WO1993005845A1

WO1993005845A1 - Method/process for the disposal of halogenated hydrocarbons and similar intractable materials

Info

Publication number: WO1993005845A1
Application number: PCT/AU1992/000493
Authority: WO
Inventors: Roger Charles Wilkinson; John Raymond Smeed; William Henry Wheeler
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-09-20
Filing date: 1992-09-18
Publication date: 1993-04-01
Anticipated expiration: 1994-03-20

Abstract

Method and apparatus are disclosed for the disposal of halogenated hydrocarbon materials such as fluorocarbon compounds. The hydrocarbon material is dispensed from a holding vessel (1) through dispersion means (5) into a reaction vessel (6) where it is hydrolysed in an aqueous alkali solution. The vaporised products of the reaction are passed through a condenser (10) which condenses said vapours back into a liquid which is returned to the reaction vessel to thereby substantially reduce the emission of unreacted hydrocarbon material. Ultrasonic, microwave and/or infrared energy may be applied to the dispersion means to assist the mixing of the hydrocarbon material with the aqueous alkali solution.

Description

METH0D/PR0CESS FOR THE DISPOSAL OF HALOGENATED HYDROCARBONS AND SIMILAR INTRACTABLE MATERIALS

This inventi'on relates to the disposal of Halogenated

Hydrocarbons and similar intractable materials.

Halogenated Hydrocarbons such as fluorocarbon compounds have been widely used by industry for example in refrigeration, aerosols and foam production . systems. Due to evidence that upon release into the atmosphere such componds damage the ozone layer there are now strict regulations governing their disposal. To comply with these regulations one method which has been used involves the high temperature combustion of these compounds. While this is more or less technically effective the plant required is expensive as is the high energy input required to maintain, the combustion process and flue gas cleaning systems.

It is therefore an object of this invention to ameliorate the aforementioned disadvantages and accordingly this invention discloses a relatively cheap low temperature wet process for the disposal of Halogenated Hydrocarbon materials or the like, the said process including the steps of hydrolysing said material by reaction in a heated or boiling aqueous alkali solution and refluxing the vaporised products thereof by condensing them into a liquid which is subsequently returned to said aqueous alkali solution.

Preferably said aqueous alkali solution is a solution of 100 grams sodium hydroxide per litre of water, alternatively calcium hydroxide, magnesium hydroxide, aluminium hydroxide or similar may be used.

The currently preferred embodiment of this invention is illustrated by the attached diagrams in which:

Figure 1 is a schematic diagram of the process, and

Figure 2 is a cross-sectional view of one of the dispersion tubes of figure 1.

If the two principal reagents are CF2CC12 and N.aOH the chemical reaction involved in the hydrolysis process can be summarised as

CF₂CC1₂ + 6NaOH— 2NaF + 2NaCl + 2NaC00H + 2H₂0

The products of this reaction are thus Sodium Fluoride, Sodium Chloride, Sodium Formate and water which are all neutral stable materials and are thus easily disposed of by conventional means.

Referring to the attached diagram the CF₂CC1₂ material is dispensed from a holding vessel 1 through pressure control and reducing valves 2 and 3 and a meter 4. The low pressure material then passes through dispersion tubes 5 and into a reaction chamber 6 where it is hydrolysed by reaction in a hot NaOH solution. Figure

2 shows a cross-sectional view of one of the dispersion tubes. It is preferably double walled with the inner conduit 6A being supplied with heated aqueous solution from the reaction chamber 6 under pressure via pump 6B and pipe 6C which extends through an auxiliary heater element 6D. the solution re-enters the reaction vessel as a jet 6E through a series of aligned orifices 6F and

6G in the inner and outer walls of the tube.. In doing so the liquid solution draws the gaseous CF2CCI2. from the outer conduit 6H (which is fed from the holding vessel 1) and down into the reaction vessel 6 in the form of small bubbles 61 entrained in the jet stream.

6E. Fresh alkali solution enters the reaction chamber at 7 and is heated to or close to boiling by any suitable means. With this embodiment the reaction chamber is of glass and stainless steel and a mains frequency resistance or a high frequency induction heating apparatus 8 is used. The resulting liquid from

•the reaction carrying the aforementioned products is removed via valve 9 for conventional disposal.

In accordance with this invention a reflux condenser 10 is located above the reaction vessel 6 to receive the vapors from the hydrolysis reaction. This condenser may comprise an inner core 10A into which the vapours pass and an outer sleeve 10B to contain the circulation of a heat absorbing fluid such as cold water 11. The effect of the condenser is to condense the vapors rising from the hydrolysis reaction and return the resulting liquid to the chamber 6 thereby preventing the escape of any halogenated material. It is envisaged that the resulting exhaust 12 from the process as measured by a gas chromatograph 13 would thus be free of any significant amounts of fluorinated hydrocarbons or products of the hydrolysis reaction.

Any residual products discharged from pipe 12 may be further reacted in a similar process to that described above and as indicated by broken lines in figure 2. In this case the components indicated by the designations 5', 6', 6B*. 6C*, 6D\ 6E'_f 7^r, 8', 9', 10', 10A\ 10B' 11" and 16'are the same as those described above with the corresponding number. The reagent in this vessel 6' however may be of the same or different composition as that in the first vessel' 6 depending on the requirement for further reaction or scrubbing activity on -the residuals.

