Introduction
In view of obtaining higher levels of process efficiency and for achieving improvement in quality of sugar, it is now high time to replace the old and obsolete technology of multi tray juice claririfier by modern and proven technology of Single Tray Juice Clarifier. The Single Tray juice clarifier incorporating most modern and latest concept of juice feed launder and clear juice take off launder to handle both defecated juice for raw sugar manufacturing as well as limed/sulphited cane juice for plantation white sugar production and also for treated filtrate juice settling in filtrate clarification system (FCS)

Technology and design parameter
In order to reduce retention time it is obvious that natural phenomenon of flocculation by way of bringing dispersed flocs together has to be artificially accelerated by adding higher molecular weight polyelectrolyte flocculant.

The quantity of polyelectrolyte flocculant which is added for activating the flocculation process is hardly in few ppm. It is therefore essential that this fractional quantity of polyelectrolyte gets properly admixtured with the incoming feed juice homogeneously, thus allowing total flocs to come together to form single heavy floc heavy enough as required for faster settling of the same.

A certain specific time is required for accomplishing reaction kinetics of building up of flocs and it has been proved by experiments and practice that the time of 45-60 seconds is required to complete flocculation activity. Preparation of polyelectrolyte solution of required concentration and its predetermined rate of dosing also forms an essential part of the total system.

While desiring to achieve reduction in retention time i.e. with lesser working volume of the equipment very obviously cross currents and juice velocity inside clarifier is carefully decided as compared to conventional clarifier having retention time of three hours. An essentially typical feature of single tray juice clarifier therefore is that it provides streamlined juice flow across the clarifier without any turbulence or cross flows.

Parameter defining capacity of Single Tray Juice Clarifier is the initial settling rate of the solids whilst the up-flow rate of the liquid must obviously be less than the settling rate of the solids at separation zone.

Bagasse has a natural tendency of absorbing air and water and during milling operation lot of the atmospheric air gets admixtured with extracted juice. Obviously the air being lighter than juice has a tendency to rise upward to the open surface which counteracts the natural phenomenon of sedimentation by gravity which is a downward movement. Hence it is very essential to remove entrapped air prior to allowing the juice to enter clarifier.

Salient features of single tray juice clarifier

»	Good clarification is achieved with less retention time.
»	Brilliant clear juice absolutely free from any suspended solids like bagacillo particles.
»	Less retention time, hence less risk of sucrose inversion loss as well as reducing the quantity of degradation products in process.
»	A good combination of well designed flash tank ensures complete removal of air from the juice and the floc-tower builds up dense heavier flocs for enhancing mud settling properties.
»	Less temperature drop due to less juice holding volume and less heat exposed area.
»	Compact mud formation for achieving better filter performance.
»	Less formation of colour imparting degradation products due to less duration of exposure to heat
»	Simple maintenance
»	Optimum consumption of polyelectrolyte flocculant by homogeneous mixing with juice at flash-floc-flow mixer. The cost involved by adding polymer flocculant is quite affordable and economical considering multifold advantages gained.

Detailed description of equipments
The total system of single tray juice clarifier consist of following equipment and accessories.

Flash-Floc-flow mixer
The unit comprises of :

»	Upper part where flashing takes place.
»	Middle part where polymer is mixed with flashed out juice.
»	Lower part where floc building is accomplished.

Flash-floc-flow mixer is fabricated from mild steel plates. It is cylindrical shape tank forming upper part of the unit. Incoming juice having temperature of 103-104 Deg.C. enters at the side wall through a tangential inlet. By virtue of difference in temperature of incoming feed juice and boiling temperature at the prevailing atmospheric pressure, air is released alongwith flashing vapours through a liberally designed vent provided at the top of the tank.

The middle and internal part of unit where polymer solution is added, is in continuation of flash tank which receives flashed out juice in concentrically located inner cylinder.

The lower part where floc building takes place is cylindrical shape outer vessel fitted with internally located overflow weir through which the floc enriched juice comes out of this unique designed unit for onward passing to feed launder of clarifier.

Clarifier
The juice is taken out from flash-floc-flow mixer with two outlets which are connected to main clarifier and then passes onto feed launder which is indeed a special feature of the design so as to avoid turbulence and cross flows of the feed juice. The main clarifier consist of main cylindrical shell, top and bottom cone, juice feed launders, clear juice take off launder, slow moving stirrer with pipe shaft having speed of 4 RPH is located at the center.

The main shell is fabricated from mild steel plates. It is cylindrical tank with conical top and bottom. The tank bottom cone with adequate slope towards mudboot is provided for easy sliding of underflow mud towards mudboot.

The central rotating pipe shaft is fitted to the horizontal gear box which gives the rotation of central shaft through drive unit assembled on mild steel fabricated frame. Scrapper arms are fitted on the central rotating shaft by arm holder with four branch connection. Trailing type scrappers are hinged to scrapper arms at specific distance. Tie rods are provided in between the arms, which can be inserted and adjusted.

Angle arm stirrer is provided in mud boot and fitted on central shaft. From the mud boot mud withdrawal is effected by gravity continuously to the mud mixer. Mud level at the bottom can be controlled by throttling valve provided near the mud boot. Test cock and liquidation connection with sump box are also provided.

Drive Head
The central rotating shaft is fitted to vertical output shaft of horizontal gear box which is mounted on mild steel fabricated heavy duty bridge frame. The drive arrangement i.e. standard electric motor and gear box are mounted on frame.

Driving sprocket is rigidly fixed on the output shaft of gear box and connected to driven sprocket mounted on input shaft of the horizontal gear box to transmit the power through chain arrangement. The entire frame of gear box, motor and horizontal gear box is rigidly fixed on strong mild steel fabricated bridge frame which is mounted on the top of the clarifier.

Flocculant solution preparation cum storage tank and dosing pump
Flocculant solution preparation tank is used for preparing polyelectrolyte solution of specific concentration. It is fitted with perforated coil. Polyelectrolyte solution is prepared and stored in the flocculant preparation tank for onward use. Low level audio-visual alarm system is provided to ensure adequate storage of polymer solution at all times. Dosing pump is used for dosing of flocculant solution from flocculant solution tank to flash-floc-flow mixer as per predetermined rate. Pump failure audio-visual alarm system is provided for continuously assured flow of polymer solution.

Two independent systems, each comprising of one polymer preparation tank and one dosing pump are provided so that one system is in operation while the other is under solution preparation.

Mud test cock sump
It is 'U' shaped, mild steel fabricated construction tank provided with drain connection.

Clear Juice liquidation sump
It is U shaped mild steel construction tank provided with drain connection.

Up-gradation of conventional clarifier to Single Tray juice clarifier
The existing conventional multi-tray type juice clarifier can be modified, incorporating the concept of single tray juice clarifier. The job can be carried out at site as per requirement.

Up-gradation of existing single tray Juice Clarifier
Up-gradation of existing single tray Juice clarifier to further reduce the present short retention time by incorporating the modified juice feed luander as well as suitably located clear juice take off launder can be carried out in-situ. Only by modifying the juice feeding and clear juice take off launder, the capacity of existing Single Tray Juice clarifier is enhanced.

Capacity and sizing
Depending upon the initial settling rate, a single unit single tray juice clarifier having capacities in the wide range to suite crushing rate upto 14000 TPD in case of defecation treatment producing raw sugar and upto 5000 TPD in case of liming and sulphitation treatment of raw juice for the production of plantation white sugar, custom built to individual requirement, is available.