Pneumatic Handling Systems (Ash & Non-Ash)
Pneumatic Handling is an effective method of conveying dry bulk material through pipes by means of air as a conveying medium. There are primarily three types of systems used; selection of which depends on properties of material to be conveyed and material movement (distance & height) required.
DEMECH supplies all three types of these systems for pneumatic handling of Fly Ash & other fine dusty material.
In all the pneumatic handling systems, the material is conveyed through the pipes with the assistance of air flow, to a closed silo.
The principle of conveying the material through pipes used in "Lean phase vacuum system" & "Lean phase pressure system" is the same. Air flow in the pipe carries the material in a homogeneous mixture and thus a minimum velocity is required to be maintained to ensure that the material does not settle down. The velocity depends on particle size and density of material. As a result the dust to air ratio is generally low and the velocities high.
In the Lean Phase Vacuum System negative pressure is created at the silo end using vacuum pumps. Atmospheric air enters through Air Intake Valves at the material feed end of the conveying pipeline. The material from hoppers is fed to the pipeline using Ash Extraction Valves. Using Cyclone separator and/or Bag Filters mounted over the Silo, material is separated from the conveying air which is sucked by the vacuum pump.
In the Lean Phase Pressure System, pressurized air is injected from the feed point end of the pipeline which carries the material to silo which is kept at atmospheric pressure. The material and air is separated in the same manner using Cyclone separator and/or Bag Filters mounted over the Silo. The material is fed to the conveying pipeline using Ash Extraction Valves. Sometimes a pressure vessel is used below the hopper which acts as a buffer storage vessel to achieve sequential evacuation of hoppers and improving overall efficiency of evacuation. The pressure requirement for this system is low to a level below 1 bar.
In the Dense Phase Pressure System the conveying air virtually pushes the material through the conveying pipe rather than carrying it. Thus in this system the Dust to air ratio is high and velocities are low, however, air pressure required is much higher requiring screw or reciprocating compressors. The air circuit needs to have a big receiver as the air is required in pulses rather than continuous flow. This system has a Pressure vessel below each hopper with a Dome Valve to isolate the vessel from hopper. To start the cycle, first the pressure vessel is filled-up by material from hopper by opening the Dome valve which closes once the vessel is filled. The material collected in the vessel is pushed out of vessel to the conveying pipe by injecting air in the vessel. Once the complete material from the vessel is pushed through the conveying pipe to the silo; the air injection is stopped and the Dome valve is again opened to allow the material to fill the vessel. Air entering silo along with material is vented out through Bag Filters. The system also requires Poppet Valve & Non Return Valve for the injection airline.
All the three systems require Tight Shut-off Valves for the purpose of pipe line selection / diversion.
DEMECH can design and supply complete pneumatic handling system along with all its associated equipment and instrumentations for handling various bulk material.
DEMECH also supplies a pre-assembled set-up called Derropot which is a cost effective solution for handling powdery material at a low rate of 1 to 2 TPH for a short distance.