1
Types of Pneumatic Conveying
Systems氣力輸送系統的種類
1 INTRODUCTION導言
Pneumatic conveying systems are basically quite simple and are eminently suitable
for the transport of powdered and granular materials in factory, site and plant
situations. The system requirements are a source of compressed gas, usually air, a
feed device, a conveying pipeline and a receiver to disengage the conveyed material
and carrier gas. The system is totally enclosed, and if it is required, the system
can operate entirely without moving parts coming into contact with the conveyed
material.氣力輸送系統組成簡單，非常適合工廠、工地的粉體和顆粒料的輸送。系統要求有一個通常是空氣壓縮氣體源、一個喂料設備、輸送管道和一個分離輸送物料和輸送氣體接收器。該系統是完全封閉的，必要情況下，該系統可以完全沒有運動部件接觸到輸送物料。
High, low or negative pressures can be used to convey materials. For
hygroscopic materials dry air can be used, and for potentially explosive materials
an inert gas such as nitrogen can be employed. A particular advantage is that
materials can be fed into reception vessels maintained at a high pressure if required.可以使用高壓、低壓或負壓來輸送物料。輸送易吸水受潮物料時要采用干燥的空氣，輸送易爆性物料可使用惰性氣體如氮氣。有需要的時候，物料也可以被輸送到一個有較高壓力的接受容器中。
1.1 System Flexibility系統靈活性
With a suitable choice and arrangement of equipment, materials can be conveyed
from a hopper or silo in one location to another location some distance away. Considerable
flexibility in both plant layout and operation are possible, such that multiple
point feeding can be made into a common line, and a single line can be discharged
into a number of receiving hoppers. With vacuum systems, materials can
be picked up from open storage or stockpiles, and they are ideal for clearing dust
accumulations and spillages. Pipelines can run horizontally, as well as vertically
up and down, and with bends in the pipeline any combination of orientations can
be accommodated in a single pipeline run. Material flow rates can be controlled
easily and monitored to continuously check input and output, and most systems
can be arranged for completely automatic operation. 使用合適的的設備，物料可以從一個料斗、料倉輸送到遠處的另一個料倉。布置靈活，操作方便，例如，可以多點喂料進一條管道，輸送到多個料倉。真空吸料系統可以從敞開的存放點吸料并輸送，并可以減少粉塵泄漏。輸送管道可方便的水平或垂直布置。管道可以向上、向下甚至向任何方向彎曲。可方便地監測物料的進料量和出料量，并對物料輸送量進行控制，在大多數的系統中這些操作都是自動進行。
Pneumatic conveying systems are particularly versatile. A very wide range of
materials can be handled and they are totally enclosed by the system and pipeline.
This means that potentially hazardous materials can be conveyed quite safely.
There is minimal risk of dust generation and so these systems generally meet the
requirements of any local Health and Safety legislation with little or no difficulty.氣力輸送系統適應性強。很大一部分物料都可以在密閉的系統和管道中進行輸送。這意味著有潛在危險的物料相當安全的運送，將粉塵泄漏的危險降到最低限度，這些系統一般都滿足任何地方衛生和安全方面的要求。Pneumatic conveying plants take up little floor space and the pipeline can be
easily routed up walls, across roofs or even underground to avoid any existing
equipment or structures. Pipe bends in the conveying line provide this flexibility,
but they will add to the overall resistance of the pipeline. Bends can also add to
problems of particle degradation if the conveyed material is friable, and suffer from
erosive wear if the material is abrasive.氣力輸送系統占地小，管道可方便的沿墻壁，屋頂布置，甚至整個的穿行在地下，以避開任何現有設備或建筑物。管道通過彎曲轉向提供這種靈活性，但這將增加管道總的阻力。易碎物料也將因為彎頭的增加，產生更多破碎而降級。并且磨削性物料會在彎頭處產生沖蝕磨損。
1.2 Industries and Materials工業和物料
A wide variety of materials are handled in powdered and granular form, and a
large number of different industries have processes that involve their transfer and
storage. Some of the industries in which bulk materials are conveyed include agriculture,
mining, chemical, Pharmaceuticals, paint manufacture, and metal refining
and processing. In agriculture very large tonnages of harvested materials such as
grain and rice are handled, as well as processed materials such as animal feed pellets.
Fertilizers represent a large allied industry with a wide variety of materials.大量不同行業都涉及以粉體和顆粒料的形式存在的多種物料的運送和存儲。一些行業，包括農業、采礦、化工、制藥、油漆制造、金屬冶煉和處理等，其中大部分原料或產品為散料。在農業方面有非常大噸位的收獲材料，如谷物和大米的處理，以及動物顆粒飼料的處理。 化肥工業中更有各種各樣的物料。
A vast range of food products from flour to sugar and tea to coffee are
conveyed pneumatically in numerous manufacturing processes. Confectionery is an
industry in which many of these materials are handled. In the oil industry fine
powders such as barite, cement and bentonite are used for drilling purposes. In
mining and quarrying, lump coal and crushed ores and minerals are conveyed.
Pulverized coal and ash are both handled in very large quantities in thermal power
plants for the generation of electricity.食品行業，食糖、面粉，咖啡，茶等物料的轉運需要氣力輸送。在石油精煉工業中，如重晶石粉，水泥，膨潤土等粉體用于鉆井。采礦業中，塊煤和粉碎礦石和礦物需要運送。
In the chemical industries materials include soda ash, polyethylene, PVC and
polypropylene in a wide variety of forms from fine powders to pellets. Sand is used
in foundries and glass manufacture, and cement and alumina are other materials
that are conveyed pneumatically in large tonnages in a number of different
industries.熱電廠產生的大量煤粉灰需要運送。化學工業的材料包括純堿，聚乙烯，聚氯乙烯和聚丙烯等粉體和顆粒料。鑄造與玻璃制造行業，需要用到砂、水泥、氧化鋁及其他材料。以上這些都是氣力輸送在不同行業中的應用。
1.3 Mode of Conveying輸送方式
Much confusion exists over how materials are conveyed through a pipeline and to
the terminology given to the mode of flow. First it must be recognized that materials
can either be conveyed in batches through a pipeline, or they can be conveyed
on a continuous basis, 24 hours a day if necessary. In batch conveying the material
may be conveyed as a single plug if the batch size is relatively small.關于物料在管道中輸送的流動模式的描述很混亂。首先必須承認，物料可以分批次的間歇輸送，必要時也可以一天24小時連續不斷的輸送。分批輸送物料時，如果一次輸送的物料量較少，可以以一個料栓的形式進行輸送。
1.3.1 Dilute Phase稀相
For continuous conveying, and batch conveying if the batch size is large, two
modes of conveying are recognized. If the material is conveyed in suspension in
the air through the pipeline it is referred to as dilute phase conveying. If the material
is conveyed at low velocity in a non-suspension mode, through all or part of
the pipeline, it is referred to as dense phase conveying. Almost any material can be
conveyed in dilute phase, suspension flow through a pipeline, regardless of the
particle size, shape or density.連續輸送,或批次輸送量較大，有兩種輸送模式。如果物料在管道中以懸浮態輸送為稀相輸送。如果材料在全部或部分管道中以低速、非懸浮態的方式進行輸送，為濃相輸送。幾乎任何材料，無論顆粒大小，形狀或密度，可以以稀相，懸浮流的形式進行輸送。
1.3.2 Dense Phase密相
In dense phase conveying two modes of flow are recognized. One is moving bed
flow, in which the material is conveyed in dunes on the bottom of the pipeline, or
as a pulsatile moving bed. The other mode is slug or plug type flow, in which the
material is conveyed as full bore plugs separated by air gaps. Moving bed flow is
only possible in a conventional conveying system if the material to be conveyed
has good air retention characteristics. Plug type flow is only possible in a conventional
conveying system if the material has good permeability.密相輸送有兩種模式。一種是移動床流，物料在管道底部形成沙丘狀移動，或作為一個脈動移動床移動。另外一種是栓柱流，物料在管道中形成充滿整個管道截面的料栓與氣栓相間的形態。只有在被輸送物料有良好的存氣性，才可以以移動床形態流動。只有在被輸送物料有良好的透氣性，才可以以栓柱流形態流動。
1.3.3 Conveying Air Velocity輸送氣速
For dilute phase conveying a relatively high value of conveying air velocity must
be maintained. This is typically in the region of 2400 ft/min for a very fine powder,
to 3200 ft/min for a fine granular material, and beyond for larger particles and
higher density materials. For dense phase conveying, air velocities can be down to
600 ft/min, and lower in certain circumstances. Because of the fine particle size
required to provide the necessary air retention, particle density does not have such
a significant effect on the minimum value of conveying air velocity in moving bed
type dense phase conveying.稀相輸送必須有較高的輸送空氣流速。輸送非常細的粉末的氣速為二四〇 〇英尺/分（注：12米/秒）左右，細顆粒狀物料為3200英尺/分鐘（16米/秒），輸送大顆粒和高密度的物料需要更高氣速。濃相輸送，氣速可降至六○○英尺/分（3米/秒），某些情況下更低。由于細顆粒大小需提供必要的空氣保留，在移動床型濃相輸送中，粒子密度對最小輸送空氣流速沒有很大影響。
1.3.4 Solids Loading Ratio固體負荷率
The solids loading ratio, or phase density, is a useful parameter in helping to visualize
the flow. This is the ratio of the mass flow rate of the material conveyed divided
by the mass flow rate of the air used to convey the material. It is expressed
in a dimensionless form. For dilute phase, maximum values that can be achieved
are typically of the order of 15, although this can be higher if the conveying distance
is short and the conveying line pressure drop is high.固體負荷率，或相密度（注：固氣比、混合比，以下叫混合比），是一種有用的參數，利于更直觀看待流動模式。它是物料質量流量與氣體質量流量的比值，是一個無量綱量。稀相一般最大到15 ，如果輸送距離短和輸送壓降高，混合比可以更高。
For moving bed flows, solids loading ratios of well over 100 can be achieved
if materials are conveyed with pressure gradients of the order of 10 lbf/in2 per 100
foot of horizontal pipeline. For plug type flows the use of solids loading ratio is not
so appropriate, for as the materials have to be very permeable, maximum values are
only of the order of about 30. Despite the low value of solids loading ratio,
materials can be reliably conveyed at velocities of 600 ft/min and below in plug
type flow.移動床流動中如果被輸送物料在水平管道中的壓力梯度達到每100英尺有10 lbf/in2（注：相當于每100米223kPa），其混合比可以遠大于100。栓流使用混合比不是太合適，因為物料必須有很好的透氣性，最高值只有約30 。盡管混合比低， 物料可以600英尺/分鐘（3米/秒）或更低速度可靠的流動。
2 SYSTEM TYPES系統類型
A wide range of pneumatic conveying systems are available, and they are all generally
suitable for the conveying of dry bulk particulate materials. The majority of
systems are conventional, continuously operating, open systems, in a fixed location.
