DC Furnace Monitoring System

Introduction

This 2 MW DC furnace was created in a picturesque location, north-west of Johannesburg, some years back. As a low cost and experimental project, the designer and supplier of the power and control system was an inspired furnace designer. We got caught up in the novelty and undertook to provide a lowest cost furnace monitoring system.

The customer is a globally significant producer of specialized nickel magnesium, ferro-nickel magnesium and other master alloys. The products are used in a wide variety of applications in the foundry, aerospace, power, petrochemical and motor industries.

Being a DC furnace, the design was intended to specifically smelt fines.

Primarily, we had to monitor 24 temperatures as well as the AC and DC power parameters.

Temperatures monitored included the exit water temperature of the furnace shell cooling, the roof ring, the thyristor temperatures as well as the transformer oil temperature and the reactor temperature.

The furnace is used to process batches of fines. The furnace is preloaded and then started while further feeding until melting is completed. Then the carbon cathode extracted, the tap hole opened and the furnace tilted to pour out the molten alloy.

Cold water is used for the furnace cooling using several rings around the furnace as well as water cooling the lid and the anode.

In addition to monitoring the furnace temperatures our system also monitors several of the key rectifier component temperatures.

In this application we used 24 digital temperature sensors with 1 x 16 Input DigiTemp Transmitter and 1 x 8 Input DigiTemp Transmitter for 24 temperature inputs, 1 x MCI for 8 analogue inputs to interface to the various current, voltage and phase angle transmitters and 1 x 8 Relay output module for the alarm outputs. All the Danntech modules communicate using RS485. These all located in the main control panel with the PC used for logging and display located some 30 metres away in a control room.