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DXD Technology
Process considerations, Product
design, features, benefits and target
application
Prepared by:
Jim Brown
Technical & Market Manager - Cement
Baker Refractories
York, PA USA
June 11, 1999
Introduction

Numerous changes in cement
pyroprocessing
– *** supplemental fuels ***
– *** alternative raw materials ***
– control system upgrades
– auxiliary equipment technology advances
Introduction
Numerous changes in cement
pyroprocessing
 Cement Market changes

– various clinker Types produced
– more frequent clinker Type changes
» meeting cement customer demands
Introduction
Numerous changes in cement
pyroprocessing
 Cement Market changes
 Burning Zone refractory service life
affected

– coating profile shifts
– thermal shock & spalling
– volatile infiltration, densification, reaction
Introduction
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 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 Refractories
Brick densification
 Magnesia fluxing
 Doloma reaction
 Spinel fluxing
 Sintering shrinkage (densification)
 Spalling
 Cracking/crushing

Effects 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 notice
the laminations developing farther back
in the brick. Low-melting calcium
aluminate formed from CaO fluxing of
the spinel component in the brick.
Effects 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 shrinkage
and densification of the brick,
alkali salts infiltrated, densified,
and are partly responsible for the
severe cracking here.
Effects on BZ Refractories
#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.
• Almag 85 w/cavity
• 14’0” dia. 4-SP
• UTZ application
• 145 days
Effects 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 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 Refractories
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.
“CaO + MgAl2O4 ==> C12A7 & C3A & CA”
Chrome-Free Brick Technology
Dolomite (doloma)
 Magnesite (magnesia/periclase)


Additives
– zirconia
– spinel(s)
– calcium zirconate
– iron oxide
– hercynite
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 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
DXD
- Low Permeability 39% MgO
56% CaO
2.5% ZrO2
Target 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 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 DXD
Granulometry Changes
A
B
C
D
E
Fractions (coarse --> fine)
DKL
DMX
DXD
F
Lab Data Comparison
3.1
16
3.0
12
2.9
8
2.8
4
2.7
0
DKL
DMX
DXD
Apparent Porosity (%)
Density (g/cm3)
Physical Changes
Baker TSR Test
Thermal Shock Resistance
% Retained Strength
60
50
40
30
20
10
0
DKL
DMX
DXD
~57% Drop in Perm. vs. DMX
Permeability
250
(cD)
200
150
100
50
0
DKL
DMX
DXD
Critical Data Tabled
DKL
DMX
DXD
Density
2.80
2.90
3.00
Porosity
15.0
14.0
11.0
205
185
80
(g/cm3)
(%)
Perm.
(cD)
Benefits 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 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’ (12.115.2m) 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 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
[email protected]