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DXD TechnologyDXD Technology
Prepared by:
Jim Brown
Technical & Market Manager - Cement
Baker Refractories
York, PA USA
June 11, 1999
Process considerations, Product design, features, benefits and target
application
IntroductionIntroduction
Numerous changes in cement pyroprocessing– *** supplemental fuels ***– *** alternative raw materials ***– control system upgrades– auxiliary equipment technology advances
IntroductionIntroduction
Numerous changes in cement pyroprocessing
Cement Market changes– various clinker Types produced– more frequent clinker Type changes
» meeting cement customer demands
IntroductionIntroduction
Numerous changes in cement pyroprocessing
Cement Market changes Burning Zone refractory service life
affected– coating profile shifts– thermal shock & spalling– volatile infiltration, densification, reaction
IntroductionIntroduction
Numerous changes in cement pyroprocessing
Cement Market changes Burning Zone refractory service life
affected Cement production goals/plan affected
– unplanned stops– piece-meal patch jobs– customers resort to “cheaper” bricks
Process Factors To ConsiderProcess Factors To Consider
Alkali, sulfur, chlorine inputs & cycling Dust circuit Flame shaping, length & control Secondary air changes (cooler upgrades) Thermal loading (process type?) Thermal shock Shell condition (mechanical stresses)
Effects on RefractoriesEffects on Refractories
Brick densification Magnesia fluxing Doloma reaction Spinel fluxing Sintering shrinkage (densification) Spalling Cracking/crushing
Effects on BZ RefractoriesEffects on BZ Refractories
•Almag 85 brick•15’0” dia. wet kiln•LTZ application•45 days
Notice the magnesia grains “floating” into the coating material. Also noticethe laminations developing farther backin the brick. Low-melting calciumaluminate formed from CaO fluxing of
the spinel component in the brick.
Effects on BZ RefractoriesEffects on BZ Refractories•Dolomax brick•15’0” dia. wet kiln•SZ application•105 days
Severe densification. Note the“lava” appearance of the coating.In addition to sintering shrinkageand densification of the brick, alkali salts infiltrated, densified,and are partly responsible for thesevere cracking here.
Effects on BZ RefractoriesEffects on BZ Refractories
• UTZ application• 145 days
• Almag 85 w/cavity• 14’0” dia. 4-SP
#2 tire application.
Note crack formation exactly at condensation point of salts. Here, the cavity back air space neither lowered shell temperature nor moved the salt isotherm closer to the hot face.
Effects on BZ RefractoriesEffects on BZ Refractories
•Dolomax 60-Z brick•15’0” dia. wet kiln•LTZ application•150 days
This is the “underside” of a spall panel. Note the very dense coating in the foreground, bottom of photo. The white deposits are sulfates/chlorides. This kiln makes Type II clinker with coal/coke fuel and a few alternative raw materials. A real “hard burner.”
Effects on BZ RefractoriesEffects on BZ Refractories
•Nokrome 87 brick•17’0” dia. 4-SP•LTZ application•35 days
Traditional spinel application with Almag 85 and Nokrome 87. The front end got a little warm and the customer switched to D6Z. Differential wear resulted in the D6Z: the first 10’ from the nose had a slightly higher wear rate than the next 18’ up to the sintering zone (DMX).
Effects on BZ RefractoriesEffects on BZ Refractories
“CaO + MgAl2O4 ==> C12A7 & C3A & CA”
A polished section photo under the reflected light microscope, magnified 121x. Shown here is a “fluxed” magnesium aluminate spinel grain. CaO from the load reacts with the alumina component of the spinel (S) forming eutectic (low-melting point) calcium aluminate liquid phases (C). The customers normally see the “macro” effect on the brick and we can always “explain” the mechanism but its nice to show them what actually happens inside. This is a rare photo.
Chrome-Free Brick TechnologyChrome-Free Brick Technology
Additives – zirconia– spinel(s)– calcium zirconate– iron oxide– hercynite
Dolomite (doloma) Magnesite (magnesia/periclase)
These are the choices we have to work with. No one has revolutionized kiln liner technology but they keep trying. Baker should be doing the same.
DXD created from DMXDXD created from DMX
Doloma zirconia (Dolomax - 1984) DXD - introduced September 1997
– Originated with Lafarge - Joppa, IL» cooperative sales/R&D process “audit” at the
plant site in June 1997
– Low permeability design» granulometry shift» higher density» lower porosity
DXDDXD- Low Permeability -- Low Permeability -
39% MgO
56% CaO
2.5% ZrO2
Target ApplicationTarget Application Sintering zone (coating area) Typical doloma placement where
DKL, DLZ or DMX has been used This product IS NOT intended to extend
the sintering zone in either direction Postmortem history with
DKL/DLZ/DMX is preferred for a solid technical angle for DXD recommendation
Design ObjectivesDesign Objectives
Reduce rate & depth of infiltration of alkali salts– reduce spall plane depth– minimize brick loss upon spalling
Maintain coatability Maintain as-manufactured spall
resistance
DMX Modification to DXDDMX Modification to DXD
A B C D E F
Fractions (coarse --> fine)
Granulometry Changes
DKL DMX DXD
Lab Data ComparisonLab Data Comparison
Physical Changes
2.7
2.8
2.9
3.0
3.1
DKL DMX DXD
Den
sity
(g
/cm
3 )
0
4
8
12
16
Ap
par
ent P
oros
ity (
%)
Baker TSR TestBaker TSR Test
Thermal Shock Resistance
0
10
20
30
40
50
60
DKL DMX DXD
% R
etai
ned
Str
eng
th
~57% Drop in Perm. vs. DMX~57% Drop in Perm. vs. DMX
Permeability
0
50
100
150
200
250
DKL DMX DXD
(cD
)
Critical Data TabledCritical Data Tabled
DKL DMX DXD
Density (g/cm3)
2.80 2.90 3.00
Porosity (%)
15.0 14.0 11.0
Perm. (cD)
205 185 80
Benefits in ServiceBenefits in Service
Reduces depth of volatile infiltration– reduces depth of densification– reduces depth of spall plane
Doloma system offers maximum coatability & refractoriness
May reduce scale buildup on kiln shell by limiting ingress of salts
Lafarge Joppa ResultsLafarge Joppa Results
Kiln #2, 16’ (4.88m), 2SP. DMX on the left and DXD on the right. Five month campaign. DMX from 45’ (13.7m) position, DXD from 52’ (15.8m) position. Although the DMX sample appears to be spalled, the DMX from 40’-50’ (12.1-15.2m) was about 2” (50mm) thinner than the DXD setting. Upon lab examination, the DXD cross section was visibly LESS infiltrated, and to a lesser depth from the hot face, than the DMX.
The EndThe End
This is the first in a series of presentations intended for technical product training and updates.
These presentations may be adapted for use with customers. If you have a specific need at an account, please call me for assistance with making changes to meet your needs: we want everyone presenting the same core message out there with respect to product features, benefits and applications.
Jim Brown
(717)771-3973