Dust Explosions T

Dust Explosions t

Piotr Wolari.ski Warsaw University of Technology, Institute of Heat Engineering*

Abstract When mixed with air many natural or artificial types of dust may explode with an energy several times higher than the equivalent mass of TNT. The origin of the dust and its basic properties, which are important from the point of view of a dust explosion, are discussed in the paper. Special attention is focused on the problems of mixture formation, ignition and the subsequent flame propagation. Methods of evaluation of the structure and burning velocities for laminar and turbulent flames are given. Conditions for flame acceleration and transition to detonation are also discussed. Finally, the influence of both inert and reactive particles on homogeneous and dust mixture explosions is presented.

1. Introduction In this paper, the basic parameters responsible Even though the first dust explosion was reported for dust explosions will be discussed. The diagram, in Italy in the 18th century [1], a serious approach showing the most important parameters which in­ was taken to the problem only at the beginning of the fluence a dust explosion, is presented in Figure 1 20th century when a coal dust explosion killed more [3]. It shows that the most important parameters than a thousand miners in France [2]. Many other are the dust properties, the parameters of dust dust explosions occurred during this century in min­ mixture, the ignition source and the explosion space ing and in other branches of industry such as the characteristics. The development of a dust explosion grain industry, textile, food processing, metallurgical, is very strongly related to these parameters. pharmaceutical and others. It is so because a typical organic dust may explode with an energy 3-5 times 2. Dust properties higher than the equivalent mass of TNT. Studies on coal dust explosions have been carried Dust may be the main product or a by-product in out since the beginning of this century in many coun­ many different industries. For example, in a coal tries, and large-scale testing facilities have been built mine, dust is usually the by-product, but in many in the USA, France, Poland, Germany, the UK, Japan power plants, pulverized coal is the main fuel. Simi­ and in other countries. Coal dust testing facilities larly in some grain industries, where dust is the were amongst the first to be used to research in­ by-product in the elevators used during storage of dustrial dust explosions. the grain, in the mills, it is the main product in the Research of dust explosions accelerated in the form of different flours. A lot of dust is also produced seventies due to the rapid growth of powder technolo­ in the food, pharmaceutical and metallurgical in­ gies and the explosion hazard associated with them. dustries. A typical natural dust which is very often More basic work in the area of dust explosions is used in dust explosion research is lycopodium, the still being carried out in different university labora­ spores of mosses. tories. Since the seventies, special meetings devoted In this paper we will discuss only dusts which to dust explosions are occasionally organized in require a gaseous oxidizer for combustion and explo­ different countries, and since 1984, International sion. So, to be explosive, a dust should be combusti­ Colloquia on Dust Explosions have been organized ble. During an explosion the dust burns rapidly and every two years, initially in Poland, and subsequently releases a large quantity of heat. A dust of high com­ elsewhere. bustion heat is potentially more explosive. But a high heat of combustion is only one of the parameters * 25 Nowowiejska Str., 00-665 Warsaw, Poland which cause a dust to be considered as potentially t Received: 11 June, 1996 explosive. For rapid combustion, a dust should have a large specific surface which will appertain if the

144 KONA No.14 (1996) INITIATION

POWER PRESSURE Et-;ERGY TE~PERATURE'I (shock wave) POSITIOt-; DENSITY

DUST z SCALE ;2 t;: ' w e: c.: GAS z ;:::; (:.; GEO~ETRY W'-.) '-.) '-.)- f- z o:;t;; ;:.<>< 0 v;o;: :=n~ OXYGEt-; '-.) DUST z~ ~~ SURFACE Of- >0.. _o INITIAL ~ EXPLOSION k== Ql'ALITY fJ)Ck::: Ui~ oo.. PRESSURE & qc.: ...... l -..:: 0.. TEMPERATURE ~:r: ;:.< OBS1ACLES wu ~ TURBULENCE

