Re: Max. Silo Discharge Rate

Posted on 17. Apr. 2007 - 05:11

There are a number of models from which you can determine

silo discharge rate.

Beverloo equation - funnel flow

Johanson equation - mass flow

It is very much dependent on silo cone geometry, outlet size / shape and material properties. For cement which is an aeratable powder one must also consider influence of air upon discharge rate.


Re: Max. Silo Discharge Rate

Posted on 17. Apr. 2007 - 05:45

Dear Henk-Jan,

A 20000 tons inverted cone cement silo is a huge one.

In 1994, I installed 4 inverted cone cement silos of approx 9000 tons capacity with the neccessary pneumatic conveying equipment.

The outloading was 150 tons/hr for each silo using 2 of the in total 6 outlets.

It proved to be easy to reach 150 tons/hr with 1 outlet

(but then the unloading was asymetrical)

If the 6 outlets could work simoultaneously, the capacity should be already 150 * 6 = 900 tons/hr.

A little bit bigger outlets with sufficient aeration should do the trick.

Getting the cement to another point with 1200 tons/hr is another challange.

We are interested




Lyle Brown
(not verified)

Re: Max. Silo Discharge Rate

Posted on 17. Apr. 2007 - 11:54

Check the calcs.

Tunra (Australia) have plenty of notes on silos in general and including prediction of discharge flows.

I was once told as a rule of thumb, assuming you get the hopper geomety correct, so that you obtain flow (that is rather than blockages) the hopper will flow sufficiently.

I suggest however, you do the calcs and confirm.

Re: Max. Silo Discharge Rate

Posted on 18. Apr. 2007 - 04:52

Dear Henk, You can have 1200 tph Discharge rate from inverted cone silo,there are good nos. of similar silos are there on the basis of Ibau-Hamburg Design. For 20,000 t cap. silo,you can have the dia. of silo between 22 to 25 m and very well give 6 extraction points@200 tph,the flow you can very well control by flow control gates.If ,you need detailed design drawings showing arrangement of entire system(except silo CIVIL design) of equipment please let us know.


Anil Seth

Re: Max. Silo Discharge Rate

Posted on 19. Apr. 2007 - 10:21

Thanks everybody for the replies!

I agree with some posts that eventually the specialist has to do the calcs, but for the purpose of preliminary/overall design, I was looking for confirmation / references what discharge rates can be achieved these days.

The silos will be close to the warf and supply to a 1200 tph shiploader by means of a conveyor belt. silos will probably have 25 m. diameter.


I'm very interested in the design drawings you have. Do you have some references of silos with mentioned discharge capacities? Otherwise I will give Ibau-Hamburg a call.



Re: Max. Silo Discharge Rate

Posted on 19. Apr. 2007 - 10:36


Getting the cement to an other point will be done by conventional troughed conveyor. Focus will have to be on a very good chute design. What "challenges" do you foresee?



Re: Max. Silo Discharge Rate

Posted on 19. Apr. 2007 - 11:53

Dear Hank,Thanks for your reply.I shall provide you the referances with in a day or two.Please note that I have worked with Ibau's collaborator in India and have designed silo feeding and discharge system for more then 20 plants in India and abroad.If you need I can design the entire system like--

1. unloading of cement by trucks/by rail in to the pit.

2.Extraction of cement from pit to the boot of silo feeding bucket elevator.

3.Silo discharge system@1200 tph.

4. Conveying system at the jetty

5.Coveying of cement by flat/pipe conveyor up to ship loading point.

Since the silo location is near to wharf where bering capacity of soil is generally poor,we advise you to go for Dome silo or flat storage.In the meantime please send me your mail id enabling me to send you information.

Regards, Anil Seth


Re: Max. Silo Discharge Rate

Posted on 19. Apr. 2007 - 04:21

Henk Jan,

1200 tons/hr shiploading is meant for big ships (40000 -50000 dwt ?) and high annual throuputs.

Big ships start loading at a level of approx. 15 m above waterlevel.

The silo is emptied at ground level on to a troughed conveyor belt (not my favorite tool for cement, because of the fluidizabilty of the cement)

Creating an elvation of 15 m-plus over a short distance, for f.i. a loading airslide, would require a vertical screwcoveyor or a bucket elevator, various transferpoints, dust control, etc.

Make a preliminary design of all known and used options and compare the various designs on investment, reliability and operating costs and then take your decision.

Pneumatic loading a big vessel through loading holes in the hatches is done frequently.



Maximum Silo Discharge

Posted on 19. Apr. 2007 - 07:53

TUNRA and Jenike & Johansen have formulae based on mass flow bins and flow-function tests. The mathematics sound like magic.

If your bin is not mass flow then you will get funnel flow of some description. Flow could vary from ZERO to a dump flooded flow which could be 8 to 10 times the TUNRA calculation. See attached notes.

Sgt. John Rozentals

CEO Bionic Research Institute