JPH0142721B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an aqueous solution evaporation concentration device for concentrating an aqueous solution such as waste water by a vapor recompression method.

[Conventional technology]

Although there are various methods for concentrating waste water using a vapor recompression method and condensing the evaporated water vapor for use, a method in which the concentration process is performed in two stages is recommended. That is, in the first concentration process, a steam recondensation method is adopted, and the intermediate concentrate concentrated in the first concentration process is reconcentrated using steam from the boiler.

The vapor recompression method can also be employed in this second concentration process, but since the boiling point of the intermediate concentrate increases significantly in the second concentration process, the power of the blower increases, which is not a good idea. Moreover, if the steam generated in the first concentration process is used in the second concentration process, the steam required in the first concentration process will often be insufficient. Therefore, steam from a separately provided boiler is generally used for this second concentration process. The amount of steam required was also considerable.

[Problem that the invention seeks to solve]

Therefore, even though concentration is carried out by the steam recompression method, steam from other sources is also required, and the running cost savings of multiple-effect concentrators are lower than that of chemical water treatment methods.

[Purpose of the invention]

It is an object of the present invention to provide a wastewater treatment system which requires less steam and, under some conditions, does not require steam from any other steam source.

[Means for solving problems]

The present invention relates to a first heat exchanger, a pressure increase device for pressurizing steam generated in the first heat exchanger, a second heat exchanger, and a flash tank provided downstream of the heated fluid of the second heat exchanger. , a pump, and a path connecting these devices, the first heat exchanger is a horizontal evaporator with the outside of the tube being the evaporation side, and at least a part of the steam discharged from the pressure increasing device is supplied to the inside of the tube. The second heat exchanger is configured to heat and condense the evaporating liquid, and the second heat exchanger is a shell-and-tube heat exchanger that passes part or all of the intermediate concentrated liquid concentrated in the first heat exchanger to the inside of the tube. The tube is configured such that the remainder of the discharged steam from the pressure increase device or the steam from the boiler is supplied to the outside of the tube and condensed therein, and the pressure increase device sucks the evaporated steam from the first heat exchanger. The intermediate concentrate, which is configured to be pressurized and heated in the second heat exchanger, is further concentrated in the flash tank to become a concentrate, and a portion is taken out of the system.
The remaining concentrated liquid passes through the concentrated liquid circulation path and is sent to the second heat exchanger again, and the steam generated in the flash tank is configured to preheat the raw liquid supplied to the first heat exchanger. This is an aqueous solution evaporation concentration device characterized by being configured as follows.

〔Example〕

An embodiment of the present invention will be explained using FIG. 1.

The stock solution is supplied from tank 1 by pump 2,
After being preheated by preheaters 3, 4, 5, and 6, it is supplied to an evaporator (first heat exchanger) 7. The first heat exchanger or evaporator 7 is a shell and tube immersion type evaporator that passes steam through a horizontal tube. Note that this evaporator may be a liquid spray type or thin film type evaporator. The raw solution is heated and concentrated in this evaporator by steam passing through the tube, and the thickened intermediate concentrate passes through a pipe 8 and is stored in an intermediate concentrate tank 9. The piping 8 is provided with a flow control valve 10 to control the water level in the evaporator to a constant level. A concentration detector 11 is attached to the pipe 8 to detect the concentration of the liquid flowing in this pipe, and a control valve 12 is used to maintain the concentration of the liquid flowing in this part at a constant value. It is designed to control the bypass flow rate of concentrate. on the other hand,
The vapor evaporated in the evaporator 7 is pressurized by a blower (pressure increase device) 14 and supplied to the heating tube 15 of the evaporator, where the stock solution is heated and condensed. The condensed water is cooled by preheaters 5 and 3, and then stored in a condensed water tank 16, and discharged to the outside by a pump 17.

Further, the intermediate concentrated liquid stored in the tank 9 is sent to the sensible heat exchanger (second heat exchanger) 21 through the pump 18, piping 19, and four-way valve 20, and is condensed outside the tubes in the heat exchanger. It is heated by steam, and both the temperature and pressure rise. Then, it is discharged into the flash tank from the decompression hole 27 in the flash tank 26 through the pipe 22, the four-way valve 20, the pipe 23, the three-way valve 24, and the pipe 25, and some steam is generated. The concentrated solution, which has become thick due to the generation of steam and has some crystals deposited, is sent to the separator 29 by pumps 28 and 28', where the solid content is separated and taken out to the outside, and the remaining liquid is pumped via the balance tank. 30, it is connected to the pipe 19 again. In addition, in order to reduce the temperature rise of the liquid in the pipes in the heat exchanger 21, the concentrated liquid from the flash tank is made to flow into the pipe 19 by the bypass pipe 31, thereby increasing the flow rate through the heat exchanger 21. ing.

In this device, the liquid to be heated flows through the tube in the heat exchanger 21 in a liquid state, so it has the advantage of being difficult to build up scale, easy to clean, and easy to adopt an automatic tube cleaning system that does not require chemical washing. . That is, in FIG. 1, when the partition of the four-way valve is at the position indicated by the solid line, the liquid in the heat exchanger tube 32 flows from left to right. A cleaning brush 33 is inserted into the tube, and the dynamic pressure of the flow inside the tube causes the brush to flow from left to right, thereby preventing scale buildup. When the brush is at its rightmost position, it is held in a tube retainer 34 with multiple holes.
After a certain period of time, the four-way valve is switched automatically or manually, and the partition of the four-way valve is set to the position indicated by the dotted line, so that the direction of flow of liquid in the tube becomes opposite to the previous direction. Therefore, the tube retainer 3
The brush held in tube 4 flows from right to left while cleaning the inside of the tube due to dynamic pressure, and is held in tube holder 35. By switching this four-way valve, scale adhesion on the inner surface of the tube can be prevented.

Furthermore, if used for a long period of time, scale will also form in the decompression hole 27 of the flash tank, making it difficult for the concentrated liquid to flow. In particular, there is a tendency for decompression holes far from the inlet to become clogged. Therefore, a cleaning brush 37 is also inserted into this dispersion pipe 36, and by switching the three-way valve 24, the brush 37 can be moved from side to side.

Further, the steam supplied to the heat exchanger 21 is partially branched from the discharge pipe from the blower 14 and is supplied from a pipe 39.

Further, the steam generated in the flash tank is supplied to the preheater 4 through a pipe 38, where it heats the stock solution and is cooled and condensed, and the condensed water is discharged to the outside by a pump 41. At this time, the stock solution is heated, so the first heat exchanger (evaporator) 7
The amount of heating can be greatly reduced. Therefore, by this amount, the heat exchanger 2 is removed from the branch pipe 39.
The amount of steam sent to 1 can be increased. Note that the size of the preheater 3 is determined by the steam temperature and capacity of the preheater 4. However, depending on the conditions, the preheater 3 or 5 may be omitted. Further, the apparatus is normally operated in a vacuum state, and therefore the inside of the machine is maintained in a vacuum state by a vacuum pump 40. In other words, the preheater 6, which becomes a pent condenser, is removed from a place where air tends to accumulate in the device.
The vacuum is maintained through this vacuum pump.

〔Effect of the invention〕

Since the present invention has the above-described configuration, the following excellent effects are produced.

(1) A large amount of heat that was previously discarded from the flash tank can be recovered.

(2) Therefore, the amount of heating required in the evaporator 7 is reduced, and normally the steam supplied to the heat exchanger 21 can be supplied only by the steam discharged from the blower 14.

[Brief explanation of drawings]

FIG. 1 is a flow diagram showing an example of the apparatus of the present invention. 1... Raw solution tank, 2... Pump, 4... Preheater, 7... First heat exchanger, 9... Intermediate concentrate tank, 21... Second heat exchanger, 26... Flush tank, 29...Separator.

Claims (1)

[Claims] 1. A first heat exchanger, a pressure increase device that pressurizes the steam generated in the first heat exchanger, a second heat exchanger, a flush tank provided on the downstream side of the heated fluid of the second heat exchanger, and a pump. and a path connecting these devices, the first heat exchanger is a horizontal evaporator with the outside of the tube being the evaporation side, and at least a part of the steam discharged from the pressure raising device is supplied to the inside of the tube. The second heat exchanger is a shell-and-tube type in which part or all of the intermediate concentrated liquid concentrated in the first heat exchanger passes through the inside of the tube. The tube is a heat exchanger, and is configured such that the remainder of the discharged steam from the pressure increase device or the steam from the boiler is supplied to the outside of the tube and condensed therein, and the pressure increase device is configured to condense the evaporated steam from the first heat exchanger. The intermediate concentrate, which is configured to be sucked and pressurized and heated in the second heat exchanger, is further concentrated in the flash tank to become a concentrate, and a portion is taken out of the system.
The remaining concentrated liquid passes through the concentrated liquid circulation path and is sent to the second heat exchanger again, and the steam generated in the flash tank is configured to preheat the raw liquid supplied to the first heat exchanger. An aqueous solution evaporation concentration device characterized by comprising: