EP3224221A1

EP3224221A1 - A refractory brick, its composition, and process for manufacturing thereof

Info

Publication number: EP3224221A1
Application number: EP15910980.0A
Authority: EP
Inventors: Somkeat SUEBTHAWILKUL; Nichapat PATCHARARUNGRUANG; Chanvit CHAWENGKUL; Thanapong PRASERTPHOL; Palakrit TINNAKORN
Original assignee: Siam Refractory Industry Co Ltd
Current assignee: Siam Refractory Industry Co Ltd
Priority date: 2015-12-29
Filing date: 2015-12-29
Publication date: 2017-10-04
Also published as: EP3224221A4; WO2017116313A1; BR112017001900A2; CN107207355A

Abstract

The present disclosure relates generally to a composition for a refractory article such as a refractory brick, having enhanced chemical infiltration resistance, anti-hydration, and low heat conductivity properties. The refractory brick composition comprises olivine 40-90 %, elastifier 5-35 %, silicon carbide 1 - 15 %, and magnesia to make up to 100% by weight of dry admixture. Anti-hydration property of the refractory brick is drastically improved and can provide an advantage of enhanced product shelf life and simple, cost effective product transportation and storage logistics. Thermal conductivity property of the refractory brick is approximately below 2.20 W/mK at the temperature range of 450 - 1200 °C, and is insensitive with respect to the firing temperature. An average permeability of the refractory brick is significantly lower than that of conventional refractory brick by at least 73%. Additionally, the present disclosure relates to a method for producing a refractory brick according to the composition disclosed herein.

Description

A REFRACTORY BRICK, ITS COMPOSITION, AND PROCESS FOR

MANUFACTURING THEREOF

Technical Field

The present disclosure relates generally to a composition for a refractory article such as a refractory brick. More particularly, the present disclosure relates to a refractory article / brick composition having enhanced chemical infiltration resistance, anti-hydration, and low heat conductivity properties. Additionally, the present disclosure relates to a method for producing a refractory article / brick according to the composition disclosed herein.

Background

Refractory bricks, fire bricks or firebricks have been widely used in lining furnaces, kilns, fireboxes, and fireplaces. Desirable properties for their performance include ability to withstand high temperature while having a very low thermal conductivity for optimal energy efficiency; high Pyrometric Cone Equivalent (PCE) under load (typically higher than 2,000 °C); high thermal shock resistance; lightweight; high mechanical strength and toughness at wide temperature range; and high chemical resistance as well as high abrasion and corrosion resistance. The pursuit of benefits and advantages of high performance refractory bricks has led to various research and development efforts over the years to improve the performance of refractory bricks. In particular, research has been conducted in an effort to ideally have or achieve all of the above-mentioned desirable properties. However, realizing particular properties results in compromising certain other properties. For instance, one can enhance, increase, or improve thermal conductivity by increasing porosity and thereby decreasing density. Unavoidably, increasing porosity will, in turn, compromise chemical infiltration resistance due to the fact that an increase in porosity will also increase permeability or infiltration capability. In addition to desirable performance-related properties, refractory bricks require protection from hydration due to water in the surrounding environment or water in liquid form either during storage or transportation and other logistical conditions. Essentially, refractory brick production requires an adequately maintained atmosphere for storage to minimize or avoid water contact or moisture absorption to prevent spontaneous cracking caused by hydration phenomena. In certain instances, finished refractory brick products are fully covered with packing materials or sheets and stored on wooden pallets. This, however, results in cracking or breakage of refractory bricks under some weather conditions. Another approach to solve this problem is by way of a package design by having a specified opening to provide sufficient ventilation during transportation. This approach will inevitably add extra cost to final products, which may decrease market competitiveness.

Alternatively, coatings over refractory bricks with anti-hydration substances have been proposed, which can provide an acceptable though non-optimal solution for this problem. For example, US patent number 3,576,666 discloses that an anti-hydration property is achieved by reacting the refractory oxide of the refractory brick with an externally applied reactive gas phase at high temperature to thereby form an insoluble protective compound on the surface of refractory brick, which is analogous to the formation of a protective oxidation film on metals such as aluminum that protects the metal from subsequent oxidation. However, such a method is relatively complicated and requires high temperature operations. More recently, chemical coating reagents have been developed to be simply applied over the surface of a refractory brick. Despite the simple application and uniform coating of chemical coating reagents, additional costs are incurred. Moreover, chemical coating reagents utilize non-aqueous medium preparations, which pose some limitations to the coating approach.

In addition to the foregoing, although aspects of refractory brick products are being investigated and improved, existing means or compositions for manufacturing high performance refractory bricks with long-term storability fail to have favorable characteristics that appropriately address certain operational performance aspects, as well as logistical and distribution considerations. In particular, while various efforts have been made to develop refractory bricks with better performance, such efforts have largely ignored or have increased the cost of producing said refractory brick products. Accordingly, a significant contribution to the art of refractory bricks would result from developing a novel refractory brick composition and product that fulfills both operational performance and storage considerations with anti-hydration properties to enhance refractory brick durability. Moreover, there is a need for preparing, manufacturing, or formulating refractory brick compositions in a more cost-effective manner.

Summary

In accordance with the first aspect of the present disclosure, embodiments are directed towards a composition for a refractory article comprising olivine 40-90 % by weight of dry admixture, elastifier 5-35 % by weight of dry admixture, silicon carbide 1 - 15 % by weight of dry admixture, and magnesia to make up to 100% by weight of dry admixture.

In the second aspect of the present disclosure, a refractory article having the composition as disclosed herein illustrates at least one of increased anti-hydration, thermal conductivity and chemical infiltration resistance properties. More specifically, the degree of anti-hydration property of the refractory article composition is between 1 -4 according to ASTM C456-93. The refractory article according to embodiments of the present disclosure exhibits a thermal conductivity having a value below 3.00 W/m at the temperature range of 200 - 1200 °C and/or an average permeability of the refractory article is in the range of 3 - 7 cD.

The third aspect of the present disclosure includes a process for manufacturing a refractory article comprising providing predetermined amounts of olivine, elastifier, magnesia, and SiC; mixing olivine, elastifier, magnesia, and SiC provided; molding the mixed composition to form a final refractory article (e.g., a refractory brick or other type of refractory object); and firing the refractory article at the predetermined temperature wherein the final refractory article comprises of olivine 50-70 % by weight of dry admixture; elastifier 10-25 % by weight of dry admixture, silicon carbide 1 -5 % by weight of dry admixture, and magnesia to make up to 100% by weight of dry admixture, and said final refractory article is characterized in that at least one of anti-hydration, thermal conductivity and chemical infiltration resistance properties has been enhanced.

Brief Description of the Drawings

Embodiments of the present disclosure are described hereinafter with reference to the FIGs., in which:

FIG. 1 is a representative process for preparing, manufacturing, producing or obtaining a refractory article according to an embodiment of the present disclosure;

FIG. 2 is a rating scale of hydration of refractory articles tested in representative Example One described below;

FIG. 3 is a correlation between thermal conductivity values and temperatures of refractory articles for refractory brick compositions according to the present disclosure and other conventional refractory brick compositions; and

FIG. 4 is a Scanning Electron Micrograph and Energy Dispersive X-ray of a refractory brick specimen of the present disclosure.

Detailed Description

Embodiments of the present disclosure are directed to a refractory article composition, such as a refractory brick composition, in which silicon carbide (SiC) primarily serves as an anti-hydration agent while simultaneously enhancing other refractory article / brick performance-associated properties, including low thermal conductivity and high chemical infiltration, and aiding or simplifying logistics issues associated with refractory articles / bricks such as refractory article / brick storage and transportation.

Herein, the terms "refractory brick composition," "refractory composition," "refractory system," "refractory specimen," "refractory sample," "refractory article," "refractory item," "refractory object," and "refractory product" can correspond or refer to or mean a refractory object or brick composition or one or more portions of a refractory object or brick in accordance with an embodiment of the present disclosure. In addition, unless otherwise stated, all percentages (%) are percent weight-by-weight, which may also be expressed as % by weight, % (w/w) or simply %. The term "dry admixture" refers to the relative percentages of the constituents or components of the dry composition separate from or prior to the (intentional) addition of water and any liquid state reagent(s). Unless otherwise stated, percentage by weight herein refers to a dry admixture. A person of ordinary skill in the art will understand the manner in which wet admixture and dry admixture weight percentages are related or convertible.

