Review and Evaluation of Alternative Chemical Disposal Technologies (1996) / Chapter Skim
Currently Skimming:
6 GAS-PHASE CHEMICAL REDUCTION TECHNOLOGY
6 GAS-PHASE CHEMICAL REDUCTION TECHNOLOGY
Pages 102-119
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 102... ...
The acronym GPCR will be used in the remainder of this report to refer to the particular process design submitted by this TPC for a gas-phase chemical reduction technology to destroy chemical agents. The process uses hydrogen and steam at elevated temperatures (up to 850°C)
|
From page 103... ...
The acid gases and other inorganic products must first be scrubbed from the reactor effluent gas and then converted to a form suitable for disposal or recycling in commerce. The reactions of organic 103 compounds containing heteroatoms are even more difficult to predict without the same kind of detailed experimental work the TPC has carried out on the feed materials it currently treats successfully.
|
From page 104... ...
The methane is converted to H2, CO, and CO2 in the steam reformer to provide enough H2 for the reactor. t -- t H2 N2 Energy Reactor 1 r Steam Waste Hot Watery Waste ~- ~ Contar 1lnated Oil Contaminated Water L Another significant factor is that the rate of reaction of carbon with steam (second reaction)
|
From page 105... ...
105 product Gas Storage Fuel Far less is understood, fundamentally or empirically, about the fate of other heteroatoms such as sulfur, nitrogen, and phosphorus that are present in the chemical agents HD and VX-in feed streams entering the GPCR reactor. The reactions of these heteroatoms have not been investigated extensively, and the interplay of kinetics and thermodynamics is difficult to predict a
|
From page 106... ...
Moreover, the hydrogenolysis of organosulfur compounds to H2S is well known from commercial hydrodesulfurization processes. For HD destruction, the overall reaction can be summarized as: SC4H~C12 + H2 = CH4 + C + CO + CO2 + H2S + HCI + other products The TPC's empirical knowledge and operational experience with other feed materials should be sufficient to develop the appropriate conditions for HD destruction.
|
From page 107... ...
Both can be managed by conventional scrubbing systems that the TPC has previously employed for other feed materials. Although the large volume of H2S from HD will require scaling up the caustic and MEA scrubbers that the TPC currently uses with other feed materials, doing so should not be arduous.
|
From page 108... ...
Regardless of the status of the scrubbing technologies, the recovery of process residuals containing the speciated products of chlorine, sulfur, phosphorus, and carbon and their conversion for ultimate disposal is clearly a complex process that will require a number of .
|
From page 109... ...
At least one scrubber is needed to manage each heteroatom-containing product that exits the reactor. The recovery subsystem that is, the scrubbers and the subsequent unit operations for generating final process residuals from the scrubber effluents, such as conversion of H2S to elemental sulfur-consists of standard unit operations (with the possible exception of operations to scrub and handle the phosphorus-containing products)
|
From page 110... ...
If regulatory approval can be obtained, the TPC has stated that it would prefer to recycle the ton containers. An alternative for treating the emptied ton containers in the SBV would be to use the Army process (hot water wash, followed by steam cleaning)
|
From page 111... ...
The reformer gas is already at high temperature when it reaches the reactor; the electric heaters in the reactor are needed only to provide enough incremental heat to reach the reaction temperature. The two agent-derived feed streams are the liquid chemical agent from the ton containers and the effluent gas stream from the SBV.
|
From page 112... ...
Pressure measurement and control are important for the process; to preserve a safe hydrogen atmosphere, negative pressure anywhere in the recirculating gas circuit must be avoided. The system pressure is maintained by continuous feed-gas inputs to the reactor and by adjusting the rate of removal of reactor effluent gas; the latter is controlled by a variable-speed blower with a gas bypass around the blower.
|
From page 113... ...
The entire system, however, consists of a number of sequential unit operations that must be tightly integrated and controlled. Agent destruction in the reactor is followed first by a sequence of chemical scrubbers and a sulfur recovery reactor, then by a cata{ytic steam reformer whose catalyst would be poisoned by breakdown of the scrubbing system.
|
From page 114... ...
The catalytic steam reformer will require close temperature control and a "clean" feed; that is, no catalyst poisons in the input gas, such as sulfur or phosphorus. The scrubbers will require constant monitoring but should be able to handle a modest range of feed rates.
|
From page 115... ...
Modes of Degradation As a result of chemical and design conditions, a number of modes of degradation may occur either in the main reactor or in the scrubbing system. In general degradation, the material may "rust away" if surface corrosion increases as the environment becomes increasingly acidic or alkaline.
|
From page 116... ...
release of reactor effluent gases from piping defects, (3) leaks in the pregasifier, and (4)
|
From page 117... ...
in reactor effluent gas, although commercial scrubbing technologies are available speciation and management of phosphoruscontaining products in the reactor effluent gas, including scrubbing technologies or other methods for managing phosphorus-containing reaction products, as well as the final form and mode of disposal of high-volume process residuals containing phosphorus effects of reactor products containing sulfur and phosphorus on the catalytic reformer and mechanisms to avoid poisoning if these products are not fully recovered in the scrubber system (The TPC's experience has been with chlorine-containing materials, which do not present the same problem.) With only preliminary information derived from VX surrogate tests using malathion, and without complete information from the initial agent tests conducted late in the study process, the pane!
|
From page 118... ...
The process-safety risk factors inherent in GPCR include safety issues associated with high-temperature hydrogen, hot water and corrosives in the scrubbers, and secondary containment. Many of the risk factors that are not specific to chemical agent have been addressed by the TPC in safety analyses and in hazard and operability reports.
|
From page 119... ...
These issues, however, are no different for an agent-processing facility than for the wastetreatment facilities that the TPC has already piloted and run commercially. Worker Safely Issues There are a number of worker safety issues associated with high temperature hydrogen, high temperature steam, hot water and corrosives in the scrubbers, and secondary containment (concerning both inadvertent leaks and maintenance activities)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.