JP4096130B2 - Waste hydrochloric acid treatment method - Google Patents

Description

【００７６】
注：実施例４では、連続槽とバッチ槽に由来する廃塩酸を等量混合して、処理した。
【００７７】
濃縮液中の鉄(Fe⁺²＋Fe⁺³)濃度が約360g/lとなる様に、廃塩酸を蒸留液と濃縮液とに分離した。蒸留液の分析結果と蒸留液および遊離HClの回収率を表２に示す。
【００７８】
【表２】

【００７９】
注：遊離HClとは、Fe⁺²＋Fe⁺³などと不結合状態の分子状のHClを意味する。
【００８０】
蒸留液回収率=蒸留液量／廃塩酸量×100
遊離HCl回収率=蒸留液量×蒸留液中遊離HCl/廃塩酸量×廃塩酸中HCl
以上の結果から、廃塩酸中の鉄濃度が高く、遊離HCl濃度が低い場合には、蒸留液中のHClが低く、HCl回収率が低いことが明らかである。
【００８１】
実施例５〜８
メッキ処理工場(B社)で発生した廃塩酸を原液とし、且つ試験温度を各濃縮条件に対応した温度とする以外は実施例１〜４の手法に準じて、処理を行った。廃塩酸の分析値および処理条件を表３に示し、蒸留液の分析結果と蒸留液および遊離HClの回収率を表４に示す。
【００８２】
【表３】

【００８３】
【表４】

【００８４】
実施例９
図１に示すフローに従って大気圧で本発明を実施した。すなわち、鋼線製造工場(C社)で発生した廃塩酸(遊離HCl=200g/l、Fe(Fe⁺²＋Fe⁺³=88g/l)を使用して、その処理を行い、蒸発缶内部温度と濃縮倍率との関係を求めた。運転時の各機器における条件は、表５に示す通りである。
【００８５】
【表５】

【００８６】
結果を表６に示す。
【００８７】
【表６】

【００８８】
表６に示す結果から明らかな様に、濃縮液の温度または比重を測定することにより、原液中の鉄濃度に対応して、濃縮倍率を決めることができる。
【００８９】
なお、濃縮液を系外に取り出した場合に、常圧下において、３倍濃縮時に濃縮液の約40％が、４倍濃縮時に約９０％が、５倍濃縮時に約１００％がそれぞれ固化した。
【００９０】
実施例１０〜１１
図１に示すフローに従って大気圧で本発明を実施した。すなわち、鋼線製造工場(d社)で発生した廃塩酸(連続槽およびバッチ槽で発生した２種の廃塩酸の等量混合物）を使用して、その処理を行った。運転時の各機器における条件は、実施例９と同様である。廃塩酸の分析値および濃縮倍率を表７に示す。
【００９１】
【表７】

【００９２】
濃縮液中の鉄(Fe⁺²＋Fe⁺³)濃度が約360g/lとなる様に、廃塩酸を蒸留液と濃縮液とに分離した。蒸留液および濃縮液の分析結果などを表８に示す。
【００９３】
【表８】

【００９４】
実施例１０および１１のいずれにおいても、安定した濃縮処理が可能であった。また、濃縮液に適量の水を添加することにより、常温下での固化は認められなかった。
【００９５】
なお、実施例１０および１１によるコスト削減率(回収塩酸の使用による塩酸購入費の低減および減容による産業廃棄物処理費の低減)を算出すると、従来法に比して(現時点基準)、実施例１０の場合で約44％であり、実施例１１の場合で約35％である。
【００９６】
実施例１２
カランドリア型蒸発缶を用い、実施例１０の手法に準じて、減圧下にメッキ工場廃液（廃塩酸）の濃縮処理を行った。処理条件を表９に示し、結果を表１０に示す。
【００９７】
【表９】

