What is the pressure of the air compressor commonly used for fermentation?

Technical description on pressure parameters of fermentation process air compressor

As the core power equipment of the fermentation process, the setting of pressure parameters of the air compressor directly affects the microbial culture efficiency and production energy consumption. The pressure requirements and system design points under different fermentation scenarios are now specified as follows:

1. Pressure specifications for aerobic fermentation process

1. Base pressure range：
   • The recommended pressure range for standard aerobic fermentation processes is 0.25-0.35MPa (gauge pressure), which can meet the metabolic needs of most microorganisms while balancing energy efficiency.
   • Large-scale fermentation systems (single tank volume>300m³) are recommended to adopt segmented gas supply design. The pressure in the main gas supply pipeline is maintained at 0.35MPa, and the branch pipelines are equipped with pressure reducing valves to adjust to 0.2-0.25MPa.
2. key influencing factors：
   • Geometric parameters of fermentation tank: For every 10 meters increase in the tank height, an additional 0.1MPa pressure needs to be compensated to overcome the static pressure of the liquid column.
   • solution physical parameters: When the viscosity of the medium is greater than 50cP, the gas supply pressure needs to be increased by 0.05-0.1MPa to ensure oxygen transfer efficiency.
   • Filtration system resistance: The precision filter set (including the main filter, pre-filter, and fine filter) produces a pressure drop of 0.03-0.05MPa, and a pressure margin should be reserved during design.

2. Special requirements for anaerobic fermentation processes

1. pressure control strategy：
   • It is recommended to maintain a micro-positive pressure environment of 0.15-0.25MPa (gauge pressure) for basic anaerobic fermentation to prevent the risk of bacterial contamination caused by infiltration of external air.
   • Special process scenarios (such as immobilized cell culture) require a pressure pulsation device to promote carrier fluidization through periodic pressure changes of 0.1MPa.
2. Key points of equipment selection：
   • Oil-free screw air compressors are preferred to avoid lubricating oil polluting the anaerobic environment.
   • Equipped with a dual-unit redundant system, when the main unit fails, it can automatically switch to the standby unit to maintain stable fermentation tank pressure.

3. System energy-saving design specifications

1. Pressure step utilization：
   • Three-level pressure design is adopted: the outlet of the air compressor is 0.5MPa→ the pressure of the air storage tank is stabilized to 0.4MPa→ the fermentation workshop is divided into two routes for gas supply (main process 0.35MPa/back-cleaning 0.25MPa).
   • Install an intelligent pressure regulating valve to automatically adjust the air supply pressure according to the real-time air consumption. The pressure can be reduced to 0.1MPa during idle time.
2. Pipe network optimization plan：
   • The main gas supply pipe diameter is designed at an economic flow rate of 8m/s, and the elbow adopts a large-radius arc transition with R>5D.
   • Annular compensation pipelines are set up every 50 meters to reduce the pressure drop during long-distance transportation. Actual measurement can reduce the pressure loss by 15%-20%.

4. Expansion of special application scenarios

1. Special design of large-scale fermentation tank：
   • Fermentation tanks with volume>500m³ shall be equipped with annular gas distribution system at the bottom, and each gas distribution branch pipe shall be equipped with independent pressure regulating valve to ensure bubble diameter <3mm at the depth of 5 meters below liquid level.
   • Install the tank top pressure balancing device, and control the pressure fluctuation in the tank within ±0.01MPa by linking the exhaust valve with the micro-pressure sensor.
2. Sterility safeguards：
   • Before entering the fermentation system, compressed air needs to undergo three stages of filtration: pre-filter (1μm) → precision filter (0.01μm) → sterilization filter (0.001μm).
   • Equipped with an online dew point monitor to ensure that the gas supply dew point is ≤-40℃ to prevent the breeding of miscellaneous bacteria in condensed water.

5. Operation and maintenance standards

1. Daily inspection requirements：
   • Record the exhaust pressure, temperature and oil level of the air compressor every 2 hours, and trigger a sound and light alarm when the parameters are abnormal.
   • Check the vibration intensity of the pipeline every week. When the amplitude is greater than 0.15mm, check the fixing status of the pipe clamp.
2. Annual maintenance items：
   • The main engine of the air compressor was overhauled and the rotor clearance was tested. When the wear amount was greater than 0.2mm, it needed to be returned to the factory for repair.
   • Verify the tripping pressure of the safety valve and replace it immediately if the error exceeds ±3%.

It is recommended that enterprises establish an energy efficiency evaluation system for compressed air systems and monitor specific power (kW/m³/min) indicators in real time by installing smart meters and flow meters. For continuous operation systems, a waste heat recovery device can be configured to use air compressor exhaust heat to prepare 60℃ process hot water, and the measured energy saving rate can reach 15%-20%.