Patent Publication Number: US-6660900-B2

Title: Process for the non-incineration decontamination of materials containing hazardous agents

Description:
RELATED APPLICATION 
     This is a continuation-in-part of U.S. patent application Ser. No. 09/781,818, filed Feb. 12, 2001, now U.S. Pat. No. 6,462,249 entitled PROCESS FOR THE NON-INCINERATION DECONTAMINATION OF MATERIALS CONTAINING HAZARDOUS AGENTS, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to processes for decontaminating contaminated materials, such as chemical weapon components, and, more specifically, to processes for  5  decontaminating contaminated materials without using incineration methods. 
     BACKGROUND OF THE INVENTION 
     The decontaminating of contaminated material can be very difficult. This is especially the case with respect to the decommissioning of chemical weapons carrying chemical warfare agents. The principal problem in this regard is how to safely remove, neutralize and dispose of the extremely toxic chemical warfare agents used in such chemical weapons. Modern technology has become increasingly successful in the neutralization of these chemical warfare agents—once the agents have been removed from the chemical weapon housing. However, after the bulk of the chemical warfare agents have been removed from the chemical weapons housings, the housings and their various components typically remain contaminated with residual amounts of the chemical warfare agents. The decontamination of these chemical weapon components remains a difficult problem. 
     Most prior art methods for decontaminating chemical weapon components have employed a two-step process. In a first step, the components are subjected to liquid chemicals or to high temperatures to remove and decompose essentially all of the chemical warfare agents adhering to the chemical weapon components. In a second step, residual vapors from the first step are incinerated to eliminate any and all residual chemical warfare agents in those vapors. 
     The incineration step has now been questioned, however, as possibly allowing potentially toxic combustion products to be released to the atmosphere. Accordingly, the incineration step has been banned in many industrial countries, including in the United States. 
     A similar but separate problem is how to dispose of organic materials, such as wood, plastic, rubber, and cloth which is contaminated with hazardous agents. Traditionally, such organic materials must be disposed of in a special hazardous materials dump site. Since such organic materials tend to be bulky, the relative cost of disposing of such materials is very high. 
     Thus, there is a need for a new method of decontaminating chemical weapon components which completely eliminates all traces of chemical warfare agents in an efficient and inexpensive manner, and without the use of an incineration step. 
     There is a further need for a new method of disposing of organic materials which have been contaminated with hazardous materials, a new method which is also efficient and inexpensive in operation and which does not require the use of an incineration step. 
     SUMMARY 
     The invention satisfies this need. The invention is a process for the low temperature, non-incineration decontamination of contaminated materials containing hazardous agents, the process comprising (a) mixing the contaminated metal components with organic solid materials to form a feed mixture containing metallic material and non-metallic material, (b) contacting the feed mixture with steam at substantially ambient pressure in a substantially dry first heated vessel for a period of at least about 15 minutes, the steam being at a temperature of at least about 560° C., whereby essentially all of the hazardous agents are removed from the contaminated metal components, and whereby all of the non-metallic material within the feed mixture is volatilized, (c) removing a first gaseous discharge stream containing hazardous agents from the first heated vessel, the first gaseous discharge stream comprising a condensible moiety and a non-condensible moiety, (d) heating the first gaseous discharge stream at substantially ambient pressure in a substantially dry second vessel to at least about 500° C. and maintaining the first gaseous discharge stream in the second vessel above at least about 500° C. for a period of at least about one second in an atmosphere containing steam, whereby at least about 99 wt. % of the hazardous agents within the first gaseous discharge stream are converted to non-hazardous agents, (e) removing a second gaseous discharge stream containing a reduced concentration of hazardous agents from the second vessel, the second gaseous discharge stream comprising a condensible moiety and a non-condensible moiety, (f) having a concentration of hazardous agents less than about 100 mg/l, (g) increasing the pH of the condensate to at least about 8.0 so as to reduce the concentration of hazardous agents within the condensate to less than about 1.0 mg/, and (h) catalytically treating the non-condensible moiety of the second gaseous discharge stream in the presence of oxygen so that the concentration of hazardous agents within the non-condensible moiety of the second gaseous discharge stream is reduced to less than about 1.0 mg/m 3  at standard temperature and pressure. 
     The process is especially applicable where the contaminated materials are chemical weapon components and the hazardous agents are chemical warfare agents. 
     The process is also especially applicable where the organic solid materials within the feed mixture comprise contaminated organic materials. 
