Critical gas pressure is used in combination with critical gas temperature and represents the critical point where distinct liquid and gas phases do not exist. In most gases, an increase in pressure can liquefy a gas at corresponding temperatures. Similarly, a large decrease in temperature can also liquefy a gas at corresponding pressures. However, when a gas is above the critical pressure, there is no temperature that will cause a phase change. A regulator is a device that can be set to control gas pressure, even the critical gas pressure. Typically, a regulator has a natural pressure drop across the internals and if a gas is approaching its critical pressure, the pressure drop will decrease the system pressure.
- High-pressure gas regulator
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Instructions
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1
Determine the critical pressure of the gas to be regulated. For instance, assume carbon dioxide is being used at or near its critical pressure of 1073 pounds per square inch.
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2
Determine the pressure drop of the carbon dioxide regulator. Assume that at a flow rate of 1,000 pounds per hour, the pressure drop is 125 psi.
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3
Set the pressure regulator at 1198 psi (1073 + 125) at a flow rate of 1,000 pounds an hour. This regulator will keep the flow of carbon dioxide at or below its critical pressure.
