JP6530225B2 - Method of producing hypochlorite aqueous solution - Google Patents

Description

  The present invention relates to a novel process for the preparation of low pH aqueous hypochlorite solutions. Specifically, in the method of producing the above-mentioned hypochlorite aqueous solution using a raw material containing water, an alkali source and a chlorine source, chlorine gas does not leak outside the system, and there is no generation of chlorine gas. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a safe hypochlorite aqueous solution stably and at low cost.

  In recent years, since the hypochlorite aqueous solution adjusted to pH 4 to 7 is excellent in the bactericidal effect to viruses etc., it is widely watched and the market is expected to expand.

  Conventionally, as a method for producing the above-described pH-adjusted hypochlorite aqueous solution, it is excellent by adding and mixing an acid solution such as sodium hypochlorite and hydrochloric acid to raw water such as tap water so as to have the above-mentioned pH It is known to produce an aqueous solution of hypochlorite which has a sterilizing capacity. For example, a method of using a complicated mixer in which a plurality of baffles are installed in the mixing section to set the flow rates of the sodium hypochlorite aqueous solution and the acidic aqueous solution and perform sufficient mixing (see Patent Document 1) There has been proposed a production method (see Patent Document 2) or the like in which an acidic aqueous solution is diluted stepwise after dilution adjustment of sodium chlorate.

  However, in the method of Patent Document 1, since the flow rates of the sodium hypochlorite aqueous solution and the acidic aqueous solution are determined, the raw material balance is temporarily broken due to a failure of the apparatus or the like, and the pH of the generated hypochlorite aqueous solution is If the amount is less than the lower limit value of the above range, in particular, 2 or less, the sodium hypochlorite aqueous solution is sprayed in a state where a large amount of chlorine gas is generated, which may cause a danger in use. Moreover, in addition to becoming expensive by using the complicated mixer which installed many baffles, it also was one of the problems that the expense, such as repair of a complicated apparatus, costs.

  In addition, in the method of Patent Document 2, it is necessary to dilute in stages, which complicates the control system for that purpose, and requires a storage tank at each stage, so that not only the equipment is enlarged but also pH control Gas that leaks from the gas phase of the storage tank or dissolves from the gas phase into the aqueous solution of hypochlorite when the pH in the storage tank temporarily decreases due to There is a concern that volatilized from the aqueous solution of hypochlorite to be sprayed.

Unexamined-Japanese-Patent No. 11-188083 Unexamined-Japanese-Patent No. 2002-273452

  Therefore, the present invention is a manufacturing method improved to solve such problems, wherein chlorine gas does not leak out of the system, and there is no generation of chlorine gas, which is safe hypochlorous acid. An object of the present invention is to provide a method for producing an aqueous acid salt solution stably and at low cost.

  As a result of intensive studies to achieve the above object, the present inventors have provided a circulation line for circulating the hypochlorite aqueous solution outside the storage tank storing the hypochlorite aqueous solution, and the circulation. The raw materials are supplied and mixed in the line, and the aqueous solution of hypochlorite is formed and the pH is adjusted, and the gas phase of the storage tank is extracted and the gas extracted into the aqueous solution of hypochlorite flowing in the circulation line To prevent the dissolution of chlorine gas in the aqueous solution of hypochlorite present in the storage tank by always making the chlorine gas present in the above-mentioned gas phase part harmless. It has been found that the present invention can prevent the leakage of chlorine gas, and the present invention has been completed.

  That is, according to the present invention, (A) a product storage step of storing a hypochlorite aqueous solution in a storage tank, and (B) a cycle of circulating the hypochlorite aqueous solution stored in the storage tank outside the storage tank. A hypochlorite aqueous solution preparation step of preparing an aqueous solution of hypochlorite by supplying a raw material to the circulation line and mixing it to prepare an aqueous solution of hypochlorite, (C) an aqueous solution of hypochlorite flowing in the circulation line, A gas phase abatement process in which the gas present in the gas phase of the storage tank is extracted and brought into contact with the gas, (D) the storage tank or circulation line has an extraction line, and part of the hypochlorite aqueous solution is removed from the system And (E) adjusting the feed ratio of the raw materials so that the pH of the aqueous solution of hypochlorite reaching the extraction line is 4 to 7, and (E) Method for producing an aqueous solution of hypochlorite.

