Super Heated Wash Water requirement for centrifugal machines with calculator
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 superheated 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 of 5 to 6kg/cm2 heated up to 115 – 120oC is known as superheated 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 the suction side of the pump. The delivery side of the pump is connected to the inlet tube side of heater the outlet of the heater is connected to the main header of superheated wash water system running behind C/F machines the other end of the main pipe should be constantly leaked out to the hot water tanks or drain using spring loaded valves.
In the present scenario for reducing steam consumption, a few sugar mills are now using system Plate-type heat exchanger for heating the super heated wash water (SHWW). Here 2nd body condensate is heated by exhaust steam.
The gravity factor of the Centrifugal machine has a significant effect on washing water requirements. High G.F. of a 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 a maximum 4 – 5% on sugar or 2 –2.5% on massecuite
SHWW requirement can be calculated in three ways:
While considering of Crushing Rate :
Data requirement (For better understanding purpose go through the same values in the 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 the PHE system and heating media is the exhaust)
Calculation
- 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 centrifugal machines:
Data requirement
- 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
Calculation
- 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 centrifugal machines nozzle data
Here we can calculate the requirement of SHWW estimated by the No. of nozzles and their capacity per machine,
Timing requirement for nozzle operation ( Basket wash + 1st wash + 2nd wash …..etc)
Now we can calculate the SHWW quantity requirement per cycle and easily find the total SHWW requirement.
To find the batch centrifugal machine capacity please go through the link
Batch Centrifugal Machine Capacity and Gravity Factor Calculation
Online Calculator of Superheated Wash Water requirement for Batch centrifugal machine
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Hello everyone! Thank you for taking the time to read about the Super Heated Wash Water (SHWW) System for Centrifugal Machines. I hope you found it insightful. Your feedback and comments are highly appreciated, so please share your thoughts.
