JPH05285491A - Treatment of ammonical liquor of coke oven - Google Patents

Abstract

PURPOSE:To efficiently reduce the COD component in the ammonical liquor generated in a coke oven using activated sludge and ozone. CONSTITUTION:The ammonical liquor generated in a coke oven 1 is subjected to activated sludge treatment and the treated liquor is subsequently subjected to ozone treatment to reduce the COD component in the ammonical liquor. In this method, the pH of the ammonical liquor to be introduced is controlled to an almost constant value within a pH range of 8-10 and the redox potential in an activated sludge treatment tank 12 is controlled to 150-300 mv to subject the ammonical liquor to activated sludge treatment and, thereafter, ozone is added to the treated water with pH 6-7 in an oxidizing treatment tank 17 under stirring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently reducing the COD component in the safe water generated in a coke oven by using activated sludge and ozone.

[0002]

2. Description of the Related Art In recent years, the global environmental problems that have come to the fore are:
From ozone depletion, global warming, acid rain and other atmospheric problems to ocean pollution such as water quality problems and hazardous waste problems. Especially for water pollution, countermeasures have recently been focused on due to the delay of the standard achievement rate.

There are many water quality countermeasures in the steel industry as well, but the ammonium hydroxide produced in the coke oven is a multi-component mixture due to the large amount of treatment and coal dry distillation.
Since the treatment method is difficult, biological sludge treatment, filtration treatment, coagulation sedimentation treatment and the like have been adopted.

The above-mentioned activated sludge treatment requires a long reaction time because it uses the oxidation reaction of living organisms and is weak to fluctuations due to the adaptability of living organisms. Therefore, it is very difficult to make the treatment tank large and finely control it. There are problems such as. In order to improve the activated sludge capacity, the coke sanctuary, Vol. 36, No. 1, 1987 has been used to control the redox potential and dissolved oxygen in the sludge tank to control the sedimentation of the activated sludge. A method is disclosed. Also, "Chemical Equipment" October issue 1
In 991, a method of decolorizing and reducing COD by adsorbing activated carbon was disclosed as a measure to comply with water quality regulations that are difficult to treat with a simple organism. Further, Japanese Patent Laid-Open No. 49-70457 discloses a method of utilizing for decolorization by blowing ozone into the treated water after activated sludge, and "Mitsubishi Electric Technique", No. 4
Volume 6, No. 5, 1972 discloses a removal method by blowing ozone into cyan and phenol wastewater.

[0005]

In the biological treatment using activated sludge described in the above conventional method, the treatment capacity of activated sludge follows large fluctuations in the water quality of the introduced treated water, that is, rapid environmental changes. However, there are problems such as the inability to do so, the slow adaptation to the environment and the death in some cases, and the simultaneous treatment of multi-component systems, which limits the treated value.

[0006] As a part of this countermeasure, for example, a combined treatment such as treatment of the treated water with activated carbon after adsorption with activated sludge has been carried out. In order to support the maximum treatment value, large equipment is required, and when treating treated water containing a large amount of macromolecules such as cheap water, physical adsorption to the surface inside the pores should be avoided. In the activated carbon method, which is the principle, there is a case where particularly large molecular weight particles cannot be adsorbed due to their large molecular diameter.

Further, when the treated water after the activated sludge treatment or the raw water is subjected to the oxidation treatment by using ozone, the ozone is consumed by the rhodan, ammonia, etc. other than the COD component, and the component such as cyan is newly added. CO occurs in the water
Since the non-COD component could not be converted to the non-COD component by the oxidation of the D component, efficient removal was impossible.

An object of the present invention is to provide a method for efficiently reducing the COD component in the ammonium hydroxide by applying activated sludge treatment and ozone treatment under specific conditions.

[0009]

According to the present invention, when reducing the COD component in the ammonium hydroxide by treating the ammonium hydroxide generated in the coke oven with activated sludge and then ozone treatment, the pH of the ammonium chloride introduced is 8 to 8. The oxidation-reduction potential in the activated sludge treatment tank is controlled to be within a range of 10 to 150-300.
It is a coke oven sewage treatment method characterized in that activated sludge treatment is carried out under mv control, and then ozone is added to the treated water of PH 6 to 7 and stirred in an oxidation treatment tank.

[0010]

According to the present invention, first, the ammonium hydroxide generated from the coke oven is mixed with an alkaline aqueous solution, sea water or fresh water to obtain a treated water having a substantially constant pH value in the range of 8 to 10. The sludge treatment load can be stably performed without excess or deficiency. The above-mentioned substantially constant value means that the pH does not change abruptly even if the pH fluctuates gently within the range of 8 to 10. Specifically, the pH of the continuously supplied treated water is The range of change within the range of 8 to 10 is managed within a range of ± 30%, for example.

