STIRRERS FOR CRYSTALLIZING EVAPORATOR

Abstract

A stirrer for a crystallizing evaporator such a crystallizing evaporator for crystallizing sucrose from concentrated beet juice. The stirrer includes at least one active flow-conducting means selected from a group consisting of a plurality of flow-conducting propellers arranged along a shaft of the stirrer and a screw running along the shaft.

Claims

1. A stirrer for a vacuum pan, suitable for circulating a solution or suspension to be crystallized in a vessel, comprising a shaft, a main propeller disposed in a primary mixing zone and connected to the shaft; and at least one active flow-conducting means on the shaft and upstream of the main propeller for active flow guidance of the solution or suspension, the at least one active flow-conducting means is selected from a group consisting of: 1) a plurality of flow-conducting propellers each having a flow-conducting propeller diameter less than 50% of a main propeller diameter of the main propeller, the plurality of propellers arranged at a distance from each other along the shaft, and 2. a screw running along the shaft, having a screw that is a diameter at most 50% of the main propeller diameter.

2. The stirrer according to claim 1, wherein the at least one active flow-conducting means is arranged directly adjacent to the primary mixing zone.

3. The stirrer of claim 1 in combination with the vacuum pan.

4. The vacuum pan according to claim 3, wherein the vacuum pan is designed for discontinuous operation.

5. A method of using the active flow-conducting means of claim 1, on the shaft of the stirrer to improve a mixing capacity.

6. The method according to claim 5 for improving the mixing capacity of the stirrer in a vacuum pan in discontinuous operation.

7. The stirrer according to claim 1, wherein the at least one active flow-conducting means comprises the plurality of flow conducting propellers.

8. The stirrer according to claim 1, wherein the at least one active flow-conducting means comprises the screw.

Description

DETAILED DESCRIPTION

[0039] The invention is described in more detail by means of the following FIGURE, without this being intended to be limiting.

[0040] FIG. 1 shows a schematic representation of a common vertical vacuum pan with vertical reactor vessel 100. In the lower region, this contains solution or suspension 140, from which the crystal product is to be obtained. At the upper end, the vapor space 125 is provided with a steam extraction. Flow-through heating elements (heat exchanger) 120 are arranged in the lower region of the vessel. An agitator shaft 150 is suspended substantially vertically (perpendicularly) from the top in the vessel 100. In a primary mixing zone 110, here directly at the lower end of the shaft, there is arranged a main propeller, i.e, blade, 160, which, upon rotation of the drive shaft 150, moves the solution or suspension located in the vessel downwards and in a primary direction towards the vessel bottom. The downwardly directed flow 144 of the solution or suspension is directed into the heating chambers 120 by the bottom-side baffle 130 on the vessel 100. By virtue of active pumping and assisted by a reduction in the density by heating the solution or suspension in the heating chamber 120 as well as by the formation of steam bubbles, it leaves the heating chamber essentially in a vertically upward direction 145. The pumping action of the main propeller 160 is assisted by fixed baffle plates 170 arranged adjacent thereto. According to the invention, active flow-directing means 180 are provided along the drive shaft 150 above the main propeller 160 and, in the immediate vicinity of the drive shaft 150, provide an active flow 147 of the solution or suspension towards the main propeller 160 in the direction of the drive shaft. This effectively supports the effect of the stirrer. A stable circular flow 144, 145, 146, 147 is formed via the compensating flows 146. Depending on the fill level 141, 142 or 143 of the solution or suspension 140 in the reactor 100, more or fewer sections or units of the flow-conducting means 180 engage with the same. The specific total energy demand on the shaft 150 is thereby always adapted to the filling level 141, 142 or 143.