It looks like Big Oil, Coal and Nuclear will overshadow any attempts at mitigating climate change - thought these myths and facts about "clean" coal might be interesting.
Myths and facts of "clean coal" technologies
MYTH # 1 Efficient Combustion Technologies can increase efficiency and reduce emissions.
Supercritical Pulverised Coal Combustion (PCC) - uses high pressures and temperatures. This can increase the thermal efficiency of the plant from 35% to 45%. This reduces emissions as less coal is used. Fluidised Bed Coal Combustion (FBC) - allows coal combustion at relatively low temperatures, which reduces NOX formation. A sorbent is used to absorb sulphur. Coal gasification - coal is reacted with steam and air or oxygen under high temperatures and pressures to form syngas (mostly carbon monoxide and hydrogen). Syngas can be burnt to produce electricity or processed to produce fuels such as diesel oil.
FACTS:
The world standard for efficiency at a power plant using pulverised fuel technology, the most common technique, stands at 37.5%. Advanced pulverized fuel technology increases the average efficiency to just 41-44 percent with a forecast improvement to 50 percent in the next 100 years. Other clean coal combustion technologies are still in early stages of development and are unlikely to improve efficiency beyond 43%.
MYTH # 2 : Coal washing lowers the level of sulphur and minerals in the coal.
FACTS:
Coal washing results in the formation of large quantities of slurry. This is placed in waste piles. Rain drains through the piles, picking up pollutants which end up in rivers and streams. This runoff is acidic and contains heavy metals.
MYTH # 3 During combustion, “clean coal” technologies utilize pollution controls for existing power plants to reduce emissions of pollutants.
Particulate emissions – can be reduced by Electrostatic Precipitators (ESPs) and fabric filters. ESPs are most widely used. Flue gases are passed between collecting plates. These attract particles using an electrical charge. NOX emissions – can be reduced by Low-NOX Burners (LNB). These reduce the formation of NOX by controlling the flame temperature and the chemical environment in which the coal combusts. Selective Catalytic or Non-Catalytic Reduction (SCR/SNCR) are expensive and less widely used. SO2 emissions - can be reduced by Flue Gas Desulpurisation (FGD). Wet FGD, or wet scrubbing, is most common and absorbs SO2 using a sulphur absorbing chemical (sorbent), such as lime. Trace elements emissions – these include mercury, cadmium and arsenic. Some emissions can be reduced by particulate controls, fluidised bed combustion and FGD equipment. Activated Carbon Injection is being trialled to remove mercury.
FACTS:
Between 7 and 30 percent of coal consists of non-combustible material that just has to be eventually disposed of. “Clean coal” technologies attempt to trap these waste products before they leave the smokestalks; waste material that is trapped is then used (despite containing a number of toxic elements) or dumped as landfill.
The use of higher quality coal – lower in ash and sulphur should reduce emissions and increase efficiency, but thermal efficiency is increased by only one percent. If clean coal is used to meet the increased electricity demand predicitions of govenments instead of cleaner renewable alternatives, there will in fact be a net increase in carbon dioxide emissions.
According to a report by the United Nations Environment Programme (UNEP) mercury and its compounds are highly toxic and pose a ‘global environmental threat to humans and wildlife.’ Exposure to it has been associated with serious neurological and developmental damage to humans. The report also states that coal-fired power and heat production is the largest single source of atmospheric mercury emissions. According to the Coal Utilization Research Council ‘there are no commercial technologies available for mercury capture at coal-fuelled power plants’. Furthermore, a US Department of Energy commissioned report, states that the consistent, long-term performance of mercury control has yet to be demonstrated. Experimental removal of mercury is prohibitively expensive at $761,000/kg mercury removed and even then 10% of the mercury still remains...
Read the rest of the myths and facts about clean coal
Thursday, January 28, 2010
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2 comments:
The use of sophisticated software systems for coal mining (thermal coal, steam coal and metallurgical coal) that is mostly burnt for power generation and steel production and adds to the greenhouse effect is valid for western countries who may allocate resources and funds to alternative and more greener sources of power. Some of the alternatives may be "safer" than the traditional mines. Unfortunately, coal reports and coal statistics show developing economies are more likely to increase their use of thermal coal & metallurgical coal in coming years because of its affordability and to meet increasing demands for electricity and steel. Whether they will embrace and utilise sophisticated software systems that no doubt add to the cost of production is yet to be seen. Ian www.coalportal.com
The call by some to reduce the use of thermal coal (steam coal) that is mostly burnt for power generation and adds to the greenhouse effect is valid for western countries who may allocate resources and funds to alternative and more greener sources of power. Coal Terminals and additional infrastructure are required in the coal supply chain. Coal reports and coal statistics show developing economies are more likely to increase their investment into & their use of thermal coal & metallurgical coal in coming years because of its affordability and to meet increasing demands for electricity and steel. Ian www.coalportal.com
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