Exhaust gases treatment converters

M ass Transfer. Exhaust gas catalytic treatment depends on the efficient contact of the exhaust gas and the catalyst. During the initial seconds after start of the engine, hot gases from the exhaust valve of the engine pass through the exhaust manifold and encounter the catalytic converter. Turbulent flow conditions (Reynolds numbers above 2000) exist in response to the exhaust stroke of each cylinder (about 6 to 25 times per second) times the number of cylinders. However, laminar flow conditions are reached a short (- 0.6 cm) distance after entering the cell passages of the honeycomb (5,49—52). 

Combustion Many organic compounds released from manufacturing operations can be converted to innocuous carbon dioxide and water by rapid oxidation (chemical reaction) combustion. However, combustion of gases containing halides may require the addition of acid gas treatment to the combustor exhaust. 

Oxygen sensors in automotive applications are used to measure the air fuel (A/F) ratio of engine exhaust gases and to control the optimum A/F ratio for perfect exhaust gas after-treatment by catalytic converters [1]. Therefore, they are also known as lambda or A/F ratio sensors. 

A benefit of stoichiometric engine operation, besides the maximized power density, is in fact the possibility to reduce NOx-emissions to negligible levels by using exhaust gas after-treatment systems [64]. With conventional automotive catalytic converters conversion ratios of more than 99.9 % percent can be reached. 

The actual metal treatment applied depends on the type of product made. BAT is to collect the exhaust gas from AOD converters using a roof canopy and to collect and treat the off-gas from nodularisation, using a bag filter. BAT is also to make the MgO-dust available for recycling. 

Carbon dioxide removal by reactive absorption in amine solutions is also applied on the commercial scale, for instance, in the treatment of flue gas (see later in this chapter). Another possible application field of the technique is gas desulfurization, in which H2S is removed and converted to sulfur by means of reactive absorption. Aqueous solutions of ferric chelates (160-162) as well as tetramethylene sulfone, pyridine, quinoline, and polyglycol ether solutions of S02 (163,164) have been proposed as solvents. Reactive absorption can also be used for NOx reduction and removal from flue or exhaust gases (165,166). The separation of light olefins and paraffins by means of a reversible chemical com-plexation of olefins with Ag(I) or Cu(I) compounds in aqueous and nonaqueous solutions is another very interesting example of reactive absorption, one that could possibly replace the conventional cryogenic distillation technology (167). 

Many gas-fired compressors that pump natural gas through millions of miles of pipelines are also equipped with exhaust catalysts to clean emissions at moderate conditions. Even fast-food restaurants are being equipped with catalysts to eliminate odors from the cooking process. The most widely used treatment of exhaust pollutants is that of the catalytic converter present in the exhaust manifold that cleans emissions from the internal combustion engines of gasoline- and diesel-fiieled automobiles and trucks. As modem commercial passenger jets fly above 30,000 feet there is a need to destroy the few ppm ozone that enters the airplane with make-up air to ensure passenger and crew comfort and safety. Radiators on select... 

C Heat exchanger D Heat storage tank E Control E Auxiliaiy burner G DC/AC converter H Gas desulphurisation unit I Water treatment J Exhaust... 

Traditionally, monolith reactors have demonstrated their performance in gas-phase reactions, particularly in the treatment of automotive exhaust gases. Today, virtually all vehicles are equipped with catalytic converters. Here we will consider three-phase applications. These have been studied by a few authors and research groups such as Moulijn and coworkers [4,5] and Irandoust and Andersson [6]. Certain industrial processes such as hydrogenation of anthraquinone in the production of hydrogen peroxide are also examples of the monolith reactor technology being established on an industrial scale. Monolith... 

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