Dear Fernando,

As I have only experience in dilute phase pneumatic conveying, I cannot really help

you with the dense phase pert of your interesting case.

Other members are invited to participate. as well.

Let us start.

-As you are referring to “stress on/in the pipe”, assume you are referring to the required

air-pressure for dense phase conveying.

I can imagine that this pressure will become very high for a pipeline of 500 m.

-By dividing the 500 m pipeline in several sections with acceptable pressure drop

and a booster station at the beginning of each section, I presume that the installation cost will be high.

-Based on the above , it is understandable that Coperion and Zeppelin are

are opting for a dilute installation.

-One alternative option is the use of pneumatic road bulk trucks (pneumatic tankers)

-For a dilute phase system design, the following information is needed :

(I will try to estimate a trend, how a possible installation could look like, as I do not have field experience nor data of PET chips)

product : (PET chips) , particle density , bulk density , particle size distribution.

Pipe line : (A full description of the various pipe routing with their length and angles)

or

horizontal length , vertical length , number of bends

pick-up of PET chips: suction nozzle , from a fluidized hopper or –floor , from a feeder

separation of PET chips: in a filter receiver vessel , rotary lock

From the PET chips product properties, it can also be determined whether the PET chips are suitable for dense phase anyway.

Dilute phase should be possible.

To be continued

and

Hear from you. ■

Fernando.

Lets see the whole picture .

Your PET should come from a grinding station , probably outside your facility .

It will come in some kind of truck, probably a non presurizable truck, with a ventury eductor. The particle size and shape should be fairly constant with a particle size spread that you do not control.

Now PET is not a difficult material to transport , it is light and of small size.

If you are considering dense phase must be by some reason , you must be seeing some kind of advantage in doing so, not only energy , but probably particle attrition , particle size.

Contact Dinamic air and also CLYDE , probably Rotoclone for a start.

Paul Solt , Jack Hilbert, David Mils, Jorge Klinzing can steer you withouth frightening you, others can tell you that ist is very dangerows , that it is critical or whatever reason, look clearly and judge who really wants to help and who wants to scare you.

There are , many supliers in mexico that can give you advise, some preffer dense phase some dilute phase .

I preffer to have an optimisation function and design with both phases , below saltation at the beguining and above saltation afterwards , keeping as close to saltation as possible with pipe expansions. But this approach depende on the knoledge you have on your product.

My gess is that you are being forced to use PET due to the skyrocketing prices of gas in mexico, you have used it and solved its particular burning characteristics, according to tour process.

How do you rceive the PET and what are your particular limitations and prefferences will make a lot of difference.

But DENSE phase might not turn to be in the long run to have the larger solid to gas ratio. NOR the lower velocity , you might end up having pistons riding ar high speeds in your pipeline, impacting your elbows and shaking the whole place.

Be carefull and see why are you limiting yourself to a below saltation system , I used to work for HYLSA some years ago and when we desided to go Pneumatic, the name dense Phase was very catching if anything else.

The engeeneering manager only wanted to hear dense phase .

It took us years to make him understand its meaning .

At the end we went into an optimizing system that endorsed primarily particle degradation. then pressure drop, everything focused into the cost of tranport and the cost of losses.

Good luck. ■

Good Day Sir

The high stresses to which Coperion and Zeppelin refer to are caused by the tremendous forces which are exerted on the pipe elbows and supports in a long dense phase system.

The forces are generated because the formaation of plugs within the pipeline is uncontrollable. While there are many devices sold which are referred to as "air management devices", and their intent is to try to match air flow with line pressure and the formation of plugs to prevent such large forces from occuring, they often are not successful enough.

I have seen pipes literally tear off of supports and flanged connections burst due to these dynamic loads. Buildings often shake like an earthquake is occuring near-by when some of these plugs make their way down the pipeline.

For this reason, reputable suppliers like Coperion and Zeppelin offer dilute phase but I'm sure what they are actually offering is what is often referred to as a "high pressure dilute phase" system.

Dilute phase with the use of conventional rotary airlocks as the line charger was traditionally limited to 8-10 psig to prevent high pressure differentials across the rotors of the airlocks.

Today, most suppliers offer rotary airlocks which can withstand differential pressures in excess 2 or 3 bar.

So, with a "high pressure dilute phase" conveying system, you get the benefit of high pressure differential capability which lets you handle higher capacities and/or longer distances, but you also get the more controllable flow regime in the pipe associated with dilute phase.

Dense Phase is a good technology when applied to the right materials and applications, however, in the case you presented, I too would recommend a "high pressure dilute phase system".

Marco Flores is our good friend and associate in Mexico and he can offer you our support in technically evaluating the bids from your suppliers if you need the assistance.

Hope this helps.

Regards ■

Dear Fernando,

Let me reply to the two basic questions that you asked:

Questions:

1. "Does some body have some experience with dense phase system at higher capacity and to convey at long distances"?

2. "Any comments concerning the preference of dilute phase Vs dense phase will be highly appreciated"

Answers:

1. Yes, I have personal experience in conveying pelleted PE in dense phase mode at a capacity of up to 50 tons per hour and conveying distance of about 500 meters. These systems were designed by NEU and Coperian but not Zeppelin. These systems have been operating without any problem for 5 to 10 years. At these rates and distances the calculated pressure drop was so high that even using 10 inch dia pipe lines, the terminal conveying velocity exceeded 10 meters/sec. The solution was to use a "drop-out station about 60% away from the pick point. This addition did add complexity to system design but once designed and installed, it met all of the project objectives.

2. This choice depends entirely on economics. Both dilute phase and dense phase systems are acceptable if properly designed, operated, and maintained. In dense phase, product attrition is mimimal, so product quality is better and product loss is less.

For further information you may contact me without any obligation.

Amrit Agarwal

Consulting Engineer

Pneumatic Conveying Consulting

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Whether you choose dilute or dense phase, do performance testing and get a performance guarantee in writing from whomever supplies the system.

The process will require all the distances and elbows to accurately design and bid the project. You must also set a specification for the degree of fines that are allowable, and how this evaluation will be done.

Finding a supplier with an actual performing system on PET at similar rates and distances would be ideal. ■

Fernando.

I guessed that much.

We faced exactly the same problem.

From your profile I believe you sell PET , and the very fine particles are not desirable.

You are in for a lot of work .

You have to find out the breaking velocity or accumulated breaking energy.

Dilited phase at those distances with sevelall elbows can be very demolishing to your particle.

Degradation will have a sort of s curve from a certain value on you have a lot of degradation , under that value you have hardly any .

There has been a lot of work done arrownd this topic, I do not know of any article covering PET especifically. Maybe somebody from the forum, has a reference.

I can tell you what we did for sponge iron. Some years ago,my phone is in the signature, but I believe you need to do your own work, if nobody elses has characterized the attrition properties of your material.

As a rule of thump, without further research , avoid elbows near the discharge , go high as soon as you can . Expand before the delivery point .

Or as has been reccomended use two systems , one mainly to elevate and a second to convey the long run horizontally .

use minimun bends maximun 3

Evaluate the losses and see if there is any money number you can put to the layout versus the loses . Then sell the idea to the top managment and educate the team . Do not , I repeat do not go arrownd every single obstacle you find, do not force the trajectory to follow the strictural layout of the actual material handling. Do not go inclined in a 13 to 25 slope following the belt conveyors ,, you will be looking for trouble .

Regards

marco ■

Supplementing what others have said, there is no doubt that attrition will occur, however, it can be minimized by controlling the velocity profile through the system by using line stepping.

Line stepping will allow the air to expand as it travels down the pipe BUT since the cross sectional area of the pipe is also increasing, the velocity will be kept under control.

If you could fabricate a tapered pipe line with the taper being the same slope as the rate of air expansion, you would have the world's first constant velocity conveying system. :-)

Line stepping is frequently used in long distance conveying.

There is no doubt that dense phase, being simply defined in this case as low velocity conveying, is preferred from a fines generation perspective, however, experience has shown that the potential for large structural failures and very expensive pipe line support systems can b e more costly than addresssing the removal of the fines at the terminal end of the system by installing an elutriator, fines separator, drum sieve, deduster or some combination.

Regards; ■

Dear Fernando,

we think that dilute phase will damage considerevouly the PET chips & should be excluded from the possibilities.

Anyway we agree that a dense phase on a so long distance will involve very high pressure loss with a big pipe diameter.

May be the solution with a booster station could be the right one.

Alternatively you should accept for the dense phase conveying a final speed higher than the speed normally used for the dense phase. This for example if you want to conveying the off grade product.

I am available for any discussion

Giovanni Stoppa

Govoni Sim Bianca Impianti spa

+ 39 051 6847286 ■

Dear Fernando,

as producer of dilute and dense phase systems with 60 years of experience, we highly recommend to make trials, because no project and no product is really identical!

The forum mentioned it already: from the point of "minimizing product attrition", dense phase systems (with booster) have advantages.

We can give you performance guarantee, when we make trials before. If you are interested, come back to us for further details!

Best Regards

Wolfgang Wengler

AMMAG, Your partner for particle systems ■

Fernando.

We have completed a number of trials at our test centre in England with dense phase conveying of pellet 500m in one stage without causing product damge or large pipe stresses.

We have installed many systems conveying fragile produc ts such as catalyst and sugar.

We have a dense phase system specifily designed to do this. It is not so difficult if you have the correct equipment and understanding of the conveying method.

We have been building low velocity dense phase systems for 25 years.

If you want to discuss further or want a budget price for a system, please email me at :-

bsnowdon@clydematerials.co.uk

Brian Snowdon ■

Fernando.

Clyde Material handling is a well known pneumatic conveying technology supplier.

They have a pilot plant and can run your material to evaluate degradation , and they might alrready have data available for Petroleoum Coque.

you must look that the test results can be scalable to your specific product..

We have worked with them in various ocations in very difficult applications and they do a good job.

Brian has received recognition for his contribution to technology in England and is a honest man.

Regards

Marco ■