KR20140009629A

KR20140009629A - Modification method for low rank coal

Info

Publication number: KR20140009629A
Application number: KR1020120075858A
Authority: KR
Inventors: 이시훈; 노남선; 문승현; 김상도; 전동혁; 임영준; 이승재; 유인수; 최호경; 유지호; 임정환
Original assignee: 한국에너지기술연구원
Priority date: 2012-07-12
Filing date: 2012-07-12
Publication date: 2014-01-23

Abstract

The present invention comprises the steps of: pulverizing coal; manufacturing coating oil by mixing and stirring middle distillate with solvent oil; manufacturing coal slurry by mixing and stirring the pulverized coal and coating oil at room temperature; separating the coating oil and coal cake from the coal slurry using a solid/liquid separator; evaporating and drying the solvent oil and water contained in the coal cake; and molding the coal cake. The modification method can produce high quality coal with high caloric value and minimize moisture reattachment and natural combustion. [Reference numerals] (AA) Coal; (BB) Grinder; (CC) Asphalt; (DD) Lamp oil; (EE) Heavy oil/Lamp oil mixer; (FF) Slurry manufacturer; (GG) Solid and liquid separator; (HH) Drier; (II) Oval briquettes molder; (JJ) Lamp oil tank; (KK) Oil and water separator; (LL) Condenser; (MM) Waste water

Description

Modification method for low rank coal

The present invention relates to a method for reforming coal, and more particularly, to a method for reforming low grade coal for reforming high moisture low grade coal into high grade coal having high calorific value and minimizing water resorption and spontaneous combustion.

As the price of crude oil has exploded in recent years, efforts to secure energy sources that can replace crude oil are increasing. Research into new energy sources that can replace existing fossil fuels such as solar energy and bioenergy is being actively conducted, but there are still many limitations in industrial use. Recently, the demand for coal is increasing again, and since most coal mines are closed in Korea, coal imports from overseas such as Australia and Indonesia have been imported.

Coal is divided into peat, brown coal, lignite, sub-bituminous coal, bituminous coal, and anthracite grades. And anthracite is divided into semi anthracite, anthracite, meta-anthracite and graphite anthracite, among which low grade coal (LRC) is from brown coal to sub-bituminous coal and from bituminous coal to high grade coal (HRC). .

High-grade coal, such as anthracite coal and bituminous coal, must be used for direct thermal combustion of coal. In order to prepare for the depletion of bituminous coal and anti-anthracite coal, which is used as a fuel for power generation, interest in the use of low rank coal (LRC) with abundant reserves and low prices is increasing.

For example, lignite, one of the lower grade coals, is lower in price than bituminous coal, but has a low moisture content of 30 to 70% and a low calorific value of 3500 to 4000 kcal / kg. Research has been actively conducted since the early 1980s.

Low grade coal has a high content of moisture and has a large weight and volume, which is not advantageous in logistics, and there is a problem in that spontaneous ignition occurs easily due to volatile matter and thus is not easy to move. Therefore, from the viewpoint of economics and stability of logistics, it is urgently required to develop a method of degrading low grade coal and suppressing spontaneous ignition.

Japanese Patent Application Laid-Open No. 233383/1995 discloses a method of mixing a mixed oil containing a heavy oil fraction and a solvent fraction with a porous carbon to heat the porous slurry and to advance dehydration of the porous carbon, And a mixed oil containing a mineral oil and a solvent oil, followed by solid-liquid separation of the slurry.

However, the method has a disadvantage in that the process is complicated by including the process of heating the raw material slurry, the equipment cost is increased, the maintenance cost is increased, and the stability of the operation is reduced.

Japanese Laid-Open Patent Publication No. 1995-233383

The present invention has been made to solve the above-mentioned conventional problems, and provides an efficient low grade coal reforming method for reforming high moisture low grade coal into high grade coal having high calorific value and minimizing water resorption and spontaneous combustion. It aims to do it.

The method of the present invention for achieving the above object, (a) pulverizing coal; (b) mixing the heavy oil with the solvent oil and stirring to prepare a coating oil; (c) preparing coal slurry by mixing and stirring the coal particles and the coating oil which have undergone the step of crushing the coal at room temperature; (d) separating the coal cake and the coating oil from the coal slurry using a solid-liquid separator; (e) evaporating and drying the moisture and the solvent oil contained in the coal cake; And (f) forming the coal cake which has been subjected to the evaporation and drying.

The present invention is also characterized in that the average particle size of the coal particles passed through the grinding step is 0.5 to 5 mm.

The present invention is also characterized in that the solid-liquid separator has a configuration that includes a high-speed rotating screw conveyor and a size adjustable screen for filtration, characterized in that the centrifugation and filtration are performed at once.

The present invention is also characterized in that petroleum oil or vegetable oil is used as the heavy oil.

The present invention is also characterized in that the vegetable oil is at least one selected from the group consisting of palm oil, olive oil, linseed oil and palm oil.

The present invention is also characterized in that the solvent oil is at least one selected from the group consisting of light oil, kerosene and lubricating oil.

The present invention is also characterized in that the coal cake which has undergone the step of evaporation and drying comprises 0.5 to 30 parts by weight of heavy oil based on 100 parts by weight of coal contained in the coal cake.

The present invention is also characterized in that it further comprises the step of cooling the coal cake passed through the evaporation and drying step.

The present invention is also characterized by adding a binder in the forming step.

By using the low grade coal reforming method of the present invention, it is possible to economically reform low grade coal into high grade coal having high calorific value and minimizing water resorption and spontaneous ignition.

Figure 1 shows the flow of each process of the low grade coal reforming method of the present invention in a flow chart with the associated apparatus.
2 is a graph showing the water content of the reformed coal according to the amount of vegetable oil contained in the reformed coal when vegetable oil (palm oil) is used as the heavy oil.
3 is a graph showing the water content contained in the reformed coal when bunker seed oil, asphalt oil and vegetable oil (palm oil) are used as the heavy oil.

Hereinafter, the method for reforming the low grade coal of the present invention will be described in detail step by step.

(a) pulverizing the coal

The average particle size of the pulverized raw coal used in the present invention is several mm to several tens of millimeters, and may include a large number of lumps of coal. A jaw crusher, a pin mill, a hammer mill, a roll mill, or the like may be used as a crusher of raw coal including lump coal.

The pulverized coal particles may be classified into coal of a predetermined size using a zigzag separator, a vibrating screen, a twist screen, or the like. In the classification process, coal having a predetermined size or more is circulated to regrind, and fine particles below a predetermined size are collected and used separately.

The average particle size of the coal pulverized in the coal crushing step of the present invention is preferably 0.5 to 5 mm.

(b) mixing the heavy oil with the solvent oil and stirring to prepare a coating oil.

The step is to prepare a coating oil by melting and stirring heavy oil in a solid state (high viscosity liquid) to facilitate transport, mixing and stirring the heavy oil uniformly in a solvent oil. The coating oil improves the formability of the pulverized coal to fuel by coating the pulverized coal surface, prevents reabsorption of moisture, and increases the calorific value of the generated fuel.

The heavy oil may be vegetable oil or petroleum oil, and in particular, vegetable oil may be more preferably used because it is inexpensive compared with petroleum oil and provides an equivalent effect. It is preferable to use the vegetable oil or petroleum oil whose boiling point is 200 degreeC or more.

The vegetable oil may be one or more selected from the group consisting of palm oil, olive oil, linseed oil, palm oil, and the like, and the petroleum oil may be petroleum asphalt, natural asphalt, bunker seed oil, coal-based heavy oil, petroleum or Coal-based distillation residues and the like can be used.

As the solvent oil, petroleum light oil, kerosene, lubricating oil or the like can be used.

The heavy oil and the solvent oil are used by mixing so that the coating oil made of these is easy to transport.

(c) mixing and stirring the pulverized coal and the coating oil at room temperature to prepare a coal slurry.

In this step, the coating oil mixed with the heavy oil and the solvent oil is filled into the mixing tank and stirred while supplying the raw coal pulverized to an appropriate particle size to prepare a coal slurry. In the manufacture of coal slurry, the coal is preferably used in 10 to 50% by weight based on the total weight of the coal slurry.

In the mixing tank, the heavy oil in the coating oil adheres to the coal surface to form coal slurry.

In particular, in the prior art, the dehydration process is performed by mixing the pulverized coal and the coating oil and then heating it to a high temperature, but the present invention mixes and stirs the pulverized coal and the coating oil at room temperature and transfers it to the next step without the heating process. It is characterized by.

In the prior art, by heating the coal slurry, the heavy oil in the coating oil is adsorbed into the pores of the dehydrated coal to prevent resorption of moisture into the dried coal and to suppress spontaneous ignition. It was confirmed that an equivalent degree of effect on spontaneous ignition was obtained in comparison with the prior art even though the heating process was not performed.

As described above, even in the normal temperature process, an effect equal to or higher than that obtained by the heating process of the prior art is obtained when the heating process is carried out, and the oil penetrates into the pores filled with the moisture by the evaporation of water, and the heavy oil is adsorbed inside the pores. While spontaneous ignition is suppressed by blocking resorption and reaction with oxygen, when no heating process is performed, heavy oil is adsorbed at the pore inlet on the surface of the coal, effectively blocking resorption of water and reaction with oxygen. It is likely that ignition is suppressed.

(d) separating the coal cake and the coating oil from the coal slurry using a solid-liquid separator

A solid-liquid separation process is carried out to separate the solid coal and the oil used as the coating oil from the coal slurry. Solid-liquid separation is mainly carried out by centrifugation and filtration.

In the step (a), fine particles of several mm or less are present even after classifying to an appropriate particle size after coal pulverization, and these fine particles are attached to the wall of the centrifuge to block the centrifugal outlet or partially to solid solution. It remains in the filtrate after separation and causes a problem of increasing viscosity while continuing to circulate.

However, in the present invention, by using a solid-liquid separator that can perform centrifugation and filtration at once, the coal cake and oil are effectively separated from the coal slurry, and at the same time, fine particles are removed so that they are attached to the wall of the centrifuge to separate the centrifugal outlet. It prevents the problem of increasing the viscosity by occluding or remaining in the filtrate after solid-liquid separation to continue circulation.

The solid-liquid separator has a configuration that includes a high-speed rotating screw conveyor and a sizable screen for filtration, the device discharges the coal cake to the outside through a high-speed rotating screw conveyor, the liquid containing oil to the screen Centrifugation and filtration are performed at once by allowing the discharge to the outside.

In addition, since fine particles not filtered through the filtration may remain in the separated coating oil, a separate centrifuge for treating such fine powder may be installed.

The coating oil separated in this step can be reused in the slurry preparation step (c).

(e) evaporating and drying the moisture and the solvent oil contained in the coal cake

In the present invention, the step of evaporating and drying the moisture and the solvent oil contained in the coal cake may be performed by a method commonly used in the art. For example, it can be evaporated and dried by heating to 120-180 ° C. using a dryer such as a steam tube dryer. The carrier may be a conventional carrier gas such as nitrogen and flue gas.

Since the gas discharged from the dryer includes water and solvent oil, it can be condensed with a condenser, and water and solvent oil can be recovered and reused with a water / oil separator.

The temperature of the coal discharged at this stage is about 100 ℃, so if it is left outside, it may ignite spontaneously. Therefore, the present invention may further perform the step of cooling the evaporated and dried coal after the execution of this step. In the cooling step, a conventional apparatus used for cooling such as a cooler may be used.

(f) forming the dried coal cake

The final dried and discharged coal is subjected to a molding process for ease of long term transfer. The molding process may be molded directly without a binder or by adding a binder depending on the moisture content of dry coal.

Although the content of the heavy oil contained in the coal reformed by the method of this invention is not specifically limited, It is preferable to contain 0.5-30 weight part with respect to 100 weight part of said coals. When contained in less than 0.5 part by weight, the effect of suppressing spontaneous combustion is insignificant, and in the case of exceeding 30 parts by weight, economic efficiency is lowered.

Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to further illustrate the present invention, and the scope of the present invention is not limited by the following examples. The following embodiments can be appropriately modified and changed by those skilled in the art without departing from the scope of the present invention.

