KR950001398B1 - Waste water treatment in acryl acid plant - Google Patents

Abstract

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Description

Wastewater treatment method of (meth) acrylic acid manufacturing plant

1 to 4 are schematic flowcharts of a wastewater treatment method of a (meth) acrylic acid manufacturing plant.

5 is a schematic flowchart of a method for producing acrylic acid,

6 is a schematic flowchart of a method for producing methacrylic acid.

The present invention relates to a wastewater treatment method of a (meth) acrylic acid production plant for purification of (meth) acrylic acid by wet oxidation in the presence of a solid catalyst. More particularly, the present invention relates to the gas phase catalytic oxidation of isobutylene and / or t-butyl alcohol containing waste acetic acid and aldehyde from a plant producing acrylic acid by gas phase catalytic oxidation of propylene and / or acrolein. And a process for purifying wastewater from a plant producing methacrylic acid, the purification being carried out in the presence of a solid catalyst to wet oxidize organic matter present in the wastewater under a continuous supply of gas containing molecular oxygen and Subsequently, most of the organics are converted to harmless compounds such as carbon dioxide and water, making the wastewater permanently purified. Moreover, this invention relates to the manufacturing method of (meth) acrylic acid which combines the purification process of wastewater.

In general, as a method for treating wastewater from a (meth) acrylic acid manufacturing plant, an activated sludge method and a catalytic combustion method have already been known in the art. As is generally known, the disadvantages of activated sludge methods require a long time to decompose organic materials and further dilute the wastewater to a concentration suitable for algae and bacterial growth, resulting in a facility for treatment with activated sludge. Inevitably, this entails a fairly large area.

In particular, in order for the wastewater of the (meth) acrylic acid manufacturing plant to be treated by the activated sludge method, since the wastewater contains aldehydes such as formaldehyde and acetaldehyde, which are toxic to the organism, the wastewater must be diluted several times, and thus the treatment efficiency by activated sludge Is deteriorated in stability, and the cost of wastewater treatment increases, and there is a problem that the treatment itself is difficult. Acetic acid accompanying the waste water is made of a material having low biodegradation efficiency and needs to be highly decomposed according to environmental conservation regulations, and activated sludge has the above problems.

When the direct combustion method is applied to the wastewater of the (meth) acrylic acid manufacturing plant, since the wastewater contains low concentrations of organic substances, a large amount of combustion aids must be used, and thus the treatment cost is high. Moreover, since such wastewater contains low-boiling organic matter as a main component, it is also difficult to carry out concentration as a pretreatment.

Accordingly, it is an object of the present invention to provide an effective and sustainable method of treating wastewater containing acetic acid and aldehydes from a (meth) acrylic acid production plant.

Another object of the present invention is to provide a wastewater treatment method having the advantage that the water obtained by wastewater treatment is renewable as feed water for a (meth) acrylic acid production plant.

These aims are to provide a molecular oxygen-containing gas to a wet oxidation reactor in which the wastewater of a (meth) acrylic acid manufacturing plant containing acetic acid and aldehyde is charged with a solid catalyst and operated at a temperature below 370 ° C. and at a pressure at which the wastewater maintains a liquid phase. It is achieved by a method of treating wastewater, characterized in that it is supplied under continuous supply of to carry out the wet oxidation of organic substances present in the wastewater. These objectives also provide a gas phase catalytic oxidation of a feed gas containing 3 to 4 carbon atoms, the resulting oxidizing gas to be absorbed into water through direct contact, and to separate (meth) acrylic acid from the resulting aqueous solution of the oxidizing gas. The wastewater by supplying the obtained wastewater containing acetic acid and aldehyde with a solid catalyst under continuous supply of molecular oxygen-containing gas to a wet oxidation reactor operated at a temperature below 370 ° C. and under pressure sufficient to preserve the liquid phase. Purifying the wastewater by wet oxidation of organic substances present in the water, and absorbing the produced oxidized gas by circulating the purified wastewater into the absorption step of the gas produced by oxidation, the production of (meth) acrylic acid Is achieved by the method.

In the present invention, since the wastewater in the (meth) acrylic acid manufacturing plant is highly oxidized, the water obtained by treatment can be regenerated into the plant feed water. Plants that produce acrylic acid by vapor phase catalytic oxidation of propylene or those that produce methacrylic acid by vapor phase catalytic oxidation of isobutylene and / or t-butyl alcohol are structurally divided into two systems. That is, oxidation system and purification system. Water is used at various locations in the plant's component units. Among other devices, a large amount of water is consumed in the (meth) acrylic acid absorption tower and the distillation column. Therefore, when the water obtained by the wet oxidation treatment is recycled and used, the (meth) acrylic acid production cost is reduced.

The treated water of the present invention obtained by wet oxidation of wastewater in a (meth) acrylic acid production plant is characterized by containing an extremely small amount of acetic acid. Since such treated water can be used in the (meth) acrylic acid manufacturing plant without any adverse effect on the plant operation, the method of the present invention allows the adoption of a closed system of the (meth) acrylic acid manufacturing plant.

The introduction of wastewater treatment observed by the present invention can allow the (meth) acrylic acid manufacturing plant to be operated without wastewater generation.

Wastewater from the (meth) acrylic acid manufacturing plant contains high concentrations of organic substances beyond that which can be effectively treated with activated sludge, so the amount to be treated must be diluted several times. In wastewater treatment by combustion, the concentration of such organic substances in the wastewater is too low. Therefore, such treatment involves a large consumption of auxiliary fuel. In contrast, the wet oxidation according to the present invention is very suitable for the wastewater treatment of the (meth) acrylic acid manufacturing plant because the wastewater can be directly treated with high efficiency.

In general, if the acetic acid concentration in the absorbed water is increased in the (meth) acrylic acid capture device, the acetic acid concentration in the waste gas containing a constant supply gas such as olefins and rarely used as the raw material device is the catalyst used to produce (meth) acrylic acid. Increase proportionally to counteract In contrast, in the wet oxidation treatment, since the treated water contains substantially no acetic acid, it can be used cyclically as an absorbent, and as a result, the (meth) acrylic acid production efficiency is improved.

Preferred specific examples are as follows. According to the present invention, the desire to complete the (meth) acrylic acid manufacturing process that does not generate harmful wastes is wet oxidation treatment of most organic substances such as acetic acid and aldehyde in the wastewater of the (meth) acrylic acid manufacturing plant using a solid catalyst. By converting them into harmless substances such as carbon dioxide and water. As a method of carrying out the wet oxidation treatment, the Zimmerman method without a catalyst has been known in the art. Many methods using various oxidation catalysts to accelerate the reaction rate have been proposed. However, treatments that depend on wet oxidation never apply to wastewater involving acetic acid and aldehydes from (meth) acrylic acid manufacturing plants.

The wastewater of the acrylic acid production plant by the treatment of the present invention includes acetic acid and aldehyde, and although not particularly limited, the wastewater usually has the following composition.

For example,

Acetic acid 0.04-10% by weight

0.02 to 3% by weight acrylic acid

Formaldehyde 0.04 to 4% by weight

0 to 2 wt% of other organic substances

Water rest

The wastewater of the methacrylic acid production plant by the treatment of the present invention includes acetic acid and aldehyde, and there is no particular limitation, but the wastewater usually has the following composition.

For example,

0.1 to 20 wt% acetic acid

0.02 to 3% by weight acrylic acid

Methacrylic acid 0.04 to 4% by weight

Aldehyde 0.02 to 3 wt%

0 to 3 wt% of other organic substances

Water rest

Considering the decomposition of acetic acid among other contaminants in the wastewater of the (meth) acrylic acid manufacturing plant, the conventional wet oxidation method is inferior in treatment efficiency and requires the use of the second treatment and the third treatment. In contrast, the wet oxidation method using the catalyst of the present invention is processed to be performed with high efficiency and the apparatus is compacted to reduce the processing cost.

The supply of gas containing molecular oxygen is preferably carried out so that the linear velocity of the catalyst layer gas is in the range of 0.6 to 20 cm / sec, preferably 1 to 12 cm / sec. The term 'actual linear velocity of gas' refers to the magnitude of the flow volume of gas in the catalyst bed divided by the catalyst bed cross-sectional area (in terms perpendicular to the vertical axis) at the existing temperature and pressure.

By maintaining the actual linear velocity of the gas in the above-defined range, the gas-liquid stirring by the gas in the catalyst layer is improved, oxygen is dissolved and accelerated in the liquid phase, and at the same time, carbon dioxide is separated from the liquid phase to improve the decomposition efficiency of the acetic acid lacking reactivity. It is possible to significantly improve. Moreover, the pressure loss of the catalyst layer can be prevented from deteriorating. In particular, when the wastewater of the (meth) acrylic acid manufacturing plant contains 0.04 to 20% by weight of acetic acid and 0.02 to 4% by weight of aldehyde, the method of the present invention is useful because it facilitates the reaction control and improves the wet oxidation efficiency. do.

Moreover, the removal efficiency of acetic acid that is adequately oxidized at the outlet of the catalyst bed is determined by the reaction temperature, pressure, and space velocity (LHSV) of the liquid in which the aldehyde of the (meth) acrylic acid plant is oxidized at 30% of the catalyst length from its inlet side. ) May be improved by fixing 50 to 100%. Moreover, aldehydes are competitively oxidized on the catalytically active point because oxidation of acetic acid is promoted as a result of aldehyde reduction. The catalyst to be used in the present invention preferably uses a titanium-containing oxide as its carrier.

More specifically, catalytically active elements such as manganese, iron, cobalt, nickel, tungsten, copper, cerium, silver, gold, platinum, palladium, rhodium, ruthenium or iridium or catalytically active elements which are insoluble or suitably soluble in water. Catalysts obtained by attaching a compound to a carrier of titania, titania-silica, or titania-zirconia are used in the present invention.

