煤化工粉尘防爆！？ 这是我近期看的一篇文章，大概翻了一下，大家随便看看，可能会有点帮助。 COAL DUST EXPLOSION HAZARDS 煤粉尘爆炸风险 by 作者 CLETE R. STEPHAN, P.E. MINE SAFETY AND HEALTH ADMININSTRATION PITTSBURGH, PENNSYLVANIA 矿业安全和健康管理协会 匹斯堡 宾西法尼亚 ABSTRACT 摘要 There are a large number of facilities throughout the world which handle coal, such as preparation plants. Many other facilities use coal as a fuel, such as cement and lime factories. Although coal can be handled safely and can be an efficient fuel, there are explosion hazards which are accentuated as the particle size is reduced. Particle sizes of coal which can fuel a propagating explosion occur within thermal dryers, cyclones, baghouses, pulverized-fuel systems, grinding mills, and other process or conveyance equipment. This paper discusses how explosions can occur within these facilities. 世界上有很多工厂需要处理煤炭，比如制剂厂。很多其它工厂以煤炭为生产原料，如水泥厂和石灰石厂。虽然煤炭能安全的处理并有效的燃烧，但随着煤炭颗粒尺寸的减小，存在爆炸的危险在增大。颗粒尺寸的原煤可以燃烧并导致连锁性爆炸，爆炸经常出现在热干燥系统，旋风除尘系统，库房和粉状燃料系统系统，磨机和其它工艺或输送设备中。本文主要讨论暴炸是如何在这些工厂中发生的。 FIRE TRIANGLE AND EXPLOSION PENTAGON 燃烧三要素和爆炸五边形（要素） There are three necessary elements which must occur simultaneously to cause a fire: fuel, heat, and oxygen. These elements form the three legs of the fire triangle. By removing any one of these elements, a fire becomes impossible. For example, if there were very little or no oxygen present, a fire could not occur regardless of the quantities of fuel and heat that were present. Likewise, if insufficient heat were available, no concentrations of fuel and oxygen could result in a fire. 需要以下三个要素同时存在才能导致燃烧：燃料，热和氧的存在，这些元素形成了燃烧三角型的三个边。如果去掉任何一个因素，燃烧是不可能发生的，举个例子，如果不存在氧气或者只有很少氧气存在，无论热量有多大，有多少燃料，都不会燃烧。同样的，如果没有充足的热量，没有一定浓度的燃料和氧气也无法燃烧。 On the other hand, for an explosion to occur, there are five necessary elements which must occur simultaneously: fuel, heat, oxygen, suspension, and confinement. These form the five sides of the explosion pentagon. Like the fire triangle, removing any one of these requirements would prevent an explosion from propagating. For example, if fuel, heat, oxygen, and confinement occurred together in proper quantities, an explosion would still not be possible without the suspension of the fuel. However, in this case, a fire could occur. If the burning fuel were then placed in suspension by a sudden blast of air, all five sides of the explosion pentagon would be satisfied and an explosion would be imminent. 另一方面，对于爆炸现象的出现，需要以下5个因素同时存在：当燃料，热和氧气，悬浮，并且在密闭空间中，形成了爆炸五边型（要素）。就像三角型一样，取除任何一个所需要因素，都可以阻止爆炸的传播（发生）举个例子，如果燃料，热源和氧气在密闭空间中，处在一个合适的范围内，但并不是悬浮状态，则不会发生爆炸，但是在该情形下，会发生燃烧。如果燃烧的燃料被阵风吹起悬浮起来，则同时满足了爆炸五边型所需的所有条件，爆炸即将发生。 1 Remembering the three sides of the fire triangle (fuel, heat, oxygen) and the five sides of the explosion pentagon (fuel, heat, oxygen, suspension, confinement) is important in preventing fires and explosions at any facility. By eliminating the possibility of either suspension or confinement, an explosion cannot occur, but a fire may occur. By eliminating the fuel, the heat, or the oxygen requirements, neither a fire nor an explosion can occur. 在工厂阻止爆炸的发生，就需要牢记燃烧三要素（燃料，热，氧气）和爆炸五要素（燃料，热，氧气，悬浮，密闭空间）。 Fuel Coal, as a primary fuel, must meet several requirements in order to be explosive. These requirements are volatile ratio, particle size, and quantity. The volatile ratio is a value established by the former United States Bureau of Mines to evaluate the explosibility of coals based on large-scale tests in the Experimental Coal Mine. To calculate the volatile ratio, a proximate analysis must be performed in the laboratory on a sample of the coal. This analysis determines the volatile matter and fixed carbon quantities of the coal along with moisture and ash. The volatile ratio is defined as the volatile matter divided by the summation of volatile matter and fixed carbon of the coal. 