CN115504852A - Method for reducing content of aldehyde substances in styrene product - Google Patents

Method for reducing content of aldehyde substances in styrene product Download PDF

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Publication number
CN115504852A
CN115504852A CN202110630166.1A CN202110630166A CN115504852A CN 115504852 A CN115504852 A CN 115504852A CN 202110630166 A CN202110630166 A CN 202110630166A CN 115504852 A CN115504852 A CN 115504852A
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styrene
product
treatment
water
washing
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周召方
刘畅
付培
王培歌
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Sinopec Sk Wuhan Petrochemical Co ltd
China Petroleum and Chemical Corp
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Sinopec Sk Wuhan Petrochemical Co ltd
China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/04—Purification; Separation; Use of additives by distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/005—Processes comprising at least two steps in series
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/10—Purification; Separation; Use of additives by extraction, i.e. purification or separation of liquid hydrocarbons with the aid of liquids

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  • Organic Chemistry (AREA)
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  • Oil, Petroleum & Natural Gas (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention discloses a method for reducing the content of aldehyde substances in a styrene product, wherein crude styrene enters an alkaline washing system to neutralize redundant acid substances after being decolored by acid substances, and the pH value of alkaline washing water after alkaline washing is ensured to be weakly acidic or weakly alkaline; after alkali washing treatment, the product enters a water washing system, and water is used for removing redundant alkali liquor and salt substances in the styrene; after washing treatment, the product enters a coalescer for dehydration treatment to remove redundant water in the product; after dehydration, the dehydrated styrene enters a refining tower for refining treatment to remove heavy component polymers, and a refined styrene product is extracted from the middle lateral line; the top of the refining column extracts topped styrene, a part of which is refluxed and a part of which is sent to a synthesis line (DN 50) for a carbon nine product. The method has the advantages of simple process, stable process operation, simplicity, practicability and the like.

Description

Method for reducing content of aldehyde substances in styrene product
Technical Field
The invention relates to a method for reducing the content of aldehyde substances in a styrene product, in particular to a method for reducing the content of aldehyde substances in the styrene product by optimizing a process flow, which aims to reduce the influence of the aldehyde substances on the quality of the styrene product and belongs to the technical field of optimizing the process flow and improving the quality of the product.
Background
The styrene is mainly used as a monomer of synthetic rubber and plastic and is used for producing styrene butadiene rubber, polystyrene and foamed polystyrene; and also for copolymerization with other monomers to produce engineering plastics for a variety of different uses. For example, ABS resin is prepared by copolymerization of acrylonitrile and butadiene, and is widely used in various household appliances and industries; SAN prepared by copolymerization with acrylonitrile is impact-resistant resin with bright color; SBS prepared by copolymerization with butadiene is thermoplastic rubber and widely used as modifier of polyvinyl chloride and polypropylene; it is also one of the raw materials for producing ion exchange resin and pharmaceuticals, and in addition, styrene can also be used in the industries of pharmacy, dyes, pesticides, mineral separation and the like. With the rapid development of national economy of China, the consumption capacity of styrene is increased year by year, although the styrene products in China are continuously increased, the requirements of downstream device production cannot be met, and the shortage of supply of domestic styrene is required.
The C8 fraction in the pyrolysis gasoline which is a byproduct for preparing ethylene by steam cracking contains about 35 percent of styrene, so far, most of the pyrolysis gasoline at home and abroad is subjected to two-stage hydrogenation treatment and then enters an aromatic extraction device, and the styrene in the pyrolysis gasoline is hydrogenated to be changed into ethylbenzene. At present, the domestic ethylene device is large-sized, the byproduct crude pyrolysis gasoline component contains 4-5% of styrene, the extraction of the styrene in the pyrolysis gasoline is in an economic scale, and the styrene product added value is high, so that the styrene in the C8 fraction of the crude pyrolysis gasoline is directly extracted, the hydrogen consumption of the pyrolysis gasoline hydrogenation device can be reduced, the quality of the mixed xylene product of the aromatic hydrocarbon extraction device can be improved, the byproduct flow can be optimized, and the economic benefit of an ethylene plant can be increased.
A petrochemical company adopts a GTC extraction technology to produce styrene, the process comprises the steps of separating, cutting into C8 and C9 fractions, hydrogenating the C8 fraction to remove phenylacetylene impurities, and extracting, decoloring and refining to obtain a styrene product. In the actual production process, the content of aldehyde at the outlet of the styrene distillation often exceeds 200mg/kg (styrene), which affects the quality grade of the styrene product.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for reducing the content of aldehyde substances in a styrene product aiming at the defects in the prior art, and has the advantages of simple process, stable process operation, simplicity, practicability and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for reducing the content of aldehydes in a styrene product comprises the following steps:
(1) Alkali washing treatment: after the crude styrene is decolorized by acidic substances, the crude styrene enters an alkaline washing system to neutralize redundant acidic substances, and the pH value of alkaline washing water after alkaline washing is ensured to be weakly acidic or weakly alkaline;
(2) And (3) water washing treatment: after the alkali washing treatment in the step (1), the product enters a washing system, and redundant alkali liquor and salt substances in the styrene are removed by using water;
(3) And (3) dehydration treatment: after the water washing treatment in the step (2), the product enters a coalescer for dehydration treatment to remove redundant water in the product;
(4) Refining treatment: after the dehydration treatment in the step (3), the dehydrated styrene enters a refining tower for refining treatment to remove heavy component polymers, and a fine styrene product is extracted from the middle lateral line;
(5) Aldehyde removal reflux treatment: the top of the refining column produces topped styrene, a portion of which is refluxed and a portion of which is sent to the synthesis line (DN 50) for the C4 product.
In the above technical solution, the process flow diagram of the method is shown in fig. 1, and specifically includes the following steps:
(1) Alkali washing treatment: mixing the crude styrene subjected to acid substance decolorization treatment and an alkali liquor in a mixer I, and then sending the mixture into an alkali washing tank, wherein the alkali liquor and residual acid substances in the crude styrene undergo neutralization reaction to obtain alkali washing water, and the alkali washing water contains the alkali liquor and salt products generated by the neutralization reaction, so that the pH value of the alkali washing water is ensured to be weakly acidic or weakly alkaline; the product obtained after the alkali washing treatment can be settled in an alkali washing tank due to the density difference, so that alkali washing water and a styrene crude product are obtained; sending alkaline washing water into a centrifugal pump I, returning a part of alkaline washing water into a mixer I for recycling, and sending the other part of alkaline washing water into a waste alkali oxidation system for treatment; washing the styrene crude product with water;
(2) And (3) water washing treatment: mixing the styrene crude product obtained in the step (1) with water in a mixer II, and then sending the mixture into a washing tank, wherein the water dissolves residual acidic substances in the styrene crude product and controls the content of the acidic substances in the styrene crude product to be less than 600ppm, and after the washing treatment is finished, a styrene product is obtained at the upper layer, and sewage is obtained at the lower layer; the sewage mainly contains desalted water, salt-containing and alkali-containing sewage and acidic substances, the sewage is sent into a centrifugal pump II, one part of the sewage is returned into a mixer II for cyclic utilization, and the other part of the sewage is sent into a sewage treatment plant for treatment; dehydrating the styrene product;
(3) And (3) dehydration treatment: sending the styrene product obtained in the step (2) into a coalescer for dehydration treatment until the water content in the styrene product is less than 0.1 percent (mass percentage);
(4) Refining treatment: feeding the styrene product obtained after dehydration treatment in the step (3) into a refining tower, after refining to remove heavy component polymers, collecting a refined styrene product at the middle lateral line, collecting topped styrene at the tower top, and enriching aldehyde substances in the topped styrene;
(5) Aldehyde removal reflux treatment: condensing the topped styrene extracted in the step (4) by a condenser, and then introducing the condensed topped styrene into a reflux tank (10), wherein the outlet of the reflux tank is provided with a centrifugal pump III, the outlet is divided into two paths, one path is connected with a reflux port of a refining tower for reflux, and the other path is extracted and sent to a C nine product synthesis pipeline (DN 50) to provide raw materials for the C nine product.
In the above technical scheme, in the step (1), the crude styrene refers to crude styrene obtained after extraction and acidic substance (maleic anhydride or nitric acid) decolorization; the purity of the crude styrene is more than or equal to 99.5 percent (wt) and the xylene is less than 0.2 percent (wt).
