High Efficiency Low Emission Coal
An important first step in reducing CO2 emissions from coal is improving the thermal efficiencies of coal fired power stations. The higher the pressure and temperature of steam used, the higher the efficiency and the lower the CO2 emissions. Higher efficiencies allow a greater amount of energy to be produced from a single unit of coal.
A one percentage point improvement in the efficiency of a conventional pulverised coal combustion plant results in a 2-3% reduction in CO2 emissions. These technologies are in existence, widely available and financially viable.
HELE technologies have been developed to increase the efficiency of coal fired plants, therefore reducing CO2 and other greenhouse gas emissions and pollutants. Efficiency in electricity generation means that less fuel is used to produce the same amount of electricity.
Efficiency improvements can be made through the use of:
- Supercritical, Ultra-Supercritical and Advanced Ultra-Supercritical Technologies
- Integrated Gasification Combined Cycle
- Fluidised Bed Combustion
Supercritical, Ultra-Supercritical and Advanced Ultra-Supercritical Technologies
Pulverised coal combustion systems using Supercritical, Ultra-Supercritical and Advanced Ultra-Supercritical technology operate at higher steam temperatures and pressures than conventional plants, meaning they have higher efficiency levels and lower CO2 emissions.
Integrated Gasification Combined Cycle
Integrated gasification combined cycle (IGCC) systems produce a gas from coal, by reacting coal with oxygen and steam to form a syngasâ€. This gas – composed mainly of hydrogen and carbon monoxide – is cleaned of impurities and then burnt in a turbine to generate electricity and to produce steam for a steam power cycle. IGCC can achieve high thermal efficiencies of up to 48% – IGCC power plants use less coal and produce lower emissions as improvements in efficiency reduce carbon dioxide emission.
Fluidised Bed Combustion
Fluidised Bed Combustion (FBC) is a flexible method of electricity production most combustible material can be burnt including coal, biomass and general waste. FBC systems improve the environmental impact of coal-based electricity, reducing SOx and NOx emissions considerably.
Efficiency improvements can be made through the use of
Carbon Capture Use and Storage
Carbon Capture Use and Storage (CCUS) technologies prevent large quantities of CO2 being released into the atmosphere. CCUS is the only technology capable of significantly reducing emissions from power generation and key industrial processes, including steel, cement and chemicals manufacturing. Emissions of carbon dioxide are stripped out of the exhaust stream from coal combustion or gasification and disposed of without entering the atmosphere.
CCUS is proven and operating today – Boundary Dam in Canada operates at over 90% capture efficiency.
It is not possible to meet our climate goals without CCUS – the Intergovernmental Panel on Climate Change has shown it would be 138% more expensive without CCUS. Fossil fuel power generation fitted with CCUS is a key part of the transition to a net zero CO2 emissions future.
How CCUS works:
Capture technologies allow the separation of CO2 from gases produced in electricity generation and industrial processes by one of three methods:
- Pre-combustion capture
- Post-combustion capture
- Oxyfuel combustion
CO2 is then transported for safe use or storage. Millions of tonnes of CO2 are transported annually for commercial purposes by pipelines, ships, and road tankers.
CO2 can be used as a value-added commodity. This can result in a portion of the CO2 being permanently stored for example, in concrete that has been cured using CO2 or in plastic materials that use CO2 as one of the ingredients. The CO2 can also be converted into biomass through algae farming using CO2 as a feedstock. The harvested algae can then be processed into biofuels that take the place of non-biological carbon sources.
CO2 is already widely used in the oil industry for enhanced oil recovery (EOR) from mature oilfields. The CO2 can therefore have a positive commercial value and can help support the deployment of CCUS and create a revenue stream for CCUS projects, as the CO2 captured becomes an economic resource.
CO2 is stored in carefully selected geological rock formations that are typically located several kilometres below the earth’s surface in a technique known as geological storage. As CO2 is pumped deep underground, it is compressed by the higher pressures and becomes essentially a liquid. There are a number of different types of geological trapping mechanisms (depending on the physical and chemical characteristics of the rocks and fluids) that can be utilised for CO2 storage. Large amounts of CO2 can be stored in deep saline water-saturated reservoir rocks, allowing countries to store their CO2 emissions for many hundreds of years.
There are now 23 carbon, capture, use and storage facilities under construction or operating. The following CCUS projects are currently operating within the coal sector:
- Boundary Dam power station in Canada is the worlds first coal fired power station to apply CCUS at scale in the power sector, and has been operating since October 2014 (capturing 1 million tonnes of CO2 per annum).
- The Abu Dhabi CCS Project (capturing 800,000 tonnes of CO2 per annum) came online in 2016 and is the worlds first commercial CCUS facility for the steel industry.
Scope exists for future CCUS projects to have much improved capture rates, including zero-emissions from coal. But more is needed to accelerate CCUS deployment and not just for coal CCUS is needed for gas too and other emitting industries, including steel, cement and chemicals.
The International Energy Agency (IEA) estimates that 13% of emission reductions by 2060 must come from carbon, capture, use and storage . This means we need a significant jump in the number of projects worldwide.