JP2003236567A - Treating method for wastewater containing inorganic sulfur compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel treating method for wastewater by which treating performance of wastewater can be more enhanced and plant investment and running costs can be reduced. <P>SOLUTION: In a wet process oxidation treatment for heating and oxidizing and/or decomposing waste water containing an inorganic sulfur compound in the presence of oxygen under the pressure at which the waste water maintains a liquid phase, the waste water is subjected to non-catalytic wet process oxidation treatment and then successively subjected to catalytic wet process oxidation treatment using a solid catalyst. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to wood digestion drainage and wooden kettle drainage of a paper / pulp manufacturing plant, fiber washing drainage, iron and steel industry coke oven drainage, photo development drainage, metal treatment drainage, sulfite gas absorption alkaline drainage, Wastewater from petrochemical products such as ethylene and BTX, coal gasification plant, petroleum refining plant, rayon manufacturing plant, dyeing plant,
The present invention relates to a method for effectively purifying wastewater containing a compound containing inorganic sulfur discharged from factories in various industrial fields such as a meat processing plant and a chemical manufacturing plant.

[0002]

2. Description of the Related Art Conventionally, as a method for treating waste water, a biological treatment method, a combustion treatment method, a wet oxidation treatment method and the like have been widely used. Among them, in the biological treatment method,
Since by-products such as excess sludge are generated, the treatment of the sludge is often a problem, and there is also a problem that a large amount of waste water is difficult to treat by this treatment. Further, in the combustion treatment method, since fossil fuel is often used as a fuel, resources are wasted and it often becomes a problem as an emission source of exhaust gas such as carbon dioxide.

On the other hand, the waste water in the liquid phase remains at high temperature.
It is said that the wet oxidation method in which the waste water is purified by oxidative decomposition while maintaining a high pressure does not cause the above problems and is excellent. There are various forms also in this wet oxidation treatment method, such as a method of treating in a gas-liquid upward cocurrent in the reaction tower, a method of treating in a gas-liquid downward cocurrent, a method of treating in a gas-liquid countercurrent, There are a method of using a catalyst in combination and a method of treating without a catalyst.

In order to obtain and exhibit high treatment performance in a wet oxidation treatment method without a catalyst, it is necessary to use severe treatment conditions of high temperature and high pressure and to prolong the reaction time, and therefore the apparatus is large. It has been pointed out that the operating costs will increase as a result.

Therefore, there has been proposed a catalytic wet oxidation treatment method in which the treatment performance is improved by using a solid catalyst. By using a solid catalyst, the reaction temperature and pressure can be lowered and the reaction time can be shortened. However, even in such a catalytic wet oxidation treatment method, depending on the type and concentration of wastewater to be treated, a large amount of catalyst is required, resulting in high equipment costs and operating costs, and durability and treatment performance of solid catalysts. I had a problem with.

[0006]

The present invention has been made in view of the above circumstances, and an object thereof is to further improve the treatment performance for wastewater containing an inorganic sulfur compound and to make a capital investment. Another object of the present invention is to provide a useful wastewater treatment method capable of reducing operating costs.

[0007]

The method for treating wastewater according to the present invention, which has been able to achieve the above object, is a method of treating wastewater containing an inorganic sulfur compound under the temperature and pressure at which the wastewater holds a liquid layer. The point is that the catalytic wet oxidation treatment is further performed after the non-catalytic wet oxidation treatment. Thus, by skillfully combining the non-catalytic wet oxidation treatment and the catalytic wet oxidation treatment, the treatment effects that were not achieved when the treatments were performed independently were exhibited.

Further, according to the present invention, it is possible to sufficiently purify waste water even under relatively mild conditions of a temperature of less than 180 ° C. and a pressure of less than 1 MPa (gauge pressure).

In the method of the present invention, the volume ratio of the non-catalytic wet oxidation treatment area to the catalytic wet oxidation treatment area is 0.5: 1 to.
It is preferably 20: 1.

