Chlorine supply demand

Table 1.1 World chlorine supply/demand (per year x 103 tons). Source Tecnon (UK) Ltd.

The U.S. chlorine supply-demand as projected by Dow analysts at the end of 1990 is shown in Fig. 12.16. Dealing with multiple issues on the environmental front and the possibility of a recession, the chlor-... 

Chlorine and Its Derivatives A. World Survey of Supply, Demand, and Trade to 1992, Tecnon Consulting Group, London, 1988. 

In contrast to this direct chlorination there is the oxychlorination of ethylene using hydrogen chloride and oxygen, the other major method now used. Since the chlorine supply is sometimes short and it is difficult to balance the caustic soda and chlorine demand (both are made by the electrolysis of brine), hydrogen chloride provides a cheap alternate source for the chlorine atom. Most of the ethylene dichloride manufactured is converted into vinyl chloride by eliminating a mole of HCl, which can then be recycled and used to make more EDC by oxychlorination. EDC and vinyl chloride plants usually are physically linked. Most plants are 50 50 direct chlorinationroxychlorination to balance the output of HCl. 

Electrochemical processes combine chemistry and electricity to meet the needs of today s society. Chlorine [303748, 303736, 303737], lye [304624], aluminum [304624], hydrogen [303854, 303855], oxygen [303858, 305263, 303855], copper, and other chemicals are vital for consumers and industry. Batteries and fuel cells supply demands for efficient and portable power. At the heart of all electrochemical processes is the electrochemical reactor. 

Fig. 12.16. U.S. chlorine supply and demand, based on many market variables. The more optimistic forecast assumed the pulp and paper segment would proceed only to a 50% reduction level, resulting in a 0.9% average annual growth rate for the 1988 to 1995 period. The second outlook assumed the recession forecast for the economy and a 70% reduction in demand from the pulp and paper segment, which would lead to no growth for chlorine. These two outlooks represent extreme cases. Dow analysis predicted that market growth figures would fall somewhere between the two. (Courtesy the Dow Chemical Company.)...

The methods described earlier for determining the total, free, or combined chlorine residual also are used in establishing the chlorine demand of a water supply. The chlorine demand is defined as the quantity of chlorine that must be added to a water supply to completely react with any substance that can be oxidized by chlorine while also maintaining the desired chlorine residual. It is determined by adding progressively greater amounts of chlorine to a set of samples drawn from the water supply and determining the total, free, or combined chlorine residual. 

Chlorine from HCl. Most organic chlorination reactions consume only half the CI2 to produce the desired product the other half is converted to HCl. Depending on demand and supply of CI2 vs HCl, chlorine recovery from hydrochloric acid is sometimes attractive. Two commercial routes are available electrolysis and oxidation (69). 

Over 90% of the HCl produced ia the United States origiaates as a coproduct from various chlorination processes direct generation of HCl from and CI2 accounts for only about 8% of the total production. Table 11 describes the production contribution of HCl from significant sources through the period 1980 to 1992 (72). Figure 6 illustrates the historical production growth of HCl ia the United States (73). The growth rate, about 5—6% from 1955 to 1975, slowed to - 1% because of disparity between supply and demand (see Table 12). The production capacity ia 1993 was about 2.92 million metric tons, down 9.6% from the 1992 production of 3.24 million metric tons (74). 

Ethylene Dichlonde and Vinyl Chloride. In the United States, all ethylene dichloride [107-60-2] (EDC) is produced from ethylene, either by chlorination or oxychlorination (oxyhydrochlorination). The oxychlorination process is particularly attractive to manufacturers having a supply of by-product HCl, such as from pyrolysis of EDC to vinyl chloride [75-01-4] monomer (VCM), because this by-product HCl can be fed back to the oxychlorination reactor. EDC consumption follows demand for VCM which consumed about 87% of EDC production in 1989. VCM is, in turn, used in the manufacture of PVC resins. Essentially all HCl generated during VCM production is recycled to produce precursor EDC (see Chlorocarbons and Cm OROHYDROCARBONS ViNYLPOLYAffiRS). 

In order to ensure the destruction of pathogens, the process of chlorination must achieve certain control of at least one factor and, preferably two, to compensate for fluctuations that occur. For this reason, some authorities on the subject stress the fact that the type and concentration of the chlorine residual must be controlled to ensure adequate disinfection. Only this way, they claim, can chlorination adequately take into account variations in temperature, pH, chlorine demand and types of organisms in the water. While possible to increase minimum contact times, it is difficult to do so. Five to ten minutes is normally all the time available with the type of pressure systems normally used for small water supplies. Many experts feel that satisfactory chlorine residual alone can provide adequate control for disinfection. In their opinion, superchlorination-dechlorination does the best job. Briefly, what is this technique and how does it operate ... 

Chlorine and sodium hydroxide are produced at the same time in a ratio to each other that cannot he changed. This is OK for the manufacturers as long as the demand for each of these products is the same. But that usually is not the case. If the demand for chlorine is low, producers decrease production because it is difficult to store chlorine. This causes sodium hydroxide to be in short supply, and prices rise, causing some users to turn to alternates such as sodium carbonate. When the demand for chlorine is high and sodium hydroxide is plentiful, prices for sodium hydroxide may fall if demand fails to meet supply. 

Consider the steam supply line and associated control instrumentation. The designer s intention is that steam shall be supplied at a pressure and flow rate to match the required chlorine demand. 

We show the cost of chlorine in the case of caustic credits from export and domestic business (Figs 1.8 and 1.9). It is one of the many paradoxes in the business that although the plant is built for the chlorine, for most of the time the profit comes from the caustic soda. (Figure 1.10 shows the origin of the chlorine in the derivative trade.) The management of the caustic return is vital to the industry. The cyclicality in the demand for caustic with the supply will continue though the number of players in the business will probably reduce. 

Environmental issues are discussed below. It is worth pointing out now that the industry has had to adapt to chlorine demand changes in this sector such as CFCs, pulp and paper and solvents. In Europe no chlorine is used in the pulp industry and it is being run-down elsewhere. Many of the plants which supplied chlorine into the pulp sector are situated a long way from other chlorine end-users and there have been closures of chlorine units, mainly in Scandinavia, Canada and the West Coast of the USA. 

With PVC being the main driver for chlorine demand there is increasing pressure on the need to obtain cheap power, salt and ethylene feedstocks. Export-driven EDC and caustic plants have some place in meeting world demand though with the need to export both chlorine, in the form of EDC, and caustic soda there can be occasions when these plants are vulnerable to low returns if demand is much lower than supply. Traditional locations for these plants have been in the US Gulf and the Middle East, but there are plans to site such plants in Venezuela and Australia with both these countries having a large caustic soda demand in alumina. 

A detailed supply-chain model, which showed that two days inventory was required to supply the forecast market demand, determined chlorine storage tank number and size. The minimum number of drums and cylinders of liquid chlorine required to be held on-site was also calculated from the supply-chain model. This approach was also extended to calculation of the number and size of storage tanks for products such as caustic soda, sodium hypochlorite and hydrochloric acid. 

The standard disinfectant for many of the world s potable drinking water supply systems (ozone and others are also widely used) and the product of choice for large cooling systems, usually available as a gas for lowest cost, but can be provided by liquids such as sodium hypochlorite (bleach) or solids such as calcium hypochlorite or isocyanurates. Any process contaminant leak tends to increase the chlorine demand, requiring additional chlorine to maintain disinfection rate. Poor penetrant of biomass and significantly reduced efficiencies over pH 8.0. 

Because the supply exceeds demand, the HCI generated often cannot be sold or reused even after purification. Although electrochemical fluorinations have been practiced commercially for many years, the main products of the reactions are typically perfluorocarbons since C-H bonds rarely survive. New methods, which avoid the need to feed chlorine and disposal of HCI are needed to prepare HCFCs and HFCs are obviously desirable. 

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