EP0887088A1 - Process and installation for the treatment of asbestos-containing absorbing mass in gas bottles - Google Patents

Abstract

A new process for the treatment of used gas bottles, particularly for acetylene, in which absorbent residues containing asbestos and/or mineral fibres comprises injection of a concentrated base solution producing a reaction resulting in a fluid slurry, evacuation of the slurry from the bottles, treatment of the slurry to eliminate asbestos and/or mineral fibres remaining, and recycling of the bottles for re-use.

Description

The present invention relates to a method of destruction of asbestos fibers contained in absorbent masses present inside acetylene gas cylinders.

The reformed acetylene gas cylinders are currently stored in large numbers in companies' fleets gas, without a reliable and above all ecological recycling solution. In indeed, gas companies want to replace absorbent masses containing asbestos contained in these bottles by others masses no longer containing asbestos. This wish is currently not feasible, the only methods known to date leading to destroy the bottles which is a financial burden which blocks this wish.

There are currently two methods of treating absorbent materials containing asbestos, contained in quantities reduced in gas cylinders.

The most common method is to cut the end bottles, to extract the absorbent mass in an area confined, to pack the said mass in regulatory bags and to store the bags in appropriate landfills. Metal is headed to the steel industry after extensive rinsing to remove particles adhering to metal. Rinsing water containing asbestos is discharged in the public circuit.

The other method is to introduce the bottles into ovens with a temperature above 1500 ° C. The merger of metal and asbestos fibers is obtained there comes out a metal substrate and silica considered inert; this method is effective, but costly very high.

These two methods are expensive and are not reassuring in terms of handling, asbestos can be spread into the atmosphere during transport, storage or manipulations.

You should know that these absorbent masses are light, the base material being from the family of calcium silicates (xonotlite). Out of the protection of the steel bottle, they are brittle and consider as plaster panels containing asbestos, which are classified under the heading of hazardous waste, identical to flocking of asbestos.

In the two methods described above, the bottle is destroyed. As for asbestos-based waste, either it is stored and is not destroyed, bringing pollution to the drainage system worn, or it is destroyed, but at great cost and without recovery.

The object of the present invention is to avoid these drawbacks and in particular to remove the absorbent masses containing asbestos out of metal bottles, preferably through their holes original, that is to say without destroying said bottles, or preventing their reuse. Advantageously, at no time, the absorbent masses containing asbestos will only be in contact with the atmosphere.

une introduction à l'intérieur de chaque bouteille d'une solution basique concentrée,

une attaque, par la solution basique, des masses absorbantes contenant de l'amiante et/ou des fibres minérales, à l'intérieur de la bouteille, jusqu'à l'obtention d'une boue fluide,

une évacuation de cette boue fluide hors de la bouteille,

un traitement de la boue fluide évacuée pour en éliminer l'amiante et/ou les fibres minérales subsistantes, et

un recyclage des bouteilles de gaz vers une réutilisation.

To solve these problems, there is provided according to the invention a method for treating used gas cylinders, in particular acetylene gas, in which there are absorbent masses containing asbestos and / or mineral fibers, comprising

an introduction inside each bottle of a concentrated basic solution,

an attack, by the basic solution, of absorbent masses containing asbestos and / or mineral fibers, inside the bottle, until a fluid mud is obtained,

an evacuation of this fluid mud from the bottle,

a treatment of the fluid sludge discharged to remove the asbestos and / or the remaining mineral fibers, and

recycling of gas cylinders to reuse.

This process advantageously makes it possible to attack the absorbent masses inside the bottles and to fluidize them in situ. This allows their extraction without affecting the physical integrity of bottles and without endangering the environment by releasing dust containing asbestos. This fluid mud can then be conducted, in a sealed manner vis-à-vis the external environment, in a known apparatus of the type described in the patent application international WO-A-97/00099. In this apparatus, the fibers asbestos and mineral fibers still suspended in the sludge liquids and already first attacked in the bottles themselves are attacked again and completely destroyed by a solution basic concentrated.

The installation placed on two trays, for example a maritime dimension of 20 feet, allows mobile treatment in situ on the gas storage area without special devices.

All the products resulting from this treatment are devoid of all asbestos fibers and other mineral fibers, personnel not be equipped with respiratory protection. All stages of processing can be carried out in a particularly closed circuit efficient and secure. No fiber can escape into the atmosphere, all the materials that can be reused and / or valued.

In the event of an incident or equipment failure, the fibers do not could not be released since the first operation destructive asbestos happens in the bottle itself, and that at when the material comes out of the bottle, the asbestos is in a silicate mud which does not allow fibers to be released in the atmosphere. In addition, the aggression on the fibers is such that they do not could no longer cause pathology if introduced improbable in a respiratory circuit.

According to one embodiment of the invention, the method includes, prior to said introduction of basic solution, a degassing of the bottle by putting it in communication with a source of depression.

According to an advantageous embodiment of the invention, the process comprises, after the treatment of the fluid mud, a separation of the latter into a recyclable liquid phase in the solution basic and in a solid phase which can be upgraded. The sentence liquid is thus recycled to the maximum, which significantly reduces any environmental pollution and lowers the cost of basic materials fresh necessary for the realization of the attack solution. The sentence solid, completely free of asbestos fibers or mineral fibers, can for example be recycled in silico-limestone compositions, usable in construction, or in the form of an adjuvant to clay intended for the manufacture of ceramic products.

Other embodiments of the invention are indicated in the claims.

Other details and features of the invention will emerge of the description given below, without limitation and with reference to the single figure appended.

The single figure schematically represents a installation for implementing the method according to the invention.

In this installation, a basic solution preparation tank 1 is provided, capable of being heated by a heating element 2 to a temperature of the order of 160 ° C. In the example illustrated, to form the basic solution an agent for the generation of OH ions is used ^- in aqueous solution, such as an alkaline or alkaline-earth base, in particular NaOH.

NaOH flakes are for example stored in the silo 3 and supplied intermittently and known per se at the preparation tank 1. This is also connected in 4 to a source of water.

An outlet conduit 5 connects the bottom of the preparation tank 1 with a heating tank 6. When the valve 7 is closed, the basic solution prepared is recycled to the top of the tank by a bypass 8, using a static mixer 9.

In the heating tank 6 there is provided an element heating 10. The basic solution is heated there for example to a temperature of the order of 260 ° C. under a vapor pressure of approximately 5 bars.

A series of gas cylinders 11 are maintained, head in bottom, in a template generally designated by the reference 12. This template includes housings 13, one per bottle, in which bottles are retained by a removable plate 14 with smaller diameter perforations than the body of bottles and allowing passage of the heads 18 of the bottles to outside.

Each housing 13 can be furnished with a heat exchanger heat 15 to maintain the temperature inside the bottles at a sufficient level especially for degassing. Template 12 can be supported on a frame not represented by an axis 16, so as to be able oscillate on this axis. A motor 17 controls this oscillation movement in a known way.

At the head of each bottle, is connected so seals a flexible hose 19 which can be detached from the bottle after cleaning it. Each flexible pipe 19 is connected to a branching with multiple channels, each closable by a valve 20 to 23 respectively.

The tank 6 is in communication with the bottles by a leads to attack solution 24 provided with a branch 25 towards each bottle and connected to valve 21 of the track branch multiple.

This multi-way branch is also connected to a gas pipe 26 by the valve 22 and to a mud pipe 27 by the valve 23.

The gas pipe 26 is connected to a vacuum pump 28, for example a water ring pump, via a trap cold 29. The outlet of pump 28 is connected to a recovery of water polluted with gas 30, which can then be evacuated by a pump 31 for treating wastewater, in particular filtering.

The mud conduits 27 are each connected to a slurry pump 32 which via the conduit 48 conducts the mass sludge absorbent to a reactor 33, via a three-way valve tracks 38 and a flexible pipe 37.

