JPS62298489A - Method for recovering ammonium metavanadate from petroleum combustion ash - Google Patents

Abstract

PURPOSE:To efficiently deposit and recover ammonium metavanadate of high purity by mixing a petroleum combustion ash with water, heating the mixture, adding ammonia thereto to specific pH, supplying an oxidizing agent thereto to separate an insoluble-component and cooling the liquid part. CONSTITUTION:The combustion ash captured by a dust collector, etc., provided in an exhaust gas flue of a boiler, etc., using petroleum fuel is mixed with the water to prepare a slurry. The slurry is heated to >=70 deg.C and the ammonia is added to the slurry to adjust the pH to 7-9. The oxidizing agent such as air is supplied to such slurry, while the temp. in the above-mentioned stage is maintained, the insoluble-component is separated and the liquid part is cooled down to <=40 deg.C to allow the ammonium metavanadate to deposit. The high- purity ammonium metavanadate is economically and efficiently recovered in such short stage.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for economically recovering high-purity ammonium metavanadate by wet processing petroleum combustion ash. It is.

[Conventional technology]

The present inventors previously proposed a method for recovering various components of petroleum-based combustion ash as economically valuable materials in Japanese Patent Application No. 60-9153.
Although he applied for a patent for the invention of No. 4! FII No. 1983-9154, he has continued to conduct research to establish a more rational method.

[Problem that the invention seeks to solve]

In the above method of wet processing of combustion ash, combustion ash and water are mixed to form a slurry, and at the same time, an auxiliary agent such as an acid or alkali is added to promote the dissolution of metals in the combustion ash. After separating the carbon, valuable materials such as metals were recovered from the liquid part through various processes. However, this method requires a large amount of auxiliary agents (acid, alkali, etc.) when dissolving the metal, and has the disadvantage that the process up to the recovery of ammonium metavanadate is long.

The present inventors have been intensively researching methods to solve these drawbacks and, in particular, to efficiently recover vanadium, which is the most valuable metal among the metals in combustion ash.

[Means for solving problems]

As a result, the inventors discovered that the following method can simultaneously promote the dissolution of metals (mainly sodium) in combustion ash, oxidize vanadium and iron, and generate ammonium metavanadate, and have achieved the present invention. .

That is, the present invention provides a method for recovering ammonium metavanadate by wet-processing combustion ash collected by a dust collector installed in the flue gas flue of a gayler or the like using petroleum-based fuel. A method for recovering ammonium metavanadate from petroleum-based combustion ash is characterized by carrying out the steps of ) to (4).

(1) Combustion ash is mixed with water to form a slurry.

(2) The slurry is heated to 70° C. or higher, the pH is adjusted to 7 to 9 in the presence of ammonia, and an oxidizing agent is supplied.

(3) Separate insoluble matter while maintaining the temperature in step (2) above.

(4) Cool the liquid part to 40° C. or lower to precipitate ammonium metavanadate.

In the present invention, petroleum-based combustion ash refers to dust generated when petroleum-based fuels such as heavy oil, asphalt, petroleum pitch, petroleum coke, or natural heavy oil are burned in gailers, and some of them are However, most of the dust is collected by dust collectors. The composition of petroleum-based combustion ash varies depending on the type of fuel, combustion conditions, whether additives are injected into the gaylor and/or dust collector, etc., but it is roughly as shown in Table 1.

Among the components of the combustion ash in Table 1, the contents of NH4 and Mg vary greatly depending on the presence or absence of additives and the amount added.

That is, in order to prevent corrosion of dust collectors and the like due to sulfuric acid gas (SO,) generated in the boiler, ammonia is generally injected, but in such a case, the NH4 content increases. The injected ammonia reacts with sulfuric acid gas to mainly generate ammonium sulfate ((NH4)2So4), and a portion to generate acidic ammonium sulfate (NH, H3O4). Hereinafter, both will be collectively referred to as ammonium sulfate.

Furthermore, in order to prevent corrosion within the M iller, it is often done to inject magnesium hydroxide or the like, but in such a case, the Mg content increases.

Although it is not clear what kind of compounds the metal components are present in the combustion ash, it is estimated as follows. That is, most of them are sulfates and/or double salts of sulfates and ammonium sulfate (for example, VO304tNISO4+MgSO4e
Fa SO4+ N I SO4” (dish 4) 2
SO4* SuesO4" (洲,)2so4etc.) Teari,
Some are oxides (e.g. EhaV, 05.NIO.