【００９８】
【表１０】

【００９９】
表９および表１０に示す結果から明らかな様に、減圧下での処理によっても、実施例１０とほぼ同様の廃液処理結果が得られている。
【図面の簡単な説明】
【図１】本発明による廃水の濃縮処理の一例を示すフローシートである。
【符号の説明】
１…廃水タンク
３…廃水ポンプ
５…ボイラー
７…圧縮機
１２…濃縮器
１４…冷却器
１５…冷却水ライン
１７…蒸留液槽
１９…スチームトラップ
２２…電磁弁
２５…濃縮液タンク
２６…充填物[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating waste hydrochloric acid containing high-concentration iron contained in a steel material washing process in a steel wire manufacturing factory, a plating factory, or the like. In more detail, the present invention aims to reuse the waste hydrochloric acid by evaporating and recovering the effective hydrochloric acid remaining in the waste hydrochloric acid conventionally treated as industrial waste as it is and reducing the volume of the waste residue. The present invention relates to a method for recycling waste hydrochloric acid.
[0002]
[Prior art]
For example, in the conventional vapor compression evaporator shown in the drawing of Japanese Patent Application Laid-Open No. 59-26184, a large number of heat transfer tubes are provided in the upper part of a sealed evaporator having a stock solution reservoir in the lower part. The raw solution sent by the raw solution pump is evaporated on the outer surface of each heat transfer tube by spraying it with a sprayer, and the vapor generated by this evaporation is compressed with a blower compressor and heated. By supplying the heated steam into each heat transfer tube through a duct, the stock solution sprayed on the outer surface of each heat transfer tube is heated and evaporated, and air or the like is discharged from each heat transfer tube. By extracting the condensable gas with a vacuum generating means such as a vacuum pump, the inside of the evaporator is kept in a reduced pressure state equal to or lower than atmospheric pressure.
[0003]
However, this type of vapor compression evaporator has the following problems.
[0004]
I. The compression efficiency of the blower compressor main body is low, the amount of electric power required to compress the unit stock solution amount is increased, the operating cost is increased, and the equipment is also increased.
[0005]
B. Since the undiluted solution is spread on the outer surface of each heat transfer tube via the spreader, there is a reduction in the heat exchanger heat transfer coefficient resulting from poor liquid dispersion.
[0006]
C. In particular, when treating waste hydrochloric acid containing a large amount of iron, etc., due to increase in the concentration rate of the liquid or continuous operation, clogging and poor dispersion due to sludge in the liquid distributor nozzle part, dirt on the outer surface of each heat transfer tube, liquid specific gravity Or, it cannot effectively cope with a decrease in heat transfer coefficient due to an increase in viscosity or the like.
[0007]
Also, removal of the outer surface adhesion scale of each tube is often difficult because the liquid is dispersed and the liquid flow rate with respect to the outer surface of the heat transfer tube is slow.
[0008]
D. As a result of the above (b) and (c), the concentration process must be performed in a state where the evaporation amount per unit cross-sectional area is always low. Therefore, in order to increase the amount of evaporation per unit time, it is necessary to increase the heat transfer area or use a blower compressor with a high compression ratio. There is a problem that increases.
[0009]
E. In particular, when waste hydrochloric acid is to be treated, the steam contains high-concentration hydrochloric acid, which greatly restricts the selection of the material such as the compressor body. Due to such restrictions on the material of the apparatus, useful hydrochloric acid remaining in the stock solution cannot be recovered, and the concentrated residue cannot be sufficiently reduced in volume.
[0010]
[Problems to be solved by the invention]
Therefore, the present invention eliminates or reduces the problems of the prior art as described above, and provides a vapor compression concentration technique that is small in size and inexpensive in equipment cost and operation cost. The main purpose is to recover hydrochloric acid and achieve high volume reduction of the concentrated residue.
[0011]
[Means for Solving the Problems]
As a result of intensive research in view of the current state of the art as described above, the present inventor has compressed low pressure steam (usually about 1 kg / cm ² · G), which has been rarely used in the past, with a compressor to raise the temperature. The new waste hydrochloric acid treatment technology has been completed by effectively using the higher temperature / high pressure steam obtained by increasing the pressure.
[0012]
That is, this invention provides the processing method of the following waste hydrochloric acid.
[0013]
1. In the treatment method of waste hydrochloric acid using an evaporator,
(1) introducing the stock solution into the liquid between the liquid surface in the evaporator and the heat transfer tube;
(2) A process of heating and evaporating the liquid in the heat transfer tube after the steam is compressed and heated by the compressor and then supplied to the outside of the heat transfer tube in the evaporator.
(3) a step of cooling the steam generated in the evaporator with a cooler and recovering it as an aqueous hydrochloric acid solution;
(4) a step of recovering vapor condensate from the outside of the heat transfer tube in the evaporator,
(5) a step of controlling the compressor output in response to a signal indicating the temperature in the evaporator and / or the amount of recovered hydrochloric acid, and (6) concentration corresponding to a signal indicating the liquid level in the evaporator. A method for treating waste hydrochloric acid, comprising a step of extracting the liquid from the bottom of the evaporator tower and sending it to a concentrate storage tank.
[0014]
2. Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein in the step (1), the bottom liquid in the evaporator is extracted with a pump and circulated to the stock solution introduction line.
[0015]
3. Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein the steam used in the step (2) is steam generated in a cogeneration facility.
