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COAL MILL FIRING SYSTEM

Inderect Firing

Existing Design : per unit Power Plant of 35 MW (Gross Out Put)

PC Boiler with Direct Firing

Boiler Capacity : 35 TPH

Design NPHR : 3083 kcal /kwh

Design Coal HHV (AR) : 4.100 Kcal/kwh

3.083

Coal flow rate = x 35 TPH

4.100

= 26,32 TPH

Proposed design of NEM has configuration :

* Direct firing: Each boiler with 3 units of Coal Mills, 2 in operation, 1 standby

* Mill capacity = 14 TPH each

Proposed design of REKIN has configuration :

* In-Direct firing: Two boilers with 3 units of Coal Mills, 2 in operation, 1 standby

* Mill capacity = 31.4 TPH each

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Inderect FiringConstraints :

1. Ramping Up requirement = 3 % load/ minute

= 1 MW / minute

Converted to Coal Consumption during acceleration is =

NPHR

= x 1 MW / minute

Coal HHV

3.083

= x 1 Ton / minute

4.100

= 0,75 Ton/minute

a) Ramping Up is From Turn Down Ratio (40 % Load) To 100 % load

or from 14 MW to 35 MW.

Rumping Up time 1435 = 21 minutes

or PC needs = 21 x 0,75

= 15,75 Ton

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b) Ramping Up from inhouse power ( 5 MW) to

full load (35 MW) :Ramping Up time 5

35 = 30 menit

Or PC needs = 30 x 0,75

= 22,5 Ton

2) Mill Maintenance :

Practically Mill need maintenance for 1 shift (8hours) per week (7 days).

We design spare time for mill maintenance at2 h/day or 14 h/week. So the operating hour is

(24 2) h/day = 22 h/day

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Mill Sizing

Indirect Firing for PC Boiler Mill Configuration follow this scheme :

Boiler

1

Boiler

2

321

Coal Mill

Pulverised coal

Bin 2

Pulverised coal

Bin 1

PC

Feeder BPC

Feeder A

PC

Feeder APC

Feeder B

NOTE :

Coal Mill Run 2 unit

Stand by 1 unit

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Coal Consumption

2 units Boiler Ramp-up to Full-Load= 2 x 26,32 TPH

= 52,64 TPH at PC Coal

2 Units Boiler Ramp up 5MW to 35MW

= 2 x 22,5 ton/ 30minutes= 45 ton/30minutes

Coal taken from PC bins during ramp up for 2 unit boiler is :

52,64= 45 ton/30minutes - ton/30 minutes

2

= 18.68 ton / minutes

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Mill Sizing

Mill configuration: 3 units, 2 operation, 1 standby Minimum mill capacity of 13,15tph is needed.

After ramp-up two mills will run to fill the PC bins of 18,68 ton whilesupplying boiler operation.

Coal needed from PC bin each boiler will be

18,68 ton

= 9,34 ton

2

PC bin is design to have retention time of 6 hours so that theminimum bin capacity is 60 ton/unit boiler.

Maximum time to fill PC to bin after ramp-up is 1 cycle of cement

plat start-up cycle, ie. 300 minutes or 5 h. So, based on 24h continues operation the minimum coal mill

capacity is 26.32 + (9.34/5) or 28.2 tph

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Mill Sizing

Mill configuration: 2 units with 2 operation Based on 24h continues operation the minimum coal

mill capacity is 26.32 + (9.34/5) or 28.2 tph

Mill Maintenance :

Practically Mill need maintenance for 1 shift (8 hours)per week (7 days).

We design spare time for mill maintenance at

2 h/day or 14 h/week. So the operating hour is

(24 2) h/day = 22 h/day

Coal Mill Size:24/22 x 28.2 tph = 30.75 tph

So the minimum coal mill capacity is 30.75 tph

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Mill Sizing

Indirect Firing for PC Boiler Mill Configuration follow this scheme :

Boiler

1

Boiler

2

21

Coal Mill

Pulverised coal

Bin 2

Pulverised coal

Bin 1

PC

Feeder BPC

Feeder A

PC

Feeder APC

Feeder B

NOTE :

Coal Mill Run 2 unit

Stand by 0 unit

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Equipment List

1. Coal Mill = 2 x 31 TPH

2. Raw Coal Silo = 2 x 150 Ton (5h retention)3. PC Bins = 2 x 60 Ton

4. PC Feeder = 4 x 15 TPH

5. Safety Equipment (CO2 inert) for 2 unit Boiler.