JPH08290177A - Treatment of cyanide-containing waste water - Google Patents

Abstract

PURPOSE: To provide a new technique capable of completely and inexpensively decomposing cyanides in a cyanide-contg. waste water with no need for an additional treatment. CONSTITUTION: A cyanide-contg. waste water is mixed with a sulfur compd., heated to 150 deg.C by the exchange of heat with a final treated liq. and then, in a first reaction tower 5, kept at a pressure for the waste water to maintain a liq. phase. The waste water is then wet-oxidized in the presence of oxygen in the amt. less than the stoichiometry necessary to decompose the cyanide compd., etc., in the waste water, and the formed sludge and/or metallic component are removed from the first reaction tower. In a second reaction tower 14, the waste water is kept at >=150 deg.C and at a pressure for the treated liq. to maintain a liq. phase and wet-oxidized in the presence of a catalyst with a metal as the active component and in the presence of oxygen in the amt. more than the stoichiometry necessary to decompose the cyan compd., etc., in the treated liq. The obtained high-temp. and high-pressure treated liq. is returned to normal temp. and pressure to separate and remove the sludge and/or metallic component, and the final treated liq. is obtained.

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 a chemical has a limit to the cyanide concentration in the waste water which can be applied from the economical aspect, 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 treated sludge, (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. In addition, according to the conventional processing method, there is a problem that the processing of the waste liquid containing high-concentration cyanide containing the cyan complex ion complicates the process and increases the processing cost.

[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. (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, which is heated to a temperature of up to 150 ° C in advance by heat exchange with the final treatment liquid, and then heated to 150 ° C or higher in the first reaction tower. Wet oxidation treatment in the presence of oxygen below the theoretical oxygen amount required to decompose cyanide compounds, nitrogen compounds, organic substances and inorganic substances in wastewater while maintaining the temperature of the wastewater and the pressure that maintains the liquid phase of the wastewater Process,
(2) A step of removing the sludge and / or metal components produced in the step (1) from the first reaction tower, (3)
The high-temperature high-pressure treatment liquid obtained in the above step (1) is used in the second reaction column in the presence of a catalyst containing at least one of a metal and a metal compound as an active component, and a cyan compound in the treatment liquid, In the presence of oxygen in excess of the theoretical amount of oxygen required to decompose nitrogen compounds, organic substances and inorganic substances,
While maintaining the temperature of 150 ° C. or higher and the pressure of the treatment liquid maintaining the liquid phase, the wet oxidation treatment step is performed, and (4) the high temperature and high pressure treatment liquid obtained in the above step (3) is returned to normal temperature and normal pressure. After that, the method for treating cyanide-containing wastewater is provided with a step of obtaining a final treatment liquid by separating and removing sludge and / or metal components.

II. (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, which is heated to a temperature of up to 150 ° C in advance by heat exchange with the final treatment liquid, and then heated to 150 ° C or higher in the first reaction tower. Wet oxidation treatment in the presence of oxygen below the theoretical oxygen amount required to decompose cyanide compounds, nitrogen compounds, organic substances and inorganic substances in wastewater while maintaining the temperature of the wastewater and the pressure that maintains the liquid phase of the wastewater Step (2), the step of removing the sludge and / or the metal component generated in the step (1) from the first reaction tower, (3) the high-temperature high-pressure treatment liquid obtained in the step (1) above In the second reaction tower in the presence of a catalyst containing at least one of a metal and a metal compound as an active ingredient and for decomposing a cyanide compound, a nitrogen compound, an organic substance and an inorganic substance in the treatment liquid. Reason In the presence of oxygen or oxygen, while maintaining the pressure 0.99 ° C. or higher temperatures and processing solution to maintain liquid phase, the step of wet oxidation treatment,
(4) A step of circulating at least a part of the gas phase obtained by the gas-liquid separation after the treatment in the step (3) to the step (1) and using it as an oxygen source in the step (1),
And (5) a step of obtaining a final treatment liquid by returning the treatment liquid of high temperature and high pressure obtained in the above step (3) to room temperature and normal pressure and then separating and removing sludge and / or metal components. A method for treating cyanide-containing wastewater, comprising:

III. (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, which is heated to a temperature of up to 150 ° C in advance by heat exchange with the final treatment liquid, and then heated to 150 ° C or higher in the first reaction tower. Wet oxidation treatment in the presence of oxygen below the theoretical oxygen amount required to decompose cyanide compounds, nitrogen compounds, organic substances and inorganic substances in wastewater while maintaining the temperature of the wastewater and the pressure that maintains the liquid phase of the wastewater Step (2), the step of removing the sludge and / or the metal component generated in the step (1) from the first reaction tower, (3) the high-temperature high-pressure treatment liquid obtained in the step (1) above In the second reaction tower in the presence of a catalyst containing at least one of a metal and a metal compound as an active ingredient and for decomposing a cyanide compound, a nitrogen compound, an organic substance and an inorganic substance in the treatment liquid. Reason In the presence of oxygen or oxygen, while maintaining the pressure temperature and the treatment liquid of 0.99 ° C. to maintain the liquid phase, the step of wet oxidation treatment, (4)
At least a part of the liquid phase obtained by gas-liquid separation after the treatment in the step (3) is circulated to the step (3) at a ratio of 1 to 10 times the amount of the treatment liquid in the step (3). Process,
And (5) a step of returning the treatment liquid of high temperature and high pressure obtained in the above step (3) to room temperature and normal pressure and then removing sludge and / or metal components to obtain a final treatment liquid. A method for treating cyanide-containing wastewater, comprising:

IV. (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, which is heated to a temperature of up to 150 ° C in advance by heat exchange with the final treatment liquid, and then heated to 150 ° C or higher in the first reaction tower. Wet oxidation treatment in the presence of oxygen below the theoretical oxygen amount required to decompose cyanide compounds, nitrogen compounds, organic substances and inorganic substances in wastewater while maintaining the temperature of the wastewater and the pressure that maintains the liquid phase of the wastewater Step (2), the step of removing the sludge and / or the metal component generated in the step (1) from the first reaction tower, (3) the high-temperature high-pressure treatment liquid obtained in the step (1) above In the second reaction tower in the presence of a catalyst containing at least one of a metal and a metal compound as an active ingredient and for decomposing a cyanide compound, a nitrogen compound, an organic substance and an inorganic substance in the treatment liquid. Reason In the presence of oxygen or oxygen, while maintaining the pressure 0.99 ° C. or higher temperatures and processing solution to maintain liquid phase, the step of wet oxidation treatment,
(4) A step of circulating at least a part of the gas phase obtained by the gas-liquid separation after the treatment in the step (3) to the step (1) and using it as an oxygen source in the step (1),
(5) At least a part of the liquid phase obtained by gas-liquid separation after the treatment in the step (3) is treated in the step (3) in an amount of 1 to 10 times the amount of the treatment liquid in the step (3). And (6) after returning the high temperature and high pressure treatment liquid obtained in the above step (3) to room temperature and normal pressure, sludge and / or metal components are separated and removed to obtain a final treatment liquid. A method for treating cyanide-containing wastewater, comprising the steps of:

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 used are cyan waste liquid discharged from these surface treatment processes, 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 wastewater is pressurized from the wastewater storage tank 1 to a predetermined pressure by the pump 2, further mixed with the oxygen-containing gas which has been prepressurized by the compressor 22, and then heated by the heat exchanger 3 to a temperature of 150 ° C. or lower. After being heated, the primary reaction tower 5 (hereinafter, referred to as a secondary reaction tower 1
Reaction column 5 unless otherwise required to distinguish
Called).

Sulfuric acid is added to the cyanide-containing wastewater supplied to the reaction tower 5 from the storage tank 25 at an appropriate position from the wastewater storage tank 1 to the reaction tower 5. Cyan-containing wastewater may contain fairly large amounts of alkali metal compounds. Therefore, the total amount of alkali metals in cyan wastewater is 1
The pH is adjusted by adding 0.25 to 0.55 times the amount of sulfuric acid per mole. Further, this addition of sulfuric acid causes a nitrogen compound (especially NO
It is also possible to suppress the formation of ₂ nitrogen and NO ₃ nitrogen). Instead of 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. In the present invention, unless otherwise specified, the expression “sulfuric acid” also includes these substances.

As a heat source of the heat exchanger 3, a high-temperature treatment from the 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) is performed. Recycle the used solution. 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 heater 4 is used for heating, or the steam generator 6 to the reaction tower 5 are used.
It is also possible to supply steam to. Further, in order to bring the temperature in the reaction tower to a predetermined temperature at the time of start-up, steam is directly fed into the reaction tower 5 to raise the temperature, or a heater 4 is provided between the heat exchanger 3 and the reaction tower 5. Can be provided to raise the temperature.

The temperature in the first reaction is usually 150 ° C.
It is about 150 ° C to 370 ° C. The higher the temperature during the reaction, the higher the rate of decomposition and removal of cyanide compounds, and the shorter the retention time of waste water in the reaction tower, but on the other hand, the equipment cost increases, so the reaction temperature is
It may be determined by comprehensively considering the concentration of cyanide compound in the wastewater, the required degree of treatment, the operating cost, the 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,
The amount is more preferably about 0.01 to 0.5 times the theoretical oxygen amount, and particularly preferably about 0.02 to 0.4 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 the oxygen source, air, oxygen-enriched air, oxygen, hydrogen cyanide as impurities, hydrogen sulfide, ammonia, sulfur oxides, organic sulfur compounds, nitrogen oxides,
Examples thereof include oxygen-containing waste gas containing one kind or two or more kinds of hydrocarbons.

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

Alternatively, the reaction can be promoted by filling the inside of the reaction tower 5 with a filling material such as a metal oxide or a metal. 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 composite metals. Examples thereof include metal oxide-based fillers containing an 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, columnar shape, crushed piece shape, powder shape, and honeycomb shape.

Sludge (for example, black Fe ₂ O ₃ as a main component when the waste water is iron cyanide complex ion-containing waste water) is accumulated in the reaction tower 5 with the passage of time. The accumulated sludge was opened in valve a and
After the sludge liquid inside is transferred to the tank 40, it can be removed by closing the valve a. Tank 40
The steam can be supplied from the steam generator 6 as necessary to completely decompose the cyanide in the sludge. Since sludge and / or metal components are gradually deposited in the tank 40, the valve b is opened and the sludge liquid is discharged. The sludge generated in the reaction tower 5 can be withdrawn semi-continuously, for example, by the lock hopper system as described above.

The cyanide-containing wastewater tends to form sludge at a temperature of about 150 ° C. or above, particularly because the decomposition reaction of cyanide is promoted. Therefore, in order to suppress the accumulation of sludge in the heat exchanger 3, if necessary, a part of the cooled final treatment liquid 20 is pumped to the treated liquid from the reaction tower 14 used for heat exchange. It is preferable that the temperature of the cyanide-containing wastewater in the heat exchanger 3 is suppressed to about 150 ° C. or lower by circulating and mixing via the lines 33 and 31 via the.

The primary treatment liquid 11 exiting the reaction tower 5 is mixed with an oxygen-containing gas whose pressure has been boosted in advance by a compressor 22, and then supplied to a secondary reaction tower 14 filled with a catalyst.

When the predetermined reaction temperature cannot be maintained during the secondary reaction, such as in winter, heating is performed by the heater 13 or the reaction tower 1 is heated from a steam generator (not shown).
It is also possible to supply steam to 4. Further, in order to bring the inside of the reaction tower 14 to a predetermined temperature at the time of startup,
It is possible to circulate the high temperature primary treatment liquid from the reaction tower 5 to raise the temperature, to directly feed steam into the reaction tower 14 to raise the temperature, or to raise the temperature by the heater 13. it can.

The treated liquid (secondary treatment liquid) from the reaction tower 14 is used as a heat source in the heat exchanger 3,
It is sent to the cooler 15 and then to the gas-liquid separator 16 to be separated into a gas phase 17 and a liquid phase 18.

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 a known metal oxide carrier and metal carrier 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. As the metal oxide carrier,
Alumina, silica, zirconia, titania, composite metal oxides containing these metal oxides (alumina-silica, alumina-silica-zirconia, titania-zirconia, etc.), metals containing these metal oxides or composite metal oxides as main components Examples thereof include oxide-based carriers, and examples of metal carriers 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 sphere, pellet, column, crushed piece, powder, and honeycomb. 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 , the aperture ratio 4
The thing of about 0 to 80% is used. 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 a fluidized bed is formed in the reaction tower 14, the amount of the supported catalyst capable of forming a fluidized bed in the reaction tower 14, that is, usually 0.01 to 2 based on the weight of 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 secondary treatment liquid discharged outside the tower after the reaction is completed. The catalyst is separated and recovered by an appropriate method such as sedimentation and centrifugation, and then used again. Therefore, considering the ease of separation and recovery of the catalyst from the secondary treatment liquid, the particle size of the supported catalyst used in the fluidized bed is more preferably 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%.

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 the separation method in the solid-liquid separator 19, known methods such as separation by gravity settling, separation by a magnet, separation by a filter press, and separation by coagulation sedimentation can be adopted.

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 treatment liquid from the secondary reaction tower 14 is separated into a gas phase and a liquid phase by a gas-liquid separator 23, and one of the gas phases containing residual oxygen that has not been used in the reaction is used. Circulating a part to the primary reaction tower 5 and using it as the oxygen source thereof,
And, except that the residual gas phase is circulated to the second reaction column 14, there is substantially no difference from the first invention of the present application.

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,
As described above, it is used as a heat source for cyanide-containing wastewater.

The supply of the oxygen-containing gas from the compressor 22 is
It is not performed on the cyanide-containing wastewater introduced into the primary reaction tower 5, but is performed only on the primary treatment liquid supplied to the secondary reaction tower 14. As a result, the practical effect that the amount of oxygen-containing gas used is reduced and the power consumption of the compressor 22 is also reduced 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 the gas-liquid separation is performed. Except for circulating the gas phase containing residual oxygen separated by the separator 23 to the reaction tower 14 and using it as a part of the oxygen source, there is substantially no difference from the first invention of the present application.

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. When the temperature in the reaction tower 14 rises due to the heat of reaction associated with the decomposition of the wastewater-containing component,
A heat exchanger (not shown) is provided at an arbitrary position in the circulation path from the gas-liquid separator 23 to the reaction tower 14 via the line 9 and the pump 26 to recover excess heat, thereby The temperature can be controlled.

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

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

In the fourth 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 to be separated. Line 24 for at least part of the gas phase
Except that it is circulated to the primary reaction tower 5 via the above, and that the separated gas phase residue is circulated to the secondary reaction tower 14 via a line 27 branching from the line 24. There is no difference from the first invention.

By the circulation of the liquid phase, the same effect as the third invention of the present application is achieved. Further, the same effect as the second invention of the present application is achieved by the circulation of the gas phase.

[0049]

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. Also, nitrogen oxides, organic substances and inorganic substances in the wastewater are substantially completely decomposed. Furthermore, a stable wastewater 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, each step is continuously carried out and the processing flow is extremely simple, so that the processing cost (equipment cost, operating cost, etc.) is remarkably reduced and the process control is facilitated. .

[0052]

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.

[0054]

[Table 1]

That is, cyanide-containing wastewater (pH 10.
6) is Na 1.087 mol·l ⁻¹ and K 0.385
Since it contained mol·l ⁻¹ , the sulfuric acid from the sulfuric acid storage tank 25 was added to the wastewater from the booster pump 2 by half the amount of the alkali metal.
After adding in a ratio of 0.74 mol·l ⁻¹ , which corresponds to double the amount,
Space velocity 1.0 Hr ^-1 (empty tower standard) and mass velocity 1
While supplying to the reaction tower 5 at 4.15 m ³ · m ^-2 · Hr ^-1 ,
Air was supplied at a space velocity of 3.4 Hr ^-1 (based on empty column, converted to standard state). The air supply amount is the theoretical oxygen amount (82.5
The amount was 0.0103 times the amount of Nm ³ / kl).

In the reaction, wastewater and air to which sulfuric acid has been added are introduced into the inlet side of the heat exchanger 3, and the temperature of the gas-liquid mixture on the outlet side of the heat exchanger 3 (the inlet side of the reaction tower 5) is controlled. A part of the final treatment liquid 20 is passed through the pump 21 and the line 33 to reach 150 ° C.
The secondary treatment liquid from the reaction tower 14 circulated by 1 was circulated and mixed to adjust the temperature. Further, the inside of the reaction tower 5 was maintained at a temperature of 220 ° C. and a pressure of 30 kg · cm ⁻² by sending steam from the steam generator 6 to the reaction tower 5. It should be noted that the reaction tower 5 was equipped with a tray tower every 70 cm.

T-CN in the primary treatment liquid was 0.1 mg.
・ L ^-1 or less, NH ₃ -N is 6700 mg ・ L ^-1 , TO
C was 5200 mg · l ⁻¹ .

Sludge formed in the reaction tower 5 and / or
Alternatively, the metal component was removed by opening the valve a provided in the lower portion of the reaction tower 5, transferring the sludge liquid in the reaction tower 5 to the tank 40, and then closing the valve a. Tank 4
The sludge accumulated in 0 was removed by introducing steam from the steam generator 6 into the tank 40 and holding it at about 220 ° C. for 30 minutes, then cooling it, and then opening the valve b to discharge the sludge liquid. went.

The sludge obtained had a reddish brown color, Fe ₂ O ₃ was the main component, and P was the other component.
_The precipitate contained ₂ O ₅ , Na ₂ O, ZnO, SiO _2, etc., and had a CN content of 1 mg · kg ⁻¹ or less, and was a precipitate having good sedimentation property.

Subsequently, the primary treatment liquid having a pH of 10.2 was supplied to the reaction column 14 at a space velocity of 0.75 Hr ^-1 (empty column standard) and a mass velocity of 14.15 m ³ · m ^-2 · Hr ^-1. Meanwhile, air was supplied at a space velocity of 90.4 Hr ^-1 (based on empty column, converted to standard state). The air supply rate is 1.
The amount was equivalent to 1 time. The reaction tower 14 was filled with a spherical catalyst (diameter 4 to 6 mm) in which a titania carrier was loaded with 2% of the weight of the carrier, ruthenium, and the internal temperature and pressure were almost the same as those of the reaction tower 5. Held

Table 2 shows the composition of the secondary treatment liquid from the reaction tower 14.

[0062]

[Table 2]

Then, the secondary treatment liquid is cooled to a temperature of 25.
It was subjected to coagulation-precipitation treatment under normal pressure at ℃.

Table 3 shows the composition and the like of the obtained final treatment liquid.

[0065]

[Table 3]

Note: As metal components, cadmium, chromium, lead, mercury and their compounds were not detected.

As is clear from the comparison between Table 1 and Table 3, according to the method of the present invention, the cyan component is decomposed substantially completely, and 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 could be removed from the lower part of the reaction tower 5. The gas phase 17 was cyan and ammonia free and consisted essentially of O ₂ , N ₂ and CO ₂ .

Comparative Example 1 Cyan-containing waste water 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.

T-CN in the primary treatment liquid was 0.51 m.
g · l ⁻¹ , and cyan was not completely decomposed.

The sludge directly withdrawn from the lower part of the reaction tower 5 through the tank 40 has a reddish brown color and contains Fe ₂ O ₃ as a main component and P ₂ O ₅ , Na ₂ O and Z as other components.
Contains nO, SiO _2, etc., CN content is 141 mg.
It was a precipitate with a low sedimentation property at a weight of less than kg ^-1 .

On the other hand, in the same manner as in Example 1, the sludge liquid was once taken out to the tank 40 provided in the lower part of the reaction tower 5, and the steam was introduced from the steam generator 6 to the sludge liquid at about 220 ° C.
The content of CN in the extracted sludge was 1 mg · kg ⁻¹ or less after holding for 30 minutes.

Example 2 and Comparative Examples 2 to 7 By controlling the circulation amount of the secondary treatment liquid 20, Table 4
As shown in, the outlet side of the heat exchanger 3 (the inlet side of the reactor 5)
The cyanide-containing wastewater was heat-treated in the same manner as in Example 1 except that the temperature of the gas-liquid mixture in Example 2 was adjusted variously.

[0073]

[Table 4]

The amount of sludge generated in the heat exchanger 3, the heater 4 and the pipes thereof due to the decomposition of the cyan complex component is based on the amount generated in Example 1 (the outlet side temperature of the heat exchanger 3 is 150 ° C.) ( 100) is shown in Table 5.

[0075]

[Table 5]

As is clear from the results shown in Table 5, when the waste water containing cyanide is heated so that the outlet temperature of the heat exchanger exceeds 150 ° C, even if sulfuric acid is added, the heat exchanger and the heater are heated. Also, since the amount of sludge generated in these pipes increases, the pressure loss increases. Therefore, it is necessary to regularly remove the generated sludge from these devices by jet water jet cleaning, chemical cleaning, etc.

That is, the time during which stable operation can be continuously performed is about 1/40 in Comparative Example 7 as compared with Example 1.
It was nothing more than With such a result, by setting the outlet side temperature of the heat exchanger 3 to 150 ° C., the operation of the entire apparatus can be stably performed for a long period of time.

In Example 2 and Comparative Examples 2 to 7, the water quality of the secondary treatment liquid was substantially the same as that of Example 1.

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

[0080]

[Table 6]

In the case of Comparative Example 8 in which the air supply amount is less than 0.01 times the theoretical oxygen amount, the proportion of T-CN in the primary treatment liquid is 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.

Even when air is supplied in an amount equal to or more than 0.5 times the theoretical oxygen amount, T- in the primary treatment liquid is reduced.
CN was 0.1 mg · l ⁻¹ or less, but it is not preferable because it has disadvantages such as an increase in compression power cost and an increase in heating fuel (or vapor amount) due to an increase in liquid evaporation amount in the system. .

In Examples 3 to 6 and Comparative Example 8, the water quality of the secondary treatment liquid was substantially the same as that of Example 1.

Further, in any of Examples 3 to 6 and Comparative Example 8, the gas phase 17 did not contain cyan and ammonia, and substantially contained O ₂ and N ₂ and CO ₂ produced by the decomposition of the cyan component. It consisted of

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 wastewater having the composition shown in Table 1 was treated so as to have substantially the same water quality as that of Example 1 (see Table 2). Table 7 shows the results when the residence time in the reaction tower 5 in Example 1 was 100.

[0086]

[Table 7]

Example 11 According to the flow chart shown in FIG. 3, the cyan complex ion-containing waste liquid having the composition shown in Table 1 was treated by the third invention of the present application.

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. The amount of separated liquid (gas phase) corresponding to the amount of the reaction tower 1
The reaction was carried out in the same manner as in Example 1 except that the solution was circulated in No. 4.

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. (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 4 times as long as that in Example 1. Was extended to.

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 (second 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 8 shows the properties of the catalyst and the secondary treatment liquid used.
Shown in

[0094]

[Table 8]

[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 ... Heater 5 ... Primary reaction tower 6 ... Steam generator 11 ... Primary treatment liquid 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 ... Exhaust gas circulation line 25 ... Sulfuric acid storage tank 26 ... Pump 27 ... Vapor phase circulation line 29 ... Secondary treatment liquid circulation line 30 ... Secondary treatment liquid circulation line 31 ... Secondary treatment liquid circulation line 32 ... Secondary treatment liquid circulation line 33 ... Final treatment liquid circulation line 40 …tank

─────────────────────────────────────────────────── ─── 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) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, which is heated in advance to a temperature of up to 150 ° C by heat exchange with the final treatment liquid, and then in the first reaction column. At a temperature of 150 ° C. or higher and a pressure at which the waste water maintains a liquid phase, a cyanide compound in the waste water,
Wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount necessary for decomposing nitrogen compounds, organic substances and inorganic substances, (2) sludge and / or metal component produced in the above step (1) Is removed from the first reaction tower, and (3) the high temperature and high pressure treatment liquid obtained in the above step (1) is used in the second reaction tower in which at least one of a metal and a metal compound is an active ingredient. In the presence of a catalyst to be used and in the presence of oxygen at a theoretical oxygen amount or more necessary for decomposing a cyanide compound, a nitrogen compound, an organic substance and an inorganic substance in the treatment liquid, a treatment liquid at a temperature of 150 ° C. or higher and After the wet oxidation treatment is carried out while maintaining the pressure for maintaining the liquid phase, and (4) the high temperature and high pressure treatment liquid obtained in the above step (3) is returned to room temperature and atmospheric pressure, sludge and / or metal components are added. To remove Ri, processing method cyan-containing waste water comprising the step of obtaining a final processing solution. 2. The addition amount of at least one of sulfuric acid, sulfur and a sulfur compound in the step (1) is 0.25 to 0.55 times (as sulfuric acid) per 1 mol of the total amount of alkali metals in the waste water. The method for treating wastewater according to claim 1. 3. The method for treating wastewater according to claim 1, wherein steam is fed into the first reaction column of step (1) to raise the temperature. 4. The catalytically active component in step (3) is iron,
The wastewater 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. Processing method. 5. (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, which is preheated to a temperature of up to 150 ° C. by heat exchange with the final treatment liquid, and then in the first reaction column. At a temperature of 150 ° C. or higher and a pressure at which the waste water maintains a liquid phase, a cyanide compound in the waste water,
Wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount necessary for decomposing nitrogen compounds, organic substances and inorganic substances, (2) sludge and / or metal component produced in the above step (1) Is removed from the first reaction tower, and (3) the high temperature and high pressure treatment liquid obtained in the above step (1) is used in the second reaction tower in which at least one of a metal and a metal compound is an active ingredient. In the presence of a catalyst to be used and in the presence of oxygen at a theoretical oxygen amount or more necessary for decomposing a cyanide compound, a nitrogen compound, an organic substance and an inorganic substance in the treatment liquid, a treatment liquid at a temperature of 150 ° C. or higher and A step of performing a wet oxidation treatment while maintaining a pressure for maintaining a liquid phase, (4) circulating at least a part of the gas phase obtained by gas-liquid separation after the treatment in the step (3) to the step (1). The acid in step (1) And (5) returning the treatment liquid of high temperature and high pressure obtained in the above step (3) to room temperature and normal pressure, and then removing sludge and / or metal components to obtain a final treatment liquid. A method for treating cyanide-containing wastewater, comprising the step of: 6. The addition amount of at least one of sulfuric acid, sulfur and a sulfur compound in the step (1) is 0.25 to 0.55 times (as sulfuric acid) per mol of the total amount of alkali metals in the waste water. The method for treating wastewater according to claim 5. 7. The method for treating wastewater according to claim 5, wherein steam is fed into the first reaction column of step (1) to raise the temperature. 8. The catalytically active component in step (3) is iron,
The wastewater 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. Processing method. 9. (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, which is heated in advance to a temperature of up to 150 ° C. by heat exchange with the final treatment liquid, and then in the first reaction column. At a temperature of 150 ° C. or higher and a pressure at which the waste water maintains a liquid phase, a cyanide compound in the waste water,
Wet oxidation treatment in the presence of oxygen in an amount less than the theoretical oxygen amount necessary for decomposing nitrogen compounds, organic substances and inorganic substances, (2) sludge and / or metal component produced in the above step (1) Is removed from the first reaction tower, and (3) the high temperature and high pressure treatment liquid obtained in the above step (1) is used in the second reaction tower in which at least one of a metal and a metal compound is an active ingredient. In the presence of a catalyst to be treated, and in the presence of oxygen in excess of the theoretical oxygen amount necessary for decomposing the cyan compound, nitrogen compound, organic substance and inorganic substance in the treatment liquid, the treatment liquid is kept at a temperature of 150 ° C. A step of performing a wet oxidation treatment while maintaining a pressure for maintaining the phase, and (4) at least a part of the liquid phase obtained by gas-liquid separation after the treatment in the step (3) above in the step (3) above. 1 to 10 times as much as the processing liquid The step of circulating to step (3), and (5) returning the high temperature and high pressure treatment liquid obtained in the step (3) to room temperature and atmospheric pressure, and finally removing sludge and / or metal components to obtain a final product. A method for treating cyanide-containing wastewater, comprising the step of obtaining a treatment liquid. 10. The addition amount of at least one of sulfuric acid, sulfur and a sulfur compound in the step (1) is 0.25 to 0.55 times (as sulfuric acid) per 1 mol of the total amount of alkali metals in the waste water. 10. The method for treating wastewater according to claim 9. 11. The method for treating wastewater according to claim 9, wherein steam is fed into the first reaction column of step (1) to raise the temperature. 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 water-insoluble or sparingly soluble compounds of these metals. Wastewater treatment method. 13. (1) At least one of sulfuric acid, sulfur and a sulfur compound is added to cyanide-containing wastewater, which is heated in advance to a temperature of up to 150 ° C. by heat exchange with the final treatment liquid, and then in the first reaction column. The presence of oxygen in an amount less than the theoretical oxygen amount necessary to decompose the cyanide compound, the nitrogen compound, the organic substance and the inorganic substance in the wastewater while maintaining the temperature above 150 ° C and the pressure at which the wastewater maintains the liquid phase. A step of performing a wet oxidation treatment below, (2) a step of removing the sludge and / or metal components generated in the step (1) from the first reaction tower, (3) a step obtained in the step (1) The high-temperature high-pressure treatment liquid is used in the second reaction column in the presence of a catalyst containing at least one metal and a metal compound as an active component and in the treatment liquid, a cyanide compound, a nitrogen compound, an organic substance and an inorganic substance. Disassemble In the presence of a stoichiometric amount of oxygen or of oxygen required that, while maintaining the pressure 0.99 ° C. or higher temperatures and processing solution to maintain liquid phase, the step of wet oxidation treatment, (4)
At least a part of the gas phase obtained by gas-liquid separation after the treatment in the step (3) is circulated to the step (1),
A step of using as an oxygen source in the step (1), (5)
At least a part of the liquid phase obtained by gas-liquid separation after the treatment in the step (3) is circulated to the step (3) at a ratio of 1 to 10 times the amount of the treatment liquid in the step (3). Process,
And (6) a step of returning the treatment liquid of high temperature and high pressure obtained in the above step (3) to room temperature and normal pressure and then removing sludge and / or metal components to obtain a final treatment liquid. A method for treating cyanide-containing wastewater, comprising: 14. The addition amount of at least one of sulfuric acid, sulfur and a sulfur compound in the step (1) is 0.25 to 0.55 times (as sulfuric acid) per 1 mol of the total amount of alkali metals in the waste water. 14. The method for treating wastewater according to claim 13. 15. The method for treating wastewater according to claim 13, wherein steam is fed into the first reaction column of step (1) to raise the temperature. 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.