I believe you have asked this question before of us.

About your system you have several issues;

you are asking us to provide all the answers for you at no charge but the problem requires an on site inspection by a supplier to solve your problems which include:

a. smaller delivery pipe to larger transfer OEM system to storage which reduces the systems delivery efficiency.

b. added compressed air to system at several points which becomes diffused and loses energy and aids nothing

c. a tilt trailer dumping system with unregulated flow.

d. siltation build up the pipe system at elbows.

e. system leaks and or damaged gaskets.

f. elbows-which slow air speed

g. static electricity build ups in some cases

An independent 6 inch rotary airlock feeder is your only real solution for this

with the properly sized pressure gradient generator which is what I believe I suggested previously.

If you cannot clean the pipes to begin with its a dead issue which is what I also told you.

Its fine to ask but help us to help you, to help us help you

You still have provided little useable information (to me anyway) which is why you need an onsite inspection from a distributor of pneumatic delivery systems which you are apparently and would have access to as you are a consultant doing work in compressed air delivery systems apparently.

lzaharis ■

5 mm lime normally does not go very well in dense phase. Your target rate is very ambitious considering the conveying properties of this size lime. You are trying to empty the tanker in 4 - 5 min.

If you give tanker details and existing airflow rates and unloading rates achieved further comments can be made. ■

Dear lotech,

Indeed, as Mr Mantoo already said, additional information is needed to evaluate your question.

Can you let us know:

-Air flows.

-Booster air injection locations in the pipeline and what booster air flows.

-Conveying rates and corresponding pressures.

Also the material (or particle density) is needed.

From these data, the material loss factor can be calculated.

Then, calculating the answers to your 6 questions is a matter of one click on a software button.

Mr Mantoo:

Calculating the unloading time:

unloading time = tons/(tons/hr)*60 = 12/50*60 = 14.4 minutes

Injecting booster air halfway a constant diameter pipeline is not the right way to go.

Booster air should be injected in the beginning of the pipeline and be accompanied by a diameter increase at the injection location.

From your post, I understand that you were able in the end to achieve the 50 tons/hr.

A preliminary calculation showed that this was probably possible at an airflow of 52 m3/min at 1.3 bar.

However, the additional information can generate more accurate figures.

Have a nice day

Teus ■

Dear Iotech,

I made some additional calculations, based on the just given information.

That the on board compressor of 350 cfm (9.9 m3/min) failed is understandable.

The lime particle size of 5 mm (5000 micron) results in a suspension velocity of approx. 14.8 m/sec, requiring an air velocity of approx 75 m/sec to keep the particles in suspension.

The second calculation with 2000 cfm from the beginning of the pipe line (including the 4” hose) and assuming 50 tons/hr at 2.5 bar resulted in a material loss factor of 5.8*10^-10, which is realistic compared to other materials.

The third calculation is with 2000 cfm and the 4” bulk trailer outlet and 4”hose replaced for 6”.

Then the pressure at 50 tons/hr reduced to 2.17 bar.

The air velocity ranges from 18 m/se to 63 m/sec

There is still sedimentation in the pipe line.

Increasing the air flow to 1.5 m3/sec (3175 cfm) and a full 6”pipe line, reduces the pressure drop to approx. 1.3 bar.

The air velocity ranges then from 44 m/sec to 90 m/sec.

There is no sedimentation.

The big particle size leads to the necessity of high velocities.

There is no way around that.

This results in high wear, especially in the bends.

Cover the bends with a closed, welded box around the outer diameter.

For more accurate conclusions, more accurate installation information and field operating data are required or consult your supplier.

All for now

Teus ■

I think all the tankers are rated at 2 barg and unloading at 2.5 bag is not recommended. Your bottle neck is the 4” outlet from the tanker which cannot be changed. Adding additional air in 6” pipe is acceptable as long as a known amount is added i.e. through a pressure regulator and a nozzle. I think you are injecting too much air in the system. To increase the system capacity and reduce the wear problem you can increase the last few meters of vertical section into the silo to 8”.

Unfortunately as I have said before this size cannot be easily dense phased. If it was a conveying vessel 4-5 barg conveying pressure with air boosters on the conveying ling could have proved successful.

Why are you after 50 tph for tanker unloading ? Tanker man is always happy for first one hour on site. If the silo is small and usage is high you should look into two separate unloading points into the silo with double the filter area. ■

Mantoo is right on and I have seen as many as 3 truck unloading stations. It boosts flexibility whilst reducing abrasion when you slow this down a bit. ■

Indeed you must be achieving 50 tph but it is at a price! Probably the unloading pipe & bends are constantly being patched. I am sure if you were happy with your system you wouldn't be asking for advice on this forum and I personally think you have been given good advice from respected forum members.

You need to reduce the conveying velocities to improve your system. If you reduce your air flow then you wont get your 50 tph so only other option is to increase the pipe size to reduce the conveying velocity. 50 tph might be your technical requirement but is it also a requirement that it has to be achieved with one tanker and not 2 tanker unloading simultaneously? ■