Patent Application
20050043578
This invention relates generally to processes for decontaminating contaminated materials, such as chemical weapon components, and, more specifically, to processes for decontaminating contaminated materials without using incineration methods.
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.
In our earlier filed patent application, now U.S. Pat. No. 6,462,249, we disclosed a method of decontaminating chemical weapon components without use of an incineration step. The method disclosed in U.S. Pat. No. 6,462,249, however, required that the exhaust gases from the method be treated catalytically with oxygen. This is an expensive step.
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 and without the use of a catalyzed oxygenation step.
The invention satisfies this need. The invention is a process for the low temperature, non-incineration decontamination of contaminated materials containing small quantities of organic materials which include hazardous agents, the process comprising (a) contacting the contaminated materials and the hazardous agents 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 materials, (b) 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, (c) 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 of at least about 500° C. for a period of at least about one second in an atmosphere containing sufficient steam whereby at least about 99.9 wt. % of the hazardous agents within the first gaseous discharge stream are converted to non-hazardous agents, (d) 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, (e) having a concentration of hazardous agents less than about 100 mg/l, (f) 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/l, and (g) treating the non-condensible moiety of the second gaseous discharge stream with a chemical absorbent 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/m3 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.
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:
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 quantities of organic materials, most of which are 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 750° 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
After being flushed out, the chemical weapon components 10 contain only small amounts of organic materials, most, if not all, of which are chemical warfare agents. These flushed out, but still contaminated, chemical weapon components 10 are next sealed within a substantially dry first heated vessel 12. Within the first heated vessel 12, the chemical warfare agents are 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 chemical warfare agents 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.
The gaseous, steam-containing phase containing the chemical warfare agents 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.
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 sufficient steam to reduce the concentration of chemical warfare agents to less than about 1 mg/m3. Such concentration of steam is typically between about 150% and about 350% of stoichiometry. 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.
The first gaseous discharge stream is maintained within the second vessel for a period of between about 1 and about 10 seconds, most typically between about 1 and about 5 seconds.
Typically, the quantity of chemical warfare agents transferred to the second vessel 18 is not absolutely known, but it can be roughly estimated. During start-up of the method, an excess of steam is delivered to the second vessel 18 so as to be sure to convert at least 99.99 wt. % of the chemical warfare agents within the first gaseous discharge stream to non-chemical warfare agents. After start-up, the quantity of steam delivered to the second vessel 18 can be throttled back while monitoring the conversion of the chemical warfare agents to non-chemical warfare agents, so as to use no more steam than necessary.
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 final treater 28, such as a charcoal filter, where it is treated with a chemical absorbent such as activated charcoal, to reduce the concentration of chemical warfare agents within the non-condensible moiety to less than about 1.0 mg/m3 (at standard pressure and temperature).
As illustrated in
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.
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.
In many cases, operation of this embodiment is facilitated by loading the chemical weapon components 10 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.
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 containing small amounts of organic materials without having to resort to incineration steps and without having to resort to catalyzed oxygenation steps. Because the process is carried out at substantially ambient pressures, capital, operating and maintenance costs are reduced to a minimum.
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.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10183580 | Jun 2002 | US |
| Child | 10677979 | Oct 2003 | US |
| Parent | 09781818 | Feb 2001 | US |
| Child | 10183580 | Jun 2002 | US |
