FIELD OF THE INVENTION:
The present invention relates to a method and system for improving the productivity of the sintering machine and in particular to a method of sintering adapted to increase the sinter machine productivity by air injection at a specified location, preferably where combustion zone thickness is high to thereby increase the air filtration velocity. The selective location of air injection during the sintering process, is directed to reduce the combustion zone thickness at the discharge end and increase the hot zone permeability for high FeO sintering operation and thereby favour eliminating the resistance offered by the high temperature zone. The method and system of the invention is adapted such that the extension of hot zone width is restricted and the rate of reaction is enhanced and in the process the speed of sintering machine is increased due to lesser resistance offered by bed with enhanced permeability, favoring improvement in productivity of the sintering process and of the machine. Imporatntly, the invention would favour increasing specific productivity of sintering machine from existing about 1.20 to about 1.28 t/m2/hr.
BACKGROUND ART:
It is well known in the art of sintering process in the steel plants, that the iron ore fines are converted to a lumpy porous mass by this process such as to make them a good quality input raw material for blast furnace having very good metallurgical properties. However, the conventional process of sintering suffers from the limitations such as the low productivity of the sintering machine attributable to the slow vertical speed of sintering, progressing from top to the bottom of bed for higher FeO% operation. The rate of reaction and speed of progress of the sintering depend on the three parameters e.g. volumetric airflow rate (m3/min), heat capacity of gas and combustion zone thickness of sinter mix. Normally, the productivity of sintering machine is increased by increasing the volumetric flow rate, sintering mix preparation, balling of sinter mix and charging of the same to sinter machine, reducing the leakages etc., improves the over all permeability. Conventionally, productivity of sintering machine is constrained by resistance offered by high temperature zone and the combustion zone thickness during the process.
It was thus an essential requirement to develop a process that would favour improvement in the vertical sintering speed of the process and productivity of the sintering machine by providing means for enhanced permeability and also restricting the hot zone width
2

extension, such as to increase the speed of vertical sintering directed from top to the bottom bed, achieved through adopting advantageously air injection in the sintering machine at preferred location.
OBJECTS OF THE INVENTION:
The basic object of the present invention is thus directed to a sintering process and system with improved productivity and increased speed of sintering vertically by adopting air injection at selective location.
A further object of the present invention is to improve productivity of the sintering machine by avoiding high combustion zone thickness such as this air injection increases the air filtration velocity and thereby the speed of sintering.
A further object of the present invention is to improve productivity of the sintering machine by reducing the resistance offered by the high temperature zone achieved through reducing the combustion zone thickness at the discharge end and increase the hot zone permeability for high FeO sintering operation.
A further object of the present invention is to inject air from the top through said hood covering the high combustion zone thickness at the discharge end through suitable centrifugal fan means generating required positive pressure such that the sintering process travels at higher speed from the top to the bottom of the bed.
A further object of the present invention is to inject air from the top through said hood covering, wherein said hood fabricated over the length of the machine so that hot zone width extension is restricted favoring enhanced rate of reaction and increased speed of sintering in the machine at lesser resistance offered by the bed.
SUMMARY OF THE INVENTION:
Thus according to the basic aspect of the invention there is provided a sintering process for increasing sinter machine productivity comprising:
monitoring the sintering process and identifying locations where combustion zone thickness is high;
3

injecting air at the specified location where said combustion zone thickness is high to thereby increase the air filtration velocity , reduce the combustion zone thickness at the discharges end and increase the hot zone permeability for increased sinter productivity.
A further aspect of the present invention directed to a sintering process for increasing sinter machine productivity wherein said air is injected from top of the sinter bed.
According to a still further aspect of the present invention directed to a sintering process for increasing sinter machine productivity, comprising:
after ignition of the sinter mix the air is sucked whereby negative pressure is generated and the sintering process travels from top to the bottom of the bed; and
identifying the position where the combustion zone touches the bottom portion of the bed and air filtration velocity is minimum due to the higher combustion zone thickness where the permeability is minimum and the temperature is > 600°C and the sintering is constrained to carry out the required air injection.
A further aspect of the present invention directed to a sintering process for increasing sinter machine productivity wherein the location of air injection is selected where the sinter process speed is minimum.
A still further aspect of the present invention directed to a sintering process for increasing sinter machine productivity wherein the air is injected from top of the sinter bed from a hood in the location 65-80% of the length of the machine from the charging side.
According to an important aspect of the present invention directed to a sintering process for increasing sinter machine productivity wherein
the sintering machine speed is increased from 1.32 to 1.42m/min;
exhaust waste gas temperature increased from 78 to 92°C; and
specific productivity of sinter machine increased from 1.20 to 1.28 t/m2/hr.
4

Another important aspect of the present invention directed to a system for sintering with increased sinter machine productivity comprising:
a sinter machine with raw mix input and sinter discharge means at the other end; injection hood;
hood for injection of air preferably by means of a centrifugal fan adapted to generate positive pressure at specified location though a duct with minimum pressure loss where said combustion zone thickness is high to thereby increase the air filtration velocity, reduce the combustion zone thickness at the discharges end and increase the hot zone permeability for increased sinter productivity.
A further aspect of the present invention directed to said system for sintering with increased sinter machine productivity wherein the injection hood is in a location 65-80% of the length of the machine from the charging side.
A still further aspect of the present invention directed to a system for sintering with increased sinter machine productivity wherein the hood is provided over the length of the machine such that the hot zone width extension is restricted.
The present invention and its objects and advantages are described in greater details with reference to the following accompanying figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1: is the schematic illustration of the air injection system at specified location for the present method of improving productivity of sintering machine according to the invention.
5

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES:
Sintering is a well-known process of converting iron ore fines into lumpy porous mass such that these sinters possess good metallurgical properties as superior quality input material to blast furnaces for making hot metal. The present invention is directed to improving the productivity of the sintering machine by increasing the speed of reaction and vertical sintering that travels from top to the bottom of bed, by injection of air from top of the sinter bed at specified location.
Reference is first invited to accompanying figure 1, which is the schematic illustration of the system of air injection at specified location according to the present invention of the method of improving productivity of sintering machine.
The productivity of sintering machine and vertical speed of sintering depends upon three parameters, namely, volumetric airflow rate (m3/min), heat capacity of gas and combustion zone thickness of sinter mix. Normally, the productivity of sintering machine is increased by increasing the volumetric flow rate, sinter mix preparation balling of sinter mix and charging of the same to sinter machine, reducing leakage etc., improves the overall permeability. The productivity of sintering machine is constrained by resistance offered by high temperature zone and the thickness and permeability of the combustion zone during sintering.
As illustrated in said figure, the air from a centrifugal fan (CF) driven by a motor(MT) supplied through piping/duct(PD), is injected from top of the sinter bed through an air injection hood (AIH) at the preferred location nearly at 65-80% of the length of the sintering machine from charging side. Sinter is obtained at the other end of the machine through a sinter discharge hood (SDH). After ignition of sinter mix fed through a raw mix hopper(RMH) in the ignition hood(IH), the air is sucked from the bottom of the conveyor through wind boxes(WB) i.e. negative pressure is generated and sintering process travels from the top to the bottom of the bed. At one particular position the combustion zone touches the bottom portion of the bed and the air filtration velocity is minimum due to the higher combustion zone thickness i.e. the permeability is minimum and the temperature is greater than 600°C. The speed of sintering is constrained so that the sintering machine speed is reduced resulting in decrease in productivity for high FeO sintering operation. The
6

location of air injection is selected where the sintering process speed is minimum and a hood is fabricated over the length of the machine so that the hot zone width extension is restricted. As the extension of the hot zone width is controlled, the air injection from top will enhance the rate of reaction and thereby the speed of sintering machine/process, due to the lesser resistance offered by the bed. As a result of this the reduction of the machine speed is avoided and thereby favoring steady and improved productivity of the sintering machine.
According to a preferred embodiment of the present invention, said air injection to the sintering process is carried out by adopting injection of air from top through a hood that is covering the high combustion zone thickness at the discharge end by installing and operative connection from a centrifugal fan of suitable capacity driven by a motor such that required positive pressure is generated at the injection point in the hood. A duct of suitable size having minimum pressure loss while transporting air from said fan, is fabricated and installed from the fan to the hood. The test results obtained during the performance of said invention using the embodiment are as follows:
- The sintering machine speed increased from 1.32m/min to 1.42m/min; Exhaust waste gas temperature increased from 78°C to 92°C; Specific productivity of sinter machine increased from 1.20 to 1.28 t/m2/hr.
It is thus possible by way of this invention to provide means for improvement in the productivity of sintering machines by selective air injection during the sintering process, in the Steel plants for feeding sinters to blast furnace as an input material having good metallurgical properties at a higher rate and thereby improving the over all productivity.
7

We Claim:
1. A sintering process for increasing sinter machine productivity comprising:
monitoring the sintering process and identifying locations where combustion zone thickness is high;
injecting air at the specified location where said combustion zone thickness is high to thereby increase the air filtration velocity , reduce the combustion zone thickness at the discharges end and increase the hot zone permeability for increased sinter productivity.
2. A sintering process for increasing sinter machine productivity as claimed in claim 1
wherein said air is injected from top of the sinter bed.
3. A sintering process for increasing sinter machine productivity as claimed in anyone of
claims 1 or 2 comprising:
after ignition of the sinter mix the air is sucked whereby negative pressure is generated and the sintering process travels from top to the bottom of the bed; and
identifying the position where the combustion zone touches the bottom portion of the bed and air filtration velocity is minimum due to the higher combustion zone thickness where the permeability is minimum and the temperature is > 600°C and the sintering is constrained to carry out the required air injection.
4. A sintering process for increasing sinter machine productivity as claimed in anyone of
claims 1 to 3 wherein the location of air injection is selected where the sinter process speed
is minimum.
5. A sintering process for increasing sinter machine productivity as claimed in claim 4
wherein the air is injected from top of the sinter bed from a hood in the location 65-80% of
the length of the machine from the charging side.
6. A sintering process for increasing sinter machine productivity as claimed in anyone of
claims 1 to 5 wherein
8

the sintering machine speed is increased from 1.32 to 1.42m/min;
exhaust waste gas temperature increased from 78 to 92°C; and
specific productivity of sinter machine increased from 1.20 to 1.28 t/m2/hr.
7. A system for sintering with increased sinter machine productivity comprising:
a sinter machine with raw mix input and sinter discharge means at the other end; injection hood;
hood for injection of air preferably by means of a centrifugal fan adapted to generate positive pressure at specified location though a duct with minimum pressure loss where said combustion zone thickness is high to thereby increase the air filtration velocity, reduce the combustion zone thickness at the discharges end and increase the hot zone permeability for increased sinter productivity.
8. A system for sintering with increased sinter machine productivity as claimed in claim 7
wherein the injection hood is in a location 65-80% of the length of the machine from the
charging side.
9. A system for sintering with increased sinter machine productivity as claimed in anyone of
claims 7 or 8 wherein the hood is provided over the length of the machine such that the hot
zone width extension is restricted.
9
10. A sintering process for increasing sinter machine productivity and a system for use in
such sintering process substantially as herein described and illustrated with reference to the
accompanying figure.