Method for removing organic oligomer in saturated ammonium sulfate liquid system discharged from crystallizer of acrylonitrile ammonium sulfate device

Abstract

The invention relates to a method for removing organic oligomers in a saturated ammonium sulfate liquid system discharged by an acrylonitrile ammonium sulfate device crystallizer, belongs to the field of chemical waste liquid resource recycling, and particularly relates to a method for removing organic oligomers in a saturated ammonium sulfate liquid system discharged by an acrylonitrile ammonium sulfate device crystallizer. The invention aims to solve the technical problem that the ammonium sulfate polymer waste liquid discharged by the crystallizer of the existing acrylonitrile ammonium sulfate device affects the stable operation of the incinerator of the environment-friendly device. After being treated by the method, the amount of the recyclable ammonium sulfate liquid is 80-90%, the amount of the separated oligomer liquid is 10-20%, the concentration of the oligomer in the separated oligomer liquid is 70-80%, and the amount of ammonium sulfate in the separated and incinerated oligomer liquid is only 1-4.5% of the amount of ammonium sulfate in the original incineration liquid, so that the influence of ammonium sulfate on an incinerator can be greatly relieved or eliminated; and long-term stable operation of the incinerator device is ensured.

Description

Technical Field

[0001] The invention belongs to the field of resource recovery and utilization of chemical waste liquid, and particularly relates to a method for removing organic oligomers in a saturated ammonium sulfate liquid system discharged from a crystallizer of an acrylonitrile ammonium sulfate device. Background Art

[0002] Acrylonitrile is an important organic synthetic raw material, belonging to the basic raw material of the national economy. It is the basic raw material for the production of three major synthetic materials: plastics, synthetic rubber and synthetic fibers, and is also an important raw material for the production of carbon fibers. Acrylonitrile has become the most basic material that is indispensable for national economic construction and people's daily life. It will be produced continuously, and the production scale is also increasing year by year. my country is the country with the largest production and use of acrylonitrile in the world, and most acrylonitrile production enterprises are large or super-large enterprises. my country's acrylonitrile production capacity has increased significantly year by year. In 2022, my country's acrylonitrile production capacity has reached 3.8 million tons / year, and in the future, China's acrylonitrile production capacity can exceed 5 million tons / year. At present, more than 95% of acrylonitrile companies in the world use BP's propylene ammoxidation method (called Sohio method, 1960) to produce acrylonitrile with propylene, ammonia and air as raw materials. All acrylonitrile companies built in my country use this method for production. In the process of producing acrylonitrile by propylene ammoxidation method, a large amount of quenching tower bottom liquid wastewater will be generated, which contains ammonium sulfate and organic oligomers ("organic oligomers" are also called "organic heavy components" or "heavy components"). According to the structural characteristics, the acrylonitrile quenching tower can be divided into two types of towers (i.e., two types of quenching towers) - two-stage quenching towers and one-stage quenching towers. The two-stage quenching tower includes an upper tower and a lower tower (i.e., the two-stage quenching tower is composed of an upper tower and a lower tower). The quenching towers of acrylonitrile units built in the earlier period are all two-stage towers. In recent years, newly built acrylonitrile units mostly use a one-stage quenching tower. At present, some companies in my country's acrylonitrile units have both two-stage quenching towers and one-stage quenching towers, and some companies have only two-stage quenching towers or only one-stage quenching towers. Due to the high product yield of the one-stage quenching tower, the tower structure and operation control are relatively simple, and a one-stage quenching tower is often used in newly built acrylonitrile units and the transformation of old acrylonitrile units. The upper and lower bottom liquids in the two-stage quenching tower contain components such as ammonium sulfate and organic oligomers (or heavy components), but the content levels and compositions vary greatly. Comparatively speaking, the ammonium sulfate content in the upper bottom liquid is higher and the oligomer content is lower, while the oligomer content in the lower tower is higher and the ammonium sulfate content is slightly lower. The lower tower also contains a small amount of catalyst used for acrylonitrile synthesis, and the composition of the bottom liquid in the lower tower is more complicated. At present, the treatment methods of the two-stage tower bottom liquid by acrylonitrile enterprises in my country are similar: (1) The upper tower bottom liquid is evaporated and crystallized by the ammonium sulfate (ammonium sulfate) device to obtain solid ammonium sulfate (ammonium sulfate fertilizer). However, in order to ensure the quality (or purity) of the ammonium sulfate solid and reduce the adhesion of organic oligomers on the solid ammonium sulfate crystals, it is necessary to continuously discharge the organic oligomers precipitated by evaporation and concentration from the crystallizer to maintain the concentration of organic oligomers in the crystallizer at an appropriate level. The organic oligomers are continuously discharged by discharging part of the concentrated liquid (called ammonium sulfate polymer waste liquid, which contains a material with a high concentration of organic oligomers and saturated concentration of ammonium sulfate) from the crystallizer, and the discharged concentrated liquid is sent to the incinerator for incineration. The condensate produced by the ammonium sulfate device is reused or discharged to the sewage station for treatment; (2) The lower tower bottom liquid is directly sent to the incinerator for incineration.

[0003] The first stage quenching tower bottom liquid mainly contains relatively high concentration of ammonium sulfate, relatively high concentration of organic oligomers and a small amount of catalyst used for acrylonitrile synthesis. At present, acrylonitrile enterprises in my country use incinerators to treat the first stage tower bottom liquid.

[0004] The bottom liquid of the lower section of the two-stage quenching tower and the bottom liquid of the first section of the quenching tower both contain high concentrations of ammonium sulfate and organic oligomers. The reason why these two bottom liquids cannot be used to obtain ammonium sulfate solid (ammonium sulfate fertilizer) by evaporation and crystallization is that the organic oligomer content in the waste liquid is high, and the viscous organic oligomers are wrapped (or coated) with the precipitated ammonium sulfate crystals during the evaporation and crystallization process, and the high-purity ammonium sulfate solid with economic value cannot be separated. At the same time, the viscous mixture (ammonium sulfate crystals and organic oligomer wrappings) will also block facilities such as crystallizers, resulting in the evaporation and crystallization equipment not being able to operate normally. At present, these two waste liquids can only be treated by incineration.

[0005] In the process of treating the quench tower bottom liquid by incineration method in my country's acrylonitrile enterprises, some enterprises adopt the method of absorbing sulfur trioxide gas in the flue gas to produce sulfuric acid to recover sulfur resources. During incineration, the ammonia nitrogen in the waste liquid is converted into nitrogen oxide gas, and the nitrogen oxide gas is discharged after being treated by the flue gas denitrification unit; some enterprises discharge the flue gas after incineration after desulfurization and denitrification treatment, and the sulfur resources are recovered by flue gas desulfurization gypsum and other methods, and the nitrogen resources in the waste liquid are not recovered. During the incineration process, the organic oligomers in the waste liquid are converted into gaseous carbon dioxide for emission. In recent years, with the increasing improvement of my country's atmospheric environmental protection laws and regulations, the improvement of flue gas emission standards and the strict implementation of environmental protection laws and regulations, many acrylonitrile enterprises have newly built or renovated incineration facilities (incinerators and supporting flue gas treatment equipment). Incineration has become a common method for treating acrylonitrile quench tower waste liquid. Therefore, maintaining the stable operation of the incinerator has become an important task for acrylonitrile enterprises.

[0006] Among the quench tower waste liquid incinerated in the acrylonitrile incinerator, the waste liquid from the ammonium sulfate unit (discharged from the crystallizer of the ammonium sulfate unit) (called ammonium sulfate polymer waste liquid) has high viscosity and high ammonium sulfate concentration (saturated concentration). The ammonium sulfate in the waste liquid undergoes complex decomposition and oxidation reactions during the incineration process. A small amount of high-temperature acidic hygroscopic gas (sulfuric acid mist, sulfur trioxide, etc.) combines with ammonia on the surface of the dust bag (bag filter), and crystallizes out ammonium sulfate salts due to the temperature drop, which adhere to the surface of the bag. Long-term accumulation causes the bag purification facilities (bag filter) to be blocked, seriously impacting the stable operation of the incinerator. In addition, the high concentration of organic oligomers in this waste liquid often leads to blockage of pipeline conveyor pumps and incineration nozzles. The ammonium sulfate polymer waste liquid discharged from the crystallizer of the acrylonitrile ammonium sulfate unit has become an important factor affecting the stable operation of the incinerator of the environmental protection device. Therefore, how to separate organic oligomers from the ammonium sulfate polymer waste liquid discharged from the crystallizer of the acrylonitrile ammonium sulfate unit, reduce the amount of waste liquid incinerated, and reduce the content of ammonium sulfate in the waste liquid incinerated has become an urgently needed technology to ensure the long-term stable operation of the acrylonitrile enterprise incinerator and the stable production capacity of acrylonitrile. Summary of the invention

[0007] The present invention aims to solve the technical problem that the ammonium sulfate polymer waste liquid discharged from the crystallizer of an acrylonitrile ammonium sulfate device affects the stable operation of the incinerator of an environmental protection device, and provides a method for removing organic oligomers in the saturated ammonium sulfate liquid system discharged from the crystallizer of an acrylonitrile ammonium sulfate device.

