Digital Control Systems for Thermal Regimes in Industrial Furnaces

This paper presents methods and solutions for controlling the thermal process in a gas fired furnace system for titan forging. The software implemented solutions aim to achieve better temperature uniformity inside the furnace chamber, possibility of choosing a more cost-effective hardware equipment for lowering initial investment cost, developing the software control in order to achieve a universal temperature furnace suitable for both low and high temperature without the need of recirculation fans, development of software control methods in order to better adjust the burners air/gas ratio in order to obtain a correct furnace atmosphere relative to titan forging technological process demands and reducing NOx emissions. The research was implemented at Zirom SA of Giurgiu within the acquisition project of a system composed of two gas fired forging furnaces with a common heat recovery system delivered by Electro-Total SRL Bucharest. The main results of the implementation are: a temperature uniformity inside the furnace’s chambers of ±5 °C according to the temperature uniformity survey test for both holding temperatures of 650 °C and 1250 °C, a control temperature precision of ±1.5 °C according to the system accuracy test, a very well maintained inside furnace pressure taking in consideration the unique design with a common heat recovery system, a very well maintained low oxidizing atmosphere (λ=1.09) inside the furnace and a very low flue gas emissions (NO x =149 mg/Nm 3 ).