JP3217706B2 - Method and apparatus for self-evaporation compression type concentration of aqueous solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-vapor compression type enrichment method in which an aqueous solution is vaporized and concentrated to a high concentration by compressing vapor generated from the aqueous solution and using it as its own heat source. It concerns the device.

[0002]

2. Description of the Related Art In general, when an aqueous solution is evaporated and concentrated to a high concentration, the boiling point of the aqueous solution increases as the concentration increases. When evaporating and concentrating to a target high concentration by a self-vapor compression type concentrating device, the heat generated by the blower compressor can transfer the heat required for evaporation by the blower compressor. Therefore, the compression ratio in the blower compressor must be increased, so that the size of the blower compressor is significantly increased. The operating costs for driving the blower compressor are significantly increased.

[0003] Conventionally, when evaporating and concentrating an aqueous solution to a high concentration, for example, as described in Japanese Patent Publication Nos. 1-44081 and 7-161 as prior art, an aqueous solution is concentrated. Combination of a low-temperature evaporator of a self-vapor compression type, in which generated steam is compressed by a blower compressor and used as a heat source for evaporating the aqueous solution, and a high-temperature evaporator that uses high-pressure steam as a heat source from a boiler or the like. First, the aqueous solution is supplied to the low-temperature evaporator of the self-vapor compression type to evaporate and concentrate it to a medium concentration, and then to the high-temperature evaporator to evaporate and concentrate to a final high concentration.

[0004]

SUMMARY OF THE INVENTION These enrichment methods are:
The aqueous solution has the advantage that it can be continuously evaporated to a high concentration with high thermal efficiency irrespective of the boiling point rise and the heat transfer coefficient decrease accompanying the evaporation concentration.
No. 161 discloses that in addition to compressing steam generated from an aqueous solution in a low-temperature evaporator and a high-temperature evaporator to use it as a heat source in the low-temperature evaporator, the remaining steam is operated by high-pressure steam from a boiler or the like. In addition, since it is compressed by a steam ejector and used as a heat source in the high-temperature evaporator, it has an advantage that the thermal efficiency is higher than that of the former.

[0005] On the other hand, however, the above-mentioned conventional concentration method requires two evaporators, a low-temperature evaporator and a high-temperature evaporator, which complicates the equipment and significantly increases the equipment cost. However, there is a problem that the cost required for evaporating and concentrating increases greatly. The present invention
It is an object of the present invention to solve this problem and to provide a concentration method for evaporating and concentrating an aqueous solution to a high concentration at a low cost, and a device therefor.

[0006]

According to the present invention, there is provided a method for supplying an aqueous solution into a self-vapor compression evaporator equipped with a blower compressor and a steam ejector. Evaporating and concentrating to a middle concentration by a single-stage compression of the steam by the blower compressor, and then compressing the middle-concentration aqueous solution by the blower compressor,
It is characterized in that it is evaporated and concentrated to a final concentration by two-stage compression with the compression of steam by the steam ejector. Is the thing.

[0007] The apparatus of the present invention comprises an evaporator having an aqueous solution storage chamber at a lower part and a heat transfer tube at an upper part, and an aqueous solution circulating means for supplying an aqueous solution in the aqueous solution storage chamber to the outside of the heat transfer pipe. A blower compressor that compresses steam generated in the evaporator, and a steam duct that communicates the discharge side of the blower compressor with the inside of the heat transfer tube.
The steam ejector is provided such that the suction side of the steam ejector communicates with the discharge side of the blower compressor, and the discharge side of the steam ejector communicates with the heat transfer tube, while the aqueous solution in the evaporator is provided in the steam duct. A steam switching valve, which is closed when evaporating and concentrating to a medium concentration, is connected to a high-pressure steam supply line for driving the steam ejector, and is opened when the aqueous solution in the evaporator is evaporated and concentrated to a medium concentration. Provide a supply valve. ".

[0008]

As described above, according to the present invention, up to the medium concentration, vaporization and concentration are performed by the single-stage compression of the steam by the blower compressor, while up to the final concentration, the blower compressor and the steam ejector are used. Evaporation concentration is performed by two-stage compression of steam by means of, and both evaporation concentration to medium concentration and evaporation concentration from medium concentration to final concentration are increased without increasing the compression ratio in the blower compressor. Since it can be carried out while maintaining the temperature difference, it is possible to evaporate and concentrate the aqueous solution to a high concentration without using two evaporators, a low-temperature evaporator and a high-temperature evaporator, as in the past.
With one evaporator, it can be achieved reliably while maintaining a high thermal efficiency of the self vapor compression type.

That is, according to the present invention, an aqueous solution can be evaporated and concentrated to a high concentration by one self-vapor compression evaporator without increasing the compression ratio of the blower compressor. And the equipment cost can be significantly reduced, and the cost required for evaporating and concentrating the aqueous solution to a high concentration can be greatly reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are described below.
The case of evaporating and concentrating an aqueous solution containing 0.3 wt% of tetramethylammonium hydroxide to 30 wt% will be described with reference to the drawings. FIG. 1 shows the relationship between the concentration of tetramethylammonium hydroxide aqueous solution and the increase in boiling point.
The temperature is approximately 0 ° C. when the concentration is 3 wt% and about 2.5 ° C. when the concentration is 15 wt%, but reaches 9.7 ° C. when the target concentration is 30 wt%.

FIG. 2 shows an apparatus for evaporating and concentrating the aqueous solution of tetramethylammonium hydroxide. In this figure, reference numeral 1 denotes a closed type evaporator provided with an aqueous solution storage chamber 2 at the lower part. At the top of the evaporator 1, a heat transfer tube group 4 formed by bundling a plurality of heat transfer tubes 3 is disposed horizontally and horizontally. One end of the heat transfer tube group 4 has an inlet communicating with each heat transfer tube 3. At the other end, the header 5 is provided with an outlet header 6 communicating with each heat transfer tube 3.

Reference numeral 7 denotes a sprayer disposed in the evaporator 1 above the heat transfer tube group 4.
By connecting a circulation pipe 10 from a circulation pump 9 having a suction side connected to the aqueous solution chamber 2 via a pipe 8, the aqueous solution in the aqueous solution chamber 2 is transferred to the circulation pump 9.
After being scattered on the outer surface of each heat transfer tube 3 in the heat transfer tube group 4, circulation is performed to return to the aqueous solution storage chamber 2.
1 is connected.

The aqueous solution reservoir 2 is provided with a water level gauge 12 for detecting the liquid level in the aqueous solution reservoir 2.
The aqueous solution supply line 13 is connected, and the aqueous solution supply line 13 is connected.
A flow control valve 14 provided therein is associated with the water level gauge 12 so as to open when the liquid level in the aqueous solution chamber 2 becomes lower than the water level gauge 12, so that tetramethyl hydroxide is provided in the aqueous solution chamber 2. An aqueous solution of ammonium having a concentration of 0.3% by weight is supplied so that the liquid level of the aqueous solution is kept substantially constant.

Reference numeral 15 denotes a blower compressor. A suction duct 16 from above the evaporator 1 is connected to a suction side of the blower compressor 15, and a discharge side of the blower compressor 15 is connected to a suction side. Is connected to the inlet header 5 in the heat transfer tube group 4 via a steam duct 17,
A steam switching valve 18 is provided in the middle of the steam duct 17.

Reference numeral 19 denotes a steam ejector. On the suction side of the steam ejector 19, the blower compressor 15 and the steam switching valve 18 of the steam duct 17 are provided.
And a discharge side of the steam ejector 19 is connected to the inlet header 5 or the steam duct 17 in the heat transfer tube group 4 via a duct 21. Further, a steam supply valve 23 is provided in a high-pressure steam supply pipe 22 for driving the steam ejector 19.

Reference numeral 24 denotes a condenser.
4 includes a plurality of heat transfer tubes 26 in a can body 25, a cooling water inlet 27 into the heat transfer tube 26, and a cooling water outlet 28 from the inside of the heat transfer tube 26.
Inside, the bottom of the outlet header 6 in the heat transfer tube group 4 of the evaporator 1 is connected via a pipe line 29, while inside the can body 25, the suction duct 16 to the blower compressor 14 or the evaporator 1 is a line 3 with a control valve 30
1, a vacuum pump 32 is connected to the can body 25 for maintaining a reduced pressure state below the atmospheric pressure in the can body 25, and condensation inside the can body 25 is performed. A condensed water pump 33 for discharging water is connected.

Reference numeral 34 denotes a control circuit. The control circuit 34 includes a steam switching valve 18 in the steam duct 17 and a high-pressure steam supply pipe 22 for driving the steam ejector 19, as described below. The steam supply valve 23, the control valve 30 in the pipe line 31 and the concentrated liquid discharge valve 11 are controlled to open and close, and the flow control valve 14 provided in the aqueous solution supply pipe 13 is connected to the water level gauge 12 This is for controlling the closing in preference to.

When evaporating and concentrating an aqueous solution containing 0.3 wt% of tetramethylammonium hydroxide to 30 wt% by the evaporating and concentrating apparatus thus configured, the control circuit 34 switches the steam in the steam duct 17. While the valve 18 is opened, the steam supply valve 23 in the high-pressure steam supply line 22 for driving the steam ejector 19,
Control valve 30 in conduit 31 and concentrate discharge valve 1
1 is closed, and further, the inside of the evaporator 1 is
A vacuum degree corresponding to a boiling point of about 70 ° C. is maintained by a vacuum pump 32, and in this state, the blower compressor 15 is operated to supply the aqueous solution supplied into the aqueous solution storage chamber 2 of the evaporator 1 to the blower compressor. Evaporate and concentrate by single-stage compression by No. 15.

In this case, the evaporating and concentrating is carried out while the aqueous solution is supplied by the water level meter 12 and the flow control valve 14 into the aqueous solution storage chamber 2 of the evaporator 1 by the amount reduced by the evaporating and concentrating. Then, by the evaporation and concentration, the aqueous solution in the aqueous solution storage chamber 2 becomes a medium concentration of 15 wt%.
Then, the control circuit 34 closes the steam switching valve 18 in the steam duct 17 and the steam supply valve 2 in the high-pressure steam supply pipe 22 for driving the steam ejector 19.
3, and each of the control valves 30 in the pipeline 31 are opened, and further, the flow control valve 14 provided in the aqueous solution supply pipeline 13 is closed prior to the water level gauge 12, and in addition, the evaporation The inside of the can 1 is maintained at a degree of vacuum corresponding to a boiling point of about 60 ° C. by adjusting an atmosphere introduction valve 35 to the vacuum pump 32 by a control circuit 34.

Thus, both the blower compressor 15 and the steam ejector 19 are driven, and the steam generated in the evaporator 1 is compressed by the blower compressor 15 and then compressed by the steam ejector 19. In other words, since the two-stage compression is performed by both the blower compressor 15 and the steam ejector 19, the aqueous solution having a concentration of 15 wt% in the aqueous solution storage chamber 2 is subjected to a large temperature difference by the two-stage compression. With the final 30 wt%
It can be concentrated by evaporation until the concentration is reached.

When the aqueous solution in the aqueous solution storage chamber 2 is evaporated and concentrated to a final concentration of 30% by weight, the evaporation and concentration are stopped, and then the concentrated liquid discharge valve 11 is opened by the control circuit 34 to concentrate the aqueous solution. The entire amount of the liquid is discharged from the aqueous solution storage chamber 2, and the operation of one batch is completed.
In FIG. 2, reference numeral 36 denotes a heat exchanger for preheating the aqueous solution to be supplied to the evaporator 1 with the condensed water discharged from the condenser 24.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the concentration of tetramethylammonium hydroxide aqueous solution and the increase in boiling point.

FIG. 2 is a diagram showing a concentration device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Evaporator 2 Aqueous solution storage chamber 3 Heat transfer tube 4 Heat transfer tube group 5 Inlet header 6 Outlet header 9 Aqueous solution circulation pump 10 Aqueous solution circulation line 11 Condensate discharge valve 13 Aqueous solution supply line 15 Blower compressor 17 Steam duct 18 Steam switching valve 19 Steam ejector 22 High-pressure steam supply line 23 Steam supply valve 24 Condenser

Continuation of the front page (56) References JP-A-4-313302 (JP, A) JP-A-57-165001 (JP, A) JP-A-59-55303 (JP, A) JP-B-41-8215 (JP, A) , B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 1/28 C02F 1/04

Claims (2)

(57) [Claims] An aqueous solution is supplied into a self-vapor compression evaporator equipped with a blower compressor and a steam ejector, and the aqueous solution is evaporated and concentrated to a medium concentration by one-stage compression of steam by the blower compressor. Self-evaporation compression concentration of the aqueous solution, wherein the intermediate concentration aqueous solution is concentrated to a final concentration by two-stage compression of vapor compression by the blower compressor and vapor compression by the vapor ejector. Method. 2. An evaporator having an aqueous solution reservoir at a lower portion and a heat transfer tube at an upper portion, an aqueous solution circulating means for supplying an aqueous solution in the aqueous solution reservoir to the outside of the heat transfer tube, and an evaporator in the evaporator. A blower compressor for compressing the generated steam, and a steam duct communicating the discharge side of the blower compressor and the inside of the heat transfer tube, further comprising a steam ejector, and a suction side of the steam ejector having a suction side of the blower compressor. A steam switching valve provided on the discharge side such that the discharge side of the steam ejector communicates with the heat transfer tube, and closed in the steam duct when the aqueous solution in the evaporator is evaporated and concentrated to a medium concentration. A high-pressure steam supply pipe for driving the steam ejector was provided with a steam supply valve which was opened when the aqueous solution in the evaporator was evaporated and concentrated to a medium concentration. DOO self-evaporation compression apparatus for concentrating an aqueous solution according to claim.