CLIAMS:We Claim:

1. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines comprising:
sinter mix permeability control means comprising a water supply control in balling drum into which water is sprayed involving water flow meters, a conveyor for carrying the wet sinter mix underneath the open bottom end of the balling drum and moisture meter, a shuttle hopper into which the wet sinter mix is delivered from the conveyor , load cells for weighing the wet sinter mix contained in shuttle hopper, a drum feeder provided at the bottom of the shuttle hopper to discharge the wet sinter mix into a sinter machine , an air compressor unit to supply controlled compressed air at predetermined pressure and flow rate including air flow control means operatively connected to the wet sinter mix contained in the shuttle hopper and a computer means adapted for favouring said controlled granulation and bed voidage for permeability maximization of sinter mix and obtaining desired near maximum permeability Pmax by increasing bed voidage activating corresponding moisture control of said feed mix in said balling drum.

2. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in claim 1 comprising means for said activating corresponding moisture control of said feed mix in said balling drum based on the said desired intended maximum permeability comprising cooperative actuator/controller assembly for controlling flow rate of water from a water pipeline into the wet sinter mix in said balling drum.

3. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 or 2 wherein said computer means is adapted to receive inputs on sinter machine speed, balling drum speed, hopper weight, air pressure, air flow, feed rate, moisture, balling drum water flow actual and generate signals for activating controlled balling drum water flow to reach permeability maximization by increasing bed voidage by moisture control of said feed mix.

4. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 to 3 comprising involving on-line information about sinter mix material parameters.

5. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 to 4 comprising a feed backward system wherein the computer means evaluates intended moisture content to be increased / decreased in the sinter mix and during the computer control operation the operator can intervene to adjust water feed control, if required, especially in case of significant change in operational regime such that in next cycle the water feed control is activated / adjusted by the computerised system based thereon.

6. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 to 5 comprising
(a) means for sensing sinter machine speed , balling drum rpm and hopper level and feeding to said computer means to ascertain operation of the sinter machine;
(b) said computer means adapted to for the sinter mix feed and determining the point of operation on said curve;
(c) said computer means adapted to compute the amount of water to be increased or decreased to reach near Pmax on moisture permeability parabolic curve.

7. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 to 6 wherein said operations (a) to (c) are repeated after every time the wet sinter mix travels from baling drum to hopper when the next feedback is collected for subsequent desired control of water flow to required to reach/maintain the near Pmax on moisture permeability parabolic curve.

8. A method for increasing productivity of sinter machines by sinter mix permeability maximization by controlled granulation and bed voidage involving the system as claimed in anyone of claims 1 to 7 comprising:

controlling sinter mix permeability comprising a water supply control in balling drum into which water is sprayed involving water flow meters, a conveyor for carrying the wet sinter mix underneath the open bottom end of the balling drum and moisture meter, a shuttle hopper into which the wet sinter mix is delivered from the conveyor , load cells for weighing the wet sinter mix contained in shuttle hopper , a drum feeder provided at the bottom of the shuttle hopper to discharge the wet sinter mix into a sinter machine , an air compressor unit to supply controlled compressed air at predetermined pressure and flow rate including air flow control means operatively connected to the wet sinter mix contained in the shuttle hopper and
involving a computer means for controlled granulation and bed voidage for permeability maximization of sinter mix and obtaining desired near maximum permeability Pmax by increasing bed voidage activating corresponding moisture control of said feed mix in said balling drum.

9. A method as claimed in claim 8 comprising activating corresponding moisture control of said feed mix in said balling drum based on the said desired intended maximum permeability comprising cooperative actuator/controller assembly for controlling flow rate of water from a water pipeline into the wet sinter mix in said balling drum.

10. A method as claimed in anyone of claims 8 to 9 comprising carrying out a feed backward method wherein the computer means evaluates intended moisture content in the sinter mix and during the computer control operation the operator can intervene to adjust water feed control, if required, especially in case of significant change in operational regime such that in next cycle the water feed control is activated / adjusted by the computerised system based thereon.

11. A method as claimed in anyone of claims 8 to 10 wherein the method is carried out after ensuring the sinter machine operation comprising the steps of
(a) sensing sinter machine speed , balling drum rpm and hopper level and feeding to said computer means to ascertain operation of the sinter machine;
(b) determining the point of operation on moisture permeability parabolic curve for the sinter mix feed and determining the point of operation on said curve through computer;
(c) generating through said computer means the amount of water to be increased or decreased to reach near Pmax on moisture permeability parabolic curve.

12. A method as claimed in claim 11 wherein said steps (a) to (c ) are repeated after every time the wet sinter mix travels from baling drum to hopper when the next feedback is collected for subsequent desired control of water flow to required to reach/maintain the near Pmax on moisture permeability parabolic curve.

Dated this the 11th day of March, 2014
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

,TagSPECI:FIELD OF THE INVENTION

The present invention relates to a permeability maximization system by controlled granulation and bed voidage of sinter mix for increasing productivity of sinter machines through water flow control in balling drum and a method for such sinter mix permeability maximization. More particularly, the present invention is directed to system and method for maximization of sinter bed permeability by water flow rate alongwith other process parameters are monitored and controlled to operate the process maintaining permeability close to the Pmax value of the parabolic permeability-moisture curve which leads to increase in sinter machine speed and thus increasing the productivity of sinter plant.

BACKGROUND OF THE INVENTION

In view of the fact that productivity of sinter machine depends on permeability of sinter bed amongst other factors, bed permeability as a function of green mix moisture was studied on a laboratory scale by varying the moisture content. Importantly , it was known that the productivity of sinter machines increases with increase in the permeability of sinter mix .The permeability of sinter mix being influenced greatly by the moisture content thereof and it was thus necessary to optimize the moisture content to sinter mix to increase the productivity of sinter machines.

Applicants provided a solution in this regard by way of a patented system/device under granted Indian Patent no. 199446 (Application No. 2113/CAL/1998 Dt. 2nd Dec 1998) titled “An automatic on-line sinter mix permeability control device for increasing the productivity of sinter machine in steel plants” wherein there was disclosed and claimed an automatic on-line sinter mix permeability control device for increasing the productivity of sinter machines in steel plants by controlling water flow to green mix at balling drum in relation to a computed optimum moisture content based on input signals relating to various operating parameters.

Inspite of the above advancement proposed by the Applicants there has been further studies carried out by the Applicants to achieve better control over the water flow control in balling drum in the process of working on the sinter mix prior to its introduction in the sinter machine to achieve better sintering capability and productivity.

In particular, sinter bed permeability is reported in Japanese Permeability Unit (JPU) and is calculated using the widely accepted equation1 for green sinter mix
JPU = (1)

Where F = Air flow rate (m3 min-1),
A = Cross sectional area of the bed (m2),
L = Height of the bed (mm)
and ΔP = Pressure drop across the bed (mm H2O).
In view of the fact that productivity of sinter machine depends on permeability of sinter bed amongst other factors, bed permeability as a function of green mix moisture was studied.

To achieve improvement in productivity of sinter machine, further studies were undertaken in one of the Steel Plants of the applicants’, involving technical advancement in online moisture control of feed mix to increase the productivity and product quality of sinter plant in order to meet the ever increasing demand of sinters for enhanced hot metal production.

In order to further investigate the possibilities of improving sinter mix permeability for enhancing sinter productivity as well as increased sinter machine speed, experiments and trials have been conducted to link the raw material characteristics and its effect on granulometry and bed voidage vis-à-vis water addition to green mix.

However, there has been a persistent need for a more reliable and quickly responding online system for moisture control of feed mix in balling drum to attain maximum bed permeability
taking into account the wide variation in feed mix characteristics and its impact on the granulation and bed voidage and consequently bed permeability, which the present invention has targeted to solve.

OBJECTS OF THE INVENTION

Thus the basic object of the present invention is directed to a sinter mix permeability maximization system and method by controlled granulation and bed voidage for increasing productivity of sinter machines.

A further aspect of the present invention is directed to a sinter mix permeability maximization system wherein a scheme for permeability optimization is developed and applied to achieve machine operation near Pmax based on a permeability-moisture curve by auto controlling appropriate amount of water flow in balling drum.

A still further object of the present invention is directed to a sinter mix permeability maximization system and method wherein appropriate instruments are provided to collect and input data on sinter machine speed, balling drum speed, hopper weight, air pressure, air flow, feed rate, moisture, balling drum water flow actual are fed to the computer and generate signals for activating controlled balling drum water flow to reach permeability maximization by increasing bed voidage by moisture control of said feed mix.

A still further object of the present invention is directed to a sinter mix permeability maximization system and method wherein the system is activated when sinter machine is in operation and production is taking place based on machine speed, balling drum rpm and hopper level.

A still further object of the present invention is directed to a sinter mix permeability maximization system and method which can be adapted to provide for a feedback control for water flow in balling drums.

SUMMARY OF THE INVENTION

Thus according to the basic aspect of the present invention there is provided a sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines comprising:
sinter mix permeability control means comprising a water supply control in balling drum into which water is sprayed involving water flow meters, a conveyor for carrying the wet sinter mix underneath the open bottom end of the balling drum and moisture meter, a shuttle hopper into which the wet sinter mix is delivered from the conveyor, load cells for weighing the wet sinter mix contained in shuttle hopper, a drum feeder provided at the bottom of the shuttle hopper to discharge the wet sinter mix into a sinter machine, an air compressor unit to supply controlled compressed air at predetermined pressure and flow rate including air flow control means operatively connected to the wet sinter mix contained in the shuttle hopper and a computer means adapted for favouring said controlled granulation and bed voidage for permeability maximization of sinter mix for obtaining desired near maximum permeability Pmax by increasing bed voidage activating corresponding moisture control of said feed mix in said balling drum.

A further aspect of the present invention is directed to said sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines comprising means for said activating corresponding moisture control of said feed mix in said balling drum based on the said desired intended maximum permeability comprising cooperative actuator /controller assembly for controlling flow rate of water from a water pipeline into the wet sinter mix in said balling drum.

A still further aspect of the present invention is directed to a sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines wherein said computer means is adapted to receive inputs on sinter machine speed, balling drum speed, hopper weight, air pressure, air flow, feed rate, moisture, balling drum water flow actual and generate signals for activating controlled balling drum water flow to reach permeability maximization by increasing bed voidage by moisture control of said feed mix.

A still further aspect of the present invention is directed to said sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines comprising a feed backward system wherein the computer means evaluates intended moisture content in the sinter mix and during the computer control operation the operator can intervene to adjust water feed control, if required, especially in case of significant change in operational regime, such that in next cycle the water feed control is activated / adjusted by the computerised system based thereon.

A still further aspect of the present invention is directed to said sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines comprising
(a) means for sensing sinter machine speed , balling drum rpm and hopper level and feeding to said computer means to ascertain operation of the sinter machine;
(b) said computer means adapted to compute the amount of water to be increased or decreased to reach near Pmax on moisture permeability parabolic curve.

Yet another aspect of the present invention is directed to said sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines wherein said operations (a) to (b) are repeated after every time the wet sinter mix travels from baling drum to hopper when the next feedback is collected for subsequent desired control of water flow to required to reach/maintain the near Pmax on moisture permeability parabolic curve.

A further aspect of the present invention is directed to a method for increasing productivity of sinter machines by sinter mix permeability maximization involving the system by controlled granulation and bed voidage as described above comprising:

controlling sinter mix permeability comprising a water supply control in balling drum into which water is sprayed involving water flow meters, a conveyor for carrying the wet sinter mix underneath the open bottom end of the balling drum and moisture meter, a shuttle hopper into which the wet sinter mix is delivered from the conveyor , load cells for weighing the wet sinter mix contained in shuttle hopper , a drum feeder provided at the bottom of the shuttle hopper to discharge the wet sinter mix into a sinter machine , an air compressor unit to supply controlled compressed air at predetermined pressure and flow rate including air flow control means operatively connected to the wet sinter mix contained in the shuttle hopper and involving a computer means for controlled granulation and bed voidage for permeability maximization of sinter mix and obtaining desired near maximum permeability Pmax by increasing bed voidage activating corresponding moisture control of said feed mix in said balling drum.

A still further aspect of the present invention is directed to said method comprising activating corresponding moisture control of said feed mix in said balling drum based on the said desired intended maximum permeability comprising cooperative actuator /controller assembly for controlling flow rate of water from a water pipeline into the wet sinter mix in said balling drum.

A further aspect of the present invention is directed to said method wherein the method is carried out after ensuring the sinter machine operation comprising the steps of
(a) sensing sinter machine speed , balling drum rpm and hopper level and feeding to said computer means to ascertain operation of the sinter machine;
(b) generating through said computer means the amount of water to be increased or decreased to reach near Pmax on moisture permeability parabolic curve.

A still further aspect of the present invention is directed to said method wherein said steps (a) to (b) are repeated after every time the wet sinter mix travels from baling drum to hopper when the next feedback is collected for subsequent desired control of water flow to required to reach/maintain the near Pmax on moisture permeability parabolic curve.

The objects 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 FIGURES

Figure 1: is the graphical plot of a typical inverted U type parabolic permeability-moisture curve for four different green-mix compositions showing bed permeability as a function of mix moisture implying optimum moisture level for a specific green mix for best permeability.

Figure 2: shows the various segments/regions of the permeability-moisture curve of Figure 1 for further analysis of the nature of variability.

Figure 3: shows the graphical plot of bed voidage as a function of mix moisture.

Figure 4: is the schematic diagram showing the total system for permeability measurement and water flow control for sinter mix permeability maximization by controlled granulation and bed voidage for increasing productivity of sinter machines according to the present invention.

Figure 5: is the schematic presentation of the ideal feed forward model wherein set point is computed based on theoretical calculation using input parameters.

Figure 6: is the schematic presentation of the feed backward model used according to the system of the present invention wherein set point is adjusted based on end results achieved.

Figure 7: is the flow chart showing the steps involved in the method of sinter mix permeability maximization using the system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention is directed to provide a system and a method for permeability maximization of sinter bed by controlled granulation and bed voidage of sinter mix for increasing productivity of sinter machines through water flow control in balling drum

In order to further investigate the possibilities of improving sinter mix permeability for enhancing sinter productivity as well as increased sinter machine speed, experiments and trials have been conducted to link granulometry and bed voidage vis-à-vis water addition to green mix in balling drum.

It is well known that sinter bed permeability is reported in Japanese Permeability Unit (JPU) and is calculated using the widely accepted equation1 for green sinter mix
JPU = (1)
Where F = Air flow rate (m3 min-1),
A = Cross sectional area of the bed (m2),
L = Height of the bed (mm)
and ΔP = Pressure drop across the bed (mm H2O).
Permeability – moisture curve
In view of the fact and based on the above stated the productivity of sinter machine was noted to depend on permeability of sinter bed amongst other factors, bed permeability as a function of green mix moisture was studied on a laboratory scale by varying the moisture content. The result show quadratic equation (parabolic relation) fitted to the experimental data. Accompanying Figure 1 shows a typical inverted U type parabolic permeability-moisture curve implying optimum moisture level for a specific green mix for best permeability. This characteristic permeability-moisture parabolic curves shows that bed permeability increases with increasing moisture before passing through a maxima (Pmax) to decrease thereafter. The green mix composition and granulometry of ore-fines determines the characteristic permeability-moisture parabolic curve (i.e. the spread and the value of Pmax). The characteristic permeability-moisture parabolic curves for four different green-mix compositions were determined in the laboratory. It was evident from these plots that even 1% deviation from the optimum moisture corresponding to Pmax leads to significant drop (~10%) in permeability.

Segmental analysis of permeability – moisture curve
To facilitate a more detailed analysis, a typical permeability curve was analysed as having three regions as shown in Figure 2, wherein Region I extends from low to intermediate moistures and over this range bed permeability steadily increases owing to a tightening of the granule size distribution and an increase in the mean granule size. Region II extends across the centre of the curve, initially increasing before passing through a maximum (Pmax) and decreasing at higher moistures. The transition between region I and region II is determined by the point where the slope of the permeability- moisture curve begins to decrease owing to the reduction in bed voidage caused by granule deformation during handling. Region III is characterized by higher moistures and a steady decrease in bed permeability with increasing mix moisture.

Bed voidage
The results of the bed voidage experiments are presented in accompanying Figure 3. The curves show that after an initial small increase at low moistures, bed voidage remained relatively constant, passing through a maximum before decreasing with further increase in moisture. The initial increase in bed voidage at low moistures can be attributed to the onset of granulation, which results in a narrowing of the granule size distribution and increase in the mean granule size. This decreases the packing efficiency by removing the smaller particles that would normally occupy the void spaces within the bed. However, at intermediate mix moistures, while the granule size distribution continued to tighten, bed voidage remained relatively constant. This result can be attributed to the increase in bed voidage being opposed by decreases caused by granule deformation during pot feeding.

Determination of Factors affecting granulation
It was found by way of the present advancement that the granulation of iron ore fines is an intricate process which is sensitive to subtle changes in the operating conditions. Froude number and space factor was generally fixed, properties associated with the feed such as size distribution, mineralogy and porosity can change over time. Water addition was also found to be another very important variable that together with porosity of the ore and level of water absorption, determines the water available for inter particle adhesion.

Size distribution
It was also traversed that the size distribution certainly affected the height of a permeability curve and moisture at, Pmax the shape is more dependant inherent properties such as porosity, pore size distribution and surface chemistry.

Water for granulation
Most importantly, it was traversed by way of the present advancement that a key requirement for the granulation of iron ore sinter mixes is the ability to form inter-particle liquid bridges. While the volume of surface water can readily be adjusted by changing the level of water addition, liquid absorption can also have a significantly affect on the water for granulation. Green bed permeability can be maintained at lower moistures if absorption is decreased by changing the physical properties of the liquid e.g. sugar addition. Liquid absorption is an important phenomenon during granulation and is partly responsible for the observed differences permeability – moisture curves.

During granulation liquid absorption will depend on a number of factors including the radius of the internal pores, the solid –liquid contact angle, the surface tension of the liquid and the type of pore- open or closed. For a perfectly cylindrical pore open at both ends, capillary pressure will drive the absorption of water until the pore is completely saturated.

The following conclusions emerged from the preceding trials:
 1% deviation from the optimum moisture leads to significant drop in permeability
 Permeability-moisture curves are parabola shaped passing through a maximum.
 The height of the permeability-moisture curve is dependent on the bed voidage and granule mean diameter. Larger granules will yield packed beds with higher permeability.
 Pmax is dependent on porosity of the mix, the level of ultra fines, pore radii and solid – liquid contact angle.
 The shape of the permeability-moisture curve is related to the availability of surface moisture for granulation

Based on the above observation, a system for feed backward automated sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines has been developed. The system and the method of the advancement is directed to maximize the permeability of the green mix for the existing operational regime by adding suitable amount of water. Higher permeability results into faster sinter making process as the bed porosity increases with permeability. Increase in permeability results in higher Burn Through Point temperature. As the sintering process becomes fast one can increase the machine speed to obtain more productivity. Apart from this working environment also becomes less dusty due to suitable amount of moisture in green mix all the time.

It was observed that continuous manual control of moisture with accuracy required in real life dynamics was difficult . Thus by way of the present invention, a scheme for permeability optimization was developed to help in achieving machine operation near Pmax by auto controlling appropriate amount of water flow in balling drum. Siemens S7 417H PLC with STEP 7 programming environment was used for permeability optimization system. Program has been developed using Ladder Logic, Functional Block Diagram (FBD) and Structured Text Language (STL). The model as adapted is based on Level-II PLC process control system and less prone to be by-passed unlike the case of supervisory computer system where the model resides on a separate computer. The software is integral part of the process control PLC and is programmed to start automatically by default whenever the PLC is put on. As the supervisory control system is embedded in the Level-II system it is closely coupled and less prone to be by-passed.

Accompanying Figure 4 is the schematic diagram showing the total system for permeability measurement and water flow control for sinter mix permeability maximization by controlled granulation and bed voidage for increasing productivity of sinter machines according to the present invention.

The system comprises a balling drum in which the required quantity of water is added on the sinter mix carried over a shuttle conveyor placed underneath the balling drum and dropped into a shuttle hopper for feeding the wet sinter mix into a sinter machine by means of a drum feeder, and an air compressor unit to blow air into the wet sinter mix contained in the shuttle hopper to determine the air permeability thereof. The electrical signals corresponding to the relevant parameters such as drop in air pressure, flow rate of air, weight and moisture content of the wet sinter mix in the shuttle hopper, balling drum rpm and sinter machine speed is fed to a computer with a software developed and installed for the purpose for online monitoring and control of the moisture level of the sinter mix by controlling water addition in balling mill to thereby ensure operation at the maximum permeability of the sinter bed.

To obtain the online information relating to process parameters and implement control, the system is equipped with appropriate instrumentation which include a water supply pipe fitted with a water controller/actuator assembly, an orifice plate, two water flow meters placed one on each side of said orifice plate, a balling drum into which water is sprayed from the outlet end of pipe, a shuttle conveyor for carrying the wet sinter mix underneath the open bottom end of the balling drum, and underneath an infrared moisture meter, a shuttle hopper into which the wet sinter mix is delivered from the shuttle conveyor, two load cells, fitted to the shuttle hopper for weighing the wet sinter mix contained therein, a drum feeder provided at the bottom of the shuttle hopper to discharge the wet sinter mix into a sinter machine, an air compressor unit to supply compressed air at predetermined pressure and flow rate , a pipe having its inlet end connected to the compressor unit and outlet end embedded in the wet sinter mix contained in the shuttle hopper and being fitted with an air pressure transducer, an orifice plate and two air flow transducers placed one on each side of the orifice plate and connected to an air pressure-drop transducer and computer means adapted to receive inputs, as electrical signals from the said respective measuring instruments, on sinter machine speed, balling drum speed, hopper weight, air pressure, air flow, feed rate, moisture, balling drum water flow actual and generate signals for activating controlled balling drum water flow to reach permeability maximization by increasing bed voidage by moisture control of said feed mix.

Thus the various process parameters used to control the water addition in balling drum through water flow actuator/controller for permeability maximization include sinter machine speed, Balling Drum Speed, Hopper Weight, Air Pressure, Air Flow, Feed Rate, % moisture, Balling drum water flow Actual, and Balling drum water flow Set Point.

Shape of hopper is tapered. Due to taper shape cross sectional area of the bed as well as the height of the bed has non-linear relation with weight of the sinter mix in hopper. The system derives the hoppers height and the surface area based on the load cell reading. Load cell reading were captured at various levels of the filled hopper. Statistical method was used for deriving curve fitting equation. These equations are used by the computer to calculate the cross sectional area of the bed and the height of the bed based on load cell value. Therefore any change in the shape or size of the hopper will need this exercise to be repeated.

Accompanying Figure 5 is the schematic presentation of the ideal feed forward model wherein set point is computed based on theoretical calculation using input parameters. Permeability optimization scheme controls the water flow in balling drum with the objective to maximize the permeability of the sinter mix. Amount of water to be added in the balling drum can be calculated based on the theoretical calculation. Feed forward model needs some of the raw material characteristics which include:
1) Raw material source
2) Full granulometry of ore fines
3) Wetability characteristics of fine
4) % of return sinter
5) Granulometry of other raw materials
 Coke breeze
 Lime stone
 Dolomite
6) Amount of calcined lime
7) Chemistry of calcined lime etc.
There is practical constraints faced on account of non-availability of continuous on-line information about sinter mix material parameters as above which is impractical in Indian steel plant operation scenario. Moreover, the raw material characteristics have variation in the steel plants. Thus the practical constraints for feed forward model forced to adopt concept of feed backward model.

Accompanying Figure 6 is the schematic presentation of the feed backward model used according to the system of the present invention wherein set point is adjusted based on end results achieved. Theoretically feed backward model is not the ideal one but the concept helped to widen the operational regime of the model and suitable for the multi variance of input raw material characteristics in Indian steel plant operation. This also permitted the model to take advantage of operator’s experience. The operators can put the balling drum water flow control operation in manual mode and thus intervene in case of drastic change of operational paradigm. Being the feed backward model the software records for such changes and starts operating from the new set point adjusted by the operator. Without this model used to take more time to reach the optimum Pmax point after drastic change in operational regime.

Output of the system is to control the water flow in the balling drum. The system can be developed involving either modes of operation – Automatic & Manual. In manual mode the system does not operate rather waits for system to be put in automatic mode for water flow set point calculation. The system is intelligent enough to determine which which part of the slope in U curve of moisture-permeability curve the process is operating. Accordingly it adopts gradual change to reach the Pmax point. In order to reach the close to Pmax point as early as possible water is initially adjusted in bigger jumps, and jumps are reduced gradually as it reaches near the Pmax point. The system thus helps to reach peak of the operational permeability curve. The model adjusts water flow to reach peak as early as possible. Initially bigger jump of water flow is administered which is reduced so as to reach close to the peak.

Accompanying Figure 7 is the flow chart showing the steps involved in the method of sinter mix permeability maximization using the system according to the present invention. It is apparent from Figure 7, that the method is carried out after ensuring the sinter machine operation comprising the steps of
(a) sensing sinter machine speed , balling drum rpm and hopper level and feeding to said computer means to ascertain operation of the sinter machine;
(b) determining the point of operation on moisture permeability parabolic curve for the sinter mix feed and determining the point of operation on said curve through computer;
(c) generating through said computer means the amount of water to be increased or decreased to reach near Pmax on moisture permeability parabolic curve.

Permeability optimization system according to the present invention operates with a feed backward model. Feed forward model is not viable where the process parameter has continuous variation in process parameters like raw material source, granulometry of ore fines, wetability of ore fines, % return sinter, granulometry of other raw materials (coke breeze, lime stone, dolomite etc.), chemistry & amount of calcined lime. The developed model adjusts to the operational regime based on the feedback.

Permeability maximization scheme according to the present invention waits to collect feedback data after each action. Based on the feedback received next action is governed. The system skips action if sinter process parameter not within pre-defined range or marginal change in permeability. It helps to rule out any uncalled-for action on account of malfunctioning of the sensor device or the sensor associated error in measurement or when machine not in operation.
The system and method according to the present invention was tried and found to ensure the following results:
Parameters Result
Water Flow Decrease by ~ 4.5%
BTP Increase ~ 250C
m/c Speed Increase ~ 4.5%
Productivity Increase ~ 4%

It is thus possible by way of the present invention to providing a sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines which favour benefits in terms of increase in air suction through sinter bed, increase in Burn Through Point temperature which leads to increase in sinter machine speed and thus the productivity. Introduction of this system, not only improved the permeability of sinter bed but also led to improvement in suction. Additionally this system led to increase in burn-through point temperature and increase in sinter machine speed. Implementation of this system improved sinter bed permeability which contributed to ~ 4% increase in productivity.
We Claim:

1. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines comprising:
sinter mix permeability control means comprising a water supply control in balling drum into which water is sprayed involving water flow meters, a conveyor for carrying the wet sinter mix underneath the open bottom end of the balling drum and moisture meter, a shuttle hopper into which the wet sinter mix is delivered from the conveyor , load cells for weighing the wet sinter mix contained in shuttle hopper, a drum feeder provided at the bottom of the shuttle hopper to discharge the wet sinter mix into a sinter machine , an air compressor unit to supply controlled compressed air at predetermined pressure and flow rate including air flow control means operatively connected to the wet sinter mix contained in the shuttle hopper and a computer means adapted for favouring said controlled granulation and bed voidage for permeability maximization of sinter mix and obtaining desired near maximum permeability Pmax by increasing bed voidage activating corresponding moisture control of said feed mix in said balling drum.

2. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in claim 1 comprising means for said activating corresponding moisture control of said feed mix in said balling drum based on the said desired intended maximum permeability comprising cooperative actuator/controller assembly for controlling flow rate of water from a water pipeline into the wet sinter mix in said balling drum.

3. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 or 2 wherein said computer means is adapted to receive inputs on sinter machine speed, balling drum speed, hopper weight, air pressure, air flow, feed rate, moisture, balling drum water flow actual and generate signals for activating controlled balling drum water flow to reach permeability maximization by increasing bed voidage by moisture control of said feed mix.

4. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 to 3 comprising involving on-line information about sinter mix material parameters.

5. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 to 4 comprising a feed backward system wherein the computer means evaluates intended moisture content to be increased / decreased in the sinter mix and during the computer control operation the operator can intervene to adjust water feed control, if required, especially in case of significant change in operational regime such that in next cycle the water feed control is activated / adjusted by the computerised system based thereon.

6. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 to 5 comprising
(a) means for sensing sinter machine speed , balling drum rpm and hopper level and feeding to said computer means to ascertain operation of the sinter machine;
(b) said computer means adapted to for the sinter mix feed and determining the point of operation on said curve;
(c) said computer means adapted to compute the amount of water to be increased or decreased to reach near Pmax on moisture permeability parabolic curve.

7. A sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines as claimed in anyone of claims 1 to 6 wherein said operations (a) to (c) are repeated after every time the wet sinter mix travels from baling drum to hopper when the next feedback is collected for subsequent desired control of water flow to required to reach/maintain the near Pmax on moisture permeability parabolic curve.

8. A method for increasing productivity of sinter machines by sinter mix permeability maximization by controlled granulation and bed voidage involving the system as claimed in anyone of claims 1 to 7 comprising:

controlling sinter mix permeability comprising a water supply control in balling drum into which water is sprayed involving water flow meters, a conveyor for carrying the wet sinter mix underneath the open bottom end of the balling drum and moisture meter, a shuttle hopper into which the wet sinter mix is delivered from the conveyor , load cells for weighing the wet sinter mix contained in shuttle hopper , a drum feeder provided at the bottom of the shuttle hopper to discharge the wet sinter mix into a sinter machine , an air compressor unit to supply controlled compressed air at predetermined pressure and flow rate including air flow control means operatively connected to the wet sinter mix contained in the shuttle hopper and
involving a computer means for controlled granulation and bed voidage for permeability maximization of sinter mix and obtaining desired near maximum permeability Pmax by increasing bed voidage activating corresponding moisture control of said feed mix in said balling drum.

9. A method as claimed in claim 8 comprising activating corresponding moisture control of said feed mix in said balling drum based on the said desired intended maximum permeability comprising cooperative actuator/controller assembly for controlling flow rate of water from a water pipeline into the wet sinter mix in said balling drum.

10. A method as claimed in anyone of claims 8 to 9 comprising carrying out a feed backward method wherein the computer means evaluates intended moisture content in the sinter mix and during the computer control operation the operator can intervene to adjust water feed control, if required, especially in case of significant change in operational regime such that in next cycle the water feed control is activated / adjusted by the computerised system based thereon.

11. A method as claimed in anyone of claims 8 to 10 wherein the method is carried out after ensuring the sinter machine operation comprising the steps of
(a) sensing sinter machine speed , balling drum rpm and hopper level and feeding to said computer means to ascertain operation of the sinter machine;
(b) determining the point of operation on moisture permeability parabolic curve for the sinter mix feed and determining the point of operation on said curve through computer;
(c) generating through said computer means the amount of water to be increased or decreased to reach near Pmax on moisture permeability parabolic curve.

12. A method as claimed in claim 11 wherein said steps (a) to (c ) are repeated after every time the wet sinter mix travels from baling drum to hopper when the next feedback is collected for subsequent desired control of water flow to required to reach/maintain the near Pmax on moisture permeability parabolic curve.

Dated this the 11th day of March, 2014
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)

ABSTRACT

TITLE: A SINTER MIX PERMEABILITY MAXIMIZATION SYSTEM BY CONTROLLED GRANULATION AND BED VOIDAGE FOR INCREASING PRODUCTIVITY OF SINTER MACHINES AND A METHOD THEREOF.

The present invention relates to a sinter mix permeability maximization system by controlled granulation and bed voidage for increasing productivity of sinter machines through water flow control in balling drum and a method of its implementation. The invention provides system and method for maximization of bed permeability as a function of green mix moisture wherein the water flow rate is controlled to operate the process maintaining permeability close to the Pmax value of the parabolic permeability-moisture curve involving continuous on-line feed backward system wherein computer evaluated intended moisture content in the sinter mix is continually fed to continuously activate corresponding changes in flow of feed water into the balling drum implemented through a Level-II PLC based process control system leading to increase in sinter machine speed and thus increasing the productivity of sinter plant.
(Figure 4)