Caustic value

Chemical MF is used in several apphcations to recover caustic values from cleaning or processing streams. An example is the caustic solution used to clean dairy evaporators, which may be cleaned for reuse by passing it through a microfilter. Significant savings in caustic purchase and disposal costs provide the incentive. Acids are also recovered and reused. Ceramic microfilters are most commonly used in these apphcations. 

The returns for the industry can be monitored (see Figs 1.1-1.3). The selling price of caustic soda is fairly transparent everywhere and chlorine pricing is transparent in the USA. Chlorine is less transparent outside the USA as most of the consumption is captive rather than merchant. The market for ethylene dichloride (EDC) is, however, transparent and chlorine values can be worked out from the selling price of the EDC and the input price for the ethylene. Knowledge of the chlorine value and the caustic value gives the value of the Electrochemical Unit or ECU. This provides a measure of the profitability of the business at any time. Convenient marker prices can be found in the US Gulf for both EDC and caustic as well as out of north-west Europe. 

Spent caustic (3800 tons/year) is sent off-site for recovery of remaining caustic value and naphthenic acids. Most catalysts are recycled for recovery of additional activity or metals. Spent cracking catalyst (6(K) tons/year) is sent to Amoco s Whiting, Indiana, refinery for use as equilibrium catalyst. Spent ultraforming catalyst is returned to metals reclaimers to recover platinum for reuse in new catalyst. Spent desulfurization catalyst and polymer catalyst are nonhazardous and are buried in an on-site landfill. Sludges from the oil/water separator are a listed hazardous waste under RCRA regulations. They are combined with other solid wastes, such... 

Recovery of Caustic Value. Byproduct sodium sulfate is not a readily marketable commodity. The United States alone generates more than 1.5 million tons per year, and those chlor-alkali plants which sell the material may not recover even the cost of crystallization [166]. Modified membrane cells that regenerate caustic soda and sulfuric acid by electrolysis of Na2S04 solution therefore have been studied. These reverse the neutralization reaction and regenerate the acid and base ... 

There being several varieties of limestone, the limes prepared from them show corresponding variations in composition. The type of analysis required on a given sample depends to some extent on the use for which the sample is intended. Though routine analysis includes the same determinations as are canied out on limestone, there are certain specific uses which depend on the caustic value of lime (CaO content), and the impurities including CaC03 are not available for reaction. It is therefore often desirable that available CaO content of lime be determined. 

Determination of available lime or free CaO in industrial lime or in milk of lime or determination of caustic value of agricultural lime iodi-metrically... 

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