Research Article EMERGING EMERGENCY DUE TO DUST EXPLOSIONS IN PROCESS INDUSTRY G. Vijayaraghavan

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1 Research Article EMERGING EMERGENCY DUE TO DUST EXPLOSIONS IN PROCESS INDUSTRY G. Vijayaraghavan Address for Correspondence Assistant Professor, Chemical Engineering, Adhiparasakthi Engineering College, Melmaruvathur , India ABSTRACT The paper describes, with the help of several representative case studies, how dust explosions commonly occur in process industry all over the world and the devastation they cause to life and property. Dust explosions also pose serious risk of environmental contamination. The near-total lack of documentation vis a vis dust explosions in India is highlighted. The paper also describes the materials involved, the initiating factors, and the fatalities typically associated with dust explosions. It makes out a case for generating awareness towards the dust explosion hazard in India. INTRODUCTION When the subject of accidents in chemical process industries is discussed in India, the focus is mainly on toxic releases such as the one that occurred in Bhopal in 1984 or on vessel bursts and accompanying fires such as the ones occurred as the HPCL refinery in Vishakapatnam on The terms VCE (Vapour Cloud Explosion), BLEVE (Boiling Liquid Expanding Vapour Explosion), pool fire, flash fire, fireball are heard most of the time there is a seminar on process industry accidents. In comparison, the phenomena of dust explosion is much less discussed or cognized. This is highly worrisome because some of the most damaging accidents in chemical and agro processing industries have been caused not by flammable liquids or gases but dusts. As many as 36 people died at Westwego, Louisiana, in 1977, in a grain dust explosion. Property worth over $32 million (Rs 160 crores) was destroyed. As detailed in the following section, heavy causalities and property damage has occurred in dust explosions throughout the world. More than 70 % of powders processed in industry being combustible, a vast majority of industrial plants that have powder-processing equipment are susceptible to dust explosions. In India, information pertaining to dust explosions is almost non- existent solely because in most accidents that occur in India, the broad term Explosion is used and recorded while the type of explosion goes unreported. Also, in public perception, explosions are what occur in pressurized vessels containing gases, liquids, or by the operation of explosives. Dust is seldom perceived as a cause for explosions. The R&D on dust explosions is also almost non-existent in India even as major advancements in other areas of accident forecasting and loss prevention continue to be achieved in India (Abbasi and Abbasi 2005). The fact is that dust explosions match or exceed the ferocity of well-known industrial disasters like the one that occurred in Felixborough (Khan &Abbasi 1998). This situation is quite different from the one existing in developed countries where dust explosions are recognized as very major industrial hazards and meticulous attention is paid towards their prevention/control. ILLUSTRATIVE CASE HISTORIES Even though mention of dust explosions is available since 1785 (Morozzo 1785 cited in Lees 2005), greater details are available only since the 20 th century. One of the earliest and most serious accidents was the grain dust explosion of the Peavey terminal elevator at Duluth, Minn., in1916. After the explosion, the cribbed grain bins caught fire, completely destroying the elevator. This was one of the worst roaring infernos in dust explosions. An explosion in a starch / corn plant at Cedar Rapids, Iowa, in 1919 killed 43 people and one at a similar plant in Peking, Illinois, in 1924 resulted in 42 deaths (Lees 1996, 2005). In the Port Colbourne elevator in Ontario, Canada, explosion occurred in steel bins, the roof being blown off entirely. The ensuing fire also damaged the head house seriously. A grain dust explosion also seriously damaged the grain elevator No. 4A of the Saskatchewan grain pools, Sept. 24, 1952, where six men were killed and 14 injured. The primary explosion in a shipping bin was followed by a secondary explosion involving large quantities of dust, which had been allowed to accumulate in the building. The roof gallery above the bins was also destroyed. Dust explosions frequently sweep feed mills. A corn dust explosion occurred in the feed mill Wayne Feeds at Waynesboro, U.S.A., May 25, Three men were killed, 13 were injured, and the violent explosion caused extensive property damage. A grain dust explosion occurred in the workhouse of the South Chicago elevator in Because of the light steel frame construction of the roof gallery on top of bins, the explosion pressure was relieved so that the concrete bins below were not seriously damaged. Another severe explosion occurred in Kansas City, Mo., in 1958, when the Murray elevator was badly damaged. The head house of steel construction was

