Claims:We Claim:

1. A process of extracting valuable enriched iron content product and enriched carbon value product from the dust and sludge generated from various iron and steel making unit of integrated steel plant. comprising;

providing a blend distribution of dust and sludge various sources suitable for magnetic susceptibility of the iron containing particles available in said various sources in a slurry holding tank ;

carrying out said extracting valuable enriched iron content product from said blend distribution in said slurry holding tank by subjecting the same to magnetic separation followed by passing through concentrate thickener to thereby generate iron concentrates as said recovered valuable enriched iron content product and tailing non-magnetic product;

subjecting the said tailing non-magnetic product to step of extracting of enriched carbon values involving column floatation and concentrate thickener.

2. A process as claimed in claim 1 wherein said step of magnetic separation comprises two stage magnetic separation involving first stage low intensity magnetic separation and second stage medium intensity magnetic separation.

3. A process as claimed in anyone of claims 1 or 2 wherein said blend distribution of dust and sludge various sources suitable for magnetic susceptibility of the iron containing particles comprises providing for blend including the maximum comprehensive iron value grade based on

where G is grade value of blend product, is constrained function depend on the magnetic susceptibility, size distribution and grade of individual admix of individual feed material, and Q is quantity of individual admix of individual feed material.

4. A process as claimed in anyone of claims 1 to 3 comprising providing said blend distribution involving
as the grade distribution admix based on the grade of individual grade of Fe, its magnetic susceptibility (X) and effective particle size distribution (d).





Wherein is constrained function for blast furnace sludge, blast furnace dust, Corex sludge, SMS sludge and DRI dust respectively.

5.A process as claimed in anyone of claims 1 to 4 wherein said step of carrying out said extracting valuable enriched iron content product from said said blend distribution is carried out in a separate extraction Fe extraction unit involving two stages magnetic separation (low intensity magnetic separation and medium intensity magnetic separation) and concentrate thickener and
said step of subjecting the tailings non-magnetic product is carried out in a separate unit for extracting enriched carbon value involving dual extraction column floatation cell ,thickener and recycling water tank.

6. A process as claimed in anyone of claims 1 to 5 wherein after said step of extracting enriched carbon value, the final tailings are collected separately.

7. A process as claimed in anyone of claims 1 to 6 wherein the water outflow from said thickeners are collected in a water recirculation holding tank for subsequent use.

8. A process as claimed in anyone of claims 1 to 7 wherein said blend distribution used comprises selectivelyblast furnace dust and sludge, SMS dust and sludge, Corex sludge and DRI dust all materials which has Iron, Carbon, flux materials and other gangue minerals obtained through controlled source conveying systems which are selectively fed into said slurry holding tank based on size distribution, specific density and magnetic susceptibility of particle.

9. A process as claimed in anyone of claims 1 to 8 wherein said providing of blend distribution in said slurry holding tank comprises controlling density of the slurry based on the desired pumping for said extracting valuable enriched iron content product and said downstream extracting enriched carbon value.

10. A process as claimed in anyone of claims 1 to 9 wherein said first stage low intensity magnetic separation generates two products (1) primary magnetic product which is collected in a holding sump through concentrator line and (2) primary non-magnetic tail product and said second stage medium intensity magnetic separation generates two products (1) secondary magnetic product which is collected through concentrate line in said holding sump and (2) secondary non-magnetic tail product, said concentrate collected at said holding sump are pumped to iron concentrate thickener.

11. A process as claimed in anyone of claims 1 to 10 wherein said secondary non-magnetic tail product is treated to enrich the carbon value which for the purpose is fed to conditioning tank where froth floatation reagents (collector and frother) are added for conditioning and generate two products (1) carbon enriched froth product and (2) gangue mineral enriched sink product (final tail).

12. A process as claimed in anyone of claims 1 to 11 wherein said concentrate enriched iron product is ready for supply downstream process selectively including for pelletisation, briquetting, sintering or any other agglomeration techniques; and
said carbon enriched product is ready for downstream utilization.

13. A process as claimed in anyone of claims 1 to 12 comprising said magnetic separation is carried out involvingprimarily Low intensity magnetic separation for separation of Ferro magnetic particles, secondary medium intensity magnetic separation for separation of paramagnetic particles and high intensity magnetic separation for further recovery of fine iron particles.

14. A process as claimed in anyone of claims 1 to 13 for selectively providing

(a) iron enriched to 60 - 65 % Fe iron concentrate which meets desire grade specification of any iron making units from 32 - 40 % Fe value with 35 - 50% Yield;
(b) the carbon valueenriched from 10 - 30 % C in feed to 65 - 85% Carbon concentrate with 15 - 25 % yield and the carbon concentrate can use in iron making or any other suitable process;
(c) ensures that Zn content in iron and carbon concentrate below 0.3 % due its diamagnetic and hydrophilic properties.

15. A system for carrying out the processofextracting valuable enriched iron content product and enriched carbon value product from the dust and sludge generated from various iron and steel making unit of integrated steel plant as claimed in anyone of claims 1 to 14 comprising:

slurry holding tank for controlled feeding of said dust and sludge from various sources to achieve said blend distribution;

means for carrying out said magnetic separation based extraction of valuable enriched iron content product and tailings of non-magnetic product;

column floatation means for extracting of enriched carbon values from saidtailings of non-magnetic product.

