JPH08290179A - Method for wet-oxidizing cyanide-containing waste water - Google Patents

Abstract

PURPOSE: To completely decompose cyanide without need for an additional treatment by adding a sulfur compd. to a cyanide-contg. waste water under specified temp., pressure and oxygen amt., removing sludge, etc., to obtain a primary treated liq. and further wet-oxidizing the treated liq. in the same way. CONSTITUTION: A cyan-contg. waste water in a waste water storage tank 1 is boosted by a pump 2, sulfuric acid is added from a sulfuric acid storage tank 25, an oxygen-contg. gas is added by a compressor 22, and the waste water is sent to a heat exchanger 3 and heated to <=150 deg.C. The heated waste water is sent to a primary reaction tower 5 and wet-oxidized at >=150 deg.C in the presence of oxygen in the amt. less than the stoichiometry necessary to make the cyanide compd., nitrogen compd. and org. and inorg. substances harmless. The sludge and metallic component are removed in a solid-liq. separator 10, and the primary treated liq. is sent to a catalyst-packed second reaction tower 14 and wet-oxidized in the same way. The treated liq. is sent to the heat exchanger 3, used as the heat source and then discharged through a gas-liq. separator 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating cyanide-containing wastewater containing free cyan, cyan complex salt, cyan complex ion, metallic cyanide (hereinafter, this wastewater may be simply referred to as cyanide-containing wastewater). .

[0002]

2. Description of the Related Art As a method for decomposing cyanide in wastewater containing cyanide, various methods such as thermal decomposition and thermal hydration are proposed in addition to a method of treating with a chemical such as chlorine-based chemicals, ozone and iron salts. Has been done.

For example, Japanese Patent Publication No. 52-45679,
"A method for treating a tetracyanonickelate / cyan waste liquid, which is characterized by performing a heat treatment at a temperature of 150 ° C or higher" is disclosed.

Japanese Examined Patent Publication No. 55-50718 discloses that "cyan waste liquid containing iron cyanide complex ions is heated to 140 ° C. or higher in the presence of 2 mol or more of alkali metal hydroxide per iron cyanide complex ion / mol of the waste liquid. A method for treating a cyan waste liquid containing iron cyanide complex ions, which is characterized by performing heat treatment at a temperature ".

Japanese Unexamined Patent Publication (Kokai) No. 1-115490 basically discloses a method of pre-heating a cyan waste liquid and then thermally hydrolyzing it by heating steam under high temperature and high pressure.

Japanese Unexamined Patent Publication (Kokai) No. 1-194997 discloses that "a thermally decomposed solution obtained by thermally decomposing cyan in a cyan-containing solution is treated with an aerobic bacterium in which a facultative anaerobic bacterium is acclimatized and modified. The method of treating the contained liquid "is disclosed.

However, the treatment with chemicals has a limit to the cyanide concentration in the waste water which can be applied from the economical point of view, and the method of adding an iron salt to form a sparingly soluble complex salt requires treatment of sludge containing cyanide. And

Further, the thermal decomposition method requires a long time for completely decomposing the cyan compound depending on the kind of the (a) cyanide complex ion.
Part of cyan remains in the sludge after treatment, (b)
Therefore, a method of further biologically treating the treated water has been proposed (see Japanese Patent Laid-Open No. 1-194997), but this method requires treatment with specific bacterial cells and also requires nitrogen removal. In some cases, ammonia stripper or biological denitrification equipment is required. (C) When the treatment method is batch type, it is not suitable for treating a large amount of wastewater,
There are problems such as.

[0009] Generally, sludge containing cyanide needs to be treated as hazardous waste. Further, according to the conventional treatment method, the treatment of wastewater containing high-concentration cyanide containing cyanide complex ions has problems that the process becomes complicated and the treatment cost becomes high.

[0010]

Therefore, the present invention provides a new technique capable of decomposing substantially completely and inexpensively cyanogen in cyanide-containing wastewater without the need for additional treatment. The main purpose is that.

[0011]

The present inventor has conducted various studies in view of the current state of the art as described above, and as a result, in the case of performing wet oxidation treatment of cyanide-containing wastewater under specific conditions, It was found that the task could be almost achieved.

That is, the present invention provides the following methods: I. A method characterized in that the following steps are continuously carried out when the cyanide-containing wastewater is subjected to a wet oxidation treatment: (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to the cyanide-containing wastewater, and the secondary treatment liquid is added. After being heated to a temperature of up to 150 ° C by heat exchange with, the cyanide compound, the nitrogen compound, the organic substance and the inorganic substance in the wastewater are kept at a temperature of 150 ° C or higher and the pressure of the wastewater to maintain the liquid phase. To obtain a primary treatment liquid by performing a wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount necessary for decomposing slag, (2) sludge and / or metal components from the high-temperature high-pressure primary treatment liquid And (3) in the presence of a catalyst containing at least one metal and a metal compound as an active ingredient in the primary treatment liquid at high temperature and high pressure, and in the treatment liquid, a cyanide compound, a nitrogen compound, and an organic compound. In the presence of oxygen in an amount equal to or more than the theoretical oxygen amount required for decomposing the organic substance and the inorganic substance, the wet oxidation treatment is performed while maintaining the temperature at 150 ° C. or more and the pressure at which the treatment liquid maintains the liquid phase. A step of obtaining a secondary treatment liquid.

II. A method characterized in that the following steps are continuously carried out when the cyanide-containing wastewater is subjected to a wet oxidation treatment: (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to the cyanide-containing wastewater, and the secondary treatment liquid is added. After being heated to a temperature of up to 150 ° C by heat exchange with, the cyanide compound, the nitrogen compound, the organic substance and the inorganic substance in the wastewater are kept at a temperature of 150 ° C or higher and the pressure of the wastewater to maintain the liquid phase. To obtain a primary treatment liquid by performing a wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount necessary for decomposing slag, (2) sludge and / or metal components from the high-temperature high-pressure primary treatment liquid And (3) a cyanide compound, a nitrogen compound, an organic substance and an inorganic substance in the treatment liquid in the presence of a catalyst containing at least one of a metal and a metal compound as an active ingredient in the first treatment liquid. In the presence of oxygen in an amount equal to or higher than the theoretical oxygen amount required for decomposing the volatile substance, while maintaining the temperature of 150 ° C. or higher and the pressure at which the treatment liquid maintains a liquid phase, the wet treatment is performed to obtain a secondary treatment liquid. And (4) a step of circulating at least a part of the gas phase obtained by gas-liquid separation of the secondary treatment liquid to the step (1) and using it as an oxygen source in the step (1).

III. A method characterized in that the following steps are continuously carried out when the cyanide-containing wastewater is subjected to a wet oxidation treatment: (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to the cyanide-containing wastewater, and the secondary treatment liquid is added. After being heated to a temperature of up to 150 ° C by heat exchange with, the cyanide compound, the nitrogen compound, the organic substance and the inorganic substance in the wastewater are kept at a temperature of 150 ° C or higher and the pressure of the wastewater to maintain the liquid phase. To obtain a primary treatment liquid by performing a wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount necessary for decomposing slag, (2) sludge and / or metal components from the high temperature / high pressure primary treatment liquid A step of separating and removing, (3) a cyanide compound, a nitrogen compound, an organic substance and an inorganic substance in the treatment liquid in the presence of a catalyst containing at least one of a metal and a metal compound as an active ingredient in the first treatment liquid. A secondary treatment liquid is obtained by performing wet oxidation treatment in the presence of oxygen at a theoretical oxygen amount or more necessary for decomposing a substance and at a temperature of 150 ° C. or higher and a pressure at which the treatment liquid maintains a liquid phase. Step, and (4) a step of circulating at least a part of the liquid phase obtained by gas-liquid separation of the secondary treatment liquid to the step (3) at a ratio of 1 to 10 times the volume of the primary treatment liquid.

IV. A method characterized in that the following steps are continuously carried out when the cyanide-containing wastewater is subjected to a wet oxidation treatment: (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to the cyanide-containing wastewater, and the secondary treatment liquid is added. After being heated to a temperature of up to 150 ° C by heat exchange with, the cyanide compound, the nitrogen compound, the organic substance and the inorganic substance in the wastewater are kept at a temperature of 150 ° C or higher and the pressure of the wastewater to maintain the liquid phase. To obtain a primary treatment liquid by performing a wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount necessary for decomposing slag, (2) sludge and / or metal components from the high temperature / high pressure primary treatment liquid A step of separating and removing, (3) a cyanide compound, a nitrogen compound, an organic substance and an inorganic substance in the treatment liquid in the presence of a catalyst containing at least one of a metal and a metal compound as an active ingredient in the first treatment liquid. A secondary treatment liquid is obtained by performing wet oxidation treatment in the presence of oxygen at a theoretical oxygen amount or more necessary for decomposing a substance and at a temperature of 150 ° C. or higher and a pressure at which the treatment liquid maintains a liquid phase. Process,
(4) At least a part of the gas phase obtained by gas-liquid separation of the secondary treatment liquid is circulated to the step (1) to obtain the step (1).
And (5) at least a part of the liquid phase obtained by gas-liquid separation of the secondary treatment liquid at a ratio of 1 to 10 times the amount of the primary treatment liquid (3). The process of circulating to.

In the following, the inventions I to IV will be referred to as the first invention to the fourth invention, respectively.
When all inventions are summarized, they are simply referred to as the present invention.

The cyanide-containing wastewater targeted by the present invention is not particularly limited, and is used for various cyanide-containing wastewater discharged from the plating industry, surface nitriding treatment of steels, liquid carburizing treatment, chemical conversion treatment and the like. Examples of the cyan liquid to be used, cyan waste liquid discharged from the surface treatment process, and the like.
These cyan-containing wastewaters further include various organic and inorganic substances (organic acids such as formic acid and acetic acid), various nitrogen compounds such as ammonia (in this specification, nitrogen such as ammonia other than cyan compounds). The compound may be simply referred to as a nitrogen compound), or an organic chlorine compound such as trichlorethylene may also be contained.

The present invention further provides Mg, Al, Si,
P, Ca, Ti, Cr, Mn, Fe, Co, Ni, C
It is also useful for treating wastewater or sludge containing one or more metal components such as u, Zn and Cd. As wastewater or sludge containing such metal components, kitchen waste,
Household wastewater including paper, plastics, human waste, paper mill wastewater, pharmaceutical factory wastewater, wastewater generated by coal liquefaction or gasification, wastewater generated by thermal decomposition of municipal waste,
Sludge generated by biological treatment of industrial wastewater (anaerobic treatment, aerobic treatment), sewage sludge, wastewater generated by oilification of sewage sludge, photographic wastewater, printing wastewater, agricultural chemicals-related wastewater, dyeing wastewater, semiconductor manufacturing plant Various kinds of waste water such as waste water or sludges are exemplified.

The first to fourth applications of the present application will be described below with reference to the drawings.
The invention will be described in detail. In the following, in order to simplify the description, a case of targeting cyanide-containing wastewater will be described.

I. First Invention of the Present Application FIG. 1 is a flow sheet showing an outline of the first invention of the present application.

The cyan-containing waste liquid from the waste water storage tank 1 is pressurized to a predetermined pressure by the pump 2, sulfuric acid is added from the sulfuric acid storage tank 25, and the oxygen-containing gas that has been pre-pressurized by the compressor 22 is mixed and then heated. 1 by exchange 3
After being heated to a temperature of 50 ° C. or lower, it is supplied to the primary reaction column 5 (hereinafter, simply referred to as the reaction column 5 unless otherwise necessary to distinguish it from the secondary reaction column 14 described later). . Cyan-containing wastewater may contain fairly large amounts of alkali metal compounds. Therefore, prior to the treatment in the reaction tower 5, by adding 0.25 to 0.55 times the amount of sulfuric acid per 1 mol of the total amount of alkali metals in the waste water,
Adjust pH of wastewater. Also, by adding this sulfuric acid,
It is also possible to suppress the production of nitrogen compounds (particularly NO ₂ state nitrogen and NO ₃ state nitrogen) in the reaction tower 14. Note that instead of sulfuric acid or together with sulfuric acid, a substance capable of producing sulfuric acid under the reaction conditions in the reaction tower 5 (for example, sulfur,
A sulfur compound such as ammonium thiosulfate) may be added to the cyan-containing wastewater. In the present invention, unless otherwise specified, the expression “sulfuric acid” also includes these substances.

The heat source of the heat exchanger 3 is a secondary reaction tower 14 (hereinafter, simply referred to as the reaction tower 14 unless otherwise necessary to distinguish it from the primary reaction tower 5).
It is possible to circulate and use the high temperature treatment liquid (secondary treatment liquid). When it is not possible to maintain a predetermined reaction temperature during the reaction, such as in winter, or when it is necessary to raise the temperature to a predetermined temperature, the waste water is heated by the heater 4, or the steam generator 6 is used to move the reaction tower 5 to the reaction tower 5. Steam can also be supplied. Further, in order to bring the temperature in the reaction tower 5 to a predetermined temperature at the time of start-up, the steam from the steam generator 6 is directly supplied into the reaction tower 5, or is provided between the heat exchanger 3 and the reaction tower 5. It is also possible to heat the waste water with the heating device 4.

The reaction temperature in the reaction tower 5 is usually 1
The temperature is about 50 ° C or higher, more preferably about 150 to 370 ° C. The higher the temperature during the reaction, the higher the decomposition rate of cyanide compounds and the shorter the retention time of wastewater in the reaction tower, but on the other hand, the equipment cost increases, so the concentration of cyanide compounds in wastewater and the required treatment It may be determined by comprehensively considering the degree of the above, operating cost, construction cost, and the like. The pressure during the reaction may be equal to or higher than the pressure at which the waste water can maintain the liquid phase at a predetermined temperature.

The amount of oxygen added to the cyanide-containing wastewater is less than the theoretical amount of oxygen required to decompose cyanide compounds, nitrogen compounds, organic and inorganic substances into harmless products,
More preferably, it is about 0.01 to 0.5 times the theoretical oxygen amount. When the amount of oxygen is less than 0.01 times the theoretical amount of oxygen, the decomposition of cyanide compounds will be insufficient, while even if it exceeds 0.5 times, the further improvement of the decomposition efficiency is recognized. I can't. As an oxygen source, air, oxygen-enriched air, oxygen, and oxygen containing one or more of hydrogen cyanide, hydrogen sulfide, ammonia, sulfur oxides, organic sulfur compounds, nitrogen oxides, hydrocarbons, etc. as impurities Waste gas etc. are illustrated.

The reaction can also be promoted by providing a plurality of trays inside the reaction tower 5.

Alternatively, the decomposition reaction can be promoted by filling the inside of the reaction tower 5 with a filler made of metal oxide, metal or the like. As such a packing, a known catalyst carrier can be used as it is. More specifically, alumina, silica, zirconia, titania, composite metal oxides containing these metal oxides (alumina-silica, alumina-silica-zirconia, titania-zirconia, etc.), these metal oxides or composites Examples thereof include metal oxide-based fillers containing a metal oxide as a main component and metal-based fillers such as iron and aluminum. Among these, zirconia, titania, and titania-zirconia, which have excellent durability, are more preferable. The shape of the filling body is not particularly limited, and may be any shape such as spherical shape, pellet shape, cylindrical shape, crushed piece shape, powder shape, and honeycomb shape.

Sludge (for example, black Fe ₂ O ₃ as a main component when the wastewater is iron cyanide complex ion-containing wastewater) may be accumulated in the reaction tower 5 with the passage of time. . In such a case, for example, the inside of the reaction tower 5 is cleaned or washed with air, water, steam, chemicals, etc.,
It is preferable to periodically remove the accumulated sludge.
Alternatively, the accumulated sludge can be continuously withdrawn from the lower part of the reaction tower 5 by a lock hopper method. Similar cleaning or washing can be performed on other devices such as the heat exchanger 3 if necessary.

The cyanide-containing wastewater tends to form sludge at about 150 ° C. or above, especially because the decomposition reaction of cyanide is promoted. Therefore, in order to suppress the accumulation of sludge in the heat exchanger 3, the cooled final treatment liquid 20 is added to the secondary treatment liquid sent from the reaction tower 14 used for heat exchange via the line 30. It is preferable to circulate and mix a part of the cyan-containing wastewater in the heat exchanger 3 to a temperature of about 150 ° C. or less by circulating the mixture from the line 33 via the pump 21.

Treatment liquid from the reaction tower 5 (primary treatment liquid)
Enters the gas-liquid separator 7 and is separated into a gas phase component 8 and a liquid phase component 9. The liquid phase component 9 is sent to the solid-liquid separator 10,
Solid-liquid separation is performed into a liquid phase 11 and a solid content (sludge) 12 under high temperature and high pressure. Solid-liquid separation can be performed by methods such as a carrier filling method, a filter filtration method, a magnetic separation method, a cyclone method, and a gravity sedimentation method. The solid-liquid separation can be continuously performed by configuring the solid-liquid separator 10 with two towers and alternately switching the separation operation and the washing operation.
Alternatively, the removal of sludge from the solid-liquid separator 10 can be performed periodically by a lock hopper method after a predetermined period.

Liquid phase after solid-liquid separation (primary treatment liquid) 11
Is mixed with the gas phase component 8 separated as described above, further mixed with an oxygen-containing gas whose pressure has been raised in advance by the compressor 22, and then supplied to the reaction tower 14 filled with a catalyst. Although not shown, the oxygen-containing gas may be supplied to the primary treatment liquid 11 or the heat exchanger 3 prior to the supply to the reaction tower 14 if necessary.
You may heat-exchange with the liquid phase 32 from.

When it is not possible to maintain a predetermined reaction temperature during the reaction in the reaction tower 14 in winter or the like, the heater 13 is used.
It is also possible to heat the primary treatment liquid or supply steam to the reaction tower 14 from a steam generator (not shown). Further, in order to bring the inside of the reaction tower 14 to a predetermined temperature at the time of start-up, heating can be performed by the heater 13, or steam can be directly fed into the reaction tower 14 to raise the temperature.

Treatment liquid from the reaction tower 14 (secondary treatment liquid)
As described above, after being used as a heat source in the heat exchanger 3 via the lines 30 and 31, it is sent to the cooler 15 and further to the gas-liquid separator 16, where the gas phase 17 and the liquid phase 18 And separated.

The liquid phase 18 obtained from the secondary treatment liquid is sent to the solid-liquid separator 19 and contains metal and / or metal contained in the liquid phase.
Alternatively, after the sludge component is removed, the final treatment liquid 20 is obtained. As a solid-liquid separation method in the solid-liquid separator 19,
Known methods such as a method using gravity settling, a method using a magnet, a method using a filter press, and a method using coagulating sedimentation can be adopted.

The difference between the primary reaction tower 5 and the secondary reaction tower 14 is that the latter is filled with the catalyst supported on the carrier.

Examples of the catalytically active component include iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold and tungsten, and water-insoluble or sparingly water-soluble compounds of these metals. More specific examples of such compounds include oxides (cobalt oxide, iron oxide, etc.), chlorides (ruthenium dichloride,
Platinum dichloride, etc.), sulfides (ruthenium sulfide, rhodium sulfide, etc.) and the like. These metals and their compounds may be used alone or in combination of two or more kinds. These catalytically active components are used in a state of being supported on known metal oxide carriers and metal carrier carriers according to a conventional method. The metal oxide carrier and the metal carrier are not particularly limited, and those known as catalyst carriers can be used. Examples of the metal oxide carrier include alumina, silica, zirconia, titania, composite metal oxides containing these metal oxides (alumina-silica, alumina-silica-zirconia, titania-zirconia, etc.), these metal oxides or composite metal oxides. Examples of the metal carrier include a metal oxide-based carrier containing a substance as a main component, and examples of the metal carrier include iron and aluminum. Among these carriers, zirconia, titania and titania-zirconia, which have excellent durability, are more preferable.

The shape of the supported catalyst is not particularly limited, and examples thereof include a spherical shape, a pellet shape, a cylindrical shape, a crushed piece shape, a powder shape, and a honeycomb shape. In the case of using a fixed bed, the reaction tower volume in the case of using such a supported catalyst packed is such that the space velocity of the liquid is about 0.5 to 10 Hr ⁻¹ , more preferably ¹ to 5 Hr.
^It is good to set it to about ^-1 . The size of the supported catalyst used in the fixed bed is usually about 3 to 50 mm, more preferably about 5 to 25 mm in the case of a spherical shape, a pellet shape, a cylindrical shape, a crushed piece shape, a powder shape, or the like. Further, as the honeycomb structure when the catalyst is supported on the honeycomb-shaped carrier and used, an opening having any shape such as a quadrangle, a hexagon and a circle is used. The area per unit volume, the aperture ratio, etc. are not particularly limited, but usually the area per unit volume is 200 to 800 m ² / m ³ , and the aperture ratio is 40.
Use about 80%. Examples of the material for the honeycomb structure include the same metal oxides and metals as those described above, and zirconia, titania, and titania-zirconia having excellent durability are more preferable.

When the fluidized bed is formed in the reaction tower 14, the amount of the supported catalyst that can form the fluidized bed in the reaction tower 14, that is, usually 0.01 to 2 based on the weight of the cyanide-containing wastewater is used.
About 0%, more preferably about 0.05 to 10% is used by suspending it in a slurry in the primary treatment liquid. When a fluidized bed is used, the supported catalyst is supplied to the reaction tower 14 in a state of being suspended in a slurry in the primary treatment liquid, and the catalyst is removed from the treated liquid discharged outside the tower after the completion of the reaction. It is separated and collected by an appropriate method such as sedimentation or centrifugation and used again.
Therefore, considering the ease of separation and recovery of the catalyst from the treated liquid, the particle size of the supported catalyst used in the fluidized bed is
More preferably, it is about 0.15 to 0.5 mm.
The amount of the catalytically active metal supported is not particularly limited, but is usually in the range of about 0.01 to 25% by weight of the carrier, more preferably about 0.1 to 3%.

II. Second Invention of the Present Application FIG. 2 is a flow sheet showing an outline of the second invention of the present application.

In the second invention of the present application, the gas-liquid mixture from the reaction tower 14 is separated into a gas phase and a liquid phase by the gas-liquid separator 23, and at least a part of the gas phase containing residual oxygen that has not been used in the reaction. Is used as a part of the oxygen source, and the remainder of the gas phase is recycled to the reaction column 5 via line 24.
4 is substantially different from the first invention of the present application in that it is circulated to the reaction tower 14 via a line 27 branched from No. 4 and that the oxygen-containing gas from the compressor 22 is supplied to the primary treatment liquid. There is no.

That is, in the second invention of the present application, at least the gas phase obtained in the gas-liquid separator 23 is adjusted so that the oxygen amount in the reaction tower 5 becomes 0.01 to 0.5 times the theoretical oxygen amount. A part is circulated to the reaction tower 5 via the line 24. At this time, the liquid phase is sent to the heat exchanger 3 via lines 30 and 31.
Therefore, oxygen cannot be supplied from the compressor 22 to the cyan-containing wastewater supplied to the reaction tower 5, but only to the primary treatment liquid supplied to the reaction tower 14.

As a result, the practical effect of reducing the amount of oxygen used is achieved.

III. Third Invention of the Present Application FIG. 3 is a flow sheet showing an outline of the third invention of the present application.

In the third invention of the present application, a part of the secondary treatment liquid separated by the gas-liquid separator 23 is circulated to the reaction tower 14 via a line 29 branching from the line 30 and a pump 26, and in the reaction. There is no substantial difference from the first invention of the present application except that a gas phase containing unused oxygen is circulated to the reaction column 14 via the line 27 and used as a part of the oxygen source. .

Due to this partial circulation of the secondary treatment liquid, the liquid linear velocity in the reaction tower 14 increases, and the adhesion of metal components remaining in the primary treatment liquid to the catalyst surface is reduced.
Due to the increase in the flow rate in the reaction tower 14 and the uniform temperature distribution in the reaction tower 14, excellent catalytic activity is maintained for a long period of time.

The circulation amount of the secondary treatment liquid is appropriately determined according to the degree of progress of the decrease in the catalytic activity, but is usually the reaction tower 14.
The amount is about 1 to 20 times, and more preferably about 1 to 10 times the amount of the primary treatment liquid supplied to the.

When the temperature inside the tower becomes too high due to the heat generated by the decomposition reaction in the reaction tower 14, a heat exchanger (not shown) is arranged between the gas-liquid separator 23 and the pump 26. By performing heat recovery by performing the heat recovery, the temperature of the secondary treatment liquid in the reaction tower 14 and in the circulation can be adjusted.

IV. Fourth Invention of the Present Application FIG. 4 is a flow sheet showing an outline of the fourth invention of the present application.

The fourth invention of the present application is a line 2 for branching a part of the liquid phase separated by the gas-liquid separator 23 from the line 30.
9 is substantially the same as the second invention of the present application except that it is circulated to the reaction tower 14 via the pump 9 and the pump 26.

By partially circulating the liquid phase into the reaction tower 14, the same effect as the third invention of the present application is achieved. Further, the same effect as that of the second invention of the present application is achieved by partially circulating the gas phase to the reaction tower 5.

[0050]

EFFECTS OF THE INVENTION According to the method of the present invention, the cyanide complex ions and cyanide in the wastewater are substantially completely decomposed, and they are hardly contained in the final treatment liquid and the sludge produced. Further, nitrogen oxides, organic substances and inorganic substances in the waste water are also substantially completely decomposed, so that a stable waste water treatment effect is achieved. .

Substantially no harmful components are found in either the gas phase or the liquid phase after the final gas-liquid separation. When an oxygen-containing waste gas is used as an oxygen source, the presence of harmful components derived from the waste gas is substantially not recognized in either the gas phase or the liquid phase. Moreover, the sludge formed is excellent in sedimentation and easy to handle.

Further, according to the method of the present invention, since the processing flow is extremely simple, the processing cost (equipment cost, operating cost, etc.) is significantly reduced, and the process control is facilitated.

[0053]

EXAMPLES Examples and comparative examples will be shown below to further clarify the features of the present invention.

Example 1 A cyan complex ion-containing waste liquid having the composition shown in Table 1 was treated according to the first invention of the present application according to the flow shown in FIG.

[0055]

[Table 1]

Cyan-containing wastewater of pH 10.6 is Na
Since it contained 1.087 mol·l ⁻¹ and K 0.385 mol·l ⁻¹ of a total of 1.472 mol·l ⁻¹ of alkali metal, the sulfuric acid from the sulfuric acid storage tank 25 was added to the wastewater from the booster pump. 0.74 mol, which is equivalent to half the amount of alkali metal
was added at a rate of l ^-1, space velocity 1.0 hr ^-1 (superficial reference)
While supplying air to the reaction tower 5 at a mass velocity of 14.15 m ³ · m ^-2 · Hr ^-1 , air was supplied at a space velocity of 3.4 Hr ^-1 (empty column standard, standard state conversion). The air supply amount was an amount corresponding to 0.0103 times the theoretical oxygen amount (82.5 Nm ³ / kl).

In the reaction, waste water and air are introduced into the inlet side of the heat exchanger 3, and the temperature of the gas-liquid mixture at the outlet side of the heat exchanger 3 (the inlet side of the reaction tower 5) is 150 ° C.
Thus, a part of the final treatment liquid 20 was circulated and mixed with the second treatment liquid from the reaction column 14 flowing through the line 30 by the pump 21 through the line 33 to control the temperature.
In addition, by sending steam from the steam generator 6 to the reaction tower 5, the temperature inside the reaction tower 5 is 220 ° C. and the pressure is 30 kg.
^-Hold to cm ^-2 . The reaction tower 5 was equipped with trays every 70 cm.

In the primary treatment liquid having a pH of 6.9 from the reaction tower 5, the metal components in the initial waste water are contained in the lower part of the reaction tower 5 and the high pressure type solid-liquid separator 10 (in this embodiment, titanium burning). It was pulled out from the lower part (using a metal filter). Primary treatment liquid 11 obtained at the outlet of solid-liquid separator 10
The composition and the like were as shown in Table 2.

[0059]

[Table 2]

The lower part of the reaction tower 5 and the solid-liquid separator 1
The sludge extracted from 0 (titanium sintered metal filter) has a reddish brown color and contains Fe ₂ O ₃ as a main component,
As other components, P ₂ O ₅ , Na ₂ O, ZnO, SiO
And the like, the CN content was 1 mg · l ⁻¹ or less, and the precipitate had a good sedimentation property.

Subsequently, the space velocity of the primary treatment liquid is set to 0.7.
5Hr ^-1 (empty tower standard) and mass velocity 14.15m ³ ·
While supplying m ⁻² · Hr ⁻¹ to the reaction tower 14, air was supplied at a space velocity of 90.4 Hr ⁻¹ (empty tower standard, standard state conversion). The air supply amount was an amount equivalent to 1.1 times the theoretical oxygen amount. In addition, a spherical catalyst (diameter 4 to 6 mm) in which 2% of the weight of the carrier was supported on ruthenium was loaded in the reaction tower 14, and the temperature and the pressure were maintained almost the same as in the reaction tower 5.

Table 3 shows the composition of the secondary treatment liquid from the reaction tower 14.

[0063]

[Table 3]

Next, the secondary treatment liquid was subjected to coagulation-precipitation treatment at a temperature of 25 ° C. under normal pressure.

Table 4 shows the composition of the final treatment liquid 20 thus obtained.
Shown in

[0066]

[Table 4]

Note: Cadmium and its compounds, total chromium, lead, and mercury were not detected as metal components.

As is clear from the comparison between Tables 1 and 4, according to the method of the present invention, the cyan component is substantially completely decomposed, and the ammonia and formic acid produced from cyan during the course of the reaction are also decomposed. In the end, it was almost decomposed. Most of the metal components were removed by the lower part of the reaction tower 5 and the solid-liquid separator 10. Further, the gas phase 17 does not contain cyanide and ammonia, and is substantially O ₂ , N ₂ and CO ₂
Consisted of

Comparative Example 1 The cyanide-containing wastewater having the composition shown in Table 1 was treated in the same manner as in Example 1 except that air was not supplied to the reaction tower 5.

0.40 mg of T-CN in the primary treatment liquid
L- ¹ and cyan was not completely decomposed. Also, NH ₃ --N in the primary treatment liquid is 6720.
a mg · l ^-1, TOD was 24800mg · l ^-1.

The sludge withdrawn from the lower part of the reaction tower 5 and the solid-liquid separator 10 has a reddish brown color, and Fe ₂ O ₃
As the main component, and other components such as P ₂ O ₅ , Na ₂ O,
Contains ZnO, SiO _2, etc., CN content is 130 mg
-Kg ^-1 , which was a precipitate with low sedimentation property.

Example 2 and Comparative Examples 2 to 7 By controlling the circulating amount of the final treatment liquid 20, as shown in Table 5, gas-liquid at the outlet side of the heat exchanger 3 (inlet side of the reactor 5). Example 1 except that the temperature of the mixture was adjusted variously
Similarly to the above, the cyanide-containing wastewater having the composition shown in Table 1 was subjected to wet oxidation treatment.

[0073]

[Table 5]

The amount of sludge produced in the heat exchanger, the heater and the pipes thereof due to the decomposition of the cyan complex component is based on the amount produced in Example 1 (the outlet side temperature of the heat exchanger 3 is 150 ° C.) (100). Are shown in Table 6.

[0075]

[Table 6]

When the waste water containing cyanide is heated so that the outlet temperature of the heat exchanger exceeds 150 ° C., the amount of sludge produced in the heat exchanger, the heater and these pipes is increased even when sulfuric acid is added. , The pressure loss increases. Therefore, by jet water cleaning, chemical cleaning, etc.,
It is necessary to regularly remove the generated sludge from these equipment.

That is, the time during which stable operation can be continuously performed is about 1 / th in Comparative Example 7 as compared with Example 1.
It was only 40. These results indicate that by setting the outlet temperature of the heat exchanger 3 to 150 ° C. or lower, the operation of the entire device can be stably performed for a long period of time.

The water quality of the secondary treatment liquid in Example 2 and Comparative Examples 2 to 7 was substantially the same as that of the secondary treatment liquid in Example 1 (see Table 3 above).

Examples 3 to 6 and Comparative Example 8 Wastewater treatment was carried out according to the second invention of the present application according to the flow shown in FIG. That is, as shown in Table 7, cyan was performed in the same manner as in Example 1 except that the amount of oxygen supplied to the reaction column 5 (the amount corresponding to the relative oxygen amount when the theoretical oxygen amount was 1) was variously changed. Wet oxidation treatment of the contained wastewater was performed.

[0080]

[Table 7]

In the case of Comparative Example 8 in which the air supply amount was less than 0.01 times the theoretical oxygen amount, the proportion of T-CN in the primary treatment liquid was 0.27 mg · l ⁻¹ . Was detected in. On the other hand, in Examples 3 to 6, T-CN in the primary treatment liquid was 0.1 mg · l ⁻¹ or less.

When air was supplied in an amount equal to or more than 0.5 times the theoretical oxygen amount, T-CN in the primary treatment liquid was 0.1 mg · l ⁻¹ or less, but the compression was Increase in power costs,
This is not preferable because it causes disadvantages such as an increase in heating fuel (or supply vapor amount) accompanying an increase in the amount of liquid evaporation in the system.

The water quality of the secondary treatment liquid in Examples 3 to 6 and Comparative Example 8 was substantially the same as that of the secondary treatment liquid in Example 1 (see Table 3 above). Also,
The gas phase 17 was cyan and ammonia free and consisted essentially of O ₂ , N ₂ and CO ₂ .

Examples 7 to 10 Example 1 except that the treatment temperature in the reaction tower 5 is variously changed.
Similarly to the above, the cyan complex ion-containing waste liquid shown in Table 1 was treated so as to have the same water quality as the primary treatment liquid in Example 1 (see Table 2). Table 8 shows the results when the residence time in the reaction tower 5 in Example 1 was 100.

[0085]

[Table 8]

Example 11 The cyan complex ion-containing waste liquid having the composition shown in Table 1 was treated according to the third invention of the present application according to the flow shown in FIG.

That is, after the reaction tower 5 was filled with titania spheres having a diameter of 5 mm, and the gas-liquid mixture in the reaction tower 14 was separated by the gas-liquid separator 23, the amount was 2.5 times the primary treatment liquid. Separated liquid (liquid phase) reaction tower 14 corresponding to the amount
The reaction was performed in the same manner as in Example 1 except that the solution was circulated in Example 1.

The water quality of the primary treatment liquid from the reaction tower 5 and the sludge after gas-liquid separation were the same as those in Example 1 (T-CN of the treated liquid was 0.1 mg · l ^-1 or less, in the sludge. Of CN = 1 mg · kg ⁻¹ or less), the residence time in the reaction tower 5 was shortened by about 12% as compared with Example 1. The sludge obtained from the lower part of the reaction tower 5 has a reddish brown color, contains Fe ₂ O ₃ as a main component, and Fe
_The precipitate contained ₃ O ₄ , P ₂ O ₅ , Na ₂ O, ZnO, SiO _{2 and the} like and had good sedimentation properties.

Similar effects were achieved when zirconia spheres or titania-zirconia spheres were used as the filler instead of the above titania.

By the circulation of the secondary treatment liquid to the reaction tower 14 as described above, the time until NH ₃ —N is detected in the final treatment liquid is about four times that in Example 1. Extended.

Examples 12 to 22 According to the flow shown in FIG. 4, the packed catalyst in the reaction tower 14 was changed variously, and the gas phase after the gas-liquid separation of the product (secondary treatment liquid) in the reaction tower 14 was changed. Circulating and supplying to the reaction tower 5 at a ratio corresponding to 0.02 times the theoretical oxygen amount, and gas-liquid separation of the product (secondary processing liquid) in the reaction tower 14 from the first processing liquid 11. The cyanide-containing wastewater was treated according to the fourth invention of the present application in the same manner as in Example 1 except that the subsequent liquid phase was circulated and supplied at a ratio of 1.5 times.

Table 9 shows the properties of the catalyst and the secondary treatment liquid used.
Shown in

[0093]

[Table 9]

[Brief description of drawings]

FIG. 1 is a flow sheet showing an outline of the first invention of the present application.

FIG. 2 is a flow sheet showing an outline of the second invention of the present application.

FIG. 3 is a flow sheet showing an outline of a third invention of the present application.

FIG. 4 is a flow sheet showing an outline of a fourth invention of the present application.

[Explanation of symbols]

 1 ... Waste water storage tank 2 ... Pump 3 ... Heat exchanger 4 ... Heating device 5 ... Primary reaction tower 6 ... Steam generator 7 ... Gas-liquid separator 8 ... Gas-phase component 9 ... Liquid-phase component 10 ... Solid-liquid separator 11 ... Primary treatment liquid 12 ... Sludge 13 ... Heater 14 ... Secondary reaction tower 15 ... Cooler 16 ... Gas-liquid separator 17 ... Gas phase 18 ... Liquid phase 19 ... Solid-liquid separator 20 ... Final treatment liquid 21 ... Pump 22 ... Compressor 23 ... Gas-liquid separator 24 ... Gas phase circulation line 25 ... Sulfuric acid storage tank 26 ... Pump 27 ... Gas phase circulation line 29 ... Liquid phase circulation line 30 ... Liquid phase circulation line 31 ... Liquid phase circulation line 32 ... Liquid phase circulation line 33 ... Final treatment liquid circulation line

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01J 23/38 B01J 23/38 M 23/42 23/42 M 23/44 23/44 M 23 / 46 23/46 M 301 301M 311 311M 23/52 23/52 M 23/70 23/70 M 23/72 23/72 M 23/745 C02F 1/58 CDCN 23/75 B01J 23/74 301M 23/755 311M C02F 1/58 CDC 321M

Claims (16)