In the above technical scheme, in the step (1), the alkali liquor is a sodium hydroxide aqueous solution with a mass content of 20%, the concentration of the alkali wash water needs to be adjusted before the alkali wash water returns to the mixer I for recycling, and the sodium hydroxide in the alkali wash water is recycled after the mass content of the sodium hydroxide is adjusted to 20%.
In the above technical solution, in the step (1), the pH of the alkaline washing water is preferably 6 to 8.
In the technical scheme, in the step (1), the settling time is 4-6h.
In the above technical solution, in the step (1), the caustic wash water is introduced into the centrifugal pump I, and the operating conditions of the centrifugal pump I are as follows: rated flow 5m 3 H, 55m of lift and 40 ℃ of operating temperature.
In the above technical scheme, in the step (2), the mass ratio of the water to the crude styrene product is 1-1.6.
In the above technical scheme, in the step (2), the sewage is pumped into a centrifugal pump II, and the operating conditions of the centrifugal pump II are as follows: flow 4.9m 3 H, 55m of lift and 40 ℃ of operating temperature.
In the above technical solution, in the step (3), the coalescer has the following operating conditions: the temperature is 40 ℃ and the pressure is 0.5Mpa (g).
In the above technical solution, in the step (4), the refining tower has the following operating conditions: the temperature of the tower top is 70-74 ℃, and the pressure is-93 to-90 KPa (g); the temperature of the tower bottom is 88-95 ℃, and the pressure is-86 to-82 KPa (g).
In the technical scheme, in the step (4), a middle measuring line of the refining tower is used for extracting a refined styrene product, and the content of a styrene polymer in the refined styrene product is less than or equal to 10mg/kg.
In the technical scheme, in the step (5), the topped styrene is extracted and sent to a carbon nine product synthesis pipeline (DN 50), and the flow rate of the extraction is controlled to be between 20 and 30 kg/h.
In the above technical solution, in the step (5), the ratio of the reflux amount to the feeding amount of the crude styrene is 2.5.
The invention also provides a device for reducing the content of aldehyde substances in the styrene product, which comprises a mixer I, an alkaline washing tank, a mixer II, a water washing tank, a coalescer and a refining tower which are connected in sequence, and is characterized in that:
mixer I, be provided with feed inlet A and discharge gate A, wherein: the feed inlet A is divided into two paths, one path is connected with a device capable of providing crude styrene, and the other path is connected with a device capable of providing alkali liquor; the discharge port A is connected with an alkaline washing tank;
the alkaline washing tank is provided with a feeding hole B, a discharging hole B1 and a discharging hole B2, wherein: the feed inlet B is connected with the discharge outlet A of the mixer; the discharge port B1 is connected with a centrifugal pump I, the outlet of the centrifugal pump I is divided into two paths, one path is connected with the feed port A of the mixer I, and the other path is connected with a waste alkali oxidation treatment system; the discharge port B2 is connected with the mixer II;
mixer II, be provided with feed inlet C1, feed inlet C2 and discharge gate C, wherein: the feed inlet C1 is connected with a discharge outlet B2 of the alkaline washing tank; the feed inlet C2 is connected with a device capable of supplying water; the discharge port C is connected with a washing tank;
the washing tank, be provided with feed inlet D, discharge gate D1 and discharge gate D2, wherein: the feed inlet D is connected with the discharge outlet C of the mixer II; the discharge port D1 is connected with a centrifugal pump II, the outlet of the centrifugal pump II is divided into two paths, one path is connected with the feed port C2 of the mixer II, and the other path is connected with a sewage treatment plant; the discharge port D2 is connected with the coalescer;
the coalescer, be provided with feed inlet E and discharge gate E, wherein: the feed inlet E is connected with a discharge outlet D2 of the washing tank; the discharge hole E is connected with the refining tower;
the refining tower, tower wall one side middle part be provided with feed inlet F, the well upper portion of tower wall opposite side is provided with discharge gate F1, upper portion is provided with the backward flow mouth, the top of the tower is provided with discharge gate F2, wherein: the feed port F is connected with a discharge port E of the coalescer; the discharge port F1 is connected with a fine styrene product harvesting device; the discharge port F2 is sequentially connected with a condenser, a reflux tank and a centrifugal pump III, the outlet of the reflux pump III is divided into two paths, one path is connected with a reflux port, and the other path is connected with a carbon nine product synthesis pipeline.
The mixer I, the alkaline washing tank, the centrifugal pump I, the mixer II, the water washing tank, the centrifugal pump II, the coalescer, the refining tower, the condenser, the reflux tank and the centrifugal pump III which are adopted in the invention are all conventional and existing equipment (and equipment with similar functions) in the prior art.
The technical scheme of the invention has the advantages that: the added pipeline has simple process and convenient control, and greatly reduces the aldehyde content in the styrene product.
Drawings
FIG. 1 is a process flow diagram of the process of the present invention;
FIG. 2 is a schematic view of the overall structure of the apparatus of the present invention;
wherein: 1 is a mixer I,2 is an alkali washing tank, 3 is a centrifugal pump I,4 is a mixer II,5 is a water washing tank, 6 is a centrifugal pump II,7 is a coalescer, 8 is a refining tower, 9 is a condenser, 10 is a reflux tank, and 11 is a centrifugal pump III.
Detailed Description
The following detailed description of the embodiments of the present invention is provided, but the present invention is not limited to the following description:
the invention provides a device for reducing the content of aldehyde substances in a styrene product, which comprises a mixer I1, an alkaline washing tank 2, a mixer II 4, a water washing tank 5, a coalescer 7 and a refining tower 8 which are connected in sequence, and is shown in figure 2:
mixer I1, be provided with feed inlet A and discharge gate A, wherein: the feed inlet A is divided into two paths, one path is connected with a device capable of providing crude styrene, and the other path is connected with a device capable of providing alkali liquor; the discharge port A is connected with an alkaline washing tank;
the alkaline washing tank 2 is provided with a feeding hole B, a discharging hole B1 and a discharging hole B2, wherein: the feed inlet B is connected with the discharge outlet A of the mixer; the discharge port B1 is connected with a centrifugal pump I3, the outlet of the centrifugal pump I is divided into two paths, one path is connected with the feed port A of the mixer I, and the other path is connected with a waste alkali oxidation treatment system; the discharge port B2 is connected with a mixer II 4;
mixer II 4, be provided with feed inlet C1, feed inlet C2 and discharge gate C, wherein: the feed inlet C1 is connected with a discharge outlet B2 of the alkaline washing tank; the feed inlet C2 is connected with a device capable of providing water; the discharge port C is connected with a washing tank 5;
washing jar 5, be provided with feed inlet D, discharge gate D1 and discharge gate D2, wherein: the feed inlet D is connected with the discharge outlet C of the mixer II; the discharge port D1 is connected with a centrifugal pump II 6, the outlet of the centrifugal pump II is divided into two paths, one path is connected with the feed port C2 of the mixer II, and the other path is connected with a sewage treatment plant; the discharge port D2 is connected with the coalescer 7;
the coalescer 7 is provided with a feed inlet E and a discharge outlet E, wherein: the feed inlet E is connected with a discharge outlet D2 of the washing tank; the discharge hole E is connected with the refining tower;
refining tower 8, tower wall one side middle part be provided with feed inlet F, the well upper portion of tower wall opposite side is provided with discharge gate F1, upper portion is provided with the backward flow mouth, the top of the tower is provided with discharge gate F2, wherein: the feed port F is connected with a discharge port E of the coalescer; the discharge port F1 is connected with a fine styrene product harvesting device; the discharge port F2 is sequentially connected with a condenser 9, a reflux tank 10 and a centrifugal pump III 11, the outlet of the reflux pump III is divided into two paths, one path is connected with a reflux port, and the other path is connected with a carbon nine product synthesis pipeline.
