dear Ms Pauleen,

An Aerzen GM90S at 1190 rpm delivers approx 40 m3/min

A 6”pipeline has an area of 0.01767 m2 , resulting in an end velocity of 38 m/sec

This is considered very high for calcium carbonate powder.

To calculate the present situation, you should gather:

-particle size distribution

-particle density

-bulkdensity

-exact pipeline routing

-Capacity at the measured pressure in the bulk truck tank.

From these data it is possible to calculate the effect of possible modifications.

success ■

Dear ms pauleen,

Calculating a pneumatic conveying system is not a matter of a formula, but a matter of executing a calculation algorithm, existing of many formulas in an iteration process.

The required input are the geometry of the pipe line, the compressor data and the product pneumatic conveying properties.

In case of an existing installation, it is possible to determine the product data with this calculation program from the field measurement.

Subsequently, modifications can be investigated with the same calculation program, using the derived product properties.

Increasing the conveying rate could be achieved by:

* Increasing pneumatic conveying efficiency

(F.i. A lower airflow could increase the efficiency more than the decrease in rate because of reduced power)

* Increasing pressure (screw compressor instead of a blower )

* Increase of pipeline diameter resulting in lower velocity losses at the same airflow and pressure. (works only when the air flow is presently too high)

* If necessary an additional booster compressor with a bigger pipeline can be installed.

If you can provide the data, a more specific answer can be given

Awaiting your reply ■

Dear Pauleen,

In my opinion these two articles will guide you if you would like to re-design your pneumatic conveying system for the increased conveying rates.

1. Theory and Design of Dilute Phase Pneumatic Conveying Systems.

2. Debottlenecking (i.e., Increasing the Capacity of) Pneumatic Conveying Systems.

Regards,

Amrit Agarwal

Consulting Engineer

Pneumatic Conveying Consulting

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Dear Ms Pauleen,

After modelling the pipeline, and based on your field information, I made the following calculation of the product resistance factor.

Assuming a pressure system.

5/5 6.5 tons/hr

Press: 6350

Press.drop : 6350

Part----------length----v-air----v-product-----press.drop-----v-wall/v-susp

1 intake-------1.0------66.6------52.6-----------1913-----------21.3

2 pipe --------2.4------72.5------66.3 -----------3179. --------22.4

3 d.tr-------------------72.5 ------66.3-----------3502.

4 bend----------------34.2 ------32.2 -----------3526.

5 pipe ---------8.3 ----36.2 ------31.6-----------4041-----------10.3

6 bend-----------------36.4------17.1 -----------4067.

7 pipe---------1.0------36.9------30.3-----------4211-----------10.4

8 bend-----------------37.0------ 16.4-----------4237.

9 pipe ---------8.1-----39.2------34.2-----------4899-----------10.8

10 bend ---------------39.4------ 18.5-----------4927.

11 pipe --------1.0----40.0 ------32.7 -----------5082. -----------10.9

12 bend----------------40.2 ------17.7-----------5111.

13 pipe --------8.1----42.9------37.2 -----------5818-----------11.3

14 bend ---------------43.1 ------20.0-----------5849.

15 pipe--------1.1-----43.8------35.5-----------6018-----------11.5

16 bend----------------44.0------19.9 -----------6049.

17 outlet -------------44.0------ 19.9 -----------6162.

18 filter----------------0.7 -------------------------6350.

v-filter 0.66 m/min

No booster

Length 30 M

Residence time 1.26 sec

Power 57.kW

Energy consumption 8.76 kWh/ton

Calcium Carbonate

Re = 3.06

Ms Pauleen

***************

PRODUKT :Calcium Carbonate

Pipeline capacity ........= 6.50 ton/hr

Convey Length = 30 m

Number of Bends = 6 -

System-pressure...........= 6350. mmwC

Q-pump....................= 0.684 m^3/s

D-begin =100 D-end =150

Q-convey-pipe ............= 0.684 m^3/s

Compr power .....= 57. kW

Outlet force .. = 397 N

loading-ratio ............= 2.11 - - (dynamic)

NO BOOSTER

Ambient temperature ......= 40.0 °C

Reynoldsnumber ..[ Re ]...= 3.06 --

spec.energy-consumption...= 8.76 kWh/ton

backpressure at pipe-end..= 0. mmwC

p-accell.excl prod.rest..= 1100. mmwC

p-suspension.............= 80. mmwC

p-lifting................= 68. mmwC

p-airfriction............= 2256. mmwC

p-productresistance......= 1616. mmwC

p-intake productcolumn...= 100. mmwC

p-intake ................= 900. mmwC

p-nozzle ................= 1913. mmwC

p-filter.................= 188. mmwC

density product/air mix ..= 3.7 kg/m^3

Mass in pipeline.= 2 kg

Empty pipe dp....= 3671 mmWC

==============================

cwp-factor = 9090. 10^-12

===============================

The calculated resistance factor of 9090 * 10E-12 is a very high factor compared to known and verified factors of other comparable products (650 x), among which CaCO3 (Calcium Carbonate).

This CaCO3, with a particle size of 140 microns was used for desulphurisation of exhaust gases of a power plant. With this calcium carbonate, your installation would perform approx 15 tons/hr at 0.635 bar pressure.

