Combustion techniques

Finally, it is by means of synergy between the refining processes and the combustion techniques that the emissions of NO due to industrial installations can be minimized. 

Combustor. In the majority of MHD plant designs the MHD combustor bums coal directly. Because MHD power generation is able to utilize pulverized coal in an environmentally acceptable fashion, there is usually no need to make cleaner fuels from coal, eg, by gasification or by beneficiation. A discussion of combustion techniques for MHD plants is available (70). 

The main combustion pollutants are nitrogen oxides, sulfur oxides, carbon monoxide, unbumed hydrocarbons, and soot. Combustion pollutants can be reduced by three main methods depending on the location of thek appHcation before, after, or during the combustion. Techniques employed before and after combustion deal with the fuel or the burned gases. A thkd alternative is to modify the combustion process in order to minimise the emissions. 

The simultaneous analysis of orthophosphate, glycerol phosphates, and inositol phosphates has been achieved by spectrophotometric analysis of the molybdovanadate complexes. Also, a sensitive and selective chemiluminescent molecular emission method for the estimation of phosphorus and sulphur is described, which is based on passing solutions into a cool, reducing, nitrogen-hydrogen diffusion flame. For organic compounds it was usually necessary to prepare test solutions by an oxygen-flask combustion technique. 

The basis of all combustion techniques is the removal of carbon as CO2 and hydrogen as H2O. When determining... 

Principles and Characteristics Combustion analysis is used primarily to determine C, H, N, O, S, P, and halogens in a variety of organic and inorganic materials (gas, liquid or solid) at trace to per cent level, e.g. for the determination of organic-bound halogens in epoxy moulding resins, halogenated hydrocarbons, brominated resins, phosphorous in flame-retardant materials, etc. Sample quantities are dependent upon the concentration level of the analyte. A precise assay can usually be obtained with a few mg of material. Combustions are performed under controlled conditions, usually in the presence of catalysts. Oxidative combustions are most common. The element of interest is converted into a reaction product, which is then determined by techniques such as GC, IC, ion-selective electrode, titrime-try, or colorimetric measurement. Various combustion techniques are commonly used. 

Takashiba, N., Nira, M., Kojima, S., Take, H., and Yoshikawa, F., Development of the Post Combustion Technique in Combined Blowing Converter, Tetsu to Flagane, 75 89 (1989)... 

These instruments employ a continuous flow of persulfate solution to promote oxidation prior to ultraviolet irradiation, and have a low system blank and low detection limit. Since all reactions take place in the liquid phase, problems suffered by combustion techniques, such as catalyst poisoning, reactor corrosion, and high-temperature element burnouts, are obviated. However, the ultraviolet-promoted chemical oxidation technique is not designed to handle particulate-containing samples, and tends to give incomplete oxidation for certain types of compounds such as cyanuric acid. 

Gershey et al. [58] have pointed out that persulfate and photo-oxidation procedures will determine only that portion of the volatile organics not lost during the removal of inorganic carbonate [30,79,92,181]. Loss of the volatile fraction may be reduced by use of a modified decarbonation procedure such as one based on diffusion [98]. Dry combustion techniques that use freeze-drying or evaporation will result in the complete loss of the volatile fraction [72,79, 92,93],... 

Improved furnace designs and combustion techniques could reduce NOx emissions from stationary sources by 40-70%. These methods are not in widespread use now. The processes for removing NOx from flue gases are in an early stage of development. 

ASTM D126 IP 107) that uses a modification of the standard wick-fed lamp. Many laboratories use rapid combustion techniques with an oxyhydrogen flame in a Wickbold or Martin-Floret burner (ASTM D2784 IP 243). 

Legislative restrictions on pollutant emissions have motivated the combustion community to seek new low-emission combustion techniques that are practical industrial energy sources. However, to meet the needs in most industrial applications, a combustion source needs to be able to maintain low-emission output over a range of heat release rates, occupy minimal volume, and have low operating costs per unit energy produced. One would like to maximize the turn-down ratio, volumetric heat release, and overall thermal efficiency while minimizing NOa , CO, and hydrocarbon emission levels. The ultra-low NO, emission performance of the CSC has been previously documented by the authors and its... 

