AU4457299A

AU4457299A - Vacuum pan

Info

Publication number: AU4457299A
Application number: AU44572/99A
Authority: AU
Inventors: Ali Karacar; Guenther Ross
Original assignee: Braunschweigische Maschb A G; BMA Braunschweigische Maschinenbauanstalt AG
Current assignee: BMA Braunschweigische Maschinenbauanstalt AG
Priority date: 1998-09-10
Filing date: 1999-08-24
Publication date: 2000-03-16
Also published as: DE19841323C1; EP0985734A3; ZA995526B; EP0985734A2

Description

P100/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "VACUUM PAN" The following statement is a full description of this invention, including the best method of performing it known to us:

IA

Vacuum pan The invention relates to a vertical continuous vacuum pan, in which continuously supplied intake juice is converted by the action of heat and agitation into seed, which is used in a downstream processing stage to produce a sugar solution (magma), wherein a totally closed, vacuum-tight container is provided, which comprises a top vapour chest, a bottomjuice area with built-in heat exchanger, a juice inlet, a bottom seed outlet, a steam inlet for steam-heating the heating chamber of the heat exchanger and a rotatable agitating device for forcing the juice into a circulation flow directed through the heat exchanger.

Such an embodiment may be gathered from EP 0 065 775 Bl. In said embodiment, the container encloses cylindrical chambers disposed one above the other as well as devices for the metered supply of the intake juice, for removing the vapour and for transferring the suspension from the top chamber to the respective chamber situated underneath. The chambers, which are separate from one another, are designed in each case in accordance with the agitated pan for the discontinuous crystallization and comprise a heating chamber, which is sweepable with heating steam and has S radially external tube-type, ribbon-type pr plate-type heating elements above the base, as well as a central downtake and an agitator mounted at the bottom in said downtake. In said case, the agitators of the first-swept chambers are high-speed mixing agitators and the agitators of the subsequent chambers are lowspeed circulating agitators. Level controllers for adjusting the 3'0 level are provided in each of the chambers just above the heating chambers. For feeding the intake juice into the chambers a feed pipe, which opens out above the agitator of the respective chamber, is connected by a control valve to a supply line. In the area below the agitator or in the base of the respective chamber a suspension outlet pipe equipped with a control valve or a control flap is provided and connected to a suspension feed pipe of the next chamber.

2 The object of the invention is to improve the efficiency and simplify the construction of the continuous vacuum pan described initially.

Said object is achieved according to the invention in that the agitating device is an agitating cylinder, which is disposed horizontally next to the heat exchanger, extends over the entire juice area length, corresponds in its construction and mode of operation approximately to the impeller of a crossflow fan, but has fewer blades on its periphery and is installed upstream of an outlet diffuser, which surrounds at least half of the outer periphery of the agitating cylinder as the latter's outlet arc.

In said case, it is advantageous when the outlet diffuser is equipped with at least one guide element preventing a flow short circuit.

A simple form of construction is guaranteed when the juice area 20 is subdivided into a plurality of juice chambers disposed horizontally in succession and/or alongside one another, which are in communication with one another in each case by means of a juice overflow and each have a separate juice inlet. In said case, a further simplification of the construction is achieved when there is associated with all of the juice chambers lying successively in container longitudinal direction a common agitating cylinder, which extends through the partitions.

However, since industrial-size installations also entail larger chamber volumes but the agitating cylinder length is limited for >0 design reasons, it appears advantageous, given a plurality of juice chambers disposed alongside one another, for each of said juice chambers to have a separate agitating cylinder lying at right angles to the chamber overflow direction and having a separate drive.

Given said design solutions, a modified design of the agitating cylinder for a plurality of chambers of different sizes is 3 possible and indeed is possible through adaptation of the rate of circulation given an identical, common speed of the driving motor, i.e. through stepped variation of the cylinder diameter.

The arrangement according to the invention of an agitating cylinder leads to a more compact construction, an advantageous arrangement relative to the heating chamber system, a relatively uniform juice circulation over the entire width of the chamber, good circulation given a low or higher viscosity of the suspension as well as a simple fashioning of the crystallizer housing in an angular form of construction with a one- and/or multi-chamber system. The agitating cylinder moreover requires only a simple bearing arrangement and a simple drive. The agitating cylinder is relatively easy to design and manufacture.

When the agitating cylinder extends through a plurality of chambers, a simple diaphragm gland between the chambers in the region of the agitating cylinder is sufficient.

The juice area of the continuous vacuum pan may be subdivided by a vertical central longitudinal wall into two substantially mirror-symmetrical chambers, each of which is equipped with an agitating cylinder.

ego The heat exchanger may take the form of a plate heat exchanger with a parallel vertical arrangement of the heating plates, .r which are connected in parallel to a common steam admission duct and have common lines for degassing and for drainage of the condensate.