Further, in the treatment tank for treating the treated water, which is controlled to a substantially constant value within the range of pH 8 to 10, with the activated sludge,
For example, the oxygen reduction potential in the activated sludge treatment tank is controlled to 150 to 300 mv by supplying an oxygen source using an air diffuser or by agitating the surface layer of the treated water with an impeller or the like to take in air as the oxygen source. Since the activated sludge is treated by the method, rhodan in the treated water is removed to 2 ppm or less, and the ammonia in the treated water is oxidized to generate 10 to 100 ppm of nitrous acid, thereby reducing the amount of ammonia and reducing the pH of the treated water to 6%. Can be set to 7 and PH treated water suitable for the subsequent oxidation treatment with ozone can be prepared.

When ozone is added to the treated water obtained by settling and separating the activated sludge from the treated sludge-containing treated water after the above-mentioned activated sludge treatment to oxidize, the pH of the treated water is increased by nitrification of nitrous acid, which is oxidized first. Since it can be reduced to 5-6, it is possible to avoid consumption of ozone to oxidation of ammonia, avoidance of cyanation by oxidative decomposition of rhodan, selective oxidation of COD component in treated water, and mixing of toxic substances such as cyanide into treated water. Can be prevented.

In the present invention, the pH value of the treated water, which is the target treated water, is usually a value of 8 or more. However, the value of the component of the ammonium hydroxide varies depending on the coke oven operating conditions and coal conditions, and the value is often high. The phenomenon shown below occurred, making the activated sludge treatment difficult. For example, if the pH of the treated water suddenly fluctuates to 10 during the process of controlling the pH of the treated water to 8, the activated sludge treatment is disturbed, a large amount of undigested COD remains, and some of the activated sludge dies. In addition, there is a problem that a large amount of ozone is consumed in the oxidation treatment with ozone after the activated sludge treatment.

Therefore, according to the present invention, in order to control the pH to a substantially constant value within the range of 8 to 10, an alkaline aqueous solution, seawater or fresh water is selectively blended to reduce the fluctuation range within a possible range.

The redox potential in the activated sludge treatment tank is 1
If it is less than 50 mv, the activated sludge becomes oxygen deficient and the activity is lowered. On the other hand, if it exceeds 300 mv, over-aeration will occur and the self-digestion phenomenon of activated sludge will occur, and nitrite will be excessively produced, and the consumption of ozone will increase during the preferential oxidation of nitrite by ozone in the subsequent oxidation treatment step. ..

Therefore, according to the present invention, an oxygen source is introduced into the treated water to control the redox potential to 150 to 300 mv. The control means can be adjusted by the amount of air supplied from the air diffuser or the number of rotations of the impeller, and naturally both means can be used in combination.

As for the amount of microorganisms in the treatment tank, it is preferable to adjust the ratio of the amount of COD to be treated per day and the volume of the microorganism tank to 1.0 to 1.5.

In the oxidation treatment with ozone after the activated sludge treatment, the treated water from which the activated sludge has been separated is stirred and mixed with ozone in a stirring tank. By this oxidation treatment with ozone, the nitrous acid in the treated water is preferentially oxidized to nitric acid, and the PH in the treated water becomes 5 to 6, and at this stage COD
Since the oxidative decomposition treatment of 1 proceeds, the ozone addition amount is adjusted according to the COD reduction amount in the treated water.

In order to further improve the efficiency of the oxidative decomposition treatment with ozone, it is desirable to make the diameter of ozone bubbles in the treated water as small as possible, and in order to make the ozone bubbles stay longer in the treated water, a number 1 using an impeller is used.
High speed stirring of 000 rpm is good. By this ozone oxidation,
Ozone consumption can be minimized and COD amount in treated water can be accurately reduced.

As a means for further increasing the utilization efficiency of ozone, as shown in FIG. 1, an ozone oxidation treatment tank equipped with the agitation treatment means is provided in multiple stages, for example, two tanks are installed.
By supplying the ozone 18 discharged from the first tank to the second tank after being supplied to the tank and being oxidized, the utilization rate of ozone is increased and the amount of ozone blown in at the time of a transient COD change becomes easy.

As described above, according to the present invention, the COD amount of the treated water is reduced on average in the activated sludge treatment against the fluctuation of the component of the ammonium hydroxide generated from the coke oven, and the transition of the treated water by the ozone treatment is performed transiently. Since the COD change can be dealt with, the COD amount in the safe water can always be controlled to be equal to or less than a certain value even if the safe water component in any coke oven operation changes.

