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Coal Fired Power plant Pulverizer CD is consuming more power

Coal Fired Power plant Pulverizer CD is consuming more power

(OP)
Dear All,

I am working in a 250MW Coal power plant. This power plant has 3 Tube mills. normally 2 are in service. These mills named as AB, CD, and EF.

The problem is whenever I take Mill CD in service. It consumes more power than other mills (Mill rating is 2350 kw, Mill AB and EF takes around 1150 kW. When operating Mill CD consumes 1300 kW. All these Mills are operating at same coal flow). In addition whenever mill CD is in service the PA Fan also consumes more power.

The way structure is designed the Mill CD is placed in between AB and EF. also the Common duct of PA fan air has similar kind of design. I attached a line diagram of mill and PA Fan. Please suggest what could be a potential issue with Mill CD. I have attached a line diagram of the Mill and PA fan.

Thanks

RE: Coal Fired Power plant Pulverizer CD is consuming more power

I presume that you have checked and the motors are actually identical? No rewinds that are not matched.
For that matter are the mills matched? Different screens or gaps perhaps.
And that you have taken field measurements at the motors to verify the power draw? and that it isn't a bad CT some place.
Does each feed have its own meter for coal flow? Have you done real weight measurement studies on them?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Coal Fired Power plant Pulverizer CD is consuming more power

Our mills ampere-age changes with ball loading.
I assume here that a tube mill is the same as a ball mill.

RE: Coal Fired Power plant Pulverizer CD is consuming more power

(OP)
Each Mill has their own Gravimetric feeder where the weight measurement done.

We done all the measurements. There are two units of 250 MW. both have the same problem..

Is it possible that PA is taking the least resistance path to Mill AB and EF? Is it possible to create artificial resistance in that.

Did anybody face similar problem?

RE: Coal Fired Power plant Pulverizer CD is consuming more power

There are a number of variables that we are not able to review remotely.

I am guessing the issue is due to an issue with the mill/its flow path, and not the mill’s motor [given the increase in PA power].

Despite this, I offer the following items for your to consider:

1. Review mills‘ condition. Confirm all three mills are “identical” through reviewing the mills’ specifications [grinding pressures, time since last overhaul, and wear rates etc]. Consider trailing swapping a motors from mills: AB, or EF; in CD.
2. Complete field measurement of relevant parameters [PA outlet pressure, mill PA pressure at: inlet, and outlet; mill’s: motor current/PF – confirm motor power, and grinding pressures etc].
3. Process feedback. Review how the mill throughput is determined [i.e. boiler temperature, somehow, or other], and confirm the feedback to all of the mills is identical [i.e. there is not a scaling error on mill CD etc, that is calling for extra throughput/PA etc].

Regards,
Lyle

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