after weighment is unloaded into the Cane Carrier. Before crushing the
cane in the Mills, it is to be prepared i.e. to be disintegrated into small
pieces so as to enable the Mills to extract more juice. This is done by
two or three sets of revolving knives called Cane Cropper, Cane Leveller and
Cane Cutter. The prepared canes will be like loose wool mat.
This prepared cane is passes through the Mills. Each Mill will have 3
Rollers. In each Mill, the Juice in cane is squeezed out twice i.e. in
between top and feed rollers and again in between top and discharge roller.
Thus in a 12 rollers tandem, this cane is pressed for 8 times and in 18 rollers
tandem 12 times. To get more sugar out of cane, water is added before last
Mill. This is called imbibition water and is weighed before adding.
This will dilute the juice in the cane so that the cane when passing through the
mill will yield more sugar.
The juice extracted from the Mill House is sent to the Boiling House for
processing. The bagasse coming out of last mill is sent to Boilers to
BOILING HOUSE OPERATION:
The juice from Mill house called
MIXED JUICE is weighed in juice Weighing Scale to know the quantity of juice.
After weighment, the juice is received in tank for pumping. Here, the filtrate
juice from vacuum filter is mixed with it.
This juice is to be clarified to
remove the impurities, coloring matters, suspended particles, etc. This is
achieved by Heat, Lime and Sulphur Gas. The juice after weighment is pumped to
the juice sulphitation vessel through the juice heater. In the juice heater the
juice is heated to 60 degree centigrade, 70 degree centigrade by Exhaust Steam
or Vapour from Vapour Cell or Quad.
This heated juice is taken in
the juice sulphitation vessel where lime and SO 2 Sulphur Di-oxide
gas are added. (The lime bought is slaked water and added as milk of lime and
sulphur is burnt with air sulphur to get SO 2 gas.)
This is mixed well and allowed
to react. The pH of this juice would be 7.1 to 7.2. This is heated to 104
degree centigrade in another juice heater and sent to Clarifier (Sedipur or
Graver) for settling the impurities.
Inside the clarifier, the
impurities settled and clear juice overflows. This juice will be transparent
and light yellowish in color and will be sparkling.
The settled mud is drawn out of
the Clarifier. This is sent to the Vacuum Filter to extract the sugar from it
as much as possible. After this, it is sent out as pressmud. This filtrate is
sent for mixing with mixed juice after weighment.
The clear juice from the
Clarifier is in diluted form. This is to be concentrated to get sugar crystals
out of it. The evaporator does most of this concentration. It contains 4
bodies and in some places another body (Vapour Cell) will also be there. The
juice is concentrated here to 60-65 Bx. The outset juice from evaporator is
called Syrup. This Syrup is treated with SO 2 gas for bleaching and
sent to Pan floor for further concentration.
The Syrup coming from Evaporator
is taken in one of the Pans along with B-magma. When concentrated the sugar
coming out of the syrup will deposit on the sugar crystal of B-magma and will
grow in size. thus, Pan is filled slowly with syrup and A-Light Molasses. The
crystals of sugar will grow to the required size. This is called A-massecuite
and is discharged in to Crystallizer where it is continuously stirred.
The A-massecuite is taken in A-Centrlfugal.
The Centrifugal will run at 980 or 1440 RPM as the case may be. The molasses is
separated from the sugar crystals and sent out of the machine. This sugar
crystals is washed with water to remove the adhering molasses. It is then dried
with steam. The sugar is discharged on to the grass hopper conveyor and taken
to the grader. In the grader, the crystals are separated as ‘S’ , ‘M’, ‘L’ as
per the size and bagged in bags.