WELCOMEWELCOME TO TO

THE PRESENTATIONTHE PRESENTATION ONON

MILLING SYSTEMMILLING SYSTEM

NTPC - SIMHADRINTPC - SIMHADRI

MILLING PLANT SPECIFICATIONMILLING PLANT SPECIFICATION• TYPE OF MILL XRP 1003 (MPSP)• NO OF MILLS PER BOILER 9• NO OF MILLS REQUIRE FOR 6

FULL LOAD• MILL CAPACITY 66.2 TPH• PF FINENESS 70% THROUGH -200

MESH• MILL SPEED 42 RPM• MILL MOTOR RATING 525 KW, 3.3 KV, 589

RPM • MILL INLET AIR TEMP 230 °C• PA FANS (COMMON) 2 NOS• SEAL AIR FANS (COMMON) 2 NOS

 

COAL CHARACTERISTICS

• GCV 3450 – 3600 KCAL/KG

• ASH > 40 %

• VM 20 – 24 %

• CARBON 20 – 33 %

• MOISTURE 12 – 16 %

• HGI 55

CONSTRUCTION & DESIGN FEATURESCONSTRUCTION & DESIGN FEATURES• SIMHADRI IS THE FIRST COASTAL BASED COAL FIRED

THERMAL POWER PROJECT OF NTPC

• BHEL HAS PROVIDED MILLS WITH MPSP (MILL PLANT SUPER PERFORMANCE) SYSTEM AT DESIGN STAGE, FIRST TIME IN NTPC

• TALL TOP CLASSIFIER• MODIFIED VENTURI ( ALSO CERAMIC LINED)• FLAP TYPE MILL DISCHARGE VALVE (CERAMIC LINED)• BEARINGLESS SPRING LOADING• DOUBLE BEARING JOURNALS• MODIFIED VANE WHEEL ASSEMBLY• CERAMIC LINED BENDS, INNER CONE, ORIFICES• CERAMIC CARBIDE DUO CAST GRINDING ROLLS

• SPRING LOADED FLOATING FOUNDATION• HIGH CHROME BULL RING SEGMENTS• BURNER INLET ISOLATION VALVES• FEEDER DISCHARGE ISOLATION VALVE• DUST GAURD SEAL• JOURNAL TILTING

CONSTRUCTION & DESIGN FEATURESCONSTRUCTION & DESIGN FEATURES

CE VS MPSP DESIGNCE VS MPSP DESIGN

S.NO PARAMETERS CE MPSP

1 GRINDING ROLL (GR) NI-HARD DUO CAST WITH CERAMIC CARBIDE

INSERTS

2 BULL RING SEGMENT (BRS) NI-HARD HIGH CHROME

3 VANE WHEEL 45 ° 30 °

4 EXPECTED RUNNING HOURS 3000 11000

5 PM SCHEDULE BI-WEEKLY FOUR WEEKLY

6 COST OF GRINDING ELEMENTS (GR + BRS)

~ 3 LACS ~ 13 LACS

MILL MAINTENANCE PRACTICES & STRATEGIES

• REGULAR AND PERIODIC PREVENTIVE MAINTENANCE

• CONDITION / WALKDOWN BASED MAINTENANCE

• PLANNED MAINTENANCE (MAJOR)

• BREAKDOWN MAINTENANCE

• TIMELY PLANNING OF SPARES AND CONTRACTS

• OPTIMIZATION / MODIFICATIONS

MILL MAINTENANCE PRACTICES & STRATEGIES

• REGULAR AND PERIODIC PREVENTIVE MAINTENANCE

• CONDITION / WALKDOWN BASED MAINTENANCE

• PLANNED MAINTENANCE (MAJOR)

• BREAKDOWN MAINTENANCE

• TIMELY PLANNING OF SPARES AND CONTRACTS

• OPTIMIZATION / MODIFICATIONS

MILL PERFORMANCE FACTORSMILL PERFORMANCE FACTORS

• MILL CAPACITY• PF FINENESS• MILL REJECTS• MILL OUTLET TEMPERATURE• MILL BOWL DP• MILL POWER CONSUMPTION

• MILL CAPACITY DEPENDS UPON FOLLOWING FACTORS

HARD GROOVE INDEXHARD GROOVE INDEX

TOTAL MOISTURE CONTENTTOTAL MOISTURE CONTENT

AIR FLOWAIR FLOW

PF COAL FINENESSPF COAL FINENESS

MILL PERFORMANCE FACTORSMILL PERFORMANCE FACTORS

• PULVERISED COAL FINENESS

THE RECOMMENDED PF COAL FINENESS IS ABOVE 70% AND 98.0 % THROUGH 200 MESH AND 50 MESH

RESPECTIVELY

INITIAL FINENESS ACHIEVED : 60 TO 70% THROUGH INITIAL FINENESS ACHIEVED : 60 TO 70% THROUGH 200 MESH 200 MESH &MORE THAN 2% RETENTION ON 50 MESH&MORE THAN 2% RETENTION ON 50 MESH

ADJUSTMENTS DONE DURING PG TEST:ADJUSTMENTS DONE DURING PG TEST:

• INCREASE IN SPRING COMPRESSION : 9.5 TO 11.5 TONS• INCREASE IN VENTURY COLLOR HEIGHT : 50 MM • REDUCTION IN INVERTED CONE CLEARANCE : 30 MM• REMOVAL OF AIR RESTRICTION PLATE • CLASSIFIER SETTING : FROM 3 TO 5