Furthermore, it is also a preferred embodiment of the present invention to heat the wastewater by injecting steam into the wastewater on the upstream side of the reaction tower.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, wastewater containing an inorganic sulfur compound is subjected to wet oxidation by heating and oxidizing and / or decomposing in the presence of an oxygen source under a pressure at which the wastewater maintains a liquid phase. When performing the treatment, a non-catalytic wet oxidation treatment (hereinafter referred to as the first
After the treatment step), the catalyst wet oxidation treatment using a solid catalyst (hereinafter sometimes referred to as the second treatment step) is performed to effectively treat the wastewater containing the inorganic sulfur compound. To do.

In the present invention, the inorganic sulfur compound is an inorganic compound other than sulfuric acid (SO ₄ ²⁻ ) containing at least one sulfur atom, and is, for example, hydrogen sulfide, sodium sulfide, potassium sulfide, hydrofluoric soda and sodium polysulfide. Sulfides such as; thiosulfates such as sodium thiosulfate and potassium thiosulfate and salts thereof; sulfites such as sodium sulfite and salts thereof;
Examples thereof include trithionate such as sodium trithionate, tetrathionate, and salts thereof.

Inorganic sulfur in waste water is converted to sulfuric acid (SO 4) when oxidation and / or decomposition is completely progressed by wet oxidation treatment.
₄ ^2- ), but in many cases it cannot be sufficiently oxidized and / or decomposed only by non-catalytic wet oxidation treatment,
In particular, when the treatment is performed under mild conditions of a temperature of less than 180 ° C. and a pressure of less than 1 MPa (gauge pressure), there is a problem that the treatment performance becomes low only by non-catalytic wet oxidation. On the other hand, in the case of catalytic wet oxidation treatment using a catalyst, the reaction proceeds sufficiently, but the catalyst treatment alone is not preferable because a large amount of catalyst is required.

Therefore, in the present invention, the waste water is treated in two stages of the first treatment step and the second treatment step, and first, the non-catalytic wet oxidation treatment is performed in the first treatment step, and then the second treatment is performed.
By performing the catalytic wet oxidation treatment in the treatment step, the treatment effect can be further enhanced as compared with the case where the treatment is performed independently.

By carrying out the non-catalytic wet oxidation treatment in the first treatment step as described above, the load on the solid catalyst at the time of introducing the waste water is reduced, and the substance having a bad influence on the treatment performance and durability of the solid catalyst. By preliminarily decomposing, the catalyst performance is sufficiently exerted in the second treatment step without being affected by these, and the inorganic sulfur compound in the wastewater is efficiently treated. As a result, the processing performance of the entire apparatus and the durability of the solid catalyst can be improved, and the equipment cost and operating cost can also be reduced.

The processing method of the present invention will be described below with reference to the drawings. However, these drawings show only one example of the embodiment of the present invention, and the apparatus used in the present invention is limited to the illustrated configuration. Not a thing.

FIG. 1 is a schematic explanatory view showing a structural example of an apparatus for carrying out the method of the present invention. First, the wastewater to be treated is pressurized from the wastewater supply line 1 by the pump 2 and sent to the heat exchanger 5 (pressurized feed). At this time,
The oxygen source introduced from the oxygen source supply line 3 is pressurized by the compressor 4 and then mixed in the waste water to be in a gas-liquid mixed phase state. The gas-liquid mixed phase wastewater obtained here is preheated by the heat exchanger 5, further heated by the heater 6, and then introduced into the lower part of the reaction tower 7, where it moves upward from below (upper). Countercurrent wet oxidation treatment (first treatment step and second treatment step
Processing steps; see FIGS. 2 and 3 below).

The space velocity (hereinafter referred to as LHSV) when the waste water is pressure-fed and fed by the pump 2 is not particularly limited and may be appropriately set depending on the wet oxidation treatment capacity. In particular, the LHSV in the second treatment step is 0. it may preferably be 1hr ^-1 or more, more preferably 0.5 hr ^-1 or more, more preferably may be adjusted so as to 1hr ^-1 or more.
Further, the upper limit of LHSV in the second treatment step is 10 hr.
^-1 or less, and more preferably 7Hr ^-1 or less, may be adjusted so as to become more and 5 hr ^-1 or less. If the space velocity in the second treatment step is less than 0.1 hr ^-1 , the amount of treatment may decrease, and excessive equipment may be required. Also, L
If the HSV exceeds 10 hr ^-1 , the treatment may not be performed sufficiently. In addition, LHSV in the first treatment step
Is calculated from the volume ratio of the first processing step and the second processing step described later.

The oxygen source introduced from the oxygen source supply line 3 is not particularly limited, but pure oxygen, oxygen-enriched gas, air, ozone, hydrogen peroxide, etc. can be used, and It is also possible to use an oxygen-containing gas generated in another plant. Among these, it is particularly recommended to use air from the economical point of view.

Further, the supply amount of the oxygen source is not particularly limited, and an amount necessary for decomposing the harmful substances in the waste water may be supplied. The preferable supply amount is 0.5 times or more, more preferably 1 time or more, further preferably 1.5 times or more, of the theoretical oxygen demand of the waste water. The upper limit of the supply amount is preferably 5.0 times or less, more preferably 4.0 times or less, and further preferably 3.0 times or less. If the supply amount of the oxygen source is less than 0.5 times the theoretical oxygen demand, the harmful substances in the waste water cannot be sufficiently decomposed. Also, 5.0
Even if it is supplied more than twice, the processing performance will not be improved because the equipment will be large. The theoretical oxygen demand here is
It refers to the amount of oxygen required to decompose oxidizable substances in waste water into ash such as nitrogen, carbon dioxide, water, and sulfates.

The wastewater in the gas-liquid mixed phase is sent to the heat exchanger 5 and preheated, and then further heated by the heater 6 and supplied to the reaction tower 7. The heating method at this time is not particularly limited. Instead, it may be heated by the heat exchanger 5 and / or the heater 6, and the reaction tower 7 may be provided with a heating means such as a heater (not shown) for heating. These heating means may be used alone or in any combination. Further, in the present invention, the heating may be performed by injecting steam (see FIG. 4, steam injection line; symbol 17 below). Usually, when heating is performed by injecting steam, if the inside of the reaction tower 7 is only the catalyst, the catalyst near the inlet is likely to be worn and damaged by the impact of steam. However, in the present invention, since the catalyst-free layer is provided in the reaction tower as the first treatment step, the impact due to steam can be buffered and such a problem does not occur.
Moreover, since the heat exchanger 5 is unnecessary by performing heating with steam, the equipment cost and the maintenance cost can be reduced.

The wastewater in the gas-liquid mixed phase supplied to the heat exchanger 5 may be heat-exchanged by the high-temperature treatment liquid treated in the reaction tower 7, or the high-temperature treatment liquid discharged from another plant. It may be heat exchanged by a liquid. As described above, the heat medium for heating the waste water is not particularly limited.

In the configuration shown in FIG. 1, the waste water is supplied to the reaction tower 7 after being brought into a gas-liquid mixed phase state and treated in an upward flow, but the waste water is supplied to the reaction tower 7. The form is not limited to such a form, and any of a method of treating in a downward flow of a gas-liquid mixed phase, a method of separately introducing a gas and a liquid into the reaction tower 7 and treating in a counterflow may be adopted. Among these, by making the continuous phase in the reaction tower 7 into a liquid phase, the contact efficiency between the inorganic sulfur compound in water and the catalyst becomes high, and further, a sulfate produced by oxidizing the inorganic sulfur compound becomes It is preferable that the continuous phase be a gas-liquid upward flow in which the continuous phase is a liquid phase because it is possible to suppress the precipitation of the resulting salt.
In addition, even in the countercurrent system in which liquid (drainage) is supplied from the lower part and gas is supplied from the upper part, the continuous phase in the reaction tower becomes the liquid phase, but in this case the gas directly hits the catalyst layer on the discharge side of the processing liquid and deteriorates the catalyst. It is not preferable because it may cause

In the region of the reaction tower 7 where the first treatment step is carried out, in order to improve the gas and liquid stirring and contact efficiency, and to reduce the nonuniform flow of the gas and liquid, a filling material and a gas and liquid are provided. Various internal crops such as dispersion plates can be used.

