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      • Global Affiliates
      • Specialist Partners
      • Resellers
    • Conditions of Sale
    • Charitable Purpose
    • Employment
    • Terms of Access
    • Privacy
    • Links
  • Projects
  • Consulting
    • SRI Consulting Guide
    • Feasibility Studies
    • Complete Process Design and Upgrade
    • Process Design and Specification
    • Process Optimisation
    • Process Support
    • Specialist Analytical Work
      • Computational Fluid Dynamics (CFD) Modelling
      • Finite Element Analysis
    • Performance Audits and Investigations
    • Scale Analysis and Chemical Cleaning
    • Tender Development / Evaluation
  • Designs
    • SRI Designs Guide
    • Clarifiers
      • High Performance Juice Clarifiers
      • Short Retention Juice Clarifiers
      • Flotation Syrup Clarifiers
    • Robert Evaporators
    • Continuous Vacuum Pans
    • Seed Crystal Conditioning Plants
    • Massecuite Reheaters
    • Cooling Crystallisers
    • Bagasse Combustion Systems
  • Products
    • SRI Products Guide
    • Chute Height Sensors
    • Dbrix Transducers
    • Milset Software
    • Colour and Turbidity Meters
    • Jigger Tube Systems
    • Can Fibre Machines
  • Training
    • SRI Training Guide
    • Engineering
      • Engineering Supervisors
      • Efficient Use of High Pressure and Process Steam
      • Extraction Theory and Practice for Milling Engineers
      • Introduction to Extraction for Shift Supervisors
      • Advanced Extraction
      • Steam Generation
    • Process
      • Chemical Process Supervision
      • Advanced Process Supervision
      • Sugar Quality and Factory Efficiency
    • Operations
      • Clarification/Filtration
      • Juice Evaporation
      • Sugar Boilers
      • Fugal Operators
    • Transport
      • TOTools
      • ACTSS/ACRSS Users Course
    • Workshops
      • Traffic Officers
      • Instrumentation and Process Control
    • Australian Sugar Industry Scholarship
    • SOTrain – Supervisor and Operator Training
  • Members
    • Technical Resources – SRI eLibrary
    • Frequently Asked Questions
    • Glossary of Terms

Frequently Asked Questions

  1. Home
  2. Frequently Asked Questions
Frequently Asked Questionsadmin2017-08-25T11:35:26+10:00

  • Flotation Syrup Clarifiers

  • Dbrix Transducer

  • Flotation Syrup Clarifiers

Why should a raw sugar factory install an SRI Flotation Syrup Clarifier and what are the financial advantages?

Many raw sugar factories produce direct consumption (plantation white or blanco directo) sugars by single or double sulphitation. Around the world there is a move to produce high quality white sugars directly in raw sugar factories. The key buyers of these high quality sugar products, such as soft drink and confectionery manufacturers, demand lower levels of residual sulphur, ash and colour.

Flotation clarification, combined with sulphitation or other processes, provides a cost effective means to achieve high quality sugars directly from a raw sugar process, with minimal effect on the overall sugar make. This is achieved through removal of a significant proportion of suspended solids, colloidal impurities (turbidity), ash and colour.

It is difficult to quantify the financial benefits without knowing the throughput, sugar pricing scheme and local chemical cost details for a given client. SRI can provide an investment analysis if such details are provided. The investment analyses performed to date, for clients in Central America indicate a typical payback period from one to two grinding seasons.

How much does it cost to install a complete syrup clarification system?

Installation costs vary between countries and clients in project scope, equipment size, local site conditions, installation standards, labour rates, freight costs, taxes and duties result in as much as a three fold range in installation costs.

Costs typically include pre-design audit, basic design supply, on-site commissioning, procurement, detailed engineering with fabrication the equipment and installation by the client.

A basic design package includes pre-design and commissioning visits, but excludes equipment supply. SRI can provide assistance with detailed engineering, equipment supply and installation supervision if required.

How much of the clarification system does SRI supply?

SRI will tailor the scope of supply to suit the client’s needs. At the most basic level SRI will provide an on-site pre-design audit, concept design drawings, design specification and on-site commissioning.

If required, SRI can provide a complete turnkey installation (including instrumentation), or any scope from the most basic supply through to the full
turnkey plant. The ideal choice for the client is contingent on the size of the unit and the locally available procurement and engineering capabilities.

What level of improvement in sugar quality can I expect from the system?

SRI’s projects in India, China, Central America and Australia have resulted in an improvement in sugar quality for its clients. However SRI cannot make any specific claims with regards to final sugar quality. Our experience has demonstrated that differences in the local conditions, cane quality, and the performance of upstream and downstream factory processes, all have an influence on the results achieved following syrup clarification.

The typical performance of the syrup clarification stage, for an installation set up and operated according to SRI recommendations is as follows:

Colour reduction, at 300ppm P205 on syrup solids and without colour precipitants:

15-20% for raw syrup or 25-35% for melt liquor
Typically 5-10% greater than achieved by other clarification systems under the same conditions (based on retrofit experience)

Colour reduction with the addition of up to 150 ppm of suitable colour precipitant:

A further 5-10%

Turbidity removalMinimum 75%
pH dropMaximum of 0.2
Reduction in viscosity>5%
Removal of suspended solids (depends on what the suspended solids are)
• For bagacillo
>80% removal
Change in R.S% 100 brixNil
Reduction in CaO% 100 brix10 - 12%
Purity rise across clarifier
from untreated to treated syrup
Too small to measure <0.5%
Sulphur Dioxide content of sugar produced5 - 15 ppm
Recovery rise across the systemNil

What other operating guidelines does the system have?

Typical operating criteria for the system are as follows:

Syrup brix (% dry solids):
(good syrup brix control is important for trouble free operation)
<64
Syrup temperature85 oC
Scum rate1-3% by volume of syrup feed

How does the SRI air saturation system compare with other air distribution systems?

The air injection system is one of the key elements of a flotation clarifier. Several different technologies are used to produce the fine air bubbles required for the flotation process.

SRI’s system uses dissolved air rather than dispersed air. Air bubbles from a dissolved air system are finer, have a much greater surface area and better dynamics than those from a dispersed air system, resulting in much more efficient removal of turbidity and fine particles.

How does SRI’s flotation clarification system differ from that of other equipment designers?

SRI’s current design is based on detailed computational fluid dynamics analysis of the syrup flows in and around the critical components. To our knowledge no other manufacturer has used this powerful tool to properly optimise their design. The result is improved performance, reduced losses, reduced maintenance requirements, and longer operational periods between cleaning stops.

What is the rate of use of consumables for the system?

Under steady operating conditions the routine use of consumables should be in the following ranges:

H3 PO4, on syrup solids
(85% food grade H3 PO4)
400-600 ppm
Lime usage, on syrup solids
(depends on lime quality)
300-800 ppm CaO
Flocculant usage, on syrup solids 8-12 ppm
Air consumption: on syrup flow<0.5 L/min at 550 kPag

Note: Colour precipitants are not listed above as they are usually not economically justifiable.

What size range is available?

SRI has designed or upgraded flotation clarification systems for rates as low as a few tonnes per hour to 100 tonnes of melt solids per hour.

Where are SRI’s systems installed?

Australian, Chinese and Indian factories and refineries have systems installed. Troubleshooting advice has also been provided for facilities in Australia and Central America.
  • Dbrix Transducer

Can I use the DBrix in my A, B and C batch pans?

Yes. The DBrix transducer is specifically designed for batch pan control and has been tried and proven for over 20 years in A, B and C batch pans around the world as a cost-effective alternative to refractometer and Coriolis effect Brix measurement.

Can I use the DBrix in my continuous pans?

Yes. SRI’s electrically heated probes are recommended to avoid the encrustation of sugar crystals that occurs with unheated probes in continuous pans.

How do I re-range the DBrix for use in a multi-purpose pan?

The DBrix exciter has two digital inputs that are used to select any one of four pre-set operating ranges. To re-range, select a different calibration set (using the digital inputs) and then use the auto set functions to range the exciter to suit the boiling duty or feed material.

What are the effects of variations in ash & temperature?

The DBrix is susceptible to changes in ash. However, it is suitable for massecuite of less than 96 true purity (94 apparent purity). Temperature compensation is needed if there are significant changes in temperature (> 2°C) caused by variations in vacuum pressure or other operating conditions, in a short period of time e.g. one minute, or if the transducer is being used to provide a measure of Brix rather than conductivity. An example of the latter case is for Brix indication of syrup from the final evaporator. Note: for pan control temperature compensation is not normally required as rapid changes in temperature must be avoided.

What is the effect of reducing sugar content?

Reducing sugar content has no effect on the DBrix reading.

Does the transducer measure supersaturation, crystal content, solution Brix or total Brix?

The DBrix measures impedance (resistance and capacitance) at radio frequency. Total Brix is inferred from the impedance measurement.

How do I use the transducer set to control my pan?

The DBrix reading can be used to control the feed to achieve a given Brix profile. The Brix profile is determined by on-site personnel in their selection of the set points for the control loops.

What are the temperature limits for the probe and exciter?

The temperature limit for the probe is 120 °C for a maximum of 10 minutes, for the exciter: 55 °C.

What are the outputs and how are they scaled?

The process measurement is available as a 4-20 mA analog signal. The scaling may be adjusted using a digital calibrator which can be plugged into the exciter.

What are the output units?

The 4 – 20 mA corresponds to a scaling of 0 to 100% of reading. The reading can be calibrated to a known Brix range using the ‘auto set’ functions. For example, the instrument can be ranged for 60 to 80 °Bx by pressing the auto set 4 mA button (on the digital calibrator) when the process is at 60 °Bx and then pressing the auto set 20 mA when the process is at 80 °Bx. The output will be shown in percent on the digital calibrator display in the “Conductivity” screen: 0 % will correspond to 60 °Bx and 100% will be displayed when the massecuite is at 80 °Bx.

How do I calibrate to measure Brix or % solids?

The output as shown on the digital calibrator is in milliamps (mA) and in percent (shown at the Conductivity and Temperature screens). There is no means to scale the readings of the calibrator to show °Bx or % solids. Scaling from mA to °Bx may be carried out in the DCS. Likewise temperature compensation (if required) may be carried out in the same way.

What is the accuracy?

The accuracy depends on the characteristics of the application and on the accuracy of the reference measurement used in the calibration and is typically ±1.0 – 2.0 °Bx (at a constant temperature and constant ash percentage).

What is the precision?

The precision depends on the characteristics of the application and on the precision of reference measurements used in the calibration and is typically 0.5 – 1.0 °Bx.

How often do I have to recalibrate?

Only for each new duty, and when the probe, RF cable or exciter are changed.

How far should the probe be from internal steel work and other probes or transducers?

The tip area of the probe should be a minimum of 75 mm from other surrounding metallic objects. Care must also be taken to minimize the chance of bridging forming when other objects are mounted beside the rest of the probe body.

Is it standards compliant?

The DBrix has been designed to comply with Euro and FCC standards but it has not been certified.

Sugar Research Institute (SRI)

Global experts in sugar milling and refining technology.

Phone: +61 411 933 500

Email: info@sri.org.au

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