Showing papers on "Spontaneous combustion published in 1992"

Method and device for controlling spontaneous combustion in cremation installations

Abstract: Method of automatically controlling the spontaneous combustion reaction of an organic body in an incineration furnace (1) comprising in particular a combustion chamber and a post-combustion chamber, means of injecting air and water (25, 26, 22) and a discharge chimney (24), characterised in that it comprises the continuous analysis of the opacity of the combustion smoke and the continuous measurement of the internal temperature of the furnace so that exceeding reference values for temperature and opacity causes respectively the reduction in the rate of injection of air (25) into the combustion chamber and/or the triggering of the injection of water by pulverisation onto the organic body until the conditions of the reaction return to normal.

Calorimetric Study of the Heat of Drying of a Sub-Bituminous Coal

Abstract: This paper presents recently measured heats of drying of Ohai sub-bituminous coal at two temperatures, 50 °C and 75 ° C, using a Calvet type microcalorimeter. The study demonstrates the heat of drying increases with the reducing of moisture content of coal in a pattern such that at least three progressive energy levels are involved. This indicates that there are three types of moisture which co-exist in the tested coal, namely free moisture, loosely bound and tightly bound moisture. These data are valuable in the mathe- matical simulation of the spontaneous ignition process in which the effect of moisture transfer is considered. The high heat of drying, as measured in this study, indicates that the extent of the moisture effect on the spontaneous igni- tion is beyond 100 ° C.

Experimental study on flammability limit of a chlorine trifuloride/dichlorosilane/nitrogen mixture

Abstract: The flammability limit of a chlorine trifluoride (CIF3)/dichlorosilane (SiH2Cl2)/nitrogen (N2) mixture was investigated experimentally. In this study, a SiH2Cl2/N2 mixture was first introduced into an explosion vessel and a CIF3/N2 mixture was then injected into the vessel. Spontaneous ignition was observed during the injection when the final CIF3/SiH2Cl2/N2 mxiture was in a flammable range. Various compositions were tested to determine the flammability diagram of a CIF3/SiH2Cl2/N2 mixture. From the flammability diagram, the lower flammability limits for spontaneous ignition were found to be 0.3 vol% for both CIF3 and SiH2Cl2. Below this limit ignition did not occur even when an electronic spark was applied.

Combustion of pyrotechnic mixtures with heat transfer from gaseous reaction products

Abstract: The existence of a steady combustion wave in the porous reacting mass of a chemical gas generator, with heat transfer to the original substance from the gaseous reaction products, has been confirmed theoretically and by experimental data. In this case, the combustion temperature exceeds the adiabatic combustion temperature. Possible combustion mechanisms are discussed.

Autoignition of a turbulent premixed gas

Abstract: Autoignition in a two-dimensional turbulent premixed gas al temperatures ranging from 1100 K to 1400 K was numerically simulated. Assuming one-step irreversible reaction, the physical parameters were arranged to simulate a 30% (2H2 + 02) + 70% N2 gas mixture. The temperature initially fluctuated about 1% resulting from a given isotropic compressible turbulent flow with an intensily of 25m/s. The temperature fluctuation affected the ignition delay time and the spacial heterogeneity of ignition. At low temperatures, the ignition occurred spottily and a propagating pressure wave appeared from the hot spot. The pressure wave completed the ignition process and strong pressure fluctuations remained. At high temperatures, almost homogeneous ignition occurred. The ignition delay time was decreased by the temperaiure fluctuations and showed a good agreement with the theoretical results of Arrhenius' law in homogeneous turbulent media. Large activation energy also contributed to heterogeneous autoignition.

Inter-cylinder injection type spark ignition internal combustion engine

Abstract: PURPOSE:To enable early warming-up at the time of a low temperature of a catalyst converter, and also prevent self-ignition of fuel during an intake stroke. CONSTITUTION:An inter-cylinder injection type spark ignition internal combustion engine is provided with an injection valve 16 for directly injecting fuel inside a combustion chamber at an early phase of an intake stroke, an ignition plug 15 for igniting air-mixture formed inside the combustion chamber 1, a detection means 14 for detecting a temperature condition of a catalyst 11 provided in an exhaust gas system, and a control means 20 for delaying an ignition timing and controlling the ignition plug 15 and the injection valve 16 to delay a fuel injection timing, as well as delaying an ignition timing as the time when the low temperature condition of the catalyst 11 is detected by the detection means 14.

Method of operating a free-piston engine; and free-piston engine operating according to this method

Abstract: In a method of operating a free-piston engine according to the diesel principle a combustion room in a cylinder is reduced by displacing a piston thereby compressing air supplied to the cylinder, fuel being injected into the combustion room allowing the mixture of air and fuel to ignite by spontaneous combustion and to expand for returning the piston. The main fuel injection is started at such a moment that more than half of the mixture of fuel and air is only combusted after the piston has already started to return. The invention also includes a free-piston engine operating in correspondance with said method.

Water Vapor Adsorption of Coal and Numerical Simulation Related to Its Effect on Spontaneous Combustion in a Low Temperature Range.

Abstract: This paper describes experimental results of water vapor adsorption of coal and numerical simulations relating to the spontaneous combustion of coal in a low temperature range. The calculation model using a thermal model as the physical effect of water vapor adsorption in addition to the oxidation due to the equilibrium exposure time concept is proposed.Coal specimens supplied by the Akabira Coal Mine, the Taiheiyo Coal Mine and the Genesee Coal Mine (Alberta, Canada) were used for the water vapor adsorption experiments. The equilibrium moisture content of coal against relative humidity and unsteady water vapor adsorption rate caused by the step change of relative humidity were measured at several temperatures. The new numerical model to express the water vapor adsorption rate is proposed.The calculation models were successfully applied to the numerical simulations of spontaneous combustion in the spherical deposit of coal. The numerical model includes heat conduction, oxygen and water vapor diffusions in the coal deposit. Numerical results show that the water adsorption has an effect to accelerate rising coal temperature at the early stage (<200 hours), but also has an effect to restrain the rise of temperature over the long period.

Ignition delays, heats of combustion, and reaction rates of aluminum alkyl derivatives used as ignition and combustion enhancers for supersonic combustors

Abstract: The work was based on adapting an apparatus and procedure developed at Southwest Research Institute for rating the ignition quality of fuels for diesel engines. Aluminum alkyls and various Lewis-base adducts of these materials, both neat and mixed 50/50 with pure JP-10 hydrocarbon, were injected into the combustion bomb using a high-pressure injection system. The bomb was pre-charged with air that was set at various initial temperatures and pressures for constant oxygen density. The ignition delay times were determined for the test materials at these different initial conditions. The data are presented in absolute terms as well as comparisons with the parent alkyls. The relative heats of reaction of the various test materials were estimated based on a computation of the heat release, using the pressure data recorded during combustion in the bomb. In addition, the global reaction rates for each material were compared at a selected tmperature and pressure.

Pyrophoricity of uranium

Abstract: Uranium metal is pyrophoric and is capable of self-ignition in air provided conditions are favorable. Based on the data in this report, spontaneous ignition of spherical particles larger than 1/16 inch in diameter would not be expected to occur in air at room temperature (25[degree]C). The rate at which the uranium surface oxidizes in air, balanced against the rate at which the heat of reaction is lost to the surroundings, determines whether spontaneous ignition can occur. Heat loss to the surrounding environment depends on the thermal conductivity of the uranium including the oxide coating, and on the temperature gradient. The ignition temperature for uranium metal particles is a function of particle geometry, size or specific surface area, heating rate gas composition as well as the quantity and distribution of powder within a storage container. The most important variable; however, affecting the ignition temperature for single samples was found by Schnizlein and Bingle to be the specific surface area (surface area per gram) of the uranium particles. The ignition temperatures calculated from ANL data for 1/16, 1/4, and 1/2 inch diameter spherical particles are 333, 375, and 399[degree]C, respectively. The accuracy is believed to be about [plus minus]l0%, which is basedmore » on theoretical and experimental results.« less

Device for generating heat by catalytic combustion

Abstract: The invention relates to a device for generating heat by catalytic combustion, e.g. in a heating installation. To achieve improvements as regards a reduction in the NOx emissions and the risk of spontaneous ignition of a fuel/air mixture, the invention proposes that some of the exhaust gas be added to the fuel. By recirculating some of the hot exhaust gas from the burner outlet to a fuel/exhaust gas mixer (1), it is possible to achieve preheating of the gas mixture.

Combustion Enhancement of Lean Mixture by Plasma Jet Ignition and Pulsed Jet Ignition

Abstract: The characteristics and performance of pulsed jet ignition are confirmed by combustion tests carried out in a disk-shaped combustion vessel with a lean methane-air mixture, in comparison to those of plasma jet ignition and standard spark plug ignition. The results show that plasma jet ignition has a greater combustion enhancement effect in its initial period than pulsed jet ignition has. After the initial period, however, pulsed jet ignition demonstrates superiority in its combustion performance. As a result, pulsed jet ignition shows a higher maximum pressure and shorter combustion period than plasma jet ignition.

Method and device for reducing moisture of waste

Abstract: PURPOSE: To provide a method and a device for reducing water content of water bearing waste materials by using combustion gas generated from combustion of waste materials in order to reduce water content during adjustment for grinding water bearing waste materials and in order to provide an inert atmosphere during a drying process and a grinding process thereof. CONSTITUTION: System constitution of a device for circulating an inert fluid medium in a substantially closed and inert atmosphere during grinding wet gob for preventing spontaneous combustion from sparks created during grinding of moisture bearing waste materials is provided. The device is a combination of a fluid circulating circuit with the grinding mill 14 to separate ground particulate gob from the circulating fluid medium and a second fluid circulating circuit in association with a boiler 20 to burn the ground gob material for creating an oxygen deficient atmosphere in the fluid circulating circuit.

Short Communication on Self-Ignition of Potato Chips Waste

Abstract: This paper describes an application of the theory of self-heating and thermal explosion of the spontaneous ignition of potato chip waste. Long term heating experiments were carried out in thermostats over the temperature range of 30-140°C in an air atmospher. Sample potato chips were set in spherical stainless stell cages of 6, 15, 20, 30, 40, 50, and 70cm diameter and their temperature changes were monitored. Physical parameters of apparent activation energy, and overall heat of reaction value were also estimated by TG-DSC analysis. Thermal conductivity of the bulk sample was measured independently. The correlations between ambient temperature and bulk size of the chips, which lead to the spontaneous-ignition, were estimated experimentally and by theoretical calculations. The estimations showed close coincidence with each other.

The prediction of spontaneous ignition hazards resulting from the hot stacking' of process materials

Abstract: A change in the normal routine at a factory, which produced a cellulose-based product, necessitated taking the individual blocks of material from a hot curing process (ca. 200 C) and packing them before they had cooled to an appreciable extent. Spontaneous ignition took place in the packaged material some hours later. Considerable damage to buildings and other losses were incurred. The ambient temperature within the store was not sufficiently high to cause thermal ignition. The problem proved to be a special but not necessarily unusual case in which the onset of ignition was governed by the initial temperature of assembly of the packaged material. These circumstances have been recognized in the fiberboard manufacturing industry for example, such that US legislation requires the cooling of newly manufactured boards below a specified temperature before stacking takes place. The authors discuss the theoretical background to this type of problem, based on an adaptation of thermal ignition theory with conductive heat transport (Frank-Kamenetskii conditions). They obtained the appropriate kinetic and thermochemical parameters for exothermic reaction in a cellulosic material in order to apply the theory. They were then able to calculate a maximum packing temperature to expedite safe but efficient storage or transport. Themore » numerical calculations to solve the spatial and time dependent energy conservation equations by use of the finite difference method required a three dimensional grid, set up as 20{sup 3} mesh points, equivalent to cube-shaped, packaged material in the practical application. Most of the calculations were performed on a personal computer.« less

Spontaneous combustion cigarette

Abstract: The utility model provides a spontaneous combustion cigarette which can achieve the purpose of combustion without the help of a foreign lighter, comprising cigarettes and a cigarette box, wherein, the lighting ends of the cigarettes are provided with lighting powder, and the outer face of the cigarette box is coated with a friction surface. When smoked, the cigarette can be lighted only by striking the end with lighting powder of the cigarette on the friction surface, and thus the purposes of convenience brought to smokers and match or other lighters saving can be achieved.

Ignition Probability in a Fuel Spray

Abstract: Application of the stochastic ignition theory to spontaneous ignition in an n-octane fuel spray injected into high-temperature air behind reflected shock waves in a shock tube is statistically investigated. The total space into which the fuel is injected is optically divided into 25 sections and the induction period of ignition in each section is separately, but at the same time, measured, using several photomultipliers. From the histogram of the ignition induction period in each section obtained by repeating the same experiment many times, the temporary and spatial distributions of ignition probability in the fuel spray are obtained.

Ignition and consolidation characteristics of natural athabasca oil sands in combustion products of lean-H2 Air

Abstract: Ignition, quenching, reignition, and consolidation characteristics of high-grade natural Athabasca oil sands when subjected to hot, low-velocity gaseous streams are established The laboratory tests were conducted using spherical samples of the oil sands in streams of the combustion products of very lean mixtures of hydrogen and air over a temperature range of 630 to 760°C and at atmospheric pressure Various quenching schemes and rates were employed, the high-temperature spontaneous ignition and/or reignition delay and total burning time, as well as mass losses, were established Effective activation energies for fresh and prequenched “modified” oil sands samples were then determined Microstructural changes and sample consolidation behavior were also examined and compared with those observed when the samples were exposed to electrically heated pure air streams under identical conditions

Influence of colored noise on particle combustion

Abstract: The influence of external noise with nonzero correlation time (colored noise) on the combustion of a single particle is investigated. An equation for the steady-state thermal regimes of the reaction is derived. Spontaneous ignition of a particle is considered.