To suit the material being conveyed, or the process, however, innovatory,
batch operating and closed systems are commonly used. Many of these systems
can be either positive or negative pressure in operation, or a combination of the
two. In this review some of the more common systems are presented.各種各樣的氣力輸送系統都有效，并普遍適合輸送干的散裝物料。大多數系統都是常規的，連續運行，開放系統，處在一個固定的位置上。 以適應物料運送或處理，或這個過程中，但是，批次輸送和封閉的系統被經常用到。這些系統可以是正壓或負壓的，或者正-負壓的。在這次綜述中介紹一些較常見的系統。
The problem of system selection is illustrated in Figure 1.1. This shows the
combinations that are possible for conventional pneumatic conveying systems with
a single air source. Only system types are presented in detail, with positive
pressure, vacuum, and combined positive and negative pressure systems
considered, in relation to both open and closed systems.圖1.1闡明了系統的選擇問題，描述常規的，具有單一的空氣源的氣力輸送系統可能的組合，詳細介紹了系統類型，包括正壓，真空，正-負系統，以及相關的開放和封閉系統。
With such a wide range and choice of system types, a useful starting point is
to consider the alternatives in pair groupings:如此范圍廣泛系統類型，如何進行選擇，一個有用的出發點是從兩個備選方案中進行選擇：
□Open and closed systems Open systems are the norm for pneumatic
conveying, particularly when conveying with air. Closed systems would
only be employed for very specific circumstances, such as with highly
toxic and potentially explosive materials.
□開放與封閉系統 開放式系統是通常的選擇，特別是當使用空氣進行輸送時。只有在特殊環境下，如輸送高度有毒和具有潛在爆炸性的物料時，才采用封閉的系統。
□Positive pressure and negative pressure systems Materials can be
sucked as well as blown and so either pressure or vacuum can be employed
for pneumatic conveying. This is often a matter of company or personal
preference.
□正壓與負壓系統 物料可以采用負壓吸送，也可采用正壓吹送，如何選擇通常是公司或個人的偏好。
□Fixed and mobile systems The majority of pneumatic conveying systems
are in fixed locations and so this is not identified as a particular case.
A variety of mobile systems are available for specific duties.
□固定和可移動系統 大多數的氣力輸送系統都放在固定位置，這并不意味著是一定的。 各種移動系統，可用于特定的職責。
Figure 1.1 Diagram to illustrate the wide range of conveying systems available for
conventional systems operating with a single air source.具有單一空氣源輸送系統的各種類型
□High and low pressure systems In pneumatic conveying, high pressure
typically means any pressure above about 15 lbf/in2 gauge. For systems
delivering materials to reception points at atmospheric pressure, 100
lbf/in gauge is typically the upper limit, due to the problems of air expansion.
Very much higher pressures (typically 300 to 400 lbf/in2) can be employed
if delivering materials to reception points maintained at pressure,
such as chemical reactors and fluidized bed combustion systems.
□高壓和低壓系統 氣力輸送中的高壓通常是指高約15 lbf/in2（注：103kPa）的壓力。系統受料點的為一個大氣壓，最大一般不超過100 lbf/in2（注：690kPa）為了保持受料點的壓力，可采用非常高的壓力（通常為300至400 lbf/in2 注：2.06至2.76Mpa）來輸送物料，如化學反應器和流化床燃燒系統。
□Conventional and innovatory systems Conventional systems are
those in which the material is simply fed into a pipeline and either blown
or sucked, and so this is not identified as a particular case since this is the
norm. Innovatory systems are those in which the material to be conveyed
is conditioned in some way, either at the feed point or along the length of
the pipeline, generally in order to convey the material at low velocity and
hence in dense phase, if the material has no natural capability for low velocity
conveying.
□常規與創新系統 常規系統將物料喂入管道，然后或吹送或吸送，這是通常做法。創新系統是將沒有低速輸送可能的物料，在喂料點及整個管道中，以低速密相的方式輸送。
□Batch and continuously operating systems Both of these types of
conveying are common in industry.
□批次與連續輸送系統 這兩種形式的輸送在工業中都很常見。
□Single and multiple systems The majority of conveying systems are
single units. It is possible, however, to combine units for certain duties.
□單個或多個系統 大多數輸送系統都是獨立單元。但也可能為了特定目的，將多個系統組合起來。
□Dilute and dense phase systems Dilute and dense phase conveying do
not relate to any particular type of system. Any bulk particulate material
can be conveyed in dilute phase. It is primarily the properties of the material
that determine whether the material can be conveyed in dense phase,
particularly in conventional conveying systems.
□稀相與密相系統 稀相和密相輸送并不和任何特定類型的系統有什么關聯。任何散料都可以稀相輸送。但物料的物性決定了物料是否可以密相輸送，特別是在傳統的輸送系統中。
□Pipeline and channel flow systems In the vast majority of pneumatic
conveying systems the material is conveyed through pipelines. Fluidized
motion conveying systems generally employ channels having a porous
base, through which air is introduced, and they are very limited with regard
to vertical conveying.
□管道與渠道流系統 絕大多數的氣力輸送系統中的物料是通過管道輸送的。流化床輸送系統通常使用多孔板來引入空氣進行輸送，它們局限于垂直的輸送。
3 CLOSED SYSTEMS封閉系統
For certain conveying duties it is necessary to convey the material in a controlled
environment. If a dust cloud of the material is potentially explosive, nitrogen or
some other gas can be used to convey the material. In an open system such
environmental control can be very expensive, but in a closed system the gas can be
re-circulated and so the operating costs, in terms of inert gas, are significantly reduced.某些物料的輸送要在一個可控環境中進行。氮氣或其他一些惰性氣體用來輸送具有爆炸性粉塵的物料，對一個開放的系統，環境控制就會非常昂貴，但在一個封閉的系統中，氣體循環利用，所以生產惰性氣體方面的運營成本，大大減少。
If the material to be handled is toxic or radioactive, it may be possible to use
air for conveying, but very strict control would have to be maintained. A closed
system would be essential in this case. Continuous conveying systems are probably
the easiest to arrange in the form of a closed loop. A typical system is shown in
Figure 1.2.如果要處理有毒或放射性的物料，有可能使用空氣輸送，但要有非常嚴格的管制，封閉系統在這種情況下可起到非常重要的作用。閉路循環中，連續輸送系統可能是最簡單形式。Figure 1.2顯示了一個典型的封閉系統。
Figure 1.2 A closed loop pneumatic conveying system.閉路循環系統
A null point needs to be established in the system where the pressure is effectively
atmospheric and provision for make up of conveying gas can be established
there. If this is positioned after the blower the conveying system can operate
entirely under vacuum. If the null point is located before the blower it will operate
as a positive pressure system.系統中存在一個壓力為大氣壓的零點，輸送空氣從零點補充進系統。如果零點在風機后面，那么。如果零點位于風機前，那么輸送系統為正壓系統。
A back-up filter would always be recommended, because positive displacement
blowers and compressors are very vulnerable to damage by dust. This is
simply a precaution against an element in the filter unit failing. There will generally
be an increase in temperature across an air mover and so in a closed loop system
it may be necessary to include a heat exchanger, otherwise there could be a
gradual build up in temperature. The heat exchanger can be placed either before or
after the air mover, depending upon the material being conveyed.因為容積式鼓風機和壓縮機非常容易因為灰塵受到損害。為了防范過濾單元失效，建議需有后備過濾器。因為空氣加壓后溫度會上升，在封閉系統中必須有熱交換器，否則溫度會逐漸上升。換熱器也可以放在空氣加壓前或之后，這取決于物料的輸送方式。
4 OPEN SYSTEMS開放系統
Where strict environmental control is not necessary an open system is generally
preferred, since the capital cost of the plant will be less, the operational complexity
will be reduced, and a much wider range of systems will be available. Most pneumatic
conveying systems can ensure totally enclosed material conveying, and so
with suitable gas-solid separation and venting, the vast majority of materials can
be handled quite safely in an open system. Many potentially combustible materials
are conveyed in open systems by incorporating necessary safety features.如果沒有嚴格的環境控制要求，一般首選開放的系統。工廠的投資減少，系統更簡單，有更多種類的系統可供選擇。大多數氣力輸送系統能夠確保物料完全密閉的輸送，配合合適的氣固分離和通風系統，絕大多數的物料通過開放的系統安全輸送，許多潛在的可燃物料配以必要的安全措施后也可采用開放的系統。
4.1 Positive Pressure Systems正壓系統
Although positive pressure conveying systems discharging to a reception point at
atmospheric pressure are probably the most common of all pneumatic conveying
systems, the feeding of a material into a pipeline in which there is air at a positive
pressure does present a number of problems. A wide range of material feeding
devices, however, are available that can be used with this type of system, from
verturis and rotary valves to screws and blow tanks, and these are considered in
detail in Chapter 2. A typical low positive pressure pneumatic conveying system is
shown in Figure 1.3.雖然正壓輸送系統中受料點通常都是大氣壓，但把如何物料喂入有正壓的管道中是個問題。有各種各樣的喂料設備可用于這種類型的系統，在第2章中將詳細介紹verturis、旋轉閥、螺旋輸送機和倉泵等喂料裝置。圖1.3顯示了一個典型的低正壓氣力輸送系統。
With the use of diverter valves, multiple delivery to a number of reception
points can be arranged very easily with positive pressure systems. Although multiple
point feeding into a common line can also be arranged, care must be taken,
particularly in the case of rotary valve feeding of the pipeline, since air leakage
through a number of such valves can be quite significant in relation to the total air
requirements for conveying.正壓系統中可以使用換向閥將物料輸送到多個料倉。雖然也多點進料到一條管線，但必須引起注意的是，特別是旋轉閥喂料進管道，多個喂料裝置的漏風量要計入總的輸送風量中。
4.2 Negative Pressure (Vacuum) Systems負壓（真空）系統
Negative pressure systems are commonly used for drawing materials from multiple
sources to a single point. There is little or no pressure difference across the
feeding device and so multiple point feeding into a common line presents few
problems. As a result the rotary valve and screw can also be a much cheaper item
