Caustic soda production

United States Caustic Soda Production. In 1987 U.S. production of caustic soda increased to 10.4 million tons (fig. 1), more than 10% over that of the previous year, furthermore, 1988 production was up another 6.7% to 11.1 million tons. The demand for caustic soda has been very strong in recent years as evidenced by both increased U.S. consumption and a strong export demand. In 1987 the United States exported 1.5 million tons, 14.5% of the total caustic soda production (6), representing a 25.5% increase over exports in 1986. Then, in 1988, caustic soda exports grew by another 4.1%. A weak doUar helped boost the 1987 exports. Growth slowed in 1988, however, as a result of an industry (and world) wide caustic soda shortage, which was caused by lower U.S. chlorine consumption and forced allocations. Because industries switched from caustic to soda ash where possible, the lower 1988 export growth was not indicative of caustic soda s export potential. 

Because chlorine and caustic soda are electrolysis coproducts and chlorine cannot be stored economically, caustic soda production has been very... 

The only caustic soda production process besides electrolysis is the soda—lime process involving the reaction of lime with soda ash ... 

Landfors J (1993) Alternative on-site caustic soda production in the paper and pulp industry, Electrochem Processing, Innovations and Progress, April 21-23, Glasgow Sunblad B (1992, Eka Nobel) Can CA 2,071,810 Chem Abstr 118 194663f... 

Fig. 15.3 The balance factoring the price of rayon-grade caustic soda production from membrane technology.

Fig. 15.4 Balancing the economics with increased caustic soda production from membrane technology for the same power consumption.

Table 2. D-statistic analysis of the ranking distribution of caustic soda production in seven major industrial countries, based on tonne per annum data [14] in brackets...

As noted IN the preceding chapter, almost all elemental chlorine is made as a by-product of caustic soda production, although the obsolete Deacon process of 1868 has been revived (with improvements) for recycling CI2 onsite in plants where chlorination of hydrocarbons forms gaseous HC1, an objectionable waste product ... 

Fig. 1. United States clilorine and caustic soda production , annual clilorine capacity O, caustic soda production O, clilorine production (6).

Chlorine (0.19% of lithosphere) is produced mainly from NaCl which is either crystallised from brines or mined. The gas is a product of the electrolysis of aqueous sodium chloride for caustic soda production, with carbon anodes and a mercury cathode. It is also a by-product of the manufacture mainly of metallic sodium, but also of magnesium and calcium, by electrolysing the appropriate fused chloride. Its chief uses are as a bleach, a bactericide, and an industrial chemical. 

The concentration of sodium hydroxide at the cathode surface is higher than that of the bulk solution in electrolysis of sodium chloride because 1 mol of water decomposes at the cathode surface per Faraday. When the solution at the cathode surface is separated from the bulk solution with a suitable separator, sodium hydroxide of higher concentration can be obtained from the cathode surface.171 The concentration of caustic soda produced from an electrolyzer is generally about 32-35%, of which 42-54% is directly and economically produced from an electrolyzer by forming a specific, thin membrane layer on the cathode side of the membrane.172 The current efficiency for caustic soda production is more than 95% in commercial production. 

Figure 6.19 Change in current efficiency of caustic soda production and concentration of caustic soda produced with cation exchange membrane material ( ) generation efficiency of H+ by bipolar ion exchange membrane current efficiency ( ) Nafion 324 (A) Nafion 110 (X) Aquatech membrane.

Table 3.2 Reversible potentials for reactions relevant to chlorine/ caustic soda production. pH s are those applicable to the various cell technologies.

Many of the world s major chlor-alkali companies have developed their own mercury cells and the designs will differ in the way they seek to obtain the maximum electrode area and in the arrangement of the auxiliary equipment. The development of the cells during almost a century of electrolytic chlorine and caustic soda production and the variation in the cells recently available are described in the texts at the end of the chapter. 

Chlorine is sold as a gas or a liquid, and caustic soda is sold as 50% or 73% solution, or as anhydrous beads or flakes. There is also a significant market for caustic soda in the concentration range of 10-25%. The caustic soda product is designated by the manufacturing technology used, namely mercury, diaphragm, or membrane cells. More than 95% of the chlorine and 99.5% of the caustic in the world are produced by these cell technologies. About 0.5% of caustic soda is made chemically from soda ash, and KOH accounts for 2.5% of the caustic produced in the world. 

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