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DXD 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
Introduction l Numerous changes in cement pyroprocessing –*** supplemental fuels *** –*** alternative raw materials *** –control system upgrades –auxiliary equipment technology advances
Introduction l Numerous changes in cement pyroprocessing l Cement Market changes –various clinker Types produced –more frequent clinker Type changes »meeting cement customer demands
Introduction l Numerous changes in cement pyroprocessing l Cement Market changes l Burning Zone refractory service life affected –coating profile shifts –thermal shock & spalling –volatile infiltration, densification, reaction
Introduction l Numerous changes in cement pyroprocessing l Cement Market changes l Burning Zone refractory service life affected l Cement production goals/plan affected –unplanned stops –piece-meal patch jobs –customers resort to cheaper bricks
Process Factors To Consider l Alkali, sulfur, chlorine inputs & cycling l Dust circuit l Flame shaping, length & control l Secondary air changes (cooler upgrades) l Thermal loading (process type?) l Thermal shock l Shell condition (mechanical stresses)
Effects on Refractories l Brick densification l Magnesia fluxing l Doloma reaction l Spinel fluxing l Sintering shrinkage (densification) l Spalling l Cracking/crushing
Effects on BZ Refractories Almag 85 brick 150 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 150 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 UTZ application 145 days Almag 85 w/cavity 140 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 Refractories Dolomax 60-Z brick 150 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 170 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 CaO + MgAl 2 O 4 ==> C 12 A 7 & C 3 A & 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 Technology l Additives –zirconia –spinel(s) –calcium zirconate –iron oxide –hercynite l Dolomite (doloma) l 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 DMX l Doloma zirconia (Dolomax - 1984) l 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
Target Application l Sintering zone (coating area) l Typical doloma placement where DKL, DLZ or DMX has been used l This product IS NOT intended to extend the sintering zone in either direction l Postmortem history with DKL/DLZ/DMX is preferred for a solid technical angle for DXD recommendation
Design Objectives l Reduce rate & depth of infiltration of alkali salts –reduce spall plane depth –minimize brick loss upon spalling l Maintain coatability l Maintain as-manufactured spall resistance
Benefits in Service l Reduces depth of volatile infiltration –reduces depth of densification –reduces depth of spall plane l Doloma system offers maximum coatability & refractoriness l 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 (12.1- 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 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 firstname.lastname@example.org