Originally Posted by korisnik

Hi all,

I have a theme for an essay at technical faculty about

coal preparation for coal fired thermal power plant.

There is one question that arises when I run sensitivity

analysis of crusher power on feed and product size.

So for power consumption I have used Bond equation:



but sensitivity analysis yields that power consumption

is affected only in very small scale by feed size, for

instance power consumption for constant product

size of 0.1 micrometers and feed size of

1 and 100 millimeters equals 11 kWh/ton

and 13 kWh/ton (for feed size respectively).

[IMG]http:

//img413.imageshack.us/img413/6223/20391192.th.png[/IMG]

Therefore I suspect that this Bond equation is

valid for only limited range of feed and product

size, or power consumption of crusher could be

estimated in other more precise way. If you have

any suggestion or solution to this problem please

comment.

Thanks in advance.

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your product size is too small.

Any coal coming from a stock pile usually goes through a sizer before it goes to the bunkers and then is gravity fed to scales and then to a hammer mill prior to being blown into the boiler for combustion.

1. coal is delivered by rail to power plant via rail or barge or truck

and then conveyed to the stockpile

2. coal is fed to coal sizer sizer

(a) sized coal is gravity fed to conveyor then to coal bunkers via

(b) cross feed conveyors to fill bunkers via gravity.

3. coal bunker.

4. gravity feed to scales.

(a) measured feeder delivery to:

5. gravity feed to hammer mill above the individual blower.

6. individual paddle fan blows coal fines to boiler for burning in the boiler air stream.

7. fly ash waste is pumped from boiler wet tub to drying and for eventual. disposal.

Why are you grinding that small when most of the if not all of the bituminous coal

ground for a pulverized coal boiler is in the range of 20-40 mesh?

You are asking for trouble simply from a flash explosion point of view due to spontaneous combustion.

lzaharis ■

If we apply the figures to staged comminutions it appears that to crush/grind from 100mm to 1mm consumes 2kWh/tonne. What says the Bond Equation about that?

You can read up about size reduction criteria in books like Wills, Taggart or Prior. The science of rock breaking hasn't changed all that much since Eli Whitney Blake built his first jaw crusher (mobile) to speed up the construction of Tobacco Road around the time of the Civil War. So you can read in confidence. Of course there are many detail developments but the actual smashing about isn't much changed.

Good luck with the essay. ■

Bond's Formula is derived from experimental data that was done utilizing a small scale mill. It is valid exactly for the size of equipment that his experiments utilized. The formula is almost used exclusively to size equipment because it is simple and because a lot of data exists. I believe that there are different correction factors available for different applications and different sized equipment, but am not sure where to find.

There are also different formulas available as well from other people. Kick, Rittinger, etc that are considered more valid over a certain range of product sizes. I would recommend trying to get the Bond's papers first and reading through them.

As far as the 11 and 13 kW-HR/Ton, it is still a ~15% increase in power consumption to crush the material and depending on your capacity, it will still add up. ■