THERMAL SCIENCE
International Scientific Journal
INVESTIGATION OF PRE-DRYING LIGNITE IN AN EXISTING GREEK POWER PLANT
ABSTRACT
The application of lignite pre-drying technologies in next generation of lignite power plants by utilizing low pressure steam as a drying medium instead of hot recirculated flue gas - combined with thermal utilization of the vaporized coal moisture - is expected to bring efficiency increase of 2-4 percentage points in future lignite power plants compared with today’s state of the art. The pre-drying concept is of particular importance in Greek boilers firing lignite with a high water and ash content. The combustion of Greek predried lignite has been investigated experimentally and via numerical simulations in our previous research. This study focuses on the potential integration of a lignite pre-drying system in an existing Greek power plant with dry lignite co-firing thermal share of up to 30%. The radiative and convective heat fluxes to the boiler and the overall boiler heat balance is calculated for reference and dry lignite co-firing conditions by an in-house calculation code. The overall plant’s thermal cycle is then simulated using commercial thermal cycle calculation software. The net plant efficiency is in this way determined for reference and dry coal co-firing conditions. According to the simulation results the integration of a pre-drying system and the implementation of dry lignite co-firing may bring an efficiency increase of about 1.5 percentage points in existing Greek boilers. It is therefore considered as an important measure towards improving plant efficiency and reducing specific CO2 emissions in existing plants.
KEYWORDS
PAPER SUBMITTED: 2011-05-09
PAPER REVISED: 2011-08-22
PAPER ACCEPTED: 2011-08-22
THERMAL SCIENCE YEAR
2012, VOLUME
16, ISSUE
Issue 1, PAGES [283 - 296]
- Klutz H-J, Moser C., Block D., "WTA Fine Grain Drying - Module for Lignite-Fired Power Plants of the Future, Development and operating results of the test plant", VGB PowerTech 11/2006
- Schwendig F., Klutz H-J, Ewers J., "The Dry Lignite-Fired Power Plant", RWE-VGB 12/2006
- Agraniotis M. et al., "Experimental investigation on the combustion behaviour of pre-dried Greek lignite", Fuel Processing Technology, 90 (2009), pp. 1071-1079
- ***, RWE Power :"WTA TECHNOLOGY-A modern process for treating and drying lignite", www.rwe.com
- FDBR-HANDBUCH: Waerme und Stroemung Technik, Essen: Vulkan Verlag, 1975
- Agraniotis M., " Substitution of coal by alternative and supporting fuels in pulverised fuel boilers towards reducing CO2 emissions",Ph.D thesis, NTUA, Athens, 2010
- Kakaras E., Ahladas P., Syrmopoulos S., "Computer simulation studies for the integration of an external dryer into a Greek lignite-fired power plant", Fuel, 81 (2002), pp. 583-593
- Agraniotis M. et al., "Numerical investigation on the combustion behaviour of pre-dried Greek lignite", Fuel, 88 (2009), pp. 2385-2391
- Agraniotis M.et al., "Dry lignite co-firing in a Greek utility boiler: Experimental activities and numerical simulations", Energy & Fuels, 24 (2010), pp 5464-5473
- Agraniotis M. et al., "Investigation of lignite pre-drying in a modern Greek power plant towards zero CO2 emissions", 2011
- Kakaras E. et al., "Ultra - supercritical power plant fired with low quality Greek Lignite", ECOS Conference 2007
- Kakaras E.et al., "Oxyfuel boiler design in a lignite-fired power plant", Fuel 86 (2007) pp. 2144-2150
- Violidakis I., "Development of a computational code for the prediction of pulverised fuel boiler's thermal data-application in a Greek steam boiler for the case of raw and dry lignite cofiring" (in Greek language), Diploma thesis, National Technological University of Athens, NTUA, Athens, Greece, 2008
- Maier J. et al., "Investigation of particle behaviour of rawand pre-dried brown coal and bituminous coal in a 20 kWand in a 500 kW test facility", 23rd Int. Conf. On Coal Utilization & Fuel Systems,Clearwater USA, March, 1998, pp. 9-13.
- Maier J. et al., "Milling, drying and combustion of low rank coal in a 500 kWth pulverized coal test facility", Proceedings , International Symposium on Clean Coal Technology, China, Xiamen, 1997
- Maier J. , Hein K.R.G. , "Effect of pre-drying on P.F. combustion, fly ash and emission behavior of different European low-rank fuels", Tagungsband: 18th Annual International Pittsburgh Coal Conference Australia, Newcastle, NSW, Dec. 3-7, 2001
- Koukouzas N. et al., "CO2 capture and storage in Greece: a case study from Komotini NGCC power plant", Thermal Science 10 (2006), 3, pp. 71-80
- Ravi Kumar N. et al., "Thermodynamic analysis of heat recovery steam generator in combined cycle plant", Thermal Science, 11 (2007), 4, pp. 143-156
- Kakaras E. et al., "Fluidized bed combustion with the use of Greek solid fuels", Thermal Science, 7 (2003), 2, pp. 33-42
- Châtel-Pélage F. et al.,"Applications of oxygen for NOx control and CO2 capture in coal-fired plants", Thermal Science, 10 (2006), 3, pp. 119-142
- Harkin T., Hoadley A., Hooper B., "Process integration analysis of a brown coal-fired power station with CO2 capture and storage and lignite drying", Energy Procedia, 1 (2009), pp. 3817-3825
- Kaß H., Tappe S., Krautz H.J., "The combustion of dry lignite under Oxy-fuel process conditions in a 0.5 MWth test plant", Energy Procedia, 1 (2009), pp. 423-430
- Bosoaga A. "The combustion of pulverised low grade lignite", Fuel, 85 (2006), pp. 1591-1598
