JPH1099639A - Mixing treatment method of collected ash of heavy oil fuel burning boiler and exhaust gas desulfurization waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stably operable treatment method mixing collected ash of exhaust gas of a boiler using heavy oil as fuel and waste water generated from an exhaust gas desulfurizer to recover valuables such as vanadium or unburnt carbon and reducing the vol. of formed sludge. SOLUTION: In a mixing treatment method of collected ash and a waste water from an exhaust gas desulfurizer, collected dust (b) of boiler exhaust gas and waste water (a) from an exhaust gas desulfurizer are mixed and a reducing agent (c) is added to the resulting mixture to reduce pentavalent vanadium to tetravalent vanadium and unburnt carbon (i) is separated while magnesium hydroxide (e) and/or aq. ammonia are added to an unburnt carbon separated soln. (m) to adjust the pH of the soln. (m) to 3-9 to separate a highly conc. vanadium-containing sediment 9 and potassium hydroxide (h) or calcium oxide is further added to the separated soln. (h) to adjust the pH of the soln. to 9-12 and this soln. is distilled to recover aq. ammonia k'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating ash collected from a boiler using heavy oil as fuel and wastewater, and more particularly to a method for treating ash collected from a thermal power plant using such fuel. The present invention relates to a treatment method which is advantageously applied to treatment of waste water.

[0002]

2. Description of the Related Art Conventionally, in a process of treating flue gas discharged from a boiler facility for burning fossil fuels such as coal and heavy oil, such as a thermal power plant, a dust collector provided in a flue gas from the boiler is used. Ash (dust dust) discharged
And effluent from the flue gas desulfurization unit (exhaust effluent) are treated separately, and the collected ash is humidified, and the effluent and effluent is treated to a water quality that meets the environmental regulation values. It was discharged out of the system from the place. On the other hand, in recent years, thermal power plants and the like have been actively working on diversification of fuels, adding water to heavy oil containing high sulfur content, natural orinoco tar, or natural orinoco tar, mixing and emulsifying, and handling at room temperature. (E.g., 70% by weight of natural orinoco tar mixed with 30% by weight of fresh water and a small amount of a surfactant and emulsified) have attracted attention as new fuels. And called heavy oil). However,
There is little accumulation of technologies established as a method for treating dust ash generated from the combustion exhaust gas of these heavy oils.

[0003] The heavy oil has an ash content,
Due to the high content of nitrogen, sulfur and heavy metals, the characteristics of dust collection ash and drainage from heavy oil fired thermal power plants are the same as those of conventional heavy oil fired power plants. It is significantly different from the above, and a new response is required. In particular, the dust ash is difficult to handle because it has a hygroscopic property and a jetting property.In addition, the volume of the dust ash is larger than that of a conventional heavy oil fired boiler, and the bulk density of the dust ash is small. And the capacity of the storage facility increases. In addition, since ammonium (NH ₄ ⁺ ) is contained in a large amount in the dust collection ash and the wastewater, it is necessary to remove ammonium from the viewpoint of environmental measures for wastewater drainage and dust collection ash treatment.

[0004] As a method for treating dust ash generated from the combustion exhaust gas of heavy oil, the present inventors have mixed the dust ash of the boiler exhaust gas with the waste water, and added a reducing agent to add pentavalent. Is reduced to tetravalent vanadium, and magnesium hydroxide and / or aqueous ammonia are added to separate a high-concentration vanadium-containing precipitate formed at a pH of 3 to 9, and the separated liquid is further treated with calcium hydroxide or oxidized water. We have proposed a method of mixing dust collection ash and wastewater from a heavy oil fuel fired boiler, which comprises the steps of recovering ammonia by adding calcium to adjust the pH to 9 to 12 and distilling ammonia (Japanese Patent Laid-Open No. 8-11).
No. 7552). An overview of this method is shown in FIG.
The case where magnesium hydroxide is used for adjustment will be described as an example.

[0005] First, the drainage effluent a, the dust ash b and the ferrous salt c as a reducing agent are mixed in the mixing step 1 to make the dust ash b into a slurry (partially dissolved). Dust ash b varies depending on the operating condition of the boiler, but includes unburned carbon (C), vanadium (V), magnesium (Mg) and fixed ammonia (N
H ₄ ⁺ ) is 5 to 10% by weight, 2 to 5% by weight, 5
10 to 10% by weight and 5 to 10% by weight. The mixing ratio of the dust ash b is 5 to 40% by weight with respect to the drainage and drainage water a, and is preferably 30% by weight or less in order to increase the processing efficiency in the subsequent steps. As the ferrous salt c, ferrous chloride or ferrous sulfate can be used. The injection rate of the ferrous salt c may theoretically be an equimolar ratio with respect to the pentavalent vanadium (V) in the mixed solution d, but an equimolar ratio or more is added in consideration of the influence of coexisting ions. Is preferred. The drainage drainage a is a weakly acidic gypsum saturated liquid, but the pH of the mixed liquid d is 2
~ 3. In this step, pentavalent vanadium (V) is reduced to tetravalent, but because the pH is low, tetravalent vanadium (V) is reduced.
Is dissolved.

The mixed liquid d obtained in the mixing step 1 is sent to the solid-liquid separation step 3, where magnesium hydroxide @ Mg (O
H) ₂ e is added and mixed. The pH at this time is 3 ~
9, preferably 4 to 8. In this step, it is preferable to add the polymer flocculant f. As the polymer flocculant, a polymer flocculant used in ordinary wastewater treatment can be used. The precipitate generated by this operation is separated by settling to obtain a precipitate g and a supernatant h (separate). The precipitate g obtained in the solid-liquid separation step 2 contains 8% by weight or more of vanadium (V), and other components include unburned carbon (C), Fe,
Al and the like. The precipitate g can be separately used as a raw material for recovering vanadium. The supernatant h contains almost no vanadium (V) (the total vanadium (V) in the supernatant h is 1 mg / liter or less).

The precipitate g is discharged out of the system, and the supernatant h is sent to the next pH adjustment step 4. In pH adjustment step 4, the pH is adjusted to 9 by adding calcium hydroxide {Ca (OH) ₂ } n.
After adjusting to １２12, it is sent to the distillation step 5. The pH of this solution is maintained at 9 to 12 for the production of gypsum and magnesium hydroxide and for increasing the efficiency of the next operation. In the distillation step 5, in addition to steam stripping, ordinary distillation operations such as vacuum distillation can be applied. By this operation, the ammonia gas k is separated from the liquid.
Will be collected as The recovery rate of ammonia in the distillation step 5 and the condensation step 6 is 95% or more of the fixed ammonia amount contained in the mixture d. The recovered ammonia water k 'is carried out of the system and can be used for neutralizing flue gas. The treatment liquid 1 remaining after the distillation in the distillation step 5 is a slurry of gypsum and magnesium hydroxide precipitated in the pH adjustment step 4, and is carried out of the system and separately treated.

By using magnesium hydroxide as an alkali agent in the solid-liquid separation step 3 as described above, the content of vanadium (V) in the precipitate g can be increased to 8% by weight or more. Further, in the pH adjustment step 4, calcium hydroxide ｛C
Since a (OH) ₂ } is used, the degree of supersaturation of gypsum in the pH adjustment step 4 and the distillation step 5 can be reduced, so that the generation of gypsum scale can be suppressed.

[0009]

According to this method, it is possible to stably treat dust collection ash and wastewater from a heavy oil fuel fired boiler, and to reduce the volume of waste and recover valuable resources. Although possible, the precipitate obtained in the solid-liquid separation step contains unburned carbon and insoluble components in dust ash in addition to vanadium hydroxide. Therefore, the purity improvement process for effectively using vanadium becomes complicated. In view of the above technical level, the present invention reduces the volume by mixing dust ash generated from a dust collector provided in an exhaust gas flue of a boiler using the heavy oil as fuel and wastewater generated from a flue gas desulfurizer. Another object of the present invention is to provide a method capable of recovering valuable materials such as vanadium and unburned carbon with high purity, reducing the volume of generated sludge, and operating stably.

