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Pneumatic conveying

pneumatic conveying resins

Our specialty is undoubtedly the pneumatic handling of dry bulk products. Since 1990, CON-V-AIR has worked in a multitude of applications, the most common being the pneumatic handling of various chemicals and minerals. We also process the pneumatic transfer of almost all food products (sugar, milk powder, flour, sesame seeds, spices etc.), many chemicals (silica, borax, calcium carbonate, urea, carbon black, zinc stearate, etc.), pharmaceuticals, and even explosive products. Our varied experience allows us to appreciate the different products used by our customers and adapt our systems to the specific needs coming from their respective areas of activity.

To prepare a proposal for the applications we also suggest our customers to start with a basic engineering study.  For the cost of a couple of thousdan dollars, we are able to sketch the system, develop a full P&ID and have foot print of the required equipment.  This allows our customers to present the investment in the system to the different stakeholders impacted by the project.

OUR SCOPE 

We offer dilute phase (lean phase), semi-dense phase and dense phase through our exclusive partner Cyclonaire.

Our systems have all types of air moving equipment to minimize the costs associated with the purchase of blowers and reduce the energy needed to operate the pneumatic transfer system. Moreover, we favor large diameter pipes that allow systems to operate at a lower pressure and gives the capability to increase the capacity in the event that the requirements of the process should change.  This gives our customers a heavy duty system that will still perform when the plant condition changes.  We are know for the manufacturing of heavy duty systems.

Eductors

CON-V-AIR has developed its own line of eductors for pneumatic handling of dry bulk products. Marketed under the brand Leap Engineered Products, our eductors are sold in many countries around the world and frequently replace rotary valves for difficult application like abrasive products, very fine particle size or inadequate otherwise.

 Typical dilute phase conveying capacity chart

  • For an equivalent length of 200 feet (20 feet eq. per elbow)
  • This table is for information purpose only

oneumatic conveying sizing chart

Industries served:

1. Chemical

  1. Battery production factory in lithium and lead
  2. Transhipment of chemical products (car and truck unloading, silo)
  3. Decontamination
  4. Explosives
  5. Gasification / ethanol
  6. Incinerator
  7. Energy production
  8. Plastic recycling

 

2. Mining

  1. Flux Handling and dosing
  2. Zinc precipitate pneumatic transfer
  3. Silo system, weighing and dosing slag and cement paste backfill (hydraulic backfill)
  4. Airslides for alumina
  5. Silo and pneumatic transfer of lime

 

3. Manufacturing

  1. Gypsum panel
  2. cat litter
  3. Plastics & Rubber
  4. Shingles and roofing membrane
  5. foundry
  6. Refinery

                                                   i. Zinc

                                                  ii. Copper

                                                  iii. Gold

                                                  iv. Cobalt

                                                   v. Nickel

g. Concrete and asphalt plant

4. Pulp and Paper

 

5. Aluminum smelters

  1. a. Alumina
  2. b. Pet coke

 

6. Food

  1. Bakery
  2. Cheese
  3. Animal feed
  4. Hatchery
  5. Coffee
  6. chocolate
  7. Wheat semolina

7. Pharmaceutical

  1. Transfer and storage of krill tailings
  2. Sugar

 8. Water and wastewater Treatment

  1. Chemical feed systems and injection system of chemical products
  2. Handling and storage of dewatered sludge and dried

See www.con-v-airsolutions.com

 

10. Process water

  1. Zero liquid discharge system in SAGD

 

Products handled

  1.  Alumina
  2. Vermiculite
  3. Hydrated lime
  4. Quicklime
  5. Activated Carbon
  6. Potassium permanganate
  7. Polymers
  8. Cement
  9. Sand
  10. Litter
  11. Dehydrated Sludge
  12. Dewatered (dehydrated or dry) sludge
  13. Plastic Granules
  14. Carbon Black
  15. Zinc Stearate
  16. Borax
  17. Soda ash (dense or light)
  18. Yeast
  19. Salt
  20. Sugar and dextrose
  21. Flour
  22. Cheese
  23. Sodium cyanide
  24. Cadmium
  25. Milk protein
  26. Spices
  27. Hot lime softening
  28. Starch

  

Technologies

1. Pneumatic conveying

  • a. Dilute phase (pressure)

i. Pneumatic conveying systems in dilute phase (pressure) consist of the following:

  • Blower (which pushes the air in the piping)
  • Pneumatic conveying pipe and elbows along with compression couplings
  • Feed System into the pipe (typically an airlock, and eductor or a screw pump)
  • The system of separation of the air powder (generally a reception filter)
  • Destination hopper
  • Device for unloading the destination tank.

