Spillback nozzles are single-fluid nozzles that atomize the liquid as a hollow cone. Compared to regular single fluid nozzles, the water is fed to the nozzle with a constant feed pressure (e.g. 35 bar), independent of the atomized flow rate.
By opening a control valve in the return line, a partial flow of the feed flow rate in the nozzle is returned to the water tank and the injection flow rate of the nozzle is controlled. The maximum atomized flow rate is achieved with the control valve closed. Uniform and fine liquid atomization is achieved across the entire control range.
Spillback line closed, spray angle approx. 80 – 85° (left) and spillback line open, spray angle approx. 100° (right)
The advantages of the return nozzles are their low operating costs (as no atomizing air is required), their large control ratio of at least 10:1 and their almost constant droplet size over the entire control range.
With the new generation of RS II-3 nozzles, the droplet size D32 at 35 bar,g could be reduced to 85 – 130 µm over the operating points of the complete series. Several case studies for gas cooling towers have shown that it is possible to reduce the evaporation distance by an average of 30%. With the significantly finer droplets, the required evaporation distance can even be reduced by up to 50% compared to conventional spillback nozzles. Thanks to the optimized evaporation path, the spillback system can be used in considerably more process cases as an alternative to the twin-fluid system.
In addition, the revision of the Lechler return nozzles resulted in further design advantages such as flow-optimized geometries, less individual parts and the possibility of assembly with standard tools.
The RS II-3 (290 series) comprises a total of seven nozzles in the volume flow range between 0.6 – 27.9 l/min and will completely replace the previous RS 3 nozzles (260 series).
Please find detailed information in the RS II-3 flyer.