Introduction
Introduction of Vacuum Filter in Indian Sugar Industry in early fifties has indeed proved its performance by eventually replacing obsolete method of whole juice filtration using plate and frame type filters. Since the introduction of vacuum filter till to date there is no change in technology which itself speaks of the simplicity and versatility of vacuum filter. However, as it generally happens, any new development has some inherent lacunae or shortcomings but are perhaps overlooked due to other major significant advantages; which exactly has happened while introducing and establishing vacuum filtration technology in Indian Sugar Industry. The introduction of vacuum filter had created other serious problems regarding the disposal of low purity cloudy and dirty filtrate as same could not be sent forward for direct evaporation. The very nature of the filtrate necessitated to mix the same alongwith mixed juice for carrying out further clarification, as there was no other alternative left with. However due to growing awareness of the disadvantages of mixing low purity high non-sugar content filtrate with high purity mixed juice, it was thought essential to treat the filtrate separately and since last ten years efforts are being put in right direction to evolve and develop such a system which can consistently produce clear juice having comparable quality parameters with that of clear juice resulting from juice clarifier so that the clear juice resulting after the treatment of filtrate can be taken directly to evaporator. However, none of such processes earlier developed could offer assured consistency with minimum inputs in terms of, installation and operating cost and simplicity in operation. Perhaps sugar industry had to wait until a trayless clarifier concept was successfully and commercially implemented where during mud settling process filtration by “upward sludge filtration” technology is accomplished for trapping of finest solid particles present in the filtrate which otherwise are difficult to settle being lighter in nature.

After the early trials of trayless clarifier concept for the treatment of filtrate the latest development in the technology of trayless clarifier was first time introduced by Suviron, having peripheral feed entry with central take off launder. In comparison with earlier concept of trayless clarifier technology, the system developed by us offers minimum feed juice velocity so that at the feeding point, there are no cross currents and hence no turbulence; and the upward juice velocity being the lowest there is not risk of particle carryover alongwith clear juice.

Equipment
A unique equipment flash-floc-flow mixer has the multiple function of flashing, building up of loose flocs into the dense and thick flocs and homogeneous mixing of very fractional proportion of polyelectrolyte added in feed juice. The Trayless Clarifier consists of feed inlet and clear juice take-off launders and mud scrapping arrangement. The bottom cone acts as a single settling tray. A specially designed feed launder system allows silent feeding of floc-enriched feed juice at a specific discharge point, without causing any local turbulence and avoiding cross flows. One no. concentrically located clear juice take-off launder with weir notches uniformly collects the supernatant clear juice which is then taken out through clear juice overflow weir box. Slow moving stirrer rotating at 4 rph and fitted with specially designed trailing type scrapper blades gently pushes the compact mud into the mud boot. The further mud thickening process is carried out in a cylindrically shaped mud boot for compacting the loose mud particles to form thick and compact mud at the bottom-most conical portion. The mud is continuously withdrawn by gravity flow towards mud mixer. The intermediate zone where the floc-enriched feed juice is discharged offers a sweeping down effect in order to trap the lighter mud particles in the cloud of settling flocs, thereby ensuring complete removal of even the finest bagacillo and other suspended particles. The other equipments like heater, dilution tanks, reaction vessel, juice receiving tank etc. being the standard and commonly used in sugar factory need not be described in details.

Advantages
Treatment of low purity filtrate and high purity mixed juice in two separate streams obviously offers following advantages :

»	Improvement in boiling house recovery The guaranteed purity rise by 3-4 units obviously has the advantage of resulting into improvement in boiling house recovery.
»	Increase in clarification house capacity The system is very ideally suitable while going into plant expansion by 20% without necessitating replacement/addition of various items in clarification section viz. Juice Clarifier, Juice reaction vessel, juice heaters, Juice pumps etc. The initial huge installation cost and capital expenditure thereof for replacing or adding various equipments in clarification house as mentioned above can be avoided.
»	Improvement in performance and capacity of vacuum filter The nature of mud in the filtrate clarifier which is more compact offers improved performance at vacuum filter station by increasing the thickness and porosity of filter cake. Thus the mud disposed per unit filtering area of existing vacuum filter is increased.
»	Reduction in colour-imparting de-gradation products The low purity filtrate having more non-sugars induce colour development during long retention time conventional juice clarifier, while the treatment of filtrate is accomplished within short period and hence the chances of increasing the colour imparting de-gradation products is reduced.
»	Reduction in CaO contents The early treatment of phosphoric acid with milk of lime precipitates the soluble CaO content, and hence the clear juice resulting from the filtrate treatment has less CaO content
»	No destruction of reducing sugars The short retention period in trayless clarifier restricts destruction of reducing sugars which otherwise might result into formation of melassigenic products.
»	Increase in the capacity of existing juice clarifier As the “filtrate returns” are separately treated, the capacity of existing juice clarifier gets accordingly increased to accommodate additional load of treated mixed juice to the extent of 20%.
»	Less Danger of microbial sucrose inversion in main juice clarifier Since the filtrate which is highly contaminated with micro-organisms is not mixed with fresh raw juice, the risk of sucrose inversion due to microbial activities during long residence time at main juice clarifier is greatly minimized.