FR2609652A1 - PROCESS FOR DESTRUCTION OF LOW TEMPERATURE CHLORINATED PRODUCTS - Google Patents

Abstract

1. Process for destroying chlorinated organic products containing more than 2 carbon atoms, in which these products are brought into contact with a bath of at least one chloroaluminate, characterized in that the initial concentration of the chlorinated organic products in the bath is 4000 ppm or less and preferably 2000 ppm or less.

Description

i

  PROCESS FOR DESTRUCTION OF CHLORINATED PRODUCTS

LOW TEMPERATURE

  The present invention relates to a method of destruction

  chlorinated organic products and more particularly

  aromatic and polychlorinated biphenyls. Some dielectric liquids contain chlorinated organic products and after some time of operation degrade and need to be replaced. We can sometimes regenerate them totally or partially. We often have to destroy a

part of these liquids.

  Chlorinated organic products and certain pesticides

  acids, chlorinated aromatics such as hexachlorobenzene, or polychlorinated biphenyls (PCBs)

  when they are burned as an ordinary flammable product.

  To avoid generating toxic products, these chlorinated products are destroyed at high temperature and under specific conditions. An article from SCI. TOTAL ABOUT. 1978, 10 (1) 51-9 describes the destruction of polychlorinated biphenyls (PCBs) by incineration with

  a residence time greater than 2 seconds.

  Another article PROC. CANCEL. MEET - AIR POLLUT. CONTROL ASSOC. 1977 (Vol 2) paper N 33 describes a destruction at 99.9995 Z

  PCBs at 1000 C with a residence time of 2 seconds.

  European patent EP 170 714 describes the destruction of PCBs by reaction with molten aluminum or a eutectic based on

  of aluminum, the reaction takes place above 382 C.

  We have now found a much simpler process for destroying these products that can work below

300 C.

  The present invention is a method for destroying chlorinated organic products having more than 2 carbon atoms, characterized in that these products are brought into contact with a bath

at least one chloroaluminate.

  Different chloroaluminates or their mixtures can be used. For example potassium chloroaluminates, lithium,

  sodium, calcium, strontium or ammonium.

  In this text is called chloroaluminate any mixture of anhydrous aluminum chloride and one or more

metal chlorides.

  Sodium chloroaluminate, which is preferably used, refers to a mixture of aluminum chloride and sodium chloride in any proportions and not just the equimolar mixture. Sodium chloroaluminate may also contain lithium chloride and / or potassium chloride. It can therefore have any mixture of aluminum chloride, sodium chloride and lithium chloride called sodium chloroaluminate and

of lithium.

  It is also preferred that the sodium chloroaluminate contain

  not less than 50 mol% of aluminum chloride and has a

  melting point below 200 C.

  The invention is concerned with all chlorinated organic products having more than 2 carbon atoms but it is especially

  useful for aliphatic, cyclic, aromatic mono-

  or polycyclic, heterocyclic. The invention relates to any

  especially perchlorinated aliphatic products and among the

  aromatic products, polychlorinated biphenyls.

  These products can be in any form. In particular, they may be in a solid phase, for example

absorbed on activated carbon.

  The process according to the invention consists in putting the

  chlorinated product in contact with the chloroaluminate bath.

  When the chlorinated product is in a solid phase this solid phase can be poured into the chloroaluminate bath

  preferably stirred. We take care to keep the melted bath

  by heating. The procedure is the same if the chlorinated products are in a liquid phase. Most often the chlorinated products that are to be destroyed are in a gaseous phase alone or mixed with light chlorinated products and / or carrier gases. For example it may be a gas resulting from combustion, so there is nitrogen containing carbon dioxide, carbon monoxide, chlorinated products and possibly oxygen. But it can be a mixture

  any gas taken in any process.

  It is preferred that the chlorinated products be in an anhydrous phase. The gas containing the chlorinated products can be dried by

  contact with an absorbent for example alumina or glycol.

  This gaseous phase containing the chlorine products to be destroyed is then brought into contact with the chloroaluminate by any means for bringing a liquid phase into contact with a gaseous phase. It can be a column A trays or packed. It is also possible in a stirred tank of chloroaluminate to introduce the gas phase by a

  plunger pipe or pipe coming through the bottom of the tank.

  The different chlorinated organic products can be

  partition between the liquid and vapor phases of the chloroaluminum bath.

  nate. The same goes for the products that accompany these chlorinated products. A packed or packed column can be used to ensure continuous circulation and stirring of the liquid and gaseous phases and good contact of the gaseous products with the chloroaluminate bath. One can also operate with a cascade of agitated reactors. We maintain organic products

  in contact with the chloroaluminate bath the time required

  to their destruction. The residence time may vary within wide limits but is generally between a few minutes

and a few hours.

  Although it is possible to operate at any temperature provided that the chloroaluminate is liquid, it is preferable to place it under

  300 C and preferably between 200 and 300 C.

  The rate of destruction of chlorinated products, particularly

  aromatics, increases with the temperature of the chloroaluminum

nate.

  It is possible to find in the gaseous phase of the chloro

  luminate, light products of decomposition of chlorinated products which were sought to destroy; for example carbon tetrachloride and / or hexachloroethane. In the vapor phase of the chloroaluminate bath, we do not find the chlorinated organic products that we sought to destroy. When the chloroaluminate bath is analyzed after respecting the contact time between chlorinated products and chloroaluminate, organic products are not found

that we sought to destroy.

  It is also possible to periodically purge the chloroalcohol bath.

  to avoid the accumulation of insoluble products or that can not remain suspended in the bath. In this purge there is also no trace of chlorinated organic products. So we see the disappearance of chlorinated products that were trying to destroy. In a preferred embodiment of the invention is added to the chloroaluminate bath one or more powdered metals selected from reducing metals such as, for example, aluminum or zinc. It is preferred to use a powder whose average particle size

  is less than 500 p. If metals are used, it eliminates completely

  chlorinated organic products as before but with a much higher speed, of the order of several times

  dozens of times the previous speed.

  There is a consumption of powder of the metal (or metals) which can mean that chloride has formed while taking

  chlorine to chlorinated organic products when they are destroyed.

  There is no limit to the amount of metal powder

  in chloroaluminate. It is preferred to use aluminum in

  powder; up to 5 or 10% by weight of aluminum powder can be

  minium in the chloroaluminate bath. It is found that the rate of destruction of chlorinated products increases with the amount of

  aluminum powder and with the temperature of the chloroaluminum bath

  nate. It is preferred to stir the bath so that the metal powder is well dispersed in the bath. The metal chloride (s) that have been produced can mix with the chloroaluminate bath and

  share between the liquid and gaseous phases. We can if necessary

  eliminate metal chlorides from the gas phase by

  treating with a hydroxide, such as soda or potash.

  The following examples illustrate the invention:

EXAMPLE 1

  In a 1-liter pyrex flask heated electrically, equipped with a propeller stirrer rotating at 300 rpm, 500 g

  of sodium chloroaluminate whose ratio AC3 = 1.

  NaCl1 The product is heated to 200 ° C., stirred, then 0.2 g of hexachlorobenzene and 0.1 g of decachlorobiphenyl are introduced. After 1 hour at C, the melt is swept for 15 minutes by a flow of water at the same time.

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Claims (7)

CLAIMS V E N D I C A T IO N S   1. Process for destroying chlorinated organic products having more than 2 carbon atoms, characterized in that   contact these products with a bath of at least one chloroaluminate.   2. Method according to claim 1 characterized in that   chloroaluminate is sodium chloroaluminate.   3. Method according to claim 2 characterized in that the sodium chloroaluminate contains at least 50 mol% of aluminum chloride.   4. Method according to one of claims 1 to 3 character-   in that the temperature of the chloroaluminate bath is lower than   re at 300 C and preferably between 200 and 300 C.   5. Method according to one of claims 1 to 4 caractéri-   in that the chloroaluminate contains at least one metal in powder.   6. Method according to claim 5 characterized in that   the metal is preferably aluminum.   7. Method according to one of claims 5 or 6   in that the average particle size of the powder is less than 500 p.