WO1995012463A1

WO1995012463A1 - Asbestos conversion apparatus and method

Info

Publication number: WO1995012463A1
Application number: PCT/US1994/012601
Authority: WO
Inventors: Tony Nocito
Original assignee: Tony Nocito
Priority date: 1993-11-02
Filing date: 1994-11-02
Publication date: 1995-05-11
Also published as: AU1047795A

Abstract

Apparatus for converting asbestos into a non-hazardous material includes a stainless steel conversion tank (11) having a high shear mixer (13) disposed therein, a filtering system (29), and a regeneration tank (49). From the regeneration tank (49), a solution is pumped through a second filter system (60) into a holding tank (63) for storage while the conversion tank (11) is being used to mix another batch of treatment solution and asbestos containing material. A neutralizing solution is provided in a wash tank (75) and periodically pumped through the other tanks in order to neutralize any remaining solutions in them and to clean the system. A scrubber system (96) consisting of a scrubber (97) and an exhaust blower (99) is connected to each of the conversion tank (11), the regeneration tank (49) and the holding tank (63) by means of a connector (101), to prevent the escape of fumes from the treatment solution into the ambient.

Description

ASBESTOS CONVERSION APPARATUS AND METHOD

Field Of The Invention This invention relates to apparatus for the efficient conversion of asbestos into an non-toxic material.

Background Of The Invention U.S. Patent No. 5,264,655, issued November 23, 1993, describes a method for converting the asbestos in asbestos containing material (••ACM") to a non-toxic substance by immersing the ACM in a treatment solution containing an acid and a source of fluoride ions to destroy the fibrous nature of the asbestos and thereby render it harmless. This process is preferably carried out by immersing the ACM in the treatment solution under conditions of high shear mixing so that the ACM is broken down and the solution is brought into intimate contact with the asbestos. It has been found that immersion in the treatment solution with high shear mixing converts the asbestos to a non-hazardous product within approximately one half hour to an hour of mixing.

This method of converting asbestos to an non- toxic material represents an extremely important step forward in the art. There is still a need, however, to configure a system for practicing this method efficiently and safely under commercial field conditions. Asbestos containing materials are present in buildings and other structures in the form of pipe lagging, spray-on asbestos fire proofing, Transite board, block fireproofing and insulating materials, and other forms. They also found in land fills where ACM removed from buildings in prior years are dumped. While ACM are being removed from buildings, it is necessary to seal off the area being abated to prevent the escape of asbestos fibers into surrounding areas and the ambient. Thus, during the removal operation and until it can be demonstrated that "clean air" conditions have been restored, the building or at least the portion thereof being abated is out of service. In order to transport ACM from the abatement site it is necessary to place the materials in double plastic bags which are sealed and marked with the name of the owner of the ACM (i.e. the owner of the building or other facility from which the materials are removed) . Most asbestos abatement jobs are performed by small to medium size contractors who are typically neither technically sophisticated nor able to make large capital expenditures.

For all of the above reasons there is a need for low cost, efficient, simple to use asbestos conversion apparatus which is capable of converting the ACM to a non-hazardous material in accordance with the method taught in the above identified patent. The apparatus should preferably be portable so as to permit the conversion operation to be performed at the abatement site, thereby obviating the need to double-bag the ACM and to transport it from the abatement site as a hazardous material. The apparatus and the method of using it needs to permit the asbestos conversion process to be performed efficiently and as rapidly as possible in order to maximize the conversion through-put, thereby minimizing the time in which the area being abated is out of service. It is also essential that the apparatus and the method of using it be such that the process is performed safely and without danger either to the asbestos abatement workers using the apparatus or to the public.

Summary of the Invention

In accordance with these and other objectives of the invention, the applicant provides an asbestos conversion apparatus and method for use in converting asbestos in asbestos containing materials to a non- hazardous material which comprises a conversion container for holding a treatment solution and the ACM during the conversion of the asbestos therein to a non-hazardous material, and a high shear mixer disposed in the conversion container for agitating the treatment solution and ACM under conditions of high shear. A regeneration container is provided for use in repeatedly reconstituting and restoring used treatment solution so that it can be re-used a number of times. A pump and a filter system is provided between the outlet of the conversion container and the inlet of the regeneration container for pumping the used treatment solution from the conversion container, through the filter system in order to remove suspended solids, and into the regeneration container for being restored by the addition of concentrates. A holding container may be provided for storing the reconstituted treatment solution. Second pumping means are provided between the outlet of the regeneration container and the inlet of the holding container for pumping the restored solution into the holding container. Third pumping means are provided between the outlet of a holding container and the inlet of the conversion container for pumping the treatment solution stored in the holding container into the conversion container for use in another conversion cycle.

In order to clean the system periodically, a wash container may be provided for containing a neutralizing solution used to neutralize any remaining treatment solution left in the other containers, and pump and valve means are provided for selectively cycling the wash solution from the wash tank through one or more of such other containers for performing such neutralization function. Description of the Drawings Fig. 1 is a schematic showing the tanks and treatment solution circulation system of the illustrated embodiment of the invention. Fig. 2 is a simplified schematic top view or the embodiment of Fig. 1.

Detailed Description Referring now to Fig. 1 of the drawings, the asbestos conversion apparatus in accordance with the invention includes a conversion tank 11 in which the ACM and treatment solution are mixed during the conversion process. The tank 11 preferably has a circular cross section and is preferably fabricated of stainless steel. A high shear mixer 13 is disposed in the conversion tank 11 for agitating the ACM and the treatment solution contained therein. The bottom 15 of the conversion tank 11 is preferably substantially dished or conical in shape in order both to prevent the existence of "dead spots" while the treatment solution and ACM are being agitated by the mixer 13, and to facilitate draining the treatment solution and converted ACM from the tanks. A valve 17 is disposed in the side of the conversion tank 11 near the bottom, for decanting liquid from the tank 11. A drain 19 is provided in the lowest point of the conversion tank 11. The drain 19 is connected through a valve 21 to the inlet of a motor driven pump 23. The outlet of the pump 23 is connected through a valve 25 and a check valve 27 to the inlet of the filtering system 29. In the illustrated embodiment of the invention, the filter system 29 is arranged in two stages. The first stage is made up of three bag filters 31 connected in parallel. The output of the check valve 27 is connected to the input of the bag filters 31 through individual valves 33. A pressure gauge 35 is provided between the output of each valve 33 and the input of the bag filter 31. The outputs of the bag filters 31 are each connected through a separate valves 37 to the second stage of the filter system 29 which is made up of a single bag filter 39. The outputs of the valve 37 are connected to the input of the bag filter 39 through a valve 41. A pressure gauge 43 is provided between the output of the valve 41 and the input of the bag filter 39. The pressure gauges 35 and 43 permit the monitoring of the pressure drop across the filtering system 29, which gives an indication of whether the filter bags are becoming overloaded.

The output of the bag filter 39 is connected through series connecting valves 45 and 47 to the input of regeneration tank 49. The regeneration tank 49 is preferably of similar capacity of the conversion tank 11, and may be formed of stainless steel or, preferably for reasons of cost, non-glass polyethylene or another plastic material which is impervious to the ingredients of the conversion solution and has adequate strength and toughness for the application. The regeneration tank holds the filtered conversion solution after each conversion cycle. While it is in the regeneration tank 49, the used solution is reconstituted by adding a concentrate of the some or all of the components of the treatment solution to bring the solution back to the appropriate concentrations. The mixer or stirrer 51 is provided in the regeneration tank 49 to stir the solution to ensure the proper mixing of the concentrates as the solution is being reconstituted. The bottom of the tank 47 has a dished or conical shape in order to facilitate mixing of the concentrates and draining of the tank.

The tank 49 is drained through an outlet provided in the center of the bottom of the regeneration tank 49. This outlet is connected to the input of a motor pump 53 through a valve 55. The outlet of the motor pump 53 is connected through another valve 57, a check valve 59, a filtering system 60 and a valve 61 to the input of a holding tank 63 which is used for storing the treatment conversion solution after it has been reconstituted in the regeneration tank 49.

The holding tank 63 is preferably of similar capacity to the regeneration tank 49 and the conversion tank 11. Like the regeneration tank 49, it is preferably formed from polyvinylchloride or another plastic material of adequate strength which is impervious to the components of the treatment solution. The bottom of the holding tank 63 is preferably conical or dished in shape similar to the regeneration tank 49. A drain is provided at the lowest point of the bottom of the holding tank which drain is connected to the inlet of a motorized pump 65 through a valve 67. The outlet of the motorized pump 65 is connected through a valve 69, check valve 71 and another valve 73 to the inlet of the conversion tank 11.

A wash tank 75 is provided for holding a neutralizing solution which is used for periodically cleaning and neutralizing the other tanks and the pumps and tubing which go to make up the system of the illustrated embodiment of the invention. The wash tank 75 may be in similar capacity, shape and materials as the regeneration tank 49 and the holding tank 63. The outlet at the low point on the bottom of the wash tank 75 is connected to the inlet of a motorized pump 77 through a valve 79. The outlet of the motorized pump 77 is connected through a valve 81 and a check valve 83 to the inlets of each of the other of the regeneration tank 49, the holding tank 63 and the conversion tank 11 through respective valves 85, 87 and 89. The inlet to the wash tank 75 is taken from the output of the filter system 29 between the series connected valves 45 and 47 through the valve 91 and the check valve 93.

Referring now to Figs. 1 and 2 of the drawings, the top of each of the tanks 11, 49, 63 and 75 is preferably covered. In the case of the conversion tank 11, holding tank 63 and the regeneration tank 49, the cover is needed to prevent the escape of fumes from the treatment solution. A vent 95 is provided in each of the tanks. A scrubber system 96 consisting a scrubber 97 and an exhaust blower 99 is connected to each of the conversion tank 11, the regeneration tank 49 and the holding tank 63 by means of a connector 101 in the cover of each of the those tanks. The exhaust blower 99 maintains a slight negative pressure in the space at the top of each of the tanks to which it is connected to prevent the escape of fumes from the treatment solution into the ambient.

In the illustrated embodiment of the invention, the scrubber 97 is formed of an activated charcoal filtering system. Other types of scrubber systems may equally well be used, so long as they are capable of dealing with the vapors generated by the treatment solution.

In operation, a batch ACM to be converted into a non-asbestos material is loaded into the conversion tank 11 by means of the lid 103. The treatment solution can then be pumped into the conversion tank 11 from the holding tank 63 through the motor pump 65 and valves 69, 71 and 73, or can be loaded into the conversion tank 11 from a separate source (not shown) . Whichever method is used, it is preferred that the integrity of the top of the conversion tank 11 be maintained during the loading of the treatment solution into the conversion tank 11 in order to prevent the possible escape of fumes into the ambient.

Either after or during the loading of the conversion solution into the conversion tank 11, the high shear mixer 13 is activated to agitate the solution and asbestos containing material. The mixing blade 14 in the illustrated embodiment of the invention is a Cowls blade. High shear mixing blades are well known in the art and any which are able to deal with the slurry formed by the treatment solution and the ACM may be used. The purpose of the high shear mixer is to help break up the asbestos fiber bundles and to bring the treatment solution into intimate contact with the individual asbestos fibers to permit the solution break the fibers down, thereby destroying the fibrous natures of the asbestos and rendering it non-hazardous.

The agitation of the treatment solution and ACM for one half hour to an hour is normally sufficient to destroy all of the asbestos in the ACM. The destruction of the asbestos can be confirmed by taking a sample of the slurry formed by the treatment solution and ACM and checking it by optical microscopy for the presence of asbestos fibers. The treatment solution is effective to reduce the solids content of the ACM by up to 80%. The remaining solid material is normally in the form of a fine particulate. While the solid particulate is still in suspension in the conversion solution, the valve 21 is opened and the motorized pump 23 is activated to pump the suspension out of the conversion tank 11 through the bag filters 31 and 39 in order to remove the suspended solids. The motorized pump 23 may be of any type which is sufficiently impervious to the treatment solutions and is able to handle the slurry of converted solids in the treatment solution. In the illustrated embodiment of the invention a diaphragm pump is used.

The mesh sizes of the bag filters 31 and 39 are determined by a treatability study normally performed prior to each asbestos abatement job using the system of the invention. In general, the mesh size for the bag filters 31 is selected such that the bag most of the suspended solids from the slurry without clogging too quickly. The mesh size for the bag filter 39 is normally chosen to be substantially finer than that of bags 31 so as to remove almost all of the remaining solids. The valves 25, 33, 37, 41, 45 and 47 are normally kept open to permit the draining of the conversion tank.

When the bag filters 31 and 39 have reached their capacity , the bags are removed, emptied and washed for reuse if possible. Bags which can not be reused are neutralized and discarded.

Once in the regeneration tank 49, the filtered treatment solution is reconstituted by adding concentrates of the chemicals contained therein, either in liquid or crystalline form. In addition, additional treatment solution can be added to bring the total solution up to the desired amount. The mixing blade 51 is used to stir the solution in order to mix in the concentrates.

After the solution has been reconstituted in the regeneration tank, it is pumped by means of the motorized pump 53 through the filtering system 60 and into the holding tank 63. The filtering system 60 in the illustrated embodiment of the invention may consist of an activated charcoal filter and is preferably included in the system in order to remove from the treatment solution excess ammonia and other contaminants, such as for example, heavy metals, which might otherwise build up.

During continuous batch operation, two of the tanks 11, 63 and 49 normally contain batches of treatment solution. During a conversion operation, the conversion tank 11 and either the regeneration tank 49 or the holding tank 63 contains a batch of the treatment solution. In any event, if the second batch of solution is in the regeneration tank 49, it must be pumped into the holding tank 63 before the batch of solution in the conversion tank 11 is pumped out through the bag filters 31 and 39 into the regeneration tank 49. As soon as the conversion tank has been emptied and refilled with fresh ACM, the reconstituted treatment solution can be pumped from the holding tank 63 into the conversion tank 11 to begin another conversion cycle. In this way the down time of the conversion tank 11 is minimized and the through-put of the system is maximized. Normally at the end of each day or shift, the treatment solutions end up in the holding tank 63 and the regeneration tank 49, from which they can be pumped into another holding tank or tanks (not shown) for storage until the next day or shift. It is preferred to wash the system at least daily by pumping the neutralizing solution from the wash tank 75 through the motorized pump 77 into one of the other tanks. It is possible to cycle the wash solution through all three of the tanks by opening the valve 85 so that the neutralization solution is pumped into the regeneration tank 49. From the regeneration tank the wash solution is pumped into the holding tank 63, the conversion tank 11, through the filters 31 and 39, and back into the wash tank through the valve 91. It is also possible to wash only the holding tank 63 and the conversion tank 11, opening the valve 87 so that the neutralization solution is pumped into the holding tank 63 by the motorized pump 77. Alternatively, it is possible to wash only the conversion tank 11 by opening the valve 89 when the neutralization solution is pumped from the wash tank 75 by the motorized pump 77. Although the invention has been described with relation to the illustrated embodiment, a number of changes can be made in the system without departing from the spirit and scope of the present invention. For instance, additional filters could be added or other filtering systems substituted for the bag filters 31 and 39. If there is a concern about the build-up of trace elements in the solution due to the repeated recycling of the conversion solution, it is possible to add an ion exchange unit or other filtering system element, for instance, between the regeneration tank 49 and the holding tank 63, in addition to or in lieu of the filter 60 in order to remove or reduce such trace elements. Alternatively, the removal of such trace elements, if necessary, could be done at the end of the day or shift when the treatment solution is pumped from the system for storage.

Claims

I CLAIM :

1. Apparatus for converting asbestos in asbestos containing material to a non-hazardous material, comprising: a first container; a high shear mixer disposed in said first container for agitating materials contained therein; a second container; a filtering system for removing particulate matter from a liquid slurry; first pumping means for pumping a liquid slurry from said first container through said filtering system to the inlet of said second container; mixing means in said second container for mixing liquids contained therein; a third container; second pumping means for pumping liquid from said second container to said third container; third pumping means for pumping liquid from said third container to said first container; a fourth container having an outlet and an inlet; means for selectively connecting the outlet of said fourth container to the inlets of said first, second and third containers; means for selectively pumping liquid from said fourth container into one of said first, second and third containers; and means coupling the outlets of said first, second and third containers to the inlet of said fourth container.

2. A method for converting asbestos in an asbestos- containing material to a non-asbestos material, comprising: placing a batch of the asbestos-containing material in an aqueous conversion solution containing an acid and a source of fluoride ions, said solution being disposed in a first container; agitating the solution with such batch disposed therein for converting the asbestos in such batch to a non-asbestos material; transporting said solution with the converted asbestos-containing material suspended therein to a second container through a filtering system for separating particulate matter from said solution; reconstituting said solution while in said second container by adding a concentrate of said acid or said source of fluoride ions or both to said solution; and transporting reconstituted conversion solution from said second container into said first container for converting another batch of said asbestos containing material in said first container.

3. The method of claim 2 wherein the step of transporting the reconstituted conversion solution to the first container includes the steps of: transporting said reconstituted solution from said second container to a third container for storage; and transporting said stored reconstituted solution from the third container to said first counter.

4. The method of claim 3 f rther including selectively cleaning said first, second or third containers by recirculating a neutralizing solution there-through.