Dear Haghighi,

Have a look at:

Pneumatic conveying, turbo- or positive displacement air mover:

https://news.bulk-online.com/?p=309

I assume that you are referring to a pressure discharge cement conveying system.

I can calculate your system with the use of a screw compressor or a turbo compressor and compare the results.

A screw compressor and a turbo compressor compress the air both adiabatically, but are different in partial load.

They are both oil free.

When comparing the two installations, it is necessary that both systems are optimal.

Best regards

Teus ■

Hey Haghighi

I would checkout this page for

Air compressors ■

The issue with turbo type compressors in cement conveying applications usually comes down to how clean the air is around the compressor and if you have very few fluctuations in conveying pressure. Tell us a little more about the application and we can assist with selecting the better technology for the system you are evaluating. ■

Originally Posted by Teus Tuinenburg

Dear Haghighi,

Have a look at:

Pneumatic conveying, turbo- or positive displacement air mover:

https://news.bulk-online.com/?p=309

I assume that you are referring to a pressure discharge cement conveying system.

I can calculate your system with the use of a screw compressor or a turbo compressor and compare the results.

A screw compressor and a turbo compressor compress the air both adiabatically, but are different in partial load.

They are both oil free.

When comparing the two installations, it is necessary that both systems are optimal.

Best regards

Teus

Dear Mr Teus

I will take a oppurtunity to participate in this subject mattter.Apparantly i got to compare the compresor type (Centrefugal or screw compressor) for fly ash dense phase pneumatic conveying system.

I understand centrifugal compressor seems to be energy efficient and cost effective for high volume due to its diffuser arrangement which contrubutes the one third of work with out any power consumption .

My vague is iam not able to compare this centrifugal compressor with screw compressor. Our consultant has asked for screw compressor , but at the sam time since the volume is high ie 17000Nm3/hr @3.5bar, i see the centrefugal compressor more appropriate.But at the same time i dont have any refernce of the said(Centrifugal comp) machine being used for this specific application.

I would like to be advised by you for selecting the type of comp for given volume and presure , with the concrete justification if any

Thanks in anticipation

GUDDU ■

Dear Guddu,

I understand the following:

-The project is a fly ash dense phase pneumatic conveying system

-The air compressor choice is between a turbo compressor (Centrifugal compressor as you call it is not the same) and a screw compressor with internal compression.

-The required compressor air displacement is 17000 m3/hr # 284 m3/min # 4.72 m3/sec at a pressure of 3.5 bar

For the calculation of the behavior of the compressor in the fly ash pneumatic conveying system, it is necessary to know the installation design and its operating parameters.

-Feeding by a double tank system or a screw feeder.

-Pipe length and pipe diameter of the system.

-Design pressure of the pneumatic system.

A screw compressor is a robust and reliable machine that takes pressure variations without any problems or additional auxiliaries.

The required air volume is not uncommon for a set of screw compressors (f.i. 3 x Aerzen VM75). In addition, using 3 compressors improves redundancy.

In case of varying pressures, which is always the case in a pneumatic conveying system, a turbo compressor needs auxiliary control equipment to prevent surging.

Driving and starting issues need to be addressed as well.

In the end, the decision is based on:

-Investment

-Technical reliability

-Energy cost

-Maintenance cost

What I can do, is calculate the pneumatic conveying system, where I use a screw compressor with internal compression in one calculation and a turbo compressor in an other calculation.

Therefore, I need the pneumatic conveying installation design.

-Pipe length horizontal

-Pipe length vertical up

-Pipe length vertical down

-Pipe diameters(s)

-Material

-Material size (distribution)

-Material (particle) density

-Material bulk density

-Material temperature

-Feeder system data (Double tank system or screw feeder)

-Operational altitude.

-Special information

In case you prefer to communicate directly, use the forum private messaging feature.

Have a nice day

Teus ■

Originally Posted by Teus Tuinenburg

Dear Guddu,

I understand the following:

-The project is a fly ash dense phase pneumatic conveying system

-The air compressor choice is between a turbo compressor (Centrifugal compressor as you call it is not the same) and a screw compressor with internal compression.

-The required compressor air displacement is 17000 m3/hr # 284 m3/min # 4.72 m3/sec at a pressure of 3.5 bar

For the calculation of the behavior of the compressor in the fly ash pneumatic conveying system, it is necessary to know the installation design and its operating parameters.

-Feeding by a double tank system or a screw feeder.

-Pipe length and pipe diameter of the system.

-Design pressure of the pneumatic system.

A screw compressor is a robust and reliable machine that takes pressure variations without any problems or additional auxiliaries.

The required air volume is not uncommon for a set of screw compressors (f.i. 3 x Aerzen VM75). In addition, using 3 compressors improves redundancy.

In case of varying pressures, which is always the case in a pneumatic conveying system, a turbo compressor needs auxiliary control equipment to prevent surging.

Driving and starting issues need to be addressed as well.

In the end, the decision is based on:

-Investment

-Technical reliability

-Energy cost

-Maintenance cost

What I can do, is calculate the pneumatic conveying system, where I use a screw compressor with internal compression in one calculation and a turbo compressor in an other calculation.

Therefore, I need the pneumatic conveying installation design.

-Pipe length horizontal

-Pipe length vertical up

-Pipe length vertical down

-Pipe diameters(s)

-Material

-Material size (distribution)

-Material (particle) density

-Material bulk density

-Material temperature

-Feeder system data (Double tank system or screw feeder)

-Operational altitude.

-Special information

In case you prefer to communicate directly, use the forum private messaging feature.

Have a nice day

Teus

Sir Here is the query

Our totalvolume require is 15144M3/hr @3.5 bar for application of dense phase conveying system .

Now as per my option i can go for 4 no screw compressor of each capacity 3786m3/hr or 2 no centrifugal compressor of capacity 10000m3/hr each.

Using two centrifugal compressor gives the considerable saveing , but i dont no what is the hidden concept of not using the centrifugal compressor. Can you enlighten me

For calculation i will depict the following parameter

Pipe length horizontal

-Pipe length vertical up 50mtr

-Pipe length vertical down 10mtr

-Pipe diameters(s) unknown

-Material Fly ash

-Material size (distribution) 50Micron

-Material (particle) density

-Material bulk density 0.75t/m3

-Material temperature 150deg

-Feeder system data (Double tank system or screw feeder)

-Operational altitude. 415 m

-Special information

Thanks in anticipation

guddu ■

dear Guddu,

As the pipe diameters are unknown, I then need to know the required capacity.

Or shall I calculate the diameter(s) through a normal air velocity and the air volume?

Thanks

Teus ■

Dear Guddu,

Sorry for comimg back with another question.

I am also missing the horizontal conveying length and the number of bends.

Cheers

Teus ■

Dear Guddu,

I determined a pipeline diameter on the basis of the given airflow of 15144 m3/min # 4.2 m3/sec and calculated the fly ash capacity for various pipe lengths with 8 bends.

The result is as follows:

Begin diameter 490 mm (20”)

End diameter 590 mm (24”)

Pressure 2.5 bar

v-begin = 5 m/sec

v-end = 27 m/sec

Length ------------- Pipe line capacity

200 m --------------- 736 ton/hr

300 m --------------- 654 ton/hr

400 m --------------- 597 ton/hr

500 m --------------- 550 ton/hr

600 m --------------- 518 ton/hr

700 m --------------- 488 ton/hr

These calculations are provisional; however, represent a fair indication of the possible capacities.

After having the right installation data, I can recalculate the capacities with the proper parameters s.a. altitude and temperatures.

The next step is the comparison of the 2 compressor types in relation to the characteristics of the pneumatic conveying installation.

The focus in this comparison is on the energy consumption per conveyed ton and the necessary auxiliary equipment for coping with pressure- and no pressure conditions.

The screw compressor follows the pressure variations without any additional auxiliary equipment, due to its positive displacement principle.

The turbo compressor however needs a diffuser control to prevent high power demand at no pressure conditions. Therefore, it is important to know the pressure-volume curve of the turbo. An oscillating pressure because of the feed back control is then possible and requires special attention.

In case of a double tank feeder system, the pressure fluctuates between almost zero to maximum, every time that a tank is emptied and filled.

I appreciate your effort to sort out this issue and am very interested in your case.

All for now

Teus ■

Originally Posted by Teus Tuinenburg

Dear Guddu,

I determined a pipeline diameter on the basis of the given airflow of 15144 m3/min # 4.2 m3/sec and calculated the fly ash capacity for various pipe lengths with 8 bends.

The result is as follows:

Begin diameter 490 mm (20”)

End diameter 590 mm (24”)

Pressure 2.5 bar

v-begin = 5 m/sec

v-end = 27 m/sec

Length ------------- Pipe line capacity

200 m --------------- 736 ton/hr

300 m --------------- 654 ton/hr

400 m --------------- 597 ton/hr

500 m --------------- 550 ton/hr

600 m --------------- 518 ton/hr

700 m --------------- 488 ton/hr

These calculations are provisional; however, represent a fair indication of the possible capacities.

After having the right installation data, I can recalculate the capacities with the proper parameters s.a. altitude and temperatures.

The next step is the comparison of the 2 compressor types in relation to the characteristics of the pneumatic conveying installation.

The focus in this comparison is on the energy consumption per conveyed ton and the necessary auxiliary equipment for coping with pressure- and no pressure conditions.

The screw compressor follows the pressure variations without any additional auxiliary equipment, due to its positive displacement principle.

The turbo compressor however needs a diffuser control to prevent high power demand at no pressure conditions. Therefore, it is important to know the pressure-volume curve of the turbo. An oscillating pressure because of the feed back control is then possible and requires special attention.

In case of a double tank feeder system, the pressure fluctuates between almost zero to maximum, every time that a tank is emptied and filled.

I appreciate your effort to sort out this issue and am very interested in your case.

All for now

Teus

Dear sir

With the limited knowledge i am fail to quantify the specific reason not to go for

centrifugal compressor. you have raised copuple of query which needs to be addressed to cater the smooth operation taking oscillation effect of pressure requirement

1) The turbo compressor however needs a diffuser control to prevent high power demand at no pressure conditions. Can you enlighten more about this reason, ie why there will be more power consumtion during no load

2) Pressure volume curve . Can you tell me why it is significant

Apart from above can you tell me the other parameters and points to be considered while comparing screw and centrigugal compressor

Well just to share with you here is the power saving

1) Total air requirement 17980NM3/HR

Screw comp centrifugal comp

Power required 450KWX(4no comp) 750KW (2No Comp)

1800KW 1500KW

From above we can perceive there is Difference of 300KW. However i hav not quantify the same for pertone conveying , but i presume the this difference will remain same.

Can you throw a light how to quantify the power consumtion fpor per tonn of conveyeing ■

Dear kj,

To keep the particles in suspension in a pneumatic conveying system it is required to maintain a constant velocity at all pressures

In a pressure system, this requirement relates to the end of the conveying pipeline and for a vacuum system, this requirement relates to the beginning of the conveying pipeline.

A screw compressor has this property automatically, because of its positive displacement principle. (Displaced volume is approx. constant as a function of the delivery pressure)

A turbo compressor requires a controlled diffusor to achieve this property.

With a fixed diffusor, the airflow changes with pressure and the power demand changes too.

The above-mentioned properties are represented in the pressure-volume diagrams of the compressors.

To compare the 2 options, the diagrams are needed.

I checked the data for the screw compressor as follows:

Total air displacement 17980 m3/hr for 4 screw compressors.

Airflow for 1 screw compressor = 4495 m3/hr (# 75 m3/min # 1.2486 m3/sec)

A screw compressor of this size :

4394 m3/min at 3.5 bar(o) requires an electric motor of 355 kW

According to your data, a motor of 450 kW is installed. (You did not state the pressure)

Assume that this power is used, then the pressure must be higher than 3.5 bar(o), which is far too high because of the then occurring outlet temperatures. (5.5 bar(o) and approx. 370 degrC)

Unless, you are referring to a two-stage compressor set.