Example 1: Reforming Low Grade Coal (using Asphalt Oil)

Coal was crushed and classified using a grinder to prepare an average diameter of 0.5 to 3 mm. Using asphalt oil as a heavy oil and kerosene as a solvent oil, the coating oil was prepared by mixing so that the concentration of asphalt is 12% by weight. The pulverized coal and the coating oil were mixed to prepare a coal slurry having a coal concentration of 15% by weight, and separated by solid-liquid separation using a centrifuge to separate the coal cake and the coating oil. The separated coating oil is recycled to be used for the production of coal slurry, and the separated coal cake (3% by weight of kerosene) is heated to 160 to 180 ° C. using a steam tube dryer to be evaporated and reformed by evaporating water and solvent oil. Coal was prepared. The produced coal was molded into briquettes using a briquette molding machine.

The steam discharged from the dryer was liquefied in a condenser and separated into an oil component and water using an oil / water separator, and the oil component was recycled together with the separated coating oil for use in the production of coal slurry, and the water was treated with wastewater.

The entire process was performed by continuous operation for 100 hours on a 5 ton / day pilot scale on a throughput basis.

The flow of the whole process is shown in FIG.

Example 2: reforming of low grade coal (using palm oil)

Low grade coal reforming experiments using vegetable oil were conducted. Unlike in the case of Example 1, this experiment was conducted on a batch laboratory scale.

Coal was crushed and classified using a grinder to prepare a diameter of 0.5 to 3 mm. Palm oil was used as a heavy oil, and kerosene was used as a solvent oil, and the coating oil was prepared by mixing so that the density | concentration of palm oil may be 1-10 weight%. The pulverized coal and the coating oil were mixed to prepare a coal slurry having a coal concentration of 15% by weight, and separated by solid-liquid separation using a centrifuge to separate the coal cake and the coating oil. The separated coating oil is recycled to be used for the production of coal slurry, and the separated coal cake (3% by weight kerosene) is heated to 140 ° C. using a steam tube dryer to evaporate the modified coal by evaporating water and solvent oil. Prepared. The produced coal was molded into briquettes using a briquette molding machine.

Example 3: Reforming low grade coal (using bunker C oil)

Coal was crushed and classified using a grinder to prepare an average diameter of 0.5 to 3 mm. Using bunker C oil as a heavy oil and kerosene as a solvent oil, a coating oil was prepared by mixing the asphalt to have a concentration of 12% by weight. The pulverized coal and the coating oil were mixed to prepare a coal slurry having a coal concentration of 15% by weight, and separated by solid-liquid separation using a centrifuge to separate the coal cake and the coating oil. The separated coating oil is recycled to be used for the production of coal slurry, and the separated coal cake (3% by weight of kerosene) is heated to 160 to 180 ° C. using a steam tube dryer to be evaporated and reformed by evaporating water and solvent oil. Coal was prepared. The produced coal was molded into briquettes using a briquette molding machine.

The flow of the whole process is shown in FIG.

Test Example 1: Evaluation of Physical Properties of Reformed Coal

(1) Evaluation of physical properties of the reformed coal produced in Example 1

The physical properties of the reformed coal prepared in Example 1 are shown in Table 1 below.

The following test results indicate that the industrial analysis is based on the arrival sample, and the elemental analysis calorific value is based on the dry sample. High fever_AR (As received) is a value calculated from the high fever value based on the dry sample.

Name of analyzer used:

TGA-701 Thermogravimeter. (LECO Co., USA)

TruSpec Elemental Analyzer. (LECO Co., USA)

SC-432DR Sulfur Analyzer (LECO.Co., USA)

Parr 6320EF Calorimeter. (PARR Co., USA).

analysis
Item Industrial analysis wt %) Elemental Analysis wt %) eminence
Calorific value
( kcal Of
kg )
eminence
Calorific Value_
AR
( kcal / k
g)
Name of sample
moisture
(M) Volatility
(VM) Ash
(Ash
) fixing
carbon
(FC) carbon
(C) Hydrogen
(H) nitrogen
(N) Oxygen
(O) Sulfur powder
(S) Round coal 28.37 35.6 2.34 33.69 67.2 5.21 1.18 23.97 0.1 6,060 4,341 Example 1 Reformed Coal 4.57 46.34 6.42 42.67 68.47 5.35 0.75 18.89 0.12 6,460 6,165

As confirmed in Table 1, in the case of coal modified by the present invention, it can be confirmed that it has a preferable component composition and excellent calorific value as compared to raw coal.