MgO, etc.), and some of them are also believed to be metal oxide complexes (eg, V2O, .nMgo, etc.). The valence of Nonazicum is a mixture of 4 and 5 valences. and,
According to the method of the present invention, there are the following advantages.

(1) Ammonium metavanadate can be recovered in a short process. The fruiting device can be simplified and is extremely economical.

(2) A high elution rate and recovery rate of vanadium can be obtained with a small amount of auxiliary agent (acid, alkali, etc.) used.

(3) High purity ammonium metavanadate can be obtained without special treatment.

(4) From the liquid part after removing ammonium metavanadate,
j9, Nl by applying the method described in Japanese Patent Application No. 60-9154.

NH4, S04, etc. can also be recovered as valuable materials,
Furthermore, by recycling the water used within the system, there is virtually no waste water, and even if there is, it can be reduced to a very small amount.

[Effect]

Hereinafter, the present invention will be explained in detail according to steps (1) to (4).

(1) Process of mixing combustion ash with water to form a slurry.

The main purpose of this process is to slurry the combustion ash to make it easier to transfer to the next process, but at the same time, most of the ammonium sulfate and some of the metals such as vanadium, nickel, iron, and magnesium are removed. Elute.

The exudation properties of metals and the existence form of eluted components in the slurry vary depending on the slurry, but the general outline is as follows. That is, sulfate and/or a double salt of sulfate and ammonium sulfate are slightly eluted, but oxides or metal oxide complexes are eluted only in small amounts. The metals (especially sodium) are sufficiently eluted in this step, and are further eluted in the next step.

The existence form of the eluted component in the slurry is NH4°so4. when the - of the slurry is about 3 or less. vo (
v is quadrivalent), M, 2+ , N+ 2+ , F, 2+
(F. is divalent) or a very small amount is in the form of ions such as vO□ (V is pentavalent). When the - of the slurry is around 3 to 9, tetravalent vanadium will not become a precipitate of VO(OH)2, and divalent iron will be partially oxidized by F@(OH)2 and dissolved oxygen in water. a small amount of FsO(OH) and/or F・(O
R), resulting in the precipitation of. As will be described later, VO(OH)2 can be dissolved in the next step.

When the pH of the slurry is further increased, in addition to the precipitation of iron and vanadium compounds, nickel and magnesium also result in the precipitation of N1(OR)2 and Mg(OH)2, respectively.

Since these cannot be easily understood in the next step, increasing the amount of these is not preferable because it may deteriorate the quality of carbon or cause loss of N1, as will be described later.

The insoluble matter is mainly carbon containing metals that remain without being eluted, such as vanadium, nickel, iron, and magnesium. The water used may be acidic, neutral, or alkaline; however, since the slurry will be made alkaline in the next step, strongly acidic water is not a good idea as it will increase the amount of neutralizing agent used; Extremely alkaline conditions are also not a good idea as they generate a large amount of insoluble precipitate.

Therefore, it is appropriate that the - value of the slurry is about 2 to 9, but it is not necessarily limited to this.

Practically speaking, it is preferable to recycle the water separated when valuables are recovered from the slurry in order to reduce the amount of waste water.

(2) A step of heating the slurry to 70° C. or higher, supplying ammonia to adjust the pH to 7 to 9, and supplying an oxidizing agent.

This process promotes the elution of vanadium in the combustion ash, and further converts the eluted tetravalent vanadium into pentavalent and divalent iron into trivalent.
The purpose is to facilitate the precipitation of the respective metal salts.

The heating, adjustment, and oxidizing agent supply operations included in this step may be performed in any order or at the same time, as long as the oxidizing agent is supplied last.

These oxidations are easily carried out when - is 7 or more (alkaline side), but the alkaline side is also suitable for elution of vanadium from combustion ash. That is, since vanadium oxides (for example, V2O5) have high solubility on the alkaline side, vanadium oxides (for example, V2O,) that were eluted in the previous step and were difficult to dissolve can also be eluted. Furthermore, since the temperature is kept high in this step, it also has the effect of increasing the metal elution rate.

- is too high, and if it is too high, a large amount of ammonia is required, which is not a good idea, so - is preferably 7 to 9, more preferably 8 to 9. As a neutralizing agent for the slurry, NH4 is essential in order to precipitate ammonium metavanadate.
Ammonia is most suitable, but if sufficient ammonium sulfate is present, an alkali such as caustic soda can also be used since it generates ammonia by reaction with ammonium sulfate.

As the oxidizing agent, air, oxygen, ozone, hydrogen peroxide, etc. can be used, but it is economically preferable to use air.

When the voice is 7 to 9 and the metal is oxidized, iron is Fed (OH)
and/or F.(OH), which precipitates. Silica also becomes an insoluble substance (8102). Vanadium, like anthonium metapanadate, is mostly dissolved in the liquid part. The reaction that produces ammonium metavanadate is thought to be as follows.

Before oxidation VO+20H'-→VO(OH)2-, ■ During oxidation VO(OH)2-)-OH"+"02-+VOi+
7H20-@VO2" + 201" -* VO5"
+H20-・θNH+VO″″→Nu4VO, 61,
@As mentioned above, when the - of the slurry is about 3 or more, the VO(OH)2 precipitate generated in the reaction of Φ is oxidized and dissolved in the reaction of @, and further, the reaction of O forms ammonium metavanadate ( Nu, VO,) is generated. In order to separate ammonium metavanadate from insoluble matter in the next step, it is necessary to dissolve ammonium metavanadate. In order to increase the solubility of ammonium metavanadate, it is preferable to maintain the temperature at a high temperature, more preferably at 70°C or higher, and more preferably at 85 to 95°C.

Ammonium sulfate concentration also has a large effect on solubility. It is preferable that the ammonium sulfate concentration is lower, so that the solubility is not higher, but in the subsequent step of precipitating ammonium metavanadate, it is preferable that the ammonium sulfate concentration is higher. Therefore, the ammonium sulfate concentration in the liquid part is 7 to 30
w*'16, preferably 10 to 20 wL% is suitable.

(3) As is clear from the explanation of the pre-process for separating insoluble materials, the main insoluble materials are panadicum, which does not dissolve, cardan containing metals such as nickel, iron, and magnesium, and iron precipitates [F. 0 (OH)
and/or F.(OH), ], silica mixed in ammonium metavanadate is also insoluble (810
2).

Ammonium metavanadate, NH4゜80 in the liquid part
"", Nt", M12+, etc. are dissolved. In order not to reduce the recovery vehicle of ammonium metavanadate, it is necessary to separate the insoluble materials at the temperature maintained in the previous step, that is, at a temperature of 70°C or higher. When the temperature decreases, a portion of ammonium metavanadate precipitates and is separated along with insoluble matter, resulting in loss.Usually, iron precipitates and silica precipitates are small in particle size, and separation requires a long time. However, according to the method of the present invention, since it is a mixture with cardan, carmen acts as a separation aid and can be separated very easily.As a separator, a decanter is of course However, a filtration method can also be adopted.

In the case of the filtration method, the leakage of insoluble matter into the liquid part can be made substantially zero, and the purity of ammonium metavanadate can be further improved.

(4) A step of cooling the liquid part to 40° C. or lower to precipitate ammonium metavanadate.

Ammonium metavanadate precipitates more easily at lower temperatures and at higher concentrations of ammonium sulfate. Therefore, it is necessary to use a special low temperature with a low ammonium sulfate concentration. When the ammonium sulfate concentration is about 10 to 30 wt%, the temperature is 40°C or less, preferably 20 to 30°C.
This is done below.

By separating the precipitated ammonium metavanadate from the liquid part and further washing with cold water, highly pure (approximately 99% or more) ammonium metavanadate can be obtained.

From this liquid part, by applying the method proposed in the above-mentioned Japanese Patent Application No. 60-9154 and Japanese Patent Application No. 60-9154, more valuable materials can be recovered, and when the valuable materials are recovered, they can be separated. The water thus produced can be recycled and used as water when slurrying the combustion ash of the present invention.

That is, according to the method disclosed in Japanese Patent Application No. 60-9153, sulfuric acid is added to the liquid part, nickel is converted into nickel ammonium sulfate, calcium hydroxide or calcium oxide is added to the F liquid, S04 is converted into gypsum, and NH4 can be recovered as ammonia.

According to a method in Japanese Patent Application No. 60-9154, calcium hydroxide or calcium oxide is added to the liquid part, and S04 can be recovered as gypsum, NH4 as ammonia, and nickel as nickel hydroxide. .

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following embodiments as long as they do not exceed the gist of the invention.

Example I The combustion ash captured by the electrostatic precipitator installed in the flue of a galler burning fuel oil C was treated according to the method of the present invention, and the results were as follows:

The composition of the combustion ash used in this example was as follows.

Composition (wt%) Carbon” 17.67 @NH4~M
g is 41g of NH, o is all carbon, SO258,3 V 2.23 Ni 1.66 F, 0.54 Mg O,60 (total > (100,00) (1) 500kg of combustion ash and pure A slurry was prepared by mixing 2,000 g of water at room temperature.The voice of the slurry at this time was 2.8.

In order to analyze the amount of metal eluted during slurrying, approximately 100 CC of the slurry was sampled, and the liquid part after carbon was analyzed by p. ) was found to be almost 100% for NH4,804, 57% for ■, 34% for N1, and 38% for Fe.
1%, and Mg was 45%.

(2) Next, blow steam into the slurry and raise the temperature to 85℃.
25qII of ammonia water was added to adjust the pH to 8.
Adjusted to 5.

Subsequently, air was blown into the slurry at a flow rate of 100 m"/H for 2 hours, during which time the temperature was maintained at 85 °C and the pH at 8.5.
Steam and 251% ammonia water were replenished to maintain the temperature. After 2 hours of air blowing, the amount of slurry increased due to steam condensation, etc., to approximately 2,750 kl? It became.

In order to analyze the amount of metal eluted, approximately 100Ω of the slurry was sampled, and the insoluble matter was separated by F at 85℃, and the liquid part was analyzed to determine the elution rate.
A significant improvement in the dissolution rate was observed. Nl was 34 inches, the same as in the previous process. F. was 0.1- or less and hardly eluted into the liquid part. This means that, as already mentioned above, what was eluted as F in the previous step becomes iron precipitate (F@0(OH) and/or F as a result of oxidation on the alkali side in this step). (OH), ). M. was 49 inches, which was only a slight improvement compared to the previous process.

(3) Next, the slurry was continuously fed to a centrifugal filter to separate the insoluble matter and the liquid part. In order to maintain the temperature, the centrifuge-filter and slurry supply line were completely insulated with steam tracing, and the liquid temperature at the outlet of the centrifuge-filter was able to be maintained at 83°C. The separated insoluble matter (mainly carbon) was washed with industrial water to obtain a carbon cake with a water content of 50%. The composition (wt) of impurities in the carbon after drying was NH40,07,5o40.15 and ash content 9.0%.

(4) Next, liquid F was placed in a container equipped with a cooling coil and cooled to 30'C while stirring to precipitate ammonium metavanadate. Cooling time was 3 hours. Subsequently, ammonium metavanadate was separated using a centrifugal filter and washed with industrial water, resulting in 8.9 kl of ammonium metavanadate with a water content of 19%. I got it. When dried and analyzed, the purity was extremely high at 99.3%, and the composition of impurities (wt%) was traces of SO4, NiO
,031Fj@0.04%, SlO,081L' were present.

The filtrate was obtained about 2.2001, and the dissolved component concentration (
kg/1001! F solution) is NH44,4,5o412.
7, Vo, 009, N10.12, Fe is O, Mg0
．． It was 064.

〔Effect of the invention〕

As mentioned above, the present invention has the following excellent effects (1) to (4).

(1) Ammonium metavanadate can be recovered in a short process. The fruiting device can be simplified and is extremely economical.

(2) A high elution rate and recovery rate of vanadium can be obtained with a small amount of auxiliary agent (acid, alkali, etc.) used.

(3) High purity ammonium metavanadate can be obtained without special treatment.

(4) N1, NH4, SO2, etc. can also be recovered as valuables from the liquid part after ammonium metavanadate has been recovered, and by recycling the water used in the system, wastewater can be virtually reduced. There may not be any, and even if there is, it may be in very small amounts.

Claims (1)

[Claims] A method for recovering ammonium metavanadate by wet-processing combustion ash collected by a dust collector installed in an exhaust gas flue of a boiler using petroleum-based fuel, etc. A method for recovering ammonium metavanadate from petroleum combustion ash, the method comprising carrying out the steps of 1) to (4). (1) Combustion ash is mixed with water to form a slurry. (2) The slurry is heated to 70° C. or higher, the pH is adjusted to 7 to 9 in the presence of ammonia, and an oxidizing agent is supplied. (3) Separate insoluble matter while maintaining the temperature in step (2) above. (4) Cool the liquid part to 40° C. or lower to precipitate ammonium metavanadate.