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.
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.
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.
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 removal | Minimum 75% |
| pH drop | Maximum 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 brix | Nil |
| Reduction in CaO% 100 brix | 10 - 12% |
| Purity rise across clarifier from untreated to treated syrup | Too small to measure <0.5% |
| Sulphur Dioxide content of sugar produced | 5 - 15 ppm |
| Recovery rise across the system | Nil |
| Syrup brix (% dry solids): (good syrup brix control is important for trouble free operation) | <64 |
| Syrup temperature | 85 oC |
| Scum rate | 1-3% by volume of syrup feed |
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.
| 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.