  In the hypochlorite aqueous solution preparation step, an ejector is provided in the circulation line of the hypochlorite aqueous solution to mix the raw materials and, at the same time, it is preferable to extract the gas present in the gas phase of the storage tank. It is.

Further, in the pH adjustment step, if the pH is out of the range of 4-7, the provision of the emergency shutdown step of the take-out line is closed, the liquid circulation rate of definitive to the circulation, relative to the volume of the storage tank (Vm ³⁾ It is also a preferable response to perform so as to be 0.2 V / hour to 30 V / hour.

  According to the present invention, even if the pH of the generated aqueous solution of hypochlorite is lowered due to a momentary imbalance of raw materials, etc. and the chlorine gas is generated from the aqueous solution of hypochlorite, Since the gas in the phase portion is constantly extracted and brought into contact with the aqueous solution of hypochlorite flowing in the circulation line to render it harmless, there is no risk of leakage of chlorine gas to the surroundings. In addition, it is possible to stably produce a safe hypochlorite aqueous solution free from the generation of chlorine gas at low cost.

Fig. 1 shows a schematic view of an apparatus used to carry out the method of the invention.

  Hereinafter, the present invention will be described in detail according to FIG. 1 showing a typical embodiment of the method for producing the hypochlorite aqueous solution of the present invention.

(A) Product Storage Step In the product storage step of the present invention, a container of a closed system is generally used as the storage tank 14 for containing a hypochlorite aqueous solution, in order to extract gas of the gas phase part described later. Further, such a storage tank is not particularly limited as long as the inner wall is made of a material that does not cause decomposition of the hypochlorite aqueous solution, and in general, the inner wall of a container made of metal such as stainless steel or copper. It is preferable to use a resin lining or the like. Furthermore, although the capacity of the storage tank may be appropriately determined in accordance with the amount of hypochlorous acid required, it is generally 0.01 to 10 m ³ .

(B) Hypochlorite Aqueous Solution Preparation Step One of the features of the present invention is to provide a circulation line 15 for circulating the hypochlorite aqueous solution contained in the storage tank 14 outside the storage tank, and using this as a raw material Is prepared, and the hypochlorite aqueous solution preparation step of preparing the hypochlorite aqueous solution is provided, and the hypochlorite aqueous solution containing the generated hypochlorite aqueous solution is returned to the storage tank. That is, by adding the hypochlorite aqueous solution prepared in the hypochlorite aqueous solution preparation step to the hypochlorite aqueous solution circulating in the circulation line 14, hypochlorous acid is obtained in one pass. By preparing an aqueous salt solution, it is possible to obtain an aqueous solution of hypochlorite more stably.

The circulation of the liquid in the liquid circulation line 15 can be carried out using a pump, but the circulation amount thereof is 0.2 V / hour to 30 V / hour, in particular, with respect to the volume (Vm ³ ) of the storage tank. It is preferable to set so as to be 0.5 V / hour to 20 V / hour. That is, when the liquid circulation amount is too small, the treatment of the gas to be extracted becomes insufficient, and it becomes difficult to uniformly maintain the hypochlorite aqueous solution in the storage tank. On the other hand, if the fluid circulation amount is too large, the power required for circulation becomes large, which is economically disadvantageous.

  Further, it is preferable that the circulation line be provided with the outlet and the return port so that the hypochlorite aqueous solution in the storage tank is as uniform as possible. Specifically, there is a mode in which the liquid outlet of the circulation line is provided at the bottom of the storage tank, and the return port is provided at the top of the storage tank so that the liquid circulates outside the storage tank. In particular, the return port provided in the upper portion of the storage tank is preferably provided at a position open to the gas phase portion of the storage tank. Here, reference numeral 23 denotes a storage tank level gauge, which controls the supply amount of the raw material by the level controller 24.

