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Pneumatic Conveying SystemsAny solid material down in size from 10 mm and smaller having free flowing/sliding characteristic can be entered into a “TUFF” Pneumatic Conveyer at one point to be transferred to other point in a closed pipe line with accompanying conveying medium of AIR. Due to a appropriate transport velocity in the pipe line, materials get conveyed in air and travel together with airflow. At pick-up and discharge points of conveyer appropriate equipment are employed to effect smooth entry and discharge of materials to and from the conveyer systems. |
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Conveyed ProductsCommon applications for dense phase systems include products with heavy bulk-densities, abrasive products, friable products, blended products and in some instances products that do not require continuous delivery to their destination. In many cases, the product needs to be evaluated based on process needs and possibly lab tested prior to final system selection to ensure the desired results can be achieved. Lab testing will also allow the product properties to be evaluated. Applications: |
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Types Of Tuff Conveying Systems
Under negative pressure
The pipeline and equipments of separation/filtration remain under negative pressure. Exhauster/Blower is generally installed at the end of the line as the last equipment.
The system is useful when materials are to be picked up from multiple points and discharged at one point. Due to the negative pressure of the pipeline and equipments, air has a tendency to leak inwards. At discharge point proper care is taken to avoid vacuum free discharge of materials.
Under Positive Pressure
The pipe line and equipments of separation/filtration remain under positive pressure. Blower is generally installed as the first equipment at the starting point of pipeline.
The system is useful when material is to be picked up at one point and discharged at multiple points. Due to positive pressure of the pipeline and equipments air has a tendency to leak outside, creating dust pollution problems. At pick-up point care is taken to enter materials into the pipeline under positive pressure and to discharge materials without air disturbance.
Conveying through Blower
Material with high moisture percentage or a mixed characteristics are conveyed through the impeller of the blower. This system facilitates easy entry of materials into pipeline starting point under negative pressure. At discharge point, the same is taken out under positive pressure condition. The system reduces needs for air locking and primary separation devices, however increases the chances of faster erosion of the impeller with more frequency of unbalancing the same due to material deposition and increasing maintenance due to frequent clogging.
Conveying Regimes
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Very low material velocity, pipeline full of material - an excellent regime for fragile materials. |
Low material velocity - with high line loading ... material moves in plug flow fashion - best regime for most applications in which power economy, pipe erosion, and material degradation issues are important. |
Higher velocity than discontinuous dense phase, but much lower than dilute phase. Used for handling powders that can be fluidized. |
Material velocity above the saltation velocity - no upper limit to the velocity - least attractive regime for operating economy - unsuitable for fragile or abrasive materials or materials with wide particle size distribution. |
Designing of Tuff Conveying Systems
Dense Phase
Pressure vessel systems are the most common dense phase system. TECHFLOW's innovative Continuous Dense Phase (CDP) and Low Pressure Continuous Dense Phase (LPCDP) offer other dense phase options. Single vessel systems typically will operate in four distinct cycles:
1. Load vessel with product
2. Pressurize vessel
3. Convey product
4. Purge
Dual vessel systems can be configured to operate in a semi-continuous dense phase manner where the first vessel loads with product while the second vessel conveys the product. The motive gas typically will be compressed air with system pressures operating up to 80 PSIG.
Dilute Phase
Pressure, vacuum, combination vacuum pressure and vacuum sequencing are the common types of dilute phase systems. The motive gas is typically generated by a positive displacement blower with pressure capability ranging from 2 - 15 PSIG. Pressure systems generally use a rotary airlock as a feed device. A vacuum system simply needs a product flow control device such as a probe box or screw feeder, although rotary airlocks are commonly used.
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Pneumatic Conveying and Recovery System |