GB2085026A

GB2085026A - Constant Density Sugar Solution

Info

Publication number: GB2085026A
Application number: GB8126245A
Authority: GB
Original assignee: Hein Lehmann AG
Current assignee: Hein Lehmann AG
Priority date: 1980-09-02
Filing date: 1981-08-27
Publication date: 1982-04-21
Also published as: IN155093B; GB2085026B; DE3032922A1; DE3032922C2

Abstract

Controlled amounts of a liquid solvent, such as water, and a filling mash separated into run-off liquid and sugar are supplied to a continuously operated centrifuge where the sugar is dissolved in the solvent, and the resultant sugar solution is drawn off from the centrifuge. In one embodiment, the density of the sugar solution is maintained constant by measuring said density and quantitatively regulating the supply of the solvent in accordance with the measurement thus made. In an alternative embodiment, the flow rates of the solvent and the filling mash are measured and the quantity ratio of these flow rates is maintained constant.

Description

SPECIFICATION Method of and Apparatus for Producing a Sugar Solution having a Constant Density This invention relates to the production of a sugar solution having a constant density or constant concentration, wherein a mixing device is supplied with controlled amounts of a liquid solvent and a filling mash separated into run-off liquid (or molasses) and sugar, the sugar is dissolved in the solvent, and the resultant sugar solution is drawn off from the mixing device, all in accordance with German Patent Application P 2910625.

The above-mentioned technique is primarily used for producing sugar having a high grade of purity, and a method of embodying this technique is described in German OS 2550496. In this latter specification, the mix-temperature of sugar temperature and liquid solvent is used as a controlling factor for density regulation. This temperature is maintained constant, thus also keeping constant the weight ratio of sugar relative to the solvent. The sugar/solvent weight ratio is a measure of concentration, or density, of the solution.

Inasmuch as the mix-temperature depends on four different factors, namely on the sugar temperature, the solvent temperature, the quantity of sugar and the quantity of solvent, it follows that three of these factors must be maintained constant with the aid of three different regulating or control systems in order to enable the fourth, namely the quantity of the solvent, to be regulated in accordance with mixtemperature. This is a very cumbersome method, not to mention the added complication the environmental temperature conditions are not without influence on the process so that operation during the daytime at higher ambient temperatures would produce a denser, i.e. more highly concentrated sugar solution than nighttime operation.

It is the aim of the present invention to provide a method of and apparatus for producing a sugar solution having a constant density, which avoids the aforementioned disadvantages, and which enables the constant density (or constant concentration) sugar solution to be produced by simple means and with a minimum risk of interference or malfunction.

According to a first aspect of the invention, a method of producing a sugar solution having a constant density comprises feeding to a mixing device (preferably a continuously operated centrifuge) controlled amounts of a filling mash which is separated into run-off liquid and sugar, dissolving the sugar with the aid of controlled amounts of a liquid solvent such as water, the supply of said solvent being quantitatively regulated in accordance with the density of the resultant sugar solution, and continuously drawing off the sugar solution from the mixing device.

Thus for producing a sugar solution of predetermined density, it is no longer necessary to regulate the amount of sugar which is fed into the centrifuge, nor do temperatures and potential fluctuations of temperature matter in the process.

This means that now only one single regulating system is needed instead of four, which affords a considerable saving in regulating equipment and also reduces the risk of breakdown or malfunction.

An exact and fast method can be obtained by measuring the density of the sugar solution using a density-measuring device or hydrometer having an associated signal transmitter which supplies to a controller an output signal dependent upon the measured density, and by applying an output signal of the controller to an adjusting member dosage means which regulates the supply of the solvent.

Apparatus for performing the above-described method comprises, according to the invention a continuously working centrifuge or hydroextractor to which are supplied controlled amounts of a liquid solvent and a filling mash separated into run-off liquid and sugar, dosage means having a member which is adjustable to regulate the supply of said solvent to the centrifuge, a densitymeasuring device or hydrometer operative to measure the density of the resultant sugar solution, and a controller operative to adjust said member of the dosage means in accordance with the density measured by the density-measuring device.

