What causes water to appear in the exhaust of an adsorption dryer when liquid spawn fermentation ?

The adsorption dryer is a critical component of the air supply system for edible mushroom fermentation tanks. A malfunction can cause downstream precision filters to fail, allowing contaminants to enter the tank and compromise the fermentation process.

During site visits to edible mushroom facilities, I routinely inspect the air supply system's operation; on several occasions, I have observed water discharging from the adsorption dryer's exhaust.

The exhaust process involves purging the regeneration tower with dry air to remove and discharge desorbed moisture. The presence of water in the exhaust indicates a malfunction in the adsorption dryer—an issue that requires immediate attention and resolution.

There are four primary causes:

1. Excessive moisture content in the inlet air

This occurs when upstream equipment fails—specifically the refrigerated dryer—allowing air with high moisture content to enter the adsorption dryer.

2. Refrigerated dryer not running

The refrigerated dryer may be turned off or have tripped due to a fault. Consequently, air with high moisture content enters the adsorption dryer; the desiccant becomes saturated, and the excess moisture is expelled through the exhaust valve's silencer during the regeneration cycle.

3. Excessive air compressor inlet temperature

This often occurs during hot summer months. High-temperature intake air heats up further during compression, exceeding the refrigerated dryer's processing capacity and allowing excessive moisture to reach the adsorption dryer.

4. Clean air demand exceeds system capacity

An increase in the number of fermentation tanks can push clean air demand beyond the air supply system's design capacity—specifically exceeding the refrigerated dryer's limits—resulting in excessive moisture entering the adsorption dryer.

While air supply system anomalies during liquid spawn production for edible mushroom fermentation tanks do not always lead to contamination—thanks to multi-stage filtration and the protection provided by the tank's own filters—they do increase the risk of contamination and complicate the testing of the liquid spawn. Therefore, it is essential to remind liquid spawn technicians to attach importance to the air supply system, regularly check its operating status, and promptly address any abnormalities.