[0016]
4). Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein the evaporator in step (2) is a Calandria type evaporator.
[0017]
5. Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein the compressor in step (2) is a screw type compressor.
[0018]
6). Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein the steam condensate recovered in step (4) is used as boiler feed water and / or as dilution water for the concentrate obtained in step (6).
[0019]
7). Item 6. The method for treating waste hydrochloric acid according to Item 5, wherein the motor rotation speed of the screw compressor is controlled by an inverter device.
[0020]
8). Item 8. The method for treating waste hydrochloric acid according to Item 7, wherein the number of revolutions of the motor of the screw compressor is controlled in accordance with the amount of vapor generated in the evaporator (the amount of recovered hydrochloric acid solution).
[0021]
9. Item 8. The method for treating waste hydrochloric acid according to Item 7, wherein the rotational speed of the motor of the screw compressor is controlled in accordance with the temperature in the evaporator.
[0022]
10. Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein a plurality of compressors are provided in the step (2).
[0023]
11. Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein a demister is provided in a space above the liquid level in the evaporator.
[0024]
12 Item 2. The method for treating waste hydrochloric acid according to Item 1 above, wherein an electromagnetic valve for periodically discharging the noncondensable gas in the evaporator is provided in the steam line outside the heat transfer tube.
[0025]
13. Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein the operating pressure in the evaporator is normal pressure or reduced pressure.
[0026]
14 Item 14. The method for treating waste hydrochloric acid according to Item 13, wherein a vacuum pump is provided on the downstream side of the solenoid valve of the steam line outside the heat transfer tube, which is interlocked with opening and closing of the solenoid valve during decompression operation.
[0027]
15. The method for treating waste hydrochloric acid according to item 1, wherein an auxiliary heat source is introduced into the bottom of the evaporator or the outlet line of the compressor in order to cope with a decrease in the evaporation amount due to contamination of the heat transfer pipe in the evaporator during start-up or long-term operation. .
[0028]
16. Item 16. The method for treating waste hydrochloric acid according to Item 15, wherein the auxiliary heat source is steam.
[0029]
17. Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein the material of the heat transfer tube is Ti-Pd.
[0030]
18. Item 2. The method for treating waste hydrochloric acid according to Item 1, wherein the concentrate is extracted from an overflow pipe communicating with the bottom of the evaporator at a position corresponding to the liquid level in the evaporator.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Although it does not specifically limit as a compressor used by this invention, It is preferable that it is a screw type compressor which was not used by the conventional concentration technique. The screw type compressor has the following characteristics.
[0032]
a. High pressure and high efficiency operation is possible from low speed rotation.
[0033]
b. High responsiveness.
[0034]
c. Small, compact and easy to install.
[0035]
d. The motor speed of the screw compressor can be controlled in accordance with the amount of generated steam.
[0036]
Such a screw type compressor usually has a structure in which a pair of male and female cylinders are built in a casing portion made of an aluminum alloy. In the following, an embodiment using a screw compressor will be described.
[0037]
When a screw type compressor having the above-described structure and exhibiting the effect is used, the equipment cost and the operation cost are significantly reduced as compared with the case of using a conventional compressor.
[0038]
As an example, the screw compressor used in the present invention has a high discharge pressure of 160 KPa, a maximum allowable discharge temperature of 160 ° C., a maximum intake amount of 760 m ³ / hr (air conversion), and a compression ratio of about 2.3. It can be demonstrated.
[0039]
The compression ratio limit of the roots blower as a conventional compressor is about 1.8, and the total heat insulation efficiency is about 45-60%, while the screw type compressor has a compression ratio of 1.5 and the total heat insulation efficiency is about 65%. The compression ratio of 2 to 2.3 can exhibit high performance of about 70%.
[0040]
The rotor of the screw-type compressor is preferably made of an aluminum alloy having a low expansion coefficient in order to reduce thermal expansion and reduce the required clearance, and a fluororesin (for example, trade name “Teflon from DuPont” on the rotor surface is used. Apply a coating material (commercially available). A plurality of compressors can be provided according to the required amount of steam.
[0041]
Conventionally, it has been difficult in terms of compressor control to perform suction and discharge by a compressor in accordance with the required amount of steam and to efficiently perform evaporation in an evaporator (hereinafter sometimes referred to as a “concentrator”). there were. In the present invention, a motor composed of a high-speed rotation type induction motor is used as a drive source of the compressor, and an inverter device is used as a rotation speed control mechanism of the motor. That is, the amount of steam generated is detected by a flow meter provided on the downstream side of the cooler, a thermometer that measures the evaporator internal temperature, etc., this input signal is sent to the controller, and the output signal from this controller is sent to the inverter. It is possible to input the steam generation amount to be constant, or to increase / decrease the rotational speed of the motor in accordance with the steam generation amount. As a result, the entire apparatus is simplified, and control at the time of start-up becomes easy.
[0042]
Further, in the steam line on the upstream side of the compressor, steam condensation on the compressor inlet side can be prevented by heat retention and / or heating by a heater.
[0043]
In the present invention, a plate heat exchanger can also be used for preheating the stock solution for the purpose of reducing the size of the apparatus and reducing the cost. In order to prevent a decrease in the heat transfer coefficient due to bubble generation in the preheater by making the pressure in the preheater and the stock solution introduction line higher than the pressure in the evaporator, A back pressure valve can be provided on the evaporator inlet side.
[0044]
If the stock solution contains a component (such as a surfactant) that may cause foaming under concentration conditions, a silicone-based antifoaming agent may be added in advance. The addition amount of the antifoaming agent may be determined in consideration of the content of the foaming component and the like, and is not particularly limited, but is usually about 30 to 500 mg / l.
[0045]
In the evaporator used in the present invention (hereinafter referred to as “Calandria type evaporator”), the Calandria type evaporator is used in order to prevent a decrease in the heat transfer coefficient due to poor liquid dispersion inside the heat transfer tube, which has occurred in the prior art. It is preferable to introduce the liquid at a position of about 15 to 50% from above the liquid depth from the inner liquid surface of the can (hereinafter sometimes simply referred to as “calandria”) to the top of the heat transfer tube. Thereby, the liquid is heated and evaporated by the compressed steam outside the heat transfer tube while being always held in the heat transfer tube. In the conventional liquid supply method, foaming may be promoted, and as a result, the concentration process may become impossible. However, in the method of the present invention, the problems such as the decrease in flow rate and the promotion of foaming due to the dispersion of the liquid are solved.
[0046]
Furthermore, by placing a packing, filter, dripping wall, etc. on the upstream side of hydrochloric acid and water vapor exiting the evaporator, it is possible to prevent entrainment of raw liquid droplets or liquid droplets in the can on the vapor side. .
[0047]
Further, if necessary, the liquid at the bottom of the Calandria tower is extracted by a pump and circulated to the stock solution introduction position, whereby the liquid flow rate in the heat transfer tube can be increased and the heat transfer coefficient can be increased.
[0048]
The steam outside the heat transfer tube heats and evaporates the liquid in the heat transfer tube, and then condenses. In the present invention, a steam trap or a condensate tank is provided in order to keep the condensate level of the steam outside the heat transfer tube inside the evaporator constant, thereby preventing loss due to discharge of the compressed steam out of the system. It is out. The condensate is discharged out of the system via a steam trap or a condensate tank, and can be reused as boiler feed water, dilution water for preventing the solidification of the concentrate extracted from the bottom of the evaporator tower, and the like.
[0049]
Non-condensable gas such as air in the calandria that affects the efficiency and power consumption of the compressor is discharged out of the calandria by opening and closing an electromagnetic valve provided in the steam line outside the heat transfer tube. Exhaust gas corresponds to the components in the gas, if necessary, after removing the prescribed components by activated charcoal adsorption, etc., or by absorbing and removing the prescribed components by bubbling the liquid in the concentrate tank. Released. The solenoid valve is automatically opened and closed by a method linked with the pressure in the calandria, an arbitrary timer setting, or the like.
[0050]
The concentrate receives a signal from the level gauge in the concentrator and is discharged from the bottom of the tower through a control valve.
[0051]
When the operating pressure in the calandria is a decompression system, a vacuum pump is provided on the downstream side of the solenoid valve provided in the steam line outside the heat transfer tube in conjunction with the opening and closing of the solenoid valve.
[0052]
If necessary, an auxiliary heat source (steam from a gas-fired boiler, etc.) may be used to increase the temperature of the entire system at start-up, or to reduce the amount of evaporation due to contamination of the preheater or Calandria heat transfer tube after long-term operation. Introduce to Calandria inner bottom or compressor outlet line.
[0053]
Hereinafter, the present invention will be described in more detail with reference to the drawings. In the following, although concentration of waste hydrochloric acid will be described, it is needless to say that the present invention can be applied to the concentration of other waste acids, waste alkaline solutions, etc. in terms of its operating principle.
[0054]
FIG. 1 is a flow sheet showing an example of the concentration treatment of waste hydrochloric acid according to the present invention. Waste hydrochloric acid to be concentrated is boosted from tank 1 through line 2 to a predetermined pressure in pump 3 and then introduced from line 4 to a concentrator (calandria type evaporator) 12. Although not shown, if necessary, a strainer can be provided on the upstream side of the pump 3 and a flow meter can be provided on the downstream side. The waste hydrochloric acid is introduced into the concentrator at a position 15 to 50% of the liquid depth from the liquid level in the concentrator 12 to the upper part of the heat transfer tube (a position facing downward from the liquid level).
[0055]
The waste hydrochloric acid is heated in the heat transfer can by steam from the boiler 5. That is, this steam is supplied to the compressor 7 through the line 6, compressed and heated here, and then supplied to the outside of the heat transfer tube of the concentrator 12 through the lines 9 and 10 to heat the liquid in the heat transfer tube. And evaporate. Thereby, the steam itself outside the heat transfer tube is condensed and liquefied. The condensate is discharged from the line 20 through the steam trap 19 from the line 18 connected to the lower part of the heat transfer tube in the concentrator 12. This condensate is reused as necessary for supplying water to the boiler 5 or for diluting water for preventing solidification of the concentrate extracted from the line 24. Furthermore, this condensed water can be used as a preheating source of the stock solution in a preheater (not shown) provided in the line 4 on the outlet side of the pump 3 prior to reuse.
[0056]
As described above, as the compressor 7, it is preferable to use a screw type compressor having a pair of male and female rotors in an aluminum alloy casing.
[0057]
The hydrochloric acid and water vapor generated in the concentrator 12 is cooled by the cooler 14 via the line 13 and condensed, and then stored in the distillate tank 17 via the line 16.
[0058]
In the upper space of the concentrator 12, a filler, a filter, a dripping wall, etc. (shown as "26") can be disposed to prevent entrainment of the raw liquid droplets or the liquid droplets in the can into the vapor. .
[0059]
Non-condensable gas such as air in the concentrator 12 that affects the efficiency and power consumption of the compressor 7 is discharged out of the evaporator by opening and closing the electromagnetic valve 22 provided in the steam line 21 outside the heat transfer tube. . The opening and closing of the electromagnetic valve 22 may be performed in conjunction with the pressure in the concentrator 12, or may be automatically performed by setting a timer. If necessary, the exhaust gas is subjected to adsorption treatment with activated carbon or the like, or is bubbled into the liquid in the concentrate tank 25.
[0060]
The concentrated liquid accumulated in the concentrator 12 is sent to the concentrated liquid through a line 24 and a control valve (not shown) from the bottom of the concentrator 12 according to a signal from a liquid level gauge (not shown) in the concentrator 12. It is discharged into the tank 25. Alternatively, the concentrated liquid can be extracted from an overflow pipe (not shown) communicating with the bottom of the concentrator 12 at a position corresponding to the liquid level in the evaporator without using a control valve.
[0061]
If it is necessary to prevent solidification of the discharged concentrated liquid, water or condensed water from the line 20 may be supplied into the line 24 or the concentrated liquid tank 25 to dilute the concentrated liquid.
[0062]
Further, if necessary, the liquid in the concentrator 12 is extracted from the liquid extraction line 24 by a circulation pump (not shown) and circulated to the raw liquid line 4 to increase the liquid flow rate in the heat transfer tube, and heat transfer When the operating pressure in the concentrator 12 that can increase the coefficient is a decompression system, a vacuum pump (not shown) that interlocks with the opening and closing of the electromagnetic valve 22 is provided on the downstream side of the electromagnetic valve 22. When operating in a reduced pressure system, it is necessary to provide a condensate pump (not shown) on the line 20 and a concentrate pump (not shown) on the line 25.
[0063]
If necessary, for example, steam from the boiler 5 is used as an auxiliary heat source for heating / heating at start-up, or in accordance with a decrease in the evaporation amount due to contamination of the heat transfer tube of the concentrator 12 after long-term operation. The gas is introduced from the line 11 via the line 6, the compressor 7 and / or the bypass line 8, and further via the lines 9 and 10.
[0064]
If the heat transfer tube of the concentrator 12 is contaminated and the heat transfer coefficient is reduced, the supply of waste hydrochloric acid is temporarily interrupted during operation, and the industrial water is supplied to remove the dirt. Can be cleaned and removed.
[0065]
The present invention not only concentrates various waste acid solutions and waste alkaline solutions, but also concentrates and reduces volumes of various industrial wastewaters, washing wastewaters, photographic developers, fixing solutions and washing wastewaters, and useful components in the stock solution Alternatively, it can be used in a wide range of fields such as distillation separation of impurities and concentration of solutions (dashi soup, juice, milk, etc.) in the food industry. The present invention can be used in other fields, and is not limited to use in the fields illustrated here.
[0066]
【The invention's effect】
According to the method of the present invention, the following remarkable effects are achieved.
[0067]
(1) Compared with the prior art, the process for concentrating the stock solution is simple and the equipment is downsized, so that the equipment costs, operating costs, etc. are reduced.
[0068]
(2) Continuously stable operation is possible.
[0069]
(3) For example, it is possible to effectively use low-pressure steam that has been hardly used in the past even though it is generated in a relatively large amount in a cogeneration facility or the like.
[0070]
(4) The useful hydrochloric acid remaining in the waste hydrochloric acid can be recovered and reused.
[0071]
(5) As a result of the recovery of hydrochloric acid and water in the waste hydrochloric acid, the amount of waste disposal can be reduced and the disposal cost can be reduced as compared with the conventional case.
[0072]
【Example】
Examples will be shown below to further clarify the features of the present invention.
[0073]
Examples 1-4
Number generated at a steel wire manufacturing plant (Company A) using a 1 liter glass concentrator (with silicone oil as a heat medium) equipped with a condenser and a distillate receiver for collecting the distillate Treatment of the seed waste hydrochloric acid (0.5 liters each) was carried out under atmospheric pressure.
[0074]
Table 1 shows analytical values and treatment conditions of waste hydrochloric acid.
[0075]
[Table 1]

[0076]
Note: In Example 4, the waste hydrochloric acid derived from the continuous tank and the batch tank was mixed in an equal amount and processed.
[0077]
Waste hydrochloric acid was separated into a distillate and a concentrate so that the concentration of iron (Fe ⁺² + Fe ⁺³ ) in the concentrate was about 360 g / l. Table 2 shows the analysis results of the distillate and the recoveries of the distillate and free HCl.
[0078]
[Table 2]

[0079]
Note: Free HCl means molecular HCl that is not bound to Fe ⁺² + Fe ⁺³ or the like.
[0080]
Distillate recovery rate = amount of distillate / waste hydrochloric acid x 100
Free HCl recovery rate = amount of distillate x free HCl in distillate / waste hydrochloric acid x HCl in waste hydrochloric acid
From the above results, it is clear that when the iron concentration in the waste hydrochloric acid is high and the free HCl concentration is low, the HCl in the distillate is low and the HCl recovery rate is low.
[0081]
Examples 5-8
The treatment was carried out according to the methods of Examples 1 to 4 except that waste hydrochloric acid generated at the plating treatment plant (Company B) was used as a stock solution and the test temperature was changed to a temperature corresponding to each concentration condition. The analysis values and treatment conditions of the waste hydrochloric acid are shown in Table 3, and the analysis results of the distillate and the recoveries of the distillate and free HCl are shown in Table 4.
[0082]
[Table 3]

[0083]
[Table 4]

[0084]
Example 9
The present invention was carried out at atmospheric pressure according to the flow shown in FIG. In other words, waste hydrochloric acid (free HCl = 200 g / l, Fe (Fe ⁺² + Fe ⁺³ = 88 g / l)) generated at the steel wire manufacturing plant (Company C) is used for the treatment, and the evaporator internal temperature Table 5 shows the conditions for each device during operation.
[0085]
[Table 5]

[0086]
The results are shown in Table 6.
[0087]
[Table 6]

[0088]
As is apparent from the results shown in Table 6, by measuring the temperature or specific gravity of the concentrate, the concentration factor can be determined according to the iron concentration in the stock solution.
[0089]
When the concentrated solution was taken out of the system, about 40% of the concentrated solution was solidified under normal pressure, about 90% when concentrated 4 times, about 90% when concentrated 4 times, and about 100% when concentrated 5 times.
[0090]
Examples 10-11
The present invention was carried out at atmospheric pressure according to the flow shown in FIG. That is, the treatment was performed using waste hydrochloric acid (an equal mixture of two types of waste hydrochloric acid generated in a continuous tank and a batch tank) generated in a steel wire manufacturing factory (Company d). Conditions in each device during operation are the same as those in the ninth embodiment. Table 7 shows analytical values and concentration ratios of waste hydrochloric acid.
[0091]
[Table 7]

[0092]
Waste hydrochloric acid was separated into a distillate and a concentrate so that the concentration of iron (Fe ⁺² + Fe ⁺³ ) in the concentrate was about 360 g / l. Table 8 shows the analysis results of the distilled liquid and the concentrated liquid.
[0093]
[Table 8]

[0094]
In any of Examples 10 and 11, stable concentration treatment was possible. Moreover, solidification at room temperature was not recognized by adding an appropriate amount of water to the concentrate.
[0095]
In addition, when the cost reduction rate (reduction of hydrochloric acid purchase cost by use of recovered hydrochloric acid and reduction of industrial waste treatment cost by volume reduction) by Examples 10 and 11 was calculated, it was implemented compared with the conventional method (current standard) In the case of Example 10, it is about 44%, and in the case of Example 11, it is about 35%.
[0096]
Example 12
Using a calandria type evaporator, the plating factory waste liquid (waste hydrochloric acid) was concentrated under reduced pressure according to the method of Example 10. The processing conditions are shown in Table 9 and the results are shown in Table 10.
[0097]
[Table 9]

[0098]
[Table 10]

[0099]
As is apparent from the results shown in Tables 9 and 10, the waste liquid treatment result almost the same as that of Example 10 was obtained by the treatment under reduced pressure.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing an example of waste water concentration treatment according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Waste water tank 3 ... Waste water pump 5 ... Boiler 7 ... Compressor 12 ... Concentrator 14 ... Cooler 15 ... Cooling water line 17 ... Distillate tank 19 ... Steam trap 22 ... Solenoid valve 25 ... Concentrate tank 26 ... Filling

Claims (3)

In the treatment method of waste hydrochloric acid using an evaporator, (1) the step of introducing the stock solution into the liquid between the liquid surface in the evaporator and the upper part of the heat transfer tube, (2) the heating steam is compressed by a compressor A process of heating and evaporating the liquid in the heat transfer tube after the temperature has been raised, and heating and evaporating the liquid in the heat transfer tube. (3) Cooling the vapor generated in the evaporator with a cooler and recovering it as an aqueous hydrochloric acid solution (4) a step of recovering vapor condensate from the outside of the heat transfer tube in the evaporator, and (5) controlling the compressor output in response to a signal indicating the temperature in the evaporator and / or the amount of recovered hydrochloric acid. And (6) treatment of waste hydrochloric acid, comprising the step of extracting the concentrate from the bottom of the evaporator tower in response to a signal indicating the liquid level in the evaporator and sending it to the concentrate storage tank Method. The method for treating waste hydrochloric acid according to claim 1, wherein in the step (1), the bottom liquid in the evaporator is extracted with a pump and circulated to the stock solution introduction line. The method for treating waste hydrochloric acid according to claim 1, wherein the steam condensate recovered in step (4) is used as boiler feed water and / or as dilution water for the concentrate obtained in step (6).

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