for feeding a pipeline in a negative pressure system than in a positive pressure
system. The filtration plant, however, has to be much larger as a higher volume of
air has to be filtered under vacuum conditions. Particular care, therefore, must be
taken when specifying these particular components. A typical system is shown in
Figure 1.4.負壓系統通常用于從多點到一點的輸送。喂料設備很少或完全沒有壓力損失，因此從多點喂料進一條管道沒有太大問題。也因此對旋轉閥和螺旋機耐壓的要求在負壓系統中比正壓系統要低。過濾裝置，然而，真空條件下過濾設備要處理更大的空氣量。因此在定這些設備的時候要特別引起注意。圖1.4顯示一個典型的負壓系統。
Figure 1.3 A typical positive pressure conveying system.一個典型的正壓輸送系統
Figure 1.4 A typical negative pressure conveying system.一個典型的負壓輸送系統
Negative pressure systems are also widely used for drawing materials from
open storage, where the top surface of the material is accessible. This is achieved
by means of suction nozzles. Vacuum systems, therefore, can be used most effectively
for off-loading ships. They are also particularly useful for cleaning processes,
such as the removal of material spillages and dust accumulations. Another
application is in venting dust extraction hoods.l負壓系統也廣泛用從露天存放點吸取頂部的物料。通過吸嘴來實現這一點。真空系統，用來卸船是最有效的。他們還特別適用于清潔處理， 比如把泄漏的物料和堆積的灰塵吸走。另外也應用在通風除塵罩上。
If a very high vacuum is used for the conveying of a material, consideration
should be given to the stepping of the pipeline part way along its length. Air is
compressible and the rate of change of volume increases considerably with decrease
in pressure. If the pipeline is not stepped, extremely high values of conveying
air velocity can occur towards the end of the pipeline. The situation is the same
for very high pressure positive pressure conveying systems. These issues are considered
in detail in Chapters 5 and 9.如果用非常高的真空來輸送物料，應當考慮沿管長擴管。可壓縮的空氣隨壓力的降低，其體積會膨脹，。如果不擴管，管道末端的空氣流速會非常高。非常高壓力的正壓輸送系統中也有同樣的現象。這些問題會在第5章和第9章中詳細論述。
Vacuum systems have the particular advantage that all gas leakage is inward,
so that the injection of dust into the atmosphere is virtually eliminated. This is
particularly important for the handling of toxic and explosive materials, or any
material where environmental considerations have to be taken into account. It is not
always necessary to employ a closed system with these materials, therefore,
provided that adequate safety measures are taken, particularly with regard to
exhaust venting.真空系統特別的優勢在于，所有氣體是向內泄漏的。 這樣，不太會有粉塵泄漏到大氣中去。在處理有毒和爆炸物料，或必須考慮對環境影響的任何物料時，這一點尤其重要。在這種情況下，可以用負壓系統取代封閉系統，而不用考慮特別的通風除塵措施。
As a result of the conveying air being drawn through the air mover, it is essential
that the exhauster should be protected from the possibility of the failure of
one or more of the filter elements in the gas-solids separation system. This can be
achieved by incorporating a back-up filter, as shown in Figure 1.2 for the closed
loop system. A negative pressure conveying system operating with a vacuum nozzle
is shown in Figure 1.5.為了保護處在輸送末端的空氣動力機械，必須有可靠的氣-固分離系統。為防止過濾器失效，有時會有備用的過濾器。圖1.2所示的封閉閉環系統中有一個備用的過濾器。圖1.5所示為一個有真空吸嘴的負壓輸送系統。
Figure 1.5 Vacuum conveying from open storage.從露天存儲點吸料的負壓系統
4.3 Combined Negative and Positive Pressure Systems負壓-正壓組合系統
Protection has to be provided for the exhauster/blower from the possible ingress of
material, as with negative pressure and closed loop systems. It should be noted
that the available power for the system has to be shared between the two sections,
and that the pipelines for the two parts of the system have to be carefully sized to
take account of different operating pressures.在負壓和閉環系統中，要防止物料可能進入排風機/鼓風機而造成損害。應當指出，系統同時為負壓段和正壓段提供動力，而且系統中的兩個部分必須認真考慮到不同的工作壓力。
Some air movers, such as positive displacement blowers, operate on a given
pressure ratio, and this will mean that the machine will not be capable of operating
over the same pressure range with the combined duty as compared with their individual
operation. This will mean that the system capability is limited in terms of
both tonnage and distance. Although there is only one air mover, two filter units
will be required. A typical system is shown in Figure 1.6.一些空氣動力機械，如容積式鼓風機，以一個特定的壓力比率工作，這將意味著，和該機器執行單一任務相比，在組合系統它不能提供同樣的壓力。也就是說，組合系統的輸送量和輸送距離都受到限制。雖然只有一個空氣動力，但有兩個過濾器單元。一個典型的系統如圖1.6所示 。
Figure 1.6 Combined negative and positive pressure system.負壓-正壓組合系統
4.4 Dual Vacuum and Positive Pressure Systems雙真空正壓系統
If the conveying potential of a system requiring the vacuum pick-up of a material
needs to be improved beyond that capable with a combined negative and positive
pressure system, whether in terms of conveying distance or material conveying
rate, then a dual system should be considered. In this combination the two conveying
elements are separated and two air movers are provided.t如果有一個需要真空上料的系統，而負壓-正壓組合系統又達不到其輸送量或輸送距離，這時可以考慮采用雙真空正壓系統。雙真空正壓系統的真空上料和正壓輸送兩部分是分開的，并由兩個空氣動力機械分別提供輸送動力。
A typical system is shown in Figure 1.7. It should be noted that as there are
two separate systems, two gas-solid separation devices also have to be provided.
Filters and valves have been omitted from the sketch of the system for clarity.一個典型的系統如圖1.7所示。應當指出的是，因為有兩個獨立的系統，兩個氣固分離裝置也必須提供。 簡圖中沒有畫出過濾器和閥門。As two air movers are provided this means that the most suitable exhauster
can be dedicated to the vacuum system and the most appropriate positive pressure
system can be used for the onward transfer of material. If the vacuum off-loading
section is only a short distance, it is possible that the material could be conveyed in
dense phase over the entire conveying distance. It is simply a matter of pressure
gradient for materials that have good air retention properties, as considered in
Chapters 4 and 7.真空和正壓部分各有一個空氣動力機械，這樣可以選擇最合適的排風機和鼓風機來適配系統能力。可以同時進行近距離的真空上料，和遠距離的密相輸送。
The system shown in Figure 1.7 is typical of a ship off-loading system. With
a high vacuum exhauster a material such as cement could be off-loaded at a rate of
about 900 to 1000 ton/h through a single pipeline. Twin vessels on the quayside
would allow continuous conveying to shore based reception vessels, which could
be some 2000 ft distant if a high pressure compressor was to be used. For the onward
conveying two pipelines would probably need to be used to achieve the 1000
ton/h.圖1.7是典型的船舶卸貨系統。配置高真空排氣機械的水泥的卸船裝置，只用一個管道可達約900至1000噸/小時的卸船量。碼頭上雙倉泵卸船機可連續輸送散料到岸上的料倉，使用高壓壓縮機輸送距離可達到約2000英尺（注：大約600m）。必要時采用兩條管線輸送，可實現1000 噸/小時的卸船量。
Figure 1.7 Typical dual vacuum and positive pressure system.典型的雙真空正壓系統
5 BATCH CONVEYING批次輸送
The systems considered so far have all been capable of continuous conveying. In
many processes, however, it may be more convenient to convey one batch at a
time. An additional classification of conveying systems, as indicated on Figure
1.1, is based on mode of operation. Conveying can either be carried out on a continuous
basis or in a sequence of isolated batches.前面所提到的系統都是連續輸送的。但在很多場合，需要批次輸送。額外的分類輸送系統，如在圖1.1所示的輸送系統種類中，有可以連續進行輸送的系統，也可以一批批的輸送的系統。
Although a batch conveying system may be chosen for a specific process
need, the mode of conveying is, to a large extent dictated by the choice of pipeline
feeding device. The majority of batch conveying systems are based on blow tanks,
and blow tanks are chosen either because of their high pressure conveying capability,
or because of the abrasive nature of the material.雖然可能是為了特定的目的選用了批次輸送系統，但這種輸送模式，在很大程度上取決于喂料裝置的選擇。大多數的批次輸送系統是基于發送罐的，選擇發送罐，有可能是因為它能高壓輸送，也可能是因為輸送的物料具有磨削性。
Two types of system are considered. In one, the batch size is relatively large,
and the material is fed into the pipeline gradually, and so can be considered as a
semi continuous system. In the other, the material is fed into the pipeline as a single
plug. Particular features of blow tanks, as material feeding devices, are considered
in Chapter 2. In this chapter the emphasis is on types of conveying system.批次輸送系統有兩種類型。一種是，批量相對較大， 物料逐步的喂入管道，可視為間歇系統。另一種是，物料以一個料栓的形式喂入管道。在第2章中講述發送罐的具體特點。本章的重點是各類輸送系統。
5.1 Semi Continuous Systems間歇系統
It should be noted that when batches of material are fed into the pipeline gradually,
there is essentially no difference in the nature of the gas-solids flow in the pipeline
with respect to the mode of conveying through the pipeline. This is certainly the
case during the steady state portion or the conveying cycle, regardless of the value
of solids loading ratio.應當指出的是，當批次的物料被逐步輸入管道，其氣-固流動性質與是哪種管道氣力輸送模式無關。不管混合比是多少，在穩定輸送期間或在輸送周期中都是這樣。（注：我的理解是，這段話的意思是，不管是連續還是批次輸送，不管混合比多少，物料在管道中流動都遵守氣-固兩相流的規律。）
The blow tanks used vary in size from a few cubic feet, to 1000 ft3 or more,
generally depending upon the material flow rate required as well as a need to
maintain a reasonable frequency of blow tank cycling. The material can be conveyed
in dilute or dense phase, depending upon the capability of the material, the
pressure available and the conveying distance, as with continuously operating systems.發送罐的容積大小從幾立方英尺，到一千立方英尺（注：約28m3）或更大，發送罐的大小通常取決于物料的輸送量需要以及合理的循環次數（注：一般認為，單個發送罐合理的循環次數為每小時8~15次）。和連續輸送系統一樣，物料既可以稀相也可以密相輸送，這取決于物性，系統允許的輸送壓力和物料輸送距離。與不斷操作系統。
With a single blow tank it is not possible to utilize the pipeline while the
blow tank is being filled with material or when the system is being pressurized.
Since batch conveying is discontinuous, steady state values of material flow rate,
achieved during conveying, have to be higher than those for continuously operating
systems in order to achieve the same time averaged mean value of material
flow rate. This means that air requirements and pipeline sizes have to be based on
the maximum, or steady state, conveying rate. The intermittent nature of the conveying
cycle is illustrated in Figure 1.8. 發送罐進料，或該系統正在加壓時，是不能進行輸送的。 由于批次輸送系統不能連續輸送，為了達到和連續輸送系統一樣的輸送量，其出力必須高于連續輸送系統。這意味著，空氣流量和管道大小必須基于最大的，或穩定輸送狀態時的輸送量。圖1.8描述的是間歇性的輸送周期。
In comparison with a continuously operating system, therefore, the batch
operating system would appear to be at a disadvantage. Blow tank systems, however,
can operate at very much higher pressures to compensate, and they can be
configured to operate continuously, as will be considered in the next chapter on
pipeline feeding systems.和連續輸送系統相比，批次輸送系統似乎不占優勢。但發送罐可以運行在非常高的壓力下，，并可以設計成連續工作，這將在下一章管道喂料系統中講到。
Figure 1.8 Sketch showing the transient nature of batch conveying.批次輸送周期示意圖
It should be emphasized that blow tanks can be operated at low as well as
high pressure, depending upon the system needs. If a material needs to be fed into a
chemical reactor or a boiler plant that is maintained at a pressure of 400 Ibf/in , for
example, the blow tank can be designed to operate at 410 Ibf/in2 for the duty. When
delivering material to a reception point at atmospheric pressure, however, air
supply pressures greater than about 100 Ibf/in" are rarely used. This is mainly
because of the problem of air expansion and the need for a stepped pipeline to
prevent excessively high values of conveying air velocity.應該強調指出，發送罐可以工作在低壓或者高壓下，這取決于系統的需求。譬如，如果物料需要被送進化學反應器或壓力有400 Ibf/in（注：約2.76Mpa）的鍋爐中，發送罐可以設計成在410 Ibf/in2下工作。當受料點的壓力是大氣壓，很少用到高于100 Ibf/in（注：約0.69Mpa）的輸送壓力。這主要是因為管道要擴管以避免由于空氣的膨脹而導致輸送氣速過大。
A typical batch conveying system based on a single blow tank is illustrated
in Figure 1.9.圖1.9描述了一個典型的單發送罐批次輸送系統。
Figure 1.9 Typical single blow tank conveying system.典型單發送罐批次輸送系統.
5.2 Single Plug Systems柱塞式系統/單栓流輸送系統
In the single plug conveying system the material is effectively extruded into the
pipeline as a single plug, although the material is generally well aerated. It is typically
about 30 ft long. This plug is then blown through the pipeline as a coherent
plug. A certain amount of material will tail off the end of the plug as it is conveyed,
but the front of the plug will sweep up material deposited in the pipeline by
the previous plug. Blow tanks are generally used as the feeding device and a typical
single plug conveying system is shown in Figure 1.10.柱塞式系統中，物料實際上是被擠壓進管道形成一個料栓，雖然物料通常有良好的透氣性。典型的料栓長約30英尺（注：約9m）。物料以一個緊密的料栓的形態沿管道移動。輸送的時候，一定數量的物料從料栓尾部脫離， 但料栓頭部會鏟起從上一個料栓脫離的物料。發送罐常用于柱塞式系統的喂料，圖1.10 所示為一個典型的柱塞式輸送系統。
The air pressure has to overcome the frictional resistance of the plug of material
in the pipeline. As a result blow tank sizes are rarely larger than 150 ft3,
unless very large diameter pipelines are employed. In terms of system design, a
cycling frequency is selected to achieve the required material flow rate, which
determines the batch size. The pipe diameter is then selected such that the frictional
resistance of the plug results in a reasonable air supply pressure to propel the
plug at the given velocity.空氣壓力要克服料栓在管道中的摩擦阻力，因此發送罐很少大于150立方英尺（注：約4m3）， 除非采用非常大的管道。在系統設計時，根據物料輸送量和選定的循環次數， 確定了發送罐的容積。然后根據系統提供的空氣壓力和一定速度下料栓的摩擦阻力來確定管徑。
The material will be conveyed at a low velocity, in what may be regarded
as dense phase, but solids loading ratios have no significance here, and steady state
conveying, as depicted on Figure 1.8, does not apply either. Single plug systems
are capable of conveying a wide range of materials, and generally at much lower
velocities than can be achieved in continuously operating systems. Many coarse,
granular materials are either friable or abrasive and can only be conveyed in dilute
phase with conventional conveying systems, and so single plug systems can represent
a viable alternative, although it would always be recommended that tests be
carried out to confirm this.物料以低速輸送，可視為密相輸送，但混合比在這里沒有任何意義，圖1.8所描述的穩態輸送和這里不一樣。大多數的物料都可以柱塞輸送，其輸送速度通常比連續輸送要低的多。許多粗顆粒物料或者易碎的、有磨削性的物料，在通常的輸送系統中只能以稀相輸送，柱塞式系統可以成為另一個選擇，但必須靠測試來確認是否可行。
Figure 1.10 Sketch of a typical single plug conveying system.一個典型的柱塞式輸送系統示意圖
Material discharge often represents a problem with this type of system. Although
the plugs of material are conveyed at a relatively low velocity, once they
are discharged from the pipeline the high pressure air released behind the plug can
cause severe erosion of the pipeline on venting.這種類型的系統的卸料往往是一個問題，。雖然料栓以相對的低速輸送，一旦料栓進入受料倉，料栓后面的高壓氣體釋放會造成對管道出料口的嚴重侵蝕。
6 INNOVATORY SYSTEMS創新系統
Unless the material to be conveyed has natural bulk characteristics such as good
air retention or permeability, it is unlikely that it will be possible to convey the
material at low velocity, and in dense phase, in a conventional continuous or semi
continuous conveying system such as those described above. Even if a high pressure
system is employed it is unlikely that such a material will convey in dense
phase, unless the pipeline is relatively short. Dense phase conveying is not synonymous
with high pressure, it is material property dependent.對前面所說的傳統的連續或間歇輸送系統而言，除非物料具有如良好存氣性或透氣性等自然的散料特性，否則不太可能以密相低速輸送。除非輸送距離相對較短，即使采用高壓系統，密相輸送的可能性也不大。密相輸送不等于高壓力，它取決于輸送物料的物性。
For materials that are either abrasive or friable, alternatives to conventional
systems may have to be considered, particularly if the materials are not capable of
being conveyed in a dense phase mode, and hence at low velocity. For friable
materials considerable particle degradation can occur in high velocity suspension
flow, and erosion of bends in the pipeline and other plant surfaces subject to
particle impact will occur if an abrasive material is conveyed in dilute phase
suspension flow.對有磨削性或易破碎的物料，特別是在傳統的輸送系統無法以低速密相輸送時，有必要考慮新型的輸送系統。易破碎的物料以懸浮流高速輸送會降級，以稀相懸浮流輸送磨削性物料，管道彎頭或其他設備表面會受到磨損。
For a material that is only slightly hygroscopic, successful conveying may be
achieved if the material is conveyed in dense phase, without the need for air drying
equipment, since air quantities required for conveying can be significantly lower
than those for dilute phase. For food products, that may be subject to a loss in flavor
in contact with air, dense phase conveying might be recommended. If any such
material is not capable of being conveyed in dense phase in conventional systems,
however, alternative systems will also have to be considered.具有輕微吸濕性的物料，可以密相形式進行輸送，而不需要空氣干燥設備。因為密相輸送用氣量比稀相要低得多。食品和空氣接觸會香味流失，建議采用密相輸送。如果這類物料不能用常規的密相系統來輸送， 要考慮其它系統來替代。
With a need to convey many materials at low velocity, much development
work has been undertaken since the late 1960's to find means of conveying
materials with no natural dense phase conveying capability at low velocity. The
innovatory systems produced as a result of these developments have centered
around some form of conditioning of the conveyed material, either at the feed point
into the pipeline or along the length of the pipeline. Since the modifications are
essentially based on the pipeline, types of conveying system have not changed
significantly.因為有很多物料需要以低速輸送，從20世紀60年代末開始的有關輸送一些本來不具備密相低速輸送條件的物料方面的研究取得了很多的成果，。創新系統的關注點是喂料點及沿整個管長的物料輸送工況的調節。實際上是基于輸送管線的改進，而輸送系統型式并沒明顯的變化。
6.1 Plug Forming Systems脈沖栓流輸送系統
The pulse phase system was developed in the late 1960's. A typical pulse phase
system is shown in Figure 1.11. An air knife, positioned at the start of the pipeline,
intermittently pulses air into the pipeline to divide the discharging material into
discrete short plugs. Blow tanks are commonly used for the feeding of materials in
this type of system also.脈沖輸送系統是從20世紀60年代末發展起來的。圖1.11是一個典型的脈沖輸送系統。脈沖氣從管道起始段的氣刀進入管道，將管道內物料分割成不連續的短栓。這種類型的輸送系統通常用發送罐來喂料。
No further conditioning of the material occurs along the length of the pipeline.
