Rotary Feeder under Pressure

Posted in: , on 10. Feb. 2012 - 09:23

Pneumatic conveying with Rotary Feeder under pressure

Dear Friends

I would like to know if it is possible to use a rotary valve on downstream of a pressure vessel for conveying powders. The pressure vessel is connected to a silo operating at atmospheric pressure. My apprehensions are:

1. This would be a batch operation as the pressure vessel would act as a lock hooper with a fill-pressurise-tranfer-depressurise-fill cycle. The rotary valve would be running idle during the non conveying steps.

2. The take off velocity across the rotary valve would be much higher due to pressure in the vessel. This would mean attrition due to partical shear.

3. capital cost would be higher due to addition of a pressure vessel and instrumentation for pressurisation/depressurisation.

However, it seems the conveying gas requirement for this system is lower than that of conventional system with rotray valve directly connected to atmospheric silo.

Request your kind help in understanding the positive and negative points of both types of systems.

Kind Regards


Re: Rotary Feeder Under Pressure

Posted on 10. Feb. 2012 - 12:31

Dear sgoel,

If I understand you correctly, your aim is to have the rotary lock operating under no differential pressure and eliminate the rotary lock gas leakage.

As there is no rotary lock gas leakage, the compressor has not to supply this leakage and can be therefore a little bit smaller.

Probably, the rotary lock can easily be operated under higher conveying pressures as only the seals have to withstand the conveying pressures and the wear of the rotor tips is eliminated by the absence of gas flowing back.

Pressurizing the pressure vessel is not required.

The pressure in the vessel increases with the pipeline conveying pressure gradually as the pipeline fills with material.

Under this start up conditions, the compressor should be big enough the supply the extra filling gas required and still supply enough gas into the conveying pipeline.

Pressurizing the tank before conveying causes at the moment of opening the air supply to the conveying pipe a back flow surge through the pressurizing pipe.

There must be a good reason to choose this system.

Have a nice day



Design Guide For Rotary Valves

Posted on 24. Jul. 2015 - 05:50

Rotary valves are the most common device for use as feeders and as air locks in pneumatic conveying systems. To help users understand their design and application my following two articles published in Chemical Engineering magazine will serve as a complete design guide on rotary valves:

1. Rotary Valves in Pneumatic Conveying Systems

2. Improving Rotary Valve Performance

These articles describe in detail the design and construction of various types of rotary valves, method for their sizing and selection, method for calculation of their leakage, and methods for venting their leakages.

Let me know if you would like to get a copy of these articles.


Amrit Agarwal

Pneumatic Conveying Consulting

Re: Rotary Feeder Under Pressure

Posted on 26. Jul. 2015 - 07:23

Dear sgoel,

The use of Rotary feeder sealed by pressure vessel is not a standard application for transfering powders from A to B.

But in highprecise applications (e.g. dosing) it is a very good alternative to or with highr systm-presss example in gasification plants.

See same possible applications in the attachment.


Best regards

Klaus Schneider