Burners for white cement kilns: Calcia Cruas (France) - Fives

PRESENTATION
Burners for white cement kilns: Calcia Cruas (France)
Gaël LE PIVER, Senior Rn’D Engineer, Fives Pillard, Marseille (France)
For the manufacture of white cement, the burning process is subject
to special requirements and the burner design must take into account
certain criteria:
Even with a very low secondary air temperature, white cement
manufacture requires a higher sintering temperature (hot and short
flame).
Clinker quenching is of main importance so as to avoid any clinker
oxidation ( coloured oxides).
The coating is thin and specific care must be taken to avoid any flame
impingement.
To complicate matters, each plant is different: secondary air temperature & windbox design, cooling technology, water
injection… which requires in each case a “tailor made” burner and, if necessary, a CFD study - for example to improve the
secondary air distribution and velocity around the burner.
SITE RESULTS
White cement burner
Kiln model
White cement structure
Cruas plant is a 600 tpd white cement kiln in southern France. Calcia was
faced with problems using their existing 3-channel burner when firing a
mixture of petcoke, high viscosity oil and waste oil. The flame shape was
to be improved with petcoke over 30% thermal load. Moreover, NOx
emissions were high (over 1,100 mg/Nm 3 @ 10 % O 2 ), leading to a high
urea consumption. The existing burner was operating with high primary air
(17% of total combustion air), which was unfavourable for the specific heat
consumption.
As a first step, Fives Pillard made a CFD study thanks to Fluent® software
and modelled the kiln and secondary air inlet in order to analyse the pathflow
& combustion with the previous burner.
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Once the weaknesses of the existing installation were identified (recirculation zone, uneven secondary air spread), various
design parameters were tested with the numerical model (secondary air windbox velocity, burner swirl…), in order to obtain
a more concentric & radiating flame.
The ROTAFLAM® Version 2 (RV2) was commissioned in April 2008. After 1 year of operation, Calcia CRUAS is satisfied:
Thanks to the concentric flame, a stable kiln operation is now possible even with pure petcoke firing.
Even with a lower primary air flow (12% of combustion air), the flame is stronger, allowing easier clinker cooking and
maintaining a high level of clinker whiteness without any flame impingement on the bricks.
The NOx was reduced from 1,100 to 800 mg/Nm3 @10 %O , almost without any further need of urea.
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The burner flexibility allows smoother operation, especially during fuel switch-over. Consequently, the kiln availability is
higher, and the process more stable.
CONCLUSION
COLD HOT
Flame temperature profile
with the 3 channel burner
Flame temperature comparison
Weaknesses of the existing installation
Radiating flux with the new burner
Flame temperature profile
with the ROTAFLAM® Radiating flux with the previous burner
The site results confirm that the help of CFD can be a decisive factor in choosing the best design parameters, particularly
in the case of a special process. Thanks to the new burner & secondary air windbox, the direct benefit for the CRUAS plant
is higher fuel mastery (easier to fire 100% petcoke), an easier and more stable kiln operation and a significant reduction in
the consumption of urea.
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