Claims:We Claim:

1. A process for lowering phosphorus content of steel slag rejects comprising the steps of:
a) cooling the steel slag;
b) crushing the steel slag to less than 6mm using steel balls;
c) screening the steel slag to obtain -6 + 0.1 mm and -0.1 mm fractions;
d) subjecting the screened -6+0.1mm fraction to the step of dry grinding to produce -0.1mm product with recycle of 150-200%; and
e) blending of generated -0.1mm and natural -0.1mm material and dry separation using air classifier of composite -0.1mm to separate coarse and fine size fractions.
2. The process as claimed in claim 1, wherein the recycle material in grinding is subjected to roll magnetic separation from which the metallic iron is separated to ease the process of grinding.

3. The process as claimed in claim 1, wherein the steel slag rejects is subjected to ball mill grinding in dry mode such that the final output from the ball mill is a material of size -0.1mm.

4. The process as claimed in claim 1, wherein the-0.1mm output of ball mill is blended with natural -0.1mm material to get a composite -0.1mm material.

5. The process as claimed in claim 1, wherein the -0.1mm material is subjected to dry separation using air classifier, wherein further the feed moisture is maintained at 4% by air drying the steel slag rejects.
6. The process as claimed in claim 5, wherein the air classifier yields a fine fraction of 49% by weight and coarse fraction of 51% by weight respectively.

7. The process as claimed in claim 1, wherein the fine fraction of dry separation using air classifier assaying 13-15% Fe with 0.96-1% P.

, Description:FIELD OF INVENTION

[001] The present invention relates to the development of process and method for separation of steel slag to reduce phosphorous content of steel slag rejects. More particularly, the present invention related to the treatment of steel slag rejects of size -6mm through dry separation (air classification) to generate a product of low phosphorous content.

Definitions of Terms and Phrases
CaO: Calcium Oxide
MgO: Magnesium Oxide
Fe (T): Total Iron
SiO2: Silicon Di Oxide
P: Phosphorus

[002] It may be noted that as per the requirement of invention disclosure, terms or phrases are used in several combination.

BACKGROUND AND PRIOR ARTS OF INVENTION

[003] Steel slag or LD slag is a by-product of steel making process that refines the pig iron to remove the impurities. Steel making process is an oxidation process wherein the impurities such as carbon, silicon and phosphorous are oxidised and subsequently removed with the addition of the fluxing agents such as lime, dolomite in the form of slag. Consequently, the steel slag generated during refining of hot metal comprises metallic iron, wustite, silicates, calcium bearing minerals. Mostly, the metallic iron of steel slag is recovered by processing the steel slag through crushing and magnetic separation. This process comprises balling of the cooled slag, crushing the cooled slag to less than 300mm followed by magnetic separation to recover the coarse metallic iron particles leaving behind the non-magnetic portion. In the second stage of the process, crushing of these non-magnetic portion to less than 80mm followed by magnetic separation is performed to recover the intermediate size metallic iron particles leaving behind the non-magnetic portion. Further in the third stage, tertiary crushing of secondary stage non-magnetic portion to less than 6mm followed by magnetic separation is processed. The final non-magnetic portion of size less than 6mm that constitutes about 75% of the total steel slag volume is being rejected due to its poor chemical and physical properties. The steel slag rejects of size less than 6mm comprises metallic iron, iron bearing minerals, calcium bearing minerals along with silicates, aluminates, ferrites and their complex formations.

[004] Alternative techniques to recover metallic content have been developed that includes the physical separation method like jigging. The Canadian patent number CA2418020 C describes the process of recovering metallic content through separation of steel slag into a metal concentrate fraction and an aggregate fraction. The Chinese patent CN 101596488 titled “Stainless steel slag iron separation technique” describes the method to recover metallic values through Jigging. The Chinese patent CN101569875 titled “Process for jigging iron from molten iron nickel slag” also mentions about recovery of metallic iron through jigging technique. The patents US 4772384, DE 3339026 A1 and EP 1312415 A1 all describe about the recovery of metallic content slag through Jigging technique.

[005] The non-magnetic fraction of steel slag is mostly discarded since it does not finds bulk application within or outside the steel plants. Research initiatives have been taken to develop processes for utilization of steel slag in cement manufacturing. The US patent 6491751B1 entitled “Method for manufacturing cement using a raw material mix including finely ground steel slag” describes the utilization of steel slag as one of the raw material mix in cement manufacture.