[0008] The method for removing organic oligomers from the saturated ammonium sulfate liquid system discharged from the crystallizer of the acrylonitrile ammonium sulfate device of the present invention is carried out according to the following steps:

[0009] 1. If Figure 1 The method of the present invention comprises three processing units: a cooling-crystallization-precipitation-separation unit 101, a primary separation unit 102 and a secondary separation unit 103; the ammonium sulfate salt produced by the cooling-crystallization-precipitation-separation unit 101 is returned to the ammonium sulfate evaporation crystallization device 104-1; the oligomer separated by the primary separation unit 102 is discharged into the first oligomer collection tank 102-1; the oligomer separated by the secondary separation unit 103 is discharged into the second oligomer collection tank 103-1, and the liquid separated by the secondary separation unit 103 is sent to the feed tank 104-2 of the ammonium sulfate evaporation crystallization device;

[0010] The specific process is as follows: the liquid material (temperature of 80°C to 82°C, containing saturated ammonium sulfate liquid, soluble oligomers and insoluble oligomers) discharged from the crystallizer of the ammonium sulfate evaporation and crystallization device enters the cooling-crystallization-precipitation-separation unit 101, which is composed of four sub-units in sequence: heat exchange cooling and cooling, cooling crystallization, sedimentation and centrifugal separation. The four sub-units all adopt conventional methods and equipment. Cooling and cooling are achieved by heat exchangers and circulating cooling water. The temperature of the incoming liquid material is reduced from 80°C to 82°C to 27°C to 32°C. Cooling crystallization precipitates part of the ammonium sulfate solid in the saturated ammonium sulfate liquid and increases the viscosity of the precipitated organic oligomers in the incoming liquid material. The temperature reduction can also reduce the solubility of organic oligomers in water, increase the precipitation amount of soluble organic oligomers, and reduce the dissolved organic oligomers in the saturated ammonium sulfate liquid. The solid ammonium sulfate precipitated by cooling and crystallization settles at the bottom of the sedimentation tank, the solid ammonium sulfate at the bottom is taken out and then separated by centrifugation to obtain the solid ammonium sulfate, the mass of the solid ammonium sulfate is 2.5% to 3.5% of the mass of the incoming liquid, and the solid ammonium sulfate is returned to the ammonium sulfate evaporation and crystallization device 104-1 for reuse (the subsequent destination of the solid in 104-1: it enters the ammonium sulfate system after being dissolved with the incoming liquid of the ammonium sulfate device); the centrifugal liquid returns to the settled solution, the precipitated organic oligomers are viscous liquid, part of which gathers and floats on the surface of the settled ammonium sulfate liquid, and part of which is suspended in the ammonium sulfate liquid layer in the form of fine liquid droplets; the settled liquid (including the ammonium sulfate liquid and the organic oligomers (dissolved and precipitated) therein) enters the primary separation unit 102 for primary separation of the precipitated organic oligomers;

[0011] Second, the primary separation unit 102 is composed of a separation tank, an air compressor and a liquid inlet pump; the structure of the separation tank is as follows Figure 4 and Figure 5The tank body 1 of the primary separation tank is cylindrical, and the ratio of the height to the diameter of the tank body 1 is (2-4):1. The liquid inlet pipe 2 is located at the upper part of the inner cavity of the tank body 1 and between the liquid surface 24 and the top of the cylinder. The liquid inlets of multiple liquid inlet and water distribution pipes 3 are connected to the liquid outlet of the liquid inlet pipe 2. The liquid inlet and water distribution pipes 3 are vertically downward, and the bottom liquid outlet of the liquid inlet and water distribution pipes 3 is placed 5cm-10cm below the liquid surface 24. The liquid inlet and water distribution pipes 3 are located on the same circumference and the distance from the central axis of the tank body 1 is 2 / 3-3 / 4 of the radius of the tank body 1. A floating matter collecting bucket 13 is arranged at the middle and upper part of the inner central axis of the tank body 1, and the floating matter collecting bucket 13 is located below the liquid inlet pipe 2. The diameter of the air-floating collecting bucket 13 is 1 / 6 to 1 / 5 of the diameter of the tank body 1, and the height is 1 / 15 to 1 / 12 of the height of the tank body 1. The upper edge of the air-floating collecting bucket 13 is almost at the same height as the liquid surface 24. The bottom of the air-floating collecting bucket 13 is conical, and the conical bottom is connected to the polymer outlet pipe 15-1. The discharge port 14 of the polymer outlet pipe 15-1 is outside the tank body 1. The angle between the polymer outlet pipe 15-1 and the horizontal line is 50° to 70°, and the pipe diameter is 1 / 6 to 1 / 4 of the pipe diameter of the air-floating collecting bucket 13 and is greater than 5 cm. A first annular aerator 16 is arranged on the inner wall of the tank body 1, and a liquid is discharged from the first annular aerator 16 to the air-floating collecting bucket 1 A plurality of second annular aerators 17 are arranged in the direction of 3 to form a plurality of concentric annular aerators equidistant from each other with the air floating collection bucket 13 as the center. The second annular aerator 17 is at the same height as the first annular aerator 16 and is located below the liquid surface 24. The height of the second annular aerator 17 is located in the middle and lower part of the air floating collection bucket 13; each annular aerator is connected to an air source pump or an air tank respectively, and operates independently during aeration; the air inlet of the first annular aerator 16 is connected to the air outlet of the first air inlet pipe 18, and the first air inlet pipe 18 is provided with a first valve 19; the first annular aerator 16 is normally open to prevent the viscous oligomer air floating from adhering to the tank. On the inner wall of the body 1; the second annular aerator 17 is an intermittent aerator, and the intermittent aeration is repeatedly operated in a periodic manner. The periodic operation mode is: a plurality of second annular aerators 17 are started in sequence from the outer ring to the inner ring at intervals of 15s to 20s, and when the second annular aerator 17 in the innermost ring is started for 15s to 20s, the aeration of all second annular aerators 17 is stopped for 10min to 20min, and the above process is repeated; the intermittent periodic aeration function is to make the floating oligomer aggregates intermittently flow into the air floating collection bucket 13 quickly, reduce the amount of ammonium sulfate liquid discharged into the air floating collection bucket 13, and increase the concentration of the discharged oligomers;

[0012] An air flotation tube 7 is arranged at the bottom of the tank body 1, the air inlet of the air flotation tube 7 is connected with the air outlet of the aerator 4, an aeration valve 5 is arranged on the air flotation tube 7, and a plurality of air outlets opening upward are evenly arranged on the air flotation tube 7; a drainage inlet 10 of a drainage pipe 23 is arranged below the air flotation tube 7 and on the central axis of the tank body 1, a drainage outlet 12 of the drainage pipe 23 is arranged at the upper middle part of the outside of the tank body 1, a first telescopic tube 6 is arranged on the drainage pipe 23, the height of the drainage outlet 12 is adjusted by the first telescopic tube 6, and a first drainage pipe valve 11 is arranged on the drainage pipe 23; the bottom of the tank body 1 is conical, and a venting outlet 9 and a venting valve 8 are arranged at the lower end of the cone; an exhaust port 22 is arranged at the top of the tank body 1, and the exhaust port 22 is connected to the enterprise waste gas collection system;

[0013] Start-up operation of the primary separation tank: close the vent valve 8 at the bottom of the tank body 1, close the aeration valve 5, open the first valve 19, close all the second annular aerators 17, open the polymer outlet pipe valve 15, and close the first discharge pipe valve 11; pump the settled liquid ammonium sulfate solution flowing out of the cooling-crystallization-precipitation-separation unit 101 in step 1 through the liquid inlet pipe 2. With the addition of the ammonium sulfate liquid material, the liquid level 24 in the tank body 1 gradually rises. When the liquid level 24 rises to 5 cm to 15 cm from the upper edge of the air floating collection bucket 13, start the aerator 4 and open the aeration valve 5 to release the air through the air floating pipe 7. The bubbles float up, and the organic oligomers precipitated in the liquid form aggregates under the action of the flotation bubbles at the bottom and float to the liquid surface 24; the first annular aerator 16 located on the outer circle of the normally open type prevents the viscous oligomer flotation from adhering to the inner wall of the tank body 1; the first drain pipe valve 11 is opened, the intermittent second annular aerator 17 is turned on and operated periodically, and the height of the drain pipe outlet 12 is adjusted by the first telescopic tube 6 so that the liquid output of the drain pipe outlet 12 and the separated oligomer liquid output from the polymer outlet 14 account for 85% to 95% and 5% to 15% of the liquid input of the tank body 1 respectively, and the separated oligomers are kept intermittently discharged;

[0014] During the continuous operation of the primary separation tank, the organic aggregates (blocks) floating on the liquid surface are insoluble organic oligomers. Under the intermittent aeration of the second annular aerator 17, they intermittently flow into the gas-floating material collection bucket 13 together with a small amount of liquid (ammonium sulfate liquid). The primary separation (organic oligomers and a small amount of ammonium sulfate liquid) are discharged from the system through the polymer liquid outlet 14 by gravity, completing the primary separation of organic oligomers. The organic oligomer content in the primary separation (the material entering the gas-floating material collection bucket 13) is about 50% to 80% (w / w), and the flow rate is about 5% to 15% of the liquid inlet volume. The ammonium sulfate liquid material after the primary separation contains about 0.1% to 0.5% (w / w) insoluble extremely fine organic oligomer particles (or liquid droplets). The ammonium sulfate liquid material (the material discharged from the discharge pipe outlet 12) enters the secondary separation unit 103 to further separate and remove the insoluble organic oligomers.

[0015] The material discharged from the polymer liquid outlet 14 flows into the first oligomer collection tank 102-1;

[0016] The residence time of the liquid from the liquid inlet pipe 2 in the tank 1 is 45min to 90min;

[0017] 3. Secondary separation unit: The secondary separation unit 103 is composed of an adsorption separation tower 30, an air compressor, a liquid inlet pump and a hot air compressor; the structure of the adsorption separation tower 30 is as follows Figure 6 As shown, the adsorption separation tower body 30 is cylindrical, the ratio of the tower height to the diameter is 1 / 4 to 1 / 5, the liquid inlet pipe 31 is 20 cm to 30 cm away from the tower top, a plurality of liquid inlet and water distribution pipes 32 are arranged in the tower and connected to the liquid inlet pipe 31, and the liquid inlet and water distribution pipes 32 open downward, the top of the adsorption separation tower 30 is provided with an exhaust port 49, and the bottom is a conical structure and is provided with a vent 47 and a vent valve 48; a hot air outlet pipe 42 is arranged near the bottom of the tower body, and the opening of the hot air outlet pipe 42 is facing downward. The hot air outlet pipe 42 is connected to the hot air compressor 41 outside the tower, the hot air outlet pipe 42 is provided with a hot air inlet pipe valve 40, a drain pipe inlet 44 of a drain pipe 50 is provided just below the hot air outlet pipe 42 and the drain pipe inlet 44 is located on the central axis of the adsorption separation tower 30, a liquid outlet 46 of the drain pipe 50 is provided outside the adsorption separation tower 30, a second drain pipe valve 45 and a second telescopic pipe 39 are provided on the drain pipe 50, and the height of the liquid outlet 46 is generally The air inlet of the aeration perforated pipe 43 is connected to the aerator 36 outside the tower, and an aeration pipe valve 37 is provided on the aeration perforated pipe 43; a lower baffle 34 is provided above the aeration perforated pipe 43, and the lower baffle 34 is a stainless steel mesh or grid; an upper baffle 33 is provided at the upper part of the inner cavity of the adsorption separation tower 30 and below the liquid inlet water distribution pipe 32 The upper baffle 33 is a mesh or grid made of stainless steel; a plurality of fixed bed packing layer monomers 35 are stacked up and down between the upper baffle 33 and the lower baffle 34, a partition 38 is arranged between each adjacent fixed bed packing layer monomer 35, and each adjacent fixed bed packing layer monomer 35 is spaced 10cm to 20cm apart, and the fixed bed packing layer monomer 35 is cylindrical; the filler of the fixed bed packing layer monomer 35 is granular, composed of hard polymer material or foaming material, and the particle volume is 1cm 3 ~5cm 3 The particle shape is spherical, columnar or blocky; the interior of the hard particle is a hollow structure, and the surface of the foam material is a honeycomb; the filler material is polypropylene, polyethylene or polyvinyl chloride; the density of the filler is less than 1.0g / cm 3 , the filler is placed in a mesh cage to form a fixed bed filler layer monomer 35;

[0018] Operation of the secondary separation unit 103: close the vent 47, close the second liquid discharge pipe valve 45, close the aeration pipe valve 37, and close the hot air inlet pipe valve 40; the liquid material from the liquid discharge pipe outlet 12 of the front primary separation unit 102 enters the adsorption separation tower body 30 of the secondary separation unit 103 through the liquid inlet pipe 31 and the liquid inlet water distribution pipe 32, and the liquid level gradually rises. When the liquid level reaches 5 cm to 15 cm below the upper baffle 33, start the aerator 36, open the aeration pipe valve 37, and the aeration gas is released from the aeration perforated pipe 43 and the bubbles rise; open the second liquid discharge pipe valve 45, and adjust the second telescopic pipe 39 to adjust the height of the liquid outlet 46 to be 3 cm higher than the level of the upper baffle 33.

[0019] During the aeration process, bubbles contact the incoming liquid from bottom to top, forming gas, liquid, a small amount of oligomers and filler contact on the surface of the filler, and extremely fine organic oligomer particles (or liquid droplets) gather and adhere to the surface of the filler. Due to the strong aggregation of the precipitated organic oligomers, the oligomers adhered to the surface of the filler can adhere to and aggregate the newly generated oligomer particles (brought by subsequent bubbles) again (multiple times or continuously). Due to the strong adhesion ability of the filler material and polymer aggregates to the non-dissolved polymer particles, the polymer microparticles (or liquid droplets) gathered by the bubble disturbance will quickly and preferentially adhere to the filler or aggregates that are contacted first, that is, after the floating bubbles aggregate the non-dissolved extremely fine oligomer particles into slightly larger particles, the slightly larger particles will not float up with the bubbles, but will quickly adhere to the filler material and oligomer aggregates that are contacted for the first time, thus forming a situation where organic oligomers are adhered and adsorbed at all height layers of the filler in the packing tower. Due to the top-down liquid inlet and discharge method, the amount of oligomers adhered and adsorbed on the surface or upper layer of the filler is large, and the amount of adhesion and adsorption gradually decreases with the height layer downward.

[0020] During the adhesion and adsorption process, it is difficult for the oligomer aggregates adhered and adsorbed by the filler under the liquid surface to be adhered and floated by bubbles again. When the oligomer aggregates adhered and adsorbed on the surface (or upper layer) of the filler reach a certain thickness, they will slowly flow along the surface of the filler below to the lower layer, showing that the entire filler layer forms an adhesion saturated layer, a near-saturated layer, an unsaturated layer, a less-adsorbed layer and a non-adsorbed layer from top to bottom in the height direction. There is no fixed interface between the adsorbed layers, but the stratification trend is obvious.

[0021] When 60% to 80% of the entire packing height layer becomes an adhesion saturation layer and a near-saturation layer, or when fine oligomer droplets are visible to the naked eye in the liquid discharged from the liquid outlet 46, the secondary adsorption separation tower 30 should be regenerated; it should be noted that in order to make the secondary separation unit 103 operate continuously, the secondary separation unit 103 is provided with two adsorption separation towers 30, and the two adsorption separation towers 30 are connected to the liquid discharge pipe outlet 12, and are operated and regenerated alternately;

[0022] The regeneration process of the adsorption separation tower 30 of the secondary separation unit 103 is as follows: when the adsorption separation tower needs to be regenerated, the feed of the liquid inlet pipe 31 is stopped, the second liquid discharge pipe valve 45 is closed, and the vent valve 48 at the bottom of the tower is opened to discharge the liquid in the tower (aqueous ammonium sulfate liquid) to the liquid inlet pipe 31 of another adsorption separation tower 30. The liquid inlet pipe 31 of the other adsorption separation tower 30 is also connected to the liquid discharge outlet 12. When the liquid in the adsorption separation tower 30 that needs to be regenerated is emptied, the aerator 36 is stopped and the aeration pipe valve 37 is closed, and the vent port 47 is quickly switched to the second oligomer collection tank 103-1; the density of the oligomer aggregates adsorbed on the surface of the filler is 1.25 g / cm 3 ~1.27g / cm 3 , with viscosity and certain fluidity, the viscosity is 2×10 at 30°C 4 mPa.s~3×10 4 mPa.s, the flow capacity in the air (flowing downward by gravity) increases, and after 18h to 24h of standing, 55% to 70% (w / w) of the oligomers adsorbed on the surface of the filler material will slowly move downward (or flow downward) under the action of gravity and separate from the fixed bed filler layer monomer 35, drip to the bottom of the tower and flow into the second oligomer collection tank 103-1;

[0023] In order to speed up the dripping and separation speed of the oligomers in the filler, the hot air inlet valve 40 is opened, and the hot air compressor 41 is turned on. The hot air enters the adsorption separation tower 30 through the hot air outlet pipe 42. The temperature in the tower increases, and the temperature of the adsorbed polymer aggregates increases accordingly. After the temperature increases, the viscosity of the oligomer aggregates decreases, the fluidity increases, and the dripping speed is significantly accelerated. The temperature in the tower is controlled at 50°C to 60°C. At a temperature of 50°C to 60°C, the oligomer aggregates adsorbed by the filler can drip down 65% to 80% (w / w) in 6h to 8h.

[0024] When the dripping rate of the oligomer flowing out of the vent 47 at the bottom of the adsorption separation tower 30 is reduced to 1 drop every 5 minutes to 15 minutes, the hot air inlet pipe valve 40 is closed, the hot air compressor 41 is turned off, the vent 47 is closed, and the gravity regeneration is completed; after gravity regeneration, the adhesion adsorption capacity of the adsorption separation tower is restored to 50% to 80%, and it can be operated and used again.

[0025] It should be noted that the fluidity of oligomers deteriorates when the temperature is low. The temperature in the tower should not be lower than 30°C to 35°C during gravity regeneration. When the ambient temperature is low, hot air or other forms of heating must be used to ensure that the temperature during regeneration is between 30°C and 60°C. However, if the temperature is too high, the surface active functional groups of the oligomer aggregates are easily oxidized (by oxygen in the air), which affects the fluidity of the oligomers and is not conducive to the subsequent resource utilization of the oligomers (such as modification, etc.).

[0026] The oligomer purity (in the second oligomer collection tank 103-1) (or content) obtained by the secondary separation unit 103 can reach 85% to 95% (w / w), which is better than the oligomer purity obtained by the primary separation unit 102; the comprehensive concentration of oligomers obtained by the two separation units (primary and secondary) (in the first oligomer collection tank 102-1 and the second oligomer collection tank 103-1) is 70% to 80% (w / w), and the flow rate is 5% to 15% (w / w) of the incoming liquid volume, and the amount of ammonium sulfate therein is only 1% to 4.5% of the amount of ammonium sulfate in the incoming liquid. If the incineration method is used, the amount of ammonium sulfate incinerated is only 1% to 4.5% of the amount of ammonium sulfate before separation and treatment by the method of the present invention. The significant reduction in the amount of ammonium sulfate incinerated can greatly alleviate or eliminate the impact on the incinerator, thereby ensuring the long-term stable operation of the incinerator device.

[0027] The content of non-dissolved extremely fine organic oligomer particles (or liquid droplets) in the ammonium sulfate liquid material (discharged through the liquid outlet 46) after the secondary separation is 0.01% to 0.05% (w / w), and the concentration of soluble oligomers is 2% to 4% (w / w). The oligomer concentration is similar to the concentration level of oligomers (heavy components) in the liquid material (upper tower bottom liquid) from the ammonium sulfate device. The ammonium sulfate liquid after the secondary separation is returned to the feed tank 104-2 of the ammonium sulfate evaporation and crystallization device for reuse. The flow rate of the liquid (discharged through the liquid outlet 46) is 95% to 99% of the amount of the liquid inlet (from the liquid inlet pipe 31) of the secondary separation unit;

[0028] The residence time of the liquid from the liquid inlet pipe 31 in the secondary adsorption separation tower 30 is 45 minutes to 90 minutes.

[0029] Special Note: (1) Process 2: If the oligomer concentration (or purity) in the primary separation oligomer liquid (discharged from the polymer liquid outlet 14) of the primary separation unit 102 is to be increased, the outlet of the polymer liquid outlet 14 is changed to be connected to an adsorption separation tower 30 of a secondary separation unit, and the liquid outlet 46 is further connected to the liquid inlet pipe 2, and the primary separation polymer liquid is subjected to secondary separation. After the secondary separation, the oligomer concentration (or purity) can be increased from 50% to 80% (w / w) in the primary separation polymer liquid to 85% to 95% (w / w). The ammonium sulfate liquid obtained by the secondary separation is returned to the liquid inlet pipe 2 of the primary separation tank 1. The process is as follows: Figure 2 shown.

[0030] (2) Process 3: The primary separation unit 102 is removed from the process flow, and the secondary separation 103 is directly performed (e.g. Figure 3 ), Process 2( Figure 2 ) and process 3( Figure 3) have similar final separation effects. The primary separation unit 102 has a faster separation speed and higher separation efficiency. However, the separation quality (referring to the oligomer concentration or purity) of the primary separation unit 102 is relatively poor (compared with the secondary separation unit 103). When the separation quality requirement is not high, process 1 ( Figure 1 ), when the separation quality requirements are high, process 2 or process 3 should be used. Comparing process 2 and process 3, the two streams of materials (polymer and ammonium sulfate liquid) in process 2 are separated twice, and the obtained polymer and ammonium sulfate liquid are of the best quality, but the subunits of process 2 are relatively complex and the process is long, and the primary separation unit makes the whole process more resistant to shock; in process 3, the material is only separated once, and the quality and purity of the ammonium sulfate liquid are relatively poor, but the process is simpler and the types of equipment are fewer. Due to the lack of primary separation process, the system's shock resistance is relatively poor.

[0031] It should be noted that if the temperature of each unit after the primary separation is lower than the temperature of the cooling-crystallization-precipitation-separation unit 101 (27°C to 32°C) due to changes in the ambient temperature, ammonium sulfate crystals will be precipitated in the nearly saturated ammonium sulfate solution, and some ammonium sulfate crystals will be adsorbed on the surface of the material or adhere to the oligomer aggregates, affecting the normal operation of the system. The following three methods are needed to eliminate the problem of ammonium sulfate crystals precipitated due to temperature reduction in the subsequent process of the primary separation unit:

[0032] (1) maintaining the temperature of the subsequent process of the primary separation unit 102 by a heat preservation method without decreasing (i.e., the temperature is not lower than the effluent temperature of the cooling-crystallization-precipitation-separation unit);

[0033] (2) adding a diluent to the liquid inlet pipe 2 of the primary separation unit 102 to ensure that the ammonium sulfate concentration in the ammonium sulfate liquid material after dilution is lower than the saturated ammonium sulfate concentration at the lowest temperature in the process unit; the diluent is water or the incoming dilute ammonium sulfate liquid of the ammonium sulfate device;

[0034] (3) The total incoming liquid is diluted so that the ammonium sulfate concentration in the ammonium sulfate liquid material after dilution is lower than the saturated ammonium sulfate concentration at the lowest temperature in the process unit: the cooling-crystallization-precipitation-separation unit 101 is eliminated in the process, and a dilution-cooling unit is set. The dilution-cooling unit includes two sub-units: dilution stirring and cooling. The dilution stirring sub-unit reduces the ammonium sulfate concentration to 95%-99% of the saturated concentration at room temperature by adding a diluent. The dilution is water or the incoming dilute ammonium sulfate liquid of the ammonium sulfate device; the cooling sub-unit reduces the temperature of the material after the incoming liquid is diluted by a heat exchanger and circulating cooling water from about 80°C to 82°C to 27°C to 32°C. The diluted and cooled incoming liquid mixed liquid (nearly saturated ammonium sulfate liquid) enters the subsequent primary separation unit 102 or secondary separation unit 103 for separation.

[0035] In summary, after the treatment by the method of the present invention, 80% to 90% (w / w, compared with the amount of the incoming liquid) of ammonium sulfate (solid to 104-1 and liquid to 104-2) can be recovered, the amount of the separated oligomer liquid (containing oligomers and ammonium sulfate liquid) is 10% to 20% (w / w, compared with the amount of the incoming liquid), and the concentration of oligomers in the separated oligomer liquid is 70% to 80% (w / w) (if according to Figure 2 The oligomer concentration can reach 85% to 95% (w / w). The amount of ammonium sulfate in the oligomer liquid incinerated after separation is only 1% to 4.5% of the amount of ammonium sulfate in the original incineration liquid, which can greatly alleviate or eliminate the impact of ammonium sulfate on the incinerator and ensure the long-term stable operation of the incinerator device.

[0036] The method of the invention has the advantages of fast separation speed, high separation efficiency, low operation cost, continuous operation and recovery of ammonium sulfate, and significant reduction in the amount of incineration waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the first process in the specific implementation mode 1;

[0038] Figure 2 It is a schematic diagram of the second process in the fourth specific implementation mode;

[0039] Figure 3 It is a schematic diagram of the third process in the fifth specific implementation mode;

[0040] Figure 4 It is a schematic diagram of the separation tank in the first specific implementation mode;

[0041] Figure 5 for Figure 4 A top view of

[0042] Figure 6 It is a schematic diagram of the adsorption separation tower 30 in the first specific implementation mode. DETAILED DESCRIPTION

[0043] Specific implementation method 1: This implementation method is a method for removing organic oligomers in a saturated ammonium sulfate liquid system discharged from a crystallizer of an acrylonitrile ammonium sulfate device, which is specifically carried out according to the following steps:

[0044] The first process: 1. Figure 1The method of the present invention comprises three processing units: a cooling-crystallization-precipitation-separation unit 101, a primary separation unit 102 and a secondary separation unit 103; the ammonium sulfate salt produced by the cooling-crystallization-precipitation-separation unit 101 is returned to the ammonium sulfate evaporation crystallization device 104-1; the oligomer separated by the primary separation unit 102 is discharged into the first oligomer collection tank 102-1; the oligomer separated by the secondary separation unit 103 is discharged into the second oligomer collection tank 103-1, and the liquid separated by the secondary separation unit 103 is sent to the feed tank 104-2 of the ammonium sulfate evaporation crystallization device;

[0045] The specific process is as follows: the liquid material (temperature of 80°C to 82°C, containing saturated ammonium sulfate liquid, soluble oligomers and insoluble oligomers) discharged from the crystallizer of the ammonium sulfate evaporation and crystallization device enters the cooling-crystallization-precipitation-separation unit 101, which is composed of four sub-units in sequence: heat exchange cooling and cooling, cooling crystallization, sedimentation and centrifugal separation. The four sub-units all adopt conventional methods and equipment. Cooling and cooling are achieved by heat exchangers and circulating cooling water. The temperature of the incoming liquid material is reduced from 80°C to 82°C to 27°C to 32°C. Cooling crystallization precipitates part of the ammonium sulfate solid in the saturated ammonium sulfate liquid and increases the viscosity of the precipitated organic oligomers in the incoming liquid material. The temperature reduction can also reduce the solubility of organic oligomers in water, increase the precipitation amount of soluble organic oligomers, and reduce the dissolved organic oligomers in the saturated ammonium sulfate liquid. The solid ammonium sulfate precipitated by cooling and crystallization settles at the bottom of the sedimentation tank, the solid ammonium sulfate at the bottom is taken out and then separated by centrifugation to obtain the solid ammonium sulfate, the mass of the solid ammonium sulfate is 2.5% to 3.5% of the mass of the incoming liquid, and the solid ammonium sulfate is returned to the ammonium sulfate evaporation and crystallization device 104-1 for reuse (the subsequent destination of the solid in 104-1: it enters the ammonium sulfate system after being dissolved with the incoming liquid of the ammonium sulfate device); the centrifugal liquid returns to the settled solution, the precipitated organic oligomers are viscous liquid, part of which gathers and floats on the surface of the settled ammonium sulfate liquid, and part of which is suspended in the ammonium sulfate liquid layer in the form of fine liquid droplets; the settled liquid (including the ammonium sulfate liquid and the organic oligomers (dissolved and precipitated) therein) enters the primary separation unit 102 for primary separation of the precipitated organic oligomers;

[0046] Second, the primary separation unit 102 is composed of a separation tank, an air compressor and a liquid inlet pump; the structure of the separation tank is as follows Figure 4 and Figure 5The tank body 1 of the primary separation tank is cylindrical, and the ratio of the height to the diameter of the tank body 1 is (2-4):1. The liquid inlet pipe 2 is located at the upper part of the inner cavity of the tank body 1 and between the liquid surface 24 and the top of the cylinder. The liquid inlets of multiple liquid inlet and water distribution pipes 3 are connected to the liquid outlet of the liquid inlet pipe 2. The liquid inlet and water distribution pipes 3 are vertically downward, and the bottom liquid outlet of the liquid inlet and water distribution pipes 3 is placed 5cm-10cm below the liquid surface 24. The liquid inlet and water distribution pipes 3 are located on the same circumference and the distance from the central axis of the tank body 1 is 2 / 3-3 / 4 of the radius of the tank body 1. A floating matter collecting bucket 13 is arranged at the middle and upper part of the inner central axis of the tank body 1, and the floating matter collecting bucket 13 is located below the liquid inlet pipe 2. The diameter of the air-floating collecting bucket 13 is 1 / 6 to 1 / 5 of the diameter of the tank body 1, and the height is 1 / 15 to 1 / 12 of the height of the tank body 1. The upper edge of the air-floating collecting bucket 13 is almost at the same height as the liquid surface 24. The bottom of the air-floating collecting bucket 13 is conical, and the conical bottom is connected to the polymer outlet pipe 15-1. The discharge port 14 of the polymer outlet pipe 15-1 is outside the tank body 1. The angle between the polymer outlet pipe 15-1 and the horizontal line is 50° to 70°, and the pipe diameter is 1 / 6 to 1 / 4 of the pipe diameter of the air-floating collecting bucket 13 and is greater than 5 cm. A first annular aerator 16 is arranged on the inner wall of the tank body 1, and a liquid is discharged from the first annular aerator 16 to the air-floating collecting bucket 1 A plurality of second annular aerators 17 are arranged in the direction of 3 to form a plurality of concentric annular aerators equidistant from each other with the air floating collection bucket 13 as the center. The second annular aerator 17 and the first annular aerator 16 are at the same height and are located below the liquid surface 24. The height of the second annular aerator 17 is located in the middle and lower part of the air floating collection bucket 13; each annular aerator is connected to a source pump or an air tank respectively, and operates independently during aeration; the air inlet of the first annular aerator 16 is connected to the air outlet of the first air inlet pipe 18, and the first air inlet pipe 18 is provided with a first valve 19; the first annular aerator 16 is normally open to prevent the viscous oligomer air floating from adhering to the tank. On the inner wall of the body 1; the second annular aerator 17 is an intermittent aerator, and the intermittent aeration is repeatedly operated in a periodic manner. The periodic operation mode is: a plurality of second annular aerators 17 are started in sequence from the outer ring to the inner ring at intervals of 15s to 20s, and when the second annular aerator 17 in the innermost ring is started for 15s to 20s, the aeration of all second annular aerators 17 is stopped for 10min to 20min, and the above process is repeated; the intermittent periodic aeration function is to make the floating oligomer aggregates intermittently flow into the air floating collection bucket 13 quickly, reduce the amount of ammonium sulfate liquid discharged into the air floating collection bucket 13, and increase the concentration of the discharged oligomers;

[0047] An air flotation tube 7 is arranged at the bottom of the tank body 1, the air inlet of the air flotation tube 7 is connected with the air outlet of the aerator 4, an aeration valve 5 is arranged on the air flotation tube 7, and a plurality of air outlets opening upward are evenly arranged on the air flotation tube 7; a drainage inlet 10 of a drainage pipe 23 is arranged below the air flotation tube 7 and on the central axis of the tank body 1, a drainage outlet 12 of the drainage pipe 23 is arranged at the upper middle part of the outside of the tank body 1, a first telescopic tube 6 is arranged on the drainage pipe 23, the height of the drainage outlet 12 is adjusted by the first telescopic tube 6, and a first drainage pipe valve 11 is arranged on the drainage pipe 23; the bottom of the tank body 1 is conical, and a venting outlet 9 and a venting valve 8 are arranged at the lower end of the cone; an exhaust port 22 is arranged at the top of the tank body 1, and the exhaust port 22 is connected to the enterprise waste gas collection system;

[0048] Start-up operation of the primary separation tank: close the vent valve 8 at the bottom of the tank body 1, close the aeration valve 5, open the first valve 19, close all the second annular aerators 17, open the polymer outlet pipe valve 15, and close the first discharge pipe valve 11; pump the settled liquid ammonium sulfate solution flowing out of the cooling-crystallization-precipitation-separation unit 101 in step 1 through the liquid inlet pipe 2. With the addition of the ammonium sulfate liquid material, the liquid level 24 in the tank body 1 gradually rises. When the liquid level 24 rises to 5 cm to 15 cm from the upper edge of the air floating collection bucket 13, start the aerator 4 and open the aeration valve 5 to release the air through the air floating pipe 7. The bubbles float up, and the organic oligomers precipitated in the liquid form aggregates under the action of the flotation bubbles at the bottom and float to the liquid surface 24; the first annular aerator 16 located on the outer circle of the normally open type prevents the viscous oligomer flotation from adhering to the inner wall of the tank body 1; the first drain pipe valve 11 is opened, the intermittent second annular aerator 17 is turned on and operated periodically, and the height of the drain pipe outlet 12 is adjusted by the first telescopic tube 6 so that the liquid output of the drain pipe outlet 12 and the separated oligomer liquid output from the polymer outlet 14 account for 85% to 95% and 5% to 15% of the liquid input of the tank body 1 respectively, and the separated oligomers are kept intermittently discharged;

[0049] During the continuous operation of the primary separation tank, the organic aggregates (blocks) floating on the liquid surface are insoluble organic oligomers. Under the intermittent aeration of the second annular aerator 17, they intermittently flow into the gas-floating material collection bucket 13 together with a small amount of liquid (ammonium sulfate liquid). The primary separation (organic oligomers and a small amount of ammonium sulfate liquid) are discharged from the system through the polymer liquid outlet 14 by gravity, completing the primary separation of organic oligomers. The organic oligomer content in the primary separation (the material entering the gas-floating material collection bucket 13) is about 50% to 80% (w / w), and the flow rate is about 5% to 15% of the liquid inlet volume. The ammonium sulfate liquid material after the primary separation contains about 0.1% to 0.5% (w / w) insoluble extremely fine organic oligomer particles (or liquid droplets). The ammonium sulfate liquid material (the material discharged from the discharge pipe outlet 12) enters the secondary separation unit 103 to further separate and remove the insoluble organic oligomers.

[0050] The material discharged from the polymer liquid outlet 14 flows into the first oligomer collection tank 102-1;

[0051] The residence time of the liquid from the liquid inlet pipe 2 in the tank 1 is 45min to 90min;

[0052] 3. Secondary separation unit: The secondary separation unit 103 is composed of an adsorption separation tower 30, an air compressor, a liquid inlet pump and a hot air compressor; the structure of the adsorption separation tower 30 is as follows Figure 6 As shown, the adsorption separation tower body 30 is cylindrical, the ratio of the tower height to the diameter is 1 / 4 to 1 / 5, the liquid inlet pipe 31 is 20 cm to 30 cm away from the tower top, a plurality of liquid inlet and water distribution pipes 32 are arranged in the tower and connected to the liquid inlet pipe 31, and the liquid inlet and water distribution pipes 32 open downward, the top of the adsorption separation tower 30 is provided with an exhaust port 49, and the bottom is a conical structure and is provided with a vent 47 and a vent valve 48; a hot air outlet pipe 42 is arranged near the bottom of the tower body, and the opening of the hot air outlet pipe 42 is facing downward. The hot air outlet pipe 42 is connected to the hot air compressor 41 outside the tower, the hot air outlet pipe 42 is provided with a hot air inlet pipe valve 40, a drain pipe inlet 44 of a drain pipe 50 is provided just below the hot air outlet pipe 42 and the drain pipe inlet 44 is located on the central axis of the adsorption separation tower 30, a liquid outlet 46 of the drain pipe 50 is provided outside the adsorption separation tower 30, a second drain pipe valve 45 and a second telescopic pipe 39 are provided on the drain pipe 50, and the height of the liquid outlet 46 is generally The air inlet of the aeration perforated pipe 43 is connected to the aerator 36 outside the tower, and an aeration pipe valve 37 is provided on the aeration perforated pipe 43; a lower baffle 34 is provided above the aeration perforated pipe 43, and the lower baffle 34 is a stainless steel mesh or grid; an upper baffle 33 is provided at the upper part of the inner cavity of the adsorption separation tower 30 and below the liquid inlet water distribution pipe 32 The upper baffle 33 is a mesh or grid made of stainless steel; a plurality of fixed bed packing layer monomers 35 are stacked up and down between the upper baffle 33 and the lower baffle 34, a partition 38 is arranged between each adjacent fixed bed packing layer monomer 35, and each adjacent fixed bed packing layer monomer 35 is spaced 10cm to 20cm apart, and the fixed bed packing layer monomer 35 is cylindrical; the filler of the fixed bed packing layer monomer 35 is granular, composed of hard polymer material or foaming material, and the particle volume is 1cm 3 ~5cm 3 The particle shape is spherical, columnar or blocky; the interior of the hard particle is a hollow structure, and the surface of the foam material is a honeycomb; the filler material is polypropylene, polyethylene or polyvinyl chloride; the density of the filler is less than 1.0g / cm 3 , the filler is placed in a mesh cage to form a fixed bed filler layer monomer 35;

[0053] Operation of the secondary separation unit 103: close the vent 47, close the second liquid discharge pipe valve 45, close the aeration pipe valve 37, and close the hot air inlet pipe valve 40; the liquid material from the liquid discharge pipe outlet 12 of the front primary separation unit 102 enters the adsorption separation tower body 30 of the secondary separation unit 103 through the liquid inlet pipe 31 and the liquid inlet water distribution pipe 32, and the liquid level gradually rises. When the liquid level reaches 5 cm to 15 cm below the upper baffle 33, start the aerator 36, open the aeration pipe valve 37, and the aeration gas is released from the aeration perforated pipe 43 and the bubbles rise; open the second liquid discharge pipe valve 45, and adjust the second telescopic pipe 39 to adjust the height of the liquid outlet 46 to be 3 cm higher than the level of the upper baffle 33.

[0054] During the aeration process, bubbles contact the incoming liquid from bottom to top, forming gas, liquid, a small amount of oligomers and filler contact on the surface of the filler, and extremely fine organic oligomer particles (or liquid droplets) gather and adhere to the surface of the filler. Due to the strong aggregation of the precipitated organic oligomers, the oligomers adhered to the surface of the filler can adhere to and aggregate the newly generated oligomer particles (brought by subsequent bubbles) again (multiple times or continuously). Due to the strong adhesion ability of the filler material and polymer aggregates to the non-dissolved polymer particles, the polymer microparticles (or liquid droplets) gathered by the bubble disturbance will quickly and preferentially adhere to the filler or aggregates that are contacted first, that is, after the floating bubbles aggregate the non-dissolved extremely fine oligomer particles into slightly larger particles, the slightly larger particles will not float up with the bubbles, but will quickly adhere to the filler material and oligomer aggregates that are contacted for the first time, thus forming a situation where organic oligomers are adhered and adsorbed at all height layers of the filler in the packing tower. Due to the top-down liquid inlet and discharge method, the amount of oligomers adhered and adsorbed on the surface or upper layer of the filler is large, and the amount of adhesion and adsorption gradually decreases with the height layer downward.

[0055] During the adhesion and adsorption process, it is difficult for the oligomer aggregates adhered and adsorbed by the filler under the liquid surface to be adhered and floated by bubbles again. When the oligomer aggregates adhered and adsorbed on the surface (or upper layer) of the filler reach a certain thickness, they will slowly flow along the surface of the filler below to the lower layer, showing that the entire filler layer forms an adhesion saturated layer, a near-saturated layer, an unsaturated layer, a less-adsorbed layer and a non-adsorbed layer from top to bottom in the height direction. There is no fixed interface between the adsorbed layers, but the stratification trend is obvious.

[0056] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that: when 60% to 80% of the entire filler height layer becomes an adhesion saturation layer and a near-saturation layer, or when fine oligomer droplets are visible to the naked eye in the liquid discharged from the liquid outlet 46, the secondary adsorption separation tower 30 should be regenerated; it should be noted that in order to make the secondary separation unit 103 operate continuously, the secondary separation unit 103 is provided with two adsorption separation towers 30, and the two adsorption separation towers 30 are connected to the discharge pipe outlet 12, and operate and regenerate alternately;

[0057] The regeneration process of the adsorption separation tower 30 of the secondary separation unit 103 is as follows: when the adsorption separation tower needs to be regenerated, the feed of the liquid inlet pipe 31 is stopped, the second liquid discharge pipe valve 45 is closed, and the vent valve 48 at the bottom of the tower is opened to discharge the liquid in the tower (aqueous ammonium sulfate liquid) to the liquid inlet pipe 31 of another adsorption separation tower 30. The liquid inlet pipe 31 of the other adsorption separation tower 30 is also connected to the liquid discharge outlet 12. When the liquid in the adsorption separation tower 30 that needs to be regenerated is emptied, the aerator 36 is stopped and the aeration pipe valve 37 is closed, and the vent port 47 is quickly switched to the second oligomer collection tank 103-1; the density of the oligomer aggregates adsorbed on the surface of the filler is 1.25 g / cm 3 ~1.27g / cm 3 , with viscosity and certain fluidity, the viscosity is 2×10 at 30°C 4 mPa.s~3×10 4 mPa.s, the flow capacity in the air (flowing downward by gravity) increases, and after 18h to 24h of standing, 55% to 70% (w / w) of the oligomers adsorbed on the surface of the filler material will slowly move downward (or flow downward) under the action of gravity and separate from the fixed bed filler layer monomer 35, drip to the bottom of the tower and flow into the second oligomer collection tank 103-1. The rest is the same as the first embodiment.

[0058] Specific embodiment three: The difference between this embodiment and specific embodiment two is that: in order to accelerate the dripping and separation speed of oligomers in the filler, the hot air inlet pipe valve 40 is opened, and the hot air compressor 41 is turned on. The hot air enters the adsorption separation tower 30 through the hot air outlet pipe 42. The temperature in the tower increases, and the temperature of the adsorbed polymer aggregates increases accordingly. After the temperature increases, the viscosity of the oligomer aggregates decreases, the flowability improves, and the dripping speed is significantly accelerated. The temperature in the tower is controlled at 50℃~60℃. At a temperature of 50℃~60℃, the oligomer aggregates adsorbed by the filler can drip down 65%~80% (w / w) in 6h~8h.

[0059] When the dripping rate of the oligomer flowing out of the vent 47 at the bottom of the adsorption separation tower 30 is reduced to 1 drop every 5 minutes to 15 minutes, the hot air inlet pipe valve 40 is closed, the hot air compressor 41 is turned off, the vent 47 is closed, and the gravity regeneration is completed; after gravity regeneration, the adhesion adsorption capacity of the adsorption separation tower is restored to 50% to 80%, and it can be operated and used again.

[0060] It should be noted that the fluidity of oligomers deteriorates when the temperature is low. The temperature in the tower should not be lower than 30°C to 35°C during gravity regeneration. When the ambient temperature is low, hot air or other forms of heating must be used to ensure that the temperature during regeneration is between 30°C and 60°C. However, if the temperature is too high, the surface active functional groups of the oligomer aggregates are easily oxidized (by oxygen in the air), which affects the fluidity of the oligomers and is not conducive to the subsequent resource utilization of the oligomers (such as modification, etc.).

[0061] The oligomer purity (in the second oligomer collection tank 103-1) (or content) obtained by the secondary separation unit 103 can reach 85% to 95% (w / w), which is better than the oligomer purity obtained by the primary separation unit 102; the comprehensive concentration of oligomers obtained by the two separation units (primary and secondary) (in the first oligomer collection tank 102-1 and the second oligomer collection tank 103-1) is 70% to 80% (w / w), and the flow rate is 5% to 15% (w / w) of the incoming liquid volume, and the amount of ammonium sulfate therein is only 1% to 4.5% of the amount of ammonium sulfate in the incoming liquid. If the incineration method is used, the amount of ammonium sulfate incinerated is only 1% to 4.5% of the amount of ammonium sulfate before separation and treatment by the method of the present invention. The significant reduction in the amount of ammonium sulfate incinerated can greatly alleviate or eliminate the impact on the incinerator, thereby ensuring the long-term stable operation of the incinerator device.

[0062] The content of non-dissolved extremely fine organic oligomer particles (or liquid droplets) in the ammonium sulfate liquid material (discharged through the liquid outlet 46) after the secondary separation is 0.01% to 0.05% (w / w), and the concentration of soluble oligomers is 2% to 4% (w / w). The oligomer concentration is similar to the concentration level of oligomers (heavy components) in the liquid material (upper tower bottom liquid) from the ammonium sulfate device. The ammonium sulfate liquid after the secondary separation is returned to the feed tank 104-2 of the ammonium sulfate evaporation and crystallization device for reuse. The flow rate of the liquid (discharged through the liquid outlet 46) is 95% to 99% of the amount of the liquid inlet (from the liquid inlet pipe 31) of the secondary separation unit;

[0063] The residence time of the liquid from the liquid inlet pipe 31 in the secondary adsorption separation tower 30 is 45 minutes to 90 minutes. The rest is the same as the second embodiment.

[0064] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that: there is also a second process: if the oligomer concentration (or purity) in the primary separation oligomer liquid (discharged from the polymer liquid outlet 14) of the primary separation unit 102 is to be increased, the outlet of the polymer liquid outlet 14 is changed to an adsorption separation tower 30 connected to a secondary separation unit, and the liquid outlet 46 is further connected to the liquid inlet pipe 2, and the primary separation polymer liquid is subjected to secondary separation. After the secondary separation, the oligomer concentration (or purity) can be increased from 50% to 80% (w / w) in the primary separation polymer liquid to 85% to 95% (w / w), and the ammonium sulfate liquid obtained by the secondary separation is returned to the liquid inlet pipe 2 of the primary separation tank 1. The process is as follows: Figure 2 The rest is the same as that of the first to third embodiments.

[0065] Specific implementation method 5: There is also a third process: the primary separation unit 102 is removed from the processing flow, and the secondary separation 103 is directly performed (such as Figure 3 ), the second process ( Figure 2 ) and the third process ( Figure 3 ) have similar final separation effects. The primary separation unit 102 has a faster separation speed and higher separation efficiency, but the separation quality (referring to the oligomer concentration or purity) of the primary separation unit 102 is relatively poor (compared with the secondary separation unit 103). When the separation quality requirement is not high, the first process ( Figure 1 ), when the separation quality requirements are high, the second process or the third process needs to be adopted. Comparing the second process and the third process, the two streams of materials (polymer and ammonium sulfate liquid) in the second process are separated twice, and the obtained polymer and ammonium sulfate liquid are of the best quality, but the subunits of the second process are relatively complex and the process is long, and the primary separation unit makes the whole process more resistant to impact; in the third process, the material is only separated once, and the quality and purity of the ammonium sulfate liquid are relatively poor, but the process is simpler and the types of equipment are fewer. Due to the lack of a primary separation process, the system's impact resistance is relatively poor. The rest is the same as the fourth specific implementation method.

[0066] Specific embodiment 6: This embodiment is different from specific embodiment 5 in that: if the temperature of each unit after primary separation is lower than the temperature of cooling-crystallization-precipitation-separation unit 101 (27°C to 32°C) due to changes in ambient temperature, ammonium sulfate crystals will be precipitated in the ammonium sulfate solution, and some ammonium sulfate crystals will be adsorbed on the surface of the material or adhered to the oligomer aggregates, affecting the normal operation of the system. The problem of ammonium sulfate crystals precipitating due to temperature reduction in the subsequent process of the primary separation unit needs to be eliminated by the following three methods:

[0067] (1) maintaining the temperature of the subsequent process of the primary separation unit 102 by a heat preservation method without decreasing (i.e., the temperature is not lower than the effluent temperature of the cooling-crystallization-precipitation-separation unit);

[0068] (2) adding a diluent to the liquid inlet pipe 2 of the primary separation unit 102 to ensure that the ammonium sulfate concentration in the ammonium sulfate liquid material after dilution is lower than the saturated ammonium sulfate concentration at the lowest temperature in the process unit; the diluent is water or the incoming dilute ammonium sulfate liquid of the ammonium sulfate device;

[0069] (3) The total incoming liquid is diluted so that the ammonium sulfate concentration in the diluted ammonium sulfate liquid material is lower than the saturated ammonium sulfate concentration at the lowest temperature in the process unit: the cooling-crystallization-precipitation-separation unit 101 is eliminated in the process, and a dilution-cooling unit is set. The dilution-cooling unit includes two subunits: dilution stirring and cooling. The dilution stirring subunit reduces the ammonium sulfate concentration to 95%-99% of the saturated concentration at room temperature by adding a diluent. The dilution is water or the incoming dilute ammonium sulfate liquid of the ammonium sulfate device; the cooling subunit reduces the temperature of the material diluted by the incoming liquid from about 80°C to 82°C to 27°C to 32°C through a heat exchanger and circulating cooling water. The diluted and cooled incoming liquid mixed liquid (nearly saturated ammonium sulfate liquid) enters the subsequent primary separation unit 102 or secondary separation unit 103 for separation. The rest is the same as the specific embodiment 5.

[0070] The present invention is verified by the following examples:

[0071] Example 1: Cooling and crystallizing salt: A northern acrylonitrile enterprise produces 80,000 tons of acrylonitrile per year. 29L of saturated ammonium sulfate liquid discharged from the crystallizer of the ammonium sulfate device was sampled. The weight was 36.76Kg and the density was 1.27g / cm 3 The sample temperature was 80.4°C; the sample was cooled to 30.6°C by a heat exchanger and circulating cooling water, and ammonium sulfate crystals were precipitated. The ammonium sulfate solid was separated by precipitation, and the solid weight was 0.96 kg. After calculation, the precipitated solid accounted for 2.8% (w / w) of the total sample mass. The density of the upper liquid after precipitation was measured to be 1.254 g / cm 3 , it can be seen that there are large blocky semi-solid oligomer aggregates on the surface of the upper liquid, and suspended black-brown liquid beads (or particles) of varying sizes can be clearly seen inside the liquid. The liquid color is brown.

[0072] Example 2: According to process 3, Figure 3 Adsorption separation of oligomers: a block of polypropylene foam (length, width and height of 1 cm to 2 cm) and a cylindrical hollow hard filler (length 1 cm, diameter 1 cm) were added to a circular cylinder with a volume of 1.1 L, i.e., an adsorption separation tower 30 (diameter 6 cm) of a secondary separation unit. The total height of the filler layer 35 was 17.7 cm, the two fillers had the same volume, the total weight of the fillers was 89.42 g, the filler pile volume was 500 mL, the distance from the metal mesh 34 to the bottom of the cylinder was 8.5 cm, and the aeration pipe 4 was 4.5 cm long. 4 cm below the metal mesh 34, aeration is performed by an air pump 36, a drainage port 44 is provided on the bottom side, a flexible drainage pipe 50 is raised to the same height as the liquid outlet 46 and the liquid level 33, a metal mesh 33 is used as a baffle to be fixed on the packing layer 35, and the height of the metal mesh 33 from the bottom drainage port 44 is 34.2 cm; the liquid from which the solid ammonium sulfate precipitate is removed in Example 1 (the upper layer liquid of the precipitate, the ammonium sulfate saturated liquid, containing the precipitated organic oligomers) is added into the circular cylinder 30 by a peristaltic pump (through Figure 631), the liquid is added from the packing layer 35, the liquid flow rate is 16mL / min-19mL / min, and the liquid is continuously fed and discharged. The oligomers quickly adhere to the surface of the surface packing and form aggregates. The bottom liquid is clear and transparent and flows out continuously. When the liquid flow rate is 12.2L, there are many adherents at about 12.4cm (from the top layer) of the packing layer, so the liquid is stopped and the liquid is discharged through Figure 6 The saturated ammonium sulfate liquid was emptied at 47. The packing layer was left to stand for 18 hours (gravity regeneration), and 235.42g of organic oligomer material dripped and flowed out. After standing for another 24 hours, a small amount of clear water layer appeared on the surface of the material. After separation and weighing, the oligomer content was calculated to be 89.5% (w / w), and the oligomer density was 1.263g / cm 3 The viscosity of the oligomer at 30°C is 2.13×10 4 mPa.s.

[0073] Aeration flotation separation Figure 6 The total organic carbon (TOC, total organic carbon) content of the clear and transparent ammonium sulfate liquid obtained by aeration flotation separation is 2.23% (w / w). If calculated based on the oligomer being polyacrylonitrile, it is equivalent to the oligomer content in the transparent ammonium sulfate liquid after aeration flotation separation being about 3.29% (w / w). This value is consistent with the heavy component concentration level range of 2% to 4% (w / w) in the liquid from the ammonium sulfate unit (104-1 and 104-2).

[0074] Example 3: Evaporation and crystallization of the ammonium sulfate solution with oligomers separated and precipitated. Take 200 mL of the precipitated upper layer liquid of Example 1 and 200 mL of the aerated flotation clear transparent liquid of Example 2 respectively, evaporate and crystallize under reduced pressure, and dry the crystals at a temperature of 120°C for 2 hours. The ammonium sulfate salt obtained from the ammonium sulfate solution without separation and removal of oligomers (Example 1) is a light yellow solid, and the organic content in the solid salt is 4.5% (w / w) (calculated as TOC); the ammonium sulfate salt obtained from the ammonium sulfate solution with oligomers separated and removed (Example 2) is white, and the organic content in the solid is 1.1% (w / w) (calculated as TOC). The salt obtained from the ammonium sulfate solution with oligomers separated and removed is significantly better than the salt obtained from the ammonium sulfate solution without separation and removal of oligomers.

Claims

1. A method for removing organic oligomers from a saturated ammonium sulfate solution system discharged from a crystallizer of an acrylonitrile ammonium sulfate device, characterized in that The method for removing organic oligomers from the saturated ammonium sulfate liquid system discharged from the crystallizer of the acrylonitrile ammonium sulfate unit is carried out according to the following steps:

1. The method comprises three processing units: a cooling-crystallization-precipitation-separation unit 101, a primary separation unit 102 and a secondary separation unit 103; the ammonium sulfate salt produced by the cooling-crystallization-precipitation-separation unit 101 is returned to the ammonium sulfate evaporation crystallization device 104-1; the oligomer separated by the primary separation unit 102 is discharged into the first oligomer collection tank 102-1; the oligomer separated by the secondary separation unit 103 is discharged into the second oligomer collection tank 103-1, and the liquid separated by the secondary separation unit 103 is sent to the feed tank 104-2 of the ammonium sulfate evaporation crystallization device; The specific process is as follows: the liquid material discharged from the crystallizer of the ammonium sulfate evaporation crystallization device enters the cooling-crystallization-precipitation-separation unit 101, which is composed of four sub-units in sequence: heat exchange cooling, cooling crystallization, sedimentation and centrifugal separation; cooling is achieved by a heat exchanger and circulating cooling water, and the temperature of the incoming liquid material is reduced from 80°C to 82°C to 27°C to 32°C, and the cooling crystallization precipitates part of the ammonium sulfate solid in the saturated ammonium sulfate liquid and increases the viscosity of the precipitated organic oligomers in the incoming liquid material; the cooling crystallization precipitates The solid ammonium sulfate is precipitated at the bottom of the sedimentation tank, the solid ammonium sulfate at the bottom is taken out and then separated by centrifugation, and the solid ammonium sulfate is returned to the ammonium sulfate evaporation crystallization device 104-1 for reuse; the centrifugal liquid is returned to the solution after precipitation, and the precipitated organic oligomers are viscous liquid, part of which is aggregated and floats on the surface of the saturated ammonium sulfate liquid after precipitation, and part of which is suspended in the saturated ammonium sulfate liquid layer in the form of fine liquid droplets; the liquid after precipitation enters the primary separation unit 102 for primary separation of the precipitated organic oligomers; 2. The primary separation unit 102 is composed of a primary separation tank, an air compressor and a liquid inlet pump; the tank body 1 of the primary separation tank is cylindrical, and the ratio of the height to the diameter of the tank body 1 is (2-4):

1. The liquid inlet pipe 2 is located at the upper part of the inner cavity of the tank body 1 and between the liquid surface 24 and the top of the cylinder. The liquid inlets of the plurality of liquid inlet and water distribution pipes 3 are all connected to the liquid outlet of the liquid inlet pipe 2. The liquid inlet and water distribution pipes 3 are vertically downward, and the bottom liquid outlet of the liquid inlet and water distribution pipes 3 is placed 5 cm to 10 cm below the liquid surface 24. The liquid inlet and water distribution pipes 3 are located on the same circumference and the distance from the central axis of the tank body 1 is 2 / 3 to 3 / 4 of the radius of the tank body 1; the tank body 1 is provided with an air-floating collecting hopper 13 at the middle and upper part of the inner central axis, the air-floating collecting hopper 13 is located below the liquid inlet pipe 2, the diameter of the air-floating collecting hopper 13 is 1 / 6 to 1 / 5 of the diameter of the tank body 1, and the height is 1 / 15 to 1 / 12 of the height of the tank body 1, the bottom of the air-floating collecting hopper 13 is conical, the conical bottom is connected to the polymer liquid outlet pipe 15-1, the discharge port 14 of the polymer liquid outlet pipe 15-1 is outside the tank body 1, the angle between the polymer liquid outlet pipe 15-1 and the horizontal line is 50° to 70°, the pipe diameter is 1 / 6 to 1 / 4 of the pipe diameter of the air-floating collecting hopper 13 and is greater than 5 cm; in the tank A first annular aerator 16 is arranged on the inner wall of the body 1, and a plurality of second annular aerators 17 are arranged from the first annular aerator 16 to the direction of the air floating object collecting bucket 13 to form a plurality of concentric annular aerators with equal spacing from each other with the air floating object collecting bucket 13 as the center. The second annular aerator 17 is at the same height as the first annular aerator 16 and is located below the liquid surface 24. The height of the second annular aerator 17 is located in the middle and lower part of the air floating object collecting bucket 13; each annular aerator is connected to an air source pump or an air tank respectively, and operates independently during aeration; the air inlet of the first annular aerator 16 is connected to the outlet of the first air inlet pipe 18 The air port is connected, and a first valve 19 is arranged on the first air inlet pipe 18; the first annular aerator 16 is normally open to prevent the viscous oligomer gas suspension from adhering to the inner wall of the tank body 1; the second annular aerator 17 is an intermittent aerator, and the intermittent aeration is repeatedly operated in a periodic manner, and the periodic operation mode is: a plurality of second annular aerators 17 are sequentially started for aeration at intervals of 15s to 20s from the outer circle to the inner circle, and when the second annular aerator 17 in the innermost circle is started for 15s to 20s, the aeration of all the second annular aerators 17 is stopped for 10min to 20min, and the above process is repeated; An air flotation tube 7 is arranged at the bottom of the tank body 1, the air inlet of the air flotation tube 7 is connected with the air outlet of the aerator 4, an aeration valve 5 is arranged on the air flotation tube 7, and a plurality of air outlets opening upward are evenly arranged on the air flotation tube 7; a drainage inlet 10 of a drainage pipe 23 is arranged below the air flotation tube 7 and on the central axis of the tank body 1, a drainage outlet 12 of the drainage pipe 23 is arranged at the upper middle part of the outside of the tank body 1, a first telescopic tube 6 is arranged on the drainage pipe 23, the height of the drainage outlet 12 is adjusted by the first telescopic tube 6, and a first drainage pipe valve 11 is arranged on the drainage pipe 23; the bottom of the tank body 1 is conical, and a venting outlet 9 and a venting valve 8 are arranged at the lower end of the cone; an exhaust port 22 is arranged at the top of the tank body 1, and the exhaust port 22 is connected to the enterprise waste gas collection system; Start-up operation of the primary separation tank: close the vent valve 8 at the bottom of the tank body 1, close the aeration valve 5, open the first valve 19, close all the second annular aerators 17, open the polymer outlet pipe valve 15, and close the first discharge pipe valve 11; pump the settled liquid ammonium sulfate solution flowing out of the cooling-crystallization-precipitation-separation unit 101 in step 1 through the liquid inlet pipe 2. With the addition of the ammonium sulfate liquid material, the liquid level 24 in the tank body 1 gradually rises. When the liquid level 24 rises to 5 cm to 15 cm from the upper edge of the air floating collection bucket 13, start aeration. The machine 4 is opened and the aeration valve 5 is opened, and bubbles are released through the flotation tube 7 to float up. The organic oligomers precipitated in the liquid form aggregates under the action of the flotation bubbles at the bottom and float to the liquid surface 24; the first discharge pipe valve 11 is opened, and the intermittent second annular aerator 17 is turned on and operated periodically, and the height of the discharge pipe outlet 12 is adjusted through the first telescopic tube 6 so that the liquid output of the discharge pipe outlet 12 and the separated oligomer liquid output from the polymer outlet 14 account for 85% to 95% and 5% to 15% of the liquid input of the tank body 1, respectively, and the separated oligomers are kept intermittently discharged; The material discharged from the polymer liquid outlet 14 flows into the first oligomer collection tank 102-1; The residence time of the liquid from the liquid inlet pipe 2 in the tank 1 is 45min to 90min; 3. Secondary separation unit: The secondary separation unit 103 is composed of an adsorption separation tower 30, an air compressor, a liquid inlet pump and a hot air compressor; the adsorption separation tower body 30 is cylindrical, the ratio of the tower height to the diameter is 1 / 4 to 1 / 5, the liquid inlet pipe 31 is 20 cm to 30 cm away from the tower top, a plurality of liquid inlet water distribution pipes 32 are arranged in the tower and connected to the liquid inlet pipe 31, the liquid inlet water distribution pipes 32 are opened downward, the top of the adsorption separation tower 30 is provided with an exhaust port 49, and the bottom is a conical structure and is provided with a vent 47 and a vent valve 48; A hot air outlet pipe 42 is arranged near the bottom of the tower body, the opening of the hot air outlet pipe 42 faces downward, the hot air outlet pipe 42 is connected to the hot air compressor 41 outside the tower, a hot air inlet pipe valve 40 is arranged on the hot air outlet pipe 42, a drain pipe inlet 44 of a drain pipe 50 is arranged directly below the hot air outlet pipe 42, and the drain pipe inlet 44 is located on the central axis of the adsorption separation tower 30, a liquid outlet 46 of the drain pipe 50 is arranged outside the adsorption separation tower 30, and a second drain pipe valve is arranged on the drain pipe 50 The height of the liquid outlet 46 is adjusted by the second telescopic tube 39; the aeration perforated tube 43 is arranged just above the hot air outlet pipe 42, the opening of the aeration perforated tube 43 faces downward, the air inlet of the aeration perforated tube 43 is connected to the aerator 36 outside the tower, and the aeration perforated tube 43 is provided with an aeration tube valve 37; the lower baffle 34 is arranged above the aeration perforated tube 43, and the lower baffle 34 is a stainless steel mesh or grille; the upper part of the inner cavity of the adsorption separation tower 30 and located at the liquid inlet water distribution pipe 3 An upper baffle 33 is arranged below 2, and the upper baffle 33 is a mesh or grid made of stainless steel; a plurality of fixed bed packing layer monomers 35 are stacked up and down between the upper baffle 33 and the lower baffle 34, and a partition 38 is arranged between each adjacent fixed bed packing layer monomer 35, and each adjacent fixed bed packing layer monomer 35 is spaced 10cm to 20cm apart, and the fixed bed packing layer monomer 35 is cylindrical; the filler of the fixed bed packing layer monomer 35 is granular, and is composed of hard polymer material or foaming material, and the particle volume is 1cm 3 ~5cm 3 The particle shape is spherical, columnar or blocky; the interior of the hard particle is a hollow structure, and the surface of the foam material is a honeycomb; the filler material is polypropylene, polyethylene or polyvinyl chloride; the density of the filler is less than 1.0g / cm 3 , the filler is placed in a mesh cage to form a fixed bed filler layer monomer 35; Operation of the secondary separation unit 103: close the vent 47, close the second liquid discharge pipe valve 45, close the aeration pipe valve 37, and close the hot air inlet pipe valve 40; the liquid material from the liquid discharge pipe outlet 12 of the front primary separation unit 102 enters the adsorption separation tower body 30 of the secondary separation unit 103 through the liquid inlet pipe 31 and the liquid inlet water distribution pipe 32, and the liquid level gradually rises. When the liquid level reaches 5 cm to 15 cm below the upper baffle 33, start the aerator 36, open the aeration pipe valve 37, and the aeration gas is released from the aeration perforated pipe 43 and the bubbles rise; open the second liquid discharge pipe valve 45, and adjust the second telescopic pipe 39 to adjust the height of the liquid outlet 46 to be 3 cm higher than the level of the upper baffle 33.

2. The method for removing organic oligomers from a saturated ammonium sulfate solution system discharged from a crystallizer of an acrylonitrile ammonium sulfate device according to claim 1, characterized in that The surface layer of the packing shows that the entire packing layer forms an adhesion saturated layer, a near saturated layer, an unsaturated layer, a less adsorbed layer and a non-adsorbed layer from top to bottom in the height direction. When 60% to 80% of the entire packing height layer becomes an adhesion saturated layer and a near saturated layer, or when fine oligomer droplets are visible to the naked eye in the liquid discharged from the liquid outlet 46, the secondary adsorption separation tower 30 should be regenerated; in order to make the secondary separation unit 103 run continuously, the secondary separation unit 103 is provided with two adsorption separation towers 30, and the two adsorption separation towers 30 are connected to the discharge pipe outlet 12, and are operated and regenerated alternately; The regeneration process of the adsorption separation tower 30 of the secondary separation unit 103 is as follows: when the adsorption separation tower needs to be regenerated, the feed of the liquid inlet pipe 31 is stopped, the second liquid discharge pipe valve 45 is closed, and the vent valve 48 at the bottom of the tower is opened to discharge the liquid in the tower to the liquid inlet pipe 31 of another adsorption separation tower 30. The liquid inlet pipe 31 of the other adsorption separation tower 30 is also connected to the liquid discharge outlet 12. When the liquid in the adsorption separation tower 30 that needs to be regenerated is emptied, the aerator 36 is stopped and the aeration pipe valve 37 is closed, and the vent port 47 is quickly switched to the second oligomer collection tank 103-1; the density of the oligomer aggregates adsorbed on the surface of the filler is 1.25 g / cm 3 ~1.27g / cm 3 , with viscosity and fluidity, the viscosity at 30°C is 2×10 4 mPa.s~3×10 4 mPa.s, the flowability in the air increases. After standing for 18h to 24h, 55% to 70% of the oligomers adsorbed on the surface of the packing material will slowly move downward under the action of gravity and separate from the fixed bed packing layer monomer 35, drip to the bottom of the tower and flow into the second oligomer collection tank 103-1.

3. The method for removing organic oligomers from a saturated ammonium sulfate solution system discharged from a crystallizer of an acrylonitrile ammonium sulfate device according to claim 2, characterized in that In order to speed up the dripping and separation speed of the oligomers in the filler, the hot air inlet valve 40 is opened, and the hot air compressor 41 is turned on. The hot air enters the adsorption separation tower 30 through the hot air outlet pipe 42. The temperature in the tower increases, and the temperature of the adsorbed polymer aggregates increases accordingly. After the temperature increases, the viscosity of the oligomer aggregates decreases, the fluidity increases, and the dripping speed is significantly accelerated. The temperature in the tower is controlled at 50°C to 60°C. When the dripping rate of the oligomer flowing out of the vent 47 at the bottom of the adsorption separation tower 30 is reduced to 1 drop every 5 to 15 minutes, the hot air inlet pipe valve 40 is closed, the hot air compressor 41 is closed, and the vent 47 is closed, and the gravity regeneration ends; After gravity regeneration, the adsorption capacity of the adsorption separation tower is restored to 50% to 80% and can be put into operation again; The residence time of the liquid from the liquid inlet pipe 31 in the secondary adsorption separation tower 30 is 45 minutes to 90 minutes.

4. The method for removing organic oligomers from a saturated ammonium sulfate solution system discharged from a crystallizer of an acrylonitrile ammonium sulfate device according to claim 3, characterized in that There is also a second process: if the oligomer concentration in the primary separation oligomer liquid of the primary separation unit 102 is to be increased, the outlet of the polymer outlet 14 is changed to be connected to an adsorption separation tower 30 of a secondary separation unit, and the outlet 46 is then connected to the liquid inlet pipe 2, and the primary separation polymer liquid is subjected to secondary separation, and the ammonium sulfate liquid obtained by the secondary separation is returned to the liquid inlet pipe 2 of the primary separation tank 1.

5. The method for removing organic oligomers from a saturated ammonium sulfate solution system discharged from a crystallizer of an acrylonitrile ammonium sulfate device according to claim 3, characterized in that There is also a third process: compared with the first process, the primary separation unit 102 is removed from the treatment process, and the secondary separation 103 is directly performed.

6. The method for removing organic oligomers from a saturated ammonium sulfate solution system discharged from a crystallizer of an acrylonitrile ammonium sulfate device according to claim 1, characterized in that If the temperature of each unit after the primary separation is lower than the temperature of the cooling-crystallization-precipitation-separation unit 101 due to changes in ambient temperature, ammonium sulfate crystals will be precipitated in the ammonium sulfate liquid, and some ammonium sulfate crystals will be adsorbed on the surface of the material or adhere to the oligomer aggregates, affecting the normal operation of the system. The following three methods are needed to eliminate the problem of ammonium sulfate crystals precipitated due to temperature reduction in the subsequent process of the primary separation unit: (1) maintaining the temperature of the subsequent process of the primary separation unit 102 from decreasing by means of a heat preservation method; (2) adding a diluent to the liquid inlet pipe 2 of the primary separation unit 102 to ensure that the ammonium sulfate concentration in the ammonium sulfate liquid material after dilution is lower than the saturated ammonium sulfate concentration at the lowest temperature in the process unit; the diluent is water or the incoming dilute ammonium sulfate liquid of the ammonium sulfate device; (3) The total incoming liquid is diluted so that the ammonium sulfate concentration in the ammonium sulfate liquid material after dilution is lower than the saturated ammonium sulfate concentration at the lowest temperature in the process unit: the cooling-crystallization-precipitation-separation unit 101 is eliminated in the process, and a dilution-cooling unit is set. The dilution-cooling unit includes two sub-units: dilution stirring and cooling. The dilution stirring sub-unit reduces the ammonium sulfate concentration to 95%-99% of the saturated concentration at room temperature by adding a diluent. The dilution is water or the incoming dilute ammonium sulfate liquid of the ammonium sulfate device; the cooling sub-unit reduces the temperature of the material after the incoming liquid is diluted by a heat exchanger and circulating cooling water from about 80°C to 82°C to 27°C to 32°C. The diluted and cooled incoming liquid mixed liquid enters the subsequent primary separation unit 102 or secondary separation unit 103 for separation.

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