Title of Invention

"A COMPOSITION FOR THE PREPARATION OF REFRACTORY USEFUL FOR OIL/GAS BASED MELTING FURNCES"

Abstract A composition for preparation of refractory material such as balls useful in oil/gas based melting furnances which comprises: high alumina aggregates (90% alumina) 80 to 92% (by wt), calcium acuminate 7 to 10% (by wt.), cement powder additives selected from find silica, alumina gel, chromium oxide, silicon carbide, alumina silicate or there mixture thereof (having particle size ranging to 0-5 to 5 microns) 1 to 2% (by wt.), water 8 to 10%(by wt).
Full Text Refractory materiais such as, halls are generally used in place of cokebed in the oil/gas tired melting furnances particularly in the furnaces employed in the production of ferrous and non ferrous castings. The melting furnace operating on liquid/gas as fuel require provision for an empty space within the furnace to enable the products of combustion to dissipate through the descending charge namely mass of materials to be melted and in the process it heats up the charge leading to its melting. For the easy escape of the products of combustion through the descending charge the refractory materials present in the furnace should have good permeability. For this purpose refractory balls are used which are supported on grate bars, which may or may not be water cooled, and are fixed within the furnace as well as in crucible furnaces. The refractory balls act as heat exchanger and help in superheating the material to be melted. Thus the production for example, of ferrous and non-ferrous castings as well as continuous casting becomes easy and feasible.
For acting as heat exchanges'the refractory balls are required to have high strength and refractoriness to so as withstand the mechanical shock due to the heavy fall of the charge of the material to be melted as well as thermal shock resulting from the passage of the molten metal through it. The size of the balls used are decided by the requirements of the permeability within the furnace shaft and it normally varies between 100 to 150 mm in diameter.
In the hitherto known refractory balls, used in such furnaces {reference may be made to the patent titled "refractory bail for Cokeless Cupola", Japanese Patent No. 4074815) the balls are mainly made of ceramic and graphite .which are formed into balls using liquid glass additives. In this process, mixing of liquid glass with ceramic
and graphite done in a mixer which is lime consuming and has a distinct and small bench life. However, the balls so prepared have inferior refractoriness.
Another known process, of preparing refractory composaiion for use in above said furnaces has been described in US Patent No.4710225 dated 01.12.1987 (inventors are Rucker. Robert A. New York, USA), where the composition includes refractory clay. ball clay and calcium allurninium cement used in such an amount to provide the refractory high temparature cement composition which is air setting, resistance and non water soluble. The refractory clay is a non-basic (acidic), size graded aggregate which can be selected from such materials as aiuminae, bauxite clays, diaspore clays, kaolinite clays and other fire clays including silica and silica aiuminae refractories. The above mentioned composition of the invention disclosed in the said patent includes refractory clay, ball clay and calcium aluminate cement blended in such amounts to provide a refractory, or a high temperature cement composition which is air-setting, acid resistant and non water soluble. The abovernentioned refractory clays may be calsigned orfired and be well suited as an ingredend of the composition.
Due to the general availability and low cost kaolinite clays, in comparision to other refractories clays the kaolinite clays may provide a preferred form of clays. In accordance with the invention disclosed in US patent the percentage of weight of refractory clays in
the composition may be in the range of 50 to 70%.
The calcium aluminate cement used in the composition includes such cement known as Fondu, Refcon, Alcoa CA-25 and Luminite. It has been found that too small an amount of clacium aluminate cement in the composition adversely effects the strength of the reflected material produced. It has been found that the percentage by weight of calcium aluminate cement in the composition is in the range of 10 - 30%.
The abovesaid process suggests that the percentage by weight of calcium aluminate cement in the composition is within the range of about 10 to 30 percent which provides
a composition yielding a strong mix and a desirable setting time. A percentage by weight
of calcium aluminate cement io the composition of about 20 percent has been found to provide a mixture of the composition with preferred strength and set time.
The amount of alumina is much less. The additives used are SiO2: 69.0%, Fe2O3: 1.5 % . Al2O3 : 18.0 %. TiO2 : 2.5 %, CaO / MgO : 7.5 % and Alkalies : 1.5 %. However, the refractory balls made by the process has low service temperature of 1315 °C, refractoriness, bulk density etc.. leading to lower service life.
In-hitherto known processes for the production of refractory materials such as balls for use for the abovesaid processes, Alumina Carbon refractory with a binder having a dense, compact shape are employed. These balls are cost prohibitive as the materials used are costly, scarce and the technology adopted is energy intensive because the process involves baking at higher temperature, (above 1400° C)
The industrialisation of a country while benefitting the country economically, also results in creating atmospheric pollution. This pollution not only adversely affects the natural phenomenon such as rain, heat etc. also affects the health of human beings and animals. Such atmospheric pollution also damages historical monuments.
The world has realised the importance of keeping the environment free from pollution. The Governments of various countries including India are framing stringent rules for avoiding generation of polluting materials and releasing to the atmosphere and also to control the pollution within permissible limits. In this context Supreme Court of India has passed orders to close down all the foundries in and around Agra which are running employing coke producing dust particles and oxides of sulphur and nitrogen which pollutes the atmosphere. These orders are directed to prevent damages to historical monuments located in that area due to the pollutants. Such an action has placed the industries in great difficulties. There is therefore, an urgent need to provide alternate furnaces which do not use coke thereby preventing pollution to the environment. Research and development efforts are being directed
towards the development of such furnaces without the use of coke,
In such furnaces which are burnt by oil/gas it is possible to employ refractory
materials preferably in the form oi'balls- which can replace coke.
The main object of the present invention is to provide a composition for the preparation of refractory materials such as balls useful in oil/gas based melting furnaces .
Another object of the present invention is to provide a composition for preparation of refractory balls using additives which act as hydraulic setting binder and has an effect on fluidity of castable & working time and also improves overall creep resistance, corrosion resistance & high temperature strength properties.
Yet another object of the present invention is to make use of high alumina refractory castables with water as a binder to make refractory balls where by mouldability is improved.
Still another object is to provide a process for the preparation of said refractory balls useful in oil / gas based melting furnaces which overcomes the above mentioned drawbacks.
The invention is based on our finding that when high alumina aggregates (90% alumina) in higher propotion such as 90- 95% b\ weight is mixed with lower propportion (7-10%) of calcium aluminate cement powdei in the presence of additives in an amount in the range of 1 -2% by weight selected from fine silica, aluma gel (A12O3) find chromium oxide (Cr2O3), Silicon Carbide or a mixture of one or more of the above, the additives
having the particle size in the range of 0.5 to 5 micrones, results in a refractory material
which can beneficially used in Oif / das burm furnaces.
The raw materials such as Dense sintered alumina grains and calcium aluminate cement and the additives such as fine MI tea, alumina gels (ALO,), chromium oxide (Cr2O3)
powder, silicon carbide (SiC) and alumino silicates are abundantly and easily available.
Accordingly, the present invention provides a process for preparation of refractory material such as balls useful in oil/gas based melting furnances which comprises: mixing thoroughly high alumina aggregates (90% alumina) atleast 80 % by wt., calcium aluminate 7 to 10% by wt., cement powder additives selected from fine silica, alumina gel, chromium oxide, silicon carbide, aluminium silicate or there mixture thereof (having particle size ranging from 0-5 to 5 microns) 1 to 2% by wt., adding water 8 to 10% by wt. and mixing thoroughly to obtain mass, moulding the said mass by known methods in to spherical ball, drying the balls in air and curing in water to obtain the refractory material.
Additives Selected from find Silica, Alumina Gel, Cromium Oxcide, Silicon Carbide.
Aluminium Silicate or there mixture thereof having particle size ranging to 0-5 to 5 microns, 1 to 2% (by wt.)
Water 8 to 10% (by wt.) According to a feature of the invention, alumina grains used may have particle size of maximum upto 4 mm.
According to another feature of the invention the calcium aluminate cement used may be of Commercial Grade and having particle size in the range of 5 to 10 microns.
The above said ingredients are mixed with water and moulded into wooden/steel moulds by hand compaction with desired shapes and sizes such as balls. The diameter of the balls may be as desired as per the requirements. The resulting shaped refractory material are air dried and cured in water to give high strength and are directly used in the furnace.
The refractory composition currently employed for the above purposes contain water resulting in low strength and considerable change in volume on heating. This is one and this is one of the major causes of refractory failure. To overcome this problem we have employed additives selected from one or more of fine Silica such as fine silica. Alumina gel (A1203). Chromium oxide (Cr203). Silicon carbide and alumino silicates in an amount ranging from 1-2% by weight. Further the additives used have the particle
size ranging from 0.5-5 microns. When such an additive is mixed with the castable body consisting of high alumina aggregate (90% alumina) and calcium aliminate cement powder a bond is developed thereby producing a refractory composition having chemical and mechanical stability which are useful for high temperature application.
The additive employed occupies voids between cement particles which could other wise be filled with water. Because of this less water is required to achieve the casting consistency, decrease the porosity and increases the bulk density of the product. Also, these fine additives have an effect on fluidity of castable and working time. This also improves the Creep Resistance, Corrosion Resistance and High Temperature Strength properties.
According to an embodiment of the present invention there is also provided a process for the preparation of refractory material such as balls using the composition present invention which comprises mixing intimately :
High alumina/ aggreregates(90% alumina) 90 to 95%(by wt)
Calcium aluminate 7 to 10%(by wt) cement powder
Additives selected from fine silica, alumina gel, chromium oxide, silicon carbide, aluminium silicate or there mixture thereof having particle size ranging from 0-5 to 5 microns. 1 to 2% (by wt.), water 8 to 10% (by wt.)
Moulding the resulting mixture into desired size and shape, drying the resulting moulded refractory material in air and curing in water for atleast 24 hours.
By the process of the of present invention refractory material such as balls which have the properties like high refractoriness, (1750-1850 °C), high mechanical strength 400 to 500 kg/cm2 and high thermal spalling resistance are produced. In comparision the known refractory material such as balls have the maximum service temperature of
1315°C.
The following examples are given by way of illustration of the invention and therefore should not be construed to limit the scope of the present invention.
Example 1
900.0 gms of dense sintered alumina grains, 80.0 gms of Calcium Aluminate cement
powder,and 10 gms of alumina gel and !0 gms of fine silica are mixed together intimately. In this admixture, 10.0% water is added and throughlly mixed. The mass is moulded into sperical ball in wooden/steel die by hand vibrating compaction.
The balls are air dried and cured in water for 24 hours to impart high strength and are directly used in the furnace. The refractory balls made by the process have crushing strength of 495 kg/cm2 and did not break even at an impact of 50 kgmeter.
Example 2
900.0 gms of dense intered alumina grains. 90.0 gms of Calcium Aiuminate cement powder and 5 gms of alumina gel and 5 gms of fine silica gel are mixed together intimately. In this admixture 10.0% water is added and mixed throughlly. The resultan
mass is moulded into spherical ball in wooden/steel die by hand vibrating compaction.
The balls are air dried and cured in water for 30 hours to give high strength. The balls can be directly used in the furnace. Refractory balls made by this process have crushing strength of 465 kg/cm2 and nd did not break even at an impact of 50 kgmeter.
The main advantages of the present invention are :
1. Energy requirement is minimum because the balls are self setting compared to
known refractory balls. I3aking at high temparature is required.
2. Uses cheaper raw materials which are abonded and easily available,
3. The refractory balls of present invention has improved creep resistance, corrosion
resistance and high temperature strength properties when compared to known
reproactory balls.