There are no particular restrictions on the material, type, size, etc. of the packing as long as it enhances the gas-liquid contact efficiency, and various packings can be used. Those which are inactive against are preferred. For example, metals, ceramics, glass, resins, etc. may be mentioned. Examples of the shape of the filler include pellets, spheres, granules, rings (Raschig rings, Lessing rings, ball rings, etc.), honeycombs, nets, and nets or plates having a woven structure. The size of these fillers is not particularly limited, but in the case of pellets, spheres, granules, rings,
It is preferable that the diameter (outer diameter) or the major axis is 3 to 5 mm. Further, when using the gas-liquid dispersion plate, as long as it can enhance the gas-liquid contact efficiency, the material, type, size, etc. are not particularly limited, for example, single-hole plate, perforated plate, Various gas-liquid dispersion plates such as a single-hole plate with a collision plate and a perforated plate with a collision plate can be used. Further, these fillers and the gas-liquid dispersion plate may be used together.

In the present invention, a solid catalyst is installed in the reaction tower 7 as the second treatment step to improve the ability to oxidize and / or decompose harmful substances. In the wastewater treatment method of the present invention, the solid catalyst that can be used in the second treatment step is a solid that is generally used in a wet oxidation treatment that has both activity and durability under the conditions of liquid phase oxidation. A catalyst can be used. Specifically, at least one element selected from titanium, silicon, aluminum, zirconium, manganese, iron, cobalt, nickel, cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium and / Alternatively, a catalyst containing activated carbon can be used. The activated carbon referred to here includes activated coke, graphite carbon, and activated carbon fiber, in addition to the normally used activated carbon.

Of these, particularly preferable are solid catalysts containing the following catalyst A component and catalyst B component. Here, the catalyst A component is at least 1 selected from iron, titanium, silicon, aluminum and zirconium.
The oxide of one element or activated carbon, and the catalyst B component is at least one selected from manganese, cobalt, nickel, cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium. It is an elemental metal and / or compound.

Specific examples of the catalyst A component include metal oxides such as titanium oxide, iron oxide and zirconium oxide, and binary or multi-component such as titanium oxide-zirconium oxide and titanium oxide-iron oxide. In addition to the system oxides (including complex oxides), activated carbon or a mixture of metal oxide and activated carbon can be used. The proportion of the catalyst A component in the solid catalyst is preferably in the range of 30 to 99.95% by mass, and the durability of the solid catalyst can be improved by using the catalyst A component in an amount of 30% by mass or more.

Specific examples of the catalyst B component include metals, oxides and complex oxides of the above elements.
The proportion of the catalyst B component in the solid catalyst is 0.05 to 70% by mass.
It is preferable that the content be 0.05% by mass or more, and it becomes possible to sufficiently oxidize and / or decompose the harmful substances in the wastewater. Among the above elements, silver, gold, platinum, palladium, rhodium, ruthenium and iridium (hereinafter referred to as “B-1 component”)
When using, the ratio (total amount) of the metal and / or compound is preferably 0.05 to 10 mass% of the solid catalyst. Even if the amount of the B-1 component used exceeds 10% by mass, the treatment performance corresponding to the used amount cannot be obtained, and since the raw material of the B-1 component is expensive, the cost of the solid catalyst is increased, which is economical. Will be disadvantageous. When using manganese, cobalt, nickel, cerium, tungsten and copper (hereinafter, referred to as "B-2 component") that are catalyst B components other than B-1 component, the ratio of the metal and / or compound is a solid catalyst. It is preferable to set it to 0.05 to 70 mass%. Of course, in the range where the total amount of the catalyst B component is 0.05 to 70 mass%, the B-1 component and the B-2 component are respectively 0.05 to 10 mass% and 0.05 to 70 mass%. It can also be used in combination.

The solid catalyst is particularly effective because it has a high catalytic activity when it contains the component B-1 as the component B of the catalyst. Among the B-1 components, platinum, palladium, rhodium,
At least one selected from ruthenium and iridium
It is preferable to contain a metal and / or a compound of a seed element because the catalytic activity becomes particularly high. Of the B-2 components, manganese, cobalt, nickel and copper are preferably used.

The shape of the catalyst is not particularly limited, and various shapes such as granules, spheres, pellets, rings, crushes, and honeycombs can be used. Among these, spheres and pellets can be formed. Those obtained are preferred.

