This document discusses considerations for firing petcoke in kilns. It notes that petcoke has higher sulfur content than coal which can increase build-ups in the kiln system. It also has lower volatiles and ash. The document provides rules for utilizing petcoke, including maintaining appropriate alkali to sulfur ratios and ensuring proper coal and petcoke preparation and feeding. It discusses grinding petcoke to a finer particle size. Combustion considerations include maintaining sufficient oxygen levels. Refractory failures can result from high temperatures or sulfur/alkali effects from burning petcoke. Denser refractories with additions like zircon or AZS castables can improve buildup resistance.

1. Petcoke firing in Kiln
K.P.PRADEEP KUMAR

2. Petcoke -shotcrete

5. Petcoke properties
The use of petcoke as a thermal energy source offers potential for
reduction of
thermal energy costs. However Petcoke has different properties from
coal which must be take into account:
• Petcoke has in general a higher sulfur content compared to normal
coal which can enhance the formation of build-ups in the kiln system.
• Petcoke has in general low volatiles and ash content.
• The volatiles of petcoke are not released below 900°C. The volatiles of
petcokeare mainly methane compared to >50% aromatic compounds in
bituminous coals. The aromatic compounds present in the coal combust
more easily
• Petcoke burns from the outside and does not explode. This causes the
problemof precalciner burnout and temperature increase in the bottom
cyclone stage
• The maximum petcoke substitution rate is related to the amount of the
circulating elements - sulfur, alkali and chlorine - which are contained in
the fuel and raw meal inputs
• The Hardgrove index of petcoke is generally lower than of coal

6. Petcoke rules
The following rules are important for the utilization of petcoke in calciner kilns:
• Alkali / sulfur
SO3 inputs <2.0% (clinker basis);
Molar ratio of Alkali / sulfur ≥ 0.4
• Coal / petcoke preparation
Controlled mixing from two feed hoppers
• Coal mill
o Petcoke fineness R 90µm <3% and R 200µm <1%
o Determine the coal mill output by trial (Hardgrove index can be
misleading, greasing effect)
• Kiln feed (raw material)
o Kiln feed uniformity
LSF, STD <1.2
SR, STD <0.04
AR, STD <0.04
o Medium term (10 min) mass-flow fluctuations <±0.5%
• Fine coal dosing
o Short term mass flow fluctuations (10 sec) <±1%
o Fluctuations in calorific value of coal/petcoke mixture <±1%
o Pressure fluctuations in transport duct at burner <±10% of average
pressure
• Combustion
o O2 content at kiln inlet sufficient high,
o O2 target = 3-4% at kiln inlet, CO <0.1% (better CO <0.05%)

9. Petcoke firing
1.Grinding
2.Combustion
3.Volatile recycle
4.Influence of refractory
5.Effect on quality of cement

10. coal mill
Table rpm =35
Table dia = 2.5 M
Capacity = 50 tph for coal
The hard groove of index of petcok is
about 40 %
And the residue of pet coke is < 3 % on 90
Microns . For this the damm ring has been
Increased by 20 mm (from 120 to 140 mm)
Sometimes the mill operates at 90% of the
Speed to have stable bed.Water spray on the
Grinding track further stabilises the bed to
Improve grinding efficiency
As thumb ruleresidue on
90 microns =volatiles* 0.5,( volatiles=7-8 %)
7*.5=3.5
Dam ring

13. Mill capacity vs HGI
coal
petcoke

14. Combustion of petcoke in pyro system

21. Flame impulse =10-11 N/Mw
0r
Momentum = 2000 t0 2500 % m/s
Coal injecction velocity =30 m/s
Petcoke injection velocity= 25 m/s

22. Jet air in pyro jet =400 m/s
Normally = 3.0 %
Normally ,25 m/s

27. Normally 3-4 %

33. Modern burners are aligned parallel to kiln axis
If it is parallel to kln axis it may impinge the charge
If the flame is short and convergent it may not impinge the flame

35. Flame is parallel to kiln axis , 3.5 to 4.0 % slope

43. Petcoke firing in calciner

48. Pyroclone and
low nox calciner
Firing point
Hgh tertiary air temperature with clnker dust laden
With rich oxygen (21 % ) is more favorable for
Petcoke firing than low NoX calciner ,though it
Has high retention time > 5 -6 seconds.

