Originally Posted by kchetan

Hello,

I need to Convey the PP (Density=550 Kg/hr, Particle Size=3000 micrometer)

from Container tilting unit to Feed Hopper at 30 TPH as well as from feed hopper to 2 Silos at 30 TPH.

and From Silos to Storage Bin at 10 TPH

Conveying Distance is about 60 m

Suggest the System like Dilute or Dense.

Thank You,

Regards,

KChetan

Dear KChetan,

You will find quite a number of people in this forum who are willing to help you (me included).

In order to give you a more specific answer to your task some more information is required:

1) Distance horizontal for each line

2) Distance vertical for each line

3) Number of elbows in each line

Based on this the lines can be calculated for Dilute Phase conveying.

Dense Phase conveying, i.e. at low velocities in plugs/slugs, is usually not applied for PP anymore, it came out of fashion due to installation cost reasons.

Only film and fibre producers still use Dense Phase. But also this can be calculated when the grade is known.

So cheer up and share some more information with the forum.

Replies are guaranteed

Best regards,

Sven ■

Dear Chetan,

The main reason for selecting dense phase over dilute phase is lower conveying velocity. For pelleted PP, it is not necessary to use lower conveying velocities because these materials do not cause streamers and angel hair, they generate mainly fines and dust. These can be easily removed at the receiving point by using a cyclone or an elutriator.

This does not mean that you should not use dense phase. Dense phase is acceptable but for your very high conveying rates the design of pipe supports will be complicated and the total investment may be much higher.

Regards,

Amrit Agarwal

Consulting Engineer

Pneumatic Conveying Consulting

Charleston, WV, USA

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Dear kchetan,

Is the “Container tilting unit” a pressurized tank container?

In that case, the pipe outlet diameter is very important as well as the onboard compressor.

For approx. 30 tons/hr over a length of 70+20 = 90 m with 10 bends, a 6” pipeline would probably be needed.

If the feeding is from an ordinary bulk truck, a rotary lock to seal off the conveying pressure is required. The rotary lock leakage has then to be accounted for.

A vacuum system could be an alternative in this situation.

Rather than designing and building the 2 pneumatic conveying systems yourself (including the required controls, filters, safety devices, etc.), it is advisable to consult an experienced manufacturer or engineering company. They can offer you the installation and build it including guarantees.

I doubt, that they will give you the calculations.

What is your interpretation of dense- and dilute pneumatic conveying?

Take care

Teus ■

Originally Posted by kchetan

Dear sir,

Density is 550 Kg / m3 as in thread it was wrongly written as 550 Kg/hr.

1) Distance horizontal for each line = 70 m

2) Distance vertical for each line = 20 m

3) Number of elbows in each line= 10

Suggest system and briefly Explain how to Choose Dense or Dilute?

I Request you If Possible, Please send me Calculations as well.

Dear Kchetan,

I ran a short calculation for dilute phase conveying and share the result here:

Atmospheric Pressure [Patm] = 0.99138035 (200m above sealevel)

Air Density ambient [kg/m3]= 1.10307741 (at 40 degree C)

Gas Ratio my [kg/kg] = 10.8

dPcon [bar/g] = 0.63

dPconm [bar/g] = 0.75

dPdesign [bar/g] = 0.86 (blower outlet pressure)

Gas Flow [m3/min] = 42.00

Gas Flow [Nm3/min] = 35.90

Leakage Flow [m3/min] = 5.00

Gas Flow Design w Leak[m3/min] = 49.40

Gas Flow Design w Leak[Nm3/min] = 42.20

Pipe Diameter from D [m] = 0.162 to 0.187 in 2 steps (internal diameter)

Start Velocity Vst [m/s] = 21

Terminal Velocity [m/s] = 25

Note: - Design pressure includes dp for filter at 20mbar, heat exchanger at 40mbar, clean gas pipe at 20mbar

- Rotary valve: volume 40ltr, filling efficiency 80%, 28rpm, 10 pockets

- Reduction of number of conveying bends strongly recommended

- Conveying pipe: internally roughend to avoid streamers and angel hair

In case you want to use a 6" line DN150/168.3x3mm only the resulting pressure would exceed 1.0 bar and the use of a roots type blower would not be possible anymore and the velocity at the end would exceed 30m/s. Therefore a stepped line was calculated. In case you can reduce the number of conveying bends to 5 or less the picture might change, however, usually container tilting stations (regular container with liner) feed the material in gravity flow to a rotary valve station installed in an underground pit, which makes reduction of bends more difficult.