In the unlikely event that harmful or halogenated materials pass through both processes, these are collected in expandable sealed containers 14 thereby allowing their recycling 15 through the process(s) to ensure thorough disposal of the Halogenated Hydrocarbons, principal organic hydrocarbons or any unacceptable byproducts.

This latter facility has not proved necessary in trials to date but is proposed as a safeguard for commercial scale operations. ^l

The use of ultrasonic, microwave and/or infrared energy is beneficial at locations 5 and 16 to assist mixing and dispersion of the Halogenated materials in the aqueous al ali solution.

It is envisaged that a process according to this invention can be operated as either a batch or continuous operation. The efficacy of the hydrolysis reaction is dependent upon a number of factors including:

- Temperature of the aqueous solution

- Rate flow of the Halogenated Hydrocarbon material usually in the gaseous state

- Method of dispersion of the Halogenated Hydrocarbon material into the aqueous solution

- Height of the reaction vessel

- Plan areas of the reaction vessel

- Use of catalytic materials

- Agitation/mixing of all materials involved in the reaction Without limiting the scope of the invention the following suitable conditions for each of these respective parameters are suggested :

- Mild boiling - 1 C to 2 C below boilingi

- Gas flow rates in the order of 50-1000 kg/hr/m of reaction vessel cross-sectional area , dependent on the actual materials being disposed of

- Dispersion of the gas can be by :

Sparge pipes (horizontal , vertical or sloped) Drilled plate distributor Sintered plate distributor Spouted/fluidised bed of catalyst particles Packed (static) bed of course catalyst particles Ultrasonic dispersion /mixing Ejector pump(s) Atomising spray nozzle(s)

- height of aqueous hydrolysing column may may be in the order of 600-2000 mm

- Plan areas of the hydrolysing column may be 0 . 002-4 m^ , however larger or smaller areas may be used successfully

- Typical catalytic materials are noble metals , alumina , platinum , silica , limestone etc .

- The agitation/mixing of the material involved in the reaction can be assisted by ultrasonics , atomising , boiling , forced circulation etc .

will thus be appreciated that this invention at least in the form of the example disclosed comprises a novel and improved means for the safe and low cost disposal of Halogenate„d Hydrocarbons. Clearly however the embodiment described is only the currently preferred form of this invention and a wide variety of > modifications may be made which would be apparent to a person skilled in the art after further experimentation.

For example the size, shape and configuration of the reactor chamber and reflux condenser as well as the composition of the alkali solution may all be varied in accordance with the type and volume of Halogenated materials to be processed.

Claims

The claims defining the invention are- as follows:

1. A method for the disposal of halogenated hydrocarbon materials, said method including the steps of hydrolysing said hydrocarbon material by reaction tLn a heated aqueous alkali solution and refluxing the vaporised products thereof by condensing them into a liquid which is subsequently returned to said aqueous alkali solution.

2. The method as claimed in claim 1 wherein said aqueous alkali solution is a solution of sodium hydroxide, calcium hydroxide, magnesium hydroxide

■or aluminam hydroxide.

3. The method as claimed in claim 2 wherein said hydrocarbon material is dispensed from a holding vessel through dispersion means into a reaction vessel holding said heated aqueous alkali solution.

4. The method as claimed in claim 3 wherein ultrasonic, microwave and/or infrared energy is applied to said dispersion means to assist the .mixing of said halogenated hydocarbon material with the aqueous alkali solution.

5. The method as claimed in claim 4 wherein said aqueous alkali solution is heated to 1 C to 2 C below boiling .

6. An apparatus for the disposal of halogenated hydrocarbon material, said apparatus comprising a I reaction vessel for holding a heated aqueous alkali solution for hydrolysis reaction with said halogenated hydrocarbon material, dispersion means for mixing said halogenated hydrocarbon material with said aqueous alkali solution, means for removing the products of said hydrolysis reaction and condenser means for receiving, condensing and returning vapours from said hydrolysis reaction to said reaction vessel to thereby substantially reduce the emission of unreacted hydrocarbon material.

7. The apparatus as claimed in claim 6 wherein the dispersion means comprises at least one double walled tube having inner and outer conduits which is^' disposed across the reaction vessel at or below the working level of said aqueous alkali solution, the outer conduit being in communication with a supply of said halogenated hydrocarbon material and the inner conduit being fed under pressure with said aqueous alkali solution so that said solution enters the reaction vessel in the form of a jet stream through pairs of aligned orifices in the inner and outer walls of_. the tube whereby said halogenated hydrocarbon material is drawn from the outer conduit and into the reaction vessel with the jet stream.

8. The apparatus as claimed in claim 7 wherein the exhaust from said reaction vessel is analysed by a gas chromatograph and any residual hydrocarbon material is introduced to a second reaction vessel.

9. The apparatus as claimed in claim 8 wherein said aqueous alkali solution is heated in said reaction vessel by a mains frequency resistance heater or a high frequency induction heater.

10. The apparatus as claimed in claim 9 wherein said condenser means is located above said reaction vessel.