JP2016221443A - Method for processing liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for processing liquid for preventing foam formation of a concentrated liquid when concentrating a liquid containing a quinone compound.SOLUTION: The method for processing liquid is a processing method for a liquid including a concentration process of concentrating a liquid containing a quinone compound and the liquid is concentrated with mass concentration of the quinone compound in a concentrated liquid after concentration of 500 ppm or less in the concentration process.SELECTED DRAWING: None

Description

  The present invention relates to a method for treating a liquid containing a quinone compound.

  A method of producing unsaturated nitriles by gas phase fluidized bed reaction using hydrocarbon, ammonia and oxygen-containing gas as raw materials is widely known as an ammoxidation reaction, and in particular, production of acrylonitrile by ammoxidation reaction of propylene, Widely used industrially. The reaction gas containing acrylonitrile by the ammoxidation reaction is used to remove unreacted ammonia by the ammonia absorption tower and then send the process liquid to the acrylonitrile absorption tower, recovery tower, purification tower, and rectification tower in order to purify the product acrylonitrile. It is carried out. In the purification, waste water is generated mainly in the ammonia absorption tower and the acrylonitrile recovery tower. In Patent Document 1, cyanides and organic pollutants (COD) contained in a process waste liquid produced when ammonitrile is used to produce acrylonitrile or methacrylonitrile by ammoxidation of propylene or isobutylene, a cyan concentration of 50 to A wastewater treatment method is described in which the process wastewater of 300 ppm and COD of 100 to 500 ppm is oxidized and then oxidized with ozone.

  In Patent Document 2, two identical or different hydrocarbon groups selected from the group consisting of a methyl group, an ethyl group, a propyl group, a butyl group, and a phenyl group are bonded to a nitrogen atom and A vinyl compound polymerization inhibitor containing, as an active ingredient, at least one of dithiocarbamic acid manganese salt, which may be a linear or branched propyl group or butyl group, is described. ing.

Japanese Patent Application Laid-Open No. 6-154771 JP-A-5-51403

  When the wastewater collected in the wastewater tank is concentrated, for example, when a production plant for acrylonitrile or the like is stopped, the concentrated solution being concentrated may foam.

  The inventor of the present application noticed that the cause of foaming was methoquinone because the concentrated liquid foamed after the residual liquid of methoquinone used as a polymerization inhibitor when purifying acrylonitrile was placed in a wastewater tank. And it confirmed that high concentration methoquinone was contained in waste water by the analysis by the acid component analysis by CE (capillary electrophoresis) and the analysis by GC-MS (gas chromatograph-mass spectrometry). From the above, it was specified that the substance causing foaming of the concentrate was methoquinone.

  In addition to methoquinone, quinone compounds such as hydroquinone are considered to be foamed when present in the concentrate.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a wastewater treatment method that prevents foaming of a concentrate when concentrating wastewater containing a quinone compound.

  In order to solve the above-mentioned problems, the present inventors have intensively studied, and as a result, have reached the following present invention.

  That is, the liquid processing method according to the present invention is a liquid processing method including a concentration step of concentrating a liquid containing a quinone compound, and in the concentration step, the mass concentration of the quinone compound in the concentrated liquid after concentration is The liquid is concentrated so as to be 500 ppm or less.

  In the liquid treatment method according to the present invention, the liquid is waste water generated from an apparatus for producing acrylonitrile or methacrylonitrile by an ammoxidation reaction.

  In the liquid treatment method according to the present invention, the quinone compound is at least one of hydroquinone and methoquinone.

  Further, the liquid treatment method according to the present invention includes a post-treatment step of performing, after the concentration step, another treatment different from the concentration on the concentrate having a mass concentration of the quinone compound of 500 ppm or less. It is characterized by.

  Further, in the liquid treatment method according to the present invention, the post-treatment step is an incineration step of incinerating the concentrate or an activated sludge treatment step of mixing the concentrate and activated sludge.

  The present invention has an effect of preventing foaming of a concentrated liquid when concentrating waste water containing a quinone compound.

It is a flowchart which shows the manufacturing process of the acrylonitrile or methacrylonitrile by the ammoxidation reaction which produces the waste water for processing with the processing method of the liquid which concerns on this invention. It is a graph which shows the relationship between the pH of the methoquinone aqueous solution obtained by the foaming test prior to the concentration test, and the maximum height of the foam on the surface of the aqueous methoquinone solution of wastewater treated by the liquid treatment method according to the present invention. It is a graph which shows the relationship between the mass concentration and the amount of foaming of the methoquinone and hydroquinone added to the concentrate obtained by the foamability test with respect to the concentrate during concentration by the liquid processing method according to the present invention.

<Liquid processing method>
The liquid treatment method according to the present invention is a liquid treatment method including a concentration step of concentrating a liquid containing a quinone compound, and in the concentration step, the mass concentration of the quinone compound in the concentrated solution after concentration is 500 ppm or less. The liquid is concentrated so that Thereby, when condensing the liquid containing a quinone compound, foaming of a concentrate can be prevented.

[Liquid containing quinone compound]
The liquid treatment method according to the present invention can treat various liquids as long as the liquid contains a quinone compound.

  The quinone compound may be a compound having a structure of o-benzoquinone or p-benzoquinone and a derivative thereof. Specific examples of the quinone compound include hydroquinone, methoquinone, 1,4-benzoquinone, 1,4-naphthoquinone, and the like. The quinone compound contained in the liquid to be treated may be one kind or plural kinds. When a plurality of quinone compounds are contained, in the concentration step, the liquid is concentrated so that the total mass concentration of the quinone compounds is 500 ppm or less.

  Examples of the liquid containing a quinone compound include waste water generated from an apparatus for producing acrylonitrile or methacrylonitrile (hereinafter also referred to as “acrylonitrile”) by an ammoxidation reaction. The present invention can be suitably used for such waste water.

  The “waste water generated from the manufacturing apparatus” does not mean only the waste water generated from the apparatus when acrylonitrile or the like is manufactured. Manufacture acrylonitrile, etc., when the equipment is being maintained when acrylonitrile, etc. is not being manufactured, when operations are being performed to stop manufacturing, when the equipment is being started up to start manufacturing, etc. It means all the waste water from the equipment for manufacturing, whether or not.

[Concentration process]
A concentration process is a process of concentrating the liquid containing a quinone compound.

  In the concentration step, the waste water may be concentrated so that the mass concentration of the quinone compound in the concentrated liquid obtained after concentration is 500 ppm or less. Furthermore, it is preferable to concentrate so that mass concentration may be 300 ppm or less.

  Further, the concentration may be performed in one step, or may be performed in multiple steps of two or more steps. Examples of the method for concentration in two stages include the following methods. That is, the first concentrated liquid obtained after concentration in the first stage and the gas evaporated when concentrated are passed through a gas-liquid separator to separate the first concentrated liquid and the gas. A second stage of concentration is performed on the first concentrated liquid. The gas separated by the gas-liquid separator may be compressed and liquefied, and returned to the concentrator that performs the first-stage concentration, or may be put into the concentrator that performs the second-stage concentration. Then, the second concentrated liquid concentrated in two stages is recovered as the finally obtained concentrated liquid.

  When the wastewater is concentrated in two stages, it is preferable to concentrate so that the mass concentration of the quinone compound in the first concentrated liquid after the concentration of the wastewater in the first stage is 500 ppm or less. What is necessary is just to concentrate so that it may also be 500 ppm or less also about the mass concentration of the quinone compound in the 2nd concentrate after condensing wastewater at the 2nd step.

  Although the specific method for concentrating is not particularly limited, heating concentration by heating is preferable. It is because it can concentrate efficiently in a short time.

  The heating temperature for heat concentration is preferably in the range of 85 ° C. or higher and 110 ° C. or lower.

  It is preferable to apply pressure when heating. The applied pressure is preferably in the range of 6 kPa to 300 kPa.

  As for the volume and mass of wastewater to be reduced by concentration, it is more preferable to reduce as much as possible as long as the mass concentration of the quinone compound is 500 ppm or less. This is because the treatment performed after the concentration is facilitated.

[Post-treatment process]
The liquid treatment method according to the present invention may include a post-treatment step of performing another treatment different from the concentration on the concentrate having a mass concentration of the quinone compound of 500 ppm or less after the concentration step.

  The concentrated solution after the concentration step is suppressed from foaming and entraining. Therefore, for example, another process for treating waste water can be performed with a lower possibility of troubles caused by foaming.

  The post-treatment process may be appropriately selected according to the purpose of the liquid treatment, and examples thereof include an incineration treatment in which the concentrated liquid is incinerated, and an activated sludge treatment in which the concentrated liquid and activated sludge are mixed. In the post-processing step, only one type of processing may be performed alone, or a plurality of types of processing may be performed together.

  The temperature at the time of incineration is preferably in the range of 800 ° C. or higher and 1100 ° C. or lower, for example.

  About activated sludge processing, according to a well-known method, a concentrated liquid and activated sludge should be mixed, and a sludge should be activated by aeration suitably according to the kind of sludge. Further, dust generated by the incineration process may be collected and added to the activated sludge.

[Example of equipment for producing acrylonitrile by ammoxidation reaction]
Next, an example of an apparatus for producing acrylonitrile or methacrylonitrile by an ammoxidation reaction will be described with reference to FIG. Thereby, the waste water which is an example of the liquid processed with the processing method of the liquid which concerns on this invention is demonstrated.

  First, hydrocarbon A, ammonia B, and oxygen-containing gas C are introduced into the reactor 11, and an ammoxidation reaction is performed using an ammoxidation catalyst.

  Examples of the hydrocarbon A include olefins such as propylene, propane, isobutylene, or a mixed gas thereof. In addition, as the oxygen-containing gas C, air that is usually low-cost is used, but if the gas contains a necessary concentration of oxygen, the remaining components are composed of a mixed gas composed of an inert gas. It is also possible.

  As the ammoxidation catalyst, for example, a well-known composite metal oxide catalyst containing an element such as phosphorus, molybdenum, iron or antimony can be used.

  The ammoxidation reaction gas D extracted from the reactor 11 is supplied to the ammonia absorption tower 12. The ammonia absorption tower 12 is also supplied with sulfuric acid water E. The ammoxidation reaction gas D is cooled in direct contact with the sulfuric acid water E. In contact with the sulfuric acid water E, the unreacted ammonia gas in the ammoxidation reaction gas D is neutralized and removed from the system as an aqueous ammonium sulfate solution F.

  The separation gas G from which unreacted ammonia has been removed is supplied to the acrylonitrile absorption tower 13. The supplied separation gas G is absorbed into the acrylonitrile absorption solvent H supplied to the acrylonitrile absorption tower 13. Specifically, the acrylonitrile absorbing solvent H absorbs by-products such as acrylonitrile, hydrocyanic acid, acetonitrile, and acrolein. Thereafter, the acrylonitrile-absorbing solvent H (bottom liquor I) that has absorbed acrylonitrile, hydrocyanic acid and the like is withdrawn from the bottom of the column. The acrylonitrile absorbing solvent H may be any solvent that does not adversely affect the subsequent process, and an aqueous solution and water in which an organic solvent is dissolved are preferable.

  The bottoms I extracted from the bottom of the acrylonitrile absorption tower 13 is supplied to the acrylonitrile recovery tower 14. In the acrylonitrile recovery column 14, water vapor having an azeotropic composition amount of gaseous acrylonitrile and hydrocyanic acid and acrylonitrile as a main component is recovered as a column top liquid K from the column top by means such as stripping or distillation and sent to the next step. It is done.