2 completely shattered and its installations destroyed by fire. A dust explosion, which was caused by welding of a spout, excessively worn by the flow of grain, occurred in the Kampffmeyer grain silo at Albern near Vienna, July 4, The welding was performed in the elevator pit, when a spark ignited the dust in the running bucket elevator. The pressure wave of the explosion went up through the elevator shaft, ripping the casing of the elevator leg, and continuing up to the roof, causing severe damage to the building and machinery. A flour dust explosion caused serious damage to the Sun flourmills in London on Aug. 7, 1965, four men died and 37 were injured when a giant blast shattered and set ablaze the mill building and a wheat storage silo of cribbed construction. The explosion is believed to have been initiated by welding a bin containing flour. In Germany, a most violent dust explosion on Dec. 14, 1970, seriously damaged the grain silos at Kiel- Nordhafen on the Kaiser Wilhelm shipping canal, connecting the North and Baltic seas. It was the worst accident of this kind in Germany. Six men died and 17 were injured. The damage to plant, building and machinery is estimated at 10 million dollars. And finally the latest important dust explosion occurred again in the United States at Destrahan near New Orleans, where a Bunge Corp. terminal elevator with an 8,000,000- bushel capacity was badly damaged. The roof gallery above the storage tanks was entirely blown off. A checked belt conveyor reportedly caused it. The heat from the explosion and the resultant fire badly damaged the concrete storage bins and the adjacent workhouse. Dry BPO (Benzoylperoxide) exploded at a BPO manufacturing plant. Dai-ichi Kasei Kogyo Co., Ltd in Aug 1990, many workers were killed and injured in this accident. The storage of an illegal quantity of dry BPO resulted in significantly more damage (Choi 2003). An explosion occurred at the Daido KakoEnka Firework manufacturing factory, Moriya, Ibaraki, in June 1992 resulting in the death of 3 persons and injury of 58, including passerby. The presumed cause of this accident was the ignition of powdery mixture of potassium chlorate &aluminium by fraction during the friction during the mixing. A fire broke out a textile mill, Shinko Seishoku Co., and Ltd., Okaharu, Kumamoto in Dec The fire caused by the ignition of dusty cotton waste as a result of electricity leak. The factory was destroyed (Vijayaraghavan 2004). A large dust explosion occurred at the Kanaya Shoe making factory in Taito, Tokyo in Dec 1994 killing 5 workers & injuring 22 persons, including passerby. The cause of the explosion was static electricity in fine rubber waste dust. A tantalum dust deflagration occurred in a bag filter dust collecting devices in April 1997, which resulted in a fatal accident.one worker, was killed, & another was seriously wounded. A Mg Al alloy exploded in a bag filter dustcollecting device at a manufacturing plant of electronic devices in Oct One worker was killed & one was injured in this accident (Choi 2003). FREQUENCY OF DUST EXPLOSIONS Dust explosions are a major hazard in many industrial processes. In operations such as crushing and grinding, conveying, classifying and storage, an explosion may occur in the presence of combustible dusts or powders. A lot of accidental dust explosions take place in industrial plants that have powderprocessing equipment. This is because more than 70% of powders processed in industry are combustible. It is essential, therefore, to accumulate as much knowledge as possible on the explosion hazards of combustible powders. It is estimated that at least one major dust explosion occurs every day in each industrialized country (Proust 2005). The same statistics claim that 9% of all 381 accidents analysed were caused by static electricity if all different kinds of products are taken into accounts whereas this percentage increases to 34% if only polymeric powders (47 explosions) are included. The HSE booklet lists a wide range of industries and operations in which serious dust fires/explosions have occurred. Vijayaraghavan (2004) gives a detailed analysis of dust explosions, excluding those in coalmines, in the period He lists 1110 explosions and 648 fatalities. Some statistical details on dust explosions are given by Lunn (1992). In the UK in the period , there were 247 reported explosions with 9 fatalities and 324 non-fatal injuries, and in the period there were 474 explosions reported with 25 fatalities and 633 non fatal injuries; 10 of the 25 fatalities in this latter period occurred in two incidents. Lunn also quote two other surveys. One is by the HSE covering the periods and , and gives breakdowns by type of event, dust involved, equipment involved and ignition source. In the total period there were 36 dust fires with injury, 123 explosions with no injury. Principal items of equipment involved were mills, grinders, filters, driers, silos/hoppers and ducts with 51(17%), 47 (16%), 43(14%), 19(6%), and 15(5%) events, respectively; 95(31%) events were classified in the category other. The second survey is by the Berufsgenossenschaftliches Institut fur Arbeitssicherheit (BIA) and gives breakdowns by plant group, equipment involved and ignition sources. In the report 1120 explosions are mentioned in the United States during the period from 1900 to 1956, of which 536 (48% of the total number