[006] Research initiatives concentrating on bulk utilization of steel slag have been able to develop processes that include utilization of steel slag as asphalt aggregates in road making, railway ballast or other construction applications. The European patent EP0494218 A1 entitled “Reuse of by-products from the manufacture of steel” describes the utilization of crushed steel slag as an asphalt mix for road making application which comprises of bitumen, steel slag material and stones. In one of the examples the proportion of crushed steel slag of size 0-2mm has been described as 34% by volume of the total mix.

[007] Though researchers have been able to utilize the steel slag as a feed constituent for cement manufacturing but the quantity of steel slag in total feed mix is very negligible when compared to actual generation of steel slag. The application in road making as asphalt aggregate has the potential to consume bulk quantity of steel slag but it has been observed that the presence of free lime results in delayed swelling of the slag aggregates thus causing volumetric expansion of the road which subsequently results in cracks on the roads.

[008] The research work carried out so far has mostly concentrated on utilization of steel slag in cement manufacturing or as road aggregates; very little work has been carried out in developing solutions for recycling of steel slag rejects within the steel plant.

[009] The steel slag rejects after metallic recovery normally comprises of about 45-50% CaO, 3-5% free lime, 2-3% MgO, 12-20% Fe, 1.5-2% P, 2-3% Al2O3 and about 15-18% SiO2. The presence of more than about 50% CaO makes it a good source of fluxing agent for sinter making. However the presence of impurities like P limits the usage in recycling application. The iron ore sintering process demands a P specification of less than 1% which if achieved would result in bulk recycling of steel slag within the steel plant itself.

[0010] Recent research works carried out by Menad et.al, 2014 have targeted recovery of low phosphorus and iron rich compounds from LD slag through low intensity (LIMS) and high intensity magnetic separation (HIMS) techniques. These processes recover ferromagnetic and paramagnetic particles at LIMS and HIMS respectively. Wu et.al 2014, have reported successful recovery of high phosphorus and calcium rich compounds in non-magnetic fraction adopting low intensity magnetic separation technique. In one of the research works by Semikina et.al, 2010, it is reported that iron oxides contained in steel slag can be converted to magnetite through controlled oxidation of LD slag at higher temperatures. The converted magnetite can then be recovered through low intensity magnetic separation techniques. Lin et.al, 2013 have attempted modification of Al2O3 for subsequent enrichment of phosphorus in calcium silicate phase. The objective was to recover low phosphorus and iron rich compounds in magnetic fraction. Most of the literature work and patents cited above suggest either the use of magnetic separation technique to separate low phosphorus and high phosphorus compounds or methods to utilize steel slag in cement making. Dilip et.al, 2016 reports the use of enhanced gravity separation technique to physically separate iron rich compounds from calcium and phosphorus rich compounds. But this process requires huge quantity of water and the presence of free lime is subjected to conversion into hydroxides which is not acceptable in sinter and pellet making. Additionally, this process requires dewatering and drying of the product prior to the application in sintering and pelletization.

[0011] The objective of this invention is to provide an alternative and better method to lower phosphorous content in steel slag rejects adopting dry separation techniques. The low phosphorous fraction thus produced from this technique can be easily utilized in iron ore pelletization or sintering process. This will enable increased recycling of steel slag within the steel plant.

OBJECTS OF THE INVENTION
[0012] An object of the present invention is to propose a process of physical dry separation route for processing steel slag rejects.

[0013] Another object of the invention is to propose a process for reducing phosphorus content of steel slag rejects.

[0014] Yet another object of the invention is to propose a techno-economic feasible process for utilizing the steel slag rejects in iron ore sintering or pelletization.

SUMMARY OF THE INVENTION
[0015] According to this invention, a process for lowering phosphorous content of steel slag rejects comprising cooling the steel slag followed by; crushing the steel slag to less than 6mm, subjecting the crushed steel slag to the step of screening to obtain -6 + 0.1 mm and -0.1 mm fractions, subjecting the screened -6 +0.1 mm fraction to the step of grinding followed by dry separation using air classifier.

[0016] The Steel Slag comprises of 44-52% CaO, 4.5-4.7% MgO, 15-18% Fe, 12-18% SiO2 and 1.2-1.3% P. The presence of metallic iron restricts usage in cement making while the presence of free lime restricts usage in road making and civil engineering applications. However the presence of high quantity of calcium oxides and silicates could be useful for application in iron ore sintering and pelletization. This potentiality of steel slag triggered the need to develop process to lower the phosphorous content of steel slag. The desired specifications of such flux require P less than 1%.

