1 气力输送参数的计算

　　1 Calculation of pneumatic conveying parameters

　　在进行计算前，需要知道物料的属性（包括真实比重、堆积比重、粒径以及其它的一些物理化学性质等等）、输送工艺要求（包括水平长度、提升高度、弯头数量、设计输送量等）。

　　Before conducting calculations, it is necessary to know the properties of the material (including true density, bulk density, particle size, and other physical and chemical properties, etc.), as well as the requirements of the conveying process (including horizontal length, lifting height, number of bends, design conveying capacity, etc.).

　　物料的属性决定物料适合采用什么输送形态，比如从钛白粉的特性就可以知道钛白粉适合于稀相输送，而不适合于密相输送。

　　The properties of materials determine what conveying form they are suitable for, for example, from the characteristics of titanium dioxide, it can be known that titanium dioxide is suitable for dilute phase conveying but not for dense phase conveying.

　　确定输送方式后就可以选择输送固气比（即输送物料质量流量：输送气体质量流量），再根据输送工艺要求确定输送管径和输送压力、输送气量等参数。

　　After determining the conveying method, the conveying solid gas ratio (i.e. conveying material mass flow rate: conveying gas mass flow rate) can be selected, and then the conveying pipe diameter, conveying pressure, conveying gas volume and other parameters can be determined according to the conveying process requirements.

　　在已确定的输送工艺要求下，通常输送管径越大、输送压力就越低、而输送气量就越高。

　　Under the determined requirements of the conveying process, the larger the diameter of the conveying pipe, the lower the conveying pressure, and the higher the conveying gas volume.

　　某项目钛白粉设计输送量5000kg/h，输送最远水平距离65米，垂直高度15米，输送弯头确定为6只。当地大气压按101kPa，气体温度简化为恒定不变，取20℃。以下过程来确定其它输送参数：

　　The designed conveying capacity of titanium dioxide for a certain project is 5000kg/h, with a maximum horizontal distance of 65 meters and a vertical height of 15 meters. The conveying elbows are determined to be 6. The local atmospheric pressure is set at 101kPa, and the gas temperature is simplified to be constant at 20 ℃. The following process is used to determine other conveying parameters:

　　1）假定输送固气比为5，可以计算得到输送气量是13.9标方/分钟（一个大气压，20摄氏度下）；固气比是指在气力输送过程中，固体物料与输送气体的质量比。这个比例对于气力输送系统的设计和运行至关重要，因为它会影响到系统的输送能力、能耗、管道磨损等方面。一般来说，固气比越高，输送相同质量的物料所需的气体量就越少，从而可以降低能耗和管道磨损，但同时也可能会增加系统的压力损失和物料的破碎率。

　　1) Assuming a solid to gas ratio of 5, the calculated gas volume for transportation is 13.9 standard cubic meters per minute (at one atmosphere and 20 degrees Celsius); Solid gas ratio refers to the mass ratio of solid materials to the transported gas during pneumatic conveying. This ratio is crucial for the design and operation of pneumatic conveying systems, as it affects the system's conveying capacity, energy consumption, pipeline wear, and other aspects. Generally speaking, the higher the solid to gas ratio, the less gas is required to transport materials of the same quality, which can reduce energy consumption and pipeline wear. However, it may also increase system pressure loss and material breakage rate.

　　气量是指在气力输送过程中，输送气体的体积或质量流量。气量的大小直接影响到气力输送系统的输送能力和能耗。在设计气力输送系统时，需要根据物料的性质、输送距离、输送方式、管道直径和压力等因素来确定合适的气量。

　　Gas volume refers to the volume or mass flow rate of gas transported during pneumatic conveying. The size of the gas volume directly affects the conveying capacity and energy consumption of the pneumatic conveying system. When designing a pneumatic conveying system, it is necessary to determine the appropriate air volume based on factors such as the properties of the material, conveying distance, conveying method, pipeline diameter, and pressure.

　　2）除尘器与排气管的阻力损失，取ΔPjx=3000 Pa。

　　2) The resistance loss between the dust collector and exhaust pipe is taken as Δ Pjx=3000 Pa.

　　3）假定输送管径是DN125（内径是125mm），输送管道出口的压力是表压3kPa，可以计算得到输送管道出口的输送气速是18.4m/s，根据经验这个气速是合适的。

　　3) Assuming the conveying pipe diameter is DN125 (inner diameter is 125mm) and the pressure at the outlet of the conveying pipeline is 3kPa gauge pressure, the conveying gas velocity at the outlet of the conveying pipeline can be calculated to be 18.4m/s. Based on experience, this gas velocity is appropriate.

