Combustion Gas Analysis

Laboratory experiments using rodents, or the use of gas analysis, tend to be confused by the dominant variable of fuel—air ratio as well as important effects of burning configuration, heat input, equipment design, and toxicity criteria used, ie, death vs incapacitation, time to death, lethal concentration, etc (154,155). Some comparisons of polyurethane foam combustion toxicity with and without phosphoms flame retardants show no consistent positive or negative effect. Moreover, data from small-scale tests have doubtful relevance to real fine ha2ards. 

Chemical Reaction Measurements. Experimental studies of incineration kinetics have been described (37—39), where the waste species is generally introduced as a gas in a large excess of oxidant so that the oxidant concentration is constant, and the heat of reaction is negligible compared to the heat flux required to maintain the reacting mixture at temperature. The reaction is conducted in an externally heated reactor so that the temperature can be controlled to a known value and both oxidant concentration and temperature can be easily varied. The experimental reactor is generally a long tube of small diameter so that the residence time is well defined and axial dispersion may be neglected as a source of variation. Off-gas analysis is used to track both the disappearance of the feed material and the appearance and disappearance of any products of incomplete combustion. 

The analysis shallbe in the following sequence oxygen concentration, then the combustible gas or vapor. 

Bossart, C. J. 1974. Monitoring and Control of Combustible Gas Concentration Below the Eower Explosive Eimit. 20th Analysis Instrumentation Symposium. May 1974. Instrument Society of America, Pittsburgh, Pennsylvania. 

The ACF is the actual cubic feet of gas measured at t, F and P, psig. SCF represents standard conditions at 70 F and 14.6 psia. The formulas provided require input information on the pressure and temperature of the fuel gas, the fuel gas analysis by volume (or mole percent if the pressures are sufficiently low), and the percent excess air. The calculation provides the air to fuel ratio required for complete combustion. 

Most combustion equipment is not controlled by means of a feedback from flue gas analysis but is preset at the time of commissioning and preferably checked and reset at intervals as part of a planned maintenance schedule. It is difficult to set the burner for optimum efficiency at all firing rates and some compromise is necessary, depending on the control valves used and the control mode (e.g. on/off, fully modulating, etc.). 

One of several different types of flue-gas analysis equipment (such as electronic, Fyrite, or Or sat types). They are used to determine boiler fuel combustion efficiency. 

The art of analyzing gases by chemical means has made vast progress since the early researches of R. W. Bunsen. Most gas analysis apparatus, however, still contains a reservoir, a combustion chamber, and an absorption vessel, and formidable-looking apparatus is foimd on inspection to be capable of assembly by a series of moderately... 

In a somewhat different type of furnace that suffered from a combustion-gas explosion, the floor beams, which were similar in size, were deflected at most 2-3 cm. A structural analysis of this explosion led to the conclusion that peak pressures were in the order of 30-40 kN/m (5-6 psi). Comparing the two damage descriptions, it is obvious that the smelt-water explosion generated pressures well in excess of 40 kN/m on the floor. 

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. 

The course of combustion reactions during flammation has been studied 78) by the application of gas analysis techniques 40), by absorption spectra 76), by temperature measurements during combustion 95, 133-135), and by the analysis of indicator cards 25, 99,110.112). 

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. 

Analyses of Hue gases are always repotted on a volume basis, dry, when an Orsai or other type of gas analysis is used. Flue gases are cooled to room temperature and bubbled through water in most gas analyses, so that the gas becomes saturated with water vapor. This would occur even if no water vapor were formed during combustion. Proportionate parts of the water vapor content of the gas will be absorbed with the different constituents of the gas so that the resulting analysis may be safely assumed to be that of dry gas. These percentages may also be expressed as 10.4 moles COi, 2.8 moles Oi. and 86.8 moles N2 each per 100 moles of dry flue gas. 

The largest application segment for filter photometers is in the area of combustion gases analysis, primarily for CO, CO2, hydrocarbons, SO2, etc. Other major areas of application include the petrochemical industry, with natural gas and other hydrocarbon process gas streams being important applications. As measurements become more complex, there is the need for more advanced instrumentation. Variable or tunable filter solutions (as described above) or full-spectrum FTIR or NIR instruments are normally considered for these applications, primarily in terms of overall versatility. Now that array-based systems are becoming available, there is a potential for an intermediate, less expensive, and more compact solution. Note that compact instrumentation tends to be environmentally more stable, and is well suited for industrial applications. 

It is well known that most of the gaseous hydrocarbons of the aliphatic series when exploded with an excess of oxygen are converted into the end-products of combustion, carbonic acid and water. This fact is made use of in quantitative gas analysis. The combustion is often not complete intermediate products can be obtained if we start with hydrocarbon derivatives instead of the hydrocarbons themselves. 

Cupric oxide reacts with CO at temperatures which are substantially higher than those at which manganese dioxide is effective. The use of copper oxide in the combustion of CO in gas analysis is well known. By itself, it is not an effective catalyst for the oxidation of CO at ordinary temperatures. It may, however, greatly increase the activity of other oxides when used in mixtures of the proper proportion. The early work of Hofmann (23) indicated that a previously prepared surface of CuO will oxidize a mixture of CO and air, but that the rate can be increased by a factor of 3 if the copper is moistened with a little alkali. The catalytic activity is further increased if a little iridium is incorporated in the oxide. It was thought that the oxidation of CO depended upon the formation of an unstable copper peroxide of the composition, Cu203 or Cu02, which reacted with CO to form C02 and CuO. The principle was proposed for a gas generator cell of the type O/Cu/alkali/Cu/CO. The reaction was, however, too slow to be of practical importance. 

The composition of the gas is given on a volumetric basis, which is the usual way of expressing a fuel-gas analysis. To use the volumetric-analysis data in combustion calculations, they must be converted to a weight basis. This is done by dividing the weight of each component by the total weight of the gas. A volume of 1 ft3 of the gas is used for this computation. Find the weight of each... 

An attempt is made to contribute to the objective analysis of the role of PVC cabling in major fires such as that at Dusseldorf airport. Questions regarding smoke and toxic combustion gas evolved by PVC cable materials have repeatedly been posed. Today, functional fillers such as aluminium hydroxide (ATH) and magnesium hydroxide (MDH) are available to optimise PVC formulations, creating extremely low smoke and much less toxic gases. The latest research developments are illustrated using... 

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