[0010]

According to the present invention, there is provided (1) a dust collecting ash collected by a dust collecting device provided in an exhaust gas flue of a boiler using heavy oil as a fuel and a gas generated from a wet flue gas desulfurization device. Mixing with wastewater to be mixed, adding a reducing agent for reducing pentavalent vanadium to tetravalent vanadium and mixing the mixture, and separating unburned carbon from the mixed liquid obtained in the mixing step A solid-liquid separation step of adding magnesium hydroxide and / or aqueous ammonia to the unburned carbon separation liquid from the unburned carbon separation step to adjust the pH to 3 to 9, and separating the generated high-concentration vanadium-containing precipitate. A pH adjustment step of adding calcium hydroxide or calcium oxide to the separated liquid from the solid-liquid separation step to adjust the pH to 9 to 12, and a distillation step of distilling and concentrating the liquid after the pH adjustment. Generated in the distillation step Mixing processing method of the exhaust de drainage and heavy oil fuel boiler fly ash characterized by comprising is composed of a condensation step of recovering ammonia water to condense the vapor,
(2) A magnesium hydroxide separation step is provided for separating calcium sulfate and magnesium hydroxide in the distillation residue concentrated in the distillation step, and the magnesium hydroxide obtained in the magnesium hydroxide separation step is subjected to the solid-liquid separation. The dust collection ash of the heavy oil fuel-fired boiler according to the above (1), which is used as part or all of the magnesium hydroxide added to the unburned carbon separation liquid discharged from the unburned carbon separation step in the process. (3) The ammonia water collected in the condensation step is used as part or all of the ammonia water added to the unburned carbon separation liquid from the unburned carbon separation step in the solid-liquid separation step. (1) the method for mixing the collected ash of the heavy oil fuel-fired boiler with the drainage and drainage of (1), and (4) the pH of the mixed solution obtained in the mixing step is 3 Wherein when obtaining, characterized in that the adjusted to 3 or less and the pH by adding sulfuric acid (1) to (3)
This is a method of mixing and collecting the collected ash and wastewater from the heavy oil fuel fired boiler.

In the present invention, the heavy oil includes heavy oil containing sulfur, natural orinoco tar, emulsion fuel obtained by adding and mixing water with natural orinoco tar, and residual oil from a petroleum refining process. .

In the method of the present invention, after the ash and waste water are mixed and slurried (partially dissolved) to reduce the volume and improve the operability such as fluidity, the vanadium in the slurry is removed. For recovery, a reducing agent for reducing pentavalent vanadium to tetravalent vanadium is added and mixed. At this time, the pH of the mixture
Is greater than 3, the pH is adjusted to 3 or less by adding sulfuric acid. The present invention is characterized by separating undissolved unburned carbon (including insoluble components contained in dust ash and insoluble components such as Fe and Al hydroxides) at this stage.

[0013] Magnesium hydroxide and / or aqueous ammonia are added to the separated liquid from which the unburned carbon has been separated to adjust the pH to 3-9.
To make the tetravalent vanadium precipitate as tetravalent vanadium hydroxide. Here, other metal hydroxides corresponding to the increase in pH from the time of the separation of the unburned carbon precipitate.
e, the concentration of vanadium in the metal hydroxide is high because insoluble components such as hydroxides of Al and the like at pH 3 or less are removed. A precipitate containing a high concentration of the precipitated vanadium hydroxide is separated, and calcium hydroxide or calcium oxide is further added to a separation solution containing no vanadium hydroxide to adjust the pH to 9 to 12, and the sulfate ion and Calcium sulfate, reacted with magnesium ions,
Magnesium hydroxide is formed and then concentrated by evaporating the water by distillation. When calcium hydroxide or calcium oxide is added, the ammonium ions in the liquid become ammonium hydroxide, which are desorbed from the liquid in the distillation step and once transferred to the gas phase, and then condensed water of steam generated in the distillation step Again and recovered as ammonia water. The ammonia water collected here can be used as part or all of the alkali agent for vanadium precipitation.

