Styrene-containing pregnant solution flash evaporation analysis system

Abstract

The invention belongs to the field of chemical equipment, and relates to an absorption liquid rich liquid flash evaporation system, in particular to a styrene-containing rich liquid flash evaporation analysis system, which comprises an absorption tower rich liquid tank and a flash evaporation kettle, a rich liquid outlet in the bottom of the rich liquid reflux washing tower is connected with the flash evaporation kettle; a gas phase outlet of the flash kettle is connected with the lower section of the pregnant solution reflux washing tower, and a barren solution outlet at the bottom of the flash kettle is connected with the absorption tower through a liquid holding column. The system is simple, 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 an absorption liquid rich liquid flash evaporation system, in particular to a rich liquid flash evaporation analysis system containing styrene. Background Art

[0002] Chemical separation of mixtures is a unique function of chemical equipment. It is a process of separating unique mixtures according to the differences in their physical and chemical properties, with the help of certain separating agents, through different operations such as component classification, concentration, enrichment, purification, refinement, isolation, etc.

[0003] According to different physical and chemical principles, mass transfer separation can be divided into: equilibrium separation process and rate separation process.

[0004] The equilibrium separation process is to transform a homogeneous mixture into a two-phase system with the help of a separating agent, and then achieve separation by utilizing the unequal distribution of the components in the mixture in the two phases in phase equilibrium, such as distillation, absorption, extraction, crystallization, adsorption, etc.

[0005] The rate separation process is to achieve separation by utilizing the difference in diffusion rates of components under the action of some driving force (concentration difference, pressure difference, temperature difference, potential difference, etc.), such as microfiltration, ultrafiltration, reverse osmosis, electrodialysis, etc.

[0006] Distillation is often used to separate the absorption liquid mixture after the absorption of organic gas. According to the different equipment used in the distillation process, distillation can be divided into rotary distillation, flash distillation, super gravity distillation, etc. According to the different operating pressures, distillation can be divided into atmospheric distillation and vacuum distillation; according to the different distillation methods, distillation can be divided into simple distillation, rectification, special distillation, special distillation includes steam distillation, azeotropic distillation, molecular distillation, etc.

[0007] Rotary evaporation is based on the principle that the rotary distillation kettle drives the liquid phase in the kettle to transfer under reduced pressure to increase the evaporation area to achieve the separation of the mixture. It is mainly used for continuous distillation of volatile solvents under reduced pressure, and is applied to the fields of chemistry, chemical industry, biomedicine, etc. Since the rotary evaporation process requires the liquid phase to rotate under reduced pressure, it is not suitable for the separation of large flow mixed liquids, and has high requirements for the sealing of the rotating parts.

[0008] Flash evaporation is based on the principle that the solubility of gaseous solutes in liquid solvents is different at different temperatures and partial pressures. The high-pressure saturated liquid is sent into a relatively low-pressure container, and the low-boiling point components are vaporized to achieve the separation process of the saturated liquid. Flash evaporation is the process in which a saturated liquid changes from one thermodynamic equilibrium state to the next thermodynamic equilibrium state. The energy for flash evaporation is provided by the solvent itself, so the temperature of the solvent decreases during the flash evaporation process. From a higher certain pressure to a lower certain pressure, the amount of solute desorbed when the desorption equilibrium is reached is certain, and the amount of solute remaining in the corresponding solvent is also certain, so there is only one control target for flash evaporation, which is the pressure of the flash evaporation.

[0009] Ultra-gravity distillation applies rotary distillation technology to the continuous distillation process in industrial production. The rotary distillation machine consists of one or more high-speed rotating rotors, and the gas and liquid pass through the rotor in a reverse spraying manner to transfer materials. The liquid is broken up by centrifugal force and then contacts the gas, which is more sufficient than the direct contact between the liquid and other liquids, and the contact surface area between the gas and liquid phases and the mass transfer and heat transfer rate and efficiency are increased, which greatly reduces the size of the equipment. The rotor with a specific structure rotates at high speed in the machine body, and the gas phase enters the machine from the gas inlet and the outer edge of the rotor. The liquid phase enters the center of the rotor from the liquid inlet. The gas and liquid phases form a gas-liquid interface with a large specific surface area and constantly updated in the rotor, which has a mass transfer and heat transfer rate and efficiency. The gas phase then leaves the bed through the gas outlet and is condensed by the condenser; the liquid phase is collected in the machine and then drawn out from the liquid outlet. However, ultra-gravity distillation is very easy to clog for systems with polymer components, and it consumes a lot of power.

[0010] Atmospheric distillation, also known as simple distillation or ordinary distillation, refers to the distillation process operated under normal pressure conditions. The solution is heated under normal pressure, and the light components with lower boiling points are vaporized and condensed to separate. The operation of vaporizing and condensing the light components with lower boiling points to roughly separate them is called distillation; the operation of repeatedly using partial vaporization and partial condensation to achieve accurate separation of the components is called rectification.

[0011] Vacuum distillation, also known as vacuum distillation, is based on the principle that the boiling point of a liquid changes with the change of external pressure. The pressure in the system is reduced with the help of a vacuum pump, thereby reducing the boiling point of the liquid. Vacuum distillation is one of the common methods for separating and purifying organic compounds.

[0012] In addition to atmospheric distillation and reduced pressure distillation, pressure distillation can be performed under pressure when the light component and the heavy component in a two-component mixture are relatively easy to separate.

[0013] Simple distillation, also known as differential distillation, is also a unipolar distillation operation, often carried out in an intermittent manner. Simple distillation is a non-steady-state process. Although the vapor and liquid formed instantly can be considered to be in equilibrium with each other, all the vapor formed is not in equilibrium with the remaining liquid. For example, making distilled water to remove dissolved solid impurities; making distilled wine to concentrate alcohol and remove part of the water, all belong to simple distillation. Due to the limitation of the phase equilibrium ratio, the separation degree of simple distillation is not high.

[0014] Distillation is the use of the distribution of different components between the gas and liquid phases, and the purpose of separation is achieved through multiple mass transfer and heat transfer between the gas and liquid phases. Distillation is usually carried out in a distillation tower, and the gas and liquid phases are contacted by countercurrent to carry out interphase heat and mass transfer. The volatile components in the liquid phase enter the gas phase, and the non-volatile components in the gas phase are transferred to the liquid phase, so that almost pure volatile components can be obtained at the top of the tower, and almost pure non-volatile components can be obtained at the bottom of the tower. The feed liquid is added from the middle of the tower. The tower section above the feed port further concentrates the volatile components in the rising vapor, which is called the distillation section; the tower section below the feed port extracts the volatile components from the descending liquid, which is called the stripping section. The vapor drawn from the top of the tower is condensed, and a part of the condensate is returned to the distillation tower from the top of the tower as reflux liquid, and the remaining distillate is the top product. The liquid drawn from the bottom of the tower is partially vaporized by the reboiler, and the vapor rises along the tower, and the remaining liquid is the bottom product. The ratio of the amount of liquid refluxed into the tower from the top to the amount of product from the top is called the reflux ratio, and its size will affect the separation effect and energy consumption of the distillation operation.

[0015] Steam distillation is based on Dalton's law. The total vapor pressure corresponding to the liquid of an immiscible mixture is equal to the sum of the partial pressures of each component gas. The total vapor pressure of the mixture at any temperature is always greater than the vapor pressure of any component. Under the same external pressure, the boiling point of a mixture of immiscible substances is lower than the boiling temperature of the component with the lowest boiling point.

[0016] Steam distillation is only suitable for the extraction of volatile components that can be distilled with steam without being destroyed, do not react with water, and are poorly soluble or insoluble in water.

[0017] Azeotropic distillation is a method of separating a mixture by distillation, utilizing the property that the boiling point of the azeotrope formed by the components in the mixture is lower than the boiling point of any component.

[0018] During the azeotropic distillation process, the added entrainer forms new azeotropes with one or more components in the original solution. These azeotropes usually have a lower boiling point, so they are preferentially distilled out of the mixture during distillation. In this way, mixtures that are difficult to separate can be effectively separated and purified. Azeotropic distillation is widely used in various separation processes in the chemical industry. However, the selection of the entrainer is crucial, and it needs to meet certain conditions, such as forming an azeotrope with the components of the original solution, having a suitable boiling point, and being easy to separate and recover.

[0019] Molecular distillation is a liquid-liquid separation technology developed along with vacuum technology and vacuum distillation technology. Its principle is to use the difference in the free motion path of different substances to achieve the separation of substances, and can achieve operations far away from the boiling point. Molecular distillation has the characteristics of low distillation pressure, short heating time, and high degree of separation. It can greatly reduce the separation cost of high-boiling point materials and extremely protect the quality of heat-sensitive substances.

[0020] As a highly efficient, new green separation technology, molecular distillation technology has incomparable advantages over conventional vacuum distillation technology. It is currently widely used in various fields such as fine chemicals, medicine, food, oils, papermaking, etc.

