Part of resoling issues is always to look for heklp from the conveying system conveying manufacturer. If you have not done so already, I would touch base with the OEM who helped you install the system. Also, since when has this issue become a problem? If it has worked before then I would focus on the wear and tear of the rotary air lock.

There are plenty of system OEM's out there who could help you with installing a system that works in your application. One would be Claudius Peters http://www.claudiuspeters.com/site/p....asp?navid=83

But I would deem conveying eductors to be suitable as well, for instance Fox Valve's conveying solution.

http://www.foxvalve.com/iindex2.html

Again, it is important to know if this is a new issue or old, and if this was a OEM based solution or yours.

Hope this may help you a little. ■

Dear Pablonr,

A rotary valve hampering the feeding of a pneumatic conveying system is not new.

Especially with very fine and light powders, the blow back through the valve pockets and the gap between the rotor and the rotary casing can cause an oscillating pressure.

A better controlled feeding could solve this problem, but will not be easy.

Consult dosing equipment experts.

Running the installation at the lowest possible pressure drop will also help.

The blow back through the rotary lock will be less, when running at lower conveying pressures.

Whether the installation is designed for the lowest possible pressure can be stated by the designer or vendor.

Using the operational data obtained so far, it must be possible to make indicative calculations.

Those calculations should show possible improvements.

As Ralf says: If the problem was not there before then look for changes in time, like wear on the rotary lock

success

teus ■

Interesting idea. I your particular case I would not use a trial and error method though. This tends to costs you more than if you are going to a reputable system OEM and spend the capital money upfront. Any such OEMs (there are a lot of them featured on the www.bulk-online.com web page) should be able to provide you with a good estimate in terms of expected conveying and air flow / pressure requirements. 7 Bar is probably a bit much; usually we see 2-3.5 BarG applications that sometimes needs to be inertized with e.g. N2. You could possibly try contacting e.g Fox Valve at steve@foxvalve.com with your system requirements and ask if this is something they would be interesting in pursuing this application with you. ■

Dear Pablonr,

The main problem is :

How to dose the carbon from a low pressure region into a higher pressure region, whereby the blow back is sealed off and the carbon can pass freely.

( in cement conveying a screwpump is used for such an application. Fuller Kynion)

The particle size of 25 micron is, may be, too small for a rotary airlock.

Depending on the various design parameters, may be, an option could be a sonic choke on the high pressure plant system (taking care of the required airflow) and a “venture-eductor” as suggested by Ralf.

Contacting Foxvalve or a representative is a good idea

Actually redesign by using the obtained experience.

What is the designed pressure, airflow and pipediameter?

take care

teus ■

Oh boy this sounds a bit too complex for what you need to do. You may be able to limit the air blow by in the valve, but it will remain a factor. If you have already tried the eductor idea I think the screw feeder pump idea from Teus is a very effective alternative. Fuller is a good address with their Kinyon pump and there is a company called WM Meyer out of IL USA that has a similar working device. http://www.rotaryvalve.com/products/...28adae8e63bd4b

They also have an example of a what I call a double dump valve that allows material to drop into your air stream via two gate type valves. http://www.rotaryvalve.com/products/flapgatevalves/

I am a bit out of my area of expertise, but be careful with your air to coal dust ratio - be sure to let your contacts know what you are conveying and how.

I am not sure why you are only getting 300mBar pressure rise out of your blowers, but I would focus on getting the system requirements and then to obtain the blowers to match (unless the pressure is limited due to the conveyed material). There are plenty of positive displacment blower reps out there that will be able to offer new, remanufatured, or used packages to you. Using plant air is usually a huge waste of energy since you would be letting an air compressor bump up the air pressure to at least 75PSI just to expand it in the pneumatic conveying system at less than 15PSI.

Good luck. ■

Dear Pablonr,

An eductor is a feeding device, that does not know anything about the length of the conveying pipeline after the injection point. The eductor only sees the pressure of the pneumatic conveying system.

How the pressure is generated, depends on the system design and actual Solid Loading Ratio.

An eductor should work on a long pipeline as well.

Your first option looks very elegant.

Nevertheless, it needs thorough engineering and designing to make it work.

The extra injected air from the eductor has to be added to the air flow of the blower, influencing the backpressure in the pipeline and/or the capacity.

The blower acts as a booster. If the eductor air flow + blower air flow is too much for the system, the blower should be reduced in air delivery.

Here you can benefit from the already made observations.

What are the designed pressure, airflow , pipe diameter and reached capacities?

success

teus ■

Dear Sirs

I represent a compnay called Clyde Materials Handling, we specilise in Pneumatic Conveying are Injection Technologies.

Our Rotofeed injection system, would be ideal for your application, we are very successfully injecting many materials from coal to PFA and copper concentrate.

Our system has not pressure differential across the feeder (conveying line to feed vessel), resulting in no wear and enabling us to convey at high pressure and distances up to 1.5km.

If you require any further information please contact me.

Richard ■