Brandenburgische Technische Universität Cottbus: BTU Innovative Kraftwerkstechnologien Unternehmen Region: InnoProfile - Die Initiativen
 

Investigation of Pressurised Drying Processes

Simulation zum Einfluss von Strömungswiderständen
Lupe Simulation zum Einfluss von Strömungswiderständen (Bild 1/2)
Gravimetrisches Messsystem für Wasserdampf- Sorptionsmessungen
Lupe Gravimetrisches Messsystem für Wasserdampf- Sorptionsmessungen (Bild 2/2)

The drying of lignite, a readily available source of energy in the region, expands the possible applications and uses of fossil fuels. For one, the combustion of dried coal reduces the amount of fuel required. This is associated with a reduction in the level of noxious emissions as well as a reduction in CO2 emissions. However the combustion of coal with a high moisture content requires the evaporation of a large quantity of water. The use of pre-dried lignite therefore leads to a reduction in the volume of the flue gas as well as a decrease in the size of plants. Furthermore during combustion a high temperature can be maintained and flame stability is also positively influenced.

In previous decades in-depth investigations focusing on the coal drying procedure were conducted. Nevertheless these were always carried out on the basis that moisture within the coal would be eliminated into the atmosphere. Previously the available scientific knowledge concerning pressurised drying processes was limited and inadequate. Conclusive scientific data is now available concerning energy expenditure for the warming of dried particles and the evaporation of water, however for the proportion of energetically eliminated pressure-dependent capillary-bound coal waters reliable data is still unavailable. By conducting investigations within the framework of this research program such data will be obtained and the theoretical basis of this process can be further developed.

The primary focus is to develop a fluid dynamic model for the specific conditions in fluidised bed drying. The need for this arises from the fact that presently all known investigations into the processes within the dryer are essentially described as phenomena, i.e. the actual drying unit is regarded as a "black box" and does not allow for any statements about fluid dynamic details within the dryer. In order for statements to be made about the behaviour of the fluidised bed or the optimisation of the heating of the dryer a detailed knowledge of velocity or the flow of particle-laden flue gas in the pressurised fluidised bed is necessary. By incorporating the results from thermodynamic modelling with this fluid dynamic model the specifics of heat and mass transfer in pressurised fluidised bed dryers can be appropriately considered.