Patent Application
20120252651
The processing of sugar to produce refined sugar can include several steps, for example, an evaporation step followed by a crystallization process. During an evaporation step, sugar liquor may be concentrated to sugar syrup. Sugar crystals may also evaporate out of solution. The sugar syrup may then be sent to crystallizers for further processing to produce sugar crystals. The resulting mixture from the crystallization step is called massecuite, which may be composed of sugar crystals in a thick, viscous liquid (molasses). The massecuite may also contain dissolved sugar and organic and inorganic impurities. To isolate the sugar crystals, the massecuite may be processed through a centrifuge to separate the sugar crystals from the liquid molasses.
During centrifuge processing, the efficiency and speed of separating the liquid molasses from the solid sugar crystals can be dependent, in part, upon the viscosity of the continuous liquid phase massecuite. Highly viscous massecuite can impede the release of the liquid molasses from the crystals during centrifugation. Viscosity reduction may not necessarily be easily accomplished because the crystals are in equilibrium with the liquid phase and any change by, for example, dilution or temperature may cause the crystals to dissolve.
There are devices available to increase the flowability of the massecuite in large mixers and heat exchangers, but because these devices are so far upstream of the centrifuge processing step, these devices may not provide as thorough viscosity reduction as desired because of the risk of dissolving crystals as mentioned above. Several pre-conditioning systems have been developed over the years including, for example, the Steven Coil by Western States, but these devices are generally reserved for heating the massecuite and agitating the massecuite to facilitate an even distribution of heat transfer. These heated mixers can be very large, and are piped between the crystallizers and centrifuges, and can have very long-residence times.
Accordingly, there is a continual need for improved centrifuge systems, and components therewith, which deliver homogeneous massecuite product to a centrifuge, it is believed that no one prior to the inventors has made or used an invention as described herein.
The system described herein is a feed pipe mixing system that is designed to be fitted immediately before the centrifuge. The feed pipe mixing system can allow thorough mixing of water, surfactants, partially diluted molasses, and/or steam with the massecuite, while having a short residence time in the system thereby avoiding crystal dissolution and facilitating sugar crystal separation from a highly viscous liquid molasses.
In one embodiment, a feed pipe mixing system for delivering a homogenous massecuite product to a centrifuge is disclosed. The feed pipe mixing system may comprise: a vertical feed pipe defining an upper end, and a lower end. The vertical feed pipe may comprise: a mixing chamber disposed between the upper and lower ends of the vertical feed pipe and operable to mix a massecuite feed with feed water, surfactants, partially diluted molasses or a combination thereof to produce a massecuite product; a massecuite inlet disposed on the side of the vertical feed pipe above the mixing chamber, wherein the massecuite inlet is configured to deliver a massecuite feed into the vertical feed pipe; a massecuite outlet disposed on the lower end of the vertical feed pipe and configured to discharge the homogenous massecuite product from the feed pipe to a centrifuge; and a feed water pipe configured to deliver feed water, surfactants, partially diluted molasses or a combination thereof to the mixing chamber for mixing with the massecuite feed.
The feed pipe mixing system may further comprising an agitator that comprises: a motor disposed on the upper end of the vertical feed pipe; an agitator shaft attached to the motor and axially extending within the vertical feed pipe; and at least one mixing pin 40849.124 attached to said agitator shaft and located within the mixing chamber.
In another embodiment, the centrifuge system may comprise a centrifuge comprising: a basket operable to separate a homogenous massecuite product into sugar and molasses, at least one sugar discharge outlet disposed at an upper end of the basket, and at least one molasses discharge outlet at a lower end of the basket; and a feed pipe mixing system operable to deliver a homogenous massecuite product to the basket. The feed pipe mixing system may comprise a vertical feed pipe defining an upper end, and a lower end, wherein the vertical feed pipe comprises: a mixing chamber disposed between the upper and lower ends of the vertical feed pipe and operable to mix a massecuite feed with feed water, surfactants, partially diluted molasses or a combination thereof to produce a homogenous massecuite product; a massecuite inlet disposed on the side of the vertical feed pipe above the mixing chamber, wherein the massecuite inlet is configured to deliver a massecuite feed into the vertical feed pipe; a massecuite outlet disposed on the lower end of the vertical feed pipe and configured to discharge the homogenous massecuite product from the feed pipe to a continuous centrifuge; and a feed water pipe configured to deliver feed water, surfactants, partially diluted molasses or a combination thereof to the mixing chamber for mixing with the massecuite feed.
