Liquid Ethylene Density Calculator

About the Liquid Ethylene Density Calculator

Ethylene (C₂H₄) is the world's most produced organic chemical, with annual global production exceeding 200 million tonnes. In its liquid state, ethylene is a cryogenic fluid with a boiling point of −103.7°C at atmospheric pressure and a critical temperature of 9.2°C. Accurate density data for liquid ethylene is essential for process design, storage tank sizing, pipeline engineering, and metering in the petrochemical industry.

Liquid ethylene density varies significantly with temperature and pressure. At its normal boiling point (−103.7°C, 1 atm), liquid ethylene has a density of approximately 567 kg/m³. As temperature increases toward the critical point (9.2°C, 50.4 bar), density decreases substantially, approaching the critical density of 214 kg/m³. Above the critical temperature, ethylene exists as a supercritical fluid where liquid and gas phases are indistinguishable.

This calculator uses established correlations to estimate liquid ethylene density across a wide range of conditions encountered in industrial practice. From cryogenic storage at atmospheric pressure to high-pressure pipeline transport, the density values help engineers calculate mass flow rates, determine vessel sizing, and ensure safe material handling. Understanding ethylene's thermophysical properties is fundamental to the design and operation of ethylene crackers, polyethylene reactors, and refrigeration systems.

When This Page Helps

Essential for petrochemical engineers designing ethylene storage, transport, and processing systems. Calculate density for tank gauging, pipeline sizing, and heat exchanger design. Also useful for cryogenic engineering and refrigeration system design.

How to Use the Inputs

1. Enter the temperature in Celsius or Kelvin.
2. Specify the pressure in bar, atm, or psi.
3. View the estimated liquid density and other thermophysical properties.
4. Use presets for common industrial conditions.
5. Check the saturation table for boiling temperatures at various pressures.
6. Compare properties at different conditions using the reference table.
7. Verify that temperature and pressure are within the liquid region.

Example Calculation

Tips & Best Practices

• Always verify you're in the liquid region — below the saturation temperature at your pressure.
• For custody transfer metering, use official NIST data rather than correlations for maximum accuracy.
• Liquid ethylene is lighter than water — it will float on water and boil violently if spilled on water surfaces.
• The thermal expansion coefficient is much larger near the critical point — density changes rapidly with temperature.
• For polyethylene reactors, ethylene is typically supercritical (above Tc) at reactor conditions.
• Safety note: liquid ethylene is extremely flammable with a wide flammable range (2.7-36% in air).

Industrial Applications

Ethylene is the primary feedstock for polyethylene (HDPE, LDPE, LLDPE), ethylene oxide, ethylene dichloride, and styrene — products that form the backbone of the plastics and chemicals industry. Steam crackers produce ethylene by thermal decomposition of hydrocarbons (ethane, naphtha, gas oil) at 800-900°C. The product ethylene is then purified by cryogenic distillation at temperatures down to −160°C, where accurate thermophysical property data is critical for column design and operation.

Storage and Transportation

Large-scale ethylene storage uses fully refrigerated tanks operating near atmospheric pressure at −104°C. These double-wall, insulated tanks can hold up to 60,000 m³ of liquid ethylene. Ethylene is also transported by pipeline (over 30,000 km of ethylene pipelines exist globally), typically as a dense-phase or supercritical fluid. Pipeline design requires accurate density and viscosity data across the operating temperature and pressure range. For marine transport, semi-pressurized or fully-refrigerated ethylene carriers transport up to 12,000 m³ per voyage.

Comparison with Other Light Hydrocarbons

Ethylene is lighter than propylene (liquid density ~610 kg/m³ at NBP) and butane (~584 kg/m³). Its critical temperature (9.2°C) is much lower than propane (96.7°C) or butane (152°C), meaning it requires cryogenic conditions for liquefaction at moderate pressures. Methane, the lightest hydrocarbon, has even lower critical temperature (−82.6°C). This progression explains why natural gas (mostly methane) requires LNG technology at −162°C, while LPG (propane/butane) can be stored as liquid at ambient temperature under modest pressure.

Frequently Asked Questions

• Why is liquid ethylene density important?

  Ethylene is transported and stored as a cryogenic liquid. Accurate density is needed for tank level gauging, custody transfer metering, pipeline hydraulics, and process design calculations. A 1% density error in a large storage tank translates to tonnes of inventory error.

• What is ethylene's critical point?

  Ethylene's critical point is Tc = 9.2°C (282.34 K), Pc = 50.42 bar (731 psi), ρc = 214.2 kg/m³. Above these conditions, ethylene is supercritical and distinct liquid/gas phases don't exist.

• How is liquid ethylene stored?

  Liquid ethylene is stored at atmospheric pressure in cryogenic tanks at −104°C, or at ambient temperature under pressure (~40-70 bar depending on temperature). Refrigerated storage is more common for large quantities due to lower pressure vessel costs.

• What is the density of ethylene gas vs liquid?

  At STP, ethylene gas has density ~1.18 kg/m³. Liquid ethylene at its boiling point is ~567 kg/m³ — about 480 times denser. This massive density difference is why liquefaction is preferred for transport and storage.

• How does pressure affect liquid ethylene density?

  Liquids are relatively incompressible. Increasing pressure from 1 to 50 bar increases density by only 1-3% for subcooled liquid ethylene. Near the critical point, however, compressibility increases dramatically.

• Is ethylene used as a refrigerant?

  Yes, ethylene (R-1150) is used in cascade refrigeration systems for achieving very low temperatures (down to −100°C). It's common in LNG plants and ethylene plants themselves. Its favorable thermodynamic properties make it efficient for cryogenic service.