JPH05131193A - Drain water treatment facility of exhaust gas desulfurization device - Google Patents

Abstract

PURPOSE:To reduce equipment cost and operation maintenance cost by providing an electric dialysis device consisting of a filter which removes a turbid component, a cationic exchange membrane which allows selective permeation of a univalent and a divalent cation and an anionic exchange membrane which allows selective permeation of only a univalent anion. CONSTITUTION:The subject drain treatment facility consists of a filter 2 which removes a turbid component so that the drained water has lower than a turbid substance concentration level at which it can be treated using an electric dialysis device which separates the drained water into concentrated drained water containing a large percentage of a solute component and a diluted liquid containing a diluted solute component, and an electric dialysis device 3 comprising a cationic exchange membrane which allows selective permeation of a univalent and a divalent cation and an anionic exchange membrane which allows selective permeation of only a univalent anion arranged alternately. If this facility is used, the drained water is treated using a high membrane separation device which separates the solute component most efficiently. Subsequently, it is possible to achieve high performance separation and reduce operation maintenance cost as well as minimize an installation area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a device that uses an alkaline agent such as limestone as an absorbent to remove SOx gas from exhaust gas in order to prevent environmental pollution of sulfur dioxide gas (hereinafter referred to as SOx gas) in combustion exhaust gas. The present invention relates to a (volume reduction) treatment facility for wastewater discharged from a flue gas desulfurization device that absorbs and separates.

[0002]

2. Description of the Related Art Wastewater discharged from a flue gas desulfurizer is a gypsum produced by reaction in the desulfurizer, solid components such as limestone that have not contributed to the reaction, chlorine gas in the exhaust gas (hereinafter referred to as C
gas) and salt components such as calcium chloride and magnesium chloride produced by the reaction between calcium and magnesium in the absorbent, silica in exhaust gas, oxides of metals such as aluminum, and the like. Not only does it contain various miscellaneous components such as combustion ash in the combustion exhaust gas, but the SOx gas and Cl gas in the exhaust gas also make the drainage liquid acidic, so it cannot be discharged to public water bodies as it is. No, it is usually processed as described below.

FIG. 2 shows an embodiment of a flow chart of a conventional waste water treatment facility, and a conventional waste water treatment method will be described with reference to this figure. The waste water from the desulfurization device, which is treated in the waste water treatment facility, that is, the liquid to be treated is temporarily stored in the stock solution tank 01 through the line aa. After this, the liquid to be treated is sent from line bb to acid decomposition tank 02, where it decomposes the acid components contained in the liquid and then solid line separation tank 03 for separating solid components via line cc. Sent to. Liquid to be treated is line cc
During the circulation of hydrogen, the hydrogen ion concentration of the liquid to be treated (hereinafter,
An alkali for adjusting the pH (referred to simply as pH), a coagulant, and the like are injected through the line dd. In the solid content separation tank 03, solid contents such as limestone, gypsum, and combustion ash in the liquid to be treated are separated,
A liquid with a thin solid content (hereinafter referred to as a cleaning liquid) and a liquid with a thick solid content (hereinafter referred to as a concentrated suspension) are discharged.

The concentrated suspension is dehydrated through the line ee.
4, and further separated into water and solids by the dehydrator 04. The water content and the solid content separated by the dehydrator 04 are discharged to the outside of the system of this wastewater treatment facility by lines ff and gg, respectively.

On the other hand, the cleaning liquid from the solid content separation tank 03 is sent to a fine filter 05 such as a sand filter through a line hh,
The solid content that could not be separated in the solid content separation tank 03 is further separated from the liquid to be treated and stored in the treatment liquid tank 06 via the line ii having an improved cleanliness. Treatment liquid tank 0
The treated wastewater in 6 is discharged into the public water area (after it is confirmed that it meets the wastewater standards) through the line jj.

[0006]

The conventional wastewater treatment facility has a complicated device configuration as described above, and the operation control method of each device is also complicated. The operation control method is the wastewater discharged from the wastewater treatment facility. In some cases, it becomes impossible to discharge the wastewater in the treatment liquid tank 06, and in the worst case, the whole system of the wastewater treatment facility is stopped.

Further, since the apparatus structure is complicated and the operation control method is complicated as described above, not only the apparatus cost and the operation and maintenance cost are high, but also the site area required for the wastewater treatment facility is vast. Become.

The present invention is intended to provide a wastewater treatment facility capable of solving the above-mentioned problems of the prior art.

[0009]

[Means for Solving the Problems] (1) Concentrated wastewater containing a large amount of solute components and diluting liquid in which the solute components are diluted with respect to the wastewater from a flue gas desulfurization device using an alkaline agent such as limestone. A filtration device that removes turbidity components so that the turbidity concentration is less than or equal to that that can be processed by an electrodialysis device that is separated into
Cation exchange membranes that selectively permeate valent cations and anion exchange membranes that selectively permeate only monovalent anions are arranged alternately, and a concentration chamber and a dilution chamber are provided between both ion exchange membranes. An electrodialyzer provided, means for sending the concentrated liquid discharged from the concentration chamber of the electrodialysis device to the final treatment step, and means for using the diluted liquid discharged from the dilution chamber as make-up water for the flue gas desulfurization device. Wastewater treatment equipment for flue gas desulfurization equipment, which is characterized by being equipped. (2) The waste water treatment facility of the flue gas desulfurization device according to (1) above, further comprising a concentrating device that evaporates and concentrates the concentrated liquid discharged from the concentrating chamber of the electrodialysis device.

[0010]

In the wastewater treatment facility according to the present invention, in order to treat the wastewater with the membrane separator having a high solute component separation performance,
High-performance separation is possible, and wastewater can be concentrated at a high ratio by combining with an evaporator.

Solid deposits can be obtained by using an electrodialysis apparatus that uses a cation exchange membrane that selectively permeates monovalent and divalent cations and an anion exchange membrane that selectively permeates monovalent ions. The sulfate ion (SO ₄ ²⁻ ) that is the main component of gypsum can be removed, and equipment failure and performance deterioration due to solid deposits in the evaporator that further concentrates the concentrated wastewater from the electrodialysis device can be prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIG. FIG. 1 shows an example of the embodiment of the present invention.
A flow chart in the case where a precoat filter (a filter in which diatomaceous earth, pearlite, etc. are adhered in a film form to a porous substrate such as ceramics) is used as a filtering device and an evaporator is used as a secondary concentrating device is shown.

In FIG. 1, 1 is a desulfurizer (not shown).
Raw water tank for temporarily storing the wastewater discharged from
2 is a precoat filter that is a device for removing suspended matter in wastewater to prevent deterioration of separation performance due to suspended matter in wastewater in the electrodialysis device 3 which will be described later. Electrodialyzer for separating concentrated wastewater (hereinafter referred to as primary concentrated wastewater) to be contained and dilute liquid in which solute components are diluted, 4 is secondary concentrated wastewater by further evaporating the primary concentrated wastewater generated by the electrodialysis device 3 Evaporating can, which is concentrated to 5
Is a secondary concentrated waste water tank for storing the secondary concentrated waste water generated in the evaporator 4, 6 is a condenser for cooling the steam generated at the time of evaporation in the evaporator 4 with cooling water, and collecting it as condensed recovery water, 7 Is a pump for supplying the wastewater from the raw water tank 1 to the precoat filter 2, 8 is a pump for supplying the treated water of the precoat filter 2 to the electrodialysis device 3, and 9 is the secondary concentrated wastewater in the secondary concentrated wastewater tank 5. The pump 10 for supplying the system to the outside of the system makes the inside of the evaporator 4 a negative pressure for promoting the evaporation of the primary concentrated waste water in the evaporator 4, and the evaporation generated in the evaporator 4 is condensed by the condenser 6 It is an evacuation device for moving to.

The waste water from the desulfurization device (not shown) is temporarily stored in the raw water tank 1 through the line a, and then the line b.
And to the precoat filter 2 via the pump 7. The precoat filter 2 is for forming a filter material such as diatomaceous earth and perlite in the form of a film on a porous substrate, and the filtration membrane filters turbid components. In this case, from the line c, the precoat filter 2 Supplying diatomaceous earth as filter material. 1 kg of diatomaceous earth was attached to a filtration area of 1 m ² . The wastewater from which the suspended matter in the wastewater has been removed by the precoat filter 2 is sent to the electrodialysis device 3 via the line d and the pump 8. The turbidity component concentration in the wastewater in the line d is set so that the concentration performance of the electrodialysis device in the subsequent stage can be maintained at a predetermined level or higher for a long period of time. In this example, the turbidity component concentration was 0.2 ppm so that continuous operation for one year was possible.

Since the pressure loss of the precoat filter 2 increases as the turbidity components in the wastewater are collected by the filter medium, the precoat filter 2 regularly filters the filter medium containing the turbidity components collected from the line R. Then, a new filter medium was supplied from line c.

Precoat filter 2 in this embodiment
As shown in Table 1, the composition of the waste water after removing the turbidity components is such that calcium chloride and magnesium chloride are the main components, and the gypsum component is dissolved in a saturated amount.

[Table 1]

In the electrodialysis device 3, the cation exchange membrane is selectively dialyzed with divalent and monovalent cations of calcium and magnesium, and the anion exchange membrane is selectively dialyzed with monovalent anion of chloride ion. A concentrated liquid containing a large amount of solute components (hereinafter referred to as primary concentrated wastewater) and a dilute solute component from the concentration chamber and the dilution chamber formed by alternately arranging these cation exchange membranes and anion exchange membranes, respectively. A diluted solution is obtained.

Table 2 shows various conditions such as the membrane area of the cation exchange membrane and the anion exchange membrane used in the electrodialysis device 3, the current density, and the membrane surface flow velocity.

[Table 2]

At this time, the gypsum remains as it is in the diluting solution because the sulfate ions (SO ₄ ²⁻ ) forming it are difficult to pass through the anion exchange membrane.

The primary concentrated waste water is supplied to the evaporator 4 through the line f.
On the other hand, the diluting liquid is sent through line g as make-up water for a desulfurizer (not shown) which is a source of the target wastewater.

The primary concentrated waste water is evaporated / concentrated in the evaporator 4 and separated into secondary concentrated waste water and steam. The evaporator 4 is of the normal external forced circulation type, and the primary concentrated wastewater is heated to 85 ° C. by a heating medium such as steam at the same time as the evaporation can 4 in order to promote evaporation in the can. Can 4 about 660
The negative pressure is mmHg. The heating medium is supplied from the line j and taken out of the evaporator 4 by the heat exchanger line k. When the concentrated primary wastewater is concentrated in the evaporator 4, gypsum, which is the main component of the solid precipitation component, does not exist in the wastewater, so that the equipment of the evaporator 4 can be prevented from malfunctioning, the pipes are blocked, and the performance is reduced.

The secondary concentrated wastewater produced in the evaporator 4 is stored in the secondary concentrated wastewater tank 5 through the line h,
It is supplied to the final disposal process of wastewater through the line i and the pump 9.

On the other hand, the vapor generated in the evaporator 4 is moved to the condenser 6 through the line 1 by the vacuum evacuation device 10 and is cooled and condensed by the cooling water of 20 ° C. in the condenser 6 to become a liquid, which is condensed and recovered. The water is taken out from the condenser 6 by the line p. The condensed and recovered water may be reused as boiler make-up water, desulfurizer make-up water, etc. depending on the quality of the water, but in the measurement in this example, the chlorine concentration was 1 ppm.
It was below. The condenser 6 of this embodiment is of a normal shell-and-tube type, and the condenser 6 is supplied with cooling water of 20 ° C. necessary for vapor condensation through a line m.
It is taken out of the system by the heat exchanger line n. The non-condensable gas remaining in the condenser 6 is discharged to the outside of the system by the line q and the vacuum exhaust device 10.

In the drainage C of each equipment outlet in this embodiment
The l concentration and the gypsum concentration are shown in Table 3.

[Table 3]

[0025]

INDUSTRIAL APPLICABILITY The present invention uses an electric device, which is easy to operate and control as a method for concentrating waste water, so that the operation and maintenance costs are low and the installation area is reduced as compared with the conventional waste water treatment method. Since the primary concentrated waste water from the electrodialysis device is further concentrated and reduced in volume by the evaporator after removing the solid deposition component, stable operation of the evaporator is possible, and operability and cost reduction in final disposal are possible. Can be converted.

[Brief description of drawings]

FIG. 1 is an explanatory view showing one embodiment of a wastewater treatment facility according to the present invention.

FIG. 2 is an explanatory diagram showing a flow chart of a conventional wastewater treatment facility.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsunori Miwada 1 Higashishinmachi, Higashi-ku, Nagoya-shi, Aichi Chubu Electric Power Co., Inc. Thermal Power Department (72) Inventor Hiroshi Yoshida Kitakanyama, Otaka-machi, Midori-ku, Nagoya-shi, Aichi No. 20 No. 1 Chubu Electric Power Co., Inc. Electric Power Research Laboratory (72) Inventor Mamoru Toriyao Kitakanyama, Otaka-cho, Midori-ku, Nagoya-shi, Aichi No. 20 No. 1 Chubu Electric Power Co. Electric Power Research Lab (72) Inventor Hiroshi Tsutsui Yoyo 2-5-1, Marunouchi, Chiyoda-ku, Tokyo Within Sanryo Heavy Industries Co., Ltd. (72) Inventor Shinichiro Otake 2-5-1, Marunouchi, Chiyoda-ku, Tokyo Sanryo Heavy Industries Co., Ltd. (72) Inventor Naohiko Ugawa Hiroshima 4-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Prefecture Mitsubishi Heavy Industries Ltd. Hiroshima Research Institute (72) Inventor Susumu Okino Kannon, Nishi-ku, Hiroshima-shi, Hiroshima 4-6-22 Machi Heavy Industry Co., Ltd. Hiroshima Research Laboratory (72) Inventor Seki Nakamura 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City Hiroshima Prefecture Mitsubishi Heavy Industries Ltd. Hiroshima Research Laboratory (72) Inventor Shiro Fukui Tokyo 2-25-14 Kameido, Koto-ku Asahi Glass Co., Ltd.Chemical Engineering Department (72) Inventor Nori Uemachi and 2-25-14 Kameido, Koto-ku, Tokyo Asahi Glass Co., Ltd. Chemical Engineering Department (72) Ryosuke Aoki Chiba City 10 Goi Kaigan, Hara City Inside the Chiba Factory of Asahi Glass Co., Ltd.

Claims (2)

[Claims] 1. An electrodialysis device that separates wastewater from a flue gas desulfurization device using an alkaline agent such as limestone into concentrated wastewater containing a large amount of solute components and diluting liquid in which the solute components are diluted can be treated. A filtration device that removes turbidity components so that the turbidity concentration is not more than
Cation exchange membranes that selectively permeate valent and divalent cations and anion exchange membranes that selectively permeate only monovalent anion are arranged alternately, and a concentrating chamber is provided between both ion exchange membranes. An electrodialyzer equipped with a diluting chamber, a means for sending the concentrated liquid discharged from the concentrating chamber of the electrodialysis device to the final treatment step, and the diluting liquid discharged from the diluting chamber is used as makeup water for the flue gas desulfurization device. And a means for treating the wastewater of the flue gas desulfurization device. 2. The waste water treatment facility of the flue gas desulfurization device according to claim 1, further comprising a concentrating device for evaporating and concentrating the concentrated liquid discharged from the concentrating chamber of the electrodialysis device.