JPH09202885A - Wet treatment of heavy oil ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To finely pulverize unburned carbon particles of a heavy oil ash, reduce the water content of a carbon cake and develop reutilizable uses. SOLUTION: This wet method for treating a heavy oil ash comprises a pulverizing step for finely pulverizing unburned carbon particles in a heavy oil ash composition as a pretreatment of a leaching step or a solid-liquid separation step in the wet method for treating the heavy oil ash. The average particle diameter of the unburned carbon particles in the pulverizing step is controlled within the range of 0.5-15μm. The pulverizing step is either a wet pulverizing (treating) or a dry pulverizing (treating) step. The reduction in water content, an increase in efficiency of leaching and washing treatments, an improvement in combustibility (ignition and burning up) and extension of uses of the recovered carbon cake can be carried out accordingly to the method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a fuel oil boiler (represented by a thermal power plant or the like using fuel oil or crude oil as a fuel). The present invention relates to a method for wet-treating heavy oil ash for effectively utilizing the product.

[0002]

2. Description of the Related Art Heavy oil ash discharged from thermal power plants, etc.
Although mainly unburned carbon, a relatively large amount (30 to 50%) of ammonia (gas) injected to neutralize the sulfuric acid mist that accompanies it and to improve the electric dust collection characteristics of carbon dust. Contains ammonium sulfate (more specifically, a mixture of ammonium sulfate and acidic ammonium sulfate).

[0003] In addition, it contains a small amount (7 to 15%) of ash composed of V, Ni, Fe, Si, Al, Ca, Mg, Na and the like derived from fuel heavy oil (component).

Conventionally, as a method for treating heavy oil ash, landfill treatment in which bags are packed and discarded as they are, and incineration volume reduction treatment using a cyclone furnace, a fluidized sintering furnace, a rotary kiln, or the like have been performed.

[0005] The amount of heavy oil ash discharged from large thermal power plants is enormous at 4000 to 6000 tons / y per 1000 MW. In addition, the ash collected by the electric dust collector (EP) has a bulk specific gravity.
Very small and 0.1~0.2 ton / m ^3, bulky.

[0006] Therefore, even if landfill treatment is performed as industrial waste, disposal requires a great deal of cost, and it is becoming increasingly difficult to secure land every year.

On the other hand, even in the incineration and volume reduction treatment, it is difficult to control the carbon in heavy oil ash and the fluctuation of calories and composition is large, so that it is difficult to control combustion.
Decomposed at 0 ℃) and oxidized at 800 ℃ or higher, the NO ₂ concentration rapidly increased, recombined and adhered in the downstream low temperature part (around 300 ℃), causing corrosion problems, burning carbon Residues contain V ₂ O ₅ , Fe ₂ O ₃ , Na ₂ SO _4, etc., which form low melting point compounds and are welded at 800-900 ° C. to cause corrosion problems (so-called vanadium attack). I have a problem.

Therefore, all incinerators strictly control the furnace temperature by means of cold air quench, hot water spray or the like, first decompose ammonium sulfate at 600 ° C., and then slowly burn carbon at 800 ° C.

As described above, the adhesion of ammonium sulfate and vanadium salt in heavy oil ash is a bottleneck in the effective use and treatment of unburned carbon. Is being promoted.

For example, Japanese Patent Application Laid-Open No. 5-156268 discloses E
P-collected ash is wet-processed, and the obtained carbon cake (water content: 20-60%) is mixed with boiler fuel heavy oil to make a mixed fuel, and slaked lime is added to the liquid leached with ammonium sulfate to recover ammonia and gypsum Then, ammonia is proposed to be returned to the flue and reused.

In Japanese Patent Application Laid-Open Nos. 60-19086 and 60-46930, heavy oil ash is wet-processed, and vanadium is precipitated and recovered while performing pH adjustment, heating, oxidation and the like. As in the above, slaked lime is added to collect ammonia and gypsum for recycling. The treatment methods according to these applications have been further improved, and ammonium vanadate compounds have been produced using ammonium sulfate in heavy oil ash, and vanadium has not been efficiently leached and crystallized using its melting temperature characteristics. Has been collected. Currently 5000to
An actual n / y plant is in operation, and the recovered carbon cake is used as fuel for cement factories.

[0012]

Under these circumstances, the present inventors have made intensive studies on the effective use of heavy oil and ash unburned carbon to find applications in various fuels, reducing materials for steelmaking, fillers for rubber and plastics, and the like. I have piled up.

For these uses, it is necessary to first perform a wet treatment to separate ammonium sulfate, vanadium salts, etc. It is clear that there are the following technical solution issues for further utilization and rationalization. I've been.

The water content of the carbon cake separated by the wet treatment is as high as 60 to 65% and the drying cost is high. Therefore, reduction measures are desired.

The particle size of industrial carbon black used as a filler for rubber and plastics is generally of the order of a single micron, which is one order of magnitude smaller than that of heavy oil ash unburned carbon. Therefore, miniaturization is required to replace them.

