JPS58162694A - Preparation of coal from which ash is removed - Google Patents

Abstract

PURPOSE:To reduce the amount of a low-boiling oil used, to carry out granulation in a short time, and to obtain economically ash removed coal having an extremely high ratio of ash removal, by using seed particles comprising a mixture of powdered coal having a low ash content and pitch. CONSTITUTION:A mixture of powdered coal having a low ash content and pitch is molded into seed particles, the particles and a low-boiling oil are blended in slurry of ash-containing powdered coal, to form granulates wherein the seed particle act as a nucleus and the powdered coal is attached to the low-boiling oil on the surface of the nucleus. The granules are washed with water, ash is removed, the granules are heated so that the low-boiling oil and water are evaporated and the granulates are decomposed, to give the desired coal from which ash is removed and to recover the seed particles. A vapor gas containing the low-boiling oil and water is condensed, separated into the liquid low-boiling oil and water, and they and the recovered seed particles are returned to the granulating process.

Description

[Detailed description of the invention] 1. This invention relates to a method for producing deashed coal.

Naturally produced coal contains a relatively large amount of ash, but this ash is composed of silica (SiO2), iron sulfide (F),
@g) It is mainly composed of alumina (AI20B) and the like, 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 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 to create a water slurry of pulverized coal containing ash. By mixing seed particles made of low boiling point oil and lipophilic granules that serve as granulation nuclei into the charcoal slurry, granules are formed in which pulverized coal is attached to the low boiling point oil on the surface of the seed particles as the core. The granules were separated from the residual slurry to remove the ash from the pulverized coal. As seed particles, (a) granular molded hard polyvinyl chloride resin or (b) coarse coal obtained by crushing coal containing ash was used (see Japanese Patent Application No. 55-141505). ).

However, when using the above-mentioned seed particles made of hard polyvinyl chloride resin, the surface is smooth, so 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 granulated coal is used, +f-h is easily broken during stirring and granulation (and coarse granulated coal has a relatively high ash content (
As a result, the ash content of the locust granules is mixed into the granulated material containing such coarse granulated coal as a core, resulting in a problem that the deashing rate decreases.

The purpose of this invention is to solve the above problems, to make it possible to produce deashed coal very efficiently because the granulation time is very short (), and to increase the ash content of the obtained deashed coal. The purpose is to provide a method for producing deashed coal that has a very low content and is extremely economical.

The method for producing deashed coal according to the present invention includes the steps of forming seed particles by molding a mixture of pulverized coal and pitch with a low ash content into particles, and adding a mixture of pulverized coal containing ash (low boiling point) to a water slurry of pulverized coal. A process of mixing oil and the above seed particles to form granules with pulverized coal attached to low boiling point oil on the surface of the seed particles as cores, and separating the granules from the slurry and washing them with water. By doing so, there are a step of removing ash, a step of heating the washed granules to evaporate low boiling point oil and water, and a step of decomposing the granules that do not contain low boiling point oil to produce deashed coal. Separation into seed particles to obtain demineralized coal, recovery of seed particles and return to the above granulation process, and condensation of evaporated gas containing low boiling point oil and water, followed by liquid low boiling point oil and This method is characterized by comprising a step of separating the oil from water and returning the liquid low-boiling point oil to the granulation step.

The method of this invention will be explained below with reference to the drawings.

The method of this invention consists of the following steps.

First step - First, seed particles made by hardening pulverized coal with a low ash content in pitch are collected. Here, as the pitch, for example, coal tar pitch, wood tar pitch, rosin pitch, etc. are used.

To produce seed particles, since pitch is solid at room temperature, pulverized coal and pitch powder are mixed, then heated to melt the pitch, and the mixture is shaped into, for example, a diameter l-
Shape into ~number of particles. 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 briquette 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 deashed pulverized coal produced 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, so the strength is weak and the seed particles are easily broken. If the pitch exceeds 8% by weight, it will be difficult to mold, and the surface of the obtained seed particles will be smooth, resulting in a long granulation time. Of course, it is more economical to use as little pitch as possible.