Features and benefits of the various embodiments of the present invention will become apparent from the following description, which includes figures and examples of specific embodiments intended to give a broad representation of the invention. Various modifications will be apparent to those skilled in the art from this description and from practice of the invention. The scope is not intended to be limited to the particular forms disclosed and the invention covers all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the claims.
While the specification concludes with claims which particularly point out and distinctly claim the invention, it is believed the present invention will be better 40849.124 understood from the following description of certain examples taken in conjunction with the accompanying drawings. In the drawings, like numerals represent like elements throughout the several views.
The drawings are not intended to be limiting in any way, and it is contemplated that various embodiments of the invention may be carried out in a variety of other ways, including those not necessarily depicted in the drawings. The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention; it being understood, however, that this invention is not limited to the precise arrangements shown.
Referring to
The continuous centrifuge system 100 can operate to separate liquid and solid phases of a suspension. Particularly in a sugar centrifuge system, the continuous centrifuge system 100 can operate to separate sugar crystals from the liquid molasses in a massecuite feed. The feed pipe mixing system 300, which is further described below, can provide homogeneous mixing of materials having different viscosities or to distribute heat evenly during heating of a fluid feed. During sugar processing, for example, the feed pipe mixing system 300 can provide homogeneous mixing of a highly viscous massecuite feed with lower viscous fluids before being fed to centrifuge 200. As used herein, “homogeneous” does not require a fully homogeneous operation. During heating of a massecuite feed, the feed pipe mixing system 300 can distribute the heat evenly throughout the massecuite feed being fed to centrifuge 200.
The centrifuge 200 may comprise a basket 210, a sugar discharge outlet 260, a molasses discharge outlet 230, and a housing 240. The basket 210 may be mounted on a vertical spindle 212 within a labyrinth 214. The labyrinth may function to separate the path to sugar discharge outlet 260 from the path to molasses discharge outlet 230. Thus, the labyrinth can essentially keep the molasses from reentering the chamber where the sugar crystals are discharged. The vertical spindle 212 may be supported in housing 240 and allows for the basket 210 to rotate about a vertical axis. Of course, other configurations may be used to support the vertical spindle 212. For example, the vertical spindle 212 may be supported on a frame structure within the centrifuge 200. The basket 210 can have an inner circular surface which conically extends in an upward direction to an upper open inlet end 216 of the basket 210. In general, the basket 210 may have various shapes, e.g., cylindrical, conical, frustoconical, etc. By way of example only, the basket 210 may be a perforated basket (e.g., 25 to 35 degree cone-shaped basket) or a vertical basket. Basket 210 may use a top (or filtering) screen, which may have a fine mesh for separation of crystals from the molasses. There may also be an intermediate screen, which provides support for the filtering screen and can allow the molasses to flow through it to one of the drainage holes (i.e., perforations) in the basket. The vertical spindle 212 and the basket 210 can be driven at various centrifugal speeds and is operable to separate a homogenous massecuite product into its sugar crystal and liquid molasses components. Basket speed can be affected by the characteristics of the massecuite (e.g., size of the sugar crystals, amount of sugar crystals, viscosity, etc.), centrifuge throughput, etc. For example, the basket 210 and vertical spindle 212 may be driven from about 800 rpm to about 2200 rpm to separate a homogeneous massecuite product into its sugar crystal and liquid molasses components. To provide another example, the basket 210 and vertical spindle 212 may be driven from about 1000 rpm to about 1800 rpm to separate a homogeneous massecuite product into its sugar crystal and liquid molasses components.
