Technical Paper
Tabular Alumina 0-5mm MA-Spinel AR78 0-1mm Reactive alumina P152SB MgO UBE95
Elkem Microsilica® Secar®
Refpac®
Peramin® (PP-fiber)
971U 71 (CAC70)
Mipore 20 (MP20) AL200
Water (%) Vibration Flow (%)
AM6 68 13 9
3.5 0.5 6 -
+0.05 (+0.1) +5.3
110 (100) Table 2: Alumina-Spinel-Magnesia LCC-model formulations (m-%) Figure 2: Steam pressure in MCC and LCC during drying [8] Test materials and test methods
The properties of the permeability enhancing active compound, REFPAC® MIPORE 20, are summarized in table 1. MP20 is a powder with a median particle diameter d50 between 10-20 µm and consisting mainly of Al2
O3 , CaO
and MgO containing mineral phases and organic active substances. MP20 has also the capability to deflocculate refractory castables, and contains hydratable calcium aluminate phases. Three different model recipes (LCC, MCC, RCC) as shown in tables 2-4 have been chosen to study the effect of MP20 on dry-out and other properties. In previous studies [7, 8] it was found that a dosage of 2.5% of PEAC (MP20) gives the best compromise between sufficient flow and green strength on one hand, and a high permeability at 110ºC which is essential for a rapid dry-out capability. In each of these 3 model formulations 2.5% CAC (either CAC70 or CAC80) are replaced by 2.5% MP20. When MP20 is used in the recipes, no additional deflocculant was added to the mixes. Trials have also been conducted with PP-fibers in the formulations AM6 and AS10. The formulations that contain MP20 have not used PP-fibers. Pastes of mixes of calcium aluminate cement (CAC), reactive alumina, and MP20 have been used to investigate the underlying mechanisms that lead to the change in permeability and dry-out capability. Permeability measurements and thermogravimetric studies on castable cubes have been conducted as described by [7, 8]. XRD, DSC/TG and SEM techniques have been used to determine the impact of MP20 on hydrate phase formation and de-hydration. Castable cubes of different sizes have been used for thermogravimetric analyses with heating rates between 20 and 300 K/h. A cement-free silica sol/gel bonded model castable AS0 (Tab 3) has been used as reference for a castable-type that is known for its rapid dry-out capability, but at the expense of very low green strength [9].
Al2 O3
CaO MgO LoI
pH (5% solution) d50
Table 1: Properties of REFPAC® 18 MIPORE 20 ENGINEER THE REFRACTORIES November 2017 Issue
39-43 % 12-15 % 16-20% 24-30% 5.5-6.5
10-20 µm
Tabular Alumina 0-5mm Calcined alumina AC44B4 React. alumina P152SB (RA) MgO UBE95
Elkem Microsilica® Secar®
971U 71 (CAC70)
Refpac® Mipore 20 (MP20) Na-TPP
Citric acid (PP-fiber)
Silica sol (30% solid) Water (%)
AS10 80 5
- -
5
10 -
+0.03 +0.02 (+0.1) -
+5.2 Vibration Flow T0 (%) 110 (95)
AS10-MP20 80 5 -
- 5
7.5 2.5 - -
- -
+5.2 105
Table 3: Alumina-Silica MCC and NCC model formulations (m-%)
Tabular Alumina 0-5mm Secar®
Refpac®
Plenium (CAC80) Mipore 20 (MP20)
Water (%) Vibration Flow T0 (%)
A15 85 15
+5.7 110
Table 4: Alumina RCC model formulations (m-%)
Results Thermogravimetry with different heating rates With a thermocouple in the center of a 10x10x10 cm3
A15-MP20 85
12.5 2.5
+5.7 100
AS0 90 -
6.5 0.5 3
- -
+0.03 +0.02 -
+7.5 -
130
www.ireng.org
AM6-MP20 68 13 9
3.5 0.5 3.5 2.5 - -
+5.3 115
castable cube
thermogravimetric analyses have been started after a curing period of 24h at 20°C and 100% rH. Samples of AS10 and AS10-MP20 have been heated with 3 different heating rates of the furnace, 20, 120 and 300 K/h. For AM6 and for the silica sol/gel bonded castable AS0 only the fastest heating schedule has been tested (300 K/h). The weight evolution of the cubes during heating has been plotted as a function of the temperature recorded in the center of the cube.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32
