Improvement of Refractory Castables with an Innovative Calcium Aluminate Binder System

Transcription

1 Improvement of Refractory Castables with an Innovative Calcium Aluminate Binder System N.Kreuels, Calucem GmbH Mannheim, Germany, Doug Ostrander, Robert Stacy, Calucem Inc. Allentown, P.A.

2 The Story, we can tell about HiPerCem What is HiPerCem compared to other Calcium Aluminate Cements Quality Control and Shelf Life Tests Comparison of HiPerCem with CAC 70/80 s in a Castable based on Tabular Alumina without MicroSilica HiPerCem in a Tabular Alumina Castable at the same addition as reference CAC s HiPerCem in an LCC Bauxite castable with recycled Bauxite Slide2

3 The Story, we can tell about HiPerCem What is HiPerCem compared to other Calcium Aluminate Cements Quality Control and Shelf Life Tests Comparison of HiPerCem with CAC 70/80 s in a Castable based on Tabular Alumina without MicroSilica HiPerCem in a Tabular Alumina Castable at the same addition as reference CAC s HiPerCem in an LCC Bauxite castable with recycled Bauxite Slide3

4 The position of HiPerCem within the segments of Calcium Aluminate Cements CaO 18% Al 2 O 3 80% White Low iron CAC 80 When looking to HiPerCem regarding the Chemical composition it ranges between the dark/iron rich products and the white/low iron CAC 29% 35% 70% CAC 70 64% HiPerCem The chemical analysis corresponds to pure Mono Calcium Aluminate 40% 36% 50% 40% CAC 50 CAC 40 The color of HiPerCem is also white and it has only a very low iron content as the CAC 70/80 Dark/Colored High iron Glossary CAC Calcium Aluminate Cement Product CaO Calcium Oxide Chemical Element CA Mono Calcium Aluminate Mineralogical Element Slide4

5 Main Characteristic: Nearly pure CA = CaO*Al 2 O 3 The only major hydraulic active phase is Mono Calcium Aluminate (CA) The amount of HiPerCem is adjusted to an equivalent ( CA) content Because HiperCem consists of only (CA), all other CaO phases, which do not contribute to rheology and setting, have been eliminated Slide5

6 Another Unique Characteristic: Steep Particle Size Distribution = Slope/n-Value d 50 and d 90 explain the difference of HiPerCem Slide6

7 Improved Flexibility in Formulation Focusing only on the CA with HiPerCem, the formulation designer has more flexibility to adjust the design of the mix to its optimum: Technically or Commercially Slide7

8 The philosophy of formulation HiPerCem requires a new way of designing a Castable Line A shows an addition of a CAC 70, which incorporates a given CaO content ( Line B ) Line C indicates the CA level which is combined with the CAC 70 content Calculating the HiPerCem content, which is necessary to get the same CA content, the corresponding additions are found in line D; The line E indicates the differences in CAC addition compared to the reference CAC ( Line A ) Line F shows the CaO content, which is linked to the according HiPerCem addition The differences of the CaO content to the reference CAC addition are shown in Line G in red The difference between HiPerCem and the CAC 70 ( Line E can be supplemented with other Fines and Fillers, as Alumina, MicroSIlica, SiliconCarbide, etc.) Slide8

9 The Story, we can tell about HiPerCem What is HiPerCem compared to other Calcium Aluminate Cements Quality Control and Shelf Life Tests Comparison of HiPerCem with CAC 70/80 s in a Castable based on Tabular Alumina without MicroSilica HiPerCem in a Tabular Alumina Castable at the same addition as reference CAC s HiPerCem in an LCC Bauxite castable with recycled Bauxite Slide9

10 High reactivity: CA as the major element for hardening CAC 70 starts setting at about the same time with varying hydration heat Regardless. the green strength (6h) is much lower CAC 80 starts to set much later with a much lower hydration heat No green strength for HPC vs. CAC 70 CAC 80 after 6 h HPC vs. CAC 80 Slide 10

11 Shelf Life evaluation Big Bag of HiPerCem was taken from Standard production and then stored under normal conditions No special shrink wrapping But rain protected Tested in two recipes CaluTab QC recipe with 20% HPC and 10% water LCC Bauxite mix with 2 % HPC Tests Ultrasonic setting Flow min BD-MOR-CCS after 24h C Slide11

12 Physical Properties/Conclusion In the CaluTab Mix the 5min flow decreases but recovers after app 7 months; now catastrophic variation Late Flow slightly erratic ( mistakes of measurement?) The USM setting shows a very regular behavior, especially initial set The strength measured in the QC mix is rather steady for 24 h, as well after firing Excellent constant values for all treatment in Bauxite mixes HiPerCem as such has a very good shelf life behavior, which does not indicate any irregularity, when stored properly. Test will be continued Tests have started of shelf life in a Slide12 mix

13 The Story, we can tell about HiPerCem What is HiPerCem compared to other Calcium Aluminate Cements Quality Control and Shelf Life Tests Comparison of HiPerCem with CAC 70/80 s in a Castable based on Tabular Alumina without MicroSilica HiPerCem in a Tabular Alumina Castable at the same addition as reference CAC s HiPerCem in an LCC Bauxite castable with recycled Bauxite Slide13

14 Tabular Castable: From a Regular Castable with a CAC 80 to an ULCC with HiPerCem #1 #2 #3 #4 #5 CAC 80 B CAC 70 A HPC/9 HPC/4,5/1 HPC/2,5/1 HPC 9,0% 4,5% 2,5% CAC 80 B 25,0% CAC 70 A 15,0% CA content 8,8% 8,7% 8,6% 4,3% 2,4% CaO content 4,8% 4,4% 3,1% 1,5% 0,9% Cast. FS 60 0,1% 0,1% 0,1% 0,1% ReaAl-B 1,5% 2,5% 4,0% 4,0% CaAl-B 2,5% 7,5% 10,5% 12,5% ALC-SG-B 1,5% 1,5% 1,5% 1,5% TabAl 0-6 mm 75,0% 79,5% 79,5% 79,5% 79,5% Total 100,0% 100,0% 100,0% 100,0% 100,0% Water/% 8,5% 5,9% 5,5% 5,1% 4,8% Recipes # 1-3: constant CA content, but lower in CaO Recipes #3 to 5: Further reduce the CA content and also reduce the CaO content Observation: permanent decrease in water for same flow STEP 1 Calculation of the CA content with a standard formulation STEP 2 Calculation of the HiPerCem CA content STEP 3 Compensation of the difference with Fines Selection of Aluminas MicroSilica, etc. is possible according to the castable design Admixture and Aggregates composition were kept constant for better comparison and not specific efficiency Slide 14

15 The working characteristics, expressed as Flow Over Time #1 #2 #3 #4 #5 CAC 80 B CAC 70 A HPC/9 HPC/4,5/1 HPC/2,5/1 Water/% 8,5% 5,9% 5,5% 5,1% 4,8% 5 min min min D Flow -100% 6% -20% -6% -4% Same CA Flow in mm as f (Time) CAC 80 B CAC 70 A HPC/9 HPC/4,5/1 HPC/2,5/1 #1 #2 #3 #4 #5 Water/% 5 min 15 min 30 min 231 fg In spite of the high reactivity of HiPerCem it can be easily adjusted to the specific needs for installation In all cases HiPerCem has the same or superior flow of the traditional formulation in spite of lower water addition For CAC 80 the working time without any retarder ends after 15 min. When HiPerCem is reduced to a minimum of 2,5% the formulation contains 1% less water compared to Standard CAC 70 at the same level and is stable over 30 min Slide15

16 velocity [m/s] The setting characteristics 7000 Ultrasonic Measurement of Tabular Mixes time [min] fg CAC 80 A CAC 70 A HPC 9% HPC 4,5% HPC 2,5% A CAC 80 starts very fast with it s setting time confirming the Flow results CAC 70 A and HiPerCem 9 and 4,5% show nearly the same setting kinetics HiPerCem with only 2,5% has the fastest setting but still with long working time Slide16

17 The Cold Crushing strength CA content 8,8 % 8,7% 8,6% 4,3% 2,4% Cold Crushing Strength/ MPa Low strength level for CAC 80 High dried strength with strong decreasing tendency for CAC 70 and HPC 9 based on the same CA content Sufficient green strengths for HPC with lower CA amount but increasing CCS, where it is needed CAC 80 B CAC 70 A HPC/9 HPC/4,5/1 HPC/2,5/1 24h 110 C C C 25% 80 B 15% 70 A 9 % HPC 4,5% HPC 2,5% HPC Slide17

