JPS6026093A - Method for producing deashed coal - Google Patents

Abstract

PURPOSE:To prepare deashed coal with a low ash content, by adding seeds to an aqueous slurry of crushed raw material coal and treating the resultant intermediate coal with a processing soln. contg. an acid and an acidic ammonium fluoride. CONSTITUTION:Dust coal obtained by crushing raw material coal to a particle diameter of 500mum or smaller is suspended in water and seeds consisting of an oil in an amt. of 10-30wt% of dust coal and lipophilic particulate solid having a particle diameter of 1-fewmm. which act as granulation nuclear, are added to the resultant aqueous slurry for agitation and granulation. The granules are separated, washed and dried to obtain intermediate coal deashed by 70-80%. The intermediate coal is dipped in a processing soln. contg. 1-12wt% hydrochloric acid, 1-10wt% citric acid and 1-10wt% ammonium fluoride, for dissolution of ash. Upon separation, washing and drying, refined coal with an ash content of below 1% is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing deashed coal, ie coal with a very low ash content.

Coal has been used as an important energy source for a long time, but since coal is a solid, it is more expensive to transport and handle than oil, so it has lost its status to oil. ing. However, in recent years, due to concerns about oil supply and soaring prices, the need for energy diversification has been recognized, and as a result, there has been a growing trend around the world to look at coal, and effective ways to use coal are being explored. It is being considered.

One example of this is the use of coal as a fuel for diesel engines, turbine engines, etc. However, in order to use coal as fuel 131 for diesel engines, there are problems that must be solved.

Coal usually contains ash at a rate of several percent to several tens of percent.

The ash composition is 40 to 60% by weight of silica (Sfe2)
, 25-35% by weight alumina (△1203), 5-2
5% by weight of iron oxide (Fe203), 1-15% by weight of calcium oxide (CaO), 0.5-4% by weight of magnesium oxide (M(10), 1-4% by weight of sodium oxide (Na20) , potassium oxide (K2O), and sulfur oxide (SO3).However, the above composition is an analysis value of ash produced by burning coal.Coal containing such ash is used as fuel for the above engine. When used, the ash in the coal causes wear on the valves, piston rings, etc. in diesel engines, and on the turbine blades in turbine engines.Therefore, in order to keep this amount of wear within acceptable limits for the engine life cycle, it is necessary to remove the ash from coal. It is said that it is necessary to remove ash and reduce its content to about 0.5%.

However, conventional coal deashing methods are divided into physical methods and chemical methods.

Known physical methods include flotation, heavy liquid beneficiation, force beneficiation, and oil agglomeration. The demineralization rate by these methods is low, 50%.
That's about it. However, in a special example of the oil agglomeration method (disclosed in JP-A-55+-141504 and JP-A-53-5-14.1505), 7
lf2 ash percentages of 0-80% can be achieved.

Regarding chemical methods, Tokuko Sho 17-466@, Tokko Sho 3
Those disclosed in No. 6-23711 and Japanese Unexamined Patent Publication No. 55-133487 are known. The classification of these is as follows.

(1) Treatment with acid (2) Treatment with alkali under high temperature and high pressure conditions (3) Oxidation treatment with oxygen, air, nitrogen dioxide, etc., then treatment with acid or alkali (4) Treatment with hydrofluoric acid or hydrogen fluoride gas Each of the above methods (1) to (4) attempts to decompose and remove the ash content by dissolving and extracting the ash content in the coal 5--4 = with chemicals, and the deashing rate is 70% at best. ~8
It is about 0%. Furthermore, each method (1) to (4) has certain drawbacks. Methods (1) and (2>) dissolve metal components in the ash composition, and cannot remove silica, which accounts for most of the composition.

Method (3) removes iron sulfide for the purpose of desulfurization, and cannot remove other components. Method (4)
attempts to remove silica, but since hydrofluoric acid and hydrogen fluoride are highly toxic and corrosive, it is difficult to handle them.

As mentioned above, the demineralization efficiency of conventional demineralization methods, physical and chemical methods, is at best 70-80%. Therefore, with such a deashing rate of 6-, it is impossible to obtain coal with an ash content of 1%, let alone an ash content of 0.5%.

In view of the above circumstances, an object of the present invention is to eliminate the drawbacks of conventional deashing methods and to provide a method for producing deashed coal having an extremely low ash content.

The method for producing deashed coal according to the present invention consists of a combination of a physical method for producing 1 q of intermediate legs from raw coal containing ash and a chemical method for obtaining refined coal from the obtained intermediate legs. , the process of pulverizing raw coal to make pulverized coal, suspending the pulverized coal in water to create pulverized coal slurry, and mixing the pulverized coal slurry with oil and seeds consisting of lipophilic granular solids such as granulation nuclei to create a slurry. A process of stirring and granulating the granules, a process of separating the granules from the slurry, washing and drying them, and a process of obtaining intermediate legs by separating the granules into coal and seeds. The chemical method involves immersing the intermediate leg in a treatment liquid containing acid and acidic ammonium fluoride to dissolve residual ash in the intermediate coal, and separating the coal from the treatment liquid and washing and drying it. The summary is that the process consists of a process of obtaining a refined product.