Make sure that there is enough straight pipe after the rotary valve to get the product accelerated. Even though this is widely contended a distance of 20xD usually does the trick.

PP pellets (at ambient termperature) create less streamers and angel hair than PE pellets, but still most process licensors recommend using an internally roughened pipe.

Dense phase or Slug/plug conveying data I will give in another post.

Best regards,

Sven ■

Originally Posted by kchetan

Dear sir,

Density is 550 Kg / m3 as in thread it was wrongly written as 550 Kg/hr.

1) Distance horizontal for each line = 70 m

2) Distance vertical for each line = 20 m

3) Number of elbows in each line= 10

Suggest system and briefly Explain how to Choose Dense or Dilute?

I Request you If Possible, Please send me Calculations as well.

Dear Kchetan,

Below the results for a low velocity dense phase (slug, plug, slow motion, Neuphase, or what ever you want to call it) conveying system.

Atmospheric Pressure [Patm] = 0.99138035

Air Density ambient [kg/m3]= 1.10307741

Gas Ratio my [kg/kg] = 36

dPcon [bar/g] = 1.8

dPconm [bar/g] = 2.1

dPdesign [bar/g] = 2.8 (compressor outlet pressure)

Gas Flow [m3/min] = 12.6

Gas Flow [Nm3/min] = 10.8

Leakage Flow [m3/min] = 7.50

Gas Flow Design w Leak[m3/min] = 21.1

Gas Flow Design w Leak[Nm3/min] = 18.0

Pipe Diameter from D [m] = 0.187 in 1 step (internal diameter)

Start Velocity Vst [m/s] = 2.75

Terminal Velocity [m/s] = 7.5

Note: Design pressure includes dp for filter at 20mbar, heat exchanger at 40mbar,

clean gas pipe at 20mbar, gas flow control unit at 600mbar

Rotary valve: 40ltr, filling efficiency 90%, 25rpm, 12 pockets

Reduction of conveying bends recommended due to pipe forces

Conveying pipe: standard cold rolled surface

Some additional comments:

- It it possible to also use a 6" DN150/168.3x3mm pipe, but the conveying pressure alone exceeds 2.5bar making a 3.5bar compressor or plant air necessary and increase the leakage gas rate of the rotary valve.

- The terminal gas velocity is then around 9m/s which will furhter increase pipe forces.

- As compared to dilute phase the conveying gas velocity is reduced by 75%, which avoids streamer creation and allows gentle product transfer.

- Once the conveying system is stopped a large amount of product remains in the pipe line and can only be flushed out with substantially higher velocities (approx. 21m/s), which requires either compressed plant air, an additional blower or a buffer tank.

- In regard to the overall energy consumption if compared to dilute phase Teus Tuinenberg has faster answers than me.

- As Amrit Agarwal correctly mentioned pipe forces, reaction force to the moving plug in bends and vertical sections, must be considered and a standard U-bolt type support philosophy will not suffice in the bend and vertical area. However, this can be calculated and designed.

In summary:

- For your comparatively short conveying line the much higher expense for dense phase conveying (blower vs. compressor; gas flow control unit vs. nil; high pressure rotary feeder (design>2.5 bar) vs. low pressure rotary feeder (design<1.0bar; additional line flushing vs. nil; some special pipe supports vs. U-bolt; energy consumption) will not be justified.

- Even if you are concerned regarding streamer creation the internally treated pipe in dilute phase conveying will reduce this problem substantially.

- Dust creation will range from 20 to 60ppm per 100m conveying length and should not pose a problem. You shouyld also look at your raw material provider and check how they convey the material. With 90% probability they use silute phase systems with a pellet cleaner to remove the dust. So the small amount of additional dust will not be a hazard to your product.

Best regards,

Sven ■

Originally Posted by kchetan

Dear sir,

Suggest system and briefly Explain how to Choose Dense or Dilute?

Dear Kchetan,

If you take your time you will find this forum full of threads regarding this topic.

If you have time please please also look up

http://www.erpt.org/014Q/rhoe-01.htm

Martin Rhodes put up a nice piece of work on this page. He describes quite detailed the theory of pneumatic conveying and added a number of movies for illustration. I think you will find most answers to your questions there.

Different than most other processes in the industry pneumatic conveying does not add value to the product itself. It is just a step to get the material from a point where it is available to the point where it is needed.

Exceptions are if you can add heating, cooling, drying, mixing processes to the conveying part.

So, for the transfer you want to spend as little money as possible maintaining the product properties as much as possible.

Questions to ask:

1) What is the capital expense?

2) What is the operation expense?

3) How much product attrition/change in product properties is acceptable?

Questions 1 and 2 can be answered by qualified vendors of pneumatic conveying systems, but for the investor those answers must be interpreted in the context of the whole plant. Land, Labour, Energy and Maintenance cost vary from continent to continent and from country to country.

For question 3 the vendors will only be able to give an estimate on expected attrition/change of properties. Whether the end-user of the system can accept this is up to the user and his reuquirements only.

Best regards,

Sven ■

Dear Sven,

First of all my compliments for the pneumatic conveying calculations and the serious approach, shown in your replies.

I also calculated the dilute phase conveying installation according your design.

Blower = 42 m3/min displacement

Pipe diameter = 162mm/187mm

Results:

Capacity = 30 tons/hr

Pressure = 7000 mmWC (0.7 barg)

SLR = 9.91

Gas velocity = 23 m/sec – 29 m/sec (influenced by the presence of material)

Material velocities = 11 m/sec – 19 m/sec – 16 m/sec

Energy consumption 2.3 kWh/ton

With an 6” (154 mm) pipeline, I calculate a pressure drop of 9000 mmWC (0.9 barg) and an energy consumption of 2.11 kWh/ton. Blower displacement = 34.8 m3/min

Compared to your calculation results, the difference could be in the factor K, but are fairly consistent with each other.

I also calculated the dense phase conveying installation, assuming that the sedimentation is continuously along the pipeline and that the remaining cross section forms the conveying channel.

Results:

Compressor = 18 m3/min displacement

Pipe diameter = 187mm

Results:

Capacity = 19 tons/hr

Pressure = 27800 mmWC (2.78 barg)

SLR = 21.8

Gas velocity = 13.7m/sec – 26 m/sec (influenced by the presence of material)

Energy consumption 3.71 kWh/ton

Remark: Calculated as continuous pneumatic conveying in the dense phase region of the Zenz diagram.

If this system is considered as a plug conveying system, then the calculation should refer to the calculation of moving plugs in a pipeline (a piston in a cylinder) and then the internal shear stresses of the plugs and the influence on these shear stresses of the pressure drop over a plug must be accounted for. (Flow mechanics like in a silo)

The plug length and the number of plugs in the pipeline are then becoming very important.

Also the expansion of the air between the plugs is an issue to consider.

How are the plugs formed? By pulsing feeding or by the pipe geometry interaction with the air velocities?

How fast are the plugs moving?

A theory based calculation of pneumatic plug conveying (dense phase conveying?) seems almost impossible to me.

Have a nice day

Teus ■

Dear Teus,

Originally Posted by Teus Tuinenburg

...

First of all my compliments for the pneumatic conveying calculations and the serious approach, shown in your replies.

...

Thanks a lot for your kind comment

Originally Posted by Teus Tuinenburg

...

I also calculated the dense phase conveying installation, assuming that the sedimentation is continuously along the pipeline and that the remaining cross section forms the conveying channel.

...

I think this assumption is not valid for pellet low velocity conveying.

Attached please find a state diagram for conveying (valid also for pellets) and according to this, if the velocity is reduced below the saltation velocity, the system will reach the "unstable zone", in which erratic pressure fluctuations do not allow a stable conveying pattern. Only when the unstable zone is passed stable plug conveying (a piston in a cylinder) is reached.

Originally Posted by Teus Tuinenburg

...

If this system is considered as a plug conveying system, then the calculation should refer to the calculation of moving plugs in a pipeline (a piston in a cylinder) and then the internal shear stresses of the plugs and the influence on these shear stresses of the pressure drop over a plug must be accounted for. (Flow mechanics like in a silo)

...

I fully agree. The calculation result I suggest refers to plug conveying using a calculation model which differs from the Zenz approach.

Originally Posted by Teus Tuinenburg

...

How are the plugs formed? By pulsing feeding or by the pipe geometry interaction with the air velocities?

...

Depending on the starting gas velocity and the chosen SLR the plugs can form naturally by and in the pipe geometry. For the case of Kchetan natural plug formation will work.

If the SLR is very low or the starting velocity is too high pulse feeding is recommended.

Originally Posted by Teus Tuinenburg

...

How fast are the plugs moving?

...

Usually the plugs move at velocities in the range of, but not higher than, the local average gas velocity, because part of the gas of the driving gas buffer will penetrate the plug through its pores, and the plug will move towards a gas buffer in its front leading to deceleration of the plug.

Only when there is no gas buffer in its front will the plug velocity increase above the local average gas velocity, which happens in the end of the pipe spool toward the receiving bin.

Originally Posted by Teus Tuinenburg

...

A theory based calculation of pneumatic plug conveying (dense phase conveying?) seems almost impossible to me.

...

B. Mi and Prof. P.W. Wypych offered in Powder Technology 81 (1994) 125-137 a calculation approach for plug conveying. Very interesting and recommend reading!

Originally Posted by Teus Tuinenburg

...

Have a nice day

Teus

...

..., and same to you,

Sven ■

Originally Posted by Sven Ludwig

Attached please find a state diagram for conveying (valid also for pellets)

Sven

Guten Tag Sven,

The attachment is missing, probably you forgot it.

Can you post the state diagram for us?

As I was always involved in big scale pneumatic conveying in dilute phase and close to dense phase, I am now getting interested in plug conveying, which still seems to me much more difficult to model as ordinary pneumatic conveying, due to the fact that soil mechanics start to play a role and permeability of the plug is generating a driving force. In the mean time the expansion of the air along the pipeline changes the air density and thereby changes the volume of the air.

It becomes a discontinuous flow instead of a continuous flow.

take it easy

Teus ■

Originally Posted by Teus Tuinenburg

href="showthread.php?p=62710#post62710" rel="nofollow">

Guten Tag Sven,

....

The attachment is missing, probably you forgot it.

Can you post the state diagram for us?

.....

take it easy

Teus

Hello dear Forum Members,

Ooops, I am sorry,

and try it again.

Regards,

Sven

Attachments

state diagram (PDF)

■

Dear kchetan,

Have you read:

Influence of electro static charge on pneumatic conveying.

https://news.bulk-online.com/?author=15

?

The issue of angel hairs and streamers is not an easy subject.

Have a nice day

Teus ■

Originally Posted by kchetan

Dear Sven Sir & Teus Sir,

I Understood everything, but basically I want to know either the dense phase system or dilute phase system would be the most efficient one concern with the Angel hairs or Streamers with ERW Pipes rather than going with Costly Internally roughed pipes (Shot Peened Pipes- internally Diamond Knerling)

Why to go for a Shot Peened Pipes? can we manage to have the lesser angel hair or streamer generation with a End Velocity 28 m/s.

Regards,

KChetan

Dear Kchetan,

Your post raises a couple of questions which should be addressed individually

1) Dense Phase conveying in plugs is conveying at very low conveying velocities, which safely avoid streamer creation.

However, every time you flush the line (to switch the destination or to avoid contamination in case of a product change), you will use high velocities and the problem of streamer creation come back.

2) In Dilute Phase (high velocity) conveying streamers are safely avoided by using shot-peened pipes.

3) Streamers and angel hair are mostly created in conveying bends and the first section of straight pipe after a bend. This can be avoided by applying special pipe bends, which form a product layer on which the product is deflected rather than sliding along the outer radius of the pipe bend.

Pelletron offers the Pellbow, Coperion offers the Gammabend and there are many more manufacturers and good products, which use the same effect.

All solutions resolve the streamer problem, but have the disadvantage of higher pressure drops if compared to regular long radius bends. To make things worse those bends cost more than a shot peened long radius bend.

4) The conveying velocity has a great impact on streamer creation and therefore I limited the terminal gas velocity in my calculation suggestion to 25m/s only.

5) In regard to installation cost I like to emphasize once more that Plug conveying is far more expensive than Dilute phase conveying. When you mention "Costly Internally roughed pipes" I worry, because the cost of internally treated pipe is on a small fraction of the cost for any other solution. On the other hand internally treated pipes solve your streamer problem for years to come.

Best regards,

Sven ■

Dear K Chetan

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Please contact us at the following.

TECHNO DESIGNS

I-39 G.I.D.C.

PHASE-IV

VITTHAL UDYOGNAGAR-388121

TELE; 02692 235532,235034

e MAIL: info@technodesignsindia.com ■