JPS6259758B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chemical deashing treatment apparatus for coal that is applied to produce deashed coal that can be transported or burned smoothly.

As is well known, in recent years there has been concern about the outlook for oil supply,
Due to the soaring prices of coal, the necessity of diversifying energy sources has been advocated, and coal has been chosen as the first candidate for its replacement, and efforts are being made to promote its effective use. Coal has been used as a major energy source since ancient times, but was replaced by the advent of oil. The main reason for this is that petroleum has become cheap and available in large quantities, but it also stems from the fact that coal is solid and contains ash, which has little utility. That is, since it is a solid, it is extremely difficult to transport, and transportation costs are high. The presence of ash in coal reduces its energy density, which alone makes it a less efficient energy source than oil without ash. Furthermore, since ash is directly emitted during coal combustion, it costs a lot of money to dispose of it at thermal power plants, which have recently become larger. Although it is not strictly limited to inorganic substances, there is also the problem of sulfur content. That is, these sulfur components produce sulfur oxides upon combustion, which is of great concern from the viewpoint of environmental pollution. Currently, Japan relies on foreign coal for a considerable amount of its coal demand, but the ash content in coal ranges from a few percent to several tens of percent, and usually 10 to 20 percent.
%, these ash contents are not used effectively and are discarded, resulting in 10-20% of the transportation cost being wasted. As described above, the problem of the ash content of coal is extremely important for the effective use of coal, and if the ash content of coal can be effectively removed, the economic effects will be immeasurable.

In addition, as coal is solid as mentioned above, it costs a lot of money to transport it, but in order to reduce costs, there are ways to reduce the cost by pulverizing coal and transporting it pneumatically, or by making it into water slurry or oil slurry. A method of transporting it as a fluid is being considered. Furthermore, when it comes to large-scale coal combustion boilers, pulverized coal combustion boilers are almost always used, and such boilers generally use coal that has been pulverized to about 80% less than 200 mesh. That is, when coal is used, it is often handled in the form of pulverized coal. Therefore, if it becomes possible to supply pulverized coal from which the ash content has been removed, it would be possible to greatly contribute to the effective use of coal.

By the way, since the supply of coal from which ash has been removed, that is, deashed coal, has become desirable in recent years, there is currently no equipment for producing deashed coal, that is, chemical deashing treatment equipment for coal. I can't find anything valid.

Now, regarding the conventional method of removing ash from coal, that is, the deashing method, it must be said that although this is being considered, there is currently no truly effective method. The ultimate technology for deashing would be coal liquefaction technology, but this is still considered a technology of the future. A relatively effective method is oil agglomeration, in which pulverized coal is suspended and stirred in a mixture of water and oil, only the coal particles are agglomerated in an oil layer, and the ash is separated into a water layer. There is also an old method of treating coal with alkali at high temperature and pressure. Also, very recently, a method of treatment with hydrogen fluoride gas has been proposed (Unexamined Japanese Patent Publication No.
55-133487), but none of them can be said to be completely practical. In other words, an effective deashing method has not yet appeared in the world.

Prior to filing this patent application, the present inventors proposed a chemical method for treating coal with a solution of hydrochloric acid or citric acid to which fluoride was added as a deashing method (see JP-A-57-151698 and Unexamined Japanese Patent Publication 1987-
(See Publication No. 162791). As the fluoride, acidic ammonium fluoride, ammonium fluoride, acidic sodium fluoride, sodium fluoride, acidic potassium fluoride, and potassium fluoride are effective, and acidic ammonium fluoride is particularly effective. When using acidic ammonium fluoride as the fluoride, 1 to 10% by weight of hydrochloric acid and 1.25 to 10% by weight of acidic ammonium fluoride (NH ₄ HF ₂ ), as described in the previously proposed application specification; or 1-10% by weight of citric acid and 1-10% by weight of acidic ammonium fluoride
Using an aqueous solution containing % by weight. The method proposed previously is a so-called wet method based on an aqueous solution reaction, does not generate harmful hydrogen fluoride gas, and has a deashing effect even at room temperature.

The wet deashing method proposed by the present inventors attempts to dissolve and remove ash in coal using a so-called solid-liquid reaction. Therefore, it is necessary to increase the contact efficiency between the coal and the deashing agent solution, that is, a solution prepared by adding fluoride to a hydrochloric acid or citric acid solution.
It is desirable to use pulverized coal as the raw material coal, preferably pulverized coal of 100 mesh or less, and to thoroughly suspend and stir the coal and deashing agent solution by some method. Furthermore, since the dissolution rate of ash is usually slow, it is necessary to allow sufficient residence time. However, in the batch treatment method, the rate of ash dissolution slows down as the treatment time increases. This is because the concentration of the deashing agent in the deashing agent solution decreases as the dissolution of ash progresses, so it is desirable to perform the treatment with a fresh deashing agent solution. Furthermore, it is desirable to increase the treatment temperature in order to increase the dissolution rate of ash. Since the deashing agent solution used to dissolve and remove ash is a corrosive liquid, it is preferable to add a corrosion inhibitor to the deashing agent solution to prevent corrosion of equipment, piping, etc., and the equipment is also made of Teflon. It is desirable to have a simple structure with few mechanical elements so that anti-corrosion processing can be easily performed.

This invention has been made in view of the above points, and its configuration will be described below based on embodiments shown in the drawings.

It should be noted that the Examples show one specific example of the present invention, and the present invention is not limited to such Examples.

Raw coal containing ash, preferably pulverized coal of 100 mesh or less, is continuously charged into a deashing treatment tank 2 from a coal input port 1 . Here, the pulverized coal is
For example, in addition to dry pulverized coal, wet pulverized charcoal, pulverized charcoal supplied as a water slurry, etc. are used. Deashing treatment tank 2
is filled with a deashing agent solution, has a partition plate 3 and a deashing agent solution supply port 16, and forms a solid-liquid fluidized bed. Here, the deashing agent solution is a hydrochloric acid or citric acid aqueous solution containing a corrosion inhibitor to which fluoride is added. The corrosion inhibitor is used to protect equipment, piping, etc. from the corrosive properties of hydrochloric acid or citric acid aqueous solutions, and commercially available ones can be used. That is, as this type of corrosion inhibitor, those used when pickling boiler tubes and plant piping can be used.

Hydrochloric acid and citric acid are effective in dissolving ash in coal, especially iron-based compounds, and fluoride is effective in dissolving ash in coal, especially iron-based compounds.
Effective in dissolving silica-based compounds. However, both these acids and fluorides have a synergistic effect, and the greatest demineralization effect can be obtained when both are present in the same solution. Here, the fluorides include acidic ammonium fluoride, ammonium fluoride,
A compound selected from the group consisting of acidic sodium fluoride, sodium fluoride, acidic potassium fluoride, and potassium fluoride is used. Among these fluorides, acidic ammonium fluoride is the most effective for demineralization. This not only has a strong deashing effect, but also has the effect of not increasing the amount of sludge during subsequent wastewater treatment because it can be decomposed, unlike the case of sodium salts and potassium salts.

As shown in the drawing, the deashing treatment tank 2 has an open upper end and operates at normal pressure.
And the temperature of the deashing agent solution is room temperature to 80°C. This deashing treatment tank 2 is separated into two chambers 2A and 2B, and a partition wall 4 is provided between the first chamber 2A and the second chamber 2B. Since the density of the coal particles introduced into the first chamber 2A of the treatment tank 2 is usually about 1.2 to 1.5 g/cm ³ , the input coal particles descend to the bottom of the deashing treatment tank 2 one after another. However, some types of coal may have a surface condition that makes them difficult to wet with water or solutions, and this can be solved by adding a suitable surfactant to the deashing agent solution. The coal particles rise to the top of the tank 2 as shown by the arrow in the figure by the deashing agent solution supplied at an appropriate flow rate from the supply port 16 at the bottom of the first chamber 2A of the deashing tank 2. The mixture is stirred in a fluidized manner. The coal particles then pass over the partition wall 4 to the second chamber 2 of the deashing treatment tank 2.
B is introduced.

As mentioned above, the density of coal itself is 1.2~1.5g/
cm ³ , but the density of ash contained in coal is
2.0 to 5.0 g/cm ³ , so as the ash is dissolved and removed from the raw coal in the deashing treatment tank 2, the density of the coal particles approaches that of the coal itself, and the density of the coal particles that have been deashed is smaller than that of undeashed coal particles. Therefore, coal particles that have been deashed in the first chamber 2A of the treatment tank 2 gather at the upper part of the same chamber 2A, cross the partition wall 4, and enter the second chamber of the deashing treatment tank.
The proportion moving to room 2B gradually increases. Fluid agitation is performed in the second chamber 2B of the deashing treatment tank 2 in the same manner as in the first chamber 2A. The dissolution rate of ash is usually slow and requires sufficient residence time. In addition, although the case where the deashing process tank 2 had two chambers 2A and 2B was shown in the Example, the deashing process tank 2 can also be added as needed.

