Production of Hypochlorite

According to this equation, an equivalent amount of hypochlorite and chloride should be formed. Hypochlorite, however, is a highly unstable substance and is easily converted into other products (see further) therefore, the liquor after chlorination always contains rather more chloride than hypo-ohlorite. 

During chlorination the heat liberated by the reaction must bo removed to 

If an excess of chlorine is admitted into the hydroxide solution the hypochlorite will be converted into chlorate the rate of this conversion is particularly high, if the temperature is allowed to exceed 40 °C. This reaction will be discussed later, when dealing with the preparation of chlorates. To prevent ovcrchlori-nation the reaction must be interrupted before all the hydroxide is used up. The small amount of hydroxide which remains in the bleaching liquor will increase its stability during storage. It is also necessary to prevent local overchlorination of the hydroxide this can be done if the chlorine is sufficiently diluted prior to its use. 

Industrially the reaction is carried out in chlorination vessels either in batches or in continuously operating units. Absorption towers are rarely used. 

In the batch process wide iron cylinders are used as chlorination vessels (of some 2.5 cubic meters content) the cylinders are rubber-lined and cooled by a coil made of rubber-lined steel or PVC. The vessels are filled with an 18% hydroxide solution and the chlorine enters the solution through PVC pipes under cooling and stirring the pipes end in distributors which are placed just above the bottom of the chlorination vessel. The vessels are closed by covers, and tail gases arc sucked off and led above the roof of the building. 

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In the electrolysis plant of Akzo Nobel in Rotterdam a hypochlorite production unit is in operation. This unit has two functions handling chlorine-containing waste gases from the plant and production of hypochlorite. The reaction is carried out in a two-step apparatus in which a liquid jet-loop reactor and a packed column are in series. In this way chlorine is converted to hypochlorite and emissions of chlorine to the atmosphere are avoided. 

Production of hypochlorite takes place in a two-step absorption unit in which 23% caustic solution is fed counter-currently to the chlorine feed-stream. In the first step -the liquid jet-loop reactor - about 90% of the chlorine is converted to hypochlorite. In step two - a packed column - a very efficient absorption [1-3] is carried out in which the chlorine concentration in the off-gas is reduced to <1 ppm. The operating window of this apparatus with respect to chlorine load is quite large and varies from 100 to 6000 kg h-1 of chlorine. This high capacity is necessary for the consumption of peak loads from the electrolysis plant during short time periods. During start-up or shutdown of one electrolyser the total chlorine peak load can vary from 100 to 300 kg in just a few minutes. 

Oxidized Starch Production Methods. Multiple methodologies were utilized to produce the corn starch products of hypochlorite and periodate oxidation. Ultimately only three of these procedures were selected as yielding functional product and will, therefore, be the only methods to be outlined here. 

This is present in neutrophils, and catalyzes the production of hypochlorite from hydrogen peroxide and chloride. The hypochlorite then reacts with superoxide to generate hydroxyl radical... 

On comparing the energy consumptions of an electrochemical production of hypochlorite liquor Avith the indirect method of producing hypochlorite from... 

ASTM C911 (formerly ASTM C433) specifies the required quality of quick- and hydrated lime for chemical uses including the production of hypochlorite bleach. High purity products are required with high available lime contents, low levels of sludge-forming impurities and a low iron oxide content (iron oxide is understood to catalyse the decomposition of calcium hypochlorite) [31.1]. 

Caustic soda is a likely source of nickel from the corrosion of the evaporators (Section 9.3.2.1). The nickel content of 50% NaOH can be reduced by addition of a corrosion inhibitor to the evaporation process (Section 9.3.4.2). Nickel can be avoided in integrated on-site production of hypochlorite by using less-concentrated NaOH from membrane cells, without evaporation. 

Other chapters deal with utility systems, cell room design and arrangement (with an emphasis on direct current supply), alternative processes for the production of either chlorine or caustic without the other, the production of hypochlorite, industrial hygiene, and speculations on future developments in technology. There is an Appendix with selected physical property data. 

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