The pulse phase system was initially proposed as a solution to the problem of
conveying cohesive bulk solids, but subsequent developments have shown that a
wider range of materials can be conveyed successfully.沿輸送管道沒有其它的調節手段。 脈沖系統最初是為了解決粘性物料的輸送難題，但隨后的發展表明， 有更廣泛的物料可采用脈沖系統來輸送。
Figure 1.11 Pulse phase conveying system.脈沖栓流輸送系統
6.2 By-Pass Systems旁路系統
.The most common by-pass systems employ a small pipe running inside the conveying
line, having fixed ports, or flutes, at regular intervals along its length. This
inner pipe is not supplied with an external source of air, but air within the conveying
line can enter freely through the regular openings provided. In an alternative
design the by-pass pipe runs externally to the pipeline and is interconnected at
regular intervals. By this means pipeline bends can also be conveniently incorporated.最常見的旁路系統是在輸送管道內部有一根小管，內管上沿管長有規律地開有固定缺口或溝槽。這個內管不通入外來的空氣，但輸送管內的空氣可以自由地經缺口進出。這種設計取代了輸送管道外部的，以一定間隔與輸送管道相通的旁路系統。管道彎頭也可以用這種方式連接。
If the material is impermeable the air will be forced to flow through the bypass
pipe if the pipeline blocks. Because the by-pass pipe has a much smaller
diameter than the pipeline, the air will be forced back into the pipeline through the
next and subsequent flutes because of the extremely high pressure gradient, and
this will effect a break up of the plug of material causing the blockage.如果管道被料栓堵住，不能透過物料的空氣會被迫從旁路管道走。由于旁通管比輸送管的直徑要小很多，在非常高的阻力下，空氣會被迫從相鄰的下一個缺口重新進入輸送管內，這樣就使得堵住輸送管的料栓被擊潰。
6.3 Air Injection Systems空氣噴射系統
A number of systems have been developed that inject air into the pipeline at regular
points along its length, as illustrated in Figure 1.12.一些系統沿管長有規律的通入空氣，如圖1.12所示 。
Figure 1.12 Various plug control systems/各種控栓（破栓）系統
While by-pass pipe systems artificially create permeability in the bulk material,
air injection will help to maintain a degree of air retention within the material.
Continuous injection of air into the pipeline, however, does mean that conveying
air velocities towards the end of the pipeline will be much higher as a result.旁路管道系統人為的增加了物料的透氣性， 噴射入空氣將有助于在物料內部保持一定程度的空氣。連續噴射空氣進入管道，并不意味著管道末端的氣速變的很高。
In some systems sensors are positioned between the parallel air line and the
conveying pipeline and air is only injected when required. If a change in pressure
difference between the two lines is detected, which would indicate that a plug is
forming in the conveying pipeline, air is injected close to that point in order to
break up the plug and so facilitate its movement. Various plug control systems,
including both by-pass pipe and air addition methods are shown in Figure 1.12.在某些系統里，在平行的空氣管道和輸送管道間設有傳感器，只是在必要時才注入空氣。如果監測兩條管線間的壓差發生變化，這表明輸送管道中的料栓在形成中，在此處附近噴射入空氣以擊潰料栓，有助于物料輸送。圖1.12中顯示了包括旁路管和補氣式的各種控栓系統。
Many of the innovatory systems are capable of being stopped and re-started
during operation. With most conventional systems this is not possible, and would
result in considerable inconvenience in clearing pipelines if a blockage should
occur as a consequence. Since they are capable of conveying materials in dense
phase, operating costs for power are likely to be lower than those for a conventional
dilute phase system. Capital costs for the innovatory systems are likely to be higher,
however, and so an economic assessment of the alternative systems would need to
be carried out.許多創新系統能夠在工作中停止輸送和重新起動。而大多數傳統系統無法做到這一點，可能導致管道堵塞而增加清空管道的麻煩。旁路系統能以密相來輸送物料，運營的電力成本很可能會低于常規稀相系統。但創新系統的固定投資很可能會更高些，因而需對兩個系統進行經濟評估。
7 FLUIDIZED MOTION CONVEYING SYSTEMS流化床運動輸送系統（注：從下文上看應是空氣斜槽輸送）
The categorizing of fluidized motion conveying systems always represents a problem.
They are not generally recognized as pneumatic conveying systems because
they only use very low positive pressure air, the material does not flow through a
pipeline, and they have been limited to flow down gradual inclines only. They are,
however, clearly not in the mechanical conveying group of conveyors. Until recent
years their application was relatively limited because the main driving force was
gravity, and so they would only operate on a downward incline, although at a very
low angle.有關流化床運動輸送系統的分類始終是一個問題。 它們不是普遍公認的氣力輸送系統，因為它們只能使用很低壓力的空氣，物料也不是通過管道來流動，而且他們局限于向下傾斜流動。但很明顯它們也不屬于機械輸送。直到最近幾年它們的應用是相對有限，因為主要的動力是重力，所以只能以一個很小的角度向下傾斜輸送。
The material is conveyed along a channel that has a continuous porous base.
Air enters the material through the porous base and fluidizes the material. In this
condition the material will behave like a liquid and flow down an inclined channel.
The channel is generally closed to keep the system dust tight.物料沿有多孔底板的槽體輸送。空氣通過多孔板進入，對物料進行流化。在此工況下，物料將表現得象液體一樣并沿向下傾斜的槽體流動。槽體通常是封閉的以防粉塵外漏。
In early systems the channel ran with the material only partly filling the
channel. The fluidizing air escaped into the space above the flowing material and
was ducted to a filtration plant. In a recent development the channel operates full
of material and is capable of running horizontally. It is possible that the channel
could be made to operate at a higher pressure and so be able to convey material up
an incline. As the channel can run full, negative pressure operation is another possibility.早期的系統中，物料只能部分充滿槽體。流化氣透過物料進入上層空間并被導入過濾裝置。近期發展到物料充滿整個槽體，能夠進行水平輸送。使槽體工作在一個較高壓力下，并可能具備向上傾斜輸送的能力。當槽體充滿物料時，負壓輸送也是可行的。
7.1 Air-Assisted Gravity Conveyors/空氣輔助重力輸送機
In situations where the flow of a material can be downwards, the air-assisted gravity
conveyor has a number of advantages over pneumatic conveying systems.
Plant capital costs can be much lower, operating costs are significantly lower, and
a wide range of materials can be conveyed at a very low velocity.在物料能向下流動的情況下，空氣輔助重力輸送相對氣力輸送系統，有很多的優勢。 投資低得多，經營成本大大降低，種類眾多的物料能以非常低的速度進行輸送。
Air-assisted gravity conveyors can be regarded as an extreme form of dense
phase conveying. The conveyor consists essentially of a channel, divided longitudinally
by means of a suitable porous membrane on which the material is conveyed.
Such a system is shown in Figure 1.13.空氣輔助重力輸送可以被看作是一種超密相輸送系統。輸送裝置主體是一個由多孔板隔開的槽體，物料順著多孔板表面被輸送。 這樣一個系統如圖1.13所示。
Figure 1.13 Air-assisted gravity conveyor.空氣輔助重力輸送
If a small quantity of low pressure air is fed through the membrane, the inter-
particle and particle/wall contact forces will be reduced and the material will
behave like a liquid. If a slight slope is imparted to the conveyor, the material will
flow. These conveyors are often referred to as 'air slides'. They have been in use
for over 100 years and are still widely used today for materials such as alumina,
cement and fly ash.如果少量的低壓空氣通過透氣層輸入，粒子間和粒子與壁的摩擦力將降低，該物料表現的像液體一樣。稍有坡度，材料就會流動起來。這些輸送裝置經常被叫做“空氣斜槽”。他們一直被使用了一百多年，如今仍被廣泛用于輸送，如氧化鋁、 水泥和粉煤灰等物料。
Air-gravity conveyors, ranging in width from 4 in to 2 ft, can convey materials
over distances of up to 300 ft, and are suitable for material flow rates of up to
about 3000 ton/h. In general, most materials in the mean particle size and density
ranges from 40 to 500 micron and 80 to 300 Ib/ft3 are the easiest to convey and
will flow very well down shallow slopes.空氣輔助重力輸送裝置，寬度從2到4英尺不等，輸送距離可達300英尺（注：約90m），輸送量可達約3000噸/小時，平均粒徑為40到500微米，密度為80至300 Ib/ft3（注：約1281~4805kg/m3）的大部分物料并能很容易地沿小角度的下斜坡度被輸送。
7.2 Full Channel Conveyors滿槽輸送裝置
Hanrot [1] describes a pressurized horizontal conveying system developed by
Aluminum Pechiney to convey alumina. The alumina was conveyed from a single
supply point to more than one hundred outlets. Electrolysis pots on a modern aluminum
smelter were required to be filled and the distance from the silo to the furthest
outlet was approximately 600 ft. Air at a pressure of about I'A lbf/in2 gauge
is required. A conveying channel is employed, as with the air-assisted gravity conveyor,
but the channel runs full of material. The system is illustrated in Figure 1.14
and this shows the principle of operation.Hanrot [ 1 ]介紹了一種由力拓加鋁開發的輸送氧化鋁的加壓水平輸送系統。氧化鋁從一個供料點輸送到超過100個受料點去。現代化鋁冶煉廠，從料倉輸送氧化鋁到最遠的電解罐，距離接近600 ft（注：約183m），輸送壓力約為1.5bf/in2（注：約10.3kPa）。采用空氣輔助重力輸送機進行輸送，物料充滿整個槽體。圖1.14描述了該系統的工作原理。
Figure 1.14 Principle of potential fluidization ducts.流化床輸送原理
Balancing columns are positioned on the conveying duct and are used for
de-dusting. This is not a continuously operating system in the application described.
It is a batch type system and its object is to meet the demands of the intermittent
filling of the pot hoppers. The system, however, is clearly capable of
continuous operation and of significant further development.輸送導槽上設置有用于除塵的平衡塔，。在此應用示例中描述的不是一個連續工作系統。這是一個間歇填滿料斗的批次輸送系統。不過，該系統顯然是有連續工作能力的，具有進一步發展的意義。
8 MOBILE SYSTEMS移動系統
All of the systems described so far have been essentially fixed systems. The only
real flexibility in any of the systems has been the capability of moving vacuum
nozzles in negative pressure systems. By the use of flexible hoses these can be
moved, and they find wide application in ship off-loading systems, and the clearing
of material from stockpiles or spillages. Many road sweeping vehicles employ
vacuum conveying for their operation.迄今為止所介紹的全部系統基本上都是固定式系統。所有系統中唯一具有真正靈活性的是負壓系統中可移動的真空吸嘴，使用可移動的撓性軟管，他們廣泛應用于船舶卸貨系統、清倉及收集灑落的物料。許多道路清掃車的作業采用的是真空輸送。
Many bulk particulate materials are transported from one location to another
by road, rail and sea. Many materials, of course, are transported in a pre-packaged
form, or in bulk containers, and can be transported by road, rail, sea or air, in a
similar manner to any other commodity. Many transport systems, however, are
specifically designed for bulk particulate materials and have a capability of self
loading, self off-loading, or both. These are generally mobile versions of the above
static conveying systems, depending upon the application and duty.許多散裝顆粒物料通過公路，鐵路和海運來進行運輸。和其它產品一樣，許多物料是有包裝的，或裝在散裝容器中。然而，許多運輸系統是專為運送散裝物料設計的，具有自行裝載或自行卸貨的功能，或兩者兼而有之。這些都是不同于固定式輸送系統的移動類型，用于特定的應用和職能。
8.1 Road Vehicles公路車輛
Road vehicles are widely used for the transport of a multitude of bulk particulate
materials, such as cement, flour, sugar and polyethylene. Road vehicles often have
their own positive displacement blower mounted behind the cab and so can offload
their materials independently of delivery depot facilities. The material containing
element on the truck can generally be tipped to facilitate discharge, which
can be via a rotary valve, or the container might double as a blow tank which can
be pressurized.公路車輛被廣泛用于運輸各種散裝物料，如水泥，面粉，食糖和聚乙烯。道路車輛常常自帶安裝在駕駛室后的正壓容積式風機，不需使用交貨倉庫設施來卸貨。通常卡車上的物料可能通過一個旋轉閥來卸料，或容器本身就是一個類似于發送罐的可加壓容器。
8.2 Rail Vehicles鐵路車輛
Rail cars or wagons generally rely on delivery depot facilities for off-loading. Because
of their length tilting is not an option and so multiple point off-loading is
often employed. They may be off-loaded by rotary valve, or the rail car may be
capable of being pressurized so that it can be off-loaded as a blow tank.火車車廂或貨車一般依靠交貨倉庫設施卸下。因為不能在一定范圍內傾斜，因此經常使用多點卸料。他們通過旋轉閥卸料，或像發送罐一樣被加壓而卸料。
Whereas road vehicles are typically designed to operate with air at 15 Ibf/in2
gauge for this purpose, rail vehicles are generally designed to 30 Ibf/in2 and can
usually be off-loaded in about one hour. The base of the rail car is usually angled
at about five degrees in herringbone fashion around each discharge point and
fluidized to facilitate removal of as much material as possible.鑒于一般公路車輛設計的工作壓力為15 Ibf/in2（注：約103kPa），鐵路車輛一般工作壓力為30 Ibf/in2（注：約206kPa），通常可在約一個小時卸完。鐵路車輛每個卸料點處的底板通常呈約5度左右角度的人字狀。通過流化盡可能的卸出物料。
8.3 Ships船舶
Large bulk carriers usually rely on port facilities for off-loading and these are generally
similar to that depicted in Figure 1.7. Intermediate bulk carriers, however,
often have on-board facilities for off-loading. Such vessels are often used for the
transfer of materials such as cement to storage depots at ports for local supply, or
to off-shore oil rigs.大型散貨船通常依賴于港口設施來卸貨，類似于圖1.7 中所描述的系統。但中間散裝船，往往靠船上的設施來卸貨。這類船只通常用于把水泥等物料輸送到港口的存儲倉庫，或送到近海石油鉆井平臺。
Materials are typically transferred from storage holds in the ship by a
combination of air-assisted gravity conveyors and vacuum conveying systems, into
twin blow tanks. High pressure air is supplied by on-board diesel driven
compressors and materials are conveyed to dock-side storage facilities through
flexible rubber hose, which solves the problems of both location and tidal
movements.物料通常是船上儲倉由空氣輔助重力輸送與真空輸送的組合系統提升進到雙倉泵。高壓空氣是由船上的柴油驅動壓縮機供給，物料通過橡膠軟管輸送到碼頭倉儲設施，通過這種方式解決了由潮汐運動引起的距離變化難題。
9 MULTIPLE SYSTEMS/多重系統
Two multiple systems have already been considered. These were the combined
negative and positive pressure system, illustrated in Figure 1.6, and the dual vacuum
and positive pressure system, illustrated in Figure 1.7. A third possibility is
the staging of pneumatic conveying systems, which would be required for very
long distance conveying. Materials are currently conveyed over distances of 5000
ft in a single stage and flow rates of 40 ton/h over this distance are not unusual.前面已經講到了兩個多重系統。這就是，圖1.6中描述的負壓-正壓組合系統 ，以及圖1.7中描述的雙真空正壓系統。第三種是是非常長距離輸送要用到的分段氣力輸送系統。目前物料單級輸送，距離超過5000英尺（注：約1500m），輸送量達到40噸/小時，并非罕見。
With much higher air supply pressures, conveying over longer distances is
possible, and with larger bore pipelines higher material flow rates can be achieved.
For very much longer distance conveying, however, staging will have to be employed.
A problem with using very high pressure air is that of the expansion of the
air and the need to step the pipeline to a larger bore part way along its length, but
this can be overcome to a large extent by discharging the material at the end of
each stage at a pressure of about 45 lbf/in2 rather than to atmospheric pressure.通過提高輸送壓力和加大管徑，更遠的距離，更大的輸送量，也是可以實現的，但此時不得不采用分段氣力輸送。使用非常高的空氣壓力，由于空氣的膨脹需要沿管程對管道進行擴管，每段末端的壓力大約是45 lbf/in2（注：約310kPa），而不是一個大氣壓。
10 SYSTEM REQUIREMENTS系統要求
The uses, applications and requirements of pneumatic conveying systems are
many and varied. A number of system requirements were highlighted at various
points with regard to the systems. Some of the more common requirements of
systems can be identified and are detailed here for easy access and reference, since
these may feature prominently in the choice of a particular system.氣力輸送系統的使用，應用和要求是多種多樣的。一些系統要求在系統的不同點被突出強調。一些較常見的系統要求在這里詳細介紹以供參考，當然在特定系統的選擇中有一些系統要求要被特別提出。
10.1 Multiple Pick-Up多點拾取
If multiple point feeding into a common line is required, a vacuum system would
generally be recommended. Although positive pressure systems could be used, air
leakage across feeding devices such as rotary valves represents a major problem.
The air leakage from a number of feed points would also result in a significant
energy loss. The air loss could be overcome by adding isolation valves to each
feed point, but this would add to the cost and complexity of the system.如果一根管道要有多點喂料，一般建議采用真空系統。雖然也可使用正壓系統，但從喂料裝置，比如旋轉閥，產生的空氣泄漏會成為一個大問題。從一些喂料點漏風引起的能量損失是個顯著的數字。在每個喂料點增加隔離閥門可以減少漏風量，但會增加費用和系統的復雜性。
10.2 Multiple Delivery多點受料
Multiple delivery to a number of reception points can easily be arranged with positive
pressure systems. Diverter valves can be used most conveniently for this purpose.