We Claim:
1. A process for preparation of refractory material such as balls useful in oil/gas
based melting furnances which comprises: mixing thoroughly high alumina
aggregates (90% alumina) atleast 80 % by wt, calcium aluminate 7 to 10% by
wt.; cement powder additives selected from fine silica, alumina gel, chromium
oxide, silicon carbide, aluminium silicate or there mixture thereof (having particle
size ranging from 0-5 to 5 microns) 1 to 2% by wt., adding water 8 to 10% by
wt. and mixing thoroughly to obtain mass, moulding the said mass by known
methods in to spherical ball, drying the balls in air and curing in water to obtain
the refractory material.
2. A process as claimed in claim 1 wherein the high alumina grains used have
particle size of maximum unto 4 mm.
3. A process as claimed in claims 1 & 2 wherein the calcium aluminate having
particle size in the range of 5 to 10 microns.
4. A process for preparation of refractory material such as balls useful in oil/gas
based melting furnaces substantially as herein described with reference to the
examples.


Documents:

1654-del-1997-abstract.pdf

1654-del-1997-claims.pdf

1654-del-1997-complete specification (granted).pdf

1654-del-1997-correspondence-others.pdf

1654-del-1997-correspondence-po.pdf

1654-del-1997-description (complete).pdf

1654-del-1997-form-1.pdf

1654-del-1997-form-19.pdf

1654-del-1997-form-2.pdf

1654-del-1997-form-5.pdf

1654-del-1997-form-6.pdf


Patent Number 199585
Indian Patent Application Number 1654/DEL/1997
PG Journal Number N/A
Publication Date 20-Oct-2006
Grant Date 08-Sep-2006
Date of Filing 20-Jun-1997
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 DILIP KUMAR BISWAS NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, INDIA
2 KAILASH KUMAR MISHRA NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, INDIA
3 BALAI KUMAR MITRA NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, INDIA
4 SHIWA DHAR SINGH NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, INDIA
5 KARUN KANT SINGH NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, INDIA
6 PATCHA RAMACHANDRA RAO NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, INDIA
PCT International Classification Number C04B 35/652
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA