JPS5911321B2 - How to clean a centrifugal thin film evaporator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning centrifugal thin film evaporators, particularly those in which the inside of the centrifugal thin film evaporator must be frequently cleaned because the processing liquid has adhesive properties, and This is suitable when the purpose is to obtain a powdered residue, or when strict control of the degree of concentration is required, where mixing of the cleaning liquid into the residue side is undesirable.

An example of a conventional cleaning method for a centrifugal thin film evaporator will be explained with reference to FIG. 1. A processing liquid is supplied from a processing liquid tank 1 through a main valve 2 to a centrifugal thin film evaporator 5 by a supply pump 3 through a flow control valve 4. Ru.

In the centrifugal thin film evaporator 5, the processing liquid descends on the evaporator heat transfer surface in the form of a wet wall due to the centrifugal force caused by the rotary blades 6.
It is heated by the heat medium supplied from the heat medium inlet 14, and the evaporated components are condensed through the condenser 7 and then stored in the condensate tank 8.

On the other hand, the residue passes through the residue valve 9 and is stored in the residue tank 10.

If the treatment liquid has adhesive properties, it will adhere to the heat transfer surface and rotor blades 6 of the centrifugal thin film evaporator 5 over time, resulting in a decrease in heat transfer capacity and overload, and it is necessary to periodically clean the inside. arise.

As an example of the cleaning method, a case will be described in which the evaporated component of the processing liquid is used as the cleaning liquid.

The main valve 2 of the processing liquid tank 1 is closed, the residue valve 9 is closed, and the cleaning liquid discharge valve 11 is opened.

Next, the cleaning liquid injection valve 13 is opened, and the cleaning liquid is supplied into the centrifugal thin film evaporator 5 by the supply pump 3 to perform internal cleaning.

The cleaning liquid passes completely through the cleaning liquid discharge valve 11 and is stored in the cleaning liquid tank 12.

However, according to conventional cleaning methods, if the processing solution is highly adhesive, the above operations must be performed frequently, and the cleaning solution may be mixed in, especially when the purpose is to obtain the residue in powder form. If this is not desired, complete sealing is required structurally, making the device complex.

Further, there are problems such as the need for time to dry the cleaning liquid even after cleaning.

The purpose of the present invention is to remove deposits without intruding the cleaning liquid into the residue side, and in particular, for items that require frequent cleaning, the supply liquid can be replaced with the cleaning liquid without completely stopping the equipment. The purpose is to simplify the cleaning operation by switching to evaporation of the cleaning liquid and cleaning the deposits at the same time.

The present invention provides a cleaning method in which the amount of cleaning liquid supplied is equal to or higher than the amount of processing liquid supplied, as a cleaning method when it is disliked that the cleaning liquid enters the residue side, such as when the purpose is powderization or highly concentrated processing. As described above, the feature is that the amount of evaporation is less than the complete evaporation amount.In particular, if an evaporable component of the processing liquid or a liquid that evaporates more easily than the processing liquid is used as the cleaning liquid, it is possible to supply an amount exceeding the supply amount of the processing liquid. This technology focuses on the fact that it can be completely evaporated.

An example of implementing the present invention will be described below with reference to FIGS. 2 and 3.

In FIG. 2, the same parts as in FIG. 1 are indicated by the same symbols.

The relationship between the amount of processing liquid supplied and the time until cleaning becomes necessary is shown at time t in FIG.

is expressed as t1.

At time t1, the main valve 2 is closed and the supply of the processing liquid is stopped.

Next, the cleaning liquid injection valve 13 is opened to supply the cleaning liquid.

The cleaning liquid is regulated by a flow control valve 4 and supplied to a centrifugal thin film evaporator 5.

At time t2, the cleaning liquid can be completely evaporated by starting the supply at an amount less than the processing liquid supply amount.
First, the vicinity of the supply port is cleaned to remove deposits and restore heat transfer characteristics.

Next, if the supply amount of the cleaning liquid is gradually increased, the cleaning area will expand accordingly, and even if the cleaning liquid is supplied in an amount larger than the supply amount of the processing liquid, complete evaporation can be achieved.

This maximum cleaning liquid supply amount Qm is determined experimentally.

In an experimental example of a centrifugal thin film evaporator with a heat transfer area of 1i, the evaporation drying capacity of the slurry liquid is 100 kg/h, and the complete evaporation amount of only water, which is the evaporated product of the slurry liquid, is 120 kg.
/h.

As the processing time for the slurry liquid increased, a thin layer of solidified slurry liquid adhered to the heat transfer surface, and the evaporative drying ability began to decline.
Supplied for 5 minutes at a supply rate of i90k9/h, and then 10kg
/h at 5-minute intervals to a maximum of 120 kg/h. As a result, the solid content adhering to the heat transfer surface falls into the residue tank 10 in a dry state, and the inside of the centrifugal thin film evaporator 5 can be cleaned. Ta.

The amount of cleaning liquid may be increased stepwise or in proportion to time as shown in FIG.

It is also possible that the maximum cleaning supply amount Qm is supplied from time t2.

Note that times t1 and t2 may be simultaneous.

Even when all components other than the evaporable components of the processing liquid are used as the cleaning liquid, cleaning can be carried out in exactly the same manner as in the above case by selecting a cleaning liquid that evaporates more easily than the processing liquid.

As described above, the present invention uses an evaporable component of the processing solution or a liquid that evaporates more easily than the processing solution as a cleaning solution for a centrifugal thin film evaporator, and gradually increases the amount from less than or equal to the supply amount of the processing solution to reduce the centrifugation. By cleaning the thin film evaporator to an amount that is less than the amount that can be completely evaporated, it is possible to remove the deposits inside the centrifugal thin film evaporator without letting the cleaning liquid enter the residue side, and prevent the intrusion of the cleaning liquid. The equipment can be simplified by eliminating the need for a sealing device to prevent drying and a drying device after cleaning, and because it is easy to operate, there is no need to stop the equipment for cleaning, allowing continuous processing. This has the effect of improving the actual operating time since cleaning can be performed.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a conventional cleaning method for a centrifugal thin film evaporator, FIG. 2 is a system diagram of a centrifugal thin film evaporator showing an example of a cleaning method according to the present invention, and FIG. 3 is a system diagram showing an example of a cleaning method according to the present invention. FIG. 3 is a diagram showing the relationship between the amount of processing liquid and cleaning liquid and time as →0. 1... Processing liquid tank, 2... Main valve, 3...
...Supply pump, 4...Flow rate control valve, 5.
... Centrifugal thin film evaporator, 6 ... Rotating blade, 7
...Condenser, 8...Condensate tank, 9...
...Residue valve, 10...Residue tank, 11...
...Cleaning liquid discharge valve, 12...Cleaning liquid tank, 13
...Cleaning liquid injection valve, 14... Heat medium inlet, 15... Heat medium outlet, 16... Processing liquid supply, 17... Cleaning liquid supply.

Claims (1)

[Scope of Claims] 1. After the processing liquid is supplied into the centrifugal thin film evaporator for a predetermined period of time to perform evaporation concentration processing, the supply of the processing liquid is temporarily stopped, and
A method for cleaning a centrifugal thin film evaporator, characterized by supplying a cleaning liquid having a larger evaporation amount than a processing liquid into the centrifugal thin film evaporator, and cleaning the inside of the centrifugal thin film evaporator while completely evaporating the cleaning liquid. 2. A method for cleaning a centrifugal thin film evaporator according to claim 1, wherein an evaporated component of the processing liquid is supplied as a cleaning liquid.