JPH06507881A - Method for producing calcium hypochlorite from concentrated hypochlorous acid solution - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Production methodProduction method of calcium hypochlorite from chlorite solution The present invention relates to the production of calcium hypochlorite. More specifically, the present invention This invention relates to an improved method for producing calcium hypochlorite using hypochlorous acid as a substance.

Calcium hypochlorite is produced by the reaction of lime and hypochlorous acid solution. Eliminating or minimizing the concentration of chloride ions in calcium chlorate solutions or slurries and avoid the formation of effluent containing both hypochlorite and chloride ions. It has been desired for a long time.

In one approach, an aqueous solution of hypochlorite, such as ethyl alcohol, tetrasalt prepared in an organic solvent such as carbonized carbon or methyl ethyl ketone, or U.S. Pat. No. 1,481,039, published by Unahi, and J.

A. Published May 11, 1971 to Wojtowicz et al. No. 3,578,393.

The use of organic solvents in the production of hypochlorous acid solutions not only increases processing costs, but also The presence of minerals as impurities in the calcium chlorite product indicates that calcium hypochlorite Lucium is undesirable because it is decomposed by various organic substances.

U.S. patent issued October 21, 1947 by E., C. Soule, et al. No. 2,429,531 discloses, for example, dibasic calcium hypochlorite and/or Hypochlorous acid with basic calcium hypochlorite such as semi-basic hypochlorite A method for producing calcium hypochlorite by neutralization or reaction is taught. Soule et al. , direct reaction between lime and hypochlorous acid or low yield and dilute concentrations of calcium hypochlorite. discovered that it generates a system. The reason for this is the formation of significant amounts of chlorate.

The formation of chlorate is attributed to the oxidation of hypochlorite ions.

Furthermore, the use of hypochlorous acid aqueous solution in the production of calcium hypochlorite is Published by R, D, Gleichert on May 26, 1964 No. 3,134,641 of J.P. Brennan. ) et al., U.S. Patent No. 4,146,578 issued March 27, 1979 ; U.S. Patent No. 4.1, issued April 3, 1979, by J.A. No. 47.761 and J. A. Tsuodwich et al., November 1983. No. 4,416,864, issued on the 22nd. but , in these methods, the hypochlorous acid solution used or the only chlorinating agent Additives, such as chlorine or alkali metal hypochlorites, rather than necessitated the use of specific chlorinating agents.

Methods using hypochlorous acid and these additional chlorinating agents produce substantial amounts of chloride. Produces calcium hypochlorite containing ions. Additionally, to recover the product chloride ions are extracted from a solution containing dissolved chloride ions and hypochlorite ions. A separation step is required to remove the solid calcium hypochlorite contained. Chloride ion The amount of effluent containing ions and hypochlorite ions that can be recycled into the process more than Therefore, excess effluent has an additional application. If this is required or not available, dispose of this excess effluent. must be treated to reduce or eliminate any hypochlorite ions present. Must be. Furthermore, hypochlorite ion concentrations are relatively low and they should be recovered. In some cases, the solution requires concentration.

To remove chloride ions from calcium hypochlorite products, Murakami (M U.S. Patent No. 4,355.0 issued on 19th IO, 1982 No. 14 proposes washing the product with copious amounts of water. death However, this method involves low concentrations of dissolved chloride and hypochlorite ions. Produced by dissolving calcium hypochlorite while generating a large amount of solution It is commercially impractical as it reduces product yield.

Prior art method for producing calcium hypochlorite by reaction between lime and hypochlorous acid The process produces a calcium hypochlorite product containing substantial amounts of chloride ions; Separation of products from effluent solution containing dissolved chloride ions and hypochlorite ions of excess effluent containing chloride and hypochlorite ions. It has several drawbacks, including its use or disposal.

This time, the use of auxiliary chlorinating agents, such as chlorine or alkali metal hypochlorites, Using concentrated solutions of hypochlorous acid to produce calcium hypochlorite in the absence of A new method for producing calcium hypochlorite has been discovered.

