Dehydration Tunnel Drying Line

The dehydration tunnel drying line is a continuous material drying equipment widely used in the industrial production field. Its core function is to achieve efficient dehydration and drying of various materials through a tunnel - type enclosed cavity structure combined with a specific heating and air supply system. It has the advantages of automation, large - scale operation and precise temperature control, and can meet the strict requirements of different industries for material drying quality and efficiency.

I. Core Components

The structural design of the dehydration tunnel drying line centers on "continuous conveying + precise drying" and mainly consists of five core systems:

1. Tunnel - type Drying Cavity

As the main body of the equipment, it is usually made of stainless steel, which has good airtightness and high - temperature resistance, effectively reducing heat loss. The interior of the cavity is divided into different functional sections such as a preheating zone, a constant - temperature drying zone and a cooling zone. The temperature and air speed in each zone can be adjusted independently to meet the full - process needs of material drying.

2. Conveying System

It mainly adopts conveying methods such as mesh belts, chain plates or pallets. The appropriate carrier is selected according to the material shape (such as granular, flaky, blocky, liquid - attached, etc.). The conveying speed can be steplessly adjusted by a frequency - conversion motor to ensure that the residence time of materials in each drying section is accurately controllable, avoiding over - drying or incomplete drying.

3. Heating and Temperature Control System

There are various flexible heating methods, such as electric heating tube heating, hot air circulation heating, infrared heating and steam heating. The selection can be made according to material characteristics (such as heat sensitivity, temperature resistance) and production costs. Equipped with an intelligent temperature control instrument and a temperature sensor, it can control the temperature inside the cavity within an accuracy range of ±1℃, ensuring stable drying quality.

4. Air Supply and Moisture Exhaust System

Through the design of fans and air ducts, uniform circulation of hot air inside the cavity is realized, avoiding uneven material drying caused by local temperature differences. At the same time, a moisture exhaust device is equipped to timely discharge the moisture generated during the material drying process, maintain a suitable humidity environment inside the cavity, accelerate the dehydration efficiency and reduce energy waste.

5. Electrical Control System

It adopts a PLC (Programmable Logic Controller) and a touch - screen operation interface, integrating functions such as start - stop, speed adjustment, temperature setting and fault alarm. It is easy to operate and has a high degree of intelligence. Some high - end equipment also supports remote monitoring and data recording, facilitating the management and traceability of the production process.

II. Working Principle

The working process of the dehydration tunnel drying line follows the logic of "continuous conveying - segmented drying - precise temperature control - real - time moisture exhaust", and the specific steps are as follows:

1. Material Feeding

Materials to be dried (such as food raw materials, plastic semi - finished products, electronic components, etc.) are evenly laid on the conveyor belt through manual or automatic feeding devices. For liquid or pasty materials, they need to be formed into a specific shape by pre - treatment equipment (such as a coating machine, a forming machine) before entering the conveying system.

2. Preheating Stage

Materials enter the preheating zone of the tunnel cavity along with the conveyor belt. At this time, the temperature inside the cavity gradually rises to the set preheating temperature (usually 60% - 80% of the material's temperature resistance). Through hot air conduction and radiation, the surface moisture of the materials evaporates initially, and at the same time, material deformation, discoloration or nutrient loss caused by a sudden temperature rise is avoided (especially for food - type materials).

3. Constant - Temperature Drying Stage

After preheating, the materials enter the core drying zone. The temperature in this zone is maintained at the set drying temperature (which can be adjusted between 40℃ and 200℃ according to material requirements). Hot air circulates continuously inside the cavity, and heat is transferred to the interior of the materials through three heat transfer methods: convection, conduction and radiation, promoting the rapid vaporization of moisture in the materials. At the same time, the moisture exhaust system is started synchronously to timely discharge the moisture generated by vaporization, maintain a low - humidity environment inside the cavity and further accelerate the dehydration process.

4. Cooling Stage

The dried materials enter the cooling zone at the tail of the tunnel. Through cold air or natural cooling, the temperature of the materials gradually drops to near room temperature, avoiding oxidation, deterioration or deformation of the materials due to direct discharge at high temperatures, and at the same time facilitating subsequent packaging, storage or deep processing operations.

5. Finished Product Discharging

The cooled and dried materials are moved out of the tunnel cavity along with the conveyor belt and collected by an automatic unloading device. Some equipment can also be linked with subsequent processes such as screening and testing to realize integrated production from drying to finished product processing.

III. Application Scenarios

With its flexible adaptability and efficient drying capacity, the dehydration tunnel drying line is widely used in many industries. The following are typical application fields and scenarios:

1. Food Processing Industry

It is often used for fruit and vegetable dehydration (such as raisins, dehydrated vegetables, dried nuts), meat drying (such as cured meat, beef jerky, pet food), grain processing (such as rice and corn drying) and snack production (such as potato chip and biscuit drying and shaping). Due to the use of food - grade stainless steel and precise temperature control, it can effectively retain the nutrients, color and flavor of food, and meet food hygiene and safety standards (such as FDA and HACCP certification requirements).

2. Plastic and Rubber Industry

It is mainly used for the drying treatment of plastic particles, plastic films and rubber products to remove moisture from raw materials, avoiding defects such as bubbles and cracks in the subsequent injection molding, extrusion and forming processes. For example, in the production of plastic bottles, the drying line is needed to remove moisture from PET particles first to ensure that the transparency and strength of the bottle body meet the standards.

3. Electronic and Hardware Industry

It is suitable for moisture - proof drying of electronic components (such as capacitors, resistors and circuit boards) and drying of surface coatings of hardware parts (such as electroplating layers and paint film curing for screws and bearings). Through low - temperature (40℃ - 80℃) slow drying or high - temperature (120℃ - 180℃) rapid curing, it ensures the insulation performance of electronic components and the coating adhesion of hardware parts.

4. Pharmaceutical and Chemical Industry

It is used for the drying of Chinese herbal medicines (such as honeysuckle and wolfberries), pharmaceutical intermediates and chemical raw materials (such as powder and granular chemical products). Due to the good airtightness and corrosion resistance of the equipment, it can prevent materials from contacting with external impurities, and at the same time meet the special requirements of the pharmaceutical industry for cleanliness (such as GMP certification) and the chemical industry for explosion prevention and corrosion resistance.

5. Building Materials and Papermaking Industry

In the building materials field, it is used for the drying and shaping of gypsum boards and fiberboards. In the papermaking industry, it is used for the drying treatment of paper and paperboards. By controlling the drying temperature and speed, it ensures the flatness and strength of boards or paper and reduces the deformation rate.

IV. Advantages and Characteristics

Compared with traditional batch - type drying equipment (such as ovens and drying rooms), the dehydration tunnel drying line has the following significant advantages:

1. Efficient Continuous Production

Adopting an assembly line operation mode, it does not require frequent start - stop of the equipment and loading/unloading of materials, and can realize 24 - hour uninterrupted production, greatly improving production efficiency. Taking food processing as an example, a medium - sized dehydration tunnel drying line can process several tons to dozens of tons of materials per day, far exceeding the processing capacity of batch - type ovens.

2. Uniform and Stable Drying Quality

Through the hot air circulation system and segmented temperature control design, the temperature and air speed inside the cavity are evenly distributed. Materials are always in a stable drying environment during the conveying process, avoiding uneven drying caused by local temperature differences. At the same time, by adjusting the conveying speed and temperature parameters, the final moisture content of materials can be accurately controlled (usually between 0.5% and 5%), ensuring consistent quality of each batch of products.

3. Energy Conservation and Consumption Reduction

The enclosed tunnel cavity reduces heat loss, and the hot air circulation system can reuse heat, reducing energy consumption. Some equipment is also equipped with a waste heat recovery device to recover the heat in the exhausted moisture to the drying zone, further improving energy utilization efficiency. Compared with traditional ovens, it can save energy by 30% - 50%.

4. High Degree of Automation

Integrated with a PLC control system and a touch - screen operation interface, it does not require a large number of manual interventions. Only 1 - 2 operators are needed to complete equipment monitoring and parameter adjustment. At the same time, it has a fault automatic alarm function (such as abnormal temperature, conveyor belt jamming, fan failure, etc.), which can timely remind for maintenance and reduce production interruption time.

5. Strong Adaptability

It can be customized in terms of cavity length (usually 5m - 30m), conveyor belt width (usually 0.5m - 2m), heating method and temperature control range according to material shape, characteristics and production requirements, meeting the drying needs of different industries and materials. For example, for heat - sensitive fruit slices, low - temperature hot air drying can be adopted; for high - temperature resistant hardware parts, high - temperature infrared drying can be used.

V. Operation and Maintenance Points

1. Operation Precautions

• Before starting the equipment, check the tension of the conveyor belt, the operation status of the fan and the temperature control system to ensure that all components are normal before starting.

• When feeding, ensure that materials are evenly laid to avoid uneven drying caused by local excessive accumulation or damage to the conveyor belt due to overloading.

• During operation, monitor the temperature, humidity and conveyor belt speed inside the cavity in real time. If abnormal parameters are found, adjust them in a timely manner.

• Before shutting down the equipment, stop feeding first. After all materials on the conveyor belt are moved out of the cavity, turn off the heating system, continue to operate the fan and conveyor belt for 10 - 15 minutes, and turn off the main power supply after the temperature of the cavity drops below 60℃ to avoid damage to the equipment due to high - temperature residual heat.

2. Daily Maintenance Points

• Daily Cleaning: After production, clean the residual materials on the conveyor belt, wipe the inner wall of the tunnel cavity and the air duct to avoid the impact of caked residual materials on subsequent drying quality or bacterial growth (especially in the food industry).

• Regular Inspection: Check the wear condition of the conveyor belt every week. If deviation or damage occurs, adjust or replace it in a timely manner; check the working status of the heating tube, fan and temperature sensor every month to ensure the normal operation of the components; perform dust removal and line inspection on the electrical control system every quarter to avoid short circuits or poor contact.

• Lubrication and Maintenance: Add lubricating oil to the moving parts such as the conveyor belt bearings and motor bearings every month to reduce wear and extend the service life of the equipment.

• Replacement of 易损 Parts: According to the equipment usage frequency and working conditions, regularly replace 易损 parts such as heating tubes, sealing rings and conveyor belts to avoid equipment failure or deterioration of drying quality due to aging of parts.

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