Fraunhofer-Center HTL offers a variety of measuring methods to analyze industrial furnace systems on site. The methods are suitable, for example, for the analysis of pusher plate furnaces, tunnel furnaces, belt furnaces, roller furnaces, ring furnaces or chamber furnaces. Objectives are the determination of the energy balance on the one hand and the determination of the temperature and atmosphere distribution in the furnace on the other hand. The recording of the energy balance serves to improve energy efficiency, the recoding of temperature and atmosphere distribution to improve product quality.
The measurement options for energy balancing range from a simple thermographic image of the furnace to the complete energetic recording of the system. For the thermography, infrared cameras are used, which measure the temperature at the outer shell of the furnace. In addition, the heat losses of the kiln furniture and the furnace accessories can be recorded. Furthermore, the energy output to the environment is determined at characteristic locations. The energy consumption or the power consumption of electrical consumers, such as fans, pumps or heaters, can be measured non-contact. In addition, flow, composition and temperature of the furnace exhaust gases are measured. Using ultrasonic measurement technology, the energy flow in the cooling water can be analyzed. For this purpose, the flow in the pipes, the temperature before and after passing the furnace as well as the energy flow is calculated without having to open the pipes.
The quality of the heat treatment depends to a large degree on the temperature distribution and the atmosphere inside the furnace and often exhibits potential for improvement of the product properties. Specially developed and calibrated temperature measuring rings are used to measure the temperature distribution inside the furnace. The measurement of the furnace atmosphere and the flow speed inside the furnace is made possible by high-temperature measuring sensors and gas extraction lances. In addition, process parameters can be obtained directly and wirelessly from the process using high-temperature sensor boxes. The measurement from the combustion chamber can be applied to batch or continuous furnaces with suitable size and temperature and includes parameters such as temperature, pressure or atmospheric flows. In inert gas furnaces, electrochemical sensors are used in the furnace exhaust air. In drying processes, a wired high-temperature scale can provide valuable information concerning the progress of drying by transferring weight, currents, temperature and humidity.
With these methods, it is possible to identify simple optimization possibilities in industrial furnaces. For example, thermal leaks and aging of the insulation are detected by analysis of the infrared images and the heat flow. Using computer simulation methods, detailed potential analyses of the furnace can also be offered at the HTL (see furnace analysis). For this purpose, the dimensions of the furnace are recorded and completed using existing design drawings. The high-temperature properties of the most important furnace materials are, as far as not known, specially measured at the HTL. Afterwards, the heat treatment is simulated in a simplified FE model of the furnace and validated based on the measured values. Further simulations can then evaluate improvements with regard to the achievable energy efficiency and product quality. This eliminates time-consuming and costly experiments, which are particularly difficult to carry out in production.