Assessment of threat arising by closed - volume explosions of fuel - air mixtures

The method of estimation of maximal parameters of combustion of gaseous mixtures in closed space is presented. Estimation of chemical composition of combustion products is based on simplified rules of decomposition of reactive medium. Exemplary calculations of temperature, pressure, heat of combustion of hydrocarbon/air mixtures are presented. The accuracy of presented method was validated by comparison with calculations performed by thermodynamic numerical code that include wide list of chemical substances present in combustion products. The obtained results confirm applicability of the proposed method to predict closed space combustion parameters of gaseous mixtures. Semi-empirical methods of estimation of flammability limits are briefly referred

Methodology for studying the combustion products composition from various materials

Изложены методология и принципы лабораторного исследования состава продуктов горения различных материалов с использованием таких инструментов, как газовая и газожидкостная хроматография, масс-эффузио-спетрометрия. Большое внимание уделено применяемым в хроматографических колонках сорбентам и их температурным режимам, а также способам приготовления образцов для исследований. Рассмотрены вопросы детектирования различных компонентов в смеси продуктов горения. Результаты исследований продуктов горения разных материалов представлены в табличной форме, при этом в скобках указаны рассчитанные индексы токсичности С, оцененные по литературным данным (смертельная для человека концентрация при получасовой экспозиции). The article discusses the issues of determining the qualitative and quantitative composition of the combustion products from synthetic and natural materials. Multicomponent mixtures of volatile combustion products contain compounds of inorganic and organic origin. To determine the composition of the combustion products from various materials there is proposed the methodology and principles of laboratory research using such instruments as gas and gas-liquid chromatography, mass spectrometry, infrared and ultraviolet spectroscopy, and visible-field spectroscopy. These methods make it possible to identify certain chemicals. For example, organic compounds are analyzed by chromatography. Inorganic substances are determined by converting them into colored compounds and by analyzing their spectrum in the visible and ultraviolet regions. When developing methods of chromatographic and spectrophotometric studies, it is proposed first of all to identify the qualitative composition of combustion products based on information about the composition of polymer molecules of the studied natural or synthetic materials. Such an assessment, as an example, was made by studying the combustion products of polyethylene. The molecular weights were determined using the MX-1312 chromatomassefusiometer. To determine the molecular weight of a substance, a mathematic formula was obtained based on mathematical processing of experimental data. A special method has been developed to reduce the processing time of effusiograms (by 10-15 times). Much attention is paid to the sorbents used in chromatographic columns, their temperature conditions, and methods of preparing samples for research. Methods of identification of various components in a mixture of combustion products using various detectors are considered. The results of studies of the combustion products from different materials are presented in tabular form, with the calculated toxicity indices, С, estimated according to the literature data (lethal concentration for humans at half-hour exposure) are indicated in parentheses.

Formation of soot in the disposal of municipal solid waste

In power plants intended for the disposal of solid household waste, the processes take place at a high temperature. For such installations, nonequilibrium processes are characteristic of a change in the composition of combustion products caused by the final rates of the ongoing chemical reactions. This affects the basic characteristics of the combustion process of municipal solid waste. A mathematical model has been created for calculating the chemically nonequilibrium composition of the fuel. Solid household and industrial waste is a high-energy fuel. It is a high energy fuel. The process of thermal neutralization of solid household waste is considered. An alternative calculation method is presented that allows one to find the composition of combustion products under conditions of nonequilibrium in the process of thermal utilization of solid domestic waste. The data on the composition and properties of solid household waste obtained by the developed method of calculation allow predicting the yield of super Eco toxicants in combustion products. On the basis of the equations of formal chemical kinetics, an alternative was created, which consists in determining the composition of combustion products taking into account the kinetics of chemical reactions. The assumption is introduced that transformations in the gas phase are elementary, one-stage. Various chemical interactions can be represented by a set of elementary stages. The most probable are mono-, biand three molecular chemical reactions. The method allows predicting the yield of Eco toxicants by finding the composition of the fuel combustion products prior to its utilization.

On a composition of combustion products at a burning of methane-fluorinated hydrocarbon mixtures in air

Выполнена расчетная оценка равновесного состава продуктов горения околостехиометрических смесей вида метан - фторированный углеводород - воздух с использованием как программного комплекса Chemical Workbench, так и предложенной в настоящей работе упрощенной методики. Найдено, что основными продуктами горения являются CO, HO, CO, HF. При этом концентрации прочих продуктов горения имеют существенно более низкие значения. С помощью программного комплекса FDS выполнен расчет динамики концентраций опасных продуктов (СО, HF) в атмосфере модельного помещения объемом 12,6 м. Найдено, что для указанного помещения предельно допустимая концентрация CO достигается через 730 с после начала горения, а HF - практически мгновенно. Результаты работы могут быть полезны при применении фторированных углеводородов для пожаротушения и флегматизации горючих газовых смесей. Calculations of equilibrium compositions of combustion products at burning of near stoichiometric mixtures of methane-fluorinated hydrocarbon-air are presented. The program tool Chemical Workbench was used. Also a Simplified method was proposed. It was found that CO, HO, CO and HF are the main combustion products, and the concentration of other products are much more lower. The results of the calculations of the concentrations of the above mentioned products (CO, HO, CO and HF) by means of the simplified method are close to that obtained by the tool Chemical Workbench ones. The concentrations of CO and HF (the main hazardous products) as a function of time were determined for a typical room volume of 12, 6 m using the program tool FDS 6. It was found that a limiting allowable concentration of CO was reached after 730 s from the burning beginning, but at the case of HF this concentration was reached almost instantaneously. The results of this study can be used at an application of the fluorinated hydrocarbons for fire extinguishing and inertization of flammable gaseous mixtures.

Effects of water injection to the fuel and air mixture on equilibrium gas composition in combustion products and selected parameters of the theoretical Otto cycle

Moisturizing the intake air by spraying water in the liquid phase significantly lowers the intake air temperature, mainly due to the high value of latent heat of evaporation. The paper presents a methodology for calculating the parameters of the air-fuel mixture after water injection and during subsequent processes of the Otto cycle: compression, combustion and expansion of exhaust gases. For octane as a fuel, exemplary calculations have been carried out to investigate the effect of water injection on the composition of combustion products and selected parameters of the theoretical Otto cycle (temperature, pressure, output power and thermal efficiency).

Determination of training conditions of fire-fighters in mobile training complexes

The conditions created during training of firefighters in the mobile training complex of the Polish company «Egeria group» are considered. Currently, the determination of the parameters of the gas environment created by the combustion of pure propane (C3H8), vaseline oil and nitrogen oxide (N2O) over a period of time remains a problematic issue. At the same time, the conditions, which are created when combustion in such cameras, namely, the approximate temperature, the composition of combustion products, their volume during training in mobile training systems remain unexplored. The determination of the amount of combustion products was carried out by solving the equations for determining the material balance of the process of combustion of propane at the maximum temperature created by the mobile training complex and room temperature. As the calculations performed in the mobile training complex during the burning of propane to obtain a high temperature, the oxygen concentration in the air will remain safe - 20.16%. This will gradually increase the content of СО2, N2 and H2O vapour, since the composition of the products of combustion in the percentage ratio will be: СО2 = 11.63%; H2O = 15.5%; N2 = 72.87%.