Toxic waste gases

If a pollutant is removed from the carrying gas stream, disposal of the collected material becomes of vital concern. If the collected material is truly inert, it may be disposed of in a sanitary landfill. If it is at the other end of the scale, it is probably considered as a toxic waste and strict laws governing its disposal apply. Disposal of hazardous wastes is regulated by governmental agencies. 

In the selection of control equipment, the most important waste-gas characteristics are volumetric flow rate, concentration and composition of organic compounds in the waste-gas, waste-gas temperature and humidity, and rbe content of particulate matter, chlorinated hydrocarbons, and toxic pollutants. Other factors influencing the equipment selection are the required removal efficiency, recovery requirements, investment and operating costs, ease of installation, and considerations of operation and maintenance. The selection of a suitable control method is based on the fundamental selection criteria presented as well as the special characteristics of the project. 

Owing to its high toxicity, phosgene waste-gas must be recycled, destroyed or, in some way, removed to prevent environmental contamination or hazards to personnel. This Section is concerned with the main methods for chemically removing phosgene from gaseous effluents, the extent to which phosgene is taken up and retained by various sorbents, and the effect of time, temperature, pressure and moisture on the sorption. 

In order to prevent SO2 emission, H2S has to be removed from gas streams prior to combustion. Apart from environmental reasons, removal of H2S from waste gas streams is also required for health reasons (H2S is a toxic gas, lethal at concentrations exceeding 600 ppm) and to prevent corrosion of equipment. Gases that can contain H2S and need treatment are, for instance, natural gas, syngas and biogas (formed in anaerobic wastewater treatment). 

The world is so dominated by the green machinery of photosynthesis that it is easy to miss the wood for the trees — to overlook the conundrum at its heart. Photosynthesis uses light to split water, a trick that we have seen is neither easy nor safe it amounts to the same thing as irradiation. A catalyst such as chlorophyll gives ordinary sunlight the destructive potency of x-rays. The waste product is oxygen, a toxic gas in its own right. So why split a molecule as robust as water to produce toxic waste if you can split... 

While no firm underlying mechanisms have been demonstrated, some authors have suggested that irreversible oxidation of the cobalt atom in vitamin B12 by nitrous oxide can lead to inactivation of enzymes dependent on this vitamin, with resultant metabolic aberrations. Such examples have included methionine synthetase and thymidylate synthetase, which are essential in the synthetic pathways leading to the production of myelin and thymidine, respectively. Should these enzymes be impaired during the sensitive periods of in utero development, the potential for malformations may unfortunately be realized. To date, no studies have been able to demonstrate conclusively that low-level exposure to nitrous oxide is associated with a meaningful disruption of crucial metabolic functions to produce the above-described toxicity however, measures including improved waste gas-scavenging systems should be taken to minimize exposure of personnel. 

Catalytic combustion is developing into a very promising ultra-low emission technique for reducing thermal-NOx produced in gas turbine systems, it was first proposed by Pfefferle in the seventies [1]. The main research is, and has been, concentrated on methane as the fuel, however a growing interest in enviroiunental issues have forced the research into renewable sources such as biomass to reduce the net emissions of CO2. Waste materials have also became important, however the problem with waste is to get a clean enough product gas for the gas turbine. This calls for a selection between different kinds of wastes like household residues, toxic wastes, etc. Up to now most combustible wastes have been deposited in landfills, but new directives from the European Parliament, EU COM (98) 558, have increased the interest for the use of industrial waste as a fuel. 

EPA Designated Toxic Waste, RCRA Waste Number U134 DOT Label Corrosive Material, UN 1052, UN 1790 Formula HE MW 20.01 CAS [7664-39-3] Composition The acid is an aqueous solution of hydrogen fluoride gas, commercially available in varying strengths 47, 53, and 79% concentrations. 

EPA Classified Toxic Waste, RCRA Waste Number U092 DOT Label Flammable Gas/Flammable Liquid (Aqueous), UN 1032, UN 1160... 

EPA Designated Toxic Waste, RCRA Waste Number P076 DOT Label Poison Gas, UN 1660... 

EPA Priority Pollutant, RCRA Toxic Waste Number U045 DOT Label Flammable Gas, UN 1063... 

The District of Columbia undertook this study because of three important observations. First, the contaminants potentially present were not industrial chemicals but were expressly designed to kiU people. Second, the containers unearthed to date are shell casings— which are thicker than the drums and cans usually associated with toxic waste dumps—or bottles, increasing the likelihood of lethal concentrations. Third, there was open air testing, which likely left behind metal contamination such as arsenic. There is mounting evidence that the Spring Valley site encompassed a massive production facihty for poison gas in addition to its development and experimentation functions. 

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