Olin Corporation

Walter J Sakowski

Budd L Duncan

Larry G Carty

John H Shaffer

Craig A Foster

Manohar C Bajaj

Calcium hypochlorite is produced by admixing a slurry of lime containing soluble impurities with a saturated calcium hypochlorite solution in a crystallizing zone. An impure slurry of coarse and small dibasic calcium hypochlorite crystals and fine insolubles in a mother liquor is formed and fed to the intermediate section of a separation zone. An aqueous sodium chloride elutriant is fed to the lower section of the separation zone to separate a slurry of fine insolubles, which is conveyed in the elutriant to the upper section of the separation zone, and small crystals of dibasic calcium hypochlorite, which can be recycled to the crystallizing zone or destroyed by chlorination, from the dibasic calcium hypochlorite solution. A slurry of purified coarse dibasic calcium hypochlorite crystals in the elutriant is removed from the lower section of the separation zone at a rate controlled to maintain a rising velocity in the lower section of the separation zone of from about 0.5 to about 7 centimeters per minute. Purified coarse dibasic calcium hypochlorite crystals are separated from a dibasic hypochlorite mother liquor and admixed with an alkali metal hypochlorite solution to produce a mixed alkali slurry which is chlorinated to form a slurry of calcium hypochlorite dihydrate crystals in a saturated calcium hypochlorite solution which crystals are separated to provide a cake of calcium hypochlorite crystals which is then dried and a saturated solution of calcium hypochlorite which is recycled to the crystallizing zone.

Continuous process for the manufacture of calcium hypochlorite

A process for producing neutral calcium hypochlorite comprises admixing lime, an alkali metal hypochlorite and dibasic calcium hypochlorite crystals in a mixing zone slurry. The mixing zone slurry is reacted with chlorine to form a paste of neutral calcium hypochlorite. The paste is then separated into a cake of neutral calcium hypochlorite and a paste liquor. A slurry of lime is fed to a crystallizer to react with the paste liquor to form a slurry of dibasic calcium hypochlorite crystals in a mother liquor. Crystals of dibasic calcium hypochlorite are then separated from the dibasic mother liquor and recycled to the mixing zone. The process of the present invention provides an efficient method of recovering calcium hypochlorite values from process liquors while reducing energy costs expended in the recovery. The process further provides rapid recovery of dibasic calcium hypochlorite for reuse in a neutral calcium hypochlorite process by optimizing separation rates.

Production of neutral calcium hypochlorite from its dibasic salt

A process for producing neutral calcium hypochlorite which comprises reacting an aqueous slurry of lime containing insoluble impurities with chlorine to form a first slurry of dibasic calcium hypochlorite crystals and insoluble impurities. The insoluble impurities are separated from the first slurry by employing separation means for classifying solids with respect to particle size. Dibasic calcium hypochlorite crystals are then separated and admixed with an alkali metal hypochlorite and recycle dibasic calcium hypochlorite crystals to form a mixing zone slurry. This slurry is reacted with chlorine to form a paste of neutral calcium hypochlorite. The paste is separated into a cake of neutral calcium hypochlorite and a paste liquor and the cake of neutral calcium hypochlorite recovered. The paste liquor is reacted with lime to form a second slurry of dibasic calcium hypochlorite crystals which are separated from their mother liquor and returned to the mixing zone as recycle dibasic calcium hypochlorite. The novel process can employ low quality lime as it effectively removes insoluble impurities. The process also efficiently recovers calcium and hypochlorite values from process streams.

Calcium hypochlorite production from its dibasic salt

A novel process for the production of granular calcium hypochlorite compositions is provided which comprises reacting neutral calcium hypochlorite with an alkaline solution comprised of an alkali metal hypochlorite and an alkali metal hydroxide. The reaction produces a slurry from which a wet cake comprised of neutral calcium hypochlorite and a residual amount of hemibasic calcium hypochlorite is recovered and dried. During the drying process in which granular calcium hypochlorite compositions are obtained, there is a substantial reduction in the loss of available chlorine from the product.

Process for manufacture of calcium hypochlorite

In a process for preparing granular calcium hypochlorite particles, wherein hydrated triple salt crystals of calcium hypochlorite, sodium hypochlorite, and sodium chloride are reacted with a chlorinated lime slurry to form particles of calcium hypochlorite dihydrate, the resulting slurry is processed to separate the calcium hypochlorite dihydrate particles and the resulting particles are dried to form granular calcium hypochlorite particles, the improvement which comprises:

Preparing calcium hypochlorite from triple salt

An improved process for precipitating and recovering lime by reacting an aqueous solution of calcium hypochlorite with an alkaline compound is described. The pH of the resulting lime slurry is maintained in the range from about 11 to about 13.0, whereby hemi-basic calcium hypochlorite crystals form in the slurry. When the slurry is filtered or otherwise separated to recover the lime, an improved filtration rate is obtained. In addition, washing of the lime cake to remove impurities such as sodium chloride is easily accomplished because of the ease of separating wash water in the presence of the hemi-basic calcium hypochlorite crystals.

Lime recovery process

A process is disclosed for reducing the available chlorine content of aqueous waste streams produced in chemical plants, especially calcium hypochlorite plants, in order to permit further purification treatment in waste purification systems which employ activated carbon. The available chlorine content is reduced by chlorinating the impure stream at a temperature in the range from about 80.degree. to 100.degree. C. at a pH in the range from about 5.5 to about 8.5. In order to avoid excessive reactor boilover, close control of these conditions is required. In addition the reaction is time dependent and the holdup time in the reactor and a subsequent hold tank ranges from about 0.5 to about 4 hours. During this reaction the available chlorine forms the corresponding chlorate in the aqueous solution which may be passed through the activated carbon bed without adversely affecting the bed operation.

Purification of waste streams containing available chlorine

A continuous process for the manufacture of calcium hypochlorite in which an aqueous slurry of lime and sodium hypochlorite is chlorinated in a mixing zone to form a sodium chloride solution containing large crystals of calcium hypochlorite which are readily separated and dried. The resulting solution containing some dissolved calcium hypochlorite is reacted with an alkali metal hydroxide to precipitate lime, which is separated and recycled to the mixing zone slurry. The lime-free solution may be used as bleach liquor or processed to precipitate solid salt useful in the preparation of brine. The remaining solution is recycled to the mixing zone slurry. Purification of fresh lime is also disclosed. The process provides an improved separation of calcium hypochlorite and sodium chloride, and recycles all solutions to minimize pollution of water resources.

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Cleveland, TN, United States of America

Walter J Sakowski