Combustion characteristics, analysis

Xiaowei Zhang, Analysis of combustion characteristics about seven kinds of biomass charcoal, Chemistry and Industry of Forest Products, 29(2009), 2-5. 

Xiu, S., Rojanala, H.K., Shahbazi, A., et al. (2012) Pyrolysis and combustion characteristics of biooil from swine manure. Journal of Thermal Analysis and Calorimetry, vol 107, pp. 823-829. 

Chemical Composition. Chemical compositional data iaclude proximate and ultimate analyses, measures of aromaticity and reactivity, elemental composition of ash, and trace metal compositions of fuel and ash. All of these characteristics impact the combustion processes associated with wastes as fuels. Table 4 presents an analysis of a variety of wood-waste fuels these energy sources have modest energy contents. 

The formation of such materials may be monitored by several techniques. One of the most useful methods is and C-nmr spectroscopy where stable complexes in solution may give rise to characteristic shifts of signals relative to the uncomplexed species (43). Solution nmr spectroscopy has also been used to detect the presence of soHd inclusion compound (after dissolution) and to determine composition (host guest ratio) of the material. Infrared spectroscopy (126) and combustion analysis are further methods to study inclusion formation. For general screening purposes of soHd inclusion stmctures, the x-ray powder diffraction method is suitable (123). However, if detailed stmctures are requited, the single crystal x-ray diffraction method (127) has to be used. 

Chemical Analysis. The presence of siUcones in a sample can be ascertained quaUtatively by burning a small amount of the sample on the tip of a spatula. SiUcones bum with a characteristic sparkly flame and emit a white sooty smoke on combustion. A white ashen residue is often deposited as well. If this residue dissolves and becomes volatile when heated with hydrofluoric acid, it is most likely a siUceous residue (437). Quantitative measurement of total sihcon in a sample is often accompHshed indirectly, by converting the species to siUca or siUcate, followed by deterrnination of the heteropoly blue sihcomolybdate, which absorbs at 800 nm, using atomic spectroscopy or uv spectroscopy (438—443). Pyrolysis gc followed by mass spectroscopic detection of the pyrolysate is a particularly sensitive tool for identifying siUcones (442,443). This technique rehes on the pyrolytic conversion of siUcones to cycHcs, predominantly to [541-05-9] which is readily detected and quantified (eq. 37). 

The side-chain chlorine contents of benzyl chloride, benzal chloride, and benzotrichlorides are determined by hydrolysis with methanolic sodium hydroxide followed by titration with silver nitrate. Total chlorine determination, including ring chlorine, is made by standard combustion methods (55). Several procedures for the gas chromatographic analysis of chlorotoluene mixtures have been described (56,57). Proton and nuclear magnetic resonance shifts, characteristic iafrared absorption bands, and principal mass spectral peaks have been summarized including sources of reference spectra (58). Procedures for measuring trace benzyl chloride ia air (59) and ia water (60) have been described. 

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. 

The material balance is consistent with the results obtained by OSA (S2+S4 in g/100 g). For oil A, the coke zone is very narrow and the coke content is very low (Table III). On the contrary, for all the other oils, the coke content reaches higher values such as 4.3 g/ 100 g (oil B), 2.3 g/ioo g (oil C), 2.5 g/ioo g (oil D), 2.4/100 g (oil E). These organic residues have been studied by infrared spectroscopy and elemental analysis to compare their compositions. The areas of the bands characteristic of C-H bands (3000-2720 cm-1), C=C bands (1820-1500 cm j have been measured. Examples of results are given in Fig. 4 and 5 for oils A and B. An increase of the temperature in the porous medium induces a decrease in the atomic H/C ratio, which is always lower than 1.1, whatever the oil (Table III). Similar values have been obtained in pyrolysis studies (4) Simultaneously to the H/C ratio decrease, the bands characteristics of CH and CH- groups progressively disappear. The absorbance of the aromatic C-n bands also decreases. This reflects the transformation by pyrolysis of the heavy residue into an aromatic product which becomes more and more condensed. Depending on the oxygen consumption at the combustion front, the atomic 0/C ratio may be comprised between 0.1 and 0.3 ... 

Numerical studies of combustion control in simple combustors with flame holders have been made. The criterion of flame stabilization, based on the unambiguously defined characteristic residence and reaction times, is suggested and validated against numerous computational examples. The results of calculations were compared with available experimental findings. A good qualitative and reasonable quantitative agreement between the predictions and observations were attained. Futher studies are planned to include mixing between fuel jets with oxidizer and to extend the analysis to transonic and supersonic flow conditions. 

The results of calculation of AP are presented in Fig. 23.5. It can be seen from AP along the length of the combustor, the elliptic nozzles provide better combustion performance than round nozzles. A better indicator of enhancement of supersonic mixing and combustion is obtained from the analysis of the impact of the fuel supply mode on the characteristic pressure-area integral for the diverging-area supersonic combustor [6, 7]. The combustion-induced pressure-area integrals for the 2D combustor (Fig. 23.1a) were calculated from the measured axial wall pressure distributions from the following relationship [7]... 

Elemental composition H 1.56%, Te 98.44%. The gas is identified by its physical properties and measured by chemical analysis. Two most confirmatory methods recommended here are (1) GC/MS, the characteristic mass ions should be in the range 126 to 132, and (2) furnace-AA or ICP emission spectroscopic analysis for metalic tellurium. For the AA analysis, hydrogen telluride gas should be passed through water and the solution acidified and analyzed for tellurim. Hydrogen may be measured by the classical combustion method involving oxidation to form water, followed by gravimetry. 

The swirl number, a dimensionless ratio of the angular momentum to the product of the axial momentum and the radium of the burner, can be varied through separate control of the two secondary air streams in order to study various burner designs. The air flows were measured using sharp edged orifices. Control of the air flows and calibration of the coal feeder made it possible to duplicate combustion conditions as determined both by exhaust gas analysis (CO, CO2, O2, NO, NOx) and aerosol characteristics. 

A database of chemical, mineralogical, and physical characteristics of North American fly ashes was assembled from the analysis of more than 178 samples of North American fly ash (McCarthy et al 1989). These fly ashes were derived from the combustion of five principal... 

The wide use of spray injection for the introduction of reactants into combustion chambers has pointed to the need for an analysis of the processes which govern combustion of liquid aerosols. This review presents the theoretical and experimental aspects involved in the burning of a single droplet. The application of the results obtained for a single droplet to the burning characteristics of liquid sprays remains a problem of fundamental importance in combustion research. 

There are three basic classifications (11 total calorific value types. (2) net calorific value types, and (3) inferential types. Net calorific value is less than the total calorific value by an amount equal to the latent heat of vaporization of the water formed during combustion. A net calorific value instrument uses a means that give results more nearly related to the net value. Thus, these types arc affected by gas composition and musl be calibrated for the gas to be tested. Inferential-type instruments depend upon such characteristics as flame appearance, maximum flame temperature, specific gravity, or gas analysis as indicative of the calorific value. 

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