FORM 2
THE PATENTS ACT, 1970
(39 of 1970) THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
TITLE OF THE INVENTION
"A PROCESS FOR PRODUCING MICRO-PELLETS FROM INDUSTRIAL
WASTE"
APPLICANT
Essar Steel Limited , 27 KM Surat Hazira Road, Hazira 394 270 Dist. Surat, Gujarat, India
Preamble of the Description
The following specification particularly describes ;he invention and the manner in which it is to be performed

FIELD OF INVENTION
This invention relates to a process for producing micro-pellets from hazardous iron bearing industrial waste particularly from steel mills. Micro-pellets produced by this process can be recycled as raw material of sinter plant in steel industry. Environmental pollution is avoided as well as recovery of residual iron from industrial waste is effected by this process.
BACKGROUND OF THE INVENTION
Effluent treatment plant (ETP) sludge is a waste product which is sticky and muddy and is generated from waste fluids of cold rolling mill and is obtained after filtering the waste fluid. This sludge contains 20-30% iron as well as heavy metals like Cr, Zn, Ni, Cu and the like. The alkalinity of this sludge tends to progressively deplete under natural weathering condition and releases out the heavy metals. As the particles in the sludge are in micro meter range, dumping of this waste clogs the soil and reduces soil permeability and results in water flooding and clogging. Fine size of the dried waste sludge also produces health hazards as it contaminates atmospheric air. This sludge is considered hazardous waste category as per the government norms. Disposal of this sludge thereof is always problematic and costly.
Steel making shop typically produces 2-5 kg dust per tonne of crude steel and this is captured in Fume Extraction system. The dust thus captured is henceforth referred as Fume Extraction system (FES) dust. The FES dust typically contains 30-40% iron.. The handling, disposal and recycling of these waste is difficult owing to the fine size of these wastes (45-1000µm).
These steel plant wastes can be recycled by different processes like pelletizing, sintering, briquetting, slurry extrusion and so on. Recycling of very fine sized wastes as such in sintering is not possible for large quantity because it affects the very sintering process

itself by reducing the permeability and thus the productivity. The fine size waste is therefore to be agglomerated to be used as raw material for sinter making/ or raw material for blast furnace. The most preferred route of recycling the iron bearing steel plant waste is through sinter making. In sinter making, the waste material is mixed with fluxes, ore fines, coke fines and heated to fuse it in form of agglomerates or sinter. The sinter thus produced is used as a raw material for blast furnace. The sintering process requires raw material particle size in millimeter range; around 80% of the particles in 1- 9.5 mm range. To make the particles of this size range from micro-fines other researchers have tried methods like briquetting, extrusion followed by heating to achieve strength.
OBJECTIVES OF THIS INVENTION
One of the objectives of this invention is to convert hazardous industrial waste in a form which is suitable for handling and transportation. This helps to reduce atmospheric and environmental pollution.
Yet another objective of this invention is to make the micro-pellets of suitable strength without additional heating and additional binders which can be used as raw material for sinter making process and recovery of metals therefrom.
A further objective of this invention is to produce micro-pellets of the desired size by controlling the rotational speed and angle of inclination of the drum in which pelletization takes place.
SUMMARY OF INVENTION
The invention relates to an agglomeration process in which proper size of particles is achieved by pelletizing and strength is achieved by drying at room temperature. These micro-pellets can be recycled by sintering without affecting the productivity and properties of sinter. Pelletizing can be done in disc pelletizer or drum pelletizer. The

premix used in micro-pellitization consists of ETP sludge, FES dust, lime fines and moisture. The percentages of each of these ingredients play a crucial role in the properties of the micro-pellets. The right combination of different inputs was achieved after doing a series of trials. Unlike the other processes, apart from plant wastes no additional binders like clay based binders were used.
BRIEF DESCRIPTION OF INVENTION
This invention relates to a process for producing agglomerates like micro pellets from industrial waste such as effluent treatment plant (ETP) sludge, dust from fume extraction system (FES) and lime fines generated from lime calcination plant.
The typical raw material composition is given below: Composition of raw materials
(All values are indicative only)

ETP* Sludge Wt % FES* Dust Wt % Lime Fines Wt. %
Fe 30 Fe 34
Si02 3.8 FeO 4.5 Si02 1.5
A1203 0.7 ZnO 1.2
CaO 11.9 CaO 10 CaO 80
MgO 1.6 MgO 6 MgO 1.06
LOI (Loss on
Ignition) 40.3
Others: Ni 26, Cu-60, Zn-3 Mn - 220, Cr(III) - 90 in mg/Kg.
*Legend: ETP-Effluent treatment plant sludge, FES-Fume extraction system dust
Nature of the raw material premix and its composition determines the bond strength of the pellets. The choice and quantity of binders play an important role in resulting properties and overall economics of the process. Several combinations of the

aforementioned raw materials were studied (ETP sludge in the range of 50 - 90%, FES : 5- 40% Lime fines: 5 - 30%.) The properties were found to be optimum when combinations consisting of:

Raw materials %
ETP Sludge 60-65
FES Dust 15-20
Lime Fines 10-15
The particle size of the raw materials is also a key factor for selecting the agglomeration process. The particle sizes of the raw materials were less than one micron. Hence pellitization method was selected.
Drum type pelletizer ( Fig 1) was found to be suitable for obtaining desired pellet size compared to other designs of pelletizer. In this process abovementioned waste are first mixed in the desired proportion and charged into one end (charging end) of pelleting drum Due to tne inclined setup of: drum the wet mix moves towards the oth^r end (discharging end) under the action of gravity. The time of travel from entry point to the exit point is known as tne retention period and this can be controlled by the angle of inclination of the drum and the speed of rotation
The key process variables of this type of pelletizer are:
1) The speed of rotation,
2) Inclination angle of pelletizing drum.
Best results were achieved when this drum is inclined at an angle of 1° to 3° from the horizontal axis. After charging, the drum is rotated at a speed of 25 to 35 revolutions per minute.
Another critical factor is the amount of moisture added during pellitization process and the way it is added Best results were achieved when atomized water is sprinkled though

the nozzles provided in the drum. This sprinkling of water increases the moisture of the mixture to 11-14 wt.% level which assists in agglomeration.
The micro-pellets produced by the above process are stored in the yard for 7 days drying period to achieve desired level of strength required for handling, transportation etc. in sinter making process. After drying the micro-pellets thus formed can be used as a charge material for sinter making.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a schematic diagram showing micro peptization unit wherein H is the hopper for feeding the premix to the drawing represented by D. I stands for the inlet for supplying water to the drum through nozzles N. Drum is disposed at an inclined angle from the hopper end to allow premix feed to travel there through.
Fig. 2. Flow sheet of the micro pelletization process, showing the overall flow of materials.
Obvious modifications and alterations know to persons skilled in the art are within the scope and ambit of the appended claims.

WE CLAIM
1. A process for producing micro pellets from industrial waste comprising the steps of premixing effluent treatment plant sludge (ETP sludge) dust from fume extraction system (FES) and lime fines and micro pelletizating the mixture in the presence of moisture and in the absence of any binders.
2. The process as claimed in claim 1 wherein said premix contains 50 to 90% of ETP sludge, 5 to 40% FES dust and 5 to 30 % of lime fines,
3. The process as claimed in claims 1 & 2 wherein said mixture has 65% of ETP sludge, 20% of FES dust, 15% of lime fines and 12% of moisture.
4. The process as claimed in claims 1 to 3 wherein micropelletization is effected by feeding said premix to an inclined drum provided with means such as nozzles to spray moisture and rotating the drum to agglomerate the premix.
5. The process as claimed in claim 4 wherein the drum is inclined at an angle of 1° to 3° and is rotated at a speed of 25 to 35 RPM.
6. Micro-pellets produced by a process as claimed in claims 1 to 5.
7. Micro pellets as claimed in claim 6 transported and recycled through sintering plant to
blast furnace for recovery residual iron therefrom.