燃料 煤，作为一种主要燃料，需要满足几个条件才会发生爆炸。这些条件是挥发份，颗粒尺寸和数量，前美国矿业局在实验性煤矿为评估煤的爆炸性能进行了大规模的实验，证明了挥发份是很有价值的（参数）。为了计算挥发率，需要在实验室先对煤样做一个初步的分析。该分析确定了煤中挥发性物质和固定炭含量，包括水份和灰份，挥发份定义是由煤中挥发性物质除挥发性物质和固定炭之和。 This method for calculating the volatile ratio produces a value independent of the natural or added incombustible in the coal. It has been determined that coals with a volatile ratio exceeding 0.12 present a dust explosion hazard. All bituminous coals fall into this category. Since anthracite coals, by definition, have a volatile ratio of 0.12 or less, they do not present an explosion hazard. It is important to note that both bituminous and anthracite coals can be involved in fires, but only bituminous coals can be involved in explosions. Another important requirement of the fuel is related to particle size. Experiments have shown that bituminous coal particles passing through a U.S. standard 20-mesh sieve can participate in a coal dust explosion. A 20-mesh sieve allows particles up to 841 microns or about 0.03 inch to pass and these are the largest particles that contribute to a coal dust explosion. 该计算模式提供了一个独立于煤炭自然特性或煤中附加不可燃成分的有价值数据，已经证明了，若煤粉中挥发份超过0.12，存在爆炸风险。所有的烟煤都属于此类，既然无烟煤通过确认，挥发份不大于0.12，它们不存在爆炸风险。非常值得注意的是，烟煤和无烟煤都会引起燃烧，但只有烟煤会导致爆炸。另一个重要的条件是粒度，实验已经证明了若烟煤的粒度小于美国标准20目筛则参与煤粉爆炸（则参与爆炸反应）20目筛子可以保证颗粒通过841微米，大约0.03英寸，这是能对爆炸产生左右的最大尺寸。（大于20目的颗粒，不会发生爆炸） As the particle size is reduced even further, a more severe explosion hazard is realized. Typically, in pulverized-fuel systems, the coal is reduced to a particle size where more than 85% will pass a U.S. standard 200-mesh sieve with openings of 74 microns or about 0.003 inch. These coal dust particles require less energy or temperature to ignite and, since heat transfers more quickly between smaller particles, the pressure and rate of pressure rise during an explosion are accentuated. 随着颗粒尺寸的缩小，爆炸危险会增加。通常在磨粉系统中，煤的颗粒尺寸通常有85%以上通过美标200目筛子，小于74微米，或0.003英寸。 点燃这些煤尘的所需要的能量更少，温度更低；既然在小颗粒中，热传递速度更快，那么爆炸产生的压力和产生速度加快了。（爆炸速度和强度增加） 2 The third requirement for explosibility is related to the quantity of coal dust available, known as the minimum explosive concentration (MEC). This is the minimum quantity of dust in suspension that will propagate a coal dust explosion and generate sufficient pressure to cause damage. The MEC for bituminous coal is approximately 0.10 ounce per cubic foot or 100 grams per cubic meter. 第三个与爆炸有关的是煤粉能达到的浓度。以知最低爆炸浓度（MEC），在该最低悬浮浓度煤粉会传播爆炸（连锁燃烧，爆炸），且产生具有破坏性的压力。 烟煤的最低煤粉爆炸浓度大约是0.10盎司/立方英尺，或者100g/立方米。 When pulverized coal dust at the MEC was dispersed in an entry, a cap lamp 10-feet within the cloud was not visible to observers standing in front of the dispersed dust. Also, a person cannot breathe in an atmosphere containing dust at the MEC. This amount of dust in the air is 25,000 times greater than the average concentration of respirable dust to which a coal miner may be exposed during an 8-hour shift. 当煤粉浓度在入口处到达最低爆炸浓度时，在被驱散的煤尘之前无法看到在煤尘中10米远带灯罩的路灯。同样，人在MEC浓度的空气中无法呼吸。该数量相当与一个普通8小时轮班矿工可吸入粉尘浓度的25000倍。 A layer of pulverized coal dust at the MEC deposited on the floor of the Experimental Coal Mine in Bruceton, Pennsylvania averaged 0.005inch thick. This thickness is almost unobservable. In other words, if footprints are visible in coal dust on the floor or the coal dust is seen on the walls of a plant, then there is enough coal dust at that particular location to propagate an explosion. 在宾西法尼亚布鲁斯顿的煤矿实验室中，MEC浓度的煤粉沉降到地板上厚度是0.005英寸厚。该厚度几乎无法观察到，换句话说，如果在工厂的地板上或墙上看到了脚印，那么现场的煤粉浓度足以引发爆炸。 