VENT INHIBITING AGENTS HOLES

HEAT OF SPECIFIC SIZE VOLATILES HUMIDITY ASH COMBUSTION GRAVITY

DlTST PROPERTY

Fig. 1. Major factors influencing dust explosion. dust particles are very small and porous. For most 3. Mixture formation organic substances, a dust is susceptible to rapid combustion if the particles are less than 300 ~tm in A dust is explosive in air (gaseous oxidizer) only when diameter. Even more explosive is dust with particles its concentration is within the so-called 'explosive of less than 100 ~-tm in diameter. Very important, limits' which define the concentration range for which and sometimes most critical, for a dust explosion is a self-sustained flame propagation is possible. For the content of volatile substances. Organic dusts with obvious reasons, the limits are called the minimum a large volatile content are usually very explosive, and the maximum explosive concentration. The mini­ even with a relatively moderate heat of combustion. mum explosive concentration is usually more easily Moisture and ash contents, bulk density and electro­ defined than the maximum. For fine organic dust, static properties also affect the explosive properties the minimum explosive concentration is usually in of dust. Typical properties of average industrial the range of 0.05-0.15 kg/m3, while the maximum dusts are shown in Table 1. one is often of an order of kilograms of dust per cubic metre. Table 1. Typical properties of average industrial dust Within the explosive limits, combustion of a dust-air ! Dust Typical Maximum mixture within a closed vessel results in a significant i parameter value value pressure rise. At the lower limit, the combustion can Heat of combustion, 1\1]/kg 15-30 -60 produce a pressure rise of an order of 2-3 bar. The Volatile content, o/o 20-80 100 maximum explosive pressure is much higher and the Particle size, I'm 10-100 up to 300 and more pressure rise can be in the range of 6-10 bar. Close Moisture, o/o 5-20 up to 50 and more Ash (mineral content), % 5-25 up to 80 and more to the maximum explosive limit the pressure rise is usually slightly higher than that at the lower explosive

KONA No.14 (1996) 145 limit. A typical graph showing the pressure rise in concentration (5] . a closed vessel as a function of the dust concentration Usually, the dispersion of the dust induces initial is shown in Figure 2. turbulence in the mixture created. The intensity For the same kind of dust, the explosive concentra­ and scale of the turbulence depends mainly on the tion varies with particle size and with moisture dispersion system and less on the type of dust dis­ content. The explosive concentration range narrows persed. The largest turbulence occurs during the when the mean particle diameter or the moisture dispersion process and thereafter, the turbulence content increases. The explosive concentration can decays. However, the ignition cannot be delayed also be changed by increasing or reducing the oxygen until the turbulence intensity has decayed completely content of the air. When the oxygen concentration since, in normal conditions, much of the dust will is reduced, the explosive concentration range of the have already fallen to the bottom of the chamber. dust will be narrower. For many organic types of Thus most experiments are carried out in turbulent dust, the mixture will no longer be explosive if the conditions. Only vibrational or fluidized bed feeders oxygen concentration of the air is reduced to 11 o/o. enable laminar or quasi-laminar conditions to be esta­ A detailed description of the minimum explosive blished in tubes. concentration was presented by Wolanski [4]. In real industrial conditions, most of the dust clouds During experimental studies of dust explosions, are created by convective flow or by the blast wave, the dust is usually dispersed by a strong air blast or which is created by primary explosion. Thus, the is dropped from the container with the help of a conditions are very similar to those used in the specially designed feeder. In such cases, the dust evaluation of explosive properties in laboratory con­ concentration is controlled by the selection of a ditions. required amount of dust to be dispersed by an air blast or by the calibration of the feeder which is used 4. Ignition to create the dust cloud. The uniformity of the dust dispersion depends significantly on the size and shape Dust may be ignited in many different ways such of the enclosure (vessel), the dispersing nozzles, the as by electrical or mechanical sparks, hot elements, air pressure and the duration of the pulse. In order and external radiation. When uniformly heated, the to ensure a relatively uniform dust dispersion, espe­ so-called 'self-ignition' of a dust cloud can be ob­ cially in a large vessel, an advanced dispersion served. Evaluations of the critical ignition parameters system and accurate timing is necessary. Only for for dust mixtures have been made for a long time small vessels may a relatively simple dispersion and many data are available. system be used. Usually, a determination of the minimum electrical In small vessels, the uniformity of the dust dis­ energy necessary for ignition, the minimum ignition persion may be tested by optical methods, but in temperature of the dust layer and the self-ignition large volumes, local measurements of the dust con­ temperature of the dust cloud is made for an explosive centration are necessary. Recent measurements of dust. It was found that for a fine dry dust, the mini­ dust dispersion in large silos and filters show a strong mum energy of an electrical spark which can cause influence of centrifugal forces on the stratification ignition may be of the order of millijoules. The mini­ of the dust and on the non-uniformity of the dust mum ignition energy usually coincides with a dust concentration close to that which gives the maximum explosive pressure. When the dust concentration varies from the optimum, the ignition energy increases and can be very large at both limits (Figure 3). Prac­ tically speaking a 10 kJ chemical igniter is a reasonable energy to use for testing a dust. The ignition energy depends not only on the con­ centration of the mixture but also on the characteris­ tics of the igniter. The minimum ignition energy is usually found using sparks with a duration of the order of milliseconds. "Short" or "long" sparks are less Dust Concentration effective [1]. It is obvious that the minimum ignition Fig. 2 Dependence of explosion pressure on dust concentration. energy changes significantly with the dust parameters

146 KONA No.14 (1996) easily volatalized particles. Such flames are very similar in nature to gaseous flames. For dust flames with polydispersed particles of a relatively large mean diameter, the flame structure is more complicated than that of a gaseous flame, even in laminar con­ ditions. Laminar flames are usually studied in vertical tubes. The dust-air mixture is created by supplying dust from the top of the tube or by a fluidized bed feeder placed at the bottom of the tube. In both cases laminar or quasi-laminar conditions are obtained. After the whole tube is filled with the dust mixture, the com­ Dust Concentration bustion is initiated by an electrical spark and the flame propagation in the tube is monitored. In order Fig. 3 Dependence of ignition energy on dust concentration. to obtain a constant velocity of flame propagation, such as particle size and humidity. If the mean particle the bottom of the tube should be kept open. size increases by lOOo/o and the moisture content With the help of Schlieren or interferometric increases by 10o/o, the minimum ignition energy can measurement, the thickness of the preheated zone be increased by two orders of magnitude. The mini­ of the laminar dust flame can be measured whilst the mum ignition energy is also significantly greater in total flame thickness is usually measured with the turbulent mixtures when compared to laminar or help of direct photography. Typical Schlieren pictures quasi-laminar mixtures. showing the preheated zone and combustion region The self-ignition temperature of the dust cloud for are presented in Figure 4 while the direct picture many types of organic dust is most often in the range of similar flames is shown in Figure 5. Data illustrat­ of 600-800 K and is usually higher than the ignition ing the preheated zone thickness and the total flame temperature of a layer of the same dust. It should thickness for two different types of organic dust are be stated, however, that this temperature depends shown in Table 2. It is seen that the total flame critically on the size and shape of the test equipment thickness of laminar dust flames is about three orders used for its evaluation. For example, the ignition of magnitude higher than that of gaseous flames. temperature evaluated in the Golbert -Greenwald To evaluate laminar burning velocities for a dust-air furnace is usually 100-150 K higher than that evaluat­ mixture, two different methods are usually used. In ed in the furnace, one metre long, of Wroclaw the "direct" method, the burning velocity is calcu­ University of Technology. Information about these lated as difference between the flame propagation temperatures is available in the literature but it should velocity and the particle velocity just ahead of the be applied to industrial conditions with great care. flame front. In the "tube" method, the relationship For a better understanding of dust ignition and between the flame propagation velocity and the burn­ flame propagation, some research is focused on the ing velocity is evaluated from measurement of the radiative ignition of dust. Ignition by laser light and tube cross-sectional area and the flame area. A visible radiation are important, since radiation plays more detailed description of such measurements a significant role in the mechanics of flame propaga­ can be found in many publications on this subject tion, especially for metallic dusts. [10]-[13]. A typical dependence of the laminar burning Many data on the ignition of dust mixtures may velocity of the dust mixture on the dust concentration be found in the literature [1], [3], [6]-[9]. is shown in Figure 6. Measurements of the turbulent burning velocity of dust-air mixtures are usually performed in a constant 5. Structure and burning velocities of dust volume chamber. However, measurements may be flames considered to be reliable only if they were performed Dust flames have been studied for many years but in relatively large vessels of one cubic metre or more, despite this, there is only a partial understanding of since the thickness of the dust flame is usually also the dust flame structure, and data on the burning quite large [12], [14]. The best measurements of velocity are limited. The best understanding was turbulent burning velocity were obtained by using achieved only for dust flames made of very small and the simultaneous measurements of the pressure

