Gas-water separation for screw air compressor

During the operation of the screw air compressor, the compressed air will carry a large amount of water (including liquid water and gaseous water vapor). If it is not effectively separated, it will cause equipment corrosion, pipeline blockage, and product quality degradation at the gas end. Gas-water separation is the core part of the screw air compressor post-processing system, its principle, equipment type, selection points and maintenance methods are as follows:

principle of 1. gas-water separation

gas-water separation is mainly based on inertial separation, gravity sedimentation, centrifugal separation and filtration adsorption such as physical principles, through a combination of different equipment to achieve efficient water removal:

1. inertial separation:
   when compressed air flows at high speed, water droplets impact the inner wall or baffle of the separator due to inertia, form a liquid film and flow down along the wall to achieve gas-liquid separation.
2. gravity settlement:
   under the action of gravity, the larger water droplets naturally settle to the bottom of the separator and are discharged through the drain valve.
3. centrifugal separation:
   by changing the direction of the air flow (such as spiral deflector), the water droplets are thrown to the wall under the action of centrifugal force to achieve separation.
4. filtration adsorption:
   the use of hydrophilic filter (such as glass fiber, stainless steel wire mesh) to capture small droplets, through the condensation of the formation of large droplets after discharge.

Main equipment for 2. gas-water separation

in the post-treatment system of screw air compressor, gas-water separation is usually realized by the following equipment combination:

1. gas tank:
   • role: As a primary separation device, by reducing the airflow speed (usually ≤ 0.3 m/s), large particles of water droplets and impurities settle to the bottom of the tank.
   • Features: Simple structure, low cost, but limited separation efficiency (about 70%-80%), regular drainage is required.
2. Pre-filter (pre-filter):
   • role: Further separate liquid water droplets and solid particles above 5μm to protect the subsequent precision filter.
   • Type: Common cyclone type or baffle type, the separation efficiency can reach more than 90%.
3. Freeze dryer:
   • role: The compressed air is cooled to 3-5°C through the refrigeration system, so that the water vapor is condensed into liquid water, and then discharged through the gas-water separator.
   • Features: It can remove most of the gaseous water, the pressure dew point can reach 2-10 ℃, but the energy consumption is high.
4. adsorption dryer:
   • role: Using activated alumina or molecular sieve and other adsorbents to further remove residual water vapor, the pressure dew point can reach -20 ℃ to -70 ℃.
   • Features: It is suitable for scenes with extremely high requirements for dryness (such as electronics and pharmaceutical industries), but it needs to be regenerated regularly and the operating cost is high.
5. Precision filter (post filter):
   • role: Filter small water droplets and oil mist above 0.01μm to ensure that the output air quality meets the ISO 8573-1 standard.
   • Type: Commonly used as a coalescing filter, the separation efficiency can reach 99.99%.

Key Points of Selection of 3. Gas-water Separation Equipment

1. processing Volume Matching:
   according to the air compressor displacement (such as 10m & sup3;/min), select the separation equipment to ensure that the processing capacity ≥ the rated flow of the air compressor, and avoid the decrease of separation efficiency caused by overload.
2. Pressure dew point requirement:
   • general industrial scenario: pressure dew point ≤ 10 ℃ (refrigeration dryer can meet).
   • High-precision scene: pressure dew point ≤-40 ℃ (adsorption dryer + precision filter combination required).
3. separation efficiency:
   • primary separation (gas tank + pre-filter):≥ 90%.
   • Deep drying (refrigeration + adsorption dryer):≥ 99.9%.
4. Material and corrosion resistance:
   select the material according to the compressed air composition (such as stainless steel for corrosive gas environment, carbon steel for ordinary air).
5. Drainage mode:
   • automatic drain valve: suitable for continuous operation scenarios, reducing manual maintenance.
   • Manual drain valve: suitable for intermittent operation or low cost scenarios.

Maintenance and Optimization of 4. Gas-water Separation System

1. regular drainage:
   • the air storage tank and pre-filter shall be drained daily to avoid secondary pollution caused by accumulated water.
   • Refrigerated dryers need to regularly check whether the condensate discharge is smooth.
2. Filter Material Replacement:
   • pre-filter element: replace every 3000-5000 hours (or alarm according to differential pressure).
   • Precision filter element: replace it every 2000-4000 hours to ensure filtration efficiency.
3. Regeneration cycle adjustment of dryer:
   • the adsorption dryer needs to adjust the regeneration time according to the amount of gas (usually switch the adsorption tower every 4-8 hours).
   • Refrigerated dryers need to clean the condenser regularly to ensure refrigeration efficiency.
4. System Leak Check:
   • regularly check the connection of pipes and valves for air leakage to avoid waste of compressed air and moisture infiltration.
5. Environmental Control:
   • keep the air compressor room well ventilated to avoid high temperature causing condensate to evaporate and re-enter the system.

5. Typical Application Scenarios and Configuration Scheme