  In the present invention, the raw material in the hypochlorite aqueous solution preparation step produces a hypochlorite aqueous solution, and the known raw materials are not particularly limited in the combination in which pH adjustment in the pH adjustment step described later is possible. used. For example, an alkali source, a combination of chlorine gas, a combination of hypochlorite such as sodium hypochlorite and an acid such as hydrochloric acid, and the like can be mentioned. Water necessary as a raw material may be supplied alone and / or in a state in which the raw material is dissolved.

  When hypochlorite is used as the raw material, the hypochlorite may be a hypochlorite formed by mixing an alkali and a chlorine gas, but an aqueous hypochlorite solution having high purity is used. When it is desired to obtain it, it is useful to use an alkali salt, specifically one having reduced sodium chloride, calcium chloride and the like. It is also possible to use hypochlorous acid hydrate represented by hypochlorous acid pentahydrate. In general, hypochlorous acid hydrate can reduce impurities such as chloric acid and bromic acid, and is effective when it is desired to obtain an aqueous solution of hypochlorite having higher purity.

  FIG. 1 shows a step of preparing an aqueous solution of hypochlorite using an alkali source as a raw material and chlorine gas, and water is supplied so as to have a predetermined flow rate, and the hypochlorous acid is produced with respect to the water flow rate. The chlorine gas flow rate is adjusted so that the chlorate aqueous solution has a predetermined concentration. The chlorine gas to be used is not particularly limited, but in general, it is general to use a pressure adjusted at about 0.1 to 0.3 MPaG by installing a pressure regulator on a liquefied chlorine gas cylinder.

  When the hypochlorite aqueous solution concentration to be manufactured is used for sterilization applications etc., the general hypochlorite aqueous solution concentration is about 1 to 1000 ppmw, and the target hypochlorite aqueous solution concentration is set The flow rate of chlorine gas may be adjusted with respect to the flow rate of water.

  After the chlorine gas supply, an alkali source is supplied to produce the hypochlorite aqueous solution. After alkali supply, mixing is performed in a mixer so that the generated hypochlorite aqueous solution becomes uniform. There are no particular restrictions on the mixer used for the above mixing, and commonly used ejectors, plate-like or cup-like collision plate stationary mixers, Kenics type, Sulzer type, etc. can be used.

  The alkali source is not particularly limited, but in general, alkali metal hydroxides and alkaline earth metal hydroxides can be used. Sodium hydroxide and potassium hydroxide can be used as the alkali metal hydroxide, and calcium hydroxide and the like can be used as the alkaline earth metal hydroxide. Moreover, since carbonates, such as calcium carbonate and magnesium carbonate, have a pH adjustment function, they can be used as a part of alkali.

  In the hypochlorite aqueous solution preparation step shown in FIG. 1, the circulation of the liquid in the circulation line 15 is performed using the circulation pump 16, and the circulation flow meter 17 and the circulation control device 18 are used to achieve a predetermined circulation flow rate. It is controlled. In addition, supply and mixing of raw materials are performed by measuring the flow rate of raw water supplied from the water line 1 to the circulation line 15 using the water flow meter 3 and adjusting the water adjustment valve 2 with the water control device 4 It supplies so that it may become a predetermined flow rate. The chlorine gas flow rate device 8 using the chlorine gas adjustment valve 6 and the chlorine gas flow meter 7 from the chlorine gas supply line 5 has a predetermined concentration of the aqueous solution of hypochlorite produced with respect to the water flow rate. Adjust the chlorine gas flow rate as follows. After chlorine gas supply, in order to form hypochlorite, alkali is supplied from alkali supply line 9 using alkali adjustment valve 10 and mixed in mixer 11 to prepare hypochlorite aqueous solution .

(C) Gas Phase Removal Step The greatest feature of the manufacturing method of the present invention is that a gas phase removal step is performed in which the gas present in the gas phase of the storage tank 14 is extracted and brought into contact. By providing such a step, the raw material balance is temporarily broken, and the pH of the generated aqueous solution of hypochlorite decreases, and chlorine gas generated from the aqueous solution of hypochlorite is extracted from the gas phase portion of the storage tank. Since it is removed in contact with the aqueous solution of hypochlorite flowing in the circulation line, the leakage of chlorine gas from the apparatus can be effectively prevented. In addition, the dissolution of chlorine in the aqueous solution of hypochlorite present in the storage tank can be effectively prevented.

  In the gas phase portion abatement process, the gas in the gas phase portion of the storage tank 14 is extracted from the extraction line 25 and supplied to the circulation line 15. For the extraction of the gas, a known device capable of extracting and sending the gas from the gas phase part of the storage tank to the circulation line, for example, a suction and exhaust device for a gas such as a compressor, is used. A suitable apparatus is an ejector used as a mixer of raw materials in the hypochlorite aqueous solution preparation process. That is, in the case of using a general mixer, in order to extract the gas present in the vapor phase portion of the hypochlorite aqueous solution storage tank, a separate device for supplying gas such as a compressor is necessary, but the ejector If it is used, simultaneously with the mixing of the raw materials in the circulation line, the gas can be extracted, and the production of the hypochlorite aqueous solution can be performed with a simpler device configuration.

  In FIG. 1, in the gas phase part removal process, the gas phase of the storage tank 14 is extracted from the extraction line 25 and supplied to the ejector 11 which is a mixer.

(D) Product Removal Step In the present invention, the product removal step is a step of providing a removal line 21 in the storage tank or the circulation line, and removing a part of the pH-adjusted hypochlorite aqueous solution out of the system. When the hypochlorous acid aqueous solution is used as a germicide, it may be sprayed directly from the removal line or may be removed and sprayed to another container.

  In FIG. 1, the produced hypochlorite aqueous solution becomes a predetermined pH by the in-reservoir pH meter 19 and the in-reservoir pH controller 20 installed at the bottom of the aqueous solution of hypochlorite solution in the circulation line. Then, the hypochlorite aqueous solution discharge valve 22 is opened through the hypochlorite aqueous solution discharge line 21 to take out the manufactured hypochlorite aqueous solution.

(E) pH adjustment step In the present invention, it is important to control the pH of the aqueous solution of hypochlorite to be produced to 4 to 7 as the pH in order to exert the bactericidal effect, and the pH adjustment step This is a step of controlling the feed ratio of the raw materials so that the pH of the hypochlorite aqueous solution reaching the line 21 falls within the above range.

  In FIG. 1, measurement is made with the storage tank supply pH meter 12 so that the circulating hypochlorite aqueous solution reaches a predetermined pH, and the storage tank supply pH meter controller 13 controls the supply amount of the alkali to The solution is supplied to a chlorate aqueous solution storage tank 14.

(Emergency shut down process)
In the present invention, it is preferable to provide an emergency shut-off step of closing the takeout line when the pH of the hypochlorite aqueous solution to be measured is out of the range of 4 to 7 in the pH adjustment step. It is preferable in order to prevent the accident which chlorine gas generate | occur | produces from chlorate aqueous solution more effectively. In FIG. 1, when an abnormality is detected by the storage tank pH meter 19 installed at the bottom of the storage tank 14, an emergency shut-off system that closes the valve 22 of the hypochlorite aqueous solution extraction line 21 operates. Thereby, the line including the storage tank of the hypochlorite aqueous solution becomes a completely sealed system, and it is possible to prevent the leakage of chlorine gas to the surroundings.

  EXAMPLES The present invention will be described in detail by way of examples, which should not be construed as limiting the scope of the present invention.

Example 1
The hypochlorite aqueous solution was manufactured using the apparatus of FIG.

