JP2013208542A - Wastewater treatment device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive wastewater treatment device of a wet type flue gas desulfurization system, which prevents re-release of mercury contained in an exhaust gas in desulfurization thereof and performs the treatment for reducing the mercury concentration in a gypsum generated when desulfurizing in an absorption tower, and to provide a wastewater treatment method using the device.SOLUTION: A wastewater treatment device of a flue gas desulfurization system is provided with: a sulfur oxide-absorbing part 6 which introduces an exhaust gas including sulfur oxide from a combustion apparatus with a boiler and has a spray nozzle for spraying a lime stone-containing absorbent liquid; an absorbent liquid-storing part 11 provided below the absorbing part; a filter part 68 having a smaller hole size than the grain size of a mercury absorbent at a position dividing the inside of the liquid-storing part 11 vertically in two; a mercury absorbent-supplying part 60 provided above the level of the absorbent liquid in the liquid-storing part 11 on the upper portion of the filter part 68; and a first absorbent liquid extraction part for extracting the absorbent liquid in the liquid-storing part 11 to the lower part of the filter part 68 to supply the liquid to an absorbent liquid circulation path.

Description

TECHNICAL FIELD The present invention relates to a wet flue gas desulfurization apparatus and method for removing sulfur oxide (SO ₂ ) and mercury (Hg) contained in combustion exhaust gas in a boiler plant for thermal power generation, and more particularly in an absorption liquid of the flue gas desulfurization apparatus. The present invention relates to a wastewater treatment apparatus and method of a wet flue gas desulfurization system that removes mercury contained in water.

An example of a boiler plant for thermal power generation that burns coal is shown in FIG. The boiler plant for thermal power generation mainly comprises a boiler 13, a denitration device 14, an air preheater (A / H) 15, a dust collector 16, and a flue gas desulfurization device (hereinafter sometimes simply referred to as a desulfurization device) 3. Is done. In the boiler 13, the coal 25 is combusted to discharge exhaust gas from the boiler 13. The denitration device 14 decomposes nitrogen oxides (NOx) contained in the gas discharged from the boiler 13. Further, the temperature of the gas discharged from the denitration device 14 is adjusted to 200 to 160 ° C. by the air preheater 15, and the dust is removed by the dust collector 16. The dust-removed gas is supplied to the desulfurization apparatus 3, and then SO ₂ is removed and the gas is discharged from the chimney 29.

A schematic configuration diagram of a conventional desulfurization apparatus 3 is shown in FIG. An inlet exhaust gas 1 is introduced from a boiler 13 into the desulfurization apparatus 3 shown in FIG. The desulfurization apparatus 3 mainly includes a spray nozzle 4, an absorption liquid circulation pump 5, a mist eliminator 8, an oxidizing gas supply unit 9, a stirrer 10, an absorption liquid reservoir 11, and the like. The exhaust gas 1 flowing into the desulfurization apparatus 3 comes into contact with the absorbing liquid 6 sprayed from the spray nozzle 4 to remove SO ₂ in the exhaust gas. The SO ₂ absorbed in the absorbent 6 becomes sulfurous acid, and the SO ₂ absorption efficiency decreases as the concentration of sulfurous acid in the absorbent 6 increases. For this reason, by supplying the oxidizing gas 27 to the absorbent 6, the sulfurous acid is oxidized to form gypsum, and the SO ₂ removal performance of the absorbent 6 is recovered. Further, an alkaline agent 19 for oxidizing sulfurous acid is appropriately added to the absorbent 6 in the desulfurization apparatus 3.

  The space between the liquid level of the absorbing liquid 6 stored in the desulfurization apparatus 3 and the spray nozzle 4 is referred to as a desulfurizing absorption part 26, and the storage part of the absorbing liquid 6 therebelow is referred to as an absorbing liquid reservoir part 11. is there.

  Moreover, the block diagram of the waste water treatment facility of a prior art is shown in FIG. The wastewater treatment equipment mainly includes a first hydrocyclone (1st H / C) 38, a second hydrocyclone (2nd H / C) 39, a belt filter 40, a circulating water tank 41, pH adjustment, heavy metal removal, and addition of a flocculant. The unit 42 is configured.

Since the gypsum concentration in the absorption liquid 6 of the desulfurization apparatus 3 increases by absorbing SO ₂ in the exhaust gas, the gypsum concentration in the absorption liquid becomes 10 to 30%, and the chlorine in the absorption liquid 6 A part of the absorbing liquid 6 is extracted so that the concentration does not exceed a certain concentration, and separated into the fluid supplied to the gypsum 49, the drainage 50 and the recirculation unit 37 using the waste water treatment facility shown in FIG. It is discharged out of the system of the desulfurization device 3. The absorbing liquid 6 is extracted from the extraction portion 36 of the desulfurization apparatus 3 and supplied to the first hydrocyclone (1st H / C) 38. The 1st H / C 38 1st H / C overflow 43 side liquid and the 1st H / C underside are supplied. Divide into liquid on the flow 44 side. The liquid discharged to the 1st H / C underflow 44 side is a slurry containing a large amount of gypsum 49 having a large particle size, and the liquid on the 1st H / C overflow 43 side is a slurry containing a large amount of gypsum 49 having a small particle size. The slurry on the 1st H / C underflow 44 side is supplied to the belt filter 40, and the dehydrated gypsum 49 on the belt filter 40 is recovered. The gypsum 49 on the belt filter 40 is washed with industrial water (not shown), and is supplied to the circulating water tank 41 together with the filtrate of the belt filter 40 as the belt filter portion discharge liquid 52.

  The slurry on the 1st H / C overflow 43 side is also supplied to the circulating water tank 41. In the circulating water tank 41, a part of the liquid is extracted and supplied from the second hydrocyclone supply unit 47 to the second hydrocyclone (2nd H / C) 39. The 2nd H / C 39 is divided into a liquid on the 2nd H / C overflow 45 side and a liquid on the 2nd H / C underflow 46 side, and the liquid on the 2nd H / C underflow 46 side is supplied to the circulating water tank 41. The liquid on the 2nd H / C overflow 45 side adjusts the pH in the wastewater 50 by adjusting the pH, removing the heavy metal, and adding the coagulant adding unit 42, and supplying TMT (trimercaptotriazine) or the like to capture the heavy metal. The solid particles are aggregated with a polymer flocculant such as the like, and the precipitated solid particles are collected as the solid material 51 with a press machine or the like (not shown). The drainage water 50 not containing the solid matter 51 is discharged to the sea or the like after the liquid temperature is adjusted appropriately by a cooling tower (not shown). However, as shown in the recirculation unit 37, liquids other than the liquid discharged to the sea or the like are recirculated as make-up water for the desulfurization device 3.

  Further, JP-A-2010-5853 discloses a gypsum in a desulfurization treatment system in which sulfur oxides in exhaust gas are desulfurized with an absorption liquid in an absorption tower, and the absorption liquid after the desulfurization treatment is oxidized with air to generate gypsum. A mercury adsorbent is added to a gypsum-containing liquid containing mercury and a mercury component to precipitate the mercury component together with gypsum from the absorbent, and at the same time, the absorbent containing gypsum and the mercury component is separated from the solid. Further, it is disclosed that a strong acid solution is added to the solid containing gypsum and the mercury component to extract the mercury component as a mercury-containing liquid, and the cleaned gypsum is recovered.

JP 2010-5583 A

  In the conventional flue gas desulfurization system shown in FIG. 6 and FIG. 7 described above, when mercury contained in coal combustion exhaust gas is removed by the desulfurization device 3, the mercury concentration in the absorbing liquid 6 increases. Since no consideration is given to this problem, there is a problem that mercury in the absorbing liquid 6 is reduced and re-released as metallic mercury in the exhaust gas. Further, a part of the mercury in the absorption liquid 6 moves from the liquid side to the solid side, that is, the gypsum 49 side. However, when the gypsum 49 contains mercury, the gypsum 49 may be reused depending on the intended use of the gypsum 49. Mercury 49 is vaporized at the landfill when gypsum board or cement is produced from gypsum 49, when it is dried or roasted, or when gypsum 49 is disposed of in landfills. There was a problem of re-emission into the atmosphere.

  In the method described in JP 2010-55883 A, gypsum and mercury components are precipitated from the absorption liquid after desulfurization treatment, and the absorption liquid is separated from the solid containing gypsum and mercury components. Since the apparatus for separating the absorption liquid from the solid containing gypsum and mercury components from the liquid by separating the absorption liquid from the solid containing the gypsum and mercury components is provided separately from the absorption tower, the equipment cost is high.

  An object of the present invention is to prevent the mercury contained in the exhaust gas from being re-released when desulfurizing the combustion exhaust gas, and to reduce the concentration of mercury in gypsum generated during the desulfurization treatment. An inexpensive wet flue gas desulfurization system wastewater treatment apparatus and method are provided.

The problems of the present invention are solved by the following means.
The invention according to claim 1 is a sulfur oxide absorbing portion provided with a spray nozzle for introducing an exhaust gas containing sulfur oxide from a combustion device including a boiler and spraying an absorbing liquid containing limestone, and a lower portion of the absorbing portion. An absorption liquid circulation path including an absorption liquid reservoir section provided, an oxidizing gas supply section provided in the absorption liquid reservoir section, and a circulation pump that circulates and supplies the absorption liquid in the absorption liquid reservoir section to the spray nozzle of the absorption section. A flue gas desulfurization-type wastewater treatment apparatus including a filter portion having a pore size smaller than the particle size of the mercury adsorbent at a position that bisects the absorption liquid reservoir in the vertical direction, and an absorption liquid reservoir above the filter portion. A mercury adsorbent supply unit is provided above the liquid level of the absorption liquid in the unit, and a first absorption liquid extraction unit for extracting the absorption liquid in the absorption liquid reservoir and supplying it to the absorption liquid circulation path below the filter unit Features A waste water treatment apparatus.

  According to a second aspect of the present invention, there is provided a second absorption liquid extraction part for extracting the absorption liquid from the upper part of the filter part in the absorption liquid reservoir, and separation of the mercury adsorbent and the gypsum slurry in the second absorption liquid extraction part. The waste water treatment apparatus according to claim 1, wherein the parts are connected.

  A third aspect of the present invention is the waste water treatment apparatus according to the first aspect, wherein a gypsum-absorbing liquid separation unit is connected to a first absorbing liquid extraction unit provided at a lower portion of the filter unit.

  A fourth aspect of the present invention is the waste water treatment apparatus according to the first aspect, wherein a stirrer for stirring the absorbent is provided above the filter portion in the absorbent reservoir.

  According to a fifth aspect of the present invention, the pore diameter of the filter portion is a diameter formed by a ring formed by intersecting 90 ° cones on the particle surface from the center to the bottom with the center of the particle of the mercury adsorbent as an apex. The wastewater treatment apparatus according to claim 1, wherein the wastewater treatment apparatus is smaller than (see FIG. 3).

  The invention according to claim 6 is the absorption provided in the lower part of the absorption part by spraying the absorption liquid containing limestone in the absorption part to the exhaust gas from the combustion device including the boiler to absorb the sulfur oxide in the exhaust gas. Exhaust gas that accumulates absorption liquid in the liquid reservoir, supplies oxidizing gas to the absorption liquid in the absorption liquid reservoir, circulates and supplies the absorption liquid in the absorption liquid reservoir to the absorption section, and makes contact with the exhaust gas In the desulfurization type wastewater treatment method, the mercury adsorbent is supplied from above the absorption liquid reservoir to the absorption liquid in the absorption liquid reservoir, and the absorption liquid reservoir is divided into two in the vertical direction from the particle size of the mercury adsorbent. The waste water treatment method is characterized in that the mercury adsorbent supplied to the absorption liquid reservoir is separated by a filter having a small pore diameter, and the absorption liquid separated from the mercury adsorbent is supplied to the absorption part.

  The invention according to claim 7 is characterized in that the mercury adsorbent is made of a chelate resin, and the polymer substrate of the chelate resin is any one of polyacryl, polyhydroxyethyl methacrylate, phenol resin, and polystyrene. 6. The waste water treatment method according to 6.

  The invention according to claim 8 is characterized in that the mercury adsorbent is composed of a chelate resin, and the coordination group of the chelate resin is any one of a thiol form, a dithiocarbamic acid form, an isothiuronium form, a dithizone form, and a thiourea form. The waste water treatment method according to claim 6.

  The invention described in claim 9 is the waste water treatment method according to claim 6, wherein the particle size of the mercury adsorbent is 300 μm or more.

  The invention described in claim 10 is the waste water treatment method according to claim 6, wherein the mercury adsorbent is either activated carbon or ion exchange resin.

(Function)
The absorption liquid reservoir provided in the lower part of the absorption part of the present invention is provided with a filter part having a pore size smaller than the particle diameter of the mercury adsorbent, and the mercury adsorbent is supplied from the upper part of the filter part, Since the mercury adsorbent cannot pass through the filter part by extracting the absorbent from the waste water and treating the waste water with the waste water treatment facility, the mercury adsorbent does not enter the gypsum side, and the mercury concentration in the recovered gypsum Will not increase.

  Further, by removing the absorbing liquid from the upper part of the filter part and separating the mercury adsorbent and the gypsum slurry, the mercury adsorbent that has adsorbed mercury can be separated, so that mercury does not migrate to the gypsum side.

  According to the first and sixth aspects of the invention, when the sulfur oxide in the exhaust gas is absorbed by the absorption liquid, the mercury component contained in the exhaust gas is adsorbed by the mercury adsorbent and stored in the absorption liquid reservoir. Since the filter part with a pore size smaller than the particle size of the mercury adsorbent is provided at a position that bisects the absorption liquid reservoir in the vertical direction, the mercury adsorbent contained in the absorbent after desulfurization treatment can be removed by the filter part. Since gypsum and mercury adsorbent can be separated and recovered, there is an effect of reducing the mercury concentration in gypsum. Also, the mercury adsorbent is supplied to the absorption liquid circulation pump by supplying the mercury adsorbent directly to the absorption liquid reservoir of the desulfurization unit and providing a mercury adsorbent separation filter section below the mercury adsorbent supply section. Therefore, the mercury adsorbent is not atomized, and the mercury adsorbent can be prevented from entering the gypsum side.

  According to invention of Claim 2, the 2nd absorption liquid extraction part which extracts absorption liquid from the upper part of the filter part in an absorption liquid reservoir part is provided, Mercury adsorption agent and gypsum slurry of this 2nd absorption liquid extraction part are provided. Since the separation unit is connected, the mercury adsorbent and the gypsum slurry can be easily separated continuously, gypsum containing no mercury can be obtained, and the mercury adsorbent can be reused.

  According to the invention described in claim 3, since the absorption liquid after removing the mercury adsorbent adsorbing the mercury component in the absorption liquid by the filter part in the absorption liquid reservoir can be supplied to the absorption liquid circulation path. Sulfur oxides in the exhaust gas can be absorbed and removed by the circulatingly supplied absorption liquid.

  According to the invention described in claim 4, since the absorption liquid in the absorption liquid reservoir flows from the top to the bottom, the mercury adsorbent separation filter is easily clogged with the mercury adsorbent. Since the stirrer that stirs the liquid stirs the absorbent, clogging of the filter portion can be prevented.

  According to the invention of claim 5, the pore diameter of the filter part is a diameter formed by a ring formed by intersecting 90 ° cones on the particle surface downward from the center with the center of the mercury adsorbent particle as a vertex. If it is smaller (see FIG. 3), the mercury adsorbent placed in the hole of the filter part can be easily removed from the filter hole by an external force acting on the mercury adsorbent (in the case of the present embodiment, an absorption liquid flow). .

  According to the seventh aspect of the invention, when a chelate resin is used as the mercury adsorbent, the chelate resin has a reaction rate sufficient to adsorb mercury, and the chelate resin has a higher mercury adsorption rate than gypsum. For this reason, the chelate resin does not re-release mercury, and there is an advantage that the amount of chelate resin used can be reduced. In addition, the time during which the chelating resin contacts the absorbing solution containing mercury is long, and the chelating resin has a merit that the amount of chelating resin used can be reduced because the adsorption rate of mercury is faster than that of gypsum.

  According to the invention described in claim 8, when a chelate resin is used as the mercury adsorbent, the coordination group of the chelate resin is any of thiol form, dithiocarbamic acid form, isothiuronium form, dithizone form, and thiourea form. By using it, mercury can be selectively adsorbed among the heavy metals in the absorbing solution, so that mercury can be efficiently removed.

  According to the ninth aspect of the present invention, the chelate resin generally has a particle size of about 300 μm to 1600 μm. For example, the mercury adsorbent has a particle size of 300 μm or more, and the pore size of the mercury adsorbent separation filter portion. Is 212 μm, since the particle size of gypsum is 100 μm or less, the gypsum passes through the mercury adsorbent separation filter part without clogging, and the mercury adsorbent stays on the upper side of the filter part, so that the gypsum and the mercury adsorbent Can be easily separated.

  According to the tenth aspect of the present invention, any solid particles such as powdered activated carbon or ion exchange resin that adsorbs mercury can be used in the present invention in addition to the chelate resin as the mercury adsorbent.

It is a block diagram which shows the waste water treatment equipment of the structure which installed the filter which has a hole diameter smaller than the particle size of the mercury adsorbent supplied to the absorption liquid reservoir part of the desulfurization apparatus which becomes this invention. It is a top view of the filter which has a pore diameter smaller than the particle size of the mercury adsorbent used as a filter of FIG. It is a figure explaining the magnitude | size of a mercury adsorbent and a filter diameter. It is the figure which showed the mercury re-release prevention effect of chelate resin. It is the figure which showed the abundance ratio of mercury in an absorption liquid. It is a block diagram of the waste water treatment apparatus of the desulfurization apparatus of a prior art. It is a block diagram of the wastewater treatment facility of a prior art. It is a block diagram of the system which processes coal combustion exhaust gas of a prior art.

  An embodiment of the present invention will be described with reference to the drawings. An example of the configuration of the flue gas desulfurization apparatus (waste water treatment apparatus) of the present invention is shown in FIG. In addition, the description of the configuration and operation common to the prior art in the configuration of the desulfurization apparatus shown in FIG. 1 is omitted.

  The mercury removal apparatus mainly includes a spray nozzle 4, an absorption liquid circulation pump 5, a mist eliminator 8, an oxidizing gas supply unit 9, an agitator 10, an absorption liquid reservoir 11, a mercury adsorbent supply unit 60, a mercury adsorbent separation filter 68, and the like. Consists of

  In this example, a chelate resin was used as the mercury adsorbent. As for the chelate resin, the polymer substrate is polyacryl, polyhydroxyethyl methacrylate, phenol resin, or polystyrene. The coordination group of the chelate resin is any of thiol, dithiocarbamic acid, isothiuronium, dithizone, and thiourea.

  In general, the chelate resin has a particle size of about 300 μm to 1600 μm, and is used as a method for removing mercury in wastewater from a waste treatment apparatus. In this case, the mercury in the absorption liquid can be removed by supplying the absorption liquid containing mercury from which suspended substances have been removed with a filtration membrane into the packed tower containing the chelate resin.

However, in the present invention, even if desulfurization is performed with the absorbent 6 containing the chelating resin, gypsum slurry and other suspensions, high mercury removal performance and prevention of mercury re-release, and further, the mercury concentration in gypsum is reduced. I found out that I can do it. Depending on the type of chelate resin, about 140 g or more of mercury can be adsorbed per liter of chelate resin.
If the concentration of the chelate resin is adjusted in accordance with the amount of mercury absorbed by the desulfurization apparatus 3, the mercury in the absorbent 6 can be adsorbed on the chelate resin side. The mercury adsorbent can be applied to the wastewater treatment apparatus as long as it is solid particles such as activated carbon or ion exchange resin that adsorbs mercury, other than chelate resin.

  FIG. 2 shows a planar structure of the filter unit 68. The filter unit 68 includes a mercury adsorbent separating filter 68a and a support 68b of the filter 68a. The pore diameter of the mercury adsorbent separating filter 68a is made smaller than the particle diameter of the supplied mercury adsorbent. When the particle size of the mercury adsorbent is 300 μm or more and the pore size of the mercury adsorbent separation filter 68a is 212 μm, the particle size of the gypsum is 100 μm or less, so that the mercury adsorbent separation filter portion 68 is not clogged with gypsum. The mercury adsorbent passes through and remains on the upper side of the mercury adsorbent separation filter 68. The reason why the hole diameter of the mercury adsorbent separation filter 68a is 212 μm is that when the particle diameter of the mercury adsorbent particles is 300 μm, a 90 ° cone is formed from the center of the mercury adsorbent particles to the top and downward from the center. If the diameter is smaller than the diameter of the ring formed intersecting on the particle surface (see FIG. 3), the mercury adsorbent placed in the filter hole can be easily applied by the external force acting on the mercury adsorbent (in this embodiment, the absorption liquid flow). This is because it can be removed from the filter hole.

  For this reason, only the gypsum slurry which does not contain a mercury adsorbent is supplied to the absorption liquid circulation pump 5. Further, when the minimum particle diameter of the mercury adsorbent is made larger than 300 μm, the pore diameter of the mercury adsorbent separation filter 68a can be increased in accordance with the particle diameter of the mercury adsorbent, and other impurities such as rust, etc. It is possible to prevent clogging of the mercury adsorbent separation filter 68a due to the above.

  Moreover, since the absorption liquid 6 in the absorption liquid reservoir 11 flows from the top to the bottom, the mercury adsorbent is easily clogged in the mercury adsorbent separation filter 68a. By providing the stirrer 12 on the upper part of the mercury adsorbent separation filter 68a, the absorption liquid 6 on the upper part of the mercury adsorbent separation filter 68a is stirred, so that the mercury adsorbent separation filter 68a can be prevented from being clogged.

  The wastewater treatment facility 67 is a facility as shown in FIG. 7, and the absorbent 6 contains the mercury adsorbent by withdrawing the absorbent 6 from the withdrawal section 36 provided at the lower part of the mercury adsorbent separation filter section 68. There will be no gypsum slurry. When the gypsum 49 (see FIG. 7) is collected by the wastewater treatment facility 67, the mercury adsorbent containing mercury does not migrate to the gypsum 49 side, so that the mercury concentration in the gypsum 49 can be reduced. Further, the absorbent 6 is extracted from the mercury adsorbent and gypsum extraction part 64, and the mercury adsorbent and gypsum slurry are separated by the mercury adsorbent and gypsum slurry separation part 66. The mercury adsorbent separated by the separation unit 66 is extracted from the mercury adsorbent extraction unit 69.

  For example, the mercury adsorbent and the gypsum slurry can be separated by using a filter having the same pore size as that of the mercury adsorbent separating filter 68a depending on the particle size difference between the gypsum 49 and the mercury adsorbent. The gypsum slurry side is returned from the gypsum slurry return portion 65 to the absorbent reservoir 11. The mercury adsorbent recovered by the mercury adsorbent and gypsum slurry separation unit 66 contains mercury and is used after being disposed of or regenerated.

  Further, when the mercury adsorbent is supplied to the absorption liquid reservoir 11 of the conventional desulfurization apparatus 3 shown in FIG. 6, the mercury adsorbent is pulverized when passing through the absorption liquid circulation pump 5 or the spray nozzle 4, and the mercury adsorbent. Therefore, it may be difficult to separate the mercury adsorbent and the gypsum 49 by the filter unit 68 using the difference in particle size.

  On the other hand, in the present invention, since the mercury adsorbent separation filter unit 68 is provided, the mercury adsorbent is not supplied to the absorption liquid circulation pump 5, so that the mercury adsorbent is not atomized and the mercury adsorption It is possible to prevent the agent from entering the gypsum 49 side. Further, the stirrer 12 at the upper part of the mercury adsorbent separating filter unit 68 can be prevented from being atomized by pulverization of the mercury adsorbent by making the stirring speed slower than the stirrer 10 at the lower part of the mercury adsorbent separating filter part 68 .

  FIG. 4 shows the result of comparison of the amount of mercury re-release in the case of desulfurization with the absorbent 6 containing a chelate resin and the case of desulfurization with the absorbent 6 not containing the chelate resin. The results shown in FIGS. 4 and 5 are obtained using a chelate resin in which a phenol resin and a thiourea type coordination group are combined.

When the chelate resin was not included, the amount of mercury re-released was 3.3 μg / m ³ N, whereas almost no mercury was re-released 5 minutes after the chelate resin was supplied. It can be seen that even when the residence time until the absorbent 6 in the absorbent reservoir 11 of the desulfurization apparatus 3 is sprayed is minimized to 5 minutes, the chelate resin has a reaction rate sufficient to adsorb mercury. . Moreover, in a packed tower containing a separate chelate resin that is normally used, the liquid passing therethrough is one-through, and it is necessary to fill a large amount of chelate resin in order to obtain a high solid-liquid contact area. Although it becomes large, in this invention, the time which the absorption liquid 6 containing mercury and this chelate resin contact is long, and there exists a merit which can reduce the usage-amount of chelate resin.

  FIG. 5 shows the abundance ratio of mercury in the gypsum and the chelate resin in the absorbent 6. When there is no chelate resin and the ratio of mercury present on the liquid side in the absorbent 6 is 100%, it can be seen that most of the mercury has moved to the chelate resin side. This is because the chelate resin has a higher adsorption rate than gypsum.

DESCRIPTION OF SYMBOLS 1 Inlet exhaust gas 2 Outlet exhaust gas 3 Flue gas desulfurization apparatus 4 Spray nozzle 5 Absorption liquid circulation pump 6 Absorption liquid 8 Mist eliminator 9 Oxidation gas supply part 10,12 Stirrer 11 Absorption liquid reservoir part 13 Boiler 14 Denitration apparatus 15 Air preheater (A / H) 16 Dust collector 19 Alkaline agent 25 Coal 26 Desulfurization absorption part 27 Oxidizing gas 29 Chimney 36 Extraction part 37 Recirculation part 38 1st H / C
39 2nd H / C 40 Belt filter 41 Circulating water tank 42 pH adjustment, heavy metal removal, flocculant addition part 43 1st H / C overflow 44 1st H / C underflow 45 2nd H / C overflow 46 2nd H / C underflow 47 Second hydrocyclone supply section 49 Gypsum 50 Drainage 51 Solid 52 Belt filter section discharge 60 Mercury adsorbent supply section 64 Mercury adsorbent and gypsum extraction section 65 Gypsum slurry return section 66 Mercury adsorbent and gypsum slurry separation section 67 Drainage Treatment equipment 68 Mercury adsorbent separation filter 69 Mercury adsorbent extraction section

Claims (10)

An absorption part of sulfur oxide provided with a spray nozzle for introducing an exhaust gas containing sulfur oxide from a combustion apparatus including a boiler and spraying an absorption liquid containing limestone; an absorption liquid reservoir provided at the lower part of the absorption part; Waste gas treatment of exhaust gas desulfurization system including an oxidizing gas supply section provided in the absorption liquid reservoir and an absorption liquid circulation path provided with a circulation pump for circulating the absorption liquid in the absorption liquid reservoir to the spray nozzle of the absorption section In the device
A filter portion having a pore size smaller than the particle size of the mercury adsorbent is provided at a position that bisects the absorption liquid reservoir in the vertical direction,
A mercury adsorbent supply unit is provided above the liquid level of the absorption liquid in the absorption liquid reservoir at the top of the filter unit,
A wastewater treatment apparatus, wherein a first absorbent extraction unit is provided at a lower part of the filter unit to extract the absorption liquid in the absorption liquid reservoir and supply it to the absorption liquid circulation path.   A second absorption liquid extraction part for extracting the absorption liquid from the upper part of the filter part in the absorption liquid reservoir is provided, and a separation part for mercury adsorbent and gypsum slurry is connected to the second absorption liquid extraction part. The waste water treatment apparatus according to claim 1.   2. A second absorption liquid extraction portion for absorbing liquid in an absorption liquid reservoir portion is provided at a lower portion of the filter portion, and a separation portion for gypsum and absorption liquid is connected to the absorption liquid extraction portion. The waste water treatment apparatus as described.   The waste water treatment apparatus according to claim 1, wherein a stirrer for stirring the absorbent is provided above the filter portion in the absorbent reservoir.   The pore size of the filter portion is smaller than the diameter formed by a ring formed by intersecting 90 ° cones on the particle surface from the center to the lower side with the center of the particle of the mercury adsorbent as a vertex. The waste water treatment apparatus according to claim 1. Absorbing liquid containing sprayed limestone is sprayed on the exhaust gas from the combustion equipment including the boiler to absorb sulfur oxide in the exhaust gas, and the absorbing liquid is stored in the absorbing liquid reservoir provided at the lower part of the absorbing section. In the exhaust gas desulfurization system wastewater treatment method, the oxidizing gas is supplied to the absorption liquid in the absorption liquid reservoir, and the absorption liquid in the absorption liquid reservoir is circulated and supplied to the absorption part and sprayed to contact the exhaust gas.
Mercury adsorbent is supplied to the absorption liquid in the absorption liquid reservoir from above the absorption liquid reservoir, and is absorbed by a filter having a pore size smaller than the particle diameter of the mercury adsorbent at a position that bisects the absorption liquid reservoir in the vertical direction. A wastewater treatment method comprising separating a mercury adsorbent supplied to a liquid reservoir and supplying an absorbent separated from the mercury adsorbent to the absorber.   The wastewater treatment method according to claim 6, wherein the mercury adsorbent is made of a chelate resin, and the polymer substrate of the chelate resin is any one of polyacryl, polyhydroxyethyl methacrylate, phenol resin, and polystyrene.   The waste water according to claim 6, wherein the mercury adsorbent comprises a chelate resin, and the coordination group of the chelate resin is any one of a thiol form, a dithiocarbamic acid form, an isothiuronium form, a dithizone form, and a thiourea form. Processing method.   The waste water treatment method according to claim 6, wherein the particle size of the mercury adsorbent is 300 μm or more.   The wastewater treatment method according to claim 6, wherein the mercury adsorbent is either activated carbon or an ion exchange resin.

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