[0021] However, due to the unique structure of the molecular distillation device, there are some obvious constraints in its promotion and application:

[0022] (1) The distance between the evaporation surface and the condensation surface must be smaller than the mean free path of light molecules, resulting in large equipment investment;

[0023] (2) At the same time, the mean free paths of light and heavy molecules in the liquid phase must be different, and the larger the difference, the better. In fact, if the distance between the evaporator surface and the condenser surface is less than the mean free path of the molecules, it is often very uneconomical. Therefore, the distance is usually slightly larger than the mean free path of the molecules and is controlled within the same order of magnitude.

[0024] (3) The operating pressure of molecular distillation is low, usually controlled at 0.4-40Pa, which requires high sealing performance of the equipment and consumes a lot of power for vacuuming, especially in chemical production units with large flow gas absorption and analysis, which consumes a lot of energy.

[0025] As an important separation and purification method, distillation technology plays an irreplaceable role in many fields. In practical applications, appropriate distillation technology is selected according to specific process requirements and material properties, and a suitable distillation device is constructed on this basis to improve separation efficiency and product quality and reduce operating costs. Summary of the invention

[0026] The purpose of the present invention is to solve the above technical problems and provide a rich liquid flash evaporation analysis system containing styrene which has a simple system, good flash evaporation effect, energy saving and consumption reduction, and is environmentally friendly.

[0027] The system of the present invention comprises a rich liquid tank of an absorption tower, a flash kettle and a rich liquid reflux washing tower, wherein the rich liquid tank of the absorption tower is respectively connected to the flash kettle and the upper section of the rich liquid reflux washing tower, and the rich liquid outlet at the bottom of the rich liquid reflux washing tower is connected to the flash kettle; the gas phase outlet of the flash kettle is connected to the lower section of the rich liquid reflux washing tower, and the lean liquid outlet at the bottom of the flash kettle is connected to the absorption tower via a liquid holding column.

[0028] The rich liquid tank of the absorption tower is connected to the flash kettle via a rich liquid heater.

[0029] 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.

[0030] The upper section of the flash kettle is a primary flash chamber, the lower section is a secondary flash chamber, the lower 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.

[0031] A reflux rich liquid atomizer and a primary flash atomizer are arranged at the upper part of the primary flash chamber, and a primary flash guide plate is arranged at the bottom; a secondary flash atomizer is arranged at the upper part of the secondary flash chamber, and a secondary flash guide plate and a lean liquid tank are arranged at the bottom, and the secondary flash guide plate is inserted into the lean liquid tank over the overflow plate; 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 via a guide pipe, the gas phase space above the semi-lean liquid tank is connected to the primary flash chamber via a gas stripping gas guide pipe, and the semi-lean liquid tank is connected to the secondary flash chamber via a semi-lean liquid heater and a secondary flash atomizer.

[0032] Aeration heads are provided in the lean liquid tank and the semi-lean liquid tank.

[0033] The gas phase outlet at the top of the rich liquid reflux washing tower is connected to a flash steam condenser, the condensate outlet of the flash steam condenser is connected to a pre-pump oil-water separator, and the non-condensable gas outlet is connected to an absorption tower via a vacuum pump.

[0034] The condensate outlet of the pre-pump oil-water separator is connected to the aeration head in the lean liquid tank and the semi-lean liquid tank in the flash kettle through the condensate tank and the condensate vaporization heater, and the oil phase outlet is connected to the vacuum discharge valve and the intermediate oil tank in sequence.

[0035] The rich liquid outlet at the bottom of the rich liquid reflux washing tower is connected to the reflux rich liquid atomizer of the flash kettle, and the outlet of the rich liquid heater is connected to the primary flash atomizer of the primary flash chamber in the flash kettle.

[0036] The upper, middle and lower parts of the liquid holding column are respectively provided with an overflow port, a lean liquid inlet and a lean liquid outlet; the overflow port is connected to the lean liquid tank through a lean liquid overflow pipe; the lean liquid inlet is connected to the lean liquid outlet at the bottom of the lean liquid tank; and the lean liquid outlet is connected to the absorption tower.

[0037] An electronic demister is provided below the top gas phase outlet of the rich liquid reflux washing tower.

[0038] The electronic demister comprises a cathode porous plate, a cathode arc plate and an anode tube. The cathode arc plate is fixed to the inner wall of a tower by insulating materials to form a cylindrical cathode cylinder. The anode tube is suspended at the central axis of the cathode cylinder by an anode tube bracket. The inner surface of the cathode arc plate is uniformly embedded with field electron emission material. The anode tube and multiple cathode arc plates are connected to the outside of the tower via insulating terminals.

[0039] The cathode porous plate is fixed on the inner wall of the tower through insulating materials and is located above the anode tube and the cathode cylinder. The cathode porous plate is connected to the outside of the tower through insulating terminals.

