JP3217402B2 - Wastewater desulfurization equipment wastewater treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an apparatus using sulfur dioxide gas (hereinafter referred to as SOx gas) in combustion exhaust gas from an exhaust gas in an apparatus using an alkali agent such as limestone as an absorbent from the viewpoint of preventing environmental pollution. The present invention relates to a (reduction in volume) treatment facility for wastewater discharged from a flue gas desulfurization unit that absorbs and separates.

[0002]

2. Description of the Related Art Waste water discharged from a flue gas desulfurization apparatus is composed of solid components such as gypsum and limestone which did not contribute to the reaction in the desulfurization apparatus, and chlorine gas (hereinafter referred to as C) in exhaust gas.
1 gas) with calcium and magnesium in the absorbent, salt components such as calcium chloride and magnesium chloride, oxides of metals such as silica and aluminum in the exhaust gas, and trapped in the desulfurization unit. In addition to containing various miscellaneous components such as combustion ash in the combustion exhaust gas, the liquidity of the wastewater is also acidic due to the SOx gas and Cl gas in the exhaust gas. No, the processing is usually performed as described below.

FIG. 2 shows an embodiment of a flow chart of a conventional wastewater treatment facility, and a conventional wastewater treatment method will be described with reference to FIG. The wastewater from the desulfurization unit that is treated by the wastewater treatment equipment, that is, the liquid to be treated, is temporarily stored in the stock solution tank 01 by the line aa. Thereafter, the liquid to be treated is sent from a line bb to an acid decomposing tank 02, which decomposes an acid component contained in the liquid, and then separates a solid component via a line cc. Sent to Liquid to be treated is line cc
During the flow of, the hydrogen ion concentration of the liquid to be treated (hereinafter, referred to as
A pH adjusting alkali and a coagulant are injected through the line dd. In the solid separation tank 03, solids such as limestone, gypsum, and combustion ash in the liquid to be treated are separated,
A liquid with a reduced solid content (hereinafter referred to as a cleaning liquid) and a liquid with a high solid content (hereinafter referred to as a concentrated suspension) are discharged.

The concentrated suspension is supplied to a dehydrator 0 via a line ee.
4 and further separated into water and solids by the dehydrator 04. The water and solids separated by the dehydrator 04 are discharged out of the system of the 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 via a line hh.
The solids that could not be separated in the solids separation tank 03 are further separated from the liquid to be treated and stored in the treatment liquid tank 06 via a line ii of improved cleanliness. Processing liquid tank 0
The treated wastewater in 6 is discharged to a public water area via a line jj (after it is confirmed that the wastewater meets the wastewater standards).

[0006]

As described above, the conventional wastewater treatment equipment has a complicated apparatus configuration, and the operation control method of each apparatus is also complicated. The operation control method is based on the wastewater discharged from the wastewater treatment equipment. In some cases, it is impossible to discharge the wastewater in the treatment liquid tank 06, and in the worst case, the entire system of the wastewater treatment equipment is stopped.

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

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

[0009]

The present invention provides the following (1) and (1).
And (2). (1) Turbidity that can be treated by 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 a dilute solution in which the solute components have become diluted. A filtration device for removing turbid components so as to have a concentration equal to or less than
Cation exchange membranes that selectively permeate valent cations and anion exchange membranes that selectively permeate only monovalent anions are alternately arranged, and a concentration chamber and a dilution chamber are provided between the two ion exchange membranes. and electrodialysis device provided, diluent discharged from the unit and the dilution chamber to be sent to the final process step a concentrated solution discharged from the concentrating compartment of said electrodialysis apparatus comprises means for use as makeup water for flue gas desulfurization system Processing equipment comprising:
Pleco filter with filter medium formed as a film on porous substrate
A wastewater treatment facility for a flue gas desulfurization unit, which is a heat filter . (2) The equipment for treating wastewater of a flue gas desulfurization apparatus according to the above (1), further comprising a concentration apparatus for evaporating and concentrating a concentrated liquid discharged from a concentration chamber of the electrodialysis apparatus .

[0010]

In the wastewater treatment equipment according to the present invention, the wastewater is treated by a membrane separation device having high solute component separation performance.
High-performance separation is possible, and wastewater can be concentrated at a high magnification by combining with an evaporator.

[0011] Further, by using an electrodialyzer using a cation exchange membrane selectively permeating monovalent and divalent cations and an anion exchange membrane selectively permeating monovalent ions, solid precipitates can be obtained. Sulfate ion (SO ₄ ²⁻ ), which is gypsum, which is a main component of, can be removed, and equipment failure and performance degradation due to solid precipitates in the evaporator that further concentrates concentrated wastewater from the electrodialysis device can be prevented.

[0012]

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

In FIG. 1, reference numeral 1 denotes a desulfurizer (not shown).
Raw water tank for temporarily storing wastewater released from
Reference numeral 2 denotes a precoat filter which is a device for removing suspended components in wastewater to prevent a decrease in separation performance due to suspended components in wastewater in an electrodialysis device 3 described later. An electrodialysis device that separates the concentrated wastewater (hereinafter referred to as “primary wastewater”) contained therein and a dilute solution in which a solute component is diluted, 4 is a secondary concentrated wastewater generated by further evaporating the primary concentrated wastewater generated by the electrodialysis device 3 Evaporator, which concentrates to 5
Is a secondary concentrated drainage tank for storing secondary concentrated wastewater generated in the evaporator 4, 6 is a condenser for cooling the steam generated during evaporation in the evaporator 4 with cooling water and recovering it as condensed water, 7 Is a pump for supplying wastewater from the raw water tank 1 to the precoat filter 2, 8 is a pump for supplying treated water of the precoat filter 2 to the electrodialyzer 3, and 9 is a secondary concentrated wastewater in the secondary concentrated wastewater tank 5 according to the present invention. A pump 10 for supplying the outside of the system has a negative pressure in the evaporator 4 for promoting the evaporation of the primary concentrated wastewater in the evaporator 4 and a condenser 6 for evaporating the evaporator 4. Vacuum evacuation device for moving the

The waste water from the desulfurization unit (not shown) is temporarily stored in a raw water tank 1 by a line a, and then stored in a line b.
And sent to the precoat filter 2 via the pump 7. The precoat filter 2 forms a filter medium such as diatomaceous earth and perlite on a porous substrate in the form of a film, and the filtration membrane filters a turbid component. Supplies diatomaceous earth as filter media. 1 kg of diatomaceous earth was applied to a filtration area of 1 m ² . The wastewater from which the turbid components in the wastewater have been removed by the precoat filter 2 is sent to the electrodialysis device 3 via the line d and the pump 8. The concentration of the turbid component in the waste water in the line d is set so that the concentration performance of the subsequent electrodialyzer can be maintained at a predetermined level or more over a long period of time. In this example, the concentration of the turbid component 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 turbid components in the wastewater are collected by the filter medium membrane, the filter medium containing the turbid components collected from the line R on a regular basis is used as the precoat filter 2. And a new filter medium was supplied from line c.

The precoat filter 2 in this embodiment
As shown in Table 1, the waste water after the removal of the turbid components has a property that calcium chloride and magnesium chloride are the main components and gypsum is dissolved in a saturated amount.

[Table 1]

In the electrodialysis apparatus 3, divalent cations and monovalent cations of calcium and magnesium are selectively dialyzed in the cation exchange membrane, and monovalent anions of chloride ion are selectively dialyzed in the anion exchange membrane. From the concentration chamber and the dilution chamber formed by alternately arranging these cation exchange membranes and anion exchange membranes, the concentrated liquid containing a large amount of solute component (hereinafter referred to as primary concentrated waste water) and the solute component are diluted. Is obtained.

Table 2 shows the conditions of the cation exchange membrane and the anion exchange membrane used in the electrodialyzer 3, such as the membrane area, current density, and membrane surface flow rate.

[Table 2]

At this time, gypsum remains in the diluent as sulfate ions (SO ₄ ²⁻ ) forming the gypsum do not easily pass through the anion exchange membrane.

The primary concentrated wastewater is sent to the evaporator 4 via line f.
The diluent is sent via a line g as makeup water for a desulfurization unit (not shown) that is a source of the target wastewater.

The primary concentrated wastewater is evaporated and concentrated in the evaporator 4 and separated into secondary concentrated wastewater and steam. The evaporator 4 is of a normal external forced circulation type, and the evaporator 4 is heated to 85 ° C. with a heating medium such as steam in order to promote evaporation in the evaporator, and at the same time, the evaporator 4 is subjected to the same evaporation. Approximately 660 cans
The negative pressure is mmHg. The heating medium is supplied from a line j and taken out of the evaporator 4 by a heat exchanger line k. When the primary concentrated wastewater is concentrated in the evaporator 4, gypsum, which is a main component of the solid precipitation component, does not exist in the wastewater, so that failure of equipment of the evaporator 4, blockage of piping, and deterioration of performance can be prevented.

The secondary concentrated effluent generated in the evaporator 4 is stored in a secondary concentrated effluent tank 5 via a line h.
The wastewater is supplied to a final disposal step via a line i and a pump 9.

On the other hand, the vapor generated in the evaporator 4 is moved to the condenser 6 via the line 1 by the vacuum exhaust device 10 and cooled and condensed with cooling water at 20 ° C. in the condenser 6 to become a liquid, which is condensed and recovered. Water is taken out of the condenser 6 by the line p. The condensed and recovered water can be reused as boiler makeup water, desulfurization equipment makeup water, etc., depending on the water quality.
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 at 20 ° C. necessary for condensation of steam 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 out of the system by the line q and the vacuum exhaust device 10.

In this embodiment, C in the drainage of each equipment outlet
Table 3 shows the l concentration and the gypsum concentration.

[Table 3]

[0025]

According to the present invention, the operation and maintenance cost is reduced and the installation area is reduced as compared with the conventional wastewater treatment method by using an electric device whose operation control method is easy as the wastewater concentration method. After the primary concentrated wastewater from the electrodialysis device is removed from solid precipitate components, the evaporator can be further concentrated and reduced in volume, so that the evaporator can be operated stably and the operability in final disposal is improved and the cost is reduced. Can be done.

[Brief description of the 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.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsunori Miwada 1 Higashi-Shinmachi, Higashi-ku, Nagoya-shi, Aichi Chubu Electric Power Co., Inc. Address No. 1 Chubu Electric Power Co., Inc. Power Technology Research Institute (72) Inventor Mamoru Toriyao 20-1 Kita-Sekiyama, Odaka-cho, Midori-ku, Nagoya-shi, Aichi Prefecture Power No. 1 Chubu Electric Power Company Power Technology Research Institute (72) Invention Hiroshi Tsutsui 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Heavy Industries, Ltd. (72) Inventor Shinichiro Kotake 2-5-1, Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Heavy Industries, Ltd. (72) Naohiko Ugawa, inventor Hiroshima Pref., Hiroshima Pref., Hiroshima Pref., Hiroshima Pref. 4-6-22 Onshinmachi Mitsubishi Heavy Industries, Ltd.Hiroshima Research Center (72) Inventor: Sumi Nakamura 4-6-22 Kanon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd.Hiroshima Research Institute (72) Inventor Shiro Fukui Tokyo 2-25-14 Kameido, Koto-ku, Tokyo Asahi Glass Co., Ltd., Chemical Engineering Department (72) Inventor Norikane Uemachi 2-14-14 Kameido, Koto-ku, Tokyo Asahi Glass Co., Ltd. Chemical Engineering Department (72) Inventor Ryosuke Aoki 10 Goi Kaigan, Ichihara City, Chiba Prefecture Asahi Glass Co., Ltd. Chiba Factory (56) References JP-A-5-31483 (JP, A) JP-A-3-165814 (JP, A) JP-A-55-81782 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 1/469 B01D 53/50 B01D 53/77 B01D 61/44

Claims (2)

(57) [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 a dilute solution with a reduced solute component. A filtration device for removing a turbid component so as to have a turbid concentration of not more than 1;
A cation exchange membrane selectively permeating the monovalent and divalent cations and an anion exchange membrane selectively permeating only the monovalent anions are alternately arranged. an electric dialyzer dilution chamber is provided, using diluted solution discharged from the means and the dilution chamber to be sent to the final process step a concentrated solution discharged from the concentrating compartment of said electrodialysis apparatus as makeup water for flue gas desulfurization system Processing equipment with means for performing
Thus, the filtration device forms a filter medium on a porous substrate in a film form.
Wastewater treatment equipment for flue gas desulfurization equipment, characterized in that it is a precoated filter . 2. The equipment for treating wastewater of a flue gas desulfurization apparatus according to claim 1, further comprising a concentration apparatus for evaporating and concentrating the concentrated liquid discharged from the concentration chamber of the electrodialysis apparatus.