JPS6345760B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for deashing coal.

Conventional technology Naturally produced coal contains a relatively large amount of ash, but this ash contains silica (SiO ₂ ),
It is mainly composed of iron sulfide (FeS) and alumina (Al ₂ O ₃ ), and is usually contained in coal at a ratio of about 7 to 25%. As a method for removing such ash from coal, the present applicant previously proposed a method using seed particles. That is, in the method described above, coal containing ash is pulverized into pulverized coal, this pulverized coal still containing ash is mixed with water to create a water slurry of pulverized coal containing ash, and this pulverized coal containing ash is mixed with water. By mixing seed particles consisting of oil and lipophilic granules that serve as granulation nuclei into the charcoal slurry, granules are formed in which pulverized coal is attached to the oil on the surface of the seed particles as cores. The pulverized coal was separated from the residual slurry to remove the ash from the pulverized coal. And as a seed particle,
(a) Granular molded product of hard polyvinyl chloride resin or
(b) Coarse coal obtained by pulverizing coal containing ash was used (see Japanese Patent Application No. 141504-1983 and corresponding Japanese Patent Publication No. 199-1988).

Problems to be Solved by the Invention However, when (a) the seed particles made of hard polyvinyl chloride resin are used, since the surface thereof is smooth, pulverized coal is difficult to adhere to the surface of the seed particles. Therefore, there was a problem that the granulation time was long. (b) When coarse charcoal is used, it is easily broken during stirring and granulation, and coarse charcoal still contains a relatively large amount of ash;
There was a problem in that the ash content of the coarse coal was mixed into the granulated material having such coarse coal as the core, resulting in a decrease in the deashing rate.

The purpose of the present invention is to solve the above problems, to produce oil-impregnated deashed coal that has a very short granulation time, can perform coal deashing very efficiently, and has a very low ash content. In addition to this, the amount of molding material used for the seed particles that serve as granulation nuclei can be reduced, and the number of molding equipment and molding steps for seed particles can be greatly reduced, making it extremely economical. The aim is to provide a method for deashing coal with high efficiency.

Means for Solving the Problems In order to achieve the above object, the present invention provides a process for forming seed particles by molding a mixture of pulverized coal and pitch, which has a low ash content, into particles, and a process for producing seed particles containing ash. A process of mixing oil and the above-mentioned seed particles with a water slurry of charcoal to form granules with pulverized coal adhering to the oil on the surface using the seed particles as cores, and separating the granules from the slurry. a step of removing ash by washing with water; a step of drying the washed granules to obtain oil-impregnated deashed coal containing seed particles; and a step of decomposing a part of the oil-impregnated deashed coal containing seed particles. and separating into oil-impregnated deashed coal and seed particles to obtain oil-impregnated deashed coal, collect the seed particles and return them to the next granulation process, and prepare the oil-impregnated deashed coal containing the seed particles. A step of forming replenishment seed particles by adding a required amount of pitch to a part of the mixture into particles, and supplying these to the next granulation process to make up for the lack of seed particles. The gist of this paper is a method for deashing coal.

Next, the production of oil-containing deashed coal by the coal deashing method of the present invention will be described in detail with reference to the drawings.

In the drawing, oil-impregnated demineralized coal is manufactured by the following steps.

First step: Natural coal containing ash is pulverized using, for example, a wet ball mill to produce pulverized coal with a particle size of several hundred μm to several tens of μm. Raw coal usually contains 7
It contains ~25% ash by weight, but the ash is also finely ground during grinding. Next, this pulverized coal containing ash is mixed with water to create a pulverized coal slurry. In some cases, coal may be pulverized into so-called ultrafine powder with a particle size of several μm. The coal is preferably pulverized in water, and after pulverization, a required amount of water is added to adjust the concentration of the slurry.

Second step: Next, a mixture of pulverized coal with a low ash content and pitch is formed into particles to form seed particles.

Here, as the pitch, for example, coal tar pitch, wood tar pitch, rosin pitch, etc. are used.

To produce seed particles, pitch is solid at room temperature, so after mixing pulverized coal and pitch, they are heated to melt the pitch, and this mixture is made into particles with a diameter of, for example, 1 mm to several mm. Shape. Compression molding is usually used as the molding method. This involves heating and compression molding the above mixture using, for example, a briquette machine. A briquetting machine is integrally equipped with such a heating mechanism and a compression molding mechanism. Note that pulverized coal with a low ash content is first produced in advance by another method, but thereafter pulverized coal deashed by the method of the present invention may be used.

Here, pitch is added at a rate of, for example, 4 to 8% by weight relative to pulverized coal having a low ash content. If the pitch is less than 4% by weight, the pulverized coal cannot be bonded sufficiently, resulting in weak strength.
The seed particles are therefore more likely to be destroyed. Moreover, if the pitch exceeds 8% by weight, molding becomes difficult and the surfaces of the obtained seed particles become smooth, resulting in a long granulation time. Of course, it is more economical to use as little pitch as possible.

Third step: Next, the pulverized coal slurry is mixed with oil and seed particles serving as granulation nuclei, and granulated. Here, the oil includes heavy oil, kerosene, light oil,
Distillation residue oil, vegetable oil, etc. are used. The amount of oil used is, for example, about 10 to 30% by weight based on pulverized coal. A small amount of surfactant may also be added to facilitate oil dispersion.

It is preferable that seed particles, which become granulation nuclei, are mixed with pulverized coal at a weight ratio of 1:1, but the total amount of seed particles and pulverized coal in the slurry is 30% by weight or less, and this The ratio of seed particles to pulverized coal may be increased or decreased within a range that does not exceed this value.

There are three methods for mixing the pulverized coal slurry, oil, and seed particles.

() Mixing seed particles into a pulverized coal slurry and then mixing oil into this slurry.

() Oil is added to the seed particles in advance so that the oil adheres to the surface of the seed particles, and then the oil-coated seed particles are mixed into the pulverized coal slurry.

() Mixing oil into a pulverized coal slurry and then mixing seed particles into this slurry.

In order to stir and granulate the above mixture, a granulating device equipped with a wire mesh stirring blade or other known granulating device is used. Since the seed particles are composed of pulverized coal that has been hardened in pitch, they have lipophilic properties.Therefore, during this granulation process, oil is attached to the surface of the seed particles, and these oil-coated seed particles are used as nuclei. As a result, the pulverized coal is successively attached to the oil on the surface of the pulverized coal, and the pulverized coal is granulated very quickly at an accelerated rate by so-called rolling granulation, so that the granulation time is very short. Furthermore, since such seed particles are used, the amount of oil used can be extremely small. On the other hand, ash that has been crushed to the same size as pulverized coal remains in the water.

Note that if the ash content in the raw coal is very high, for example, about 20% by weight, a primary deashing treatment may be performed before granulation. That is, when pulverized coal slurry, seed particles, and oil are mixed, a liquid phase containing pulverized coal, seed particles, and oil,
It is separated into a slurry consisting of water containing ash. This slurry containing ash is separated from a liquid phase containing pulverized coal, and then the liquid phase containing pulverized coal is washed with clean water. This removes a significant amount of ash.

Fourth step: Next, the granules made of pulverized coal, oil, and seed particles are separated from the slurry and washed to remove ash. This operation is carried out by, for example, pouring the slurry containing the granules onto a filter and spraying washing water from above. In some cases, the separated granules may be centrifuged to further remove moisture.
The slurry containing ash is then led to a water treatment device equipped with a thickener, a filter, etc., and treated to separate it into ash and water.

Fifth step: Next, the washed granulated material consisting of pulverized coal, oil, and seed particles is dried to completely remove moisture, and oil-impregnated demineralized coal containing seed particles is obtained.
The thus obtained granules made of oil-impregnated demineralized coal containing seed particles can be used as is as a fuel. That is, since the pitch in the seed particles is flammable and has a very low ash content, the granulated material containing the seed particles can be used as is as a fuel.

Sixth step: Part of the oil-impregnated deashing coal containing seed particles is decomposed, for example, by applying vibration, and the oil-impregnating deashing coal is separated into pellet-like oil-impregnating deashing coal and seed particles, thereby obtaining oil-impregnating deashing coal. , collect the seed particles. The seed particles are then returned to the second granulation step.

Note that the seed particles to be returned will have some oil attached to them, but you can add more oil to these seed particles and then return them to the granulation process, or you can return them as is without adding oil. It's okay.

Seventh step: Since the seed particles are made by hardening pulverized coal in pitch, they gradually wear out through repeated use. Therefore, a part of the oil-impregnated pulverized coal containing the seed particles is taken out, pitch is mixed with it, and the mixture is heated and compression molded to produce seed particles, which are then replenished.

That is, the dried granules obtained in the fifth step still contain the oil-impregnated demineralized coal as well as the seed particles, and therefore contain a small amount of pitch. Therefore, the insufficient amount of pitch is mixed with this, and replenishment seed particles made of pulverized coal and pitch are formed in the same manner as in the second step, and the obtained seed particles are used in the second production process. Supplied to the grain process to make up for the lack of seed particles.

Note that oil such as heavy oil remains in the granules after drying, but since the seed particles are compressed under extremely high pressure, the oil oozes out onto the surface of the particles, causing The pulverized coal is then solidified sufficiently with pitch. Moreover, there is no problem in the subsequent granulation process.

In addition, drying of the granules is carried out at the boiling point of water (100℃).
From the above, since it is carried out at a temperature of about 110℃,
The temperature of the dried granules is sufficiently high, so when adding pitch to a part of the granules to form seed particles, there is no need to heat the pitch. may also heat it.

Note that in the case of finally producing deashed coal that does not contain oil, this oil-containing deashed coal may be further subjected to an oil removal treatment. For example, when heavy oil is used as the oil, this treatment is performed by extracting the heavy oil with a solvent.

Examples Next, examples of the present invention will be described together with comparative examples.

Example Raw coal containing ash (Horonai 60 charcoal, ash content 25.6% by weight) is pulverized to produce pulverized coal with a particle diameter of 74 μm or less, which is 200 meshes or less, and water is mixed with this to produce pulverized coal containing ash. Make a charcoal water slurry.
The pulverized coal concentration in the slurry is 5% by weight (based on raw coal)
And so.

On the other hand, compared to pulverized coal with a low ash content of 4.84% by weight, coal tar pitch powder
0.1% by weight) was added at a rate of 5% by weight, and after heating with a briquette machine, compression molding was performed. The compression molding pressure is 30Kg/ ^cm2 ,
The resulting seed particles have a diameter of about 2 mm and a height of about 2
It has a cylindrical shape of mm.

Next, these seed particles were added to the ash-containing pulverized coal slurry at a rate of 5% by weight, and heavy oil A was added at a rate of 15.5% by weight based on the raw coal. Then, 1,600 g of the slurry containing the seed particles and A heavy oil was placed in a container with an inner diameter of 115 mm and a height of 180 mm, and a container with an opening of 5 mm and a diameter of 75 mm made by knitting stainless steel wire with a diameter of 0.5 mm. The mixture was introduced into a granulation apparatus equipped with a circular wire mesh stirring blade, and the wire mesh stirring blade was rotated at a speed of 2000 rpm to carry out granulation for 3 minutes.

Next, the granules were taken out from the remaining slurry, washed with water, and then dried at 110°C.

As a result, the granulation rate of pulverized coal was 55%. The ash content of this oil-impregnated deashed coal granule was 4.8% by weight including seed particles.

Here, the granulation rate (%) was calculated using the following formula.

In addition, the calculation of the granulation rate is performed after decomposing the oil-impregnated demineralized coal containing seed particles and separating it into oil-impregnated deashed coal and seed particles, and then removing heavy oil A from the oil-impregnated deashed coal using a solvent. The demineralized coal obtained was subjected to this test.

Granulation rate = Weight of granulated demineralized coal / Weight of input raw coal (ash content) x
100 Next, part of the oil-impregnated demineralized coal containing seed particles is decomposed and separated into oil-impregnated deashed coal and seed particles to obtain oil-impregnated deashed coal, and the seed particles are collected and used for the next production. It was returned to the granulation process. Further, 3% by weight of pitch powder was added to the required amount of the oil-impregnated demineralized coal containing the seed particles, so that the overall ratio of pitch to the pulverized coal was about 5% by weight. Then, as in the above case, this mixture is heated with a briquette machine and compression molded to produce replenishment seed particles, and these seed particles are supplied to the next granulation process to make up for the lack of seed particles. The granulation operation was carried out for 3 minutes. After the granules were washed with water and dried, the granulation rate of the pulverized coal was measured and found to be 66%, and the ash content of the oil-impregnated demineralized coal, including seed particles, was 4.75% by weight.

Comparative Example Next, for comparison, 5 weight of hard vinyl chloride resin seed particles having a cylindrical shape with a diameter of about 3 mm and a height of 1.5 mm and a specific gravity of 1.4 were added to the pulverized coal slurry containing the ash content adjusted in the above example. %, and A heavy oil is added at 15% by weight to the raw coal.
It was added at a ratio of

A slurry containing these seed particles and heavy oil A
A granulation operation of 1600 g was carried out for 3 minutes in the same manner as in Example 1 above. After washing and drying the granules, the granulation rate of pulverized coal was measured and found to be 13%.
It was very low.

Next, this granulated material was separated into oil-impregnated deashed coal and seed particles by vibration, and the ash content of the oil-impregnated deashed coal was measured and found to be 4.84% by weight.

Although the size of the seed particles used differs between the above examples and comparative examples, they are all cylindrical and used at a rate of 5% by weight relative to the pulverized coal slurry, that is, 80g each. . Therefore, when comparing the total surface areas of both, the total surface area of the seed particles of the example (80 g): 171 cm The total surface area of the seed particles of the comparative example (80 g): 152 cm, and the ratio is 1:0.89.

Here, the granulation rate of the example is 55% and 66%, and the granulation rate of the comparative example is 13%, so the difference is very large, and even if the total surface area of the seed particles of the example is It is clear that the seed particles used in the method of this invention have a significantly superior granulation rate, even when converted on the assumption that the total surface area of the seed particles is the same as that of the seed particles.

Effects of the Invention As described above, the method for deashing coal according to the present invention includes a step of forming seed particles by forming a mixture of pulverized coal with a low ash content and pitch into particles, and a step of forming seed particles with pulverized coal containing ash. A process of mixing oil and the above-mentioned seed particles with a water slurry to form granules with pulverized coal adhering to the oil on the surface using the seed particles as cores, and separating the granules from the slurry. A step of removing ash by washing with water, a step of drying the washed granules to obtain oil-impregnated deashed coal containing seed particles, and a step of decomposing a part of the oil-impregnated deashed coal containing seed particles. Separate into oil-impregnated deashed coal and seed particles to obtain oil-impregnated deashed coal, and
A process of collecting seed particles and returning them to the next granulation process, and a process of adding a required amount of pitch to a part of the oil-impregnated deashed coal containing the seed particles, forming a mixture into particles for replenishment. Since the process consists of producing seed particles and supplying them to the next granulation process to make up for the lack of seed particles, the granulation time is very short, and therefore coal demineralization is possible. Processing can be carried out very efficiently,
The production time of oil-impregnated deashed coal can be shortened. Moreover, the obtained oil-impregnated deashed coal has a very low ash content and is of good quality. In addition, the seed particles are collected and reused, and supplementary seed particles are supplied to make up for the shortage by using a mixture of a part of the oil-impregnated demineralized coal containing the seed particles and a required amount of pitch. Since it is made by molding the seed particles into a shape, the amount of molding material for the seed particles, that is, pitch, can be extremely reduced, and the number of molding equipment and molding steps for the seed particles can be greatly reduced. It has the effect of being highly economical.

[Brief explanation of the drawing]

The drawing is a flow sheet showing an embodiment of the invention.

Claims (1)

[Claims] 1 A step of forming seed particles by molding a mixture of pulverized coal and pitch with a low ash content into particles, and mixing oil and the above seed particles into a water slurry of pulverized coal containing ash. A process of forming granules with pulverized coal adhering to oil on the surface of the granules as cores, a process of removing ash by separating the granules from the slurry and washing them with water, and a process of removing the ash content by separating the granules from the slurry and washing them with water. A step of drying the material to obtain oil-impregnated deashed coal containing seed particles, and a step of decomposing a part of the oil-impregnated deashed coal containing seed particles to separate it into oil-impregnated deashed coal and seed particles, and producing oil-impregnated deashed coal by decomposing a part of the oil-impregnated deashed coal containing seed particles. As soon as you get it,
A process of collecting seed particles and returning them to the next granulation process, and a process of adding a required amount of pitch to a part of the oil-impregnated demineralized coal containing the seed particles to form a mixture into particles for replenishment. A coal deashing method comprising the steps of producing seed particles and supplying them to the next granulation step to compensate for the lack of seed particles.