Benxihu (Honkeiko) Colliery ( simplified Chinese : 本溪湖煤矿 ; traditional Chinese : 本溪湖煤礦 ) was a coal mine in Benxi , Liaoning, China, first mined in 1905. Originally an iron and coal mining project under joint Japanese and Chinese control, the mine came under predominantly Japanese control. In the early 1930s, Japan invaded the northeast of China, and Liaoning province became part of the Japanese-controlled puppet state of Manchukuo . During the Second Sino-Japanese War , the Japanese forced Chinese labourers—some of whom had been captured from local military organizations—to work the colliery under very poor conditions. Food was scarce and workers did not have sufficient clothing. Working conditions were harsh, and diseases such as typhoid and cholera flourished due to poor sanitation and water supplies. Typically miners worked 12-hour shifts or longer. The Japanese controllers were known to beat workers with pick handles, and the perimeter of the mine was fenced and guarded. Many describe the conditions as slave labour.
39-465: On April 26, 1942, a gas and coal- dust explosion in the mine sent flames bursting from the mine shaft entrance. Miners' relatives rushed to the site but were denied entry by a cordon of Japanese guards, who erected electric fences to keep them out. In an attempt to curtail the fire underground, the Japanese shut off the ventilation and sealed the pit head. Witnesses say that the Japanese did not evacuate
78-441: A Recommended exposure limit (REL) of 1 mg/m (measured by MSHA) or 0.9 mg/m (measured by ISO/CEN/ACGIH) over an 8-hour workday. It is always the best practice to maintain a clean workplace and control any hazardous material, especially with a fugitive combustible dust such as coal dust. Many explosions from combustible dust are due to accumulation on walls, floors, and other surfaces. The accumulation of uncontrolled coal dust in
117-478: A common procedure to undergo is the three C's: contain, capture, and clean. Following this procedure can help prevent unnecessary inhalation or explosions from occurring if following correctly. The Occupational Safety and Health Administration (OSHA) has set the legal limit ( Permissible exposure limit ) for coal dust exposure in the workplace as 2.4 mg/m (5% SiO 2 ) over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set
156-611: A common source of explosions, causing an estimated 2,000 explosions annually in Europe. The table lists notable incidents worldwide. Incidents in France and the US: Protecting process plant, grain handling facilities, etc. from the risk of dust hazard explosions: Coal dust#Explosions Coal dust is a fine- powdered form of coal which is created by the crushing, grinding, or pulverization of coal rock. Because of
195-507: A dust explosion: Many common materials which are known to burn can generate a dust explosion, such as coal dust and sawdust . In addition, many otherwise mundane organic materials can also be dispersed into a dangerous dust cloud, such as grain , flour , starch , sugar , powdered milk , cocoa , coffee , and pollen . Powdered metals (such as aluminum , magnesium , and titanium ) can form explosive suspensions in air, if finely divided. A gigantic explosion of flour dust destroyed
234-492: A frequent hazard in coal mines , grain elevators and silos , and other industrial environments. They are also commonly used by special effects artists, filmmakers , and pyrotechnicians , given their spectacular appearance and ability to be safely contained under certain carefully controlled conditions. Thermobaric weapons exploit this principle by rapidly saturating an area with an easily combustible material and then igniting it to produce explosive force. These weapons are
273-583: A high risk often use lamps designed for underwater divers , as they have no risk of producing an open spark due to their sealed waterproof design. Good housekeeping practices, such as eliminating build-up of combustible dust deposits that could be disturbed and lead to a secondary explosion, also help mitigate the problem. Best engineering control measures which can be found in the National Fire Protection Association (NFPA) Combustible Dust Standards include: Dust clouds are
312-538: A mill in Minnesota on May 2, 1878, killing 14 workers at the Washburn A Mill and another four in adjacent buildings. A similar problem occurs in sawmills and other places dedicated to woodworking . Since the advent of industrial production–scale metal powder –based additive manufacturing (AM) in the 2010s, there is growing need for more information and experience with preventing dust explosions and fires from
