Features:
- Hygienic design
- Handles products with a wide particle size distribution
- Excellent control of product temperature and moisture content
General Process Description
From the storage the raw product is brought into the cyclone de-stoner by means of a belt conveyer. The water carries the potatoes into the washing drum, where an (adjustable) layer of potatoes is present, creating thus intensive rubbing of the individual potatoes. The washing process is enhanced by overhead sprays in the drum.
A screw conveyer subsequently transports the potatoes to the weighing hopper, that doses a pre-set amount of potatoes into the steam vessel. Steam pressure is built-up in the vessel and held during a pre-set time, while a rotating arm stirs the potatoes. Thereafter the steam is relieved very fast into the expansion vessel. As a result the skin explodes of the potatoes. The batch is emptied into the extraction screw, transporting the potatoes to the dry peel remover. In the counter-flow screw washer the remaining peels, sand and other foreign objects are washed off.
The specifications of the final product determine whether the potatoes are sliced or processed as whole. Sliced potatoes pass the vibrating screen washer. Removed free starch is collected in a concentration pocket and is evacuated continuously for further treatment in a starch recovery system. The sliced or whole potatoes are generally delivered to the blancher.
From the slicing unit and vibrating screen washer, the potatoes are fed into the blancher and subsequently to the cooler, or bypass this via the flume system to the even flow screw conveyor. In the cooler the product is cooled in a counter current flow with water.
The potatoes are dosed in a cooker. Condensate is removed continuously. At the end of the cooking section the potato mash drops in screw conveyors for delivery in the powder back-mixer. Additives are mixed in the additive station and pumped to the inlet of the back-mixer. Wet product is dosed into the back-mixer onto the already present powder coming from the silo. Rotating shafts provided with hammers gently mix the wet cooked potatoes and the dry powder.
A moving belt transports and holds the product mixture for an adjustable time to equalize the moisture in the powder. At the end of the belt the powder drops into an after-mixer to loosen the wet powder before entering the coarse scalper screen for removal of coarse product. The sieved fraction drops in a product transport system to bring it to the initial dryer.
Product flows from above in the dryer in a spiral downwards in the mixing zone above the blade ring in the bottom section where hot air (high temperature) is introduced. Water will partly be evaporated and discharged with the used (and cooled down) drying air through the central opening in the top of the chamber.
Depending on particle size and air velocities, fines will be taken with the process air and recovered in the cyclones. The coarser and heavier product, with a higher moisture content, drops through an opening in the short cylinder at the inside of the blade ring and below the cone, into the discharge hopper with screw discharge for dosing into a product transport system. The fine powder separated by the cyclones is also directed to this transport system.
All incoming process air is filtered and passes through a glass-tube type heat exchanger. The supply fan brings the air via the special blade ring arrangement in the dryer. The energy for drying is extracted from hot air. An exhaust fan pulls the air through a set of cyclones and discharges it to the outside. The fans are equipped with frequency controllers for adjustment of air flows and static pressures at vital parts in the installation.
A product transport system brings the powder from the initial dryer to the secondary dryer. The process in this unit is identical with that of the initial dryers.
The powder from the secondary dryer is dosed into the pneumatic cooling transport system. At the end, the powder is discharged from the cyclones onto the fraction sifters. Powder discharged from the cooling system passes sieves for separation of non granulated oversized product. The sieved powder is transported to a silo for intermediate powder storage.
From this silo, the potato powder is transported to the back-mixer. Via another discharge the surplus of powder is sieved once more and then dried to the desired residual moisture content for packaging. After drying the powder is cooled. The oversized particles coming from the final sieves are returned to the silo.
For the final dryer the cooler is located below the dryer chamber and has a similar set-up, but without the heater.
