HISTORY OF EQUIPMENT AND PROCESS DEVELOPMENT
Mills:
Before
mechanization vertical three-roller mill was commonly used up to start of 19th
century. The mills were driven by animal, wind or water power.
Fig.11.1 cane unloading by crane in1910
Fig 11.2 revolving cane equalizer in 1910
Collinge in 1794 first made a design of mill with three
horizontal rollers arranged in triangle. In 1871, Rousselot, a French engineer, of Martinique made some
improvement in the design. All the modern mills are based on
this design. At the same time hydraulic loading of mill roller was also
employed.
Fig 11.3 Mill with hydraulic pressure
Cranes were used for unloading the cane in 1910. Rotating knives to work as equalizer or leveler were introduced in 1870-72. The crushers and shredders were introduced in 1883 – 1887. However before 1920 there were many factories which were not having proper cane preparatory devices like cutters or shredder. Some factories were having crusher in place of cutter or shredder.
Fig.11.4 Mill design by Rousselot
The introduction of steam as motive power was implemented at the
end of the 18th century. Due to this fabrication of large size mills
made possible. Three mill trains with use of imbibition water were installed in
Louisiana and Australia in1892. Slow speed horizontal steam engine was standard
method of driving the mills. Small steam turbines were used to drive the mills
from 1947, which is now general in modern plants.
Noel Deerr in his book (1916) gives mill capacities as follows:
Diffusers:
The diffusion process as applied to the cane
sugar industry first came into prominence about 1884, several of plants remain
in successful operation. . In 1910 there were many plant working with diffuser.
However some factories in Mauritius and Hawaiian Islands have reverted to
milling because of faulty designs of difffuser, difficulty in constant even
supply of cane, excess fuel consumption.
Fig.11.5 Diffuser
Juice clarification:
Use of phosphate for juice clarification was started in 1862 in
USA. Mr Beans has teken the patent of it. Use of sulphur dioxide gas for cane
juice clarification was first tried in the year 1865 in Mauritius. In 1905 Prinsen Geerling describes sulphitation
process for clarification of cane juice.
Scientist Horlof first followed the process of hot liming and
sulphitation at 70-75°C. It improved the precipitation of calcium sulphite and
reduced the scaling problem in juice heaters. Hence this process is called as
Horloff’s process.
f
Fig.11.6 Batch type defecators
Hundreds of different chemicals/substances have been tried as clarifying agents. Lime is being used for almost 2000 years. The
other common substances
phosphate/phosphoric acid and sulphur are being used in last about150 years.
The defecation process has been established in the mid of 19th
century. It was batch operation The juice was being treated with milk of lime
being heated in open tanks to boil and allowed to settle. The supernatant clear
juice was run off to evaporators. Continuous process started first in Australia
in 1890.
Fig. 11.7 Defecation process
The above
figure gives the defecation equipment and process followed. There are two horizontal juice heaters, one
liming tank and a continuous clarifier.
Fig. 11.8 Hatton's automatic clarifier
The clear juice obtained was send to
evaporator and the scum containing suspended solids was send to scum received
in tanks where it was limed and allowed
to settle, the clear supernatant liquor being decanted and added to the main
juice. The scum then passed through the filter presses, the clear filtered
liquor being passed to the evaporator.
Multi-tray subsiders or clarifiers of the Dorr type were
introduced in West Indies in 1918.
Peter Honig
started the use of pH measurement for better control over the process.
The modern continuous process has achieved a great reduction in
the total capacity of settlers required as well as a vast reduction in labour
requirement. Prototype SRI trayless clarifier was installed at Gin Gin sugar
mill in 1969 designed for a crushing rate of 120t/hr. Now trayless clarifiers
are commonly installed in mills.
Filtration of scum or muddy juice was
carried out by filter presses or Taylor filter or sand filtration.
Rotary vacuum drum filter (RVDF),
patented in 1872, is one of the oldest filters used in the
industrial liquid-solids separation. It offers a wide range of industrial
processing flow sheets and provides a flexible application of dewatering,
washing and/or clarification. However use of
rotary vacuum filter in sugar industry has started much late, in the mid of 20th
century.
Carbonation
process:
The
carbonation process, which is quite generally adopted in beet sugar factories,
has only been applied to the manufacture of cane sugar in a few few factories
in Java and India. This process gave bad results when first introduced into
cane sugar factories owing to the presence of glucose in cane juice. However
the efforts of Geerligs and Winter made the process practicable. By this process its direct consumption was
manufactured.
However, Noel Deerr remarks that the best
white sugars of Mauritius made by a defecation process combined with the use of
sulphur and phosphoric acid are equal to any that he has seen prepared by the
carbonation process. The single carbonation process was adapted to factories
having inferior quality cane and is not adapted for making white sugars.
Evaporator:
In the original method of concentrating juice to form crystals was
by boiling in shallow open pans with direct heating, either from an open fire
or by means of fire enclosed in brickwork (Dutch oven). Use of steam was
introduced at about 1800.
Multiple effect evaporation was invented by NORBERT RILLIEUX in
Louisiana in 1844. Rillieux’s
first patent showed two jacketed vacuum pans
(Howard’s original pan)
coupled together in double effect, i.e. the vapour from the first acting as
heating medium to the second. The jacketed pans were soon replaced by
evaporators with horizontal steam tubes.
In 1851 the first vertical tube evaporator was introduced, from which
modern designs have been developed. The principle was extended in turn from
double to triple, quadruple and quintuple effect. In 1880 Rillieux announced
the idea of bleeding vapours from the evaporators to replace steam at the
vacuum pans. This practice is now extensively adopted.
The first multiple evaporator was invented in 1834 by
Norbert Rillieux, of Louisiana, and was a double effect horizontal submerged
tube apparatus. Evaporator sets conforming to his original design with some
differences were in use. Noel Deerr has described seven different evaporator
set in his book. Some of which were of horizontal tubes.Noel Deer has also
described 'Long Tube Vertical Rising Film' what we now call as semikestner or kestner.
Fig.11.9 Triple effect evaporator
Kestener
Van Trooyen has given particulars of a Kestner quadruple at ‘Pasto-Viejo’ Porto Rico. Each body is a vertical cylinder 24 feet high and 3 feet 6 inches in diameter, made in two pieces with an expansion joint ; the separating chamber is 7 feet in diameter and 6 feet high, except in the last body where it is seven feet high. The heating surface of the first three vessels was consisting of 250 tubes, 23 feet long and 1½ inches outside diameter. The fourth vessel there were 130 tubes, also 23 feet long and 2¾ inches diameter.
Vacuum pans
Howard in 1813 has invented vacuum pan. this
was really beginning of a new era. His name is
also associated with the invention of the filter-press. Howard’s
original vacuum pan was essentially the shallow pan with a cover, that make the
pan airtight. The cover from the top was provided with vapour pipe condenser
and vacuum pump. Vacuum was obtained by condensing the vapour
given off by a jet of water allowed to gravitate down from an overhead tank. A steam jacket below the lower portion of the
pan itself was for heating. Necessary accessories such as proof stick and sight
glasses were also provided.
The heating surface provided by the jacket was found insufficient
and coil pans with internal heating surface by providing spiral coils working
on high pressure steam were developed.
In earlry years of 20th century
mostly were coil pans. The heating surface consists of a number of helical
copper coils, reaching from the bottom to a little above the centre of the pan,
and so arranged as to divide the heating surface as uniformly as possible. The
coils were generally 4½ inches in diameter. They are supported by stay rods
fixed to the side of the pan. Now coil pans are obsolete and not used in
industry except for manufacture of bold sugar (खडीसाखर) in mini plants.
Latter on calandria pans also have been developed with
modifications in vertical tube evaporator. Since 1930, systematic study of pan
operation and performance has confirmed the importance maximum massecuite
height in the pan to avoid excessive hydrostatic head. Attention has also been
given on minimizing resistance to circulation of the massecuite, therefore
modern low head pans are designed that give good performance with low pressure
vapours.
Fig.11.11 vacuum pan
Crystallizers:
The receivers in which the massecuites were
received in order to be cooled in motion are either U shaped or horizontal
cylindrical vessels were called as crystallizing tanks. Crystallisation
in motion was first described in a patent by WULFF in Germany in 1884. A shaft fitted at
both ends passing horizontally through the centre of the vessels is attached
the stirring arrangement with worm gears.
The crystallizing tanks are made either plain or provided with a jacket, into
which hot /cold water can be admitted. So that massecuite cooing rate can be
controlled. The use of crystallizers provided with stirring equipment has
gradually become general. However the development was slow. With modifications
in the old designs various types of crystallisers using water cooling elements
have been introduced since 1930.
Fig. 11.12 crystallizer
Centrifugals:
In old days, the separation of massecuite into sugar crystals and
mother liquor was carried out by pouring the massecuite into perforated
cast-iron vessels. The molasses dripping
conducted with holes while sugar crystals were washed by pouring sugar
solution. Mother liquor / molasses was separated by
force of gravity. The centrifugal machines that were being used in textile industry was
tried in sugar industry. Noel Deerr has described the
centrifugals as one of the world’s great inventions. He mentioned that centrifugals were perhaps
introduced into the sugar industry in 1849, by Dubrunfaut. David Mecolley Westton a Scottish engineer working in Hawaii in 1852 patented a
design of centrifugal with flexible suspension. This design then became standard. There were two different type -
fixed bearing and suspended pattern ; again they were divided into under and
over-driven machines, or according to the method of driving, direct coupled,
friction cones, belt, electric, or water drive.
Fig.11.13 A battery of
centrifugals
The sugar hoppers and elevators were in use in the industry from
the end of 19th century.
Since beginning of the sugar industry bagasse is being used as
fuel in sugar industry, both for sugar boiling and power generation. Originally
bagasse was burned after air / sun drying. The first boiler furnaces designed
for burning bagasse straight from the mills were introduced in Cuba in about
1880.
Fig. 11.14 centrifugal machine design
Referances:
1
Cane sugar – by Noel Deerr, 1911,
2
Cane sugar and its manufacture – by
H C Prrinsen Geerligs, 1924,
3
On cane sugar and its manufacture -
by H C Prisen Geerligs, 1902,
4
Plantation white sugar manufacture
– by W H Th Harloff and H Schmidt,
5
Practical white sugar manufacture –
by H C Prinsen Geerligs, 1915,
D B Jambhale Consulting Sugar Technologist,
Former Technical Adviser VSI Pune