In the second step, natural coal containing ash is pulverized using, for example, a wet ball mill to produce micro-ring coal of several tens of ptrlD with a particle size of several hundred μml. Raw coal usually contains 7 to 25% ash by weight, but due to pulverization, the ash content becomes finer (
Shattered. Next, this pulverized coal containing ash is mixed with water to create a pulverized coal slurry.In some cases, the coal is pulverized into so-called ultra-fine powder with a particle size of several μm.The pulverization of coal is carried out in water. It is preferable that after pulverization, a required amount of water is further added to adjust the concentration of the slurry.

Third step: Next, the pulverized coal slurry is mixed with a low boiling point oil and the seed particles that will become granulation nuclei, and granulated. Here, the low boiling point oil is one having a low latent heat of vaporization (and low viscosity), such as kerosene, light oil, gasoline, etc.

The amount of low boiling point oil used is, for example, approximately lθ to pulverized coal.
30 weight attack. A small amount of surfactant may also be added to facilitate oil dispersion.

The seed particles that serve as granulation nuclei are made of pulverized coal with a low ash content hardened with pitch as described above, and have a particle size of III
It has a size of ~number-. It is usually preferable to mix such seed particles with pulverized coal at a ratio of 1:1, but the total amount of seed particles and pulverized coal in the slurry is 30% by weight or less, and within a range not exceeding this value. Of course, the ratio of seed particles to pulverized coal may be increased or decreased.

There are three ways to mix the pulverized coal slurry, low-fish oil, and seed particles.

(I) Mix seed particles into a pulverized coal slurry and then mix a low boiling point oil into the slurry.

(Yuu) A low boiling point oil is added to the seed particles in advance to adhere the low boiling point oil to the surface of the seed particles, and then the oil-coated particles are mixed into the pulverized coal slurry.

(To) Mix low-boiling point oil with pulverized coal slurry, and then mix seed particles with 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 fine ash charcoal hardened with pitch, they have lipophilic properties. Therefore, during the granulation process, low boiling point oil is attached to the surface of the seed particles, and this oil-coated seed The pulverized coal is sequentially attached to the oil on the surface of the particles, using the particles as nuclei, and the pulverized coal is granulated very rapidly at an accelerated rate by so-called transfer granulation, and therefore the granulation time is extremely short. Furthermore, since such seed particles are used, the amount of low boiling point 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 low boiling point oil are mixed, the mixture is separated into a liquid phase containing pulverized coal, seed particles, and oil, and a slurry consisting of water containing ash. This slurry containing ash is separated from the liquid phase containing pulverized coal, and then the liquid phase containing pulverized coal is washed with fresh water. This removes a significant amount of ash.

Step 41: Next, the granules made of pulverized coal, low boiling point 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 onto the filter. In some cases, the separated granules may be centrifuged to further remove moisture. The slurry containing ash is then introduced into a water treatment equipment equipped with a thickener and a filtration machine for treatment.
Separates into ash and water.

Fifth step: Next, the washed granules made of pulverized coal, low boiling point oil, and seed particles are heated to evaporate the low boiling point oil and water. Here, steam or electric heat is used as the heat source.

Step 61: By decomposing the granules that do not contain low-boiling point oil, for example by applying vibration, and separating them into powdered deashed coal and seed particles, deashed coal is obtained and one seed particle is obtained. The particles are collected and returned to the third granulation step.

In this case, the seed particles may be returned to the granulation process after adding the low-boiling point oil, or may be returned as they are without adding the low-boiling point oil.

Since the seed particles are made by hardening pulverized coal with pitch, they gradually wear out through repeated use, and their total amount decreases. For this reason, seed particles are created and the depleted amount is replenished as appropriate.

In this case, seed particles may be produced using a portion of the demineralized coal finally obtained by the method of the present invention.

Seventh step: After condensing the evaporated gas containing low-boiling oil and water, it is separated into liquid low-boiling oil and water, and the liquid low-boiling oil is returned to the granulation process.

The deashed coal produced in this manner has sufficient ash removed and can be effectively used as a fuel.

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

Example Raw coal containing ash (Daido coal, ash content 11.6%) is pulverized to produce pulverized coal of 200 mesh or less, that is, a particle size of 74 mm or less, and water is mixed with this to contain ash. Make a water slurry of pulverized coal.The concentration of pulverized coal in the slurry is 5.
Weight% (based on raw coal).

