Flow Correlated Positioning of Spray Nozzles in Flue Gas Scrubbers

Project Number 263

In modern gas scrubbers for the flue-gas desulphurisation of hard coal or lignite fired power stations the washing liquid is atomised by numerous nozzles. Different nozzle-types are used such as spiral-, hollow -, and full cone-nozzles.

The nozzles in FGD-scrubbers are mostly arranged in several spraying or nozzle levels. The arrangement of nozzles within a specific level and the arrangement of levels to each other corresponds to knowledge at the end of the eighties, when FGD-plants were upgraded in the German power plants.

More stringent emission limit values for sulphur dioxide and the increasing additional combustion of waste derived fuels push FGD scrubbers increasingly to the limit of their efficiency. Therefore it is in interest of the plant operators to minimize weak spots in FGD scrubbers.

Large potential for this offers the absorption chamber with their nozzles. By an aimed and optimized arrangement of nozzles with help of suitable, robust CFD-simulations with special consideration on droplet collision it is possible to increase the separation efficiency of FGD scrubbers today, in order to adapt them to stricter limit values.

In the simulation of the two-phase flow of a FGD-scrubber this becomes possible by combination of nozzle arrangement and collision modelling. By the use of such a simulation tool it is possible to minimize some well-known problems in FGD-scrubbers like wall effects and duct formation of the flue gas. So plant designers and plant operators can be given an assistance for the optimization of wet scrubbers.

This can be achieved with integration of the collision model and the realizations from the two preceding research projects "Fluid Dynamic within FGC Plants” (202) and "FGD Nozzle-Positioning” (230) as well as new algorithms for nozzle positioning into a commercial CFD-program.

The project is carried out by the Chair of Environmental Technology of the Dortmund University (person in charge: Markus Feldkamp) and is accompanied by the Working Panel "Flue Gas Cleaning Technology". The results are expected at the beginning of 2007.