The invention also provides a method for reducing the content of aldehyde substances in a styrene product, and the flow chart is shown as figure 1, and the method comprises the following steps:
(1) Alkali washing treatment: mixing the crude styrene subjected to acid substance decolorization treatment and an alkali liquor in a mixer I1, and then sending the mixture into an alkali washing tank 2, wherein the alkali liquor and residual acid substances in the crude styrene undergo neutralization reaction to obtain alkali washing water, and the alkali washing water contains the alkali liquor and salt products generated by the neutralization reaction, so that the pH value of the alkali washing water is ensured to be weakly acidic or weakly alkaline; the product obtained after the alkali washing treatment can be settled in an alkali washing tank 2 due to the density difference, so that alkali washing water and a styrene crude product are obtained; sending alkaline washing water into a centrifugal pump I3, returning a part of the alkaline washing water into a mixer I for recycling, and sending the other part of the alkaline washing water into a waste alkali oxidation system for treatment; washing the styrene crude product with water;
(2) And (3) water washing treatment: mixing the styrene crude product obtained in the step (1) with water in a mixer II 4, and then sending the mixture into a washing tank 5, wherein the water dissolves residual acidic substances in the styrene crude product and controls the content of the acidic substances in the styrene crude product to be less than 600ppm, and after the washing treatment is finished, a styrene product is obtained at the upper layer, and sewage is obtained at the lower layer; the sewage mainly contains desalted water, salt-containing and alkali-containing sewage and acidic substances, the sewage is sent into a centrifugal pump II 6, one part of the sewage is returned into a mixer II for cyclic utilization, and the other part of the sewage is sent into a sewage treatment plant for treatment; dehydrating the styrene product;
(3) And (3) dehydration treatment: sending the styrene product obtained in the step (2) into a coalescer 7 for dehydration treatment until the water content in the styrene product is less than 0.1 percent (mass percentage);
(4) Refining treatment: feeding the styrene product obtained after dehydration treatment in the step (3) into a refining tower 8, after refining to remove heavy component polymers, extracting a fine styrene product from the middle lateral line, extracting topped styrene from the tower top, and enriching aldehyde substances in the topped styrene;
(5) Aldehyde removal reflux treatment: condensing the topped styrene extracted in the step (4) by a condenser 9, and then introducing the condensed topped styrene into a reflux tank 10, wherein an outlet of the reflux tank is provided with a centrifugal pump III (11), the outlet is divided into two paths, one path is connected with a reflux port of a refining tower for reflux, and the other path is extracted and sent to a C nine product synthesis pipeline (DN 50) for providing raw materials for the C nine product.
The invention will now be illustrated with reference to specific examples:
in the following examples of the invention, the purity of the crude styrene is not less than 99.5% (wt), the xylene is less than 0.2% (wt), and the alkali solution is 20% sodium hydroxide aqueous solution.
Example 1:
a method for reducing aldehydes in a styrene product, comprising the steps of:
(1) Alkali washing: mixing crude styrene (3.5 t/h) subjected to acid substance decolorization treatment and alkali liquor (44 kg/h) in a mixer I1, then sending the mixture into an alkaline washing tank 2, and performing neutralization reaction by using the alkali liquor and residual acid substances in the crude styrene to ensure that the pH value of alkaline washing water after alkaline washing is about 7; the product obtained after the alkali washing treatment can be settled in an alkali washing tank 2 due to the density difference, and alkali washing water and a styrene crude product are obtained after settlement treatment (the treatment time is 4 hours); the alkali washing water enters a centrifugal pump I3 (the rated flow rate of the centrifugal pump I is 5m3/h, the lift is 55m, and the operating temperature is 40 ℃), part of the alkali washing water is returned to a mixer I for cyclic utilization after the concentration of the alkali washing water is adjusted, and the other part of the alkali washing water is sent to a waste alkali oxidation system for treatment; washing the styrene crude product with water;
(2) Washing with water: mixing the styrene crude product (3.5 t/h) obtained in the step (1) with water (65 kg/h) in a mixer II 4, and then sending the mixture into a washing tank 5, wherein the water dissolves residual acidic substances in the styrene crude product and controls the content of the acidic substances in the styrene crude product to be less than 600ppm, and after washing treatment, the styrene product is obtained at the upper layer and sewage is obtained at the lower layer; the sewage mainly contains desalted water, salt-containing and alkali-containing sewage and acid-containing substances, and is sent to a centrifugal pump II (the flow rate is 4.9 m) 3 In the temperature of 40 ℃) of the operation temperature, returning a part of sewage to the mixer II for recycling, and sending a part of sewage to a sewage treatment plant for treatment; dehydrating the styrene product;
(3) And (3) dehydrating: sending the styrene product obtained in the step (2) into a coalescer 7 for dehydration treatment until the water content in the styrene product is less than 0.1 percent (mass percentage); the coalescer is operated under the following conditions: temperature 40 deg.C, pressure 0.5Mpa (g);
(4) Refining treatment: feeding the styrene product obtained after dehydration treatment in the step (3) into a refining tower 8, wherein the operating conditions of the refining tower are as follows: the temperature of the tower top is 70-74 ℃, and the pressure is-93 to-90 KPa (g); the temperature of the tower kettle is 88 to 95 ℃, and the pressure is minus 86 to minus 82KPa (g); after the heavy component polymer is removed by refining, a styrene fine product is extracted from a middle measuring line, and the content of the styrene polymer in the styrene fine product is less than or equal to 10mg/kg; the top of the tower is extracted with topped styrene (enriched with aldehydes);
(5) Removing aldehyde and refluxing: leading the topped styrene extracted in the step (4) into a reflux tank 10 after being condensed by a condenser 9, wherein an outlet of the reflux tank is provided with a centrifugal pump III 11, the outlet is divided into two paths, one path of the outlet is connected with a reflux port of a refining tower for reflux, and the reflux ratio is 2.5:1 (the ratio of the reflux amount to the feeding amount of the crude styrene), and feeding the recovered product in one path (the recovered flow is 25 kg/h) into a carbon nine product synthesis pipeline (DN 50).
After the scheme is implemented, the content of the styrene refined product aldehyde is not more than 100mg/kg and about 60mg/kg, and the requirement of a high-grade product is met.
Comparative example:
(1) Under the conditions of no alkaline washing and no water washing, crude styrene is decolored and then directly enters a refining tower, the operating conditions of the refining tower are the same as those of the embodiment 1, a styrene product is extracted from a lateral line, and topped styrene is extracted from a tower top and is condensed and then enters a reflux tank for total reflux operation.
After the device runs for 30 days, the content of aldehyde in the styrene product exceeds 200mg/kg and is 250 +/-5 mg/kg, and the requirement of the specification of the styrene product cannot be met.
(2) Under the conditions of no alkaline washing and no water washing, crude styrene is decolored and then directly enters a refining tower, the operating conditions of the refining tower are the same as those of the embodiment 1, a styrene product is extracted from the top of the tower, the styrene product is condensed and then enters a reflux tank, a part of the styrene product is extracted, a part of the styrene product is refluxed, and the reflux ratio is 2.5:1 (ratio of reflux to crude styrene feed).
After the device runs for 15 days, the content of aldehyde in the styrene product exceeds 200mg/kg and is 250 +/-5 mg/kg, and the requirement of the specification of the styrene product cannot be met.
(3) Under the conditions of alkali washing and water washing, the crude styrene directly enters a refining tower after alkali washing and water washing, the operation conditions of the refining tower are the same as those of the embodiment 1, a styrene product is extracted from a lateral line, and topped styrene is extracted from the top of the tower and enters a reflux tank for total reflux operation after being condensed.
After the device runs for 60 days, the content of aldehyde in the styrene product exceeds 200mg/kg and is 210 +/-5 mg/kg, and the requirement of the specification of the styrene product cannot be met.
(4) Under the conditions of alkaline washing and water washing, crude styrene is decolored and then directly enters a refining tower, the operating conditions of the refining tower are the same as those of the embodiment 1, a styrene product is extracted from the top of the tower, the styrene product is condensed and then enters a reflux tank, a part of the styrene product is extracted, a part of the styrene product is refluxed, and the reflux ratio is 2.5:1 (ratio of reflux to crude styrene feed).
After the device is operated for 25 days, the content of aldehyde in the styrene product exceeds 200mg/kg and is 210 +/-5 mg/kg, and the requirement of the specification of the styrene product cannot be met.
(5) Under the conditions of alkaline washing and water washing, crude styrene is decolored and then directly enters a refining tower, the operating conditions of the refining tower are the same as those of the embodiment 1, a styrene product is extracted from the top of the tower, the styrene product is condensed and then enters a reflux tank, a pipeline (DN 50) reaching a carbon nine product is added to an outlet of a reflux pump, a part of the styrene product is directly extracted, and a part of the styrene product is extracted (the extraction flow is 25 kg/h) and then is sent to the carbon nine product.
After the device runs for 180 days, the content of aldehyde in the styrene product exceeds 200mg/kg and is about 205 +/-5 mg/kg, and the requirement of the specification of the styrene product cannot be met.
From the above results, it can be seen that: under the condition that a pipeline (DN 50) leading to a carbon nine product is not added at the outlet of the reflux pump, the aldehyde substances are easy to be enriched in the refining tower, the enriched aldehyde substances are easy to be brought into the styrene product, the quality of the styrene product is influenced, and the aldehyde substances can not influence the quality of the styrene product only by sending the enriched aldehyde substances out of the system.
By combining the factors, after the crude styrene is decolorized, the crude styrene enters a styrene refining tower after alkali washing, water washing and dehydration, a side line is extracted, a pipeline (DN 50) reaching a carbon nine product is added at the outlet of a reflux pump, and a part of the topped styrene is extracted into the carbon nine product, so that the aldehyde substances in the styrene product can be greatly reduced, and the styrene product can meet the quality requirement.
The above examples are only for illustrating the technical concept and features of the present invention, and are not intended to limit the scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered in the protection scope of the present invention.

Claims (10)

1. A method for reducing the content of aldehydes in a styrene product is characterized by comprising the following steps:
(1) Alkali washing treatment: after the crude styrene is decolorized by acidic substances, the crude styrene enters an alkaline washing system to neutralize redundant acidic substances, and the pH value of alkaline washing water after alkaline washing is ensured to be weakly acidic or weakly alkaline;
(2) And (3) water washing treatment: after the alkali washing treatment in the step (1), the product enters a washing system, and redundant alkali liquor and salt substances in the styrene are removed by using water;
(3) And (3) dehydration treatment: after the water washing treatment in the step (2), the product enters a coalescer for dehydration treatment to remove redundant water in the product;
(4) Refining treatment: after the dehydration treatment in the step (3), the dehydrated styrene enters a refining tower for refining treatment, heavy component polymers are removed, and fine styrene products are extracted from the middle side line;
(5) Aldehyde removal reflux treatment: the top of the refining tower extracts the topped styrene, one part of which flows back, and the other part of which is sent to a synthesis pipeline of a carbon nine product.
2. The method according to claim 1, characterized in that the method comprises in particular the steps of:
(1) Alkali washing treatment: mixing the crude styrene subjected to acid substance decolorization treatment and an alkali liquor in a mixer I (1), and then sending the mixture into an alkali washing tank (2), wherein the alkali liquor and residual acid substances in the crude styrene undergo a neutralization reaction to obtain alkali washing water, and the alkali washing water contains the alkali liquor and salt products generated by the neutralization reaction, so that the pH value of the alkali washing water is ensured to be weakly acidic or weakly alkaline; the product obtained after the alkali washing treatment can be settled in an alkali washing tank (2) due to the density difference, so that alkali washing water and a styrene crude product are obtained; sending alkaline washing water into a centrifugal pump I (3), returning a part of alkaline washing water into a mixer I for recycling, and sending the other part of alkaline washing water into a waste alkali oxidation system for treatment; washing the styrene crude product with water;
(2) And (3) water washing treatment: mixing the styrene crude product obtained in the step (1) with water in a mixer II (4), and then sending the mixture into a washing tank (5), wherein the water dissolves residual acidic substances in the styrene crude product and controls the content of the acidic substances in the styrene crude product to be less than 600ppm, and after the washing treatment is finished, a styrene product is obtained at the upper layer, and sewage is obtained at the lower layer; the sewage mainly contains desalted water, salt-containing sewage, alkali-containing sewage and acidic substances, the sewage is sent into a centrifugal pump II (6), one part of the sewage returns to a mixer II for cyclic utilization, and the other part of the sewage is sent into a sewage treatment plant for treatment; dehydrating the styrene product;
(3) And (3) dehydration treatment: sending the styrene product obtained in the step (2) into a coalescer (7) for dehydration treatment until the water content in the styrene product is less than 0.1 percent (mass percentage);
(4) Refining treatment: feeding the styrene product obtained after dehydration treatment in the step (3) into a refining tower (8), after refining to remove heavy component polymers, collecting a fine styrene product from the middle lateral line, collecting topped styrene from the top of the tower, and enriching aldehyde substances in the topped styrene;
(5) Aldehyde removal reflux treatment: condensing the topped styrene extracted in the step (4) by a condenser (9) and then introducing the condensed topped styrene into a reflux tank (10), wherein an outlet of the reflux tank is provided with a centrifugal pump III (11), the outlet is divided into two paths, one path of the outlet is connected with a reflux port of a refining tower for reflux, and the other path of the outlet is extracted and sent to a C nine product synthesis pipeline (DN 50) to provide raw materials for the C nine product.
3. The method of claim 2, wherein: in the step (1), the alkali liquor is a sodium hydroxide aqueous solution with the mass content of 20%, the concentration of the alkali washing water needs to be adjusted before the alkali washing water returns to the mixer I for recycling, and the alkali washing water is recycled after the mass content of the sodium hydroxide is adjusted to 20%.
4. The method of claim 2, wherein: in the step (1), the alkaline washing water has a pH value of 6-8; the settling time is 4-6h.
5. The method of claim 2, wherein: in the step (1) and the step (2), the mass ratio of the water to the crude styrene product is 1-1.6.
6. The method of claim 2, wherein: in the step (3), the coalescer is operated under the following conditions: the temperature is 40 ℃ and the pressure is 0.5MPa (g).
7. The method of claim 2, wherein: in the step (4), the refining tower has the following operating conditions: the temperature of the tower top is 70-74 ℃, and the pressure is-93 to-90 KPa (g); the temperature of the tower bottom is 88-95 ℃, and the pressure is-86 to-82 KPa (g).
8. The method of claim 2, wherein: in the step (5), the topped styrene is extracted and sent to a carbon nine product synthesis pipeline (DN 50), and the flow rate of the extraction is controlled between 20 and 30 kg/h.
9. The method of claim 2, wherein: in the step (5), the ratio of the reflux amount to the feeding amount of the crude styrene is 2.5.
10. The utility model provides a reduce device of aldehyde substance content in styrene product, includes consecutive blender I (1), alkali wash jar (2), blender II (4), washing jar (5), coalescer (7), refining tower (8), its characterized in that:
mixer I (1), be provided with feed inlet A and discharge gate A, wherein: the feed inlet A is divided into two paths, one path is connected with a device capable of providing crude styrene, and the other path is connected with a device capable of providing alkali liquor; the discharge port A is connected with an alkaline washing tank;
the alkaline washing tank (2) is provided with a feeding hole B, a discharging hole B1 and a discharging hole B2, wherein: the feed inlet B is connected with the discharge outlet A of the mixer; the discharge port B1 is connected with a centrifugal pump I (3), the outlet of the centrifugal pump I is divided into two paths, one path is connected with the feed port A of the mixer I, and the other path is connected with a waste alkali oxidation treatment system; the discharge port B2 is connected with a mixer II (4);
mixer II (4), be provided with feed inlet C1, feed inlet C2 and discharge gate C, wherein: the feed inlet C1 is connected with a discharge outlet B2 of the alkaline washing tank; the feed inlet C2 is connected with a device capable of providing water; the discharge port C is connected with a washing tank (5);
washing jar (5), be provided with feed inlet D, discharge gate D1 and discharge gate D2, wherein: the feed inlet D is connected with the discharge outlet C of the mixer II; the discharge port D1 is connected with a centrifugal pump II (6), the outlet of the centrifugal pump II is divided into two paths, one path is connected with the feed port C2 of the mixer II, and the other path is connected with a sewage treatment plant; the discharge port D2 is connected with a coalescer (7);
the coalescer (7) is provided with a feed inlet E and a discharge outlet E, wherein: the feed inlet E is connected with a discharge outlet D2 of the washing tank; the discharge hole E is connected with the refining tower;
refining tower (8), tower wall one side middle part be provided with feed inlet F, the well upper portion of tower wall opposite side is provided with discharge gate F1, upper portion is provided with the backward flow mouth, the top of the tower is provided with discharge gate F2, wherein: the feed port F is connected with the discharge port E of the coalescer; the discharge port F1 is connected with a styrene fine product harvesting device; the discharge port F2 is sequentially connected with a condenser (9), a reflux tank (10) and a centrifugal pump III (11), the outlet of the reflux pump III is divided into two paths, one path is connected with a reflux port, and the other path is connected with a carbon nine product synthesis pipeline.
CN202110630166.1A 2021-06-07 2021-06-07 Method for reducing content of aldehyde substances in styrene product Pending CN115504852A (en)

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