Refractory manufcturing,properties

1. Refractory manufacturing
Refractory testing

and
Refractory properties

2. In general any material which in service > 600 deg C is called refractory

Is ita material which should withstand high temperature only ?

The right definition is that it should withstand high temperature,resistance to
thermal and thermo chemical load, posses high volume stability, resistant to
erosion and abrasion, be tough , and resistant to chemical corrosion

etc. Or otherwise it should have high RUL, high PCE, low conductivity , high
hot MOR, high creep resistance and optimum CCS etc

There is no refractory material which posses all the above
properties 100 %

Overall it is a compromise with all the above properties.
Choice of refractories depend on the operating and mechanical
conditions of the kiln.

3. Refractories

Silica based
refractories, fire clay
bricks

Magnesia, Magnesia
Chromium , Magnesia
Alumina , Dolomite

Alumino silicates
Alumina bricks,Zirconia

based refractories,
like zirconal, zircon, etc

4. refractory clays Kaolins extended with

Are Clay chamotte or non plastic argillacious matter

bricks unwetted by water Al208 content = 30 to 45 %
1)Cyanite,andalusite,and siliminite
2) natural hydrated
alumina(hydrargillite,bohemite,and disapore
contained in bauxite)
3) Artificial calcined hydrated alumina, and Class A = 45 - 60 % Al208
High alumina natural and electro fused alumina Class B= 60 - 70 % AI208
bricks ( Alpha -alumina or Class C= > 75 % Al203
Silica bricks Dinas

Magnesit ( MgC03), Dolomite

Magnesia ( MgCOB.Ca008), Mg(OH)2,Mgo Obtained from

bricks

dolomite,saline water and sea water
MgO and Al203 together sintered or fused
MgO from sea water and alumina from

Spinel bricks alumina industries ,alpha alumina etc)

5. Raw material user _

y
1600 °C

Acidic

| |
D nIEBEE

6. “ron ete

1775°C

SiO2

1850 °C

ZrO2

Al203

2135°C

Cr203

MgO

1890 °C

7. SiO2 Al203 Cr203 CaO ZrO2 MgO

8. A melting point
Deg c
3000

6” Zro2
275
2500 Q

2 Cr203

2250 ©

1203

2000

SiO2
1750

150
14 13 12 11 10 9 8 7 6 5 4 8 2 1

basic neutral acidic PH value

9. mixing

10. Bauxite Corundum

Al,0;;: up to 89 % Al,O,: up to 99,8 %
SiO,: 4-10 % (Os:
iO, x E SiO),
Bee EEE
N AS
LOA: 1700 °C LOA: 1850 °C
Fireclay SIC crystals ( Silicon carbide)

Al,0,: 30 - 45 %
SiO,: 50-63%

LOA: 1450 ©

11. Zircon crystals u. - :

al 6. | a :
= A
a ‘
,
RR... -
=e »
fe e E
=. i A
ur! 4 EN .
PE + ;

MAGNESIA-CHROMITE AND
CHROME-FREE MAGNESIA
SPINEL BRICKS

12. 2

Drying tower / classifier| Binder & liquids elevator
Vibrating screen
Storagë silos y storage

Clay crusher

Clay mill

Tunnel kiln

+=

Tunnel cars
— Finished product storage E cd

13. Refractory manufacturing process
Schematic diagram of refractory manufacturing

Raw Rough middle
material @ crushing | crushin:

g | distribution

MIE
Kb |S le

Measuring x 5 —
quantity [mixing | | moulding | inspection | packing shipping

m

14. Refractory clay mine

Opencast mining

= =
—#
=

widen «Pa

Under ground mining

15. Cone crusher

Bild 4: Siebanlage mit Silobiihne.

Picture 4: Sieve with silo platform.

Bild 3: Kegelbrecher fúr Sintermagnesia.

Picture 3: Cone crusher for sintered magnesia.