[Claims] 1. A method which comprises continuously performing the following steps in wet-treating cyanide-containing wastewater: (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, After preheating to a temperature of up to 150 ° C by heat exchange with the secondary treatment liquid, while maintaining a temperature of 150 ° C or higher and a pressure at which the wastewater maintains a liquid phase, cyan compounds, nitrogen compounds, organic compounds in the wastewater Process of obtaining a primary treatment liquid by wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount required for decomposing substances and inorganic substances, (2) Sludge from the high temperature and high pressure primary treatment liquid And / or a step of separating and removing a metal component, and (3) in the presence of a catalyst containing at least one of a metal and a metal compound as an active component in the high-temperature, high-pressure primary treatment liquid and in the treatment liquid, nitrogen. Wet oxidation treatment in the presence of oxygen at a theoretical oxygen amount or more necessary for decomposing compounds, organic substances and inorganic substances, while maintaining a temperature of 150 ° C. or higher and a pressure at which the treatment liquid maintains a liquid phase. The step of obtaining the secondary treatment liquid by. 2. The method for treating cyanide-containing wastewater according to claim 1, wherein steam is fed into the reaction vessel of step (1) to raise the temperature. 3. The addition amount of at least one of sulfuric acid, sulfur and a sulfur compound in step (1) is 0.25 to 0.55 per 1 mol of the total amount of alkali metal in the cyan-containing wastewater.
The method for treating cyanide-containing wastewater according to claim 1, wherein the amount is twice as much. 4. The catalytically active component in step (3) is iron,
The cyan according to claim 1, which is at least one selected from the group consisting of cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold and tungsten, and compounds of these metals which are insoluble or sparingly soluble in water. Treatment method of wastewater containing. 5. A method comprising continuously performing the following steps when wet treating cyanide-containing wastewater: (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, After preheating to a temperature of up to 150 ° C by heat exchange with the secondary treatment liquid, while maintaining a temperature of 150 ° C or higher and a pressure at which the wastewater maintains a liquid phase, cyan compounds, nitrogen compounds, organic compounds in the wastewater Process of obtaining a primary treatment liquid by wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount required for decomposing substances and inorganic substances, (2) Sludge from the high temperature and high pressure primary treatment liquid And / or a step of separating and removing a metal component, (3) in the presence of a catalyst containing at least one of a metal and a metal compound as an active component in the primary treatment liquid and in the treatment liquid, a cyanide compound, a nitrogen compound and an organic compound. Stuff Quality and inorganic substances in the presence of more than the theoretical amount of oxygen required to decompose oxygen in the presence of a temperature of 150 ℃ or more and the pressure of the treatment liquid to maintain a liquid phase, by wet oxidation treatment Step (4) of obtaining the treatment liquid, and (4) at least a part of the gas phase obtained by gas-liquid separation of the secondary treatment liquid is circulated to the above-mentioned step (1) and used as an oxygen source in the step (1). Process. 6. The method for treating cyanide-containing wastewater according to claim 5, wherein steam is fed into the reaction vessel of step (1) to raise the temperature. 7. The addition amount of at least one of sulfuric acid, sulfur and a sulfur compound in step (1) is 0.25 to 0.55 per 1 mol of the total amount of alkali metal in the waste water containing cyanide.
The method for treating cyanide-containing wastewater according to claim 5, wherein the amount is double. 8. The catalytically active component in step (3) is iron,
The cyan according to claim 5, which is at least one selected from the group consisting of cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold and tungsten, and compounds of these metals which are insoluble or sparingly soluble in water. Treatment method of wastewater containing. 9. A method comprising continuously performing the following steps in wet-treating cyanide-containing wastewater; (1) adding at least one of sulfuric acid, sulfur and a sulfur compound to cyanide-containing wastewater, After preheating to a temperature of up to 150 ° C by heat exchange with the secondary treatment liquid, while maintaining a temperature of 150 ° C or higher and a pressure at which the wastewater maintains a liquid phase, cyan compounds, nitrogen compounds, organic compounds in the wastewater To obtain a primary treatment liquid by wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount required for decomposing substances and inorganic substances, (2) sludge and high-temperature high-pressure primary treatment liquid And / or a step of separating and removing a metal component, (3) a cyanide compound, a nitrogen compound, an organic substance in the treatment liquid in the presence of a catalyst containing at least one of a metal and a metal compound as an active component in the primary treatment liquid And a secondary treatment by performing a wet oxidation treatment in the presence of oxygen at a theoretical oxygen amount or more necessary for decomposing the inorganic substance while maintaining a temperature of 150 ° C. or more and a pressure at which the treatment liquid maintains a liquid phase. A step of obtaining a liquid, and (4) at least a part of the liquid phase obtained by gas-liquid separation of the secondary treatment liquid is circulated to the step (3) at a ratio of 1 to 10 times that of the primary treatment liquid. Process. 10. The method for treating cyanide-containing wastewater according to claim 9, wherein steam is fed into the reaction vessel of step (1) to raise the temperature. 11. The addition amount of at least one of sulfuric acid, sulfur and a sulfur compound in step (1) is 0.25 to 0.5 per 1 mol of the total amount of alkali metal in the cyan-containing wastewater.
The method for treating cyanide-containing wastewater according to claim 9, wherein the amount is 5 times. 12. The catalytically active component in step (3) is
10. At least one selected from the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold and tungsten, and compounds of these metals which are insoluble or sparingly soluble in water. Method for treating wastewater containing cyanide. 13. A method comprising continuously performing the following steps when wet treating cyanide-containing wastewater: (1) at least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, After preheating to a temperature of up to 150 ° C by heat exchange with the secondary treatment liquid, while maintaining a temperature of 150 ° C or higher and a pressure at which the wastewater maintains a liquid phase, cyan compounds, nitrogen compounds, organic compounds in the wastewater To obtain a primary treatment liquid by wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount required for decomposing substances and inorganic substances, (2) sludge and high-temperature high-pressure primary treatment liquid And / or a step of separating and removing a metal component, (3) a cyanide compound, a nitrogen compound, an organic substance in the treatment liquid in the presence of a catalyst containing at least one of a metal and a metal compound as an active component in the primary treatment liquid Quality and inorganic substances in the presence of more than the theoretical amount of oxygen required to decompose oxygen in the presence of a temperature of 150 ℃ or more and the pressure of the treatment liquid to maintain a liquid phase, by wet oxidation treatment A step of obtaining a treatment liquid,
(4) At least a part of the gas phase obtained by gas-liquid separation of the secondary treatment liquid is circulated to the step (1) to obtain the step (1).
And (5) at least a part of the liquid phase obtained by gas-liquid separation of the secondary treatment liquid at a ratio of 1 to 10 times the amount of the primary treatment liquid (3). The process of circulating to. 14. The method for treating cyanide-containing wastewater according to claim 13, wherein steam is fed into the reaction vessel of step (1) to raise the temperature. 15. The addition amount of at least one of sulfuric acid, sulfur and a sulfur compound in step (1) is 0.25 to 0.5 per 1 mol of the total amount of alkali metal in the cyan-containing wastewater.
The method for treating cyanide-containing wastewater according to claim 13, wherein the amount is 5 times as much. 16. The catalytically active component in step (3) is
14. At least one selected from the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold and tungsten, and compounds of these metals which are insoluble or sparingly soluble in water.
The method for treating wastewater according to.