Such a system was illustrated in Figure 1.3. This shows a separate filter unit
mounted on each reception hopper. If the situation allows, a common unit could be
used, but care would have to be taken with the specification and layout.正壓輸送系統很容易實現送到多個接收點。換向閥可用于最方便地實現這一目的。在圖1.3中描述了這樣的一個系統。在每個受料斗上設有一個單獨的過濾器。如果情況允許，也可采用一個公用的過濾器，但要注意必須采取的規格和設備布置。
The problem with vacuum systems performing this function is equivalent to
the problem of using a positive pressure system for the multiple pick-up of
materials, which is one of multiple point air leakage. In this case, however, it is
ingress of air into the system. Any air leaking into a conveying system pipeline
along its length will by-pass the material feed point and this could result in the
conveying air velocity being too low to convey the material.用真空系統實現一對多的輸送產生的問題，相當于用正壓輸送系統實現多對一的輸送，都是存在多點漏風。但在這種情況下，對真空系統是空氣漏進到系統內。任何空氣從管道上泄漏進輸送系統，相當喂料點增加了一路旁路，這可能導致（喂料點）輸送空氣流速過低。
10.3 Multiple Pick-Up and Delivery多點拾取，多點受料
The suck-blow, or combined vacuum and positive pressure system, illustrated in
Figure 1.6 is ideal for situations where both multiple pick-up and delivery is required.
The pressure drop available for conveying is rather limited with this type
of system and so if it is necessary to convey over a long distance, a dual system
would be more appropriate. In this the vacuum and positive pressure conveying
functions are separated and a high pressure system can be used to achieve the distant
conveying requirement, as shown in Figure 1.7.圖1.6顯示的吸-送，或負壓-正壓組合系統，適合于多對多的輸送。 這種系統能提供的輸送壓力是相當有限的，所以對長距離的輸送，一個雙真空正壓系統將更為合適。如圖1.7所示的雙真空正壓系統中，真空和正壓系統是相互獨立的，因此能提供高的輸送壓力來達到遠距離輸送。
10.4 Multiple Material Handling多種物料搬運
If it is required to handle two or more materials with the one system, reference
should be made to the conveying characteristics for each material to be conveyed.
It is quite likely that the air requirements for the materials will differ to a large
extent, and that different flow rates will be achieved for each material, for identical
conveying conditions.如果在同一個系統中需要能輸送兩個或兩個以上的物料，系統要達到每一種物料輸送的要求。 很可能在相同輸送條件下，每種物料輸送所需空氣量大不相同，而系統必須實現這種差異。
In this case it will be necessary to base the air requirements, to be specified
for the air mover, on the material requiring the highest conveying line inlet air
velocity. Consideration will then have to be given to a means of controlling the air
flow rate, to lower values, for the other materials, if this should be required. Alternatively
the same air flow rate can be used for each material but different pipeline
bores will have to be used to achieve the conveying air velocity values required.在這種情況下，有必要根據物料所需最大的輸送空氣入口流速來選定氣源機械。有必要時，要考慮采用一種措施來控制空氣流量以適應輸送其它種類物流時較低的空氣量要求。或者，采用同樣的空氣流量，不同（內徑）的輸送管道來輸送各種材料。
Since it is likely that the flow rate of each material will be different, the
feeding device, or devices, will have to meet the needs of every material, in terms
of flow rate and control. The solutions will also differ between a system in which
there is a change of material to be conveyed, and a system in which different materials
are to be fed from one or a number of different supply hoppers.因為每種物料的輸送量會有所不同，喂料設備要滿足每種物料在流量方面的控制要求。一個系統中物料以不同輸送量來輸送，和一個系統中有多種物料從一個或多個不同供料斗中喂料，的解決方案是不同的。
10.5 Multiple Distance Conveying不同距離輸送
If it is required to convey a material over a range of distances, such as a road
tanker supplying a number of different installations, or a pipeline supplying a
number of widely spaced reception points, consideration will again have to be
given to differing material flow rates and air requirements. It is possible for both
of these to change if there is a change in conveying distance, for whatever reason.如果物料需要輸送不同距離，如槽車要提供給一些不同的設施，或管道輸送到一些分布很遠的受料點，必須再次考慮到不同的物料輸送量和所需空氣流量。不管什么原因下的輸送距離的變化，都可以引起輸送量和空氣流量同時改變。
For a given air supply, in terms of delivery pressure and volumetric flow
rate, the material flow rate achieved will decrease with increase in conveying distance.
As a consequence the material feeding device will either need to be controlled
to meet the variation in conveying capability, or the feed rate will have to
be set to the lowest value for the longest distance.對于給定的空氣供應，從提供的壓力和空氣體積流量來看，隨輸送距離的增加，輸送量將減少。因而，喂料裝置需要得到控制以滿足不同輸送能力，或喂料量將被設置為最長距離下的最小喂料量。
For materials capable of being conveyed in dense phase there is the added
problem of the possibility that the air flow rate will also need to be increased if
there is a significant change in conveying distance.材料能夠以密相輸送有增加問題的可能性，即如果輸送距離顯著變化，空氣流量也將需要增加。（注：存疑。原文：For materials capable of being conveyed in dense phase there is the added
problem of the possibility that the air flow rate will also need to be increased if
there is a significant change in conveying distance.）
10.6 Conveying From Stockpiles從儲存點的輸送
If the material is to be conveyed from a stockpile, then a vacuum system using
suction nozzles will be ideal. The type of system required will depend upon the
application and conveying distance. For a short distance a vacuum system will
probably meet the demand on its own.如果物料是從儲存點來輸送，帶吸嘴的真空系統是理想選擇。該類型的系統需要將取決于應用和輸送距離。短距離的輸送，真空系統可能滿足要求。
Where access is available to a free surface, as in ship off-loading, vacuum
nozzles can transfer material under vacuum to a surge hopper. If this is not the final
destination for the material it could be the intermediate hopper in a combined
positive and negative pressure conveying system, or the supply hopper for the
second part of a dual system, from where the material could be blown onward.凡能獲得自由表面的地點，如在船舶卸貨，真空噴嘴可在真空下把物料送到一個緩沖料斗。如果這不是物料輸送的最后的目的地，它可能是負壓-正壓組合輸送系統的中間料斗，或是雙真空正壓系統第二部分的供料斗，從那里物料可被正壓吹送。For clearing dust accumulations and spillages, and surplus material deposited
in stockpiles, mobile units are particularly useful. These are generally suckblow
systems with a vacuum nozzle. Although they can be small versions of a
continuously operating suck-blow system, they are more usually batch conveying
systems with the transfer hopper acting also as a blow tank. Material is first drawn
into the hopper/blow tank under vacuum, and when it is full it is pressurized and
conveyed on to the reception point.清潔泄漏粉塵和儲存點灑落物料，移動單元特別有用。這些一般是有真空噴嘴的吸-吹系統。雖然他們可以是小規模的連續吸-吹系統，他們更可能是有類似發送罐的輸送倉的批次輸送系統。物料首先真空提升進料斗/發送罐，當料斗裝滿后就加壓輸送到受料點。
10.7 Start-Up With Full Pipeline滿管啟動
If there is likely to be a need to stop and start the conveying system while it is
conveying material, a system capable of doing this will need to be selected. This is
rarely possible in conventional systems, and so consideration will have to be given
to innovatory systems.如果需要在物料輸送過程中，停止并啟動輸送系統，需要選擇能做到這一點的輸送系統。常規系統很少能做到這一點，因此將不得不考慮創新系統。
Many of these systems are capable of starting with a full pipeline, although
their capabilities on vertical sections may need to be checked, particularly if the
stoppage is for a long period. The possibility of power cuts, from whatever source,
should also be taken into account here.許多這類系統能夠在管道充滿時啟動，雖然它們在垂直段的能力要校核，特別是有很大一段堵住的時候。這里要考慮電力切斷的可能性。
11 MATERIAL PROPERTY INFLUENCES物料性能的影響
The properties of the materials to be conveyed feature prominently in the decisions
to be made with regard to the selection of a pneumatic conveying system. As with
'System Requirements', considered above, some of the more common material
properties can be identified and are detailed here for easy access and reference.輸送物料的性質對一個氣力輸送系統的選擇有突出的影響。正如 '系統要求'所說 ，考慮上述情況，一些較常見的物料性能在這里列出并詳細說明以供參考。
11.1 Cohesive粘性
Problems may be experienced with cohesive materials in hopper discharge, pipeline
feeding and conveying. If there is any difficulty in discharging a cohesive
material from a rotary valve, a blow-through type should be used. If there is any
difficulty in conveying a cohesive material in a conventional system, then an innovatory
system should be considered. The pulse phase system, for example, was
developed for the handling of such fine cohesive powders.有粘性物料在料倉卸料，管道喂料及輸送中都會碰到一些問題。如果粘性物料通過一個旋轉閥卸料有困難，應該采用直通型旋轉閥。如果常規系統輸送粘性物料有困難，應該考慮創新系統。比如，脈沖輸送系統可用于輸送有粘性的細粉料。
11.2 Combustible可燃性
There is a wide range of materials which, in a finely divided state, dispersed in air,
will propagate a flame through the suspension if ignited. These materials include
foodstuffs such as sugar, flour and cocoa, synthetic materials such as plastics,
chemical and pharmaceutical materials, metal powders, and fuels such as wood
and coal. If a closed system is used the oxygen level of the conveying air can be