This method involves a mixture of chloride and hypochlorite ions, which requires disposal. No effluent is produced. Additionally, calcium hypochlorite products have high assay values. , high purity and suitable for use with chlorine or alkali metal hypochlorites as chlorinating agents Therefore, it does not contain chloride ions formed. Additionally, this method uses a small amount of fresh water. produce a calcium hypochlorite slurry containing a high concentration of solids; Energy costs are reduced as rallies can be dried with low energy requirements can be reduced.

The other benefits mentioned above are lime or lime containing more than 30% by weight of Ca(OH)t. A chlorine solution consisting of a slurry and a hypochlorous acid solution containing at least 35% by weight of HOC1. containing at least 30% Ca(OCI)t and an alkali metal in a solution of calcium hypochlorite substantially free of ions and chloride ions. consisting essentially of producing a slurry of calcium hypochlorite dihydrate crystals , obtained in a method for producing calcium hypochlorite.

More specifically, the novel process of the present invention uses as one reactant at least 3 HOCI A concentrated chlorous acid solution containing 5% by weight is used. Preparation of these highly purified concentrated HOC1 solutions The production method uses highly concentrated hypochlorous acid vapor, chlorine monoxide gas, and a controlled amount of water vapor. A method for producing a gaseous mixture containing This gaseous mixture is composed of J, P, In the method described in U.S. Pat. No. 4,147,761 by Nunn et al. Therefore, it can be manufactured.

Gas containing high concentrations of hypochlorous acid vapor and chlorine monoxide gas and a controlled amount of water vapor The mixture can also contain varying amounts of chlorine gas. taken away, for example Al This gaseous mixture is used to remove solid particles such as potassium metal chloride particles. It can be passed through a separation means. To produce concentrated solutions of hypochlorous acid, e.g. , from about -5°C to about +20°C, preferably from about 0°C to about +10°C. By condensing a gaseous mixture at low temperatures, such as the temperature in the The mixture is converted into hypochlorous acid. The conversion of gaseous mixtures depends on the temperature of use. Operate at autogenous pressure.

This concentrated solution of hypochlorous acid contains about 35% to about 75% by weight HOCI, preferably HOCI. CI from about 40 to about 60% by weight, more preferably from about 42 to about 55% by weight, most preferably from about 40 to about 60% by weight. or about 45 to about 50% by weight. The hypochlorous acid solution contains, for example, chloride ions and Virtually free of ionic impurities such as alkali metal ions and low concentrations of dissolved salts Contains elements. For example, the concentration of chloride ions is less than about 50 ppm; The genus ion concentration is less than about 50 ppm. The dissolved chlorine concentration in the hypochlorous acid solution is Less than about 3% by weight, preferably less than about 1% by weight.

In the method of the invention, the concentrated hypochlorous acid is first reacted with lime.

The lime used has an active lime content of about 85 to about 99%, preferably about 90 to about 98%. In this case, activated lime refers to the weight of Ca(OH)t in the lime. Defined as volume %. The lime used usually contains iron compounds, silica, aluminium, etc. um salt, magnesium salt, manganese, uncalcined limestone (calcium carbonate and carbonate mag Contains impurities such as nesium) and trace amounts of other compounds. these impurities The material represents about 1 to about 15% by weight of lime, preferably about 2 to about 8% by weight. low concentration More preferred are limes with a certain degree of heavy metal compounds, such as iron and manganese compounds. .

The lime slurry used in the novel process of the present invention contains more than 30% by weight of Ca(OH)t. including. For example, the lime slurry contains about 32% to about 45% Ca(OH)2 by weight, preferably Preferably from about 33% to about 44% by weight, more preferably from about 35% to about 43% by weight.

Reactions of these thick lime slurries result in the formation of effluents that must be recycled or disposed of. virtually eliminate. In the method of the present invention, the concentrated lime slurry is added to the concentrated lime slurry. Add to the condensate solution and mix. Homogeneous or homogeneous neutral calcium hypochlorite dihydrate The reaction is carried out with vigorous stirring to ensure the formation of a clear slurry. this Since the process is preferably operated continuously, e.g. by adding concentrated lime slurry to the hypochlorous acid solution at a rate that maintains the correct pH. This allows the reaction to be controlled. The pH is suitably between about 1O and about 10°8. within a range, preferably about 10.2 to about 10.5.

The reaction between the chlorite solution and the concentrated lime slurry is preferably less than about 10°C and 30°C. or at a temperature in the range of less than about 10°C to 25°C. Hypochlorous acid solution The use of this or this exothermic solution is maintained at low temperatures, e.g. less than about 10°C. It will provide some of the cooling required for the reaction.

formula.

2HOC1+　Ca(OH)2-----1>　Ca(OCI)2.2H20( A slurry of neutral calcium hypochlorite is produced by the reaction expressed by 1). .

This product is calcium hypochlorite dihydrate in an aqueous solution of calcium hypochlorite. It is a thick slurry of solids or suspensions. Ca (OCR), at least 30 times 96, preferably from about 35 to about 50% by weight, in a solid-liquid separation process. The slurry contains about 10% to about 30% by weight, preferably about 15% to about 30% by weight. It has a suspended solids content of approximately 30% by weight. This slurry contains alkali metal ions. Qualitatively free of calcium, such as lime, calcium chloride, and calcium chlorate. Contains less than about 4% by weight of um salts.

In a preferred embodiment, a portion of the produced calcium hypochlorite dihydrate is used. to “wet” the lime and form a lime slurry. This calcium hypochlorite 2 The hydrate slurry reacts when mixed with lime, resulting in the following formula: % formula %) (2) Dibasic calcium hypochlorite crystals are produced in the reaction represented by:

When a part of the slurry of calcium hypochlorite dihydrate is reacted with lime, this The amount of water used in the process is significantly reduced. Dibasic calcium hypochlorite The slurry is then reacted with a manufactured chlorite solution to form neutral calcium hypochlorite 2 Produce a slurry of hydrate crystals.

This reaction is expressed by the formula % formula % (3) Represented by

The process of the present invention can be carried out in a Hatch method or with hypochlorous acid solution and lime. Continuously feed slurry, dibasic calcium hypochlorite or mixtures thereof into the reactor. It is preferable to operate while supplying. Depending on the rate of addition of reactants, less about 10% by weight, preferably about 10 to about 30% by weight, more preferably about 15% by weight A reaction mixture comprising a slurry having a suspended solids concentration within the range of about 30 wt. arise.

A slurry of neutral calcium dihydrate crystals is continuously recovered from the reaction mixture. . This slurry is substantially free of alkali metal ions and has very low concentrations, i.e. ie, less than about 3% by weight, preferably less than about 2% by weight, of chloride ions.

In an alternative embodiment, calcium hypochlorite is extracted from a slurry of calcium hypochlorite. The mother liquor is recovered by separating the dihydrate crystals. This mother liquor is small A concentrated solution containing 15% by weight of Ca(OCR)2 and usually about 20 to about 25% by weight of Ca(OCR)2. It is a liquid. This concentrated hypochlorite solution contains very low concentrations of impurities. , can be used or sold as a bleach solution, or made from lime slurry Used for construction.

This slurry can be used directly to treat water systems, such as swimming pools. or, generally, dried and stored before use.

Spray dryer, turbo drying that uses a suitable temperature range to reduce moisture to the desired level The slurry is dried by known means using a machine or vacuum dryer. preferable The drying method uses a fluidized spray dryer with a fluidized bed of granular particles, and The off-sized product is agglomerated to adjust the particle size before feeding. .

The dried calcium hypochlorite product is then subjected to preliminary sizing or other For use in aqueous or other applications, with or without treatments such as pelletization. and put it in a suitable container. During product drying or in size sorting operations, drying Collect the calcium hypochlorite. In one embodiment of this method, the dried Mix these fine particles of calcium chlorite with a lime solution.

This eliminates hypochlorite without forming effluents or requiring other particulate disposal means. Enables recovery of calcium acid valuables.

The novel method of the present invention uses a highly concentrated solution of hypochlorous acid and a concentrated lime slurry. Requires the use of supplementary chlorinating agents such as chlorine or alkali metal hypochlorites , thus producing calcium hypochlorite in the reaction mixture without The material is substantially free of chloride ions.

This method involves chloride and hypochlorite ions and requires separation, treatment, and disposal. Does not produce the required effluent. Therefore, this method operates as a "closed circuit" I can do it.

A preferred embodiment of the invention is a solid-liquid separation device such as a vacuum filter. This significantly reduces both capital and maintenance costs.

The hydrated calcium hypochlorite product produced by the method of the present invention contains Ca( OCI)t at least 70% by weight, such as from about 80 to about 95%, preferably Contains about 80 to about 95% by weight. Hydrated calcium hypochlorite is preferably 4 to about 20% by weight. Preferably, the water content is in the range of about 7 to about 20% by weight.

Hydrated calcium hypochlorite produced by currently practiced commercial methods is , to allow the necessary moisture for improved safety and handling of the product The concentration of Ca (QCI) must be reduced.

The method of the present invention has the necessary moisture content for improved safety, and also contains Ca (OC I) Produce hydrated calcium hypochlorite with a very high assay value of x.

The high purity calcium hypochlorite product produced by the method of the present invention is surprisingly substantially free of alkali metal chlorides and less than about 4% by weight of calcium chloride; Preferably it comprises less than about 3% by weight, more preferably less than about 2.5% by weight.

To further illustrate the invention, the following examples are included without intending to limit the invention. I will post it. All parts and percentages are by weight unless otherwise specified.

Example 1 In the hypochlorite oxidation reactor, Dibasic calcium hypochlorite crystal slurry having a total solids content of 30.7%, It was fed continuously at a rate of 535 parts/hour. At the same time, HOC1 concentration of 50% by weight An aqueous hypochlorous acid solution having a formula was added at a rate of 113 parts/hour. Stir the reaction mixture The temperature was maintained at approximately 30°C. A slurry of calcium hypochlorite dihydrate is obtained. is carried to the filter, which removes 20.9% Ca by weight. (QCI) 37.9% by weight of C from calcium hypochlorite mother liquor containing x a(OCI)tl! Calcium hypochlorite cake containing 56.9% moisture and 56.9% water content. Separated. This calcium hypochlorite dihydrate cake is dried by convection heat radiation and heating. Dry with a convector heating dryer, 85.1 wt% Ca(OCI)t, 4.7 wt% moisture and 1.4 wt% chloride. A product containing calcium was obtained. Detecting alkali metal ions in this product I couldn't do it.

This mother liquor is recycled to the crystallizer reactor. and mixed with additional lime to produce a dibasic calcium hypochlorite slurry. This was then supplied to a hypochlorite oxidation reactor.

Example 2 237 parts by weight of chlorine monoxide, 65.5% by weight of 01□ and 1.8 parts by weight of water vapor. The gaseous mixture having an average concentration of The entrained solid particles of metal chloride were removed. Contains solids at a temperature of 85-90°C The gaseous mixture was maintained at a temperature of about 0°C and a pressure of about 3-4 Torr Gauge. - a portion of the chlorine oxide and substantially all of the water vapor are condensed through a shell-and-tube heat exchanger; In this way, an aqueous hypochlorous acid solution containing 40 to 55% by weight of HOCI was produced. Next The chlorite solution has a pH of approximately 1, and the dissolved chlorine concentration has been determined to be approximately 1% by weight. It was. This manufactured chlorous acid solution is continuously fed into the hypochlorite oxidation reactor at a rate of 113 parts/hour. provided. A dibasic calcium hypochlorite slurry was also added to this reactor. parts/hour. The reaction mixture was stirred and maintained at a temperature of approximately 30°C. Next A slurry of calcium chlorite dihydrate is obtained, which is carried to the filter. , 20.8% by weight of Ca (QCl) by filter! containing hypochlorite From the calcium acid mother liquor, Ca (QCI)2 concentration of 42.7% by weight and 53.8% A calcium hypochlorite cake was separated having a moisture content of . This hypochlorite calcium The sium dihydrate cake was dried using a convection heat dissipation/heating dryer, and the weight of 84.1 % Ca (OCI) z and 78% water by weight 06% and calcium chloride by weight 12% by weight 96% A product containing was obtained. It is impossible to detect alkali metal ions in this product. I couldn't come.

This mother liquor is recycled to the crystallization reactor and mixed with additional lime to produce dibasic hypochlorite A calcium acid slurry was produced and fed to the hypochlorite oxidation reactor.

The dibasic calcium hypochlorite crystal slurry was added to the hypochlorite oxidation reactor depending on the pH. It was fed continuously at a controlled rate. At the same time, it contains 47% by weight of HOC1 When hypochlorous acid solution is added at a rate of approximately 0.5 gallons per minute (gpm), approximately 38% of Ca(OCI)2, total alkalinity as Ca(OH)z of 0.3%, and 1° 3% calcium and sodium chloride salt and 0.5% Ca (ClO2) A base 1-like slurry was obtained containing 2 and 60% water (the balance). hypochlorite The temperature of the oxidation reactor is controlled by cooling brine (br) passed through a cooling coil immersed in the reactor. The temperature was maintained at 20°C to 25°C by circulating the inine). hypochlorous acid and In order to quickly and reliably disperse the dibasic slurry into the paste slurry, Continue to stir vigorously. A portion of this paste was spray dried to contain 81.6% Ca( OCI)z and total alkalinity as Ca(OH)t of 5.8% and 1.8% of total alkalinity as Ca(OH)t. 8. chloride salt of lucium and sodium and 2.5% Ca(CIOl)z; A product with an average analysis value of 820 of 5% was obtained. Other parts of the paste are salted Recirculated to the basic calcium hypochlorite crystallizer at a rate of approximately 0.3-0.4 gprn. I let it happen.

The dibasic crystallizer system consists of a crystallization reactor, a lime slurry replenishment tank, and a hypochlorite oxidation reactor. It consists of a reactor supply tank and a hydroclone. there were. Approximately 4 gp of the dibasic slurry produced in this crystallizer is added to the hydroclone. It was fed at a rate of m. The underflow of the concentrator is hypochlorite. dropwise into the elementary oxidation reactor feed tank. Dilute hydroclone overflow ( overf low) is fed to a lime slurry replenishment tank, which contains stone Ash was added at a rate of approximately 100 lb/hr.

To control the total water balance to maintain 60% water in the paste slurry. A small amount of water was also added to the lime slurry replenishment tank. This lime slurry is reused Feed the dibasic crystallizer with the circulating pasty slurry to remove a slight excess of free lime. A dibasic calcium hypochlorite slurry containing the following was produced. Dibasic crystallization reactor The dibasic slurry is recirculated into a shell-and-tube heat exchanger using low-pressure steam. The temperature was maintained at 30'C to 35C by heating. The flow in this dibasic crystallizer system The analytical values were as follows.

%Ca(OCI)t 12.8 19.1 23.5%Ca((IN)t(TA )”+5.4 13.4 20.2%CaCl*/NaCl 1.+1.2 1.1% It, 0 (Remaining! I) 70.7 64.3 55.21 Al force degree Example 4 HOC] concentrated solution (47-50%) at a rate of approximately 7 gallons/minute. Therefore, the hypochlorite oxidation reactor was operated continuously. In this hypochlorite oxidation reactor, A concentrated slurry of slaked lime (40-42% Ca(OH)2) can also be used as a paste slurry. at a controlled rate so that the pH of the sample is maintained at about 10.2. reactants to high Shear mixer (Lightning” m1xer, Mixing Equip ment Co.

Mixing was performed using a Rochester N, Y, ). Part of paste slurry paste in the hypochlorite oxidation reactor by continuously withdrawing the The level of slurry was controlled.

The average analysis value of this pasty slurry is 35% Ca (QCl) 2.0.2 % Ca (OH) x, 0. 5% Ca Cl! , 0.5% Ca ( CI Os) was 2 and 820, which was 63.8%. Remove this page from the storage container. The slurry in the form of a stream is directly fed into a fluidized bed spray dryer and dried to a concentration of 78-80%. of Ca (QC1)2 and 11-14% of 8.0 (remainder) A lucium product was obtained.

