Seeking advice from experts on pneumatic conveying issues
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Our company uses pneumatic conveying for the transport of its powdered products; the material flows from the dryer into a rotary valve, and then a Roots blower is used to blow the material into the storage bin. However, during operations last year, accumulation of material above the rotary valve occurred on several occasions, resulting in poor discharge from the dryer. This is especially severe during load application. But there are no problems during stable operation under high load. Initially, it was suspected that the rotary valve was leaking, with the fluidized gas flowing upward and pressing against the material, resulting in poor material discharge; however, no large gaps were found after opening it for inspection. Both the inlet and outlet of the rotary valve have triangular protrusions; I’m not sure what purpose they serve Does forward and reverse rotation have an impact on material discharge?
It’s hard to determine; it’s best to have a schematic diagram of the installation layout
Distribution cone? Prevent larger foreign objects from getting stuck in the rotary valve or Roots blower at the same time?
It is supposed to serve the purpose of distributing the material; blockages can occur for various reasons such as damp material or sedimentation. If blockages happen frequently, it is possible to install a vibrating device on the hopper.
Is there an exhaust port on the valve body? Is there an evacuation chamber above the rotary valve? As the load increases, the delivery pressure rises, and naturally, the air leakage from the rotary valve increases as well. Also, I’m not quite sure what “stable operation under high load” means. . . ”What does it mean? The triangular protrusion is a jam prevention device. Forward and reverse rotation has almost no effect on unloading.
It describes some issues; high load refers to normal full-load operation
From your description, it seems to be the PP unit’s RF801; has there been any change in the clearance of the rotary valve?
1. That triangular protrusion is likely intended for shunting; such a design is commonly used in granules (see figure below) to prevent material from getting stuck and being sheared. The powder won’t get stuck, so there’s no need for this. Have you measured the gap to see how large it is, and whether it has increased? The gap between the blade and the housing is usually around 0.1–0.5 mm; it’s not possible to detect any significant difference by visual inspection. The clearance for domestic valves is 0.3–0.5, while that for imported valves is 0.1–0.3. 2. Does the rotary valve have a designed exhaust port? 3. Poor material discharge when loading increases may be due to an increased air volume from the fan, whereas the rotating valve does not have sufficient capacity for discharging material. And yet you say it’s fine to operate at full capacity, which is strange. Factors such as pressure and temperature also need to be considered.
Expert, the rotary valve I’m using here also gets clogged frequently. Is it a problem with the valve itself? Are there any factors affecting him due to the cyclone separator and bag filter backwashing mentioned above?
1. The protrusion is a design to prevent material jamming； 2. As for air leakage, if you can see that the gap is very large, then the valve is no longer functional. According to the valve’s maintenance instructions, measure the gap between the rotor and the housing; if this condition has persisted since the unit was put into operation, it is likely a problem with the rotary valve, and it can be replaced with a valve from Koppeln or Zepplin.
Add an automatic air hammer to strike regularly.