Thermal pollution converter

The requirement of the second law that all heat absorbed cannot be completely converted into work in a cyclic process, i.e. that part of it must be rejected, is very painful here. About 3/4 of the heat absorbed in the boiler/superheater is rejected in the condenser. And not only do we lose it, but it is a main source of thermal pollution. 

Aluminas are used in various catalytic applications, a-, y-, and -aluminas are all used as support materials, the first one in applications where low surface areas are desired, as in partial oxidation reactions. The latter two, and especially y-alumina, in applications where high surface areas and high thermal and mechanical stability are required. One of the most prominent applications of y-alumina as support is the catalytic converter for pollution control, where an alumina washcoat covers a monolithic support. The washcoat is impregnated with the catalytically active noble metals. Another major application area of high-surface aluminas as support is in the petrochemical industry in hydrotreating plants. Alumina-supported catalysts with Co, Ni, and/or Mo are used for this purpose. Also, all noble metals are available as supported catalysts based on aluminas. Such catalysts are used for hydrogenation reactions or sometimes oxidation reactions. If high... 

Zeolites have also proven applicable for removal of nitrogen oxides (NO ) from wet nitric acid plant tail gas (59) by the UOP PURASIV N process (54). The removal of NO from flue gases can also be accomplished by adsorption. The Unitaka process utilizes activated carbon with a catalyst for reaction of NO, with ammonia, and activated carbon has been used to convert NO to N02, which is removed by scrubbing (58). Mercury is another pollutant that can be removed and recovered by TSA. Activated carbon impregnated with elemental sulfur is effective for removing Hg vapor from air and other gas streams the Hg can be recovered by ex situ thermal oxidation in a retort (60). The UOP PURASIV Hg process recovers Hg from clilor-alkali plant vent streams using more conventional TSA regeneration (54). Mordenite and clinoptilolite zeolites are used to remove HQ from Q2, clilorinated hydrocarbons, and reformer catalyst gas streams (61). Activated aluminas are also used for such applications, and for the adsorption of fluorine and boron—fluorine compounds from alkylation (qv) processes (50). 

Once formed, the primary redox products are converted in subsequent thermal reactions steps to the final compormds Area and Dox- When oxygen is the electron acceptor and a pollutant like phenol is the electron donor, carbon dioxide and water are the final redox products (Scheme 2). The primary reductive redox product is superoxide which can be converted to the strongly oxidizing OH radical via protonation, disproportionation of HO2 and reductive photocleavage of the produced H2O2. Instead of water oxidation, the oxidative primary step may consist of the oxidation of the pollutant producing a phenoxy radical and a proton. Such complete photooxidation reactions are often termed as mineralization and in general titania is employed as the photocatalyst 4-7). 

Monolithic catalytic converters continue to receive attention in the literature because of their applications in air pollution control and clean energy production. They differ from packed-bed reactors in their configuration as there are many parallel channels coated with a layer of catalyst. The flow in the channels is typically laminar. Because of its large void fraction, it is expected that the temperature transients will exhibit a significant impact on the performance of the monolith, particularly with respect to thermal stability. 

The power plants burning coal and municipal waste incinerators are sources of mercury pollution. During thermal processes, all mercury is first converted into elemental form, but during cooling different derivatives can be formed, according to the matrix composition of the flue gas. 

To be detectable, mercury must be present in elemental form. Thus for gaseous samples a thermal conditioner unit converts, in the presence of a catalyst, all mercury species present in the sample into elemental form. For liquid samples as polluted water, a first treatment by an acidic oxidizing mixture exchanges mercury compounds into Hg(II) ions that are then reduced to elemental mercury with a tin salt. 

The most abundant carbon-containing compound in the stratosphere and mesosphere is carbon dioxide (CO2). By interacting with infrared radiation, this gas plays an important role in the thermal budget of the atmosphere, and the 30% increase in its concentration resulting mainly from fossil fuel burning has provided a significant forcing to the climate system of about 1.5 Wm 2 (IPCC, 2001). Carbon dioxide does not play any substantial role in the chemistry of the atmosphere except in the lower thermosphere, where its photolysis is an important source of carbon monoxide (CO). This latter gas, which is also released at the Earth s surface by incomplete combustion (pollution) and is partially transported to the stratosphere, is converted to CO2 by reaction with the hydroxyl radical (OH). 

A variety of thermal treatment technologies can be applied to remediate organic contaminants in solid matrices. The common methodology in each of the thermal treatment techniques is to apply elevated temperatures to oxidize, pyrolyze, or volatilize combustible pollutants. The main products from the combustion processes are carbon dioxide and water. Nitrogen in the air and any halogens, phosphorus, and sulfur in the waste typically are converted to acidic vapors. 

If water is treated with ultrasonic waves, small micro-bubbles are created. Those cavitation bubbles collapse violently with adiabatic heating creating temperatures up to 5000 K and pressures of 975 bars. Under these conditions the thermal dissociation of water forms H and OH radicals. H radicals combine with present oxygen to form HO2 radicals. These and other intermediate radicals can then further react with other water ingredients. Organic pollutants are converted either by the radicals attack or they might undergo direct pyrolytic reactions in the cavitation bubbles [108-111]. 

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