Combustion experience

The major objective of the experimental program was to obtain data that could be used to assess the accuracy of existing models for vapor cloud dispersion. The combustion experiments were designed to complement this objective by providing answers to the question, What would happen if such a cloud ignited ... 

Initially, the number of scientific publications on combustion was very small. At that time combustion experiments were conducted at chemical laboratories. From the very beginning up to present times, chemistry has contributed a lot to the understanding of combustion at the molecular level. 

Catalytic combustion experiments have been performed in a flow reactor operating below the lower explosion limits using HC/02/He mixtures. The product analysis was done by gas chromatography. FT-IR spectra have been recorded with a Nicolet Magna 750 instrument, using conventional IR cells connected with evacuation-gas manipulation apparatus. The powder was pressed into self-supporting disks, calcined in air at 773 K and outgassed at 773 K for 20 minutes before experiments. 

The parent 1,2,4-triazole has been investigated as a potential reference compound for use in combustion experiments of compounds that contain nitrogen atoms using a micro-bomb calorimetry experiment. Urea was used previously as a standard but the chemical and physical stability of 1,2,4-triazole lends itself to such a role <2000MI949>. 

To validate the numerical work and to study the phenomena that play a role in fixed bed combustion, experiments with a fixed bed reactor (Fig. 8.8) were performed [15]. Essentially, the reactor consists of an insulated metal tube filled with biomass. The biomass is ignited at the top, while air is supplied at the bottom of the reactor. The conversion front can be tracked with thermocouples. A mass balance is used to record the conversion of the biomass. As the results of the previous section are for coal conversion, the two sets of results can not yet be compared directly. 

The basic output from a combustion experiment made with an isoperibol calorimeter is a temperature-time curve, such as the one represented in figure 7.2. In the initial or fore period (between ta and tf and in the final or after period (between tf and tf), the observed temperature change is governed by the heat of stirring, the heat dissipated by the temperature sensor, and the heat transfer between the calorimeter proper and the jacket. The reaction or main period begins at tu when, on ignition, a rapidtemperature rise results from the exothermic... 

Each of these dissociation reactions also specifies a definite equilibrium concentration of each product at a given temperature consequently, the reactions are written as equilibrium reactions. In the calculation of the heat of reaction of low-temperature combustion experiments the products could be specified from the chemical stoichiometry but with dissociation, the specification of the product concentrations becomes much more complex and the s in the flame temperature equation [Eq. (1.11)] are as unknown as the flame temperature itself. In order to solve the equation for the n s and T2, it is apparent that one needs more than mass balance equations. The necessary equations are found in the equilibrium relationships that exist among the product composition in the equilibrium system. 

Thus methyl radicals are consumed by other methyl radicals to form ethane, which must then be oxidized. The characteristics of the oxidation of ethane and the higher-order aliphatics are substantially different from those of methane (see Section HI). For this reason, methane should not be used to typify hydrocarbon oxidation processes in combustion experiments. Generally, a third body is not written for reaction (3.85) since the ethane molecule s numerous internal degrees of freedom can redistribute the energy created by the formation of the new bond. 

Under atmospheric conditions, a low rank coal (0.5-1 mm particle size) from Spain was burned in a fluidized bed reactor at seven different temperatures (50 °C increments) beginning at 650 °C. The combustion experiment was also conducted at different amounts of excess oxygen (5 to 40%) and different flow rates (700 to 1,100 L/h). At 20% excess oxygen and a flow rate of 860 L/h, the amount of acenaphthene emitted ranged from 1,272.4 ng/kg at 650 °C to 6,800.0 ng/kg at 750 °C. The greatest amount of PAHs emitted was observed at 750 °C (Mastral et al., 1999). 

Under atmospheric conditions, a low rank coal (0.5-1 mm particle size) from Spain was burned in a fluidized bed reactor at seven different temperatures (50 °C increments) beginning at 650 °C. The combustion experiment was also conducted at different amounts of excess oxygen (5 to... 

In this step, experiments may be performed such as operational tests, mixing experiments, combustion experiments and other types of experiments. Simulations can be performed with similar parts or samples in an attempt to recreate the situation at the time of the failure. Pilot nms of the process or system may also be performed. 

If one is able to collect the combustion products after a combustion experiment, the combustion temperature can be determined from the energy conservation relationship for the reactants and products. For example, when iron and potassium perchlorate react to produce heat, the reaction products and heat of reaction, Q(r), can be determined by reference to thermochemical tables (NASA SP-273). In this case, the reaction of iron (0.84 mass fraction = 0.929 moles) and potassium perchlorate (0.16 mass fraction = 0.071 moles) is represented by... 

Apparent activation energies in the range 70-90 kJ mol are typically obtained in dry (i.e. no H2O in the feed) combustion experiments when assuming simple first-order kinetics in CH4 combustion. However, it has been emphasized that such activation energies must be corrected to higher values by properly accounting for H2O inhibition [78]. 

In combustion experiments, there are two key considerations first, generating a flame and second, detecting the species of interest. Gaseous flows in a flame can be classified as laminar (streamlined layers) or turbulent. While these flames can be analyzed directly, it is less confounding to study flame chemistry through controlled generation of reactive species in one of a wide variety of experimental apparata. 

A larger-scale tyre combustion experiment was performed by Lemieux Ryan (1993) in order to collect emission data from a simulated open waste tyre fire. In addition to identifying a large number of organic compounds, including... 

Howe, W. C. 1991. Fluidized bed combustion experience with waste tires and other alternate fuels. Proceedings 1991 Conference on Waste Tires as a Utility Fuel. Electric Power Research Institute, Palo Alto, CA, EPRI GS-7538, 10/1-10/20. 

For CO, reforming of methane. KIT-1 performed better than Al20, or La,0 as support. Ni/KIT-1 co-impregnated with 3 wt% Ca lasted 20 h without deactivation, and CO, and methane conversions close to the thermodynamic equilibrium were obtained. According to TG/DTA. coke formed during a given reaction increased in the order of Ni/Ca/KIT-1 < Ni/K1T-1 < Ni/Al,0, < ICI 46-1. Methane combustion study showed the activity pattern of Pd/KIT-1 > Pd/MCM-41. Pd/HMS > Pd/Al,0, > Pd/SiO,. MIBK combustion experiment demonstrated that catalyst ignition temperature can be lowered by ca. 30-35 °C when Pt was supported on KIT-1. MCM-41. MCM-48 and HMS produced similar results. 

To use particles in combustion experiments, it is often necessary to know their size and distribution. Single drops suspended from silica filaments may easily be measured by photographic means. However, when the drops are small and moving at high velocity, the problem becomes much more difficult. 

Determine the molecular formula of a compound of molecular weight 80 and elemental percentage composition by weight of C = 45.00, H = 7.50, and F = 47.45. Write structures for all the possible isomers having this formula. (See Exercise 1-15 for a description of how percentage composition is determined by combustion experiments.)... 

A 115-mg sample of eugenol, the compound responsible for the odor of cloves, was placed in an evacuated flask with a volume of 500.0 mL at 280.0°C. The pressure eugenol exerted in the flask under those conditions was found to be 48.3 Torr. In a combustion experiment, 18.8 mg of eugenol burned to give 50.0 mg of carbon dioxide and 12.4 mg of water. What is the molecular formula of eugenol ... 

Results from a subsequent in situ combustion experiment on this site (18), to produce shale oil from oil shale, indicated that combustion could be sustained in an explosively fractured zone. 

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