  In the acrylonitrile recovery tower 14, gaseous impurities such as acetonitrile are extracted as a mixed gas J from the upper stage to the vicinity of the middle stage. This is sent to the acetonitrile separation column 21 to separate gas components such as acetonitrile, and the residual water N is returned to the acrylonitrile recovery column 14 for use. Furthermore, when impurities remaining in the acrylonitrile recovery tower 14 increase, the accumulation of impurities in the acrylonitrile recovery tower 14 is prevented by appropriately extracting the liquid in the tower as the impurities M.

  In the acrylonitrile recovery tower 14, the bottom liquid after removing the top liquid K and the mixed gas J is appropriately extracted. The waste water L extracted from the acrylonitrile recovery tower 14 is treated by the liquid treatment method according to the present invention. As will be described later, since the quinone compound is used as a polymerization inhibitor in a later process, the possibility that the quinone compound is contained in the waste water L is low in the production process. However, the waste water L when the polymerization inhibitor (quinone compound) is recovered during the production stop operation is suitably treated by the liquid treatment method according to the present invention. That is, the concentration of the quinone compound is controlled when the operation of the apparatus is stopped and the residue of each tower and each tank provided in the apparatus is collected in a wastewater tank (not shown) via the acrylonitrile recovery tower 14. Thus, foaming and splashing can be suppressed by concentration. Here, based on the foamability of the quinone compound obtained by the present inventors, the concentration of the quinone compound in the wastewater L may be controlled.

  The tower top liquid K is supplied to the dehydrating acid tower 15 to separate the hydrocyanic acid O in the tower top liquid K. The remaining liquid after the cyanide O is separated is taken out as a bottoms P from the tower bottom. In the dehydration acid tower 15, hydroquinone, which is a quinone compound, is supplied in order to suppress polymerization of acrylonitrile. Hydroquinone is stored in another tank (not shown), and is supplied to the dehydration acid tower 15 as necessary.

  Next, the bottoms P is supplied to the acrylonitrile purification tower 16 and dehydrated. The dehydrated liquid is taken out from the bottom of the tower as dehydrated canned liquid Q.

  In the acrylonitrile purification tower 16, hydroquinone is supplied in order to suppress polymerization of acrylonitrile. Hydroquinone is stored in another tank (not shown), and is supplied to the acrylonitrile purification tower 16 as necessary.

  The dewatered effluent Q sent to the rectification column 17 is purified to obtain acrylonitrile R. In the rectification column 17, methoquinone, which is a quinone compound, is supplied to suppress polymerization of acrylonitrile. Metoquinone is stored in a separate tank (not shown) and is supplied to the rectification column 17 as necessary.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

<Foaming test>
The relationship between the mass concentration of methoquinone and the height of bubbles on the surface of the aqueous solution of methoquinone was investigated. Specifically, the foaming test was performed using three types of aqueous methoquinone solutions having different mass concentrations of methoquinone in the aqueous solution.

  The pH of each aqueous solution was changed from 5.5 to 10.0, and the maximum height of bubbles at each pH was measured using a blow tube foaming test apparatus.

  The relationship between the pH of the aqueous solution of methoquinone and the maximum height of bubbles on the surface of the aqueous solution of methoquinone was plotted on a graph. The results are shown in FIG. FIG. 2 is a graph showing the relationship between the pH of the aqueous solution of methoquinone and the maximum height of bubbles on the surface of the aqueous solution of methoquinone, where the horizontal axis indicates pH, the vertical axis indicates the maximum height of bubbles (cm), the white circle is 50 ppm, The results when the black triangle is 1000 ppm and the white triangle is 1500 ppm are shown.

  As shown in FIG. 2, it was shown that foaming occurs when the mass concentration of methoquinone in the aqueous solution is high.