The reactor 33 is mounted on an oscillating platform 34 supported by an axis 35 around which it is capable of tilting. The tilting movement is generated in a known manner under the action of a system consisting of a hydraulic cylinder or pneumatic and connecting rods and generally designated by the reference 36.

The reactor is surrounded at least partially by a heating chamber 39 and it is mounted on the platform 34 so as to ability to rotate around its longitudinal axis under the action of a motor training 40.

The reactor is connected at 41 directly to a conduit feed coming for example from the preparation tank (at 42).

The three-way valve 38 also gives access to a outlet conduit 43 which leads to a phase separation device liquid and solid. In the example illustrated, it is a filter press 44. The solid cakes are collected in a collection bin 45 and the filtrate is recycled through recycling conduit 46 to a buffer tank 49, in turn in communication with the preparation tank 1, by a connecting duct 47.

The installation according to the invention operates in the manner next :

The acetylene gas cylinders 11 are installed, open, in the housings 13 of the template 12 which is then closed by the plate 14. A flexible pipe 19 is connected to the original opening of each cylinder and valves 20 and 22 of the multi-way branching are open, while the valves 21 and 23 are closed. The pump 28 is started and a residue is thus vacuumed of gas still contained in the bottles in a cold trap 29. An aqueous acetone solution is recovered in tank 30 to be then led to further use or treatment by the pump 31.

In preparation tank 1, a basic solution concentrated attack is prepared. It is heated to a temperature from 160 to 240 ° C at a pressure of 2 to 10 bars and it has a NaOH molar concentration of 12.5.

The preparation solution is fed so discontinuous to the heating tank 6 in which it is brought to a temperature above 180 ° C., advantageously of the order of 190 to 270 ° C, preferably 260 ° C. In this tank the solution attack is preferably maintained under a vapor pressure of 2.5 to 7 bars, advantageously of the order of 5 bars.

After closing valve 22 and opening the valve 21, under the vapor pressure of tank 6 and the call for vacuum created by degassing in bottles 11, the attack solution gets into the bottles. The valves 20 and 21 are then closed and the etching solution is left for approximately 10 to 20 minutes within bottles which are subject to an oscillating movement around axis 16. During this time, the absorbent masses are totally liquefied and the asbestos fibers and the mineral fibers they contain a first attack.

Valves 20 and 23 are then opened and the sludge fluidized are removed from the bottles using the mud pumps 32. It it is possible to envisage a succession of openings and closings alternating valves to clean the interior of the bottles with pressurized etching solution.

The sludge is then directed to reactor 33 which is supplied with basic solution of 35 molar concentration. This solution can be formed from the basic solutions used for the attack and rinsing the bottles. It can also partially come from directly from the preparation tank 1.

In the reactor, the basic attack solution is under a pressure of 2 to 10 bars, advantageously 2.5 to 7 bars, and preferably 3 to 4 bars, and at a temperature above 180 ° C, advantageously of the order of 190 to 270 ° C, preferably 240 ° C.

The sludge is stirred in the reactor which is brought into rotation for example at 24 rpm around its longitudinal axis. We can provide inside the reactor swing chains for get good treatment. After 30 minutes, the fibers are melted.

The contents of the reactor are then brought to the filter press 44 where the solid phase-liquid phase separation takes place.

The liquids are directed to the buffer tank 46 for a reheating and introduction into the preparation tank 1.

Solids from cakes removed from the filter press are directed to recovery treatments.

Empty, cleaned bottles are reusable. Those with failures are directed to recovery in steel industry.

• Le transport onéreux des bouteilles à traiter vers un centre de destruction est évité.
• Destruction totale et irréversible des fibres d'amiantes et minérales.
• Aucun rejet dans l'atmosphère.
• Aucun rejet dans les décharges.
• Aucun rejet toxique dans les eaux usées.
• Métaux de récupération entièrement propres pour la sidérurgie.
• Aucune altération de la bouteille destinée au réemploi.
• Méthode simple et économique.
• Emploi d'autres déchets dans le recyclage valorisant.

Some advantages of the process according to the invention are as follows:

• Expensive transportation of the bottles to be treated to a destruction center is avoided.
• Total and irreversible destruction of asbestos and mineral fibers.
• No release to the atmosphere.
• No discharge into landfills.
• No toxic discharge into wastewater.
• Completely clean recovery metals for the steel industry.
• No alteration of the bottle intended for reuse.
• Simple and economical method.
• Use of other waste in recycling recycling.

a) les formules silico-calcaires

b) les adjuvants à l'argile en remplacement du Feldspath dans les formules céramiques.

For the recovery of solid materials from the treatment of absorbent masses and which have become free of asbestos fibers and mineral fibers, the following two possibilities can be provided, among others:

a) silico-limestone formulas

b) clay adjuvants to replace Feldspar in ceramic formulas.

Recovered materials can be considered as raw materials in the two valuation systems by increased interstitial bonds and marked improvement in technical criteria of the various materials of these families. It is therefore of a raw material which has all its utility and therefore not of a second choice valuation as is often the case.

It should be understood that the present invention is not in in no way limited to the embodiments described above and that many modifications can be made without leaving its frame as indicated in the appended claims.

Claims (12)

Process for treating used gas cylinders, in particular acetylene gas, in which absorbent masses containing asbestos and / or mineral fibers are found, comprising an introduction inside each bottle of a concentrated basic solution, an attack, by the basic solution, of absorbent masses containing asbestos and / or mineral fibers, inside the bottle, until a fluid mud is obtained, an evacuation of this fluid mud from the bottle, a treatment of the fluid sludge discharged to remove the asbestos and / or the remaining mineral fibers, and recycling of gas cylinders to reuse. Method according to claim 1, characterized in that it comprises prior to said introduction of basic solution, degassing of the bottle by putting it in communication with a source of depression. Process according to either of Claims 1 and 2, characterized in that it comprises the attack of the absorbent masses in the bottle by the basic solution under a vapor pressure of 2 to 10 bars, advantageously from 2.5 to 7 bars, preferably from 5 bars, and at a temperature above 180 ° C., advantageously of the order from 190 to 270 ° C, preferably from 260 ° C. Method according to any of claims 1 to 3, characterized in that the treatment of the fluid sludge discharged includes feeding it to a reactor and attacking this fluid mud by a basic solution concentrated at a pressure of steam from 2 to 10 bars, advantageously from 2.5 to 7 bars, preferably from 3 to 4 bars, and at a temperature above 180 ° C., advantageously on the order of 190 to 270 ° C, preferably 240 ° C, and a agitation until a mass free of asbestos and mineral fibers. Method according to claim 4, characterized in that it includes an admission of a supplement of basic solution in the reactor. Method according to any of claims 1 to 5, characterized in that the basic solution for the treatment of sludge evacuated fluid is an aqueous solution of NaOH 30 to 40 molar, of preferably 35 molars. Method according to any of claims 1 to 6, characterized in that it comprises an attack with the basic solution of several bottles simultaneously and a treatment in the same fluid sludge reactor from these bottles. Method according to any of claims 1 to 7, characterized in that the above introduction is carried out by a original opening of the bottle, as well as any degassing prior to this bottle. Method according to any of claims 1 to 8, characterized in that the fluid mud obtained as a result of the attack in the bottle is free of solid absorbent masses. Method according to any of claims 1 to 6, characterized in that it comprises, after the treatment of the mud fluid, a separation of this into a recyclable liquid phase in the basic solution and in a solid phase which can be upgraded. Method according to claim 10, characterized in that the solid phase is valued in silico-limestone compositions or in the form of an adjuvant to clay intended for products ceramics. Method according to any of claims 1 to 11, characterized in that it comprises, after the evacuation of the mud fluid out of the bottle, additional introduction of solution basic concentrated inside each bottle, a final wash of the bottle, and a treatment of the washing solution similar to that undergone by the aforementioned fluid mud.

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