Although the distillation residue may be carried out of the system and treated separately, it is desirable to provide a magnesium hydroxide separation step after the distillation step to separate and recover calcium sulfate and magnesium hydroxide. When magnesium hydroxide is used as an alkali agent for vanadium precipitation in the solid-liquid separation step, it is preferable to reuse the magnesium hydroxide separated here as part or all thereof. After separating calcium sulfate and magnesium hydroxide, the liquid containing no solids is taken out of the system and treated.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

1. Reduction and precipitation of vanadium in the mixing step, the unburned carbon separation step, and the solid-liquid separation step are performed by the following actions. (1) V in the liquid phase of the mixture of dust ash and wastewater
(Pentavalent) is reduced to V (tetravalent) by Fe (divalent) added as a reducing agent at a pH of 3 or less.
This main reaction occurs in a dissolved state and is represented by the following formula.

Embedded image V ₂ O ₅ → V ₂ O ₇ ^4- (pentavalent) or VO ₂ ⁺ (pentavalent) (dissolution reaction) (1) 1/2 V ₂ O ₇ ^4- (pentavalent) → VO ₂ ( (Valent) (dissolved) (2) Fe ²⁺ (divalent) → Fe ³⁺ (trivalent) (3) Here, divalent iron is mentioned as an example of the reducing agent, but pentavalent vanadium is used as a reducing agent. Other reducing agents can be used without any problem as long as they can be reduced to a low value and do not affect the treatment method. The unburned carbon is insoluble in the acidic solution and is removed in the unburned carbon separation step.

(2) The unburned carbon separation liquid of the above item (1)
Magnesium hydroxide @ Mg (O
H) ₂ } or aqueous ammonia (NH ₄ OH)
When coagulation and sedimentation treatment is performed as H3 to H9, VO (O
H) ₂ (tetravalent) precipitates.

Embedded image VO ₂ (tetravalent) + Mg (OH) ₂ → VO (OH) ₂ ↓ + Mg ²⁺ (4) VO ₂ (tetravalent) + 2NH ₄ OH → VO (OH) ₂ ↓ + 2NH ₄ ⁺ (5)

(3) Since magnesium hydroxide {Mg (OH) ₂ } or aqueous ammonia (NH ₄ OH) is used as the alkaline agent in the above item (2), hydroxide ions (OH ⁻ ) are dissolved. It does not react with the Ca ions and is used only for neutralizing acidic components (such as H ⁺ ). In parallel with this, magnesium ion (Mg ²⁺ ) or ammonium ion (NH ₄ ⁺ ) reacts with sulfate ion (SO ₄ ²⁻ ) to make magnesium sulfate (MgSO ₄ ) or ammonium sulfate {(NH ₄ ) ₂ SO ₄ }. However, this substance is dissolved in the solution due to its high solubility, and VO (OH) ₂
Even after the solid-liquid separation, they are present in the liquid and supplied to the next pH adjustment step. The reaction here is as follows.

Embedded image H ⁺ + OH ⁻ → H ₂ O (6) Mg ²⁺ + SO ₄ ^2- → MgSO ₄ (7) 2NH ₄ ⁺ + SO ₄ ^2- → (NH ₄ ) ₂ SO ₄ (8)

2. Functions in the pH adjustment step, distillation step, condensation step and magnesium hydroxide separation step. In the pH adjustment step, calcium oxide (CaO) or calcium hydroxide {Ca (OH) ₂ } is used as an alkaline agent, and thus has the following effects.

(1) In the pH adjustment step, calcium oxide (CaO) or calcium hydroxide {Ca (OH) ₂ } is added to the supernatant of the coagulation sedimentation step to adjust the pH to 9 to 12, whereby gypsum is obtained. (Calcium sulfate) precipitates and the gypsum supersaturation of the liquid decreases. In parallel with this, dissolved magnesium ions (Mg ²⁺ ) precipitate and precipitate as magnesium hydroxide {Mg (OH) ₂ }. Even when only ammonia water is used as the alkaline agent in the solid-liquid separation step, magnesium hydroxide precipitates because the dust ash contains Mg.

(2) When this liquid is distilled, the ammonia in the supernatant liquid changes from a liquid to a gas by the reaction shown in equations (9) and (10), and when cooled, the ammonia gas is produced by the reaction shown in equation (11). The liquid condenses into a liquid (aqueous ammonia), and the aqueous ammonia is recovered. Part or all of the recovered ammonia water can be reused as part or all of the alkali agent for vanadium recovery in the solid-liquid separation step.

Embedded image NH ₄ ⁺ + OH ⁻ → NH ₄ OH (liquid) (9) (OH ⁻ is supplied from calcium hydroxide) NH ₄ OH (liquid) → NH ₃ (gas) ↑ + H ₂ O (10) NH ₃ (gas) + H ₂ O → NH ₄ OH (liquid) (11)

(3) In the distillation step, the liquid is concentrated.
As a result, the dissolved gypsum newly precipitates and becomes gypsum scale, and there is a concern that the heat transfer rate in the distiller decreases. However, as described in the above item (1), the precipitated solid gypsum is contained in the supply liquid of the distiller. Is present and the gypsum becomes a seed crystal, so that the problem due to the gypsum scale does not occur.

(4) Gypsum precipitated in the pH adjustment step and gypsum precipitated due to concentration of the liquid in the distillation step and magnesium hydroxide {Mg (OH) ₂ } precipitated in the pH adjustment step are included in the residual liquid in the distillation step. It is included. This residual liquid may be carried out of the system and treated separately. However, it is preferable that the gypsum and magnesium hydroxide precipitated by providing a magnesium hydroxide separation step are separated from the supernatant and reused. The separation step is composed of two steps: a step of separating gypsum and magnesium hydroxide, and a step of separating magnesium hydroxide from a liquid. Both types of separation are performed using centrifugal force using a liquid cyclone or sedimentation centrifuge, etc.
Crystals are separated by adjusting the difference in crystal size and the applied centrifugal force in the separator. In addition, an ordinary solid-liquid separation method such as weight classification or suspension classification can be applied according to the state of the liquid.

(5) By returning part or all of the separated magnesium hydroxide to the solid-liquid separation step, it can be reused as part or all of the alkali agent for vanadium recovery.

[0024]

【Example】

(Embodiment 1) One embodiment of the present invention will be described with reference to FIG. This example uses magnesium hydroxide as an alkali agent in the solid-liquid separation step. First, the drainage effluent a, the dust ash b, and the ferrous salt c as a reducing agent are mixed in the mixing step 1 to turn the dust ash b into a slurry (partially dissolved). Dust ash b varies depending on the operating condition of the boiler,
Unburned carbon (C), vanadium (V), magnesium (M
g) and fixed ammonia (NH ₄ ⁺ ) are 5 to 1 each.
0% by weight, 2-5% by weight, 5-10% by weight and 5-10%
% By weight. The mixing ratio of the dust ash b is 5 to 40% by weight with respect to the drainage and drainage water a, and is preferably 30% by weight or less in order to increase the processing efficiency in the subsequent steps. Also the first
As the iron salt c, ferrous chloride or ferrous sulfate can be used. The injection rate of the ferrous salt c may theoretically be an equimolar ratio with respect to the pentavalent vanadium (V) in the mixed solution d. It is preferred to add.

The drainage drainage a is a weakly acidic gypsum saturated liquid, but usually the pH of the mixed liquid d is 2-3. If the pH at this stage exceeds 3, the pH is adjusted to 3 by adding sulfuric acid.
Hereinafter, it is preferably adjusted to 2-3. In this step, pentavalent vanadium (V) is reduced to tetravalent, but tetravalent vanadium (V) is dissolved due to low pH. The mixed liquid d obtained in the mixing step 1 is sent to the unburned carbon separation step 2, where the unburned carbon i is separated. Unburned carbon i contains 95% by weight or more of carbon (C), and other components are Si, Al
And the like. This unburned carbon i can be used separately as a raw material for carbon or the like.

The unburned carbon separation liquid m obtained in the unburned carbon separation step 2 is sent to the solid-liquid separation step 3, where magnesium hydroxide {Mg (OH) ₂ } e is added and mixed. The pH at this time is 3 to 9, preferably 4 to 8. In this step, it is preferable to add the polymer flocculant f. As the polymer flocculant, a polymer flocculant used in ordinary wastewater treatment can be used. The precipitate generated by this operation is separated by settling to obtain a precipitate g and a supernatant h (separate). The precipitate g obtained in the solid-liquid separation step 3 contains 30% by weight or more of vanadium (V), and other components are Fe, C
a, Mg and the like. The precipitate g can be separately used as a raw material for recovering vanadium. The supernatant h contains almost no vanadium (V) (the total vanadium (V) in the supernatant h is 1 mg / liter or less).

The precipitate g is discharged out of the system, and the supernatant h is sent to the next pH adjustment step 4. In pH adjustment step 4, the pH is adjusted to 9 by adding calcium hydroxide {Ca (OH) ₂ } n.
After adjusting to １２12, it is sent to the distillation step 5. The pH of this solution is maintained at 9 to 12 for the production of gypsum and magnesium hydroxide and for increasing the efficiency of the next operation. In the distillation step 5, in addition to steam stripping, ordinary distillation operations such as vacuum distillation can be applied. By this operation, the ammonia gas k is separated from the liquid.
Will be collected as The recovery rate of ammonia in the distillation step 5 and the condensation step 6 is 95% or more of the fixed ammonia amount contained in the mixture d. The recovered ammonia water k 'is carried out of the system and can be used for neutralizing flue gas. The treatment liquid 1 remaining after the distillation in the distillation step 5 is a slurry of gypsum and magnesium hydroxide precipitated in the pH adjustment step 4, and is carried out of the system and separately treated.

By using magnesium hydroxide as an alkali agent in the solid-liquid separation step 3 as described above, the content of vanadium (V) in the precipitate g can be increased to 30% by weight or more. Further, since calcium hydroxide {Ca (OH) ₂ } is used in the pH adjustment step 4, the degree of supersaturation of gypsum in the pH adjustment step 4 and the distillation step 5 can be reduced, so that the generation of gypsum scale can be suppressed.

(Embodiment 2) A second embodiment of the present invention will be described with reference to FIG. In this example, a magnesium hydroxide separation step is provided in addition to the process of Example 1, and the recovered magnesium hydroxide is reused in the solid-liquid separation step. First, in the same manner as in the first embodiment, the drainage / drainage a and the dust ash b are treated in each of the mixing step 1 to the condensation step 6. At this time, magnesium hydroxide e separated in a magnesium hydroxide separation step 7 described below is used as magnesium hydroxide {Mg (OH) ₂ } e used in the solid-liquid separation step 3, but otherwise the same as in Example 1. .
Next, the distillation residue o in the distillation step 5 is separated into a gypsum slurry p and magnesium hydroxide e in a magnesium hydroxide separation step 7. In the magnesium hydroxide separation step 7, separation means such as a liquid cyclone and a sedimentation centrifuge can be used. The separated magnesium hydroxide e is returned to the solid-liquid separation step 3 in the preceding step. The treatment liquid 1 separated in the magnesium hydroxide separation step 7 is subjected to an appropriate solidification treatment and then discharged out of the system. In addition, when magnesium hydroxide used in the solid-liquid separation step 3 alone is insufficient at the beginning of the reaction or during the reaction, it may be appropriately supplied from outside the system.

(Embodiment 3) A third embodiment of the present invention will be described with reference to FIG. This example uses ammonia water as an alkaline agent in the solid-liquid separation step 3. In the same manner as in the first embodiment, the drainage / drainage a and the dust ash b are treated in each of the mixing step 1 to the condensation step 6. At this time, the aqueous ammonia k ′ obtained by recovering the alkali agent used in the solid-liquid separation step 3 in the condensation step 6 is used. The remaining ammonia water is discharged out of the system. The distillation residue o in the distillation step 5 is separated into a gypsum aqueous slurry p and magnesium hydroxide e by magnesium hydroxide separation 7. The magnesium hydroxide is carried out of the system and reused, or is subjected to an appropriate solidification treatment together with the treatment liquid 1 after the separation of gypsum and magnesium hydroxide in the magnesium hydroxide separation step 7, and then discharged out of the system. Is done. In addition, when the ammonia water used in the solid-liquid separation step 3 is insufficient with only the recovered product at the beginning of the reaction or during the reaction, it may be appropriately supplied from outside the system.

[0031]

According to the present invention, the following effects are obtained in addition to the effects of the prior art shown in FIG. (1) Valuables such as vanadium (V) and unburned carbon (C) can be recovered with high purity from dust ash and wastewater, and resources can be reused. (2) By providing an unburned carbon separation step before the solid-liquid separation step, the vanadium (V) content in the precipitate obtained in the solid-liquid separation step is 8% by weight or more in the prior art of FIG. However, it can be increased to 30% by weight or more. This facilitates the operation of further increasing the purity for use as a valuable resource. (3) The unburned carbon separated in the unburned carbon separation step can be reused as a raw material for carbon, but can be incinerated even if not reused, and has the effect of reducing the volume of waste. .

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of the present invention.

FIG. 2 is a flowchart showing a second embodiment of the present invention.

FIG. 3 is a flowchart showing a third embodiment of the present invention.

FIG. 4 is a flowchart showing an example of the related art.

Claims (4)

[Claims] A pentavalent vanadium is obtained by mixing dust ash collected by a dust collector provided in a flue gas flue of a boiler using heavy oil as fuel and wastewater generated from a wet flue gas desulfurization unit. A mixing step of adding and mixing a reducing agent for reducing the carbon to tetravalent vanadium, an unburned carbon separation step of separating unburned carbon from the mixture obtained in the mixing step, and a step of leaving the unburned carbon separation step. A solid-liquid separation step of adding magnesium hydroxide and / or ammonia water to the unburned carbon separation liquid to adjust the pH to 3 to 9, and separating the generated high-concentration vanadium-containing precipitate; A pH adjusting step of adjusting the pH to 9 to 12 by further adding calcium hydroxide or calcium oxide to the liquid, a distillation step of distilling and concentrating the liquid after the pH adjustment, and condensing vapor generated in the distillation step And recover ammonia water And a condensing step for mixing the collected ash and the wastewater from the heavy oil fuel fired boiler. 2. A magnesium hydroxide separation step for separating calcium sulfate and magnesium hydroxide in the distillation residue concentrated in the distillation step, wherein the magnesium hydroxide obtained in the magnesium hydroxide separation step is separated from the solidified magnesium hydroxide. 2. A heavy oil fuel-fired boiler according to claim 1, wherein the magnesium hydroxide is used as part or all of magnesium hydroxide added to the unburned carbon separation liquid discharged from the unburned carbon separation step in the liquid separation step. A method of mixing ash and wastewater. 3. The method according to claim 1, wherein the ammonia water recovered in the condensation step is used as part or all of the ammonia water added to the unburned carbon separation liquid discharged from the unburned carbon separation step in the solid-liquid separation step. A method for mixing and discharging waste ash and wastewater from a heavy oil fuel fired boiler according to claim 1. 4. The method according to claim 1, wherein when the pH of the mixed solution obtained in the mixing step exceeds 3, the pH is adjusted to 3 or less by adding sulfuric acid. A method of mixing and collecting dust and ash from heavy oil fuel fired boilers.