Chlorinated hydrocarbon wastes Depending on the disposal options they can be either a boon or a bane to the chemical industry Chlorinated hydrocarbons are one of the largest-volume products manufactured by the chemical industry. These raw materials are important as intermediates for other products as well as being main products in their own right. In the manufacture of chlorinated solvents or monomers, the yield of waste by-products is often as much as 5% of the main product. For example, the manufacture of 300 000 tons/y of chlorinated solvents may result in 4000 to 15 000 tons/y of various wastes, containing more than 60-70% chlorine by weight. Wastes are also generated in the manufacture of vinyl chloride monomer and epichlorohydrin. A still-unanswered question is whether federal and state authorities have complete information on the volume of chlorinated hydrocarbon waste material generated by all producers of chlorinated hydrocarbons. Prevalent disposal practices include deep-well disposal, burning the wastes in land-based incinerators, and burning them at sea. Governments of industrialized countries have prohibited the direct discharge of these wastes into rivers or lakes, but such wastes have been found in landfills at hazardous waste dump sites. Although burning these wastes aboard incinerator ships at sea is practiced, sea incineration cannot recover any of the wastes’ valuable components for subsequent recycling, nor can it recover any of the calorific value of the waste chemicals, which is considerable.
French ingenuity The French company C h l d Chimie, a subsidiary of Elf and Total, developed a process that effectively destroys chlorinated hydrocarbons by incineration while simultaneously producing high-quality hydrochloric acid. It also recovers 70-75% of the heating value of the waste as high-quality steam. The 280A
Environ. Sci. Technol.. VoI. 17, NO.7. 1983
process is named VRC from the French “valorisation des rtsidus chlorts” (valorization of chlorinated residues); it gets a value for the chlorinated hydrocarbon residue. The plant at Saint Auban, in the south of France, disposes of more than 2 metric tons/h; high-quality hydrogen chloride is recovered as 33% aqueous HCI or, after distillation, as 100%HCI gas. The process was developed at Saint Auban, a former defense plant, by scientists from several companies: Phhiney, St. Gobain, Progil, RhanePoulenc, and Chlot Chimie. The furnace operates at a temperature of 1200 OC with a residence time of 5-6 s. It burns low-viscosity liquid wastes and viscous fluids as well as mixtures including gases and solid particles. For six years Chlot Chimie operated a pilot plant at Saint Auban. In 1972-74 another unit was built next to this plant that incinerates 16000 tons/y of chlorinated wastes and produces the
stoichiometrically corresponding volume of HCI and steam. This plant has run continuously since start-up, except during power failures, and is operating at capacity today. The process is nine years old, and one key U S . chemical spokesman said that it shows great promise. Similar plants have been licensed and built in Spain (one), Morocco (one), Russia (four), and in the U S . (one, Borden Chemical). A new West German plant is now being designed, and negotiations are under way for two new U S . plants and three European plants. Development is being handled by Pyroclor, Inc. (Munich, West Germany, and Chatham, N.J.) Operational detail The Saint Auban plant can burn wastes containing up to 74% chlorine without the need for additional fuel. At Saint Auban the use of patented burners of the LEA type provides complete combustion of chlorinated
Economics of VRC plant :hlorinated hydrocarbon wastes 20 000 metric tonsly Iisposai cost $300-350lmetric ton rota1 COS! of disposal $6-7 miiiionly JCR plant investment for a plant that could dispose 0 20 000 metric tonsly is 510 million.
51 mtliionly Operational costs
$1 millionly
Annual cost
$2 million 33 000 metric tonsly 33% H
solution or 10 000 metric tonsly luu%
I
Income from HCI gas ($150lmetricton) Income from stea Znnual income
51.5 rniiiion 50.5 millior $2.0millior
0013-936X/83/0916-0290A$01.50/0
@
1983 American
Chemical Society
Valorization of chlorinated residues" Sections Incineration
Waste
ELr
Quench washing
--+r
Steam 20 bar
HCI absorption
Muriatic acid Neutralization storage
HCI distillation
HCI compression
- * - - >
a The first industrial unit was built in France at Saint-AUbm m 1974-75 It has been On-stream almost unmterwpledly ever m c e , Wlth an operal~ve RllablllQ Of more than 95% (350 dly] and tOtSl absence Of C O I ~ O P ~ problems O~ &urn: ChloBChme
wastes. This burner, developed and patented by ChloC Chimie, received a prize from the French government for energy-saving industrial equipment. The LEA system requires no pressure on the liquid and is fed by gravity with very little head. It requires a maximum air pressure of 0.4 bar. During the pilot study, scientists found that the exothermicity of the combustion process is important; an optimum incineration temperature of 1200 'C should be maintained with a minimum of air. An excess of air introduces a considerable volume of nitrogen into the process, which lowers the partial pressure of HCI in thecombustion gases. In turn, this leads to more difficult absorption in water and dilution of the acid solution. To counteract this, the absorption water must be drastically cooled, and intricate multistage circuits are required. In the VRC process the heating value of the waste is used to generate steam. A boiler is installed between the point where the combustion gases leave the furnace and the quench. (The quench is a piece of equipment, made of graphite, that reduces the temperature of the combustion gases.) Up to 70-75% of the heating value is recovered, and the combustion gases are cooled to 350 OC before entering the quench. The VRC unit can burn wastes'with a heating value as low as 2200 cal/kg (3700 Btu/lb) without additional supporting fuel.
The temperature in the quench is controlled by recycling cooled HCI solution. The same solution is sprayed directly into the washing tower. The unit recovers 99-99.5%of thechlorine contained in the wastes as HCI. In the quench, the gases are cooled to 50-80 OC. The steam is produced at 20 bars (280 psi) and 220 "C. In operation, there is a cooling loop connected to the washing tower so that no HCI absorption takes place in the washing tower. An isothermal absorption process is used to produce the 33% HCI solution. To obtain gaseous HCI, an azeotropic distillation of the 33% HCI solution is conducted in a special column. Even with the high efficiency of the furnace and quench, some small amounts of HCI and chlorine still must be prevented from escaping into the atmosphere. This is accomplished by contacting the gases with sodium hydroxide, which produces sodium chloride and sodium hypochlorite, as well as some bicarbonate formed from the COz in the combustion gases. No direct water injection should be made in the furnace because even small volumes can quickly disturb the system's water balance. To adjust the water balance an aqueous solution of HCI is recycled to give optimum temperature adjustment and a water/HCl equilibrium corresponding to the best recovery rate of 33% aqueous solution of HCI.
The new disposal option Chemical producers faced with the problem of disposing of chlorinated hydrocarbon wastes have a few options. They can send the wastes to a waste disposal company or build recycling plants such as the Chlot Chimie plant. A third alternative that will soon be available is to send the wastes to a plant that operates on the Chlot Chimie patent. This process recovers 99-99.5% of the chlorine contained in the chlorinated waste either as a 33% solution of HCI or as 100% HCI gas. The latter contains fewer than 100 ppm water and can be used for industrial chemical syntheses such as oxychlorination. The VRC plant is the only system approved by the French Ministry of Environment for the disposal of chlorinated wastes. Environmental authorities in Holland and Germany are also interested in the VRC system as an alternative to incineration of chlorinated wastes at sea. Several chemical and waste disposal companies as well as environmental authorities in other countries are considering such plants for disposing of their wastes. Of particular interest is that several test runs at the Saint Auban plant have shown the process to be extremely effective in the destruction of polychlorinated biphenyls, which are very difficult to destroy. The EPA observed these test runs and also provided analytical assistance. -Stanton Miller Envirm. Sci. Technol., V0I. 17. No. 7, 1983
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