The upper explosive limit is not well-defined and experiments have shown that a coal dust loading of 3.8 ounces per cubic foot would propagate a low-velocity explosion and that a 5.0 ounces per cubic foot loading would quench itself within 10 feet of ignition. The presence of other flammable dusts or gases can lower the MEC of the coal, which increases the hazard. On the other hand, the hazard can be lessened with the addition of ash, rock dust, inert gas, and any other inert material. 爆炸浓度的上限并没有完美的测定；实验表明，3.8盎司/立方英尺的煤尘浓度会引发低强度的爆炸，5.0盎司/立方英尺的浓度会将在点燃处10远的距离熄灭（距离燃火中心外10米处熄灭）。其它可燃性灰尘和气体可导致煤的MEC值降低，在另一方面，如果增加灰份的含量，岩石粉，惰性气体和其它惰性材料可降低爆炸风险。 Heat The heat requirements to complete the fire triangle or the explosion pentagon can be in the form of temperature or energy. The ignition temperature of a coal dust cloud decreases as the volatile content increases. At high volatile contents, the ignition temperature of a coal dust cloud approaches a limiting temperature as low as 440C (824F). The ignition temperature of a Pittsburgh Seam coal dust cloud is fairly constant as the particle size increases to about 180 microns. Further increases in size result in rapid rise in the ignition temperature requirements. As the particle size decreases, the coal dust becomes easier to ignite. 热 满足燃烧三要素和爆炸五边型所需的热通常以温度和能量的形式表现出来。煤尘的点燃温度随着煤挥发性的升高而降低，在高挥发份时，煤粉的点燃温度接近极440度的限温度（华氏824），匹斯堡煤层煤粉的粒度在180微米以下时点燃温度几乎是个常数，随着颗粒尺寸的增加，需要更高的煤粉的点燃温度。随着颗粒尺寸的缩小，煤粉更加容易点燃。 The ignition temperature of a coal dust layer also decreases as the volatile content increases. At high volatile contents, the ignition temperature of a coal dust layer approaches a limiting temperature as low as 160C (320F). With dust layers on hot surfaces, the minimum ignition temperature decreases sharply as the thickness of the deposit is increased. This is due to the fact that thicker dust layers capture and hold heat more readily. 煤粉层的点燃温度随着挥发份的升高而降低。，在高挥发份时，煤粉层的点燃温度接近与极限温度160C，当煤粉聚集在热表面上时，最低点燃温度随着煤粉沉集厚度的增加迅速降低。这实际上是由于较厚的粉尘可吸收和储存了热量更迅速。 To illustrate the variety of coals, the minimum ignition temperatures to ignite clouds of various ranks of coal are as follows: 举个例说明不同的煤种，煤粉雾的最低点燃温度归类如下 煤等级或种类 最低点燃温度 波卡洪塔思 煤层烟煤 610 匹斯堡 煤层烟煤 525-560 次烟煤 混合煤（收到基） 475 次烟煤 混合煤（干基） 455 褐煤 （收到基） 450-600 褐煤 （干基） 425-555 Visually, a temperature of approximately 537EC (1000EF) is obtained when an object is heated to a dull red in a darkened room. Resistors in controllers or other electrical components may exceed this temperature. Also, temperatures at the top of a 200-watt incandescent bulb approach 250EC and, at the top of a 1500-watt incandescent bulb, can exceed 300EC. 从视觉上来说，温度大约537度时，（1000华氏度）当在黑暗的房间里可以看到暗红色。一些控制器里的电阻或者其它电器部件可能超过该温度。同样的，200瓦百炽灯可以达到250度，1500瓦白炽灯的最高温度可超过300度。 There is also a variation in the minimum ignition temperature of coal dust layers as follows: 以下还有几个不同煤种的最低点燃温度 煤等级或种类 最低点燃温度 匹斯堡煤层 170 罗得岛（克兰斯敦）无烟煤 520 伊利挪死 7号烟煤 160 波卡洪塔斯煤层烟煤 220 Electrical or frictional sparks can also provide the heat source for initiating a fire or explosion. Experiments have shown that a coal dust cloud can be ignited directly by frictional sparks in the absence of methane. Dust clouds of lignite and subbituminous coals can ignite with as little as 30 millijoules of energy. Bituminous coal from Kentucky and from the Experimental Coal Mine (Pittsburgh Seam) in Bruceton, Pennsylvania required 30 and 60 millijoules, respectively, as the minimum ignition energy of a cloud. Below a moisture content of between 5%-8%, there is no effect on the explosibility parameters for minus 200-mesh Pittsburgh Seam coal dust. Beyond 8% moisture, the minimum amount of energy required for an explosion increases dramatically and, at 15% moisture, about ten times more energy is required. 电和摩擦火花同样能提供点燃火焰和爆炸所需的热源，实验已经证明了煤粉可以在没有甲烷的环境里直接被磨擦火花点燃，无烟煤和次烟煤的粉尘雾可以被0.03焦能量点燃。从肯塔基和实验煤矿（匹斯堡）布鲁斯通宾西法尼亚来的煤粉“雾”最少分别需要0.030和0.060焦能量。