(2) Evaluation of physical properties of the reformed coal produced in Example 2

The moisture content according to the vegetable oil content of the reformed coal prepared in Example 2 was measured and shown in FIG. As can be seen from Figure 2, in the case of coal modified with vegetable oil according to the present invention it can be seen that the content of water is reduced compared to unmodified coal.

(3) Evaluation of physical properties of the reformed coal produced in Examples 1 to 3

The moisture content of the modified coal prepared in Example 1 (using asphalt oil), Example 2 (using palm oil) and Example 3 (using Bunker C oil) was measured and shown in FIG. 3. As can be seen from FIG. 3, it can be seen that coal modified with petroleum based oil and vegetable oil (palm oil) according to the present invention contain almost the same amount of water. These results indicate that low-cost vegetable oil can be used to reform low grade coal more economically.

Test Example 2. Evaluation of spontaneous flammability of reformed coal

Coal slurry mixed with raw coal, oven-dried coal, pulverized coal and coating oil is used to confirm that even if the coal slurry is not heated as in the prior art, the equivalent effect is higher in spontaneous ignition compared to the conventional technique. The reformed coal prepared by performing the dehydration process by heating, and the cross point temperature (CPT) of the reformed coal of Example 1 were measured and compared, and the results are shown in Table 2 below. Higher CPT values indicate that spontaneous combustion is suppressed.

Type of coal CPT ( Cross Point Temperature ) Round coal 131 ° C Oven Dry coal 140 ° C Coal The slurry Reformed coal produced by heating and dehydration process ^** 163 ℃ Example 1, reforming coal 158 ℃

** The reformed coal prepared by heating the coal slurry to perform a dehydration process was prepared in the same manner as in Example 1 except that the coal slurry was heated to conduct a dehydration process.

As shown in Table 2, the reformed coal (Example 1) according to the present invention exhibited almost the same spontaneous ignition properties as the reformed coal produced by heating the coal slurry to perform a dehydration process.

Claims

(a) pulverizing coal;
(b) mixing the heavy oil with the solvent oil and stirring to prepare a coating oil;
(c) preparing coal slurry by mixing and stirring the coal particles and the coating oil which have undergone the step of crushing the coal at room temperature;
(d) separating the coal cake and the coating oil from the coal slurry using a solid-liquid separator;
(e) evaporating and drying the moisture and the solvent oil contained in the coal cake; And
(f) forming a coal cake which has undergone the evaporation and drying step;
How to reform low grade coal.

The method of claim 1,
The average particle size of the coal particles passed through the grinding step is characterized in that 0.5 ~ 5 mm, low grade coal reforming method.

The method of claim 1,
The solid-liquid separator has a configuration that includes a high-speed rotating screw conveyor and a size adjustable screen for filtration, characterized in that performing the centrifugation and filtration at once, low-grade coal reforming method.

The method of claim 1,
Reforming method of low grade coal, characterized in that the use of petroleum oil or vegetable oil as the heavy oil.

5. The method of claim 4,
The vegetable oil is characterized in that at least one selected from the group consisting of palm oil, olive oil, linseed oil and palm oil, low-grade coal reforming method.

The method of claim 1,
The solvent oil is characterized in that at least one selected from the group consisting of light oil, kerosene and lubricating oil.

The method of claim 1,
The evaporated and dried coal cake is characterized in that it comprises 0.5 to 30 parts by weight of heavy oil based on 100 parts by weight of coal contained in coal cake, reforming method of low grade coal.

The method of claim 1,
The method of claim 1, characterized by further comprising the step of cooling the coal cake after the evaporation and drying.

The method of claim 1,
Reforming method of low grade coal, characterized in that for adding a binder in the forming step.