Continuously operating centrifugal

A continuously operating centrifugal or centrifuge for centrifuging sugar massecuites and for remashing the centrifuged sugar, comprises a ring conduit with nozzles for mixing liquid directed at the upper wide end of the centrifugal basket. The ring conduit is arranged in a housing having a cover, above a frustum-shaped centrifugal basket equipped with screens and rotating about a vertical axis of rotation. A conical baffle member is arranged radially outside of the upper edge of the centrifugal basket for intercepting the sugar crystals. A cover ring is mounted at the upper end of the centrifugal basket at a small distance from the ring conduit. The radial width of the cover ring corresponds at least to the spraying range of the nozzles for the mixing liquid. The conical baffle member is shaped like a frustum and opens upwardly. The centrifuge includes a mixing compartment enclosed by smooth walls.

BACKGROUND OF THE INVENTION 
The invention relates to a continuously operating centrifugal or centrifuge 
for centrifuging sugar massecuites and for remashing the centrifuged 
sugar. Such centrifuges may include conventionally a ring conduit with 
nozzles for directing mixing liquid at the upper wide end of the 
centrifugal basket. 
The ring conduit is arranged in a housing having a cover above a 
frustum-shaped centrifugal basket equipped with screens and rotating about 
a vertical axis of rotation. A conical baffle member is arranged radially 
outside the upper edge of the centrifugal basket for intercepting or 
catching the sugar crystals. 
The idea of remashing the sugar centrifuged in a continuously operating 
sugar centrifuge before it leaves the centrifugal in order to thus obtain 
a new massecuite which may readily be fed without any further treatment, 
especially without any further mixing treatment into a following 
centrifugal, has been mentioned in several publications. These 
publications, however, preferably emphasize other problems. For example: 
the prevention of damage to the sugar crystal, or the prevention of the 
formation of lumps or of so-called tailings, or the discharge of the 
centrifuged sugar in a liquid medium have been emphasized heretofore. 
Thus, it is not surprising, that such known, prior art centrifugals are 
not capable of performing a technologically satisfactory mashing work. 
The U.S. Pat. No. 2,883,054, for example, is concerned with a continuously 
operating horizontal centrifugal, having a basket, the rotational axis of 
which extends horizontally. The wide end of the frustum-shaped centrifugal 
basket merges into a sugar collecting compartment, which is designed as a 
torus opening towards the axis of rotation of the centrifugal basket. A 
ring conduit is arranged inside the sugar collecting compartment and 
concentric to the outer circular arc of said torus, said ring conduit is 
connected to a supply line for a treating agent and has exit orifices for 
said treating agent. The orifices are directed at the inner surface of the 
torus. The treating agent to be used may be either solvent liquid for 
again solving, or a liquor for remashing, or hot compressed air for drying 
the centrifuged sugar. 
The remashing may at best be performed in this known centrifugal to the 
extent that a product of an inhomogeneous consistency is obtained, because 
the crystal mash formed in the top region of the sugar collecting 
compartment flows downwardly along both sides due to gravity, whereby the 
mash is hit on one side by the sugar crystals moving in the discharge 
direction, while on the other side the mash is hit by sugar crystals 
flying in the opposite direction which decelerate the mash and thus 
enriches it with sugar to a substantially greater extent than on the first 
side. Thus, at the lowest point of the sugar collecting compartment, two 
streams of different consistencies meet, which do not mix into a 
homogeneous product without any subsequent mechanical treatment. 
Furthermore, small or larger quantities of material cannot be prevented 
from coming off the top of the sugar collecting compartment and falling 
down. These material quantities might differ considerably in their 
consistencies from the confluent material streams, whereby the 
inhomogeneity of the product is also substantially increased. 
The primary problem solved by the sugar centrifugal according to German 
Patent Publication (DAS) No. 2,025,828 is to completely prevent the 
formation of lumps in centrifuging the crystals in continuously operating 
centrifugals. To solve this problem, the upper end of the centrifugal 
basket is encircled by a fixed intercepting ring, wherein the introduced 
liquid rotates with a circumferential speed which is lower than the speed 
of the centrifugal basket. The rotation of the liquid ring or of the 
liquid-crystal mixture formed in this ring is produced by the air friction 
caused by a discharge flange which, depending to the type product, dips 
more or less into the intercepting ring and is secured to the centrifugal 
basket. The liquid may be introduced into the intercepting ring in 
different ways. The liquid-crystal mixture is removed from the ring at a 
single point on the circumference of the intercepting ring through an 
outlet connection. 
This known centrifugal of German Patent Publication No. 2,025,828 leaves 
room for improvement in its structural features. When switching from one 
to another production, a great deal of assembly work is necessary for 
fitting the required discharge flange. For this purpose the intercepting 
ring must be disassembled among other required work. Routine cleaning work 
is similarly troublesome. Without subsequent mechanical mixing it is not 
possible to feed the produced liquid-crystal mixture as a massecuite 
directly into a following centrifugal because a high rotational speed of 
the intercepting ring results in sedimentation in said ring, i.e., 
de-mixing in the intercepting ring, whereas lower speeds do not produce a 
mixing energy high enough to ensure the homogeneity of the liquid-crystal 
mixture at the outlet connection. 
The U.S. Pat. No. 3,238,063 describes a centrifugal wherein a circular pipe 
is arranged at some distance from the upper wide end of a frustum-shaped 
centrifugal basket, that is, above a flat end ring attached to the upper 
basket end. Mixing liquid or--if the sugar shall be remashed--mashing 
liquid is sprayed out of the circular pipe at the sugar crystals flying 
over the end ring. A vertically suspended baffle plate made of elastic 
material is arranged radially outside of the end ring. The baffle plate is 
intended to intercept the sugar crystals without destroying the crystals 
and without the formation of bumps. However, a product that may be fed 
directly as a massecuite into a following centrifugal without any further, 
treatment, especially mixing, cannot be produced, because there are too 
many ways in which, quite accidentally, differently concentrated 
liquid-crystal mixtures may result or occur. For example, the mashing 
liquid is sprayed onto the sugar crystals from a comparatively large 
distance, namely, from the upper edge of the centrifugal basket in the 
radial direction of the basket whereby a widely fanned out spray pattern 
is obtained. Such a spray pattern permits the very strong air turbulences 
prevailing in continuously operating centrifugals to attack the sprayed-on 
liquid over large areas and to prevent, or unpredictably impair the 
desired intimate mixing of crystals and liquid. The vertically suspended 
baffle plate also produces inhomogeneity. As a result of the air 
turbulences which more or less break up the mixing liquid, the sugar 
crystals hit the baffle plate in differently moistened states. This fact 
aside, varying adhesivenesses also result in different situations despite 
the elasticity of the baffle plate. Part of the sugar flows off downwardly 
together with the mashing liquid, part of the sugar temporarily adheres 
and steadily picks up other centrifuged sugar crystals whereby the sugar 
is enriched with crystals, while the impinging liquid separates out and 
flows off downwardly. The result is an inhomogeneous product. Past 
experiences have shown that elastic materials for the baffle plates can 
withstand the wearing stress brought about by the sugar crystals impinging 
on the plate at a high velocity for a very short time only, which made 
practical use impossible. However, if the elastic baffle plate in this 
centrifugal is replaced by a steel plate, the crystals are destroyed and 
the product is not suitable as a massecuite. 
U.S. Pat. No. 4,008,098 discloses a continuously operating sugar centrifuge 
wherein the sugar crystals passing over the upper edge of the centrifugal 
basket are sprayed from above with solving liquid and are then intercepted 
by a fixed wall or baffle ring which is arranged in an inclined position 
relative to the direction of crystal flight. The inclination of this 
baffle ring is such, however, that the material is deflected downwardly 
from the point of interception in such a way that it is impossible for the 
material to return to the interception area. The hard surface of the 
baffle ring contributes to crystal crushing and its inclination ensures 
that the crystals always hit the hard crystal-crushing surface. This known 
construction of a centrifugal may be suitable for returning the sugar into 
solution but it is not suitable for a most gentle crystal handling as is 
required for mashing. The baffle ring in the prior art centrifuge of U.S. 
Pat. No. 4,008,098 causes crystal destruction. Even the so-called "pad" 
formation which is known as such does not lent itself to preventing 
crystal destructions because in known centrifuges wherein the centrifuged 
sugar was to be mashed again the pad formation has been the cause of an 
uncontrollable inhomogeneous consistency of the produced mash. 
OBJECTS OF THE INVENTION 
In view of the foregoing it is the aim of the invention to achieve the 
following objects singly or in combination: 
to provide a continuously operating mashing type centrifuge which supplies 
a homogeneous product that may be fed directly as a massecuite, without 
any further after-treatment, into a centrifugal; 
to substantially avoid the crystal destruction in a mashing centrifuge and 
to treat the sugar crystals as gently as possible; 
to construct the centrifuge with a deflection plate or conical baffle 
section inclined for the formation of a relatively soft sugar crystal pad 
on which the impinging sugar crystals will not be destroyed; and 
to minimize air turbulences in the centrifuge. 
SUMMARY OF THE INVENTION 
The centrifuge according to the invention is characterized in that a cover 
ring is mounted at the upper end of the centrifugal basket at a small 
distance from a ring conduit. The radial width of said cover ring 
corresponds at least to the spraying range of the nozzles for the mashing 
liquid. A conical baffle section is frustum-shaped and opens or flares out 
upwardly, preferably at a predetermined angle such as 45.degree. relative 
to the vertical. The mashing space in the present centrifuge is enclosed 
by walls having smooth surfaces to minimize air turbulences in the 
centrifuge.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS ILLUSTRATING THE BEST 
MODE OF THE PRESENT INVENTION 
FIGS. 1 and 2 show a continuously operating centrifugal 1, which is charged 
with massecuite 3 by means of a proportioning slide valve 2. 
After passing through a feeding device 4, the massecuite 3 flows into a 
frustum-shaped centrifugal basket 6 equipped on the inside thereof with 
screens 5. Said basket 6 is rotatable about a vertical axis and is driven 
by a motor 7. 
The liquid component of the massecuite 3 is collected in a liquid 
collecting compartment 8; the sugar crystals travel across the screen 5. 
Wash liquid may be ejected by the wash water nozzles 9. 
At the upper end of the centrifugal basket 6 the sugar crystals pass over a 
cover ring 10. A ring conduit 11 is mounted at a small distance above the 
cover ring 10. Mashing liquid 12 is sprayed directly at the cover ring 10 
out of the ring conduit 11. 
A vertically downwardly pointing ring wall 15 is secured to the cover of 
the outer housing 14 of the centrifuge 1. The ring wall 15 extends to the 
upper edge of the centrifugal basket so closely that substantially no air 
turbulences may escape outwardly from the inside of the centrifugal basket 
6. Any air eddies still escaping are reduced to such an extent that they 
are unable to change the direction of the jets of the mashing liquid 12. 
The cover ring 10 has such a radial width that the mashing liquid jets 12 
hit it under all circumstances. 
A conical baffle section 16 is secured to the outer housing 14, radially 
outside of the cover ring 10. The baffle section 16 is formed as an 
upwardly opening frustum in a preferred embodiment, the generatrix of the 
frustum is inclined by approximately 45.degree. from the vertical and the 
point of interception of the sugar crystals on the conical baffle section 
16 is located substantially in the middle of the generatrix. 
A cylindrical mash discharge compartment 17 is connected to the inner, 
lower end of the conical baffle section 16. The mash discharge compartment 
17 has a helical, downwardly sloping bottom 18. 
Sugar crystals passing over the cover ring 10 are thoroughly and evenly 
wetted by the mashing liquid 12 directed by the jets at the cover ring 10. 
Any mashing liquid 12 not hitting any sugar crystals reaches the cover 
ring 10 and is carried along by said ring whereby, just as the sugar 
crystals, it is centrifuged outwardly towards the conical baffle section 
16. Thus, a homogeneously composed mixture of wetted sugar crystals and 
mashing liquid is produced by this process everywhere on the 
circumference. 
When this mixture hits the conical baffle section 16, the inherent kinetic 
energy makes it move up on the slope of the conical baffle section 16, as 
indicated by the arrow 24 in FIG. 2. When the kinetic energy has been used 
up, gravity makes the material flow downwardly as indicated by the arrow 
19, so that it enters the interception area again. 
This movement as indicated by the arrows 19, 20 produces a soft pad 20 
which prevents destruction of the impinging crystals. At the same time, 
the impinging sugar crystals cause a thorough mixing and kneading in the 
pad 20. A homogeneous mixture is produced, which flows down as mash into 
the mash discharge compartment 17 as indicated by the arrow 21. This 
product may be fed, without any homogenizing after-treatment, as a 
massecuite into a centrifuge. 
All the wall surfaces surrounding the mixing compartment 17, which is 
outwardly also enclosed by the conical baffle section 16, are plain and 
smooth to prevent air eddies or turbulences. 
Mashing liquid, which preferably has a constant initial pressure of 
approximately 2 bar, is supplied to the ring conduit 11 through a feed 
pipe 22 including at least one control valve 23. The automatic control of 
the quantity of the massecuite 3 flowing in, of the pressure, and of 
quantity of the mashing liquid 12 supplied, ensure a product having a 
constant quality. 
The present centrifuge operates as follows. The mashing liquid is sprayed 
onto the suitably wide cover ring 10 and thus onto the sugar sliding over 
the cover ring 10. The distance between the ring conduit 11 and the cover 
ring 10 is so small that any air eddy is substantially prevented from 
entering into the jets of liquid. Even if, in spite of all countermeasures 
taken, occasional air eddies get into the range of the liquid jets, such 
stray eddies do not have any or substantially no influence on the 
direction of the liquid jets. Due to the fact that the mashing liquid jets 
are concentrated on the cover ring 10, part of the mashing liquid is 
brought into a direct intimate contact with the sugar crystals, while that 
part of the mashing liquid hitting the cover ring 10 itself is entrained 
by the high circumferential speed of the ring 10 and thrown into the same 
zone in which the sugar crystals also move. Thus, a homogeneous mixture is 
produced already during the flight of the liquid and of the sugar 
crystals. 
This mixture first travels upwardly on the conical baffle section 16 under 
the action of a kinetic energy as shown by arrow 24. After traversing a 
short distance, that is, as soon as the kinetic energy is used up and 
gravity becomes predominant, the mixture moves down again as indicated by 
arrow 19 and gets into the interception area at the lower end of the 
baffle section 16. Thus, a soft pad 20 of flowing-back material is formed 
according to the invention, at the point of interception between the hard 
wall of the conical baffle section 16 and the impinging homogeneous 
liquid-crystal mixture. 
This pad 20 has the advantage that it prevents the crystals from being 
damaged. The kinetic energy of the homogeneous liquid-crystal mixture 
impinging on this pad 20 is imparted to the material and causes a thorough 
mixing or kneading, before the mash thus produced flows off downwardly out 
of the interception area. The homogeneity of the liquid-crystal mixture 
impinging on the conical baffle 16 or rather on the continuously formed 
material pad 20, the prevention of the detrimental effects of air eddies, 
and the fact that there are constant conditions everywhere on the cover 
ring 10 and on the conical baffle 16, have the advantageous effect that a 
completely homogeneous product flows off the interception area. Such 
homogeneous product may be fed, without any further homogenization as a 
massecuite into a centrifugal. 
Although the invention has been described with reference to specific 
example embodiments, it is to be understood, that it is intended to cover 
all modifications and equivalents within the scope of the appended claims.