351-519: A naked flame need not be the only one: over one half of the dust explosions in Germany in 2005 were from non-flame sources. Common sources of ignition include: However, it is often difficult to determine the exact source of ignition when investigating after an explosion. When a source cannot be found, ignition will often be attributed to static electricity . Static charges can be generated by external sources, or can be internally generated by friction at
390-415: A powerful explosion when finely divided, and can be ignited by even a small spark. A dust explosion can cause major damage to structures, equipment, and personnel from violent overpressure or shockwave effects. Flying objects and debris can cause further damage. Intense radiant heat from a fireball can ignite the surroundings, or cause severe skin burns in unprotected persons. In a tightly enclosed space,
429-400: A precaution known as "inerting". Typically this uses nitrogen , carbon dioxide , or argon , which are incombustible gases which can displace oxygen. The same method is also used in large storage tanks where flammable vapors can accumulate. However, use of oxygen-free gases brings a risk of asphyxiation of the workers. Workers who need illumination in enclosed spaces where a dust explosion is
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#1732797338382468-433: A surface area of 0.048 square metres (0.52 sq ft). However, if it were broken up into spherical dust particles 50 μm in diameter (about the size of flour particles) it would have a surface area of 120 square metres (1,300 sq ft). This greatly-increased surface area allows the material to burn much faster, and the extremely small mass of each particle allows them to catch on fire with much less energy than
507-745: A workplace is a dangerous situation that needs to be eliminated. The control of coal dust can be improved by implementing the use of dust-approved vacuums, dust collection systems, methods to reduce fugitive coal dust, and following general housekeeping procedures. To prevent explosions, it is best to promote and execute good hygiene practices in the workplace by controlling both the coal dust and any possible ignition sources. Some ignition sources that may need to be controlled or used carefully around coal dust includes heavy machinery, electrical components, and open flames or sparks. The main attempts at preventing explosions due to coal dust include using safety lamps , adding stone dust coffers to mine galleries to dilute
546-721: Is a greater explosion risk than a full one. This is due to the increase of space in the store for oxygen and dispersion to take place. The worst mining accidents in history have been caused by coal dust explosions , such as the disaster at Senghenydd in South Wales in 1913 in which 439 miners died, the Courrières mine disaster in Northern France which killed 1,099 miners in 1906, the Luisenthal Mine disaster in Germany, which claimed 299 lives in 1962, and
585-423: Is ground into dust using a device called a powdered coal mill . The resulting product, called powdered coal or pulverized coal , is then generally used in a fossil fuel power plant for electricity generation . Pulverized coal is a significant dust explosion hazard, as large quantities are suspended in air for transfer from the mill to the power plant. Explosions have occurred when the flow drops and flames in
624-563: Is now part of the production mix. Although not strictly a dust, paper particles emitted during processing – especially rolling, unrolling, calendaring/slitting, and sheet-cutting – are also known to pose an explosion hazard. Enclosed paper mill areas subject to such dangers commonly maintain very high air humidities to reduce the chance of airborne paper dust explosions. In special effects pyrotechnics , lycopodium powder and non-dairy creamer are two common means of producing safe, controlled fire effects. To support rapid combustion,
663-427: Is the rapid combustion of fine particles suspended in the air within an enclosed location. Dust explosions can occur where any dispersed powdered combustible material is present in high-enough concentrations in the atmosphere or other oxidizing gaseous medium, such as pure oxygen . In cases when fuel plays the role of a combustible material, the explosion is known as a fuel-air explosion. Dust explosions are
702-411: The acute hazard of forming an explosive mixture in air and the chronic hazard of causing pulmonary illness in people who inhale excessive quantities of it. The distribution of the particle-size of coal dust is frequently measured in mesh . The British slang term for cheap fuel consisting of coal dust (slack) containing small lumps of coal (nuts) is nutty slack . For use in thermal power plants , coal
741-404: The air for a large amount of time. Coal dust suspended in air is explosive—coal dust has far more surface area per unit weight than lumps of coal, and is more susceptible to spontaneous combustion . However, five elements are needed for an explosion to occur: oxygen, an ignition source, coal dust, dispersion of the coal dust, and confinement of the dust. For instance, a nearly empty coal store
780-416: The brittle nature of coal, coal dust can be created by mining , transporting, or mechanically handling it. Grinding or pulverizing coal to a dust form before combusting it improves the speed and efficiency of burning, which makes the coal easier to handle. However, coal dust is hazardous to workers if it is suspended in air outside the controlled environment of grinding and combustion equipment. It poses
819-416: The bulk material, as there is no heat loss to conduction within the material. When this mixture of fuel and air is ignited, especially in a confined space such as a warehouse or silo, a significant increase in pressure is created, often more than sufficient to demolish the structure. Even materials that are traditionally thought of as nonflammable (such as aluminum), or slow burning (such as wood), can produce
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#1732797338382858-433: The burning chamber pass back along the ductwork delivering fuel. Coal dust is a fugitive combustible dust - a dust that is both a pollutant and combustible when dispersed into the air. Due to the small particle size and combustible nature of this dust, there is a risk of an explosion and inhalation. The control of coal dust is difficult due to the coal dust being such a fine particle, allowing it to escape and be suspended in
897-407: The burns. The Japanese at first reported the death toll to be 34. Initial newspaper reports were short, as few as 40 words, and downplayed the scale of the disaster, characterizing it as a minor event. Later the Japanese erected a monument to the dead. This stone gave the number of dead as 1,327. The true number is believed to be 1,549, 34% of the miners working that day. It was the worst disaster in
936-412: The coal dust, watering workings and ensuring efficient ventilation of all the workings. Another means of preventing explosions is by placing rock dust in the coal mine, which is usually pulverized limestone dust, which absorbs thermal energy from the heated gasses. Rock dusting has been used since the early 1900s, but there have been technological improvements since then. Since then, NIOSH developed
975-399: The dust must consist of very small particles with a high surface area to volume ratio , thereby making the collective or combined surface area of all the particles very large in comparison to a dust of larger particles. Dust is defined as powders with particles less than about 500 micrometres in diameter, but finer dust will present a much greater hazard than coarse particles by virtue of
1014-402: The external atmosphere. Secondary dust explosions are the result of dust accumulation inside a building being disturbed and ignited by the primary explosion, resulting in a much more dangerous uncontrolled explosion that can affect the entire structure. Historically, fatalities from dust explosions have largely been the result of secondary dust explosions. There are five necessary conditions for
1053-463: The history of coal mining and the second-worst recorded industrial accident. Of this number, 31 fatalities were Japanese, the remaining 1,518 were Chinese. The Japanese continued to operate the mine until the end of World War II in 1945, when they were defeated and forced to withdraw from China. Following the Japanese withdrawal, the Chinese workers took control of the site. With the liberation after
1092-475: The industry. In the coal mining industry, a methane explosion can initiate a coal dust explosion, which can then engulf an entire mine pit. As a precaution, incombustible stone dust may be spread along mine roadways, or stored in trays hanging from the roof, to dilute the coal dust stirred up by a shockwave to the point where it cannot burn. Mines may also be sprayed with water to inhibit ignition. Some industries exclude oxygen from dust-raising processes,
1131-484: The larger total surface area of all the particles. Below a certain value, the lower explosive limit (LEL), there is insufficient dust to support the combustion at the rate required for an explosion. A combustible concentration at or below 25% of the LEL is considered safe. Similarly, if the fuel to air ratio increases above the upper explosive limit (UEL), there is insufficient oxidant to permit combustion to continue at
1170-730: The most powerful non-nuclear weapons in existence. If rapid combustion occurs in a confined space , enormous overpressures can build up, causing major structural damage and flying debris. The sudden release of energy from a " detonation " can produce a shockwave , either in open air or in a confined space. If the spread of flame is at subsonic speed, the phenomenon is sometimes called a " deflagration ", although looser usage calls both phenomena " explosions ". Dust explosions may be classified as being either "primary" or "secondary" in nature. Primary dust explosions may occur inside process equipment or similar enclosures, and are generally controlled by pressure relief through purpose-built ducting to
1209-450: The necessary rate. Determining the minimum explosive concentration or maximum explosive concentration of dusts in air is difficult, and consulting different sources can lead to quite different results. Typical explosive ranges in air are from few dozens grams/m for the minimum limit, to few kg/m for the maximum limit. For example, the LEL for sawdust has been determined to be between 40 and 50 grams/m . It depends on many factors including
Benxihu Colliery - Misplaced Pages Continue
1248-410: The pit fully before sealing it, trapping many Chinese workers underground to suffocate in the smoke. The Soviet Union later investigated and blamed the actions of the Japanese for needlessly increasing the death toll. It took workers ten days to remove all the corpses and rubble from the shaft. The dead were buried in a mass grave nearby. Many victims could not be properly identified due to the extent of
1287-522: The sudden depletion of oxygen can cause asphyxiation . Where the dust is carbon based (such as in a coal mine), incomplete combustion may cause large amounts of carbon monoxide (the miners' after-damp ) to be created. This can cause more deaths than the original explosion as well as hindering rescue attempts. Much research has been carried out in Europe and elsewhere to understand how to control these dangers, but dust explosions still occur. The alternatives for making processes and plants safer depend on
1326-471: The surfaces of particles themselves as they collide or move past one another. Dusts have a very large surface area compared to their mass. Since burning can only occur at the surface of a solid or liquid, where it can react with oxygen, this causes dusts to be much more flammable than bulk materials. For example, a 1 kilogram (2.2 lb) sphere of a combustible material with a density of 1 g/cm would be about 12.4 centimetres (4.9 in) in diameter, and have
1365-578: The time. Coalworker's pneumoconiosis, or black lung disease , is caused by inhaling coal dust, typically dust produced in coal mining . Government agencies in the United States have set exposure limit guidelines for coal dust inhalation. For safe handling/storage of coal dust, the dust must be controlled, maintained, and protected properly. With the presence of coal dust within multiple industries, such as: mining, energy generation, and concrete production, different approaches are necessary. However,
1404-605: The traces of excess metal powder sometimes left over after laser sintering or other fusion methods. For example, in machining operations downstream of the AM build, excess powder liberated from porosities in the support structures can be exposed to sparks from the cutting interface. Efforts are underway not only to build this knowledgebase within the industry but also to share it with local fire departments, who do periodic fire-safety inspections of businesses in their districts and who can expect to answer alarms at shops or plants where AM
1443-587: The type of material used. Typically, normal atmospheric oxygen can be sufficient to support a dust explosion if the other necessary conditions are also present. High-oxygen or pure oxygen environments are considered to be especially hazardous, as are strong oxidizing gases such as chlorine and fluorine . Also, particulate suspensions of compounds with a high oxidative potential, such as peroxides , chlorates , nitrates , perchlorates , and dichromates , can increase risk of an explosion if combustible materials are also present. There are many sources of ignition, and
1482-521: The war, the Soviet Union investigated the accident. They found that only some of the workers died directly from the gas and coal-dust explosion. Most deaths were from carbon monoxide poisoning produced when the Japanese closed the ventilation and sealed the pit head after the initial explosion. 41°19′40″N 123°46′25″E / 41.32778°N 123.77361°E / 41.32778; 123.77361 Dust explosion A dust explosion
1521-415: The worst: the explosion at Benxihu Colliery , China, which killed 1,549 in 1942. Such accidents were usually initiated by firedamp ignitions, the shock wave of which raised coal dust from the floor of the mine galleries to make an explosive mixture. The problem was investigated by Michael Faraday and Charles Lyell at the colliery at Haswell County Durham of 1844, but their conclusions were ignored at
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