The sugar discharge passageway 220 is the passage created between the labyrinth 214 and the housing 240 of centrifuge 200. The separated sugar crystals fall through sugar discharge passageway 220 and exit out of sugar discharge outlet 260. There may be one or more sugar discharge outlets associated with centrifuge 200. The molasses discharge outlet 230 may be disposed at a lower end of the basket 210. The molasses separated from the sugar crystals may be discharged through the molasses discharge outlet 230. There may be one or more molasses discharge outlets associated with centrifuge 200.
The centrifuge may also comprise a wash pipe 246 for introducing a volume of wash liquid into the basket 210 area and a centrifuge steam pipe 244 for introducing steam into the basket 210 area. Use of the wash pipe 246 or centrifuge steam pipe 244 may be necessary at or near spin speed to remove contaminants and the molasses film that may remain on the sugar crystals. As shown in
In operation, as shown in
The massecuite feed may be delivered into basket 210 from a storage or supply tank (not pictured) or may come directly from a prior sugar processing step, e.g., crystallization. The feed flows into the basket 210 through feed pipe mixing system 300 to a central opening 250 at the top of the housing 240. The feed pipe, which is also shown in
The centrifuge loading conditions may vary depending upon the feed rate and viscosity when introducing the feed into centrifuge 200. The feed may be delivered into the basket 210 while basket 210 is rotating at a relatively low speed. Regardless of incoming rate, the feed first touches the basket at its bottom and then travels upward by centrifugal force.
Referring to
Referring to
The rotary union 342 may be operable to dispense low viscosity fluids, e.g., water, surfactant, partially diluted molasses or a combination thereof into the feed pipe. As described above, the addition of these low viscosity fluids can also reduce the massecuite viscosity. Specifically, the addition of surfactants can reduce the surface tension of the massecuite and facilitate the separation of sugar crystals from the liquid molasses, i.e., purging. The total amount of low viscosity fluids added may range from about 0% to about 8% by weight of massecuite. In another example, the total amount of low viscosity fluids added may also range from about 0% to about 6% by weight of massecuite. The addition of low viscosity fluids (e.g., water, surfactants, partially diluted molasses, etc.) to a highly viscous massecuite can lead to difficulty or an inability of the two fluids to readily mix without the use of feed pipe mixing system 300. The feed pipe mixing system 300 can work to reduce the amount of low viscosity fluids necessary to add to a saturated suspension of sucrose and water to lower the massecuite viscosity. Therefore, feed pipe mixing system 300 can aid in minimizing a shift in the equilibrium in favor of dissolution where sucrose crystals may dissolve back into solution.
In addition, because a small amount of low viscosity water or surfactants (e.g., 1 centipoises at 20° C.) or slightly more viscous dilute molasses may be added to the high viscosity massecuite, they may not mix readily without the use of feed pipe mixing system 300. The feed pipe mixing system 300 can avoid the problem of very limited mixing that may occur in the feed pipe after the fluids have been added. If no mixing occurs within the feed pipe, some mixing may occur when the combined fluids and massecuite enter the high-speed rotating components of the centrifuge. However, the residence time is often less than a few seconds and mixing may not be efficient or homogeneous. Therefore, the use of feed pipe mixing system 300, can work to minimize inefficient or non-homogeneous mixing. As depicted in
Referring to
The right-angle motor 345 depicted in
The agitator shaft 350 may be attached or coupled to either right-angle motor 345 or in-line motor 346 and can extend axially within the vertical feed pipe 305. Referring to
The agitator shaft 350 may be a simple solid shaft, as depicted in
At least one mixing pin 355 may be attached to the agitator shaft 350 and located within the mixing chamber 320. The at least one mixing pin 355 may radially extend from the agitator shaft 350. The surface area of the at least one mixing pin, the number of mixing pins, and speed of rotation will all increase mixing. If a pin is in the form of a blade that is too sharp, it may induce mixing, but can also cause damage to the crystals. The at least one mixing pin 355 should mix fluids with limited or low shear. In addition, the at least one mixing pin should cause minimal breakage of friable particles, such as sugar crystals.
The at least one mixing pin 355 may have a number of configurations. For example, the at least one mixing pin 355 may be arms, rods, blades or any other vane-like structures that induce movement of a fluid. The at least one mixing pin 355 may be single staggered axially-spaced pins angularly placed on the agitator shaft 350. Alternatively, groups of two or more may be placed angularly around the agitator shaft 350, e.g., diametrically opposite as shown in
The at least one mixing pin 355 can be mounted on an agitator shaft 350 that is centered or off center relative to vertical feed pipe 305 and/or mixing chamber 320. As shown in
The feed pipe mixing system 300 may further comprise a fluid flow control device 365 disposed at the massecuite inlet 325 that is configured for controlling entry of the massecuite feed into vertical feed pipe 305. The fluid flow control device 365 may be a fluid flow regulating valve that may be a butterfly valve, a knife valve, gate valve, etc. Of course, other suitable valves or fluid flow control devices may be apparent to those of ordinary skill in the art in view of the teachings herein.
The feed pipe mixing system 300 may further comprise a steam jacket region 370, having a steam inlet 380, as shown in
The steam jacket region 370 may be disposed upstream of the mixing chamber 320. Alternatively, the steam jacket region 370 may be disposed in the mixing chamber 320 region. Steam may enter the steam jacket region 370 through a steam inlet 380, which optionally is regulated through a control valve. Alternatively, the steam inlet 380 may permit entry of steam directly into vertical feed pipe 305. In one example, steam inlet 380 may be disposed on the side of vertical feed pipe 305 just upstream of the mixing chamber 320. In another example, steam inlet 380 may be disposed on the side of vertical feed pipe 305 in the mixing chamber 320 region.
The temperature of the massecuite fluid may be measured using a temperature sensor and controlled by an automatic temperature controller, which throttles the control valve to admit the required amount of steam for providing and maintaining a desired temperature. Of course, the massecuite fluid temperature may be increased and/or maintained by other methods. For example, massecuite fluid temperature may be increased and/or maintained by indirect methods, such as, contact with a stationary or rotating heated surface.
While several devices and components thereof have been discussed in detail above, it should be understood that the components, features, configurations, and methods of using the devices discussed are not limited to the contexts provided above. In particular, components, features, configurations, and methods of use described in the context of one of the devices may be incorporated into any of the other devices. Furthermore, not limited to the further description provided below, additional and alternative suitable components, features, configurations, and methods of using the devices, as well as various ways in which the teachings herein may be combined and interchanged, will be apparent to those of ordinary skill in the art in view of the teachings herein.
Versions of the devices described above may be actuated mechanically or electromechanically (e.g., using one or more electrical motors, solenoids, etc.). However, other actuation modes may be suitable as well including but not limited to pneumatic and/or hydraulic actuation, etc. Various suitable ways in which such alternative forms of actuation may be provided in a device as described above will be apparent to those of ordinary skill in the art in view of the teachings herein.
Versions of the devices described above may have various types of construction.
By way of example only, any of the devices described herein, or components thereof, may be constructed from suitable metals, ceramics, plastics, or combinations thereof. Various suitable ways in which these and other modifications to the construction of devices described herein may be carried out will be apparent to those of ordinary skill in the art in view of the teachings herein.
Having shown and described various versions in the present disclosure, further adaptations of the devices and systems described herein may be accomplished by appropriate modifications by one of ordinary skill in the art without departing from the scope of the present invention. Several of such potential modifications have been mentioned, and others will be apparent to those skilled in the art. For instance, the examples, versions, geometrics, materials, dimensions, ratios, steps, and the like discussed above are illustrative and are not required. Accordingly, the scope of the present invention should be considered in terms of the following claims and is understood not to be limited to the details of structure and operation shown and described in the specification and drawings.
