Stoichiometry combustion analysis

The assumption is made at present that elemental combustion analysis for carbon, hydrogen, and fluorine provides a good approximation to the extent of incorporation of fluoroalkyl residues, i.e. alcohols and ethers. We have ruled out trifluoromethylcarbonyl groups since no evidence is seen for their presence in either the infrared spectra or the 19F-NMR spectra. Thus, our values for percent modification reflect the best fit of the combustion data to an idealized stoichiometry for the product in Equation 1, where (m+n+o) = 100, and the percent modification (% mod.) is given by the expression [100 x (m+o)/(m+n+o)], equivalent to the number of fluoroalkyl residues per one hundred methylenes. An appropriately normalized formula was used to fit the data for polypropylene (sample 10). 

Treatment of a benzene solution of VI with an excess of nickel chloride in methanol resulted in the precipitation of a yellow powder. This was recrystallized from methanol to give air-stable yellow-orange crystals (60%) with the stoichiometry (VI) NiCl2 -3MeOH (by combustion analysis). When this recrystallized complex was treated with excess aqueous sodium cyanide in the presence of CgDg at room temperature for 10 min VI was regenerated, but now the 3 3P NMR absorptions at 6 -58.1 and -64.0 ppm were in an area ratio of 95 5. Similar treatment of VII with nickel chloride led to a dark oily precipitate which required considerable manipulation to partially purify it. Treatment with sodium cyanide as above led to the regeneration of VII also enriched in the major isomer (85 15). 

In flame calorimetry, it is not easy to measure directly with good accuracy the mass of reactants consumed in the combustion. Therefore, the results are always based on the quantitative analysis of the products and the stoichiometry of the combustion process. In the case of reaction 7.73, the H20 produced was determined from the increase in mass of absorption tubes such as M, containing anhydrous magnesium perchlorate and phosphorus pentoxide [54,99], When organic compounds are studied by flame combustion calorimetry, the mass of C02 formed is also determined. As in bomb calorimetry, this is done by using absorption tubes containing Ascarite [54,90]. 

Paper II presents a hypothetical method to indirectly measure the key quantities of a PBC, that is, the mass flow and the stoichiometry of the conversion gas, as well as the air excess numbers of the conversion and combustion system, defined in paper I. It also includes a measurement uncertainty analysis. 

A theoretical model of the combustion of biomass is illustrated by the complete oxidation of giant brown kelp. Note that kelp, for which complete analytical data were available, is used here simply to illustrate the utility of the model, which is applicable to all biomass species. Based on the empirical formula derived from the elemental analysis of dry kelp at an assumed molecular weight of 100, the combustion stoichiometry is... 

An analysis of the thermodynamic data (7) revealed that the amount of remaining combustible components strongly depends on the specific character of the chosen oxide. Based on the thermodynamic data for a more accurate stoichiometry for the reduced iron oxide, i.e. Feo.9470, a CO2/CO ratio of only 2.2 will be established above the oxide, a ratio far less favourable for an efficient conversion of the producer gas. This deviation... 

Samples of various stoichiometries were prepared by sintering mixtures of the hydrides and graphite in the appropriate ratios under vacuum ca. 10 bar) at 1673 K. Determination of carbon (combustion), oxygen and nitrogen (reducing fusion under He), as well as phase analysis (X-ray diffraction and metallography) are mentioned, but no details were given. Elementary analysis indicated metallic impurities in amoimts smaller than 300 parts per million. 

We have already discussed under practical stoichiometry how the air requirements can be estimated based on the fuel composition (ultimate analysis). The primary and secondary air requirements for combustion of pulverized coal or coke are best estimated by mass and heat balance at the mill. In Appendix 6A we show a calculation taken from Musto (1997) for the primary and secondary air required for coal pulverizer with 4.5 metric ton per hour (10,0(X)lb/hr) coal feed rate at initial moisture of 15 percent which is required to be ground and dried to 2 percent with a 200 HP mill. In order to estimate the actual primary and secondary air, one has to make some estimation of the evaporation rate, the amount of gas entering the coal mill, and the bleed air required so that the quantity of air that should be vented from the hood off-take can be properly estimated. It shows that for a take-off gas temperature of 315°C (600° F) and vent gas temperature of 76°C (170°F) and allowing ambient air infiltration of 10 percent at 15°C (60°F) the primary air will be about 22 percent of stoichiometric air and 21 percent of total air. The remaining air (about 79 percent) will be the secondary air. With this information we can size a burner using a burner pipe diameter based on a Craya-Curtet parameter of choice bearing in mind the conditions that ensure the desired jet recirculation patterns described in Chapter 3. 

---