JP2001129537A - Evaporative concentration apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To periodically monitor the gypsum scale bonded to the heat transfer pipe of an evaporative concentration apparatus to remove the same. SOLUTION: A scale detector 20 monitoring the surfaces of the heat transfer pipes 16 arranged in an evaporator 11 through the observation window 17 of the evaporator 11 is arranged. The scale detector 20 comprises a light source 18 and a photo-detection part 19 and periodically monitors the gypsum scale bonded to the heat transfer pipes 16 when a holding liquid 12 is circulated to be evaporated. When more than a predetermined quantity of scale is bonded, automatic acid washing is performed to remove the scale. The unmanned operation of an evaporative concentration apparatus is enabled and the operation cost thereof is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an evaporative concentration apparatus, and more particularly, to an evaporative concentration apparatus suitable for treating calcium sulfate-containing wastewater, which is flue gas desulfurization wastewater from a coal-fired power plant.

[0002]

2. Description of the Related Art In many coal-fired power plants, a limestone-gypsum flue gas desulfurization unit is used to remove sulfur components in fuels that cause pollution. The flue gas desulfurization effluent discharged from the flue gas desulfurization device generally contains high concentrations of sulfate ions and calcium ions. Conventionally, flue gas desulfurization effluent is discharged after being treated by a method such as coagulation sedimentation treatment.In recent years, it has been proposed by each plant engineering manufacturer to introduce an evaporative concentration device to improve treatment efficiency. ing.

In general, when evaporating and concentrating waste water containing calcium sulfate, gypsum scale easily adheres to a heat transfer section such as a heat transfer tube, and this scale adhesion lowers the energy efficiency of the operation of the apparatus. Several means for preventing such scale adhesion are known, and techniques such as pH adjustment, addition of gypsum particles as seed crystals, and addition of a scale dispersant have been proposed (for example, Japanese Patent Application Laid-Open No. 9-13607
No. 8 and JP-A-10-192838).

[0004]

Even if the gypsum scale adhesion prevention technology described in the above publication is adopted, its prevention effect is limited, and the gypsum scale actually adhering to the heat transfer tube is appropriately cleaned by pickling. The fact is that it has been removed. In this case, if the evaporating and concentrating apparatus is operated while the gypsum scale is attached to the heat transfer tube, the gypsum scale is hardened even if the operation is performed for a relatively short time, and the desired effect can be obtained even after performing acid washing. I can't. For this reason, it is necessary to constantly monitor the adhesion state of the gypsum scale, and there has been a problem that the operation cost of the evaporating and concentrating apparatus increases due to the monitoring.

[0005] In view of the above, the present invention can automatically remove gypsum scale even if it adheres.
It is an object of the present invention to provide an evaporative concentration apparatus that enables unmanned operation and reduces operation costs.

[0006]

In order to achieve the above object, an evaporating and concentrating apparatus according to the present invention comprises: an evaporator having a heat transfer tube for heating therein; and a circulating liquid to be poured into the heat transfer tube. A evaporating and concentrating apparatus for evaporating and condensing the retained liquid, wherein the evaporating and concentrating apparatus periodically monitors a surface of the heat transfer tube and outputs a scale detection signal when scale adhesion is detected; A washing device for washing the heat transfer tube in response to a signal.

According to the evaporative concentrator of the present invention, the presence or absence of scale adherence to the heat transfer tube surface is periodically detected, and when the scale is detected, the heat transfer tube is automatically cleaned. Unmanned operation becomes possible, and the operation cost of the apparatus can be reduced.

Here, in a preferred embodiment of the evaporative concentration apparatus of the present invention, the circulating apparatus is stopped before the scale detector detects the presence or absence of scale adhesion. in this case,
Poor visibility due to spraying of circulating fluid is eliminated, and the accuracy of detecting the presence or absence of scale adhesion is improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings based on embodiments of the present invention. FIG.
FIG. 1 is a schematic block diagram illustrating a configuration of an evaporative concentration device according to an embodiment of the present invention. The evaporator 1 has an evaporator 1 having a cylindrical shape as a whole and a conical bottom.
1, a holding liquid 12 containing calcium sulfate to be treated is stored at the bottom of the evaporator 11.

The retained liquid 12 in the evaporator 11 is
Of the evaporator 1 by the circulation pump 13 arranged below the
1 is withdrawn from the bottom of the evaporator 1 via a pipe 14.
It is guided to a distributor 15 installed at the top of the inside 1, and is sprayed inside the evaporator 11 by the distributor 15. Inside the evaporator 11, a large number of heat transfer tubes 16 extending in the horizontal direction are arranged in a line in the horizontal direction and the vertical direction. The retained liquid sprayed by the distributor 15 falls onto the heat transfer tubes 16, is heated by the steam flowing in the heat transfer tubes 16, evaporates the water content, and falls as a concentrated liquid to the bottom of the evaporator 11.
By repeating the circulation of the retained liquid, the retained liquid, which is wastewater from a power plant or the like, is concentrated. The wastewater is supplied through the drainage supply line 22 and the wastewater supply valve 23 by an amount corresponding to the decrease in the retained liquid due to the evaporation, and the concentrated liquid is passed through the concentrated liquid takeoff valve 24 and the concentrated liquid discharge line 25 at an appropriate frequency. The volume and the concentration of the retained liquid are kept almost constant by performing automatic control for discharging water.

A viewing window 17 is provided on a side surface of the evaporator 11, and a scale detector 20 including a light source 18 and a light detection unit 19 is provided outside the evaporator 11 in the viewing window 17. . The light from the light source 18 passes through the viewing window 17 and is incident on the surface of the heat transfer tube 16, and the reflected light passes through the viewing window 17 and enters the photodetector 19. The output signal of the light detection unit 19 is input to the control unit 21.
Upon receiving this, the control unit 21 determines whether or not scale adheres to the heat transfer tube surface. The control unit 21 controls the operation of the evaporative concentration device 10 based on this determination.

FIG. 2 is a flow chart showing the operation of the evaporative concentration apparatus. Upon receiving the start command (step S1), the concentrating apparatus shifts to a start step (step S2), in which an attached pump, a heater, and the like are started according to a sequence program, drainage is supplied into the evaporator, and circulated by the circulation pump. . When certain temperature conditions, pressure conditions, and the like are satisfied, evaporation of the retained liquid starts, and the process proceeds to the concentration step (Step S3). During this concentration step, the elapsed time is measured according to the time setting of the timer (step S4).

[0013] After a predetermined time has passed after the shift to the concentration step, the circulation of the retained liquid is stopped (step S5), and the output of the photodetector is examined to determine whether or not scale has adhered (step S6). If it is determined that there is no abnormality in the output of the photodetector (no scale is attached), the process returns to the concentration step of step S3, and the concentration is performed while circulating the retained liquid. Step S
If it is determined in step 6 that the output of the photodetector is abnormal and that the scale is attached, the flow shifts to the cleaning step of step S7.

In the cleaning step of step S7, a cleaning liquid such as an acid is introduced from a cleaning liquid introduction pipe not shown in FIG.
Chemical cleaning of the heat transfer tube is performed by circulating a cleaning solution for about an hour. Next, the process proceeds to step S8, where the output of the photodetector is checked again to determine whether the heat transfer tube has been effectively cleaned. If it is determined that the desired cleaning effect has not been obtained, the number of times of cleaning is determined in step S9, and the process returns to the cleaning step of step S7 to repeat the chemical cleaning. If it is determined in step S9 that the number of times of the cleaning process has exceeded the predetermined number N within the predetermined time, it is determined that the desired cleaning effect cannot be finally obtained, an alarm is issued, and the apparatus is stopped (step S11).

On the other hand, if it is determined in step S8 that the desired cleaning effect has been obtained, the flow shifts to step S10, confirms the initial settings of the apparatus, and shifts again to the concentration step in step S3, or Whether to shift to the stop step of step S11 is determined based on the initial setting.

In the above embodiment, the scale detector 20 is provided outside the evaporator 11 in consideration of the high temperature and corrosive atmosphere inside the evaporator 11 of the evaporator. However, a scale detector may be arranged inside instead. Generally, gypsum scale attached to a heat transfer tube weakens reflected light as compared with the case of a metallic glossy surface of the heat transfer tube, so that gypsum scale can be attached to the heat transfer tube by detecting reflected light. It is preferable to use a light emitting diode (LED) or a semiconductor laser as a light source, and as the light detecting unit 19, besides a normal light sensor, a monochrome CCD
Cameras and color CCD cameras can be used. When a color CCD camera or the like is used, the white color of the gypsum scale can be easily detected. In particular, when the gypsum scale contains iron, the color becomes reddish. In this case, it is particularly preferable to use a color CCD camera.

To determine the output level of the light detecting section 19, a threshold value experimentally determined in advance is set. In particular, it is preferable to set the light source 18 and the light detection unit 19 in advance at a position where the reflection on the surface of the heat transfer tube 16 is good, and then set the threshold value thereon. Further, the position on the heat transfer tube 16 where the gypsum scale is likely to adhere greatly differs from device to device depending on the structure of the evaporator 11, the arrangement of the distributor 15, and the like. Therefore,
It is preferable to investigate the position of the heat transfer tube to which the gypsum scale easily adheres for each device.

Although the present invention has been described based on the preferred embodiment, the evaporating and concentrating apparatus of the present invention is not limited to the configuration of the above-described embodiment, but rather the configuration of the embodiment. Various modifications and changes from
It is included in the scope of the present invention.

[0019]

As described above, according to the evaporating and concentrating apparatus of the present invention, the scale adhering to the surface of the heat transfer tube is periodically monitored, and when the adhering of the scale is detected, the scale is detected. Since the configuration in which the evaporating and concentrating device is removed by the cleaning device is employed, an unmanned operation of the evaporating and concentrating device can be performed, and the operation cost of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of an evaporative concentrator according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the evaporative concentrator of FIG.

[Explanation of symbols]

 10: Evaporation concentrator 11: Evaporator 12: Retained liquid 13: Circulation pump 14: Circulation pipe 15: Distributor 16: Heat transfer tube 17: Viewing window 18: Light source 19: Light detection unit 20: Scale detector 21: Control unit 22 ： Drainage supply line 23 ： Drainage supply valve 24 ： Concentrated waste liquid discharge valve 25 ： Concentrated liquid discharge line

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B01D 53/77 C02F 5/00 610J B08B 9/023 620B C02F 1/00 G01N 21/47 B 5/00 610 B01D 53/34 125R 620 B08B 9/02 D G01N 21/47 (72) Inventor Tomoko Akiyama 1-2-8 Shinsuna, Koto-ku, Tokyo Organo Corporation F-term (reference) 2G059 AA05 BB08 CC01 EE02 GG01 GG02 HH02 KK04 MM05 3B116 AA13 AB53 BB62 CD42 CD43 4D002 AA02 AC01 BA02 BA20 CA01 DA05 DA16 EA07 FA03 GA02 GA03 GB20 HA05 4D034 AA11 BA07 CA18 4D076 AA06 AA07 BA14 BA23 CD42 CD43 DA05 DA25 EA08 JA03 JA03

Claims (2)

[Claims] 1. An evaporating and concentrating apparatus, comprising: an evaporator internally having a heat transfer tube for heating; and a circulating device for circulating a retained liquid and pouring the retained liquid into the heat transfer tube. The surface of the heat tube is periodically monitored, and a scale detector that outputs a scale detection signal when scale adhesion is detected; and a cleaning device that cleans the heat transfer tube in response to the scale detection signal. Evaporating concentrator. 2. The evaporating and concentrating apparatus according to claim 1, wherein a circulation device is stopped before the scale detector detects the presence or absence of scale adhesion.