Rotor Air Cooled Dehumidifier for Battery Raw Material Workshop

Rotor Air Cooled Dehumidifier for Battery Raw Material Workshop Constant Temperature Dehumidification

In lithium battery production, the environmental temperature and humidity control of the raw material workshop (such as lithium salt, cathode materials, anode materials, diaphragm and other storage and pretreatment areas) directly affects the raw material activity, stability and subsequent processing performance. High humidity will lead to raw material moisture absorption caking (such as lithium iron phosphate moisture absorption after the decline in electrical conductivity), chemical reaction (such as lithium metal in contact with water exothermic), and even trigger a safety risk; and temperature fluctuations may change the physical characteristics of the raw material (such as particle size, fluidity). Rotor dehumidifier with “deep dehumidification + easy to integrate with temperature control system”, become the core equipment for constant temperature dehumidification of battery raw material workshop.

The core of rotor dehumidifier is the moisture absorbing rotor and temperature and humidity control system, through the “adsorption dehumidification + regeneration cycle + temperature compensation” three steps to achieve the goal:

1. Rotor dehumidification basic principle (deep dehumidification core)

moisture absorbing rotor: the surface of the rotor is full of porous moisture absorbing materials (commonly used in the battery workshop molecular sieve or modified silica, high chemical corrosion resistance, and low humidity), and the rotor can be used in the battery workshop for the production of low temperature dehumidification. The surface of the rotor is covered with porous moisture absorbing material (molecular sieve or modified silica gel is commonly used in battery workshops, which is highly resistant to chemical corrosion and has high moisture absorbing efficiency at low humidity). The rotor rotates slowly (usually 10-20 revolutions/hour) and is divided into the “treatment zone” and the “regeneration zone”.

Dehumidification process: high humidity air (high humidity) in the workshop flows through the “treatment zone” of the rotor, water vapor is adsorbed by the moisture-absorbing material (physical adsorption, no chemical reaction), and the humidity content of the air is greatly reduced (can be reduced to ≤1% RH), becoming low humidity air.

Regeneration process: At the same time, high-temperature regeneration air (usually 120-180 ℃, generated by electric heating, steam or gas heating) flows through the runner “regeneration zone”, the water vapor adsorbed by the moisture-absorbing material is evaporated and brought out, so that the runner restores the moisture-absorbing capacity and completes the cycle.

2. Synergistic design for thermostatic control (key to temperature stabilization)

The dehumidification process alone will be accompanied by temperature changes (hygroscopicity is an exothermic reaction, and the temperature of the processed air will increase by 5-10°C), which need to be balanced by the following systems:

Pre-cooling / Surface Cooler: Before dehumidification, high humidity air is first cooled down by the surface cooler (removing part of the sensible heat, and at the same time lowering the humidity content), to reduce the load of moisture absorption of the rotor, and to avoid high temperature after dehumidification.

Reheater / Heater: If the low humidity air after dehumidification has a low temperature (e.g. in winter), it will be warmed up to the set temperature (20-25℃) by a heater (electric heating or hot water coil).

Closed-loop temperature control system: High-precision temperature and humidity sensors (accuracy ±0.5℃, ±1% RH) are installed in the workshop, and the real-time feedback data is given to the PLC control system, which automatically adjusts the output power of the meter cooler and heater to ensure that the temperature of the air supply is stabilized in the target range.

Through the closed-loop process of “dehumidification and heat release → surface cooling → reheating and temperature adjustment”, the air sent into the workshop finally meets the requirements of “low humidity” and “constant temperature” at the same time.

Battery raw material workshop dust, chemical characteristics and safety regulations, the requirements of rotor dehumidifier must be optimized for the design:

1. Corrosion and pollution resistant design

raw material workshop may exist lithium salt dust (such as LiPF₆), in the presence of water to form acidic substances, the need to use corrosion-resistant materials (such as 316 stainless steel) to make air ducts, rotor frames;

moisture absorbing materials preferred molecular sieve (acid-resistant superior to silica gel) to avoid the decay of moisture absorption performance after long-term use. Prefer molecular sieve for moisture absorbing material (better than silica gel in acid resistance), to avoid the attenuation of moisture absorbing performance after long-term use.

2. Explosion-proof and safety performance

Some of the raw materials (such as graphite powder) belong to combustible dust, the workshop should meet the explosion-proof standard (such as Ex tD A21), dehumidifier motors, fans need to be explosion-proof (such as Ex dⅡBT4);

regeneration heater needs to be equipped with over-temperature protection devices (such as temperature sensors + automatic power off), to avoid high temperatures triggering the combustion of dust.

3. Cleanliness control

Raw materials need to avoid impurity contamination, dehumidification system needs to be integrated with multi-stage filtration: primary filtration (G4) intercepts large particles of dust, intermediate filtration (F8) removes particles above 1μm, and high-efficiency filtration (H13) can be added in some areas with high demand for cleanliness (e.g., diaphragm pre-processing).

Rotor and air duct design needs to be smooth with no dead ends, to avoid the build-up of dust that can breed bacteria.

4. Low energy consumption and stability

The regeneration energy consumption is high in deep dehumidification (≤1% RH). Heat recovery devices (such as rotor heat exchanger) can be used to recover the waste heat of the regenerated exhaust air to preheat the fresh air and reduce the energy consumption for heating (energy saving of 20-30%).

Key components (such as rotor drive motor, heater) are designed with redundancy (one for each), to avoid a single point of failure that leads to the exceeding of the humidity standard in the workshop.

1. Selection of core parameters

dehumidification: according to the volume of the workshop (length × width × height), the number of air changes (usually 15-20 times / h, high humidity raw materials take the upper limit), the initial humidity (such as the outside world 30 ℃ / 60% RH) and the target humidity (such as 1% RH) calculations, need to take into account the amount of raw materials, such as bags of raw materials to open the moisture absorption and dissipation of humidity;

regeneration of heat sources: preferably steam heating (lower cost) or electric heating (temperature control precision) Regenerative heat source: prefer steam heating (lower cost) or electric heating (high precision of temperature control, suitable for explosion-proof workshop), gas heating needs to pay attention to explosion-proof safety;

Temperature control range: Ensure that the adjusting capacity of heater/epidermic cooler covers 20-25℃, and the fluctuation is ≤±0.5℃;

Rotor area: Calculate based on the processing air volume and wind speed (1.5-2.5m/s is recommended), the bigger the area, the higher the dehumidification efficiency (but the volume of the equipment increases). The larger the area, the higher the dehumidification efficiency (but the volume of equipment increases).

2. Daily operation and maintenance

Daily inspection: monitor the temperature and humidity of the workshop (make sure it is within the set range), regeneration temperature (avoid too high or too low), filter differential pressure (need to be cleaned/replaced if it is more than 1.2 times of the initial value);

Weekly maintenance: clean the primary/intermediate filters, and check the smooth rotation of the rotor (to avoid jams that lead to uneven dehumidification);

Monthly maintenance: calibrate the temperature and humidity sensors (use a standard meter to compare. Monthly maintenance: calibrate the temperature and humidity sensor (compare with a standard meter, and adjust if the deviation exceeds 0.5℃ or 1% RH), and check the sealing of explosion-proof parts;

Annual maintenance: replace the high-efficiency filter (if any), test the performance of moisture-absorbent materials (e.g., determine the decay of adsorption capacity by weighing, and replace the rotor if necessary), and clean the dust in the air ducts (to avoid corrosion or clogging).