Brix measurements, supersaturation, sugar crystallization and seeding point control
Edible sugar manufacturing is a delicate process that requires process control and instant, accurate Brix (massecuite solids content) measurement of raw and in-process liquids for best product quantity and quality, measured with for example mean aperture (MA) and coefficient of variation (CV). Only high-quality liquid and crystal sugars are acceptable. In crystal sugar manufacturing, the absolute goal is to produce the maximum amount of even quality crystals, avoiding fines and conglomerates.
Sugar production involves two distinct operations: processing sugar cane or sugar beets into raw sugar and processing the raw sugar into refined sugar.
As sugar refining is a highly energy-intensive process where raw juice is subjected to multiple processing steps to remove impurities, the right process control tools help to maximize yield and minimize the cost of production. Overall, the sugar industry is a large water consumer as each production step requires water. The water and energy consumption during manufacturing can be significantly reduced, contributing to mill's or refinery's sustainability, by using modern technology equipment, such as Vaisala K-PATENTS® Process Refractometer.
Sugar crystallization is often the main production process, and mass-producing quality and constant sugar at a competitive price require robust measurement devices that are not affected by varying process conditions from the liquid phase to massecuite nor by increasing crystal content during a strike.
Supersaturation is the driving force of crystal growth, and the speed of crystallization depends on this multivariable function of several parameters. Supersaturation has an optimal range, where sugar crystals grow evenly and widely. Outside the range, the crystals will stop growing and might even melt or start to form new crystals spontaneously creating fines and conglomerates requiring reprocessing. The Zutora SeedMaster-4 is a unique device specifically created for sugar crystallization, providing the parameters necessary for sugar crystallization.
Vaisala K‑PATENTS refractometers and the Zutora SeedMaster-4 provide:
Measure Brix accurately and in-line in all beet sugar miling and refining processes, including extraction, evaporation, crystallization and centrifugation (desugarization) and chromatographic separation for best yield and product quality with savings on energy and production costs.
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Vaisala K‑PATENTS® Process Refractometer is used throughout the processing for optimization and to ensure efficiently working subprocesses and sugar beet mill and refinery.
Control extraction process for efficiently working process and mill
Control steam flow and achieve constant juice concentration in evaporation stages
Yield good quality sugar crystals without fines and conglomerates
Final molasses concentration quality, higher efficiency of desugarization process
In-line and real-time Brix measurement to improve the chromatographic separation and successfully recover betaine
Measure Brix accurately and in-line in all cane sugar milling and refining processes, including affination, decolorization, evaporation, crystallization and recovery process for best yield and product quality with savings on energy and production costs.
Vaisala K‑PATENTS® Process Refractometer is used throughout the processing for optimization and to ensure efficiently working subprocesses and cane sugar mill and refinery.
Measure real-time the concentration of the liquor to clarification, implement process monitoring and control during the affination process.
Increase yield, control wash for the sweet water washing line, detect the interface between sweet water ad syrup, automate control of regeneration process
Ensure high-quality product with continuous Brix measurement of juice and syrup
Yield good quality crystals without fines and conglomerates monitor supersaturation,
implement automatic or manual seeding
Final molasses, dilution concentration control, molasses separation control, wastewater line monitoring and seeding point control
Measure Brix concentration of sugar or molasses, monitor crystallization process for quality yield.
Maintain target concentration of sugar or molasses and citric acid, monitor crystallization process
Monitor Total Dissolved Solids (TDS) and detect sugar shots or excessive amount of sugar in boiler feed water prior damages occur, monitor and control accurately, continuously and in-line the organic load (TOC) content in effluent or sweet-water streams.
Detect sugar shots in the feed water prior equipment damage occur
Measure Total Organic Carbon (TOC) accurately and in-line and create control strategy with the help of Dissolved Solids (SD) measurement
Massecuite solids content and mother liquor concentration are commonly monitored parameters in the vacuum pan as they are used to control the crystallization process and therefore have an effect on the end product quality, the sugar crystals. Massecuite solids content is the mixture of crystals and mother liquor resulting from the crystallization process and mother liquor concentration is the liquid phase in the massecuite during crystallization. Massecuite solids content, or total sugar content, is typically determined using a microwave meter or nuclear density probe whereas mother liquor concentration (dissolved sugar) is measured using a refractometer. The measurement scale is usually Brix.
Online monitoring of batch cooling crystallization
Batch cooling crystallization is a widely practiced production process in several industries. In the sugar industry, it is mainly used as the first step to produce massecuite (footing magma) to seed batch or continuous evaporating crystallizers and to increase the final exhaustion of sugar from the basic raw material (beet or cane). In the pharmaceutical industry, it is used to produce the
final product directly. Cooling crystallization is carried out in different types of equipment, the typical ones having cooling coils or jacketed vessels with built-in stirrers.
Crystal growth is a favorite subject of crystallization research. Due to the complexity of the process, there are several more or less different approaches to its study. Most of the theoretical studies rely on mass, energy, and population balance equations, kinetic correlations, and model formulations sometimes based on questionable assumptions and simplifications. Combined methods (theoretical plus small scale laboratory experiments) can provide useful information on the effect of one or the other parameter on crystal growth, but they are usually restricted to the study of a single (or only a few) crystals in well-controlled environments.
The problems of crystal growth in industrial-scale crystallization, when there are billions of crystals in the massecuite are rarely studied, and if so, the validation of the findings is rare or is completely missing. Production of good quality sugar however should be based on an in-depth knowledge of the processes which characterize mass production. The major difficulty of the study of crystal growth in large populations was the long-standing lack of appropriate instruments needed to monitor on-line the governing parameters of crystal growth.
With the introduction of the SeedMaster Instruments on-line data acquisition of the most important parameters of crystallization, including supersaturation, the crystal content, and mother liquor purity became reality in quite a few mills and refineries of the world.
It is generally acknowledged that supersaturation is the most important parameter in sugar crystallization. It has a key role in determining product quality and yield, cost of production, profitability, and survival of the manufacturer. Besides supersaturation, the other important parameters are crystal content, mother liquor purity (or purity drop), and massecuite solids content (“Brix”).
Sugar crystallization is a process of key importance. Currently, a large percentage of crystallized sugar is produced under manual control using instruments that arguably do not provide actionable information, and apparently resemble methods used several decades ago. This kind of approach is completely unfit to mass-produce quality sugar at a competitive cost.
In Part 1 of this paper some of the most important details of sugar crystallization, like product quality, cost of production, crystal growth, pan circulation, and seeding were discussed. The role and importance of supersaturation in all of these details were duly emphasized. See ISJ (2008), 110 (1315): 403-413. In Part 2 the emphasis is placed on real-life case studies and on some new tools which can be used to shed light on the inner workings of a crystallizer in real-time and use the information for advanced control of crystallization.
There is a growing realization of the importance of supersaturation in sugar crystallization. It has a profound effect on product quality and on the cost of production as well, parameters that determine the chances of survival of plants all over the world. http://vaisala.prod.acquia-sites.com/sites/default/files/documents/VIM-GLO-LM-Sugar-article_seedmaster%202_%20in_isj_2006_vol.108.pdf
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