pet coke best practise

7/27/2019 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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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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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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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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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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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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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

pet coke best practise

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