JPH09108698A - Ammoniacal liquid treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of treating ammoniacal liquid in which treatment cost is lowered. SOLUTION: Ammoniacal liquid still treatment water 5 is sent to an acidic tank 17 to make it acidic water 19 adjusted to an acidic area of about pH3-5. The acidic water 19 is sent to a filter 14 and is separated into filtrate 15 and filter cake 16. The filtrate 15 is sent to a neutralization tank 6 to turn it into neutralized water 30 adjusted to about pH7. The neutralized water 30 is sent to an aeration tank 9 together with dilution water 10 and is subjected to activated sludge treatment by using microorganisms in the aeration tank 9. Neutralized water 30a is discharged as discharge water to outside the system via a flocculating and settling basin 11 and an activated carbon adsorption tank 12. Further, the filter cake 16 is sent to a combustion facility 24 to subject it to combustion treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ammonium hydroxide treatment method for treating ammonium hydroxide generated when cooling generated gas discharged from, for example, a vertical continuous forming coke oven.

[0002]

2. Description of the Related Art Generally, in a room furnace type coke oven for producing coke by dry-coiling coal, an annoying water is produced when the produced gas (coke oven gas) is cooled. In this cheap water,
A large amount (high concentration) of substances (components) are mixed (dissolved) and exhibit a high BOD (biochemical oxygen demand) concentration.
Therefore, from the viewpoint of environmental regulations, it is not possible to discharge the safe water as it is, and it is necessary to treat the safe water to reduce the BOD concentration of the safe water.

A conventional method for treating ammonium hydroxide will be described with reference to FIG. FIG. 4 is a flow chart showing a method for treating cheap water, and simultaneously shows two typical types of treating methods for treating cheap still water. The low-water 2 is supplied to the low-water still 1, where it is heated by the steam 3 to remove gas components 4 such as ammonia dissolved in the low-water 2 and become low-water still-treated water 5 from the low-water still 1. Is discharged.

[0004] As a method for treating the treated water 5 of still water still,
As described above, there are two typical treatment methods, one is the activated sludge treatment method and the other is the combustion treatment method. First, a method for treating activated sludge will be described. Ammonia still-treated water 5 which is generally alkaline (usually pH value =
7.5-9.5) is sent to the neutralization tank 6, and in this neutralization tank 6, an inorganic acid agent (inorganic acid) 7 such as sulfuric acid or hydrochloric acid is added.
Is added to the ammonium hydroxide still-treated water 5 to make the neutralized water 8 whose pH value is adjusted to about 7. The neutralized water 8 is supplied to the aeration tank 9 together with the diluting water 10, and in the aeration tank 9, the neutralized water 8 is treated with activated sludge using microorganisms. The neutralized water 8a that has been treated with activated sludge is used in the coagulation sedimentation tank 11 and the activated carbon adsorption facility 1
It is discharged to the outside of the system as discharged water 13 via 2

Next, the combustion treatment method will be described. The low-water still-treated water 5 is sent to the concentrating tower 20, where the low-water still-treated water 5 is concentrated by a heating medium 21 such as steam to be evaporated water 22 and concentrated water 23. The concentrated water 23 is sent to the combustion facility 24 and burned.

[0006]

The ammonium hydroxide is treated by the above method, but the concentration of dissolved components in the ammonium hydroxide generated during the operation of the vertical continuous forming coke oven is generally the same as that of the conventional chamber furnace. Shows a higher tendency than that from the type coke oven,
Highly toxic to microorganisms used in activated sludge treatment. Therefore, in order to prevent the killing of microorganisms, the dilution ratio of the neutralized water 8 in the aeration tank 9 needs to be 2-3 times higher than that in the case of the low water generated in the conventional chamber-type coke oven. There is a problem that a large amount of neutralized water 8a is generated, the size of the treatment equipment after the aeration tank 9 is forced to increase, the equipment construction cost and the running cost increase, and the treatment cost increases. on the other hand,
The combustion treatment method has a problem that the treatment cost (operating cost) of cheap water is high because the consumption of heating energy for evaporation of water is large.

In view of the above circumstances, it is an object of the present invention to provide a low water treatment method capable of reducing the treatment cost.

[0008]

[Means for Solving the Problems] A method for treating ammonium hydroxide of the present invention for achieving the above object is a method for treating ammonium hydroxide generated when a gas discharged from a coke oven is cooled. (1) degassing the ammonium hydroxide water to make ammonium hydroxide still water, acidifying the ammonium hydroxide still water to acidic water, filtering the acidic water to separate into filtered water and filter cake, The method is characterized by including a step of neutralizing the filtered water into neutralized water and treating the neutralized water with activated sludge. (2) Incineration of the filtered cake.

[0009]

The present inventors have found the following (a) to (c) as a result of various experiments and studies for achieving the above object. (A) The gel-like polymer substance suspended in ammonium hydroxide is a toxic substance, and the gel-like polymer substance can be contained and separated in a filter cake (precipitate) by a filtration treatment. (B) The main component of the filter cake is a gel-like polymer substance. (C) As shown in FIG.
As the H value increases and becomes more acidic, the removal rate of the filter cake (precipitate) by the filtration treatment increases. Therefore, according to the method for treating ammonium hydroxide of the present invention, the ammonium hydroxide treated water is converted to acidic water. Is separated into filtered water and filter cake, and the filtered water is neutralized and then aerated, so substances that are highly toxic to microorganisms (mainly gel-like polymer substances) are separated as filter cake. It Therefore, the toxicity of the filtered water is relatively reduced, and when diluting the filtered water into neutralized water, the dilution ratio of the filtered water with seawater etc. can be made smaller than before and the equipment can be downsized. You can Further, the filter cake can be treated by a general method such as combustion treatment. Therefore, the processing cost of the cheap water can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the ammonium hydroxide treatment method of the present invention will be described below with reference to the drawings. FIG. 1 is a flow chart showing a method of treating ammonium hydroxide, and the same elements as those in the flow chart of FIG. 4 are designated by the same reference numerals. Still water treated water discharged from still water still 1 5
Is sent to the acid tank 17. In this acidic tank 17, inorganic acids 7 such as sulfuric acid are added to the ammonium hydroxide still water 5, and the ammonium hydroxide still water 5 is made into acidic water 19 whose pH value is adjusted to an acidic range of about 3 to 5. It The acidic water 19 is sent to the filter 14, where the acidic water 19 is separated into the filtered water 15 and the filter cake 16, and the filtered water 15 is sent to the neutralization tank 6. In the neutralization tank 6, the inorganic bases 18 such as caustic soda are added to the filtered water 15, and the filtered water 15 is made into the neutralized water 30 whose pH value is adjusted to about 7. Neutralization water 30 is dilution water 1
0 is sent to the aeration tank 9 and is treated with activated sludge in the aeration tank 9 using microorganisms. The activated sludge-treated neutralized water 30a is discharged out of the system as discharged water 13 via the coagulating sedimentation tank 11 and the activated short adsorption facility 12. On the other hand, the filter cake 16 is sent to the combustion equipment 24 and burned.

FIG. 2 shows the pH of the acidic water supplied to the filter.
The relationship between the value and the filter cake removal rate is shown. As shown in FIG. 2, as the pH value of the acidic water 19 supplied to the filter 14 is lower, the removal efficiency of the filter cake (gelled polymer substance) is improved. However, the lower the pH value of the acidic water 19 is, the lower the pH value of the filtered water 15 is, which is economically disadvantageous because the pH value of the filtered water is returned to about 7 for neutralization in the neutralization tank 6. Therefore, in the acidic tank 17, it is a good idea to study and determine the most economical pH value according to the property of the cheap water. When the pH value of the acidic water 19 is set to about 5 to 7, the removal efficiency of the filter cake is low and it is considered that a large amount of toxic substances are contained in the filtered water, so the dilution ratio in the neutralization tank 6 is lowered so much. I can't.

Table 1 and FIG. 3 show a comparison of the experimental results of treating the ammonium hydroxide by the above-mentioned ammonium hydroxide treatment method and the conventional ammonium hydroxide treatment method. The numbers on the curves in FIG. 3 indicate the operation numbers in Table 1.

[0013]

[Table 1]

In this experiment, the operations of the ammonium hydroxide still and the aeration tank were all performed under the same conditions. In an experiment (run No. 5) in which the dilution ratio was 6 times that of the conventional method, BOD increased immediately after the operation and a decrease in the treatment capacity was observed. Also, an experiment in which the dilution ratio was increased to 12 times (operation No. 6)
Then, although it is a reasonable result, since the dilution ratio is as high as 12 times, it is economically disadvantageous as described above. In the example, good results were obtained even at a dilution ratio of 3 times.

[0015]

As described above, according to the ammonium hydroxide treatment method of the present invention, it is decided to filter ammonium hydroxide treated water in an acidic region, and then neutralize and aerate.
The toxicity of filtered water is relatively reduced, and the dilution ratio at the time of neutralization can be reduced as compared with the conventional method, and the equipment can be downsized and the operating cost can be reduced, and the cheap water treatment cost can be reduced. .

[Brief description of the drawings]

FIG. 1 is a flow chart showing a method for treating ammonium hydroxide according to one embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the pH value of acidic water supplied to a filter and the filter cake removal rate.

FIG. 3 is a graph showing changes in BOD concentration of discharged water for 1 hour.

FIG. 4 is a flow chart showing a conventional method for treating ammonium hydroxide.

[Explanation of symbols]

 1 Stunning water still 2 Stunning water 3 Steam 4 Gas component 5 Stabilized still water 6 Neutralizing tank 8 Neutralizing water 9 Aeration tank 14 Filtering machine 15 Filtered water 16 Filter cake 17 Acidic tank 19 Acidic water 24 Combustion equipment

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C02F 9/00 503 C02F 9/00 503C 1/20 1/20 B 3/12 3/12 V ( 72) Inventor Yu Takahashi, 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Inside Kawasaki Steel Co., Ltd. (72) Inventor Tatsuya Ozawa, 1 Kawasaki-cho, Chuo-ku, Chiba City Chiba Steel Co., Ltd. ( 72) Inventor Tsuneo Aihara, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Chiba Works

Claims (1)

[Claims] 1. A method for treating low water produced when cooling the generated gas discharged from a coke oven, wherein the low water is degassed to produce low water still water, and the low water still is used. A step of treating the treated water to be acidic water, filtering the acidic water to separate into filtered water and a filter cake, neutralizing the filtered water to neutralized water, and treating the neutralized water with activated sludge And a step of incinerating the filter cake.