FIELD OF INVENTION:

The present invention relates to a rapid setting refiactory binder mix capable of forming a hard bonded refiactory composition. The refiactory shapes or products have good wear resistance after firing and hence useful for applications involving high temperature and abrasion.
The present invention also relates to a process for preparing the rapid setting refractory binder mix.

BACKGROUND OF INVENTION:

The invention relates generally to refractory castable composition which is formulated by mechanical vibration. Refiactory material for vibration forming is required to be thixotropic. The refractory material loses its viscosity and becomes flowable and upon the removal of vibration, the separate pieces knit together and become stiff So as to permit removal of molding form without deformation.
Generally castables are normally bonded with high temperature calcium alumina cement bond. The setting of refractories varies with amount of cement when conventional refractories lined in furnaces, the failure in thermal shock is the problem associated with convectional refiactory material. If furnace lining comes contact with molten metal, an

adverse chemical reaction can occur. This adverse reaction, as observed in calcium alumina cement system is considered as weak link in the ability of concrete to resist molten metal attack.
On other hand chemical phosphate bonded refractory have several advantages over conventional calcium aluminates bonded cement product. The advantage of phosphate bond is that it not affected by molten metals. Another benefit is, phosphate bond material gives better wear or abrasion resistance properties when suitable aggregates are selected. Phosphate bond comes with different types and often have basic component such as magnesium oxide which reacts with phosphate in the presence of water, where upon hardening occurs.
US 20140096704 discloses a Magnesium phosphate cement binder systems and method for providing magnesium phosphate cements. Magnesium phosphate cement binder system may include magnesium oxide calcined at a temperature of up to 1000°C, phosphate material and other aggregate system.
US 6,787,495 discloses a refractory material derived from a mixture comprising: potassium phosphate, magnesium oxide, tri-calcium phosphate. The invention relates to a phosphate based refractory application.
US 5,954,872 discloses a dry phosphate cement mixture and process for manufacture. The dry mixture includes A1(H2P04)3, a group IIA metal bonded to oxygen, and an aggregate. The process for manufacturing cement includes associating the dry reagent with water. The total reagent concentration formulated such that only nominally exothermic reactions are observed. The process accommodates variable setting times and provides resulting concrete which exhibits formidable structural integrity,

EP0824092 discloses a refractory binder that consist mixture of aqueous phosphate and silica sol. The silica sol has been found to gel and set in a effective and useful way. Preferably, the refractoiy binder further incorporates a small amount of magnesia as an accelerator. This invention also provides a method of binding a refractory material such, for example, as alumina, zirconia mullite or aluminium silicate by using a refractory binder according to the invention.
US 3,730,744 discloses a refractory ceramic composition suitable for use in casting refractory shapes and making a ceramic product. The composition comprises a ceramic aggregate which has a particle size distribution suitable for the production of a ceramic article. The aggregate particles are bonded together by an aluminium dihydrogen orthophosphate bonding solution which is cured with a curing agent capable of solution to gel the same. The composition is capable of being cast in a mold, and hardens in situ. The cast article has high cold strength. Subsequent relatively intense heating produces the ceramic product
US 3,960,580 discloses a quick-setting magnesium oxide-ammonium concretes are extended by addition of oxy boron such as sodium borate. The incorporate of oxy boron in the composition has also been found to increase the extended or overall compressive strength.
Most of the disclosures are on use of Magnesium based cement for concrete application which is for room temperature application. For use in refractories at high temperature suitable magnesium based bonding and selection of refractory aggregates are required. Hence the method of preparation of magnesium phosphate bonding and manufacturing of refractory shapes for high temperature applications are required.

OBJECTS OF INVENTION
An object of the present invention is to propose a rapid setting refractory binder mix capable of forming a hard bonded refractory composition.
Further, object of the present invention is to propose a process for preparing rapid setting refractory binder mix capable of forming a hard bonded refractory composition.
Another object of the present invention is to propose a refractory composition for casting refractory shapes and products to overcome the disadvantages of prior Art.
Still another object of the present invention is to propose phosphate bonded refractory compositions which sets early and also gives good erosion resistance and high temperature properties when fired
Yet another object of the present invention is to propose method of preparation of Magnesium based phosphate bonding to use as binder in refractory composition.
Still further object of the present invention is to propose magnesium phosphate bonded refractory which can be used for high temperature abrasive environment

BRIEF DESCRIPTION OF THE INVENTION:
According to this invention there is provided a ceramic composition suitable for casting
refractory shapes comprising:
about 75 % brown fused alumina
10 to 15% reactive alumina
5 to 10% micro silica
5 to 10% binder
at least 1% retarding agent
6.2 to 7% water
In accordance with this invention there is provided a method for preparing a ceramic composition suitable for casting refractory shapes comprising:
mixing magnesium oxide and sodium hydroxide in a ratio of 9:1 to form refractory mix,
adding water to the said refractory mix to form a slurry paste,
calcining a caustic magnesium oxide,
crushing the said caustic magnesium oxide into fine powder,
mixing the fine powder with mono-potassium phosphate in a ratio of 2:3 in an aqueous medium,
adding a small quantity of retarding agent to prepare a binder composition,
mixing the said binder composition to the refractory mix,
subjecting the slurry paste to the step of drying in an oven,
sinting the cured composition at a temperature range of 1300°C to 1500°C.