16. A system as claimed in claim 15 wherein said means for carrying out said magnetic separation based extraction comprises first stage low intensity magnetic separation and second stage medium intensity magnetic separation operatively connected to a concentrate thickener and said column floatation means for extracting of enriched carbon values is also operatively connected to a concentrate thickener.

17. A system as claimed in anyone of claims 15 to 16 comprising:
a magnetic separation base extraction unit comprises of slurry holding tank, two stages magnetic separation (low intensity magnetic separation and medium intensity magnetic separation) and concentrate thickener alongwith high intensity magnetic separation for further recovery of fine iron particles and

extracting of enriched carbon values unit comprisesof a dual extraction column flotation cell, thickener and recycling water tank;

said extracting of enriched carbon values unitdelivers two products which are final tailing and enriched carbon material respectively and includes a water recirculation holding tank, the water come from the overflow section of all thickener stored in this tank and adapted to be recirculates for further operation of same.

18. A system as claimed in anyone of claims 15 to 17 comprising source conveying system fitted with flow control transmitter to control the blend distribution based on size distribution, specific density and magnetic susceptibility of particle;

slurry holding tank for storing said blend feed and having its own water line connection along with density meter transmitter for attaining desired density ;

pump means to pump desired blend to said primary magnetic units to generate two products concentrate (1) primary magnetic product which is dipped to holding sump through concentrate line segment and (2) primary Non-magnetic tail product, which is fed through primary tail line ,

said primary non-magnetic tail product operatively fed to said secondary magnetic unit to generate two products concentrate (1) secondary magnetic product which dipped to holding sump through concentrate line segment and (2) Secondary Non-magnetic tail product,

a sump junction for collecting the concentrate from first and second magnetic units said sump unit operatively connected to iron concentrate thickener for generating the concentrate enriched iron product to utilize in downstream process (Pelletisation, briquetting, sintering or any other agglomeration techniques) through sink flow line;

the Secondary Non-magnetic tail product of secondary magnetic unit is fed to conditioning tank through pipe line ,said conditioning tank having several source terms for addition of froth flotation reagents (collector and frother) to generate two products (1) Carbon enriched froth product and (2) gangue mineral enriched sink product (final tail), said carbon enriched product being utilized to downstream process.

Dated this the 27th day of July, 2019
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199

, Description:FIELD OF THE INVENTION
The present invention relates to a process of extracting valuable enriched iron content product and enriched carbon value product from the dust and sludge generated from various iron and steel making unit in steel plant and a system to implement the process. More particularly, the present invention is directed to the processing of waste, which involves separation of iron and carbon values from dust and sludge generated from metallurgical plants (Blast furnace unit, Corex unit, DRI Unit, SMS sludge), which contains mineral matter consisting of hematite, magnetite, ferrous oxide, alumina oxide, siliceous oxide, calcium oxide and other trace oxide elements along with carbon material. The said mineral matter and carbon containing materials are dumped due to its unspecified end use specifications. The present invention involves a system for recovery of iron minerals (hematite, magnetite, wustite etc.) with the application of magnetic separation wherein, two stage magnetic separations are incorporated for the processing the said generated dust and sludge. The specified magnetic separation unit involved in this process for improving the grade of iron value are low intensity magnetic separatorand medium intensity magnetic separator. After iron bearing minerals recovery, the carbon rich tailing is subjected todual extraction column (DEC) flotation. The said input dust and sludge material to processing is mixed on the basis of mineralogical aspect and particle size distribution.

BACKGROUND OF THE INVENTION
The iron and steel making units generate dust and sludge waste around 25 - 40 kg/thm. These dust and sludge consists of valuable mineral matter such as Hematite, Magnetite, Ferrous oxide and carbon material along with gangue content. The aforementioned mineral matter and carbon material is dumped due to its unspecified end used specifications which can increase the environmental threat as well loss ineconomic value.This material has significant carbon and iron content to make it an attractive recycling proposition. If carbon and iron oxides separated by beneficiation, these can be reused in the Iron making process or the Blast Furnace through agglomeration process. The gainful utilization and recycling of these wastes will improve the economics of operation and prevent degradation of the ambient environment. It is therefore important to study all these waste prior to their processing for converting them to value added wealth in one form or other. In the present investigation, characterisation and beneficiation studies was carried for separation of iron and carbon by magnetic separation and flotation process respectively.

Das et al. (The European Journal of Mineral Processing and Environmental Protection Vol. 2, No. 2, 1303-0868, 2002, pp. 61-68) discloses the work on treatment of blast furnace flue dust to recover valuable carbonand iron by processing through flotation and magnetic separation method. The samples essentially contained unburnt coke and iron rich grains as the value added products. Flotation technique was employed to recover the carbon values present in the sample. It was possible to obtain a product containing around 80% carbon with more than 90% recovery from the flue dust samples using diesel oil and MIBC as the collector and frother respectively. The results obtained by the column flotation technique were quite encouraging due to its obvious advantages over conventional cells. Iron rich grains (magnetite, hematite, wustite and Fe metals) were recovered by low intensity magnetic separation (LIMS) technique. Magnetic separation of flotation tailings gave an iron concentrate of 61-64% Fe with 50-56% over all recovery from the feed grade of 52% Fe

Yehia et al., (The European Journal of Mineral Processing and Environmental Protection, Vol.5, No.2, 1303-0868, 2005, pp. 184-189) described the methodology to utilize the waste generation (flue dust of blast furnace). In this study, the flotation method is implied initially to recover the unburnt carbon value as froth product and the sink product is dried and fed to dry magnetic separation for enhancement in grade of iron value from feed grade 28% Fe to concentrate grade 54.8% Fe.

Patent US4396423 described a process that subjects the flue dust to a carbiding step in a fluid bed reactor in the presence of a reducing agent and a carbon supplying agent to break down the zinc ferrite structure and converting the iron to iron carbide. This is followed by heating the product of the carbiding step to recover zinc by vaporization.An alternative procedure is the recovery of iron carbide and zinc by magnetic separation from the gangue after the carbiding step and before separation of zinc from iron carbide.

CN106119557B invention comprises the steps that the blast furnace gas slime is dried, crushed and fine ground; blast furnace gas slime powder is obtained and leached with a sulphuric acid solution for zinc extraction. Besides, the filter residues obtained through leaching and the iron residues obtained through de-ironing are mixed evenly, iron concentrate powder is obtained through wet grinding and magnetic separation after magnetizing roasting under controlled proper conditions, flotation is carried out on tailings subjected to magnetic separation, and carbon in the tailings is recovered.

CN107604110 invention comprises of blast furnace gas ash that is led into an air classification-air magnetic sorting system, and the gas ash with the large particle size is separated through air classification to obtain air separation of iron concentrate; magnetic materials in the gas ash with the small particle size are separated through air magnetic sorting to obtain the magnetic separation iron concentrate, and the air separation iron concentrate and the magnetic separation iron concentrate are directly returned to the sinteringand smelting work procedures; and the secondary gas ash collected by a bag-type dust collector is zinc-rich mineral powder. Through the air classification and air magnetic sorting physical iron separation technique, the iron concentrate can be economically and conveniently separated from the blast furnace gas ash, the total iron recovery rate of the iron concentrate reaches 87% or more, the zinc-rich mineral powder can be obtained, and harmless treatment of the blast furnace gas ash is achieved.

CN102392125 disclosed an invention comprising magnetization roasting on the blast furnace gas dust (sludge), converting the weak magnetic iron ore in the gas dust (sludge) into strongly magnetic mineral, then recovering through magnetic separation, and recovering excess carbon powder through flotation.

CN105063254B discloses the method for separating the iron, the zinc and the carbon in the blast furnace sludge comprises the steps that the blast furnace sludge is oxidized after being directly magnetically roasted; wet magnetic separation is conducted after proper ore grinding, so that iron concentrate from magnetic separation and tailing zinc-rich materials are obtained; zinc in the zinc-rich materials is extracted by means of a leaching agent, so that a zinc-rich solution and carbon powder are obtained.

The present invention thus attempts to solve the problem and limitation of prior art relating to recover the iron bearing minerals and carbonby implementing stage wise magnetic separation of iron rich concentrate followed by froth floatation of carbon material for their beneficial use in subsequent utilization in steel plant processes likepellet making and sintering process.The iron bearing recovery is through two stage magnetic separation; the first stage employing low intensity magnetic separation followed by second stage of medium intensity magnetic separation. The two stage magnetic separation process was established for proper blend ratio of sludge and dust based on magnetic susceptibility, particle size distribution and mineralogical characteristic.The carbon value from generated magnetic separation tailing was recovered and enriched using dual extraction column floatation cell and using reagents like synthetic collector and methyl isobutyl carbinol(MIBC) frother. Instead of using oil as collector, synthetic collector was used for carbon recovery because the use of oil as collector causes water contamination and cannot be recirculated in the beneficiation circuit. The tailing of magnetic separated iron minerals contains 20-30% carbon.

OBJECTS OF THE INVENTION
The basic object of the present invention is directed to a processofextracting valuable enriched iron content product and enriched carbon value product from the dust and sludge generated from various iron and steel making unit in steel plant.

A further object of the present invention is directed to a process of separation of iron and carbon from the blend mixture of steel plant dust and sludge waste, wherein the blend is prepared based on the magnetic susceptibility, mineralogical, and size specification of sludge and dust generated from steel making unit and iron making unit.

A still further object of the present invention is directed to a process of separation of iron and carbon from the blend mixture of steel plant dust and sludge waste wherein very large difference of magnetic susceptibility and mineralogical properties is made to exist between iron bearing material and carbon material in blend, therefore for removal of iron and carbon materials from the finely distributed sludge and dust can be treated by adopting adequate mixing proportion based on particle size distribution and mineralogical aspect followed by magnetic separation unit in the first phase of the process.

A still further object of the present invention is directed to a process of separation of iron and carbon from the blend mixture of steel plant dust and sludge waste wherein in the second phase of operation, the reject product of the first phase is subjected to froth flotation method, whereby the concentration of the un-burnt carbon content extracted as a froth product is enhanced to a fixed carbon value.

A still further object of the present invention is directed to a process of separation of iron and carbon from the blend mixture of steel plant dust and sludge waste wherein products of the magnetic separation fulfils the specification of pellet or other agglomerate material, whereby total Fe is greater than 61% and the gangue material (alumina and Silica) less than 8%.

