Showing papers on "Spontaneous combustion published in 1990"

Gas phase and catalytic ignition of methane and ethane in air over platinum

Abstract: The ignition of gas phase combustion by a heated catalytically active surface involves dynamic coupling of transport processes and chemical kinetics. Researchers have observed that surfaces with high catalytic activity require higher surface temperatures to ignite gas phase combustion, compared to nonactive surfaces, and that this difference is greatest for a stoichiometric mixture. In this work an analysis of the ignition of surface-catalyzed oxidation is developed along with an experimental technique for independently monitoring both surface and gas phase ignition such that the dynamics of these two events can be decoupled. Experiments suggest that the sharp maximum in surface temperature required for gas phase ignition observed in previous work is an artifact caused by transient heating of the surface as ignition occurs. Analysis of surface ignition was also used to investigate the kinetics of methane and ethane oxidation on platinum.

The dual reciprocity boundary element method for spontaneous ignition

Abstract: This paper studies the non-linear heat conduction problem of spontaneous ignition of a reactive solid by using the dual reciprocity formulation of the boundary element method. First, critical values of the Frank-Kamenetskii parameter δ are computed for some common geometrical shapes. Then, transient analyses are carried out for values of δ below and above δc, producing the expected behaviour, with ignition occurring for δ > δc.

Method and apparatus for injecting fuel into a combustion chamber of an air compressing, spontaneous ignition, internal combustion engine

Abstract: A method and apparatus for injecting fuel into a combustion chamber of an air compressing, spontaneous ignition, internal combustion engine are provided. An adjustment member of an injector is actuated electrically and is controlled via an electronic circuitry, with the fuel quantity being withdrawn from a pressure chamber. The adjustment member acts upon a release sectional area of a restrictor. An adjustment member in the form of a magneto strictive rod is provided. The release sectional area is controlled by a control voltage, generated by the electronic circuitry, and can be chronologically modulated.

The inhibition of spontaneous ignition by flame‐retarding cotton fabrics

Abstract: The spontaneous ignition behavior of flame-retarded cotton cellulose has been investigated using differential thermal analysis (DTA). One durable, phosphonium salt-urea-ammonia polycondensate (Proban CC), and one nondurable, ammonium polyphosphate (Amgard TR) commercially flame-retardant-treated fabrics have been studied. The information obtained is compared to that previously reported for untreated cotton cellulose. The onset of spontaneous ignition, temperature Ti, was determined as a function of [O2] in the flowing O2/N2 atmosphere to which samples were exposed in the DTA furnace, whose temperature was raised at a known linear heating rate. The activation energy Ep for the rate-determining pyrolysis reaction was calculated. In the case of the Amgard TR fabric, Ep increased from 145 kJ mol−1 at 21% O2 to 261 kJ mol−1 at 50% O2, whereas that for the Proban fabric increased from 230 to 400 kJ mol−1. A plot of 1/Ti vs. In [O2] shows two linear regions that interact at about 40% O2, which is just above the limiting oxygen index values for these two flame-retarded samples. This intersection is interpreted as indicating that the combustion mechanism of these flame-retarded fabrics changes as [O2] passes through this 40% level. Below this value, significant amounts of char remained after the DTA experiment, suggesting that volatiles only were ignited, whereas above this value, both volatiles and char were burnt away. This is supported by evidence from the DTA traces. The difference in slopes of the two regions of the 1/Ti vs. [O2] plots is used to obtain a value for Eox, the activation energy for gaseous oxidation. Values for Eox of 270 and 536 kJ mol−1 were obtained for the Amgard TR and Proban CC fabrics, respectively. These are considerably higher than is the value of 215 kJ mol−1 previously reported for untreated cotton. Thus, one of the ways in which these flame retardants reduce the ease of combustion of the cotton is by increasing the activation energy for the oxidation of the evolved organic species.

Method and device for adjusting the ignition phase in the operation of a spark ignition engine

Abstract: The invention relates to a method and a device for adjusting the ignition phase in the operation of a spark ignition engine, especially in the case of high air ratios. In order to stabilise the combustion sequence, it is proposed according to the invention that shortly prior to the spark discharge into the ignition area a small quantity of a gaseous additive is injected at a pressure in excess of the combustion chamber pressure at the time of ignition, the additive or the additive-air mixture having a high diffusion rate, wide ignition limits and a high flame propagation speed.

Mine environmental engineering

Abstract: VOLUME II: NOISE Definition, Physical Properties, and Specifications Noise Control Noise Control in Mining Operations Hearing Protectors Assessment and Measurement of Noise Noise Control on Mining Machines ILLUMINATION Definitions and Physical Properties Light Sources The Eye and Vision Photometric Measurements Mine Illumination METHANE IN COAL MINES Introduction Methane Emission in Longwall Faces Problems of High Gassiness in Mining Outburst of Gas Methane Drainage Methane Layering Mathematical Modeling of Flow and Emission of Methane Methane Control Expert System Explosibility of Methane MINE FIRE Introduction Modes of Mine Fire Propagation Temperatures Developed by Timber Fires Effects of Mine Fire on Mine Ventilation Computer Simulation of Effects of Mine Fire on Mine Ventilation SPONTANEOUS COMBUSTION OF COAL Introduction Causes of Spontaneous Combustion Prevention of Spontaneous Combustion HEAT AND HUMIDITY Psychrometry in Mining Sources of Heat in Mines Heat Emission Measurement in Longwall Coal Mining Refrigeration Systems Theory of Heat Transfer into Mine Air and Computer Simulation of Mine Climate Measurement of Rock Physical Properties Influencing Mine Climate

Factors affecting the pyrophorisity of spent bleaching clay

Abstract: Artificial cakes of bleaching clay/vegetable oil have been studied for their pyrophoric character using both Differential Scanning Calorimetry and a constant-temperature, fixed-interval, spontaneous heating (CaTFISH) test developed in this laboratory. It was determined that this is a two-step process involving a first-stage low-temperature spontaneous heating reaaction followed by a second-stage high-temperature spontaneous heating reaction. The latter is characterized by charring and, in some cases, flaming combustion. A study of relevant variables has established that clay type, filter cake age, oil retention, moisture, and the presence of antioxidant significantly affect the spontaneous heating characteristics of clay/oil masses. Oil type was not found to be a significant variable in these studies.

Supersonic combustion engine and method of combustion initiation and distribution

Abstract: A supersonic combustion air breathing jet engine and method of igniting fuel. The engine has means for providing a spatially controlled combustion distribution of fuel with an ignitor that provides a volumetrically diffuse discharge of energy to initiate a controlled relatively rapid combustion of fuel in a combustion zone such that combustion distribution in relatively high speed gas flows through the combustion zone can be initiated and controlled without dependence upon a flame holder or relatively high local static gas temperature in the combustion zone.

Heat processing apparatus using liquified gas

Abstract: In a heat processing apparatus in which a gas/air mixture is piezoelectrically ignited to heat the combustion catalyst by the ignited flame for taking place subsequent flameless catalytic combustion of the gas mixture, a portion of the gas in the flaming combustion space is directly discharged to the outside not passing through the combustion catalyst upon flame ignition, while the entire amount of the gas in the combustion space is introduced to the combustion catalyst after reaching the catalytic combustion, by using a discharge gas control mechanism interlocked with the operation of the ignition button, as well as the opening degree of the external air ports is changed variably so as to provide suitable gas/air ratios upon ignition, flame extinguishment and usual catalytic combustion respectively by the air flow rate control member also interlocked with the ignition button.

Autoignition of Heavy Fuel Oil Sprays at High Pressures and Temperatures

Abstract: This paper reports on an experimental study of the autoignition behavior of several heavy fuel oils in a large constant-volume combustion chamber with single-shot injection. In the experiments the pressure and the temperature of the air in the combustion chamber before fuel injection varied between 30 and 70 bar and between 730 and 920 K. Illumination delay and pressure delay values have been correlated with these pressures and temperatures. It is shown that for all but one of the fuels examined, ignition delay ranking changes little with the choice of ignition delay definition, but more with the pressure and temperature conditions in the combustion chamber. The usefulness of the Calculated Carbon Aromaticity Index is discussed.

Spontaneous combustion and explosion of finely pulverized coal.

Abstract: Danger of spontaneous combustion and dust explosion at coal handling and utilizing facilities is outlined.Spontaneous combustion is a resultant phenomenon of competition of the rates of heat generation and heat loss. Influence of factors on the initiation is described on the basis of the thermal explosion theory.Explosion characteristics of dust clouds are described in relation to the assessment and protection-suppression measures.It is emphasized that decreasing particle size increases the hazard of spontaneous combustion and dust explosion but there are little data for the assessment for finely pulverized coals.

Suppression Methods for Deep Seated Coal Fires

Abstract: : This study was a joint US Coast Guard/Maritime Administration effort to identify fire prevention and/or suppression techniques for spontaneously induced coal cargo fires The four test series conducted investigated spontaneous ignition, permeation, fire quench, and coal column fire characteristics The spontaneous ignition tests identified variables that could be controlled in an attempt to prevent combustion Results showed spontaneous ignition difficult to predict and, therefore, control The permeation studies evaluated carbon dioxide and nitrogen as suppression agents Results indicated the retention time of nitrogen in a coal pile to be far greater than the retention time of carbon dioxide The fire quench tests compared these agents applied to a hot fire Results showed both equally effective at displacing oxygen The coal column tests applied these agents to a deep-seated fire at different locations Results supported those of the permeation studies and showed mid-level injection of the agents to be most effective Thus, the study indicates a portable system that applies nitrogen to the middle of the coal pile to be most effective Large-scale work should be done to verify this Keywords: Coal; Coal fires, Carbon dioxide, Nitrogen, Suppression, Permeation, Injection, Coal colliers

Fundamental Principles of Thermal Explosions and Recent Applications

Abstract: This paper may serve as a useful opening to the Advanced Study Institute because it deals with the most basic of thermal instabilities — the sudden explosion of a uniformly heated mass of material: thermal explosion. Its application to energetic materials is wide, spreading from the autoignition of chemically unstable materials, through combustion processes to the safety of explosives exposed to fire, and to the sustaining of detonation waves. We set out some of the fundamentals, look at some old problems in a new way, and study some new applications, including programmed ambient temperatures.

New additives improving the spontaneous ignition resistance of fuels

Abstract: Fuel additives. Use of new additives for improving the spontaneous ignition resistance of fuels, characterised in that these additives are in the form of a micellar compound consisting of the combination of a metal salt of a nonsulphurous organic acid with a metal compound, at least one of the metals in the said salt or the said compound being known as a metal improving the octane number of the fuels. Application to the improvement of spontaneous ignition resistance.

Oxygen enriched combustion device of solid fuel

Abstract: PURPOSE:To burn the solid fuel effectively, pressurize, transfer, and store said solid fuel in safety by separating nitrogen in the air, transferring or supplying it to a storage facility and supplying oxygen-enriched residual gas in which nitrogen is separated to a furnace which burns said solid fuel. CONSTITUTION:The nitrogen produced by a pressure swing nitrogen adsorbing device 1, is pressurized by a blower 5 and transferred into a solid fuel storage bottle 7 and used to prevent spontaneous ignition of the solid fuel or to apply pressure. On the other hand, the discharged gas produced in the process where nitrogen is adsorbed and separated by the pressure swing nitrogen adsorbing device 1, contains the residual oxygen two or three times ordinary air, enters a blower 2 from an exhaust air pipe 27, pressurized and blown into a furnace 4 by way of a supply pipe 3. By way of a supply machine 9, the solid fuel 8 is injected into the furnace 4, passing through an injector 11 by a primary air blown by a primary air blower 10. The solid fuel is burnt by this air and the aforesaid oxygen-enriched air. Therefore, the theoretical combustion gas temperature rises up to 200 to 300 deg.C so that burning out time may be shorten sharply, thereby reducing unburnt loss.