Title of Invention	PROCESS FOR MAKING IMPROVED HIGH ALUMINA REFRACTORY CEMENT CONTAINING MG-AL SPINEL FROM DOLOMITE.
Abstract	The present invention relates to the process for developing high alumina refractory cement comprising spinel phase and the said spinel phase comprises magnesia and alumina from dolomite and calcined alumina source. The said process comprises steps like selection of viable compositions comprising suitable percentages of dolomite containing cementing phases, preparation of refractory cement samples from said compositions for treating of cementing properties, characterization and optimization of different phases of refractory cement based on X-ray diffraction properties and identification and formation of high alumina refractory cement comprising 30 to 35 % spinel phase.

Title of Invention

PROCESS FOR MAKING IMPROVED HIGH ALUMINA REFRACTORY CEMENT CONTAINING MG-AL SPINEL FROM DOLOMITE.

Abstract

The present invention relates to the process for developing high alumina refractory cement comprising spinel phase and the said spinel phase comprises magnesia and alumina from dolomite and calcined alumina source. The said process comprises steps like selection of viable compositions comprising suitable percentages of dolomite containing cementing phases, preparation of refractory cement samples from said compositions for treating of cementing properties, characterization and optimization of different phases of refractory cement based on X-ray diffraction properties and identification and formation of high alumina refractory cement comprising 30 to 35 % spinel phase.

