The Fraunhofer-Center HTL offers a variety of measurement methods to analyze industrial furnaces on site and identify any potential for improvement. These methods are suitable for the analysis of pusher plate, tunnel, conveyor, roller, ring, chamber or drying furnaces and drying chambers. The goals are the analysis of the energy balance of furnaces on the one hand and the assessment of the temperature and atmosphere distribution in the furnace on the other. The former is used to improve energy efficiency, the latter to improve product quality.
The measuring capabilities for the energy balance range from a simple thermographic imaging of the furnace through the wireless data transfer from within the burning process right up to the complete energetic analysis of the system. Infrared cameras which measure the temperature at the outer shell of the furnace are used for the thermography. The heat losses at the charge and additives can be detected as well. Additionally, the energy transfer to the environment is determined at characteristic points. The energy and power consumption of electrical equipment (fans, pumps, heaters) can be detected without contact. In addition, flow and temperature of the furnace exhaust gases are measured. With ultrasonic measuring technology, the energy flow in the cooling water can be examined. For this purpose the flow in the pipes as well as the temperature determined before and after the furnace section can be and the energy flow is calculated without having to open the pipes.
The quality of the heat treatment depends strongly on the distribution of temperature and atmosphere inside the furnace; and experience has shown that the quality of the heat treatment often exhibits great opportunities to improve the product features. For the measurement of the temperature distribution in the furnace, specifically-designed and calibrated temperature measurement rings are used. The measurement of furnace atmosphere and the flow velocity inside the furnace is made possible by high-temperature probes and gas sampling 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 appropriate 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. During drying processes, a wired high-temperature scale can provide valuable information on the progress of drying, by transferring weight, flows, temperature and humidity.
With these methods, the Fraunhofer-Center HTL is able to identify simple opportunities for optimization of industrial furnaces. For instance, thermal leaks and aging of the insulation are detected through an analysis of the infrared images and the heat flow. With the aid of computer simulation methods, a detailed analysis of potential savings can be offered. The dimensions of the furnace are recorded and completed by present design drawings. The high temperature properties of the main furnace materials are - if not already known - measured at Fraunhofer-Center HTL. Then, the heat treatment is simulated in a simplified FE model of the furnace and validated using the measured values. Through further simulations possible improvements in terms of achievable power efficiency and product quality can be assessed. This eliminates time consuming and costly experiments which are difficult to perform, especially during production.