According to this invention, since the deashing process is carried out using a physical method and a chemical method that have completely different deashing mechanisms, it is possible to sufficiently remove ash from the coal, and the coal has an extremely low ash content. Ash charcoal can be produced. therefore,
Even when the demineralized coal produced according to the present invention is used as a fuel for diesel engines and turbine engines, for example, it is possible to suppress the amount of wear in these engines within permissible limits, and also to reduce transportation and cargo handling costs. can be reduced.

7- This invention will be explained in detail below.

There are two methods for producing deashed coal: a physical method to remove most of the ash from raw coal containing ash to obtain an intermediate leg, and a chemical method to obtain refined coal by further removing residual ash from the obtained intermediate leg. It consists of a combination of methods.

The physical method includes the following four steps. This physical method is described in detail in the above-mentioned JP-A-55-141504 and JP-A-55-141505, so a brief explanation will be given below.

First, natural coal containing ash, that is, raw coal, is pulverized into pulverized coal having an average size of 35 meshes (particle size: 500 μm) or less, preferably an average size of 100 meshes (particle size: 149 μm) or less. This pulverized coal is then suspended in water to create a pulverized coal slurry.

Next, the pulverized coal slurry is mixed and stirred with oil and seeds made of lipophilic granular solids serving as granulation nuclei to be granulated. As the oil, kerosene, heavy oil, distillation residue oil, vegetable oil, etc. are used. The amount of oil used is 10 to 30% by weight based on the pulverized coal. As seeds, particle size 1+
Particles made of synthetic resin such as hard polyvinyl chloride or coarse charcoal with a size of nm to several mm are used. The mixing ratio of seeds to pulverized coal is preferably 1:1.

Next, the pulverized coal granules that have aggregated in the oil layer in the slurry are separated from the slurry, washed and dried.

Then, the intermediate legs are obtained by decomposing the granules and separating them into coal and seeds.

By the above physical method, 70 to 80% of the ash contained in the raw coal is deashed.

The ash content of the intermediate leg refined in this way depends on the ash content of the raw coal, but is approximately several percent 10-.

The chemical method includes the following two steps.

First, the intermediate coal is immersed in an aqueous solution 1 (1 treatment solution) to dissolve the residual ash in the intermediate coal. is 2 to 10.0% by weight of citric acid and 1 to 10% by weight or 2 to 10% by weight of acidic ammonium fluoride (Nl).
-1411F2). The lower limit of the concentration range of each of the above drugs is the value at which the drug's effect is no longer fully exhibited, and the effect of the drug reaches a saturation value, and any further increase in the drug will unnecessarily increase the drug cost.4-1. The value is the upper limit. By adding a surfactant, particularly a degreasing agent, to the treatment liquid, the water wettability of the coal becomes good and the dissolution of ash is promoted.

Next, coal is separated from the treated liquid, washed and dried to obtain a purified product. Separation of coal from the treatment liquid is performed, for example, by filtration.

The demineralization rate by this chemical method is about 70 to 80%.

If deashing treatment is carried out by a chemical method following the above-mentioned physical method, assuming that the deashing rate of both methods alone is 70 to 80%, simple calculations can be made by combining both methods. A demineralization rate of 91 to 96% can be achieved. By using this method and rate, it becomes possible to obtain purified coal with an ash content of 1% or less, although it depends on the ash content of the raw coal.

What should be noted here is that, in contrast to the combination of physical and chemical methods with different demineralization mechanisms, high demineralization rates as described above can be obtained even when each method is repeatedly performed independently. This means that it cannot be done. This is because, as is clear from the examples described later, the demineralization rate decreases from the second time onwards. The mechanism is not clear, but physical methods cannot remove the fine ash that is crushed into pulverized coal and scattered in the IC coal particles, and chemical methods can reduce the ash composition (above). It is conceivable that ash cannot be removed because it contains ash that is difficult to dissolve in the chemical.

What is even more remarkable is that if the process of physical and chemical methods is reversed, the high demineralization rate as mentioned above can be achieved by 15J
This means that it cannot be done. In other words, most of the ash can be removed if the first stage is treated chemically, but some of the fine ash particles scattered in the coal particles remain, so these are treated in the second stage. It cannot be removed by physical methods. Further, by post-processing using a physical method, ash of a composition that remains undissolved in the chemical may be entangled with the coal content and granulated. Therefore, by processing the first stage by physical methods,
The high deashing rate mentioned above can be achieved by removing most of the ash, reducing the proportion of ash that is difficult to dissolve in chemicals, and efficiently removing this through post-processing using chemical methods. becomes.

Next, embodiments of the invention will be described.

Example 1 First, as a preliminary treatment using a physical method, the ash content was 7.
90% by weight Breasol charcoal (au-14-strariaic acid) is made into raw coal, which is crushed to give 200% by weight.
Metsushiko's pulverized coal was suspended in water to create a pulverized coal slurry.Next, seeds were mixed into the pulverized coal slurry.The seeds were made of hard polyvinyl chloride and had a diameter of approximately 3 mm and a height of approximately 1.5 mm. It has a short cylindrical shape, and the ratio (2) is 1.4, which is similar to the specific gravity of coal.The amount of pulverized coal and seeds in the slurry is 5% by weight.Then, the slurry contains 20% by weight of pulverized coal. 8% by weight of kerosene was added.Then, this slurry was granulated by stirring in a container with a diameter of 85φ at a rotational speed of 1900 ppm for 7 minutes using three wire mesh blades.Then, the slurry was granulated. The granules were separated and washed with water, and the washed granules were dried.The granules were then decomposed by vibration and separated into coal and seeds, resulting in a blue intermediate leg. The ash content of the legs was measured to be 1.74% by weight, which is a deashing rate of 78.1% from the raw coal.

Next, as a post-processing process using a chemical method, 20g of the intermediate leg was immersed in 200cc of a treatment solution containing 5% by weight of hydrochloric acid and 5g of acidic ammonium fluoride, and this was kept at 80°C and left for 3 hours. The residual ash in the intermediate coal was dissolved. Thereafter, the treated liquid was filtered to separate the coal content, which was washed and dried to obtain 1 q of purified coal. The ash content of the purified product was determined to be 0.69% by weight. This is a demineralization rate of 60.1% from the middle leg and 91.3% from raw coal.
It is. Further, when a degreasing agent was added to the above treatment liquid in an amount of 1% by weight of coal, a refined product with an ash content of 10.51% was obtained.

This means that the demineralization rate from the middle leg is 70.5%, and the raw coal is 15- The demineralization rate is 93.5%.

For comparison, both the first and second stages were decalcified using a chemical method. The processing conditions are the same as in the chemical method described above, with no degreasing agent added. According to this, the deashing rate from raw coal is 69.2%, and the deashing rate from the intermediate leg is 32.5%, and the deashing rate from the intermediate leg is 32.5%, and the ash content is 2.43% by weight. A purified product with an ash percentage of 79.2% and an ash content of 1.14% was obtained. The above results are summarized in Table 1.

(Leaving space below) 17- 16- Table 1 ″' = A□ Lori Physical Physical Chemistry Note 1) (Number in parentheses: Deashing rate from intermediate coal 2) Chemical method*: 112 Addition of fat agent 18- Example 2 Datong coal (produced in China) with an ash content of 12.1% by weight was used as raw coal and deashed under almost the same treatment conditions as in Example 1. However, under the treatment conditions in Example 2, The treatment conditions differ from those in Example 1 in that the amount of kerosene added was 25.0% by weight based on the pulverized coal, and the slurry stirring time was 20 minutes. The ash content of the intermediate coal obtained was 3.18% by weight, which means that the deashing rate from the raw coal was 73.7%.The intermediate coal was then processed in a later stage using a chemical method. The ash content of the purified product was 0.73% by weight.
The deashing rate from intermediate coal is 77.0%, and the deashing rate from raw coal is 94.0%.

Also, as in Example 1, for comparison, the previous stage and 19- Demineralization treatment using chemical methods was carried out in both the pre- and post-processing stages.

According to this, the deashing rate from raw coal is 80°2%, and the deashing rate from the intermediate type is 62.1%, and the deashing rate from the intermediate type is 62.1%, and the deashing rate from raw coal is 62.1%. A purity of 92.5% and an ash content of 0.91% by weight were obtained. The above results are summarized in Table 2.

(Margin below) 20- 21-

Claims (1)

[Claims] It consists of a combination of a physical method for obtaining intermediate legs from raw coal containing ash and a chemical method for obtaining clean coal from the obtained intermediate legs. A process of suspending charcoal in water to create a pulverized coal slurry, a process of mixing the pulverized coal slurry with oil and seeds consisting of lipophilic granular solids that serve as granulation nuclei, and stirring the slurry to granulate it; It consists of a process of separating the granules from the slurry, washing and drying them, and a process of obtaining intermediate legs by separating the granules into coal and seeds. The clean coal is immersed in a treatment liquid containing acidic ammonium fluoride to dissolve residual ash in the intermediate coal, and the coal is separated from the treatment liquid and washed and dried.
A method for producing deashed coal, which comprises the steps of: