JPS5853561B2 - How to operate a centrifugal thin film evaporator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a centrifugal thin film evaporator, and in particular, the present invention relates to a method of operating a centrifugal thin film evaporator. It rotates while in contact with the heat transfer surface, applying centrifugal force to the processing liquid and forming a thin film.
It is suitable for a centrifugal thin film evaporator that evaporates the processing liquid into a slurry or powder form by scraping off the thin film at the same time as the evaporation.

Conventional centrifugal thin film evaporators operate with a constant supply rate and rotating speed of the rotor blades, which are determined according to the properties of the supplied liquid and the processing purpose, and the control device is designed to keep the supply rate constant. Most of them were designed to keep the temperature conditions of the equipment constant.

At best, the supply amount was controlled in order to obtain a constant concentration of evaporation residue.

For this reason, if the processing liquid adheres to the heat transfer surface or rotor blade and gradually grows as a solid, or if this property changes during processing, the specified The centrifugal force button that changes the rotation speed and the scraping force that the rotor blade scrapes off the heat transfer surface cannot remove the deposits, and the deposits on the heat transfer surface and the rotor blade reduce heat transfer performance. This may lead to overloading of the rotor blades or loss of balance of the rotor blades.

For this reason, there was a drawback that the operation had to be temporarily stopped after a certain period of operation in order to wash and remove the deposits.

An object of the present invention is to enable continuous operation for a long period of time for processing liquids having such adhesive properties.

Among centrifugal thin film evaporators, particularly those of the scraping type, as the number of rotations of the rotor blades increases, the centrifugal force and scraping force of the rotor blades increase, and the effect of removing deposits becomes greater.

However, when the scraping force increases, the formed thin film is scraped off by the rotary blades, and the processing liquid is biased towards the rotary blades, which reduces the heat transfer effect. The original strengths of the device cannot be utilized.

Furthermore, there are disadvantages such as direct contact between the heat transfer surface and the rotor blade, resulting in severe wear and the need for excessive driving power.

The main point of the present invention is to focus on the characteristics of high rotational speeds that have not been used in the past. In order to remove the deposits that have grown without being scraped off during this operating time, in the next step, the feed rate is reduced or stopped, and at the same time the rotation speed of the rotor is increased, and after removing the deposits, the rotation speed is increased again. By returning the rotation speed to a predetermined number and at the same time restarting operation with a predetermined supply amount, repeating this operation enables stable continuous operation over a long period of time.

An embodiment of the present invention is shown in FIGS. 1 and 2.

In FIG. 1, the processing liquid is stored in a storage tank 1 and sent by a supply pump 2 through a control valve 3 to a centrifugal thin film evaporator 6.

When the centrifugal thin film evaporator 6 is turned on, the processing liquid is formed into a thin film by the action of the centrifugal force of the rotary blades 7, evaporated by the heat from the heat medium jacket 8, and discharged from the paper outlet 9.

At the same time, the evaporation residue is scraped off by the scraping action of the rotary blades 7 and is discharged from the bottom discharge port 10 in the form of slurry or powder.

At this time, the relationship between the supply amount of processing liquid and the rotation speed of the rotor blade is as follows.
It is predetermined and peeled according to the properties of the processing liquid and stored in the control device 11.

This controls the control valve 3 and adjusts the supply amount.

At the same time, the continuously variable transmission 13 for driving the rotary blades is adjusted.

An example of the relationship between the supply amount of the processing liquid and the rotational speed of the rotor blade is shown in FIG.

For a certain period of time from the start of operation, the processing liquid is supplied in a constant amount as in the conventional case, and at the same time, the rotary blade 70 is operated at a predetermined rotation speed.

In the case of a treatment liquid that has adhesive properties, deposits gradually accumulate on the heat transfer surface and the rotor blade 7, making it impossible to continue operation with just one treatment.

Therefore, at time t1, the supply amount is reduced or stopped, and at the same time the number of revolutions of the rotary blade 70 is increased, and the centrifugal force button and the scraping force are increased to remove the deposits.

At time t2 after the deposits have been removed, the rotational speed is returned to the predetermined rotational speed, and at the same time, the supply amount is also slightly returned to the original amount.

After that, repeat the above operation.

As described above, the present invention can prevent deposits that adhere to and grow in a centrifugal thin film evaporator by periodically varying the supply amount of the processing liquid and varying the rotational speed of the rotor blades in accordance with this variation value. It has the effect of removing the gas and enabling continuous operation over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a centrifugal thin film evaporator, and FIG. 2 is a diagram showing an example of the relationship between supply amount and rotation speed. 1... Storage tank, 2... Supply pump, 3.
...Control valve, 4...Return valve, 5...
・・Flow rate detector, 6・・Centrifugal thin film evaporator, 7・
...Rotary blade, 8 ... Heat medium jacket, 9
... Paper outlet, 10 ... Bottom discharge port, 11 ... Control device, 12 ... Transmission device, 13 ... Continuously variable speed Machine, 14...
・Heat medium inlet, 15... Heat medium outlet.

Claims (1)

[Claims] 1. A rotary blade attached to a rotating shaft slides on a heat transfer surface by centrifugal force, forms a thin film of processing liquid on the heat transfer surface, evaporates it, and at the same time has the effect of scraping off the thin film. In the third method of operating a centrifugal thin film evaporator to obtain a slurry-like or powder-like evaporation residue, the supply amount of the processing liquid is periodically varied, and the rotation speed of the rotor blade is varied according to this variation value. A method of operating a centrifugal thin film evaporator, characterized in that: 2. Periodically stop the supply of the processing liquid, and during this stop, rotate the rotor at a higher rotation speed than the rotation speed during the processing liquid supply, and after a certain period of time, return to the rotation speed during the processing liquid supply. A method of operating a centrifugal thin film evaporator according to claim 1, characterized in that a processing liquid is supplied at the same time.