JPS5921841Y2 - Falling film evaporator - Google Patents

Description

[Detailed description of the invention] The present invention supplies steam into a hollow plate-shaped heating element, while causing a processing liquid (for example, black liquor in a pulp mill) to flow down on the outer surface of the plate, evaporating a part of it, and
This invention relates to an improvement of a falling film type evaporator that concentrates the remainder.

In this type of evaporator, when the processing liquid is supplied to the shell bottom liquid or to the suction pipe of the circulation pump, the pressure in the evaporation line is kept constant, so the temperature of the supplied processing liquid decreases to evaporation. If the temperature is higher than the in-line liquid temperature, flash evaporation occurs and bumping phenomenon occurs, causing problems, so the liquid is supplied to the gas phase at the bottom of the shell.

In addition, if the boiling point of the treated liquid is high, or if the heat transfer coefficient decreases significantly due to the increase in concentration, a weir is installed to divide the shell liquid phase into several parts, creating a difference in the concentration of the liquid in each divided group. Generally, the aim is to reduce the rise in the average boiling point or improve the average heat transfer coefficient.

In such an evaporation can, the concentration of the concentrated liquid drawn out is the same as that of the feed liquid or the intermediate concentrated liquid that overflowed the weir.
It becomes the mixed concentration with the concentrated liquid flowing down on the heat transfer surface.

For this reason, in terms of heat transfer, the liquid is concentrated to a higher concentration than the extracted liquid, which causes a decrease in the apparent heat transfer coefficient and further causes scale problems.

The present invention has been devised to overcome the drawbacks of the known technology such as slanting. , an evaporator having a test repeater for supplying a processing liquid onto the outer surface of a heating element, and a circulation pipe interposed with a pump for circulating the processing liquid accumulated at the bottom of the shell to the test repeater, The bottom of the shell is divided by a weir into the treated liquid supply side and the extracted concentrated liquid side, and a distributor, a heating element, and a circulating system for the treated liquid are installed inside the shell in two parts on each of the treated liquid supply side and the extracted concentrated liquid side. , a concentrate receiver is provided at a distance downward from the lower end of the heating element on the side of the concentrated liquid to be extracted, and a concentrate extraction pipe is communicated with the receiver.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

1 is the shell of the evaporator, which is usually cylindrical in shape.

The bottom of the shell 1 is partitioned by a weir 18 into a treated liquid supply side and a sampled concentrated liquid side.

Inside shell 1, there are two
A plurality of divided hollow heating elements 2 are provided.

Spacer bars 3 are attached to both sides of the hollow heating element 2 in the row direction (direction perpendicular to the plate-shaped heating element).

As a result, the mutual spacing between adjacent hollow heating elements 2 is kept constant.

A heating steam port 4 is provided in the upper part of the shell 1 and communicates with the hollow part of the hollow heating element 2 via a steam header 5.

A condensate header 6 is connected to the bottom of the hollow portion and communicates with the condensate output lower.

A distributor 8 divided into two parts, like the hollow heating element 2, is provided above the hollow heating element 2.

A large number of holes are provided on the bottom of the distributor 8,
A treatment liquid is adapted to be supplied onto the outer surface of the heating element 2.

A processing liquid supply port 9 is provided on the lower side of the shell 1 .

A concentrated liquid receiver 17 is provided at a certain distance downward from the lower end of the heating element 2 on the side of the extracted concentrated liquid, and a concentrated liquid extraction pipe 14 is provided on the bottom plate of this receiver 17.

A circulation pipe 11 is connected to the bottom of the shell 1, and a cylindrical strainer 12 is provided at this connection.

A circulation pump 13 is interposed in the circulation pipe 11 in the middle thereof, and supplies the fluid to be heated at the bottom of the shell 1 to the distributor 8.

An evaporative vapor outlet 16 is connected to the upper part of the shell 1 via a mist collection plate 15.

The processing liquid introduced into the processing liquid supply side of the shell 1 through the supply port 9 is supplied from the bottom of the shell 1 through the circulation pipe 11 to the processing liquid supply side distributor 8 by the circulation pump 13.

In this way, the processing liquid is distributed and supplied to the upper part of the outer surface of the heating element 2 on the processing liquid supply side, flows down the outer surface of the heating element 2 on the same side, and accumulates as an intermediate concentrated liquid at the bottom of the shell.

On the other hand, heating steam is introduced into the hollow part of the heating element 2 on the same side through a heating steam supply 4 and a header 5.

This heating vapor evaporates a portion of the liquid on the outer surface of the heating element 2 on the same side, and the evaporated vapor flows out to both sides of the heating element 2 and passes through the mist collection plate 15 at the top of the shell 1. and is sent to the next stage of equipment (not shown) through outlet 16.

The intermediate concentrated liquid on the processing liquid supply side overflows from the weir 18 and accumulates on the extracted concentrated liquid side.

The intermediate concentration on the extracted concentrated liquid side is determined by evaporating a part of the liquid from the distributor 8 through the heating element 2 and turning it into a concentrated liquid, which enters the concentrated liquid receiver 17 and is concentrated without mixing with the liquid supplied from the supply port 9, as described above. The liquid is extracted from the liquid extraction pipe 14.

As described above, in the present invention, the bottom of the shell 1 is partitioned by the weir 18, and is divided into the processing liquid supply side and the extracted concentrated liquid side, and the concentrated liquid receiver 17 is provided only on the extracted concentrated liquid side. The concentrated extraction liquid and the supplied treated liquid are taken out without mixing, and the concentration of the concentrated liquid flowing down from the lower end of the heat transfer surface remains at the predetermined sampling concentration, making it extremely easy to operate the evaporator. It has the following effects.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view showing one embodiment of the present invention;
The figure is a schematic diagram of FIG. In the figure: 1... Shell, 2... Hollow heating element, 3... Spacer bar, 4...
...Heating steam inlet, 5...Steam header, 6.
... Condensate header, 7 ... Condensate outlet, 8 ... Taste repeater, 9 ... Processing liquid supply port, 11 ... Circulation Pipe, 12...Cylindrical strainer, 13...
... Circulation pump, 14 ... Concentrate extraction pipe,
15...Mist collection plate, 16...Evaporation vapor outlet, 17...Concentrate receiver, 18...
...Weir.

Claims (1)

[Scope of utility model registration request] A shell 1, a plurality of hollow plate-shaped heating elements 2 provided in the shell 1, and a text repeater 8 provided above the plate-shaped heating elements 2 and supplying a processing liquid onto the outer surface of the heating elements. and a circulation pipe 11 interposed with a pump 13 for circulating the processing liquid accumulated at the bottom of the shell to the sample repeater 8,
The bottom of the shell 1 is divided by a weir 18 into a processing liquid supply side and a sampled concentrated liquid side, and a sample repeater 8, a heating element 2, and a processing liquid are installed inside the shell 1 on each of the processing liquid supply side and the sampled concentrated liquid side. The circulation system is divided into two parts, and a concentrate receiver 17 is provided downwardly from the lower end of the heating element 2 on the side of the extracted concentrate, and a concentrate receiver 17 is connected to the receiver 17.
A falling film type evaporator characterized in that 4 is communicated with each other.