FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL
Specification
(See section 10 and rule 13)
FIELD OF PROCESS CONTROL EQUIPMENT
(a) TATA CONSULT ANY SERVICES LTD.
an Indian Company
of Bombay House, 24, Sir Homi Mody Street, Mumbai 400 001, Maharashtra, India, and
and
(b) TATA SPONGE IRON LTD.
an Indian Company
of P. O. Joda, Dist. Keonjhar, Orissa 758 034, India
THE FOLLOWING SPEC IFICATION DESCRIBES THE INVENTION.

Field of Invention
This invention relates to the field of process control equipment.
In particular the invention relates to system for optimizing kiln operations.
Background of Invention:
A Rotary kiln is a pyroprocessing device used to raise materials to a high temperature and produce sponge iron or direct reduced iron in a continuous process using iron ore and coal. The kiln is a cylindrical vessel, inclined slightly to the horizontal, which is rotated slowly about its axis. The material to be processed is fed into the upper end of the cylinder. As the kiln rotates, material gradually moves down towards the lower end, and may undergo a certain amount of stirring and mixing. Hot gases pass along the kiln, sometimes in the same direction as the process material, but usually in the opposite direction. The hot gases may be generated in an external furnace, or may be generated by a flame inside the kiln. Such a flame is projected from a burner-pipe which acts like a large Bunsen burner. The fuel for this may be gas, oil or pulverized coal.
The temperature profile inside the kiln, available on-line, is accurate only during the initial period of a sponge iron rotary kiln campaign and its accuracy deteriorates over a period of time due to accretion. The operator then is left with essentially no on-line information about the process to optimize and control the process. The operator has to take corrective actions based on hourly laboratory analysis and kiln shell temperatures. There are


several variables, such as air flow rates, coal flow rates and kiln speed, that can be manipulated in order to control the process. Since these corrective measures are taken manually, which to a large extent depend on operator's judgment, the kiln performance is bound to be sub-optimal. In addition to this, accretion inside the kiln compounds the problems faced by plant engineers and operators.
Thus there was a need for a tool which will improve the plant productivity and optimize the kiln operations.
Objects of invention:
The object of this invention is to provide a system for optimizing the operations of a kiln.
Another object of this invention is to provide a tool which will help in increasing kiln campaign life.
Still one more object of this invention is to provide a tool which will help to increase the kiln throughput.
Another object of this invention is to provide a tool which will help in reducing the consumption of coal.
Yet another object of this invention is to provide a tool which will increase the plant profitability.

Still one more object of this invention is to provide a tool for kiln optimization which is easy to use.
Yet another object of this invention is to provide a system which works as an advisory optimization system in on-line mode and which works as a simulator in off-line mode
Summary of the Invention:
The tool in accordance with this invention envisages means for optimizing the operations of a rotary kiln comprising,
a computational engine;
means for detecting flow rate of iron ore, coal and air;
means to detect the temperature inside the kiln at various points;
means for detecting the moisture content of iron ore and coal;
means for detecting the speed of rotation of the rotary kiln;
means to predict the temperature profile inside the kiln;
means to predict the performance parameters of the rotary kiln;
analysis and logic means for analyzing the results of the system; and
means to predict degree of metallization.
In accordance with one practical embodiment of this invention, said optimization system comprises a set of computational means for computing the overall material and energy balances for gas and solid phases, material balances for individual species in each phase and height of the solids bed along the kiln length. The optimization system is based on fundamental principles of heat and mass transfer between solids, gases and the kiln wall.


The system for modeling of kinetics of reactions involving hematite, magnetite, carbon, oxygen, carbon monoxide and hydrogen, and the flow of solids inside the kiln are incorporated into the system. In order to predict gas and solid phase temperature and concentration profiles along the kiln length, the rotary kiln is divided into a number of slices or computational elements. The generic computational slice incorporates input streams for injection coal and secondary air also so that the effect of modifying the locations as well as properties of these lateral inputs can be simulated. For this purpose the material and energy balances for gas and solid phases and mass balances for individual species in each phase are solved by the system.
In accordance with one practical embodiment of this invention, the optimization system includes a database which is accessed by the computational engine and inputting means for inputting real time and laboratory analysis data relating to the kiln for tuning the operations of the kiln. The gas and solid temperature profiles measured using Quick Response Thermocouples and the metallization achieved are used for tuning and validating the simulation and optimization system.
In accordance with one practical embodiment of this invention, the system includes analysis and logic means for challenging the computational engine with hypothetical possible scenarios in the kiln to determine the effect of important variables such as iron to carbon ratio on metallization, rate of accretion etc. These challenges result in simulated results which can be analyzed and optimized to identify conditions for increasing kiln throughput while maintaining sponge iron quality within desirable limits.


In accordance with one practical embodiment of this invention, the system for optimization of kilns can be employed in a predictive mode to determine optimum settings, for variables such as feed and injection coal flow rates, and primary and secondary air flow rates for a given iron ore flow rate, while maintaining metallization at an optimum level. The optimization system predicts the internal kiln conditions from feed to discharge end and the outputs for a given set of input parameters. It can predict the steady-state results of the rotary kiln by using the model in accordance with this invention.
In accordance with one practical embodiment of this invention, the optimization system works in off-line or on-line mode. In on-line mode the system is interfaced with the actual plant through a PLC or DCS. It can be subsequently employed in future for system based on-line optimization and control. The optimization system can be employed for different operating conditions and for raw materials of different quality.
Brief Description of the Accompanying Drawings:
The invention will now be described with reference to the accompanying drawings, in which
Figure 1 of accompanying drawings illustrates a block diagram showing the various input and output parameters for the optimization system;
Figure 2 of accompanying drawings illustrates a block diagram showing the structure of the optimization system; and


Figure 3 of accompanying drawings illustrates a block diagram of the optimization system, PLC and the rotary kiln in operative conditions.
Detailed Description of the Accompanying Drawings:
According to this invention there is provided a tool for optimizing the operations of a rotary kiln comprising,
a computational engine;
means for detecting flow rates of iron ore, coal and air;
means to detect the temperatures inside the kiln at various points;
means for detecting the moisture content of iron ore and coal;
means for detecting the speed of rotation of the rotary kiln;
means to predict the temperature profile inside the kiln;
means to predict the performance parameters of the rotary kiln;
analysis and logic means for analyzing the results of the system; and
means to predict degree of metallization.
The rotary kiln optimization system comprises a set of differential equations, which includes overall material and energy balances for gas and solid phases, material balances for individual species in each phase and height of the solids bed along the kiln length.
Fig 1 of the accompanying drawings illustrates a system showing the inputs and outputs for a rotary kiln. The optimization system is required to be given flow rates of iron ore, coal and air. The optimization system outputs the temperature profile of the rotary kiln, which can be used to tune the kiln operations to obtain maximum throughput.


Fig 2 of accompanying drawings illustrates a block diagram showing the structure of the system for the rotary kiln optimization. The system is based on fundamental principles of heat and mass transfer between solids, gases and the kiln wall. Appropriate systems for kinetics of reactions involving hematite, magnetite, carbon, oxygen, carbon monoxide and hydrogen, and the flow of solids inside the kiln are incorporated into the model. In order to predict gas and solid phase temperature and concentration profiles along the kiln length, the rotary kiln is divided into a number of slices or computational elements. The generic computational slice incorporates input streams for injection coal and secondary air also so that the effect of modifying the locations as well as properties of these lateral inputs can be simulated. For this purpose the material and energy balances for gas and solid phases and mass balances for individual species in each phase can be solved by the system in accordance with this invention. The system includes a database which is accessed by the computational engine and inputting means for entering real time and laboratory analysis data relating to the kiln for tuning the operations of the kiln. The gas and solid temperature profiles measured using Quick Response Thermocouples and the metallization achieved are used for tuning and validating the system.
The system includes analysis and logic means for challenging the computational engine with hypothetical possible scenarios in the kiln to determine the effect of important variables such as iron to carbon ratio on metallization, rate of accretion etc. These challenges provide results which can be analyzed and optimized to identify conditions for increasing kiln throughput while maintaining sponge iron quality within desirable limits.


The rotary kiln system of this invention can be employed in a predictive mode to determine optimum settings for variables such as feed and injection coal flow rates, and primary and secondary air flow rates for a given iron ore flow rate, while maintaining metallization at an optimum level. The optimization system can predict the internal kiln conditions from feed to discharge end and the outputs for a given set of input parameters. It can predict the steady-state results of the rotary kiln by using the system in accordance with this invention.
The optimization system works in off-line or on-line mode. In on-line mode the system is interfaced with the actual plant through a PLC or DCS It can be subsequently employed in future for model-based on-line optimization and control. The model can be employed for different operating conditions and for raw materials of different quality.
Fig 3 of accompanying drawings illustrates a block diagram of the optimization system, PLC/DCS and the rotary kiln in operative conditions. The system in accordance with this invention is connected to the PLC. The PLC is in turn connected to the rotary kiln. In off-line mode the optimization system works as a simulator, and in on-line mode it optimizes the operations of the rotary kiln.
While considerable emphasis has been placed herein on the various components of the preferred embodiment, it will be appreciated that many alterations can be made and that many modifications can be made in the preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiment as well as other embodiments of the invention will be apparent to those skilled in the


art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.