MILL PERFORMANCE FACTORSMILL PERFORMANCE FACTORS

• MILL REJECTS

DENSITY BASED SEPARATION ON THE BOWL LEADS TO DENSITY BASED SEPARATION ON THE BOWL LEADS TO MILL REJECTS MILL REJECTS

AT SIMHADRI, THE MILLS ARE REJECTING THE AT SIMHADRI, THE MILLS ARE REJECTING THE MATERIALS WHICH ARE DIFFICULT TO GRIND LIKE MATERIALS WHICH ARE DIFFICULT TO GRIND LIKE STONES STONES AND PYRITES. THE TOTAL MILL REJECTS ARE AND PYRITES. THE TOTAL MILL REJECTS ARE AROUND 2-10 AROUND 2-10 KG PER HOURKG PER HOUR

STONE IS VERY LESS IN RAW COALSTONE IS VERY LESS IN RAW COAL

MILL PERFORMANCE FACTORSMILL PERFORMANCE FACTORS

• MILL OUTLET TEMPERATURE

GENERALLY THE RECOMMENDED VALUE OF MILL GENERALLY THE RECOMMENDED VALUE OF MILL OUTLET TEMPERATURE IS 100-X (X = % OF OUTLET TEMPERATURE IS 100-X (X = % OF VOLATILE VOLATILE MATTER IN THE COAL)MATTER IN THE COAL)

AT SIMHADRI WE ARE MAINTAINING THE MILL AT SIMHADRI WE ARE MAINTAINING THE MILL OUTLET TEMP AT 75 TO 85°C AS THE VOLATILE OUTLET TEMP AT 75 TO 85°C AS THE VOLATILE MATTER IN MATTER IN OUR COAL IS LESS AND THE MOISTURE OUR COAL IS LESS AND THE MOISTURE IS HIGHIS HIGH

MILL PERFORMANCE FACTORSMILL PERFORMANCE FACTORS

• MILL BOWL DIFFERENTIAL PRESSURE

THE RECOMMENDED VALUE BOWL DP IS 300 MMWC THE RECOMMENDED VALUE BOWL DP IS 300 MMWC AT FULL LOAD AT FULL LOAD

HIGHER ASH CONTENT, HIGHER REJECTION, LOW AIR HIGHER ASH CONTENT, HIGHER REJECTION, LOW AIR FLOW, EXCESS FINENESS AND ERODED MILL FLOW, EXCESS FINENESS AND ERODED MILL

INTERNALS INTERNALS LEAD TO HIGHER BOWL DPLEAD TO HIGHER BOWL DP

• POWER CONSUMPTION

THE POWER CONSUMED BYTHE POWER CONSUMED BY THE MILL MOTOR THE MILL MOTOR SHOULD NOT EXCEED THE SHOULD NOT EXCEED THE RATED CAPACITY. AT RATED CAPACITY. AT SIMHADRI THE CURRENT DRAWN BY MILL MOTOR AT SIMHADRI THE CURRENT DRAWN BY MILL MOTOR AT FULL LOAD IS WELL WITHIN THE LIMITSFULL LOAD IS WELL WITHIN THE LIMITS

MILL PERFORMANCE FACTORSMILL PERFORMANCE FACTORS

IT IS ALWAYS SUGGESTED THAT BOWL MILL PARAMETERS SHOULD BE OPTIMIZED FOR SATISFACTORY PERFORMANCE OF THE MILLS AND TO IMPROVE THE LIFE OF MILL COMPONENTS

AT SIMHADRI PG TEST IS JUST COMPLETED. OPTIMIZATION OF SPRING COMPRESSION IS IN PROGRESS

OPTIMISATION OF BOWL MILL PARAMTERS

THE FOLLOWING MODIFICATIONS WERE DONE WITHOUT AFFECTING THE MILL DESIGN/FLOW CONDITIONS (DURING ERECTION & COMMISSIONING) :

LUBE OIL SKID RELOCATION

INCREASE OF DISCHARGE PIPE DIA OF LUBE OIL SYSTEM FRO ¾” TO 1”DURING COMMISSIONING

LOCKING SYSTEM MODIFICATION OF JOURNAL STOP BOLT

EXTENSION OF SPRING SHAFT

PROVISION OF ON-LINE MILL REJECT CHOKING REMOVAL PORT

MODIFICATIONS

DATA FOR MILL PERFORMANCE FACTORS AT SIMHADRI

S.NO. DESCRIPTIOIN RATED PARAMETERSACTUAL PARAMETERS

1 ) Capacity66.3 tph 65

02)Fineness X Passing through200 mesh) >70% >80%

Retention on 50 mesh 2.00% <1%

03) Mill outlet Temp. 87 deg c 80-85 deg c

04) Bowl DP Maxm 300 mm WC 300 to 340 mmWC

05) Mill Amperage Mill 137A 120-125A

06) Rejects   Low

07) OTHERS,    

Volatile matter 22min <22%

Moisture 12.00% .12-14 %

Mill air inlet temp. 265 deg c 250 -270 deg c

PA Flow 95 tph 90-105 tph

HGI 55 >55

GCV 3300 Kcal/kg ~3300 k cal/kg

Ash ~40 >40

THANK YOUTHANK YOU