16. Hydraulic press

17. | Iso static press machine

18. Tunnel dryer

19. Tunnel tn

20. Magnesia containing bricks

High alumina bricks
Fire clay bricks

Light weight insulating bricks

mag chrome, mag spinel,
dolomite,hercynite, galaxite
based,

zirconia based

60 - 70 % Al,O,
30 % Al,O,

Unshaped refractories or castables - conventional,

low cement castable,

ultra low cement castables,
insulation castables

21. Raw materials for Magnesia bricks are

+ Natural magnesite , MgOO3 , Coarse crystalline ,
fine crystalline

Synthetic magnesia,sea water magnesia , salt brine

The principal constituent determining the characteristic
properties of magnesia refractories is periclase

Properties of periclase

Melting point 2800 deg . C
. Thermal conductivity 3-4w/ mk
Thermal expansion 14%

22. Magnesia bricks, MgO, > 80%
Magnesia spinel bricks, MgO , 80-90%
Magnesia hercynite bricks, MgO, 80 - 96 %

Magnesia Zirconia bricks MgO, 85 - 96 %

Magnesia chromite MgO, 55 - 80 %

Chromite bricks Cr2 03=25%
MgO =25%
Forsterite MgO and SiO2

Dolomite MgO = 60 % and CaO=40 %
Magnesia, galaxite bricks Mgo=91% ‚and MnO=2.6%

23. Mineral
Periclase
Forsterite

Monticellite
Merwinite
Dicalcium silicate
Magnesium ferrite
Dicalcium ferrite
Tri calcium silicate
Brown mellarite
Dolomite
Andalusite

Mullite
Siliminite

Formula
MgO
2 MgO.SiO2
CaO.MgO.SiO2
3 CaO.MgO.2Si02
2Ca0.Si02
MgO.Fe203
2 CaO.Fe203
3Ca0.Si02
4Ca0.Al203.Fe203
Ca0.MgO
AI203.Si02
3A1203.2Si02
Al203.Si02

Abbreviation Fusiontemp ,Deg C

M
M2S
CMS

C3MS2
C2S
MF
C2F
C3S
C4AF
CM
AS

AS

2800 deg C
1890
1495
1575
2130
1750
1435
1900
1395
2450

1840
1545

24. Andalusite Al208.Si02 AS
Mullite 3A1203.25102 184
Siliminite AI209.S¡02 AS 1545
Corundum 205
Hercynite Fe0.Al203 FA 176
Galaxite Mno.A1203 mA
Magnesia aluminaSpinel Mg0.Al203 MA 2135
Gehelinite 20a0.A1203,5i02 C2AS 159
Calcium aluminate Ca0,Al208 CA 160
Anorthite Ca0.A1203.2Si02 CAS2 155
Dicalcium ferrite 20a0.Fe203 CF 145
Myenite 12Ca0.7Al203 C1247 1455
Gehelinite 2Ca0.Al203.8i02 C2AS 159
Calcium aluminate Ca0,A1208 CA 160
Anorthite Ca0.A1208.25102 CAS2 155
Dicalcium ferrite 20a0.Fe203 CF 145

Myenite 120a0.7A1203 C12A7 1455

25. Type of brick

Location where it is used

70 % Alumina bricks

Cooling zone ,burning zone,
transition zone

60 % Alumina bricks

transition zone,calcining zone, t.a.duct
calciner, cooler area

40-50 %Alumina bricks

calcining zone, t.a.duct
calciner, cooler area

30 % Alumina bricks

t.a.duct, ,calciner, cooler area,pre-heater
cyclones

Magnesia chrome bricks
Dolomite bricks

Burning zone

Magesia spinel bricks

cooling zone,burning zone ,transition zone

Hercynite ‚nochrome
Galaxite no chrome

transition zone

26. __ Refractory properties

Physical properties

1)Bulk density g / cm?

2)Apparent porosity %

3)Cold crushing strength N/ mm?