As an example, a normal bulk truck of cement would perform 19 tons/hr at 6350 mmWC of pressure at the modelled pipeline.

Recalculations with bigger pipelines and lower air volumes, using the calculated resistance factor, can improve the capacity a little bit, but never the required 50%

A fact is that the air volume is far too high (velocities range from 72 m/sec to 45 m/sec).

These can be lowered by reducing the blower speed (at cost of reduced volumetric efficiency) or increasing the pipeline diameter.

However, by increasing the pipeline diameter, any increase in capacity is severely punished by the CALCULATED resistance factor.

Therefore, I suspect that the installation has some unknown problems (f.i. too small or not fully open valves, internally caked pipe lines, unknown orifices and/or too much backpressure at the end of the pipeline or something else)

That should be checked first and repeat measuring and recording a full unloading.

Before you can decide on modifications to increase the capacity, you should firstly investigate the proper functioning of the existing installation.

success ■

Dear Pauleen,

I will be glad to send a copy of these articles to you. Please send your request to my email address given below.

Regards,

Amrit Agarwal

Consulting Engineer

Pneumatic Conveying Consulting

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

all,

we have completed this project and it was a sucess.

thanks all for your help.

we have installed screen mesh in our convey lines to capture any contaminations.

installed are two screen mesh. The first one is 1"X 1" then followed by 3/4" X 3/4" which are 12" apart.

Due to foreign materials still present after screening,we plan to reduce the screen mesh size.

Is it possible we still reduce the size of the mesh without blower high pressures and clogging on the mesh.

What would be the minimum screen mesh size for this requirement.

thank you.

powder being conveyed is calcium carbonate. ■

Hello Himex,

That is awesome. What kind of contaminants did you find? Was this due material caking up? How do you have to clean the screens from now on? All the best. ■

Ralf,

Examples of contaminants that are found are:

strings, pieces of sack material, powder lumps, assorted pieces of metal,

pieces of cloth.

We clean the screens by removing the plexiglass fastened by wingnuts.

Once removed, we remove all contaminats caught on the screens.



Is it possible we reduce the size of the screen mesh?

replace the 1" mesh to 3/4" and the 3/4" mesh to 1".

Originally Posted by RalfWeiser

Hello Himex,

That is awesome. What kind of contaminants did you find? Was this due material caking up? How do you have to clean the screens from now on? All the best.

■

Hello Himex,

I am not sure why you would switch the 3/4" to a 1" or am I misunderstanding you? ■

sorry. i meant 3/4" to 1/2".

my apologies.■

Hi there,

going with a finer mesh should not pose a problem per se', but screen usually incur a higher flow and pressure loss. You can always revert back to a good old college try and see how badly the material plugs up the screens. Is the bulk material quality poor or where do all the contaminants come from? ■

Hello himex, Ralf,

Placing a screen in the conveying line of a pressure pneumatic conveying system is not

uncommon.

To compensate for the decreased cross sectional area, the, so called, lump catcher has an increased overall diameter.

If you want to decrease the opening size of the screen (increasing the mesh size), then the screen itself must be enlarged.

The box space before the screen must be sized for a reasonable amount of capacity for foreign parts in order to reach a reasonable operating period between cleanings.

BR

Teus ■

Hi Teus,

I miust admit that I assumed for the screen box to remain the same size. I am sure that the box could be modified relatively easy. ■

Hello Teus, Ralf,

The screen is made of a spool (of the same diameter) connected by flanges onto the convey line.

please see attached photo.

Thank you for sharing your insights on our querries.

Attachments

screen_mesh (JPG)

■

Hi Himex,

the pictures really helped me understand what you are faced with. As Teus suggested you could increase the pipe size in diameter and install finer screen sizes. You could do that with bell reducers. Of course you could more creative with so called "witch's hat" style strainers that due to their shape increase the total available surface area without increasing the pipe diameter. ■

Dear Teus, Ralf,

If i just increase my mesh size without increasing my pipe diameter,will i have cloggings or high pressures.(short term plan).

What are the calculations to be made if we are going to install a "witch's hat" style strainer.(long term plan)

Do you have examples/photos of these strainers?

we would really like to improve our screens since contamination is really a big issue in our raw materials.

Thank you.

himex ■

Hi Himex,

Here are a few links to conventional strainer manufacturers. The concept is simply relying on the conical shape providing you with much more surface area as opposed to the "flat plate" design you have now. The standard perforated material these companies use obviously will not work for your specific issue. If I was stuck in your position I would web search suppliers like this in your local area and contact them with your 3/4" and 1/2" screen size request and lets say a 300% open area. Let them propose a suitable conical strainer design that you can install in the pipe spool. This would roughly speaking not even produce the restriction that you are seeing with your 1" and 3/4" flat screens even if you left the pipe size as is. I always recommend placing a delta p gauge with pick up points in the up and down stream area of the strainers that will help you gauge when it is time to clean them out.

http://www.grottofilters.com/p-temporary-conical.htm

http://newarkwire.rtrk.com/?scid=797...h=/strain.html

http://www.strainwell.com/conical-stariners.html ■