18 Permanent Linear Change (PLC) 0,80% 0,60% 0,40% 0,20% CA content 8,8 % 8,7% 8,6% 4,3% 2,4% 0,69% 0,56% PLC after Firing 0,19% CAC 80 starts shrinking at C CAC70 and HPC/9 show high expansion due to CA2/CA6 formation The HPC mixes that have lower cement content have a high volume stability 0,00% -0,20% -0,40% -0,25% 0,00% CAC 80 B CAC 70 A HPC/9 HPC/4,5/1 HPC/2,5/1 0,00% -0,06% -0,13% -0,06% -0,25% C C Slide18

19 The Hot Modulus of Rupture confirms the performance of HPC H.M.O.R./MPa/1.500 C ,4 17,1 16, ,4 11, CAC 80 B CAC 70 A HPC/9 HPC/4,5/1 HPC/2,5/1 In spite of the same CA content the H.M.O.R. increases from CAC 80 to HPC/9 by 50% Reducing the HPC content by half does not decrease the H.M.O.R. significantly An HPC addition of only 2,5% leaves the H.M.O.R. at the same level as with CAC 80 Slide 19

20 % Linear Change Refractoriness under Load 1,50 1,00 0,50 Refractoriness under Load in %/f (T) CA 6 Formation T 0,5 CAC CAC HPC/ HPC/4, ,00-0,50-1, Temperature/ C CAC 80 CAC 70 HPC/9 HPC/4,5 HPC/2,5 HPC/2, T 05: Increases strongly with HPC CAC 80 shows a fast weakening with a strong reaction at 300 C ( decomposition of hydrates ) HPC, especially with same CA level as reference has a stable expansion ( CA 6 formation ) Lower contents of HPC confirm volume stability Slide20

21 The Story, we can tell about HiPerCem What is HiPerCem compared to other Calcium Aluminate Cements Quality Control and Shelf Life Tests Comparison of HiPerCem with CAC 70/80 s in a Castable based on Tabular Alumina without MicroSilica HiPerCem in a Tabular Alumina Castable at the same addition as reference CAC s HiPerCem in an LCC Bauxite castable with recycled Bauxite Slide21

22 Tabular Castable: Comparison on a 4,5% Cement addition : HiPerCem vs. CAC 70 s LN: # 11/HPC/1 #12/HPC/2 #13/CAC70A #14/CAC70C HiPerCem 4,5% 4,5% CAC 70 A 4,5% CAC 70 C 4,5% CA content 4,3% 4,3% 2,6% 3,4% CaO content 1,5% 1,5% 1,3% 1,3% Cast. FS 60 0,1% 0,1% 0,1% 0,1% CL 370 4,0% 4,0% 4,0% 4,0% CT 9 FG 10,5% 10,5% 10,5% 10,5% CTC 10 SG 1,5% 1,5% 1,5% 1,5% The test series Compare at the level of 4,5 % addition the influence of two different CAC s versus HiPerCem Keep the admixture the same HPC was tested with two different water additions for adjustment of the flow TabAl ,5% 79,5% 79,5% 79,5% Total 100,0% 100,0% 100,0% 100,0% Water/% 5,1% 5,0% 5,0% 5,0% CAC 70 A contains 1,7% less CA than HiPerCem CAC 70 C has a higher content of CA and is only 0,9% lower in the total formulation Slide 22

23 The working characteristics, expressed as Flow Over Time Flow LN Tabular Alumina 4,5 % CAC , 1 % 5% water 0 # 11/HPC/1 #12/HPC/2 #13/CAC70A #14/CAC70C 5 min 15 min 30 min HiPerCem and CAC 70 A have similar flow with the same water content as well the flow decay CAC 70 C needs more water, as it has a poorer flow and a steeper flow decay HiPerCem with only 0.,1 % water more has a much better flow, without segregation during setting Slide23

24 The Modulus of Rupture 20,0 18,0 17,3 17,1 M.O.R./MPa LN Tabular Alumina 4,5 % CAC 16,0 15,6 14,9 14,9 14,9 14,0 13,2 13,5 12,0 10,0 8,0 6,0 5,5 5,9 4,9 4,7 4,0 2,0 0,0 # 11/HPC/1 #12/HPC/2 #13/CAC70A #14/CAC70C 24h 110 C 1000 C 1300 C Due to higher CA content HiPerCem has better green strength The influence of slightly higher water with #11 is nearly negligible High strength compared to the other CAC s especially after firing Slide24

25 The Cold Crushing Strength CCS/MPa LN Tabular 4,5% CAC # 11/HPC/1 #12/HPC/2 #13/CAC70A #14/CAC70C 24h 110 C 1000 C 1300 C The same development as with the M.O.R. Higher strength: Green as well after firing Surprising: in spite of higher water addition and better flow also best strength values: i.e. low sensitivity to water addition CAC 70 C is spite of second highest CA content lowest strength values Slide25

26 The Stories, we can tell about HiPerCem What is HiPerCem compared to other Calcium Aluminate Cements Quality Control and Shelf Life Tests Comparison of HiPerCem with CAC 70/80 s in a Castable based on Tabular Alumina without MicroSilica HiPerCem in a Tabular Alumina Castable at the same addition as reference CAC s HiPerCem in an LCC Bauxite castable with recycled Bauxite Slide26

27 Cost efficiency: an example with Bauxite Mixes BA 70 A BA HPC 1 BA HPC 2 BA HPC 3 BA HPC 3/1 HPC 2,0% 2,0% 2,0% 2,0% CAC 70 A 6,0% CA content 3,5% 1,9% 1,9% 1,9% 1,9% CaO content 1,8% 0,7% 0,7% 0,7% 0,7% MS 955 U 4,0% 4,0% 4,0% 4,0% 4,0% GKE MF 10,0% 14,0% 8,0% 8,0% 8,0% Bauxite <0,09 15,0% 15,0% 19,0% 19,0% 19,0% Bauxite ,0% 10,0% 12,0% 6,0% 6,0% Bauxite 1-6 mm 45,0% 45,0% 45,0% 22,5% 22,5% Bauxit Rec. 1-6 mm ) 28,5% 28,5% Andalusite ,0% 10,0% 10,0% 10,0% 10,0% Total 100,0% 100,0% 100,0% 100% 100% B 4 H 0,10% 0,10% 0,10% 0,10% 0,10% Cast. FS 20 Water (%) 6,0% 6,0% 6,0% 6,0% 6,3% Chemical composition of Bauxite aggregates Virgin Recycled SiO 2 7,7% 14,5% Al 2 O 3 86,5% 76,0% TiO 2 3,0% 3,3% Fe 2 O 3 1,4% 2,8% CaO 0,6% 0,6% Source is the back-up lining of Steel ladles Step 1 ( yellow line ) reduction of cement and replacement with Alumina( #2) and Bauxite fines ( #3) Step 2 ( green line ) Partial replacement of the Bauxite aggregates with recycled Bauxite Slide27

28 Rheology Flow STEP 1 LN Flow STEP BA 70 A BA HPC 1 BA HPC 2 5 min 15 min 30 min 100 BA HPC 3 BA HPC 3/1 5 min 15 min 30 min STEP 1: The flow is not negatively influenced with the replacement of CA70 with HiPerCem and Alumina or HiPerCem and Bauxite Fines STEP 2: Replacing part of the Bauxite with Recycled materials requires some more water: 6,3 % instead of 6 % water Slide28

29 Physical Properties: Cold Crushing Strength CCS/MPa Step CCS/MPa Step BA 70 A BA HPC 1 BA HPC 2 24h 110 C 1000 C 1300 C BA HPC 3 BA HPC 3/1 24h 110 C 1000 C 1300 C STEP 1: Green strengths at 24h are low with the replacement of HiPerCem and Alumina; whereas when replaced with Bauxite fines are at an adequate level Fired strength distinctively higher STEP 2: With 6 % water a very high strength level similar to virgin material is achieved Slide29 With adjusted water addition, CCS are lower but still higher than CAC Reference

30 Bauxite LC Castables Slag test: Crucibles with Steel slag, fired at C, 5 h 6 % CAC 70 = 1,7 % CaO 3 % HPC = 1,0 % CaO Test temperature at challenging C; simulation for application in delta section of an EAF The reference with 6 % CAC 70 shows heavy penetration, especially in the bottom area The reduction to 3 % HPC shows a good improvement under these heavy conditions. The crucible shows reduced infiltration and shows a better texture on the outer surface Slide30