Heavy oil ash unburned carbon as a fuel material has lower flammability than pulverized coal. (It is considered that the coke is partially coke.) Therefore, when co-firing in a pulverized coal-fired boiler or the like, improvement of flammability is required.

[0017]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for wet-treating heavy oil ash to separate insoluble carbon and water-soluble substances, recovering each of them, and recycling or discarding them. In the wet processing method of heavy oil ash for
As a pretreatment of the leaching step or the solid-liquid separation step, a pulverizing step of pulverizing carbon particles in the heavy oil ash composition is included.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention includes, as a pretreatment of a leaching step or a solid-liquid separation step in a wet treatment of heavy oil ash, a pulverizing step of pulverizing unburned carbon particles in a heavy oil ash composition. The degree of formation controls the average particle diameter of the unburned carbon particles in the range of 0.5 to 15 μm. As will be described later, it is preferably in the range of 2 to 8 μm. Then, the pulverizing step for making the unburned carbon particles fine is a wet pulverizing treatment or a dry pulverizing treatment. The wet grinding treatment is performed as a pretreatment of the solid-liquid separation step, and in some cases,
The leaching process is included, and the dry pulverization process is performed as a pretreatment for the solid-liquid separation process.

Here, the pulverization is a mechanical (physical) pulverization for reducing the water content of the unburned carbon particles,
Its action is to destroy the water retention mechanism of the unburned carbon particles.

That is, the properties of the unburned carbon particles are such that the average particle diameter is 20 to 40 μm and the specific surface area is 10 to 40 m ² / g;
It has a feature that the moisture content is unusually large as compared with general powders having the same particle diameter and specific surface area. The particle shape is a hollow golf ball. [Heavy oil or crude oil is sprayed into the boiler (furnace) as fine droplets during the combustion process, and the volatile components inside and on the surface of the droplets burn while burning, resulting in heavy oil ash burning unburned carbon (heavy oil ash It is considered that the main component) is bound to a porous spherical shape. ]
Although this hollow portion contains water (interstitial water), it cannot be dehydrated by a general solid-liquid separation operation because the particles themselves are small, and shows a large water content for the above specific surface area. I have. Therefore, in order to reduce the water content, it is effective to destroy the hollow particle shape and remove pore water (internally contained water).

With respect to the effect of the particle size on the water content, when a general powder is refined by pulverization and the average particle size is reduced by one order, the specific surface area (although it varies slightly depending on the particle shape) is about It becomes about 10 times larger, and the attached water (adsorbed water) also increases accordingly. This point is the same for the unburned carbon particles of heavy oil ash (therefore, a range of an average particle diameter suitable for fine pulverization is required. As described later), crystallization water (in sediment particles) and capillary water (sediment water) are also required. (Adjacent part of particles)
, The water content can be reduced by about 30%.

A preferred embodiment will be described with reference to the drawings. FIG. 1 shows the flow sheet, wherein a is a dissolution tank, b is a wet pulverizer, c is a solid-liquid separator, d is a drier, and e is
Is an ammonium sulfate filtrate tank, f is a lime slurry tank, g is an ammonium sulfate metathesis reaction tank, h is an ammonia diffusion tower, i is an ammonia absorption tower,
j is a gypsum slurry storage tank and k is an ammonia water storage tank. In addition, a numerical code is a substance to be handled.

First, EP collected ash (1) is dissolved in make-up water (6) or cake washing liquid (2) of solid-liquid separator (c) in dissolving tank (a). And elute water-soluble substances such as ammonium sulfate and vanadium salts while adjusting the pH. The dissolving tank (a) is a mixing dissolving tank with a stirrer, and the EP collection ash (1) may be uniformly dispersed in the liquid, and dissolution within 30 minutes is sufficient.

Next, the solution (4) is sent to a wet pulverizer (b) to pulverize the suspended unburned carbon particles. The wet pulverizer (b) may be a wet vibration mill, a wet ball mill, a wet tower mill, or the like, which can pulverize to a predetermined particle size within 1 hour.

However, the degree of this pulverization (particle size range) is important, and it should not be too much or not enough. Excessive pulverization (micronization) has an adverse effect on the water content reduction effect of the present invention, and causes an increase in pulverization power cost and deterioration of the downstream filtration performance. Range (average particle size in the range of 0.5 to 15 μm, more preferably 2 to 8 μm)
It is important to adjust the pulverization time and the pulverization strength of the pulverizer in order to control the pulverization time in the range of μm. The former dissolution tank (a)
Since the treatment for eluting some metal salts such as ammonium sulfate and vanadium salt in the above is functionally possible even in the wet pulverizer (b),
When the EP collecting ash (1) can be directly and stably supplied depending on the model, the dissolution tank (a) may be omitted.

The slurry (5) pulverized to a predetermined particle size is sent to a solid-liquid separator (c), and separated into carbon and a filtrate containing ammonium sulfate. The collected carbon cake (7) is sufficiently washed with make-up water (6), and if necessary, dried with a dryer (d), and is reused as a fuel, a filler, a reducing material, and the like.

On the other hand, the separated filtrate (8) containing ammonium sulfate is sent to a metathesis reaction tank (g) for metathesis of ammonium sulfate in the same manner as in the prior art, and a lime slurry (12) is added to cause a metathesis reaction, and ammonia gas is added. Collect (13) and gypsum slurry (14).

Since the gypsum slurry (14) that has left the metathesis reaction tank (g) contains dissolved ammonia, air (15) is blown into the ammonia stripping tower (h) to diffuse ammonia gas (16), and the ammonia absorbing tower (14). absorbed in water (6) in i)
It is recovered as aqueous ammonia (3) having a concentration of about 15%.

Gypsum slurry (1
Since 7) contains a small amount of unreacted lime, it is sent to the flue gas desulfurization unit of the power plant for batch processing.

The recovered ammonia water (3)
Others are used for adjusting the pH of the dissolution tank (a), and the others are sent to the power plant and reused for injecting ammonia into the flue.

[0031]

【Example】

An embodiment of the present invention will be described below with reference to the drawings.

The heavy oil ash discharged from the heavy oil boiler for the thermal power plant is converted into a vibration mill (manufactured by Kawasaki Heavy Industries, Ltd .; Model T-2).
50, motor rotation speed 800rpm), solid content concentration 10wt%
And the slurry was vacuum filtered and washed, and the water content and particle size (average particle size) of the obtained carbon cake were measured. The measurement results are shown in Table 1 and FIG.

[0034]

[Table 1]

As shown in the results, after grinding for about 1 hour, 63
% Water content could be reduced to 43% water content. Here, when the effect of reducing the water content on the order of 40% is considered to be effective, the average particle size is in the range of 0.5 to 15 μm. Further pulverization to a submicron has no effect of reducing the water content (instead of increasing), increases the required power cost, and makes filtration difficult. In the method of the present invention, if the water retention mechanism (hollow particle shape) of unburned carbon can be destroyed, the object (reduction of water content) is achieved. ~ 8 μm
A range can be recommended.

[0036]

According to the present invention, the present invention has the above-mentioned structure, and according to the present invention, it is possible to (1) reduce the water content and increase the efficiency of the leaching / cleaning treatment, and (2) improve the flammability (ignition and burnout). And (3) the use of the recovered carbon cake can be expanded.

Specific items are listed below. Due to the effect of reducing the water content, the drying cost of the carbon cake can be reduced, and depending on the application, the drying step can be omitted, and overall economic effects can be expected. Due to the effect of reducing the water content, the dissolved mass of ammonium sulfate and the like contained in the water adhering to the carbon cake is also reduced, so that the leaching separation efficiency is improved. The miniaturization (pulverization) improves the leaching efficiency of a soluble metal salt such as a vanadium salt and the cleaning efficiency. Combustibility (ignition and burn-out) is improved by miniaturization (pulverization), and the fuel can be reused as boiler fuel. Along with miniaturization (3 μm or less) and improvement of leaching and washing efficiency, it is expected that a material that can be substituted for industrial carbon black (especially the use of carbon cake as a filler for rubber and plastics, etc.) will be developed.

[Brief description of drawings]

FIG. 1 is a flow sheet for explaining an embodiment of the present invention.

FIG. 2 is a data plot showing water content vs. grinding time, which is a measurement result of a carbon cake obtained in one example of the present invention.

[Explanation of symbols]

 a dissolution tank b wet pulverizer c solid-liquid separator d drier e ammonium sulfate filtrate tank f lime slurry tank g ammonium sulfate double decomposition reaction tank h ammonia emission tower i ammonia absorption tower j gypsum slurry storage tank k ammonia water storage tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriaki Higashi 4-33 Komachi, Naka-ku, Hiroshima City, Hiroshima Prefecture Chugoku Electric Power Co., Inc. (72) Katsumi Fukuda 2-946 Minamikannon-cho, Nishi-ku, Hiroshima City, Hiroshima Prefecture -No. 602 (72) Nobuhiro Kitamura 6-33-603 Daito, Hatsukaichi-shi, Hiroshima (72) Inventor Kazuhiro Matsumoto 2-8-34, Kusatsuminami, Nishi-ku, Hiroshima-shi, Hiroshima (72) Kazuhiko Ishimura, Hiroshima 29-37-9 Hachiman East 1-chome, Saiki-ku, Hiroshima City

Claims (4)

[Claims] 1. A method of wet-treating heavy oil ash for wet-treating heavy oil ash to separate insoluble unburned carbon (particles) and a soluble substance, recovering each of them, and recycling or discarding them. A wet processing method for heavy oil ash, comprising a pulverizing step of pulverizing unburned carbon particles in a heavy oil ash composition as a pretreatment of a leaching step or a solid-liquid separation step. 2. The method according to claim 1, wherein the average particle size of the unburned carbon particles in the pulverizing step is controlled in the range of 0.5 to 15 μm. 3. The method according to claim 1, wherein the pulverizing step is wet pulverization. 4. The method according to claim 1, wherein the pulverizing step is dry pulverization.