当水分含量在5%~8%之下，并没有有效的匹斯堡煤粉爆炸参数，当水分含量超过8%时，爆炸所需的最小能量急剧增加，当水分含量超过15%的时候，（爆炸）需要超过10倍以上的能量。 Also, the minimum ignition energy of coal dust varies with oxygen content of the atmosphere, volatile content, and the amount of fine dust that will pass a U.S. standard No. 200-mesh sieve (74 microns). Coals are easier to ignite with increases in the oxygen content, or the volatile content, or in the amount of fine coal. However, there is a limiting value of minimum ignition energy which varies for each coal. All coal dusts should be regarded as prone to ignition when exposed to the frictional sparks of badly maintained machinery or when they become contaminated with tramp metal. For mixtures of coal dust and flammable gas, the critical minimum ignition energy is that which affects the gas. When ignited, the gas releases sufficient energy to suspend and ignite a coal dust cloud. 同样的，在含氧的空气中，煤粉爆炸的最低能量，挥发份含量和通过美标200目的筛的细煤粉（74微米）含量，随着氧含量，挥发份含量，洗煤含量的增加爆炸危险性增大。然而，无论如何不同煤种仍然存在最低爆炸能量。所有被暴露在维护不好的机器产生的火花下，或者密闭在坚实机器中的煤粉都应当被认为是具有爆炸性的。对煤粉和易燃气体混合物来说，关键的最低爆炸能量主要受气体确定，当被点燃时，气体释放的能量足以使煤粉悬浮并点燃煤粉。 Oxygen 氧气 As the volatile content of a coal increases, less oxygen is required to complete the fire triangle or the explosion pentagon. Less oxygen is also required as the rank of the coal decreases. Semi-anthracite has a very low volatile content and lignite is at least as volatile as high-volatile bituminous coals. However, at ambient temperatures, the oxygen content must be reduced to below 13% to prevent ignition of bituminous coal dusts with a strong ignition source. 随着煤炭挥发性含量的增加，完成燃烧三要素及爆炸五边型的氧气量减少，半无烟煤有非常低的挥发份含量，褐煤的挥发份含量同高挥发份的烟煤一样，然而，在室温度下，在强火源存在的条件下，氧气含量必须减少到13%以下来阻止烟煤被点燃。 Suspension 悬浮 For fires to occur, suspension is not a necessary step but completion of the explosion pentagon does require that the fuel be placed in suspension. 对燃烧来说，悬浮并不是必须的条件，但是完成爆炸的传播，需要燃料处在悬浮状态。 There is certainly danger present whenever coal dust is placed in suspension because, 煤粉处在悬浮状态下非常危险，因为在大多数环境中， in most circumstances, it need only find a heat source to initiate an explosion. 仅仅需要热源就能引起爆炸。 If a coal dust layer on the floor is smoldering, an explosion is imminent if the layer is somehow placed into suspension. 如果煤粉层在地面上闷烧，如果煤粉层不知何顾被置到悬浮状态，爆炸即将来临。 In this case, heat to satisfy the fire triangle and the explosion pentagon is already present. 在这种情况下，着火三要素和爆炸五边型所需的热都满足了。 The speed and duration of the moving air in an explosion is capable of dispersing additional coal dust from the floor, walls, overhead beams, and equipment. A hurricane causes substantial damage when the wind speed is 150 to 200 miles per hour (230 to 爆炸中有一定速率和持久性的移动空气（气流）可以吹起地板，墙上，高空支架和设备上的煤尘，当（爆炸）产生的飓风速率达到150~200公里/小时（230~290米/秒）可以引起附带的损害。 290 feet per second). In most coal dust explosions, the air speed exceeds 200 miles per hour. In fact, a coal dust explosion will generally die out if the air speed is less than 100 miles per hour (150 feet per second). 大多数煤粉引起的爆炸风速都超过了200公里/小时。通常情况下，如果煤粉爆炸产生的风速低于100公里/小时（150米/秒）爆炸会有可能会熄灭（不引起连锁爆炸）。 The maximum explosion pressure developed is about 90 psig for Pittsburgh Seam coal. The maximum rate of pressure rise for Pittsburgh Seam coal is 2000 psi per second. These parameters are important in predicting the violence or destructive powers capable of being generated when a particular dust is suspended and ignited. Since the maximum pressure is 90 psi for Pittsburgh Seam coal and the rate of pressure rise is 2000 psi per second, it is easily seen that only about 0.045 seconds elapse before the maximum pressure is realized. In a pulverized-fuel system using Pittsburgh Seam coal and designed to withstand 50 psi, vents must rupture within 25 milliseconds, otherwise pressures become excessive and equipment in the system is destroyed. 匹斯堡煤层煤煤最大的爆炸压力磅/平方英寸，最大匹斯堡煤产生的压力速率为2000磅/平方英寸。该参数对预测煤粉在悬浮情况下被点燃爆炸产生的强度和破坏性非常重要。既然最大压力为90磅/平方英寸，爆炸压力产生速率为2000磅/秒，那么就非常容易估算达到最大压力所需的时间仅有0.045秒。匹斯堡煤层和设计需要坚持50磅/平方英寸，排风口必须要在0.025秒内破裂。否则，压力超限，系统中设备会被损坏。 Good housekeeping practices are extremely important inside a plant because process equipment is not always able to withstand the internal pressures generated by an explosion. Once the explosion flame and pressures burst from the confinement into the plant, a secondary explosion may be fueled by any additional dust suspended by the blast. When good housekeeping practices have eliminated coal dust in the plant, there would not be any fuel to allow a continuation of the explosion flame. This secondary explosion is responsible for the most damage to the plant itself. Also, the secondary explosion is usually responsible for the loss of lives or the serious injuries to personnel that occur. 在一个工厂里，好的管理经验非常重要，因为工艺设备并不总是能抵御住由爆炸产生的内部压力。爆炸火焰和压力从密闭空间中爆发出来，蔓延到工厂中；附加（其它的）粉尘很有可能被爆炸产生的气流吹起而为第二波爆炸提供原料（引起第二次爆炸）当一个好的管理者清除了工厂中的煤粉后，就不会有其它使爆炸连续发生的燃料存在了。大多数工厂遭到破坏的主要原因就是二次爆炸引起的。同样，二次爆炸的出现造成了很多伤亡和人身伤害。 Confinement 密闭空间 Confinement is not a leg of the fire triangle, but to complete the explosion pentagon, it is essential. Basically, confinement keeps the fine coal particles in close proximity after they are placed in suspension. Without the closeness, heat transfer could not occur rapidly enough to allow continued propagation. Without confinement, a propagating explosion is not possible, but rather, only a large fireball with no appreciable forces associated with it. If an explosion is vented to the atmosphere outside the plant, confinement is eliminated and only part of the coal forced out of the vent will be burned, with the remaining unburned coal falling to the ground. As with the suspension leg of the explosion pentagon, if confinement is lost, the air speed will drop, additional coal dust will not be placed in suspension, and the explosion will extinguish. 密闭空间并不是燃烧三要素之一，但却是爆炸五边型的组成部分 最基本的，密闭空间使悬浮的煤粉颗粒彼此接近。 没有充分的接触（密度）热传递速率不可能达到产生爆炸的要求。 没有密闭空间爆炸传播也不太可能，有可能的只是一个大的没有什么破坏力的火球。 如果爆炸是连接到工厂之外的大气中，且并不密闭，那么仅会有一点煤会冲出通风口，并会燃烧。也会有部分未燃烧的煤沉降在地面上。 因为悬浮是爆炸五边型存在所需要的，如果密闭条件不存在了，（爆炸产生的）空气流速将会降低，其它的煤粉尘也就不会处在悬浮状态，爆炸将会停止。 EQUIPMENT CONSIDERATIONS 设备条件。 There are many explosion hazards associated with facilities utilizing pulverized-fuel systems. However, with an understanding of the explosion phenomena, these types of accidents can be avoided. The same knowledge applies to preparation plants where large tonnages of coal are processed. Each area where coal is handled and each piece of equipment in the process poses individual hazards. Some of those areas and equipment are discussed in subsequent sections of this report. 知识同样可以用在煤预处理厂的大吨位煤处理工艺中。煤一处煤炭处理环节和工艺中每一台设备都处在独立的风险中（都有单独发生爆炸的可能）有些区域和设备将在以下部分进行讨论。 然而，如果充分了解了爆炸的参数，这种事故应该是可以避免的。 于磨粉系统相联的很多设备都存在爆炸的风险。 Raw Coal Stockpile 原煤储存 The raw coal for a pulverized fuel system is usually received from a variety of sources and the size is generally limited to approximately 2 inches or smaller. This raw coal is typically stored on an outside stockpile where it is moved around by front- end loaders. The fire and explosion hazards associated with this stockpile are usually limited to spontaneous combustion. Hot material must never be loaded into the pulverized-fuel system. There is a definite possibility of an explosion occurring within the pulverizer because all sides of the explosion pentagon could occur simultaneously. It is recommended that these hot spots be removed from the coal stockpile and spread until cooled. 磨粉系统前附带的原煤储存系统通常会接收约2英寸或小于2英寸下的不同的煤种，这些原煤通常露天储存在运输工具周围与其有关的爆炸风险通常仅限于自发性燃烧。灼热的材料永远不容许接近磨粉系统，瞬间同时满足爆炸五边型所有条件的可能是明确存在的。