Thermal Abatement

The following reactions take place in the reducing section  

N2O From a Waste Compound to a Reactant for Downstream Applications 

A growing number of gas-phase applications are being investigated in which N2O is the co-reactant, for example, the oxidation of methane to methanol, the epoxidation 

In the BIC/Solutia process, using a zeolite that contains only small amounts of iron, benzene can be oxidized to phenol with a selectivity of over 95% at around 300 °C, but N2O selectivity is lower than 95% [He]. 

Despite the remarkable performance of this innovative process, which was scaled up to the pilot unit, the BIC/Solutia process has not yet been put into commercial operation. This may be due to rapid catalyst deactivation caused by tar deposition, to low efficiency with respect to N2O and to the poor economics of such small-sized phenol plants, suited to balance the AA process unit, as compared to bigger, traditional plants for phenol production. An alternative option would be to build large phenol plants and produce N2O separately. For instance, a patent belonging to Solutia [llg] discusses the use of a Bi/Mn/Al/0 catalyst for the oxidation of ammonia to nitrous oxide. N2O selectivity is reported to be about 92% at 99.2% conversion. The cost of N2O is projected to be about 25% that of H2O2 [llh]. 

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Figure 7.6 shows a simplified outline of the reductive thermal abatement process. 

TABLE 25-28 Thermal Afterburners Conditions Required for Satisfactory Performance in Various Abatement Applications... 

Thermal and catalytic incinerators, condensers, and adsorbers are the most common methods of abatement used, due to their ability to deal with a wide variety of emissions of organic compounds. The selection between destruction and recovery equipment is normally based on the feasibility of recovery, which relates directly to the cost and the concentration of organic compounds in the gas stream. The selection of a suitable technology depends on environmental and economical aspects, energy demand, and ease of installation as well as considerations of operating and maintenance. 7 he selection criteria may vary with companies or with individual process units however, the fundamental approach is the same. 

When a mixture of compounds is to be treated, more limitations may be placed upon the selection of a suitable abatement method. There may be several compounds in the waste gas, some being unsuitable to one method, while others are unsuitable to another method. In such cases, thermal incineration may be the best solution. When recovering mixtures, additional separation equipment may be needed for recycling the reclaimed compounds. 

Photocatalysis is a fundamental feature of life processes on our planet [1] (it provides photosynthesis in plants and bacteria) and of the chemistry of its atmosphere [2]. Work is under way to develop photocatalytic technologies for abatement of environmental problems [3,4]. Photocatalysis is anticipated to become in the coming years important also for selective organic synthesis [4]. In a more distant future thermal catalytic processes induced by heating with solcir radiation, together with photocatalytic processes may become important for environmentally friendly technologies of solar energy utilization [5-9]. 

McAdams, R. (2001) Prospects for non-thermal atmospheric plasmas for pollution abatement, J. Phys. D Appl. Phys. 34, 2810-21. 

Hammer, T. (2002) Non-thermal plasma application to the abatement of noxious emissions in automotive exhaust gases, Plasma Sources Sci. Technol. 11, A196-A201. 

An electrostatic dust ignition can occur when the discharge releases sufficient thermal energy within a sufficiently short period of time and small volume to ignite the suspended dust. Electrostatic ignition is complicated by the fact that there are a number of distinct ESD mechanisms important in electrostatic hazards and hazard abatement (Glor, 1988). 

Supported metal catalysts are used in a large number of commercially important processes for chemical and pharmaceutical production, pollution control and abatement, and energy production. In order to maximize catalytic activity it is necessary in most cases to synthesize small metal crystallites, typically less than about 1 to 10 nm, anchored to a thermally stable, high-surface-area support such as alumina, silica, or carbon. The efficiency of metal utilization is commonly defined as dispersion, which is the fraction of metal atoms at the surface of a metal particle (and thus available to interact with adsorbing reaction intermediates), divided by the total number of metal atoms. Metal dispersion and crystallite size are inversely proportional nanoparticles about 1 nm in diameter or smaller have dispersions of 100%, that is, every metal atom on the support is available for catalytic reaction, whereas particles of diameter 10 nm have dispersions of about 10%, with 90% of the metal unavailable for the reaction. 

The transformation of straw and agrofood residues with high sulfur and ash content requires the development of materials for sulfur abatement at high temperature, tar cracking and as monolith for syngas production by exothermic or autothermal processes thanks to catalysts supported on materials with a high thermal conductivity. 

Smoke abatement from the thermal reduction batch processor (TRBP) smoking rooms and the measurement and management of carbon monoxide and other products of incomplete combustion generated in these rooms. (These processes were not adequately addressed in the EDP.)... 

The carbon micronization system (CMS) is used for the disposal of agent-contaminated, activated charcoal that was used as an agent filtration medium in the pollution abatement system of the plant cascade ventilation system. CMS is a system that grinds the solid carbon granules into micronized particles so that the carbon can be thermally treated in its furnace. 

Chemical, Physical, and Mechanical Tests. Manufactured friction materials are characterized by various chemical, physical, and mechanical tests in addition to friction and wear testing. The chemical tests include thermogravimetric analysis (tga), differential thermal analysis (dta), pyrolysis gas chromatography (pgc), acetone extraction, liquid chromatography (lc), infrared analysis (ir), and x-ray or scanning electron microscope (sem) analysis. Physical and mechanical tests determine properties such as thermal conductivity, specific heat, tensile or flexural strength, and hardness. Much attention has been placed on noise /vibration characterization. The use of modal analysis and damping measurements has increased (see Noise POLLUTION AND ABATEMENT). 

To maintain environmental impact at a minimum, cooling-tower systems must be designed to abate both thermal and chemical pollution in blowdown stream. The latter is accomplished by treating blowdown prior to discharge or reuse. Sedimentation and other methods prepare blowdown streams for discharge to the natural environment. Evaporation or reuse permits a closed cooling system. 

On a different front, one of the first successful modelings of a practical combustion system was achieved, that of the formation of NO in a jet engine combustor.227 The method proposed for nitric oxide abatement is being incorporated into the next generation of aircraft jet engines. Later, essentially complete agreement between experiment and numerical modeling was achieved for the thermal explosions of methyl isocyanide in spherical vessels.228... 

Dell Abate, M. T., Canali, S., Trinchera, A., Benedetti, A., and Sequi, P. (2000). Thermal methods of organic matter maturation monitoring during a composting process. J. Ther. Anal. Cal. 61, 389-396. 

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