[0017] The process involves air cooling of the steel slag, stage wise crushing to -6mm followed by screening the crushed slag rejects at 0.1mm, ball mill grinding of -6+0.1mm material to less than 0.1mm. The below 0.1mm size material is then subjected to dry separation process using air classifier to lower the phosphorus content.

[0018] The size fraction -6+0.1mm is then subjected to ball mill grinding in a dry grinding mill to entirely grind the material to -0.1mm size. The ball mill grinding media consists of steel balls of different diameters. The grinding is done in a batch mode for 40-45 minutes of grinding time. After 45 minutes the material is taken out and again screened using 0.1mm size to screen out the oversize and undersize fractions. The oversize fraction +0.1mm is recycled and mixed with the fresh feed to ball mill grinding, while the undersize -0.1mm material (named as generated) is mixed with the natural -0.1mm material. The process of grinding and screening is repeated until the whole material is ground to -0.1mm size. Most of the metallic content is recycled to the ball mill and hence magnetic separation is preferred to ease the process of grinding.

[0019] The composite -0.1mm material which is a mix of natural -0.1mm material and generated -0.1mm material. This material is then subjected to dry separation technique adopting air classifier. The air classifier is a device that uses air as a separation media to separate products by size and density. Several different methods of implementation of air classifiers are available such as gravitational, fluidized bed etc. The separation of the particles occurs in the separation zone where particles interact with air flow. The basic separation zone of air classifier is centrifugal counter flow zone.

[0020] The separation of coarser and fine fractions results in a preferential separation of high calcium bearing minerals in the finer fraction, while the high iron bearing minerals in coarse fraction. Since finer fractions exhibit low phosphorous content, calcium silicate phases are recovered, it is seen that there is a sharp separation of phosphorus in coarser and finer fractions. The yield of finer fractions ranges from 40% to 50% with an assay corresponding to 0.97% to 1% P that is acceptable for sinter or pellet making. The final concentrate is below or equal to the limit of 1.0% P, which is normally acceptable for recycling in iron ore sintering and pelletization. The advantage of this process based on dry separation which not requires dewatering or drying of the material before re-use in the steel plants. This process also ensures no reactivity of the calcium oxides into other forms of hydroxides due to the presence of water that normally happens in wet gravity separations.

[0021] The present invention discloses and claims a process for lowering phosphorus content of steel slag rejects comprising the steps of cooling the steel slag; crushing the steel slag to less than 6mm using steel balls; screening the steel slag to obtain -6 + 0.1 mm and -0.1 mm fractions; subjecting the screened -6+0.1mm fraction to the step of dry ball mill grinding to roll magnetic separation from which the metallic iron is separated to produce -0.1mm product with recycle of 150-200%; and blending of generated -0.1mm and natural -0.1mm material and dry separation using air classifier with the feed moisture is maintained at 4%of composite -0.1mm to separate fine and coarse size fractions in 49% by weight and 51% by weight respectively, wherein the fine fraction of dry separation using air classifier assaying 13-15% Fe with 0.96-1% P.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Fig. 1: Dry separation of ground LD slag wherein 1: Input Slag -6mm, 2: Ball Mill, 3: Sump, 4: Pump, 5: Hydrocyclone, 6: Air Classifier, 7. Tailings, and 8. Output Concentrate
Fig. 2: Particle size distribution of steel slag rejects, wherein the X-axis shows the size in microns, and the Y-axis shows cumulative weight percentage (%).

DETAILED DESCRIPTION OF THE INVENTION
[0022] At the very outset of the detailed description, it may be understood that the ensuing description only illustrates a particular form of this invention. However, such a particular form is only exemplary embodiment, and without intending to imply any limitation on the scope of this invention. Accordingly, the description is to be understood as an exemplary embodiment and teaching of invention and not intended to be taken restrictively.

[0023] Throughout the description and claims of this specification, the phrases “comprise” and “contain” and variations of them mean “including but not limited to”, and are not intended to exclude other moieties, additives, components, integers or steps. Thus, the singular encompasses the plural unless the context otherwise requires. Wherever there is an indefinite article used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0024] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification including any accompanying claims, abstract and drawings or any parts thereof, or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0025] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. Post filing patents, original peer reviewed research paper shall be published.

