Theoretical Pressure Calculation
To determine the minimum pressure required to inject compressed air into the tank, one must overcome both the existing internal gas pressure and the hydrostatic pressure exerted by the water column.
- Hydrostatic pressure of the water column:The hydrostatic pressure generated by a 20-meter-high water column is approximately 1.96 bar (Calculation formula: P=ρgh, the density of water is approximately 1000 kg/m³) m³, the acceleration due to gravity is taken as 9. 8m /s²).
- Existing gauge pressure of the storage tank:It is known that the current gauge pressure of the storage tank is 1 bar.
Therefore, the theoretically minimum pressure at the injection point is the sum of the two pressures: 1.96 bar + 1 bar =2.96 bar. This means that the pressure of the compressed air must be greater than 2.96 bar Only then can one successfully enter the bottom of the storage tank.
Pressure requirements in practical engineering
In practical industrial applications, meeting the theoretical minimum pressure alone is insufficient. To ensure that compressed air is delivered at a reasonable flow rate and to overcome various system resistances, a sufficient pressure margin must be provided.
- Pipe and Valve Resistance:When air flows through ducts, elbows, check valves, and control valves, pressure losses occur, typically requiring an increase in 0.5 bar To 1 bar The margin.
- Dynamic Volatility:During the gas-injection process, the liquid level may fluctuate, and gas‑demand variations at the point of use can occur; therefore, the gas supply pressure must remain stable.
Taking all factors into consideration, it is recommended that the working pressure for compressed air injection be set at3.5 bar To 4.0 barBetween.
Compressor Selection and Safety Recommendations
After determining the required pressure, selecting the air compressor and designing the system also requires attention to the following key considerations:
- Exhaust pressure:The air compressor’s rated discharge pressure should be slightly higher than the system’s operating pressure; it is recommended to select a rated pressure of 7 bar or 8 bar A conventional industrial air compressor, with the outlet pressure regulated by a pressure-reducing valve to ensure stable air supply.
- Traffic matching:In addition to pressure, the air compressor’s discharge capacity must meet process requirements. Insufficient flow will result in excessively long injection times and fail to achieve the desired process outcomes.
- Safety Protection:The storage tank must be equipped with a safety valve and a pressure gauge. The set pressure of the safety valve shall be higher than the normal operating pressure but lower than the tank’s design pressure, in order to prevent overpressure resulting from operator error or failure of the pressure-reducing valve.
- Backflow prevention design:A check valve must be installed on the compressed air line to prevent water from a 20-meter‑high column from flowing backward into the compressor system during pressure fluctuations or shutdowns.