　　4）稳定输送的阻力损失可以用以下公式计算Pe是管道出口压力，=104000 Pam是固气比，=5K是阻力损失系数，=1（此系数在0.5~1.5之间，与多种因素有关）λa是管道摩擦系数，DN125管道，=0.03Leq是管道当量长度，=190m

　　4) The resistance loss of stable transportation can be calculated using the following formula: Pe is the outlet pressure of the pipeline,=104000 Pam is the solid gas ratio,=5K is the resistance loss coefficient,=1 (this coefficient ranges from 0.5 to 1.5 and is related to various factors), λ a is the friction coefficient of the pipeline, DN125 pipeline,=0.03Leq is the equivalent length of the pipeline,=190m

　　管道当量长度是将垂直管道、弯头、其他管件、阀门都换算成水平管道的长度，通常将1m垂直管道按2m水平管道来计算当量长度，对粉体，一个弯头的当量长度是10m，对球阀，当量长度是5mD是管道内径，=0.125mρe是出口空气密度，=1.24kg/mVe是出口空气速度，=18.4m/s计算得到：ΔPm=42561 Pa

　　The equivalent length of a pipeline is the length of a vertical pipeline, elbow, other fittings, and valve converted to a horizontal pipeline. Typically, a 1m vertical pipeline is calculated as a 2m horizontal pipeline to determine the equivalent length. For powder, the equivalent length of an elbow is 10m, and for ball valves, the equivalent length is 5m. D is the inner diameter of the pipeline,=0.125m ρ e is the outlet air density,=1.24kg/m Ve is the outlet air velocity,=18.4m/s, calculated as Δ Pm=42561 Pa

　　5）物料的加速度阻力损失，公式略，ΔPac=1478 Pa

　　5) The acceleration resistance loss of materials, formula omitted, ΔPac=1478 Pa

　　6）供料器的阻力损失，公式略，旋转阀的阻力ΔPN=1330 Pa

　　6) The resistance loss of the feeder, formula omitted, the resistance of the rotary valve Δ PN=1330 Pa

　　7）以上阻力相加得到，输送阻力损失ΔP=48368Pa=48.4 kPa

　　7) The above resistance is added together to obtain the conveying resistance loss Δ P=48368Pa=48.4 kPa

　　8）采用罗茨风机时还需计算罗茨风机排气管道输送管道入口的阻力损失，此阻力通常较小，此处略。

　　8) When using a Roots blower, it is also necessary to calculate the resistance loss at the inlet of the exhaust pipeline of the Roots blower, which is usually small and omitted here.

　　9）对气源机械选型时，计算的阻力值需乘以1.2~1.5的裕量系数，计算的气量值需乘以1.1~1.2的裕量系数。

　　9) When selecting gas source machinery, the calculated resistance value needs to be multiplied by a margin factor of 1.2-1.5, and the calculated gas volume value needs to be multiplied by a margin factor of 1.1-1.2.

　　计算得到输送阻力损失后，就可以判断输送管道选择是否合适，单级罗茨风机排气压力低于98kPa，计算的阻力数值在此范围内，因此上面的管道选择是正确的，对压缩机来说，这个值就太低了，因此管道可以选的更小。

　　After calculating the transportation resistance loss, it can be determined whether the selection of the transportation pipeline is appropriate. The exhaust pressure of the single-stage Roots blower is below 98kPa, and the calculated resistance value is within this range. Therefore, the pipeline selection above is correct. For the compressor, this value is too low, so the pipeline can be selected smaller.

　　以上计算就基于旋转阀卸料的正压输送，如果旋转阀下采用文丘里喷射器，那么还需要进一步的计算文丘里喷射器的阻力。

　　The above calculation is based on the positive pressure conveying of the rotary valve discharge. If a Venturi injector is used under the rotary valve, further calculation of the resistance of the Venturi injector is required.

　　文丘里的基本型式是具有先缩小再扩大的流道，最小的地方称为喉部，喉部处的气流速度是最高的，通常是~200m/s，甚至接近音速，根据能量守恒的帕努利公式可以知道，气流速度高，那么气体压力就低，因此通过设计，可以在喉部处让气体压力下降到等于或略低于大气压力，这样物料就可以自由流动进喉部处，因为不存在和供料方向相反的漏气。在扩管段，气速迅速下降转换为压力来推动物料。文丘里喷射器/供料器的结构简单，常由于短途输送可以自由流动的小颗粒物料，但是文丘里也有很大的局限性，在扩散段，动力能只有大约1/3转换为压力能来输送物料，其自身的阻力损失很大，这其中涉及到很复杂的热力学计算，这里就略过不讲，但可以定性的说，如果要达到喉部处等于大气压力，文丘里本身的阻力输送≈后面输送管道的总输送阻力，回到上面的计算结果，就可以知道，如果要达到这一效果，总的阻力损失应该是96.8kPa。这也就是为什么文丘里不用于长距离输送的原因，距离越远，管道阻力损失就越大，文丘里自身的阻力损失也就越高。