Full Text	Field of invention The present invention relates to a process of developing high alumina refractory cement with improved thermo-mechanical properties. More particularly, the present invention relates to the process of developing improved high alumina refractory cement comprising a mixture of 40-50 % dolomite and 50-55 % calcined alumina adapted for improving the thermo-mechanical properties of the cement by incorporating Mg-AI spinel. Background of invention At present refractory cements are obtained by fusing or sintering a mixture of aluminous and calcareous materials. The aluminous and calcareous materials are mixed in a suitable proportion. The resultant product thus obtained is grinded to a fine powder. Different qualities of cements are obtained based on the relative quantity of calcium-based phases like CA, C12A7, C5A3, C2S, etc. High alumina cements are used in low cement castable (LCC) and ultra low cement castable (ULCC) as bond to impart strength. Though a lot of studies have been done on the impact of these calcium aluminate phases in castable, still this castable cannot be used as working lining where the temperature is more than 1600 °C. Castable containing Calcium Aluminate phases reacts with SiO2, MnO2 etc. present in the slag and thus get dissolved fast. From CaO-MgO-AI2O3 system, it is founu mat an addition of alumina in dolomite results in a slow drop in refractoriness from 2400 °C to 1700 °C. A similar addition of alumina to lime yields melting points as low as 1500 °C. These are not only more refractory, but have been shown to give substantially longer lives when used to bond magnesia castable. Drawbacks of known art The main disadvantage of the conventional process for making high alumina refractory cement is that the compositions containing proper ratio of Mg-Al spinel and calcined alumina having better thermo-mechanical properties cannot be produced. Another disadvantage is that, since limestone is taken as source of CaO (calcium oxide), the addition of alumina to lime yields melting point as low as 1500°C. Further disadvantage is that the cement containing calcium aluminate produced by the process is less refractory and therefore cannot be used in operating conditions of ladle and other refractory lining where the temperature is more than 1600°C. Yet further disadvantage is that the wear of the castable containing calcium aluminate phases formed by the process is very high in the slag zone as the calcium aluminate phases react with SiO2, MnO2 etc. present in the slag dissolving very fast. Thus there is a need for a process of developing high alumina refractory cement with good thermo-mechanical properties comprising a defined ratio of dolomite and calcined alumina producing Mg-AI spinel. Objects of invention The basic object of the present invention is to prepare high alumina refractory cement containing Mg-AI spinel from dolomite. Another object of the present invention is to consider dolomite as a source of calcium oxide instead of limestone. Dolomite has magnesium oxide alongwith calcium oxide. Further object of the present invention is to produce both calcium aluminate cement and spinel as sintered product after firing calcium oxide with aluminous materials. 2 The other object of the present invention is to provide cement with improved refractoriness, which would serve better in operating conditions of iadfe and other refractory linings. Summary of invention Thus according to the main aspect of the present invention there is provided A process for developing high alumina refractory cement comprising cement phases and spinel phase; the said spinel phase comprising Magnesia and Alumina from dolomite and calcined alumina, the said process comprising: (i) selection of viable compositions comprising suitable percentage of dolomite and calcined alumina for providing defined cement phases alongwith Mg-AI spinel phase; (ii) characterization and optimization of different phases of said refractory cement and spinel by X-ray diffraction; (iii) identification and formation of high alumina refractory cement alongwith 30-35 wt% of spinel without free MgO. Detailed description of invention in the process for developing high alumina refractory cement with Mg-AI spinel phases, different raw materials used are raw dolomite and calcined alumina. From the raw materials the selection of viable compositions comprising suitable percentages of dolomite containing cementing phases is carried out. For this initially different batches are made containing 10 to 90% by weight of dolomite in dolo-alumina system as given in Table-I. 3 TABLE -1 INITIAL FORMULATION OF BATCH The chemical analysis of such raw dolomite, calcined alumina and various formulations are given in Table-ll. 4 TABLE - II CHEMICAL COMPOSITION Samples are made from batches as indicated in Table 1 in the form of small discs of diameter 29 mm and around 5 mm thick under the specific pressure of 1.5t/cm2, using polyvinyl chloride as binder. Raw dolomite lumps are crushed in a jaw crusher followed by roll crusher. After that it is dry ground in a ball mill to pass through 200 BS rush and the powdered dolomite and calcined alumina are mixed intimately in required proportions as shown in TABLE - I in a planetary mixer. Powder mixtures are granulated using binder for better flow and compaction. They are then pressed in a cover press taking a definite amount of powdered granulated mix. After pressing, samples are dried at 110 °C for 24 hours in a hot air oven and then tested for green density by taking weights and geometrical dimensions. Samples are sintered at 1400 °C for 180 minutes in a 17OO°C chamber furnace with super kanthal heating elements at the rate of 5°C per minute and then analyzed for phases present using XRD. Physical examination of sintered samples is also done before testing for phases. Based on the phases observed from initial studies, further formulations are made which would contain cement phases. These formulations have 30 to 60% by weight of dolomite. Compositions of these batches are given in Table-Ill. TABLE - 111 FORMULATION OF CEMENT FORMING BATCHES Such samples are prepared and sintered at 1350 °C, 1400 °C and 1500 °C for different soaking times ranging from 10 to 240 minutes. Some samples are also sintered at 1600 °C and 1650 °C for phase identifications. Sintered samples are tested for bulk density and phase identification. 5 For large scale operation, 5kg batches of selected compositions are made. Briquettes are made in the form of small rectangular blocks of dimensions 50mm x 50mm x 100mm. These are sintered at 1500 °C for 6 hours duration. After firing samples are grounded in a pot mill to fineness of 200 mesh. Powder samples are tested for specific gravity, particle size, surface area, water for normal consistency, setting time and identification of phases. Samples are analyzed for identification of phases by Bruker D8 Advance X-ray Diffraction Unit at 40 mA (milliampere) and 40 volt with Cu-tube. The analysis reveals that compositions IV and V contains sufficient amount of cementing phases as well as Mg-AI spinel. Sample No.VI contains cementing phases and spinel but it also contains free MgO. Therefore, it cannot be used as refractory cement. The amount of main cementing phase i.e. CA is nil in composition III. Thus composition IV and V are identified and used for formation of the alumina refractory cement. These are crushed and grounded to pass -200 mesh sieve. Samples are tested for specific gravity, surface area, normal water consistency, initial and final setting times and strength. The results are given in Table IV. The setting time is varied between 2 hrs 30 minutes for composition IV and 2 hrs 50 minutes for composition V. Commercial cement being used for castabte also take this time for setting. Therefore, no additions are required for controlling this initial setting. However, final setting time is around 3 hrs 35 min to 4 hrs. During application of cement in plant condition initial setting time allows appropriate time for casting. 6 TABLE - IV CEMENTING PROOPERTIES OF DOLOMITE CEMENT Ultra low cement castables are made using developed cement in the laboratory. Samples are tested for apparent porosity (AP), bulk density (BD), cold crushing strength (CCS), permanent linear change (PLC) and hot modulus of rapture (MOR). Slag resistance test is also carried by crucible test. A hole is made into the castable block. It is fired at 1500 °C for 3 hours. Basic oxygen furnace (BOF) slag is put in the hole and fired again at 1600 °c for 4 hours. After the test, slag corrosion is measured by cutting the block into two halves. For micro-structural studies by scanning electron microscope samples are metallic mounted and coated with gold. Samples of ultra low cement castables as above using developed cement Nos. IV and V are tested for various cementing properties including physical and thermal properties such as apparent porosity, bulk density, old crushing strength, permanent linear change, hot modulus of rapture (MOR) of slag resistance. Test results of developed castables are given in Table - V. 7 TABLE - V TEST R ESULTS OF DEVELOPED CASTABLES USING CEMENT COMPOSITIONS IV &V Different cementing phases are formed in different compositions sintered at 1400°C. Table-VI describes the samples produced due to sintering. The first sample DA9 produces 66% by weight of Corundum, 6.2 % by weight of spinel and 27.8 % by weight of Hibonite. The other phases are not produced in this sample. The next sample DA4 produces 44.3 % by weight of Corundum, 16.5 % by weight of spinel and 39.3 % by weight of Hibonite. The other phases are not produced using this sample. In the figure the third sample D3A7 on sintering produce 21 % by of Corundum, 29.4 % by weight of spinel, 42.6% by weight of Hibonite and 7 % by weight of CA2. Another sample D2A3 produces 13 % by weight of Corundum, 48.6 % of spinel, 7.9 % weight of CA, 26.2 % weight of CA2 and 4.2 % weight of C5A3. The next sample DA produces 6 % weight of Corundum, 44.2 % by weight of spinel, 42.2 % by weight of CA, 4.6 % by weight of CA2 and 3 % by weight of Periclase. Another sample D3A2 on sintering produces 62.4 % by weight of spinel, 23.6 % by weight of 8 C5A3 and 9.4 % by weight of Mayenite. The next sample D7A3 produces 30.2 % by weight of spinel, 28.4 % by weight of C5A3, 10.7 % by weight of Mayenite, 26.3 % by weight of Periclase and 4.5 % by weight of CaO. Next sample D4A on sintering produces 7.7 % by weight of Mayenite and 92.3 % by weight of Periclase. The last sample D9A shown in the graph produces 36.1 % by weight of C3A, 54.1 % by weight of Periclase and 9.8 % by weight of CaO. TABLE - VI PHASES FORMED IN DIFFERENT COMPOSITION SINTERED AT 1400°C FOR 3 HOURS On sintering at 1450 °C for 2 hrs. different composition produce different phases as shown in Table-VII. Composition I contains 6.4% AI2O3l 30.3% MA, 27.9% CA2, 22.7% CAe, 3.5% C3A, 9.1% CMA and 3.7% C9A3. Composition II contains 6.1% AI2O3, 32.5% MA, 38.3% CA2 7.4% CA6 and 11.9% C5A3. Composition IV contains 4.4% AI2O3, 31.7% MA, 38.1% CA, 10.9% CA2, 3.8% CA6 and 10.9 C3A5. Composition V contains 1.3% AI2O3, 35.6% MA, 53.1% CA, 4.9% CA2 and 5.2% CAe. 9 Composition VI contains 1.9% AI2O3l 39.4% MA, 22.7% CA, 26.5% C12A7and 9.5% CXA11. TABLE - VII AMOUNT OF PHASES PRESENT IN DIFFERENT COMPOSITION SINTERED AT 1450 °C/2 hrs. On sintering at 1500 °C for 2 hrs. different composition produce different phases as shown in Table-VIII. Composition I contains 11.8% MA, 23.4% CA2, 30.3% CA6and 24.6% CMA. Composition II contains 2.08% AI2O3, 37.5% MA, 39.06% CA2, 2.86% CA6and 9.9% C3A2. Composition III contains 19.1% MA, 48.3% CA2\| 3.2% CA6, 12.9% C3A and 15% CMA. Composition IV contains 25.7% MA, 30.9% CA, 30.2% CA2 and 3.8% CA6. Composition V contains 29.3% MA, 66.5% CA and 4.2% CA2. Composition VI contains 1.9% AI2O3,11.4% MgO, 47.5% MA, 32.9% C3A and 6.4% C12A7. 10 TABLE - VIII AMOUNT OF PHASES PRESENT IN DIFFERENT COMPOSITION SINTERED AT 1500 °C/2 hrs. Brief description of accompanying figures Figure 1 illustrates the phases formed in different compositions sintered at 1400 °C for 3 hours. Figure 2a illustrates the densification curves for composition I. Figure 2b illustrates the densification curves for composition II. Figure 3a illustrates the densification curves for composition III. Figure 3b illustrates the densification curves for composition IV. 11 Figure 4 illustrates the densification curves for composition V. Figure 5 illustrates the XRD pattern of composition I, sintered at 1500 °C/2 hrs. Figure 6 illustrates the XRD pattern of composition II, sintered at 1500 °C/2 hrs. Figure 7 illustrates the XRD pattern of composition III, sintered at 1500 °C/2 hrs. Figure 8 illustrates the XRD pattern of composition IV, sintered at 1500 °C/2 hrs. Figure 9 illustrates the XRD pattern of composition V, sintered at 1500 °C/2 hrs. Figure 10 illustrates the XRD pattern of composition VI, sintered at 1500 °C/2 hrs. Figure 11 illustrates the amount of phases present in different samples, sintered at 1450 °C/2 hrs. Figure 12 illustrates the amount of phases present in different compositions, sintered at1500°C/2hrs. In figure 1 the graph describes various phases present in different compositions. The x-axis of the graph represents different cementing phases and the y-axis represents the weight percentages of the phases formed in different compositions. From figure 1 it is observed that samples containing 10 to 30% by weight of dolomite do not contain any cementing phases. Composition containing 70 to 90% weight of dolomite though contains some cementing phases but these samples also contain large amount of free MgO. Hence samples containing 10 to 30 and 70 to 90% by weight of dolomite are not considered for further investigation. Composition containing 30 to 60% by weight of dolomite are selected for further investigation. 12 Figure 2a illustrates the densification behaviour of composition I with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in sintering time and temperature at the early parts of soaking. At sintering temperature of 1350 °C, it is observed that there is a decrease in the density upto a time of about 55 minutes. Then between the time slab of 55 and 120 minutes (approx) there is a steady increase in BD. Then there is no further increment in BD and the curve takes the form of a straight line. From figure 2a it is also observed that at a sintering temperature of 1400 °C there are number of crests and troughs in the curve indicating frequent variation in BD upto time of 120 minutes (approx) after which the rate of increase of bulk density is slow. At 1450 °C the slopes of the curves indicates the sharp variations in BD upto a time span of 55 minutes (approx) after which it is almost flat upto 200 minutes. At 1500 °C between time span of 120 and 200 minutes there is a steady increase in BD. Figure 2b illustrates the densification behaviour of composition II with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in sintering time and temperature at the early parts of soaking. At sintering temperature of 1350 °C, it is observed that there is a slight decrease in the density upto a time of about 55 minutes. Then between the time slab of 55 and 120 minutes (approx) there 13 is a slight increase in BD. Then there is no further increment in BD and the curve takes the form of a straight line. From figure 2b it is also observed that at a sintering temperature of 1400 °C there is a increase in BD upto 30 °C after which BD starts decreasing at a very slow rate upto 200 minutes. At 1450 °C the slopes of the curve almost overlap with that at 1400 °C upto a time span of 55 minutes (approx) after which it increases slowly upto 200 minutes. At 1500 °C upto 55 minutes the slopes of the curve indicate moderate variation in BD and between time span of 55 and 200 the curve is almost flat indicating minute variation in BD. Figure 3a illustrates the densification behaviour of composition III with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in sintering time and temperature at the early parts of soaking. At sintering temperatures of 1350 °C, 1400 °C and 1450 °C the variation in the values of BD is less. At 1500 °C upto 55 minutes (approx) the slopes of the curve indicate large variation in BD. After that between time span of 55 and 200 minutes the value of the BD almost saturates. Figure 3b illustrates the densification behaviour of composition IV with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in 14 sintering time and temperature at the early parts of soaking. At sintering temperature of 1350 °C, it is observed that the curve is almost flat between 0 and 200 minutes maintaining the value of BD at 1.5 g/cm3 (approx). From figure 3b it is also observed that at a sintering temperature of 1400 °C there are number of crests and troughs in the curve indicating frequent variation in BD upto time of 120 minutes (approx) after which the value of BD slowly drops around 1.5 g/cm3. At 1450 °C the slopes of the curves indicates the decrease in BD upto 30 minutes and a slow increase in BD between 30 and 55 minutes after which the value of BD saturates around 2 g/cm3. At 1500 °C between time-spans of 0 and 200 minutes there is a slight variation in the value of BD around 2.5 g/cm3. Figure 4 illustrates the densification behaviour of composition V with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in sintering time and temperature at the early parts of soaking. At sintering temperature of 1350 °C and 1400 °C, it is observed that the values of BD in both the curves vary roughly around 1.5 g/cm3. At 1450 °C the slopes of the curve indicates the sharp fall in the value of BD upto 30 minutes and increment in the value of BD upto a time span of 55 minutes (approx) after which it is almost flat upto 200 minutes. At 1500 °C the value of bulk density (BD) increases slightly above 2.5 g/cm3 after which the value of BD decreases upto 55 minutes and then the curve is almost flat. Figure 5 illustrates the XRD pattern of composition I sintered at 1500C/2hr in which X-axis represents 29 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi- 15 quantitative % of phases present. The phases present are Spinel - 21.9%, Grossite (CA2) - 26.9% hibonite (CA6) - 40.9% and C3A. Figure 6 illustrates the XRD pattern of composition II sintered at 1500C/2hr in which X-axis represents 29 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi-quantitative % of phases present. The phases present are Spinel - 33.1%, Grossite (CA2) - 57.9% hibonite (CAe) - 5.9% and corundum - 3.1%. Figure 7 illustrates the XRD pattern of composition III sintered at 1500C/2hr in which X-axis represents 26 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi-quantitative % of phases present. The phases present are Spinel - 25.3%, Grossite (CA2) -44.0% hibonite (CAe) - 3.8%, C3A - 16.7% and corundum - 3.1%. Figure 8 illustrates the XRD pattern of composition IV sintered at 1500C/2hr in which X-axis represents 29 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi-quantitative % of phases present. The phases present are Spinel - 25.7%, Grossite (CA2) - 40.3%, CA - 30.9%, hibonite (CAe) - 3.8%, C3A - 16.7% and corundum -3.1%. Figure 9 illustrates the XRD pattern of composition V sintered at 1500C/2hr in which X-axis represents 26 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi-quantitative % of phases present. The phases present are Spinel - 29.3%, Grossite (CA2) - 18.9% CA-51.8%. Figure 10 illustrates the XRD pattern of composition VI sintered at 1500C/2hr in which X-axis represents 26 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the 16 semi-quantitative % of phases present. The phases present are Spinel - 47.5%, corundum - 1.9%, C3A - 32.9%, C12A7 - 6.4% and MgC - 11.4%. Figure 11 illustrates the amount of phases present in different samples when sintered at 1450 °C for 2 hrs. The x-axis of the graph represents compositions I, II, III, IV, V and VI whereas the y-axis represents the amount of different phases. Figure 12 illustrates the amount of phases present in different samples when sintered at 1500 °C for 2 hrs. The x-axis of the graph represents compositions I, II, III, IV, V and VI whereas the y-axis represents the amount of different phases. 17 We claim 1. A process for developing high alumina refractory cement comprising cement phases and spinel phase; the said spinel phase comprising Magnesia and Alumina from dolomite and calcined alumina, the said process comprising: (i) selection of viable compositions comprising suitable percentage of dolomite and calcined alumina for providing defined cement phases alongwith Mg-AI spine! phase; (ii) characterization and optimization of different phases of said refractory cement and spinel by X-ray diffraction; (iii) identification and formation of high alumina refractory cement alongwith 30r35 wt% of spinel without free MgO. 2. A process as claimed in claim 1 wherein the viable compositions comprise 40-50 wt% of dolomite 50-55 wt% calcined alumina. 3. A process as claimed in claims 1 and 2 wherein dolomite and calcined alumina sintered at 1450-1500°C give 30-35 wt% spinel and 65-70 wt% cementing phases containing CA and CA2. 4. A process as claimed in claims 1 to 3 wherein characterization and optimization is carried out in steps wherein initial step comprise formation of samples of different batches of the compositions containing dolomite and calcined alumina in small discs of diameter 29 mm and 5 mm thick under pressure of 1.5 t/cm2 with a binder. 5. A process as claimed in claim 4 wherein the binder used is polyvinyl chloride adapted to provide high mechanical strength and compaction to the spinel phase. 18 6. A process as claimed in claims 1 to 5 wherein next step for characterization and optimization comprises sintering of samples at 1350°C, 1400°C, 1450°C and 1500°C for soaking times ranging between 10 and 240 minutes. 7. A process as claimed in claims 6 wherein the sintered samples are ground to fineness of - 200 mesh (BS). 8. A process as claimed in claims 1 to 7 wherein the samples are further analyzed for detail characterization and optimization by X-ray diffraction unit at 40 mA and 40 volt. 9. A process as claimed in claims 1 to 8 wherein XRD pattern identified for phases of sample of composition IV comprising 45 wt% dolomite and 55 wt% calcined alumina indicate 31.7 wt% spinel and 49 wt% cementing phases CA and CA2. 10. A process as claimed in claims 1 to 9 wherein XRD pattern identified for phases of sample of composition V comprising 50 wt% dolomite and 50 wt% calcined alumina indicate are 35.6 wt% spinel and 58 wt% cementing phases CA and CA2. 11 .A process as substantially described and illustrated with reference to accompanying figures. 19 The present invention relates to the process for developing high alumina refractory cement comprising spinel phase and the said spinel phase comprises magnesia and alumina from dolomite and calcined alumina source. The said process comprises steps like selection of viable compositions comprising suitable percentages of dolomite containing cementing phases, preparation of refractory cement samples from said compositions for treating of cementing properties, characterization and optimization of different phases of refractory cement based on X-ray diffraction properties and identification and formation of high alumina refractory cement comprising 30 to 35 % spinel phase.