The catalyst is composed of 75 to 99.9% by weight of male body, preferably 85 to 99.9% by weight, and 25 to 0.05% by weight of metal or compound of the catalytically active element described above, preferably 15 to 0.1% by weight. Catalytically active element compounds selected from the group consisting of manganese, iron, cobalt, nickel, tungsten, copper, cerium and silver are used as compounds in amounts ranging from 0 to 15% by weight, while platinum, palladium, rhodium, ruthenium and iridium The catalytically active element compound selected from the group consisting of is used in an amount of 0 to 5% by weight, preferably 0 to 3% by weight (but the mixture of the two compounds is in an amount in the range of 0.1 to 15% by weight). Used). Among the other catalysts to be used in the present invention, catalysts in which at least one metal selected from the group consisting of platinum, palladium, rhodium and ruthenium are attached on the carrier at 0.1 to 5% by weight, preferably 0.1 to 3% by weight are particularly free Is used. Catalysts with such platinum group metals attached on titania-zirconia carriers have proven very desirable. In particular, when such a catalyst uses a binary composite oxide composed of 20 to 90 mol% of titania and 80 to 10 mol% of zirconia, it is exceptionally high in activity, resistance to hot water, acid resistance and durability, and thus contains aldehyde and acetic acid ( It is suitable for treating the waste water of the meta) acrylic acid manufacturing plant.

The catalyst can be formed in the art in any shape such as, for example, pellets, beads, honeycombs and rings. The reactor to be used in the present invention may be any of a variety of known types, such as a single tube cylindrical reactor of thermal insulation and a reactor equipped with a heat exchanger function. In the two special reactors, the reactor which gave heat exchange ability was found to be preferable to the other reactors.

The conventional wet oxidation method selects a single tube cylindrical reactor that does not have heat exchange capacity than other reactors. Reactors of this type cannot treat highly concentrated wastewater because they are not observed to remove the heat of reaction resulting from the decomposition of the wastewater.

Even in the wastewater of the (meth) acrylic acid manufacturing plant treated by the method of the present invention, the concentration of pollutants in water varies, for example, in a wide range of 0.1 to 20% depending on the change in operating conditions. When a high concentration of wastewater is substantially supplied, the amount of heat to be generated increases, the liquid temperature in the reaction column is significantly increased, and the reaction cannot proceed because water is passed through the liquid phase as a whole. In such a case, the amount of heat generated must be controlled by diluting the wastewater. Dilution of waste water is undesirable because it results in an increase in the amount of treated water.

The treatment in question has a remarkable effect by using a heat exchanger type reactor as a reactor having a structure capable of sufficiently removing the heat of reaction.

By using such a heat exchanger reactor, even if the waste water of the (meth) acrylic acid manufacturing plant has a high concentration, heat is completely removed, and thus it can be easily processed without using any excessive pressure. Even though the wastewater is low in concentration and the amount of heat generated is small, there is no need to excessively increase the reaction pressure in view of the liquid temperature rise function caused by the generation of heat. Furthermore, the amount of heat to be removed can be increased or reduced, resulting in very precise control by controlling the amount of heat transfer medium by cooling the heat exchanger in proportion to the concentration and amount of wastewater in the (meth) acrylic acid manufacturing plant. Moreover, the heat of reaction recovered in the reactor can be recycled internally in the form of steam via heat transfer media and sent to a steam generating boiler used to effectively preheat the wastewater. Such reaction heat regeneration reduces the operation cost and facility cost of the apparatus.

Among other heat exchanger reactors, cylindrical shell and tube heat exchanger reactors have proved to be particularly preferred. This type simplifies the reactor structurally and facilitates the design and maintenance of the reactor, while at the same time restricting the passage of wastewater inside the inner tube, reducing the number of component parts involved in the use of highly corrosion-resistant materials and reducing the cost of the reactor. (Figure 1).

In the method of the present invention, the pressure loss of each gas supply nozzle is 0.05 kg by using a cylindrical tubular heat exchanger type reactor having a gas supply apparatus equipped with a gas supply nozzle at the bottom of each reaction tube (inner tube). / Cm 2 or more, preferably maintained in the range of 0.1 to 1 kg / cm 2.

As used herein, the term 'pressure loss of each gas supply nozzle' refers to the size of the pressure difference generated under the gas flow between the nozzle and the gas to be supplied to the nozzle multi-purpose. Molecular oxygen-containing gases usable herein include, for example, air, pure oxygen, and oxygen-rich air.

By having each gas supply nozzle at the bottom of the reaction tube, the cylindrical multi-tube heat exchanger type reactor according to the present invention can supply the molecular oxygen-containing gas to each reaction tube in the same amount. As a result, the wastewater can also be supplied to each reaction tube together with the gas from the gas supply nozzle. In order for the same amount of gas to be supplied from the gas supply nozzle to the reaction tube, the pressure loss of each nozzle is 0.05 kg / cm 2 or more, preferably in the range of 0.05 to 2 kg / cm 2 and more preferably 0.1 to 1 kg. / Cm 2. If the pressure loss is less than 0.05 kg / cm 2, the flow amount of gas from each nozzle is changed to cause a large drift, making it difficult to supply the same amount of gas to the reaction tube.