　　The basic form of a Venturi is to have a channel that first narrows and then expands, with the smallest part called the throat. The airflow velocity at the throat is the highest, usually around 200m/s, even close to the speed of sound. According to the Panoulli formula of energy conservation, if the airflow velocity is high, the gas pressure will be low. Therefore, through design, the gas pressure can be reduced to be equal to or slightly lower than atmospheric pressure at the throat, so that the material can flow freely into the throat because there is no leakage in the opposite direction of the feeding direction. In the expansion section, the rapid decrease in gas velocity is converted into pressure to push the material. The structure of the Venturi injector/feeder is simple, often due to the free flow of small particles in short distance transportation. However, Venturi also has great limitations. In the diffusion section, only about one-third of the kinetic energy is converted into pressure energy to transport materials, and its own resistance loss is significant. This involves complex thermodynamic calculations, which will be skipped here. However, it can be qualitatively said that if we want to achieve atmospheric pressure at the throat, the resistance of Venturi itself is approximately equal to the total conveying resistance of the subsequent conveying pipeline. Returning to the above calculation results, we can know that if we want to achieve this effect, the total resistance loss should be 96.8 kPa. That's why Venturi is not used for long-distance transportation. The farther the distance, the greater the resistance loss of the pipeline, and the higher the resistance loss of Venturi itself.

　　采用文丘里输送，电功耗通常是2倍于普通的正压输送。当然，如果不需要文丘里喉部的压力降到等于或低于大气压力，那其自身阻力也就没有那么高，但这又偏离了采用它的目的。

　　Using Venturi conveying, the electrical power consumption is usually twice that of ordinary positive pressure conveying. Of course, if the pressure at the throat of the Venturi does not need to drop to equal or lower than atmospheric pressure, its own resistance will not be as high, but this deviates from the purpose of using it.

　　根据以上叙述可以得到的结论是：如要达到5t/h的输送量，罗茨风机加旋转阀的正压输送可以选DN125管道，采用压缩空气的仓泵输送，可以选小于DN125的管道，采用文丘里方式的输送，必须选大于DN125的管道，并且能耗比正压输送要高很多。

　　Based on the above description, the conclusion can be drawn that in order to achieve a conveying capacity of 5t/h, the positive pressure conveying of Roots blower with rotary valve can choose DN125 pipeline and use compressed air bin pump for conveying. Pipelines smaller than DN125 can be selected, and the conveying method of Venturi must choose pipelines larger than DN125, and the energy consumption is much higher than that of positive pressure conveying.

　　2除尘设备的选择

　　What 2. Selection of dust removal equipment

　　除尘器的规格与处理风量和所选的过滤风速有关。除尘器的规格可以用过滤面积来区分，过滤风速=处理风量（m/min）/过滤面积（m），注意：过滤风速的单位是m/min。

　　The specifications of the dust collector are related to the processing air volume and the selected filtering air speed. The specifications of a dust collector can be distinguished by its filtration area. The filtration air speed is equal to the processing air volume (m/min) divided by the filtration area (m). Note that the unit of filtration air speed is m/min.

　　过滤风速的选择主要和过滤元件的材质、入口气体含尘浓度、含尘的性质等等有关。对车间除尘等入口气体含尘浓度低的场合，布袋除尘器的过滤风速可以选1~3m/min；对气力输送场合，因为除尘器入口含尘浓度极高，因此过滤风速要降低，布袋除尘器通常选0.7~0.9m/s，滤筒除尘器通常选0.5~0.7m/s，如果物料粉尘细、粘，这个值要取下限。

　　The selection of filtering wind speed is mainly related to the material of the filtering element, the dust concentration of the inlet gas, the properties of the dust, and so on. For situations where the dust concentration in the inlet gas of workshop dust removal is low, the filtration wind speed of bag filter can be selected as 1-3m/min; For pneumatic conveying applications, due to the extremely high dust concentration at the inlet of the dust collector, the filtration wind speed needs to be reduced. Bag dust collectors usually choose 0.7~0.9m/s, and filter cartridge dust collectors usually choose 0.5~0.7m/s. If the material dust is fine and sticky, this value should be taken as the lower limit.

