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Table 4. Average Annual Growth Rate of selected U.S. plastic products. Source: Chemical and Engineering News (1985); Chemical and Engineering News (1997). Product Polyethylene – low density Polyethylene - high density Polypropylene Polystyrene Polyvinyl Chloride and copolymers 2.4 Industrial Gases (SIC 2813) 1974-1996 1985-1996 4.0% 4.3% 6.9% 5.8% 7.9% 8.0% 2.7% 3.7% 4.7% 6.3% The production of industrial gases is a relatively energy intensive process, and this sector accounted for 6% of carbon dioxide emissions from within the chemical sector in 1994. Nitrogen and oxygen production have historically counted for about half the value of shipments in the sub- sector (Lipinsky and Ingham, 1994) and are typically the second and third largest produced chemicals. These two gases are produced mainly through cryogenic air separation where air is cooled and pressurized until it becomes a liquid with the various gases extracted through fractional distillation. However other technologies are increasingly being used such as pressure swing absorption and membrane separation. Energy consumption for oxygen production has been estimated at 2.0 GJ/tonne (OTA, 1993). Assuming these intensities, energy consumption for these two gases in 1994 would account for over 85% of SIC 2813. Since 1985 the production of nitrogen and oxygen has grown by over 4% annually. 2.5 Nitrogenous Fertilizers (SIC 2873) The production of ammonia, a key component in the manufacture of nitrogenous fertilizers, is a highly energy intensive process. Roughly 80% of ammonia production is used as fertilizer feedstock in the U.S. (Lipinsky and Ingham, 1994). Like methanol, ammonia is produced through the high-pressure synthesis of gases (carbon dioxide, hydrogen, and nitrogen). Ammonia production accounts for over 85% of the energy consumption in SIC 2873. The production of these products has grown on the order of 1% annually since 1974. 2.6 Alkalies and Chlorine (SIC 2812) One of the main uses of chlorine (around 30%) is as an intermediate feedstock for polyvinyl chloride (PVC) which has been growing rapidly over the past decade (Lipinsky and Ingham, 1994). Chlorine is also used as a bleaching agent in pulping operations. The production of chlorine is a highly electricity-intensive process requiring between 3065 kWh/tonne and 3960 kWh/tonne depending on the cell type (Pletcher and Walsh, 1989). In the process an electric current is used to separate molecules into their constituents. The products of the process include chlorine and caustic soda. Table 5 shows estimated energy consumption for the various cell types. Steam consumption in diaphragm cells is greater since more energy is required to concentrate the brine. We assume a weighted energy intensity of 12.8 GJ/tonne based on the 1994 shares (see Chapter 5). 5 1PDF Image | Energy use and energy intensity
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