推荐将这些热的物品远离煤堆，并分散放置，直到其冷却为止。 Raw Coal Storage Bin 原煤储仓 If there are no hot spots in the coal, the front-end loader will load the coal onto a conveyor belt, which feeds a coal storage bin. These bins are usually equipped with mechanical sensors to detect high-level or low-level coal storage. There is also an emergency chute for unloading the bin in the event of a problem inside the bin. Coal in the bin may be susceptible to spontaneous combustion; however, some airflow is required to provide the oxygen necessary for heating. However, thermocouples are sometimes located inside the bin to give warning of a fire, but carbon monoxide sensors would be more reliable for detecting an incipient fire. The raw coal empties from this bin onto a weigh scale. The weigh scale is a short conveyor belt that monitors the weight and the feed rate of the raw coal to the pulverizer. When any problems are detected in the system, the coal feed to the pulverizer is stopped completely. 如果在煤中没有发热物品，前端的装载机会将原煤装载到传送皮带上，进入煤粉储仓。这些储仓中通常装配有器械或 电子传感器 来测定贮煤的高度或低度。若煤仓内部存在问题，同样需紧急（专用）斜槽来放空煤仓。煤在煤仓中有自燃倾向，然而发生该现象，需要一些空气气流来提供燃烧发热所需的氧气。然而，有时利用在煤仓中间来放制热电偶来提供燃烧报警，但是对初期的燃烧来说，采用 二氧化碳探测器 要可靠的多。从煤粉仓倒空的原煤进入秤中，重量秤是一个小的皮带传输机，监控到磨煤机中原煤的加料速率。如果检测到系统存在任何问题，磨机的加料系统将完全停车。 Coal Pulverizer 磨机 Under normal operating conditions, coal is dropped from the weigh scale into a rotary airlock before it enters the pulverizer. The rotary airlock allows the coal and its inherent moisture to enter the pulverizer, but prevents any outside air from entering the system. Generally, the outside air has a higher oxygen content than the air circulating in the system and this additional oxygen 。 could lead to completion of the explosion pentagon and potential disaster. Coal that passes through the rotary airlock falls on the grinding table inside the pulverizer. The coal feed rate and the size of the grinding table are variable. For example, a C. E. Raymond 443 Roller Mill has a table diameter of 44 inches and 3 grinding rollers and, reportedly, can handle up to 25 tons per hour of raw coal. The coal is ground between the rollers and the rotating grinding table and is thrown outward by centrifugal force. 。 It is typical for a mill to pulverize the coal to where 85-97% of the coal will pass a U.S. standard No. 200-mesh sieve. The finer the coal, the greater the explosion hazard. As the coal is being ground, hot air enters the bottom of the pulverizer and passes up through the pulverizer. The air is used for its drying and conveyance abilities. This hot air can come either from the clinker cooler or can come from the kiln hood. However, hot air from the clinker cooler is generally around 400EF as opposed to hot air from the kiln hood which is between 900EF and 1200EF. These elevated temperatures can lead to heating in any coal that has deposited along internal surfaces. The main explosion hazard associated with a pulverizer is related to start up and shutdown procedures. When a system goes down under load, all the coal falls out of suspension. The internal surfaces are at elevated temperatures and the process of spontaneous combustion begins immediately. If the system is then restarted without full knowledge of internal conditions, an explosion could occur when the hot particles are suspended. 在通常的操作情况下（工况），在进入磨机前，煤从秤上直接进入一个旋转的气密仓中（气塞？气闸？）。 气闸保证原煤和内水进入磨粉机，但阻止其它外部空气进入系统。 通常情况下，外部空气的氧含量大于循环系统中气体的氧气含量。 这部分氧含量会满足爆炸五边型，并产生潜在的危害 煤经过气密仓后回进入到磨机内部的磨碗上。 根据煤加入速率和尺寸不同，磨机的磨台尺寸是不同的。 原煤在辊和旋转的磨碗上磨粉，并在离心力的作用下甩向外部 举个列子，CE的443雷蒙磨磨机尺寸44英寸，有三个磨辊；根据报道，磨机能力可以达到25吨每小时（原煤）。 这种常用的磨机可保证85~97%的煤粉通过200目美标筛网。煤粉越细，爆炸风险越大。 在磨粉过程中，热空气从磨机底部通入，穿过整个磨机。这些热空气用来干燥和运输。这些热风来自熟料冷却风或转炉罩，燃而，来自熟料冷却风的温度在400华氏度左右，相对的，来自转炉罩的热风温度在900~1200华氏度左右。这些提高的温度可以加热任何单独沉积在内表面上的煤。磨机爆炸的风险主要来自开停车过程。 当系统从运行到停车时，所有悬浮状态的煤粉都沉降下来。 在提高温度的条件下，在内表面的几乎是瞬间发生了燃烧。 如果再不知道系统内部状况的情况下重新启动，当热的颗粒被悬浮起来，爆炸就会出现。 Primary Fan 主风扇 The drive motor at the base of the mill can provide power for both the mill and the primary air fan, if the fan does not have a separate motor. The one advantage to having a single-drive motor is economical. The major disadvantage is that, in the event of a pulverizer shutdown, there is no way to pneumatically clear the coal out of the mill because the primary fan would also be down. This could lead to spontaneous combustion problems inside the mill that would make restarting the system hazardous. Before restarting, it must be verified that no hazardous conditions exist within the system. The primary fan does force the coal particles into the kiln. If this fan is downstream from the pulverizer, it exerts a negative pressure, or suction, on the pulverizer. With higher pressures outside the pulverizer, typically nothing leaks out while a little air may leak in. However, a disadvantage to this sequence is the fact that pulverized coal will pass through the rotating blades of the primary air fan. This is not a problem unless an ignition source occurs within the fan. On the other hand, if the primary air fan is upstream of the pulverizer, then it exerts a positive pressure on the pulverizer. In this case, fine coal particles may find their way out of the mill through any small crack or fracture in the mill or through parts of the mill that are not well sealed. This leads to accumulations of coal dust in the plant and, if an explosion ruptures the pulverized-fuel system, it could use this coal dust as additional fuel for a serious secondary explosion. 如果风扇没有单独的电机，磨机的驱动电机可同时提供磨机和主风扇的动力。有一个优点就是使用单个电机比较经济。这会导致在磨机中发生自发性燃烧，并使机器重动产生爆炸风险。在重起前，必须证明在系统中不存在发生爆炸的危险情况。主要的缺点是，在磨机停机的情况下，无法充气将原煤从磨机中清理出来，因为此时间主风扇也停机了。主风扇强制将煤粉输送到转炉中，如果该风扇在磨机下流物流（抽气？）那么磨机中存在负压或抽吸作用；磨机外部压力相对较高，通常没有漏出物，有少许空气会进入，缺陷就是如下所述的实际上粉化后的煤炭会穿过主风扇旋转的叶片。这并不存在什么问题，除非叶片上存在火源。在另一方面，如果主风扇在磨机上流物流中，磨机中存在正压。这样的话就会有细小的煤粉颗粒从磨机上任何小的裂缝和破碎之处或从磨机部件中的焊接不良的焊缝中出来。这会导致煤粉在工厂内沉积，如果爆炸使磨机破裂，那么会导致这些（沉积）的煤粉发生二次爆炸。 Dust Cyclone 旋风除尘器 。 After the coal has been pulverized to a fine enough size, the circulating air lifts it out of the top of the pulverizer and through a classifier. When these fine coal particles pass out of the classifier, they may be transported through a duct leading to a dust cyclone. The coal-dust-laden airstream enters the cyclone where separation of the pulverized coal and circulating air is accomplished. The cyclone is designed such that the pulverized coal falls into the bottom of the cyclone, while the clean circulating air is allowed to pass out of the top of the cyclone. However, the cyclone is capable of removing approximately 95% of the coal fines from the circulating air. The other 5% of coal fines will pass out of the top of the cyclone and continue through the system fan. A limited amount of coal is stored in the base of the cyclone for a short period of time. The rotary valve then feeds the coal into the airstream of the primary air fan. Immediately, the coal dust is blown into the kiln. It has been reported by an operator of a semi-direct system that only about 25 pounds of fine coal dust would be in the cyclone at any time. Without any bulk storage of pulverized coal in the system, a shutdown of the pulverizer will stop the continuing coal feed to the kiln. 当煤粉被研磨到足够的洗度，循环空气将其从顶部带出，并进入一个分离器中。当细煤粉颗粒通过分离器后，将通过管道被输送到一个旋风除尘器中。带者煤粉的空气流进入旋风除尘器后，将同循环空气分离，空气完成（再次利用？）旋粉除尘器设计煤粉落入除尘器底部，干净的循环空气容许从除尘器顶部离开。然而，旋风除尘器只能除掉循环风中95%的煤尘，其它5%的煤风会通过循环除尘器顶部并且继续通过系统风扇。 在短时间内会有一定数量限的煤粉储存在旋风除尘器的基础之上，旋转阀然后将煤粉加入到主空风扇的空气流中。 接着，煤粉被吹入转炉中。 据操作者报道，在任何时候在半直接的（间歇式？）旋风除尘系统中只有25磅细煤粉。（除尘器中几乎没有煤粉沉积，连续运转） 在系统中没有任何煤粉聚集，磨粉机的停车既可停止向转炉中加煤。 