In this article explained about centrifugal section and Sugar house equipment capacity calculation for process house of sugar industry viz., Pug mills, Batch and continuous centrifugal machines, Magma mixers, sugar melter, pumps for magma & molasses, Superheated wash water system, Sugar hoppers, Sugar dryer, sugar elevator & grader.
Centrifugal Section and Sugar House Equipment in Boiling House of Sugar Factory
Objectives of centrifugal section
Once the mother liquor is exhausted to practical limit only thing is remain to separate crystals in order to obtained the commercial form. This operation is carried out in a centrifugal machine by the principle of centrifugal force.
The basic function of centrifugal station is separation of sugar crystal from mother liquor (molasses). In this process required special attention for the following points to arrive centrifugal section equipment capacity.
a) Effective separation of crystals from mother liquor by avoiding of crystal damage for bagging sugar.
b) Minimum use of washing water.
c) Minimum use of power consumption.
d) Control systems used at Centrifugal.
The centrifugal section with the sugar house consists of the following major equipment
a) Pug mills
b) Batch centrifugal
c) Continuous Centrifugal
d) Magma mixers
e) Molasses receiving tank (runoff tanks)
f) Pumps for magma & molasses
g) Superheated wash water system
h) Transient Heater
i) Sugar receiving hoppers
j) Sugar dryer, sugar elevator, and sugar grader
k) Sugar bin
Pug Mill
The plug mill has ‘U’ shape and is fixed in the above centrifugal machines staging with drive. Generally, all pugmills are equipped with an agitator to keep the massecuite in constant motion in a pugmill. ( Generally, an agitator is not required for ‘C’ fore worker centrifugal machine, and this pug mill is equipped with a water jacket to circulation hot water for treatment of massecuite.)
The level of massecuite in pug mill is always maintained at more than 70% to provide positive massecuite head when charging to the centrifugal machine.
The capacity of pug mill will depend on a number of centrifugal machines and their capacity. The retention time in the pug mill is around 12 to 15 minutes.
For example 3 numbers of 1750 kg/charge machines with 20 cycles/hour. Then
Massecuite quantity = 1.750 MT/cycle x 20 cycles/hour x 3 nos. = 105 MT/hr.
= 105 / 1.4 = 75 M3/hr = 1.25 M3/min.
Take 12 minutes of retention time then 1.25 x 12 = 15 m3 holding volume required.
Batch centrifugal
Batch centrifugal machines consist of cylindrical basket designed to receive the massecuite to be treated, carried on a vertical shaft, driven from its upper part by a motor. The basket is perforated with numerous holes to allow the molasses to escape.
The basket is open at the top to allow massecuite to be feed in to it, and the bottom opening allows sugar to discharge when the machine is stopped.
Batch centrifugal machines capacity requirement
Crushing Capacity – 5000 TCD ( 230 TCH on 22hr basis)
A massecuite % cane – 28 %
A m/c quantity – 230 x 28% = 64.4 T/hr
Consider 150% extra – 64.4 x 150% = 96.6 T/hr
(To compensate for breakdowns in sugar house)
The capacity of each machine – 1750 Kg/charge
Number of average cycles – 18 cycles/hr
Each Machine capacity – 1750 x 18 = 31.5 T/hr
No. of machines required – 96.6 / 31.5 = 3.06
Hence 3 nos. of Centrifugal machines are required for A-Massecuite + 1 stand by = 4 nos.
(Practically 3 machines can handle that capacity)
For more information on Batch Centrifugal Machine Capacity and Gravity Factor with online calculator
Superheated wash water system
Superheated water is used for batch centrifugal machines for better washing and getting good quality sugar.
The superheated wash water system heats the hot condensate water to 112 ± 3 oC by steam, and 5 to 7 kg/cm2 pressure with high head centrifugal pump.
Quantity of water required – 5 % on massecuite or 10% on sugar produced
For more information please go through the below link
Continuous Centrifugal
Generally, Continuous centrifugal machines are used for B and C massecuite curing. Continuous operation is ideal from the mechanical point of view, the machine runs at a constant speed without stopping, is fed by a continuous stream of material, furnishes a constant output of sugar, and requires less no. of operators.
Crushing Capacity – 4000 TCD ( 182 TCH on 22hr basis)
B m/c % cane – 13 %
B m/c quantity – 182 x 13 % = 23.7 T/hr
Consider 150% extra – 23.7 x 150% = 36 T/hr
Capacity of Machine – 16 to 18 T/ hr (Ø1500)
No. of machines required – 36 / 18 = 2 Nos.
C m/c % cane – 8 %
C m/c quantity – 182 x 8 % = 14.6 T/hr
Consider 150% extra – 14.6 x 150% = 22 T/hr
Capacity of Machine (CFW) – 8 to 10 T/ hr
No. of machines required – 22 / 8 = 2.75 Nos. ≈ 3 nos.
CAW % cane – 3 %
C m/c quantity – 182 x 3 % = 5.5 T/hr
Consider 150% extra – 5.5 x 150% = 8 T/hr
No. of machines required – 1 No.
Transient Heater
The transient heater is used for heating of low grade massecuite up to saturation temperature (50-52 0C) to reduce the viscosity and easy purging of massecuite.
In a transient heater, low-grade massecuite is heated uniformly with vapour/steam or condensate water.
For more information please go through the below link
Magma Mixer
When massecuite is to be double-cured or even single cured ( in the case of low-grade massecuite), the centrifuged sugar is to be mixed with syrup or clarified juice or hot water to form magma. The magma preparation is generally done in magma mixers. These mixers are double paddle type with drive under centrifugal machines help in well mixing of sugar with diluting liquid. The arm shall be strong enough to break the lumps of sugar and mix well with liquid.
The capacity of the magma mixer will depend on number of centrifugal machines and its capacity. The retention time in a magma mixer is around 10 to 12 minutes.
For example, take three numbers of 1500 mm dia “ B” continuous machines having a capacity of 16 T/hr to 18 T/hr.
Machine capacity – 16 T/hr each
Number of machines – 3
B sugar quantity per machine – 7.2 T/hr @ 100 brix ( 45% sugar considered)
B magma quantity per machine- 9 T/hr @ 80 brix
Total B magma quantity – 27 T/hr @ 80 brix (If used water for magma preparation)
Take 12 minutes of retention time then 5.5 T = 5.5 / 1.4 = 4 M3 holding volume required upto 80% level.
The length of the mixer shall be suitable for all centrifugal machines.
Sugar Melter
Please go through the below link for complete details
Pumps for molasses and magma
The ”B” magma is pumped to sugar melter for melting or pan section for seed purpose. C fore worker magma is pumped to either pug mill of after worker machine (in case of double curing) or sent to seed crystallizer or melter depending on massecuite scheme with the help of magma pumps.
The molasses pumps are used to pump the molasses from the molasses receiving tank to pan supply tanks for further process. The C molasses is sent to the final molasses storage tank with the help of molasses pump.
Always Molasses and magma pumps capacity shall be arrived based on the number of centrifugal machines in operation and their capacity.
For examples
Capacity of each machine – 1750 Kg/charge
Number of centrifugal machines in operation – 3 nos.
Number of average cycles – 20 cycles/hr
Each Machine capacity – 1750 x 20 = 35 T/hr
Total massecuite cured – 31.5 x 3 = 105 T/hr
A-Heavy molasses % massecuite – 45% (maximum)
A-Light molasses % massecuite – 15% (maximum)
Quantity of A-Heavy molasses – 105 x 45% = 47.2 T/hr
Quantity of A-Light molasses – 105 x 15% = 16 T/hr
Hence two nos. (1 working + 1 standby) of A-heavy molasses pumps are required with capacity of 60T/hr and two nos. (1 working + 1 standby) of A-light molasses pumps are required with a capacity of 20 T/hr.
The molasses receiving or runoff tanks of usually 2 to 3 m3 capacity is required for each type of molasses.
B magma pump capacity
Machine capacity – 16 T/hr each
Number of machines – 3
B sugar quantity per machine – 7.2 T/hr @ 100 brix (45% sugar considered)
B magma quantity per machine- 9 T/hr @ 80 brix
Total B magma quantity – 27 T/hr @ 80 brix (If used water for magma preparation)
Total B magma quantity – 43.2 T/hr @ 80 brix (If used syrup @ 60 brix for magma preparation)
Hence two nos. (1 working + 1 standby) of B magma pumps are required with a capacity of 40 T/hr (Generally, for 5000 TCD plant required 3 nos. (2 working + 1 standby) of B centrifugal machines with 16 T/hr capacity)
Hint: Quantity of magma calculation while using syrup in magma preparation
Take syrup quantity required for magma = Q T/hr
B sugar quantity = 21.6 T/hr
B sugar Brix = 100
Syrup Brix = 60
Final magma brix
Then
(100 x 21.6) + (Q x 60) = (21.6+Q) x 80
For the above equation Q = 21.6
Final magma quantity = 21.6+21.6 = 43.2 T/hr
Gross Hopper
The sugar after separation from molasses in centrifugal machines is conveyed via sugar conveyor normally hoppers. The sugar discharged from high-grade centrifugal machine is still wet and to be dried and further cooled, graded before bagging and stored in godown.
Generally, the grasshopper consist of a wide, flat, and shallow trough, supported on flexible strips inclined at 60 degree to horizontal. The trough is given repeated vibration by means of an eccentric, rotating about 300 rpm.
The Capacity of hopper is calculated by the formula
Q = S A n k d
Q = Output of sugar conveyor in kg/min.
S = use full vertical cross section area of hopper through which sugar is discharged in m2
A = Moment of sugar per stroke in meters
n = rotational speed of eccentric, 300 rpm
k = coefficient of slip (0.5)
d = Apparent density of sugar, (800 to 950 kg/m3)
Sugar dryer
Crushing Capacity – 230 TCH
Recovery % cane – 12 %
Sugar Quantity – 230 x 12% = 27.6 T/hr
Consider 150% Extra – 27.6 x 1.5 = 41.4 T/hr ≈ 40 T/hr
(Note: Here considered 50% extra capacity because it is single equipment and shall be absorbed loads and breakdowns in process)
Sugar house equipment capacity is always better to calculate on the existing number of “A” centrifugal machines capacity.
Sugar elevator & Sugar Grader
Cooled and dried sugar has to be graded for which it has to be elevated for delivery to grader. The elevator consists number of buckets running on return pulley at the bottom and driven by a similar pulley at the top of the elevator.
The capacity of elevator is calculated as
Q = GVN
Q = Output of sugar in kg/min.
G = Weight of sugar conveyed / bucket in kg.
V = Speed of belt m/min.
N = No. of bucket per meter of belt length.
Sugar grader
The sugar so obtained consists of heterogeneous crystals and needs to be well-sieved and graded before it is marketed. The main aim is particle size classification which is done by screens. The classification is usually achieved by using wire mesh or perforated plate through which particles smaller than the screen aperture may pass, while the largest fraction is carried over the surface.
Sugar grader capacity shall be considered 2 nos. having 20 T/hr each
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