Patent GB-1019356-A (GB)
Title: Method,means and plant for measuring and adjusting continuously the degree of purity of sugar solutions
IPC: G05D21/02
Filed: 1963-01-03
Abstract: In testing and adjusting the purity P of a sugar factory juice at a predetermined temperature, distilled water, or a juice of known purity and concentration, is mixed with the original juice to bring the concentration of the mixture, e.g. measured in degrees Brix, to a value at which the electrical resistivity of the mixture is at a minimum, and the electrical resistivity is then measured.  Electrical resistivity is a function of purity according to the equation log r =aP4+b where P is the percentage purity, r  is the electrical resistivity in ohms/cm.2/cm. and a and b are constants depending on whether the log is to the base 10 or e.  As shown in Fig. 1, a sample of the juice flowing through a pipe 1 is drawn off, through a pipe 2, valve 3, pipe 4, pump 5 and pipe 8 into a jacketed cylindrical, open-mouthed vessel 9. Distilled water, e.g. having a resistivity of 10,000 ohms/cm.2/cm., or juice of known purity and concentration is fed, from a pipe 20, through a pipe 19, valve 18, pipe 17, pump 15 and pipe 14 into the vessel 9 and mixed with the sample of juice, as by introducing a compressed neutral gas, such as air, into the vessel through perforations in the annular, submerged <PICT:1019356/C6-C7/1> portion 11 of a pipe 10.  The mixture of predetermined concentration (Brix) overflows, from the vessel 9, through a pipe 22 and a very accurate thermostat T in which the mixture passes through a coiled pipe 25 and a chamber 40 submerged in water maintained at a constant temperature corresponding to the testing temperature, which does not vary beyond the limits \sB0.05  DEG C. and is attained by the mixture on reaching the chamber.  Two electrodes 41 and 42 inserted in the chamber are connected to the terminals 49 and 48 of an automatically self-balancing, Kohlrausch-type bridge B comprising a current-input transformer 53, a main potentiometer wire 54, two equal, unvarying, replaceable resistances 57 and 58, a galvanometer 55 provided with a field-winding 63 connected to a shunted condenser 64, a movable frame and feeler, which moves a slider 56 along the wire 54, a shunt 61 and a protecting resistance 62.  Potentiometers 59 and 60 are provided, respectively, for rough and fine adjustment of the bridge. The slider 56 is connected, by mechanical gear 65, with the pen 67 of a recording device E comprising a travelling strip of paper 66 carrying purity-time scales, Fig. 4, on which a trace 68, indicating purity variations, is drawn by the pen.  The gear 65 may be connected by rod mechanism 70 with pneumatic (as shown) or electrical apparatus R of known type, Fig. 2, controlling a valve 83 in a pipe 85 through which high-purity juice is fed, from a vat 86, into a vat 89, in which the said juice is mixed with low-purity juice, supplied, at a constant rate from a vat 91, through a valve 90a and a pipe 90, to produce a blended juice of a desired purity.  A fixed sleeve 88 and a propeller 93 are provided, in the vat 89, to facilitate mixing. The blended juice overflows, from the vat 89 through a pipe 98, into storage vat 99.  A sample of the blended juice may be passed from the vat 89 into the pipes 2 and 4 and through the apparatus according to Fig. 1 to be tested for purity.