The present disclosure relates to a calandria, which is used in an apparatus for crystallizing sugar cane syrup. More particularly, the present disclosure relates to an annular type steam jacketed tubeless calandria, which is partitioned into a number of sectors for better crystallization of massecuite.
BACKGROUND OF THE INVENTION:
The crystallisation stage of sugar recovery and manufacture from concentrated cane juice is commonly performed in continuous/batch pans, which include a calandria, into which steam or vapour is fed to cause heating and boiling of the massecuite (sugar crystals and molasses). . Vigorous circulation is highly desirable both for even crystal growth and for good heat transfer from the calandria.
An apparatus (batch pan) for crystallization of sugar cane comprises a closed vessel, whose interior is under sub-atmospheric pressure, a heating calandria at the bottom of the vessel, and a mechanical agitator/circulator for accelerating the massecuite heating cycle in the calandria. During each production cycle, the closed vessel is filled with a sufficient volume of syrup to cover the calandria at the bottom of the vessel, this volume of syrup is concentrated to bring it to a state of supersaturation and the syrup is grained. Circulation in vacuum pans is promoted by the bubbles of vapour due to heating in the tubes. These bubbles tend to rise, growing as they do so and agitate the mass and lift it towards the surface while the circulation is caused and accelerated by this motion force, it is on the other hand, slowed down by the resistance due to the shape and disposition of the calandria tubes and the resultant pressure drop.
US 7195674B2 titled "Continuous pan crystallizer" related to a continuous pan crystallizer for use in the sugar industry includes a heated zone in the form of a steam chamber below a calandria. The heated zone heats massecuite in the area below the calandria in the pan and

reduces massecuite density and viscosity and promotes the vigorous circulation required for even crystal growth.
US 5223040A titled "Batch process and apparatus for crystallizing syrup" relates to a batch process and an apparatus for producing sugar crystals from syrup in a discontinuously operated crystallization apparatus comprising a heating calandria, which comprises the steps of graining a batch of concentrated syrup by adding seed crystals thereto to form a predetermined volume of magma causing sugar crystals in the syrup to grow by subjecting the magma to evaporation in heat exchange with the calandria and adding syrup while maintaining the mother liquor at a desired level of supersaturation to obtain massecuite, and increasing the brix of the massecuite to a desired value to obtain a final volume of massecuite.
US 1586814titled "calandria for evaporatorsof sugar mills" relates to an evaporator tank equipped with a calandria provided with the usual central downtake passage, top plate, and bottom plate between which extend the usual circulation pipes. Steam inlets bare provided at opposed points in the calandria. Steam is the preferred heating medium. The non-condensible gases are expelled through outlet pipes leading to the outside by means of conduits.
The above mentioned prior art documents have the drawbacks of conventional calandria.
OBJECT OF THE INVENTION:
An object of the present disclosure is to increase the crystal yield and reduce the boiling time.
Another object of the present disclosure is to provide ease of cleaning of the heating surface.
SUMMARY OF THE INVENTION:
These and other features, aspects, and advantages of the present subject matter will become better understood with reference to the following description. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify

key features or essential features of the subject matter, nor is it intended to be used to limit the scope of the subject matter.
An aspect of the present disclosure is to provide a calandria of a sugar cane juice vacuum pan, the calandria comprising: two annular members having an inner wall and an outer wall, a plurality of radially oriented steam conduits with inlet on the outer wall, characterized by a plurality of concentric steam jackets for circulating steam, the plurality of the radially oriented steam conduits being in fluidic communication with each steam jacket that intersects the conduit in the radial direction, the plurality of radially oriented steam conduits dividing the annular space between the outer wall and the inner wall into a number of sectors, a plurality of axially oriented massecuite circulation passages between each two adjacent steam jackets in each sector for massecuite circulation, wherein the calandria is tubeless and the space between the plurality of concentric steam jackets ispartitioned into plurality of massecuite circulation passages as per size of the calandria for increased sugar crystal yield.
An embodiment of the present disclosure provides that the steam jackets which have substantially parallel annular walls which are closed at the top and bottom by slanting rounded surfaces.
Another embodiment of the present disclosure provides that the top of steam jacket has a circular shape or a semi oval shape to avoid the deposition of massecuite.
Another embodiment of the present disclosure provides that jackets are arranged at an appropriate distance to allow free circulation of massecuite and effective heat transfer.
Still another embodiment of the present disclosure provides that the steam inlet is arranged through an inlet manifold which is in fluidic communication with a plurality of steam jackets.
Still another embodiment of the present disclosure provides that the steam jackets are provided with a plurality of condensate boxes at bottom ends of the steam jackets for removal of condensate.

Yet another embodiment of the present disclosure provides that the bottom ends of the steam jackets are in fluidic communication with an outlet manifold, which is in fluidic communication with the condensate box.
Yet another embodiment of the present disclosure provides that the number of the sectors is 3 to 8.
Still another embodiment of the present disclosure provides that a circulator is disposed in lower portion of the downtake enclosed by the inner surface of the inner cylindrical wall for facilitating circulation of the massecuite.
Still another embodiment of the present disclosure provides that the circulator is driven by a motor positioned near bottom of the vacuum pan.
Still another embodiment of the present disclosure provides that the circulator is driven by a motor positioned near top of the vacuum pan.
Yet another embodiment of the present disclosure provides that the steam jackets are provided with a plurality of outlets at the top the end of the steam jackets for removal of non-condensable gases.
Still another embodiment of the present disclosure provides that each of the sectors is provided with a plurality of radially extending baffles in the space between the steam jackets to regulate the circulation of the massecuite.
BRIEF DESCRIPTION OF THE DRAWINGS:
The above and other objects and features of the present invention will become apparent from the following description of the invention, when taken in conjugation with the accompanying drawings, which respectively show:

Figure 1: General Arrangement of the Pan with tubeless calandria and typical circulator;
Figure 2: tubeless calandria according to the present invention;
Figure 3: Conventional tube type calandria;
Figure 4: Cut section of the tubeless calandria;
Figure 5: Comparison of tubeless calandriaand conventional tubular calandria;
DETAILED DESCRIPTION WITH REFERENCE TO THE ACCOMPANING DRAWINGS:
If the circulation is to be improved, for a given type of pan, it is often necessary to increase the centre well or the annular space and thus decreases the heating surface. In the same way increasing the tube diameter would improve the circulation, but at the expense of heating surface. For a given calandria, the heating surface is inversely proportional to tube diameter. When the tube diameter is increased, the diameter of the center well or the width of the annular space must be increased in order to consume optimal proportions.
The present disclosure provides a tubeless calandria,which is used in an apparatus for crystallizing sugar cane syrup or massecuite.In the tubeless calandria of the present invention, the restriction of tube diameter is removed and it enhances the circulation with optimum heating surface. Parameters such as type of calandria, downtake size and pan geometry determine the quality of sugar produced. The present disclosure provides an annulus type tubeless calandria to achieve better performance in terms of improved circulation, reduced boiling time and high crystal yield. In a tubeless pan the resistance is minimum and it enhances the circulation.
The following points are considered in the construction of tubeless pan to achieve desired result:-1. The maximum height of massecuite (a typical solution for sugar crystal generation), which should be as small as possible, to avoid resolution of crystals.
2. The circulation which should be as rapid as possible in order to give rapid working and a good exhaustion.
3. The graining volume which should be as small as possible in order to permit the maximum exhaustion with the minimum volume of massecuite per tonne of cane.
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4. The heating surface required to give the desired S/V (heating surface area / volume of massecuiteuptostrike level) ratio.
Referring to figures1, which shows the general arrangement of the pan with tubeless calandria and circulator. An apparatus (batch pan) for crystallization of sugar cane comprises a closed vessel, whose interior is under sub-atmospheric pressure, a heating calandria at the bottom of the vessel, and a mechanical agitator/circulator for accelerating the circulation of the syrup fed into the vessel through the calandria.
Referring to figure 2, in the pan of present disclosure, the heating surface is made up of concentric narrow steam jacket (1) and the massecuite circulation passage (2) between the jackets. The concentrically placed steam jackets are arranged into a plurality of sections, and herein these are arranged into four quadrants. The calandria is divided into four parts for optimized performance herein. With further smaller division, there is smaller temperature gradient across that particular portion of calandria and hence better performance is achieved, but it is at the cost of piping and heating surface. However, for very much large size calandria, the division may go further upto 6 or at extreme 8.
Instead of short tubes like in conventional calandria, steam jackets are utilized with large downtake to facilitate circulation of massecuite. Natural circulation is enhanced due to lesser restriction of movement of particles in the massecuite compared to tubular calandria pan.
As the mass proceeds upward, when these spots reach the level where the local vapour pressure corresponds to their boiling points, a flash takes place with the release of vapour bubbles. In this set up it is rapid and enhances the circulation. As exhaustion depends very much on the design of the vacuum pan, particularly, on the extent to which they facilitate and speed up the circulation of the massecuite at the end of the strike, this design facilitates good exhaustion. This arrangement moreover greatly facilitates the distribution of steam in the calandria and the location of incondensable gas outlets (5). Figure 3 shows conventional tube type calandria.
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Referring to figure 4, the top of steam jacket (1) is designed with sharper end of semi oval shape to avoid massecuite getting deposited. However, any end connection with smooth curve can be considered for ease of welding, and easy material flow from outside.
Referring to figure 5, which shows comparison between tubeless calandria and conventional tubular calandria. In the tubeless calandria, the distance between jackets is suitably provided for good allowance for the circulation of massecuite, which also gives effective heat transfer. At the end of each jacket an opening at the top is given for removal of light non condensable gases (5). An opening at the bottom of each jacket is given for removal of condensate box (4). Steam entry is through steam boxes 180 degree to each other through which the steam enters and the condensate box (4) is placed 90 degree to the steam conduits(3). There are two condensate boxes (4) 180 degree to each other. A plurality of concentric steam jackets (1) for circulating steam, the plurality of the radially oriented steam conduits being in fluidic communication with each steam jacket that intersects the conduit in the radial direction, the plurality of radially oriented steam conduits(3) dividing the annular space between the outer wall and the inner wall into a number of sectors, a plurality of axially oriented massecuite circulation passages (2) between each two adjacent steam jackets in each sector for massecuite circulation.
ADVANTAGES:
> Improved circulation with reduction in energy consumption
> Reduced boiling time
> Reduced washing time
> Higher crystal yield and reduction in purity of low grade molasses
> Better exhaustion due to improved circulation
> Lower coefficient of variation of crystals
> Slag generation will be less and with cleaning will be much easier.
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Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the scope of the disclosure should not be limited to the description of the preferred embodiment contained therein.

We claim:

1.A calandria of a sugar cane juice vacuum pan, the calandria comprising:
two annular membershaving an inner wall and an outer wall, a plurality of radially oriented steam conduits (3) with inlet on the outer wall, characterized by a plurality of concentric steam jackets (1) for circulating steam, the plurality of the radially oriented steam conduits being in fluidic communication with each steam jacket that intersects the conduit in the radial direction, the plurality of radially oriented steam conduits (3) dividing the annular space between the outer wall and the inner wall into a number of sectors, a plurality of axially oriented massecuite circulation passages (2) between each two adjacent steam jackets in each sectorfor massecuite circulation,whereinthe calandria is tubeless and the space between the plurality of concentric steam jackets is partitioned into plurality of massecuite circulation passages as per size of the calandriafor increased sugar crystal yield.
2. The calandria as claimed in claim l,wherein the steam jackets have substantially parallel annular walls which are closed at the top and bottom by slanting rounded surfaces.
3. The calandria as claimed in claim 1,wherein the top of steam jacket (1) has an circular shape or a semi oval shape to avoid the deposition of massecuite.
4. The calandria as claimed in claim 1,wherein jackets are arranged at an appropriate distance to allow free circulation of massecuite and effective heat transfer.
5. The calandria as claimed in claim 1,wherein the steam inlet is arranged through an inlet manifold (6) which is in fluidic communication with a plurality of steam jackets.
6. The calandria as claimed in claim 1, wherein the steam jackets are provided with a plurality of condensate boxes (4) at bottom ends of the steam jackets for removal of condensate.

The calandria as claimed in claim 1,wherein thebottom ends of the steam jackets are in fluidic communication with an outlet manifold, which is in fluidic communication with the condensate box (4).
The calandria as claimed in claim 1, wherein the number of the sectors is 3 to 8.
The calandria as claimed in claim 1, wherein a circulator is disposed in lower portion of the downtake enclosed by the inner surface of the inner cylindrical wall for facilitating circulation of the massecuite.
The calandria as claimed in claim 1, wherein the circulator is driven by a motor positioned near bottom of the vacuum pan.
The calandria as claimed in claim 1, wherein the circulator is driven by a motor positioned near top of the vacuum pan.
The calandria as claimed in claim 1, wherein the steam jackets are provided with a plurality of outlets (5) at the top the end of the steam j ackets for removal of non-condensable gases.
The calandria as claimed in claim 1, wherein each of the sectors is provided with a plurality of radially extending baffles in the space between the steam jackets to regulate the circulation of the massecuite.