Insulation Material

In the selection of raw materials, it is essential to choose insulating materials with a porous structure and low thermal conductivity.

The relative density of the thermal insulation material chosen based on the application temperature should be sufficient and the thickness effective. As a result, the temperature gradient between the inside and outside is small, leading to less thermal damage and a significant environmental protection and energy-saving effect.

3. Structural Layers: Standard tunnel furnaces are constructed with metal composite materials for internal surface connections and support points, which have high thermal conductivity,不利于 environmental protection and energy conservation. To facilitate disassembly, ensure non-separable connections, and enhance load-bearing capacity, significant improvements have been made to the metal material connection components located below the lower limit of the internal surface, in reducing the extent of heat transfer damage.

Second, system control

Throughout the drying process, the heating power is generally set to quickly reach the operating temperature, reducing the time to slow down. Once the temperature stabilizes, with the automatic control system of multiple electric heaters in operation, the temperature can be maintained at the output power, ensuring excellent actual effects in terms of environmental protection and energy conservation.

In the past, tunnel kiln management, particularly during non-production modes, typically involved one of two approaches: shutting down the equipment or maintaining a slight pressure difference within the tunnel environment. If the equipment is stopped, it is opened for self-cleaning prior to production; if the pressure difference is maintained, production can be resumed before production begins.

For the first type of treatment, from the perspective of aseptic control, it is actually very dangerous. Because if the tunnel furnace stops running, the internal environment of the furnace (Class A) is actually connected to the ambient environment (Class C or D), which means there is a risk of Class A contamination. The heating and high-temperature sections can be subjected to high-temperature sterilization, but the cooling section (low temperature) cannot be sterilized, and the self-cleaning process itself cannot eliminate microbial contamination. After production resumes, if the cooling section is contaminated, the sterility of the product cannot be guaranteed. This production method poses a high risk of aseptic contamination.

In the case of the latter method, from the perspective of aseptic control, micro-pressure differentials hinder external contamination, while microbial contamination is exogenous. By blocking the exogenous contamination source, asepsis can be maintained, thus the aseptic risk of the latter method is relatively low.

However, equipment cannot run indefinitely; there will always be times when it needs to be stopped, such as for maintenance. So, how should the environment inside the tunnel oven be handled? In the past, after tunnel oven maintenance, space sterilization methods (VHP or formaldehyde) were used for sterilization. Personally, I believe this method poses little risk, but it is important to note:

When conducting space sterilization validation, consider the sampling points within the tunnel oven.

2. After disinfection, personnel entering the tunnel kiln area should promptly activate the tunnel kiln's laminar flow to maintain a slight pressure difference inside; this is not just before production starts. During the preparation phase for production, if personnel enter the area, it introduces new sources of contamination. Failure to activate the laminar flow and maintain the slight pressure difference poses a risk of secondary contamination.

The above is the traditional method of operation. Today, in a discussion with friends, we mentioned that some new equipment will add sterilization features to the cooling section of tunnel furnaces (e.g., 170 degrees Celsius for 90 minutes).

From a conceptual standpoint, this is feasible, and if well implemented, it would also be beneficial for ensuring the sterility of tunnel ovens. For instance, after production, we can shut down the machinery and then disinfect the tunnel oven before production resumes, which can save energy consumption of the tunnel oven and maintain a micro-pressure difference. However, from a practical perspective, I believe there are still some issues worth exploring:

1. By employing dry heat sterilization, we recognize that achieving uniformity in dry heat sterilization is actually quite challenging. For dry heat sterilization ovens, maintaining even heat distribution under relatively enclosed conditions is difficult. If not ensured, temperatures must be raised; will the extended operation of the cooling section be affected?

2. If sterilization is required, the machine is shut down after the tunnel furnace production is completed, and then resumed. With such high frequency, would the energy consumption be lower than maintaining a low pressure difference? If it's only used frequently, as previously analyzed, shutting down is not advisable; if a small pressure difference is maintained in between, is this only to address the sterilization issue after the cooling section is shut down? Isn't VHP the same? Is it practical?

The basic principle of the tunnel furnace involves using far-infrared for controlled heating inside the furnace. It is constructed with ceramic and stainless steel, allowing infrared light to reach every corner for even heating and energy transfer to the objects. The high-tech insulation material boasts excellent thermal insulation and strong heat retention. The heating process can utilize far-infrared heating system technology with well-placed heating elements, resulting in low energy consumption. Internal hot air circulation enhances energy efficiency. The control system employs PID microcomputer technology, with three heating zones: indirect drying, analyzing the products dried in the tunnel furnace and their low moisture content.

A tunnel furnace is an industrial heating equipment with wide applications, such as food processing, electronic assembly, and chemical production, which require baking or heating processes. The basic working principle of tunnel furnaces primarily involves three methods: high-temperature heating, microwave heating, and infrared heating. As tunnel furnaces are inherently high-energy consumption products, with the strong promotion of energy conservation and emission reduction policies, technological transformations in the production field of tunnel furnaces are proceeding at a high pace. After a long period of understanding and analysis, most manufacturers are striving to develop various types of heating elements. Currently, most tunnel furnaces utilize four heating methods: electric heating, gas heating, thermal oil heating, and hot air heating. China's tunnel furnace industry has reached a certain stage and is basically catching up with developed countries. However, in terms of energy conservation, there is still much to be desired. The future development trend of tunnel furnace products will be towards low-energy consumption.