<Concentration test of wastewater>
[Example 1]
1 kg of recovery tower waste water with a hydroquinone mass concentration of 15 ppm in waste water was charged into a 1 L glass separable flask with a jacket, and concentrated to 0.05 kg by heating at 101 ° C. while pressurizing at 215 kPa.

  The height of the foam on the concentrated liquid surface during concentration was about 3.0 cm, and the foam could be stably concentrated without entrainment of bubbles.

[Example 2]
Metoquinone was added to 1 kg of recovery tower wastewater having a mass concentration of hydroquinone in the wastewater of 15 ppm so that the mass concentration of methoquinone in the recovery tower wastewater after the addition was 50 ppm. The recovery tower wastewater after the addition of methoquinone was put into a 1 L glass separable flask with a jacket, and concentrated to 0.33 kg by heating at 100 ° C. while being pressurized at 213.5 kPa.

  The height of the foam on the concentrated liquid surface during the concentration was about 2.5 cm, and the foam could be stably concentrated without entrainment of the foam.

Example 3
Metoquinone was added to 1 kg of recovery tower waste water having a hydroquinone mass concentration of 15 ppm so that the mass concentration of methoquinone in the recovery tower waste water after addition was 100 ppm. The recovery tower waste water after the addition of methoquinone was put into a 1 L glass separable flask with a jacket, and it was concentrated to 0.46 kg by heating at 101 ° C. while being pressurized at 216.0 kPa.

  The height of the foam on the concentrated liquid surface during the concentration was about 3 cm, and the foam could be stably concentrated without entrainment of bubbles.

Example 4
1 kg of recovery tower waste water having a hydroquinone mass concentration of 15 ppm in waste water was diluted 15 times with pure water so that the hydroquinone mass concentration in the recovered recovery tower waste water was 1 ppm. The recovered waste water after dilution was put into a 1 L glass separable flask with a jacket, and concentrated to 0.05 kg by heating at 101 ° C. while being pressurized at 215.6 kPa.

  The height of the foam on the concentrated liquid surface during the concentration was about 1.5 cm, and the foam could be stably concentrated without entrainment of bubbles.

[Comparative Example 1]
Metoquinone was added to 1 kg of recovery tower waste water having a hydroquinone mass concentration of 15 ppm so that the mass concentration of methoquinone in the recovery tower waste water after addition was 600 ppm. The recovery tower waste water after the addition of methoquinone was put into a 1 L glass separable flask with a jacket, and concentrated by heating at 101 ° C. while being pressurized at 215.6 kPa.

  During the concentration, the height of the foam on the surface of the concentrated liquid was about 5 cm, and a part of the concentrated wastewater was foamed and flowed into the effluent, so the concentration was interrupted.

[Comparative Example 2]
Metoquinone was added to 1 kg of recovery tower waste water having a hydroquinone mass concentration of 15 ppm so that the mass concentration of methoquinone in the recovery tower waste water after addition was 1000 ppm. The recovery tower waste water after the addition of methoquinone was put into a 1 L glass separable flask with a jacket, and concentrated by heating at 101 ° C. while being pressurized at 215.6 kPa.

  During the concentration, the height of the foam on the surface of the concentrated liquid was about 9 cm, and most of the concentrated wastewater was foamed and flowed into the effluent, so the concentration was interrupted.

[Comparative Example 3]
Metoquinone was added to 1 kg of recovery tower wastewater having a hydroquinone mass concentration of 15 ppm so that the mass concentration of methoquinone in the recovery tower wastewater after addition was 1500 ppm. The recovery tower waste water after the addition of methoquinone was put into a 1 L glass separable flask with a jacket, and concentrated by heating at 101 ° C. while being pressurized at 215.6 kPa.

  During the concentration, the height of the foam on the surface of the concentrated liquid was about 9 cm, and most of the concentrated wastewater was foamed and flowed into the effluent, so the concentration was interrupted.

<Bubbling test when methoquinone and hydroquinone are added to the concentrate>
In order to establish a control standard value for the mass concentration of methoquinone and hydroquinone added to the concentrate, methoquinone and hydroquinone were respectively added to the concentrate obtained by first concentrating waste water (waste liquid) collected from the recovery tower of the acrylonitrile production plant. The foaming property test was conducted.

  The recovery tower of the manufacturing plant is a plant that recovers, purifies, and purifies acrylonitrile, acetonitrile, and hydrocyanic acid, which are active ingredients, from the process liquid of the absorption tower that is the preceding process. Moreover, primary concentration refers to concentrating waste water 0.01 to 0.9 times under heating conditions.

  In addition, the foaming phenomenon was not seen in the concentrate which concentrated the waste water collect | recovered immediately after the start-up of a plant.

  Metoquinone was added to the concentrate to prepare a solution having a mass concentration of methoquinone in the range of 100 ppm to 800 ppm. For comparison, a concentrated solution to which no methoquinone was added was also subjected to subsequent tests.

  In addition, hydroquinone was added to the concentrated solution to prepare a solution having a hydroquinone mass concentration in the range of 200 ppm to 800 ppm.

  About each solution which added methoquinone or hydroquinone, the foaming amount (cm) in each mass concentration of methoquinone and hydroquinone was measured. The amount of foaming was measured by measuring the height of the foam.

  The results are shown in FIG. FIG. 3 is a diagram showing the results of examining the amount of foaming with respect to the concentration of the quinone compound in the concentrated liquid. When white circles add methoquinone, the white squares show results when hydroquinone is added. Further, in FIG. 3, the concentration of methoquinone in the concentrated liquid when foaming occurs during actual operation of the production plant, such as operation and stoppage, is also indicated by black squares.

  Moreover, in order to suppress the foaming amount to about 4 cm, it was found that the concentration of hydroquinone is preferably 500 ppm or less.

  In addition, the maximum mass concentration of methoquinone, which is the same foaming amount as the foaming amount when the hydroquinone mass concentration in the concentrate is 500 ppm, is 100 ppm, and these concentrations may be used as a reference when managing the manufacturing plant. It turned out to be more preferable.

  The present invention can be used in a method for treating a liquid containing a quinone compound.

DESCRIPTION OF SYMBOLS 11 Reactor 12 Ammonia absorption tower 13 Acrylonitrile absorption tower 14 Acrylonitrile recovery tower 15 Dehydration acid tower 16 Acrylonitrile purification tower 17 Rectification tower 21 Acetonitrile separation tower A Hydrocarbon B Ammonia C Oxygen-containing gas D Ammoxidation reaction gas E Sulfate water F Ammonium sulfate Aqueous solution G Separation gas H Acrylonitrile absorbing solvent I Bottom liquid J Mixed gas K Tower top liquid L Waste water M Drained impurities N Residual liquid O Blue acid P Bottom liquid Q Dehydrated bottom liquid R Acrylonitrile

Claims (5)

A liquid treatment method comprising a concentration step of concentrating a liquid containing a quinone compound,
In the concentration step, the liquid treatment method of concentrating the liquid so that the mass concentration of the quinone compound in the concentrated liquid after concentration is 500 ppm or less.   The liquid treatment method according to claim 1, wherein the liquid is wastewater generated from an apparatus for producing acrylonitrile or methacrylonitrile by an ammoxidation reaction.   The liquid treatment method according to claim 1, wherein the quinone compound is at least one of hydroquinone and methoquinone.   4. The post-treatment step according to claim 1, further comprising a post-treatment step of performing another treatment different from the concentration on the concentrate having a mass concentration of the quinone compound of 500 ppm or less after the concentration step. Liquid processing method.   The liquid processing method according to claim 4, wherein the post-treatment step is an incineration step of incinerating the concentrate or an activated sludge treatment step of mixing the concentrate and activated sludge.

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