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Introduction To Cassava Starch production

Come from:Nanning Bangke    Date:2008-4-17
A Brief  Introduction To Cassava Starch production Line
1 General on raw material
   Cassava(Manihot esculenta Crantz), a species of sub-bush, is perennial plant which grows a circular roots that are greatly different from quantity and size because of different variety. Cassava root contains high starch content while it holds less protein, lipoids and ash. The fresh root of some good variety of cassava includes 25%~32% starch content on which cassava is shown as a good raw material for starch.
2 Design scheme
2.1 Principle of cassava starch extraction
 Cassava starch production is a physical process in which starch in cassava root is separated from fiber, protein and inorganic and organic impurities. In production process, cassava starch is divorced from its suspension in water aiming at recovering it in accordance with the character of starch’s insolubility in water and heavier gravity than water by means of using water and specialized mechanical equipment.
2.2 Design scheme
   Bangke’s design scheme of cassava production is matured, advanced, scientific and rational in process which contains 4 sections: crushing, sifting, separation and drying. Production efficiency and starch extraction rate are increased using Bangke’s two patents technologies in which starch milk is separated first from coarse fiber and then from fine fiber(cellulose) respectively to substitute the traditional sieving process.
3 Cassava starch production flow (see fig.1)
4 Description of Cassava starch production flow
4.1 Raw material preparation
   Fresh cassava root is moved to scraper conveyor.
4.2 Raw material conveying
4.3Raw material cleaning
Fresh cassava root is input into the drying cleaner of soil-removing and peeling in which screw guide plate fixed on inner wall of the cylinder cage pushes forward cassava root when the cylinder cage rotates. Cassava roots collide and rub themselves and also against the wall one another to remove soil and peel of under the centrifugal force. After soil-removing and peeling of cassava roots go into the agitation water cleaner.
4.4First step of water cleaning
  U-tank water cleaner with screw propeller is used in the first step of water cleaning. Water goes into the U-tank in which a shaft with screw propeller is equipped. Cassava roots are agitated turned around the shaft and propelled forward to clean soil and peel again. Then Cassava roots go into the second step water cleaning.
4.5Second step of water cleaning
  Cylinder cleaner is used in the second water cleaning. The cylinder cleaner consists of 3 clearing sections: rough washing , bathe washing and thorough washing ,where water is fed and cassava roots run along with the cylinder and go ahead to further eliminate soil and peel in the status of spaying ,flushing bathing rubbing and cleaning. Water, as a cleaning media, is used at the rate of 1 : 4 . After cleaning thoroughly soil, 95% of peel is removed, the cleaned cassava roots move to crushing section.
4.6 Crushing section
This section adopts hammer crusher which destroys the tissue of cassava and makes the very small granular of starch decompose and depart from the roots. The hammer knives, hammer jaw, teeth ,grill disc and rubbing plate strike, rasp cut and squeeze the continuous fed cassava roots which release starch particles that turn into raw starch milk when mixing with the water as a media in the proportion of 1:1.
The second step of crushing process is applied for full breaking down cassava root tissue which becomes finer granular of starch that separates thoroughly to increase the extraction rate.
      The requirement for the first crushing ensures the starch milk to go throughΦ8.0 to 16.0mm pore of basket sieve of centrifuge while the second crushing enables starch milk to flow through Φ1.2~1.4mm pore of basket sieve of centrifuge.
After crushing, starch milk is sent into basket sieve of centrifuge in the first stage of separation.
 4.7 First stage separation section
First stage separation section utilizes 4 upright continuous centrifuges which separate starch milk from coarse cassava residue in 3 steps and fine residue in 1step sequentially(See production flow sheet). Starch milk is washed again and again and separates from cellulose (mostly cell wall).
4.8 First stage separation section
 Starch milk after sieving by centrifuge in the first step and the second step is delivered to fine basket sieve in upright continuous centrifuge in which starch milk is further sieved from the more finer cellulose to be pure starch milk that contains fiber less than 0.02% and reaches 5~6 Bé in concentration. Coming out from the fine basket sieve in the centrifuge, starch milk goes to the filtration section while some dilute starch juice returns to the centrifuge in the first step for recycling sieving.  A little of un-fully breached down material drained out from the centrifuge in the third step reflows to the crusher in the second step for circulating and cassava residue is carried to pile ground.
4.9 Sand-removing procedure
   Cyclone separator is used in sand removing procedure. Starch milk is pumped into the cyclone separator of which starch milk is shed out from the top and sand is discharged from bottom because of the principle of gravity. After sand-removing, starch milk proceeds to filtration procedure.
4.10 Filtration procedure
     Rotary filter is applied in filtration process in which impurities is further cleaned out to ensure that no block happens to the latter process equipment. Impurities is retained by filtering drum and carried to the bottom of filter by hair brush, then discharged when starch milk is input into the filtering drum. After filtration, starch milk flows out from pipe which connects to the second stage of separation section.
4.11 Second stage separation section
   This stage includes 2 steps in which butterfly separator is provided to divorced insoluble protein and the remaining soluble protein and other impurities from starch milk following to the principle of gravity disparity of water, starch and protein of yellow juice aiming at washing , refining and concentrating of starch milk. Starch milk is 5~6 Bé in concentration for input while 20~22 Bé for output. After 2 steps separation in the second separation section, the concentrated starch milk is fed into dewater procedure.
4.12 Dewater procedure
   Blade discharge centrifuge is served for dewater procedure in which water in the concentrated starch milk is thrown out to facilitate drying. Water content in the wet starch after dehydrated must be lower than 38%. The dewatered wet starch is moved to drying and cooling section.
4.13 drying and cooling section
Air dryer is installed in the drying and cooling system where the dewatered wet starch is dried. The feeder inputs the wet starch into the starch projetor which casts the wet starch into the drying pipe where the fresh air after being heated by heater mixes with the wet starch which is suspended on hot air flow and finally dried by means of heat-exchange in the process of substance transmission because of the strong back pressure resulting from the pneumatic effect of the blower. The temperature of air flow
Is controlled at 130~180℃。
4.13 Cooling procedure
The dried starch is led to the air cooling system for cooling and turned into the starch that contains water equal or less than 13.5%.The cooled starch is sent to the finishing sieve procedure
4.14 Final starch product sieving procedure
 Horizontal finishing sieve is laid in the final starch product sieving procedure where the dried starch is sieved. The fine powder of starch (suitable) can go through the screen of the sieve and drop down to the hopper for packing while the coarse powder of starch, held on by the sieve comes out from another outlet for packing and returns to the whole production process for recycling of dissolving, separation, sieving drying, etc.  
4.15 Packing procedure
   Pack the fine powder of starch from the outlet 1of the hopper into bag.
   Transport the starch product bag into the storage house.
5        Main parameters of the process
5.1 Water for cleaning cassava root is in the proportion of 1:4
5.2 Water for crushing cassava root is in the proportion of 1:1.
5.3 The starch milk can go through ø8.0~16.0mm pore of screen after the first step in the first stage of crushing.
5.4 The starch milk can go through ø1.2~1.4mm pore of screen after the second step in the first stage of crushing.
5.5 Starch contains fiber impurity less than 0.02% after spiting by centrifuge and washing and it is 5~6 Bé in concentration.
5.6 Starch milk is 5~6 Bé in concentration for input in the first step of separation at second stage while 12~22 Bé in concentration for outlet.
5.7 8~10 Bé in concentration for input in the second step of separation at second stage while 20~22 Bé in concentration for outlet.
5.8 20~22 Bé in concentration for the inlet of blade discharge centrifuge
5.9 Wet starch contains 38% water.
5.10 The final finish starch product starch that contains water equal or less than 13.5%.
5.11 Requirement for fresh cassava root
   Starch content > 25%,fresh,no spoil and mold, no soil and stone.
5.12 Requirement for water supply
  Turbidity:< 0.1,hardhess: :<100PH,SO2:<0.5ppm,Fe:<0.9ppm
  pressure: > 0.2 mPa, no floating material。
5.13 Starch recovery rate: > 96%  (?)
5.14 Consumption
5.15 water consumption:  <15t/t starch product
5.16Electricity consumption: <180kwh/t starch product.
5.17 Coal consumption (on standard of coal):
5.18 Starch quality:
    First grade rate: more than 98%, following to the standard of QB1840-93.
6        Features of the cassava starch production process
Bangke supplies different capacity of production line:
 200t/d fresh cassava root processing ( starch production:≥50t/d).
400t/d fresh cassava root processing ( starch production:≥100t/d).
800t/d fresh cassava root processing ( starch production:≥200t/d).
 1200t/d fresh cassava root processing ( starch production:≥300t/d).
 1600t/d fresh cassava root processing ( starch production:≥400t/d).
 2000t/d fresh cassava root processing ( starch production:≥500t/d).
6.1 Less land occupation, economic investment and lower energy consumption resulting from the combination of plane flow and vertical flow.
6.2 Short production flow which takes only 30 minutes from raw material input to final product output.
6.3 Continuous production process, high efficiency of equipment.
6.4 Process water can be reused to save water resource and reduce pollution drainage.
6.5 The whole production process is operated at normal temperature and atmospherically pressure except the procedure of drying.
6.6 New technology has been applied to upgrade further the production level and give the full play to the capacity of equipment resulting in cutting down the number of equipment, lowering down energy consumption and production cost, enhancing production output and improving product quality.
7 Other requirement relative to the production line
7.1 Cassava root must be fresh to ensure starch product quality and increase of recovery.
7.2 Rub off entirely peel of cassava root on which most cyanide toxin connives.
7.3 The process consumes quite amount of water which must meet the edible standard.
7.4 Equipment and pipeline are not allowed to make of iron with which cyanide turns into blue ferrous cyanide that stains starch causing an influence on product quality All of the equipment should better be mode of stainless steel or polyvinyl chloride
7.5 A great deal of material is delivered in the production process where more pumps are used to transmit material when equipment runs at high speed.
7.6 Because starch is easy to drop down and fiber is a uniformed material, therefore, flange and flexible joint should be mounted in the bender of pipeline which is convey-
niently dismounted for cleaning when block happens. But the drying system is an exception.
7.7 Clean equipment and ground very often to keep a clean and hygienic condition   for production process in order to secure product quality.
7.8 All the pools and tanks of starch milk must be coated preventing from erosion.
7.9 Control and eliminate various easy burning sources such as smoking, wedding and sparking fire from static electricity in the drying process to secure production.
7.10 Power source for all equipment:380/220V±10%,50HZ
8 Service
 Bangke offers the technical service as following:
8.1 The design conditions for production building, equipment layout and process flow sheet.
8.2 Responsible for installation, test-run and technical instruction of the production line, as well as training of operator.
8.3 The production line is applicable to producing starch from dried cassava chip if it is properly adjusted.

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