ammonia absorption tower, where it selectively contacts a phosphoric acid solution to form ammonium phosphate. The vapor is then heated and desorbed in a stripping tower to produce high-concentration ammonia vapor, which is then used to prepare concentrated ammonia water. Although phosphoric acid washing exhibits strong selectivity for ammonia, absorbing only trace amounts of acidic gases such as hydrogen sulfide from the coal gas, it is limited by process defects such as uneven gas-liquid contact within the absorption tower and unbalanced temperature distribution in the stripping tower. Furthermore, operational issues such as fluctuations in phosphoric acid solution concentration and insufficient precision in controlling operating parameters mean that the ammonia vapor obtained after stripping still carries trace amounts of phosphoric acid droplets and organic amine byproducts, ultimately hindering the improvement of the quality of the concentrated ammonia water. Poor-quality concentrated ammonia water can have a cascading effect on subsequent production systems, as impurities easily deposit and scale in pipes, valves, and heat exchangers, causing equipment blockages and reduced heat exchange efficiency. Utility Model Content

[0004] The problem to be solved by this utility model is to provide a concentrated ammonia purification device with low energy consumption, high yield and high ammonia purity.

[0005] To solve the above problems, the technical solution adopted by this utility model is as follows: This concentrated ammonia water purification device includes a raw material heat exchanger, a raw material evaporator, a molecular sieve membrane assembly, a product condenser, a product tank, and a vacuum pump; the raw material feed pipe is connected to the raw material evaporator through the raw material heat exchanger, and the outlet pipe of the raw material evaporator is connected to the feed port of the molecular sieve membrane assembly; the molecular sieve membrane assembly is provided with a tubular arrangement of molecular sieve membrane tubes, each of which is fitted with a protective sleeve; the outlet of the molecular sieve membrane assembly is connected to the product condenser through the raw material heat exchanger; the outlet pipe of the product condenser is connected to the inlet of the product tank; a non-condensable gas pipeline is provided at the top of the product tank, and this non-condensable gas pipeline is connected to the vacuum pump.

[0006] In the above-mentioned concentrated ammonia purification device, a more specific technical solution may be as follows: a first shell side is formed between the inner wall of the outer shell of the molecular sieve membrane assembly and the outer wall of the protective sleeve; a second shell side is formed between the inner wall of the protective sleeve and the outer wall of the molecular sieve membrane tube; and a tube side is formed inside the molecular sieve membrane tube. The outlet of the tube side of the molecular sieve membrane assembly is connected to the product condenser through the raw material heat exchanger. The inlet of the first shell side of the molecular sieve membrane assembly is connected to a steam pipeline, and the outlet of the first shell side is connected to a condensate pipeline.

[0007] In some possible implementations, the protective sleeve is a metal sleeve made of 304 stainless steel or 316L stainless steel.

[0008] In some possible implementations, the raw material heat exchanger is a shell-and-tube heat exchanger, in which purified ammonia flows in the tube side and the raw material to be treated flows in the shell side.

[0009] In some possible implementations, the molecular sieve pore size of the molecular sieve membrane tube is 0.3-0.5 nm, and the material of the molecular sieve membrane tube is ZSM-5 molecular sieve or SAPO-34 molecular sieve.

[0010] In some possible implementations, a pressure regulating valve is provided on the non-condensable gas line between the vacuum pump and the product tank. This pressure regulating valve is interlocked with the tube-side pressure sensor of the molecular sieve membrane assembly to maintain a pressure difference of 0.05-0.08 MPa between the tube side and the second shell side.

[0011] In some possible implementations, the second shell side of the molecular sieve membrane assembly has an impurity discharge port at its bottom, which is connected to a large tank of residual ammonia water via a pipe, and the pipe is equipped with a shut-off valve and a flow metering device.

[0012] In some possible implementations, a three-way valve is installed on the raw material feed pipe, with its two inlets connected to the liquid ammonia water pipeline and the ammonia vapor pipeline, respectively, to achieve selective feeding of liquid ammonia water and ammonia vapor from the top of the ammonia stripping tower.

[0013] In some possible implementations, a flow controller is provided on the steam line of the first shell side, which is interlocked with a temperature sensor in the second shell side to control the steam flow to maintain the temperature in the second shell side at 60-80°C.

[0014] In some possible implementations, a product discharge pipe is provided at the bottom of the product tank, and a purity detection device and an automatic sampling valve are installed on the product discharge pipe. The purity detection device is interlocked with the feed regulating valve of the product tank.

[0015] By adopting the above technical solution, this utility model has the following beneficial effects compared with the prior art: 1. Because this utility model is equipped with a raw material heat exchanger, it uses purified ammonia water as the raw material for preheating, which saves the amount of steam required for raw material preheating and the amount of low-temperature water required for product cooling, thus reducing energy consumption; the molecular sieve membrane tube is fitted with a protective sleeve, which extends the service life of the membrane tube, and the steam outside the sleeve can be used to maintain the temperature of the raw material inside the sleeve; the raw material of this device can be ammonia water or ammonia vapor, and the direct feeding of ammonia vapor from the top of the ammonia stripping tower can further save steam consumption; the process flow is short, the operation is simple, and the footprint is small.

[0016] 2. Because the molecular sieve membrane module adopts a tubular structure with molecular sieve membrane tubes and a molecular sieve pore size of 0.3-0.5nm, it can selectively retain water, organic impurities and other ineffective components in concentrated ammonia water, allowing only ammonia molecules to permeate rapidly. Compared with traditional distillation and adsorption processes, the separation selectivity is improved by more than 30%, and high purity can be achieved in a single purification, significantly shortening the processing cycle.

[0017] 3. By interlocking the pressure regulating valve and the tube-side pressure sensor, a stable pressure difference of 0.05-0.08 MPa is precisely maintained between the tube side and the second shell side, forming a continuous permeation driving force. This avoids the problem of increased mass transfer resistance during membrane separation, ensuring that the ammonia permeation rate remains stable within the high-efficiency range per unit time. The processing capacity of the device is significantly improved compared to conventional membrane separation equipment.

[0018] 4. Because the molecular sieve membrane module of this utility model adopts a three-chamber structure of "first shell side - second shell side - tube side", the first shell side is circulated with steam to achieve indirect heating, which not only ensures the temperature conditions required for membrane separation and avoids local overheating leading to membrane performance degradation, but also makes the temperature and pressure distribution around the membrane tube more uniform through the buffering effect of the second shell side, reducing the deformation of the membrane tube caused by thermal stress, and further improving the reliability of the device in long-term operation. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the present invention.

[0020] Figure 2 This is a diagram showing the internal structure of the molecular sieve membrane assembly of this utility model.

[0021] In the diagram: 1. Raw material evaporator; 2. Molecular sieve membrane module; 3. Raw material heat exchanger; 4. Product condenser; 5. Product tank; 6. Vacuum pump; 7. Pressure regulating valve; 8. Shut-off valve; 9. Flow metering device; 10. Raw material feed pipe; 11. Three-way valve; 12. Liquid ammonia water pipeline; 13. Ammonia vapor pipeline; 14. Product discharge pipe; 15. Outlet pipeline; 16. Non-condensable gas pipeline; 17. Feed regulating valve; 21. Molecular sieve membrane tube; 22. Protective sleeve; 23. First shell side; 24. Second shell side; 25. Tube side. Detailed Implementation

[0022] To make the above-mentioned objectives, features, and advantages of this utility model more readily understood, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model; however, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0023] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "fixation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0024] like Figure 1 , Figure 2The embodiment shown proposes a concentrated ammonia purification device, including a raw material heat exchanger 3, a raw material evaporator 1, a molecular sieve membrane assembly 2, a product condenser 4, a product tank 5, and a vacuum pump 6. The raw material feed pipe is connected to the raw material evaporator 1 via the raw material heat exchanger 3, and the outlet pipe of the raw material evaporator 1 is connected to the feed port of the molecular sieve membrane assembly 2. The molecular sieve membrane assembly 2 contains tubular molecular sieve membrane tubes 21, each with a protective sleeve 22. The outlet pipe of the molecular sieve membrane assembly 2 is connected to the product condenser 4 via the raw material heat exchanger 3. The outlet pipe 15 of the product condenser 4 is connected to the inlet of the product tank 5. A non-condensable gas pipeline 16 is installed at the top of the product tank 5 and is connected to the vacuum pump 6. A first shell-side 23 is formed between the inner wall of the outer shell of the molecular sieve membrane assembly 2 and the outer wall of the protective sleeve 22. A second shell side 24 is formed between the outer walls of the molecular sieve membrane tube 21, and a tube side 25 is formed inside the molecular sieve membrane tube 21. The outlet of the tube side of the molecular sieve membrane assembly 2 is connected to the product condenser 4 through the raw material heat exchanger 3. The inlet of the first shell side 23 of the molecular sieve membrane assembly 2 is connected to a steam pipeline, and the outlet of the first shell side is connected to a condensate pipeline. A flow controller is installed on the steam pipeline of the first shell side 23. The flow controller is interlocked with the temperature sensor in the second shell side 24 to control the steam flow to maintain the temperature in the second shell side 24, which is 60-80℃. Steam is introduced into the first shell side to achieve indirect heating, which not only ensures the temperature conditions required for membrane separation, but also makes the temperature and pressure distribution around the membrane tube more uniform through the buffering effect of the second shell side, reducing the deformation of the membrane tube caused by thermal stress, and further improving the long-term reliability of the device. The protective sleeve 22 is a metal sleeve made of 304 stainless steel. Stainless steel or 316L stainless steel forms a double protective structure of membrane tube and protective sleeve. On the one hand, it can buffer the impact pressure during raw material feeding, preventing the membrane tube from rupturing due to uneven stress; on the other hand, the stainless steel material is resistant to ammonia corrosion and high temperature, which can isolate the first shell-side vapor from direct contact with the membrane tube, reduce the aging rate of the membrane tube, and extend the service life of the membrane module to 3-5 years, more than double that of the design without protective sleeve. The raw material heat exchanger 3 is a shell-and-tube heat exchanger. The purified ammonia flows in the tube side, and the raw material to be treated flows in the shell side. The raw material heat exchanger adopts a shell-and-tube structure, and the purified ammonia and the raw material to be treated exchange heat in opposite directions, that is, the purified ammonia flows in the tube side and the raw material flows in the shell side, avoiding cross-contamination between raw material and finished product. At the same time, it ensures uniform pretreatment temperature of raw material, reduces separation effect deviation caused by raw material temperature fluctuation, and controls the product purity fluctuation range within ±0.1%, with quality stability significantly better than traditional processes; the molecular sieve membrane tube 21 has a molecular sieve channel pore size of 0.3-0.The molecular sieve membrane tube 21 is made of ZSM-5 molecular sieve. A pressure regulating valve 7 is installed on the non-condensable gas pipeline between the vacuum pump 6 and the product tank 5. This pressure regulating valve is interlocked with the pressure sensor of the tube side 25 of the molecular sieve membrane assembly 2 to maintain the pressure difference between the tube side 25 and the second shell side 24, which is 0.05-0.08 MPa. An impurity discharge port is installed at the bottom of the second shell side 24 of the molecular sieve membrane assembly 2. This impurity discharge port is connected to the remaining ammonia water tank via a pipeline. A shut-off valve 8 and a flow metering device 9 are installed on the pipeline. A three-way valve 11 is installed on the raw material feed pipe 10. The two inlets of this three-way valve are connected to the liquid ammonia water pipeline 12 and the ammonia vapor pipeline 13, respectively, to achieve selective feeding of liquid ammonia water and ammonia vapor from the top of the ammonia stripping tower. A product discharge pipe 14 is installed at the bottom of the product tank 5. A purity detection device and an automatic sampling valve are installed on this product discharge pipe. The purity detection device is interlocked with the feed regulating valve 17 of the product tank 5.

[0025] The specific process for purifying concentrated ammonia in this embodiment is as follows: Implementation Method 1: Concentrated ammonia water with a concentration of 15%-25% from the residual ammonia water stripping section, containing 3000mg / L-5000mg / L of oil and approximately 10000-20000mg / L of acidic gases (H2S, CO2). It first enters the shell side of the raw material heat exchanger 3, exchanging heat with the purified high-temperature ammonia water flowing in the tube side. The raw material ammonia water is preheated to 60-80℃, while the purified ammonia water is cooled to 40-50℃. After heat exchange, the raw material ammonia water enters the raw material evaporator 1, where it vaporizes under steam heating at 0.1 MPa-0.3 MPa, forming a mixed gas of ammonia vapor and water vapor. This mixed gas enters the second shell side 24 of the molecular sieve membrane assembly 2. The vacuum pump 6 is started to evacuate the tube side 25 of the molecular sieve membrane assembly 2, creating a vacuum of 0.05-0.08 MPa between the tube side 25 and the second shell side 24. The pressure difference causes ammonia and water molecules to pass through the molecular sieve channels on the surface of the molecular sieve membrane tube 21 into the tube side 25, while large organic impurities such as tar and naphthalene are retained in the second shell side 24. The purified ammonia vapor in the tube side 25 passes sequentially through the tube side of the raw material heat exchanger 3 and the product condenser 4, and is cooled to 20-30°C before condensing into concentrated ammonia water, containing approximately 16% to 26% ammonia. The concentrated ammonia water contains 30 mg / L to 100 mg / L of oil and approximately 20 to 300 mg / L of acidic gases (H2S, CO2) before entering the product tank 5 for storage. The non-condensable gas at the top of the product tank 5 is extracted by the vacuum pump 6 and returned to the negative pressure gas pipeline. The large molecular impurities retained in the second shell side 24 are treated as ammonia waste and returned to the remaining ammonia water tank through the pipeline for further processing.

[0026] Implementation Method 2: Concentrated ammonia water with a concentration of approximately 21% from the ammonium phosphate washing section, containing 1000 mg / L to 3000 mg / L of oil and approximately 100 to 500 mg / L of acidic gases (H2S, CO2). It first enters the shell side of the raw material heat exchanger 3, exchanging heat with the purified high-temperature ammonia water flowing in the tube side. The raw material ammonia water is preheated to 60-80°C, while the purified ammonia water is cooled to 40-50°C. After heat exchange, the raw material ammonia water enters the raw material evaporator 1, where it vaporizes under steam heating at 0.1 MPa - 0.3 MPa, forming a mixed gas of ammonia vapor and water vapor. This mixed gas enters the second shell side 24 of the molecular sieve membrane assembly 2. The vacuum pump 6 is started to evacuate the tube side 25 of the molecular sieve membrane assembly 2, creating a vacuum of 0.05-0.08 MPa between the tube side 25 and the second shell side 24. The pressure difference causes ammonia and water molecules to pass through the molecular sieve channels on the surface of the molecular sieve membrane tube 21 into the tube side 25, while large organic impurities such as tar and naphthalene are retained in the second shell side 24. The purified ammonia vapor in the tube side 25 passes sequentially through the tube side of the raw material heat exchanger 3 and the product condenser 4, and is cooled to 20-30°C before condensing into concentrated ammonia water, containing approximately ~20% ammonia. The concentrated ammonia water contains 30mg / L to 100mg / L of oil and approximately 20-100mg / L of acidic gases (H2S, CO2) before entering the product tank 5 for storage. The non-condensable gas at the top of the product tank 5 is extracted by the vacuum pump 6 and returned to the gas negative pressure pipeline. The large molecular impurities retained in the second shell side 24 are treated as ammonia waste and returned to the remaining ammonia water tank through the pipeline for further processing.

[0027] In this embodiment, the raw material evaporator can be heated by steam or electricity, and the product condenser preferably uses low-temperature water.

[0028] In other embodiments, when the raw material is ammonia vapor at a temperature of 90-110°C from the top of the ammonia stripping tower, it can be directly fed into the second shell side 24 of the molecular sieve membrane assembly 2 through the feed pipe, without passing through the raw material heat exchanger 3 and the raw material evaporator 1. The subsequent separation, condensation and storage processes are the same as those in the above embodiments. This method can further save steam consumption and reduce energy consumption.

[0029] This utility model can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model shall be included within the protection scope of this utility model.

Claims

1. A concentrated ammonia water purification device, characterized in that: The system includes a raw material heat exchanger (3), a raw material evaporator (1), a molecular sieve membrane assembly (2), a product condenser (4), a product tank (5), and a vacuum pump (6). The raw material feed pipe is connected to the raw material evaporator (1) through the raw material heat exchanger (3), and the outlet pipe of the raw material evaporator (1) is connected to the feed port of the molecular sieve membrane assembly (2). The molecular sieve membrane assembly (2) is equipped with a tubular arrangement of molecular sieve membrane tubes (21), and each molecular sieve membrane tube (21) is fitted with a protective sleeve (22). The outlet of the molecular sieve membrane assembly (2) is connected to the product condenser (4) through the raw material heat exchanger (3), and the outlet pipe of the product condenser (4) is connected to the inlet of the product tank (5). A non-condensable gas pipeline is installed on the top of the product tank (5), and the non-condensable gas pipeline is connected to the vacuum pump (6).

2. The concentrated ammonia purification apparatus according to claim 1, characterized in that: The inner wall of the outer shell of the molecular sieve membrane assembly (2) forms a first shell side (23) between the outer wall of the protective sleeve (22) and the outer wall of the molecular sieve membrane tube (21), and the inner wall of the protective sleeve (22) forms a second shell side (24) between the outer wall of the molecular sieve membrane tube (21). The interior of the molecular sieve membrane tube (21) forms a tube side (25). The outlet of the tube side of the molecular sieve membrane assembly (2) is connected to the product condenser (4) through the raw material heat exchanger (3). The inlet of the first shell side (23) of the molecular sieve membrane assembly (2) is connected to a steam pipeline, and the outlet of the first shell side is connected to a condensate pipeline.

3. The concentrated ammonia purification apparatus according to claim 2, characterized in that: The protective sleeve (22) is a metal sleeve, which is made of 304 stainless steel or 316L stainless steel.

4. The concentrated ammonia purification apparatus according to claim 2, characterized in that: The raw material heat exchanger (3) is a shell-and-tube heat exchanger, in which the purified ammonia flows in the tube side and the raw material to be processed flows in the shell side.

5. The concentrated ammonia purification apparatus according to claim 2 or 4, characterized in that: The molecular sieve pore size of the molecular sieve membrane tube (21) is 0.3-0.5 nm, and the material of the molecular sieve membrane tube (21) is ZSM-5 molecular sieve or SAPO-34 molecular sieve.

6. The concentrated ammonia purification apparatus according to claim 5, characterized in that: A pressure regulating valve is installed on the non-condensable gas pipeline between the vacuum pump (6) and the product tank (5). The pressure regulating valve is interlocked with the pressure sensor of the tube side (25) of the molecular sieve membrane assembly (2) to maintain the pressure difference between the tube side (25) and the second shell side (24), which is 0.05-0.08 MPa.

7. The concentrated ammonia purification apparatus according to claim 2, characterized in that: The second shell side (24) of the molecular sieve membrane assembly (2) is provided with an impurity discharge port at its bottom. The impurity discharge port is connected to the remaining ammonia water tank through a pipe. A shut-off valve and a flow metering device are provided on the pipe.

8. The concentrated ammonia purification apparatus according to claim 1, characterized in that: A three-way valve is installed on the raw material feed pipe. The two inlets of the three-way valve are connected to the liquid ammonia water pipeline and the ammonia vapor pipeline, respectively, to achieve selective feeding of liquid ammonia water and ammonia vapor from the top of the ammonia stripping tower.

9. The concentrated ammonia purification apparatus according to claim 2, characterized in that: A flow controller is installed on the steam line of the first shell side (23). The flow controller is interlocked with the temperature sensor in the second shell side (24) to control the steam flow to maintain the temperature in the second shell side (24) at 60-80°C.

10. The concentrated ammonia purification apparatus according to claim 2, characterized in that: The bottom of the product tank (5) is provided with a product discharge pipe, and a purity detection device and an automatic sampling valve are provided on the product discharge pipe. The purity detection device is interlocked with the feed regulating valve of the product tank (5).

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