WO1997014760A1 - Method for processing iron-containing materials and products produced thereby - Google Patents

Abstract

A method for producing iron oxide of essentially spheroidal structure is disclosed. Scrap steel is melted (1), then impacted by high pressure water (2) in the presence of oxygen to form a synthetic iron oxide (3). If it is desired to make a material having a granular structure a further grinding, crushing or impacting step is carried out (4). The synthetic iron oxide is then dried, heated (5), air quenched (6) and classified according to grit size (7). It may then be subjected to further grinding (8) and classifying (9) until a suitable size distribution is obtained.

Description

METHOD FOR PROCESSING I ON- ONTAINING

MATERIALS AND PRODUCTS PRODUCED THEREBY

Background of the Invention

Field of the Invention The present invention relates generally to the processing of iron-containing materials which may be formed during the manufacture of iron and steel. More particularly, the present invention relates to a new and useful composition and method for cutting and cleaning metals, metal alloys, stone, plastics and ceramics using water jetting, and methods for processing waste products formed during the manufacture of iron and steel to produce reusable metallic products. Statement of the Prior Art.

Governmental agencies, owners of steel structures and steel fabricators go to considerable expense in cleaning steel surfaces of old failing paint, rust and scale, or preparing new steel prior to or after fabrication for the application of surface coatings (e.g., corrosion preventive paints) . Currently known surface cleaning technology includes dry abrasive blasting, hand tool cleaning, power tool cleaning, acid cleaning and solvent cleaning. However, many existing structures contain lead-based paints which may produce extremely hazardous dust if cleaned by conventional blast cleaning. The United States Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) are very interested in new technology which will reduce risk to workers and the environment in preparing surfaces; currently, expensive containment is required. One alternative to dry blasting is the use of high pressure water jet blasting, or water jetting, to remove paint and scale. High pressure water blasting (less than 20,000 psi) and ultra high pressure water blasting (greater than 20,000 psi) (collectively, water jetting) is an evolving process for cutting virtually any solid object including metals and metal alloys (e.g., steel). The advantage of water jetting is that it does not generate dust and thus reduces the need for containment systems. Water jetting is also used when heat or flame cannot be tolerated when cutting metal surfaces, for example, when cutting a hole in a fuel storage tank. Another advantage of water jetting steel is that it does not "heat treat" the steel being cut, as is the case of flame cutting methods.

One disadvantage of such water jetting, however, is that without an effective abrasive additive, water jetting does not cut steel or clean large surfaces as efficiently or as quickly and the necessary equipment is very expensive and requires a high degree of maintenance by qualified people, thus putting a premium on productivity. Water jetting without abrasive additive does not impart a suitable profile or anchor pattern, which is required for proper adhesion of most coating systems nor does it provide productivity comparable to that obtained with dry abrasive blasting.

Materials currently being used for water cutting and cleaning include silica sand, garnet, and coal slag. These products are typically used for dry blast cleaning of steel but do not have the density required to be an effective cutting media for water jetting. Also, because all three of these products are silica-based, there is the added potential for causing silicosis from the fine dust generated when these products break down during the water jetting process.

The synthetic iron oxide product of the present invention overcomes the problems cited above regarding density and silicosis. Due to their higher densities, synthetic iron oxides make a faster, more efficient cutting media compared to the silica-based products. Synthetic iron oxide is silica- free, thus presenting no potential silicosis hazard from dust generated during the water jetting/cutting operations. Moreover, by combining their increased cutting efficiency with their elimination of silicosis hazard and lower overall cost, synthetic iron oxides offer a major improvement to the abrasive injected water jetting/cutting industry.

In dry blast cleaning applications, on the other hand, cast steel shot or steel grit produced from fractured cast steel shot have traditionally been used as a superior substitute for one-cycle or limited recyclable mineral abrasives (e.g., silica sand, garnet, etc.) . Since about 1984, however, METgrain™ (a trademark of Chesapeake Specialty Products, Inc., Baltimore, Maryland) steel abrasives of the types produced in accordance with the teachings of U.S. Patent No. 4,115,076, U.S. Patent No. 4,190,422, and U.S. Patent No. 4,432,803 (each of which is assigned to the assignee of the present invention and incorporated herein by reference) from scarfer spittings became increasingly popular. Not only was such METgrain™ useful as a steel abrasive, but also in ballast and as a bottom pour shot in steel casting as a chilling agent.

Scarfer spittings (also known as "scarfer scale") generally comprise a waste product from steel mills. Scarfing itself a process for removing surface defects from steel ingots, billets or bars by means of a gas torch, while scarfer spittings are the spherical-like waste particles of such process. Such scarfer spittings ranged in size from less than a 100-mesh sieve size to more than two inches. In the past, scarfer spittings were recycled in steel mills to recover the iron they contained. A portion of the scarfer spittings would be mixed with mill scale, ore fines and the like for use as part of the charge to a sinter strand. Thereafter, inventions of the likes of those disclosed in the aforementioned '076, '422, and *803 patents found a use for such scarfer spittings. More recently, however, sources of scarfer spittings as a whole have been decreasing in light of more efficient, or wholesale elimination, of methods of conditioning iron and steel used in state-of-the-art steel making.

Accordingly, the invention described and claimed herein not only comprises a synthetic iron oxide material comprising generally spheroidal and/or granular particles suitable for use as an additive to high pressure and ultra high pressure cutting and cleaning systems, and a method for using said material, but also comprises methods for processing waste products formed during the manufacture of iron and steel to produce reusable metallic products, and the media produced thereby.

Summary of the Invention It is a general object according to a first preferred embodiment of the present invention to provide a material and method for cutting or cleaning metal or metal alloys in a cost-effective manner. More specifically, it is an object of the present invention to do so in a manner which reduces the production of dust and/or noxious fumes. It is a further object of the present invention to do so in a manner which results in a profile or anchor pattern on the surface of the metal or metal alloy. Even more specifically, it is yet a further object of the present invention to do so using a material which can be easily recovered after use, as by magnetic separation to enhance disposal or reuse.

Experiments have shown that the novel synthetic iron oxide materials according to the present invention to be a suitable additive to high pressure and ultra high pressure water jetting for cutting solids such as metals, metal alloys or ceramics, or to clean surfaces (e.g., steel surfaces) of mill scale, rust and surface preparations (e.g., paint) . The novel materials produced by one method according to the present invention, when introduced into a water stream, enhance cutting performance and thus makes water jetting more effective and more competitive with prior art methods.

The characteristic features of one presently preferred embodiment of the invention include greater than 70% iron content, a specific gravity of about 5 to 6, and bulk density of approximately 180 pounds per cubic foot. It is preferred to use particles within the range of -30 to +100 mesh ASTM standard sieve size, although particle sizes above and below these mesh sizes can be used in special applications.

Among the advantages of the synthetic iron oxide according to the present invention is its low cost. It may be produced by refining and melting iron or steel scrap into steel (as in traditional steel making technology) or from by- products of various iron and steel manufacturing processes such as steel making and steel abrasive manufacture. The synthetic iron oxide according to the present invention may also be produced from by-products which result from the casting steel or iron, crushing steel shot in the production process of producing steel grit, or scarfing steel ingots, billets or blooms. Thus, it has the additional advantage of recycling what would otherwise be waste products.

The synthetic iron oxide according to the present invention is also magnetic and, therefore, easily recovered by magnetic separation for recycling or reuse.

When used for cutting or cleaning steel, synthetic iron oxides according to the present invention have the additional advantage that, other than oxygen content, their chemical composition is similar to the steel surface. Accordingly, there is a greatly reduced potential for contamination.

The novel additive has good flow characteristics, which is necessary not only for the water jetting equipment to effectively operate but also for ease of use in traditional ballast applications. Precise metering of the product improves productivity. The flow characteristics are maintained by its particle shape and size distribution. An additional advantage for blast cleaning is the novel compound has a hardness of 6 on the mohs scale versus 6.5-7.5 for garnet, but it has a specific gravity of 6 as opposed to garnet which only has a specific gravity of 3.5-4.3. The synthetic iron oxide according to the present invention has approximately 40% more mass than garnet and an even greater percent of mass than the other mineral abrasives typically used in blast cleaning and cutting. Since cleaning and cutting efficiency is a function of transmitted energy, which is proportional to the mass of the additive, the novel synthetic iron oxides according to the present invention are more productive than most mineral abrasives due to the greater mass of iron oxide compared to other mineral abrasives.

When compared to naturally occurring iron oxides, which have densities comparable to those made in accordance with the present invention, the novel structure disclosed herein confers the advantage of increased productivity in water jetting or dry blasting. Naturally occurring iron oxides break down too readily, thus dissipating energy in fracture and reducing the energy available for doing useful work. Iron oxide is superior to garnet in other respects, such as cost and environmental impact. Not only is the novel product less costly in terms of materials, but also less costly in terms of disposal and impact on (or cost of complying with) environmental regulations. The recovered spent abrasive may be used as an ingredient in cement manufacture or may be used for the manufacture of sinter or pellets for iron and steel making.

It is a general object according to a second preferred embodiment of the present invention to provide methods of processing granulated slag and iron rejects to form metallic particles which are particularly suitable for use as abrasive media, ballast media, and bottom pour media.

In light of the growing scarcity and expense of scarfer spittings, alternative sources of raw materials for making granulated iron and steel particles similar to METgrain™ have long been desirable. Two such alternative sources, it has been found, are by-products of iron making and steel making. Slags covered by this invention are slags usable for cement additive as the slag by-product of blast furnace slag resulting from iron making or slags from basic oxygen furnace (BOF) and open hearth steel making. The cement industry, for example, typically recovers the complex calcium, magnesium, aluminum silicates from such slag and wastes the iron rejects or reverts them to iron/steel manufacture. To be suitable for remanufacture by cement companies, the slag is generally granulated by high pressure water striking the molten slag, although other processes may be utilized in producing the base granulated slag. The cement companies then utilize a magnetic separator to pull off iron rejects before final grinding of the complex calcium, magnesium, aluminum silicates. Such highly abrasive iron rejects would otherwise be destructive to the cement companies' grinding mills. Accordingly, the cement companies typically avoided use of the iron rejects and recycle them back to iron and steel making manufacturers. It has been found, however, that these wasted products of iron and steel making and cement manufacture (i.e., iron slag, steel slag, and iron rejects) are valuable sources of raw materials for making metallic particles suitable for use as abrasive media, ballast media, and bottom pour media if processed according to a second preferred embodiment of the present invention. Such metallic particles are less costly and equally effective as their prior art alternatives (e.g., cast steel shot or grit and METgrain™) . They are also environmentally friendly because they nearly completely recycle the iron and steel contained in their raw materials. Moreover, they make superior ballast media because of their resultant specific densities in the range of about 7.0 or higher. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its advantages and objects, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the present invention are illustrated. While applicable to the cleaning or cutting of any solid surface such as metal or ceramic surface material, one embodiment of the invention will be illustrated in the context of a typical low carbon or "mild" steel. Likewise, while applicable to iron and steel slag in general, another embodiment of the invention will be illustrated in the context of iron rejects as the raw materials.

Further aspects, details and features of the presently preferred embodiments of this invention will become readily apparent from the following detailed description thereof, when considered in conjunction with the accompanying drawings wherein:

Brief Description of the Drawings Figure 1 is a schematic of the process of making the novel synthetic iron oxides according to one embodiment of the present invention;

Figure 2a illustrates the structure of one alternative embodiment (spheroidal) of the synthetic iron oxide according to the present invention under 15x magnification which is especially suitable for cutting steel plate (JETgrain) ;

Figure 2b illustrates the structure of another alternative embodiment (granular) of the synthetic iron oxide according to the present invention under 15x magnification which is especially suitable for cleaning a steel surface (JETgrit) ;

Figure 3 illustrates the structure of prior art garnet abrasives;

Figures 4a and 4b are schematics of alternative prior art air assisted induction systems suitable for use with the synthetic iron oxides according to the present invention;

Figure 5 is an illustration of a typical Venturi nozzle induction system suitable for drawing the novel synthetic iron oxides according to the present of the invention into the water stream of a water jetting system, for the purposes of cleaning or cutting; and

Figure 6 is a schematic of the method of processing granulated slag/iron rejects according to another embodiment of the present invention. Detailed Description of the Preferred Embodiments

Referring now to the drawings, wherein like characters designate like or corresponding parts throughout the several views, there is shown in Figure 1 a method for producing synthetic iron oxide characterized by essentially spheroidal structures will be described in greater detail herein below.

The starting material is an iron-bearing compound (in the preferred embodiment, steel) . Scrap steel has been found to be suitable and has the advantage of being inexpensive and recycling what might otherwise be a waste product. The steel is melted (1) , then impacted by high pressure water (2) in the presence of oxygen to create a synthetic iron oxide (3), with or without a steel core, having an essentially spheroidal structure (10) as shown in Figure 2. In the alternative, the invention may be produced by the recovery of scarfing scale as produced by automatic or hand scarfing of steel surfaces. The resulting granular products are processed in accordance with the flow chart shown in Figure 1. Figure 2a is derived from a

15x magnification photograph of material produced according to the above process, and clearly shows the essentially spheroidal structure (10) of the synthetic iron oxide particles (3) , as compared to prior art abrasive particles shown in Figure 3.

A compound so made and having the particle shape and size distribution described below has been found to provide a suitable material for surface cleaning and preparation.

If it is desired to produce a material having an essentially granular structure, a further grinding, crushing or impacting step (4) is carried out. Particles treated in this fashion have an essentially granular structure, as shown in Figure 2b. Figure 2b is derived from a 15x magnification photograph of material produced according to the above process, and clearly shows the essentially granular structure

(11) of the synthetic iron oxide particles (3) . A compound so made and having the particle shape and size distribution described below has been found to provide a suitable material for cutting.

Following the above steps, the synthetic iron oxide (3) may be dried, heated (5) so as to produce dry particles, air quenched (6) and classified according to grit size (7) . Should the resulting size distribution not be satisfactory, the synthetic iron oxide (3) may be subjected to further grinding (8) and classifying (9) until a suitable size distribution is obtained.

In order to determine the effectiveness of the novel synthetic iron oxides according to the present invention, a mixture of spheroidally- and granularly-shaped synthetic iron oxides was produced according to the above process. The size distribution of the resulting mixture and of a prior art conventional garnet abrasive is shown in Table 1 on the following page. Table 1 is a laboratory report of the typical size characteristics not only of the novel abrasive materials according to the present invention and of typical prior art garnet abrasives. Particle size distribution may be increased or

decreased as specified by the user, depending upon work requirements to change cutting or cleaning characteristics.

The chemical composition of the resulting compound is shown in Tables 2 and 3 below and on the following page. Such table represent laboratory reports of chemical analyses which show typical compositions of the synthetic iron oxides according to the present invention (which may be derived from low carbon or high carbon steel or iron production processes) . Therefore, carbon content may suitably range from about 0.4% to 3.5%, while iron content may range from about 70% - 85%.

Table 2. JETgrit Chemical Composition

Element. Wt. %

Carbon 0.23

Manganese 0.439

Phosphorous 0.008

Sulfur 0.008

Silicon 0.13

Iron 81.8

Lead <0.005

Chromium 0.034

The experimental abrasives and conventional garnet abrasive were respectively introduced into a conventional water jetting fluid under high pressure of 10,000 psi and ultra high pressure water blasting of greater than 20,000 plus psi.

