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Applying clean coal technology

by Rudy P. SysAdmin at howtofindthemoney

Clean coal technology

A new generation of coal-burning power plants with energy processes that reduce air emissions and other pollutants.

Coal power plants technology must adapt to the changing political climate towards environmental issues.

Clean coal technologies are several generations of technological advances that have led to more efficient combustion of coal with reduced emissions of sulfur dioxide and nitrogen oxide.

Wet scrubbers
Integrated Gasification Combined Cycle (IGCC)
Flue Gas Desulfurization
Low Nitrogen Oxide (NOx) Burners
Selective Catalytic Reduction (SCR)
Electrostatic Precipitators
Carbon Capture and Storage (CCS)

1. Wet scrubbers

When the emissions reach the flue of the furnace limestone and water are sprayed

The SO2 reacts with the calcium carbonate (limestone) to form gypsum (calcium sulfate). The gypsum is collected and used for construction.

2. Integrated Gas Combined Cycle (IGCC)

IGCC uses a coal gasification system to convert coal into a synthesis gas (syngas) and produce steam.

The hot syngas is processed to remove sulfur compounds, mercury and particulate matter before it is used to fuel a combustion turbine generator, which produces electricity.
The heat in the exhaust gases from the combustion turbine is recovered to generate additional steam
This steam, along with that from the syngas process, then drives a steam turbine generator to produce additional electricity.

The integration of these technologies provides the high efficiency of the combined-cycle design with the low cost of coal

Integrated Gas Combined Cycle (IGCC) advantages:

Efficiencies currently approaching 50%, IGCC power plants use less coal and produce much lower emissions of carbon dioxide than conventional power plants
Higher output: Using syngas in a gas turbine increases its output
The gasification process in IGCC enables the production of not only electricity, but a range of chemicals, by-products for industrial use, and transport fuels

3. Carbon capture and storage

Process consisting of the separation of CO2 from industrial and energy-related sources, transport to a storage location and long-term isolation from the atmosphere.

Three processes in the CCS technology

Capturing the CO2 produced from industrial or power generation processes
Transporting the CO2 to an underground geological formation which is suitable geological formations
CO2 can be used as fluid in “Enhanced Oil Recovery”, where CO2 pushing the remaining oil.

The CO2 is grabbed after the fossil fuel is burned. The burning of fossil fuels produces something called flue gases. In a post-combustion process, CO2 is separated and captured from the flue gases that result from the combustion of fossil fuel

CO2 is trapped before the fossil fuel is burned. That means the CO2 is trapped before it's diluted by other flue gases. Coal, oil or natural gas is heated in pure oxygen, resulting in a mix of carbon monoxide and hydrogen. This mix is then treated in a catalytic converter with steam, which then produces more hydrogen, along with carbon dioxide.

The power plant burns fossil fuel in oxygen. This results in a gas mixture comprising mostly steam and CO2. The steam and carbon dioxide are separated by cooling and compressing the gas stream.

Gasification

the process of producing syngas–a mixture consisting primarily of methane (CH4) carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2) and water vapor (H2O)–from coal and water, air and/or oxygen.

Coal gasification reaction

In coal gasiﬁcation, four principal reactions are crucial:

Steam gasiﬁcation
Carbon dioxide gasiﬁcation
Hydrogasiﬁcation
Partial oxidation reaction

1. Steam gasiﬁcation

The steam gasification reaction is endothermic.

2. Carbon dioxide gasification

Carbon dioxide reacts with carbon to produce carbon monoxide and this reaction is called Boudouard reaction. This reaction is also endothermic in nature, similar to the steam gasification reaction.

3. Hydrogasification

Direct addition of hydrogen to coal under high pressure forms methane. This reaction is exothermic and requires high temperature and pressure.

4. Partial oxidation

Combustion of coal involves reaction with oxygen, which may be supplied as pure oxygen or as air, and forms carbon monoxide and carbon dioxide. Principal chemical reactions between carbon and oxygen involve:

Coal gasification scheme

Coal to chemical (CTC)

Coal to olefins technology

Olefins are one of the most important oil derivatives widely used in industry.

To reduce the dependence of olefins industry on oil a number of coal-to-olefins (CTO) processes have been developed:

UOP/Hydro MTO
DMTO developed by Dalian Institute of Chemical Physics of Chinese Academy of Science
SMTO by Sinopec
Lurgi MTP
FMTP by Tsinghua University

A CTO plant based on the technology was built by Shenhua Group and successfully put into commercial production on January 2011 with capacity 0.7 Mt/a olefins (0.3 Mt/a ethylene, 0.3 Mt/a propylene, and 0.1 Mt/a C4 ).

Process flow diagram

Coal to liquid fuel (Coal liquefaction)

Coal to liquid fuel block flow diagram

Coal to liquid fuel

Fischer-Tropsch process

Converting a mixture of hydrogen and carbon monoxide—derived from coal, methane or biomass—to liquid fuels uses hydrogen (H2) and carbon-monoxide (CO) to make different types of hydrocarbons with various H2:CO ratios