Where the centrifuge includes a baffle and a deflector ring limiting the baffle, any density variations in the sugar solution can be detected immediately if a sample-extractor pipe connection is provided in the region of the deflector ring and is connected to the density-measuring device.

According to a second aspect of the present invention, a method of producing a sugar solution having a constant density comprises feeding to a mixing device (preferably a continuously operated centrifuge) controlled amounts of a filling mash which is separated into run-off liquid and sugar, dissolving the sugar with the aid of controlled amounts of a liquid solvent, the flow rates of the solvent and the filling mash each being measured and the quantity ratio of both flow rates being maintained constant, and continuously drawing off the resultant sugar solution from the mixing device.

The rate of flow of the solvent is preferably measured with the aid of a flow-meter having an electric or pneumatic signal output. Desirably, a signal representative of the flow rate of the filling mash is obtained by measuring the current consumption or effective energy output of a motor which drives a basket of the centrifuge.

Admittedly, this method is based on the assumption that the crystalline content in the filling mash is largely constant, but this is generally so in any case.

According to the invention, apparatus for performing the method described in the last two preceding paragraphs comprises a continuously working centrifuge to which are supplied controlled amounts of a liquid solvent and a filling mash separated into run-off liquid and sugar, first dosage means having a member which is adjustable to regulate the flow rate of the solvent, second dosage means having a member which is adjustable to regulate the flow rate of the filling mash, a first flow meter operative to measure the flow rate of the solvent, a second flow meter operative to measure the flow rate of the filling mash, and a ratio controller which adjusts said member of the first dosage means in accordance with the flow rate measured by the second flow meter.

The invention will now be further described by way of example, with reference to the accompanying drawing which diagrammatically illustrates two examples of apparatus for performing the methods of the invention. The lefthand half of the drawing represents a section through apparatus comprising a densitymeasuring device for carrying out a first embodiment of the method according to this invention, while the right-hand half of the drawing is a section through apparatus comprising a quantity-ratio-regulating system for applying a method according to another embodiment of the invention.

In each of the apparatuses shown in the drawing, a sugar solution consisting of sugar and liquid solvent is produced with the aid of a centrifuge. The sugar solution which is obtained in this manner has a high and constant density or concentration, which contributes considerably to improved further processing characteristics of the sugar solution. The centrifuge comprises a conical upwardly expanding basket 1 with a vertical axis.

The basket 1 is driven by a motor 20. A housing 2 encases the internal fittings of the centrifuge. The upper part of this housing may serve as a first baffle 3 for theisugar which is spun off the hydroextractor edge 4 of the centrifuge basket.

Slightly below the level of this edge 4 a continuous first annulus 5 is secured to the housing 2 which limits the first baffle wall 3 on the underside. Above this first annulus 5 is an annular conduit 6 or ring passage 6 with orifices which direct the emerging liquid, for example the mash liquid, against the first baffle 3 and/or the free-flying sugar. The first deflector ring 5, which is arranged between 10 and 30 mm underneath the extractor edge and at right angles to the baffle wall, is 30 mm wide.

An exchangeable second baffle 1 6 is secured to the inside of the housing cover 17. Within this second baffle 16 there is provided a ring pipe 18 for the liquid solvent. The baffle 1 6 and the ring pipe 1 8 are jointly and detachably secured to the housing cover 1 7 and the latter is adapted to be raised, for example about hinges.-The ring pipe 18 for the solvent comprises orifices through which the solvent, in particular water or an unsaturated sugar solution, is directed at the second baffle 1 6 and/or the free-flying sugar The second baffle 1 6 reaches down to about 40 mm beneath the level of the edge 4 on the basket 1.It is limited by an inwardly directed second deflector ring 1 9 which extends at right angles thereto and is only a few millimeters (for example 5 mm) wide. All of the sugar which is flung off the edge 4 impinges on the second baffle wall 16 so that in this arrangement the first baffle with its associated first ring pipe 6, designed for the initial mashing or mixing operation, remain ineffective.

A partition wall 7 in the housing interior relatively separates spaces 8 and 9 respectively designed for the run-off liquid and the sugar. The outer space 9 has an inclined bottom 10. Each of these spaces is provided with an outlet orifice 11, 12 arranged in the region of its lowest point, the two outlets 11, 12 being situated vertically one above the other with a syphon plate 13 therebetween. The syphon plate 1 3 is open at its top and bottom ends and co-acts with the housing wall to form an upwardly widening outflow passage. The outlet orifice 11 is closed. A heater device is fitted in the outer space 9, and comprises a ring pipe 14 with orifices through which the heating fluid, especially steam, may emerge approximately in the longitudinal direction of the ring pipe 14, that is to say in an approximately tangential direction.

The apparatus shown in the left-hand half of the drawing further comprises a sample-extractor pipe connection 21 in the region of the ring 1 9 which leads directly to a hydrometer or similar density-measuring device 22 arranged externally of the centrifuge. The sample-extractor pipe 21 permits a small branch current of the sugar solution to be drawn off, conducted through the hydrometer and then returned, for example, to the centrifuge. A liquid solvent feed pipe 23 leads into the ring pipe 18. This feed pipe 23 includes an adjusting device 24 for regulating the liquid solvent supply dosage. A signal transmitter 25 which is associated with the density-measuring device 22 is operatively connected with a controller 26 with a guide-beam unit. Controller 26 and adjusting member 24 are mutually coupled.

The apparatus shown in the left-hand half of the drawing works in the following manner. A filling mash, delivered for example by a mashpreparing centrifuge, is fed centrally into the centrifuge through an adjusting member 27, for example a dosing valve, and is then separated inside the centrifuge into run-off liquid and sugar.

The run-off liquid is drawn off through the pipe 1 5. The sugar which is flung off the edge 4 accomplishes a short length of free flight whereupon it impinges against the second, near baffle wall 1 6 where a strong grain-destruction effect is produced by the high impingement velocity. In this region the sugar is then dissolved by means of the liquid solvent which is discharged through ring pipe 1 8. The water/sugar solution runs down inside the vessel over the deflector ring 1 9 and collects in the outer space 9. The outlet orifice 11 is closed.In order to ensure that the sugar solution thus obtained from the sugar and solvent is automatically maintained at a constant high density level, a small amount of the solution is drawn continuously off either from space 9 or, preferably, through the sampling pipe 21 and is fed through the density-metering device 22. The device 22 ascertains the actual density or concentration of the sugar solution at any given time and applies the actually measured value x through its associated signal transmitter 25 to the controller 26. The controller 26 compares the actual valuexwith a predetermined ideal value and sends a corresponding output signal to the adjusting member 24 for solvent supply dosage.If the measured value of density in the sugar solution is higher than the ideal value, that is to say, if the density or concentration of the sugar solution is too high, the dosing valve associated with the adjusting member 24 will be opened wider until the required degree of concentration or density is established. If the actually measured density value is below the ideal value, that is to say if the density of the sugar solution is below strength, the dosing valve will reduce the supply of solvent until the desired density is established.

The apparatus shown in the right-hand half of the drawing comprises a quantity-ratio control system. This consists of a current transformer 30 acting as signal transmitter which picks up the current or effective output consumption of the motor 20 through a motor supply cable 31. The transformer 30 is connected to a controller 32 which in turn actuates an adjusting member 28 for the filling mash, for example a pneumaticallydriven dosage valve. The feed pipe 23 which leads to the ring pipe 1 8 includes a flow-meter 27 with a signal transmitter 29 followed, in the direction of solvent flow, by an adjusting member 24 for solvent dosage. The signal transmitter 29 is in operative association with a controller 34 and the latter with the adjusting member 24.The output signal of the transformer 30 is also applied to a ratio-controller 33 and the output of the latter is applied to the controller 34 which regulates the amount of solvent supply to the centrifuge.

