dear sir

we are supplying the dense phase system for fly ash.

kindly send your enquiry and contact details to submit our proposal.

best regards

sanjay agarwal

sanjayagarwal.delhi@gmail.com ■

parth engineering comp pvt. ltd.

ff06 , national arcade , plot no 4 , ghazipur LSC

TEL 011 22247974 CELL 9313055225 , 226

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Take fly ash Partical density as 1790kg/m^3,bulk density as 750kg/m^3, partical mean diameter as 100um.

conveying pipeline layout: horizontal length 1000m,vertical length 0m,bends number:5,valves number :2

calculation results:

fludizing vessel volume:2.5m^3

conveying time in pipeline:3min;

mean conveying velocity:19m/s

pipeline bore:231mm

solid loading ratio :13.7;

air volumetric flow:47.8Nm^3/min;

calculation fly ask conveying capacity:47.1t/h

i am not sure this calculation results is correct or correspond with reality very well.but i think it supplies you a reference to your design.

if you have any suggestion and commence ,please contact with me. my QQ number:22264251, QQ group number:31073767 MSN:JimLee170@hotmail.com

BR ■

Mr Jim

Your calculations relate to a continuous conveying system, this will require either 2 parallel blow tanks or a lock vessel arrangement. If you are proposing single vessel then I am afraid the calculations are wrong. In my opinion 1000 m conveying distance is not financially attractive on running costs and power consumption. ■

Dear above,

Base on the mentioned remarks and figures, I ran the computer and came up with the attached results.

Mr Jim did not mention the calculated pressure drop, which is a very important figure in pneumatic conveying.

Also the calculated conveying time of 3 min. seems to be too long

That indicates a particle velocity of 1000/180 = 5.55 m/sec.

Compared to a mean velocity of approx. 13.55 m/sec (not the end-velocity of 19 m/sec),

the particle velocity slip would be 13.55 – 5.55 = 8 m/sec (# 8/13.55 = 60 %)

Furthermore, the vessel content is low compared to the pipeline volume, resulting in high

purge time losses.

success

teus

Attachments

flyash1000m (ZIP)

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Mr Matoo, you are right the calculation results is based on the continous conveying system, there are two parallel bow tanks in this system.the volume of them are all 2.5m^3. In my calculation,i take the end(outlet) velocity(19m/s) as the mean velocity. the whole pressure drop of this conveying system is about 2.2Bar.So the inlet velocity is about 19/(2.2+1)=5.9375m/s. the real mean velocity is (outletvelocity+inletvelocity)/2=12.47m/s.Solid loading ratio is 13.6. the accurate calculation result of the conveying time is 2.9min.Datail calculation result please look at the attachment which is calculated by computer. if it is necessary i would like to translate it into english.

BR

Attachments

calculation (ZIP)

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As I stated before for twin blowtank continuous conveying system the calculations are fine apart from residence time which is bit contentious as stated by above. ■

Originally Posted by Teus Tuinenburg

Dear above,

Base on the mentioned remarks and figures, I ran the computer and came up with the attached results.

Mr Jim did not mention the calculated pressure drop, which is a very important figure in pneumatic conveying.

Also the calculated conveying time of 3 min. seems to be too long

That indicates a particle velocity of 1000/180 = 5.55 m/sec.

Compared to a mean velocity of approx. 13.55 m/sec (not the end-velocity of 19 m/sec),

the particle velocity slip would be 13.55 – 5.55 = 8 m/sec (# 8/13.55 = 60 %)

Furthermore, the vessel content is low compared to the pipeline volume, resulting in high

purge time losses.

success

teus

Sir how do i determine the purge time for given parameter of vessel volume (kettle content) and pipline volume?

Any equation will be helpful ■

Dear kj,

The purge time of a pneumatic system is not that easy to calculate.

The purge time starts when the kettle is empty and the pipeline is still filled with material over the full length and the pressure is still the conveying pressure..

The purge time ends when the pipe line is empty over the full length and the pressure drops to the empty pipe line pressure.

The time, required for purging ist hen approx. equal to the residence time of the particles in the pipeline.

An approximation is:

purge time = factor * Conveying length / average particle velocity.

The factor depends on the pressure, where the purge time is considered ended.

Have a nice day

Teus ■

Originally Posted by Teus Tuinenburg

Dear kj,

The purge time of a pneumatic system is not that easy to calculate.

The purge time starts when the kettle is empty and the pipeline is still filled with material over the full length and the pressure is still the conveying pressure..

The purge time ends when the pipe line is empty over the full length and the pressure drops to the empty pipe line pressure.

The time, required for purging ist hen approx. equal to the residence time of the particles in the pipeline.

An approximation is:

purge time = factor * Conveying length / average particle velocity.

The factor depends on the pressure, where the purge time is considered ended.

Have a nice day

Teus

Ok thanks

But how would i determine the factor? . ■

Dear kj,

The factor represents the part of the pipeline that is empty (purged) at the moment that you define the purging is complete.

If the pipe is still fully filled, the factor is: empty length/total length = 0 : pressure = conveying pressure

If the pipe is completely empty (purged) the factor is: empty length/total length = 1 : pressure = empty pipeline pressure.

Success

Teus ■

Originally Posted by Teus Tuinenburg

Dear kj,

The factor represents the part of the pipeline that is empty (purged) at the moment that you define the purging is complete.

If the pipe is still fully filled, the factor is: empty length/total length = 0 : pressure = conveying pressure

If the pipe is completely empty (purged) the factor is: empty length/total length = 1 : pressure = empty pipeline pressure.