controlled to an acceptable level, or nitrogen can be used. If an open system is to
be used, then adequate safety devices must be put in place. One possibility is to
use a suppressant system. Another is to employ pressure relief vents and other
safety features.有很多細磨過的物料，分散在空氣中時，如果點燃會四處擴散（爆炸）。這些物料包括： 食品，如糖，面粉和可可，合成材料，如塑料， 化工和醫藥原料，金屬粉末，及燃料，如木材和煤。如果是一個封閉式系統，要將輸送空氣中的氧含量控制到可以接受的水平，或使用氮氣。如果是一個開放的系統，要設置適當的安全裝置。一種是使用撲滅系統。另一種是采用泄壓噴口和其他安全功能。
11.3 Damp or Wet潮濕或含水
Materials containing a high level of moisture can generally be conveyed in conventional
systems if they can be fed into the pipeline, and do not contain too many
fines. Most of the handling problems with wet materials occur in trying to discharge
them from hoppers. Fine materials may not discharge satisfactorily from a
conventional rotary valve and so a blow through type should be used.如果不含太多細料的高含水物料能喂進管道，就能通過常規的輸送系統來輸送。大部分的處理問題發生在含水物料從料斗中卸料時。細料用常規旋轉閥卸料不是很令人滿意，應該使用直通型的。
Fine materials which are wet will tend to coat the pipeline and bends, and
gradually block the line. Lump coal having a large proportion of fines is a particular
problem in this respect. Single plug blow tank systems and some of the innovatory
systems are capable of handling this type of material. If a conventional system
must be used, the problem can be relieved by heating the conveying air, if the material
is not too wet.含水的細料可能粘附在管道和彎頭內壁，并逐步堵住管道。有很大比例細粉的塊煤是這方面的一個代表。柱塞式發送罐系統和一些創新系統能夠處理這種類型的物料。如果必須使用常規系統，如果材料是不是太潮濕，這個問題可以加熱輸送空氣得到緩解。
11.4 Electrostatic靜電
If the build up of electrostatic charge is a problem when conveying a material, the
air can be humidified. This process can be carried out on-line and does not usually
require a closed system. In dense phase the quantity of air which needs to be conditioned
is much less than in dilute phase systems, and so for materials capable of
being conveyed in dense phase, the operating costs for air quality control will be
lower. The entire system and pipe-work network should be earthed.如果輸送物料時，靜電會累積，可加濕輸送空氣。這一過程可以在線進行并且通常不需要一個封閉的系統。密相輸送系統所需空氣量比稀相輸送系統要低很多，因此物料密相輸送，空氣方面的成本將較低（注：這一句好像和本小節內容無關^_^）。整個系統和管網應接地。
11.5 Erosive磨蝕性
If the hardness of the particles to be conveyed is higher than that of the system
components, such as feeders and pipeline bends, then erosive wear will occur at all
surfaces against which the particles impact. Velocity is one of the major parameters
and so the problem will be significantly reduced in a low velocity system. If a
dilute phase system must be used, feeding devices with moving parts, such as rotary
valves and screws, should be avoided, and all pipeline bends should be protected.如果輸送顆粒的硬度高于系統組成部分，如喂料器和管道彎頭，粒子將對這些表面有沖蝕磨損。速度是其中一個重要參數，所以在低速系統中，這個問題將大大減少。如果必須使用稀相系統，應當避免采用有移動部件的喂料設備，如旋轉閥和螺旋機，所有管道彎頭也應該得到保護。
11.6 Friable易碎性
If degradation of the conveyed material is to be avoided, a system in which the
material can be conveyed at low velocity should be considered. The magnitude of
particle impacts, particularly against bends in the pipeline, should be reduced as
this is one of the major causes of the problem. Damage caused by attrition as a
consequence of particle to particle and particle to wall surfaces must also be taken
into account. Pipeline feeding devices which can cause particle breakage, such as
screws, should also be avoided.如果要考慮輸送物料因破碎而降級，應當考慮低速輸送。應減少粒子群的碰撞，特別是對管道彎頭的撞擊，這是物料破碎產生的主要原因。粒子間及粒子和壁面間的磨損也要計算進去。也應避免使用能引起粒子破碎的管道喂料設備，如螺旋輸送機。
11.7 Granular顆粒
Granular materials can be conveyed with few problems in pneumatic conveying
systems provided that they can be fed into the pipeline. Problems with feeding can
occur with top discharge blow tanks and conventional rotary valves. Air will often
permeate through granular materials in top discharge blow tanks and the materials
will not convey, particularly if the blow tank does not have a discharge valve.
Granular materials containing a large percentage of fines, and which are not capable
of dense phase conveying, may block in a top discharge line. In rotary valves,
shearing of granular materials should be avoided, and so a valve with an off-set
inlet should be used.只要顆粒料能喂進管道。就能較容易地進行氣力輸送。對上引式倉泵和常規旋轉閥等喂料裝置會有些問題。上引式倉泵中，特別是在沒有出料閥門的情況下，空氣通常會穿透顆粒料粒狀物料，而導致物料不能被輸送。含有很大比例細粉的顆粒料不能以密相輸送，在上引式管道中會引起管道堵塞。應避免使用可能擠壓顆粒料的旋轉閥，需選擇有偏置入口的旋轉閥。
11.8 Hygroscopic吸濕性
If a material is hygroscopic the air used for conveying can be dried to reduce the
moisture level to an acceptable level. This process can be carried out on-line and
does not usually require a closed system. For a material which is only slightly hygroscopic,
successful conveying may be achieved if the material is conveyed in
dense phase, without the need for air drying equipment, since air quantities required
for conveying can be significantly lower than those for dilute phase
conveying.如果物料具有吸濕性，應干燥輸送空氣使其含水量保持在可接受的水平上。這一過程可以在線進行并且通常并不需要一個封閉的系統。對略有吸濕性的物料，可采用密相輸送的形式，因為所需的空氣量大大低于稀相輸送系統而不需要空氣干燥設備。
11.9 Low Melting Point低熔點
The energy from the impact of particles against bends and pipe walls at high velocity
in dilute phase conveying can result in high particle temperatures being generated.
The effect is localized to the small area around the point of contact on the
particle surface, but can result in that part of the particle melting. The problem is
accentuated if the particles slide on the pipe wall and around pipeline bends. Plastic
pellets such as nylon, polyethylene and polyesters are prone to melting when
conveyed in suspension flow.粒子與彎頭和管壁高速碰撞產生的熱量會使粒子溫度升的很高。效果局限在粒子碰撞點附近一小塊表面上，但可能會導致該部分粒子融化。如果粒子沿管壁和彎頭外側內壁滑動，那么問題就更大了。塑料丸粒，如尼龍，聚乙烯和聚酯以懸浮流輸送時很容易發生融化。
Velocity is a major variable and so the problem will generally be significantly
reduced for most materials in a low velocity, dense phase system. If such
materials have to be conveyed in dilute phase a roughened pipeline surface may
help to reduce the problem considerably as this will prevent the particles from
sliding.速度是一個重要的因素，因此大多數物料而言，低速密相輸送時問題程度會明顯降低。如果這類物料不得不以稀相來輸送，采用表面粗糙的管道可能有助于減少問題，因為這將大大防止顆粒滑動。
11.10 Radioactive放射性
Radioactive materials must be conveyed under conditions of absolute safety, and
so it would be essential to employ a closed system so that strict control of the conveying
environment could be maintained. A vacuum system would also be necessary
to ensure that no conveying air could escape from the system, or material in
the event of a bend eroding, for some of these materials do tend to be rather abrasive.放射性物料必須在絕對安全的條件下輸送，并這樣就必須采用一個封閉的系統，以便嚴格控制的輸送環境可維持不變。可以采用真空系統以確保沒有輸送空氣外泄，或物料不從磨損的彎頭處（泄漏），因為其中一些材料往往是相當粗糙的。
11.11 Toxic有毒
If toxic materials are to be handled, strict control of the working environment must
be maintained. A vacuum system, therefore, would be essential to ensure that there
could be no possibility of material leakage. If the conveying air, after filtration,
could be vented safely to the atmosphere, an open system would be satisfactory. If
not, a closed loop system would have to be used.有毒物質的處理，必須維持嚴格控制的工作環境。真空系統可以完美的確保有沒有任何物料泄漏的可能性。如果過濾后的輸送空氣，可安全排放到大氣，一個開放的系統也可滿足條件。如果不能，那么必須采用一個閉環系統。
11.12 Very Fine超細
A problem of pipeline coating can occur with very fine powders in the low micron
and sub-micron range, such as carbon black and titanium dioxide. These materials
tend to adhere to the pipe wall when conveyed in conventional systems. The coating
gradually builds up and can cause a marked reduction in the pipe section area,
and hence a reduction in conveying capacity. Many of the innovatory systems are
capable of handling this type of material successfully.微米和亞微米級的超細粉體用常規輸送系統輸送時會粘附在管道內壁上形成涂層，如炭黑和二氧化鈦。涂層逐步積累，并可能導致管道流通面積明顯減少， 從而減少了輸送量。有許多創新系統有能力成功地處理這類材料。
If a conventional system is to be used the material should be conveyed
through a flexible pipeline or hose so that the material build-up can be shaken free
on a regular basis. It is quite likely that the natural pulsations that occur within the
system would be sufficient to vibrate the material free to enable it to be reentrained
in the conveying line.如果常規系統是通過撓性管道或軟管來輸送物料，那么有規律的搖晃會使涂層脫離。就像是發生在系統內的自然脈動將足以震動粘附的物料，使之脫離并被輸送走（注：原文用了一個詞“reentrained”-重新登上火車，比喻物料加入到輸送行列里去。這里不太容易找到合適的語句去表達，所以采用了意譯，在前面很多處及以后更多的地方都會采用這種翻譯手法，以其在不曲解原意的情況下節省思考的時間^_^）。
引文
1. J-P. Hanrot. Multi-point feeding of hoppers, mounted on aluminum smelter pots, by
means of potential fluidization piping. Proc 115th An Mtg, The Metallurgical Soc of
AIME. pp 103-109. New Orleans. March 1986.
