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Par-boiling & Drying
E.Jayakumar, B.E (Mech).,M.Tech (FPE).,MIE.,FIV.,Charted Engineer (India)(M-153913-7),Approved Valuer (F-25667)(VII)-Machinery and Plant .Free Lancer,AGRO TRADE LINK A turn key solutionE.Mail: jayakumaryuan@gmail.com: Mobile: +91 9444025375, +919940819765Phone: 04362-278398 :,Skype: Easupatham
Par-Boiling
Partial cooking of rice intact with husk is called parboiling.
Involves soaking, steaming, drying and milling.
Parboiled rice takes less time to cook and is firmer and less sticky
Advantages
Milling
• Dehusking is easier and costs less
• Fewer broken• Increased head and total rice
output Storage
• More resistant to insect attack Cooking
• Loses less starch and keeps longer• More fiber than regular rice
System Material feeding (Elevator) Pre Cleaner Over Head Storage Soaking Tanks Steaming tanks Water Pipe line Steam pipe line Drainage system Water circulation system Material discharge (Belt Conveyors)
https://www.youtube.com/watch?v=rFbCkD0Eb0Q
Processing
Soaking
Impregnating moisture to the required level before cooking operation.
Steaming
Raising the temp of paddy to near saturation temp of water in the presence of steam.
Drying The paddy is left at high temp and moisture level of 32%
At his stage the paddy is liable for bacterial and fungus attack
Hot aid blown through it in the dryers
It involves lot of techniques to get uniformly dried grain with desired
moisture
Techniques
Single boiled rice (white belly rice)
Double Boiled Rice - Fully translucent rice
Hot soaking method - Fully translucent rice
Steamed rice (Cured rice)
Process for Single Boiled Rice -White belly Rice
Pre-cleaning
De-stoning
Transfer to overhead bins
Discharge raw paddy in to roomtemperature water in soaking tanks
MS/SS Soaking Tanks
Remove chaff and immature grains floating on water surface
Soak for 6 to 12 h (Capacity: 2-3 tones with steaming and water circulation
arrangement)
Capacity of tank 2-3 tonesWith steaming and water circulation
arrangement.or
Soaking tank capacity of 5-10 tones
Process for Single Boiled Rice -White belly Rice Cont..
Circulate the water Drain and tempering for 2 h
Steam the paddy for 1 to 2 min after steam emergence on top
Discharge the paddy quickly from
steaming tank into cooler
Dry the paddy in Drier(Circulatory/ fluidized bed type cooler)
(Moisture content to 14%)
Unload the paddy to Storage bin / Milling Section
If 5 – 10 tones soaking tank, steam the soaked paddy in steaming vessel of capacity 0.5 to 1.0 tone / continuous
steaming vessel kept below the soaking tankNumber of tanks matching the drier capacity
Process for Double Boiled Rice - Fully translucent rice
Pre-cleaning
De-stoning
Transfer to overhead bins
Discharge raw paddy in to soaking cum steaming tanks
MS/SS Soaking Tanks
Steam for 5 min
Add water RT water to steamed paddy (1.5 times to the paddy)
Capacity of tank 2-3 tonesWith steaming and water circulation
arrangement.or
Soaking tank capacity of 5-10 tones
Process for Double Boiled Rice Cont..
Circulate the water for half an hour
Remove floating chaff and immature
Soak for 12 to 24 hrs depending on the Variety till complete saturation of paddy
Drain the water and temper for 2 hrs
Unload the paddy to Storage bin / Milling Section
Steam paddy for 1 to 2 min after steam emergence at top
Discharge the paddy quickly from steaming tank into cooler
Dry the paddy in Drier
If 5 – 10 tones soaking tank, steam the soaked paddy in steaming vessel of capacity 0.5 to 1.0 tone / continuous
steaming vessel kept below the soaking tankNumber of tanks matching the drier capacity
Process for Hot soaking Method - Fully translucent rice
Pre-cleaning De-stoning
Transfer to overhead bins
Pump hot water 95ºC in to soaking tank or
Inject steam into RT water in soaking tank to raise Temperature to 95ºC
Discharge raw paddy into hot water
Circulate for ½ h so that the hot soak water attains 650C
Soak for 3 to 5 h according to the paddy variety
Drain water and temper for 2 h
Capacity of tank 2-3 tonesWith steaming and water circulation
arrangement.or
Soaking tank capacity of 5-10 tones
Process for Hot soaking Method Cont..
Steam for 1 to 2 min after emergence of steam on top
Quick discharge of steamed paddy from steaming tank to cooler
Dry the paddy in Drier
Unload the paddy to Storage bin / Milling Section
If 5 – 10 tones soaking tank, steam the soaked paddy in steaming vessel of capacity 0.5 to 1.0 tone / continuous
steaming vessel kept below the soaking tank
Number of tanks matching the drier capacity
Circulatory/fludised bed type cooler
IBR Boiler
Process for cured/steamed rice
Discharge raw paddy in to
soaking tanks
Steam for few min as per requirement (5-15 min)
Transfer to Tempering bin (3-4h)
Drying(Hot air temperature 65°C)
Temper the paddy for 12 h before milling
IBR Boiler
CuringThe accelerated effect of ageing in rice is
called curing. It can be achieved by steaming of fresh paddy /paddy stored for few months.
Drying
Grain Drying Principles and methods
◦ Reduce the moisture from grain to a safe level of storage .
◦ It is a critical step for maintaining grain quality and minimize the storage and processing losses.
◦ Drying is need because the high moisture grain will cause heat build up (Hot spot) from respiration of microorganisms, low thermal diffusivity of grain ,increased the mold growth, reduced starch and sugar content.
Why drying need?
High moisture grain will cause : Heat build - up (Hot spot)
From respiration of microorganisms and grain itself Low thermal diffusivity of grain Increased the temperatures accelerate the mold growth, Reduced starch and sugar content.
Drying mechanism
Two fundamental steps occur during drying
◦ Water migration migration from grain interior to surface.◦ Water evaporation from the surface to the surrounding air.
Moisture content decreases rapidly at first but slows down as grain dries.
Drying rate decreases with moisture content increases with air temperature.
Removal of water from grain during drying causes a reduction in grain quantity
Moisture content can be calculate :
Drying mechanism
Moisture Shrink % =
Equilibrium moisture content:
During drying, moisture content depends on temperature and relative humidity of surrounding air
When surrounding air is “dry” grain would loss moisture.
When surrounding air is “humid” grain would absorb moisture
Drying air Properties :
Vapor Pressure◦ Partial pressure exerted by the water vapor molecules in moist
air.
Relative humidity◦ Ratio of the mole fraction of water vapor in the air to the mole
fraction of water vapor in saturated air
Humidity ratio◦ Mass of water vapor per unit mass of dry air
Dry bulb temperature◦ Air temperature indicated by an ordinary thermometer
Wet bulb temperature ◦ Air temperature indicated by thermometer whose bulb is
covered with a wet wick
Dew point temperature-◦ Temperature at which moisture condensation will occur as air is
cooled
Drying air Properties :
Enthalpy-◦ Heat content of the moist air per unit mass of dry air above a
certain reference temperature.
Specific volume◦ Volume per unit mass of dry air.
Specific Heat◦ Measurable physical quantity of heat energy required to change
the temperature of air by a given amount.
Drying air Properties :
Effect of Drying on grain qualities:
Low and uniform moisture content
Minimum broken and damage kernels
Low susceptibility to subsequent breakage
Retained nutritional value
High viability
Good visual and organoleptic properties.
Drying Methods
Sun dryingMechanical Drying
L.S.U Dryer Developed at Louisiana state university (LSU) Continuous mixing type dryer Developed specifically for rice to ensure gentle treatment,
good mixing & good air to grain contact Consists of rectangular chamber, holding bin, blower with
duct, grain discharging mechanism and air heating system Layers of inverted V shaped channels are installed in the
drying chamber; heated air is introduced through these channels at many points
Alternate layers are air inlet & outlet channels; arranged one below the other in an offset pattern
Inlet port consists of few full size ports & two half size ports; all ports are of same size arranged in equal spacing
Ribbed rollers are provided at the bottom of drying chamber for the discharge of grain
L.S.U Dryer
1. Garner 2. Duct 3. Dry material outlet 4. Hopper 5. Continuous flow 6. Door 7. Roof
Process
Dry the paddy at 100°C of Hot air till the on line moisture meter shows 20%
At the moisture of 18-17% transfer the paddy to tempering bin( 3-4 h)
Reduce the hot air temperature to 80°C till the paddy moisture percent falls to 14 -13%
Temper the paddy for 12 h before milling
Future is not something we wait it is something we should create
-Swami VivekanandaE.Mail: jayakumaryuan@gmail.com: Mobile: +91 9444025375, +919940819765Phone: 04362-278398 :,Skype: Easupatham
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