Pneumatic conveying design guide :

ii. Diluted in stage systems are adapted to transfer less than 10 kilograms per kilogram of powder conveying air. Typically, our pneumatic conveying systems in dilute phase are designed to transfer approximately 6 kilograms of product per kilogram of dry bulk conveying air.

iii. The diameter of the pneumatic conveying line is adjusted to this concentration ratio of powder / air and the pressure drop that will be generated by the operation of the system. If the loss calculated load is too large, we increase the diameter of the transfer line.

iv. The typical pressure of a dilute phase conveying system fed by a rotary valve will be of the order of 6 to 10 psi.

v. When feeding from an eductor, the typical pressure will be less than 5 psi.  More in the range of 2,7 psi or lower.  However, the pressure required to be supply to the eductor has to be about 4 x greater than the conveying pressure.  Air will also be vacuumed by the material inlet.  This amount of air should be taken into account when sizing the system.  Assume that 100% of the motive fluid flow can be drawn by the eductor by the material inlet when the pressure is low on the discharge side.  This will have an impact when the material is fed from a screw feeder into the eductor and the flow changes over time.  The quantity of air sucked by the eductor will also vary.

vi. Consequently, pneumatic transfer systems in dilute phase (also known in English lean phase) are always designed to operate at operating pressures below 15 psi. This point is the limit beyond which the regulation applies with regards to pressure vessels. To make a pneumatic transfer beyond this pressure, additional measures are required (certified welders, complex engineering, manufacturing more expensive).

vii. In most applications of pneumatic handling in dilute phase, the product is fed continuously to the pipe. The most frequently used is the feeder rotary valve. Care must be taken for optimal operation of rotary valves. In particular,

1. Airlock RPM. The higher the speed of rotation will be, the greater leakage through the rotary valve will be. For very fine products such as flours, the leak reduces the effective volume of the unit and sizing should be done accordingly.  At 10 psi, an airlock of 14 inches turning at 14 RPM will leak about 30 cubic feet / minute.

2. Abrasion. For abrasives, the ends and the body of the rotary valve must be hardened to increase its lifetime. Offset rotary valves are also used to avoid filling the alveoli and to better control the problems related to abrasion in the rotors and the bodies of rotary valves.

3. The shear. The same technique is used to reduce breakage of larger particles in the rotary valves, ie avoid filling the pockets of the airlock. This reduces attrition and increases the life of the valve.

viii. EDUCTOR

1. Another device for supplying a pneumatic conveyor line by positive pressure in a dilute phase mode is the eductor. The eductor uses the venturi effect to feed the line. A high speed air jet creates a vacuum that sucks the powder. Then, a venturi converts part of the static pressure to velocity pressure to push the material in the transfer line.  The most common application of eductors is the continuous chemical feed of sorbent in the gas treatment industry. Activated carbon, lime or sodium carbonate are drawn from the output of a volumetric feeder to the injection points in the gas pipes. By mixing these adsorbents with the gas to be treated before the baghouse, it is thus possible to remove the mercury, acidity and other products harmful to the environment.

2. Another advantage of eductors for pneumatic transfer lies in the fact that they have no moving parts. They are very popular for applications with abrasive products and food products because they are easy to clean. The possible maximum conveying rates are however lower than for other air handling devices. They are recommended for small conveying rates.

b. Semi dense phase

i. Pneumatic transfer with a semi-dense phase systems is achieved at a concentration ratio of powder / air greater than 10. These systems carry the powders at a pressure less than 15 psi. However, as these are batch systems, we do not have to worry about leakage through rotary locks. Thus, by increasing the pressure, we do not increase the leakage and therefore, the systems are more efficient. The most common application of this type of system is the pressurized truck or railcar unloading into a silo. One can reach flow rates of the order of 20 to 30 tonnes / hour in a line of 4 "(100mm). In the factory, a transportation tank is filled at atmospheric pressure and then emptied into the conveying pipe. As the pressure of operation is below 15 psi, it is not as regulate the pressure vessels.

c. Dense phase

i. The dense phase systems are very similar to the systems in semi dense stage except that they operate at pressures above 15 psi. Therefore, special attention should be given to the design and manufacture of tanks and transfer lines are governed by the regulations on pressure vessels. Typically, an operating pressure of 40-50 psi is normal. The concentration ratio of product / air is of the order of 40. The most common applications include manipulation of the cement, sand and other abrasive or brittle products (carbon black). By transferring the products at a higher pressure, we can reduce abrasion in transfer lines and elbows and reduce breakage of the particles.

d. Suction (Vacuum)

i. The vacuum pneumatic conveying systems have many advantages. Using suction to enter the product in the line avoids backflow into the local atmosphere of fine powders. Also, there is no shear to enter the product in the line.

ii. The transfer capacity for suction system is limited. As is atmospheric pressure which enters the transfer line, the theoretical limit of the application will be dictated by the atmospheric pressure. The capacities of these designs will therefore generally be lower than for pressure systems having the same line diameter.

2. Pneumatic conveying Components

a. Blowers

i. Positive displacement (bi-lobe, tri-lobe)

1. To design a successful pneumatic transfer system in diluted phase, it is important that the air displacement machine used has a performance curve doesn't fluctuate depending on the pressure drop it sees. Such systems may be subject to different operating hazards, it is possible that an amount of powder greater or less is in the transfer line at any time. It is therefore essential to maintain air speed at all times to avoid blockages. Positive displacement blowers are the ideal tools for this work. The operating pressures are up to 15 psi pressure and up to twenty inches of mercury in vacuum while providing a flow stability over a wide pressure variation range.  Special caution should be made with regards to noise levels.  Acoustical enclosure should always be considered.

ii. Regenerative blowers

1. For lower pressure applications, regenerative blower provides an excellent price / performance ratio. Up to 6 psi pressure and 8 inches of mercury vacuum. They are also quiet compared to pd blowers.

 
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Pneumatic conveying
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