The GMI Global, LLC, organized a two day conference, Cement Business and Industry (CBI), India and South Asia, at Mumbai, on 9-10 October 2013. The venue was Hilton International Airport Hotel. Dr J D Bapat gave a presentation on “Petcoke as Fuel for Cement production: Benefits and Challenges”. Good number of Indian and international organisations were represented in the Conference, some of which are mentioned below: Lafarge India CW Group Afghan Ministry of Mines Magnesita Claudius Peters Projects GmbH Ultratech Cement RNCOS Business Consultancy Ambit Capital National council for Cement and Building Materials HGH Systems Task force for Business and Stability Operations, US Department of Defense Geicycle Business, ACC PwC India Shree Cement RNB Cement DPTS Enterprises Reliance Cement World Business Council for Sustainable Development Zuari cement Prism Cement Tata Strategic Management Group The Indian Cement Industry today prefers petcoke as an alternate fuel for cement manufacturing for various reasons. The important among them are as follows: (a) High calorific value > 8,000 kcal/kg (3500-4500 kcal/kg conventional), low ash content and low volatile matter (but high sulphur content, up to 7%) (b) Resource conservation thru production of higher grade cement or utilisation of marginal and low grade raw materials (c) Saving in transport cost due to lesser fuel load (d) Saving in the initial cost (fuel cost constitutes about 48% of the cost of cement production) However the burning of petcoke also throws some challenges, like: (a) Low hard groove index: difficult to grind (b) Low volatile matter: difficult to burn (c) High sulphur: Condensation of sulpahtes and chlorides in preheater section results in jamming of process flows, termed as volatile cycles Dr Bapat, in his presentation, discussed how these challenges are effectively met by the cement industry. The delegates actively participated in q/a session, that followed.

1. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
BENEFITS & CHALLENGES
by
Dr J D BAPAT
http://www.drjdbapat.com
CBI INDIA & SOUTH ASIA
OCTOBER 9-10, 2013, MUMBAI

2. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
WHAT IS PETCOKE
● CONVENTIONAL FUEL: PULVERISED MINERAL COAL
● PETCOKE: A SOLID, CARBONACEOUS RESIDUE PRODUCED BY THERMAL
DECOMPOSITION OF HEAVY PETROLEUM FRACTIONS OR CRACKED STOCKS,
OR BOTH (ASTM 2005).
PETCOKE TYPES RELEVANT FOR CEMENT PRODUCTION:
● GREEN DELAYED PETCOKE: PRIMARY SOLID CARBONIZATION PRODUCT
FROM HIGH BOILING HYDROCARBON FRACTIONS OBTAINED AT TEMP OF 475-
490 C, OVER EXTENDED PERIODS OF 12-36 h (.) CONTAINS 4-15% VOLATILES
(IUPAC 1995) (.) DELAYED PROCESS COKE IS PRODUCED BY A SEMI-
CONTINUOUS BATCH PROCESS & ACCOUNTS FOR MAJORITY OF COKE
PRODUCTION.
● FLUID PETCOKE: PRODUCED BY CONTINUOUS FLUIDIZED BED PROCESS (.)
TYPICALLY CONTAINS LESS VOLATILE MATTER THAN DELAYED PROCESS
GREEN COKE (2.5-6%)
● IUPAC: INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY

3. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION

4. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
WHY PETCOKE
● HIGH CALORIFIC VALUE > 8,000 kcal/kg (3500-4500 kcal/kg CONVENTIONAL),
LOW ASH CONTENT & LOW VOLATILE MATTER (BUT HIGH SULPHUR CONTENT,
UP TO 7%)
● RESOURCE CONSERVATION THRU PRODUCTION OF HIGHER GRADE CEMENT
OR UTILISATION OF MARGINAL & LOW GRADE RAW MATERIALS
● SAVING IN TRANSPORT COST DUE TO LESSER FUEL LOAD
● SAVING IN INITIAL COST

5. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
CEMENT PRODUCTION COST ANALYSIS
BASIS: CONSIDER PROCTION COST AS 100
FUEL 48
POWER 36
RAW MATERIALS 14
STORAGE 2
--------------------------------------------
TOTAL 100

6. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
CHARACTERISTICS OF PETCOKE VIS-À-VIS CONVENTIONAL FUELS
FUEL ASH (%) VM (%) S (%) HGI CV (kcal/kg)
PETCOKE 0.4-1.0 2.5-15 6-7 37-45 8200-8300
BITUMINOUS COAL (I) 25-40 24-30 0.5-0.9 60-65 3500-4500
BITUMINOUS COAL (IMP) 7-15 25-31 0.6-1.0 48-50 6500-7000
LIGNITE 18-20 30-32 2-3 40-48 8000-8200
I = INDIA & IMP = IMPORTED

7. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
CHALLENGES IN PETCOKE BURNING
● LOW HARD GROOVE INDEX: DIFFICULT TO GRIND
● LOW VOLATILE MATTER: DIFFICULT TO BURN
● HIGH SULPHUR: CONDENSATION OF SULPAHTES AND CHLORIDES IN
PREHEATER SECTION RESULTING IN JAMMING OF PROCESS FLOWS,
TERMED AS VOLATILE CYCLES

8. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
CHALLENGES IN PETCOKE BURNING: DIFFICULT TO GRIND
●LOW HGI, HENCE DIFFICULT TO GRIND
●REQUIRES FINER GRINDING DUE LOW VOLATILES: 1.5% ON 90 MICRON
(INSTEAD OF CONVENTIONAL 15% ON 90 MICRON)
● POSSIBLE SOLUTION:
● TO REDUCE RESIDUE: INCREASE AIR SEPARATOR RPM IN VRM (.)
TYPICAL: REPLACING DIRECT DRIVE WITH V-BELT PULLEY DRIVE
● TO INCREASE VRM OUTPUT: REDUCE MILL INTERNAL DIA (.) TYPICAL:
40% REDUCTION (.) LOWER OUTPUT PARTLY COMPENSATED BY HIGHER
CALORIFIC VALUE
● FOR STABLE & UNIFORM BED FORMATION: INCREASING DAM RING
HEIGHT, WATER SPRINKLING & REDUCING TABLE SPEED

9. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
CHALLENGES IN PETCOKE BURNING: DIFFICULT TO BURN
● LOW VOLATILES MAKE PETCOKE DIFFICULT TO BURN i.e. LATE IGNITION
& LONGER FLAME
● HENCE PROPER MIXING OF FUEL & AIR ESSENTIAL
● IMPROPER BURNING CAN RESULT IN POOR QAULITY CLINKER
● POSSIBLE SOLUTION:
● USE HIGH MOMENTUM BURNER: TYPICAL – GRECO BURNER

10. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
HIGH-MOMENTUM GRECO BURNER
EXTERNAL AIR
TANGENTIAL AIR
PETCOKE
DISPERSION AIR
COOLING AIR
MIXING AIR

11. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
HIGH MOMENTUM BURNER
● OPERATES WITH OUTER, HIGH-MOMENTUM FLOW OF PRIMARY AIR (EXTERNAL AIR) (.)
HIGH MOMENTUM AND HIGH EXIT VELOCITY (IN JETS) RESPONSIBLE FOR THE SLIM, FIRM
SHAPE OF BURNER FLAME
● SWIRLING AIR (TANGENTIAL AIR & DISPERSION AIR) INTENSIVELY MIX PULVERIZED
COAL RESULTING IN RAPID & STABLE FLAME FORMATION
● SHORTER & RADIENT FLAME
● Nox REDUCED DUE TO LOW PRIMARY AIR AT HIGH MOMENTUM
● FLAME GEOMETRY EASY TO CONTROL, AS SEEN FROM KILN SHELL THERMAL PROFILE
● ALL BURNER CHANNELS ARE SEPARATELY ADJUSTABLE & THEIR FUNCTION CAN BE
CLEARLY FOLLOWED
● GRECO BURNER IS DESIGNED TO MINIMISE WEAR

12. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
HIGH MOMENTUM GRECO BURNER: TYPICAL DESIGN PARAMETERS
● PRIMARY AIR PRESSURE 2000 – 5000 mm WG
● PRIMARY AIR EXCESS FACTOR 4 – 10%
● FUEL CONVEYING AIR 2.5 – 3.5% OF STOICHIMETRIC AIR
● FUEL/AIR RATIO 3.2 – 6 kg/Nm3 AIR
● SPECIFIC BURNER MOMENTUM* 6 – 14 N/MW BURNER THERMAL POWER
*NOTE: SPECIFIC BURNER MOMENTUM =
(PRIMARY AIR MASS FLOW, kg/s) (PRIMARY AIR VELOCITY, m/s) / (BURNER THERMAL POWER, MW )

13. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
CHALLENGES IN PETCOKE BURNING: VOLATILE CYCLES
● ALKALIES (K2O/Na2O), LIME FROM RAW MEAL & SO2 FROM PETCOKE
BURNING CAN COMBINE IN COLDER ZONES, NAMELY IN KILN INLET &
RISER DUCT TO FORM COATING (.) COATINGS EXERT MECHANICAL &
THERMAL STRESS ON REFRACTORIES & REDUCE THEIR LIFE (.) SO2 FROM
PETCOKE BURNING SHOULD BE PREVENTED TO LEAVE THE KILN
● POSSIBLE SOLUTIONS:
● IMPROVE REFRACTORY LINING & PROVIDE BLASTERS TO CLEAN
COATING
● REDUCE MATERIALS RESIDENCE TIME IN KILN
● INCREASE COAL RESIDENCE TIME IN CALCINER
● IMPROVE RAW MIX DESIGN
●ALLOW SUFFICIENT OXYGEN AT KILN INLET

14. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
CHALLENGES IN PETCOKE BURNING: VOLATILE CYCLES
● SULPHUR-TO-ALKALI RATIO (Q) DECIDES THE TYPE OF COATING
FORMED
Q = (%SO3/80) / [(Na2O/62) + (K2O/94) – (Cl/71)]
● SULPHUR EXCESS, Q > 1 = HARD COATING
● ALKALI EXCESS, Q < 1 = SOFT COATING

15. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
CHALLENGES IN PETCOKE BURNING: VOLATILE CYCLES
● TO PREVENT SO2 GAS LEAVE THE KILN, IT MUST COMBINE WITH OXIDES OF Ca,
Na & K & LEAVE WITH CLINKER AS SULPAHTES (.) IN BURNING ZONE, SUFFICIENT
LIQUID MUST BE FORMED FOR THESE REACTIONS TO ACCUR (.) EASE WITH WHICH
THESE REACTIONS TAKE PLACE IS TERMED AS COMBINABILITY OR BURNABILITY (.)
● WITH HIGHER SULPHUR FROM FUEL, IT IS DESIRABLE TO IMPROVE BURNABILITY
OR REDUCE COMBINABILITY TEMPERATURE (.) DESIRED CHANGES IN RAW MIX
DESIGN COULD BE MADE IN LINE WITH THE FOLLOWING FORMULA:
● COMBINABILITY TEMPERATURE, CT, (deg C) = 436 +21(%AIR) + 10(LSF) + 3(RAW
MEAL RESIDUE ON 150 MICRON) + 32(AM) - 20(%SO3) – 20(FLUORIDES)
● SUFFICIENT EXCESS O2 (> 2%) ALSO REQUIRED FOR REACTIONS TO COMPLETE:
CaO + SO2 + ½O2 = CaSO4
● SULPHATE IN CEMENT EXPRESSED AS SULPHURIC ANHYDRIDE OR SO3 = SO4 x
0.833 (.) SO3 IN CLINKER MAY BE MAINTAINED AT 1.5-2%

16. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
CHALLENGES IN PETCOKE BURNING: VOLATILE CYCLES
●IMPROVING REFRACTORY LINING
● PROVIDE SILICON CARBIDE BASED CASTABLE REFRACTORIES AT THE
KILN INLET & RISER DUCT (.) THESE REFRACTORIES FORM VITRIOUS
LAYER ON THE SURFACE WITH LESS ADHERENCE PROPERTIES
● REDUCING MATERIALS RESIDENCE TIME INSIDE KILN
● REQUIRED FOR MORE FRESH RAW MATERIALS REACTING WITH SO2
FROM PETCOKE TO FORM SULPHATES (.) IT IS DONE BY INCREASING KILN
SPEED
● INCREASING COAL RESIDENCE TIME IN CALCINER
● REQUIRED FOR COMPLETE COMBUSTION (.) IT IS DONE BY INCREASING
CALCINER HEIGHT

17. PETCOKE
AS
FUEL FOR CEMENT PRODUCTION
PROBLEMS FACED IN PETCOKE BURNING
● INCREASE IN NOX EMISSIONS: HIGHER CV CAUSES HIGHER “IN-FLAME”
TEMPERATURES & CREATES HIGHER NOX EMISSIONS, REQUIRING NOX
CONTROL TECHNOLOGIES TO STAY WITHIN REGULATORY EMISSION LIMITS
● HIGHER POWER INCREASE IN FINISH MILLS (kwh/t): LONGER BURNING ZONE
(LESS VOLATILE FUEL), PRODUCES SMALLER CLINKER PARTICLES, MORE
DIFFICULT TO GRIND
● HIGHER SPECIFIC HEAT CONSUMPTION (kcal/kg): HIGHER O2 LEVELS REQUIRE
MORE SECONDARY AIR TO BE HEATED, INCREASING SP. HEAT CONSUMPTION
● POWER INCREASE ON PREHEATER & COOLER FANS: TO MAINTAIN ADEQUATE
O2 LEVELS
● CHANGE IN KILN FEED-TO-CLINKER FACTOR: DUE TO VERY LOW ASH, MORE
KILN FEED IS REQUIRED PER UNIT MASS OF CLINKER(.) KILN FEED
COMPOSITION ALSO CHANGES
● ABRASIVENESS REQUIRES HIGHER MAINTENANCE ON COAL MILL
● REFRACTORY LIFE AFFECTED DUE TO COATING FORMATION

18. THANKS!!!
drjdbapat.com