Coal Dust Particles Research Articles

Chlorophyllin: a potent antimutagen against environmental and dietary complex mixtures

Chlorophyllin, the sodium and copper salt of chlorophyll, was tested for its ability to inhibit the mutagenic activity of a variety of complex mixtures — extracts of fried beef, fried shredded pork, red grape juice, red wine, cigarette smoke, tobacco snuff, chewing tobacco, airborne particles, coal dust and diesel emission particles — in strain TA98 of Salmonella typhimurium. Chlorophyllin was highly effective against the mutagenicity (90–100% inhibition) of 8 of these 10 mixtures. The mutagenicity of the other 2 mixtures was inhibited 75–80% at the highest concentration of chlorophyllin studied. Control and reconstruction experiments showed that chlorophyllin was not toxic to Salmonella at the concentrations used. The antimutagenic activity of chlorophyllin was heat-stable. The mechanism of the antimutagenicity of chlorophyllin in these experiments is not known; however, chlorophyllin is an antioxidant. Scavenging of radicals and/or interaction with the active group of mutagenic compounds may be responsible for its antimutagenic activity. The data reported here indicate that chlorophyllin is potentially useful as an antimutagenic agent.

Inhibition and extinction of explosions in heterogeneous mixtures

The mass concentrations of various inhibitors required to extinguish explosions in stoichiometric methane-air and coal dust-air mixtures were measured in laboratory-scale systems of 8- and 20-L volumes. The additives studied were N 2 , CF 3 Br, CaCO 3 , KHCO 3 , and NH 4 H 2 PO 4 . The experimental method involved spherically-developing, adiabatic explosions at constant volume in which the test mixtures were taken to conditions of complete extinction. Strong, pyrotechnic ignition energies in the range of hundreds to thousands of joules were used in order to insure that inerting limits were truly independent of ignition energy. The order of effectiveness for the inhibitors was phosphate>nitrogen>CF 3 Br>carbonates. Essentially the same relative order of effectiveness was observed against methane as against coal dust; however, much higher absolute concentrations of the solid additives were required against methane than against coal dust. The phosphate, which was the most effective against either coal dust or methane, required 100 g/m 3 of the 7 μm powder to inert the most reactive coal dust concentration, and 280 g/m 3 of the same size powder was needed to extinguish stoichiometric methane. A preliminary theoretical analysis is presented based on a comparison of the measured inerting levels with those predicted from adiabatic, equilibrium thermodynamics using the established concept of limit flame temperatures. Three categories of thermodynamic systems are involved: fully-homogeneous ones, singly-heterogeneous ones, and doubly-heterogeneous ones. There are two types of singly-heterogeneous systems: those involving a solid fuel only and those involving a solid inhibitor only. The flammability and/or extinction behavior in the heterogeneous cases is controlled by limitations on the rates of devolatilization of the solid phase reactants. Preliminary data are presented for the rates of devolatilization of particles of coal dust, NH 4 H 2 PO 4 , and CaCO 3 pyrolyzed by a laser flux which simulates the flame heating flux. The data show that their measured rates of devolatilization are consistent with the inhibitor's measured effectiveness in extinguishing explosions.

Studies of coal dust wetting by surfactant solutions

Factors which influence the rate of wetting of coal dust by aqueous surfactant solutions have been studied by means of the Walker Test. The rate of wetting increases with (a) increasing surfactant concentration, (b) increasing temperature, (c) larger sized coal dust particles, (d) a bigger dust sample, and (e) increasing area of the wetting surface. Studies of wetting by a homologous series of ethoxylated nonionic surfactants show wetting rates passing through a maximum at about ten moles of ethoxylation per mole of hydrophobe. A direct comparison of the traditional Draves Test for wetting power with the Walker Test shows a high degree of correlation. A study of coal dust wetting by an infusion procedure shows poor correlation with both the Draves and Walker methods.

Actions of wetting agents on coal dust

The rate of wetting of coal dust by aqueous solutions of surface active agents (surfactants) has been studied. It has been shown that surfactant is adsorbed onto the coal surface during the wetting process. Rates of wetting by solutions of the widely used sodium salt of di(2-ethylhexyl)sulphosuccinic acid (Aerosol OT) are strongly influenced by low concentrations (1–2 mg/l) of dipositive metal ions. After wetting, electron spectroscopy for chemical analysis (ESCA) has been used to show the presence of these metal ions and the surfactant on the surface of the particles of coal dust.