3 explosions) have occurred in industries handling grain, feed and flour. In these 536 explosions, 392 persons were killed, 1015 were injured and the material losses amounted $75,888,500. This indicates that dust from grain products is most dangerous because it ignites and propagates flames easily, the source of heat required being small. Included this category are flour, dust from wheat and other grains and seeds, which are the materials of flour milling and ingredients of the food industries. Some detailed studies were conducted in developed countries.a report of dust explosions in U.S.A. from consists of information on 75 most serious explosions out of 1125 recorded (Eckhoff 1991). This covered a wide range of dusts wood, food and feeds, metals, plastics, coal, paper and chemicals. A report on statistics for Federal Republic of Germany for dust explosion during the period gives a brief description of specific type of plant, specific plant item, dust type likely ignition source, number of fatalities injuries and material losses (Jaske and Beck, 1989). The total number of explosions recorded was 426 for It was estimated that the recorded explosions represent only 15 per cent of the total dust explosions of Federal Republic Germany from was therefore about 2840 (142 per year). The data from Federal Republic of Germany, presented in Figure 1 can be compared directly with the data from U.S.A. There are differences in the distribution of the number of explosion accidents on various dust categories (Mittal et. al 1999). For example Food and feed represents 25 percent of all explosions in Federal Republic Germany, whereas in U.S.A this percent was greater than 50. On the other hand, the percent of explosions involving metal dusts was about twice as high in Federal Republic Germany than in U.S.A. This probably reflects the extra violence and radiation of flames of metals like Mg, Al, and Si. These differences in explosions from both the countries reflect both a change with time, from first to second part of the century and differences between the structures of the industry. Table 1Dust explosions in Japan (Nifuku 2000) Year Explosions Death Injuries Totals Figure 1 Frequencies of dust explosion for various groups of dust in U.S.A and Germany.

4 Considering some statistics of dust explosion, among a total of 248 cases reported in Japan between 1952 and 1990, there were 44 cases of agricultural products (food and feed), 13 of coal, 29 of inorganic materials, 60 of metals and alloys, 32 of chemical synthetic materials, 46 of intermediate and additives, 23 of cellulose materials and one miscellaneous (Matsuda, 1993). As the probable ignition source, static electricity is listed (25.7%) as the cause of the dust explosion cases between 1981 and 1990 (Matsuda, 1993). Proust (1996) has summarized some of the statistics as under, In Germany, it is estimated that the number of dust explosions in industry might be the order of 160 per year (period ). In the USA. From 1900 to 1956, more than 1000 dust explosion accidents in the industry were reported and among them 50% occurred in the food and feed industry; for the period Only 250 dust explosions which occurred in the feed industry were reported. In Japan, from 1969 to 1973, a figure of 187 dust explosions in the grain storage facilities is given. In U.K., more than 400 dust explosions during the period were reported. In France, statistics do not seem to be available but it might be estimated that the order of magnitude of the frequency of dust explosions in the industry might be one accident per working day. CAUSES OF DUST EXPLOSION Surveys of industrial dust explosions incidents show that, in a substantial percentage, friction and mechanical failure and flames and flaming material are known ignition sources. Surveys for the UK (Abbott, 1985; Porter.1989) covering , and reviewing 303 events, showed friction and mechanical failure to be the reason for ignition in 18 % of these incidents, and flames and flaming material to be responsible in another 15 %. Overheating and spontaneous heating featured in a further 17 %. Similarly, a survey by the BerufsgenossenschaftlichesInstitut fur Arbeitssecherheit (BIA) (Jeske and Beck, 1989) showed mechanical causes to be the most frequent sources if ignition, with smouldering nests the second most frequent (Lunn 2003). The relevant percentages from BIA survey were 26% for mechanical sparks 11% for smouldering nests and 9% for mechanical heating. Figure 2 correlates frequencies of dust explosions with the probable ignition sources. Mechanical sparks are frequent ignition sources in dust collectors, mills and grinding plants. Electrostatic discharges were the dominating ignition sources in mixing plants but electrostatic discharge ignition occurred almost solely with plastic dusts ( Mittal et. al 1999).Presumably, mixers are quite frequent in plant producing and handling plastic dust and the combination of mixture and plastic dusts is favorable for generating electrostatic discharge. Figure 3 shows the involvement of various categories of plant items in explosions in general and that for two dusts wood / wood products and coal in particular. This reflects differences between typical processes for producing, storing and handling the various categories of powders and dusts. Figure 2. Frequencies of dust explosions caused by various types of ignition sources in Germany