Example 5 A concentrated solution of HOCI (47-50%) is dispensed at a rate of approximately 7.5 gallons/minute. The hypochlorite oxidation reactor of Example 4 was operated continuously. This hypochlorite In the oxidation reactor, add a dilute chlorinated lime solution (6.5% Ca (QC)) 2.2% of Ca (OH) 2.25 CaC12,0.2% of Ca C10s and the balance Water) was also supplied at a rate of approximately 1 gallon/minute. Concentrated slurry of slaked lime (38-4196 Ca(OH)2), the pH of the paste slurry is maintained at approximately 10.2. was added continuously at a controlled rate to ensure that the Combine the reactants in a high shear mixer (Lig old n ing" m1xer, Mixing Equipment Co.

Mixing was performed using a Rochester N, Y, ). Part of paste slurry paste in the hypochlorite oxidation reactor by continuously withdrawing the The level of slurry was controlled. The average analysis value of this pasty slurry was 33 ．． 5% Ca (QCI) 2.0. 3% Ca(OH)a, 08% (: a C+ 2.0.4% Ca’ (C10a) 2 and 6596 H20 It was. From the storage vessel, feed this pasty slurry directly into a fluidized bed spray dryer. 78-80% Ca(QCl)2 and H2O of ll-1496. A calcium hypochlorite product containing (remainder) was obtained. While operating this dryer, Fine particles of calcium hypochlorite collected from exhaust are mixed with lime. The dilute solution was fed to a scrubber to obtain a chlorinated lime solution. This chlorinated lime The solution was recycled to the hypochlorite oxidation reactor.

Continuation of front page (81) Specified times EP (AT, BE, CH, DE.

DK, ES, PR, GB, GR, IT, LU, MC, NL, SE), 0A (BP , BJ, CF, CG, CI, CM, GA, GN, ML, MR, SN, TD, TG. ), AU, BB, BG, BR, CA, FI, HU, JP, KP.

KR, LK, MG, MW, No, PL, RO, RU, S (72) Invention Person: Schafer, John, sex.

Noururado Sark, Cleveland, Tennessee, United States 37311 Le 1511 (72) Inventor Neuendorf, Greg, Yi.

Tray, Wynwood, Cleveland, Tennessee, United States 37312 Le N, Double, 1395

Claims (3)

[Claims] 1. In the method for producing calcium hypochlorite, lime or more than 30% by weight Lime slurry containing Ca(OH)2 is substantially free of ionic impurities and HO a chlorinating agent consisting essentially of a hypochlorous acid solution containing at least about 35% by weight Cl; containing at least 30% Ca(OCl)2 and with alkali metal ions. substantially free of chloride ions and has a calcium chloride concentration of less than about 3% by weight. A slurry of calcium hypochlorite dihydrate crystals in a calcium hypochlorite solution The above-mentioned manufacturing method is characterized by manufacturing. 2. In the continuous production method of calcium hypochlorite, lime and ionic impurities are consisting of a hypochlorous acid solution substantially free of HOCl and containing at least about 35% by weight of HOCl. Calcium hypochlorite dihydrate crystal sulfate is produced by reacting it with a chlorinating agent containing A first portion of this calcium hypochlorite dihydrate crystal slurry is Separate and mix this first portion of calcium hypochlorite dihydrate crystal slurry with lime. together to form a dibasic calcium hypochlorite crystal slurry; Add the calcium chlorite crystal slurry to the reaction mixture, then add the calcium hypochlorite crystal slurry to the reaction mixture. The continuous production as described above, characterized in that the second portion of the silium dihydrate crystal slurry is recovered. Construction method. 3. In the method for producing calcium hypochlorite, Ca(OH)2 is about 32 to about 4 An aqueous slurry of lime containing 5% by weight is added to an aqueous slurry containing at least about 40% by weight HOCl. in a reaction mixture with a chlorinating agent consisting of a chlorite solution at a temperature of about 15°C to about 30°C. The rate of addition of the aqueous lime slurry brings the pH of the reaction mixture to approximately 10 to about 10.8 with essential mixing, Ca(OCl) Calcium hypochlorite in a calcium hypochlorite solution containing at least 30% by weight of Obtain a slurry of ium dihydrate crystals, and then dry the slurry to essentially producing a solid product consisting of calcium hypochlorite and water. The above manufacturing method.