Iron Estimations. These were carried out by extracting the iron with "iron-free HC1 (/—0.2 p.p.m.), followed by measurement using a square w ave polarograph. Reproducibility and accuracy on samples in which known amounts of ferric acetylacetonate had been placed were poor (zb50%). Wet combustion techniques followed by estimations using the square wave polarograph gave worse results than the procedure described. 

According to equilibrium calculations, CO and NO are only important at high temperatures. As the temperature decreases, CO and NO are converted to CO2 and N2, respectively, and the exhaust concentrations are estimated to be below 1 ppm. Furthermore equilibrium calculations indicate that any NO in the exhaust will be present as NO2, and not NO. Comparison with values observed in combustion exhaust shows that neither CO nor NO is in equilibrium. Carbon monoxide emissions range from 10 ppm to 1%, depending on the fuel and the combustion technique. For nitrogen oxides, emissions can be significant from combustion systems and most (about 95%) of the NO emitted is in the form of NO, not N02. 

Selenium can also be separated from the bulk of the coal samples by the combustion technique described by H. L. Rook (7), which was originally used in a neutron activation analysis. The equipment was... 

For general purpose tracer work, however, and particularly in polymer chemistry, the liquid scintillation counter surpasses all other instruments in its sensitivity and adaptability. There is no question on the author s mind that at the present time such an instrument would be the first choice, particularly where tritium, carbon-14 or sulphur-35 were involved. Samples for assay are dissolved in a phosphor whose major solvent usually consists of toluene, toluene-alcohol, or dioxan. Many polymers and low molecular weight compounds are readily soluble in these solvents. Prospective users should not be deterred by alleged complications due to "variable quench effects" as these effects are readily corrected for via internal or external standards or the channels ratio method (7, 46, 91). Dilution quench corrections, though valid, are tedious and unnecessary. Where samples are insoluble in phosphor they may be suspended (e.g. as gels or as paper cut from chromatograms, etc.) or they can be burnt and the combustion products absorbed in a suitable phosphor solution. A modification of the Schoniger flask combustion technique is particularly suitable for this purpose (43—45). 

Biogenic silicon (BSI) was determined, with minor modifications, by the method of DeMaster (17). As adapted, the technique involved time-course leaching of <20-mg samples of particulate matter in 30 mL of 1.0% Na2C03 in a water bath at 85 °C. Silica in leachates was quantified either colorimetrically (Technicon autoanalyzer procedure) or by nitrous oxide flame atomic absorption. A high-temperature catalytic-combustion technique (Perkin Elmer 240C) was used for particulate organic carbon determinations. Particulate inorganic (carbonate) carbon was measured on the same instrument by CO 2 evolution after treatment of the particles with phosphoric acid. 

The above work concentrated most of its attention on the use of zinc chloride as the molten halide and on the use of bituminous coal extract as feed to the process. Hydrocracking of the extract (1) and regeneration by a fluidized-bed combustion technique of the spent catalyst melt (2) from the process were both demonstrated in continuous bench-scale units. 

On the other hand, the use of the total count method (7) largely forfeits the advantages which are inherent in the tracer method. Because the samples are extracted rather than assayed by combustion techniques, incomplete material recovery becomes a contributing factor. Furthermore, since the extracts are counted without preceding purification, the results cannot discriminate between residual gibberellie acid and possible degradation products. In spite of potentially increased sensitivity, the total count method offers no advantages over the bioassay or fluorometric procedures. 

Soviet researchers indicated that thermal stimulation from above the ground was not economically viable. Trofimuk et al. (1982) suggested alternatives of pressure reduction, inhibitor injection, geothermal stimulation, or in situ combustion techniques. Recovery techniques modeled in the Western Hemisphere were by either pressure reduction or thermal stimulation. The first of these was by McGuire (1982), followed by Holder et al. (1984a), Burshears et al. (1986), and workers in the CSM laboratory (Selim and Sloan, 1985, 1987, 1989 Yousif et al., 1988, 1990). 

Tefft, M. L., and G. M. Gustin Improved Combustion Techniques for the Microdetermination of Nitrogen in Organic Compounds with an Automatic Analyzer. Microchem. J. 10, 175 (1966). 

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