　　对上面的计算气量13.9Nm/min，除尘器处压力接近大气压力，温度假定是20摄氏度，那么除尘器的处理气量也基本上是13.9m/min，布袋除尘器过滤面积需要20m，滤筒除尘器需要28m。20m2的布袋除尘器需要直径125长1m的布袋50个，或者直径125长2m的布袋25个。

　　Based on the above calculation, the gas flow rate is 13.9Nm/min. The pressure at the dust collector is close to atmospheric pressure, and the temperature is assumed to be 20 degrees Celsius. Therefore, the processing gas flow rate of the dust collector is basically 13.9m/min. The filter area of the bag filter requires 20m, and the filter cartridge dust collector requires 28m. A 20m2 bag filter requires 50 bags with a diameter of 125 and a length of 1m, or 25 bags with a diameter of 125 and a length of 2m.

　　同体积的摺式滤筒比布袋过滤面积要大3~5倍，但存在折叠缝中清灰较困难的缺点，所以处理同样风量，滤筒除尘器过滤面积要比布袋除尘器选的大一些。在钛白粉除尘应用上应选用浅底的摺式滤筒，以降低清灰难度。

　　A foldable filter cartridge with the same volume has a filtration area 3-5 times larger than a bag filter, but it has the disadvantage of difficulty in cleaning dust in the folding seams. Therefore, for the same air volume, the filtration area of the filter cartridge dust collector should be larger than that of the bag filter. In the application of titanium dioxide dust removal, shallow bottomed pleated filter cartridges should be selected to reduce the difficulty of dust cleaning.

　　3旋转阀加罗茨风机与仓泵加压缩机的对比

　　3 Comparison between Rotary Valve with Roots Fan and Warehouse Pump with Compressor

　　1）采用旋转阀加罗茨风机，输送管道、切换阀门和除尘器大，采用仓泵加压缩机则要小。但压缩机系统这部分费用要比罗茨风机高很多，因此两者成本对比上看，费用应该接近，或者压缩机方案略高。

　　1) Using a rotary valve and Roots blower requires a larger conveying pipeline, switching valve, and dust collector, while using a bin pump and compressor requires a smaller size. But the cost of the compressor system is much higher than that of the Roots blower, so the cost comparison between the two should be similar, or the compressor scheme should be slightly higher.

　　2）从气源机械的功率来看，罗茨风机方案可能更节能。原因是由于钛白粉不能密相输送，在本项目的设计条件下，采用压缩空气来输送，输送阻力也就0.15~0.2MPa左右，而压缩机的排气压力有0.7MPag，相对于罗茨风机与输送压降相适应的排气压力，压缩机做功要高很多。还有明确的一点是气动阀门、除尘器清灰、破拱器等都需要提供压缩空气，对罗茨风机方案来讲，也需要提供一套压缩空气系统。

　　2) From the power of the gas source machinery, the Roots blower scheme may be more energy-efficient. The reason is that titanium dioxide cannot be transported in a dense phase. Under the design conditions of this project, compressed air is used for transportation, and the transportation resistance is only about 0.15~0.2 MPa. The exhaust pressure of the compressor is 0.7 MPag, which is much higher than the exhaust pressure of the Roots blower that is compatible with the transportation pressure drop. Another clear point is that compressed air is required for pneumatic valves, dust collectors, arch breakers, etc. For Roots blower solutions, a set of compressed air systems is also needed.

　　3）从对产品品质的影响上看，压缩机方案，可以方便地除水除油，提供比罗茨风机方案更高品质的输送气。

　　3) From the perspective of its impact on product quality, the compressor solution can easily remove water and oil, providing higher quality conveying gas than the Roots blower solution.

　　4）从系统适应性上看，罗茨风机压缩后排气压力越高，排气更可能达到过饱和，而钛白粉很细，水分将对输送带来麻烦。压缩机的后处理系统则可以提供干燥清洁的输送气。但系统不幸堵料时，压缩机方案可以用更高的压力来排堵，而罗茨风机没有这种便利条件。对于本项目输送距离较远，特别是岔道多的情况，堵料这种情况要予以充分考虑。

　　4) From the perspective of system adaptability, the higher the exhaust pressure of the Roots blower after compression, the more likely the exhaust is to reach supersaturation, while titanium dioxide is very fine, and moisture will cause trouble for transportation. The post-processing system of the compressor can provide dry and clean conveying gas. But when the system unfortunately gets stuck, the compressor scheme can use higher pressure to remove the blockage, while the Roots blower does not have this convenient condition. For this project, the transportation distance is relatively long, especially in the case of many forks, and the situation of material blockage should be fully considered.

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