The present invention will be described in detail below with reference to the drawings. FIG. 2 is an explanatory diagram of an example of a processing flow for implementing the present invention.

The coke oven gas generated in the coke oven 1 is led to the cooler 3 through the pipe 2 to remove ammonia, sulfide,
A gas liquid containing an organic substance such as cyanide, an inorganic compound, and phenol is stored in the raw sewage water tank 5 through the pipe 4. A large amount of ammonia, cyanide compounds, hydrogen sulfide, etc. are removed from the raw water by a distillation column 8 through a pipe 7 by a pump 6. PH mixed with seawater or water
The treated water adjusted to a substantially constant value within the range of 8 to 10 is introduced into the activated sludge treatment tank 12 through the pipe 10 by the pump 9.

The activated sludge in the treatment tank 12 is 1 per tank.
With the daily COD processing amount ratio adjusted to 1.0 to 1.5,
The redox potential in the tank 12 is adjusted to 150 to 3 by the air pipe 13.
Air is introduced so that the pressure becomes 00 mv. The method of supplying the air to the activated sludge in the treatment tank 12 may be not only the introduction method using the above-mentioned piping but also a method using air entrainment by an impeller or the like (not shown).

The treated water treated with the activated sludge is piped 14
Is introduced into the settling tank 15 to separate the activated sludge from the treated water. The separated treated water is introduced into the ozone stirring tank 17 through the pipe 16 and stirred with the ozone 18 by the stirrer 19. At this time, the number of rotations of the stirrer is preferably such that the ozone bubble diameter is 1 mm or less and the residence time is about 5 minutes. The temperature is preferably about 30 ° C.

FIG. 1 shows a mode in which two oxidation treatment tanks 17 for ozone 18 are arranged. Treated water and ozone are introduced into the first tank, and the impeller 19 agitates them at high speed to proceed with the oxidation treatment. The treated water extracted from the first tank is introduced into the second tank through the pipe 16. On the other hand, the exhaust gas containing ozone extracted from the first tank is introduced into the second tank. Ozone can be adjusted by newly adding ozone to this exhaust gas.

The treated water that has been subjected to the oxidation treatment is guided to a drainage facility (not shown) such as a drainage channel for treatment.

[0028]

[Example] PH of coke oven is 9 and water temperature is 30
After adjusting with diluting water, steam, etc. to the desired degree, guide it to the activated sludge tank, and adjust the amount of activated sludge in the activated sludge tank to the tank outlet weir height,
Adjust the daily COD treatment amount ratio per activated sludge tank to about 1.0 to 1.5 by squeezing the discharge pipe, etc., and supply an oxygen source to the activated sludge tank with a diffuser pipe to reduce the redox potential 15
The test was carried out by adjusting to 0 to 250 mV.

The results are shown in Table 1. Test No. 1 and 2 are examples of the present invention, in which COD reduction and rhodane reduction at a constant ozone amount and generation of cyan and the like can be controlled, and efficient water treatment can be performed. Incidentally, No. No. 3 is a comparative example, in which COD and rhodane were poorly reduced, and cyan was generated.

[0030]

[Table 1]

[Brief description of drawings]

FIG. 1 is an explanatory view of a two-tank type device for stirring and mixing treated water and ozone.

FIG. 2 is an explanatory diagram of an example of a processing flow for implementing the present invention.

[Explanation of symbols]

 1 ... Coke oven 2, 4 ... Gas piping 3 ... Cooler 5 ... Anhydrous tank 6 ... Pump 7 ... Piping 8 ... Distillation tower 9 ... Pump 10 ... Piping 11 ... Diluting water 12 ... Activated sludge treatment tank 13 ... Air supply pipe 14 ... Piping 15 ... Settling tank 16 ... Piping 17 ... Mixing tank 18 ... Ozone 19 ... Impeller

Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication C02F 9/00 A 8515-4D (72) Inventor Shoichi Yamaguchi 5-3 Tokai-cho, Tokai City Nippon Steel Corporation Inside Nagoya Steel Works

Claims (1)

[Claims] 1. The pH of the ammonium hydroxide introduced when the ammonium hydroxide generated in the coke oven is treated with activated sludge and then treated with ozone to reduce the COD component in the ammonium hydroxide, is a substantially constant value within the range of 8 to 10. It is characterized by controlling the oxidation-reduction potential in the activated sludge treatment tank to 150 to 300 mv and treating the activated sludge, and then adding ozone to the treated water of PH6 to 7 in the oxidation treatment tank and stirring. Method of treating coke oven sewage.