Clean coal technology research
Eskom will continue its reliance on coal as its primary
energy source for the foreseeable future, although it plans
to reduce the coal component of its generating capacity to
70% within 20 years. Clean coal technologies that use coal
for power generation in more environmentally acceptable
and economically viable ways will form part of this mix.
A number of clean coal technologies exist now and
are expected to be available over the next 20 years.
Examples of these are supercritical pulverised fuel, coal
beneficiation, subcritical and supercritical circulating
fluidised-bed combustion (FBC), fluidised-bed gasification
(FBG), integrated gasification combined cycle (IGCC),
and underground coal gasification (UCG). All of these
technologies have advantages and disadvantages that need
to be understood. Clean coal technologies are thus part of
the Eskom research programme that focuses on assessing
the different technologies under local conditions.
| 1MW (thermal) pilot scale pulverised fuel combustion test facility and
fluidised-bed combustion and gasification pilot test facility located at
the Eskom Research and Innovation Centre in Johannesburg. |
Eskom has developed a number of research resources that it uses in its assessment of clean coal technology options. Some of these include facilities such as a drop tube furnace, a single-burner 1MW (thermal) pilot scale combustion test facility, capable of firing 250 kilograms of coal per hour, and a FBC/FBG pilot test facility that is able to operate at a 150kW (thermal) capacity in either combustion or gasification mode.
The unique properties of local coal have limited the applicability of international experience and have resulted in the development of a substantial in-house coal research programme. This research programme focuses on optimising the use of coal at existing power stations, and alternative cleaner coal technologies for new plant have been developed over a number of years. The clean coal technologies component of this research has been increasing with the increased pressure placed on the use of coal from an environmental point of view.
Clean coal technologies are aimed at using coal for power generation in more environmentally acceptable and economically viable ways. There are two basic approaches associated with clean coal technologies. One is to develop more thermally efficient systems that use less coal to generate the same amount of power with an associated reduction in emissions. This has the advantage of reducing the extent of flue gas cleaning required. The other is to enhance and develop new methods to effectively clean the emissions in an affordable manner. Eskom’s research programme is currently addressing both of these approaches with the aim of achieving plant efficiencies of 50% or more and reducing emissions. An important factor in all of this is ensuring that capital costs are kept as low as possible while retaining reliability.
Advanced laboratories and simulation facilities support all the research initiatives, and recently Eskom has added a QEMSCAN® to enhance its understanding of the mineral/phase composition and transformations of our coal and ash.
A major current focus is the demonstration of underground coal gasification as an alternative method of using our coal resources. This technology, in combination with a combined-cycle (or simple-cycle) gas turbine, will have the potential to generate power at high efficiencies of 50% or more compared with the present coal stations’ efficiencies of around 36%. The gas produced can also be effectively cleaned, reducing the emissions from combustion substantially when compared to conventional coal combustion. The technology also opens up coal resources that have been considered unminable.
Research into clean coal technologies is being carried out around the world, and Eskom enhances its research programme by leveraging research memberships and cooperative agreements in a number of countries. A motivating factor for international collaboration is that issues such as carbon capture and sequestration are too big for any one company or even country to solve on its own. Eskom believes that its involvement in international research programmes on clean coal technologies will contribute to more rapid and significant advances, and will allow Eskom to optimise the implementation of these technologies. |