5 40 Frequency 20 Wood/wood products Total Coal Dust 0 Storage Units Dust Collecting Units Pulverizing Units Conveying Systems Group of Installations Dryers Furnaces Mixing Plants Others and unknowns Figure 3 Frequencies of dust explosions caused by various types of Industrial Installations in Germany Number of explosions Table 2 Proportions of ignition sources in dust explosions % Ignited by friction sparks %Unknown % Ignited by friction sparks + unknown Period Table 3Dust explosion involving different materials (Nifuku 2000) Dust Type Explosions Death Injuries Coal Inorganic Metals Food and Feed Chemical synthetic materials Intermediate additives Cellulosic materials Miscellaneous Table 4Principle items of equipment involved in dust explosions Silos, bunkers % Dedusting units, separators % Grinding and crushing systems % Conveying systems % Dryer 8. 0 % Firing plant 5. 4 % Blender 4. 7 % Grinding and polishing machines 4. 5 % Scales 0. 5 % Others 16.4% UNITS AND MATERIAL INVOLVED IN DUST EXPLOSION According to an analysis by Matsuda (1993) of dust explosions, among a total of 248 cases reported between 1952 and 1990, there were 44 cases of agricultural products (food and feed), 13 of coal, 29 of inorganic materials, 60 of metals and alloys, 32 of chemical synthetic materials, 46 of intermediate and additives, 23 of cellulosic materials and one miscellaneous. CONCLUSION From the case studies and accident-related statistics presented in this paper, it is evident that dust explosions are among the most frequent and destructive of the types of accidents that occur in process industry. The paper also brings out the severity of harm in terms of loss of lives and property besides environmental contamination that generally accompanies dust explosions. Surprisingly very little awareness and almost no information exists on dust explosions in India. This makes it imperative that efforts are vested towards generating awareness and stimulating R&D on dust explosions in India. REFERENCES 1. Abbasi, Tasneem, and Abbasi, S. A. (2005). The expertise and the practice of Loss prevention in the Indian process industry. Trans IChemE (UK), 83 (B5)

6 2. Abbot, J. A. (1985). BMHB Survey of dust fire and explosions in the UK British Materials Handling Board, ISBN Choi K.S (2003), Doctorial Dissertation Report, Ibaraki University, Japan. 4. Eckhoff, R. K. (1991). Dust Explosions in the Process Industry. Butterworth-Heinemann. 5. Gummer, J., and Lunn, G. A. (2003). Ignitions of explosive dust clouds by smouldering and flaming agglomerates. Journal of Loss Prevention in the Process Industries, Jeske, A., and Beck, H. (1989). Evaluation of dust explosions in the Federal Republic of Germany, EUROPEX Newsletter No 9, p Khan, F. I., and Abbasi, S. A. (1998). Risk Assessment in the Chemical Process Industries: Advanced Techniques. (New Delhi: Discovery Publishing House), xii+364 pages. 8. Lees, F. P. (1996). Loss prevention in the Process Industries-Hazard Identification, Assessment, and Control, Vol. 2, (London: Butterworth Heinemann). 9. Lees, F. P. (2005). Lees Loss prevention in the Process Industries (Partially updated by S. Mannan) Vols 1-3, (Oxford: Elsevier - Butterworth Heinemann). 10. Lunn, G. (1992). Dust Explosion Prevention and Protection Part 1 Venting. 3 rd Edition. Institution of Chemical Engineers. 11. Matsuda, T. (1993). Dust explosion incidents in Japan. In Proceedings of the Second IUPAC Workshop on Safety in Chemical Production, Yokohama. pp Mittal, M., and Singh, S. (1999). Risk assessment to size vents for dust explosion in industries. Chemical Engineering World, Nifuku et al, M., Matsuda, T., and Enomoto, H. (2000). Recent developments of standardization of testing methods for dust explosion in Japan. Journal of Loss Prevention in the Process Industries, Porter, B. (1989). Industrial incidents. Paper presented at Dust Explosions: Assessment, Prevention and Protection, 24 th November, London. 15. Proust, C. (1996). Dust explosions in pipes: a review. Journal of Loss Prevention in the Process Industries, Proust, C. (2005). A few fundamental aspects about ignition and flame propagation in dust clouds. Journal of Loss Prevention in the Process Industries,xx Vijayaraghavan, G. (2004). Impact Assessment, Modelling, and Control of Dust Explosions in Chemical Process Industries.MTech thesis, Department of Chemical Engineering, Coimbatore Institute of Technology.