Tapioca Starch Processing Line For Tapioca Extract Processing

System Flow Chart

Technical description

1. Reception and washing unit

In the Reception and washing unit, stems and branches mixed in the harvested tapioca roots and impurities such as sand will be get rid of, peels as well as woody tissues of tapioca roots will be removed. The unit is designed to clean the tapioca roots so that rasping machines in the next procedure can work well.

The fresh tapioca roots are taken afield to the factory by truck. After being weighed and sampled for starch content determination the fresh roots will be unloaded to the raw material storage platform.

When production begins tapioca roots will be taken by a shovel loader out of raw material storage platform into the reception-hopper installed with electromagnetic vibrancy feeder at the bottom. After initially sand removing the roots are dropped onto the belt of an inclined belt conveyor where stems and branches are picked out and woody tissues of tapioca roots are manually cut off.

On the other end of belt is a squirrel cage type dry cleaner which will get rid of the sand and peels without water. The sand and peels pass through the meshes of dry cleaner and then are collected to a sand collecting gutter for periodical clean-up.

After dry cleaning the roots are sent to two three-stage paddle washers for water cleaning stage by stage. Roots will be soaked in fresh water firstly. Under agitation the tapioca roots in the water rub each other and thus mud and sand are cleaned off. To reduce water consumption, the water used in the first-stage cleaning process can be overflow water from hydrocyclone unit.

After three-stage washing the clean roots are placed onto inspection belt of the inclined belt conveyor for second check and then sent to the rasping unit directly.

2. Rasping and pumping unit

Rasping unit is used to break the starch granules   in tapioca roots and make combined starch content in   the fiber reduced to the lowest level. The efficiency of rasper is vital to the yield of commercial starch. Always every production line is equipped with two sets raspers for alternate saw blade replacement so that the production line can run continuously.

Clean tapioca roots coming from washing unit will firstly be chopped into small pieces. Chopped pieces fall into the hopper with “W” type bottom and then go via the four screw conveyors with variable speed control into the rasper to be ground into tapioca slurry.  Process water is added to facilitate the rasping process. 

What comes out of rasper is the mixture of free starch granules, fiber, combined starch, protein, sugar as well as mineral elements, i.e, tapioca slurry. The tapioca slurry flows down the collecting chute to the slurry tank and then is pumped to the cyclone de-sanding unit by the screw pump (slurry pump) installed on the bottom of the slurry tank.

3.Cyclone de-sanding unit

The unit is designed to remove remaining sand in the tapioca slurry and protect the screens of centrifugal sieves in the following procedure.

The tapioca slurry coming from rasping unit enters into the desanding cyclones at a tangent under pressure. Due to the centrifugal force the light-phase particles in the slurry separate from the heavy-phase particles in the process of high-speed rotation. Light-phase particles such as starch and fiber will leave the de-sanding cyclones in the terms of overflow from the top while the heavy-phase particles sink to the bottom and then drop to the sand collecting pot which is supplied with upward water to avoid starch loss.

At the bottom of the sand collecting pot is air chamber valves which will open automatically to eliminate the sand inside.

The de-sanding tubes in the desanding cyclones are specially designed ceramic tubes and highly wear resistant.

4. Centrifugal extracting unit

In the centrifugal extracting unit, most of the free starch in tapioca slurry will be extracted. This Unit is another key chain to improve the yield of commercial starch.

The production line with capacity of 120 tons commercial starch per day includes three-stage centrifugal sieves in series.

After desanding the tapioca slurry are pumped to the first-grade centrifugal sieve unit. In the process of rotation the starch milk go through the screen and pumped directly to the concentrating and washing Unit.  

The tapioca pulp screened out by the first-grade centrifugal sieve unit are subsequently pumped by fiber pulp to the second-grade centrifugal sieve (recovering centrifugal sieve) for recovering of starch and the fiber pulp coming from first recovering sieve are pumped likewise to the third-grade centrifugal sieve for the further recovering of starch and after three-grade extraction there are almost no starch inside the fiber pulp which is sent later to the fiber pulp dewatering unit.

The starch milk extracted from the second-grade centrifugal sieve and the third-grade centrifugal sieve unit will be pumped both to the process water supplying unit for the first-grade centrifugal sieve unit.

The screen of sieve basket is flushed from two opposite direction. The process water spraying from the front of screen helps to turn over the slurry to extract more starch while the process water spraying regularly from the back of the screen wash off the pectin and fibers which tend to block up the screen. Such spraying device enables centrifugal sieve to work continuously for longer time.