Success

Teus

Taking this subject forward in attempt to eradicate my vague in this regard , i recall the previous thread

You said

1) To my understanding the purging starts after conveying time finished , so that sum of all teh time (purging+kettle filling+kettle pressurizing+conveying time ) represents the total cycle time . Now if that is true than purging will start after conveying completed . Please articulate on my understanding

You said

Now if that holds correct that implies the purging time is 75% of conveying or residence time. Please explain the co-rrelation of this approach with first point

Now you said

This implies the purge time is equal to residence or conveying time .

Sir please explain the final approach i consider to calculate the pipeline purging time . If your latest thread of

implication holds good then pelase explain to calculate the factor ? ■

Dear kj,

Again, the purging time of a pipeline starts after the kettle is empty and the pipeline is still filled with material.

The purging time ends when the pipeline is purged for a defined length.

The defined, purged length is related to the conveying pressure.

Example:

Conveying pressure of filled pipeline = 2.5 bar

Pressure of empty pipeline = 0.1 bar

Pressure of half filled pipeline = (2.5-0.1) * (1- 0.5) = 1.2 bar

Pressure of 75% purged pipeline = (2.5-0.1) * (1- 0.75) = 0.6 bar ( purge end pressure)

As the purging of a pipeline is a transient event, this method has to be regarded as a practical approximation.

The factor (in the example 0.75) depends on the chosen purge end pressure.

Success

Teus ■

Originally Posted by Teus Tuinenburg

href="showthread.php?p=69919#post69919" rel="nofollow">

Dear kj,

Again, the purging time of a pipeline starts after the kettle is empty and the pipeline is still filled with material.

The purging time ends when the pipeline is purged for a defined length.

The defined, purged length is related to the conveying pressure.

Example:

Conveying pressure of filled pipeline = 2.5 bar

Pressure of empty pipeline = 0.1 bar

Pressure of half filled pipeline = (2.5-0.1) * (1- 0.5) = 1.2 bar

Pressure of 75% purged pipeline = (2.5-0.1) * (1- 0.75) = 0.6 bar ( purge end pressure)

As the purging of a pipeline is a transient event, this method has to be regarded as a practical approximation.

The factor (in the example 0.75) depends on the chosen purge end pressure.

Success

Teus

Sit

To put the matter in more easy way , pelase refer attached your design sheet

1) Purge time determined in this is 86 Sec . Would you pelase explain how ?

Attachments

flyash conveying 1200m (PDF)

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Dear kj,

As explained before:

purge time = factor * residence time.

In the example design sheet:

purge time = 0.75 * 114.29 = 86 seconds

Have a nice day

Teus ■

Originally Posted by Teus Tuinenburg

Dear kj,

As explained before:

purge time = factor * residence time.

In the example design sheet:

purge time = 0.75 * 114.29 = 86 seconds

Have a nice day

Teus

This implies

1) To purging time is always 75% of residence time

2) What is difference between residence time and discharge time. I understand the residence time is the time requuired to convey the material from source to destination , whereas dischrage time is the total time (Conveying time + Cycle gap timer time) to convey the material . Please correct me with my understanding ? ■

Dear kj,

The factor depends on how far the conveying pressure is dropped until the level that you consider as “pipeline purged”.

Reread reply #16 of this thread.

The discharge time is defined as the time that there is flowing material out of the kettle.

The discharge time starts when the kettle is pressurized and the discharge valve opens.

The discharge time ends at the moment when the kettle is empty and the pipeline is full.

Discharge time = Kettle content / capacity

Have a nice day

Teus ■

Originally Posted by Teus Tuinenburg

Dear kj,

The factor depends on how far the conveying pressure is dropped until the level that you consider as “pipeline purged”.

Reread reply #16 of this thread.

The discharge time is defined as the time that there is flowing material out of the kettle.

The discharge time starts when the kettle is pressurized and the discharge valve opens.

The discharge time ends at the moment when the kettle is empty and the pipeline is full.

Discharge time = Kettle content / capacity

Have a nice day

Teus

Sir

What is real significance of discharge time? , because as i understand

Total time per cycle = Vave filling time + Pressurizing time +Conveying (residence) time + Purging time + venting time

For instance in the previous attached sheet

589.9 (Total time) = 19.6(pressurizing)+86(purging) +114 (residence) +2 (valve time) kettle idle time

Hence kettle idle time= 368 second

Please comment ■

Dear kj,

No, this is not complete:

The total time per cycle is the sum of the subsequent events during the unloading of a pressure vessel between the opening of the pressurizing valve until the closing of the discharge valve.

Therefore:

Total time per cycle = Pressurizing time +Conveying (vessel emptying) time + Purging time + valve time + filling time in case of a one vessel system.

Hence:

589.9 (Total time) = 19.6(pressurizing)+86(purging) +482.2 (vessel emptying) +2 (valve time) kettle idle time

Take care

Teus ■

Originally Posted by Teus Tuinenburg

Dear kj,

No, this is not complete:

The total time per cycle is the sum of the subsequent events during the unloading of a pressure vessel between the opening of the pressurizing valve until the closing of the discharge valve.

Therefore:

Total time per cycle = Pressurizing time +Conveying (vessel emptying) time + Purging time + valve time + filling time in case of a one vessel system.

Hence:

589.9 (Total time) = 19.6(pressurizing)+86(purging) +482.2 (vessel emptying) +2 (valve time) kettle idle time

Take care

Teus

Sir , i once again drag the matter to my previous query

what is major difference between discharge time and resdence time?

My perception is , discharge time starts after vessel is empty and pipeline is full with material

Residence time implies the material convey time , henec if we have to take the realy cycle time into consideration , that shall replace teh discharge time by residence time (convey time) balance time shall be idle time

please articulate ■

Dear kj,

It is a matter of definition.

Discharge time is the time that the vessel is being discharged.

Residence time is the time that a particle is traveling in the pipe line.

Have a nice day

Teus ■