Then the pneumatic conveying design is a high-pressure system.

If it is a high pressure system and you are concerned about energy consumption, then my advise is to reconsider the pneumatic conveying design.

In my opinion, this 450 kW motor is never fully loaded in the installation and this figure must not be used in comparisons.

Evaluating and judging a pneumatic conveying design requires much more information than the nameplate data of two incidental motors.

The power consumption per conveyed ton can be calculated when the complete design is available.

The efficiency of the pneumatic conveying design depends largely on the chosen velocities, SLR and pressures.

Be careful

Teus ■

dear mr. haghighi

salam

I am mehdi Jazini.I work at acement co. in iran and i decided to use turbo comp. for conveying cement to silo.I saw you've done some reserch about this subject and i want to know if you can help me in this topic.I thank you very much for this and i hope to hear frome you soon.

i leave my mail for you that you can contact me.

best regards

Jazini

Originally Posted by haghighi

Hello

we want compare turbo air compressor with screw air compressor to used in cement line. please help me.

Best Regards

Haghighi

■

Dear mehdi,

Have a look at:

Pneumatic conveying, turbo- or positive displacement air mover:

https://news.bulk-online.com/?p=309

Your intended pneumatic conveying installation for cement can be calculated for the various compressor types available.

Combining the pneumatic conveying installation calculations with the compressor (or vacuum pump) characteristics, the different aspects of the air mover choice will become apparent.

In general, pneumatic cement conveying installations use positive displacement pumps (pressure or vacuum) s.a. oil free blowers and screw compressors with internal compression.

Take care

Teus ■

Dear Haghighe,

Both the turbo compressor and the screw compressor are acceptable for supplying conveying air in pneumatic conveying. Choice would depend upon the total investment. For a single conveying system, total investment for an air suppy system using a screw compressor should be less than that for a turbo-based system because a screw compressor is a positive displacement compressor. Since turbo compressors are not positive displacement, they need additional equipment

Regards,

Amrit Agarwal

Consulting Engineer

Pneumatic Conveying Consulting

Charleston, WV, USA

Email: polypcc@aol.com

Ph 304 346 5125 ■

Originally Posted by Teus Tuinenburg

Dear mehdi,

Have a look at:

Pneumatic conveying, turbo- or positive displacement air mover:

https://news.bulk-online.com/?p=309

Your intended pneumatic conveying installation for cement can be calculated for the various compressor types available.

Combining the pneumatic conveying installation calculations with the compressor (or vacuum pump) characteristics, the different aspects of the air mover choice will become apparent.

In general, pneumatic cement conveying installations use positive displacement pumps (pressure or vacuum) s.a. oil free blowers and screw compressors with internal compression.

Take care

Teus

Dear \mr. Teus

i sow your Topic at the add. you have given me.But in this sotuation i have no choice because i have ordered me turbo comp. and now i have to use it.I want to know what to do to use it for this duty and how can i install it for the best output.

what you have written means that it is not suitable for this duty but what i have now is a turbo comp. that i have to install and use.so i want to know if you can help me use it at the best situation?

thanks. ■

Dear jazini.

When you have already ordered the turbo compressor, you must also have a cement pneumatic conveying design.

From the design calculations, the working pressure range is now known.

Ask your turbo supplier how the turbo must be operated with constant mass flow and variable pressure.

Normally, this would require a regulated throttle valve in the outlet of the turbo.

This creates constant pressure on the turbo and a variable pressure after the regulating valve and on the pneumatic conveying system.

Turbo pressure = valve pressure drop + system pressure drop

The disadvantage of such a system is that the turbo is working always at constant power, regardless the system pressure.

This results in a very high energy consumption per conveyed ton, unless the conveying rate is 100% continuous, which is the case with f.i. a screw feeder installation.

However, then the screw feeder spoils the energetic efficiency.

If you supply more information about the conveying system itself, I can recalculate and compare with other compressor types.

Have a nice day

Teus ■