AU2020102881A4 - ITPI- Steel and Mining Waste Management: INTELLIGENT TECHNOLOGY AND PROCESS MANAGEMENT FOR STEEL INDUSTRY AND MINING WASTE - Google Patents

Abstract

Our Invention "ITPI- Steel and Mining Waste Management" is a method for providing a composite capping cover for maintaining the surface of a sulphide bearing tailing and mine waste containing deposit moist thereby substantially eliminating oxidation of the sulphidic particulate in the deposit and the formation of heavy metal salts. The invented also includes atmospheric precipitation and the composite capping cover comprising a fine particulate layer, a fine-granular particulate layer and a coarse granular particulate layer. The size of the particles making up the individual layers having been selected such that the hydraulic conductivity of the layers increases successively, while the matric suction value within the layers decreases. The slag disposal method for disposing of slags produced in furnaces during iron or steel making processes comprises employing the steps of magnetic sorting of masses of crude slags of a size greater than a value ranging between 300 to 400 mm obtained from the furnaces into slags rich in iron (above about 51 to 59 percent) and slags not rich in iron (below 51 percent) and then applying a compressive force to the slags rich in iron to cause a coarse crushing and/or deformation to reduce the size and at the same time increase the iron content due to the breaking and separation of the slags from the metal. Further magnetic sorting and sieving after grinding are provided to obtain concentrates having high iron content and to improve recovery efficiency the specific recycle materials are blended with hot slag and wet sludge to make a recyclable steelmaking revert. The specific recycle materials are kish, lime, glass, ferro manganese and the like and also the specific materials are blended with the slag and sludge individually or in any desirable combination to form a steelmaking revert. The recycle materials are blended with the slag and sludge, the recycle blend slag/sludge mixture is allowed to rest to bring the moisture content to less than 10% by weight and also the steelmaking revert and process for making the same reduce the need for steelmaking raw materials by employing recycle materials from landfills and also reduce the cost. 21 ^r---GREATE~R THAN J.MC ~~~~ 3C3-00 r. 50MiO %50-~60 0 DEPORI6T ION 501C>-500: ralrn L-ow- HIGH IRON CONTrENT I RON CONTJ~EPFT TECHNIQUE C X>Nseawa4 PON% ag 21 1 6 8 Cafam LA gulds-e FIG. re 1:o ISAFO HR FAFRTEBDMN FALAGDIPOA MTHD

Description

^r---GREATE~R THAN J.MC ~~~~ 3C3-00 r.

50MiO %50-~60 0

DEPORI6T ION

501C>-500: ralrn

L-ow- HIGH IRON CONTrENT IRON CONTJ~EPFT

TECHNIQUE

C X>Nseawa4

PON% ag 21 16 8

Cafam LA gulds-e FIG. re 1:o ISAFO HR FAFRTEBDMN FALAGDIPOA MTHD

ITPI- Steel and Mining Waste Management: INTELLIGENT TECHNOLOGY AND PROCESS MANAGEMENT FOR STEEL INDUSTRY AND MINING WASTE

FIELD OF THE INVENTION

Our invention "ITPI- Steel and Mining Waste Management" is related to INTELLIGENT TECHNOLOGY AND PROCESS MANAGEMENT FOR STEEL INDUSTRY AND MINING WASTE and also to the treatment of waste products of mining and mineral processing of ores and industrial minerals for rendering such environmentally acceptable. BACKGROUND OF THE INVENTION

The mining industry is engaged in mining and recovering ores of metals and minerals from the ground, subsequently processing the ores and minerals to provide raw materials, which are then further processed to obtain products of commercial use and value. The mined ores and minerals often contain the value metal compounds or the commercially usable minerals in amounts less than 15 wt.%, and therefore the ore or the mineral, needs to be subjected to various separation and concentration processes for recovery.

The mineral separation process usually comprises several steps, eventually yielding a concentrate of the desired metal compound or mineral and waste rock and tailings. The tailings may still contain low levels of the mineral or the value metal compound; however, the bulk of the tailings consists of gangue minerals, silicates, waste rock, and other substances accompanying the ore or mineral in the ground. It is noted that when the value metal is in a form of a sulphidic compound, the tailings usually contain substantial amounts of iron sulphide, which is often the host mineral of the value metal compound in the ground.

The tailings produced in the mineral separation process steps are often in the form of an aqueous slurry, such as tailings, which may be dry or may require flotation separation process. The particle size of tailings ranges from very fine to granular or sandy, often referred to as slimes and tailing sands, respectively. The tailings together with waste rock referred to as waste products of mining processes. Tailings and similar mine waste products have often been deposited and left at the side of mining operations as, tailing piles or dumps, deposits in ponds, filled into the pits in the ground such as mine shafts and may be subsequently flooded. Such remains of mining operations were often an eyesore, but most detrimentally, the oxidation products could lead to contamination of the regional surface and ground waters.

Environmental regulations now require that a mining company takes the responsibility for the visual appearance of the surroundings of the mine and appropriate steps to ensure that the tailings and similar waste rock produced, and the effluent generated, do not contaminate the regional waters nor the environment. Furthermore, regulations also require that when a mine is decommissioned the mining area is left in such state that unpleasant, unsightly and harmful consequences of the mining operation, be that actual or potential, are controlled or eliminated. One of the most significant harmful effects of improper tailing management is the possible chemical contamination of the regional waters.

The regional waters may become contaminated as a result of escaped water soluble mining process reagents or oxidation products of substances in the mine waste products. A few examples are remains of the flotation separation and similar reagents in the tailings, but more particularly, because of atmospheric oxidation of the sulphide contained in the tailings. These can lead to acid generation and the formation of sulphates and other heavy metal compounds, which are subsequently solubilized and mobilized by rain. The water-soluble compounds may interact with the surroundings of the tailing deposit in a manner that can cause contamination, unless properly intercepted and treated. The subject of tailing management is discussed in several publications, and has become an important part of the initial mine design and mine operation, and the required closure planning conducted by responsible mining companies.

A procedure sometimes practiced in handling tailings, is to feed a thickened slurry of the tailings at a point above the pile, allowing the tailings slurry to run down the sides of the pile. The tailing sands usually settle above the fines and the run-off water collects at the bottom. The run-off water may be treated subsequently to remove or neutralize harmful components. A method of treatment of mineral tailings is described in published Canadian patent application 2,090,141, which was filed by Peter Davies on February 23, 1993. The treatment includes separating the tailings, physically, into a slime or fine fraction and a coarse fraction, then depositing alternating layers of these in the tailing deposit pile, thus allowing the effluent to escape more readily while the layers get compacted by their own weight. It is noted, however, that such tailing treatment methods are usually not recommended for sulphidic tailings and/or sulphide containing waste rock, which may yield undesirable oxidation products when exposed to atmospheric oxidation.

The tailing management is to improve the appearance of tailing piles, by providing new growth surfaces for vegetation. Successful revegetation, however, is usually costly and the soil deposited on top of the tailings needs to be deep enough to isolate the roots of the plants from the underlying tailings, especially if the oxidation products generated in the tailings are detrimental to plant growth. The soil layer has to be able to sustain growth of the plants, however, a thick soil layer on top of a sulphide bearing tailing deposit may have little or no effect on the continued oxidation, nor on the solubility of heavy metal salts and acids already present therein.

PRIOR ART SEARCH

GB2219617A *1988-06-091989-12-13David William Blowes Treatment of mine tailings. US5118219A*1991-03-211992-06-02Chemstar Lime Company Method of capping tailings ponds. US5141362A*1989-06-301992-08-25Kuegler Jost Ulrich Process for producing a sealing for waste dumps and the like.

DE4106799A1*1991-03-041992-09-0Rheinische Braunkohlenw Reducing contamination of ground water by lignite mining spoil - by covering spoil deposits with permeable material layer of low di:sulphide content, and at least in part, surrounding by sealing and/or buffer layers. US5550315A *1995-03-231996-08-27Sandia Corporation Anisotropic capillary barrier for waste site surface covers. US1207503A*1916-06-271916-12-O5Cairy Clyde Conover Method of recovering clay and slag from used retorts. US1339300A *1920-05-04Process for the magnetic sizing and grading oeore. US2175484A *1936-11-191939-10-10Vanadium Corp Of America Dry concentration of carnotite ores. US2264204A*1939-09-091941-11-25Eric H Heckett Method and apparatus for reclaiming metal. US2352712A *1941-11-241944-07-04Eric H Heckett Recovery and use of scrap steel. US2728454A*1952-07-221955-12-27Heckett Engineering Insupportable apparatus for reclaiming metal scrap. US2710796A1954-05-261955-06-14United States Steel Corp Method of making iron bearing material for treatment in a blast furnace. US4091545A1975-03-081978-05-3ONippon Kokan Kabushiki Kaisha Method for removing water and grease deposit from rolling mill sludge. US4133756A1976-02-201979-01-09Sumitomo Heavy Industries, Ltd. Method for dehydrating a mixed dust slurry. USRE30060E1975-07-011979-07-3lBethlehem Steel Corporation Method for agglomerating wet-collected fume for use in metallurgical furnaces and agglomerates produced thereby. US4606530A1984-03-281986-08-19Victor Litchinko Installation and process for continuously charging a reactor with solid material and heating said material with the gases emitted from said reactor. US4711662A1986-06-111987-12-08Nippon Jiryoku Senko Co., Ltd. Process for the simultaneous treatment of dust, sludge and steel slag.

OBJECTIVES OF THE INVENTION

1. The objective of the invention is to invent a method for providing a composite capping cover for maintaining the surface of a sulphide bearing tailing and mine waste containing deposit moist thereby substantially eliminating oxidation of the sulphidic particulate in the deposit and the formation of heavy metal salts. 2. The other objective of the invention is to the invent a method for atmospheric precipitation and the composite capping cover comprising a fine particulate layer, a fine-granular particulate layer and a coarse-granular particulate layer. The size of the particles making up the individual layers having been selected such that the hydraulic conductivity of the layers increases successively while the matric suction value within the layers decrease. 3. The other objective of the invention is to invent a slag disposal method for disposing of slags produced in furnaces during iron or steel making processes. It includes employing the steps of magnetic sorting of masses of crude slags of a size greater than a value ranging between 300 to 400 mm obtained from the furnaces into slags rich in iron (above about 51 to 59 percent) and slags not rich in iron (below about 51 percent). Then applying a compressive force to the slags rich in iron to cause a coarse crushing and/or deformation to reduce the size and at the same time increase the iron content due to the breaking and separation of the slag from the metal. 4. The other objective of the invention is to suggest the magnetic sorting and sieving after grinding to obtain concentrates having high iron content and to improve recovery efficiency. The specific recycle materials blended with hot slag and wet sludge makes a recyclable steelmaking revert. 5. The other objective of the invention is specific recycling of materials such as kish, lime, glass, ferro-manganese, etc. The specific materials are blended with the slag and sludge individually or in any desirable combination to form a steelmaking revert. 6. The other objective of the invention is to recycle materials, blended with the slag and sludge. The recycled blend slag/sludge mixture is allowed to rest to bring the moisture content to less than 10% by weight and also the steelmaking revert and process for making the same. This will reduce the need for steelmaking raw materials by employing recycled materials from landfills and reduce the cost.

SUMMARY OF THE INVENTION

The harmful effluents generated in steel and mining industries seep into the ground water providing an impervious lining for a cavity. This method has serious drawbacks. There are known processes for capping or providing a hard cover or sealing layer over municipal waste or industrial waste deposits, in particular for covering landfill sites and waste dumps. Composite layers utilized in such processes may be made of naturally occurring materials, such as gravelly moraine, loam, sand, and similar substances, mixed with larger particles of gravel, sand and the like, in specific particle size distribution ranges. The layers made of such mixtures are frequently reinforced with a geotextile to provide a composite sealing layer. Such a process is described, for example, in U.S. patents 5,141,362 and 5,374,139, issued to J-U. Kugler on Aug. 25,1992 and Dec. 20,1994, respectively.

The Kugler patents teaches a self-sealing cap for waste dumps, comprising mixtures of fine particles capable of flowing and sealing cracks that have formed. The cap supported on a geotextile mat, is overlain by a filter layer and a soil layer. Other processes for synthetic hard covers over municipal waste piles, admix building waste and binders such as cement kiln dust, bentonite, fly ash, Portland cement and the like, which may also be mixed with cellulose or plastic fibres and other organic or processed carbon bearing materials.

The covers are required to eliminate bad odour, or damage by birds and animals, or in some cases to contain effluent formation, but not to control oxidation. Furthermore, the effluent generated by municipal waste is not necessarily harmful to the environment and in any case, it can be treated to render it harmless. In contrast, acid drain water generated in the oxidation of sulphidic mine tailing deposits cannot be readily eliminated or treated. As was discussed above, methods to provide a hard cover is not considered to be applicable to deposits of sulphidic mine tailings and sulphidic waste rocks, as a protective or oxidation preventive measure. A method for providing a cap for tailing ponds is described in U.S. patent 5,118,219, issued to D.D. Walker Jr. on June 2, 1992. The cap is intended to prevent the drying out of such ponds and thereby eliminate dusting. The capping cover is made of lime, a sulphate component, a pozzolanic material and water, and allowed to harden. It is known to introduce carbonaceous substances in direct contact with the sulphidic tailings to consume oxygen and thereby to prevent, or at least hinder, oxidation. In one form of utilizing a carbon containing material, in particular carbon in the form of dead vegetation and similar materials, the organic carbon containing material is mixed in with the sulphide bearing tailing particles, with the objective of acting in-situ as adsorbent for the acid produced as well as a reductant, thereby avoid oxidation.

The treatment of sulphide bearing mine tailings by providing organic carbon layers in the tailing deposit directly below the water table and mixing particulate organic carbon source with the sulphide bearing tailing particles disposed above the water table, is described in Canadian patent 1,327,027 issued to Blowes et al. on February 15, 1994. The position of the carbon layer and the amount of carbon mixed with the tailings are calculated based on the depth of the sulphidic tailings above the water table. The water table level may, however, shift with time and season, or all the carbon mixed in within the tailings may be consumed, thereby allowing the tailings to oxidize without hindrance. There are several studies currently undergoing trials, involving various carbonaceous substances capable of consuming oxygen, directly overlaying sulphidic tailing deposits. Such carbon containing substances include wood shavings, compost, treated sewage sludge and municipal waste, dried and chopped vegetation, and substances of similar nature.

However, whether a single capping layer containing predominantly carbon bearing substances is capable of preventing the oxidation of the underlying sulphide bearing deposit for a prolonged time period is not yet known. It may be assumed that if the organic carbon is not mixed in some way or anchored to a material which is able to retain water, the carbon containing material may dry out and be blown away. In other words, it seems that a predominantly carbonaceous material containing cover layer on top of the sulphidic tailings deposit is likely to lose its effectiveness in the long term. There have been other known studies in which various natural particulate layers were provided over sulphidic tailing deposits, but those have not been shown to prevent the oxidation of the underlying sulphidic materials, or they have been found to require additional and costly effluent treatment.

It may be concluded from the above, that there is a need for an inexpensive method to eliminate or at least, substantially slow down the oxidation of sulphide bearing tailing and waste rock deposits. It is the object of the present invention to provide a composite capping cover over sulphide bearing tailing and waste rock deposits, made of layers of readily available and inexpensive materials, and which requires substantially no maintenance. A new method has been found for diminishing and preferably eliminating the oxidation of sulphides contained in tailings and mine waste materials, by providing a subaerial composite capping cover over a deposit of sulphide containing tailings and sulphide bearing mineral waste materials.

The sulphidic particulate material in the deposit has low hydraulic conductivity, and a slope enclosing an angle greater than 0.5% with the horizontal. The method for obtaining a composite capping cover over the deposit of sulphidic particulate material comprises depositing a first particulate layer made of an inert, fine substance, having average particle size between 10 tm and 200 tm, hydraulic conductivity greater than "7cm/sec, and matric suction value greater than 4 cm of water. The deposited first particulate layer is extended over the surface of the deposit in depths in excess of 4 cm. The method further comprises depositing a second particulate layer containing an inert, fine-granular substance, having average particle size between 200 and 5000 tm and hydraulic conductivity between10 "3cm /sec and 1 cm /sec.

The hydraulic conductivity of the fine-granular particles containing second particulate layer is at least an order of magnitude higher than the hydraulic conductivity of the first particulate layer and the ratio of the matric suction value of the fine-granular particles contained in the second particulate layer to that of the fine particles in the first particulate layer is less than 1:2. The deposited second particulate layer is extended over the first particulate layer in depths which is at least 1.5 times the matric suction value of the fine-granular particles making up the second particulate layer, measured in centimetres of water. A third particulate layer is subsequently deposited over the sulphidic particulate deposit, comprising an inert, coarse-granular substance, having average particle size greater than 3 mm and hydraulic conductivity higher than 1 cm/sec. The third particulate layer is extended over the second particulate layer in depths in excess of 6 cm.

An organic carbon bearing substance may be mixed with the inert, fine substance comprised in the first particulate layer or with the fine-granular substance comprised in the second particulate layer, prior to being deposited. The method for providing a composite subaerial capping cover for a deposit of sulphidic particulate material an additional layer of a particulate substance capable of sustaining growth of vegetation, is deposited in a layer below and adjacent the third particulate layer comprising an inert, coarse-granular substance. A method for providing a subaerial composite capping cover over sulphide containing tailings and sulphide bearing mine waste materials, comprising the steps of:

i) providing a deposit of sulphidic particulate material comprising at least one of the group consisting of sulphide mineral containing tailings, sulphide bearing waste rock and sulphide bearing mine waste material, said sulphidic particulate material having low hydraulic conductivity, said deposit having a peak and a slope enclosing an angle greater than 0.5with the horizontal.

ii) depositing a first particulate layer over said deposit of sulphidic particulate material, said first particulate layer comprising an inert, fine substance having average particle size between 10 m and 200 m and hydraulic conductivity higher than 10 7 cm/sec, matric suction value greater than 4 cm of water, said first particulate layer being deposited to yield said first particulate layer extending over said deposit of sulphidic material in depths in excess of 4 cm.

iii) depositing a second particulate layer over said deposit of sulphidic particulate material, said second particulate layer comprising an inert, fine-granular substance, having average particle size between 200m and 5000 m, hydraulic conductivity between 10"3 and 1 cm /sec, the hydraulic conductivity of said second particulate layer being at least one order of magnitude higher than the hydraulic conductivity of said first particulate layer, and a matric suction value, the ratio of the matric suction value of said second particulate layer to the matric suction value of said first particulate layer being less than 1:2, said second particulate layer being deposited to provide said second particulate layer extending over said first particulate layer to a depth which is at least 1.5 times the matric suction value measured in cm of water, of said second particulate layer; and,

iv) depositing a third particulate layer over said deposit of sulphidic particulate material, said third particulate layer comprising an inert, coarse-granular substance, having average particle size greater than 3 mm and hydraulic conductivity higher than 1 cm /sec, said third particulate layer being deposited to provide said third particulate layer extending over said second particulate layer in depths in excess of 6 cm.

Material Av. Particle Size Test 1 Test 2 Test 3

Waste Rock > 3 mm 10 cm 10 cm 10 cm

Granulated Slag 750 pm 5 cm 10 cm 20 cm

Gold Tailings 28 sm 10 cm 10 cm 10 cm

S-cont. Tailings < 20 pm 10 cm 10 cm 10 cm

Filter Bed N/A 5 cm 5 cm 5 cm

Av. Evaporation Rate mm/day: 0.86 0.44 0.15

It is well known in the art of steelmaking that iron bearing dust and sludges generated by steelmaking furnaces and related steel processing facilities contain valuable materials useful in the steelmaking operations. Such waste materials contain iron oxides in an amount up to about 50% by weight, and it is very desirable to recover the iron for use as a steelmaking charge material. In the case of wet sludges, and especially in the case of wet BOF scrubber sludge, high moisture content has made the wet sludge very difficult to handle in a recycling stream. These sludges also contain high proportions of iron oxides that also are desirably recovered through recycling to the steelmaking furnace.

Filter cake produced from wet scrubber typically has a moisture content of about 30% by weight, or higher. The sludges have a relatively high viscosity, causing them to have poor handling characteristics. The sludges stick to conveyors and machinery when attempts are made to convey them as reverts in a recycling stream. They often form sticky agglomerations that clog and shut down equipment and machinery. For example, under test conditions, it has been found that wet sludge having a moisture content of >10% has a flow rate of less than 10 pounds of sludge per minute. Such a low flow rate makes these wet materials very unsuitable for recycling as a steelmaking revert.

Steelmaking dusts are relatively dry, and powdery. In instances where waste steelmaking dust is recycled, the dry powdery conditions of the material may cause environmental dusting problems. To control dusting, water is normally applied to the dry material, thus increasing the moisture content and potentially creating the handling problems attributable to sludges. Attempts to produce a steelmaking revert by combining wet sludges with dry steelmaking dusts have generally been unsuccessful because such reverts introduce high levels of undesirable elements and compounds into the steelmaking process. For example, if sludge from a hot dip coating line is introduced into a recycle stream, zinc levels in the final revert material can be raised to where the blended revert is unsuitable for use in a steelmaking operation. Combining steel plant wastes must be carefully monitored for chemistry to avoid introducing deleterious elements into the steelmaking process.

BRIEF DESCRIPTION OF THE DIAGRAM

FIG. 1: is a flow chart of a first embodiment of a slag disposal method. FIG. 2: is a flow chart of a second embodiment of the slag disposal method. FIG. 3: is a flow diagram illustrating the steps of the process for treating wet steelmaking sludge to produce a steelmaking reverts. FIG. 4: is a graph showing flow rate measurements in relation to sludge moisture content. FIG. 5: is a schematic view of a basic oxygen furnace installation with which to carry out the invention. DESCRIPTION OF THE INVENTION

Referring first to FIG. 1 showing a first embodiment of the invention, masses of crude slags having particle sizes greater than a value between 300 and 500 mm, produced in a blast furnace, a converter or an electric furnace during iron or steel making processes, are subjected to a first magnetic sorting step by a magnetic sorter into slags rich in iron having an iron content higher than 50 to 60 percent and slags not rich in iron having an iron content lower than 50 to 60 percent. The slags rich in iron having an iron content higher than 50 to 60 percent are then fed to a crusher which applies a compressive force to the slags to coarsely crush or deform these slags into particle sizes smaller than a value ranging between 300 and 500 mm while separating these slags and obtaining a portion having increased iron content.

As also shown in FIG. 1, the crude slags having particle sizes greater than value ranging between 300 and 500 mm and not rich in iron, having an iron content lower than 50 to percent, are disposed of by a conventional technique which entails being crushed by a compression crusher (rocking crusher) of the same type as that used in ordinary rock crushing.

The coarsely crushed and deformed slags having reduced sizes below a value ranging between 300 and 500 mm, a portion of which have increased iron content, are subjected to a second magnetic sorting to separate that portion of the slags having high iron content from the slags having low iron content. The slags having high iron content (above 80 percent in the test described below) are then collected and used as concentrates for iron or steel making processes while the slags having low iron content are disposed by conventional techniques.

In consequence, crude slags having particle sizes greater than a value ranging between 300 to 500 mm and an iron content above 50 to 60 percent are continuously and efficiently crushed into slags having particle sizes below that value and increased iron content, and these slags of increased iron content are collected so as to be used as concentrates for iron or steel making processes. Applicants conducted a test in which 100 tons of crude slags, obtained from a blast furnace and having sizes above 400 mm and an iron content of 50 to 60 percent, were disposed of by the disposal method of this embodiment. As a result, concentrates usable in iron or steel making process, having sizes below 250 mm and an iron content of 80 to 85 percent, were recovered at a high efficiency within quite a short time of about 3 hours.

By way of comparison, when 100 tons of the same crude slags as above, having sizes above 400 mm and iron content of 50 to 50 percent, were disposed of by a conventional method employing dropping a weight, it took about 40 hours for the slags to be disposed of satisfactorily. In addition, the work was quite dangerous due to scattering of fragments of slags and iron. As will be realized from the foregoing description, the described first embodiment of the slag disposal method in accordance with the invention permits an efficient recovery of concentrates having an iron content of 80 percent or higher from crude slags having particle sizes greater than a value ranging between 300 to 500 mm and an iron content of 50 to 60 percent. In addition, the disposal of the slags can be completed in a short period of time and with enhanced safety because there is no scattering of slag or iron fragments.

The concentrates obtained through the slag disposal method of the described embodiment may be further subjected to grinding to obtain concentrates having an iron content exceeding 90 percent. This second embodiment employs the same steps as in the first embodiment through the coarse crushing and deformation step and including the first magnetic sorting step, but the second magnetic sorting step is conducted in a manner different from that of the first embodiment, namely, in the second embodiment the coarsely crushed and deformed slags having particles of reduced size and increased iron content are subjected to a second magnetic sorting step so as to be sorted into slags having iron contents of different levels, above 90 percent, between 50 to 60 percent and 90 percent, and below 50 to 60 percent. The extracted slags having an iron content above 90 percent are collected to be used directly as concentrates in iron or steel making processes and the slags having an iron content of below 50 to 60 percent are disposed of by the conventional techniques previously described.

The slags having iron content of less than 90 percent but above the 50 to 60 percent level are subjected to a grinding step to further reduce the size of the slags. The ground product is sieved through a vibrating sieve having a mesh size of 40 mm. As shown in FIG. 2, ground material having a high iron content exceeding 90 percent is left on the mm sieve and this material is collected as concentrate for further use in iron or steel making processes. The slags which are passed through the 40 mm sieve are disposed of as waste because of their small iron content.

Using this second embodiment of the invention, a test was conducted to dispose of 100 tons of crude slags obtained from a blast furnace having sizes of above 400 mm and an iron content of 50 to 60 percent. As a result, concentrates usable in iron and steel making processes, having sizes smaller than 250 mm and an iron content exceeding 90 percent, were recovered efficiently in about 40 hours. By way of comparison, when the same amount of crude slags was disposed of by a conventional method employing dropping of a weight, it took about 50 hours to attain the same result as above. In addition, the work was quite dangerous due to scattering of fragments of iron and slags.

The invention permits a continuous and highly efficient recovery of concentrates having an iron content exceeding 90 percent from crude slags having a size greater than a value ranging between 300 and 500 mm and an iron content of 50 to 60 percent. In addition, the disposal is completed in quite a short time without any danger attributable to the flying of iron and slag fragments. Various apparatus and methods have been developed in the past to reduce the moisture content and/or recover iron from wet sludges. For example, U.S. Reissue Pat. No. 30,060 teaches a process that instantaneously vaporizes the water in sludges by spraying the sludge into a hot (12000F.) gas stream. U.S. Pat. Nos. 4,091,545 and 4,133,756 teach using a hot gas to reduce the moisture content of wet sludge. U.S. Pat. Nos. 5,114,474, 4,725,307, 4,711,662 and 2,710,769, teach mixing wet sludges and dust with molten slag to produce reverts. The mixture is crushed for recycling after the slag cools and solidifies.

An article in "33 METALPRODUCING," March 1997, discloses a process that forms BOF waste sludge into briquettes. The apparatus used in the process includes a rotary kiln or dryer to remove water from the sludge, a roll-press, screw conveyors, and pug mills. A recycling plant of that sort requires a large capital investment. Moreover, the rotary kiln consumes energy to generate heat for drying the sludge, thus increasing operating costs. The article also discloses using heated molasses as a binder to form the briquettes. The heated molasses also adds cost to the recycling process.

U.S. Pat. No. 5,871,561 discloses a process wherein steelmaking dusts containing iron oxides generated from electric furnaces are formed into briquettes with reducing agents. The briquettes are fired in furnaces to obtain metal that can be recycled as steelmaking material. The briquettes are made either by a press machine or by the addition of binder material. Both means of making the briquettes increase the cost of steelmaking.

U.S. Pat. No. 5,785,737, to Lynn et al., assigned to the assignee hereof and the disclosure of which is incorporated herein by reference, solved the foregoing problems. The process of the '737 Lynn patent provides a steelmaking revert with improved flow rate properties in a recycling stream. Wet sludge and hot slag are combined into a hot slag/sludge mixture, after which the hot slag/sludge mixture is allowed to rest for a period sufficient to allow the hot slag to cause water vaporization and reduce the moisture content of the slag/sludge mixture to <10% by weight. The dehydrated slag/sludge mixture may be recycled as a steelmaking revert. Although the foregoing problems associated with steelmaking were successfully addressed by the '737 patent, there is still a need to further enhance steelmaking operations.

Steel manufacturing operations are costly, and the high manufacturing costs extend to the procurement of raw materials. The process of mining and beneficiating ores and raw materials is a very labor intensive and expensive part of the steelmaking process. Further, disposing of the waste from the hot steelmaking operations as well as from the downstream and finishing operations, can create environmental problems. For example, fine powdery kish produced during steel making may disperse into the air unless appropriate steps are taken. Although the carbon content of the kish suggests that it may be recycled into the steelmaking operations, the fine consistency of the kish makes handling very difficult. The low mass of the kish prohibits it from penetrating the frothy, slag covered surface of the steelmaking furnace, causing it instead to blow out of the furnace. Such a problem is not specific to kish, but to any fine material which has a low mass.

In addition to kish, other waste materials contain raw materials that are used in steelmaking, but like kish are difficult to recycle because of their physical form or low mass. Ferro-manganese is a waste material that has proven difficult to recycle. Ferro manganese (about 76% Mn, about 15% Fe) is used during steelmaking as a deoxidizer. Addition rates of ferro-manganese to steelmaking furnaces amount to about one ton per heat. Recovery of ferro-manganese from slag rich in ferro-manganese results in low grade fines (about 50%). Ferro-manganese slag has not been suitable for recycling because of the handling required. Other waste materials that are difficult to recycle include glass from municipal recycling facilities, and the like. Such waste materials typically are landfilled, thus creating additional environmental problems.

The invention is directed to a recycle steelmaking revert composed of a carrier containing a slag/sludge mixture blended with other materials and waste materials useful in the steelmaking process. The recycle materials include, but are not limited to, kish, glass, deoxidizing agents such as ferro-manganese, lime fines, and the like. The specific recycle materials are blended into the slag/sludge mixture individually, or the specific recycle materials are blended into the slag/sludge mixture in different combinations. The steelmaking reverts comprising the recycle material blended into the slag/sludge carrier preferably has a moisture content of <10% by weight and >4% by weight in order to preclude undesirable dusting.

The invention is also directed to a method of preparing the recycle blends. The process includes the steps of blending one or more of the recycle materials into wet sludge and hot slag, followed by combining the wet sludge and the hot slag with the blended recycle materials into a recycle blend hot slag/sludge mixture. The recyclable blend hot slag/sludge mixture is allowed to rest for a period sufficient to allow the hot slag to vaporize and reduce the moisture content of the mixture to <10% by weight. The recycle blend slag/sludge mixture may then be recycled as a steelmaking revert or combinations of recycle blends may be recycled as a combination revert as steelmaking operations may require.

Advantageously, the recycle blend slag/sludge mixture and process for making it enhance steelmaking operations. Difficult to handle recycle materials are readily blended in slag and sludge to form a recyclable steelmaking revert that can be immediately used, or can be conveniently stored for later use. Recycling of the materials replaces steelmaking raw materials, and the cost of obtaining such raw materials. Additionally, the present invention eliminates disposal problems for waste materials both for the steel industry and for municipalities. Additionally, the prior costs for landfilling waste materials are thus eliminated, permitting the steelmaking operation to be more productive and efficient. The wastes now become valuable commodities.

The steelmaking revert of the present invention is composed of various waste materials blended into a slag/sludge carrier. Many waste materials found at steel plants, municipal dumps, and the like contain raw materials that can be employed in steelmaking. Such raw materials include, but are not limited to, iron oxides, graphic carbon, scrap steel, rubber, deoxidizing agents, and the like. Such waste materials are found in recycle materials such as kish, glass, ferro-manganese and lime fines.

The waste materials employed to make the recycle blends of the invention are blended with BOF scrubber sludge and hot slag produced during steelmaking. As disclosed in my referenced '737 patent, alternating layers of hot slag and wet sludge are used to form a dry slag/sludge mixture having a moisture content of <10% by weight that is suitable for being readily handled for introduction into a steelmaking furnace. The slag/sludge mixture has sufficient unit mass to the steelmaking surface when the mixture is introduced into the furnace. Glass, kish, lime, ferro-manganese and the like are added to the sludge and slag as the layers are being created to make a steelmaking revert containing recycle material. The slag/sludge mixture serves as a carrier for the material that is to be recycled, thus allowing it also to penetrate the steelmaking surface.

Additionally, the recycle blends formed by the slag/sludge and recycle material may be mixed together in various combinations as desired by the steel manufacturer. For example, glass recycle blend may be combined with kish recycle blend. Thus, the steel maker may create a carefully tailored addition as steelmaking conditions change and/or as different types of steel requiring different additives are made. Preferably, if the material is not as fine as kish or lime fines, the specific recycle material is ground to a fine state at the site of revert making. Once the specific recycle material is blended into the hot slag and sludge, the hot slag and sludge containing the specific recycle material has alternating layers of slag and sludge. The recycle material slag/sludge mixture is preferably allowed to rest for a time such that the hot slag portion vaporizes moisture from the mixture to less than about 10% by weight. Most preferably, the slag/sludge mixture with the recycle material is allowed to rest such that the slag portion vaporizes moisture from the revert to about 3%-4% by weight. The reduced moisture content of the revert provides for an improved flow rate property in a recycling stream as discussed below.

As best shown in FIG. 1 modem steelmaking pollution control devices, such as bag houses, precipitators, cyclones and scrubbers generate large quantities of iron bearing dusts and sludges. The waste materials have a high value due to the iron and carbon content. However, many of these waste materials are very high in water content due to the wet environmental processes, such as wet scrubbers, that are used to control steelmaking emissions. In a preferred embodiment as best shown in FIG. 1 a basic oxygen furnace, (BOF) 10 and hood 11 are positioned above the mouth of the BOF to collect fume and gas that are emitted during the steel refining process.

The fume and hot gases are collected in a wet scrubber 12, and the wet scrubber sludge is sent to a thickener 13 where water is removed. A further downstream step in the process typically includes either batch or continuous filtration of the wet sludge. The filtering step is carried out in press 14 where a wet filter cake 15 is produced. The filter cake, or sludge, has a moisture content of about 30% water by weight. As heretofore mentioned, wet BOF sludge contains iron oxides in amounts of up to about % by weight, and it is very desirable to recover the iron for use as a charge material in the steelmaking operation. Iron recovered from the sludge can supplement the iron that is otherwise required to produce steel. The high viscosity of the wet sludge makes it very difficult to handle the material as a steelmaking revert. It has been discovered that if the moisture content of the wet sludge can be reduced to less than about 10% water by weight, the flow rate properties of the sludge are improved and the sludge can be conveniently handled as a steelmaking revert. It has also been discovered that a preferred moisture content of more than about 3%-4% water produces a superior sludge flow rate as a revert.

For example, in the graph of FIG. 2, flow rate is plotted against the moisture content of four different mixture ratios ranging from a slag/sludge ratio of 0.05:1 up to a ratio of :1. The flow rate tests were conducted in a 2 cubic foot bin having a 65 degree sloped floor to discharge the slag/sludge mixture through a 2½ square inch opening in the bin. The plotted data in FIG. 2 clearly shows that at a preferred 1:1 ratio, the slag/sludge flow rate decreases rapidly when the moisture content of the mixture exceeds 7% water by weight. Above about 8% water content, the flow rate of the material is considered only marginally acceptable. Above 10%, the flow rate becomes very poor and at a moisture content above 11%, there is no material flow.

In order to use wet BOF sludge as a revert in a steelmaking process, it is necessary to reduce the moisture content of the wet sludge to a level where the water in the sludge is less than 10% by weight. As clearly shown in FIG. 2, the moisture content should be reduced to a preferred range of between about 3%-4% to achieve optimum flow, as shown in the plotted data. It has also been discovered, during actual use in a pilot test, that when the moisture content of the wet sludge material falls to a level below 3% dusting can become a problem. If this happens, water must be added to the slag/sludge mixture to bring the moisture content back up into the preferred 3%-4% moisture range to eliminate dusting.

Dehydrating wet sludge is extremely energy intensive. The prior patents disclose sludge drying operations that consume large amounts of energy to generate heat for vaporizing the water in the sludge. It has been discovered that hot slag, at a temperature below the molten liquid state, provides a heat source that can be used with the wet BOF sludge to vaporize the water and lower the moisture content of the sludge. The molten slag has in the past been allowed to cool prior to disposal, so hot slag is found in abundance at steelmaking facilities.

The prior patents teach mixing molten slag with steelmaking dusts and sludges to recover iron from steelmaking waste. Uncontrolled mixing of molten slag with wet sludge is extremely dangerous. Mixing molten slag with water can cause terrifying explosions. In the past, such explosions at steelmaking operations have resulted in injury and death to employees. The prior patents even warn of this problem. For example, Pinkerton discloses, in U.S. Pat. No. 2,710,796, that "Excessive water, however, must be avoided; the generation of steam is too violent." Explosive conditions are completely avoided when hot, not molten, slag is combined with wet sludge to drive off water from the sludge. The present invention avoids the prior problems by using hot but not molten slag to dehydrate the sludge.

Referring again to FIG. 1, hot slag from supply 16 is combined with wet sludge from supply 15 to form a hot slag/wet sludge alternating layer mixture at 17. The preferred and most convenient method for combining the hot slag and wet sludge is to blend alternating batches taken from the supplies 15 and 16. This produces a preferred 1:1 slag/sludge mixture ratio. Care should be taken during blending of the hot slag and wet filter cake or sludge to avoid rapid steam generation. Combining the materials with a front end loader or the like into a bed comprising alternating 1-2 feet thick layers of hot slag and wet filter cake or sludge avoids excess steam generation. This procedure allows for safe evolution of steam, and uniform drying of the filter cake or sludge. Reclaiming the layered pile 17 after curing for about 16 hours results in a uniform blend of the two materials suitable for any downstream processing, i.e., crushing screening, and/or magnetic separation. This procedure is readily done with front-end loader bucket used at most slag processing sites in the steel industry.

The slag/sludge mix rate can be changed to produce slag/sludge ratios up to about :1 or down to about 0.5:1. However, when the slag/sludge ratio is changed to increase the slag content in the mixture, the metallurgical impact on finished product quality must be considered. It must be remembered that slag additions introduce removed impurities back into the steelmaking vessel. For example, in most instances, phosphorous is considered detrimental to the quality of steel. Metallurgists attempt to entrap phosphorous and other impurities within the slag cover that floats on the surface of the molten steel bath in the steelmaking vessel. These impurities are removed from the molten steel as the slag is systematically tapped. Hence, increasing the slag content of the slag/sludge mixture needs to consider the possible increased phosphorous levels that might result.

Table I: contains the parts by weight chemistry for a 1:1 slag/sludge mixture resulting from BOF slag and BOF scrubber sludge. The table shows that the slag contains 0.7% phosphorous by weight and the sludge contains about 0.06% phosphorous. The resulting combined mixture has about 0.3% by weight phosphorous at a 1:1 slag/sludge mixture ratio. This is an acceptable phosphorous level for BOF charge material. If the 1:1 mixture ratio is changed to increase the slag content, the phosphorous level will increase. For example, if the slag taken from supply 16 is combined with sludge from supply 15 at a 2:1 slag/sludge ratio, the slag/sludge mixture will contain about 0.49% P; at a 5:1 ratio the mixture will contain about 0.59% P; and at a 10:1 ratio it will contain about 0.64% phosphorous.

Various other undesirable elements and compounds can be inadvertently introduced into the recycling stream when different waste materials found throughout a steelmaking operation are added to the slag/sludge mixture. In the above instance we show that the slag/sludge mixture contains an acceptable 0.3% phosphorous level. However, if hot-dip and tin mill sludges were added to the slag/sludge mixture, the zinc and chrome levels of the mixture would increase. Excessive amounts of either zinc or chrome could have deleterious effects on the steel. Therefore, it can be seen that steel makers must carefully monitor revert chemistries in consideration of end use requirements and specifications to avoid introducing undesirable impurities into finished steel products.

As best shown in FIG. 3, vessel 10 is disposed below hoppers 30, 32, 34, and 36. Each of the hoppers has a gate 38, any of the gates 38 being selectively activated, for example, by a hydraulic cylinder and piston assemble, servo motor, or the like, in order to cause the gate 38 to be moved between the closed position of FIG. 3 to an open position. In the open position, materials in hopper 30 will fall into vessel10. There is a limited amount of usable space above vessel 10, due to size considerations and the like, thus precluding an essentially unlimited number of gravity flow hoppers from being positioned above vessel 10. Conveyor 40 is in communication with hopper 30 in order to supply material thereto. There is a conveyor for each of the hoppers, or alternatively one conveyor may be used to feed all hoppers and thus further reduce space requirements. The conveyor receives material to be added to the hopper 30, after which gate 38 is opened at the appropriate time in order to allow the material to fall into vessel 10. We have found that conveyor 40 to the hopper 38 may feed the recycle blend of the invention, thus permitting the materials to be supplied to the vessel 10 as desired.

Many of the materials to be recycled have a relatively low mass, such as kish. These materials have heretofore been difficult to add to vessel 10 because the atmospheric currents would cause the material to be blown from the vessel 10. In addition, the relatively low mass precluded the materials from piercing the slag layer conventionally overlying the steel bath in the vessel 10. The slag/sludge mixture has a sufficiently high mass to permit the other materials to be carried along into the bath, so that they may be utilized in the steel making process as desired.

Additionally, we envision that a number of individual recycle blends may be prepared in advance for use as needed. Thus, one blend containing glass fines may be prepared, and one with lime, ferro-manganese, etc. Additionally, combinations of two or more materials may be prepared, in order to be available as needed. Thus, if the steel making operator decides that one or more materials in the form of recycle blends are needed, the materials may be removed from storage by a front end loader or the like and supplied to the input end of conveyor 40. Alternatively, the front end loader might prepare a blend from a plurality of previously prepared recycle blends, in order to provide vessel 10 with the particular materials that are at that time required. Thus, the constituent recycle blend may be varied from a number of previously prepared blends as steel making requirements change with time, type of steel, etc.

The specific recycle material may be added individually to make a single specific type revert, or two or more of the recycle materials may be combined to make a revert. The various combinations and proportions of the specific recycle materials in the blends are unlimited. The standard slag/sludge carrier blended with the specific recycle material has a total iron content of from about 45% to about 60% by weight. Elemental iron ranges from about 5% to about 10%, ferrous iron ranges from about % to about 20%, and ferric iron ranges from about 25% to about 30% by weight. Sulfur and phosphorous range from about 0.05% to about 0.5% by weight. Zinc ranges in amounts of from about 0.5% to about 1.0%; manganese ranges from about 1.5% to about 2.5%; calcium from about 10% to about 13%; magnesium ranges from about 2.0% to about 6.0%; silicon ranges from about 2.0% to about 5.0%; and aluminum ranges from about 0.2% to about 1.0% by weight of the carrier.

The average range, however, for glass fines in the recyclable blends is from about 8.0% to about 15.0% by weight, preferably, from about 10% to about 13% by weight. The lime fines range is from about 1% to about 8.0% by weight, preferably, from about 5% to about 7% by weight. Kish ranges from about 5% to about 15% by weight, preferably, from about9%toabout 12%. The deoxidizing agents, such as ferro-manganese middling fines, range from about 2% to about 12% by weight, preferably, from about % to about 10%. contains one chemical analysis of a slag/sludge standard carrier when blended with six specific recycle materials within the scope of the present invention. The numerical values in are in percent by weight. The desired proportion of each recycle material added to the slag/sludge carrier is based upon the specification of the desired finished steel product. Based upon data provided by BOF operators, computers are used to accurately calculate the desired amounts of recycle material to blend with the carrier.

The slag/sludge mixture containing the blended recyclable material is allowed to rest or cure for an extended time period as shown at17 in FIG.1. This enables energy emitted from the hot slag to vaporize water in the sludge and reduce the total water content of the mixture to less than about 10% by weight. The water content of the slag/sludge is monitored with meters 18 to determine when the moisture content of the mixture falls below the 10% level. Actual pilot plant operations have shown that the slag/sludge mixture should be allowed to rest or cure for a time period of up to about 16 hours to vaporize a sufficient amount of water to reduce the moisture content to the preferred 3%-4% moisture level.

After the recycle material blend slag/sludge mixture is dehydrated to the desired 3% 4% moisture range, its flow rate properties are satisfactory and it is sent downstream for additional processing. These additional processing steps can include magnetic separation 19, screening 20 and/or sintering 21. In mixtures that contain high zinc levels of about 0.9% and above, the mixtures are not considered suitable for use in a sinter bed operation 21, and mixtures are charged directly into the BOF with or without magnetic separation and/or screening as shown by lines 22 and 22 a. In recycle blend slag/sludge mixtures where the zinc concentration is lower than about 0.9% by weight, the mixture can be added to the sinter bed 21 with or without magnetic separation and/or screening as shown by lines 23 and 23 a. However, it should be understood that low zinc level recycle blend slag/sludge mixtures could be charged directly into a BOF without sintering.

It has been discovered that fine particles, about 20 mesh (-0.03 in.), in the reclaimed recycle blend slag/sludge mixture that has particles ranging up to about 0.5 inches in size, can present a problem if the recycle blend slag/sludge revert is charged directly into a BOF. It has also been discovered that such fine particles can be fed directly into a sinter plant without presenting any known problems in the sintering operation. When the smaller 20 mesh fines are charged directly into a BOF, they may be carried out of the vessel with the off-gases. This overloads the gas cleaning scrubber system and negates the recycling effort.

In order to solve this problem, lime can be added to the wet filter cake or sludge 15 in an amount of about 1% by weight if there is no lime already in the blended recycle materials. It is believed that the lime addition causes micropelletization of the fines during crushing and screening operations downstream from the blending process shown at 17. The many conveyor-to-conveyor transfer points, and the various water sprays located throughout a recycling operation, cause the lime to act as a binder and enhance agglomeration of the recycle blend slag/sludge fines into micro pellets. This reduces the amount of 20 mesh fines within the dried recycle blend slag/sludge mixture and makes the revert more suitable for charging directly into a BOF vessel.

Under actual plant conditions the lime blended, and the agglomerated recycle blend slag/sludge mixture, was charged into a BOF without any noticeable increase of fines in the off-gases. The lime blending techniques also reduced dusting problems during handling and charging of the blended material. As a result, the moisture content of the recycle blend slag/sludge mixture can be further reduced to a preferred range of between about 2%-4% by weight when lime additions are blended with the filter cake.

Advantageously, the invention reduces the cost of steelmaking by providing an alternative source of raw materials by employing waste materials from landfill and steel plants. No new facilities are needed to practice the invention; thus, no additional capital expenditure is required. Accordingly, the present invention provides major capital savings for both steel plants and municipalities. At the same time potential hazards to the environment are avoided. It should be understood that this process is not limited to steelmaking operations. Any hot dross can be used as a heat source to dehydrate wet sludge produced by metal refining or smelting operations, and that such dross/sludge mixtures can be recycled back into their respective refining or smelting operations.

Claims (7)

WE CLAIM

1. Our Invention "ITPI- Steel and Mining Waste Management" is a method for providing a composite capping cover for maintaining the surface of a sulphide bearing tailing and mine waste containing deposit moist thereby substantially eliminating oxidation of the sulphidic particulate in the deposit and the formation of heavy metal salts. The invented method also provides by atmospheric precipitation and the composite capping cover comprises a fine particulate layer, a fine-granular particulate layer and a coarse-granular particulate layer, the particle sizes of the particles making up the individual, the layers having been selected such that the hydraulic conductivity of the layers increases with successive layers while the matric suction value within the layer's decreases. The slag disposal method for disposing of slags produced in furnaces during iron or steel making processes comprises employing the steps of magnetic sorting of masses of crude slags of a size greater than a value ranging between 300 to 400 mm obtained from the furnaces into slags rich in iron (above about 51 to 59 percent) and slags not rich in iron (below 51 percent) and then applying a compressive force to the slags rich in iron to cause a coarse crushing and/or deformation to reduce the size and at the same time increase the iron content due to the breaking and separation of the slags from the metal. Further magnetic sorting and sieving after griding are provided to obtain concentrates having high iron content and to improve recovery efficiency the specific recycle materials are blended with hot slag and wet sludge to make a recyclable steelmaking revert. The specific recycle materials are kish, lime, glass, ferro-manganese and the like and also the specific materials are blended with the slag and sludge individually or in any desirable combination to form a steelmaking revert. The recycle materials are blended with the slag and sludge, the recycle blend slag/sludge mixture is allowed to rest to bring the moisture content to less than 10% by weight and also the steelmaking revert and process for making the same reduce the need for steelmaking raw materials by employing recycle materials from landfills and also reduce the cost.

2. According to claims# the invention is to a method for providing a composite capping cover for maintaining the surface of a sulphide bearing tailing and mine waste containing deposit moist thereby substantially eliminating oxidation of the sulphidic particulate in the deposit and the formation of heavy metal salts.

3. According to claim1,2# the invention is to the invented method also provides by atmospheric precipitation and the composite capping cover comprises a fine particulate layer, a fine-granular particulate layer and a coarse-granular particulate layer, the particle sizes of the particles making up the individual, the layers having been selected such that the hydraulic conductivity of the layers increases with successive layers while the matric suction value within the layer's decreases.

4. According to claim,2,3# the invention is to the slag disposal method for disposing of slags produced in furnaces during iron or steel making processes comprises employing the steps of magnetic sorting of masses of crude slags of a size greater than a value ranging between 302 to 400 mm obtained from the furnaces into slags rich in iron (above about 51 to 59 percent) and slags not rich in iron (below about 51 to 59 percent) and then applying a compressive force to the slags rich in iron to cause a coarse crushing and/or deformation to reduce the size and at the same time increase the iron content due to the breaking and separation of the slags from the metal.

5. According to claim,2,3# the invention is to the magnetic sorting and sieving after griding are provided to obtain concentrates having high iron content and to improve recovery efficiency the specific recycle materials are blended with hot slag and wet sludge to make a recyclable steelmaking revert.

6. According to claim,2,4,5# the invention is to the specific recycle materials are kish, lime, glass, ferro-manganese and the like and also the specific materials are blended with the slag and sludge individually or in any desirable combination to form a steelmaking revert.

7. According to claiml,2,5,6# the invention is to the recycle materials are blended with the slag and sludge, the recycle blend slag/sludge mixture is allowed to rest to bring the moisture content to less than 10% by weight and also the steelmaking revert and process for making the same reduce the need for steelmaking raw materials by employing recycle materials from landfills and also reduce the cost.

FIG. 1: IS A FLOW CHART OF A FIRST EMBODIMENT OF A SLAG DISPOSAL METHOD.

FIG. 2: IS A FLOW CHART OF A SECOND EMBODIMENT OF THE SLAG DISPOSAL METHOD.

FIG. 3: IS A FLOW DIAGRAM ILLUSTRATING THE STEPS OF THE PROCESS FOR TREATING WET STEELMAKING SLUDGE TO PRODUCE A STEELMAKING REVERTS.

FIG. 4: IS A GRAPH SHOWING FLOW RATE MEASUREMENTS IN RELATION TO SLUDGE MOISTURE CONTENT.

FIG. 5: IS A SCHEMATIC VIEW OF A BASIC OXYGEN FURNACE INSTALLATION WITH WHICH TO CARRY OUT THE INVENTION.