Hydrocyclones for the separation of yeast and protein particles

The development and operation of hydrocyclone designs for the separation of solid particles from liquid with low time constant, such as removing yeast from beer and protein particles from wort in the brewing industry, are investigated. Nylon powder in water is used for preliminary study of solid-liquid separation. Fixed brewing yeast in sucrose water solution is mainly used in laboratory tests to model the conditions near the brewing site. Fresh wort and healthy baking yeast in DYPG and brewing yeast in beer are also used.The work investigated the effects upon hydrocyclone performance of material parameters (particle size, concentration and temperature of dispersions), operating parameters (feed flowrate or pressure drop, split ratio) and geometrical parameters (hydrocyclone type, inlet size, outlet size, relative length, outer diameter and end shape of vortex finder). Understanding of these effects is reinforced by the analysis of flowfield and residence time distribution inside hydrocyclones.Among a variety of hydrocyclones tested, Colman-Thew hydrocyclone is found to give far better separation of yeast than others. Through the modification of the hydrocyclone, the yield or split ratio F is increased by 25% without fall in clarification efficiency at given pressure drop. Systematic study on geometrical effects shows that the separation performance can be further improved. Calculations for suggested hydrocyclone network indicate that both good clarification and high yield should be attainable.The size of outlet is found to have a weak effect on separation performance at given feed flowrate when back pressure is applied, whilst the effect of the relative length of a hydrocyclone depends on hydrocyclone size and the value of time constant of dispersions. Correlations between operating and geometrical parameters are demonstrated. With the application of the hydrocyclone for use with other mixtures and dispersions in mind, a relation between the relative length, hydrocyclone size and the time constant is developed by which hydrocyclone performance or relative length may be predicted. And a general procedure of designing or developing hydrocyclones is presented.