The pressure loss difference between the plurality of nozzles of the gas supply device of the present invention is within 40% and preferably within 25%. If the pressure loss difference in the nozzle is greater than 40%, gas is not easily supplied to the reaction tube in the same amount, and as a result, the waste water is not accompanied by the same amount. Therefore, drift easily occurs in gas and waste water, resulting in a decrease in treatment efficiency.

The nozzle of the gas supply device of the present invention is only necessary to have a structure capable of imparting a pressure difference to the passage gas. The gas can be supplied to the nozzle of the gas supply device by using a radially arranged pipe, an annular pipe, or a small air storage tank (FIG. 3).

In the present invention, the wet oxidation is more effectively performed by using a cylindrical tubular heat exchanger type reactor in the first processing step and a single tube cylindrical reactor in the second processing step. Because most of the wet oxidation reaction of the present invention takes place in close proximity to the reactor inlet and the heat of reaction is also concentrated at this location. Specifically, the reactor with heat exchange capacity is used in the first step requiring the removal of the reaction heat, and the single tube cylindrical reactor without heat exchange capacity receives waste water with low residual calorific value from the heat exchange reactor to thermally insulate the rest of the reaction. It is used in the second stage of advancing. By constructing the above-described apparatus, it is possible to reduce the size of the cylindrical tubular heat exchange type reactor and to lower the installation cost (FIG. 2).

Embodiments of the present invention will now be described below with reference to the accompanying drawings. 1 is a schematic view showing a wastewater treatment apparatus of a (meth) acrylic acid manufacturing plant as an embodiment of the present invention. First, the wastewater drained from the (meth) acrylic acid manufacturing plant via the line 13 is transferred to the heat exchanger 5 through the wastewater supply pump 7 and preheated therein, and then supplied to the reactor 1. The reactor 1 has a plurality of inner tubes mounted in the barrel 12. A dispersion plate (not shown) is disposed below the reaction tube if necessary. In the meantime, molecular oxygen-containing gas via line 14 is compressed by compressor 6 and then supplied to reaction tube 11 in reactor 1 via line 19. The compressed molecular oxygen-containing gas may be sent via line 20 and fed to the heat exchanger 5 together with the wastewater. Optionally, a portion of the compressed molecular oxygen-containing gas is sent via line 19 and the remainder is supplied to reactor 1 via line 20. The heat transfer medium is supplied to the circulation pump 3 via the line 15 to the space surrounding the inner tube (reaction tube) 11 on the inner surface of the reactor 1 and used to remove the heat of reaction generated during the reaction process. The heat transfer medium is then discharged to heat exchanger 4 via line 16, which exchanges heat with the coolant transferred via line 17 to cool the heat transfer medium and recover heat therefrom. . Wastewater treated by reactor 1 is drained via line 18, cooled by heat exchanger 5 and then supplied to gas-liquid separator 8, which is separated into harmless gas and water. In the gas-liquid separator 8, the liquid level is maintained at a constant height by detecting the liquid level by the liquid level controller LC and operating the liquid level control valve 9, and the internal pressure is detected by the pressure controller PC to detect the existing child pressure. By operating the control valve 10 maintains a constant size. Optionally, the treated water drained through the liquid level control valve 9 via the line 21 can be used as feed water for (meth) acrylic acid absorption of the (meth) acrylic acid absorption tower of the (meth) acrylic acid manufacturing plant.

2 is a schematic diagram showing another embodiment of the present invention using a cylindrical tubular heat exchanger reactor in the first stage and a single tube cylindrical reactor in the second stage.

The first reactor 21a of the heat exchanger type is the same as the reactor of FIG. In the single tube cylindrical second reactor 21b, the solid catalyst is placed to fill the inside of the single tube and the insulating material 42 is placed to surround the single tube.

First, the wastewater of the (meth) acrylic acid manufacturing plant via the line 33 is transferred to the heat exchanger 25 by the wastewater supply pump 27 and preheated therein and then supplied to the first reactor 21a. In the meantime, the molecular oxygen-containing gas supplied via the line 34 is compressed by the compressor 26 and then supplied to the reaction tube 31 of the first reactor 21a via the line 40. If necessary, the compressed molecular oxygen-containing gas is transferred via line 39 and supplied to the heat exchanger 25 together with the waste water. Otherwise, some of the compressed molecular oxygen-containing gas is transmitted via line 39 and fed to the first reactor 21a. The heat transfer medium is supplied to the space surrounding the inner tube (reaction tube) 31 of the first reactor 21a via the line 35 by the circulation pump 23 and used to remove the heat of reaction generated during the reaction process. After that, it is discharged via the line 36 and supplied to the heat exchanger 44 to exchange heat with the cooling water via the line 37 therein to cool the heat transfer medium to recover the reaction heat therefrom. The wastewater treated by the first reactor 21a is supplied to the second reactor 21b and treated therein, discharged via the wastewater line 38 and cooled by the heat exchanger 25, followed by a gas-liquid separator 28. ), Which separates into harmless gas and water.

In the gas-liquid separator 28, the liquid level is detected at the existing liquid level by the liquid level controller LC and the liquid level control valve 29 is operated to maintain a constant height, and at the same time, the internal pressure is maintained by the pressure controller PC. The pressure is controlled and the pressure control valve 30 is maintained at a constant size. Optionally, the treated water drained through the liquid level control valve 29 via the line 41 may be used as a feed water for absorbing (meth) acrylic acid of the (meth) acrylic acid absorption column of the (meth) acrylic acid manufacturing plant. .

3 is a schematic view showing one embodiment of the cylindrical tubular heat exchanger 49 to be used in the present invention. The solid catalyst is placed to fill the reaction tube 51 of the cylindrical tubular heat exchanger (49). Wastewater of the (meth) acrylic acid production plant is supplied to the reactor 49 via the line 53. In the meantime, molecular oxygen-containing gas via the line 59 is supplied through the nozzle 60. The heat exchange medium is supplied to the space surrounding the reaction tube 51 of the reactor 49 by the circulation pump 48 to cool the reactor therein, and is discharged to the heat exchanger 54 via the line 55 and Heat exchange with the cooling water supplied via line (57).

4 is a schematic view showing another embodiment of the present invention. The apparatus of this embodiment is the same as the apparatus of FIG. 1, except that the single tube cylindrical reactor 61 is used in place of the cylindrical tubular heat exchanger reactor and the reaction heat recovery apparatus is removed. In Fig. 4, the reference numerals of the parts of Fig. 1 plus 60 denote the same parts.

FIG. 5 is a schematic flowchart illustrating a method for producing acrylic acid including treating wastewater by wet oxidation therein. The reaction product gas obtained from the gas phase catalytic oxidation of propylene and / or acrolein with molecular oxygen-containing gas is introduced into the acrylic acid trap 101 via line 91. In the collecting device 101, the gas is quenched and condensed to convert a substantial portion of acrylic acid and acetic acid into an aqueous solution. The gas part avoiding condensation is absorbed and collected at the top of the collecting device 101 by the cooling absorbent containing the polymerization inhibitor and supplied via the line 92. The aqueous acrylic acid solution is discharged from the bottom of the collecting device 101 via the line 93. The wastewater obtained in the treatment is discharged from the upper portion of the collecting device 101 via the line 94.

The aqueous acrylic acid solution discharged via the line 93 is supplied to the azeotropic dehydration tower 102. In the azeotropic dewatering column 102, the azeotropic agent via line 96 via line 95 in such a way that the steam distilled through the top of the column forms an azeotropic mixture of water and azeotropic agent. It is introduced through the top of the tower. In the meantime, acrylic acid, acetic acid and other high boiling materials that do not contain water or azeotropic agents are discharged through the column bottom and then treated in an acrylic acid rectification (not shown) step to be discharged as a finished product.

The liquid distilled through the top of the azeotropic dehydration column 102 is introduced into the separation tank 104 and separated into an azeotropic agent phase and an aqueous phase therein. The water phase is sent to the azeotropic agent recovery column 103 via line 98. The azeotropic agent and water portion are distilled through the top of column 103 and sent to separation tank 104 via line 99 and recovered therein.

In the meantime, the liquid containing aldehyde and acetic acid and no azeotropic agent is drained through the bottom of the azeotropic agent recovery column 103 via line 100. If necessary, the liquid portion is circulated through the line 105 to the acrylic acid collecting device 101 and used again as an absorbent material. The remainder of the liquid is sent via line 13 to the wet oxidation stage of the wastewater. Reference numeral 106 denotes a supply line for the polymerization inhibitor.

The wet oxidation step is the same as the step shown in FIG. Likewise, the steps shown in FIGS. 2 through 4 may be introduced instead of the steps shown in FIG. The wastewater treated in this step is circulated to the acrylic acid collecting device 101 via the line 107 and used as an absorbent material.

Wastewater discharged via line 100 is freed of organic components by wet oxidation with a solid catalyst. As the azeotropic forming agent recovery column 103 adopts wet oxidation as a purification means for wastewater treatment, a closing and integrating apparatus for treating wastewater resulting from acrylic acid production and production can be realized. Moreover, the operations to be performed for the production and conditions contained therein can be easily changed since the wastewater treatment can be adjusted to suit the amount and composition of wastewater that varies with the operating load.

The treated water purified by wet oxidation can be used as an absorbent of the acrylic acid collecting device 101 because it does not contain any substance which adversely affects acrylic acid. Regeneration of treated water reduces the consumption of feed water and contributes to lower acrylic acid production costs.

6 is a schematic flowchart showing a method for producing methacrylic acid including the wastewater treatment step by wet oxidation therein. The reaction product gas obtained by vapor phase catalytic oxidation of isobutylene and / or t-butyl alcohol with molecular oxygen-containing gas is introduced into methacrylic acid condensation column 121 via line 111. In this condensation column 121, since gas is condensed by quenching, most of methacrylic acid and acetic acid are converted into an aqueous solution. The gas part avoiding condensation is absorbed and collected at the top of the condensation column 121 by the cooling absorbent containing the polymerization inhibitor and supplied via the line 112. The methacrylic acid aqueous solution is drained from the bottom of the condensation column 121 via line 113. The wastewater generated by the treatment is drained from the top of the condensation column 121 via the line 114.

The methacrylic acid aqueous solution drained via the line 113 is supplied to the methacrylic acid extraction column 122 while the solvent for extracting methacrylic acid is filled from the bottom to the extraction column 122 via the line 128 The two are in countercurrent contact with each other such that methacrylic acid is extracted into the solvent phase and drained via line 116 and the aqueous phase is drained via line 117. After extraction, the solvent phase is distilled in the solvent separation column 124 and the solvent is recovered and circulated to the methacrylic acid extraction column 122. In contrast, crude methacrylic acid is discharged via line 115 to produce the product via a methacrylic acid purification step (not shown).

Meanwhile, after methacrylic acid extraction, the aqueous phase is introduced into the solvent recovery column 123 to be distilled via the line 117, and the solvent to the methacrylic acid extraction column 122 via the lines 119 and 128. The liquid containing aldehyde and acetic acid in the water phase is drained via line 120 at the bottom of the solvent recovery column 123. If necessary, this liquid portion is circulated to methacrylic acid condensation column 121 via line 125 and used again as an absorbent material. The remainder of the liquid is sent via line 13 to the wet oxidation stage of the wastewater. Reference numeral 126 denotes a supply line of the polymerization inhibitor.

The wet oxidation step is the same as the step shown in FIG. Likewise, the steps shown in FIGS. 2-4 may be introduced instead of the steps in FIG. The wastewater treated in this step is circulated to methacrylic acid condensation column 121 via line 127 and used as an absorbent. Wastewater drained via line 120 is freed of organic components by wet oxidation with a solid catalyst. By adopting wet oxidation as a purification means for wastewater treatment of the solvent recovery column 123, a closing and integrating apparatus for treating wastewater resulting from the production and production of methacrylic acid can be realized. Moreover, the operations to be performed for the production and conditions contained therein can be easily changed since the wastewater treatment can be adjusted to suit the amount and composition of the wastewater according to the defense of the operating load.

The treated water purified by wet oxidation can be used as an absorbent of the methacrylic acid condensation column 121 because it does not contain any substance which adversely affects methacrylic acid. The regeneration of the treated water contributes to reducing the consumption of feed water and thus to reducing the manufacturing cost of methacrylic acid.

The present invention will now be described in detail with reference to examples.

Example 1

A device constructed as shown in FIG. 1 was used to treat wastewater from an acrylic acid manufacturing plant. The reactor 1 is equipped with twenty reaction tubes (inner tubes) 11 each having an inner diameter of 50 mm and a length of 10 m in the barrel. The reaction tube 11 is filled with a pellet catalyst (having 0.5 wt% of Pt attached on a carrier of a titanium-zirconium compound oxide) having an average inner diameter of 5 mm and a length of 6 mm in a catalyst layer length of 8 m. An air dispersion plate (not shown) was installed below the reaction tube. Wastewater from the acrylic acid manufacturing plant (having the composition shown in Table 1) transferred via line 13 was 60l / hr per air and reaction tube conveyed via line 14, and each flow rate of 9,600N l / hr. (I.e., combined with the total flow rate 1.2m3 / hr and 192Nm3 / hr at the actual linear velocity of gas 3.4cm / sec and supplied to the reactor 1 at a reaction pressure of 75kg / cm2G and a reaction temperature of 250 ° C). The composition and treatment efficiency of the treated water extracted from the line 21 are shown in Table 1.

TABLE 1

ND: not detected

Example 2

A treatment apparatus configured as shown in FIG. 1 was used to treat the waste water of the methacrylic acid manufacturing plant. The reactor 1 is equipped with twenty reaction tubes (inner tubes) 11 each having an inner diameter of 50 mm and a length of 10 m in the barrel. The reaction tube 11 is filled with a pellet catalyst (having 0.5 wt% of Pt attached on the carrier of the titanium-zirconium compound oxide) having an average inner diameter of 5 mm and a length of 6 mm in a catalyst bed length of 8 m. An air dispersion plate (not shown) was installed under the reaction tube. The wastewater from the methacrylic acid manufacturing plant (with the composition shown in Table 2) transferred via line 13 was flown at 80 lhr and 20,800 N l / hr per hour and air transferred via line 14 ( That is, the total linear flow rate of 1.6 m 3 / hr and 416 Nm 3 / hr) is supplied to the reactor 1 at an actual linear velocity of gas of 7.4 cm / sec and wetted at a reaction pressure of 75 kg / cm 2 G and a reaction temperature of 250 ° C. Is oxidized. Table 2 shows the composition and treatment efficiency of the treated water extracted from the line 21.

TABLE 2

Example 3

The wastewater of the acrylic acid manufacturing plant was treated by the method of Example 1, but the reactor type was changed to a single tube cylindrical reactor (inner diameter of 220 mm, height of 10 m and catalyst bed height of 8 m) as shown in FIG. The amount of was changed to 0.9 Nm 3 / hr, the amount of air to 112 Nm 3 / hr (via line 79), and the actual linear velocity of the gas was changed to 2.1 cm / sec. The results are shown in Table 3.

Example 4

It carried out according to the method of Example 3, but the flow volume of air was changed to 216 Nm <3> / hr (via line 80), and the actual linear velocity of gas was changed to 4.0 cm / sec. The results are shown in Table 3.

TABLE 3

[Examples 5 to 7]

The wastewater of the acrylic acid manufacturing plant was treated by the method of Example 1, but the catalyst was changed. The composition of the catalyst and the results are shown in Table 4.

TABLE 4

TZ: Titanium and zirconium composite oxide carrier (TiO ₂ / ZrO ₂ = 60/40 wt% ratio)

TiO ₂ : titania carrier

Example 8

Performing the method of Example 3, the reactor using an inner diameter of 500mm, a height of 3m and a catalyst bed height of 1.55m, the actual linear velocity of the gas is 0.4cm / sec, the treatment efficiency of acetic acid is 95.8% Confirmed.

Example 9

Performing the method of Example 4, the reactor is used having six consecutively arranged catalyst beds having an inner diameter of 80 mm, a height of 12 m, and a height of 10 m each, and the actual linear velocity of the gas is 30 cm / sec. It was confirmed that the treatment efficiency was 98.2%. The pressure loss in the catalyst increased significantly to 11 kg / cm 2.

Example 10

In the treatment method of Example 3, the liquid was sampled at a position of 30% of the length of the catalyst layer from its inlet side to measure the treatment efficiency. The efficiency was found to be 79% for acetic acid, 92% for acrylic acid, 100% for formaldehyde, and 89% for other organic materials.

Example 11

The wastewater of the methacrylic acid manufacturing plant was treated by the method of Example 2, but the type of reactor was a single tube cylindrical reactor having an adiabatic structure (220 mm, 10 m in inner diameter and 8 m in height of catalyst bed) shown in FIG. The amount of wastewater was changed to 1.2 m 3 / hr, the amount of air was changed to 225 Nm 3 / hr (via line 79), and the linear velocity of the gas was changed to 4.7 cm / sec. The results are shown in Table 5.

Example 12

The method of Example 11 was repeated but the air flow rate was changed to 264 Nm 3 / hr (line 80) and the actual linear velocity of the gas was changed to 4.9 cm / sec. The results are shown in Table 5.

TABLE 5

[Examples 13 to 15]

The wastewater of the acrylic acid manufacturing plant was treated by the method of Example 2, but the catalyst was changed. The composition and results of such catalysts are shown in Table 6.

TABLE 6

TZ: Titanium and zirconium composite oxide carrier (TiO ₂ / ZrO ₂ = 60/40 wt% ratio)

TiO ₂ : titania carrier

Example 16

Using the method of Example 11, but using a reactor having an inner diameter of 700mm, a height of 3m and a catalyst bed height of 0.79m, it was confirmed that the actual linear velocity of the gas is 0.46cm / sec, the treatment efficiency of acetic acid is 91%. .

Example 17

The reactor was carried out in the same manner as in Example 11, but the reactor had an inner diameter of 90 mm, a height of 12 m, and a height of six catalyst beds arranged in series, with an actual linear velocity of 28 cm / sec and acetic acid treatment efficiency. It confirmed that it was 96.2%. The pressure loss of the catalyst layer increased significantly up to 7 kg / cm 2.

Example 18

In the treatment of Example 11, the liquid was sampled at 30% of the length of the catalyst bed from its inlet side to measure the treatment efficiency. The efficiency was found to be 72% for acetic acid, 88% for acrylic acid, 86% for methacrylic acid, 98% for aldehyde, and 85% for other organic materials.

Claims (21)

Continuous supply of molecular oxygen-containing gas to a wet oxidation reactor filled with a solid catalyst and operated at a temperature below 370 ° C. and at a pressure at which the waste water maintains a liquid phase, for wastewater of a (meth) acrylic acid manufacturing plant containing acetic acid and aldehyde. A wastewater treatment method, characterized in that it is supplied under the water and subjected to wet oxidation of organic substances present in the wastewater. The wastewater treatment method according to claim 1, wherein the solid catalyst has a titanium-containing oxide as its carrier component. 3. The solid catalyst of claim 2, wherein the solid catalyst comprises at least one metal compound or platinum selected from the group consisting of manganese, iron, cobalt, nickel, tungsten, copper, cerium, and silver with a carrier having a titanium-containing oxide as a component thereof; A catalytically active component comprising at least one metal selected from the group consisting of palladium, rhodium, ruthenium and iridium, wherein the amount of the carrier is in the range of 75 to 99.5% by weight and the amount of the catalytically active component is 25 to Waste water treatment method characterized in that in the range of 0.05% by weight. The catalyst according to claim 3, wherein the solid catalyst has at least one metal selected from the group consisting of platinum, rhodium, ruthenium, and palladium as its catalytically active component, wherein the amount of the metal is from 0.1 to based on the total amount of the catalyst. Waste water treatment method characterized in that the range of 5% by weight. The method of claim 1, wherein the wet oxidation reactor filled with the solid catalyst has heat exchange capacity. The wastewater treatment method according to claim 1, wherein the treated water obtained by wet oxidation of the wastewater is used as feed water of the plant. The wastewater treatment method according to claim 1, wherein the supply of the injected oxygen-containing gas is performed such that the actual linear velocity of the gas in the catalyst layer is in the range of 0.6 to 20 cm / sec. The wastewater treatment method according to claim 1, wherein the wastewater of the (meth) acrylic acid production plant contains acetic acid having a concentration in the range of 0.04 to 20% by weight and a combined concentration of aldehyde in the range of 0.02 to 4% by weight. . The wastewater treatment method according to claim 2, wherein the carrier having a titanium-containing oxide as its component is at least one oxide selected from the group consisting of titania, titania-silica and titania-zirconia. The wastewater treatment method according to claim 9, wherein the oxide is a binary composite oxide composed of 20 to 90 mol% of titania and 80 to 10 mol% of zirconia. The wastewater treatment method according to claim 1, wherein the waste material of the (meth) acrylic acid production plant comprises 50 to 100% of its aldehyde already oxidized at a position of 30% of the length of the catalyst layer from its inlet side. Vapor-catalyzed oxidation of a feed gas containing 3 to 4 carbon atoms olefins, the resulting oxidizing gas to be absorbed into water through direct contact, separation of (meth) acrylic acid from the resulting aqueous solution of the oxidizing gas, acetic acid and aldehyde The organic waste present in the wastewater by supplying the obtained wastewater containing a solid catalyst under continuous supply of molecular oxygen-containing gas to a wet oxidation reactor which is charged with a solid catalyst and operated at a temperature below 370 ° C. and at an input sufficient to preserve the liquid phase. Purifying the wastewater by wet oxidation of the material, and absorbing the produced oxidized gas by circulating the purified wastewater to the absorption step of the gas produced by oxidation, the production of (meth) acrylic acid Way. The method for producing (meth) acrylic acid according to claim 12, wherein the solid catalyst has a titanium-containing oxide as its carrier component. 14. The solid catalyst of claim 13, wherein the solid catalyst comprises at least one metal compound or platinum selected from the group consisting of manganese, iron, cobalt, nickel, tungsten, copper, cerium, and silver with a carrier having a titanium-containing oxide as a component thereof; A catalytically active component comprising at least one metal selected from the group consisting of palladium, rhodium, ruthenium and iridium, wherein the amount of the carrier is in the range of 75 to 99.95% by weight and the amount of the catalytically active component is 25 to A method of producing (meth) acrylic acid, characterized in that in the range of 0.05% by weight. 15. The catalyst according to claim 14, wherein the solid catalyst has at least one metal selected from the group consisting of platinum, rhodium, ruthenium and palladium as its catalytically active component, wherein the amount of the metal is from 0.1 to based on the total amount of the catalyst. It is in the range of 5 weight%, The manufacturing method of (meth) acrylic acid characterized by the above-mentioned. The method for producing (meth) acrylic acid according to claim 12, wherein the wet oxidation reactor filled with the solid catalyst has heat exchange capacity. The method for producing (meth) acrylic acid according to claim 12, wherein the supply of the molecular oxygen-containing gas is performed such that the actual linear velocity of the gas in the catalyst layer is in the range of 0.6 to 20 cm / sec. 13. The method according to claim 12, wherein the wastewater of the (meth) acrylic acid manufacturing plant contains acetic acid at a concentration in the range of 0.04 to 20% by weight and a combined concentration of aldehyde in the range of 0.02 to 4% by weight. Method for producing acrylic acid. The method for producing (meth) acrylic acid according to claim 13, wherein the carrier having a titanium-containing oxide as its component is at least one oxide selected from the group consisting of titania, titania-silica and titania-zirconia. 20. The method for producing (meth) acrylic acid according to claim 19, wherein the oxide is a binary composite oxide composed of 20 to 90 mol% of titania and 80 to 10 mol% of zirconia. 13. The (meth) acrylic acid of claim 12, wherein the waste material of the (meth) acrylic acid manufacturing plant contains 50 to 100% of its aldehyde already oxidized at a position of 30% of the length of the catalyst layer from the inlet side thereof. Manufacturing method.