Combustion, catalytic

Today the removal of hydrocarbons, with boiling points higher than CO2, is carried out almost exclusively by catalytic combustion. The potassium permanganate wash once used for oxidising easily oxidable hydrocarbons is nowadays only used for the purification of CO2 obtained in connection with fermentation processes (e.g. in breweries). 

The catalytic oxidation takes place with precious metal catalysts (platinum and/or palladium on aluminium oxide carriers) at temperatures between 200 and 600 °C. When the reactor exit temperature reaches only about 450 °C the remaining methane has to be removed in the CO2 stripper. If the required oxygen is added to the CO2 in the form of air, then the nitrogen mixed with the CO2 has also to be separated again in the COj stripper. The CO2 partial pressure is lower and therefore the recovery rate is lower (see Fig. 6.6). 

4 Improvement ofthe Carbon Dioxide Recovery Rate 

With low concentration of CO2 in the raw gas, the CO2 recovery rate at common liquefaction temperatures is small, as is apparent from Fig. 6.6. An improvement in the recovery rate can, for example, be achieved by means of lower hquefaction temperatures. In order to avoid the required installation ofa cascade refrigeration unit with different refrigerants and additional compressors and equipment, liquefied CO2 can be used as refrigerant for the cold generation in a so-called open refrigeration cycle at a sufficiently low temperature level. 

A large part of the CO2 in the residual gases of the stripping column and the liquefier can be liquefied against evaporating CO2, at —50 °C, for example. The liquefied CO2 is separated and evaporated at about 5.5 bara. The evaporation enthalpy is exactly adequate to compensate the required liquefaction enthalpy. The evaporated CO2 is mixed with the inlet flow of the second stage of the COj compressor. Thus the open CO2 cycle with only small amounts of additional equipment (see process flows depicted in bold print in Fig. 6.9) represents an economical alternative to a cascade refrigeration unit. 

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Final purification of argon is readily accompHshed by several methods. Purification by passage over heated active metals or by selective adsorption (76) is practiced. More commonly argon is purified by the addition of a small excess of hydrogen, catalytic combustion to water, and finally redistiHation to remove both the excess hydrogen and any traces of nitrogen (see Fig. 5) (see Exhaust control, industrial). With careful control, argon purities exceed 99.999%. 

A flame-ionization, total hydrocarbon analyzer determines the THC, and the total carbon content is calculated as methane. Other methods include catalytic combustion to carbon dioxide, which may be deterrnined by a sensitive infrared detector of the nondispersive type. Hydrocarbons other than methane and acetylene are present only in minute quantities and generally are inert in most appHcations. 

PGM catalyst technology can also be appHed to the control of emissions from stationary internal combustion engines and gas turbines. Catalysts have been designed to treat carbon monoxide, unbumed hydrocarbons, and nitrogen oxides in the exhaust, which arise as a result of incomplete combustion. To reduce or prevent the formation of NO in the first place, catalytic combustion technology based on platinum or palladium has been developed, which is particularly suitable for appHcation in gas turbines. Environmental legislation enacted in many parts of the world has promoted, and is expected to continue to promote, the use of PGMs in these appHcations. 

Catalytic combustion is feasible for purification processes only when impurities are at concentrations <10% of lower flammabiUty limit and when bulk stream already consists of oxidation products, eg, airstreams, off-gases, and other inerts. 

Gaseous vent streams from the different unit operations may contain traces (or more) of HCl, CO, methane, ethylene, chlorine, and vinyl chloride. These can sometimes be treated chemically, or a specific chemical value can be recovered by scmbbing, sorption, or other method when economically justified. Eor objectionable components in the vent streams, however, the common treatment method is either incineration or catalytic combustion, followed by removal of HCl from the effluent gas. 

P. Kesselting, Catalytic Combustion, ia F. Weiaberg, ed.. Advanced Combustion Methods, Academic Press, Inc., New York, 1986. 

The main converter, which is located downstream of the EHC, heats to functional temperature much more quickly because of catalytic combustion of exhaust gases that would otherwise pass unconverted through the catalyst during the cold start period. The EHC theoretical power required for a reference case (161) was 1600 watts to heat an EHC to 400°C in 15 s in order to initiate the catalytic reactions and obtain the resultant exotherm of the chemical energy contained in the exhaust. Demonstrations have been made of energy requirements of 15—20 Wh and 2 to 3 kW of power (160,161). Such systems have achieved nonmethane HC emissions below the California ULEV standard of 0.025 g/km. The principal issues of the EHC are system durabihty, battery life, system complexity, and cost (137,162—168). 

Baking Particulates (dust), CO, SO2, hydrocarbons, and fluorides High-efficiency cyclone, electrostatic precipitators, scrubbers, catalytic combustion or incinerators, flares, baghouse... 

New research in combustors such as catalytic combustion have great promise, and values of as low as 2 ppm can be attainable in the future. Catalytic combustors are already being used in some engines under the U.S. Department of Energy s (DOE), Advanced Gas Turbine Program, and have obtained very encouraging results. 

Catalytic combustion is a process in which a combustible compound and oxygen react on the surface of a catalyst, leading to complete oxidation of the compound. This process takes place without a flame and at much lower temperatures than those associated with conventional flame combustion. Due partly to the lower operating temperature, catalytic combustion produces lower emissions of nitrogen oxides (NOx) than conventional combustion. Catalytic combustion is now widely used to remove pollutants from... 

Dalla Betta, Ralph A., Nicholas, S.G., Weakley, C.K., Lundberg, K., Caron, T.J., Chamberlain, J., and Greeb, K., Field Test of a 1.5 MW Industrial Gas Turbine with a Low Emissions Catalytic Combustion System, ASME 99-GT-295. 

Dutta, P., Cowell, L.H., Yee, D.K., and Dalla Betta, R.A., Design and Evaluation of a Single-Can Full Scale Catalytic Combustion System for Ultra-Low Emissions Industrial Gas Turbines, ASME 97-GT-292. 

These two research areas share the common characteristic of involving inorganic solids in the combustion process. Catalytic combustion research focuses on using the solid to facilitate the oxidation of well-known fuels such as hydrogen and methane. Materials synthesis research focuses on using combustion as a means to react the solids either with each other or a gas, such as nitrogen (which in this case acts as an oxidizer), to make new solid materials. 

With Recup. Inch generator Ceramic 2.5 5.3 30. 08. 30. 03 (catalytic combustion) Capstone... 

The advantage is an oxidation temperature of 500°F compared to non-catalytic combustion of 1500°F. The active ingredients used were platinum, as well as the base metal oxides of cobalt, nickel, manganese, chromium, and iron. The support material included nickel-chromium ribbons, ceramics rods, beads, and pellets (13-17). 

Hikiforov N.N. Bakham, The Effect of Aluminum Additives On the Operational Effectiveness of the Catalytic Combustion Agent Fe203 , Rept No FTD-HT-23-627-74 (1973)... 

G.L. Haller, and S. Kim. ACS Petroleum Division Preprints, Symposium in Catalytic Combustion in 213th National ACS Meeting, 155-158 (1997, April 13-17) San Francisco, CA. 

M. Haruta, A. Ueda, S. Tsubota, and R.M.T. Sanchez, Low-temperature catalytic combustion of methanol and its decomposed derivative over supported gold catalysts, Catalysis Today 29, 443-447 (1996). 

Hayes, R.E. and Kolaczkowski, S.T. (1997) Introduction to Catalytic Combustion, Gordon and Breach Science Publishers, Amsterdam. 

Qean and efficient processes production of at) mc chemicals witiiout salt, replaconent of HE or H2SO4, catalytic combustion, hi tempoature selective oxidation firel cells ... 

Catalytic combustion of diesel soot particulates over LaMnOs perovskite-type oxides prepared by malic acid method has been studied. In the LaMn03 catalyst, the partial substitution of alkali metal ions into A site enhanced the catalytic activity in the combustion of diesel soot particulates and the activity was shown in following order Cs>K>Na. In the LarxCs MnOj catalyst, the catalytic activity increased with an increase of X value and showed constant activity at the substitution of x>0.3... 

In such a device, the electrons liberated at the anode by the oxidation of methanol circulate in the external electrical circuit, producing electrical energy, and reach the cathode, where they reduce the oxidant, usually oxygen from air. The overall reaction thus corresponds to the catalytic combustion of methanol with oxygen, i.e.,... 

H. Sadamori, T. Tanioka and T. Matsuhisa, "Proceedings of the International Workshop on Catalytic Combustion", Ed., H. Arai, Catalysis Society of Japan, (1994), pi 58... 

Fig. 8 Catalytic combustion of methane over LaBAliiOi9-o (B = Cr, Mn, Fe, Co, Ni, and Cu). Reaction condition is the same in Figure 7...

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