The Orifice Viscometer: a New Technique for Measuring Rheological Properties of Massecuites and Molasses

I A simple, cheap and reliable method of measuring rheological properties of massecuites and molasses is described. This involves measuring the head loss across an orifice for a given flow rate. Comparisons between results obtained with the orifice viscometer and a pipeline viscometer are presented. INTRODUCTION I The measurement of the rheological properties of massecuites and molasses is important not only for research purposes but also in the design of flow system, e.g. sizing of pipes, specification of pumps etc. and in the control of the crystallizatio~i process. While standard techniques are available for measuring the viscosity of molasses, very few lend themselves to the measurement of massecuite viscosities. A t the 16th and 17th ICUMSA1J sessions, the rotating cylinder method had been recommended as a standard technique for measuring viscosity of molasses. The lack of suitable techniques for massecuites has been emphasized. The presence of the solid pKase in the massecuites limits the use of conventional measuring techniques, The Brookfield viscometer, for example, i s unsuitable for massecuites because of the tendency for crystals to segregate in the viscometer cup. Other methods have been criticized by several workers as being unsatisfactory. In this spectrum, the 16th ICUMSA session has recommended the study of flow properties of massecuites to develop a standard measuring techique. Following these recommendations, work was carried out by Ozer2 and White6 on a pipeline viscometer. Basically, this involves extruding massecuites from a large diameter reservoir through a small diameter tube of known length and calculating the pressure drop across the tube. Following satisfactory reports on this technique, Moritsug3 recommended that the pipe flow method be further studied to develop i t as a standard measuring technique. This method i s suitable for molasses as well. Moreover, tests3n5 carried out on the flow of viscous materials through orifices indicated that the orifice flow method could well be used as a viscosity measuring technique and an apparatus incorporating a single orifice cduld be constructed as a simple viscometer for extremely viscous materials. Its suitability for measuring rheological properties of massecuites and molasses had to be studied. Before describing the orifice flow method the factors describing the flow characteristics of massecuites and molasses are discussed.