Download - Pet Coke Best Practise
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Benchmarks, Facts and Methodology
for 100% Petcoke
By Tom Lowes
BCI Global Alternative Fuels Manager
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Scope of Paper
Information on petcoke
Problems of petcoke use
Typical examples of high petcoke use Facts relating to petcoke use
How to overcome the problem areas
Sustainable high petcoke use without loss of output
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Information on petcoke
All petcoke has low volatiles, with a maximum of
14%, while low (1.5%) S levels exist, they are
normally too expensive
Typical for use in Cement Production
Green delayed ~ 5% S, Hardgrove 50+ 10-14% Vols
Shot coke ~ 5% S, Hardgrove 40, 10-14% vols
Flexicoke ~ 6-7% S, Hardgrove 30 , 5-7% vols
A mix of Green/Shot normally used, howeverbecoming scarce at a good price
Future use of petcoke will need to look at 6.5% S
with 40 Hardgrove to get a good price ~ $10/tonne
less - Potential BCI saving ~ $40m pa.
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Perceived problems of petcoke use
Build up
Stops
Reduced clinker Increased SO2 emission (long kilns/Lepols)
Decreased refractory life
Clinker quality
Less stable kiln operation
Reduced output
Hassle
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Typical examples of high petcoke use
100 % petcoke in several Italcementi plants
All Asland preheater and Lepol kilns in Spain use
100% petcoke
France only 10% coal, rest petcoke and waste fuels Lafarge have a long dry and a wet process kiln on
100% petcoke
CBR Antoing precalciner with 50% petcoke/50%
waste - 1.8% SO3 on clinker, same size kiln asCauldon more output.
Votorantim, 12 works, 45% in 1998, 85% in 1999,
2000 target 95%.
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Typical examples of high petcoke use
How?
A thorough understanding,
Investment
Team Work, determination to beat the petcokedemon!!
This has been generally lacking in BCI to date
The Competitors Works are operating with:-
Precalciner - 2.5% SO3 in clinker Preheater - 2% SO2 on clinker
Lepol - Input 2% SO3 on clinker with 25% bleed
Long Kilns - 1.75% Input SO3 on clinker
Some kilns with Alkalies as low as 0.4 Na2O eq
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Facts relating to petcoke use
For 800 kcals/kg works and 5% S petcoke, SO3
increase in clinker is 1.4%
Typical raw meal SO3 is 0.1-0.8% SO3, ie @ 0.15-1.3 SO3 on clinker, some however pyrittic and goes
up stack
Trick is to control SO3 input and Alkali cycles to
ensure that Hot Meal has a @ max 3.5% SO3,otherwise you are in deep trouble.
It is this lack of control and the knowledge what to
do that has caused problems with petcoke usage in
the past
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Facts relating to petcoke use
All works different problems re petcoke, but
common problems with occasional exceptions
No real information on SO3 cycles Generally too high/worry about build up
No Process Engineer with sufficient time /knowledge
to get on top of them
No or far from optimal use of LINKman These are barriers to high uses of petcoke in BCI
So how do the others achieve 100%
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100% Petcoke - European Benchmarks
Precalciner - Antoing - same kiln size as Cauldon,
120 tph with 50% petcoke, 50% waste, extra 6%
output with 100% petcoke
1.8% SO3 on clinker with 50% petcoke
How:-
Automatic shift SO3 sample, burning adjusted if
volatilisation > 55%, 3.5% max target for SO3 60 blasters, numerous gas riser pressure tapping and
poke holes, focused shift cleaning
Works commitment to success, 90 men
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100% Petcoke - European Benchmarks
Vibo Valencia - Precalciner - 100% petcoke -
similar size kiln Cauldon, but small
preheater/precalciner, designed for 2000 tpd
100% petcoke 10 years
petcoke residue 6/7% + 90u, > 10% produced large
build up due to not being burnt in the precalciner and
reducing CaSO4 in the bed.
2.5% SO3 on clinker
3-3.5% SO3 hot meal, bad build up at 4-5%
40-60 blasters plus water jetting once per day
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100% Petcoke - European Benchmarks
Vibo Valencia
SrSO4 in raw meal, hence needed to lower
combinability temperature to avoid dissociation and
bunging up gas riser
CaF2 added to raw meal to 0.3% F on clinker, 11%
90u residue, 96% LSF,
High run time expert system, no operator over-rides
Firing pipe 1.5-2 m into kiln to help cooler operate by
nodulising dusty clinker in kiln.
