Flash kettle

Abstract

The invention belongs to the field of chemical separation equipment, and relates to mixed liquid distillation separation equipment, in particular to a flash evaporation kettle which comprises a flash evaporation kettle body and a flash evaporation kettle crown, an inner cavity of the flash evaporation kettle body is axially communicated with an inner cavity of the flash evaporation kettle crown, and the flash evaporation kettle crown is located over the flash evaporation kettle body. The flash evaporation kettle is provided with at least two stages of flash evaporation chambers from top to bottom, and a liquid storage tank is arranged at the bottom. The device is simple in structure, good in flash evaporation effect, low in investment and operation cost, energy-saving, consumption-reducing, free of waste gas and waste water discharge and environment-friendly.

Description

Technical Field

[0001] The invention belongs to the field of chemical separation equipment and relates to mixed liquid distillation separation equipment, in particular to a flash still. Background Art

[0002] Distillation is a process that utilizes the difference in volatility of the components in a mixture to evaporate and vaporize the low-boiling-point components by heating, and then cools and condenses the steam to separate them. It has the advantages of simple operation, strong adaptability, and high separation efficiency. It is one of the important methods for separating and purifying liquid mixtures [Ma Fengxian. Research on the Development Status of Low-Energy Chemical Separation Technology [J]. Chemical Engineering Design Communications, 2021, 47(04): 50-51]. Due to the different properties of the components of the mixed liquid, there are different distillation operation modes corresponding to different distillation operation modes. Different distillation operation modes require the use of different distillation equipment to achieve a higher mixture separation effect. Therefore, with the continuous improvement and innovation of distillation technology, new distillation devices that meet the requirements of new distillation technologies have also made great progress.

[0003] For atmospheric distillation and reduced pressure distillation carried out at different operating pressures, the main equipment include tower distillation equipment and kettle distillation equipment. This type of equipment must be equipped with corresponding pressure-resistant structures to meet the requirements of the operating pressure. For simple distillation, rectification, special distillation, etc. carried out in different distillation methods, it is necessary to set up special structures that are conducive to feeding, discharging, and mass transfer according to the continuity of the operating process, the purity of component separation, the properties of the components to be separated and purified, etc. to meet the separation and purification effects.

[0004] The distillation unit structure required for special distillation operations is more targeted and less universal for mixtures. The distillation separation of special mixed liquids often requires special distillation equipment.

[0005] For example, molecular distillation has low pressure and short heating time, which requires more special equipment structure. At present, the main molecular distillation equipment includes falling film molecular distillation device, scraped film molecular distillation device and centrifugal molecular distillation device.

[0006] In the field of styrene-containing tail gas solvent absorption, which is used in the fields of synthetic resins, ion exchange resins and synthetic rubber, where styrene is an important monomer, the absorbent needs to be regenerated and the styrene component needs to be recovered. Since the saturated vapor pressure of the styrene component is high at room temperature and it is highly volatile, the conventional distillation tower is used to regenerate the absorbent, which requires large equipment investment and high operating costs. At the same time, since styrene is easy to polymerize, it is easy to cause blockage of supergravity distillation and molecular distillation equipment, making them unable to operate.

[0007] Distillation and flash evaporation are two important separation technologies that are widely used in the fields of chemical industry, petroleum, pharmaceutical industry, etc. Distillation has high separation accuracy and wide adaptability, but high energy consumption; flash evaporation has the advantages of simple equipment, low energy consumption, and large processing capacity, but limited separation accuracy. In practical applications, appropriate separation technology should be selected according to specific process requirements and material properties, and a suitable distillation unit should be constructed on this basis to improve separation efficiency and product quality and reduce operating costs. Summary of the invention

[0008] The purpose of the present invention is to solve the above technical problems and provide a flash evaporator with simple structure, good flash evaporation effect, energy saving and consumption reduction, and environmental friendliness.

[0009] The system of the present invention comprises a flash evaporation kettle body and a flash evaporation kettle crown. The inner cavities of the flash evaporation kettle body and the flash evaporation kettle crown are axially connected, and the flash evaporation kettle crown is located directly above the flash evaporation kettle body.

[0010] The flash kettle is provided with at least two stages of flash chambers from top to bottom, and a liquid storage tank is provided at the bottom.

[0011] The upper section of the flash kettle is a primary flash chamber, the lower section is a secondary flash chamber, the bottom liquid storage tank is divided into a lean liquid tank and a semi-lean liquid tank by an overflow plate, the primary flash chamber is communicated with the semi-lean liquid tank, and the secondary flash chamber is communicated with the lean liquid tank.

[0012] A primary flash atomizer is arranged at the top of the primary flash chamber, and a primary flash guide plate is arranged at the bottom; a secondary flash atomizer is arranged at the top of the secondary flash chamber, and a secondary flash guide plate is arranged at the bottom of the secondary flash chamber located above the semi-lean liquid tank, and the front end of the secondary flash guide plate is inserted into the lean liquid tank; the secondary flash guide plate and the overflow plate separate the semi-lean liquid tank from the secondary flash chamber; the primary flash chamber is connected to the semi-lean liquid tank through the primary flash guide pipe.

[0013] The gas phase space above the semi-lean liquid tank is connected to the primary flash chamber via a gas stripping gas air guide pipe; the secondary flash chamber is connected to the primary flash chamber via a flash gas air guide pipe.

[0014] The stripping gas guide pipe is located outside the flash still.

[0015] Aeration heads are provided in the lean liquid tank and the semi-lean liquid tank.

[0016] The top of the flash kettle crown is provided with a flash gas outlet, and the bottom is communicated with the flash kettle body. An electronic demister, a cold rich liquid nozzle, a washing filler and a gas-liquid flow distribution sieve plate are arranged in sequence from the top to the bottom of the crown.

[0017] The electronic demister comprises a plurality of cathode arc plates located at the periphery of the inner wall of the crown and a corresponding anode tube located at the center, wherein the inner surface of the cathode arc plate is uniformly embedded with field electron emission material; the anode tube and the plurality of cathode arc plates are connected to the outside of the tower via insulating hot wire poles.

[0018] A cathode porous plate is also arranged above the anode tube and the plurality of cathode arc plates, and the cathode porous plate is also connected to the outside of the tower via an insulating hot wire column.

[0019] In view of the problems existing in the background technology, the inventor has made the following improvements:

[0020] (1) A multi-stage flash chamber is arranged in the flash kettle, and a connected lean liquid tank and a semi-lean liquid tank are arranged correspondingly. On the one hand, by arranging two-stage flash evaporation in one flash kettle, the decomposition effect is enhanced. On the other hand, the first-stage flash chamber and the second-stage flash chamber are not connected to each other to ensure the flash evaporation effect. An aeration head is arranged in the tank at the bottom of the kettle to organically combine the multi-stage flash evaporation with the gas lift, improve the rich liquid distillation effect, save space, improve the vacuum pumping effect, and save the operating cost of the vacuum pump.

[0021] (2) A flash kettle crown is set on the top of the flash kettle. The flash steam is introduced into the flash kettle crown and then discharged. An electronic demister, a cold rich liquid nozzle, a filler and a gas-liquid flow distribution screen plate are sequentially arranged in the crown. The cold rich liquid nozzle is set, and the cold rich liquid introduced directly contacts the flash steam. The fine droplets in the flash steam are captured, reducing the absorbent loss. At the same time, the cold rich liquid directly contacts the flash steam, directly cooling the flash steam, recovering the coldness of the rich liquid and reducing the coldness required for the flash steam condensation. On the other hand, within the operating temperature range (30-60℃), the saturated vapor pressure is greatly affected by temperature (4.245kPa at 30℃, 7.381kPa at 40℃, and 19.932kPa at 60℃). The incoming cold rich liquid is in direct contact with the flash steam, and the flash steam is cooled down. A large amount of water vapor condenses and enters the rich liquid. The rich liquid then enters the first-stage flash chamber for first-stage flash evaporation. Almost all the water in the rich liquid is vaporized and enters the flash steam. After the rich liquid refluxes to the washing tower, most of it is condensed again. With the circulation of water, the water vapor concentration in the first-stage flash steam becomes higher and higher, and the reflux rich liquid condenses and absorbs more and more water until a balance state of reflux rich liquid absorbing water is formed. When the rich liquid in the water balance state returns to the flash kettle for atomization flash evaporation, the gas lift effect of water vapor is intensified, which can significantly improve the distillation effect.

[0022] (3) An electronic defogger is provided, in which an anode tube is arranged in the center, multiple cathode arc plates are arranged on the periphery, and a cathode porous plate is arranged on the top surface. After the flash steam in the rich liquid reflux washing tower is cooled by rich liquid washing and fine droplets are captured, it enters the electronic defogger upward; after the cathode porous plate, anode tube, and cathode arc plate of the electronic defogger are powered on, the field electron emission material embedded on the inner surface of the cathode arc plate emits electrons, and moves toward the center under the action of the electric field force between the anode tube and the cathode arc plate installed at the central axis of the electronic defogger; during the movement of the electrons, the electrons collide with the flash steam. The particle size of the fine droplets in the flash steam is much larger than the diameter of the gas molecules, and the probability of collision with the electrons is much higher than that of the gas molecules. The probability of molecules colliding with electrons; after the fine mist droplets collide and capture electrons, the mist droplets are negatively charged. Under the action of the electric field force and the drag force of the upward flowing airflow, the mist droplets move upward along the center. When they move to the area below the cathode porous plate, the electric field force of the cathode porous plate blocks the charged fine mist droplets from continuing to move upward, forcing them to move toward the central anode tube; the fine mist droplets are captured after moving to the surface of the anode tube, while the mist droplets that are not captured by the surface continue to move upward. Due to the negative charge, they are intercepted by the cathode porous plate, thereby achieving the purpose of effective demisting, greatly improving the demisting effect and efficiency. Compared with the traditional demisting device, the demisting effect of the electronic demisting device in the present invention can capture more than 99.9% of the fine mist droplets. .

[0023] The invention has simple structure, good flash evaporation effect, low investment and operation cost, energy saving and consumption reduction, no waste gas and waste water discharge, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Structural diagram of the present invention.

[0025] Figure 2 This is the front view of the electronic defogger.

[0026] Figure 3 for Figure 1 Middle AA section view.

[0027] Figure 4 for Figure 1 Middle BB section view.

[0028] Figure 5 for Figure 1 Middle CC section view.

[0029] Figure 6 This is a fitting curve diagram of the Henry constant determined experimentally in the present invention.

[0030] Wherein: 1: flash evaporator body; 1-1b: primary flash atomizer; 1-1c: secondary flash atomizer; 1-2a: primary flash guide plate; 1-2b: secondary flash guide plate; 1-3: guide pipe; 1-4b: flash gas guide pipe; 1-4c: air stripping gas guide pipe; 1-6a: lean liquid tank; 1-6b: semi-lean liquid tank; 1-7a: semi-lean liquid aeration head; 1-7b: lean liquid aeration head; 1-8: overflow plate;

[0031] 2: flash kettle crown; 2-1: crown body; 2-2: washing filler; 2-3: cold rich liquid nozzle; 2-4: gas-liquid flow distribution sieve plate;

[0032] 3: Electronic defogger;

[0033] 3-1, insulated hot wire column; 3-2, cathode porous plate; 3-3, insulating gasket; 3-4, cathode arc plate; 3-5, anode tube; 3-6, anode tube bracket; 3-7, porous plate insulating seat; 3-8, field electron emission material;

[0034] ① Lean liquid tank aeration port; ② Lean liquid discharge port; ③ Semi-lean liquid tank aeration port; ④ Semi-lean liquid outlet; ⑤ Cold rich liquid inlet; ⑥ Secondary flash evaporation inlet; ⑦ Primary flash evaporation inlet; ⑧ Flash gas outlet; ⑨ Kettle crown connecting port. DETAILED DESCRIPTION

[0035] The system of the present invention is further explained below in conjunction with the accompanying drawings:

[0036] See also Figure 1 The flash kettle comprises a flash kettle body 1 and a flash kettle crown 2 located directly above the flash kettle body 1, and the inner cavities of the flash kettle body 1 and the flash kettle crown 2 are axially connected.

[0037] Among them, the upper section of the flash evaporation kettle body 1 is a primary flash evaporation chamber, the lower section is a secondary flash evaporation chamber, and the bottom liquid storage tank is divided into a lean liquid tank 1-6a and a semi-lean liquid tank 1-6b by an overflow plate 1-8; a primary flash evaporation atomizer 1-1b is arranged on the upper part of the primary flash evaporation chamber, and a primary flash evaporation guide plate 1-2a is arranged on the bottom; a secondary flash evaporation atomizer 1-1c is arranged on the upper part of the secondary flash evaporation chamber, and a secondary flash evaporation guide plate 1-2b is arranged on the bottom of the secondary flash evaporation chamber located above the semi-lean liquid tank 1-6b, and the secondary flash evaporation guide plate 1-2b The front end is inserted into the lean liquid tank 1-6a, and the secondary flash guide plate 1-2b and the overflow plate 1-5 separate the semi-lean liquid tank 1-6b from the secondary flash chamber; the primary flash chamber is connected to the semi-lean liquid tank 1-6b through the guide pipe 1-3, and the gas phase space above the semi-lean liquid tank 1-6b is also connected to the primary flash chamber through the gas stripping gas guide pipe 1-4c located outside the flash kettle body; the lean liquid tank 1-6a and the semi-lean liquid tank 1-6b are correspondingly provided with a lean liquid aeration head 1-7b and a semi-lean liquid aeration head 1-7a.

[0038] Lean liquid discharge outlet ② and semi-lean liquid discharge outlet ④ are correspondingly arranged at the bottom of the lean liquid tank 1-6a and the semi-lean liquid tank 1-6b at the bottom of the flash kettle body 1, the lean liquid aeration head 1-7b is connected to the lean liquid tank aeration outlet ①, and the semi-lean liquid aeration head 1-7a is connected to the semi-lean liquid tank aeration outlet ③; the first-level flash inlet ⑦ on the flash kettle body 1 is connected to the first-level flash atomizer 1-1b, and the second-level flash inlet ⑥ is connected to the second-level flash atomizer 1-1c.

[0039] See also Figure 2 The flash vapor outlet⑧ is arranged at the top of the flash kettle crown 2, and the bottom is connected to the flash kettle body 1 through the kettle crown connecting port⑨. The electronic demister 3, the cold rich liquid nozzle 2-3, the washing filler 2-2 and the gas-liquid flow distribution sieve plate 2-4 are arranged in sequence from the crown top to the crown bottom. According to the needs, the washing filler 2-2 and the gas-liquid flow distribution sieve plate 2-4 are a group, and multiple groups can be arranged. The cold rich liquid nozzle 2-3 is connected to the cold rich liquid inlet⑤ on the flash kettle crown 2.

[0040] See also Figure 3-5 , wherein the electronic demister comprises a plurality of cathode arc plates 3-4 located at the periphery of the inner wall of the tower, an anode tube 3-5 and a cathode porous plate 3-2 located at the center, an insulating gasket 3-3 is arranged between the cathode arc plates 3-4 through the inner wall of the tower, and a field electron emission material 3-8 is uniformly embedded in the inner surface; the anode tube 3-5 is fixed in the tower through an anode tube bracket 3-6, and the cathode porous plate 3-2 is fixed in the tower through a porous plate insulating seat 3-7, and the anode tube 3-5, the plurality of cathode arc plates 3-4 and the cathode porous plate 3-2 are all connected to the outside of the tower through an insulating hot wire column 3-1.

[0041] Process:

[0042] In the flash kettle 1: the hot rich liquid (temperature is 65-70°C) is atomized and sprayed into the primary flash chamber and the secondary flash chamber by the primary flash atomizer 1-1b and the secondary flash atomizer 1-1c respectively; the semi-lean liquid after flash evaporation and analysis of the rich liquid in the primary flash chamber falls into the semi-lean liquid tank 1-6a through the guide pipe 1-4c and is led out from the semi-lean liquid outlet ④; the lean liquid after flash evaporation and analysis of the rich liquid in the secondary flash chamber falls into the lean liquid tank 1-6b along the secondary flash guide plate 1-2b and is led out of the flash kettle body 1 through the lean liquid outlet ②; the flash gas in the secondary flash chamber is merged into the primary flash chamber through the flash gas guide pipe 1-4b, and then enters the flash kettle crown 2 upward from the top of the flash kettle body 1 through the kettle crown connecting port ⑨.

[0043] Water vapor or other low-boiling-point component gas (such as carbon dioxide, nitrogen, etc.) insoluble in the absorbent is introduced into the lean liquid aeration head 1-7b and the semi-lean liquid aeration head 1-7a of the lean liquid tank 1-6a and the semi-lean liquid tank 1-6b in the flash kettle to further strip the residual styrene component in the lean liquid and the semi-lean liquid. The stripping gas overflowing from the semi-lean liquid tank 1-6b is introduced into the primary flash chamber through the stripping gas guide pipe 1-4c to merge with the flash gas; the stripping gas overflowing from the lean liquid tank 1-6a directly enters the secondary flash chamber and merges with the flash gas;

[0044] In the flash kettle crown 2: the flash steam passes through the gas-liquid flow distribution sieve plate 2-4 and the packing layer 2-2 from bottom to top, and is countercurrently contacted and washed with the rich liquid (25-30℃) sprayed from the cold rich liquid nozzle 2-1 from top to bottom, and is finally defogged by the electronic demister 3 and then led out from the flash steam outlet ⑧ at the crown top.

[0045] When the washed flash gas passes through the electronic defogger 3 in the energized state, the anode tube 3-5 provides a strong electric field, the field electron emission material 3-8 emits electrons, and the mist particles passing through the field capture the electrons and move to the surface of the anode tube 3-5 (electric field force). The mist droplets not captured by the surface continue to move upward, and because they are negatively charged, they are intercepted by the cathode porous plate 3-2, thereby achieving the purpose of efficient defogger.

[0046] The rich liquid in this embodiment comes from the absorption tower, and refers to the absorbent that has absorbed styrene. The absorbent is a high-boiling point organic solvent whose boiling point is 150° C. higher than that of styrene, and is preferably diethyl phthalate.

[0047] See also Figure 6 The Henry constant of the solution after diethyl phthalate absorbs styrene is: 23.04kg / (moL·kPa).

[0048] The device is used for styrene absorption rich distillation, with a flash efficiency of over 90%. Compared with the distillation process using a distillation tower, it reduces investment by over 50%, saves energy consumption by over 50%, and reduces operating costs by over 50%.

Claims

1. A flash kettle, comprising a flash kettle body and a flash kettle crown, characterized in that: The flash kettle body and the flash kettle crown have inner cavities that are axially connected, and the flash kettle crown is located directly above the flash kettle body.

2. The flash kettle according to claim 1, characterized in that The flash kettle is provided with at least two stages of flash chambers from top to bottom, and a liquid storage tank is provided at the bottom.

3. The flash kettle according to claim 2, characterized in that The upper section of the flash kettle is a primary flash chamber, the lower section is a secondary flash chamber, the bottom liquid storage tank is divided into a lean liquid tank and a semi-lean liquid tank by an overflow plate, the primary flash chamber is communicated with the semi-lean liquid tank, and the secondary flash chamber is communicated with the lean liquid tank.

4. The flash still according to claim 3, characterized in that: The first-stage flash chamber has a first-stage flash atomizer at the top and a first-stage flash guide plate at the bottom; the second-stage flash chamber has a second-stage flash atomizer at the top, and the bottom of the second-stage flash chamber is provided with a second-stage flash guide plate located above the semi-lean liquid tank, and the front end of the second-stage flash guide plate is inserted into the lean liquid tank; The secondary flash distillation guide plate and the overflow plate separate the semi-lean liquid tank from the secondary flash distillation chamber; The primary flash chamber is connected to the semi-lean liquid tank via a primary flash draft pipe.

5. The flash kettle according to claim 4, characterized in that: The gas phase space above the semi-lean liquid tank is connected to the primary flash chamber via a gas stripping gas air guide pipe; the secondary flash chamber is connected to the primary flash chamber via a flash gas air guide pipe.

6. The flash kettle according to claim 5, characterized in that The stripping gas guide pipe is located outside the flash still.

7. The flash kettle according to claim 5, characterized in that: Aeration heads are provided in the lean liquid tank and the semi-lean liquid tank.

8. The flash kettle according to any one of claims 1 to 7, characterized in that: The top of the flash kettle crown is provided with a flash gas outlet, and the bottom is communicated with the flash kettle body. An electronic demister, a cold rich liquid nozzle, a washing filler and a gas-liquid flow distribution sieve plate are arranged in sequence from the top to the bottom of the crown.

9. The flash kettle according to claim 8, characterized in that The electronic demister comprises a plurality of cathode arc plates located at the periphery of the inner wall of the crown and a corresponding anode tube located at the center, wherein the inner surface of the cathode arc plate is uniformly embedded with field electron emission material; the anode tube and the plurality of cathode arc plates are connected to the outside of the tower via insulating hot wire poles.

10. The flash kettle according to claim 9, characterized in that A cathode porous plate is also arranged above the anode tube and the plurality of cathode arc plates, and the cathode porous plate is also connected to the outside of the tower via an insulating hot wire column.

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