In order to ensure that the resulting sugar solution will automatically have a constant and high degree of density or concentration, the transformer 30 continuously monitors the current consumption of the motor 20. The current consumption, or effective output energy consumption of the motor is directly proportional to the amount of inflow of filling mash and may thus be used as the actual value x of the filling mash quantity. This actual valuex is applied to the controller 32 of which the output signal y influences the adjusting member 28. For example, if the power consumption of the motor increases, this provides an indication of the fact that the amount or quantity of filling mash which is fed into the centrifuge per unit time likewise increases.If a maximum permitted level is reached or exceeded, the controller 32 sends a corresponding signal to the adjusting member 28 which restricts the inflow of filling mash until the desired predetermined ideal value has been restored. If on the other hand the power consumption of the motor drops, the adjusting member 28 will be opened wider to admit more filling mash to the centrifuge. Thus, the supply of filling mash is maintained always at a constant figure.

A further control circuit is formed by the adjusting member 24 for solvent dosage, the flow meter 27 for the solvent, its associated signal transmitter 29 and the controller 34. This control circuit has the function of maintaining the quantity of solvent fed into the centrifuge per time unit at a constant predetermined ideal value W.

The two control circuits are interconnected through the ratio controller 33 in such a way that the ideal value W of the solvent control circuit varies proportionally with the actual value x for filling mash feed. The extent of the variation can be adjusted with the aid of the ratio controller 33.

Thus, the ratio controller has the function of adjusting the desired density or concentration in the sugar solution.

Claims

1. A method of producing a sugar solution having a constant density, comprising feeding to a mixing device controlled amounts of a filling mash which is separated into run-off liquid and sugar, dissolving the sugar with the aid of controlled amounts of a liquid solvent, the supply of said solvent being quantitatively regulated in accordance with the density of the resultant sugar solution, and continuously drawing off the sugar solution from the mixing device.

2. A method as claimed in Claim 1, wherein the mixing device is a continuously operated centrifuge.

3. A method as claimed in Claim 1 or 2, wherein the density of the sugar solution is measured by means of a density-measuring device, an associated signal transmitter supplies to a controller an output signal which is dependent upon said measured density, and the controller applies an output signal to an adjusting member of dosage means which regulates the supply of the solvent.

4. Apparatus for performing the method claimed in any one of Claims 1,2 and 3, comprising a continuously working centrifuge to which are supplied controlled amounts of a liquid solvent and a filling mash separated into run-off liquid and sugar, dosage means having a member which is adjustable to regulate the supply of said solvent to the centrifuge, a density-measuring device operative to measure the density of the resultant sugar solution, and a controller operative to adjust said member of the dosage means in accordance with the density measured by the density-measuring device.

5. Apparatus as claimed in Claim 4, wherein the centrifuge is provided with a baffle, a deflector ring limiting the baffle, and a sample-extractor pipe connection in the region of the deflector ring, the density-measuring device being connected to the pipe connection.

6. A method of producing sugar solution having a constant density, comprising feeding to a mixing device controlled amounts of a filling mash which is separated into run-off liquid and sugar, dissolving the sugar with the aid of controlled amounts of a liquid solvent, the flow rates of the solvent and the filling mash each being measured and the quantity ratio of both flow rates being maintained constant, and continuously drawing off the resultant sugar solution from the mixing device.

7. A method as claimed in Claim 6, wherein the mixing device is a continuously operated centrifuge.

8. Apparatus for performing the method claimed in Claim 6 or 7, comprising a continuously working centrifuge to which are supplied controlled amounts of a liquid solvent and a filling mash separated into run-off liquid and sugar, first dosage means having a member which is adjustable to regulate the flow rate of the solvent, second dosage means having a member which is adjustable to regulate the flow rate of the filling mash, a first flow meter operative to measure the flow rate of the solvent, a second flow meter operative to measure the flow rate of the filling mash, and a ratio controller which adjusts said member of the first dosage means in accordance with the flow rate measured by the second flow meter.

9. Methods of producing a sugar solution having a constant density, substantially as hereinbefore described with reference to the accompanying drawing.

10. Apparatus for producing a sugar solution having a constant density, substantially as hereinbefore described with reference to the accompanying drawings.