Monolithic graphitic castable refractory

Abstract

A monolithic refractory castable material comprises from about 25 to about 80 weight percent of graphite, from about 1 to about 15 weight percent of a water dispersible, curable phenolic novolac resin, and from about 70 to about 15 weight percent of one or more refractory aggregates, based on the weight of the monolithic refractory castable material. The monolithic refractory castable material is water dispersible and may be delivered to a structure surface by casting, pumping, shotcreting or gunning processes. In one embodiment, the monolithic refractory castable material may be employed to install or replace a blast furnace lining.

Claims

1. An aqueous mixture of water and a monolithic refractory castable material, the monolithic refractory castable material comprising from about 40 to about 80 weight percent of graphite, from about 1 to about 15 weight percent of a water dispersible, curable phenolic novolac resin, and from about 50 to about 15 weight percent of one or more refractory aggregates, based on the weight of the monolithic refractory castable material, wherein the aqueous mixture comprises from about 1 to about 25 weight percent water, based on the weight of the monolithic refractory castable material, is free of organic solvent, is deliverable to a surface by pumping, shotcreting or gunning, and is settable to a solid form at room temperature after such delivery.

2. The aqueous mixture of claim 1, wherein the graphite comprises synthetic graphite.

3. The aqueous mixture of claim 1, wherein the monolithic refractory castable material comprises from about 5 to about 10 weight percent of the water dispersible, curable phenolic novolac resin, based on the weight of the monolithic refractory castable material.

4. The aqueous mixture of claim 1, wherein the one or more refractory aggregates comprise from about 1 to about 40 weight percent SiC, and from about 1 to about 10 weight percent carbon black, pitch, Al.sub.2O.sub.3, Cr.sub.2O.sub.3, ZrO.sub.2, SiO.sub.2, TiO.sub.2, Si.sub.3N.sub.4, B.sub.4C, TiC, CaO.6Al.sub.2O.sub.3, Si.sub.2ON.sub.2, Sialon, aluminum metal powder or silicon metal powder, or a mixture of two or more thereof, based on the weight of the monolithic refractory castable material.

5. The aqueous mixture of claim 1, wherein the monolithic refractory castable material comprises from about 50 to about 70 weight percent of graphite, from about 5 to about 10 weight percent of the water dispersible, curable phenolic novolac resin, and from about 35 to about 15 weight percent of the one or more refractory aggregates, based on the weight of the monolithic refractory castable material.

6. The aqueous mixture of claim 1, wherein the one or more refractory aggregates comprise carbon black, pitch, SiC, Al.sub.2O.sub.3, Cr.sub.2O.sub.3, ZrO.sub.2, SiO.sub.2, TiO.sub.2, Si.sub.3N.sub.4, B.sub.4C, TiC, CaO.6Al.sub.2O.sub.3, Si.sub.2ON.sub.2, Sialon, aluminum metal powder, copper metal flake, or silicon metal powder, or a mixture of two or more thereof.

7. The aqueous mixture of claim 1, wherein the monolithic refractory castable material comprises silica fume and the silica fume is included in an amount of up to about 10 weight percent, based on the weight of the monolithic refractory castable material.

8. The aqueous mixture of claim 1, wherein the monolithic refractory castable material comprises calcium aluminate and/or calcium oxide and the calcium aluminate and/or calcium oxide is included in an amount of up to about 10 weight percent, based on the weight of the monolithic refractory castable material.

9. The aqueous mixture of claim 1, wherein the monolithic refractory castable material further comprises up to about 1 weight percent of a dispersant.

10. A method of applying a material to a structure surface, comprising delivering the aqueous mixture of claim 1 to the structure surface via casting, pumping or shotcreting.

11. A method of installing or repairing a refractory lining on a blast furnace surface, comprising delivering the aqueous mixture of claim 1 to the blast furnace surface via casting, pumping or shotcreting.

12. A method of applying a material to a structure surface, comprising forming the aqueous mixture of claim 1 at a location adjacent the structure surface, and delivering the aqueous mixture to the structure surface via a nozzle.

13. A method of installing or repairing a refractory lining on a blast furnace surface, comprising forming the aqueous mixture of claim 1 at a location adjacent the blast furnace surface, and delivering the resulting mixture to the blast furnace surface via a nozzle.

14. An aqueous mixture of water and a monolithic refractory castable material, the monolithic refractory castable material comprising from about 40 to about 80 weight percent of graphite, from about 1 to about 15 weight percent of a water dispersible, curable phenolic novolac resin, from about 50 to about 15 weight percent of one or more refractory aggregates, and calcium aluminate and/or calcium oxide, wherein the calcium aluminate and/or calcium oxide is included in an amount of up to about 10 weight percent, based on the weight of the monolithic refractory castable material, wherein the aqueous mixture comprises from about 5 to about 25 weight percent water based on the weight of the monolithic refractory castable material, is free of organic solvent, is deliverable to a surface by pumping, shotcreting or gunning, and is settable to a solid form at room temperature after such delivery.

15. The aqueous mixture of claim 14, wherein the monolithic refractory castable material comprises from about 5 to about 10 weight percent of the water dispersible, curable phenolic novolac resin, based on the weight of the monolithic refractory castable material.

16. The aqueous mixture of claim 1, comprising from about 5 to about 15 weight percent water, based on the weight of the monolithic refractory castable material.

17. The aqueous mixture of claim 1, comprising from about 5 to about 25 weight percent water, based on the weight of the monolithic refractory castable material.

18. The aqueous mixture of claim 14, wherein the monolithic refractory castable material comprises silica fume and the silica fume is included in an amount of up to about 10 weight percent, based on the weight of the monolithic refractory castable material.

19. A method of applying a material to a structure surface, comprising delivering the aqueous mixture of claim 14 to the structure surface via casting, pumping or shotcreting.

20. A method of installing or repairing a refractory lining on a blast furnace surface, comprising delivering the aqueous mixture of claim 14 to the blast furnace surface via casting, pumping or shotcreting.

Description

DETAILED DESCRIPTION

(1) The present invention is directed to monolithic refractory castable materials which are water dispersible and exhibit an advantageous combination of properties.

(2) The present materials may be used, inter alia, as blast furnace linings and for repairing blast furnace linings, for example, to lengthen the service life of an existing lining and allow rapid repair of existing carbonaceous brick or block work. The present materials may also be employed as original linings or may be used to repair existing carbonaceous brick or machined carbonaceous work in any high temperature metallurgical or chemical processing vessel operations.

(3) The present materials are water friendly, exhibit good pumpability and flow in processing equipment, for example, shotcrete equipment, bond and adhere to existing carbonaceous brick and to like materials. For example, the materials can be shotcreted on a surface and dried with low heat, e.g., from a turbo dryer. The materials exhibit good thermal conductivity, thermal shock resistance, strength, abrasion resistance, alkali resistance, and dry out ability.

(4) The monolithic refractory castable materials are graphite-based. In one embodiment, the graphite is synthetic graphite, although other types of graphite, for example super graphite comprising crushed double densified graphite, or the like may be employed. The materials typically comprise from about 25 to about 80 weight percent of graphite, or, more specifically, from about 40 to about 80 weight percent of graphite, or, more specifically, from about 50 to about 70 weight percent of graphite. Unless otherwise stated, all weight percents described herein are based on the weight of the monolithic refractory castable material, prior to mixing with water. The graphite provides the compositions with good thermal conductivity. In a specific embodiment, the materials according to the invention, after application, prefiring in coke, have a thermal conductivity greater than about 5 W/mK, more specifically greater than about 10 W/mK, or more specifically greater than about 15 W/mK, for example after prefiring in coke at 2700 F. for 4 hours ( diameter and thick disc size sample tested by Dynalene using a Laser Flash Analysis).

(5) The monolithic refractory castable materials also comprise a water dispersible, curable phenolic novolac resin. To those skilled in the art, making an aqueous carrier work with graphite based systems is difficult because the graphite naturally is hydrophobic, and thus not highly wettable. The present invention overcomes this obstacle by use of the water dispersible, curable phenolic novolac resin. Such resins are known in the art and available from, for example, Hexion Specialty Chemicals, formerly Borden Chemical, under the Durite line of products. See for example, the Gerber U.S. Pat. No. 6,046,252, which describes a water dispersible mixture of Durite phenolic novolac resins of molecular weight 1000-1300 and molecular weight of 4000-8000 (2:8 weight ratio). Typically, the water dispersible phenolic novolacs resins are rendered curable by the inclusion of a curing agent therein. A suitable curing agent is hexamethylenetetramine (hexa) which often is included in commercially available phenolic novolac resin, for example in an amount of about 1-10 weight percent, based on the resin, or, more specifically in an amount of about 4-6 weight percent, based on the resin. The resins are typically used in dry powder form and are included in the inventive compositions in an amount of from about 1 to about 15 weight percent, or, more specifically, from about 5 to about 10 weight percent.

(6) The monolithic refractory castable materials further comprise one or more refractory aggregates in order to provide, inter alia, abrasion resistance and, optionally, other desired properties. The monolithic refractory castable materials typically comprise from about 70 to about 15 weight percent of the one or more refractory aggregates, or, more specifically, from about 50 to about 15 weight percent, or, more specifically, from about 35 to about 15 weight percent of the one or more refractory aggregates. In a specific embodiment, the one or more refractory aggregates comprise carbon black, pitch (natural and/or synthetic), SiC, Al.sub.2O.sub.3, Cr.sub.2O.sub.3, ZrO.sub.2, TiO.sub.2, Si.sub.3N.sub.4, B.sub.4C, TiC, CaO.6Al.sub.2O.sub.3, Si.sub.2ON.sub.2 (silicon oxynitride), Sialon (ceramic alloys based on silicon, aluminum, oxygen and nitrogen), aluminum metal powder, copper metal flake, or silicon metal powder, or a mixture of two or more thereof. In another specific embodiment, the one or more refractory aggregates comprise from about 1 to about 40 weight percent SiC, and from about 1 to about 10 weight percent carbon black, pitch, Al.sub.2O.sub.3, Cr.sub.2O.sub.3, ZrO.sub.2, SiO.sub.2, TiO.sub.2, Si.sub.3N.sub.4, CaO.6Al.sub.2O.sub.3, B.sub.4C, TiC, Si.sub.2ON.sub.2, Sialon, aluminum metal powder or silicon metal powder, or a mixture of two or more thereof, based on the weight of the monolithic refractory castable material.

(7) The monolithic refractory castable materials may optionally further comprise other materials conventionally employed in refractory materials for their known advantages, as desired. For example, the monolithic refractory castable materials may comprise up to about 10 weight percent of silica fume and/or up to about 10 weight percent of calcium aluminate and/or calcium oxide. Optionally, the monolithic refractory castable material may further comprise a dispersant, either organic or inorganic, or a mixture thereof, in an amount up to about 1 weight percent, or, more specifically, up to about 0.1 weight percent.

(8) The monolithic refractory castable material may be mixed with water for delivery to a desired surface. Thus, in another embodiment, the invention is directed to a mixture of the monolithic refractory castable material with water. A sufficient amount of water is added to render the mixture castable, pumpable and/or shotcretable. In one embodiment, the monolithic refractory castable material is mixed with from about 1 to about 25 weight percent water, based on the weight of the monolithic refractory castable material. In a specific embodiment, the monolithic refractory castable material is mixed with from about 5 to about 15 weight percent water, based on the weight of the monolithic refractory castable material.

(9) A method of applying a material to a structure surface in accordance with the invention comprises mixing the monolithic refractory castable material and water, and delivering the resulting mixture to the structure surface via casting, pumping or shotcreting. Alternatively, the monolithic refractory castable material may be applied by gunning, wherein the material is pneumatically conveyed to a location adjacent to the structure surface and mixed with water. The mixture is delivered to the structure surface via a nozzle. Such methods are suitable, inter alia, for installing or repairing a refractory lining on a blast furnace surface or a metallurgical or chemical processing vessel.

EXAMPLE

(10) A composition is prepared comprising, on a weight basis, about 64% synthetic graphite, about 19% silicon carbide, about 6% alumina, about 2% calcium oxide, and about 9% water dispersible, curable phenolic novolac resin.

(11) The composition is employed in laboratory shotcrete application and prefired in coke at 2700 F. and exhibits a Young's modulus of about 500,000 psi, a maximum strength of about 2600 psi, a thermal expansion coefficient (10.sup.6) of 4, and a thermal conductivity of about 15 W/mK.

(12) The composition is lab shot in 222 cubes and prefired in coke to 2200 F. for 2 hours. Half the samples are thermal cycled 5 times at 1800 F. in coke in and out of the furnace. Cold crushing strength is measured on all samples and shows a loss of only about 16% in cold crushing strength as a result of the thermal cycling.

(13) Lab samples obtained via the shotcreting method (wet gunned) are subjected to abrasion resistance according to ASTM C704. Volume lost (cm.sup.3) in room temperature samples is 22.71 and in samples prefired at 2700 F. is 19.41.

(14) The example and specific embodiments set forth herein are illustrative in nature only and are not to be taken as limiting the scope of the invention defined by the following claims. Additional specific embodiments and advantages of the present invention will be apparent from the present disclosure and are within the scope of the claimed invention.