[0026] Integrated steel plant generates solid wastes such as steel slag or LD slag wherein metallic iron is recovered and slag rejects are dumped at the site. Due their poor physical and chemical properties, these steel slag rejects are not found for any bulk application. The rate of steel slag rejects that generated is about 100 kg/ton of steel and requires huge land filling. Steel Slag rejects generated comprises 44-52% CaO, 4.5-4.7% MgO, 15-18% Fe, 12-18% SiO2 and 1.2-1.3% P. The presence of free lime and metallic iron in steel slag rejects restricts their usage in road making and cement making application respectively. However the presence of more than 50% of calcium bearing minerals in steel slag rejects is a good resource of flux in sinter or pellet making. Besides, iron oxide and metallic iron could be an extra benefit for application in sintering and pelletization. The presence of 1.5% phosphorous limits the steel slag rejects to be used in sintering or pelletization. This potentiality of steel slag has triggered the need to develop a process to lower phosphorous from steel slag rejects. However, the presence of free lime content in steel slag rejects compelled to select a process of dry separation instead of wet gravity separation to lower the phosphorous content. This process can ensure that no reactivity of free lime and requirement of dewatering or drying of the product obtained in the separation process. The required specifications of these steel slag rejects that can be used as fluxing agent in sintering process should have phosphorous content less than or equal to 1%. This process can recycle the steel slag rejects internally in the steel plant.

[0027] The process of treatment of molten steel slag, cooling and metal recovery from steel slag comprises:
? Pouring of molten steel slag in a steel slag pit.
? Splashing of water over the top of molten steel slag for cooling.
? Exposing the slag to atmosphere air cooling for a period of 24-30 hours.
? Channelling of air cooled solidified steel slag to storage yards and balling of steel slag to crush it to less than 300mm sized material.
? Secondary and tertiary crushing of steel slag to 80mm and 6mm followed by magnetic separation to separate metallic iron content from -80mm and -6mm material.
? Magnetic separation of non-magnetic portion and screening of this portion at 0.1mm particle size.
? Ball mill grinding of -6+0.1mm material to less than 0.1mm and preparing whole material passing 0.1mm particle size.
? The -0.1mm material is then subjected to dry gravity separation adopting air classifier to reduce the phosphorus content of the material less than 1%.

[0028] The air cooled steel slag rejects collected from the storage yards of integrated steel plant is initially mixed thoroughly for proper mixing of the sample. A representative sample of steel slag rejects are taken through cone and quartering method for characterization studies. This sample is subjected to chemical analysis using ICP (inductively coupled plasma) analysis. Particle size distribution of steel slag rejects is shown in Figure 3. It indicates 14% and 41% of material passes through 106microns and 500 microns respectively. Mineralogical phase composition of steel slag rejects is shown in Table 1. In summary, the mineralogical phases that steel slag rejects contains are calcium ferrites, calcium silicates with or without iron, Calcium aluminates with iron, iron oxides, free lime etc. These fractions may vary with respect to the operation and quenching conditions. The representative sample of steel slag rejects is crushed to less than 6mm using Gyratory crusher and Jaw crusher. The -6mm size of steel slag rejects is pass through a ball mill to grind the material to the required sizes before passing the material to dry screening at two different screen sizes: 0.5mm and 0.1mm to prepare the material in two different sizes of -0.5mm and -0.1mm fractions. In the steady state operation of the grinding process, 70% of material is recovered through screening and the rest 30% material was recycled to the grinding. Prior to grinding, the specific energy consumption required to grind the material is assessed for -0.5mm and -0.1mm respectively. Bond work index of steel slag rejects at 0.5mm is about 15-18kWh/t and at 0.1mm is about 20-25kWh/t respectively.

Table 1: Mineralogical phase composition of Steel Slag rejects
Mineral Phase Chemical composition %
Alite C3S 3 CaO*SiO2 1.8
Belite C2S 3 CaO*SiO2 19.7
Aluminate C3A 3 CaO*Al2O3 7.8
Brownmillerite 4 CaO*Al2O3*Fe2O3 4.0
Mayenite Ca12Al14O33 2.6
Rutile TiO2 0.4
Wustite FeO 15.2
Magnetite Fe3O4 1.2
Srebrodolskite 2 CaO*Fe2O3 16.9
Free Lime CaO 3.4
Portlandite Ca(OH)2 4.1
XRD-Amorphous 23

[0029] The process of grinding is preferred to be dry grinding in a batch or continuous ball mill (For Ex. FLDsmith) to entirely grind the material to -0.5mm and -0.1mm sizes. The ball mill grinding media consists of steel balls of different diameters. The grinding is either done in a dry batch mode or continuous mode. During the dry ball mill locked cycle grinding, the material is ground for 40-45 minutes of grinding time to generate 70% of 0.5mm sized material with recycle of 30% over sized material to the feed in the continues operation. Since, steel slag rejects comprise some portion of metallic iron, recycle material to ball mill feed carries this portion and hence magnetic separator is preferred. The process of grinding and screening is repeated until the whole material is ground to -0.5mm size. During the dry ball mill locked cycle grinding, the material is ground for 60-75 minutes of grinding time to generate 0.1mm sized material.

[0030] Further the dry ball mill grinding is performed in presence of a suitable grinding aid (dispersants, solvents, polymers) that helps to achieve a consistent grinding mill output measured in terms of evenness in size. The dosage of the grinding aid was kept between 100g/ton to 300 g/ton of dry feed. This material is then subjected to dry separation in an air classifier.

[0031] Air classifier (Vijimech) is a device that uses air as a separation media to separate products by size and density. Several different methods of implementation of air classifiers are available such as gravitational, fluidized bed etc. The separation of the particles occurs in the separation zone where particles interact with air flow. The basic separation zone of air classifier is centrifugal counter flow zone. The centrifugal counterflow zone uses a flat air vortex inside the cylindrical chamber. The air flow is fed into the chamber by a tangential inlet and exit in the centre of the chamber. The particles which are fed at the top of the air classifier will rotate with the radial flow and this rotation means that the particles will subject to centrifugal (inertial) forces. Separation is controlled by the balancing the centrifugal forces and the drag forces. Due to centrifugal force, coarse particles will drift outwards from the exit and downwards due to gravity. The fines will follow the air flow with drag forces towards the centrally placed exit. An industrial air classifier will however process large number of particles in different sizes and the air flow will be turbulent. The turbulence and particle to particle interaction will affect how individual particles will follow the air flow and thus the separation will depend on more factors than just the velocity of the air flow. Independent of separation zone used in air classifier, a reliable air flow is necessary. The air flow can either be created by using an external or an internal aerodynamic system. Using an external system means that the fans and dust collectors will be installed in a separate unit which is connected to the air classifier through pipes. The denser and coarse particles experience high centrifugal forces than drag forces and hence this material will be collected at the bottom and near the wall of the air classifier. The lighter and finer particles experience high drag forces than centrifugal forces and being lifted by the air to the top of the air classifier before entering the collecting chamber located at the centre of the air classifier.

[0032] The key operating variables of an air classifier are:
• Feed particle size
• Feed flow rates
• Feed moisture content
• Air velocity

[0033] Dry separation through air classifiers were performed representative steel slag rejects sample ground to -0.5mm and -0.1mm. The initial moisture content of the steel slag rejects was analysed using standard method. It was observed that moisture of steel slag rejects varies from 4-7%. Initial tests were conducted with these two moistures of 4% and 7% steel slag rejects of -0.5mm sized material. It was indicated that yield of the low phosphorous fraction of steel slag rejects is 18-20% with 7% moisture due to problem of poor flowability of feed into the air classifier. The same sample of steel slag rejects was air dried and the yield was improved to 21-25% with 4% moisture feed into the air classifier. The tests were conducted by varying the parameters of air motor speed (air velocity) and feed flow rates by regulating the speed of the vibro-feeder of air classifier. The effect of steel slag rejects feed particle sizes of -0.5mm and -0.1mm were tested.

[0034] The separation of denser and lighter fractions results in a preferential separation of steel slag rejects to achieve low phosphorous fine fraction and high phosphorous coarse fraction. The yield of low phosphorous fine fraction ranges from 20% to 30% for -0.5 mm feed particle sizes. This fraction assay corresponding to 25-30% yield is 12-15%Fe with 0.75% P. The fine fraction (concentrate) is much below the limit of 1.0% P, which is normally acceptable for recycling in iron ore sintering. The yield of low phosphorous fine fraction ranges from 45% to 50% for -0.1 mm feed particle sizes. The following example shows typical coarse and fine fractions grade and yield values.