    
    
     DRAWINGS 
     These features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying figures where: 
     FIG. 1 is a process flow diagram illustrating the process of the invention; 
     FIG. 2 is a diagrammatic cross-sectional side view of flushing apparatus useable in the invention; 
     FIG. 3 is a diagrammatic cross-sectional side view of a heated vessel useful in the invention; 
     FIG. 4A is a diagrammatic cross-sectional side view of a second heated vessel useful in the invention; 
     FIG. 4B is a cross-sectional view of the heated vessel illustrated in FIG. 4A, taken along line  4 B— 4 B; 
     FIG. 5 is a diagrammatic cross-sectional side view of a third heated vessel useful in the invention; and 
     FIG. 6 is a detailed perspective view of an auger useful in the invention. 
    
    
     DETAILED DESCRIPTION 
     The following discussion describes in detail one embodiment of the invention and several variations of that embodiment. This discussion should not be construed, however, as limiting the invention to those particular embodiments. Practitioners skilled in the art will recognize numerous other embodiments as well. 
     The invention is a process for the low temperature, non-incineration decontamination of contaminated materials containing small amounts of hazardous agents. By “hazardous agents,” it is meant any chemical compound or material which is considered harmful to humans and/or other life forms. Hazardous agents are typically organic in nature, but can also be toxic metals or metal compounds which are volatilized at temperatures between 560° C. and 700° C. Such metals include mercury and lead. 
     The invention is especially applicable to the decontamination of chemical weapon components, wherein the hazardous agents are chemical warfare agents. By the term “chemical warfare agents,” it is meant any chemical which, through its chemical action on life processes, can cause death, temporary incapacitation or permanent harm to humans or animals. 
     In the process, as illustrated in FIG. 1, the chemical weapon components  10 , such as missile warheads or bombs, are opened and the chemical warfare agents contained therein are flushed out. That portion of the chemical warfare agents flushed out of the chemical weapon components  10  are then removed to a separate treating facility (not shown) for pacification. 
     After being flushed out, the chemical weapon components  10  continue to be contaminated with small amounts of the chemical warfare agents. These flushed out, but still contaminated, chemical weapon components  10  are next mixed with organic solid materials to form a feed mixture  11  containing metallic material and non-metallic material. The feed mixture  11  is sealed within a substantially dry first heated vessel  12 . Within the first heated vessel  12 , the feed mixture  11  is contacted with steam at a substantially ambient pressure for a period of at least about 15 minutes, typically for a period of between about 15 minutes and about 4 hours, most typically for a period between about 15 minutes and about 2 hours. By “substantially ambient pressure,” it is meant at a pressure between about 14.5 psia and about 14.7 psia. The temperature of the steam in contact with the feed mixture  11  within the first heated vessel  12  is at least about 560° C., and is typically between about 560° C. and about 750° C. By this contacting step, essentially all of the chemical warfare agents within, and adhering to, the chemical weapon components  10  are removed from the chemical weapon components  10  and transferred into a gaseous steam-containing phase. Also within the first heated vessel  12 , essentially all of the non-metallic material, including the organic solid materials within the feed mixture  11  is volatilized into the gaseous steam-containing phase. 
     The gaseous, steam-containing phase in the first heated vessel  12  is removed from the first heated vessel  12  via a first discharge line  16  as a first gaseous discharge stream. This first gaseous discharge stream comprises a condensible moiety and a non-condensible moiety. The first gaseous discharge stream comprises a significant quantity of oxidizable material. Because the chemical warfare agents are contaminated with only a small amount of hazardous agents, the proportion of the oxidizable material in the first gaseous discharge stream is negligible compared to the oxidizable material provided by the organic solid materials within the feed mixture  11 . 
     After removal from the first heated vessel  12 , the first gaseous discharge stream is heated in a substantially dry second vessel  18  at substantially ambient pressure to at least about 500° C. (typically between about 500° C. and about 700° C.). Within the second vessel  18 , the first gaseous discharge stream is maintained at a temperature of at least about 500° C. for a period of at least about one second in an atmosphere containing steam at a concentration between about 150% and about 350% of stoichiometry, preferably between about 250% and about 300% of stoichiometry, and most preferably between about 225% and about 275% of stoichiometry. The percent of stoichiometry is easily calculated from the known quantity of oxidizable material within the organic solid materials portion of the feed mixture  11 . As noted above, the portion of oxidizable material within the first gaseous discharge stream provided by the hazardous materials within the chemical weapon components  10  is negligible. 