In the context of the present disclosure, the use of "/" in a FIG. or associated text is understood to mean "and/or" unless otherwise indicated. The recitation of a particular numerical value or value range herein is understood to include or be a recitation of an approximate numerical value or value range (e.g., +/- 20%, +/- 15%, +/- 10%, +/- 5%, +/- 2%, or +/- 0%).

Aspects of a Refractory Article / Brick Composition

In various embodiments, a refractory article / brick composition in accordance with the present disclosure can include (in a dry admixture): ( 1 ) olivine 40-90 % by weight, (2) spinel 5-35 % by weight, (3) SiC 1 - 15% by weight, and (4) Magnesia to make a total of 100% by weight.

Embodiments of the present disclosure employ naturally raw olivine substance, [e.g., magnesium iron silicate with the formula (Mg⁺², Fe⁺²)₂Si0₄], which is commercially available in the market with specified grain size ranging from fine to coarse grains. In various embodiments, the olivine substance used in the refractory brick composition has a Gaussian grain-size distribution. It will be understood by persons having ordinary skill in the relevant art that synthetic olivine can also be used alone or in combination with naturally raw olivine. Typically, the two endmembers of olivine, namely: forsterite (Mg- endmember: Mg₂Si0₄) and fayalite (Fe-endmember: Fe₂Si04) can be specified or selected upon formulating the refractory brick composition. For instance, forsterite may be selected at 75% or 100% and the remainder is favalite at 25% or 0%. Minor impurities are acceptable including enstatite, monticellite, and/or merwinite. In multiple embodiments, a refractory brick composition in accordance with the present disclosure has olivine at the amount of 40-90%, or more particularly in several embodiments, 45- 80%. In a representative embodiment, olivine content in the present disclosure is selected to be 50 - 70 %.

Embodiments of the present disclosure further include an elastifier at the amount of 5- 35% by weight. Elastifiers can be selected from a group of spinel, magnesia alumina, Hercynite, or magnesia chrome. More preferably, magnesium spinel or spinel (collectively referred hereafter as "spinel") with a chemical formula MgAI₂0₄ is incorporated at the amount of 5-35%, or more specifically in various embodiments at the amount of 10-25%, to form a refractory brick composition in accordance with the present disclosure. In a representative embodiment, olivine content in the present disclosure is selected to be 18%.

Embodiments of the present disclosure also include silicon carbide (SiC) or carborundum. The refractory brick composition according to the present disclosure can utilize commercially available SiC as a synthetic SiC, which can be provided in varying particle size(s) (e.g., from 10 micron to 5 millimeter), particle size distribution (such as Guassian distribution)), purity (e.g., >=90% of SiC having iron [Fe] as allowable impurity), and/or form(s) (such as powder / flour). The amount of SiC in the refractory brick composition in various embodiments of the present disclosure is determined at 1 - 15%, or 3- 10%, or more specifically 3-5% depending upon embodiment details.

Magnesia (MgO) is incorporated with previously described olivine, spinel, and SiC to make up to 100% by weight of refractory brick composition. More preferably, MgO used in the present disclosure can include or be high iron magnesia. Acceptable impurities in MgO include silicates and/or iron oxides. Magnesia used in the present disclosure can be in the flour or powder form, fused magnesia and/or sintered magnesia, synthetically dead- burned or caustic magnesia. Aspects of a Process for Preparing or Producing a Refractory Article / Brick Composition FIG. 1 is a flowchart of a representative process 100 for preparing, manufacturing, producing or obtaining a refractory article such as a refractory brick having a composition according to an embodiment of the present disclosure.

The process 100 for preparing, manufacturing, producing or obtaining a refractory article according to an embodiment of the present disclosure typically occurs in a batch-wise manner. In a first process portion 1 10, a predetermined volume of each of the constituents, namely olivine, spinel, magnesia, and SiC are provided or introduced.

Optionally or typically, in a second process portion 120 depending upon the source, properties, or characteristics of olivine, spinel, magnesia and/or SiC, each or some or all of the constituents can be crushed into a target particle size and/or particle size distribution, for instance, in the range from 10 micron to 5 millimeter. Each of the constituents can be screened (e.g. by way of a sieve) and preconditioned to achieve desirable or intended particle size, particle size distribution, and/or moisture content.

The ratio or weight percentage of each of the constituents can be determined, specified, or selected and undergone a mixing step in a third process portion 130. A ball mill can be utilized for making fine particles while a jaw crushing machine or jaw crusher may be used for coarse particles or granules.

Upon uniform mixing, the resulting admixture obtained can be molded, pressed, or shaped into a target shape to form a refractory brick, article, or product in a fourth process portion 140.

The pressed or shaped refractory article can be dried by entering into a dryer including an air dry technique in a fifth process portion 150. In a sixth process portion 160, the refractory article is fired at a temperature of 950 - 1 ,450 °C. In several embodiments the refractory article is fired at a temperature of 1 ,000 - 1 ,400 °C. In specific embodiments, the refractory article is fired at a temperature of 1 ,200 - 1 ,350 °C. Upon completion of firing, a final refractory article, item, object, or product is obtained and can be packed and stored for distribution. It is further noted that refractory articles having a composition according to the present disclosure can be produced or obtained from either a molded or unmolded batch.

The following representative Examples One through Three describe experiments showing effects, functions, and/or properties corresponding to or of a composition in accordance with embodiments of the present disclosure. It will be understood by a person of ordinary skill in the art that the scope of the present disclosure is not limited to the following representative examples. REPRESENTATIVE EXAMPLES

EXAMPLE ONE

Anti-hydration property test: Effect ofSiC content incorporated in a refractory brick Experiments were conducted to evaluate, measure, and determine anti-hydration properties or characteristics of a refractory brick having a composition according to an embodiment of the present disclosure. Anti-hydration properties were tested by utilizing pressure and heat as an accelerator for hydration reaction according to ASTM C456-93: "Standard Test Method for Hydration Resistance of Basic Bricks and Shapes". In brief, ASTM C456-93 covers measurement of the relative resistance of basic brick and shapes to hydration.

In example one, six refractory brick compositions, namely refractory brick compositions (A), (B), (C), (D), (E) and (F), were prepared having a size of 1 x 1 x 1 inch. Each refractory brick composition tested in Example One had constant weight percentage of olivine and spinel while varying SiC amount from 0-15 % by weight, hence a slight difference in magnesia content to make a total composition up to 100 % by weight. Details of refractory brick compositions (A) - (F) are as follows: Refractory brick composition (A)

Refractory brick composition (A) included approximately 60% Olivine, 30% Magnesia, 10% Spinel, and 0% SiC by weight.

Refractory brick composition (B)

Refractory brick composition (B) included approximately 60% Olivine, 29% Magnesia, 10% Spinel, and 1 % SiC by weight. Refractory brick composition (C)

Refractory brick composition (C) included approximately 60% Olivine, 27% Magnesia, 10% Spinel, and 3% SiC by weight.

Refractory brick composition (D)

Refractory brick composition (D) included approximately 60% Olivine, 25% Magnesia, 10% Spinel, and 5% SiC by weight.

Refractory brick composition (E)

Refractory brick composition (E) included approximately 60% Olivine, 20% Magnesia, 10% Spinel, and 10% SiC by weight.

Refractory brick composition (F)

Refractory brick composition (F) included approximately 60% Olivine, 1 5% Magnesia, 10% Spinel, and 15% SiC by weight.

After preparation of each of the refractory brick compositions, refractory bricks were produced according to the process 100 previously described with above-described formulations, and more specifically, at three different firing temperatures, namely, 1 ,200 1 ,300 and 1 ,400 °C and at varying three firing intervals or durations, namely 60, 180 or 300 minutes. A selection of position to cut a testing specimen from each produced refractory brick was carefully considered to minimize error. More particularly, position numbers 3, 4, 9, 10, 15, 16, 21 , and 22 according to the below representation, were chosen for testing.

The testing specimens were placed in an autoclave chamber at a pressure of 80 psi (552 kPa) and temperature of 324 °F ( 162 °C), and equipped with pressure- and temperature- measuring devices, a vent cock, and safety equipment. More specifically, the testing protocol starts with heating the autoclave with the pressure release valve open; after a steady flow of steam is obtained through the valve, continuing to purge for 3 minutes to remove all air, closing the valve, bringing the autoclave to 80 psi (552 kPa) and at 324°F ( 162°C) in a total time of 1 hour, maintaining the autoclave at 80 ± 5 psi (552 ± 50 kPa) at 324 ± 4°F ( 162 ± 2°C) for 5 hour, allowing sufficient cooling to lower the autoclave to 20 to 30 psi ( 138 to 207 kPa) with the release valve closed, and then carefully opening the relief valve to reduce the autoclave to atmospheric pressure in a total time between 30 and 60 minutes. More details of a testing protocol with an autoclave chamber is known among the persons with ordinary skill in the relevant art. Upon reaching a predetermined or intended testing duration, the testing specimens were collected, observed for hydration degree, and photographed immediately. The degree of hydration was rated from 1 - 4 as follows:

1 = Unaffected (i.e., no hydration phenomena)

2 = Surface hydration (i.e., hydration has occurred at the surface of testing specimens)

3 = Cracking or crumbling

3.1 = crack at the surface

3.2 = deep crack at various sides of the testing specimen

3.3 = crack into pieces at the corner area(s)

3.4 = crack into pieces and unable to maintain cubical shape

4 = Disintegration (break into powder or grain)

Results

As shown in Table 1 below and illustrative FIG. 2, hydration degrees of refractory brick specimens were rated lower when SiC content was increased over the tested firing temperatures and firing durations. For instance, at the firing temperature of 1 ,300 °C and a firing interval of 60 minutes, hydration degree was 3.4 in the absence of SiC in a refractory brick, and hydration degree consistently decreased when SiC content increased from 1 - 15 % (i.e., hydration degree decreased from 3.4 down to 3.3, 2, 1 , 1 and 1 as SiC content was elevated from 0, 1 , 3, 5, 10, and 15%, respectively.)

It was observed that increasing firing temperature from 1 ,200 - 1 ,400 °C does not dramatically affect hydration degree. It was further noted that increasing firing interval from 60 to 180 minutes tends to increase hydration degree at each firing temperature and each SiC content. Table 1 : Rating of hydration degree

Conclusions

Incorporation of a predetermined amount of SiC into a refractory article or brick having a composition according to an embodiment of the present disclosure can provide, facilitate, effectuate and/or improve anti-hydration properties as indicated by a numerical reduction in hydration rating score, and/or as indicated in another manner, for instance, by way of representative photographs from collected specimens.

EXAMPLE TWO

Thermal conductivity property evaluation: Effect of temperature and varying composition Experiments in Example Two were performed to evaluate thermal conductivity of a refractory brick or brick structure having a composition in accordance with present disclosure. Thermal conductivity refers to the property of a material to conduct heat, and can predict the rate of energy loss through the material. It is desirable to choose a refractory brick having minimal, low, or substantially low thermal conductivity in order to minimize or prevent heat transmission or energy loss and achieve better thermal insulation property. Thermal conductivity was investigated by placing thermocouples and positioning test specimens in a thermal conductivity tester based on a conventional wire method (e.g., using a thermal conductivity tester with a power supply unit, a controller and a hood type furnace). Three refractory brick compositions, namely refractory brick compositions (A), (B), and (C) were prepared to a standard shape having 230 x 1 15 x 64 mm in size. Detailed compositions of refractory brick compositions (A) and (B) are enumerated as follows:

Refractory brick composition (A)

Refractory brick composition (A) included approximately 60% Olivine, 27% Magnesia, 10% Spinel, and 3% SiC by weight.

Refractory brick composition (B)

Refractory brick composition (B) included approximately 80% Magnesia, 20% Spinel by weight.

For all brick densities considered, three specimens per refractory brick composition were prepared and organized in accordance with the following sample structure:

Details of specimens are as follows:

Brick No. l was mortised to create two mortices. The first mortice was formed at the middle of the brick, while the second mortice was formed in a triangle shape as shown below:

230 mm -

Brick No.2 was mortised at the middle, as illustrated below:

< 115 mm >\

230 mm Brick No.3 was prepared in a standard size with no mortise.

Specimens of Brick Nos. 1 and 2 were prepared in the same manner as the foregoing, whilst Brick No. 3 was specifically a ceramic fiber or insulation brick.

Subsequent to the preparation of each refractory brick specimen, refractory Brick No. 1 was placed on an alumina frame, followed by an adjustment of the hot wire and thermocouple position in order to insert or embed them into the prepared mortice. Said mortice was filled by tabular alumina slurry or fused spinel slurry to cover the mortices. Then refractory Brick No. 2 was placed over Brick No. 1 and a reference thermocouple was placed in a mortice formed, followed by filling the mortice in a similar manner to the refractory Brick No. 1 . Finally, Brick No. 3 was laid down on Brick No. 2. Then the specimens were loaded into a chamber corresponding to a thermal conductivity tester.

Input data and/or parameters input into the thermal conductivity tester were determined, selected or specified as follows:

Temperature: desired testing temperature

Heating rate: 2-5 °C

Sample length: 230 mm

Sample width: 1 15 mm

Total sample height: 64 mm Subsequent to inputting all parameters, the tester was allowed to run and obtain the thermal conductivity values.

Results

FIG. 3 illustrates a correlation between thermal conductivity values and temperatures varied in the range of 200- 1 ,200 °C from refractory bricks having a composition according to embodiments of the present disclosure. The thermal conductivity of refractory brick composition (A) slightly decreased with increasing of temperature in the range of 200 - 400 °C, while thermal conductivity of refractory brick A remained relatively constant at 2.00 W/mK in the range of 450 - 1200 °C. Thermal conductivity values of refractory brick composition (B) greatly decreased when the temperature increased over the testing temperatures. In other words, the thermal conductivity of refractory brick composition (A) was insensitive or essentially insensitive to the temperatures used during firing unlike brick compositions (B).

Comparing thermal conductivity values between refractory brick compositions (A) and (B), it is observed that thermal conductivity values of refractory brick composition (A) are significantly, dramatically, or drastically and surprisingly lower than that of conventional refractory brick compositions (B).

Conclusions

Thermal conductivity of refractory brick provided by the present disclosure at 3% of SiC (composition (A)) is significantly lower than that of Magnesia spinel brick (composition B). Moreover, it also indicates that refractory bricks prepared by several embodiments in accordance with the present disclosure have low thermal conductivity with insensitivity toward higher operating temperatures, and/or have high thermal insulation properties. That is, the refractory bricks provided or produced in accordance with embodiments of the present disclosure can have wider temperature ranges for applications with better, enhanced, improved, or superior insulation properties (e.g., compared to conventional refractory brick compositions), resulting in less energy loss, as compared to the conventional refractory bricks.

EXAMPLE THREE

Permeability property evaluation

Experiments in Example Three were performed to determine permeability of a refractory brick having a composition in accordance with present disclosure. Permeability reflects the chemical infiltration resistance property of a material. It is desirable to choose a refractory brick having low permeability for durability and associated operating costs upon its application or usage.

Permeability was investigated by measuring air volume flowing through a refractory specimen by using an air permeability tester (e.g. a PROLIFIC air permeability tester). A permeability test was carried out according to an ASTM standard, more specifically, ASTM C577-96 Standard Test Method for Permeability of Refractories. Refractory brick specimens according to a representative embodiment in the present disclosure comprised or were formed of olivine at 60%, magnesia 27 %, spinel 10% and SiC at 3% by weight. Briefly, refractory brick specimens were prepared in the size of 51 x 51 x 51 ± 1 mm by a cutting machine and were identified on particular side surface as follows:

A denotes as a compressive face; B denotes as a side face; C denotes hot/cold face The reduced pressure (values are recorded and symbolized as "P") in the PROLIFIC air permeability tester was set at 32.00±0.05 kPa and the resulting air flow rate was then measured. The experiment was repeated by varying the reduced pressure (P) to 18.70±0.05 and 9.30±0.05 kPa. Permeability values were obtained by calculation as follows:

Peameability (centidarcys, cD) = 9.76 x 60 x F / P

wherein F = air flow (litre/minute) and P = reduced pressure (kPa)

Table 2: Permeability values of the refractory bricks

No Sample Permeability (cD)

Position Average Face

A B C

1 3 5.46 5.29 5.42 5.66

1 4 5.85 5.55 5.47 6.54

1 3 5.29 5.22 5.35 5.29

2 4 4.77 4.77 4.76 4.78

2 3 4.39 4.32 4.54 4.30

2 4 5.88 5.82 6.01 5.81

Grand Average 5.27 Results

As shown in Table 2, an average permeability of the refractory bricks having olivine at 60%, magnesia 27 %, spinel 10% and SiC at 3% by weight is 5.27 cD. Typically, an average permeability of conventional refractory bricks without SiC incorporated therein is 20-30 cD, as will be readily understood by individuals having ordinary skill in the relevant art. Therefore, refractory brick compositions according to the present disclosure can have substantially or dramatically and surprisingly lower value of permeability by 73.7-82.4%, as compared to conventional refractory brick compositions. Conclusions

Refractory brick compositions according to embodiments of the present disclosure demonstrate a significant reduction in air permeability. Hence, it indicates that a refractory brick composition according to embodiments of the present disclosure possesses a significantly or greatly enhanced, improved, or superior chemical infiltration resistance by at least 73.7 %, as compared to conventional refractory bricks.

EXAMPLE FOUR

Scanning Electron Micrograph for Re fractory Brick Microstructure Evaluation

Experiments in example 4 were carried out to inspect the microstructure of a refractory brick having a composition in accordance with the present disclosure. Scanning Electron Micrograph (SEM) is utilized to scan a refractory brick sample with focused beams of electrons to obtain the refractory brick sample's topography, and the constituents in the composition were determined by an Energy Dispersive X-ray (EDX) analysis. A refractory brick sample in Example 4 comprises or is made of 40-90% of olivine, 5-35% of spinel, 1 -15% of SiC, and MgO at the percent weight to make up to total 100%. Details of the sample preparation and procedure are explained below.

A protocol for determining topography and constituents of refractory brick composition from the prepared sample using SEM is detailed in the following successive steps: Sample casting step: The refractory brick was prepared by a sample cutting machine to 2.0 x 2.0 x 2.0 cm in size, then dried at 1 10 °C. Resin and hardener were mixed together at a mixing ratio 5: 1 for I minute at 18 gram per sample. Releasing agent was applied to a mold then said resin was poured into the mold under vacuum for 7- 10 minutes and allowed to sit or be left for 8 hours and then demolded.

Sample cutting: The demolded sample was cut at least 1.5 mm in depth with a normal cutting speed of 375 rpm. Sample polishing: At least three samples were polished by a grinder/polisher (Model

Metaserv) using diamond paste for polishing and water or polishing oil for lubrication. Finally, the samples were dried.

Results and Conclusions

As shown in FIG. 4, SEM and EDX peak analysis indicated the presence of SiC on magnesia and magnesia silicate in a refractory brick composition according to embodiments of the present disclosure.

EXAMPLE FIVE

Effect of SiC particle size on a refractory brick property

Experiments in Example five were performed to obtain an appropriate SiC particle size that results in the most desirable property of a refractory brick having a composition in accordance with present disclosure.

Refractory brick specimens in example five were prepared by having an identical amount of SiC (i.e. at SiC of 5% by weight) and varying SiC particle size from fine to coarse grain (i.e. fine grain at the particle size range of 10 μιτι - 5 mm versus coarse grain at the particle size larger than 5 millimeter). Two refractory brick properties, namely modulus of rupture (MOR) and cold crushing strength (CCS) were measured by a standard technique known in the art. Table 3: MOR and CCS properties of refractory bricks having different SiC particle size

Results and Conclusions

Table 3 depicting the results of experiments in example 5 demonstrates that, comparing at an identical SiC amount, both refractory brick properties; more specifically, modulus of rupture (MOR) and cold crushing strength (CCS) of a refractory brick with fine SiC particle (i.e. particle size of 10 μπι - 5 mm) having a composition in accordance with the present disclosure are substantially higher than those of a refractory brick with coarse SiC particle (i.e. particle size of > 5 mm). More particularly, decreasing the particle size of SiC from a coarse to fine range can significantly or very significantly increase MOR and CCS of the refractory brick by approximately 4 fold.

Particular embodiments of the present disclosure are described above for addressing at least one of the previously indicated problems. While features, functions, processes, process portions, advantages, and alternatives associated with certain embodiments have been described within the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the disclosure. It will be appreciated that several of the above-disclosed features, functions, processes, process portions, advantages, and alternatives thereof, may be desirably combined into other different applications or compositions The representative embodiments disclosed herein as well as various presently unforeseen or unanticipated alternatives, modifications, variations or improvements thereto, which may be subsequently made by one of ordinary skill art based upon the description herein, are encompassed by the following claims.

Claims

composition for a refractory article comprising:

- olivine 40-90 % by weight of dry admixture;

- elastifier 5-35 % by weight of dry admixture;

- silicon carbide 1 - 15 % by weight of dry admixture; and

- magnesia to make up to 100% by weight of dry admixture

2. The composition according to claim 1 , wherein the olivine is in the range of 50- 70% by weight.

3. The composition according to claim 1 , wherein the elastifier is selected from at least one of spinel group, magnesia alumina, Hercynite, or magnesia chrome.

4. The composition according to claim 1 , wherein the spinel is in the range of 10- 25% by weight.

5. The composition according to claim 1 , wherein the silicon carbide is in the range of 1 - 10% by weight.

6. The composition according to claim 1 or 5, wherein the silicon carbide is in the range of 1 -5% by weight.

7. The composition according to claim 1 , 5 or 6, wherein the silicon carbide has a particle size in the range of 10 micron to 5 millimeter.

8. The composition according to claim 1 , wherein the silicon carbide is microscopically located or resided upon a magnesia structure.

9. The composition according to claim 1 , wherein the refractory article can be in a form of molded or unmolded batch.

10. The composition according to claim 1 , wherein the refractory article has at least one of increased anti-hydration, thermal conductivity and chemical infiltration resistance properties.

1 1 . The composition according to claim 1 or 10, wherein the degree of anti-hydration property of the refractory article composition is between 1 -4 according to ASTM C456-93.

12. The composition according to claim 1 or 10, wherein the refractory article exhibits a thermal conductivity having a value below 3.00 W/m at the temperature range of 200 - 1200 °C.

13. The composition according to claim 1 , 10 or 12, wherein the refractory article exhibits a thermal conductivity having a value below 2.20 W/mK at the temperature range of 450 - 1200 °C.

14. The composition according to claim 1 , 10, 12 or 13, wherein the refractory article exhibits a thermal conductivity having a value below 2.20 W/mK at the temperature range of 450 - 1200 °C and insensitive towards the firing temperature at entire said temperature range.

15. The composition according to claim 1 or 10, wherein an average permeability of the refractory article is at the range of 3 - 7 cD

16. The composition according to claim 1 or 15, wherein an average permeability of the refractory article is significantly lower than that of a conventional refractory article by at least 50%.

17. The composition according to claim 1 , 15 or 16 , wherein an average permeability of refractory article is significantly lower than that of a conventional refractory article by at least 73%.

18. A refractory article comprising olivine 40-90 % by weight of dry admixture; elastifier 5-35 % by weight of dry admixture, silicon carbide 1 - 1 5 % by weight of dry admixture, and magnesia to make up to 100% by weight of dry admixture.

19. The refractory article according to claim 1 8 wherein the refractory article comprises of olivine 50-70 % by weight of dry admixture; elastifier 10-25 % by weight of dry admixture, silicon carbide 1 -5 % by weight of dry admixture, and magnesia to make up to 100% by weight of dry admixture

20. The refractory article according to claim 18 or 19 wherein the refractory article comprises of olivine 50-70 % by weight of dry admixture; elastifier 10-25 % by weight of dry admixture, silicon carbide having particle size in the range of 10 micron to 5 millimeter 1 -5 % by weight of dry admixture, and magnesia to make up to 100% by weight of dry admixture.

21. A process for manufacturing a refractory article; the process comprising:

- providing predetermined amounts of olivine, elastifier, magnesia, and SiC;

- mixing olivine, elastifier, magnesia, and SiC provided;

- molding mixed composition to form a final refractory article; and

- firing the refractory article at the predetermined temperature

wherein the final refractory article comprises of olivine 50-70 % by weight of dry admixture; elastifier 10-25 % by weight of dry admixture, silicon carbide 1 -5 % by weight of dry admixture, and magnesia to make up to 100% by weight of dry admixture, and said final refractory article is characterized in that at least one of anti-hydration, thermal conductivity and chemical infiltration resistance properties has been enhanced.

22. The process for manufacturing a refractory article according to claim 2 1 , wherein the predetermined firing temperature is 1 ,000-1 ,400 "C.

23. The process for manufacturing a refractory article according to claim 21 or 22, wherein the predetermined firing temperature is 1 ,200- 1 ,350 °C.

24. The process for manufacturing a refractory article according to claim 21 , further comprising crushing each of the constituents or preconditioning to achieve desirable particle size and moisture content in association with providing predetermined amounts of olivine, elastifier, magnesia, and SiC; mixing olivine, elastifier, magnesia, and SiC provided; molding mixed composition to form a final refractory article; and firing the refractory article at the predetermined temperature.

25. The process for manufacturing a refractory article according to claim 21 , further comprising drying the molded refractory article.