[0035] Metal recovery process of LD slag is depicted hereunder in diagram:

[0036] The following examples are given to illustrate the process of the present invention and should not be construed to limit the scope of the present invention:

Example 1:
Dry Grinding using a Ball Mill:

[0037] The size fraction -6+0.1mm is then subjected to ball mill grinding in a dry grinding mill to entirely grind the material to -0.1mm size. The ball mill grinding media consists of steel balls of different diameters. The grinding is done in a batch mode for 40-45 minutes of grinding time. After 45 minutes the material is taken out and again screened on a screen of 0.1mm size to screen out the oversize and undersize fractions. The oversize fraction +0.1mm is recycled and mixed with the fresh feed to ball mill grinding, while the undersize -0.1mm material, named as generated, is mixed with the natural -0.1mm material. The process of grinding and screening is repeated until the whole material is ground to -0.1mm size. Most of the metallic content is recycled to the ball mill and hence magnetic separation is preferred to ease the process of grinding.

Example 2:
Dry Separation of products by size and density using air as separation media:

[0038] The composite -0.1mm material which is a mix of natural -0.1mm material and generated -0.1mm material. This material is then subjected to dry separation technique adopting air classifier. The air classifier is a device that uses air as a separation media to separate products by size and density. Several different methods of implementation of air classifiers are available such as gravitational, fluidized bed etc. The separation of the particles occurs in the separation zone where particles interact with air flow. The basic separation zone of air classifier is centrifugal counter flow zone.

[0039] The yield of finer fractions ranges from 40% to 50% with an assay corresponding to 0.97% P that is acceptable for sinter or pellet making. The final concentrate is much below the limit of 1.0% P, which is normally acceptable for recycling in iron ore sintering.
Table 2:
Results of dry separation using air classifier with -0.1mm LD slag rejects

Product Wt% Fe(T) P
Coarse 51 16.64 1.36
Fine 49 13.32 0.97
Total 100 15.01 1.2

REFERENCES/ CITATIONS:

PATENT CITATIONS:

Patent/ Patent Application No. Filing date Publication date Applicant Title
CA2418020 C Feb 04, 2003 Sept 13, 2011 Jean Brodeur Steel slag processing jig system.
CN101569875 Apr 29, 2008 Nov 04, 2009 Xiao Feng Process for jigging iron from molten nickel iron slag.
US 4772384 June 03, 1986 Sept 20, 1988 Klaus Schonert, Rolf Gerstenberg Jigging method and apparatus for gravity separation in the fine and finest particle size ranges.
DE3339026A1 Oct 27, 1983 May 09, 1985 Klaus Prof DR Ing Schonert Jigging process for the separation of fine grained mixture according to the particle density
EP1312415A1 Nov 16, 2001 May 21, 2003 Trading and Recycling company Sint Truiden Method of recovering stainless steel from stainless steel slags
6491751B1 May 26, 1999 Dec 10, 2002 Texas Industries, Inc Method for manufacturing cement using a raw material mix including finely ground steel slag
EP0494218A1 Sept 26, 1990 July 15, 1992 Tarco Vej A/S Reuse of by-products from the manufacture of steel

NON-PATENT CITATIONS:

1. Menad, N. , Kanara, N. and Save, M. 2014 “Recovery of high grade compounds from LD slag by enhanced magnetic separation techniques”. International Journal of Mineral Processing, 126, pp-1-9.

2. Wu, X.R., Yang, G.M., Li, L.S., Lu, H.H., Wu, Z.J. and Shen, X.M. 2014. “Wet magnetic separation of phosphorus containing phase from modified BOF slag”. Ironmaking and Steel making.Vol 31, No 5, pp-335-341.

3. Semykina, A., Shatokha, V. and Setharaman, S. 2010. “Innovative approach to recovery of iron from Steelmaking slags”. Ironmaking and Steelmaking. Vol 37, No.7, pp-536-540.

4. Lin, L., Bao,Y.P., Wang,M. and Zhour, H.M. 2013. “ Influence of Al2O3 modification on phosphorus enrichment in P bearing steemaking slag”. Ironmaking and Steelmaking. pp 1-7.

5. Dilip, M., Rajendra, K. R., Kaushik, C., Abhay, S. P., Mukherjee, A. K., and Dubey, A. K. 2016. “Phosphorous partitioning and recovery of low-phosphorous iron-rich compounds through physical separation of Linz-Donawitz slag.” International Journal of Minerals, Metallurgy and Materials, 23(7), pp 751-759.