KONA No.14 (1996) 147 a)

b)

Fig. 4. Computer-enhanced Schlieren pictures of lycopodium-air laminar flame (a) and wheat dust-air laminar flame (b) clearly showing preheated zone area and combustion regions

a) b)

Fig. 5. Direct picture of laminar dust flames: a) lycopodium, c 0.048 kgfm3, b) wheat dust,c 0.15 kgfm3

148 KONA No.14 (1996) Table 2. The thickness of the preheated zone and total flame 6. Accelerating flames thickness for laminar flames of lycopodium and wheat Accelerating flames propagating in ducts, tubes, Preheated zone Total flame Dust concentration thickness thickness channels or galleries have been studied experi­ Dust [kgfm3] I [m] [m] mentally for many years in different laboratories I Lycopodium 0.030 0.006-0.01 0.95 and also in both large surface and underground 0.038 0.006-0.01 0.85 facilities. A large number of experimental data is 0.048 0.005-0.009 1.05 I 0.066 0.006-0.016 1.25 available and the general behaviour of such flames I Wheat 0.12 0.012-0.031 1.42 is relatively well understood [1], [2], [15]. Despite 0.15 0.007-0.036 1.57 this, the accurate prediction of the development of 0.17 0.007-0.013 1.65 I a dust explosion in a channel is difficult. This is due variation inside the chamber and of the flame front to the problems of mixture formation which for dust position. Such measurements should be performed mixtures, is very closely connected to the flame for different turbulence intensities and scales. A propagation, the acceleration of the flame and the typical relationship between both the turbulent and eventual transition from deflagration to detonation. laminar burning velocities and the turbulent intensity A transition from deflagration to detonation is possible is shown for wheat and lycopodium dusts in Figure 7. even for mildly explosive types of dust. Such relationships can easily be integrated into The condition necessary for the acceleration of the computer models of dust explosions. It should be flame is the creation of convective flow just ahead noted, however, that this relationship may only be of the propagating flame. This induced flow is pro­ used for the simulation of dust explosions on a large duced by the expansion of the combustible products. scale where the extent of the explosion is much For a typical mixture with a dust concentration close bigger than the total flame thickness. to the flammable limit, the density ratio across the flame is at least three, but for a stoichiometric mixture 1.0 it may be eight or even more. The fast combustion "' of the mixture produces a rapid expansion of hot .!!!_ 0.8 products of combustion and thus creates pressure 5 lycopodium _:;. waves which propagate ahead of the flame front. ·s 0.6 ~0 c 0 "' "' "'/ Such pressure waves induce a convective flow. The ~ "' oo/ "' ~~6 "' convective flow favours further dust dispersion and .§"' 0.4 ./ "' c increases the turbulence of the mixture. The in­ ::l 00~"' 0 wheat cc creased turbulence intensifies the burning velocity 0.2 and a further acceleration of the flame is observed. 0 The acceleration of the flame in such a process 01 0.2 O.:l 0.4 is related to the reactivity of the mixture. Dust Concentration (kglm"J Figure 8 shows the propagation of the flame in Fig. 6 Typical dependence of the laminar burning velocity of the gallery of the Experimental Mine "Barbara" for dust-air mixtures on dust concentration different initial concentrations. At the low concentra­ tion, c = 0.05kg/m3, the flame propagates some distance from the strong ignition and is then even­ tually quenched. At the highest concentration, a 6 lycopodium, 0.07 kgfmJ small acceleration of the flame can even be seen. It may be that this concentration, equal to 0.075 kg/m3 4 is the limiting concentration which allows a self­ sustained flame propagation. These results are similar to those obtained in vertical tubes. 0~wheat, 0.2 kgfm3 In short channels, that is a 100-metre-long surface gallery where the dust was only dispersed for 60 m, 0~------~------~------~------~- 4 8 12 16 only a limited acceleration of the flame was observed at the low dust concentration. When the dust con­ centration was increased, the flame accelerated to Fig. 7. Ratio of turbulent burning velocity to laminar burning velo­ city as a function of ratio of turbulent intensity to laminar as much as a few hundred m/s. A static pressure burning velocity V '!UL for wheat and lycopodium dusts rise greater than 2 bar was also observed. However,

KONA No.14 (1996) 149 in a longer gallery, a significant flame acceleration was observed. In one case the flame reached a velocity recorded at a relatively low concentration. Figure 9 of nearly seven hundred m/s and a pressure of 5.6 shows the variation of the flame position with time in bar. In another case, a transition to detonation was the 400-metre-long underground gallery of the Experi­ recorded. The transition from deflagration to detona­ mental Mine "Barbara" for different grain dust con­ tion was observed close to a distance of 200 m from centrations, ranging from 0.1 to 0.2kg/m3. The highest the initiator that is at the end of the dust zone. The concentration used in the experiments was still lower velocity measured at the transition was about 2000 m/s. than stoichiometric and about half the concentration The pressure could be estimated from the damage at which the maximum values of the explosive para­ caused to the gallery to be about 50 bar. Such con­ meters were obtained in a constant volume chamber. ditions are typical for a transition from deflagration At a concentration of 0.1kgfm3, the flame propagates to detonation. Even higher transition parameters basically with a constant velocity of the order of one were measured by Gardner eta!. [16], who recorded hundred m/s. For a grain dust concentration of a velocity of 2800 m/s and a pressure higher than 0.15kgfm3, a continuous acceleration of the flame was 80 bar. From such experiments it can be inferred observed up to about three hundred m/s and the that even for organic types of dust, a detonative pressure rose to four bar. However, at a concentra­ combustion is possible in real industrial conditions. tion of 0.2kgfm3, a very rapid flame acceleration was If it happens, it may cause very serious damage. For most organic dust mixtures, the measured detonation velocity is in the range of 1450-1650 m/s and the corresponding pressures in the detonation front are in the range of 15-30 bar. However, as already illustrated, very dangerous conditions arise during the transition from deflagration to detonation. Detonation itself is the most dangerous mode of com­ bustion of a dust-air mixture but, fortunately, many conditions have to be met to initiate it. And for this reason it does not occur very frequently in uncontrolled explosions in industry.

7. Influence of inert particles on flame pro­ pagation 20 40 I (rn) Fig. 8 Diagram showing variation of the flame position with It is well known that the addition of fine inert par­ time along a 100-rnetre-long gallery for different grain ticles is a very good method of suppressing dust dust concentrations. Initiator-10 rn3 of CH4-air mixture; explosions. Barriers of fine stone dust are commonly length of dust zone: 60 rn used in mines for the suppression of methane, dust or hybrid mixture explosions [2] . However, the 3 0.10 kg 1rn l addition of an insufficient amount of inerting particles

+ 0 - 0.1~ may result in the acceleration of flames in ducts 0.20 [18], [19]. A similar and even stronger effect is

2 obtained when relatively large inert particles are added to a combustible mixture. The addition of such particles may result in acceleration of the flame, faster transition to detonation and an extension of the lower limit of detonation [20, 21]. For gaseous mixtures, the mechanism of flame acceleration is strictly related to the microscale turbulence. Such turbulence increases the rate of o~--~--~--~--~----~--~------~~ 80 160 240 320 reaction and speeds up the flame propagation. For a I (rn) very high velocity, when shock waves are generated, Fig. 9. Variation of the flame position with time in a 400-metre­ non-isentropic interactions of the shock waves cause long underground gallery for different dust concentrations; length of dust zone: 200 m additional energy dissipation and thus the temperature

150 KONA No.14 (1996) is increased. The increase in temperature of the For this reason, an uncontrolled dust explosion reacting mixture further speeds up the flame propaga­ usually causes significant damage and may result tion and the probability of a transition to detonation. in serious injuries. This is due to the fact that even Local heating of the gaseous mixture in the region at the limiting concentration, a dust explosion creates of bow shocks associated with the particles is also a significant pressure rise. important. This can eventually lead to the formation Many organic and some metallic kinds of dust are of so-called "hot spots" and ignition of the mixture also easy to ignite and, once ignited, the flame ahead of the propagating flame. which is formed may accelerate. This can eventually Studies of the influence of inert particles when result in a transition to detonation. The detonation added to reactive particles were conducted by Klemens velocity for dust-air mixtures is usually in the range et al. [22]. It was found that unlike in gaseous of 1450-1650 m/s and the pressure rise in the detona­ mixtures, the addition of inert particles does not tion front may be as high as 30 bar. The highest have a discernible effect on the probability of detona­ pressures, up to 82 bar, were recorded during a tion, but does increase the maximum temperature transition from deflagration to detonation. The addi­ and pressure. This pressure rise is higher for tion of inert particles always results in a decrease larger inert particles. In all cases the addition of of the detonation velocity, but the temperature and inert particles causes a temperature rise in the pressure in the detonation front may be even higher. detonation front of as much as 400-:-- 600K. The Dust explosions are usually very complicated in addition of inert particles always decreases the nature and detailed studies are necessary to fully detonation velocity. For an obvious reason, the same explain of the phenomena observed and to better concentration of small inert particles causes a larger predict their initiation and development. In this velocity deficit than that for larger particles. This paper only the most important aspects of dust relationship is shown in Figure 10. As with gaseous explosions were mentioned. mixtures, increased addition of inert particles hinders the transition to detonation and significantly de­ References creases the propagation velocity of the flame. A very 1) Eckhoff, R.K.: Dust Explosions in the Process In­ large addition of inert particles eventually quenches dustries, Batterworth-Hinemann, 1991. combustion. Inert particles of smaller diameter are 2) Cybulski, W.: Coal Dust Explosions and Their Suppres­ more efficient in impeding the transition to detonation sions, Warsaw, 1975. and in inhibiting ignition. The greater effectiveness of 3) Wolanski, P.: Explosion Hazards of Agricultural Dust, smaller particles is basically due to greater heat and Proceedings of the International Symposium on Grain momenum transfer. Dust, Manhattan, KS, 1979, pp. 422-446. 4) Wolanski, P.: Minimum Explosive Concentration of Dust-Air Mixtures, Proceedings of the Sixth Inter­ 8. Conclusions national Colloquium on Dust Explosions, Deng Xufan, Many organic and inorganic types of dust are very P. Wolanski, (Ed.), Northeastern University Press, Shenyang, 1994, pp. 206-219. explosive when mixed with air. The explosive energy 5) Hanert, F., Vogl, A.: Measurement of Dust Cloud of a typical industrial dust can be higher than the Characteristics in Industrial Plants, Dust Explosion explosive energy of the equivalent mass of TNT. Protecting People, Equipment, Buildings and Environ­ ments, Conference Documentation, IBC, London, "" sand 0.10-0.16 Ill Ill 1995, pp. 12-63. ~ 1800 o sand 0.40-0.60 llllll 6) Field, P.: Dust Explosions, Elsevier, Amsterdam, 1982. 7) Wolanski, P.: Grain Dust Explosion and Control, Warsaw 0 University of Technology, Warsaw, 1993. 0 3 1600 0 8) Van der Wei, P.G.]., Lemkowitz, S.M., Leschonski, §"' 0 S., and Scarlett, B.: Ignition of Dust Clouds Using :ii Pulsed Laser Beams, Proceedings of the Sixth Inter­ national Colloquium on Dust Explosions, Deng Xufan, P. Wolanski (Ed.), Northeastern University Press, Shenyang, 1994, pp. 125-140. Concentration of sand Cs (kgfm:l) 9) Itagaki, H., and Matsuda, T.: Thermal Ignition of Fig. 10 Influence of inert sand particle concentration on detona­ Activated Carbon Dusts, Proceedings of the Sixth tion velocity of flax dust with concentration 0.91 kgfm3 International Colloquium on Dust Explosions, Deng in 95% 0 2, 5% N2 atmosphere

KONA No.14 (1996) 151 Xufan, P. Wolanski (Ed.), Northeastern University 16) Gardner, B.R., Winter, R.]., and Moore, M.J.: Press, Shenyang, 1994, pp. 141-145. Explosion Development and Deflagration-to-Detona­ 10) Proust, C.: Experimental Determination of the Maxi­ tion Transition in Coal Dust/Air Suspensions, Twenty­ mum Flame Temperature and of the Laminar Burning first Symposium (International) on Combustion, The Velocities for some Combustible Dust-Air Mixtures, Combustion Institute, 1986, pp. 335-343. Proceedings of the Fifth International Colloquium on 17) Alexander, C.G., Harbaugh, A.S., Kauffman, C.W., Dust Explosions, Pultusk near Warsaw, 1993, pp. Li, Y.C., Cybulski, K., Dyduch, Z., Lebecki, K., Sliz, 161-184. ]., Klemens, R., Wolanski, P., Zalesinski, M.: The 11) Mazurkiewicz, ]., Jarosinski, ].: Temperature and Establishment of Dust Detonation, Archivum Com­ Laminar Burning Velocity of Cornstarch Dust-Air bustionis, Vol. 13, 1993, No. 3-4, pp. 261-269. Flames, Proceedings of the Fourth International 18) Jarosinski, ]., Klemens, R., and Wolanski, P., In­ Colloquium on Dust Explosions, Porabka-Kozubnik, vestigation of inert particles influence on gaseous 1990, pp. 82-94. flame structure near the lean flammability limit, 12) Wolanski, P. (Ed.): Investigation of Flame Structure Proceedings of the First International Colloquium on During Laminar and Turbulent Burning in Dust-Air Explosibility of Industrial Dusts. Baran6w. 1984, pp. Mixtures, Dust Explosions, Protecting People, Equip­ 8-10. ment, Buildings and Environment, Conference Docu­ 19) Goral, P., Klemens, R., and Wolanski, P., Mechanism ments, London, 1995, pp. 168-224. of Gas Flame Acceleration in the Presence of Neutral 13) Pedersen, L.S., Van Wingerden, K.: Measurement Particles, Progress in Astronautics and Aeronautics, of Fundamental Burning Velocity of Dust-Air Mixtures Vol. 113, 1987, pp. 325-335. in Industrial Situations, Dust Explosions, Protecting 20) Wolanski, P., Liu, ].C., Kauffman, C.W., Nicholls, People, Equipment, Building and Environment, Con­ ].A., and Sichel, M., The Effect of Inert Particles on ference Documents, London, 1995, pp. 140-167. Methane-Air Detonation, Archivum Combustionis, 14) Tezok, F.I., Kauffman, C.W. Sichel, M., and Nicholls, Vol. 8, 1988, pp. 15-32. ].A.: Turbulent Burning Velocity Measurements for 21) Wolinski, M., Wolanski, P., Gaseous Detonation Pro­ Dust-Air Mixtures in a Constant Volume Spherical cesses in Pressure of Inert Particles, Archivum Com­ Bomb, Dynamics of Reactive Systems, Part II: bustionis", Vol. 7, 1987, pp. 353-370. Modelling and Heterogeneous Combustion, Progress 22) Klemens, R., Kapuscinski, M., Wolinski, M., and in Astronautics and Aeronautics, Vol. 105, 1985, pp. Wolanski, P., Investigation of Organic Dust Detonation 184-195. in the Presence of Chemically Inert Particles, Com­ 15) Bartknecht, W.: Explosions, Course, Prevention, bustion and Flame, Vol. 99, 1994, pp. 742-748. Springer-Verlag, New York, 1981.

Author's short biography P. Wolariski

Prof. P. Wolanski graduated from Warsaw University of Technology (1966) and obtained his doctorate (1971) and habilitation (1979) in the field of combustion. Since graduation he has been working at The Institute of Heat Engineering of Warsaw University of Technology. He is a specialist in the fields of dust explosions, combustion in engines and detonation. He has worked as a visiting scientist and as a visiting professor at The University of Michigan and at The Institute of Theoretical and Applied Mechanics of the USSR Academy of Sciences in Novosibirsk. He has been an organizer and co-organizer of seven International Colloquia on Dust Explosions. He is currently President of The Polish Combustion Institute.

152 KONA No.14 (1996)