Full Text

Field of invention
The present invention relates to a process of developing high alumina refractory cement with improved thermo-mechanical properties. More particularly, the present invention relates to the process of developing improved high alumina refractory cement comprising a mixture of 40-50 % dolomite and 50-55 % calcined alumina adapted for improving the thermo-mechanical properties of the cement by incorporating Mg-AI spinel.
Background of invention
At present refractory cements are obtained by fusing or sintering a mixture of aluminous and calcareous materials. The aluminous and calcareous materials are mixed in a suitable proportion. The resultant product thus obtained is grinded to a fine powder. Different qualities of cements are obtained based on the relative quantity of calcium-based phases like CA, C12A7, C5A3, C2S, etc.
High alumina cements are used in low cement castable (LCC) and ultra low cement castable (ULCC) as bond to impart strength. Though a lot of studies have been done on the impact of these calcium aluminate phases in castable, still this castable cannot be used as working lining where the temperature is more than 1600 °C. Castable containing Calcium Aluminate phases reacts with SiO2, MnO2 etc. present in the slag and thus get dissolved fast.
From CaO-MgO-AI2O3 system, it is founu mat an addition of alumina in dolomite results in a slow drop in refractoriness from 2400 °C to 1700 °C. A similar addition of alumina to lime yields melting points as low as 1500 °C. These are not only more refractory, but have been shown to give substantially longer lives when used to bond magnesia castable.

