JPS6334795B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for removing ammonia from ammonium water generated in a coke oven. In the process of carbonizing coal to produce coke for steelmaking, moisture, moisture, and decomposed water in the coal are distilled out, producing so-called ammonium water. This ammonium water is recycled to cool and clean the coal gas produced during coal carbonization, and excess ammonium water is discharged outside the factory after undergoing activated sludge treatment, coagulation sedimentation treatment, and activated carbon adsorption treatment. ing. It is known that the treatment efficiency of this activated sludge treatment decreases when the ammonia concentration is high. For this reason, in the past, ammonium water was diluted 5 to 6 times for activated sludge treatment, but in this case, the aeration tank, sedimentation tank, etc. used for treatment became larger, and the construction costs for coagulation sedimentation treatment and activated carbon adsorption treatment increased. Both operating costs will be significantly higher. Therefore, as a pretreatment for activated sludge treatment, methods have recently been used to remove free ammonia (NH ₄ OH), fixed ammonia (NH ₄ Cl), etc. present in aqueous aqueous solution. In this method, fixed ammonia is removed by adding an alkali to the aqueous solution to convert the fixed ammonia into free ammonia, and then driving off the free ammonia with steam. The alkali to be added is
There is NaOH, Ca(OH) ₂ (slaked lime), but NaOH
Since Ca(OH)2 is expensive, Ca(OH) ₂ is generally used. However, when Ca(OH) ₂ is used, precipitation due to temperature changes and scaling due to impurities occur, and cleaning must be performed every 1 to 2 months, which is time-consuming and requires activated sludge treatment during the cleaning period. There are problems that have a negative impact on To prevent this, conventional methods have been to install a backup device or to perform simple distillation that removes only free ammonia, but this method is inefficient and reduces steam consumption to about 230 kg/m ³ ammonium chloride. There are many drawbacks. The present inventor considered a method of using a thermo-compressor as a method of significantly reducing the amount of steam used, but this method also has the problem of clogging of the pressure reducing tank and distiller of the thermo-compressor. The present invention was made in view of the above circumstances, and
The purpose of this is to add a scale dispersant to the ammonium water before putting it into the distiller or thermo compressor to prevent blockage caused by slaked lime, and to efficiently remove ammonia from the ammonium water. The purpose of the present invention is to obtain a method for removing ammonia in ammonium water that can remove ammonia. That is, in the present invention, fixed ammonia in ammonium water is decomposed with slaked lime to form free ammonia, and then a scale dispersant is added to the ammonium water, which is then sequentially introduced into a distiller and a thermocompressor. This method of removing ammonia in ammonium water is characterized by removing free ammonia by inhaling steam and steam in a thermocompressor. The present invention will be explained below with reference to the drawings. The figure is a system diagram showing an example of a method for removing ammonia in ammonium water. In this method, ammonium water 2 1 generated in a coke oven and stored in an ammonium water tank ₁ is introduced into a first distiller 6 through a prefilter 3 and heat exchangers 4 and 5. In the first distiller 6, free ammonia 8 in the ammonium chloride water is removed by steam 7. Ammonium water 2 ₂ from which ammonia has been removed passes through the heat exchanger 5 and enters the reaction tank 9, where it is converted into slaked lime (Ca(OH) ₂ ).
10 is added. This slaked lime 10 decomposes fixed ammonia (NH ₄ Cl, NH ₄ SCN, etc.) in aqueous solution into free ammonia. The amount of slaked lime added is usually 2 ₂ 1 m ³ of ammonium water.
(NH ₄ ⁺ 1500ppm) to about 3000 to 4000g/m ³ . Next, the ammonium water 2 ₃ in the reaction tank 9 is put into the tanker 11 to precipitate and remove the reaction product with the slaked lime, and then introduced into the stock solution tank 12. In this stock solution tank 12, a scale dispersant 13 is added to prevent reactants from adhering to the guide and causing blockage. The scale dispersant 13 includes phosphonic acid type and polymer type ones, and the amount added is about 5 to 10 ppm per 1 m ³ of ammonium water. In this case, polymer-based materials are preferable because they are effective even when added in small amounts. This scale dispersant 13 has no toxicity to activated sludge bacteria. Next, ammonium water 2 ₄ to which scale dispersant 13 was added
is introduced into the second distiller 14. In the second distiller 14, free ammonium in the ammonium water is removed by steam ₁₅₁ . Free ammonium is introduced as steam 7 into the first distiller 6 . Furthermore, the ammonium water ₂₅ from which free ammonia has been removed enters the thermocompressor 16, and further passes through the heat exchanger 4 and is treated with activated sludge. This thermo compressor 16
This is to increase the amount of steam ₁₅₁ introduced into the second distiller 14, and the steam ₁₅₂ is passed through the ejector 17 to the thermo compressor 16.
The amount of steam (steam 15 ₁ ) entering the second distiller 14 is increased. As a result, the amount of steam used (steam 15 ₂ )
The aim is to reduce energy consumption to approximately 103Kg/m ³ and save energy. Next, examples of the present invention will be described. Experimental Example 1 The oxygen absorption rate of activated sludge was measured to examine whether a scale dispersant would be an inhibitor of biological treatment. That is, a polymeric dispersant (Cryfloat D-501, trade name) was used as a scale dispersant, and a predetermined amount of this was added to ammonium water according to the method of the present invention. This ammonium water is used as a BOD source, and the oxygen absorption rate is determined for the sludge (24-25℃) that has been acclimated with this ammonium water.
Measured using a DO meter. The results are shown in Table 1. For comparison, the results are also shown in the same table for those in which no scale dispersant was added. The BOD at the time of measurement was 300 ppm.

[Table] From the table above, the oxygen absorption rate does not change much between when a scale dispersant is added and when it is not added.
Furthermore, since the amount of scale dispersant added is usually 500 ppm or less, it can be seen that the use of scale dispersant has no effect on activated sludge treatment. Example 2 The following experiment was conducted to examine the scale adhesion prevention effect of a scale dispersant. Add 10 ppm of polymer scale dispersant (Cryfloat D 601) to ammonium water containing slaked lime.
The mixture was passed through a short tube with an inner diameter of 10 mm and a length of 100 mm at a flow rate of 4/min, and the weight of deposits, the inner diameter of the short tube, and the deposition rate were measured 14 days later. For comparison, the weight of deposits and the rate of deposition on the inner diameter of the short tube were measured in the same manner for the sample without additives. Furthermore, based on these measurement results, the scale adhesion inhibition rate by the scale dispersant was measured. The composition of ammonium water to which slaked lime was added is shown in Table 2, and the measurement results are shown in Table 3. Example 3 The scale adhesion inhibition rate was also measured in the same manner for a sample to which 20 ppm of the above polymer scale dispersant was added. The results are shown in Tables 2 and 3.

【table】

【table】

[Table] As is clear from the above results, according to the present invention, the amount of steam used can be significantly reduced by using a thermo-compressor, and the addition of a scale dispersant can prevent clogging of the thermo-compressor and distiller. It has remarkable effects, such as preventing this and maintaining its function for a long period of time, allowing stable activated sludge treatment and eliminating the need for cleaning costs.

[Brief explanation of the drawing]

The drawing is a system diagram showing an example of the method for removing ammonia in ammonium water according to the present invention. DESCRIPTION OF SYMBOLS 1... Ammonium water tank, 2 ₁ to 2 ₅ ... Ammonium water, 6... First distiller, 9... Reaction tank, 10... Slaked lime, 11... Chickener, 12... Stock solution tank, 13... Scale dispersant, 14
...Second distiller, 16...Thermo compressor, 17
...Egiector.

Claims (1)

[Claims] 1. After decomposing the fixed ammonia in the ammonium water with slaked lime to form free ammonia, add a scale dispersant to the ammonium water, then put it into a distiller and a thermo-compressor in order, and add steam and thermo-compressor to the distiller. A method for removing ammonia in ammonium water, which is characterized by removing free ammonia by blowing steam in a tsser.