Chemistry of inorganic compounds – Halogen or compound thereof – Hydrogen halide
Patent
1982-06-22
1984-08-07
Thomas, Earl C.
Chemistry of inorganic compounds
Halogen or compound thereof
Hydrogen halide
423488, C01B 700, C01B 703
Patent
active
044643519
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to the elimination of environmentally harmful products of manufacturing processes. In particular it relates to processes for the disposal of organic materials such as heavy halogenated wastes.
By heavy halogenated wastes (HHW) we mean halogenated aromatic and aliphatic compounds where the hydrogen to halogen ratio is less than one. Typical aromatic and polyaromatic heavy halogenated wastes include such compounds as hexachlorobenzene (HCB), polychlorinated biphenyls (PCB's) and octachlorostyrene (OCS). Residues or "heavy ends" from industrial processes frequently contain various mixtures of these and halogenated aliphatic compounds such as hexachloroethane (HCE), perchloroethylene (PCE), and hexachlorobutadiene (HCBD). A number of pesticides also fall within this class including some which can persist for very long periods in the environment.
BACKGROUND ART
Incineration has been widely used for the destruction of domestic and industrial waste but these heavy halogenated wastes are not readily handled by this means. The combustion of such wastes is incomplete and harmful amounts can escape into the atmosphere or into soil and water. Furthermore some of the reaction products formed in this partial combustion are also harmful.
Incineration in cement kilns has been proposed but many kiln operators are reluctant to allow their facilities to be used because of the difficulty and uncertainty in ensuring that harmful combustion products are not formed and released adventitiously. No kiln operator in Australia, for example, has even permitted a trial incineration of chlorinated hydrocarbons. Deep land burial has often proved the only option but in countries such as Australia suitable geological formations do not appear to be available.
It is an object of our process to provide a means of combustion of heavy halogenated wastes that gives essentially quantitative destruction of these wastes without the formation of highly toxic or environmentally persistent combustion products. It is a further object of our process to recover the halogen in a useful form.
DISCLOSURE OF INVENTION
Accordingly we provide a process of disposing of organic materials by thermal destruction in a hydrogen/oxygen flame which process comprises passing a mixture of heavy halogenated wastes in the vapour phase and a carrier gas comprising hydrogen through burning means provided with gaseous oxygen.
The carrier gas comprising hydrogen performs three important functions. First, the carrier gas carries the heavy halogenated wastes (HHW) to the burning means. Secondly, the hydrogen ensures a high temperature in the hydrogen/oxygen flame for complete destruction of the HHW. Thirdly, the hydrogen converts the halogen into hydrogen halide.
The preferred carrier gas is hydrogen itself, but other compositions comprising at least 80% v/v of hydrogen may be used. Suitable compositions, for example, are some of the hydrogen-rich hydrocarbon streams found in oil refineries.
Some of the heavy halogenated wastes referred to hereinbefore have a relatively low vapour pressure at ambient temperatures and may in fact be solid. Such materials are heated to a temperature at which an adequate amount of vapour will be continuously removed by the flow of carrier gas. The temperature is controlled so that the amount of HHW vapour is not excessive since this would lead to a low hydrogen/HHW vapour ratio with subsequent incomplete combustion in the flame. While temperature controlling means can be used as a sole form of control of this ratio, in one preferred embodiment of our invention a first stream of carrier gas is passed over the heated chlorinated hydrocarbons, and this is diluted with a second stream of carrier gas before passing the mixture of gases into the flame. The second stream of carrier gas is pre-heated, typically by passage through a tube in or above the HHW, before being mixed with the first stream containing HHW vapour. The first stream of carrier gas can pass over the surface of the heated HHW, or, preferabl
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Mok King K.
Sencar Joze
Vasak Vladimir
ICI Australia Limited
Thomas Earl C.
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