5. Fiber pulp dewatering unit

Fiber pulp from above-mentioned third-grade centrifugal sieves will be dewatered in this unit. After the dewatering the fiber pulp will be taken away from the dewatering centrifugal sieve by the screw conveyor for further processing.

The fluid down the screen of the sieves is pumped to previous extracting unit to be used as process water.  

6. Concentrating and washing unit

Concentrating and washing unit is designed to get rid of related substances such as fiber and protein in the starch milk. So it is the most important unit in the whole production line and affect the quality of end-products.  The concentrating and washing unit includes three units: concentrating hydrocyclone unit, recovering hydrocyclone unit and washing hydrocyclone unit.

The starch milk from last procedure are brought into concentration hydrocyclone unit for initial concentration. Overflows from concentrating hydrocyclone unit are pumped to two-grade recovering hydrocyclone unit. Underflows (starch milk) are pumped into the following washing hydrocyclone unit for purifying grade by grade with counter-current process water.

From the outlet at the bottom of the last-grade washing hydrocyclone in series we get good-quality starch milk at over 22 Baume which is subsequently pumped to a stainless steel storage tank with agitating device for further dewatering treatment.

In the process overflow from each washing hydrocyclone returns to be the feed of the hydrocyclone put ahead of it. Overflows arising from recovering hydrocyclone unit are disposed as effluent directly and underflows returns to the concentration hydrocyclone unit.

Fine fiber sieve unit is auxiliary part of hydrocyclone unit. It is connected with the outlet for overflows of first -grade washing hydrocyclone unit. When the starch milk in the hydrocyclone unit contains much fine fiber and coarse substances, the device is activated and then the overflow flow directly from the first-grade washing hydrocyclone to the fine fiber centrifugal sieve to screen out unnecessary fine fiber.

7. Starch milk dewatering unit       

After washing the starch milk have high water content and is not suitable to be dried directly. So it need dewatering first to meet the requirements on the inlet moisture of flash dryer and then be dried.

The working principle of Peeler centrifuge is as follows: when the drum runs at full tilt, the valve of the feed inlet will open automatically and thus stalk milk flow down the feed tube into the inner drum and spread across the inner face of filter cloth due to the centrifugal force.  Liquid-phase particles pass through the filter cloth and are soon taken out,  while the wet starch cake accumulates in the drum.

When the starch cake are accumulated to a fixed level, the valve of the feed inlet will close automatically.The valve of washing inlet will open at the same to release the flushing fluid inside to flush the solid-phase starch cake for a while and then close. The drum subsequently begin spinning again  and during the process solid-liquid particles are dewatered. And the scraper will be activated to scrape in radial direction the starch cake which will fall down collecting chute to the tilted unloading hopper outside and then transferred to the feed inlet of flash dryer. After that the scrape will return to the formal place.Flushing valve opens subsequently and the filter cloth will be flushed and cleaned. Above is a whole working circle.   

The working pattern of peeler centrifuge is intermittent and so the production line need to be equipped two peeler centrifuge at the same time to keep the continuous operation.

The performance of peeler centrifuge is good and the operation is steady and simple.  The dewatered starch cake have lower water content and reduce greatly the energy consumption of flash dryers in the next drying unit .

8. Flash drying unit

In flash drying unit the wet starch cake will be dried by the flash dryer to meet related requirements of commercial starch.

The wet starch cakes are brought to the feed inlet of flash dryer by the feed screw conveyor with hoppers and then move with the filtered hot air which is firstly heated by heat exchanger and  then blown into the air duct. In the process of moving to cyclone separator, the wet stack cakes are dried and the wet vapor are expelled by the induced draft fan. 

Dried starch fall down to the bottom of cyclone separator then are carried to the airlock by cyclone screw conveyor and then brought into the starch mixing silo. With the assistance of lever feeder installed at the bottom of mixing silo the starch are brought to the bucket elevator and further transferred to the reversible screw conveyor. 

If the dry starch fail to meet the requirement of water content, the starch will be brought back to starch mixing silo.

When the water content in the dry starch is up to the standard, the reversible screw conveyor will bring the dry starch to the vibration sifter for fineness grading. Gelatinized and coarse particles will be sifted out. Qualified starch are stored in the stainless steel starch product silo for packaging and marketing.

The flash dryer adopts specially designed big bent pipe and so reduces energy consumption greatly.

9. Weighing and packaging

The final product in the starch silo will be bagged by automatic packaging machine. Commercial starch generally has two packaging sizes:25kg/bag and 50kg/bag.