[0040] In view of the problems existing in the background technology, the inventor has made the following improvements:

[0041] (1) A rich liquid reflux washing tower is provided in conjunction with a flash kettle to achieve rich liquid reflux. The rich liquid reflux washing tower is provided downstream of the flash kettle gas phase outlet. The flash steam after atomization and flash evaporation in the flash kettle enters the rich liquid reflux washing tower through the flash kettle gas phase outlet, and contacts with the rich liquid from the absorption tower sprayed in from the top of the tower through the packing layer in countercurrent, exchanges heat and captures fine droplets; cold rich liquid is sprayed into the rich liquid reflux washing tower, and the rich liquid is in direct contact with the flash steam. Fine droplets in the flash steam are captured, reducing 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.

[0042] On the other hand, within the operating temperature range (30-60°C), the saturated vapor pressure of water is greatly affected by temperature (4.245 kPa at 30°C, 7.381 kPa at 40°C, and 19.932 kPa at 60°C). The incoming 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 enters the flash kettle through the first-stage flash atomizer 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 through 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 and flash evaporation, the gas lift effect of water vapor is intensified, which can significantly improve the distillation effect.

[0043] (2) A multi-layer structure is set in the flash kettle for multi-stage flash evaporation, and the equipment structure is compact and safe. A multi-stage flash chamber is set in the flash kettle, and a gas stripping section is set at the bottom of the kettle. The multi-stage flash evaporation and gas stripping are organically combined to improve the rich liquid distillation effect, save space, improve the vacuum pump effect, and save the operating cost of the vacuum pump.

[0044] The flash evaporation kettle of the flash evaporation analysis unit has at least two flash evaporation chambers, and correspondingly connected lean liquid tanks and semi-lean liquid tanks are arranged. The rich liquid is first introduced into the upper first-stage flash evaporation chamber and sprayed out by the first-stage flash evaporation atomizer for flash evaporation. The semi-lean liquid after flash evaporation falls into the semi-lean liquid tank through the first-stage flash evaporation guide pipe, and then is drawn out and heated by the semi-lean liquid heater and sent to the second-stage flash evaporation chamber of the lower stage for spraying by the second-stage flash evaporation atomizer for secondary flash evaporation. The lean liquid falls into the lean liquid tank through the second-stage flash evaporation guide plate. The front end of the second-stage flash evaporation guide plate is inserted below the liquid level of the lean liquid tank to form a liquid seal, which separates the second-stage flash evaporation chamber from the gas stripping area above the semi-lean liquid tank. On the one hand, by arranging two-stage flash evaporation in one flash evaporation kettle, the analysis effect is enhanced. On the other hand, the first-stage flash evaporation chamber and the second-stage flash evaporation chamber are not connected to each other, so as to ensure the flash evaporation effect.

[0045] (3) An aeration head is set in the lean liquid tank and the semi-lean liquid tank. The condensed water separated by the flash steam condenser and the pre-pump oil-water separator is heated and vaporized by the condensed water vaporization heater and then introduced into the aeration head in the form of water vapor. The lean liquid tank and the semi-lean liquid tank can be gas-lifted, which truly realizes the reuse of the condensed liquid, saves energy and reduces consumption, and is environmentally friendly.

[0046] (4) Setting a liquid holding column to eliminate "cavitation". Taking into account the "cavitation" problem of the lean liquid drawn out from the bottom of the flash kettle, a liquid holding column is set to increase the pressure before the pump to extract the lean liquid. Since the working pressure of the flash kettle is maintained below 4 kPa (absolute pressure), which is much lower than the atmospheric pressure, when the lean liquid is directly drawn out from the bottom of the flash kettle through a pump and enters the absorption-adsorption unit at normal pressure, the pressure difference before and after the pump is large, and the residual styrene components and dissolved water in the lean liquid will produce "cavitation", which not only affects the stability of the pump operation, but also causes the pump blades to be impacted and corroded. Setting a liquid holding column to draw the lean liquid from the bottom of the liquid holding column into the absorption tower increases the liquid phase pressure at the pump inlet, effectively overcoming the "cavitation" phenomenon.

[0047] (5) Control the negative pressure of the flash chamber, flash steam condenser and pre-pump oil-water separator below an absolute pressure of 4 kPa. First, reduce the polymerization of the recovered styrene component. When the styrene temperature reaches 60°C, the polymerization rate intensifies. When it is below 4 kPa, the boiling point of styrene is lower than 55°C, and the polymerization of styrene at this temperature can be ignored; second, under an absolute pressure of 4 kPa, the rich liquid temperature only needs to be controlled at around 60°C to achieve a high decomposition effect, and the temperature resistance requirements for the equipment and its sealing materials are not high, reducing equipment investment; third, the operating pressure of 4 kPa can save investment and operating costs. When the operating pressure is too low, the load of the vacuum pump used increases, and at the same time, the equipment strength and sealing requirements of the vacuum system are higher. When the operating pressure is higher than 4 kPa, it is not conducive to the decomposition of styrene.