     Typically, the first gaseous discharge stream is maintained within the second vessel for a period of between about 1 and 10 seconds, most typically between about 1 and about 5 seconds. The term “stoichiometry” in this sense is meant to indicate the quantity of steam theoretically capable of reacting all of the chemical warfare agents within the first gaseous discharge stream to non-chemical warfare agents. By this step, at least about 99 wt. %, typically at least about 99.9 wt. % and, most typically, at least about 99.99 wt. %, of the chemical warfare agents within the first gaseous discharge stream are converted to non-chemical warfare agents. 
     The gaseous mixture within the second vessel  18  is removed from the second vessel  18  via a second gaseous discharge line  20  as a second gaseous discharge stream. This second gaseous discharge stream also comprises a condensible moiety and a non-condensible moiety. The second gaseous discharge stream is passed through a condenser  22 , wherein the condensible moiety of the second gaseous discharge stream is condensed to condensate. In a typical embodiment of the invention, the concentration of chemical warfare agents within this condensate is less than about 100 mg/l. 
     The pH of the condensate is then increased to at least about 8.0 (typically in a condensate treating vessel  24 ), so as to reduce the concentration of chemical warfare agents within the condensate to less than about 1.0 mg/l. 
     The non-condensible moiety of the second discharge gaseous stream is removed from the condenser  22  via an overhead line  26  to a reactor  28  where it is catalytically treated in the presence of oxygen so as to reduce the concentration of chemical warfare agents within the non-condensible moiety to less than about 1.0 mg/m 3  (at standard pressure and temperature). This catalytic treatment step can be carried out in one of a large number of catalytic oxidation processes known in the art, such as the Thermatrix Blameless Oxidation process licensed by Thermatrix, Inc. of California, Edge II™ licensed by Alzeta Corporation of California and Econ-Abator Catalytic Oxidation Systems licensed by Huntington Environmental Systems of Illinois. The CATOX Process licensed by Honeywell, Inc. of Morristown, N.J. has been found to be particularly effective in the oxidation of chemical warfare agents within the non-condensible moiety of the second discharge stream to non-chemical warfare agents. This process is disclosed in detail in U.S. Pat. No. 6,080,906, the entirety of which is incorporated herein by this reference. 
     In a typical embodiment, the throughput through the reactor  28  limits the overall throughput through the process. Accordingly, the feed rate of the feed mixture  11  is determined by the maximum throughput through the reactor  28 . 
     As illustrated in FIG. 2, the chemical weapon components  10  can be flushed out using a flushing apparatus  30  comprising a primary flushing vessel  32  and a secondary flushing vessel  34 . In the primary flushing vessel  32 , the chemical weapon components  10  are initially opened and the mobile chemical warfare agents contained therein are dumped into the bottom of the primary flushing vessel  32  for removal to the separate treating facility  36 . After substantially all of the mobile chemical warfare agents have gravitated out of each chemical weapon component  10 , the chemical weapon component  10  is placed into the secondary flushing vessel  34 . 
     The secondary flushing vessel  34  contains a rotating carousel  38  which is partially submerged within a quantity of liquid flushing agent  40 , such as water or other solvent. The carousel  38  rotates individual chemical weapon components  10  into and out of the flushing agent. Both above and below the liquid level  42 , high pressure sprayers  44  are capable of spraying liquid flushing agent into the open ends  46  of the chemical weapon components  10  to flush out additional amounts of chemical warfare agents. 
     Preferably, the carousel  38  is adapted to retain each chemical weapon component  10  at an angle of between about 30° and about 90° with respect to the horizontal so that the open end  46  of each chemical warfare component  10  is canted downwardly when the chemical weapon component  10  is disposed at the top of the carousel  38  and is canted upwardly when rotated to the bottom of the carousel  38 . By this design, the chemical weapon components  10  within the carousel  38  automatically drain when rotated to the top of the carousel  38  and automatically draw liquid into each chemical weapon component  10  when rotated to the bottom of the carousel  38 . 
     After exiting the secondary flushing vessel  34 , the chemical weapon components  10  are placed into the first heated vessel  12  where they are contacted with steam as described above. As illustrated in the drawings, the first heated vessel  12  can be equipped with electrical heating coils  47  so that the first heated vessel  12  can be heated electrically, preferably by induction heating. 
     Operation of the first heated vessel  12  can be carried out in a batch-wise mode or can be carried out in a semi-batch, semi-automatic or fully automatic modes. FIG. 3 illustrates the operation of the first heated vessel  12  in a semi-batch mode. As illustrated in FIG. 3, the first heated vessel  12  houses a pair of discrete bundles  48  of chemical weapon components  10 . Typically, each bundle  48  is a palletized plurality of chemical weapon components  10 . Each bundle  48  is subjected to two separate applications of heated steam. After each application, the forward-most bundle  48   a  is removed from the outlet end  50  of the first heated vessel  12 , the rearward-most bundle  48   b  is moved forward within the first heated. vessel  12  and a new bundle  48   c  is disposed within the first heated vessel  12  at the inlet end  52  of the first heated vessel  12 . 
     In another embodiment (not shown), chemical weapon components  10  are loaded onto one or more trays which are pushed through the first heated vessel  12  in a similar fashion as the bundles  48  described immediately above. 
     FIGS. 4A and 4B illustrate a semi-automatic embodiment. In this embodiment, a plurality of elongate racks  54  are disposed within the first heated vessel  12 . Each rack  54  is adapted to accept, end-to-end, a plurality of individual chemical weapon components  10 . A charging mechanism (not shown) is disposed at the inlet end  52  of the first heated vessel to charge one chemical weapon component  10  at a time into the inlet end  56  of one of the racks  54 . As one chemical weapon component  10  is charged into the inlet end  56  of a rack  54 , a fully decontaminated chemical weapon component  10  is removed at the outlet end  58  of that rack  54  by a discharging mechanism (not shown). Either the charging and discharging mechanisms or the racks  54  rotate about the longitudinal axis  59  of the first heated vessel  12  so that the charging mechanism loads a chemical weapon component  10  into each of the racks  54  in repeated, serial fashion. By this operation, all of the racks  54  are serially loaded and unloaded. 
     FIG. 5 illustrates yet another embodiment of the invention. This embodiment of the invention can be operated in either a semi-automatic or full automatic configuration. In this embodiment, an auger  60  is disposed within the first heated vessel  12 . Its configuration is suitable for chemical weapon components  10  of relatively reduced size, such as pre-shredded chemical weapon components  10 . In this embodiment, as the auger  60  slowly rotates, chemical weapon components  10  are slowly moved from the inlet end  52  of the first heated vessel  12  towards the outlet end  50  of the first heated vessel  12 . 
     In many cases, operation of this embodiment is facilitated by loading the feed mixture  11  within the first heated vessel  12  with a filler material, such as crushed limestone, aluminum silicate or granulated charcoal. Typically, the filler material is comprised of clumps having a width between about ¼ inch and about 1 inch, typically between about ¼ inch and about ½ inch. In a typical operation, such filler material comprises between about one third and about two thirds of the volume of loose material within the first heated vessel  12 . The filler material is removed at the outlet end  50  of the first heated vessel  12  with the fully decontaminated chemical weapon components. The filler material is then separated from the chemical weapon components  10 , such as by screening or air blasting. Thereafter, the filler material can be recycled for repeated uses within the process. 
     FIG. 6 illustrates in detail an auger configuration useful in this embodiment. In this configuration, the auger  60  is composed of an axially rotating central member  62  to which is attached a plurality of outwardly radiating support members  64 . The support members  64  are disposed in a spiral about the central member  62 . At the distal end of each support member  62  is an auger blade  66 . In the embodiment illustrated in FIG. 6, each auger blade  66  is L-shaped, having a lateral component  68  and a vertical component  70 . The auger blades  66  are attached to the support elements  64  in an adjustable fashion, such as by being attached with a bolt and nut  72 . By being adjustable, the angle of the individual auger blades  66  can be optimally adjusted to smoothly move loose material through the first heated vessel  12 . 
     For many materials, it has been found that varying the angle of the auger blades  66  along the length of the auger  60  can be beneficial. In some operations, it can actually be beneficial to angle some of the auger blades  66  to nudge material backwards within the first heated vessel  12  while the remainder of the auger blades  66  are angled to push the material forward. Such a configuration has been found to be advantageous in maintaining the smooth flow of certain materials through the first heated vessel  12 . 
     The invention has been found to provide an extremely effective method for decontaminating chemical weapon components without having to resort to incineration steps. Because the process is carried out at substantially ambient pressures, capital, operating and maintenance costs are reduced to a minimum. 
     The invention has also been found to provide an extremely effective method of disposing of contaminated organic materials without having to resort to incineration steps. 
     The invention can also provide an effective method for minimizing the overall quantity of a “mixed” waste containing organic contaminants and radioactive contaminants. The non-radioactive portion of any such mixed waste can be substantially eliminated by use of the invention, thus minimizing the overall quantity of waste which must be disposed of. The invention has also been further found to provide an effective method for decontaminating other contaminated materials containing hazardous agents, such as contaminated soils. 
     Having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the instant invention as set forth hereinabove and as described hereinbelow by the claims.