Drawbacks of known art
The main disadvantage of the conventional process for making high alumina refractory cement is that the compositions containing proper ratio of Mg-Al spinel and calcined alumina having better thermo-mechanical properties cannot be produced.
Another disadvantage is that, since limestone is taken as source of CaO (calcium oxide), the addition of alumina to lime yields melting point as low as 1500°C.
Further disadvantage is that the cement containing calcium aluminate produced by the process is less refractory and therefore cannot be used in operating conditions of ladle and other refractory lining where the temperature is more than 1600°C.
Yet further disadvantage is that the wear of the castable containing calcium aluminate phases formed by the process is very high in the slag zone as the calcium aluminate phases react with SiO2, MnO2 etc. present in the slag dissolving very fast.
Thus there is a need for a process of developing high alumina refractory cement with good thermo-mechanical properties comprising a defined ratio of dolomite and calcined alumina producing Mg-AI spinel.
Objects of invention
The basic object of the present invention is to prepare high alumina refractory cement containing Mg-AI spinel from dolomite.
Another object of the present invention is to consider dolomite as a source of calcium oxide instead of limestone. Dolomite has magnesium oxide alongwith calcium oxide.
Further object of the present invention is to produce both calcium aluminate cement and spinel as sintered product after firing calcium oxide with aluminous materials.
2

The other object of the present invention is to provide cement with improved refractoriness, which would serve better in operating conditions of iadfe and other refractory linings.
Summary of invention
Thus according to the main aspect of the present invention there is provided A process for developing high alumina refractory cement comprising cement phases and spinel phase; the said spinel phase comprising Magnesia and Alumina from dolomite and calcined alumina, the said process comprising:
(i) selection of viable compositions comprising suitable percentage of
dolomite and calcined alumina for providing defined cement phases
alongwith Mg-AI spinel phase; (ii) characterization and optimization of different phases of said refractory
cement and spinel by X-ray diffraction; (iii) identification and formation of high alumina refractory cement alongwith
30-35 wt% of spinel without free MgO.
Detailed description of invention
in the process for developing high alumina refractory cement with Mg-AI spinel phases, different raw materials used are raw dolomite and calcined alumina. From the raw materials the selection of viable compositions comprising suitable percentages of dolomite containing cementing phases is carried out. For this initially different batches are made containing 10 to 90% by weight of dolomite in dolo-alumina system as given in Table-I.
3

TABLE -1 INITIAL FORMULATION OF BATCH

The chemical analysis of such raw dolomite, calcined alumina and various formulations are given in Table-ll.
4
TABLE - II CHEMICAL COMPOSITION

Samples are made from batches as indicated in Table 1 in the form of small discs of diameter 29 mm and around 5 mm thick under the specific pressure of 1.5t/cm2, using polyvinyl chloride as binder. Raw dolomite lumps are crushed in a jaw crusher followed by roll crusher. After that it is dry ground in a ball mill to pass through 200 BS rush and the powdered dolomite and calcined alumina are mixed intimately in required proportions as shown in TABLE - I in a planetary mixer. Powder mixtures are granulated using binder for better flow and compaction. They are then pressed in a cover press taking a definite amount of powdered granulated mix. After pressing, samples are dried at 110 °C for 24 hours in a hot air oven and then tested for green density by taking weights and geometrical dimensions. Samples are sintered at 1400 °C for 180 minutes in a 17OO°C chamber furnace with super kanthal heating elements at the rate of 5°C per minute and then analyzed for phases present using XRD. Physical examination of sintered samples is also done before testing for phases.
Based on the phases observed from initial studies, further formulations are made which would contain cement phases. These formulations have 30 to 60% by weight of dolomite. Compositions of these batches are given in Table-Ill.
TABLE - 111 FORMULATION OF CEMENT FORMING BATCHES

Such samples are prepared and sintered at 1350 °C, 1400 °C and 1500 °C for different soaking times ranging from 10 to 240 minutes. Some samples are also sintered at 1600 °C and 1650 °C for phase identifications. Sintered samples are tested for bulk density and phase identification.
5

For large scale operation, 5kg batches of selected compositions are made. Briquettes are made in the form of small rectangular blocks of dimensions 50mm x 50mm x 100mm. These are sintered at 1500 °C for 6 hours duration. After firing samples are grounded in a pot mill to fineness of 200 mesh. Powder samples are tested for specific gravity, particle size, surface area, water for normal consistency, setting time and identification of phases.
Samples are analyzed for identification of phases by Bruker D8 Advance X-ray Diffraction Unit at 40 mA (milliampere) and 40 volt with Cu-tube. The analysis reveals that compositions IV and V contains sufficient amount of cementing phases as well as Mg-AI spinel. Sample No.VI contains cementing phases and spinel but it also contains free MgO. Therefore, it cannot be used as refractory cement. The amount of main cementing phase i.e. CA is nil in composition III.
Thus composition IV and V are identified and used for formation of the alumina refractory cement. These are crushed and grounded to pass -200 mesh sieve. Samples are tested for specific gravity, surface area, normal water consistency, initial and final setting times and strength. The results are given in Table IV. The setting time is varied between 2 hrs 30 minutes for composition IV and 2 hrs 50 minutes for composition V. Commercial cement being used for castabte also take this time for setting. Therefore, no additions are required for controlling this initial setting. However, final setting time is around 3 hrs 35 min to 4 hrs. During application of cement in plant condition initial setting time allows appropriate time for casting.
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TABLE - IV
CEMENTING PROOPERTIES OF DOLOMITE CEMENT

