Why do refinery gases have the lowest boiling points of all the crude oil fractions?

Refinery gas molecules are the smallest, with one to four carbon atoms each. The weak forces between small molecules need little energy to overcome.

Why are refinery gases cooled and liquefied before they are stored?

A liquefied gas occupies a tiny fraction of the volume of the same mass of gas. Liquefaction makes large quantities practical to store and transport as feedstock.

How are refinery gases liquefied?

Refinery gases are liquefied by cooling them, compressing them, or both. Propane and butane become liquid under moderate pressure at room temperature and are kept in pressurised tanks.

CCEA A-Level Environmental Technology 3930

Fossil Fuels

Topic overview Coal, oil and gas in modern society Reserves, lifespan and accessibility Fossil fuel combustion and the IPCC evidence Carbon trading schemes Fossil fuel demand, emerging economies and fuel security Environmental impacts of fossil fuel use

Global Action on Energy Conservation and Climate Change

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Macrogeneration

Topic overview Conservation of energy and the simple generator Thermal power stations and steam turbines Direct and indirect renewable electricity Electricity transmission through the National Grid Smart grids and interconnectors Combined heat and power

Microgeneration

Topic overview Microgeneration technologies Benefits of home and community microgeneration The heat pump cycle and coefficient of performance Air source and ground source heat pumps

Energy From Wind

Topic overview Horizontal and vertical axis wind turbines Kinetic energy, wind power and the Betz limit Power curves, rated output and energy losses Swept area, blade length and turbine mass Air density, hub height and turbine siting Power control, yawing and survival speed Choosing a location for a commercial wind farm

Energy From the Sun

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Energy From Biomass

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Energy Storage

Topic overview Intermittency and reliability of renewable supply Why renewable energy needs storing Pumped hydro and compressed air energy storage Where energy storage is most beneficial

Plastics for the Future

Topic overview Crude oil as a fuel and a feedstock Refinery gases and the making of polymers Persistent plastic waste and the Great Pacific Garbage Patch Toxic gases from incinerating plastics Biodegradable, photodegradable and compostable plastics Testing photodegradable plastic against polythene Bio-derived polyethylene and a sustainable plastics future

Renewable Energy Investigations

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Sustainable Development

Topic overview Population growth and demand for resources The I = PAT equation and the role of technology Ecological footprints, carbon footprints and One Planet Living

Waste Management

Topic overview Landfill dependence and the landfill tax Waste types, priority waste streams and EU directives The waste management hierarchy Recycling at a Materials Recovery Facility Landfill decomposition, methane and leachate Engineered landfill: dry tomb and bioreactor designs

Waste to Energy Technologies

Topic overview Embodied energy Incineration with energy recovery Digester design: solids content, residence time and staging Stages of anaerobic digestion and biogas CHP Composting and catering waste

Land Contamination and Remediation

Topic overview Contaminated land, risk and traditional remediation Bioremediation principles and bioreactor systems Micro-organisms that degrade named pollutants Bioremediation benefits and genetically engineered microbes Phytoremediation of metals and other elements Phytoextraction with Indian mustard and alpine pennycress Biohydrometallurgy and phytomining of ores

Hydrogen Fuel Cells

Topic overview Hydrogen as a fuel: properties and storage Hydrogen production: steam reforming, electrolysis and photocatalysis How a fuel cell works and the PEM cell Alkaline, phosphoric acid, molten carbonate and solid oxide fuel cells Fuel cell applications and the challenges of hydrogen

Transport System Challenges

Topic overview Four key challenges for future transport New vehicle technologies and their infrastructure Bioethanol production and the heat energy of ethanol Biodiesel and the biofuel debate Strategies to reduce transport demand

Energy Performance of Buildings

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Emerging Technologies

Topic overview Tidal stream and tidal barrage power Wave energy converters Environmental impacts of wave and tidal energy Smart materials and smart systems Carbon capture and storage Geo-engineering, direct air capture and bio-photovoltaics

Sustainable Urban and Rural Communities

Topic overview Energy and buildings in sustainable urban developments Transport, waste and brownfield sites Water, drainage and urban green space Energy, water and waste for isolated rural dwellings Local food and communication technology in rural areas

The Code for Sustainable Homes

Topic overview Purpose, levels and assessment of the Code Energy, carbon dioxide and water categories Materials, surface water run-off and waste categories Pollution, health and wellbeing, management and ecology categories Measuring the performance of an existing building Performance profiles, improvements and evaluation

Plastics for the Future

Refinery gases and the making of polymers

3 things to know
AS 1

Overview

Fractional distillation and refinery gases, liquefied petroleum gas, cracking ethane and naphtha, monomers and polymers, the addition polymerisation of ethene, polypropylene and PVC, and thermoplastics and thermosets.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What happens to crude oil during fractional distillation?

Key term

Why is a fractionating column hottest at the bottom and coolest at the top?

Key term

Which fraction leaves the top of the fractionating column?

Questions from this subtopic

Each one with the model answer underneath.

1
What happens to crude oil during fractional distillation?
Model answer
Crude oil is heated until most of it vaporises, and the vapour rises up a tall column. Fractions condense at different heights according to their boiling points.
2
Why is a fractionating column hottest at the bottom and coolest at the top?
Model answer
The hot vapour enters near the base of the column. The vapour loses heat as it rises, so the top of the column is coolest.
3
Which fraction leaves the top of the fractionating column?
Model answer
Refinery gases leave the top of the column because they have the lowest boiling points. Refinery gases are small hydrocarbons such as methane, ethane, propane and butane.
4
Why do refinery gases have the lowest boiling points of all the crude oil fractions?
Model answer
Refinery gas molecules are the smallest, with one to four carbon atoms each. The weak forces between small molecules need little energy to overcome.
5
Why are refinery gases cooled and liquefied before they are stored?
Model answer
A liquefied gas occupies a tiny fraction of the volume of the same mass of gas. Liquefaction makes large quantities practical to store and transport as feedstock.
6
How are refinery gases liquefied?
Model answer
Refinery gases are liquefied by cooling them, compressing them, or both. Propane and butane become liquid under moderate pressure at room temperature and are kept in pressurised tanks.

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Fossil Fuels

Global Action on Energy Conservation and Climate Change

Macrogeneration

Microgeneration

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