Such a plate heat exchanger may take the form of a multi-chamber S" heat exchanger, which according to the invention is characterized in that the heating plates extend through all of the juice chambers disposed successively in longitudinal direction of the container and in the partition-penetrating region are slipped in each case by means of a downwardly open slot extending only over a part of the height of the heating 4 plate onto an upwardly open slot in the upper region of the partition.

In an alternative solution, the heat exchanger may alternatively be a tubed calandria which, viewed in vertical cross section, forms a square standing on one point and, viewed in longitudinal direction, comprises successively disposed tube sections, which alternate with tube portions offset by 900 and lying in each case parallel to and with clearance alongside one another, the open ends of which project through a casing-side chamber housing into the circulation flow of the juice, wherein the chamber housing swept in longitudinal direction by the steam comprises a bottom condensed water outlet and a top degassing connection.

Said construction enables a variable design of the pipe lengths for adaptation of the heating area to the product volume, a variable design of the pipeline, a simple configuration of the heating chamber with good conditions for the feed and return lines, an easy adaptation of the heating area to the apparatus size as well as a good flow behaviour of the medium by virtue of the air-lift principle. In said case, the medium flow is effectively assisted by means of agitating cylinders disposed at both longitudinal sides of the tubed calandria approximately at mid-height of the latter.

Finally, the construction according to the invention also enables a container in the form of a horizontal cylinder.

Further features of the invention are the subject matter of the sub-claims and, in conjunction with further advantages of the invention, are described in detail with reference to embodiments.

Several forms of construction of the invention serving as examples are illustrated in the drawings. The drawings show: Figure 1 Figure 2 Figure 3 Figure 4 a vertical cross section through a continuous vacuum pan; to an enlarged scale, a detail from Figur 1; to a slightly reduced scale compared to Figure i, in side view and in vertical longitudinal section a continuous vacuum pan with three successively disposed chambers and a common agitating cylinder; in plan view and in horizontal longitudinal section an evaporative crystallizer with five chambers disposed in two adjacent rows and with an agitating cylinder associated with each of the two rows; in side view a heating plate 8, which is to extend through three successively disposed chambers; to a slightly enlarged scale compared to Figure a vertical cross section through the view according to Figure in a view according to Figure 1 a modified continuous vacuum pan; a diagrammatic view of a continuous vacuum pan and a modified embodiment in a view according to Figure 7.

2.0 S S Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 S S Figure 1 shows a totally closed, vacuum-tight container 1 with a substantially rectangular bottom surface, such as may be seen A from the embodiment according to Figure 4. Formed body 1 encloses a bottom juice area 2 and a top vapour chest 3. The juice area 2 is subdivided by a vertical central longitudinal wall 4 into two approximately mirror-symmetrical chambers 5 or rows of chambers. Figure 4 shows an example of this, in which the five chambers disposed successively in chamber overflow direction 6 are designated consecutively 5a, 5b, 5c, 5d and Se.

Installed in the juice area 2 is a steam-heated heating chamber which, in the embodiment according to Figure 1, is a plate heat exchanger 7 with a parallel vertical arrangement of the heating plates 8, which are connected in parallel to a common steam admission duct 9. The juice area 2 further comprises a juice inlet 10 and a bottom seed outlet 11, wherein a juice inlet and a seed outlet 11 are associated with each chamber 5. The juice level in the juice area 2 or in the individual chambers thereof is denoted by the reference character 12.

20 The vapour area 3 is equipped at the top with an entrainment separator 13.

Disposed in each of the two chambers 5 shown in Figure 1, at the bottom next to the plate heat exchanger 7, is a horizontal agitating cylinder 14 which extends over the entire juice area length and corresponds in its construction and mode of operation approximately to the impeller of a crossflow fan. Said agitating cylinder 14 is disposed upstream of an outlet diffuser 15, which is formed by the adjacent wall of the container 1 and surrounds 0 at least half of the outer periphery of the agitating cylinder 14 as the latter's outlet arc (see, in particular, also Figure To prevent a flow short circuit, the outlet diffuser 15 is equipped in its flow-off region with a vortex generator 16 and a baffle 17. Said components 16, 17 direct the juice stream symbolized by arrows 18 into the bottom flow-in region of the plate heat exchanger 7 and prevent a backflow of juice between agitating cylinder 14 and plate heat exchanger 7.

The juice introduced at the suction side of the agitating cylinder 14 is set by the agitating cylinder 14 into a circulation flow 18, whereby the juice flows from the bottom--up through the freely sweepable cross sections between the heating plates 8 of the plate heat exchanger 7. An intensive cyclic flow is generated with simultaneous recirculation of the juice in the chamber 5. During said process, the filling level 12 of the juice in each chamber 5 is kept just above the heating plates 8 of the plate heat exchanger 7.

It is particularly evident from Figure 2 that the agitating cylinder 14, given a small cylinder diameter, has short curved blades 19 of a length, arising from the ratio of outside diameter Da to inside diameter Di, of around 0.7. The entry and exit angle a of the blades 19 is around 250 300. The inner blade angle 3 of the blades 19 relative to the agitating cylinder centre is 90* Each agitating cylinder 14 preferably has twelve blades 19.

0 Figure 3 shows a juice area having three chambers 5a, 5b and which are disposed horizontally in succession in longitudinal direction of the container 1 and which are separated from one another in each case by a partition 20 but in communication with one another via the juice overflow 6. Each of said three chambers has a separate seed outlet 11, although all three juice chambers have a common vapour chest 3 and entrainment separator 13.

:30 It is further evident from Figure 3 that the agitating cylinder 14 extends through the three juice chambers Sa, 5b, Sc and hence also through their partitions 20. In said case, the agitating a cylinder 14 is drivable at one end by an electric motor 21 via a gear unit 22 and supported at its end remote from the drive in a self-aligning bearing 23.

Additionally indicatedin Figure 3 are the steam admission duct 8 9 for the plate heat exchanger and a line 24, common to all of the heating plates, for drainage of the condensate.

Figure 4 shows a juice area having five chambers 5a to 5e, each of which has an inlet 25 for an intake solution. An agitating cylinder 14 is associated with each of the two parallel rows of chambers.

Figures 5 and 6 show a heating plate 8 of lightweight construction. Each heating plate 8 in said case comprises two contoured metal sheets 27, 28 joined to one another by spot welds 26. The heating plates 8, in addition to the common line 24 for drainage of the condensation product, have a common line for degassing.

In the embodiments according to Figures 3 and 4, the heating plates 8 may extend through all of the juice chambers 5a, 5b, or 5d, 5e disposed successively in longitudinal direction of the 20 container 1. In the partition-penetrating region, each heating plate 8 is slipped by means of a downwardly open slot 29 ~extending only over part of the height of the heating plate 8 onto an upwardly open slot (not shown in detail in the drawing) in the top region of the respective partition In the modified embodiment shown in Figure 7, the container 1 takes the form of a horizontal cylinder. The heat exchanger here is formed by a tubed calandria 30 which, viewed in vertical cross section, forms a square standing on a point and, viewed in 0 longitudinal direction, comprises successively disposed tube sections 31 (see also Figure which alternate with tube portions 32 offset by 90' and lying in each case parallel to and with clearance alongside one another. The open ends of the tube portions 32 project through a casing-side chamber housing 33 into the circulation flow 18 of the juice. The chamber housing 33 has a steam admission connection 34, through which the steam flows in longitudinal direction through the chamber housing 33.

The chamber housing 33 has a bottom condensed water outlet and a top degassing connection 36.

Whereas in the embodiment according to Figure 1 the agitating cylinder 14 is disposed in the bottom region of the juice area 2 and of the plate heat exchanger 7, according to Figure 7 the two agitating cylinders 14 are situated at the two longitudinal sides of the tubed calandria 30 roughly at mid-height of the latter. The outlet diffuser 15 associated with each agitating cylinder 14 is defined, here, by suitable baffles 37 in the container 1.

In the modified embodiment according to Figure 9, the shape of the container 1 resembles that of Figure 1 but is somewhat flatter. Here too, the juice area 2 is subdivided by a central longitudinal wall 4 into two chambers 5, in each of which a tubed calandria 30 is disposed.

S.

S

Claims

1. Vertical continuous vacuum pan, in which continuously supplied intake juice is converted by the action of heat and agitation into seed, which is used in a downstream processing stage to produce a sugar solution (magma), wherein a totally closed, vacuum-tight container is provided, which comprises a top vapour chest a bottom juice area with built-in heat exchanger 30), a juice inlet a bottom seed outlet a steam inlet for steam-heating the heating chamber of the heat exchanger 30) and a rotatable agitating device for forcing the juice into a circulation flow (18) directed through the heat exchanger 30), characterized in that the agitating device is an agitating cylinder which is disposed horizontally next to the heat exchanger 30), extends over the entire juice area length, corresponds in its construction and mode of operation approximately to the impeller of a crossflow fan but has fewer blades (19) on its periphery and is installed upstream of an outlet diffuser which surrounds at least half of the outer periphery of the agitating cylinder (14) as the latter's outlet arc.

2. Vertical continuous vacuum pan according to claim 1, characterized in that the outlet diffuser (15) is equipped with at least one guide element (16, 17) preventing a flow short circuit.

3. Vertical continuous vacuum pan according to claim 1 or 2, characterized in that the juice area is subdivided into a plurality of juice chambers (Sa 5e) disposed horizontally in succession and/or alongside one another, which are in communication with one another in each case by means of a juice overflow and each have a separate juice inlet 11

4. Vertical continuous vacuum pan according to claim 3, characterized in that all of the juice chambers have a common vapour chest Vertical continuous vacuum pan according to claim 3 or 4, characterized in that associated with all of the juice chambers (5a, b, c) disposed successively in container longitudinal direction is a common agitating cylinder (14), which extends through the partitions

6. Vertical continuous vacuum pan according to claim 3 or 4, characterized in that, given a plurality of juice chambers disposed alongside one another, each of said juice chambers has a separate agitating cylinder (14) lying at right angles to the chamber overflow direction and having a separate drive (21, 22).

7. Vertical continuous vacuum pan according to one of the preceding claims, characterized in that the agitating cylinder (14) is drivable at one end by an electric motor (21) via a gear unit (22). S" 8. Vertical continuous vacuum pan according to claim 6, 25 characterized in that the agitating cylinder (14) is supported at its end remote from the drive (21, 22) in a S- self-aligning bearing (23).

9. Vertical continuous vacuum pan according to one of the "0 preceding claims, characterized in that the agitating cylinder given a small cylinder diameter, has short curved blades (19). S 10. Vertical continuous vacuum pan according to claim 9, characterized in that the length of the blades which arises from the ratio of outside diameter (Da) to inside diameter is around 0.7.

11. Vertical continuous vacuum pan according to one of the preceding claims, characterized in that the entry and exit angle of the blades (19) of the agitating cylinder (14) is 250 300.

12. Vertical continuous vacuum pan according to one of the preceding claims, characterized in that the inner blade angle of the blades (19) relative to the agitating cylinder centre is around 900.

13. Vertical continuous vacuum pan according to one of the preceding claims, characterized in that each agitating cylinder (14) has eight to twenty four, preferably twelve blades (19).

14. Vertical continuous vacuum pan according to one of the preceding claims, characterized in that the juice area (2) is subdivided by a vertical central longitudinal wall (4) into two approximately mirror-symmetrically designed chambers each of which is equipped with an agitating cylinder (14).

15. Vertical continuous vacuum pan according to one of the preceding claims, characterized in that the heat exchanger is a plate heat exchanger with parallel vertical arrangement of the heating plates which are connected in parallel to a common steam admission duct

16. Vertical continuous vacuum pan according to claim characterized in that the heating plates also have common lines (24) for degassing and for drainage of condensate.

17. Vertical continuous vacuum pan according to claim 15 or 16, characterized in that the heating plates are of a lightweight construction, wherein each heating plate (8) comprises two contoured metal sheets (27, 28) joined to one another by spot welds (26).

18. Vertical continuous vacuum pan according to claim 3 and one of claims 15, 16 or 17, characterized in that the heating plates extend through all of the juice chambers disposed successively in longitudinal direction of the container and in the partition-penetrating region are slipped in each case by means of a downwardly open slot (29) extending only over part of the height of the heating plate onto an upwardly open slot in the upper region of the partition wall

19. Vertical continuous vacuum pan according to one of claims to 18, characterized in that the agitating cylinder (14) is disposed in the bottom region of the juice area and of the plate heat exchanger

20. Vertical continuous vacuum pan according to one of claim 1 S. to 14, characterized in that the heat exchanger is a tubed calandria (30) which, viewed in vertical cross section, forms a square standing on one point and, viewed in longitudinal direction, comprises successively disposed tube sections which alternate with tube portions (32) offset by 900 and lying in each case parallel to and with clearance alongside one another, the open ends of which project through a casing-side chamber housing (33) into the circulation flow (18) of the juice, wherein the chamber 0 housing (33) swept in longitudinal direction by the steam comprises a bottom condensed water outlet (35) and a top degassing connection (36).

21. Vertical continuous vacuum pan according to claim characterized in that an agitating cylinder (14) is disposed at both longitudinal sides of the tubed calandria substantially at mid-height of the latter. 14

22. Vertical continuous vacuum pan according to one of the preceding claims, characterized in that the container (1) takes the form of a horizontal cylinder. DATED this Twenty-fourth day of August 1999. BRAUNSCHWEIGISCHE MASCHINENBAUANSTALT AG By its Patent Attorneys FISHER ADAMS KELLY :j 1