Counteraction of poly(4-vinylpyridine-n-oxide) on the depression of viral interferon induction by coal dust

The depressive activity of coal dust on interferon induction by influenza was markedly subverted when either coal dust or LLC-MK2 cell monolayers were pretreated with poly (4-vinylpyridine-N-oside). The polymer alone neither induced interferon synthesis, inhibited viral induction of interferon, influenced viral multiplication, nor affected cellular-induced resistance by interferon. Absorption of the polymer to coal dust not only occurred at a more rapid rate than to cell monolayers, but also less polymer was required to pretreat coal dust than cell monolayers to achieve comparable amelioration of interferon production. The polymer effectively negated the adverse activity of coal dust particles, irrespective of the latter's size (is less than 2.0 to 74.0 mum). Virus multiplication in the presence of coal dust=treated cell monolayers attained a level that was twofol higher than that noted with either polymer-pretreated coal dust or polymer-pretreated cell monolayers. Interferon production was almost completely inhibited in the presence of coal dust; pretreating coal dust or cells with the polymer abrogated this inhibitory activity of coal dust. It is tentatively suggested that coal dust particles per se directly interact with cell membranes to subvert interferon induction and that the formation of an absorbed polymerlayer on these complexes prevents their interaction.

Size Distribution Measurement of Airborne Coal Dust by Optical Particle Counters

An optical particle counter has been calibrated for size distribution measurement of airborne coal dust particles. A differential electrical mobility analyzer was used with a fluidized bed dust feeder to produce uniform coal dust particles of a known size for calibration for particles <2.4 μm. For larger particles, the optical counter was calibrated with a microscopic technique. The output pulse height of the optical counter was found to be significantly lower for coal particles than for spherical oil drops of the same particle size. The geometrical standard deviation, σg, of the output pulse height distribution of the optical counter for monodisperse aerosols was found to increase from about 1.1 for spherical oil particles to about 1.8 for the irregularly shaped coal particles. Although this broadening effect reduced the ability of the counter to resolve small particle size differences, a numerical inversion procedure was developed which allowed the original size distribution to be recovered.

Initiation of weak coal-dust explosions in long galleriesand the importance of the time dependence of the explosion pressure

Weak coal-dust explosions in galleries (large horizontal tubes) are defined in the paper asthe early stages of what may eventually become a self-sustaining, steady-state situation, if the scale is large enough. An initiating explosion producing a pressure rise of at least 12 kPa is needed to start an explosion from any additional dust that lies beyond the initiating zone; entrainment of this additional dust leads to the main explosion. In long galleries, initiating explosions in the range 16±2 kPa are mostly used. The early stages of the main explosion resemble explosions in which combustion of a very low concentration of coal-dust particles is taking place over a considerable volume at any given time, rather than explosions in which a flame, having a more or less definable front and rear, is propagating through a preformed explosive mixture. The explosions are described in terms of the general shape of the pressure changes occurring at a point near the outermost extent of the flame that is produced by the initiation explosion alone. The initial pressure rise is determined by the form of the initiating explosion and is followed by a roughly exponential pressure increase (from atmospheric pressure), whose time constant depends on the nature of the coal-dust, its dispersion, and the dimensions and characteristics of the gallery. The effects on the development of the explosion of the presence of short dust deposits, suppressive devices, and the ignition of predispersed clouds are briefly discussed. It is concluded that, in weak explosions, propagation results from dust being swept from the floor into the zone of combustion behind the flame front. However, as pressures increase to above, say, 100 kPa, other mechanisms become responsible and, perhaps, a pre-detonation regime sets in.

The Penetration of Filter Paper by Coal-Dust Particles in the Respirable Size Range

The Penetration of Filter Paper by Coal-Dust Particles in the Respirable Size Range

The significance and application of shape factors in particle size analysis

By use of a new method for measuring the thicknesses of individual sub-sieve particles with the optical microscope and being able to measure the dimensions of their projected images as well, the surface and volume shape factors of the particles can be calculated. An expression can be derived for the ratio of the particle's projected diameter to its Stokes' diameter in terms of these factors. Results of the examination of coal dust particles revealed a large variation in the shape factors between particles, which should also be found for particles of other materials. It is shown that in the application of shape factors to the correlation of results obtained by different methods for particle size analysis, the variation of these factors should be taken into account. The method of application has been devised for use when comparing results of the microscope method with those of sedimentation methods, both gravimetric and light extinction. This method has been compared with the normal way in which only the average shape factor is applied. Differences occurred which could account for some of the past difficulties when the correlation of the sizing methods was attempted. The largest particles of a sub-sieve fraction of a powder seen under the microscope have shape factors different from those of the smaller sizes.

Inter-laboratory checks on the counting of coal dust particles on thermal precipitator slides

The paper describes experiments carried out by the Medical Research Council and the National Coal Board to compare the results obtained by observers in different laboratories when counting coal dust particles on thermal precipitator slides. Serious differences were discovered which have now largely been removed within the National Coal Board by the institution of regular interlaboratory checks. These checks have also aided the development of improved methods of mounting and counting the slides.

Rate of combustion of coal-dust particles

Rate of combustion of coal-dust particles