On the other hand, coal tar pitch powder (ash content 0.1%) was added to pulverized coal with a low ash content of 2.81%.
They were added in a proportion of % by weight, heated using a briquette machine, and then compression molded. The compression molding pressure is a011/d, and the size of the obtained seed particles is about 2 cm in diameter and about 2' in height.

next. Then, the seed particles were added to the pulverized coal slurry containing ash at a ratio of 5% by weight, and kerosene was added at a ratio of 15% by weight to the raw coal, and a granulation device equipped with a wire mesh stirring blade was added. The stirring blades were rotated at a speed of 200 rpm to carry out granulation for 20 minutes. After that, the granules are separated from the slurry and washed with water to remove the ash, and the washed granules are heated to evaporate the kerosene and water, and then the granulation rate of pulverized coal is determined. When measured, it was 33
．． It was 2%. Next, the kerosene-free granules were decomposed by vibration to obtain powdered decalcified coal. On the other hand, the separated seed particles were collected and returned to the granulation process for reuse. Further, after condensing the evaporated gas containing kerosene and water, it was separated into liquid kerosene and water, and the liquid kerosene was returned to the granulation process for reuse. The ash content of the deashed coal thus produced was measured and found to be 3.17% by weight.

Comparative Example Next, for comparison, seed particles made of hard vinyl chloride resin with a diameter of about 2 cm and a height of 21 cm are added at a rate of 5% by weight to the pulverized coal slurry containing the ash content prepared in the above example. In addition, 15% by weight of kerosene based on raw coal Iζ
30% in the same manner as in the above example.
A granulation operation was performed for 1 minute. After washing the granules with water and drying them, the granulation rate of the pulverized coal was kept constant and was 22%. The ash content of the deashed coal obtained by vibrating the granulated material and separating it from the seed particles was almost the same as in the above example.

As mentioned above, the method for producing deashed coal according to the present invention includes the steps of forming seed particles by molding a mixture of pulverized coal with a low ash content and pitch into particles, and making a water slurry of pulverized coal containing ash. A process of mixing low boiling point oil and the above seed particles to form granules with pulverized coal adhering to the low boiling point oil on the surface of the seed particles with the seed particles as cores, and separating the granules from the slurry. By washing with water,
a step of removing ash; a step of heating the washed granules to evaporate low-boiling point oil and water; and a step of decomposing the granules that do not contain low-boiling point oil into deashed coal and seed particles. separate,
De-raw coal is obtained, seed particles are collected and returned to the above granulation process, and evaporated gas containing low boiling point oil and water is condensed, and then separated into liquid low boiling point oil and water. This process consists of the step of returning the liquid low-boiling point oil to the granulation process, and since it uses seed particles made of a mixture of pulverized coal and pitch with a low ash content, it has a low boiling point. The amount of oil used is small (1) and the granulation time is very short, so deashed coal can be produced very efficiently, and the time for producing deashed coal can be shortened. The resulting deashed coal has a very low ash content and is of good quality.Moreover, the low boiling point oil and seed particles are recyclable, making it extremely economical.

[Brief explanation of the drawing]

The drawing is a flow sheet showing an embodiment of the invention. that's all Patent applicant: Hitachi Zosen Corporation 4 other people

Claims (1)

[Claims] Seeds are produced by forming seed particles by molding a mixture of pulverized coal and pitch with low ash content into particles, and by mixing low boiling point oil and the above seed particles into a water slurry of pulverized coal containing ash. A process of forming granules with particles as cores and pulverized coal attached to low-boiling oil on the surface, a process of separating the granules from the slurry and washing them with water to remove ash, and a process of washing. Heating the granulated material,
A process of evaporating low-boiling point oil and water, and decomposing the granules that do not contain low-boiling point oil to separate them into deashed coal and seed particles to obtain deashed coal, and collecting the seed particles to perform the above-mentioned process. a step of returning the evaporated gas containing the low boiling point oil and water, and then separating the liquid low boiling point oil and water, and returning the liquid low boiling point oil to the granulation step. A method for producing decalcified coal consisting of: