Design and Fault Analysis of a High Voltage Igniter used in Blast Furnace

Abstract

The project is aimed at designing a pilot ignition system for different purposes and thus analyse its faults and rectify it. The applications can be as varying as blast furnace, which is the main objective of the project, to solid fuel based propulsion systems. The project work can be easily divided into two parts, one is the designing of the electrical circuit most suitable for the application and secondly the investigation of the reasons of failure of that circuit with practical run time data provided by the Rourkela Steel Plant.
The circuit design of a High Voltage Igniter coil was done only after weighing other techniques available to ignite a fuel. The advantage of a high voltage impulse circuit is evident from the kinetic model of fuels which are mostly alkanes or the mixture of several alkanes. The previously postulated circuit models and existing standard IEC 60060-61 has been adhered to and the simulation of those circuits were done using MATLAB/Simulink. The varying output performance and high transient fluctuation renders most of the HV impulse circuits not so useful in igniter application. The standard and the postulated circuits are for lightening or switching surge generations meant for testing equipment and not for heavy duty industrial application such as pilot igniter.
Hence, a combination of several techniques such as high voltage impulse generation, high current impulse generation and high frequency impulse generation has been done to find out one circuit which has the virtues of all these techniques. This circuit is also aided by additional wave shaping technique and selective pulse generation scheme according to the fuel being fed to the system. The scheme enables the circuit to automatically adjust its pulse duration according to the amount of amount of heat energy needs of that particular hydrocarbon/ hydrocarbon mix. The MATLAB code is functional for major industrial gaseous fuels such as Natural Gas, LPG, Acetylene, Coke-oven gas and EGM (Enriched Gas Mixture).
The next attempt has been done to provide a theoretical approach towards the sequential operation of the igniter which can be controlled by PLCs (Programmable Logic Controllers). The circuit and the sequence have been designed using NE555 timer and high rated thyristor and transistor such as BT151 and TIP122. Real time fuel based testing of the hardware circuit is the goal for the future along with the need to creating a PLC code for the sequential algorithm conceptualized till now.