System Fan 系统风扇 The clean air that flows out of the top of the cyclone passes into the system fan. Primarily, the system fan provides an airstream to transport fine coal from the pulverizer to the cyclone. Basically, the circulating air travels in a loop comprising the system fan, the pulverizer, the dust cyclone, and the connecting ducts. In this respect, the air provided by the system fan enters the pulverizer, but only that air passing through the primary fan enters the kiln. 旋风除尘器顶部流出干净的空气经过系统风扇。主要的，系统风扇提供了将煤从磨机传送到除尘器所需的空气流。基本上，循环空气在一个包含系统风扇，磨机旋风除尘机及连接管道组成的圈内循环。空气由系统风扇提供，进入磨机，但是只有通过主风扇的空际进入转炉。就象前面描述的，磨好的煤粉不经过任何开放式风扇的叶片，实际上（保持）系统风扇干净是一个优点，然而当讨论到旋风除尘器，需要提及那5%的煤粉没有被去除。这就意味着在密闭循环中存在煤粉聚集的可能性，包括系统风扇在内。在这些地方有充足的氧气和燃料，只需要一个热源（点燃源）就可以发生燃烧或爆炸。在该条生产线上，开车和停车是关键时刻。在停车过程中，会发生焖烧并导致自燃。如果在下次启动前没有发现该现象，焖烧中的煤很有可能被系统风扇吹起，满足爆炸五边形所需。 As previously stated, the pulverized coal does not pass through the blades of any operating fan. The fact that the system fan is a clean fan is an advantage. However, when discussing the dust cyclone, it was mentioned that about 5% of the coal fines are not removed. This indicates that accumulation of coal fines can occur in the closed loop, including the system fan. With sufficient fuel and oxygen in an area, only an ignition source need be present for a fire or explosion to occur. Along these lines, start-up and shutdown are critical times. During shutdown, an accumulation of coal may begin to smolder in a state of spontaneous combustion. If this condition is not detected before start-up, the smoldering coal could be placed into suspension by the system fan and the five sides of the explosion pentagon would be satisfied. Baghouse 袋式除尘器。 The air that passes out of the top of the cyclone, with the 5% coal dust, is transported to a baghouse. This baghouse is designed with many filter-type bags hanging vertically, which are capable of removing the remaining coal dust from the circulating air. In the baghouse, all the coal dust is captured in filter- type bags and the air circulating from the system fan is vented to the atmosphere. The primary advantage is twofold: first, all coal dust can be used as fuel; secondly, the air vented to the atmosphere carries a high-moisture content and is not recirculated through the system. This allows hot, dry air from the kiln hood or clinker cooler to be mixed with air from the system fan before entering the pulverizer. The moisture content of this air is lower than that which is vented to the atmosphere from the baghouse because it is not involved in coal drying until it enters the pulverizer. 从旋风除尘器顶部经过的气流包含5%的煤尘，该部分被输送到袋式除尘器中， 该除尘器有许多垂直过滤袋组成，可以除去循环空气中残留的煤粉。在袋式除尘器中，所有的煤尘被捕捉在带中，循环空气被系统风扇排放到大气中。 明显的优点是双重的；首先，所有煤尘都可以作为燃料利用；其次，排放到大气中的空气水分含量较高，并不能在系统中循环利用。因此需要来自转炉罩和冷渣机的热的干燥的气体同空气混合后进入磨粉机。该部分气体的水份含量要比从袋式除尘器而来的气体要低，直到气体进入磨粉机。 Kiln 转炉（窑炉） After the coal-laden primary air passes through the primary air fan, it is blown through the burner pipe and directly into the kiln. The burner pipe is a long cantilever, which can extend 35 feet of more into the kiln, but is usually limited to 10-15 feet. The rotation and slope of the kiln cause the raw material to fall towards the lower end of the kiln where the burning zone is located. It is in this burning zone that the process of transforming the raw material to clinker takes place at around 2800EF. This temperature and the length of the flame are directly related to the volatile matter and the moisture in the coal. 在带有煤粉的主气流通过主风扇后，通过燃烧管直接吹入窑炉中。 该温度和火焰的长度直接和物料的挥发份及水份有关。 炉窑的的倾斜角度使燃料向转炉较低的底部移动，那里是燃烧区。 在将原料输送到冷渣机前，工艺发生的工艺温度在2800华氏度左右。 燃烧管是个长管，可以延伸到35米或更长，进入窑炉，但是通常限制长度10~15米。查看更多6个回答 . 3人已关注
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