In order to reduce the vibration of the solid catalyst, a pressing material layer made of metal, ceramic, glass or the like is provided on the upper portion (treatment water discharge side) of the solid catalyst layer used in the treatment method of the present invention. It is preferable to provide. The pressing material layer preferably has a shape that follows the deformation or movement of the solid catalyst layer and does not hinder the pressing effect even if the solid catalyst layer moves or deforms. Specifically, there are molded articles such as SUS metal balls and pellets or titania pellets, and granular glass.

Further, in the lower part (drainage supply side) of the above-mentioned solid catalyst layer, wear of the solid catalyst due to collision of gas and liquid is reduced, the solid catalyst is supported, and clogging of the lower grid etc. by the solid catalyst is prevented, It is also preferable to provide a support layer of a solid catalyst for preventing an increase in pressure loss. Specifically, SU
In addition to metal balls and pellets made of S, molded articles such as titania pellets, and granular glass, wire mesh and various packings can be used.

In addition to the solid catalyst, various packings and internal crops may be installed in the second treatment step in order to improve gas-liquid stirring and contact efficiency and reduce gas-liquid nonuniform flow. Particularly, when the packed bed of the solid catalyst is long, it is effective to divide the solid catalyst layer into a plurality of layers. Specifically, it is effective when the catalyst layer length is 1000 mm or more, and is more effective when the catalyst layer length is 1500 mm or more. It is preferable to install a dispersion device for reducing the nonuniform flow of gas and liquid at the beginning of the second treatment step or at the bottom of each layer divided into a plurality of layers. This dispersing device can be used in various shapes and materials,
For example, a dispersion device used in a reaction tower, a distillation tower, a diffusion tower or the like of a chemical plant can be used.

In the configuration shown in FIG. 1, the case where the first treatment step and the second treatment step are installed in one unit is shown, but these steps may be provided in separate reaction columns. When using separate reaction towers, a gas-liquid conduit tube is provided and connected from the upper part of the reaction tower of the first treatment step to the lower part of the reaction tower of the second treatment step.
However, when a plurality of reaction towers are used, the equipment cost rises and the maintenance cost also rises. Therefore, it is preferable to use one reaction tower. That is, it is preferable that the first treatment step and the second treatment step exist in the same reaction tower. In this case, the non-catalyst wet treatment step, which is the first treatment step, and the catalyst wet treatment step, which is the second treatment step, are provided from the side of the waste water supply line of the reaction tower.

When the reaction tower of the first treatment step and the reaction tower of the second treatment step are separate, gas-liquid separation can be performed between the two. In the case of gas-liquid separation, the gas-liquid conduit tube that connects the reaction tower of the first treatment step and the reaction tower of the second treatment step can be independent of the gas-phase conduit tube and the liquid-phase conduit tube. The phase can be discharged to the outside of the system to use only the liquid phase conduit. A new oxygen source may be added to the second treatment step to improve the treatment performance.

The volume ratio of the wet oxidation treatment region between the first treatment step and the second treatment step in the reaction tower 7 is 0.5: 1 to 20: 1 in the first treatment step: the second treatment step. Preferably
It is more preferably 0.5: 1 to 15: 1 and even more preferably 0.5: 1 to 10: 1. When wastewater containing an inorganic sulfur compound is treated in the first treatment step, thiosulfates and salts thereof are often produced as intermediate products or by-products. In order to further oxidize these intermediate products or by-products, it is effective to carry out a catalytic wet oxidation treatment using a solid catalyst as the second treatment step.
The volume ratio between the first treatment step and the second treatment step is preferably determined in consideration of the reactivity of the substance to be treated. That is,
If the substance to be treated is persistent, it is preferable to increase the volume of the second treatment step than the first treatment step,
Further, when the substance to be treated is easily degradable, it is preferable to make the volume of the first treatment step larger than that of the second treatment step.

The reaction temperature of the wet oxidation reaction in the reaction tower 7 is influenced by other conditions, but if it exceeds 370 ° C., the waste water cannot be kept in the liquid phase state, and the equipment becomes large and the running cost increases. Therefore, the reaction temperature is preferably 370 ° C. or lower, more preferably 280 ° C. or lower, and further preferably lower than 180 ° C. On the other hand, if the temperature is lower than 80 ° C, it becomes difficult to carry out the wet oxidation reaction efficiently.
Or more, more preferably 100 ° C. or more, and further preferably 1
It is desirable that the temperature be 10 ° C. or higher.

In the wet oxidation reaction of the present invention, it is desirable to appropriately adjust the pressure so that the waste water can maintain the liquid phase,
The pressure is appropriately selected depending on the correlation with the reaction temperature. In particular, when the reaction temperature is less than 180 ° C., it is preferably less than 1 MPa (gauge pressure) from the viewpoint of cost such as equipment investment and operating cost.

The type and shape of the reaction tower used in the present invention is not particularly limited. The reaction tower may be either a single tube type or a multi-tube type, and a plurality of these may be used in combination, but one single tube type reaction tower is used, and the first treatment step is performed therein. It is preferable to perform the treatment of the second treatment step.

The treatment liquid treated in the reaction tower 7 is appropriately cooled by the heat exchanger 5 and the cooler 8 if necessary, and then separated into a gas and a liquid by the gas-liquid separator 9. At this time, the heat exchanger 5 and the cooler 8 can be used alone or in combination.

In the gas-liquid separator 9, the liquid level controller (L
It is desirable to detect the liquid level using C) and control the liquid level control valve 10 so that the liquid level in the gas-liquid separator 9 becomes constant. Here, “constant” means that the liquid level is within a certain value or within a certain range.

Further, the treated water may be cooled and then discharged through a pressure adjusting valve (not shown), and then separated into gas and liquid by the gas-liquid separator 9.

The liquid separated by the gas-liquid separator 9 is discharged through the treated water discharge line 11, which may be sent to the treated liquid tank, or subjected to a known method such as biological treatment. It can be further processed.

It is desirable that the pressure is detected by a pressure controller (PC) and the pressure control valve 12 is operated to maintain the pressure at a predetermined value, that is, less than 1 MPa (gauge pressure) in the present invention. The gas separated by the gas-liquid separator 9 may be discharged into the atmosphere through the exhaust gas discharge line 13, or may be further processed by a known method.

The pH of the wastewater containing the inorganic sulfur compound after the treatment is preferably adjusted by supplying an alkaline component before or during the treatment so that the pH is in the neutral to alkaline range. This is also because the oxidation reaction of the inorganic sulfur compound existing in the waste water by the solid catalyst is accelerated especially from neutral to alkaline. Especially under the condition of less than 180 ° C., the effect is remarkable. Further, in the wet oxidation treatment under the acidic condition where sulfuric acid and the like exist, the corrosion of the material of the wet oxidation treatment equipment becomes severe, and the durability of the equipment may be significantly impaired.

When the pH is adjusted by adding an alkali metal ion, an inorganic acid or the like to the waste water, the addition position is not particularly limited. In the treatment method of the present invention, it may be added to the raw water of the wastewater, before or after the first treatment step, or in the first treatment step, and before or after the second treatment step, or the second treatment step. May be added in. Further, the addition amount may be controlled by constantly adding a fixed amount, or by controlling the pH or ion amount of the liquid. Further, it is possible to appropriately dilute the waste water.

[0048]

EXAMPLES The effects of the present invention will be specifically shown by the following examples, but the technical scope of the present invention is not limited to these examples.

Example 1 When treating harmful substances in waste water, wet oxidation treatment was performed for 3,000 hours using the apparatus having the configuration shown in FIG.
The wastewater used for treatment was discharged from the chemical plant.
The wastewater had the composition shown in. In Table 1, "%"
Indicates "mass%".

[0050]

[Table 1]

The reaction tower 7 has a diameter of 400 mm and a length of 4,0.
A cylindrical shape of 00 mm was used. The details of the reaction tower 7 used are shown in FIG. As the non-catalyst layer, the lower part 15 of the reaction tower 7
Contains SUS3 with a diameter of 5 mm and a length of 5 mm as the filling material.
188 liters of 16 Raschig rings were installed so that the layer length would be 1,500 mm. 250 liters of catalyst is installed on the upper part 14 and the catalyst layer length is 2,000 mm.
So that The catalyst used was a catalyst in which palladium was supported on an oxide of titanium-zirconium (palladium 0.3% by mass). The shape of the catalyst is 5mm in diameter and 7mm in length
It was in the form of pellets.

125 from pump 2 from drainage supply line 1
The wastewater is pressure-fed at a flow rate of liter / hr, and air is supplied from the oxygen source supply line 3 as oxygen source at 21 Nm ³ / h.
It was introduced at a flow rate of r (corresponding to twice the theoretical oxygen demand), pressurized by the compressor 4, and then mixed into the waste water. The wastewater in a gas-liquid mixed phase obtained here was heated by the heat exchanger 5 and further heated by the heater 6, and then supplied to the reaction tower 7 and subjected to wet oxidation treatment at a treatment temperature of 160 ° C. The treatment liquid treated in the reaction tower 7 was introduced into the gas-liquid separator 9 after being cooled by the heat exchanger 5 and the cooler 8. In the gas-liquid separator 9,
The liquid level is detected by the liquid level controller (LC), the liquid level control valve 10 is operated to maintain a constant liquid level, and
The pressure was detected by a pressure controller (PC), the pressure control valve 12 was operated, and the pressure control valve 12 was operated to maintain a pressure of 0.9 MPa (gauge pressure). The treatment liquid was discharged from the treated water discharge line 11.

As a result, the measured COD (Cr) concentration of the treated water was 990 mg / liter, and the COD (Cr) treatment efficiency calculated from this value was 96%. In addition, no sulfide ion was detected in the treated water, and no decrease in treatment performance was observed in the treatment for 3,000 hours.

Example 2 As the reaction column 7, a cylindrical column having a diameter of 400 mm and a length of 4,000 mm having the specifications shown in FIG. 3 was used. In the lower part 16 of the reaction tower, gas-liquid dispersion plates (perforated plates) were installed at intervals of 300 mm so that the non-catalyst layer length was 3,300 mm, and 38 liters of catalyst was installed in the upper part 14 of the catalyst layer. Long is 3
It was set to be 00 mm. As the catalyst, a catalyst in which platinum was supported on a titanium-iron oxide (0.3% by mass of platinum) was used. The shape of the catalyst was a pellet having a diameter of 5 mm and a length of 7 mm. Otherwise, the same processing as in Example 1 was performed.

As a result, the measured COD (Cr) concentration of the treated water was 1400 mg / liter, and the COD (Cr) treatment efficiency of the COD treated water calculated from this value was 94%. In addition, no sulfide ion was detected in the treated water,
In the treatment for 3,000 hours, no reduction in treatment performance was observed.

Example 3 In Example 2, the lower part of the reaction tower 16 was installed so that the layer length of the part where the gas-liquid dispersion plate was installed was 3,000 mm (375 liters), and 63 liters of the catalyst were placed thereon. It was installed so that the catalyst layer length was 500 mm. A single-hole plate with a collision plate was used as the gas-liquid dispersion plate. As the catalyst, a catalyst in which ruthenium was supported on a titanium-iron oxide (ruthenium 0.3% by mass) was used. The shape of the catalyst is 5 mm in diameter and 7 m in length.
m pellets. Otherwise, the same processing as in Example 1 was performed.

As a result, the measured COD (Cr) concentration of the treated water was 2200 mg / liter, and the COD (Cr) treatment efficiency of the treated water calculated from this value was 91%. In addition, no sulfide ion was detected in the treated water,
During the treatment for 000 hours, no deterioration in treatment performance was observed.

Example 4 When treating harmful substances in waste water, wet oxidation treatment was carried out for 2,000 hours using the apparatus having the construction shown in FIG. The wastewater used for the treatment was the wastewater having the composition shown in Table 2 discharged from the chemical plant. The apparatus shown in FIG. 4 has a basic configuration similar to that shown in FIG. 1, and the corresponding parts are designated by the same reference numerals, but in this configuration, instead of providing the heat exchanger 5, In addition, an injection line 17 is provided to introduce steam into the system.

[0059]

[Table 2]

At this time, as the reaction tower 7, the one shown in FIG. 2 was used. In the lower part 15 of the reaction tower 7, 425 liters of SUS316 Raschig ring having a diameter of 5 mm and a length of 5 mm was installed as a packing so that the layer length was 3,400 m. 25 liters of catalyst was placed on the upper portion 14 so that the catalyst layer length was 200 mm. As the catalyst, a catalyst in which ruthenium was supported on an oxide of titanium (0.5% by mass of ruthenium) was used. The shape of the catalyst is 5m in diameter
A pellet having a length of m and a length of 7 mm was used.

90 from the drainage supply line 1 by the pump 2
Waste water is pressure-fed at a flow rate of liter / hr, while air from the oxygen source supply line 3 serves as an oxygen source at 22 Nm ³
It was introduced at a flow rate of / hr (equivalent to twice the theoretical oxygen demand), pressurized by the compressor 4, and then mixed into the waste water.
The waste water in the gas-liquid mixed phase obtained here is heated by injecting 0.9 MPa (gauge pressure) steam from the steam injection line 17, and further heated by the heater 6,
It was supplied to the reaction tower 7 and a wet oxidation treatment was performed at a treatment temperature of 160 ° C. The treatment liquid treated in the reaction tower 7 was cooled by the cooler 8 and then introduced into the gas-liquid separator 9. In the gas-liquid separator 9, the liquid level controller (LC) detects the liquid level, the liquid level control valve 10 is operated to maintain a constant liquid level, and the pressure controller (PC) detects the pressure. The pressure control valve 12 was operated and operated so as to maintain a pressure of 0.9 MPa (gauge pressure). The treatment liquid was discharged from the treated water discharge line 13.

As a result, the measured COD (Cr) concentration of the treated water was 1800 mg / liter or less, and the COD (Cr) treatment efficiency calculated from this value was 95%. In addition, no sulfide ion was detected in the treated water,
No deterioration in processing performance was observed in the time processing.

[0063]

According to the method of the present invention, it is possible to efficiently oxidize and decompose an inorganic sulfur compound and convert it into an inorganic sulfate, carbon dioxide, water and ash. In addition, as a post-treatment, no biological treatment is required at all, and the treated wastewater can be directly discharged, or even if a biological treatment is required as a post-treatment, substances that have an adverse effect on living organisms have been decomposed and It is not necessary to adjust the wastewater after the oxidation treatment except for pH. For this reason, the amount of treated wastewater is reduced, and biological treatment equipment is not required at all, or is much smaller than conventional equipment, the treatment process is simplified, and it is advantageous in terms of capital investment and running cost. It was possible to provide a simple wastewater treatment method.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of the apparatus configuration for carrying out the method of the present invention.

FIG. 2 is a schematic view showing an example of a reaction tower according to the present invention.

FIG. 3 is a schematic view showing another example of the reaction tower according to the present invention.

FIG. 4 is a schematic view showing another example of the apparatus configuration for carrying out the method of the present invention.

[Explanation of symbols]

1 Drainage supply line 2 pumps 3 Oxygen source supply line 4 compressor 5 heat exchanger 6 heater 7 Reaction tower 8 cooler 9 gas-liquid separator 10 Liquid level control valve 11 Treated water discharge line 12 Pressure control valve 13 Exhaust gas discharge line 14 catalyst 15 filling 16 Gas-liquid dispersion plate 17 Steam injection line

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toru Ishii             Hyogo prefecture Himeji city             1 Within Nippon Shokubai Co., Ltd. F-term (reference) 4D050 AA13 AB40 BB01 BC01 BC02                       BC06 BD02 BD06 BD08

Claims (4)

[Claims] 1. A method comprising subjecting wastewater containing an inorganic sulfur compound to non-catalytic wet oxidation treatment at a temperature and pressure at which the wastewater holds a liquid phase, and then further performing catalytic wet oxidation treatment. A method for treating wastewater containing an inorganic sulfur compound. 2. The waste water at a temperature of less than 180 ° C., and
The method for treating wastewater according to claim 1, wherein the wet oxidation treatment is performed at a pressure lower than MPa (gauge pressure). 3. The method for treating wastewater according to claim 1, wherein the volume ratio of the non-catalytic wet oxidation treatment area to the catalytic wet oxidation treatment area is 0.5: 1 to 20: 1. 4. The wastewater is heated by injecting steam into the wastewater on the upstream side of the reaction tower.
4. The method for treating wastewater according to any one of 3 to 3.