Thermal properties

1)Refractoriness under load (RUL)
°C
ty
in

2) PCE ( pyrometric cone equivalent)
SK (Arton cone in ASTM standard)

3)Thermal expansion ‚lin % (PLC)
at 400°
800%
12000c

27. 4)Thermal shock resistance (TSR)
at 950° c in air
or
Water quenching cycles

5) Thermal conductivity at
300%
700%
1000%
"Chemical analysis.
MgO
Al203
Cr203
Fe203
CaO
SiO2
ZrO2
MnO2 etc

28. Density of all refractories is an indirect measure of their
capacity to store heat

The porosity of a refractory is a measure of % pores to the
(summation of open and closed pores)total weight of

a brick. This property is significant to decide
upon its resistance to penetration by slags and fluxes ,its
permeability to gases and its thermal conductivity

Porosity is controlled by the following
1) by controlling the texture of the bricks
2) by controlling the size of the particles
3) by method of making
4) by controlling the firing temperature

29. Porosity affects

30. Cold crushing strength of a refractory material represents its
strength .In other words it tells us how much load it can bear
in cold condition

The mechanical strength (CCS) of refractory brick is governed
largely by the amount and the character of the matrix material
between the larger grains. Good tool to provide for evaluating
the degree of bond formation during production. It indicates the
ability of the brick to withstand abrasion and impact in low
temperature application.

31. CCS testing machine

Bild 66a: Prüfapparaturen zur Bestimmung der
Kaltdruckfestigkeit.

Picture 66a: Testing apparatus to check cold crushing
strength.

Bild 66b: Der Priifzylinder. “ à Bild 66c: Probekórper nach
fy Testende

Picture 66b: The test cylinder.
Picture 66c: Specimen after

end of test.

32. Cold crushing equipment and CCS values

Brick grade CCS (N / mm2 Ea Le
Silica 15-20 EU ru er

Fire clay 12-70 u
Corundum 35 - 80 M
Magnesia 50-110 | K i|
Magnesia chromite 30 - 70 at, i
Magnesia spinel > 40 | me a
Insulating Brick 3-20 | | | | |
” FLIA |
PT ¡PES

34. Transition of a solid material into the liquid form under
the influence of heat. A true melting point is temperature
at which the solid and liquid phase of the composition
co-exist in equilibrium.

It is the ability of a refractory to remain rigid at a given
temperature. It is an indirect indication of the amount
and the viscosity of any liquid which it may contain.

The reference samples are called seger cones in
DIN standards and Norton cones in ASTM standards.

35. Standard samples

Test sample

36. Seger cones before and after firing

37. Seger Cone No. "| Melting temp. Seger Cone No. "| Melting temp.
according to according to ISO T

1! Small Seger cone, Temperature increase 2.5 °C/min. = 150 °C/h

Today the seger cone equivalent is only of low importance, it is nowadays
still used for kiln control, especially for the production of fireclay and tile bricks.

38. The three methods evolved are
+ Determination of the refractoriness under load
+ Determination of the refractoriness load ( diifferential)

« Determination of the thermal expansion under load ( creep)

39. Characteristic temperatures are Brick grade toc

ta: 0.3 mm compression from the Fire clay 1300 -1550
temperature the temperature of Corundum 1600 - 1750
highest expansion Silica > 1660
(0.6 % compression of test sample) Magnesia chromite > 1550

t : 10 mm compression from the Magnesia-hercynite 1600
temperature of highest expansion Dolomite 1700
(20 % compression of test sample) Magnesia spinel > 1700

t , : temperature of breaking sample. Carbon brick non-
softening

40. Determination of the refractoriness under load (differential)

Curve example of refractoriness under load

Extension
% | mm
| Si
0.8404 Characteristic temperatures are

t: temperature of highest expansio
(Dax (%): maximum expansion)

400 800 1200

02 Internal thermocouple temperature slew a 0.5% compression from the
temperature of highest expansio

04 = 08%

E Rs u tt 1/5 % compression from the
i 1 = 1470°C temperature of highest expansior

eee
. 2 = 2.5% {1480 °C) temperature of breaking sample

41. Determination of the thermal expansion under
load ( creep)

Curve example of Creep under load
Curve example of Creep under Load Characteristic values of creep curves

D (el. Maximum expansion of
the loaded sample

Zn 2
flow rate: V2 = fn)
10

=
El
2
o
E
lu]

me (1)

Shrinking

Dwell Temperature

42. Creep test equipments

43. This is a measure of the resistance of a refractory body

to the combined effects of heats of load. This test helps

to study the behavior of a refractory product when
subjected to a constant load under conditions of
progressively rising temperature.

The ground mass / matrix helps to bond the entire mass of
a refractory brick strongly together. The amount and the
strength of the glass is fixed by the alumina - silica ratio,
fluxing oxide content and the temperature of firing.

It is an important parameter to decide upon the safer limit
of service temperature in a given situation.
Contributing factors to the increased resistance to the
pressure are
a) More thorough distribution of liquid throughout the brick
b) The growth of crystals through the influence of heat
c) Crystallization of a portion of the liquid during cooling.

44. In a brick held at constant temperature and pressure,
gradual solution of solid material up to the limits of its
solubility in the liquid may cause some increase in the
viscosity of the liquid. This increase is dependent on
the nature of ground mass, glass content. Higher
glass content will result higher deformation in this
situation. This property of refractoriness is called high

temperature creep. Lower deformation will ensure
rigidity under the service condition.

The creep is the measurement of deformation of a
refractory product as a function of time when it is
subjected to a constant load and heated at a specified
temperature.

45. ae View point

+— Steel casing

Corundum, magnesite
or mullite tube

est specimen
Coarse amorphous

carbon insulating brick lining

Metal electrode Carbon or mullite rod

46. RUL testing machine and creep test machine
E “y 7

47. Creep curves

10
12

14 =
1000 1100 1200 1300 1400 1500 1600

Bild 59: Druckfeuerbeständigkeits-Kurven von
feuerfesten Steinen:

1. Schamotte

2. Sillimanit

3. Chrommagnesia

4. Silika (-Gewólbe)

5. Silika (- a ci

48. 1800

1600

1000 1200 1400

800

©)
o
©
2
=
=
ö
o
=
ö
E

400 600

0 200

(%) UOISUSIXO / einsseig

49. Creep measurement of various high alumina refractories
under 25 psi load at 2600 © F for 0 0 hours

% alumina - low alkali

50. Linear expansion (Permanent linear change)
High temperature reheat test may
be used to reveal
1) if a brick has been fired long enough
or ata high temperature
2) whether a brick has adequate
refractoriness and volume stability
It is expressed as a percentage ,
preferably by the ratio of the length
of the test piece after heating and
the original value of the length

Equipments used to
determine
Thermal expansion

51. 1000 deg c L= 1013 mm
2000 deg c L = 1026 mm
Magnesia: Thermal expansion = +1.3% at 1000 degc
Alumina oxide : Thermal expansion =+0.8% at 1000 degc

Fire clay Thermal expansion = +0.5% at 1000 degc

52. Thermal expansion curves

200 800 1000 1200

Picture 63: Thermal expansion of refractory bricks:
1.Magnesia + 2, Chrome-Magnesia » 3. Chromite + 4. Silica

5. Zirconia + 6. Corundum 99% + 7. Corundum 90% + 8. Fireclay
9. Sillimanite « 10. Zircon + 11. Silicon Carbide.

53. Thermal expansion is important in service , as the effect of expansion has
to be taken into account during refractory installation and construction of
large installations ( expansion joints). The expansion curves of most of
refractories is more or less linear with increasing temperature or reversible.

2 — — — SEE

54. Thermal spalling results from stresses caused by
unequal rates of expansion and contraction in different
parts of brick and usually associated with rapid changes
of temperature.

In cement rotary kiln the brick lining needs to be
spalling resistant as the lining is subjected to
continuation variation of temperature because of
rotary motion of kiln.

TSR ( thermal shock resistance ) is given in cycles.
Quenching is done by air or water

55. Se Equipments for thermal
shock resistance test

56. The coefficient of thermal conductivity is defined as the quantity of
heat that flows across unit area in unit time if the temperature
gradient across this area is unity.

Thermal conductivity K is given as
k(T,-T¿) A, Keal/hr-m-°C or BTU/ hr -sq.ft - 9 F

d Q = amount of heat
Ti = hot face temperature
T2 = cold face temperature
A area cross section
t = time
d = thickness

Thermal conductivity of a refractory decreases with increase in porosity.
Increase and decrease of thermal conductivity at elevated temperature
also depends on amount of glass, liquid and crystallinity of the material.

57. 600

Thermal conductivity of
fired refractory bricks

1. Insulating refractory bricks
2. Zirconia

3. Dry- pressed fire clay
4. Fused silica

5. Forsterite

6. Chromite
7.Corundum 90 %

8. Magnesia- chrome
9.Zircon silicate.

10. Corundum 99 %

11. Carbon

12.Silicon carbide 40%
13. Magnesia

14. Silicon carbide

800 1000 1200 deg c

58. Thermal conductivity

Thermal conductivity depends
on temperature , chemical
and mineralogical,
composition of the brick ,
porosity, pore size and brick
firing temperature

Material Thermal conductivi
at 1000 © C (W/(m.K

Magnesia 44
Magnesia chromite 2.5
Magnesia —spinel 2.8
Magnesia hercynite 2.6
Alumina 3.0
Insulating brick 0.6
Iron 28.0

59. Determination of modulus of rupture
In order to determine the magnitude of the rupture stress of

refractoies , the resistance to deformation under bending load
is measured.

F
| Pressure load

Tensile load ®

The bending strength can be
calculated by means of the eguation
6 bending = 3.F.l / (2.b.h2)

| = distance between blades

b = width of sample

h= height of sample

60. Structural configuration of the refractory material as well as the
amount and properties of occurring melts characterize the HUMOR

HMOR (N /mm?)
Testing temperature (deg C) 1200 1400 1500
Magnesia , low iron content >14 aut

Magnesia , high iron content > 12 5

Magnesia — Chromite 5

High alumina 18

Zirconia

62. Hot MOR Test

1200 °C

64. - The specific feature of
this method of testing is the
= determination of fracture
mechanical parameters at
"= higher temperatures , up to
“222 1200 deg C

Grooved
split

65. Influence of of the aggregates on the secondary
load bearing capacity of the softening behavior

Normalweight Concrete SLWAC

0 =dense aggregate

¡a

Increase <——— Concrete-to-concrete friction ——> Decrease

66. By quantifying all the constituents present in refractory, it is
possible to assess the chemical properties and melting behavior
of a given refractory.As it is important to know the % Al203 in
high alumina brick, % MgO in magnesite brick , and % SiO2 in
silica brick etc. ,the determination of minor constituents has

also been recognized as controlling factors in the performance

of many refractories. The chemical composition is of great
importance with respect to attack by slag , glass melts , flue
dusts and vapors. In general the principle applies that a brick is
more resistant the lower the rate of chemical reaction gradient
between the slag and brick is. Therefore, where the acid slag
is expected , acid bricks are preferably used , and basic bricks
where basic slag is expected.

67. According to the behavior during contact reaction ,
the following groups of bricks can be differentiated.

Acid group - fused (99% SiO2), Silicon carbide bricks,
Zircon crystobalite . Zircon silicate

Basic group - dolomite, magnesia, magnesia chrome,
chrome magnesia forsterite

Inert or neutral - carbon , high alumina chromite
group

68. Cup corrosion test

Alkali test of a high alumina brick Alkali test of a sic containing
with K2CO3 high alumina brick with K2CO¢

69. ‘Mineralogical investigations by X-ray diffraction
Determination of the mineral phases composition of material

X-ray diffraction diagram of a used magnesia —spinel brick grade
salt infiltrated

x
a.
E
3
fe}
2
pd
>
va)

2-Theta - Scale

70. * Light micoscopy ( transmitted light and reflected light
microscopy

« Microprobe analysis ( WDS, EDS)

* Scanning electron microscopy

Advantages of these micrlogies opposite other investigation
methods

Diagnosis of mineral phases composition in raw materials ,
refractory products etc and their configuration
( textural/ structural criterions, pore shape and size etc

71. Mineralogical investigations
Reflected light microscopy

Pictures of magnesia - spinel brick grades with different raw
material composition

72. Microprobe Analysis

73. Mineralogical investigations
Scanning electron microscopy (SEM)
Hydration of Magnesia .
crack formation ,caused by
| formation of
p brucite(Mg(OH)2
hexagonal, tabular-like brucite
AAA

74. Minerological investigations

Scanning Electron Microscopy (SEM)

Salt efflorescences (salt crystals) on a packing cardboard due to see water impact

75. Ankral S
65-(Mg
chrome)

Perilex -
83 (Mg
chrome)

Bazal Z
extra
(Mg

chrome)

Rexal S
extra
(Spinel
bricks)

Chem. Comp. eis e

(gm/cm3) (%)

29-305 17-19

Density porosity

Therm Therm.
exp. Condct.

(W/mK) (cycles
at 1000 at 950
DC Se)

PCE TSR (air

ta tb, at 1200
A =|) 726%

>1650 >1700> 42 1.04

1600 >1700 42

76. Ganon cana AR, os UL po Therm Trerm- rar (ar

at (W/mK) (cydes

(%) gm/cm3 (%) (N/mm?) eS es o 120.0; AO at 250

C % 6 >)
Al mag -

ene 2.85-3 16-18 50 >1700>1700>42 14 28 >10
brick s)
Al mag -
85 SLC

ee 09 17 55 >1700>1700 42 14 27, 100
spinel
bricks)
Ankral R

en 3 16 4 >1700 >1750 42 15 3 >101
brick s)
Ankral R

(ene 2.95 16 >40 >1700>1750>42 1.49 26 >100
bricks)

77. Buk App.

phe ms Comp Density porosity 008 FLE
(%) (gm/cm3) (%) Nmm? 3
eo,
M= 91-94
AS-90 00507
(Spinel 29 17 >40 1700
brick s) ES
C=08
Bou.
M= 89-93
Mag Pure A= 5-8
93) creo
(Spinel F= 0.5
bricks) C= 2
Bi
M= 93-96
Mag Pure A= 3-5
-95 Cr=0
(Spinel F=05
bricks) C= 1
S<07
M = 84-89
Refra A= 9-12
Mag -85 Cr=0
a Sas 29 17-19 45
bricks) C= 1.4
S=09

PCE Therm Therm.

tb (°C)

exp. Condet. ‘SR (air)

at (W/mK) (cycles
sc 1200 at1000 at950
Seen °c °C)

29 >100

29 16-18 50 >1700 >1700 >42 15 29 100

25 12 218) 50 >1700 >1700 >42 1.6 3 100

>1700 >1700 >42 1.4 27 100

78. Chem. Bulk App. Therm Therm. 7
Comp. Density porosity CCS RUL PCE exp. Condet. TOR (air!

(W/mK) (cycles

ta tb at 1200
% m/em3) (% 2 sc at 1000 at 950
(%) (9 ) (%) (N/mm?) (eq co 00% a a
Ferro Mag M=87 - 92
90 A=4-6
(Monee) Cie 29 18-20 50 1600 >1600 42 1.5 26 100
hercynite)
(Spinel
bricks)
R-63
(Magnesia-
hercynite) À 34 17 > 50 >1600 >1700 42 15 27 >100
(Spinel
bricks)
Ankral X2
(Magnesia- 2.98 15 90 > 1700 27 >100
galaxite) 67")
MnO = 2.6
A= 70%
vaw-70 AD as 2.65 23 >55 1460 ay 2 19 30
aa le 2.65 23 >55 1500 36 25 1.9 30

70 Fe203 = 25

79. Thank you
for your

Kind attention