Each of these abrasives was tested using a JET Edge™ (a trademark of Chesapeake Specialty Products, Inc., Baltimore, Tai2l≤_l JETgrain Chemical Composition

Element. t. %

Carbon 0.14

Manganese 0.483

Phosphorous 0.006

Sulfur 0.007

Silicon 0.08

Iron 77.7

Lead <0.005

Chromium 0.006

Maryland) Ultra High Pressure Hydra Blast system, a conventional prior art water jetting system. Referring now to Figures 4a and 4b, the operation of the system is essentially as follows. Each abrasive material is placed into abrasive hopper (20) and passes through abrasive metering valve (21) into a line (22) leading to nozzle (23) ; optionally, compressed air may be introduced into line (22) to assist in moving the abrasive along line (22) . High pressure water (24) is also fed to nozzle (23) . Alternatively, the abrasive material may be introduced as a wet slurry as shown in Figure 4b, where water (25) is added to the abrasive in mixing hopper (26) to form a water/abrasive slurry before entering line (22) , and where a slurry pump (27) is added to line (22) to assist in pumping the slurry to nozzle (23) .

In either alternative, the abrasive is mixed with the high pressure water (24) at the nozzle (23) , as shown in greater detail in Figure 5, by means of a conventional Venturi induction chamber (28) . The abrasive-laden high pressure water (29) was directed against the target material.

The results of the test are compiled in the chart in Tables 4 through 6 on the following pages. As shown in Table 4, the JETgrain composition compares favorably with the more expensive conventional garnet in cutting rate. As shown in Tables 5 and 6, when used to clean a test plate covered with alkyd paint and primer covered with extensive rust, both novel compositions achieved superior results versus garnet and natural oxide in cleaning steel plate with rust and scale and old paint on steel. Using PRESS-O-FILM™ (a trademark of Testex, Inc., of Newark, Delaware) tape, the profile pattern was measured by micrometer and found to be a consistent 4.5 mils, and anchor pattern suitable for anchoring a new surface coating material. If desired, the profile may be altered by increasing pressure or particle size (to obtain a deeper profile) , or by decreasing pressure or particle size (to obtain a reduced profile) .

The compositions according to this first embodiment of the present invention may be Used to blast clean steel bridges, water towers, standpipes, railcars, ship hulls, ship tanks, ship decks, pipelines and numerous other coated surfaces. They may also be used as an abrasive additive to cut steel pipe, steelplate, steel beams or steel fabricated structures using ultra high pressure water jetting systems (greater than 20,000 psi) . Thus, there has been described compositions and method for cutting and cleaning metals, metal alloys, and ceramics that have a number of novel features and advantages and a manner of making and using a first embodiment of the present invention.

Table 5

High Pressure Water Painted Surface Cleaning Test

Abrasive Injection via Venturi

Cπttinσ Media Garnet JETgrit JETgrain Hematite

Water pressure 35,000 35,000 35,000 35,000

Abrasive Venturi Venturi Venturi Venturi pressure

Steel thickness 1/2" flange 1/2" flange 1/2" flange 1/2" flange

J 3/16" plate 3/16" plate 3/16" plate 3/16" plate I

Degree of Near white Near white Near white Near white cleaning

Time of clean 5 min. 30 sec. 1 min. 28 sec. 2 min. 1 min. 45 sec.

Cleaning rate 109 sq. ft./hr. 408 sq. ft./hr. 300 sq. ft./hr. 342 sq. ft./hr.

Abrasive 11 pounds 6 pounds 9 pounds 8 pounds consumed

Abrasive 1.1 lbs./sq. ft. 0.6 lbs./sq. ft. 0.9 lbs./sq. ft. 0.8 lbs./sq. ft. consumption

Area 10 sq. ft. 10 sq. ft. 10 sq. ft. 10 sq. ft.

Table 6 High Pressure Water Rust and Mill Scale Surface Cleaning Teεt

Abrasive Injection via Venturi

Cu inσ Media Garnet JETgrit

Water pressure 35,000 35, 000

Steel thickness 3/16" plate 3/16" plate

Area cleaned 8 sq. ft. 8 sq. ft.

Time of clean 4 min. 2 min. 40 sec.

Square ft . /hour 120 288

Amount cutting media 6 pounds 12 pounds

Abrasive consumption 0.75 lbs./sq. ft. 1.5 lbs./sq. ft.

Profile 5.0 mils 4.5 mils

Referring now to Figure 6, there is shown a schematic of the method of processing air-cooled, water-cooled and granulated slag or iron rejects according to another embodiment of the present invention. Iron rejects of cement manufacturing using granulated iron slag is fed into a first holding means (e.g., the hopper of suitable pulverizing means) at step (100) . The input may optionally be dried at step (102) . Suitable pulverizing means may comprise any conventional slow-speed or medium-speed pulverizing means such as those described below. High-speed pulverizing means (e.g., hammer mills and comb crushers) are much more expensive and may be avoided in practicing the methods according to this embodiment of the present invention.

Conventional slow-speed pulverizing means typically consist of a rotating drum with a tumbling charge of steel balls. They are, for example, used for all types of coal but are particularly adaptable to abrasive materials such as anthracite, iron slag, and steel slag. Exemplary of such slow- speed pulverizing means are "ball mills" (i.e., pulverizers that consist of a horizontal rotating cylinder, up to three diameters in length, containing a charge of tumbling or cascading steel balls, pebbles, or rods) or "ball grinders". Medium-speed pulverizing means are used, for example, for all grades of bituminous coal, and may suitably comprise the contrarotation ball-race type or the bowl and roller type. One particularly suitable type of bowl and roller type is a "ring-roller mill" in which material is fed past spring-loaded rollers that apply force against the sides of a revolving bowl. While a vibratory ball mill is preferably used according to this second embodiment of the present invention, any mechanical conditioning enabling the production of metallic granules comprising a plurality of distinct sizes would be suitable. The milled product output from step (104) is then air classified and mechanically sized at step (106) to separate metallic product contained within the milled product from a first fines revert product which may be suitably recycled at step (108) to a cement manufacturer.

The metallic product (which may still contain residual non-magnetic reverts) is then magnetically classified at step (110) to separate such non-magnetic reverts contained within the metallic product from a refined product. A cyclone impactor may be optionally utilized at step (112) one or more times for further refinement of the refined product. In either case, the refined product is again air classified at step (114) to separate metallic granules comprising a plurality of distinct sizes from a second fines revert product. Such second fines revert product may then be recycled at step (116) to a cement manufacturer.

The metallic granules output from step (114) may then be screened as the market dictates to produce separate supplies of the plurality of distinct sizes. For example, a market grade #8 sieve is used at step (118) to segregate metallic granules of a first distinct size for use as bottom pour. The output from step (118) is then screened on a market grade #12 sieve at step (120) to segregate metallic granules of a second distinct (e.g., G-25) size. Next, the output from step (120) is screened on a market grade #18 sieve at step (122) to segregate metallic granules of a third distinct (e.g., G-40) size. The output from step (122) is then screened on a market grade #24 sieve at step (124) to segregate metallic granules of a fourth distinct (e.g., G-50) size. Next, the output from step (124) is screened on a market grade #35 sieve at step (126) to segregate metallic granules of a fifth distinct (e.g., G-80) size. The output from step (126) is finally screened on a market grade #50 sieve at step (128) to segregate metallic granules of a sixth distinct suitable for use as bottom pour, high density media (i.e., ballast media), or water jet abrasives. It should be readily apparent that any number of distinctly sized metallic granules may be segregated according to this embodiment of the present invention by substituting other or more market grade sieves. In any case, the output from each sieve may suitably be stored in second and subsequent holding means such as those shown at steps (130) through (140) in Figure 5. Such distinctly sized and segregated metallic granules may then be blended together, or with other media (e.g., METgrain™) for use as abrasives, ballast, and bottom pour. The effectiveness of such media produced in accordance with this second embodiment of the present invention has been amply demonstrated using widely accepted standard tests. In use as an abrasive, for example, this novel media has been tested using a conventional Ervin Durability tester with a standard test procedure which is widely recognized for steel shot and grit. As shown in Table 7 on the following page, this novel media demonstrated a recyclability factor in excess of 100 cycles before 100% replacement. In actual field usage, it can be expected that this novel media will readily achieve a minimum of 20 reuses which, in turn, means a reduction of about 95% of the generated dust and waste versus conventional, single-use mineral abrasives such as garnet.

It should be noted that each product listed in Table 7 represents the iron rejects from different granulated iron making slags, as processed according to this second embodiment of the present invention. Moreover, such product was screened to the size Table 7 Test for Recyclability as an Abrasive for Blast Cleaning

Product A 154 cycles

Product B 159 cycles

Product C 181 cycles

Product D 192 cycles

specification for G-40 steel grit, and the take out screen for spent abrasive was an ASTM standard #50 mesh. Typically, from 80% to 95% of the crushed or granulated slag generated by steel mills is composed of non-magnetic particles or magnetic particles containing a high percentage of non-ferrous product. Granulated slag as an iron making by¬ product utilized by cement makers, however, is of low iron content. When the cement makers use their processes of liberating complex calcium, magnesium, aluminum silicates from such granulated slag, the iron fines (i.e., iron rejects) by¬ products typically contain about 30% to 70% or iron or more. One distinct benefit of the methods according to this second embodiment of the present invention is the relative purity of the finished media. Such media easily obtains a 90% iron purity, and preferably 95% or higher. This more highly concentrated product thereby yields a medium with high specific gravities, as demonstrated by the data set forth in Table 8 on the following page. The novel media according to this second embodiment of the present invention preferably have a specific gravity of 6.0 or more, and even more preferably 7.0 or more. If desired, hematite and agnatite may be added to the novel media to achieve higher packing densities for use in ballast media.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles and that various modifications, alternate constructions, and equivalents will occur to those skilled in the art given the benefit of this disclosure. Thus, the invention is not limited to the specific embodiment described herein, but is defined by the appended claims.

Table 8

>

High Density Product for Ballast and Bottom Pour Applications

Product Density (lbs./cu. ft.) Specific Gravi y

LQQ≤SL Packed

Product Al

As received 196 232

Milled 243 255 7.2

Product A2

As received 204 216

I ro

4 Milled 249 284 7.2 I

Product B

As received 207 222 5.3

Milled 244 264 6.9

Product C

As received 117 134 4.2

Milled 216 242 6.1

Milled and impacted 222 255 6.5

Steel mill slag (< W ) 125 136

Steel mill slag 154 168 (magnetically separated)

Claims

ClaimsWhat we claim as our invention is:

1. A synthetic iron oxide compound comprising essentially spheroidal particles.

2. An abrasive material for cleaning or cutting metal or metal alloy by water jetting, comprising synthetic iron oxide comprising essentially spheroidal particles.

3. An abrasive material as in Claim 2 wherein substantially all of said particles are of a size between 30 mesh and 140 mesh.

4. An abrasive material as in Claim 2 wherein substantially all of said particles are of a size between 30 mesh and 100 mesh.

5. An abrasive material as in Claim 2 wherein said particles have a specific gravity of about 6.0.

6. An abrasive material as in Claim 2, wherein the synthetic iron oxide comprises 70 weight percent iron or more, the remainder being oxygen and elements typically found in carbon or alloy steel.

7. An abrasive material for cleaning or cutting metal or metal alloy by water jetting, comprising synthetic iron oxide comprising essentially granular particles.

8. An abrasive material as in Claim 7 wherein substantially all of said particles are of a size between 30 mesh and 140 mesh.

9. An abrasive material as in Claim 7 wherein substantially all of said particles are of a size between 30 mesh and 100 mesh.

10. An abrasive material as in Claim 7 wherein said particles have a specific gravity of about 6.0.

11. An abrasive material as in Claim 7, wherein the synthetic iron oxide comprises at least 70 weight percent iron, the remainder being oxygen and elements typically found in carbon or alloy steel .

12. An abrasive material for cutting and cleaning the surface of metals in situ, comprising synthetic iron oxide having particles the majority of which are of size between 30 mesh and 100 mesh and a specific gravity of about 6.0.

13. A method for cutting metal or metal alloys, comprising the steps of providing an additive as in Claim 1, introducing said additive into a water jetting apparatus, and directing a stream from said water jetting apparatus toward the metal or metal alloy to be cut, under suitable pressure.

14. A method for cleaning the surface of a metal or metal alloy comprising the steps of providing an abrasive material as in Claim 1, introducing said abrasive material into a water jetting apparatus, and directing a stream from said water jetting apparatus toward the metal or metal alloy to be cleaned, under suitable pressure.

15. A method for producing an abrasive product comprising the steps of impacting molten iron-bearing material with water at high pressure in the presence of oxygen to create said abrasive product, with or without an iron or steel core, having an essentially spheroidal structure.

16. A method of processing slag, comprising the steps of: feeding said slag into a first holding means; milling said slag within said first holding means to produce a milled product; air classifying said milled product to separate metallic product contained therein from a first fines revert product; magnetically classifying said metallic product to separate non-magnetic reverts contained therein from a refined product; and air classifying said refined product to separate metallic granules contained therein from a second fines revert product, said metallic granules comprising a plurality of distinct sizes.

17. The method according to claim 16, wherein said slag comprises iron slag.

18. The method according to claim 16, wherein said slag comprises steel slag.

19. The method according to claim 16, wherein said slag comprises air-cooled, water-cooled, or granulated slag.

20. The method according to claim 16, further comprising the step of drying said slag before said feeding step.

21. The method according to claim 16, further comprising the step of impacting said refined product before said step of air classifying same.

22. The method according to claim 21, wherein said impacting step comprises the step of cycling said refined product through a cyclone impactor a preselected number of times .

23. The method according to claim 16, further comprising the step of screening said metallic granules to segregate one or more of said distinct sizes from the other distinct sizes.

24. The method according to claim 23, wherein said screening step comprises the step of feeding said metallic granules through a #8 sieve to segregate a first distinct size.

25. The method according to claim 24, wherein said creening step further comprises the step of feeding said metallic granules through a #12 sieve to segregate a second distinct size.

26. The method according to claim 25, wherein said screening step further comprises the step of feeding said metallic granules through a #18 sieve to segregate a third distinct size.

27. The method according to claim 26, wherein said screening step further comprises the step of feeding said metallic granules through a #24 sieve to segregate a fourth distinct size.

28. The method according to claim 27, wherein said screening step further comprises the step of feeding said metallic granules through a #35 sieve to segregate a fifth distinct size.

29. The method according to claim 28, wherein said screening step further comprises the step of feeding said metallic granules through a #50 sieve to segregate a sixth distinct size.

30. The method according to claim 23, further comprising the step of blending said metallic granules of a plurality of said distinct sizes to yield a bottom pour medium.

31. The method according to claim 23, further comprising the step of blending said metallic granules of a plurality of said distinct sizes to yield a ballast medium.

32. The method according to claim 23, further comprising the step of blending said metallic granules of a plurality of said distinct sizes to yield an abrasive medium.

33. A method of processing iron rejects from cement manufacturing, comprising the steps of: feeding said iron rejects into a first holding means; pulverizing said iron rejects within said first holding means to produce a pulverized product; air classifying said pulverized product to separate metallic product contained therein from a first fines revert product; magnetically classifying said metallic product to separate non-magnetic reverts contained therein from a refined product; impacting said refined product; air classifying said impacted refined product to separate metallic granules contained therein from a second fines revert product, said metallic granules comprising a plurality of distinct sizes; and screening said metallic granules to segregate one or more of said distinct sizes from the other distinct sizes.

34. The method according to claim 33, further comprising the step of drying said iron rejects before said feeding step.

35. The method according to claim 33, wherein said screening step further comprises the step of providing a plurality of sieves of preselected mesh.

36. The method according to claim 35, wherein said plurality of sieves are selected from the group consisting of a #8 sieve, a #12 sieve, a #18 sieve, a #24 sieve, a #35 sieve, and a #50 sieve.

37. A bottom pour medium produced by the method according to claim 35.

38. A ballast medium produced by the method according to claim 35.

39. An abrasive medium produced by the method according to claim 35.