Ultra low cement castables are made using developed cement in the laboratory. Samples are tested for apparent porosity (AP), bulk density (BD), cold crushing strength (CCS), permanent linear change (PLC) and hot modulus of rapture (MOR). Slag resistance test is also carried by crucible test. A hole is made into the castable block. It is fired at 1500 °C for 3 hours. Basic oxygen furnace (BOF) slag is put in the hole and fired again at 1600 °c for 4 hours. After the test, slag corrosion is measured by cutting the block into two halves. For micro-structural studies by scanning electron microscope samples are metallic mounted and coated with gold.
Samples of ultra low cement castables as above using developed cement Nos. IV and V are tested for various cementing properties including physical and thermal properties such as apparent porosity, bulk density, old crushing strength, permanent linear change, hot modulus of rapture (MOR) of slag resistance. Test results of developed castables are given in Table - V.
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TABLE - V
TEST R ESULTS OF DEVELOPED CASTABLES USING CEMENT
COMPOSITIONS IV &V

Different cementing phases are formed in different compositions sintered at 1400°C. Table-VI describes the samples produced due to sintering. The first sample DA9 produces 66% by weight of Corundum, 6.2 % by weight of spinel and 27.8 % by weight of Hibonite. The other phases are not produced in this sample. The next sample DA4 produces 44.3 % by weight of Corundum, 16.5 % by weight of spinel and 39.3 % by weight of Hibonite. The other phases are not produced using this sample. In the figure the third sample D3A7 on sintering produce 21 % by of Corundum, 29.4 % by weight of spinel, 42.6% by weight of Hibonite and 7 % by weight of CA2. Another sample D2A3 produces 13 % by weight of Corundum, 48.6 % of spinel, 7.9 % weight of CA, 26.2 % weight of CA2 and 4.2 % weight of C5A3. The next sample DA produces 6 % weight of Corundum, 44.2 % by weight of spinel, 42.2 % by weight of CA, 4.6 % by weight of CA2 and 3 % by weight of Periclase. Another sample D3A2 on sintering produces 62.4 % by weight of spinel, 23.6 % by weight of
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C5A3 and 9.4 % by weight of Mayenite. The next sample D7A3 produces 30.2 % by weight of spinel, 28.4 % by weight of C5A3, 10.7 % by weight of Mayenite, 26.3 % by weight of Periclase and 4.5 % by weight of CaO. Next sample D4A on sintering produces 7.7 % by weight of Mayenite and 92.3 % by weight of Periclase. The last sample D9A shown in the graph produces 36.1 % by weight of C3A, 54.1 % by weight of Periclase and 9.8 % by weight of CaO.
TABLE - VI
PHASES FORMED IN DIFFERENT COMPOSITION SINTERED AT 1400°C FOR 3 HOURS

On sintering at 1450 °C for 2 hrs. different composition produce different phases as shown in Table-VII. Composition I contains 6.4% AI2O3l 30.3% MA, 27.9% CA2, 22.7% CAe, 3.5% C3A, 9.1% CMA and 3.7% C9A3. Composition II contains 6.1% AI2O3, 32.5% MA, 38.3% CA2 7.4% CA6 and 11.9% C5A3. Composition IV contains 4.4% AI2O3, 31.7% MA, 38.1% CA, 10.9% CA2, 3.8% CA6 and 10.9 C3A5. Composition V contains 1.3% AI2O3, 35.6% MA, 53.1% CA, 4.9% CA2 and 5.2% CAe.
9

Composition VI contains 1.9% AI2O3l 39.4% MA, 22.7% CA, 26.5% C12A7and 9.5% CXA11.
TABLE - VII
AMOUNT OF PHASES PRESENT IN DIFFERENT COMPOSITION SINTERED AT 1450 °C/2 hrs.

On sintering at 1500 °C for 2 hrs. different composition produce different phases as shown in Table-VIII. Composition I contains 11.8% MA, 23.4% CA2, 30.3% CA6and 24.6% CMA. Composition II contains 2.08% AI2O3, 37.5% MA, 39.06% CA2, 2.86% CA6and 9.9% C3A2. Composition III contains 19.1% MA, 48.3% CA2| 3.2% CA6, 12.9% C3A and 15% CMA. Composition IV contains 25.7% MA, 30.9% CA, 30.2% CA2 and 3.8% CA6. Composition V contains 29.3% MA, 66.5% CA and 4.2% CA2. Composition VI contains 1.9% AI2O3,11.4% MgO, 47.5% MA, 32.9% C3A and 6.4% C12A7.
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TABLE - VIII
AMOUNT OF PHASES PRESENT IN DIFFERENT COMPOSITION SINTERED AT 1500 °C/2 hrs.

Brief description of accompanying figures
Figure 1 illustrates the phases formed in different compositions sintered at 1400 °C for 3 hours.
Figure 2a illustrates the densification curves for composition I. Figure 2b illustrates the densification curves for composition II. Figure 3a illustrates the densification curves for composition III. Figure 3b illustrates the densification curves for composition IV.
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Figure 4 illustrates the densification curves for composition V. Figure 5 illustrates the XRD pattern of composition I, sintered at 1500 °C/2 hrs. Figure 6 illustrates the XRD pattern of composition II, sintered at 1500 °C/2 hrs. Figure 7 illustrates the XRD pattern of composition III, sintered at 1500 °C/2 hrs. Figure 8 illustrates the XRD pattern of composition IV, sintered at 1500 °C/2 hrs. Figure 9 illustrates the XRD pattern of composition V, sintered at 1500 °C/2 hrs. Figure 10 illustrates the XRD pattern of composition VI, sintered at 1500 °C/2 hrs.
Figure 11 illustrates the amount of phases present in different samples, sintered at 1450 °C/2 hrs.
Figure 12 illustrates the amount of phases present in different compositions, sintered at1500°C/2hrs.
In figure 1 the graph describes various phases present in different compositions. The x-axis of the graph represents different cementing phases and the y-axis represents the weight percentages of the phases formed in different compositions. From figure 1 it is observed that samples containing 10 to 30% by weight of dolomite do not contain any cementing phases. Composition containing 70 to 90% weight of dolomite though contains some cementing phases but these samples also contain large amount of free MgO. Hence samples containing 10 to 30 and 70 to 90% by weight of dolomite are not considered for further investigation. Composition containing 30 to 60% by weight of dolomite are selected for further investigation.
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Figure 2a illustrates the densification behaviour of composition I with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in sintering time and temperature at the early parts of soaking. At sintering temperature of 1350 °C, it is observed that there is a decrease in the density upto a time of about 55 minutes. Then between the time slab of 55 and 120 minutes (approx) there is a steady increase in BD. Then there is no further increment in BD and the curve takes the form of a straight line. From figure 2a it is also observed that at a sintering temperature of 1400 °C there are number of crests and troughs in the curve indicating frequent variation in BD upto time of 120 minutes (approx) after which the rate of increase of bulk density is slow. At 1450 °C the slopes of the curves indicates the sharp variations in BD upto a time span of 55 minutes (approx) after which it is almost flat upto 200 minutes. At 1500 °C between time span of 120 and 200 minutes there is a steady increase in BD.
Figure 2b illustrates the densification behaviour of composition II with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in sintering time and temperature at the early parts of soaking. At sintering temperature of 1350 °C, it is observed that there is a slight decrease in the density upto a time of about 55 minutes. Then between the time slab of 55 and 120 minutes (approx) there
13

is a slight increase in BD. Then there is no further increment in BD and the curve takes the form of a straight line. From figure 2b it is also observed that at a sintering temperature of 1400 °C there is a increase in BD upto 30 °C after which BD starts decreasing at a very slow rate upto 200 minutes. At 1450 °C the slopes of the curve almost overlap with that at 1400 °C upto a time span of 55 minutes (approx) after which it increases slowly upto 200 minutes. At 1500 °C upto 55 minutes the slopes of the curve indicate moderate variation in BD and between time span of 55 and 200 the curve is almost flat indicating minute variation in BD.
Figure 3a illustrates the densification behaviour of composition III with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in sintering time and temperature at the early parts of soaking. At sintering temperatures of 1350 °C, 1400 °C and 1450 °C the variation in the values of BD is less. At 1500 °C upto 55 minutes (approx) the slopes of the curve indicate large variation in BD. After that between time span of 55 and 200 minutes the value of the BD almost saturates.
Figure 3b illustrates the densification behaviour of composition IV with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in
14

sintering time and temperature at the early parts of soaking. At sintering temperature of 1350 °C, it is observed that the curve is almost flat between 0 and 200 minutes maintaining the value of BD at 1.5 g/cm3 (approx). From figure 3b it is also observed that at a sintering temperature of 1400 °C there are number of crests and troughs in the curve indicating frequent variation in BD upto time of 120 minutes (approx) after which the value of BD slowly drops around 1.5 g/cm3. At 1450 °C the slopes of the curves indicates the decrease in BD upto 30 minutes and a slow increase in BD between 30 and 55 minutes after which the value of BD saturates around 2 g/cm3. At 1500 °C between time-spans of 0 and 200 minutes there is a slight variation in the value of BD around 2.5 g/cm3.
Figure 4 illustrates the densification behaviour of composition V with variation in temperatures. In the figure x-axis represents time during which the temperature is varied and the y-axis represents the variation in the bulk density expressed in g/cm3. In the curve it is observed that there is a large variation in the bulk density with respect to time and temperature at the early parts of soaking between 0 and 100 minute. Between the time span of 100 and 200 minute the variations in bulk density (BD) are marginal with respect to the changes in time. From the figure it is realizable that there is no specific trend of increase in BD with respect to the changes in sintering time and temperature at the early parts of soaking. At sintering temperature of 1350 °C and 1400 °C, it is observed that the values of BD in both the curves vary roughly around 1.5 g/cm3. At 1450 °C the slopes of the curve indicates the sharp fall in the value of BD upto 30 minutes and increment in the value of BD upto a time span of 55 minutes (approx) after which it is almost flat upto 200 minutes. At 1500 °C the value of bulk density (BD) increases slightly above 2.5 g/cm3 after which the value of BD decreases upto 55 minutes and then the curve is almost flat.
Figure 5 illustrates the XRD pattern of composition I sintered at 1500C/2hr in which X-axis represents 29 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi-
15

quantitative % of phases present. The phases present are Spinel - 21.9%, Grossite (CA2) - 26.9% hibonite (CA6) - 40.9% and C3A.
Figure 6 illustrates the XRD pattern of composition II sintered at 1500C/2hr in which X-axis represents 29 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi-quantitative % of phases present. The phases present are Spinel - 33.1%, Grossite (CA2) - 57.9% hibonite (CAe) - 5.9% and corundum - 3.1%.
Figure 7 illustrates the XRD pattern of composition III sintered at 1500C/2hr in which X-axis represents 26 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi-quantitative % of phases present. The phases present are Spinel - 25.3%, Grossite (CA2) -44.0% hibonite (CAe) - 3.8%, C3A - 16.7% and corundum - 3.1%.
Figure 8 illustrates the XRD pattern of composition IV sintered at 1500C/2hr in which X-axis represents 29 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi-quantitative % of phases present. The phases present are Spinel - 25.7%, Grossite (CA2) - 40.3%, CA - 30.9%, hibonite (CAe) - 3.8%, C3A - 16.7% and corundum -3.1%.
Figure 9 illustrates the XRD pattern of composition V sintered at 1500C/2hr in which X-axis represents 26 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the semi-quantitative % of phases present. The phases present are Spinel - 29.3%, Grossite (CA2) - 18.9% CA-51.8%.
Figure 10 illustrates the XRD pattern of composition VI sintered at 1500C/2hr in which X-axis represents 26 angle in degree and the Y-axis represents the intensity of the peak in counts. It also illustrate the phases present in the composition with the
16

semi-quantitative % of phases present. The phases present are Spinel - 47.5%, corundum - 1.9%, C3A - 32.9%, C12A7 - 6.4% and MgC - 11.4%.
Figure 11 illustrates the amount of phases present in different samples when sintered at 1450 °C for 2 hrs. The x-axis of the graph represents compositions I, II, III, IV, V and VI whereas the y-axis represents the amount of different phases.
Figure 12 illustrates the amount of phases present in different samples when sintered at 1500 °C for 2 hrs. The x-axis of the graph represents compositions I, II, III, IV, V and VI whereas the y-axis represents the amount of different phases.
17

We claim
1. A process for developing high alumina refractory cement comprising cement
phases and spinel phase; the said spinel phase comprising Magnesia and
Alumina from dolomite and calcined alumina, the said process comprising:
(i) selection of viable compositions comprising suitable percentage of
dolomite and calcined alumina for providing defined cement phases
alongwith Mg-AI spine! phase; (ii) characterization and optimization of different phases of said refractory
cement and spinel by X-ray diffraction; (iii) identification and formation of high alumina refractory cement alongwith
30r35 wt% of spinel without free MgO.
2. A process as claimed in claim 1 wherein the viable compositions comprise 40-50
wt% of dolomite 50-55 wt% calcined alumina.
3. A process as claimed in claims 1 and 2 wherein dolomite and calcined alumina
sintered at 1450-1500°C give 30-35 wt% spinel and 65-70 wt% cementing
phases containing CA and CA2.
4. A process as claimed in claims 1 to 3 wherein characterization and optimization
is carried out in steps wherein initial step comprise formation of samples of
different batches of the compositions containing dolomite and calcined alumina in
small discs of diameter 29 mm and 5 mm thick under pressure of 1.5 t/cm2 with a
binder.
5. A process as claimed in claim 4 wherein the binder used is polyvinyl chloride
adapted to provide high mechanical strength and compaction to the spinel phase.
18

6. A process as claimed in claims 1 to 5 wherein next step for characterization
and optimization comprises sintering of samples at 1350°C, 1400°C, 1450°C
and 1500°C for soaking times ranging between 10 and 240 minutes.
7. A process as claimed in claims 6 wherein the sintered samples are ground to
fineness of - 200 mesh (BS).
8. A process as claimed in claims 1 to 7 wherein the samples are further
analyzed for detail characterization and optimization by X-ray diffraction unit
at 40 mA and 40 volt.
9. A process as claimed in claims 1 to 8 wherein XRD pattern identified for
phases of sample of composition IV comprising 45 wt% dolomite and 55 wt%
calcined alumina indicate 31.7 wt% spinel and 49 wt% cementing phases CA
and CA2.
10. A process as claimed in claims 1 to 9 wherein XRD pattern identified for
phases of sample of composition V comprising 50 wt% dolomite and 50 wt%
calcined alumina indicate are 35.6 wt% spinel and 58 wt% cementing phases
CA and CA2.
11 .A process as substantially described and illustrated with reference to accompanying figures.

19
The present invention relates to the process for developing high alumina refractory cement comprising spinel phase and the said spinel phase comprises magnesia and alumina from dolomite and calcined alumina source. The said process comprises steps like selection of viable compositions comprising suitable percentages of dolomite containing cementing phases, preparation of refractory cement samples from said compositions for treating of cementing properties, characterization and optimization of different phases of refractory cement based on X-ray diffraction properties and identification and formation of high alumina refractory cement comprising 30 to 35 % spinel phase.

Documents:

00622-kol-2004-abstract.pdf

00622-kol-2004-claims.pdf

00622-kol-2004-correspondence.pdf

00622-kol-2004-description(complete).pdf

00622-kol-2004-drawings.pdf

00622-kol-2004-form-1.pdf

00622-kol-2004-form-18.pdf

00622-kol-2004-form-2.pdf

00622-kol-2004-form-3.pdf

00622-kol-2004-letters patent.pdf

00622-kol-2004-p.a.pdf

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Patent Number

207106

Indian Patent Application Number

622/KOL/2004

PG Journal Number

21/2007

Publication Date

25-May-2007

Grant Date

23-May-2007

Date of Filing

30-Sep-2004

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

RESEARCH & DEVELOPMENT CENTRE FOR LRON & STEEL,DORANDA,RANCHI-834002

Inventors:

#	Inventor's Name	Inventor's Address
1	JAGADISH PRASAD	RE-SEARCH AND DEVELOPMENT CENTER FOR IRON AND STEEL,STEEL AUTHORITY OF INDIA LTD.,DORANDA,RANCHI-834002,
2	PRASANTA NANDI	RESEARCH AND DEVELOPMENT CENTER FOR IRON AND STEEL,STEEL AUTHORITY OF INDIALTD.,DORANDA RANCHI-834002,
3	KAUSHLESH KUMAR	RESEARCH AND DEVELOPMENT CENTER FOR IRON AND STEEL,STEEL AUTHORITY OF INDIALTD.,DORANDA RANCHI-834002,
4	LAKSHMAN TIWARI	RESEARCH AND DEVELOPMENT CENTER FOR IRON AND STEEL,STEEL AUTHORITY OF INDIALTD.,DORANDA RANCHI-834002,
5	BANSI DHAR CHATTARAJ	RESEARCH AND DEVELOPMENT CENTER FOR IRON AND STEEL,STEEL AUTHORITY OF INDIALTD.,DORANDA RANCHI-834002,

PCT International Classification Number

C-04B 7 /22

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA