1 氣力輸送參數(shù)的計(jì)算

　　1 Calculation of pneumatic conveying parameters

　　在進(jìn)行計(jì)算前，需要知道物料的屬性（包括真實(shí)比重、堆積比重、粒徑以及其它的一些物理化學(xué)性質(zhì)等等）、輸送工藝要求（包括水平長度、提升高度、彎頭數(shù)量、設(shè)計(jì)輸送量等）。

　　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.).

　　物料的屬性決定物料適合采用什么輸送形態(tài)，比如從鈦白粉的特性就可以知道鈦白粉適合于稀相輸送，而不適合于密相輸送。

　　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.

　　確定輸送方式后就可以選擇輸送固氣比（即輸送物料質(zhì)量流量：輸送氣體質(zhì)量流量），再根據(jù)輸送工藝要求確定輸送管徑和輸送壓力、輸送氣量等參數(shù)。

　　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.

　　在已確定的輸送工藝要求下，通常輸送管徑越大、輸送壓力就越低、而輸送氣量就越高。

　　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.

　　某項(xiàng)目鈦白粉設(shè)計(jì)輸送量5000kg/h，輸送最遠(yuǎn)水平距離65米，垂直高度15米，輸送彎頭確定為6只。當(dāng)?shù)卮髿鈮喊?01kPa，氣體溫度簡化為恒定不變，取20℃。以下過程來確定其它輸送參數(shù)：

　　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）假定輸送固氣比為5，可以計(jì)算得到輸送氣量是13.9標(biāo)方/分鐘（一個(gè)大氣壓，20攝氏度下）；固氣比是指在氣力輸送過程中，固體物料與輸送氣體的質(zhì)量比。這個(gè)比例對(duì)于氣力輸送系統(tǒng)的設(shè)計(jì)和運(yùn)行至關(guān)重要，因?yàn)樗鼤?huì)影響到系統(tǒng)的輸送能力、能耗、管道磨損等方面。一般來說，固氣比越高，輸送相同質(zhì)量的物料所需的氣體量就越少，從而可以降低能耗和管道磨損，但同時(shí)也可能會(huì)增加系統(tǒng)的壓力損失和物料的破碎率。

　　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.

　　氣量是指在氣力輸送過程中，輸送氣體的體積或質(zhì)量流量。氣量的大小直接影響到氣力輸送系統(tǒng)的輸送能力和能耗。在設(shè)計(jì)氣力輸送系統(tǒng)時(shí)，需要根據(jù)物料的性質(zhì)、輸送距離、輸送方式、管道直徑和壓力等因素來確定合適的氣量。

　　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）除塵器與排氣管的阻力損失，取ΔPjx=3000 Pa。

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

　　3）假定輸送管徑是DN125（內(nèi)徑是125mm），輸送管道出口的壓力是表壓3kPa，可以計(jì)算得到輸送管道出口的輸送氣速是18.4m/s，根據(jù)經(jīng)驗(yàn)這個(gè)氣速是合適的。

　　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）穩(wěn)定輸送的阻力損失可以用以下公式計(jì)算Pe是管道出口壓力，=104000 Pam是固氣比，=5K是阻力損失系數(shù)，=1（此系數(shù)在0.5~1.5之間，與多種因素有關(guān)）λa是管道摩擦系數(shù)，DN125管道，=0.03Leq是管道當(dāng)量長度，=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

　　管道當(dāng)量長度是將垂直管道、彎頭、其他管件、閥門都換算成水平管道的長度，通常將1m垂直管道按2m水平管道來計(jì)算當(dāng)量長度，對(duì)粉體，一個(gè)彎頭的當(dāng)量長度是10m，對(duì)球閥，當(dāng)量長度是5mD是管道內(nèi)徑，=0.125mρe是出口空氣密度，=1.24kg/mVe是出口空氣速度，=18.4m/s計(jì)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）物料的加速度阻力損失，公式略，ΔPac=1478 Pa

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

　　6）供料器的阻力損失，公式略，旋轉(zhuǎn)閥的阻力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，輸送阻力損失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）采用羅茨風(fēng)機(jī)時(shí)還需計(jì)算羅茨風(fēng)機(jī)排氣管道輸送管道入口的阻力損失，此阻力通常較小，此處略。

　　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）對(duì)氣源機(jī)械選型時(shí)，計(jì)算的阻力值需乘以1.2~1.5的裕量系數(shù)，計(jì)算的氣量值需乘以1.1~1.2的裕量系數(shù)。

　　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.

　　計(jì)算得到輸送阻力損失后，就可以判斷輸送管道選擇是否合適，單級(jí)羅茨風(fēng)機(jī)排氣壓力低于98kPa，計(jì)算的阻力數(shù)值在此范圍內(nèi)，因此上面的管道選擇是正確的，對(duì)壓縮機(jī)來說，這個(gè)值就太低了，因此管道可以選的更小。

　　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.

　　以上計(jì)算就基于旋轉(zhuǎn)閥卸料的正壓輸送，如果旋轉(zhuǎn)閥下采用文丘里噴射器，那么還需要進(jìn)一步的計(jì)算文丘里噴射器的阻力。

　　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縮小再擴(kuò)大的流道，最小的地方稱為喉部，喉部處的氣流速度是最高的，通常是~200m/s，甚至接近音速，根據(jù)能量守恒的帕努利公式可以知道，氣流速度高，那么氣體壓力就低，因此通過設(shè)計(jì)，可以在喉部處讓氣體壓力下降到等于或略低于大氣壓力，這樣物料就可以自由流動(dòng)進(jìn)喉部處，因?yàn)椴淮嬖诤凸┝戏较蛳喾吹穆?。在擴(kuò)管段，氣速迅速下降轉(zhuǎn)換為壓力來推動(dòng)物料。文丘里噴射器/供料器的結(jié)構(gòu)簡單，常由于短途輸送可以自由流動(dòng)的小顆粒物料，但是文丘里也有很大的局限性，在擴(kuò)散段，動(dòng)力能只有大約1/3轉(zhuǎn)換為壓力能來輸送物料，其自身的阻力損失很大，這其中涉及到很復(fù)雜的熱力學(xué)計(jì)算，這里就略過不講，但可以定性的說，如果要達(dá)到喉部處等于大氣壓力，文丘里本身的阻力輸送≈后面輸送管道的總輸送阻力，回到上面的計(jì)算結(jié)果，就可以知道，如果要達(dá)到這一效果，總的阻力損失應(yīng)該是96.8kPa。這也就是為什么文丘里不用于長距離輸送的原因，距離越遠(yuǎn)，管道阻力損失就越大，文丘里自身的阻力損失也就越高。

　　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.

　　采用文丘里輸送，電功耗通常是2倍于普通的正壓輸送。當(dāng)然，如果不需要文丘里喉部的壓力降到等于或低于大氣壓力，那其自身阻力也就沒有那么高，但這又偏離了采用它的目的。

　　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.

　　根據(jù)以上敘述可以得到的結(jié)論是：如要達(dá)到5t/h的輸送量，羅茨風(fēng)機(jī)加旋轉(zhuǎn)閥的正壓輸送可以選DN125管道，采用壓縮空氣的倉泵輸送，可以選小于DN125的管道，采用文丘里方式的輸送，必須選大于DN125的管道，并且能耗比正壓輸送要高很多。

　　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除塵設(shè)備的選擇

　　What 2. Selection of dust removal equipment

　　除塵器的規(guī)格與處理風(fēng)量和所選的過濾風(fēng)速有關(guān)。除塵器的規(guī)格可以用過濾面積來區(qū)分，過濾風(fēng)速=處理風(fēng)量（m/min）/過濾面積（m），注意：過濾風(fēng)速的單位是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.

　　過濾風(fēng)速的選擇主要和過濾元件的材質(zhì)、入口氣體含塵濃度、含塵的性質(zhì)等等有關(guān)。對(duì)車間除塵等入口氣體含塵濃度低的場合，布袋除塵器的過濾風(fēng)速可以選1~3m/min；對(duì)氣力輸送場合，因?yàn)槌龎m器入口含塵濃度極高，因此過濾風(fēng)速要降低，布袋除塵器通常選0.7~0.9m/s，濾筒除塵器通常選0.5~0.7m/s，如果物料粉塵細(xì)、粘，這個(gè)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.

　　對(duì)上面的計(jì)算氣量13.9Nm/min，除塵器處壓力接近大氣壓力，溫度假定是20攝氏度，那么除塵器的處理氣量也基本上是13.9m/min，布袋除塵器過濾面積需要20m，濾筒除塵器需要28m。20m2的布袋除塵器需要直徑125長1m的布袋50個(gè)，或者直徑125長2m的布袋25個(gè)。

　　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.

　　同體積的摺式濾筒比布袋過濾面積要大3~5倍，但存在折疊縫中清灰較困難的缺點(diǎn)，所以處理同樣風(fēng)量，濾筒除塵器過濾面積要比布袋除塵器選的大一些。在鈦白粉除塵應(yīng)用上應(yīng)選用淺底的摺式濾筒，以降低清灰難度。

　　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旋轉(zhuǎn)閥加羅茨風(fēng)機(jī)與倉泵加壓縮機(jī)的對(duì)比

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

　　1）采用旋轉(zhuǎn)閥加羅茨風(fēng)機(jī)，輸送管道、切換閥門和除塵器大，采用倉泵加壓縮機(jī)則要小。但壓縮機(jī)系統(tǒng)這部分費(fèi)用要比羅茨風(fēng)機(jī)高很多，因此兩者成本對(duì)比上看，費(fèi)用應(yīng)該接近，或者壓縮機(jī)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）從氣源機(jī)械的功率來看，羅茨風(fēng)機(jī)方案可能更節(jié)能。原因是由于鈦白粉不能密相輸送，在本項(xiàng)目的設(shè)計(jì)條件下，采用壓縮空氣來輸送，輸送阻力也就0.15~0.2MPa左右，而壓縮機(jī)的排氣壓力有0.7MPag，相對(duì)于羅茨風(fēng)機(jī)與輸送壓降相適應(yīng)的排氣壓力，壓縮機(jī)做功要高很多。還有明確的一點(diǎn)是氣動(dòng)閥門、除塵器清灰、破拱器等都需要提供壓縮空氣，對(duì)羅茨風(fēng)機(jī)方案來講，也需要提供一套壓縮空氣系統(tǒng)。

　　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）從對(duì)產(chǎn)品品質(zhì)的影響上看，壓縮機(jī)方案，可以方便地除水除油，提供比羅茨風(fēng)機(jī)方案更高品質(zhì)的輸送氣。

　　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）從系統(tǒng)適應(yīng)性上看，羅茨風(fēng)機(jī)壓縮后排氣壓力越高，排氣更可能達(dá)到過飽和，而鈦白粉很細(xì)，水分將對(duì)輸送帶來麻煩。壓縮機(jī)的后處理系統(tǒng)則可以提供干燥清潔的輸送氣。但系統(tǒng)不幸堵料時(shí)，壓縮機(jī)方案可以用更高的壓力來排堵，而羅茨風(fēng)機(jī)沒有這種便利條件。對(duì)于本項(xiàng)目輸送距離較遠(yuǎn)，特別是岔道多的情況，堵料這種情況要予以充分考慮。

　　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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