[0048] (4) Control the amount of condensed water discharged from the oil-water separator before the pump to the condensate tank, increase the oil-water interface level in the oil-water separator before the pump, and discharge excess condensate. Since part of the water vapor brought in by the tail gas during the absorption process is absorbed by the absorbent, the boiling point of water is lower than that of styrene during flash evaporation analysis, and the water vaporizes first and enters the flash steam together with the water vapor introduced. After condensation, it enters the condensate, which breaks the water balance of the system and the excess water needs to be discharged. Keeping the amount of condensed water discharged from the oil-water separator before the pump to the condensate tank constant and raising the oil-water interface to a higher position is conducive to discharging the water absorbed by the absorbent from the tail gas together with the oil phase, thereby reducing the styrene concentration in the water phase; it is conducive to improving the styrene recovery rate. Because the higher the level of the oil-water interface, the more thorough the separation of the oil phase at the water phase outlet level, thereby reducing the styrene concentration in the water vapor circulating into the flash kettle.

[0049] (5) Maintaining the balance of water vapor and water in the flash kettle is beneficial to improving the recovery rate of styrene. The amount of aerated water vapor entering the flash kettle is controlled to be 0.5-0.7% (mass ratio) of the amount of rich liquid entering the kettle. The excess water brought into the rich liquid is discharged together with the condensate oil phase through the increase of the oil-water interface in the oil-water separator before the pump to maintain the balance of water vapor and water in the flash kettle, which is beneficial to improving the recovery rate of styrene. Experiments show that when the rich liquid contains a certain amount of water, the desorption rate of styrene increases significantly. Since the water vapor partial pressure in the flash steam is much higher than the styrene partial pressure, and the saturated vapor pressure of water is greatly affected by temperature within the operating temperature range (7.381 kPa at 40°C; 19.932 kPa at 60°C), the rotary evaporation experiment shows that the maximum desorption rate is achieved when all the water in the rich liquid is evaporated (that is, when the water phase disappears). This technical solution aerates the lean liquid and semi-lean liquid with water vapor for a long time (about 75 kg / h, 3000 m 3 ), the gas-liquid ratio is high, about 200-300:1, which is beneficial to further reduce the residual styrene concentration in the lean solution.

[0050] (6) An electronic demister is arranged below the top gas phase outlet of the rich liquid reflux scrubber, and adopts a structure 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 scrubber is cooled by rich liquid washing and fine droplets are captured, it enters the electronic demister upward; after the cathode porous plate, anode tube, and cathode arc plate of the electronic demister 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 demister; during the movement of the electrons, they collide with the flash steam, and the particle size of the fine droplets in the flash steam is much larger than the diameter of the gas molecules, and they collide with the electric field. The probability of electron collision is much greater than the probability of gas molecules colliding with electrons; after the fine mist droplets collide and capture electrons, the mist droplets are negatively charged, and 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, and when they move to the area below the cathode porous plate, under the action of the electric field force of the cathode porous plate, the charged fine mist droplets are blocked from continuing to move upward, and are forced to move toward the central anode tube; the fine mist droplets are captured after moving to the surface of the anode tube, and the droplets not captured by the surface continue to move upward, and are intercepted by the cathode porous plate due to their negative charge, thereby achieving the purpose of effective demisting, greatly improving the demisting effect and efficiency. Compared with the traditional demisting device, the electronic demisting device in the present invention can capture more than 99.9% of the fine mist droplets.

[0051] The system of the invention has simple control, low equipment investment, high flash evaporation efficiency, low operating cost, energy saving and consumption reduction, no waste gas and wastewater discharge, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 System diagram of the present invention.

[0053] Figure 2 This is the front view of the electronic defogger.

[0054] Figure 3 for Figure 1 Middle AA section view.

[0055] Figure 4 for Figure 1 Middle BB section view.

[0056] Figure 5 for Figure 1 Middle CC section view.

[0057] Figure 6 This is a fitting curve diagram of the Henry constant determined experimentally in the present invention.

[0058] Wherein: 1: flash kettle; 1-1a: reflux rich liquid atomizer; 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; 1-4a: upper air guide pipe; 1-4b: second air guide pipe; 1-4c: air stripping air guide pipe; 1-5: lean liquid overflow 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;

[0059] 2: Rich liquid reflux washing tower; 2-1: Reflux rich liquid nozzle; 2-2: Washing filler; 2-3: Storage tank under the tower;

[0060] 3: Electronic defogger;

[0061] 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;

[0062] 4: Flash steam condenser; 5: Vacuum pump; 6: Oil-water separator; 7: Condensate tank; 8a: Condensate vaporization heater; 8b: Rich liquid heater; 8c: Semi-lean liquid heater; 9: Oil tank; 10a: Rich liquid reflux pump; 10b: Condensate pump; 10c: Primary flash pump; 10d: Secondary flash pump; 10e: Lean liquid discharge pump; 10f: Lean liquid circulation pump; 11: Vacuum unloading valve; 12: Liquid holding column; 13: Rich liquid tank of absorption tower. DETAILED DESCRIPTION

[0063] The system of the present invention is further explained below in conjunction with the accompanying drawings:

[0064] The system of the present invention comprises an absorption tower rich liquid tank 13, a flash kettle 1 and a rich liquid reflux washing tower 2, wherein the liquid phase outlet of the absorption tower rich liquid tank 13 is divided into two paths, one of which is connected to the first-stage flash atomizer 1-1b of the flash kettle 1 through a rich liquid heater, and the other is connected to the reflux rich liquid nozzle 2-1 of the upper section of the rich liquid reflux washing tower 2, and the rich liquid outlet at the bottom of the rich liquid reflux washing tower 2 is connected to the reflux rich liquid atomizer 1-1a of the flash kettle 1; the gas phase outlet of the flash kettle 1 is connected to the lower section of the rich liquid reflux washing tower 2, and the lean liquid outlet at the bottom of the flash kettle 1 is connected to the lean liquid nozzle 2-1 of the upper section of the rich liquid reflux washing tower 2 through a continuous The liquid column 12 is connected to the absorption tower; the gas phase outlet at the top of the rich liquid reflux washing tower 2 is connected to the flash steam condenser 4, the condensate outlet of the flash steam condenser 4 is connected to the pre-pump oil-water separator 6, and the non-condensable gas outlet is connected to the absorption tower via the vacuum pump 5; the condensate outlet of the pre-pump oil-water separator 6 is connected to the semi-lean liquid aeration head 1-7a and the lean liquid aeration head 1-7b in the lean liquid tank 1-6a and the semi-lean liquid tank 1-6b in the flash kettle 1 via the condensate tank 7 and the condensate vaporization heater 8a, and the oil phase outlet is connected to the vacuum unloading valve 11 and the intermediate oil tank 9 in sequence.

[0065] The upper section of the flash kettle is a primary flash chamber, and the lower section is a secondary flash chamber. The lower 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 reflux rich liquid atomizer 1-1a and a primary flash atomizer 1-1b are arranged at the upper part of the primary flash chamber (the reflux rich liquid atomizer 1-1a is located above the primary flash atomizer 1-1b), and a primary flash guide plate 1-2a is arranged at the bottom; a secondary flash atomizer 1-1c is arranged at the upper part of the secondary flash chamber, and a secondary flash guide plate 1-2b is arranged at the bottom. The rear end of the flash guide plate 1-2b is fixed on the wall of the flash kettle 1, and the front end passes over the overflow plate 1-8 and is inserted into the lean liquid tank 1-6a; 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 via the guide pipe 1-3, and the gas stripping area above the semi-lean liquid tank 1-6b is also connected to the primary flash chamber via the gas guide pipe 1-4c; the semi-lean liquid tank 1-6b is connected to the secondary flash atomizer 1-1c via the semi-lean liquid heater 8c. Lean liquid aeration heads 1-7b and semi-lean liquid aeration heads 1-7a are provided in the lean liquid tank 1-6a and the semi-lean liquid tank 1-6b respectively.

[0066] The upper, middle and lower parts of the liquid holding column 12 are respectively provided with an overflow port, a lean liquid inlet and a lean liquid outlet. The overflow port is connected to the lean liquid tank 1-6a through a lean liquid overflow pipe 1-5, the lean liquid inlet is connected to the lean liquid outlet at the bottom of the lean liquid tank 1-6a, and the lean liquid outlet of the liquid holding column 12 is connected to the absorption tower.

[0067] The rich liquid reflux washing tower 2 is provided with an electronic demister 3, a reflux rich liquid nozzle 2-1, a washing filler 2-2 and a storage tank 2-3 under the tower in sequence from top to bottom, 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 correspondingly, 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.

[0068] Process:

[0069] Take a certain artificial stone production plant as an example. The two artificial stone production lines of the plant produce 20,000-25,000 Nm of styrene-rich tail gas. 3 / h, the concentration of styrene in tail gas is 1500-2000mg / Nm in summer 3 , 300-500mg / Nm in winter 3 The tail gas mainly comes from production units such as mixing, feeding, unloading, spreading, vacuuming, pressing, film lifting, and drying. The main pollutants include styrene, non-methane total hydrocarbons, etc.

[0070] The rich liquid tank 13 of the absorption tower collects the rich liquid (temperature 20-30°C) that absorbs styrene from the bottom of the absorption tower. The rich liquid exiting the rich liquid tank 13 of the absorption tower is divided into two streams. The first stream, at a rate of 10-11 tons / hour, is heated to 60-65°C and sent to the first-stage flash atomizer 1-1b of the flash kettle for atomization, spraying, and analyzing to recover the styrene component. The second stream, at a rate of 4-5 tons / hour, is sent to the reflux rich liquid nozzle 2-1 of the rich liquid reflux washing tower 2 for spraying, countercurrent contact, washing, and heat exchange with the flash steam from the flash kettle 13. The rich liquid (temperature 25-35°C) exiting the rich liquid reflux washing tower 2 is sent to the reflux rich liquid atomizer 1-1a of the flash kettle 1 for atomization, spraying, and analyzing to recover the styrene component.

[0071] In the flash evaporator 1: the temperature of the absorption liquid for flash evaporation is gradually increased with its circulation volume to improve the flash evaporation efficiency. The temperature of the rich liquid entering the first flash evaporation chamber is controlled at 60-65°C, and the flow rate of the rich liquid is controlled at 10-15 tons / hour; the temperature of the rich liquid entering the second flash evaporation chamber is controlled at 65-70°C, and the flow rate of the rich liquid is controlled at 20-25 tons / hour. The semi-lean liquid after rich liquid flash analysis is sprayed out by the reflux rich liquid nozzle 2-1 and the primary flash atomizer 1-1b, and falls into the semi-lean liquid tank 1-6a through the guide pipe 1-4c, and then is extracted, heated to 65-70°C, and sent to the secondary flash chamber by the secondary flash atomizer 1-1c for spraying for secondary flash evaporation, and the obtained lean liquid falls into the lean liquid tank 1-6b along the secondary flash guide plate 1-2b and is then led out of the flash kettle 1; the flash gas in the secondary flash chamber is merged into the primary flash chamber through the lower air guide pipe 1-4b, and then is led out of the flash kettle 1 together with the flash gas in the primary flash chamber through the top upper air guide pipe 1-4a.

[0072] Water vapor or other low-boiling-point component gas (such as carbon dioxide, nitrogen, etc.) insoluble in absorbent is introduced into 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 to merge with the flash gas; the lean liquid in the lean liquid tank 1-6a is drawn out through the lean liquid outlet and then returned to the absorption tower through the liquid holding column 12 as a circulating absorbent to wash the tail gas containing styrene, and the overflow liquid at the top of the liquid holding column 12 is returned to the lean liquid tank 1-6a through the lean liquid overflow pipe 1-5.

[0073] The gas phase from the flash kettle 1 is sent to the rich liquid reflux washing tower 2 through the upper gas guide pipe 1-4a. In the rich liquid reflux tower: the flash gas passes through the packing layer 2-2 from bottom to top, and is countercurrently contacted and washed by the rich liquid sprayed from the reflux rich liquid nozzle 2-1 from top to bottom, and is finally defogged by the electronic demister 3 and then led out from the top of the tower. When the washed flash gas passes through the electronic demister 3 in the energized state, the anode tube 3-5 provides a strong electric field, and the field electron emission material 3-8 emits electrons. 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. Due to the negative charge, they are intercepted by the cathode porous plate 3-2, thereby achieving the purpose of efficient demisting.

[0074] The gas phase after washing and demisting at the top of the rich liquid reflux washing tower 2 is sent to the flash steam condenser 4 to separate the condensate and non-condensable gas. The separated condensate is separated into styrene components and condensed water by the pre-pump oil-water separator 6. The separated condensed water is collected by the condensate tank 7, and then heated and vaporized by the condensate vaporization heater 8a. It is passed as water vapor into the semi-lean liquid aeration head 1-7a and the lean liquid aeration head 1-7b in the lean liquid tank 1-6a and the semi-lean liquid tank 1-6b in the flash kettle 1, which is used for gas stripping the styrene components in the lean liquid and semi-lean liquid to realize the condensate circulation; the separated non-condensable gas is returned to the absorption tower after the vacuum pump group. It is preferred to control the operating pressure of the flash kettle 1, the flash steam condenser 4 and the pre-pump oil-water separator 6 to be below the absolute pressure of 4kPa.

[0075] In this embodiment, the rich liquid from the absorption tower refers to the absorbent that has absorbed styrene. The absorbent is a high-boiling point organic solvent whose boiling point is 150° C. or more higher than that of styrene, and is preferably diethyl phthalate.

[0076] See also Figure 6 The Henry constant of the solution after diethyl phthalate absorbs styrene is: 23.04kg / (moL·kPa).

[0077] More than 98% of the styrene components in styrene tail gas are recovered, and the tail gas is purified to meet emission standards. The absorbent consumption is less than 0.1kg / t-styrene. Compared with the distillation process, it saves more than 50% of energy consumption and reduces the recovery cost by more than 50%.

Claims

1. A flash evaporation analysis system for rich liquid containing styrene, comprising an absorption tower rich liquid tank and a flash evaporation kettle, characterized in that: The rich liquid tank of the absorption tower is respectively connected to the flash kettle and the upper section of the rich liquid reflux washing tower, and the rich liquid outlet at the bottom of the rich liquid reflux washing tower is connected to the flash kettle; the gas phase outlet of the flash kettle is connected to the lower section of the rich liquid reflux washing tower, and the lean liquid outlet at the bottom of the flash kettle is connected to the absorption tower via a liquid holding column.

2. The flash evaporation analysis system for rich liquid containing styrene according to claim 1, characterized in that: The rich liquid tank of the absorption tower is connected to the flash kettle via a rich liquid heater.

3. The flash evaporation analysis system for rich liquid containing styrene 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.

4. The flash evaporation analysis system for rich liquid containing styrene according to claim 3, 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 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.

5. The flash evaporation analysis system for rich liquid containing styrene according to claim 4, characterized in that: The first-stage flash chamber is provided with a reflux rich liquid atomizer and a first-stage flash atomizer at the top, and a first-stage flash guide plate at the bottom; the second-stage flash chamber is provided with a second-stage flash atomizer at the top, and a second-stage flash guide plate at the bottom, and the second-stage flash guide plate is inserted into the lean liquid tank over the overflow plate; 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 guide pipe, the gas phase space above the semi-lean liquid tank is connected to the primary flash chamber via a gas stripping gas guide pipe, and the semi-lean liquid tank is connected to the secondary flash atomizer via a semi-lean liquid heater.

6. The flash evaporation analysis system for rich liquid containing styrene according to claim 5, characterized in that: Aeration heads are provided in the lean liquid tank and the semi-lean liquid tank.

7. The flash evaporation analysis system for a rich liquid containing styrene according to claim 1, characterized in that: The gas phase outlet at the top of the rich liquid reflux washing tower is connected to a flash steam condenser, the condensate outlet of the flash steam condenser is connected to a pre-pump oil-water separator, and the non-condensable gas outlet is connected to an absorption tower via a vacuum pump; an electronic demister is provided below the gas phase outlet at the top of the rich liquid reflux washing tower.

8. The flash evaporation analysis system for rich liquid containing styrene according to claim 7, characterized in that: The condensate outlet of the pre-pump oil-water separator is connected to the aeration head in the lean liquid tank and the semi-lean liquid tank in the flash kettle through the condensate tank and the condensate vaporization heater, and the oil phase outlet is connected to the vacuum discharge valve and the intermediate oil tank in sequence.

9. The flash evaporation analysis system for rich liquid containing styrene according to claim 5, characterized in that: The rich liquid outlet at the bottom of the rich liquid reflux washing tower is connected to the reflux rich liquid atomizer of the flash kettle, and the outlet of the rich liquid heater is connected to the primary flash atomizer of the primary flash chamber in the flash kettle.

10. The flash evaporation analysis system for rich liquid containing styrene according to claim 1, characterized in that: The upper, middle and lower parts of the liquid holding column are respectively provided with an overflow port, a lean liquid inlet and a lean liquid outlet; the overflow port is connected to the lean liquid tank through a lean liquid overflow pipe; the lean liquid inlet is connected to the lean liquid outlet at the bottom of the lean liquid tank; and the lean liquid outlet is connected to the absorption tower.

11. The flash evaporation analysis system for rich liquid containing styrene according to claim 7, characterized in that: The electronic defogger comprises a cathode porous plate, a cathode arc plate and an anode tube. The cathode arc plate is fixed to the inner wall of the tower by insulating material to form a cylindrical cathode cylinder, and the inner surface of the cathode arc plate is uniformly embedded with field electron emission material; the anode tube is suspended at the central axis position of the cathode cylinder by an anode tube bracket, and the cathode porous plate is fixed to the inner wall of the tower by insulating material, and is located above the anode tube and the cathode cylinder. The cathode porous plate, the anode tube and the plurality of cathode arc plates are all connected to the outside of the tower via insulating terminals.

Images