Super Heated Wash Water requirement for centrifugal machines with calculator
- 1 Super Heated Wash Water requirement for centrifugal machines with calculator
- 1.1 Sugar washing :
- 1.2 Super heated wash water (SHWW):
Sugar washing :
Washing in a centrifugal is designed to remove the high color molasses layer adhering to crystal surface.
This is an important part of the cycle and needs careful attention to detail if the required sugar quality is to be achieved without excessive dissolution of sugar. The sprays must be set up to spread the water uniformly across the height of the inside of the sugar layer.
In Water washing, the water is applied in fine spray on the surface of sugar. The water washes the molasses film and removes it and at the same time it unavoidably dissolves small amount of sugar.
The sprays are set up in an empty basket, and allowance must be made for the thickness of the cake in setting the sprays.
To avoid harmful effects of purity drop, the amount of washing has to be kept minimum. It is theoretically given that wash water is to applied when 75 % of molasses has been eliminated.
Super heated wash water (SHWW):
For better washing and get good quality sugar, super heated wash water is used for washing. In case of self-discharge batch type centrifugal, both water and steam is adopted. The super heated wash water system heat the hot condensate water to 115 ± 5 oC by steam. . The supply of water to pump suction is from overhead condensate tank. And temperature is about 70-80oC. Water under pressure 5 to 6kg/cm2 heated up to 115 – 120oC is known as super heated water.
The steam required to get the temperature should be applied at pressure of 7 kg/cm2 & 160oC – 180oC . The inlet hot water is supplied to suction side of pump. The delivery side of pump is connected to inlet tube side of heater the outlet of heater is connected to main header of super heated wash water system running behind C/F machines the other end of main pipe should be constantly leaked out to hot water tanks or drain by means of spring loaded valves.
In present scenario for reducing steam consumption, few sugar mills are now using system Plate Type heat exchanger for heating the super heated wash water (SHWW). Here 2nd body condensate heated by exhaust steam.
Gravity factor of Centrifugal machine has significant effect on washing water requirement. High G.F. of machine will require less water and vice versa
Quantity of water & steam to the sugar washing :
As per Noel Deer values are
Water required for washing 10 % on weight of sugar or . 5 % on massecuite.
Steam required for washing 20 % on weight of sugar or . 10 % on massecuite.
But practically SHWW only is sufficient for washing maximum 4 – 5% on sugar or 2 –2.5% on massecuite
SHWW requirement can be calculate in three ways:
While considering of Crushing Rate :
Data requirement (For better understanding purpose go through the some values in example)
- Crushing rate 230TCH
- A m/c % on cane = 30
- A m/c quantity per hour = Crushing rate x m/c %cane = 69 T/hr
- SHWW quantity on m/c = 5% on m/c (taken maximum value)
- Water inlet temperature = 85oC
- SHWW temperature requirement= 120 oC
- Heating media Temperature (Exhaust) = 125 oC (here consider PHE system and heating media is exhaust)
- Heating media latent heat = 522.5 Kcal/Kg (At 125oC)
- SHWW requirement = 3.45 kg/ hr
- Take 100% extra = 6.9 T/hr (To overcome the stoppages)
- Steam requirement for SHWW system= SHWW requirement (Kg/hr) x ( Water O/L temp. – Water I/L temp.)/ Latent heat. = 0.46 T/hr
- Steam % Cane for SHWW system = Steam requirement for SHWW system x 100 / TCH = 0.20
While considering of centrifugal machines:
- Machine Capacity = 1750 kg/charge
- Water quantity on m/c = 5 % on m/c (taken maximum value)
- No. of cycles per hour = 22
- No. of machines = 3
- Water inlet temperature = 85oC
- SHWW temperature requirement = 120 oC
- Heating media Temp. (Exhaust) = 125 oC
- Heating media Latent heat= 522.5 Kcal/Kg
- SHWW required per machine = Machine Capacity x Water quantity on m/c x No. of cycles per hour = 1925 kg/ hr
- Total SHWW required for all machines = SHWW required per machine x No. of machines = 5775 kg/hr
- Take 50% extra due to re circulation = 8.6625 T/hr
- Steam requirement = 0.58 T/hr
While considering of centrifugal machines nozzle data
Here we can calculate requirement of SHWW can estimate by the No. of nozzles and its capacity per each machine,
Timing requirement for nozzle operation ( Basket wash + 1st wash + 2nd wash …..etc)
Now we can calculate SHWW quantity requirement per cycle than easily find the total SHWW requirement.
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