Another object of the present invention is directed to a process of separation of iron and carbon from the blend mixture of steel plant dust and sludge waste wherein the product of magnetic separation unitcan be utilized downstream towards the pelletisation or agglomeration unit because of the finer particle size distribution and this product facilitate as a feed material for any iron making unit.
Yet another object of the present invention is directed to a process of separation of iron and carbon from the blend mixture of steel plant dust and sludge waste wherein the process leads to reduce the deleterious material as gangue minerals, along with other trace minerals and utilization of the waste material as a suitable feed for iron making unit in the form of iron as well as carbon value.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to a process ofextracting valuable enriched iron content product and enriched carbon value product from the dust and sludge generated from various iron and steel making unit of integrated steel plant comprising,

providing a blend distribution of dust and sludge various sources suitable for magnetic susceptibility of the iron containing particles available in said various sources in a slurry holding tank ;

carrying out said extracting valuable enriched iron content product from said blend distribution in said slurry holding tank by subjecting the same to magnetic separation followed by passing through concentrate thickener to thereby generate iron concentrates as said recovered valuable enriched iron content product and tailing non-magnetic product;

subjecting the said tailing non-magnetic product to step of extracting of enriched carbon values involving column floatation and concentrate thickener.

A further aspect of the present invention is directed to a process wherein said step of magnetic separation comprises two stage magnetic separation involving first stage low intensity magnetic separation and second stage medium intensity magnetic separation.

A still further aspect of the present invention is directed to a process wherein said blend distribution of dust and sludge various sources suitable for magnetic susceptibility of the iron containing particles comprises providing for blend including the maximum comprehensive iron value grade based on

where G is grade value of blend product, is constrained function depend on the magnetic susceptibility, size distribution and grade of individual admix of individual feed material, and Q is quantity of individual admix of individual feed material.

Another aspect of the present invention is directed to a process comprising providing said blend distribution involving
as the grade distribution admix based on the grade of individual grade of Fe, its magnetic susceptibility (X) and effective particle size distribution (d).





Wherein is constrained function for blast furnace sludge, blast furnace dust, Corex sludge, SMS sludge and DRI dust respectively.

Yet another aspect of the present invention is directed to a process wherein said step of carrying out said extracting valuable enriched iron content product from said blend distribution is carried out in a separate extraction Fe extraction unit involving two stages magnetic separation (low intensity magnetic separation and medium intensity magnetic separation) and concentrate thickener and
said step of subjecting the tailings non-magnetic product is carried out in a separate unit for extracting enriched carbon value involving dual extraction column floatation cell ,thickener and recycling water tank.

A further aspect of the present invention is directed to a process wherein after said step of extracting enriched carbon value, the final tailings are collected separately.

A still further aspect of the present invention is directed to a process wherein the water outflow from said thickeners are collected in a water recirculation holding tank for subsequent use.

A still further aspect of the present invention is directed to aprocess wherein said blend distribution used comprises selectivelyblast furnace dust and sludge, SMS dust and sludge, Corex sludge and DRI dust all materials which has Iron, Carbon, flux materials and other gangue minerals obtained through controlled source conveying systems which are selectively fed into said slurry holding tank based on size distribution, specific density and magnetic susceptibility of particle.

A still further aspect of the present invention is directed to aprocess wherein said providing of blend distribution in said slurry holding tank comprises controlling density of the slurry based on the desired pumping for said extracting valuable enriched iron content product and said downstream extracting enriched carbon value.

Another aspect of the present invention is directed to aprocess wherein said first stage low intensity magnetic separation generates two products (1) primary magnetic product which is collected in a holding sump through concentrator line and (2) primary non-magnetic tail product and said second stage medium intensity magnetic separation generates two products (1) secondary magnetic product which is collected through concentrate line in said holding sump and (2) secondary non-magnetic tail product, said concentrate collected at said holding sump are pumped to iron concentrate thickener.

Yet another aspect of the present invention is directed to aprocess wherein said secondary non-magnetic tail product is treated to enrich the carbon value which for the purpose is fed to conditioning tank where froth floatation reagents (collector and frother) are added for conditioning and generate two products (1) carbon enriched froth product and (2) gangue mineral enriched sink product (final tail).

A further aspect of the present invention is directed to aprocess wherein said concentrate enriched iron product is ready for supply downstream process selectively including for pelletisation, briquetting, sintering or any other agglomeration techniques; and
said carbon enriched product is ready for downstream utilization.

A still further aspect of the present invention is directed to aprocess comprising said magnetic separation is carried out involvingprimarily Low intensity magnetic separation for separation of Ferro magnetic particles, secondary medium intensity magnetic separation for separation of paramagnetic particles and high intensity magnetic separation for further recovery of fine iron particles.

A still further aspect of the present invention is directed to aprocess for selectively providing

iron enriched to 60 - 65 % Fe iron concentrate which meets desire grade specification of any iron making units from 32 - 40 % Fe value with 35 - 50% Yield;
the carbon valueenriched from 10 - 30 % C in feed to 65 - 85% Carbon concentrate with 15 - 25 % yield and the carbon concentrate can use in iron making or any other suitable process;
ensures that Zn content in iron and carbon concentrate below 0.3 % due its diamagnetic and hydrophilic properties.

Yet another aspect of the present invention is directed to asystem for carrying out the processofextracting valuable enriched iron content product and enriched carbon value product from the dust and sludge generated from various iron and steel making unit of integrated steel plant as described above comprising:

slurry holding tank for controlled feeding of said dust and sludge from various sources to achieve said blend distribution;

means for carrying out said magnetic separation based extraction of valuable enriched iron content product and tailings of non-magnetic product;

column floatation means for extracting of enriched carbon values from saidtailings of non-magnetic product.

A further aspect of the present invention is directed to a system wherein said means for carrying out said magnetic separation based extraction comprises first stage low intensity magnetic separation and second stage medium intensity magnetic separation operatively connected to a concentrate thickener and said column floatation means for extracting of enriched carbon values is also operatively connected to a concentrate thickener.

A still further aspect of the present invention is directed to asystem comprising:
a magnetic separation base extraction unit comprises of slurry holding tank, two stages magnetic separation (low intensity magnetic separation and medium intensity magnetic separation) and concentrate thickener alongwith high intensity magnetic separation for further recovery of fine iron particles and extracting of enriched carbon values unit comprisesof a dual extraction column flotation cell, thickener and recycling water tank;said extracting of enriched carbon values unitdelivers two products which are final tailing and enriched carbon material respectively and includes a water recirculation holding tank, the water come from the overflow section of all thickener stored in this tank and adapted to be recirculates for further operation of same.

A still further aspect of the present invention is directed to asystem comprising source conveying system fitted with flow control transmitter to control the blend distribution based on size distribution, specific density and magnetic susceptibility of particle;

slurry holding tank for storing said blend feed and having its own water line connection along with density meter transmitter for attaining desired density ;

pump means to pump desired blend to said primary magnetic units to generate two products concentrate (1) primary magnetic product which is dipped to holding sump through concentrate line segment and (2) primary Non-magnetic tail product, which is fed through primary tail line ,

said primary non-magnetic tail product operatively fed to said secondary magnetic unit to generate two products concentrate (1) secondary magnetic product which dipped to holding sump through concentrate line segment and (2) Secondary Non-magnetic tail product,

a sump junction for collecting the concentrate from first and second magnetic units said sump unit operatively connected to iron concentrate thickener for generating the concentrate enriched iron product to utilize in downstream process (Pelletisation, briquetting, sintering or any other agglomeration techniques) through sink flow line ;

the Secondary Non-magnetic tail product of secondary magnetic unit is fed to conditioning tank through pipe line ,said conditioning tank having several source terms for addition of froth flotation reagents (collector and frother) to generate two products (1) Carbon enriched froth product and (2) gangue mineral enriched sink product (final tail), said carbon enriched product being utilized to downstream process.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1-shows the process flow sheet diagram of iron and carbon recovery from waste according to present invention.
Figure 2- shows the overall system layout involving the various equipments in selective sequential manner to implement the process flow for iron and carbon recovery process according to present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
The present invention is directed to a process of separation of iron and carbon from the blend mixture of steel plant dust and sludge waste by stage wise magnetic separation of iron followed by dual column froth floatation to recover carbon from the blend mixture of steel plant dust and sludge waste. The blend is prepared based on the magnetic susceptibility, mineralogical, and size specification of sludge and dust generated from steel making unit and iron making unit. The sludge and dust generated from the said unit are finely agglomerated whose particle size distribution of 80% passing is varies from 70 micron to 150 micron. The composition of the said sludge and dust consist: Total Fe 31 to 62%, Carbon 11 to 28%, Zn 0.01 to 0.6 %, and SiO24 to 10% and the remaining other oxide 2 to 20%. There is very large difference of magnetic susceptibility and mineralogical properties between iron bearing material and carbon material, therefore for removal of iron and carbon materials from the finely distributed sludge and dust can be treated by adopting adequate mixing proportion based on particle size distribution and mineralogical aspect followed by magnetic separation unit in the first phase of the process. In the consequent, second phase of operation, the reject product of the first phase is subjected to froth flotation method, wherein the concentration of the un-burnt carbon content extracted as a froth product is enhanced to a fixed carbon value of 58 % to 80%. The products of the magnetic separation fulfils the specification of pellet or other agglomerate material, wherein; Total Fe is greater than 61% and the gangue material (alumina and Silica) less than 8%. Hence, the product of magnetic separation unit will downstream towards the pelletisation or agglomeration unit because of the finer particle size distribution and this product facilitate as a feed material for any iron making unit. Thus, this invention leads to reduce the deleterious material as gangue minerals, along with other trace minerals and utilization of the waste material as a suitable feed for iron making unit in the form of iron as well as carbon value.
The basic aspect of the present invention is the preparation of blend based on mineralogical, magnetic susceptibility, and size distribution and enrichment of iron and carbon value to meet its specification for downstream processes such as palletisation and other agglomeration techniques, whose specification should be suitable to facilitate the iron making unit performance. The dust and sludge material generated from iron making unit and steel making unit consists of iron bearing material, carbon, lime containing material, silica and alumina along with oxide of trace elements containing material. The chemical specification of the said dust and sludge consisting total Fe percentage ranging from 31% to 62% with accomplished gangue load varies from 8% to 20%, whereas the unburnt content of carbon varies from 11 to 28% by weight. As per the mineralogy, the presence of Fe (metallic) or wustite in the DRI dust and SMS dust and sludge may create barrier as per metallurgical properties to the downstream process like palletisation. Hence, for selecting the beneficiation route it is necessary to put expectation of magnetic susceptibility, particle size distribution and mineralogical characteristic to form a proper blend ratio of said dust and sludge.
Further, this invention deals with the preparation of proper blend of the said dust and sludge, based on particle size distribution and mineralogical characteristics,for the effective utilization of iron bearing materials and reduction of undesired mineral matter as well. The table below shows physical specification i.e. magnetic susceptibility of said dust and sludge.

Table-1: Magnetic susceptibility of said dust and sludge materials
Source of dust and sludge Magnetic susceptibility(*10-7 m3/kg)
Blast furnace Dust 11.48
Blast furnace Sludge 10.48
Corex Sludge 8.47
SMS dust and sludge 15.21
DRI dust 13.15

The Table 1 illustrates that the magnetic susceptibility of SMS dust and sludge and DRI dust is very high with respect to other materials due to the presence of Fe (metallic) fraction as shown in Table 2. Henceforth, the prognosis algorithm has been developed to prepare the blend proportion of the said material mix which should have magnetic susceptibility range in between 8-11*10-7m3/kg. The mixed magnetic susceptibility of 8-11*10-7 m3/kg is suitable to extract valuable iron value from the said blend prepared from dust and sludge by adopting magnetic separation technology.

Table 2: Blend of dust and sludge based on mineralogical and magnetic susceptibility
Essay % distribution
Dust and Sludge Wt. % Distribution Fe(Total) Fe (Met) SiO2 Al2O3 CaO ZnO C
BF Dust 38.39 36.93 0 11.32 5.92 3.13 0.11 19.69
BF Sludge 33.13 33.76 0 10.48 7.31 3.25 0.35 21.55
Corex Sludge 18.48 35.19 0 8.46 4.62 4.65 0.02 23.63
SMS dust and sludge 5 62.26 19.01 1.38 0.35 10.85 0.14 1.53
DRI dust 5 56.11 13.4 5.47 4.57 4.57 0.01 4.01
Blend Proportion 100 37.78 1.62 9.72 5.79 3.90 0.16 19.34
Blend Mag. Susceptibility 10.86 *10-7 m3/kg

The above Table-2, illustrate that the magnetic susceptibility of the blend prepared is 10.86*10-7m3/Kg which is very much suitable for low intensity and medium intensity magnetic separation. The maximum distribution of blast furnace sludge and dust, carried by this blend preparation based on the mineralogical aspect and magnetic susceptibility.

Table-3: particle size distribution (PSD) of said dust and sludge materials
Size (µm) Blast furnace (BF)dust wt. % Corex sludge wt. % BF sludge wt. % SMS sludge wt.% DRI, Wt.%
-150+75 12.17 10.5 3.71 1.68 11.9
-75+63 3.29 3.14 0.88 5.91 8.9
-63+45 8.16 5.74 1.69 7.11 12.5
-45+32 9.5 5.29 2.17 2.08 6.9
-32+25 6.72 3.38 1.98 1.6 4.5
-25+10 22.29 11.53 13.86 7.52 12.9
-10+2 25.79 34.66 41.36 37.17 24.8
-2 12.08 25.76 34.35 36.93 17.6

Table-4: Blend proportion based on Particle size distribution of said dust and sludge materials
Weighted distribution (%) of Sludge and dust for Blend
Attribute Blast furnace dust Corex sludge BF sludge SMS sludge DRI Total Blend
Blend - 1 35 25 25 10 5 100
Blend - 2 30 30 25 10 5 100
Blend - 3 25 30 30 10 5 100
Blend - 4 20 20 35 15 10 100
Blend - 5 20 20 30 15 15 100

Table-5: Blend of dust and sludge based on mineralogical, PSD and magnetic susceptibility
Size (µm) Blend mix -1 Blend mix -2 Blend mix -3 Blend mix -4 Blend mix -5
-150+75 8.58 8.49 8.07 7.27 7.68
-75+63 3.19 3.19 3.06 3.37 3.77
-63+45 6.05 5.93 5.61 5.69 6.23
-45+32 5.74 5.53 5.17 4.72 4.96
-32+25 4.08 3.91 3.67 3.40 3.53
-25+10 15.55 15.01 14.59 14.03 13.99
-10+2 32.99 33.43 34.21 34.62 33.79
-2 23.83 24.51 25.63 26.89 26.05
Magnetic susceptibility 8.93 9.78 10.73 13.25 13.39
Fe (Metallic) and wustite 5.08 5.13 5.71 7.48 7.65

The particle size distribution of said material also has its importance towards the selection of magnetic separation unit. The Table 3 illustrates that the blast furnace sludge, corex sludge and SMS sludge have relatively finer particle size distribution with respect to the other said dust material. In SMS Sludge and DRI dust, the presence of ferromagnetic particles (Fe-metallic, FeO and Fe2O3), is finely distributed in respect of particle size distribution. Hence, the surface area exposed to the drum of low intensity magnetic separation tends to attract 60-70% of liberated coarser hematite particles (paramagnetic particles) due to high terminal velocity. Along with that, the coarser particle, 30-40% of finer particles (ferromagnetic particles)are also attracted on the same drum of low intensity magnetic separator due to consolidated trickling impingement of flux density of magnetic field intensity to attract finer ferromagnetic particles. On the same, the scavenging process of rejects of the low intensity magnetic separator carried out at medium intensity magnetic separator, where the exposures of finer ferromagnetic and paramagnetic particles are predominant over the relative coarser particles. Due to the relatively high magnetic field intensity of medium intensity magnetic separation and high surface area of feed particles tends to enhance the performance of said unit.

Another aspect of present invention relates to a process for separating iron bearing compounds and carbon from wastes generated from iron and steel making units. After the preparation of proper blend, the blend mix is poured in slurry holding tank, where the overall Fe grade of feed is reached a range of 32 to 40% of Fe. In this holding tank, proper pulp density (1.1 to 1.25 gm/cc) of the said blend are prepared and fed to the first stage of magnetic separation of low intensity magnetic separator. Hence, to achieve the desired Fe value with grade more than 61% Fe content, magnetic separation process is incorporated, wherein the high magnetic susceptible material are extracted as magnetic product. The non-magnetic portion of products are again fed to second stage magnetic separation preferably addressed as medium intensity magnetic separation, where relatively lesser magnetic susceptible materials are attracted to enhance the overall yield and recovery of valuable iron.

Another important aspect of present invention is to recover the carbon values from the tail product of second stage magnetic separation. For recovery of carbon value from the feed carbon content of 17 to 25% of fixed carbon in this present invention dual extraction column (DEC) froth flotation process is adopted. For the froth flotation method the different synthetic carbon collector has been employed to make the carbon particle surface hydrophobic, in the subsequent addition of reagents frothing reagent is also added to make the bubbles stable. In this invention, dual extraction column flotation cell provides a two stage (rougher and cleaner) of froth flotation operation in a single phase of operation; henceforth this flotation process enriched the carbon content upto the range 60% to 75% of fixed carbon content in concentrate as a froth product. The sink product of this said unit operation consists of majorly gangue minerals matter and un-liberated valuable minerals henceforth this product are rejected to tailing thickener as a discarded materials.

Another aspect of the present invention is to recirculate the desired water quantity for continuous operation of enhancing iron value and carbon value from the said blend mixed. The products from magnetic separation and froth flotation are subjected to individual thickeners. By the application of flocculation and coagulation reagents in the thickener the TDS and TSS of water quality reached to desired value (120-150PPM), hence this water from the overflow segment of thickener stored in different holding tank, and can be utilised further.

As stated hereinbefore, the present invention is directed to a process of extracting valuable iron content and carbon content from the dust and sludge generated from the iron making and steel making unit of integrated steel plant. The preparation of mixed blend reverts a major challenge on selection of unit operation and their parameters, hence the chemical, physical (size distribution specific density and magnetic susceptibility of particle) and mineralogical features plays a pivotal role to select two stage magnetic separation for enhancing the grade of Fe in concentrate as per specification of iron ore palletisation followed by dual extraction column flotation for achieving enriched fixed carbon value as fuel. The various features of the present invention are now described in relation to accompanying drawings wherein:

Accompanying Figure 1 shows the process flow sheet diagram of iron and carbon recovery from waste for reduction of gangue containing compound and up-gradation of Fe and carbonvalue from the said sludge and dust. The said material, blast furnace dust and sludge, SMS dust and sludge, Corex sludge and DRI dust are depicted as 101,102,103 and 104 respectively.The 101,102,103 and 104 are fed to the segment 11 which consists of slurry holding tank, two stages magnetic separation (low intensity magnetic separation and medium intensity magnetic separation) and concentrate thickener. The 11 generates two final products viz. iron concentrates 113 and the tailing non-magnetic product. The tailing non-magnetic product is fed to unit 12 for extracting enriched carbon value. The unit 12 consists of a dual extraction column flotation cell, thickener and recycling water tank. The unit 12 delivers two productsin 118 and 119, which are final tailing and enriched carbon material respectively. The 12 unit consist 120 which is water recirculation holding tank. The water come from the overflow section of all thickener stored in this tank and can be recirculates for further operation of same.

Accompanying Figure 2 is a view illustrating an outline of a novel process method to produce reduced gangue containing compound and up graded iron oxide (Fe- enriched compound) and carbon from the said dust and sludge.
As shown in Figure 1, process steps involves seven major unit operations namely slurry preparation unit 209, first stage magnetic separation unit 212, second stage magnetic separation unit 215, concentrate thickener 219 for iron recovery, carbon thickener 226, dual extraction column flotation 223 and recycle water tank 228.
The said material as mentioned in figure 1 as 101,102,103 and 104 have its source conveying system such as 201,203,205 and 207 respectively. All this source conveying system are fitted with flow control transmitter 202,204,206 and 208, which controls the blend distribution as per the prognosis algorithm created based on size distribution, specific density and magnetic susceptibility of particle.The said proportioned material fed to slurry holding tank 209 which has its own water line connection along with 228. The 209 has a digital density meter transmitter 210, once the desired density reached inside the 209 as per blend proportion the pump 211 pump the slurry with high head to the 212. The 212 has two products concentrate (1) primary magnetic product which dipped to holding sump 218 through concentrate line segment 213 and (2) primary Non-magnetic tail product, which fed to 215 through primary tail line 214. The 215 has also two products concentrate (1) secondary magnetic product which dipped to holding sump 218 through concentrate line segment 216 and (2) Secondary Non-magnetic tail product. The concentrate from 212 and 215 after collecting at sump junction 218 are pumped to iron concentrate thickener 219, after the thickening process the concentrate enriched iron product 113 as mentioned in figure 3 is supposed to utilize in downstream process (Pelletisation, briquetting, sintering or any other agglomeration techniques) through sink flow line 220.

The Secondary Non-magnetic tail product of 215 is again treated to enrich the carbon value from the same. Thus, the secondary non-magnetic tailingis fed to conditioning tank 222 through pipe line 217. The conditioning tank has several source terms for addition of froth flotation reagents (collector and frother) through 221. After proper conditioning,the said material flows from 222 and fed to 223 where two products is generated (1) Carbon enriched froth product and (2) gangue mineral enriched sink product (final tail). The carbon enriched product is utilized to downstream process through 224 followed by thickener operation 226 and 227, whereas the final tail are rejected or dumped to 225. The thickener (226 and 219) overflow water after treating with coagulation and flocculation are stored in 228 and from the source term 229 it can recycle further.

Establishment of Dust and sludge Blending Model
Objective Function
To establish linear programming model, the quantities of generated dust and sludge from iron and steel making unit from every spot are designed as decision variables, the maximum comprehensive iron value grade as objective function, satisfying the constraints of iron value quality ability and other demand of every spot generation of said material based on the particle size distribution and magnetic susceptibility. The magnetic susceptibility has its own function in relates of mineralogical constrains.
In this present invention the recurrence feed material are: blast furnace sludge, blast furnace dust, Corex sludge, SMS sludge and DRI dust whose generation are Q1, Q2, Q3, Q4 and Q5 respectively.
For the maximization of grade quality, the linear equation established is given below:
max?G=(?_(i=1)^n¦?f_i Q_i ?)/Q_i
Where G is grade value of blend product, f_i is constrained function depend on the magnetic susceptibility, size distribution and grade of individual admix of individual feed material, and Q is quantity of individual admix of individual feed material.
The constrained function f_i is a dependent variable and the below equation of f_i gives the grade distribution admix based on the grade of individual grade of Fe, its magnetic susceptibility (X) and effective particle size distribution (d).
f_1=(?_1×G_1)/(d_1^3 )
f_2=(?_2×G_2)/(d_2^3 )
f_3=(?_3×G_3)/(d_3^3 )
f_4=(?_4×G_4)/(d_4^3 )
f_5=(?_5×G_5)/(d_5^3 )
f_1to5is constrained function for blast furnace sludge, blast furnace dust, Corex sludge, SMS sludge and DRI dust respectively. The effective particle size of each individual are derived here by adopting the Rosin-Rammeler particle size distribution model.
Recovery of iron and carbon after Blend preparation
The invention of the present process was established by conducting trials for separation of iron and carbon from the said blend of sludge and dust material. Experimental results ofthesaid material are shown below.
Table 8: Results of iron recovery from dust and sludge waste
Product Wt.,% C,% Fe,%
Stage- I: LIMS Feed 100 19.34 37.78
Mag 28 6.27 61.63
N Mag 72 24.43 28.51
Stage- II: MIMS Feed 72 24.43 28.51
Mag 12.3 6.32 61.24
N Mag 59.7 28.16 21.77
Total Mag (Final Iron Product) 40.3 6.3 61.5
LIMS: Low Intensity Magnetic Separator; MIMS: Medium Intensity Magnetic Separator

Table 9: Results of carbon recovery from iron recovery processtailing.
Product Wt.% w.r.f. Wt.,% C,% Fe,%
Feed 59.7 100 28.16 21.77
Carbon Concentrate 17.22 28.85 72.2 8.51
Final Tailing 42.48 71.15 10.3 27.15
Wt. % w.r.f.: Weight percentage with respect to overall feed

Results of table 8 shows that iron values from the said material enriched from 37.78% to 61.5 % with 40.3 % yield. Also results reveal that carbons present in the iron concentrate 6.3% C. The tailings of iron recovery subjected to flotation process. The reagent used in flotation process are synthetic oil collectors (0.8 kg/t) and pine oil as frother (0.1 kg/t) which results to enriched carbon value from 28.16% to 72.2% with yield 28.85%.

It is thus possible by way of the present invention to provide aprocess for the recovery of iron and carbon values from waste materials such asdust and sludge generated in iron and steel making unit.The blend was prepared based on the magnetic susceptibility, mineralogical, and size specification of sludge and dust. The process include the first stage separation of magnetic separation removes ferromagnetic iron particles with low intensity magnetic separator and second stage of magnetic separation recovers paramagnetic iron particles with medium intensity magnetic separation. After iron bearing minerals recovery the carbon rich tailing subjected toDual extraction column (DEC) flotation. The product of magnetic separation unit willbe utilized downstream towards the pelletisation or agglomeration unitbecause of the finer particle size distribution and this product facilitate as a feed material for any iron making unit. Thus, this invention leads to reduce the deleterious material as gangue minerals, along with other trace minerals and utilization of the waste material as a suitable feed for iron making unit in the form of iron as well as carbon value.