DETAILED DESCRIPTION OF THE INVENTION:
The present invention directed to a development of refractory comprising: Dry mix of refractory composition and binder formed by reaction of caustic calcined magnesium oxide and active reagent mono potassium phosphate. Where in ad-level of binder ranges from 5 to 10% by weight of total mix. In preferred embodiment of invention, the refractory mix further includes an aqueous medium is substantially polar solvent such as water. In which caustic magnesium oxide ad-level is 2 to 4% and mono potassium phosphate ad-level is 3 to 6%. In a preferred embodiment of the invention, the process further comprises the step by varying addition of this binder with refractory mix consist of alumina aggregates and silica. The refractory products thus prepared showed high temperature resistance and erosion resistance
While the invention is susceptible of embodiment in many different forms, there is described in detail a specific embodiment with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention described here in below.
When caustic magnesium oxide and mono potassium phosphate are charged with water, an acid-base reaction is occurs. The concentration of ad-level directly affects the exothermic reaction. Specifically, the experiments were conducted with varying amount of addition of cement Where in following experimental procedure was used:

First, with cement addition used up to 5%. Which involves caustic magnesium oxide and mono potassium phosphate, Charged with water added to the refractory mix. Second with addition of 10% cement binder, refractory castables were developed. Refractory aggregates such as brown fused alumina, tabular alumina, etc can be used depending on the application. Next, prepared test samples are cured, dried at 110°C and sintered at temperature 1300°C to 1500°C.
Next, test samples were primarily analysed for physical, mechanical and thermal properties. Additionally, analytical test data relating to net structural composition was provided. Thus additional test for 1400°C sintered samples included wear resistance, average erosion volume (AEV) at different angle of impact (30 ° and 90°) and relative abrasion Index (RAI) at room and high temperature. Refractory under Load (RUL) and refractoriness : (Pyrometric cone equivalent -PCE) are also tested for refractory samples.
EXAMPLE 1
In this example, the following dry reagent and their respective percent composition by weight were used:


The brown fused alumina consisted with different size aggregates included: 1 to 3 mm, 0 to 1 mm and 200 mesh materials. Moreover, the micro silica used was 5% which is 200 meshes in size. Furthermore 5% prepared cement binder added with 6.2% by wt. water is added and normally exothermic reaction was observed. Then, different shapes of refractories are formed by using molds.The chemical composition of refractory mix in the experiment provides setting in 21 min. The test samples are cured at room temperature, dried at 110°C for 5 hrs and sintered at temperature range 1300°C to 1500°C. Test data was collected by conventional methods provides bulk density, porosity and cold crushing strength (CCS) mentioned in Table. 1.

EXAMPLE 2
In this example, the following dry reagent and their respective percent composition by weight


The brown fused alumina consisted with different size aggregates included: 1 to 3 mm, 0 to I mm and 200 mesh materials. Moreover, the micro silica used was 5% which is 200 meshes in size. Furthermore 10% prepared cement binder added with 7% by wt. water is added and normally exothermic reaction was observed. Then, different shapes of refractories are formed by using molds. The chemical composition of refractory mix in the experiment provides setting in 21 min. The test samples are cured at room temperature, dried at 110°C for 5 hrs and sintered at temperature range 1300°C to 1500°C. Test data was collected by conventional methods provides bulk density, porosity and cold crushing strength (CCS) mentioned in Table.2

To summarise the benefits of the present invention, the relevant experimental data collected for sample sintered at 1400°C has been summarised in Table.3 here in below:

As evident of Table.3 cement concentration of used in above examples ranges from 5 to 10% and as can be observed, such low uses of active reagent is nominal exothermic dry

synthesis and cost effective refractory concrete installation. Furthermore, in every
experiment, the structural integrity of refractory remained very high as an evident from the favourable values. Finally, although EXAMPLES 1 and 2 revealed that setting time can be varied.

WE CLAIM:

1. A ceramic composition suitable for casting refractory shapes comprising:
about 75 % brown fused alumina
10 to 15% reactive alumina 5 to 10% micro silica 5 to 10% binder at least 1% retarding agent 6.2 to 7% water
2. A method for preparing a ceramic composition suitable for casting refractory shapes
comprising:
mixing magnesium oxide and sodium hydroxide in a ratio of 9:1 to form refractory
mix,
adding water to the said refractory mix to form a slurry paste,
calcining a caustic magnesium oxide,
crushing the said caustic magnesium oxide into fine powder,
mixing the fine powder with mono-potassium phosphate in a ratio of 2:3 in an
aqueous medium,
adding a small quantity of retarding agent to prepare a binder composition,
mixing the said binder composition to the refractory mix,
subjecting the slurry paste to the step of drying in an oven,
sinting the cured composition at a temperature range of 1300°C to 1500°C.

3. The method as claimed in claim 2, wherein the said slurry paste was dried at a temperature of about 110°C.
4. The method as claimed in claim 2, wherein the said caustic magnesium oxide was calcined at 1000°C for 3 hours.
5. The method as claimed in claim 2 wherein the said retarding agent is boric acid.
6. The method of manufacturing of refractory castables or shapes, comprises of following
steps:
known quantity of refractory raw material refractory aggregates such high alumina and ceramic bonds such as micro silica mixed with refractory binder as claimed in I, an aqueous mix containing binder composition added to refractory composition in respective percentages and mixing thoroughly,
flowable refractory mix is poured in mold and vibrated, the composition knit together and forms a hard mass, which is then cured, dried and sintered at temperature ranges from 1300 to 1500°C
7. The method as claimed in claim 6, the refractory binder mixed in refractory
composition in the range of 5 to 10%.