  The water control device (4) was controlled to supply 20 L / h while measuring with a water flow meter (3) from a water supply line (1) using a water flow rate adjustment valve (2). The chlorine gas corresponding to this water is equivalent to the water flow rate by the chlorine gas control device (8) using the chlorine gas flow meter (7) from the chlorine gas supply line (5) with the chlorine gas flow rate adjustment valve (6) .2 NL / h was supplied. Thereafter, a 20 wt% sodium hydroxide solution was supplied at 10.7 g / h from an alkali supply line (9) using an alkali adjusting valve (10). Sodium hydroxide is mixed with a hypochlorite aqueous solution storage tank (14) and a volume of 20 L while suctioning by a ejector as a mixer (11), and the pH is measured with a storage tank supply pH meter (12), and a storage tank It adjusted by the alkali adjustment valve (10) so that it might become target pH 5 with a supply pH control apparatus (13). The pH-adjusted hypochlorite aqueous solution is stored in the hypochlorite aqueous solution storage tank (14), and the circulation line (15) causes the circulating flow meter (17) to use 150 L by using the circulation pump (16). It circulated, adjusting the flow rate with the circulation control device (18) so as to be / h. Water and chlorine gas were supplied to the circulating fluid in this order. Confirm that the generated hypochlorite aqueous solution is adjusted to pH 5 with the storage tank pH meter (19) with the storage tank pH controller (20), and the following from the hypochlorite aqueous solution discharge line (21) It discharged | emitted by the chlorite aqueous solution discharge valve (22), and it was able to obtain 20 L / h of hypochlorite aqueous solution of 200 ppmw and pH 5 as sodium hypochlorite. No chlorine was detected as a result of measuring the vapor phase portion of the generated aqueous solution of hypochlorite with a chlorine detector capable of measuring up to 1 ppm.

1 ... water supply line 2 ... water adjustment valve 3 ... water flow meter 4 ... water control device 5 ... chlorine gas supply line 6 ... chlorine gas adjustment valve 7 ... chlorine gas Flow meter 8 ... chlorine gas control unit 9 ... alkali supply line 10 ... alkali adjustment valve 11 ... mixer 12 ... storage tank supply pH meter 13 ... storage tank supply pH controller 14 ... Storage tank 15: circulation line 16: circulation pump 17: circulation flow meter 18: circulation control device 19: storage tank pH meter 20: storage tank pH controller 21: extraction Line 22 ... Hypochlorite solution discharge valve 23 ... Storage tank level gauge 24 ... Storage tank level control device 25 ... Gas extraction line

Claims (6)

  (A) a product storage step of storing a hypochlorite aqueous solution in a storage tank, and (B) a circulation line which circulates the hypochlorite aqueous solution stored in the storage tank outside the storage tank, The raw material is supplied to the circulation line and mixed to prepare an aqueous solution of hypochlorite, and (C) a liquid flowing in the circulation line, the gas present in the gas phase of the storage tank A vapor phase part abatement process to be brought into contact with air by extraction, (D) A product extraction process having a takeout line in the storage tank or circulation line and taking out a part of the hypochlorite aqueous solution out of the system, and (E) A pH adjusting step of controlling the feed ratio of the raw materials so that the pH of the hypochlorite aqueous solution reaching the extraction line is 4 to 7; producing a low pH hypochlorite aqueous solution Method.   In the hypochlorite aqueous solution preparation step, an ejector is provided in the circulation line of the hypochlorite aqueous solution, and the ejector mixes the raw materials and extracts the gas present in the gas phase of the storage tank. The manufacturing method of the hypochlorite aqueous solution of Claim 1.   The said pH adjustment process WHEREIN: When pH of the hypochlorite aqueous solution measured falls out of the range of 4-7, the emergency blocking process of making an extraction line close is further included according to Claim 1 or 2. Method of producing chlorite aqueous solution. Liquid circulation amount definitive in the circulation, relative to the volume of the storage tank (Vm ^3), hypochlorite aqueous solution according to any one of claims 1 to 3 is 0.2V / time ～30V / Time Manufacturing method. The method for producing a hypochlorite aqueous solution according to any one of claims 1 to 4, wherein the raw material is water, an alkali or chlorine gas. The method for producing a hypochlorite aqueous solution according to any one of claims 1 to 4, wherein the raw material is water, an aqueous solution of alkaline hypochlorite and an acid.

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