Contents:
- What is critical point?.
- Supercritical fluid – Definition.
- Super heated vapor – Definition.
- Applications of supercritical fluid.
- Applications of super heated vapor.
- Difference between Supercritical Fluid and super heated vapor.
Before understanding supercritical fluid and Superheated vapor,we must understand the concept of critical point in phase diagram.
What is Critical point?
The temperature and pressure above which the substance becomes supercritical.
For example:
Carbon dioxide (CO₂): Critical temperature ~31.1°C, critical pressure ~73.8 atm.
Water (H₂O): Critical temperature ~374°C, critical pressure ~218 atm.
Critical Temperature (Tc):.
- The highest temperature at which a substance can exist as a liquid, regardless of the applied pressure.
- Above the critical temperature, the substance cannot be liquefied, no matter how much pressure is applied. Instead, it transitions into a supercritical fluid.
- Units: Typically measured in Kelvin (K) or Celsius (°C).
Critical Pressure (Pc):
- The minimum pressure required to liquefy a substance at its critical temperature.
- At this pressure and temperature, the liquid and gas phases become indistinguishable, forming a single, homogeneous supercritical phase.
- Units: Typically measured in atmospheres (atm), bar, or Pascals (Pa).
Supercritical fluid – Definition
A supercritical fluid is a state of matter that occurs when a substance is subjected to a temperature and pressure above its critical point, where it exhibits properties of both a gas and a liquid.
In this state, the fluid does not have a distinct liquid or gas phase but instead combines characteristics of both:
It has the density of a liquid, allowing it to dissolve substances like a solvent.
It has the viscosity of a gas, enabling it to flow easily and diffuse rapidly through materials.
Applications of Supercritical Fluids:
Supercritical CO₂ Extraction: Used in decaffeinating coffee, extracting essential oils, and cannabis processing.
Chemical Reactions: Used as a reaction medium in green chemistry due to its environmentally friendly nature.
Power Generation: Supercritical water is used in advanced power plants to improve efficiency.
Materials Processing: Used in cleaning, drying, and manufacturing of materials like aerogels.
High Solvent Power: Many supercritical fluids are excellent solvents, which is useful in applications like extraction.
Super heated vapor – Definition:
refers to a vapor (or gas) that has been heated to a temperature higher than its saturation temperature (the temperature at which the liquid boils at a given pressure), without increasing the pressure. In this state, the vapor is no longer in equilibrium with its liquid phase.
Superheated vapor is completely free of liquid droplets.
Example :
For water at 1 atmosphere (101.3 kPa):
The boiling (saturation) temperature is 100°C.If steam at 1 atm is heated to 120°C, it becomes superheated steam.
Applications of Super heated vapor:
Steam Turbines: Superheated steam is used in turbines for power generation to improve efficiency and prevent condensation.
Industrial Drying: It is used in drying processes due to its high heat content and low moisture.
Chemical Processes: Superheated vapor is employed as a reaction medium in some industrial processes.
Difference between Supercritical Fluid and super heated vapor:
A superheated vapor is in the gas phase and above its boiling point at a given pressure.
A supercritical fluid exists above the critical temperature and pressure, where the distinction between liquid and gas phases disappears.
Also Read :
- Phase Diagrams.
- pvt Relations.
- Triple point.
