Lithium Industry Rotor Dehumidification Unit

Lithium Industry Rotor Dehumidification Unit

In the lithium industry, humidity control of the production environment is one of the core links to ensure product quality and production safety. Especially the key processes of core manufacturing (such as screeding, coating, roller pressing, slitting, stacking / winding, etc.), the environmental humidity requirements are extremely high (usually need dew point temperature ≤ -40 ℃, some high-end production capacity requirements ≤ -50 ℃ or even -60 ℃), ordinary refrigeration dehumidification or adsorption dehumidification equipment is difficult to meet the rotary dehumidification unit because of its high efficiency dehumidification in low humidity environments, the lithium-ion battery industry, become the mainstream choice. Choice.

The core of rotor dehumidification unit is adsorption rotor, and its working principle is based on “adsorption - regeneration” cycle:

Adsorption process: when the moisture-containing air passes through the adsorption area of the rotor, the adsorbent (commonly used silica gel, molecular sieve, or composite adsorbent material) inside the rotor physically adsorbs the moisture in the air, and outputs the dry air with low humidity for sending into the workshop.

Regeneration process: the rotor rotates slowly (usually 8-15 revolutions / hour), adsorbed moisture into the regeneration section of the region, the high temperature (generally 120-180 ℃) of the regeneration air heated, so that the adsorption of moisture desorption and with the regeneration of the exhaust discharge, the rotor to restore the adsorption capacity to achieve continuous dehumidification.

This principle makes the rotor dehumidifier in the treatment of low dew point air (especially dew point ≤ -30 ℃) efficiency is much higher than the freezing dehumidification (freezing dehumidification limit dew point of about 1-5 ℃), so it can meet the lithium industry's ultra-low humidity needs.

In lithium production, moisture is a key “impurity” that affects the performance and safety of the battery:

Moisture will react with lithium salts (such as lithium hexafluorophosphate) in the electrolyte, generating corrosive gases such as HF and destroying the internal structure of the battery;

Moisture will lead to gassing and bulging of the battery cell in the charging and discharging process, and even lead to a short-circuit and combustion risk;

High humidity High humidity will lead to moisture absorption of pole materials (e.g. cathode materials, diaphragm), affecting coating uniformity, roll density and consistency of the battery cell.

In order to adapt to the harsh environment of lithium workshop (high cleanliness, potential corrosion, dust pollution), rotor dehumidification units need to be designed:

1. Multi-stage Dehumidification System Integration

It is difficult for single-stage rotor to treat high humidity air (such as outdoor air in summer) directly to below -40℃, so it is common to use a combination of “pre-treatment + rotor dehumidification” solution:

Pre-treatment section: the dew point of the air is lowered to 10-15℃ by freezing and dehumidifying the air to remove a large amount of sensible and latent heat to reduce the load of the rotor;

Deep dehumidification section: the dew point is further adsorbed by the rotor to reduce the dew point to less than -40℃;

(optional) secondary cooling section: if the workshop needs to control the temperature (usually 20-25℃), it can be used to cool down the dry air and prevent the residual heat of the regeneration process from affecting the room temperature.

2. Anti-corrosion and clean design

There are dust of positive electrode materials (such as ternary materials, lithium iron phosphate) and volatiles of electrolyte (containing fluorine and lithium) in the lithium workshop, which are corrosive to a certain extent, and the air-contacting parts inside the unit (such as the fan, pipeline and filter frame) should be made of 304/316 stainless steel to avoid rusting and corrosion;

is equipped with high-efficiency air filters (HEPA, H13 or above) to ensure that the cleanliness of the dry air sent to the workshop is up to 40℃. Equipped with high-efficiency air filter (HEPA, H13 grade or above) to ensure that the cleanliness of the dry air sent into the workshop reaches Class 1000 (ISO 6) or above, preventing dust from contaminating the batteries.

3. Precise control and stability

adopts PLC + touch screen control system, real-time monitoring of workshop temperature and humidity, rotor regeneration temperature, air volume and other parameters, through frequency conversion to adjust the speed of the feeder fan, regeneration fan, to ensure that the dew point fluctuation ≤ ± 2 ℃;

equipped with dew point sensor (accuracy ± 1 ℃), when the humidity exceeds the standard, automatic alarm and start the backup dehumidification module (large workshops are usually designed with N +1 redundancy), to avoid interruption of production. 4. Energy Saving Optimization

4. Energy Saving Optimization

The regeneration process of rotor dehumidification consumes a large amount of thermal energy (60%-80% of the total energy consumption of the unit), so the lithium industry reduces the energy consumption by the following ways:

Preferred regeneration heat source: steam heating (high efficiency, low cost) or heat pump auxiliary heating (energy saving of more than 30% compared with electric heating);

Waste heat recovery: recover heat from regeneration exhaust gas through heat exchanger to preheat the fresh air;

Time-sharing operation: reduce the load of dehumidification in non-production hours and maintain the workshop at a slightly positive pressure (5-10Pa), which reduces the energy consumption.