Process Gula

Application Data Sheet ADS 2000-15/rev.B July 2004

Food and Beverage Industry

SUGAR REFINING PROCESS This application data sheet describes the applications of the REFRAC A1 on-line refractometer in both cane and beet processing to produce crystalline sugar. There are numerous identified applications. All these applications require mixing a stream of unknown sugar concentration before it enters a subsequent processing stage. BACKGROUND Sucrose is produced from sugar cane and sugar beets. In a cane sugar process, the juice is extracted and clarified by heating in the presence of Calcium Oxide (CaO). The resulting juice is evaporated to 65% solids and crystallized as raw sugar. The raw sugar crystals are washed and decolorized through beds of carbon or bone char and then passed through ion exchange. Finally, the liquor is partially evaporated to yield liquid sugar or is further dried to produce crystallized sugar. After this processing, molasses remains; traditionally, molasses is then removed as a waste product. Molasses, however, contains a relatively high level of sugar and is viewed as one of the few remaining sources for increased yield. Historically, isolating sugar from this source has been uneconomical. However, two recent advances have improved the profitability of the molasses-to-sugar conversion process. First, new plants designed specifically with this capability have taken molasses from older refineries and recovered the crystalline sugar. Second, advances in refractometers for on-line, continuous applications and in the related control loop systems have boosted recovery beyond any previous technology. THE PROCESS There are several applications in sugar processing where the REFRAC A1 can be used to determine the sugar concentration, commonly expressed as BRIX. One of the most important applications is the final sugar/molasses (Figure 1) separation. The vapor from the upstream evaporation is put into the “C” pan for final evaporation. In an adjacent tank, the heavy residual slag syrup is mixed with the heavy magma from upstream and the B-molasses from the previous evaporators. In this process, the REFRAC A1 can be installed directly into the tank (“C” pan) with a wash

nozzle to measure the BRIX. The wash nozzle is recommended in order to clean the YAG-sapphire prism as it becomes coated by the molasses and sugar. Ensuring the cleanliness of the prism is critical in determining an accurate BRIX value, because refractive index is an optical measurement. Knowledge of the BRIX value on the “C” pan allows for optimization of the evaporator pan, by providing information which leads to increased recovery of sugar. Other measurements where BRIX measurements can be made include the multiple evaporators, and A and B pans. INSTRUMENTATION The REFRAC A1 is well suited for this application for several reasons: The electronics unit can control up to three sensor heads, which is ideal if a plant requires monitoring the output of the Green tank, the input to the molasses tank, and at another sampling point. Figure 2 shows a High BRIX Installation in which these 3 measurements can be made from a single REFRAC A1 unit. The sensor head and the electronics unit can be separated by up to twenty meters, protecting the electronics unit from the heat of the process. Optional watercooled heads are also available to endure operation up to 150°C (302°F). In addition, the sensor heads can be standardized online to ensure conformity to laboratory analysis when crosschecking is required.

FIGURE 1. Sugar/Molasses Separation

INSTRUMENTATION Model REFRAC A1 Refractometer • Automatic BRIX or refractive index measurement of binary or quasi-binary liquid mixtures. • Reliable measuring head featuring a YAG-sapphire prism, CIP capability, and high resolution photo diode array. • Air or water cooling to withstand hot processes. • Direct process control with digital, RS232 or RS485, and dual limit comparator, analog outputs, two alarms, and diagnostic temperature correction. • NO CALIBRATION REQUIRED

The electronics unit and the sensor head are shown in the photo above. For additional information refer to product data sheet, 71-REFRAC.

REFRAC A1

MOLASSES

FIGURE 2. High BRIX Installation — Beet Sugar Crystallization

Emerson Process Management Rosemount Analytical Inc. 2400 Barranca Parkway Irvine, CA 92606 USA Tel: (949) 757-8500 Fax: (949) 474-7250 http://www.raihome.com © Rosemount Analytical Inc. 2004