Pagi Prem,

To:

1)It might work if you fit a couple of belt scales. If the mine has a sampling facility, why not, yours can be discarded in favour of the weighers. Sampling is only going to tell you what you had after a couple of days in the oven. Weighing will tell you what you are putting through right now;

2)Chevron;

3)Your 44,000tpile seems large for what you want to achieve. A faster slew will jettison material better and the drop height could be lessened to alleviate dust. Your wheel loader driver would also feel/be safer with a lower pile and you can run the trucks nearer the pile edge etc.

How far are you from Ombilin? Finlays put quite a few of their radial stackers around that neck of the woods. ■

Hello,

The blending operation implies mixing of different materials. The word homogenisation implies mixing of different grades of one material. Functionally the blending or homogenisation operation is same. Here word blending has been used for ease of writing / reading.

Simultaneous reclaiming of coal - A from its stockpile, and coal - B from its stockpile, and then discharging them on common outgoing conveyor, to achieve mixing is not uncommon. Often we find the material coming from 2 / 3 mining points getting mixed on single conveyor, to get some degree of blending without extra cost.

In above process coals are getting mixed. Therefore, it is obvious that coals being blended as above is more homogeneous compared to feeding coal – A one time, and coal – B other time. Such mixing signifies ‘instantaneous’ mixing. In your case you have introduced ‘mixing with respect to small time duration also’ by conical pile and then again reclaiming it for use. If you introduce belt weigher on each mixing conveyor with special automatic control logic for yes / no situation, then the system will have protection against negligence / carelessness, etc. i.e. protection against operational faults. Your proposed system relies on consistent manual care that both conveyors are conveying specific quantity all the time.

Regular blending system creates blended stockpile, by stacking materials as they are coming during say two weeks time. The stacking operation is done in specific pattern of layers, complementary to the type of reclaiming operation. Then reclaimer being used cuts all the layers at a time, and thereby finally reclaimed material represents specific mixture of ‘Material – A, average of 2 weeks’ and ‘Material – B, average of 2 weeks’. Thus statistical reliability of quality of such blending is more superior. Such system is inevitable when blended materials are getting converted into high class product.

In your case, less ideal blending of coal implies more frequent adjustment of feed-rate into boiler, and some (marginal ?) reduction in thermal efficiency of the boiler. You can discuss with the boiler supplier.

As I remember, a coal handling plant in USA (somewhere near Newyork) has 2 stockpiles, each with its own bucket wheel reclaimer and reclaiming conveyor. Both the reclaiming conveyor (and their machines) work simultaneously to discharge onto outgoing single conveyor at the stockyard end. That means the outgoing conveyor will have mixture of coal – A and coal – B. The knowledgeable or concerned people can correct my this information, if need be.

In this installation having bucket wheel reclaimers, getting properly mixed material will be more demanding such as when machine – A is reclaiming top bench, and that time machine – B should also reclaim top bench, etc. The mixing proportion is likely to be more erratic during reclaiming of stockpile ends. This operation phase influence will be proportionately less with respect to total operational time.

It is to noted that material coming from mine is created by nature. So it will always have variations in characteristics. The particular grade (when being mentioned in one figure) from particular mine implies average quality. So this aspect will have adverse effect on the blending efficiency when both coals are worst or best, and simply mixed on conveyor.

Above describes relative merits. Your proposed system is also doing blending as per its inherent features.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 2012.

Author of Book: ‘Belt Feeder Design And Hopper Bin Silo’

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India. Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Thinking again: I would use 2 Stamler machines on opposite sides of the spine conveyor. Put the 2 weighers downstream of the discharges and that's it. You can tip directly onto the Stamler apron until it gets flooded and only then do you need to tip onto a very nearby surge pile(s). This saves wheel loader effort and does away with 2 belt conveyors.

Then you can introduce a diverter after the blending 1 conveyor to load trucks. The coal passing between truck positioning can then be diverted to your radial stacker for throwing around the 44,000t pile.

I can't understand why you need a large pile though. There is no shortage of haulage in Indonesia. Pile life is 44 hours. If the power plant is out you have to stop both mines transport systems and probably the mines themselves. If one mine fails then the other one has to stop as well because of blend impasse. Miners and process engineers, to a large extent, have failed to realise that mobile storage is more flexible than fixed storage. Trucks and trains can be filled and parked ready or moved somewhere else, and fast. Supermarkets can supply hundreds of shops with a range of thousands of products within two days from manufacture, Why? Because they keep it moving. After a spell in large scale retail logistics I recognised that bulk handling is really in the Dark Ages. Ask any cow in Europe when the milk it produced on Monday afternoon will get to the point of sale and it will tell you Tuesday morning. The same is true for that cow's yoghurt, butter and cheese.

Congratulations for realising that there are more effective methods to blend stuff without employing tremendous CAPEX which only works half of the time and when it does get started it inevitably goes down. Along that theme, your system requirement borders on an emergency reclaim situation plus a blender. You/we have killed 3 birds with 1 stone.

Well done. ■