CLIAMS:We Claim:
1. A process for producing micro pellets from mixed sludge for using the same in iron ore sintering comprising
providing sludge collected from a sludge source including Blast Furnace(BF), Sinter plant(SP) and Basic Oxygen Furnace (BOF) in a high intensity mixer for desired homogenization;
addition of lime and water in desired proportion for micro pelletization in a mixer ;
screening and obtaining the micro pellets to desired size range for use in iron ore sintering.

2. A process for producing micro pellets from mixed sludge as claimed in claim 1 comprising
providing said mixed sludge 0.02 to 0.05 % by wt. preferably 0.02% , burnt lime 2% % by wt. moisture/water 14 to 16 wt% preferably 16wt% in an Erich mixer(High Intensity Mixer);
feeding samples of said mixed sludge and lime into pan of Erich mixer where the micro pellets are prepared by starting granulator at pan rpm 32 and rotor rpm 800 for dry mixing continued upto about one minute for mixing;
increasing pan rotation to 64 rpm and reducing rotor speed to 400 rpm after one minute for micro pelletisation;
taking out micro pellets from mixer/granulator produced after 10-15min preferably 15 min of rotation and screening through 1mm and 3mm screen to obtain desired micro pellets of more than 90 % above 1mm size.

3. A process for producing micro pellets from mixed sludge as claimed in claims 1 or 2, wherein optimum moisture, retention time for granulation and speed of pan and rotor of the high intensity mixer are selectively determined with varying time and moisture to obtain desired quality of pellets for sintering.

4. A process for producing micro pellets from mixed sludge as claimed in claims 1 to 3, wherein micropelletization is carried out maintaining rotation of Pan in clockwise direction and that of rotor in anti-clockwise direction.

5. A process for producing micro pellets from mixed sludge as claimed in claims 1 to 4, wherein micro pellets obtained are adapted for reduced rate of lime consumption for producing sinter in a downdraft sintering machine.

6. A process for producing micro pellets from mixed sludge as claimed in claims 1 to 5, which ensure reduced rate of raw material consumption for the production of sinter using such micro pellets in the integrated steel plant.

Dated this the 26th day of August, 2014
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

,TagSPECI:FIELD OF THE INVENTION
The present invention relates to a process for producing micro pellets from mixed sludge for use of the same in iron ore sintering. More particularly, the present invention is directed to a process for producing micro pellets using sludge generated during steel making, iron making and sintering process during flue gas cleaning in steel plants by optimizing the process parameters for producing micro pellets using said mixed sludge produced through homogeneous mixing in a high intensity mixer. Calcined lime was added to the mixed sludge to obtain sustainable strong pellets. Calculated amount of water was added with sludge for pelletisation. The green mix is pelletized and screened to obtain micro pellets which are cured for use in sintering.

BACKGROUND OF THE INVENTION

Sludge obtained from Basic Oxygen Furnace, Blast Furnace, and Sinter Plant contains appreciable amount of iron oxide and lime. Disposal of this sludge, causes environmental problems due to high moisture (35-40%) associated with it. Recycling of the same to the sinter plants is gaining importance in the integrated steel plants for utilization of the same as environment friendly process. Some of the prior work is directed to utilization of the iron bearing sludge in pellet production for subsequent use in sintering/steel making. However, no attempt has been made to produce micro-pellets.

US 6921427 states about a process for cold briquetting and pelletization of ferrous or non-ferrous ores or mineral fines by iron bearing hydraulic mineral binder wherein a process for cold briquetting and pelletization of ferrous or non-ferrous or mineral fines is disclosed using iron bearing hydraulic mineral binders for metallurgical applications, said process consisting the steps of: mixing 80-95% by ferrous weight of a metallurgical/mineral/carbonaceous/oil contaminated dust/fines/sludge with 3-10% by Wt. of an iron bearing hydraulic mineral binder and optionally with 2-6% by Wt. water and 0.05 to 0.20% by Wt. of a surface active agent to form a homogenized dry mix/slurry, pelletizing/compacting the dry mix/slurry to form an agglomerated mass, and curing the agglomerated mass for 3-20 days by exposing the agglomerated mass to atmospheric air for 10-14 hours followed by moisture treatment.

There has been thus a need in the steel industry to make more environment friendly utilization of iron bearing sludge generated in different unit operation in steel plants. The present invention is an attempt to utilize sludge which has been recycled in different forms; with some initial condition without any agglomeration, in slurry form and as pellets/ micro- pellets.

OBJECTS OF THE INVENTION

The basic object of the present invention is thus directed to provide a process for producing of micro pellets from sludge and use of the same in iron ore sintering.

A further object of the present invention is directed to a process for producing micropellets from mixed sludge obtained from Basic Oxygen Furnace, Blast Furnace, and Sinter Plant contains appreciable amount of iron oxide and lime, for utilization in iron ore sintering.

A still further object of the present invention is directed to a process for producing micropellets from mixed sludge which ensure utilization of sludge obtained as by-product, during sintering operation, iron making and steel making process and its disposal through environment friendly manner.

A still further object of the present invention is directed to a process for producing micropellets from mixed sludge which implements a new process called micro pelletizaion.

Another object of the present invention is directed to a process for producing micropellets from mixed sludge which considers the process optimization during micro pelletization through high intensity mixer.

Yet another further object of the present invention is directed to a process for producing micropellets from mixed sludge and use of the same in iron ore sintering with quantitative as well as qualitative optimization of laboratory pot sintering process.

A further object of the present invention is directed to a process for producing micropellets from mixed sludge and use of the same in iron ore sintering directed to reduced rate of lime consumption for producing sinter in a downdraft sintering machine.

A still further object of the present invention is directed to a process for producing micropellets from mixed sludge and use of the same in iron ore sintering favouring reduced rate of raw material consumption for the production of sinter in the integrated steel plant.

A still further object of the present invention is directed to a process for producing micropellets from mixed sludge and use of the same in iron ore sintering which can be globally acceptable for the utilization in any sinter plants of the integrated steel plants.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a process for producing micro pellets from mixed sludge for using the same in iron ore sintering comprising
providing sludge collected from a sludge source including Blast Furnace(BF), Sinter plant(SP) and Basic Oxygen Furnace (BOF) in a high intensity mixer for desired homogenization;
addition of lime and water in desired proportion for micro pelletization in a mixer ;
screening and obtaining the micro pellets to desired size range for use in iron ore sintering.

A further aspect of the present invention is directed to a process for producing micro pellets from mixed sludge comprising
providing said mixed sludge 0.02 to 0.05 % by wt. preferably 0.02% , burnt lime 2 % by wt. moisture/water 14 to 16 % preferably 16 wt % in an Erich mixer(High Intensity Mixer)
feeding samples of said mixed sludge and lime into pan of Erich mixer where the micro pellets are prepared by starting granulator at pan rpm 32 and rotor rpm 800 for dry mixing continued up to about one minute for mixing;
Increasing pan rotation to 64 rpm and reducing rotor speed to 400 rpm after one minute for micro pelletisation;
Taking out micro pellets from mixer/granulator produced after 10-15min preferably 15 min of rotation and screening through 1mm and 3mm screen to obtain desired micro pellets of more than 90 % above 1mm size.

A still further aspect of the present invention is directed to a process for producing micro pellets from mixed sludge, wherein optimum moisture, retention time for granulation and speed of pan and rotor of the high intensity mixer are selectively determined with varying time and moisture to obtain desired quality of pellets for sintering.

A still further aspect of the present invention is directed to a process for producing micro pellets from mixed sludge, wherein Micropelletisation is carried out maintaining rotation of Pan in clockwise direction and that of rotor in anti-clockwise direction.

A still further aspect of the present invention is directed to a process for producing micro pellets from mixed sludge, wherein micro pellets obtained are adapted for reduced rate of lime consumption for producing sinter in a downdraft sintering machine.

A still further aspect of the present invention is directed to a process for producing micro pellets from mixed sludge, which ensure reduced rate of raw material consumption for the production of sinter using such micro pellets in the integrated steel plant.

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

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

Figure 1: is the flow chart showing the steps of the process for producing micro pellets using mixed sludge according to the present invention.

Figure 2: is the schematic representation of the laboratory scale set up of pot sintering unit to produce sinter using micro pellets produced according to the process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWING

The present invention is thus directed to a process for producing micro pellets using sludge generated during steel making, iron making and sintering process during flue gas cleaning in steel plants by optimizing the process parameters for producing micro pellets using said mixed sludge produced through homogeneous mixing in a high intensity mixer and use of such micro pellets in iron ore sintering. The details of the steps for producing micro pellets from mixed sludge and use of such micro pellets in iron ore sintering according to the present invention are described with the help of following example:

Example:

For Micro pellet preparation, all sludge were dried for better mixing. All sludge (BF, SP, LD) were mixed as per ratio of annual generation (50, 30, and 20% by weight) of individual sludge provided by Applicants’ Bhilai Steel Plant. High intensity mixer used for micro pelletisation consists of circular Pan (5 ltr. capacity) and a Rotor. Pan rotation varies from 32 to 64 and Rotor speed varies from 400 rpm to 800 rpm. It is important to mention here that rotation of Pan is clockwise whereas it is anti-clockwise for Rotor.

For experimental purpose sludge collected from Blast Furnace(BF), Sinter plant(SP) and Basic Oxygen Furnace (BOF) of Bhilai Steel Plant. Physico-chemical analyses of different sludge samples were carried out. Homogenous mixing of sludge was carried out in a high intensity mixer. Chemical analysis of mixed sludge was also conducted. Calcined lime was added to the mixed sludge to obtain sustainable strong pellets. Calculated amount of water was added with sludge for pelletisation.

Sample taken: Mixed sludge – 2 kg, Burnt Lime – 30-40 gm(1.5-2.0%), Water or moisture – 11 to 18%, Time of rotation of Erich mixer – 5 to 15 min. Samples of mixed sludge and lime were fed into the Erich mixer where the micro pellets were prepared. Granulator was started at pan rpm 32 and rotor rpm 800 for dry mixing. After one minute, pan rotation was increased to 64 rpm and rotor speed was reduced to 400 rpm for micro pelletisation. Micro pellets thus produced were taken out after 5 min, 10 min, and 15 min interval and screened through 1mm and 3mm screen respectively. Optimum moisture content and time for granulation were determined by conducting a series of experiments with varying time for rotation and moisture.It was found that 14% to 16 % moisture and 10 to 15 min duration is good for Micro pellets of more than 90 % above 1mm size.

After optimization of the above parameters micro pellets were produced using 16 % moisture and 15 min rotational time of mixer. For the validation of the optimized parameters, micro pellets thus produced were tested in pot sintering system. A series of pot sintering tests were carried out by using mixed sludge in the form of micro pellets varying from 0 to 30 kg/t of sinter with 5 kg increment.

Accompanying Figure 1 is the flow chart showing the steps of the process for producing micro pellets using mixed sludge according to the present invention.

The prepared micro pellets (0 to 20 kg/t with sinter mix) were tested in a laboratory pot sintering unit. For this purpose, sludge in the form of micro pellets was mixed with iron ore, lime stone and dolomite fines with coke breeze as sinter charge mix. This mixing were conducted during granulation of sinter charge mix. The produced sinter was stabilized by dropping it on a metal sheet from two meter height. Thereafter, the stabilized sinter was screened through 5 mm, 10 mm, 25 mm and 40 mm screen, respectively. The sinter sample of above 5 mm size fraction was taken and ground to below 72 mesh for chemical analysis. Sinter productivity was calculated. The physical strength was determined by rotating 15 kg sinter sample of 10 to 40mm size fraction in ISO drum tumbler. Some experiments were also conducted to study the effect of micro pellets using sludge on sintering process and quality of product sinter. Results of such micro pelletisation and pot sintering tests show the improvement in productivity and quality of sinter.

Accompanying Figure 2 show the schematic presentation of the pot sintering unit used for the production of iron ore sinter using micro pellets obtained according to the present invention.

Following are the observation/results of pot sintering test using the micro pellets produced according to the present invention:
(I) Improvement in yield i.e. +5 mm sinter fraction in the range by 2-3 %;
(II) Reduction in (-) 5 mm sinter i.e. decrease in return sinter generation by 2-3%;
(III) Strength of sinter (DTI) showed improvement by 2-3 %;
(IV) Reduction in consumption of iron ore fines & dolomite will be about 11-12kg/t and 4-5kg/t respectively by use of mixed sludge @ 20kg/t.

Following conclusion can be drawn based on above results of the pot sintering test conducted with micropellets in sinter charge as given above:
(I) The result of trials at RDCIS show that addition of mixed sludge in micro pellets form in sinter charge mix up to 2 % by wt. have no negative effect in sintering process and quality of sinter.
(II) There will reduction in consumption of iron ore fines & dolomite.
(III) As high grade iron ore reserve is limited and depleting continuously, hence use of sludge shall provide opportunity to recover Fe value from wastes and result in conservation of iron ore fines.
(IV) Use of sludge shall reduce additional land requirement for dumping of sludge.

We Claim:
1. A process for producing micro pellets from mixed sludge for using the same in iron ore sintering comprising
providing sludge collected from a sludge source including Blast Furnace(BF), Sinter plant(SP) and Basic Oxygen Furnace (BOF) in a high intensity mixer for desired homogenization;
addition of lime and water in desired proportion for micro pelletization in a mixer ;
screening and obtaining the micro pellets to desired size range for use in iron ore sintering.

2. A process for producing micro pellets from mixed sludge as claimed in claim 1 comprising
providing said mixed sludge 0.02 to 0.05 % by wt. preferably 0.02% , burnt lime 2% % by wt. moisture/water 14 to 16 wt% preferably 16wt% in an Erich mixer(High Intensity Mixer);
feeding samples of said mixed sludge and lime into pan of Erich mixer where the micro pellets are prepared by starting granulator at pan rpm 32 and rotor rpm 800 for dry mixing continued upto about one minute for mixing;
increasing pan rotation to 64 rpm and reducing rotor speed to 400 rpm after one minute for micro pelletisation;
taking out micro pellets from mixer/granulator produced after 10-15min preferably 15 min of rotation and screening through 1mm and 3mm screen to obtain desired micro pellets of more than 90 % above 1mm size.

3. A process for producing micro pellets from mixed sludge as claimed in claims 1 or 2, wherein optimum moisture, retention time for granulation and speed of pan and rotor of the high intensity mixer are selectively determined with varying time and moisture to obtain desired quality of pellets for sintering.

4. A process for producing micro pellets from mixed sludge as claimed in claims 1 to 3, wherein micropelletization is carried out maintaining rotation of Pan in clockwise direction and that of rotor in anti-clockwise direction.

5. A process for producing micro pellets from mixed sludge as claimed in claims 1 to 4, wherein micro pellets obtained are adapted for reduced rate of lime consumption for producing sinter in a downdraft sintering machine.

6. A process for producing micro pellets from mixed sludge as claimed in claims 1 to 5, which ensure reduced rate of raw material consumption for the production of sinter using such micro pellets in the integrated steel plant.

Dated this the 26th day of August, 2014
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

ABSTRACT

TITLE: A PROCESS FOR PRODUCING MICRO PELLETS FROM MIXED SLUDGE FOR USE IN IRON ORE SINTERING.

The present invention relates to a process for producing micro pellets from mixed sludge for use of the same in iron ore sintering. More particularly, the present invention is directed to a process for producing micro pellets using sludge generated during steel making, iron making and sintering process during flue gas cleaning in steel plants by optimizing the process parameters for producing micro pellets using said mixed sludge produced through homogeneous mixing in a high intensity mixer. Calcined lime was added to the mixed sludge to obtain sustainable strong pellets. Calculated amount of water was added with sludge for pelletisation. The green mix is pelletized and screened to obtain micro pellets which are cured for use in sintering.