The coal whose ash content has been sufficiently dissolved and removed in the deashing treatment tank 2 then overflows from the deashing outlet 5 together with the deashing agent solution and is introduced into the dehydrator 6, where the deashing coal and the deashing agent solution are combined. separated into Here, as the dehydrator 6, a centrifugal separator, a filtration machine, or the like can be used. Most of the deashing agent solution is returned to the deashing agent solution preparation tank 11 again, but a portion is extracted and sent to the wastewater treatment device 10 where metals such as Si, Al, and Fe dissolved in the deashing agent solution are removed. Ions are removed as sludge, and the treated solution is returned to the deashing agent solution preparation tank 11 and used for circulation.

On the other hand, since hydrochloric acid or citric acid and fluoride are attached to the coal dehydrated by the dehydrator 6, this coal is introduced into the cleaning tank 7. Then, while circulating the cleaning water with the circulation pump 8, the cleaning tank 7
The chemical solution adhering to the coal is washed inside. Note that a plurality of cleaning tanks 7 may be installed as necessary. The thoroughly washed coal is extracted from the washing tank 7 and guided to the dehydrator 9. Note that the amount of water to be replenished to the cleaning tank 7 corresponds to the amount of water taken out together with the sludge and product coal. Also, conventional techniques are used for such washing.

Next, the dehydrated coal in the dehydrator 9 undergoes a drying process if necessary, and then becomes product coal. The water separated by the dehydrator 9 is returned to the deashing agent solution preparation tank 11 again. The deashing agent solution preparation tank 11 also has the function of a decanter, and has a partition plate 12 and a sediment discharge port 13. In this preparation tank 11, the deashing agent is replenished so that the solution has a predetermined concentration. The prepared deashing agent solution is passed through the pump 14 to the control valve 1.
After the flow rate is adjusted by 5, the deashing agent solution is supplied to the deashing treatment tank 2 through the deashing agent solution supply port 16. Note that the dissolution rate of ash increases as the treatment temperature increases, so if the deashing agent solution is heated and the deashing treatment tank 2 is kept warm, the deashing efficiency will further increase, which is preferable. The temperature should be between room temperature and 80°C, and there is no need to heat it above 80°C.

As described above, the present invention enables deashing of coal to be carried out continuously and efficiently, and also has the following effects.

(i) Since the pulverized raw coal and the deashing agent solution are agitated by fluid agitation in the solid-liquid fluidized bed type deashing treatment tank 2, there is no need for mechanical agitation, and the mechanical agitation power is reduced. is not necessary. In addition, the deashing equipment operates at a relatively low temperature of room temperature to 80°C and under normal pressure, so it is very easy to operate and requires less heat and power, making it extremely economical. is high. Furthermore, since the structure of the deashing layer 2 is very simple, anti-corrosion treatment using Teflon or the like against corrosive solutions can be easily applied, and corrosion of the treatment layer 2 can be effectively prevented.

(ii) By employing the continuous deashing treatment layer 2, coal in which ash has been sufficiently dissolved and removed in the deashing treatment layer 2 is continuously discharged, making it possible to effectively perform coal deashing treatment. can.

[Brief explanation of the drawing]

The drawing is a flow sheet showing an embodiment of the invention. 2... Deashing treatment tank, 2A... First chamber, 2B...
2nd chamber, 4... Partition wall, 6... Dehydrator, 7... Washing tank, 9... Dehydrator, 10... Wastewater treatment device, 11
... Deashing agent solution preparation tank, 16 ... Deashing agent solution supply port.

Claims (1)

[Claims] 1. A fluoride selected from the group consisting of acidic ammonium fluoride, ammonium fluoride, acidic sodium fluoride, sodium fluoride, acidic potassium fluoride, and potassium fluoride is added to an aqueous solution of hydrochloric acid or citric acid. one or more solid-liquid fluidizers operating under normal pressure, filled with a deashing agent solution, having a deashing agent solution supply port 16 at the bottom, and configured to supply pulverized coal near the bottom; A deashing treatment tank 2 consisting of a layer tank, a dehydrator 6 that separates deashed coal from a deashing agent solution, and a wastewater treatment device 10 that processes a part of the deashing agent solution after the deashing process.
and a deashing agent solution preparation tank 11, the pulverized raw material coal supplied near the bottom of the deashing treatment tank 2 is made to flow in the deashing treatment tank 2 by the deashing agent solution flow, The ash in the pulverized raw coal is dissolved and removed, the deashing coal and the deashing agent solution are separated by the dehydrator 6, and most of the separated deashing agent solution is sent to the deashing agent solution preparation tank 11. A portion of the sludge is removed in the wastewater treatment device 10 and sent to the preparation tank 11, and the deashing agent solution is circulated and supplied from the preparation tank 11 to the deashing treatment tank 2. A chemical coal deashing treatment device characterized by: