I would prefer dilute phase because of its simpler design and operation and probably lower investment.

Regards,

Amrit Agarwal

Pneumatic Conveying Consulting Services

polypcc@aol.com ■

I agree,

Use either a Fuller Kinyon or Ibau or CP pump and LP blower

Lean phase.

Ta

James ■

Dennis

It was at least 10 years ago, but the system we ended up with was based on the best ecomonic outcome - the choice was open and put to competitive tender. LP came out on top.

This is for 100+ tph of cement - various grinds and blends.

Cheers

James ■

For fine powders such as cement both dilute phase and dense phase conveying systems will work. Selection of either system should be made on other factors which include capital cost, operating cost, and simplicity of design and installation.

A single rotary valve is a continuous feeding device Vs a single blow tank which is a batch feeder. However, rotary valves handling powders must have a body vent and a leakage collection system to recycle the carried-over powder back into the rotary valve and to vent out the leakage gases properly. The amounts of leakage and carry-over gases and powders are much more in dense phase systems due to their higher conveying pressure. These gases require a separate dust collector, and sometimes a suction blower also, to prevent dust emission to the atmosphere.

On the other hand the blow tank system is has no leakage or carry-over gas issues, so if batch operation is acceptable, they should be preferred.

Regards,

A. T. Agarwal

Consulting Engineer

Pneumatic Conveying Consultants

polypcc@aol.com

Ph and Fax: 304 346 5125

www.powderandbulk.com/pcc ■

Dear Sir,

Refering to your inquiry at bulk-online we are anwering as follow:

For such a short conveying distance 75 m horizontal and 25 m vertical we think a dilute phace conveying system will work efficiantly enough.

For Sfr. 800.- we can calculate for you the needed comressor airflow, as well as the conveying pipe size and dedusting filter data.

Please visit our website www.intec-kohler.ch

For further information please do not hesitate to contact us

Best regards Peter Kohler ■

If you want to use our services, we will be happy to provide our services for the design of this system without any fee because it is a simple job for us.

Just send us your request.

Regards

A. T. Agarwal

Consultant

Pneumatic Conveying Consultants

polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Because cement will convey very easily in either dilute or dense phase flow the economics have to be looked into carefully. Dense phase equates to higher pressures, lower air flow rates and smaller bore pipelines than dilute phase and so types of plant and components and hence capital costs can vary widely. Operating costs are much easier as they will be dramatically lower for dense phase. If a plant is used 24 hours a day and 7 days a week the savings on operating power generally outweigh any difference in capital cost, particularly with low prevailing interest rates. Compare bids for capital cost and then evaluate the differences in operating costs for a full analysis. ■

A true analysis has to include the consideration of maintenance manhour costs and spare parts as well.

Rotary airlocks and pressure tank systems operating in the dilute phase will use more of both as compared to operating in the dense phase (including two phase flow). Screw pumps, while more energy intensive, will most time yield the lowest operating costs outside of power consumption. ■

I had done a capital cost comparison some time back. Dense phase came out with lower investment than dilute phase but the lowest cost case was the one that used a blow tank as a feeder. In addition, blow tanks had lower operating cost because they had no rotating parts.

Regards,

A. T. Agarwal

Consulting Engineer

Pneumatic Conveying Consulting Services LLC

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

From a capital cost perspective, I don't disagree that your analysis may be correct.

The point I suggested was aimed at the on-going operating costs including maintenance and spare parts based on duty cycle. ■

I sell lean phase pumping systems elsewhere in the world.

What is evident again and again are the following points in comparison:

- the initial capital cost is not that different

- the further away the less suitabe is dense phase

- dense phase has an advantace in power consumption (lean phase has one more electrical motor

- have you carefully thought about maintenance cost? Dense phase valving is still a major maintenance issue.

Ring or email some cement works - certainly lean phase in cement works seems to be much more prevalent for the transport of cementitious products.

Ts ■

From my 40 years of experience in pneumatic conveying, what I have learnt is that dilute phase conveying systems are simpler to design and run than dense phase systems. I try to use dilute phase technology unless there is a definite reason not to use it, such as particle attrition and conveying line erosion due to the higher dilute phase conveying velocities. Cement can be conveyed in both modes, but unless there is a commanding capital and operating cost benefit, which depend on plant location and local economics, I think that dilute phase systems should be preferred.

Regards,

A. T. Agarwal

Consulating Engineer

Pneumatic Conveying Consulting LLC

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Everyone can make an argument and defend a position on either approach as long as the subject is discussed in a general forum

If we're discussing a small cement transfer system in a batch concrete plant which is used on an intermittent basis, that's one condition, if we're talking a 250 mtph finish mill grinding system, running on a continuous basis, (7) days a week, that's a completely different condition.

There are of course places and applications where lean phase is better and those where dense phase is better. This is true not only in cement but many other industrial applications as well.

By the way, I don't believe we all our using the same definition for a dense phase system with respect to the cement application. ■

Most fine powders such as cement can be conveyed in any of three regimes; dilute, dense, and mixed dilute/dense, as long as they maintain permeability. There is no sharp cut-off point between dilute and dense phase, there always is a transition region which can also be called "mixed flow regime". Mixed flow regime offers some advantages such as low conveying velocities combined with low conveying pressures.

Regards,

A. T. Agarwal

Consulting Engineer

Pneumatic Conveying Consulting Services LLC

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Agree completely, which is why the application and duty cycle greatly influences the decision as to which type of system and corresponding hardware is chosen. ■

Avoid rotary valves (limited in op pressure and high maintenance costs, air leakage) and screw pumps (high feeding costs and high maintenance costs). I suggest a blow-tank-fed fluidised dense-phase pneumatic conveying system - this will be the most efficient system (if designed/operated properly) and also it will last the longest (in terms of wear).

peterwypych@uow.edu.au ■