52. Why we must have O 2 when we
do petcoke firing

56. Ref VDZ,Dusseldorf

65. Longer flame elonagte the burning zone and transition zone where the meal
Has more retention time and make it favorable for more evaporation

77. REFRACTORY FAILURES
Refractory failures are generally very difficult to identify the root cause failure
mechanism.
The main reasons are:
•Very few people truly understand the non-linear properties of the
•refractory, the thermo-chemical reactions of the refractory with the
•process environment and the thermo-mechanical interactions of the refractory
and steel shell.
•Correct information regarding the service conditions of the existing refractory
is rarely compiled by the plant.
•There are so many variables that could affect the brick reliability during
a typical campaign
•that it would be impossible to isolate the direct effect of any.
•Most refractory (especially kiln brick) failures are a result of a complex
combination of multiple variables.

78. Sulfur / Alkali – The most obvious affects of burning Pet Coke
on cement plant refractory have been the destructive forces
of sulfur / alkali. These destructive forces are seen in brick
spalling, brick capping, shell corrosion, anchor corrosion,
alkali penetration, expansive refractory reactions and direct
damage from buildup removals. Depending on the fuel sources,
pet coke can have anywhere from 1-7 wt% more sulfur and is
typically in the 4-6% range. This change in fuel composition
Creates a large change in the sulfur / alkali ratio and the resulting
cycles.

79. Direct Refractory Damage – “Direct” refractory damages are of a
physical nature due to mechanical forces. These damages and
the failure analysis are usually easily identified and corrected in
a timely manner.
Examples of “direct damage” include the following: Misaligned
kiln, kiln shell damage, incorrect shimming of the kiln tires,
direct flame impingement of a misaligned burner, over-firing a
burner, sulfur ring buildups, abrasion in high wear areas and
normal wear and tear of the system.
Direct Refractory Damages that are related to fuel variations
might include:
•Excessive temperatures (due to coke combustion) in the
“burning zone” brick
•which show 1 ½” to 2” of severe penetration of high liquid phase
is an indication of excessive temperature. This can be accompanied
with thick coating and extremely hard to remove (also indicating high
liquid phase).
• Deep cobbling of brick is a result of excessive temperatures
which left residual stress in the brick.

80. •AZS castables have been found to offer excellent buildup
•resistance in cement application. The AZS grain imparts great
thermal shock (water blasting) resistance, low thermal expansion,
low thermal conductivity and excellent abrasion resistance. The AZS
fused grain products are an upgrade over the products with just the
Zircon additive. Numerous trials have shown that it is more effective to
utilize an AZS refractory rather than Silica Carbide. The AZS refractory
has shown as good if not better results for buildup resistance, lower conductivity
for better designs, and better resistance to alkali/steam reactions that
limit the service life of Silicon Carbide.
•Standard 50-70% alumina products can be upgraded with a zircon
flour addition of 4-8% in the matrix. The zircon addition can fill interstices
sites within the refractory matrix and impart a “non-wetting” type property
to the system to help repeal alkali impregnation.This type of product is
recommended not only in buildup areas of the Tower but also in the Cooler and
Tertiary Air Ducts.
•Denser spinel kiln brick with less porosity / permeability are being evaluated to help
decrease kiln shell corrosion. The trade off is that this type of brick will generally
have a higher modulus of elasticity and may not lead to shorter term reliability.
•Monolithic materials with high percentage of calcium alumina cement should be
avoided in any application above 1400 deg. F.
•Any firebrick should be of the high-fired variety to avoid expansive reactions.

89. Thank you