Petcoke no problem a way of life. 115 men
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SO3 Cycles - A Practical Model
Dictated by Molar Ratio (MR)in Clinker
K2SO4 boiling point 1690 C, Na2SO4 >
However need kiln gases to evaporate
Above a MR of 1, ie for 0.6 Na2O and SO3 of
0.6*80/62 = 0.77 % SO3, CaSO4 forms, below a
MR of 1, K2CO3 forms
CaSO4 dissociated at 1450C and form hard
deposits and is a major constituent in forming
rings in the kiln
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SO3 Cycles - A Practical Model
All sulphates under reducing conditions decomposeto a certain degree, but CaSO4 breaks down at >
1050C in contact with solid C or say > 1000 ppm
CO.
Need to avoid free CaSO4 and reducing conditions.
Langbenite is the Double CaSO4 salt of K2SO4, ie
2CaSO4.K2SO4, which decomposes at 1520C.
Hence free CaSO4 can be eliminated from therecirculating gases providing MR with K2O is < 3,
providing that the kiln burning is under control
and the combinability temperature is < 1520C
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SO3 Cycles - A Practical Model
For successful high levels of petcoke utilisation it is
essential that:-
the SO3 in the hot meal is not > 3.5% This can be achieved via good kiln operation, but
the first essentials for a fighting chance are:-
SO3 in clinker is not > 3*K2O/1.175+Na2O*1.29 if the
combinability temperature is > 1450C and < 1520C If a MR > 3 is required to get 100% petcoke c.f. Na2O
equiv. < 0.4, then a combinability temperature 99 appear, the CT is > 1520C, which is
heading for build up and ring territory
In addition a poor LSF control will cause operator
to always aim for caution and operate at the
equivalent to > 1520 always to avoid flushes!!
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CT versus +90u AIR for Clinker LSF's
1350
1400
1450
1500
1550
1600
1 2 3 4 5
Acid Insoluble Residue
CT
95
97
99
101
Buiild up and rings
with poor LSF
control
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100% Petcoke - Practical aspects
With the CT and LSF under control, the kiln now
needs to be burnt to avoid high SO3 recirculation,
via overburning and reducing conditions, ie:-
Back End Oxygen high enough to avoid reducing
conditions in main flame, ie no CO at back end from
flame ~ 3.5% , CO max < 500ppm
1-2% Free lime
Precalciner O2 ~ 3.5% set at a level to ensure no
unburnt carbon in hot meal
Fuel ground fine enough for burnout in precalciner, cf
5-10% +90u, normally 10-12% okay for main burner
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100% Petcoke - Practical aspects
Avoid high SO3 (Max 55%) recirculation via:-
Flame central on axis and not impinging on burning
zone
Flame sufficient momentum to avoid reducing
conditions (OFT
Maximum use of LINKman
Adequate blending if not 100%
Deal with build up via
Installation of blasters - essential for 3.5 SO3 hot
meal, ~ 2.5% SO3 only possible without blasters
Gas riser pressure sensors , Poke holes
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100% Petcoke - Practical aspects
Before beginning carry out a study into what
affects SO3 cycles and how to control them, with
the help of BCTC
Without petcoke SO3 volatilisation,ie (SO3 hot meal - SO3 clinker)*100/SO3 hot meal, must
not be > 40%, otherwise full petcoke potential will not
be realised
The following graph gives petcoke targets as afunction of SO3 in raw meal, combinability
temperature and alkalies for a precalciner process,
which highlights the role both these raw material
characteristics
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SO3 in Clinker for %'s of 5% S petcoke as a
function of RM SO3 for 800 kcals/kg Precalciner
0
0.5
1
1.5
2
2.5
3
0.1 0.3 0.5 0.7
RM SO3
ClinkerSO3
100%
75%
50%
2 % SO3 max for 0.6% Na2O
eq clinker, with a CT > 1450
C and < 1520C
2.5% SO3 possible for a 0.6% Na2O
eq clinker with a CT < 1450CMax SO3 only 1.3% for a works
with Na2O eq 0.4 and a CT >1450 C but < 1520C
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100% Petcoke - Facts
Will it loose output
Yes in experimental phase, but can be won back
No gain with pain You never get ought for nought
With a bit of nouse, drive, process technology
problems should be overcome
Important for BCTC Benchmark for 50% of primefuel costs
Essential for zero fuel costs target
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100% Petcoke - Way Forward
Establish a target, based on sound principles and
develop and action plan to achieve it with BCTC
Get works commitment Develop a team approach
Need to be focused to win the petcoke battle to use
high levels without loss of output
Go for it as has Votorantim whos achievement isstrongly linked to to team work and technical
understanding
WE HAVE THE TECHOLOGY!!!
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But can we emulate Votorantim?
Quote from Votorantim, Success with petcoke is due to having the
people teamed up and fully committed