KR101461012B1 - Coal Modification Process using Waste heat recovery - Google Patents

Abstract

The present invention relates to a method for re-using waste heat generated in a process of modifying coal which uses palm oil residue and, more specifically, to a method for modifying coal using waste heat from steam generated in the process, comprising the steps of crushing coal into an average particle size of 10 mm or less by using a crusher; melting palm oil residue at a melting tank; homogeneously mixing the crushed coal with the melted palm oil residue by using a mixer; drying and stabilizing moisture in coal, while the mixture of the coal and palm oil residue is coated on the surface of coal by blowing delivery gas via FD fans in a drier-stabilizer; cooling the coal that has passed through the drying and stabilization step by using a cooler; and molding the coal that has passed through the cooling step by using a molding device. Thus, exhaust gas which is discharged from the drier-stabilizer is transferred to a cyclone, and is supplied to the mixer, the melting tank and a delivery gas pipe of the drier-stabilizer, after removing the pulverized coal.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a coal-

The present invention relates to a method for recovering and reusing waste heat in a coal reforming process using a palm pan oil gasifier, and more particularly, to a method for recovering and reusing waste heat using a waste heat of a steam generated in a process, The present invention relates to a coal reforming method capable of preheating raw coal.

Efforts are continuing to secure energy sources that can replace crude oil in the short term in preparation for rising crude oil prices and mid- to long-term crude oil depletion. Recently, researches on new energy sources that can replace existing fossil fuels such as solar energy and bio energy have been actively carried out, but there is still a limit to industrial use. As a result, demand for coal is increasing again. In Korea, coal is being imported from overseas countries such as Australia and Indonesia because most mines are abandoned.

Coal is divided into peat, brown coal, lignite, sub-bituminous coal, bituminous coal and anthracite grades, and bituminous coal is further divided into low volatiles, medium volatiles, , And anthracite is divided into semi-anthracite, anthracite, meta-anthracite and graphite anthracite, among which brown coal is classified as low grade coal (LRC) and bittern coal is classified as high grade coal (HRC).

High-quality coal, such as semi-anthracite and bituminous coal, should be used in order to directly generate coal by burning coal. However, since bituminous coal and semi-anthracite coal are expensive and reserves are small, studies have been conducted since the 1980s to utilize low grade coal (LRC: Low Rank Coal), which has relatively rich reserves and low prices, with high quality.

For example, lignite, which is one of the low-grade coal, is low in price compared to bituminous coal, but has a water content of 30 to 70% and a low calorific value of 2500 to 4000 kcal / kg, to be.

In addition, low-grade coal has a high weight and volume due to high moisture content, which is not advantageous in logistics, and other than moisture, there is also a problem that spontaneous ignition easily occurs due to volatilization contained in coal, which makes migration difficult. Therefore, it is required to develop a method for improving the quality of low grade coal and suppressing spontaneous combustion, from the viewpoint of economic efficiency and stability of logistics.

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, since the expensive solvent oil is used together with the heavy oil, it is recovered through solid-liquid separation, but a considerable amount of the solvent oil remains in the coal, complicating the reforming process and increasing the cost of reforming. It is inevitable to develop a reforming method capable of maximization.

Japanese Laid-Open Patent Publication No. 1995-233383

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method of utilizing waste heat of exhaust gas generated in a process of directly coating coal, Thereby improving the economical efficiency of the coal reforming process.

In order to solve the above-mentioned problems, the present invention relates to a process for producing a coal-fired power plant, which comprises melting a palm oil residue and mixing it with pulverized coal particles for drying-stabilizing, It is possible to economically lower the grade of coal by reusing it, thus completing the present invention.

It is suitable for coal coating because it shows a characteristic that it becomes a dilute liquid at the temperature where the solid or coal is dried at room temperature and cools the coal evenly and becomes solid at room temperature after drying.

The present invention relates to a method for recovering waste heat to reform coal, comprising the steps of: (a) pulverizing coal with an average particle size of 10 mm or less using a pulverizer; (b) melting the palm oil residue in a melting tank; (c) homogenously mixing the melted palm pan oil with the pulverized coal using a mixer; (d) a drying-stabilizing step of blowing a carrier gas using an FD fan in a dry-stabilizer to coat the surface of the coal mixed with the coal, and drying moisture in the coal at the same time; (e) cooling the coal through the drying-stabilizing step using a cooler; And (f) shaping the coal through the cooling step using a molding machine, wherein the exhaust gas discharged from the dry-stabilizer is transferred to a cyclone to remove pulverized coal, and then the mixture, the melting tank, To a supply line for supplying the carrier gas of the dry-stabilizer.

The present invention also relates to a method for recovering waste heat to reform coal, comprising the steps of: (a) pulverizing coal to an average particle size of 10 mm or less using a pulverizer; (b) melting the palm oil residue in a melting tank; (c) homogenously mixing the melted palm pan oil with the pulverized coal using a mixer; (d) a drying-stabilizing step of blowing a carrier gas using an FD fan in a dry-stabilizer to coat the surface of the coal mixed with the coal, and drying moisture in the coal at the same time; (e) molding the coal through the cooling step using a molding machine, and (f) cooling the coal through the drying-stabilizing step using a cooler; A waste heat recovery coal reforming method in which the exhaust gas discharged from the dry-stabilizer is transferred to a cyclone to remove pulverized coal and then supplied to a feed pipe for supplying the carrier gas of the mixer, the melting tank, and the dry- to provide.

The present invention also provides a waste heat recovery coal reforming method wherein the mixer, the melting tank, and the supply pipe of the transportation gas include a heating jacket and supply the exhaust gas from which the pulverized coal is removed to the heating jacket .

The present invention also provides a waste heat recovery coal reforming method wherein the mixer is insulated, the screw inside the mixer includes a baffle, and the screw has a cavity to allow hot exhaust gas to pass therethrough.

The present invention also provides a waste heat recovery coal reforming method wherein a plurality of the screws are provided and the direction of rotation with the adjacent screw is opposite.

The present invention also provides a method for modifying a waste heat recovering coal, wherein the palm pan oil is mixed with 0.5 to 30% by weight of the coal in the step of homogeneously mixing the palm pan oil with the pulverized coal.

The present invention also relates to a process for the preparation of a dry-stabilizer, characterized in that the drying-stabilizing step is carried out in an indirect heat exchange dry-stabilizer, wherein the drying-stabilizer internal temperature is from 100 to 115 ° C, Wherein the coal is moved and has a residence time of 20 to 70 minutes.

The present invention also provides a waste heat recovery coal reforming process wherein the moisture of the dry coal after the drying-stabilization step is dry-stabilized to 5 to 20 wt%.

The coal reforming method of recovering and reusing the waste heat of the present invention can recover the heat from the exhaust gas produced in the drying-stabilizing step and reuse it, thereby making the low grade coal economically high-grade.

Figs. 1A and 1B are conceptual diagrams of a coal reforming method of the present invention.
2 is a stabilization process of the present invention.
3 is a process diagram of the present invention.
4A is a schematic diagram of a mixer to which a heat exchange function is added.
Figure 4b is a cross-sectional view of the mixer with the addition of a heat exchange function.
Figure 5 is a graph of the temperature profile in a heat exchanger for transport gas preheating during transport gas preheating.
Figure 6 is a graph of the temperature profile in a heat exchanger for transport gas preheating during transport gas + coal preheat.
7 is a graph of the temperature profile in a coal preheating mixer during transport gas + coal preheat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Prior to the detailed description of the present invention, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It should be understood that equivalents and variations may be present.

Here, in the entire drawings for explaining the embodiments of the present invention, those having the same functions are denoted by the same reference numerals, and a detailed description thereof will be omitted.

As shown in FIG. 1A, the present invention is subjected to a crushing-mixing-drying / stabilizing-cooling-molding process.

(a) pulverizing the coal

The raw coal is pulverized in the pulverizer (1). The pulverizer 1 of the pulverized raw coal used in the present invention may be a jaw crusher, a pin mill, a hammer mill, a roll mill, or the like.

The average particle size of the pulverized coal in the coal pulverization step of the present invention is preferably 10 mm or less.

(b) Fusing palm oil residue

(Steam / air) discharged from the drying-stabilizer 7 to heat the palm pan oil to convert it into a liquid. As shown in FIG. 3, the waste heat is filtered by the cyclone 9 and then moved to a heating jacket for heating the palm pan oil to melt the palm pan oil located in the melting tank 12.

(c) homogeneously mixing the palm oil residue with the pulverized coal

The step of mixing the melted palm pan oil with the pulverized coal is the mixing step shown in Fig. The mixer 4 in which the mixing step is performed is composed of a heat insulating material 23. In order to discharge the condensed water generated inside the screw by gravity, the mixer is inclined so that the flow of the exhaust gas is directed downward and the water trap 25 ). In the embodiment of the present invention, preheating of the raw coal is carried out in the mixer 4, the screw 21 in the mixer comprises a baffle 22, which passes through the hot exhaust gas through the cavity inside the screw, It is possible. In addition, a plurality of screws located inside the mixer, including baffles, rotate the direction of rotation with the adjacent screw in the opposite direction, so that stirring of coal and palm pan oil is smooth. The mixer is equipped with a drive motor (24) so that coal can move inside. In an embodiment of the present invention, the palm pan oil mixed is an amount corresponding to 0.5 to 30% by weight of the coal. Palm oil is a residue of palm fatty acid distillate (PFAD) and palm sludge oil (PSO) in Indonesia and Malaysia. It is a solid at room temperature and has a high calorific value of 9,000 kcal / kg or more.

In the above step, since the palm pan oil and the coal are physically mixed, the palm pan oil is not coated on the surface of the coal but mixed with each other. The coal mixed with the palm pan oil passed through the mixer (4) is transferred to the silo (5). These mixers refer to Figs. 4A and 4B, respectively, which are shown schematically and in section.

(e) a dry-stabilization step in which the palm pan blended with coal is melted and coated on the surface of the coal and simultaneously the moisture in the coal is dried

In the silo (5), the coal mixed with the palm pan oil is transferred to the dry-stabilizer (7) through the screw feeder (6). In the dry-stabilizer, the palm pan residues on the surface of the coal are melted to coat the surface, and the moisture of the coal is evaporated. In the mixing step, the palm pan oil adhered to the surface of the coal melts as the temperature rises and diffuses to the entire surface of the coal (Fig. 2 melting step). After that, the water in the pores of the coal is evaporated by the heat transfer (Fig. 2 evaporation step), and the pellet is diffused on the surface to penetrate into the pores (Fig. 2 penetration step). In one embodiment of the present invention, the form of the dry-stabilizer is an indirect type heat exchange type, has a sufficient residence time of 20 to 70 minutes, and has a form in which the movement of coal is allowed to take place and the mixing effect can be generated. In one embodiment of the present invention, the dry-stabilizer is equipped with a drive motor 8 so that movement of the coal is possible inside. In one embodiment of the present invention, the dry-stabilizer may be evaporated and dried by heating to about 120 to 180 DEG C using a steam tube dryer or a rotary disk dryer. The drying-stabilizer may include a steam supply device for heating and a condensed water discharge device after use of the supplied steam. The dry-stabilizer 7 may be a conventional carrier gas such as nitrogen and exhaust gas, and blows the carrier gas using a forced draft (FD) fan 14. The transporting gas can recover the waste heat and be preheated.

The internal temperature of the dry-stabilizer is maintained at about 100 to 115 캜, and since the melting point of the palm pan oil is 40 to 60 캜, the melting of the palm pan oil and the drying of the coal moisture proceed simultaneously. Since the coal surface coating of palm pan oil is sufficiently accomplished within 20 minutes, the drying-stabilizer residence time can be adjusted to about 20 to 70 minutes depending on the moisture content of the coal. The moisture content of the dried coal is 8 to 15% by weight.

(e) cooling step of the coal after the dry-stabilization step

The temperature of the coal discharged from the drying-stabilizer is as high as about 100 ° C., so there is a possibility of spontaneous ignition if left unattended. Accordingly, the present invention further performs the step of cooling the dry-stabilized coal using the cooler 10 after performing this step. As the coal is kept at the heated temperature until the previous stage, the palm pan oil is kept coated with the liquid phase on the surface of the coal. However, as the coal is cooled to the normal temperature in the above step, the palm pan oil coated on the coal is again deformed into a solid phase ), Thereby preventing the adsorption of moisture and minimizing the spontaneous ignition tendency, thereby maximizing the stabilization effect. In the cooling step, a conventional device used for cooling, such as the cooler 10, may be used.

The exhaust gas discharged from the drying-stabilizer is sent to the cyclone 9 to collect the pulverized coal contained in the exhaust gas and supply it to the molding machine 11. In one embodiment of the present invention, the exhaust gas from which the pulverized coal is removed is discharged using ID (Induced Draft) fans (15, 16, 17).

(f) molding the coal through the cooling step

The finally dried and discharged coal is molded using a molding machine 11 for the purpose of facilitating long-term transportation. At this time, the moisture remaining in the coal and the palm pan oil act as a binder of the molding, and the palm pan coated on the surface of the coal serves to prevent moisture reabsorption and increase the calorific value. The molding process is performed by pressing coal, and in one embodiment of the present invention, the briquettes are manufactured by the molding process.

As shown in FIG. 1B, the order of the cooling step and the molding step may be changed.

The present invention also features a method of reusing heat from the steam produced in the drying-stabilizing step and feeding it to the carrier gas of the mixer, the melting tank and the dry-stabilizer. The waste heat of the steam generated in the drying-stabilizer 7 is recovered, and the pulverized coal is filtered in the cyclone 9 as shown in FIG. 3 and then moved to a heating jacket for heating the palm pan oil, Can be used to melt the reason. In one embodiment of the present invention, hot gas generated in the dry-stabilizer is supplied to the melting tank to maintain the internal temperature of the tank at 70 to 90 ° C. The dissolution of the palm pan dissolved in the melting tank is transferred to the liquid palm pan private feeder, and the liquid level adjustment valve maintains a constant liquid level. In addition, a perforated plate having a perforation in a row is provided at the lower end of the liquid liquor palm pan feeder so that the liquid palm pan liquor flows down by gravity.

When the palm pan oil is melted before mixing, it is possible to increase the homogeneity of the mixture of coal and palm pan oil by spraying the liquid palm pan oil directly to the mixer, and it is effective to reduce the mixing amount of palm pan oil. The palm pan furnace is supplied through a liquid palm pan private feeder (2) located on the belt conveyor (3) on which the pulverized raw coal is conveyed in order to mix the liquefied palm pan oil well with the pulverized raw coal.

Hereinafter, the present invention will be described in more detail by way of examples using computer simulations. 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. When the heat energy recovery process is not included

Assuming production of 10% water by modifying coal with 50% moisture, assuming production standard of 3000 tons per day, raw coal should be supplied at 225 ton / h and 100 ton / hr of water should be evaporated. The amount of transport gas was assumed to be 210 ton / h of air with a relative humidity of 50% (dry air 208 ton / h, moisture 2 ton / h). Assuming that the steady-state temperature of the dry-stabilizer is 110 ° C and the external temperature is 25 ° C, the heat required for the dry-stabilizer is as follows.

Q ₁ = Coal sensible (dry basis) + water sensible heat + water vaporization heat + steam sensible heat + sensible residual moisture in coal + transport gas sensible heat (dry basis) + water sensibility in transport gas

Coal Sensible Heat = m _{coal (DB)} x c _{p, coal} x (110 - 25)

Water sensible heat = m _w × c _{p, w} × (100 - 25)

Heat of water evaporation = amount of water evaporation × λ

Water vapor sensible heat = water evaporation amount × c _{p, s} × (110-100)

Sensible heat of residual water in coal = (m _w - moisture evaporation) × c _{p, w} × (110-100)

Transport gas sensible heat = m _{a (DB)} x c _{p, a} x (110 - 25)

Moisture sensible heat in transport gas = m _ma x c _{p, s} x (110-25)

Here, m _{coal (DB)} is the mass of the mass flow rate, m _w is water content in coals of the dry basis, the coal flow rate, m _{a (DB)} is the mass flow rate of the water content in the mass flow rate, m _ma of dry basis, transport gas transport gas, c _{p, coal} is the specific heat (0.25 kcal / kg) of dry basis, of coal, c _{p, w} is a specific heat of water (1 kcal / kg), c p, s is the specific heat of water vapor (0.5 kcal / kg), c p, a (0.24 kcal / kg) and λ is the latent heat of evaporation of water (539 kcal / kg). As a result of calculation by inputting the respective values, the heat amount required for the drying-stabilizer is 69.7 Gcal / h.

Example 2. In the case of transport gas preheating

Assuming the minimum temperature gradient required at the heat exchanger is 10 ° C, the maximum temperature of the carrier gas is 100 ° C. The amount of heat required to heat the transport gas to 100 캜 is as follows.

Q ₂ = transport gas sensible heat (dry basis) + water sensibility in transport gas

= 208,000 × 0.24 × (100 - 25) + 2000 × 0.5 × (100 - 25) = 3.8 Gcal / h

The recycle energy to be used for the preheating is composed of 208 ton / h of dry air and 102 ton / h of moisture as 110 ° C exhaust gas from the dry-stabilizer. The calorific value of the recycle energy is as follows.

Q ₃ = exhaust gas sensibility (dry basis) + sensible moisture in exhaust gas + condensation heat + condensate sensible heat

= 20800 × 0.24 × (110 - T ₁ ) + 102000 × 0.5 × (110-100) + m _c × 539 + m _c × (100 - T ₁ )

Where m _c is the mass flow rate of the condensate and T ₁ is the temperature of the transport gas after heat exchange. The amount of water is determined by the amount of moisture at which the relative humidity becomes 100% when the temperature of the transport gas is determined. If the temperature at which Q ₂ and Q ₃ are equal is calculated by the trial and error method, the final temperature of the exhaust gas is 78 ° C and the amount of the reaction water is 3 ton / h. The heat exchanger internal temperature profile is shown in Figure 5, which indicates that there is no problem in reusing waste heat. Thus, the heat required for the dry-stabilizer is 65.9 Gcal / h, which reduces the calorific value by 5.5% compared to the case where heat energy is not recovered.

Example 3. In the case of transport gas + coal preheating

Assuming that the minimum temperature gradient required in the mixer is 20 ° C, the maximum temperature of the raw coal is 90 ° C. The amount of heat required to heat the raw coal to 90 ° C is as follows.

Q ₄ = Coal sensible heat (dry basis) + moisture sensibility

= 112500 x 0.25 x (90 - 25) + 112500 x 1 x (90 - 25) = 9.1 Gcal / h

The final temperature of the exhaust gas used to preheat the carrier gas is 77 DEG C, as calculated in the same manner as in Examples 1 and 2, assuming that the exhaust gas is used to preheat the carrier gas and coal at a ratio of 1: The amount of water is 9 ton / h. The final temperature of the exhaust gas used to preheat the coal is 74 ° C and the amount of water is 28 ton / h. The internal temperature profiles of the transport gas preheat heat exchanger and the coal preheat mixer are shown in Figures 6 and 7, respectively, indicating that there is no problem in reusing waste heat. Therefore, the heat required for the dry-stabilizer is 56.8 Gcal / h, which is 18.6% less than when heat energy is not recovered.

1. Grinder 2. Liquid palm pan feeder
3. Belt Conveyor 4. Mixer
5. Silos 6. Screw Feeder
7. Dry-stabilizer 8. Drive motor
9. Cyclone 10. Cooler
11. Molding machine 12. Melting tank
13. Heat exchanger 14. FD fan
15, 16, 17. ID fan 21. Screw
22. Baffle 23. Insulation
24. Drive motor 45. Water trap

Claims (8)

A method for recovering waste heat to reform coal,
(a) pulverizing coal with an average particle size of 10 mm or less using a pulverizer;
(b) melting the palm oil residue in a melting tank;
(c) homogenously mixing the melted palm pan oil with the pulverized coal using a mixer;
(d) a drying-stabilizing step of blowing a carrier gas by using a forced draft (FD) fan in a drying-stabilizer to coat the surface of the coal mixed with the coal, and drying the water in the coal at the same time;
(e) cooling the coal through the drying-stabilizing step using a cooler; And
(f) molding the coal through the cooling step using a molding machine,
Stabilizer is transferred to a cyclone to remove pulverized coal and then supplied to a supply pipe for supplying the carrier gas of the mixer, the melting tank, and the drying-stabilizer,
The mixer is thermally insulated, the screw inside the mixer includes a baffle, the screw has a cavity inside which the hot exhaust gas can pass,
Waste heat recovery Coal reforming method.
A method for recovering waste heat to reform coal,
(a) pulverizing coal with an average particle size of 10 mm or less using a pulverizer;
(b) melting the palm oil residue in a melting tank;
(c) homogenously mixing the melted palm pan oil with the pulverized coal using a mixer;
(d) a drying-stabilizing step of blowing a carrier gas by using a forced draft (FD) fan in a drying-stabilizer to coat the surface of the coal mixed with the coal, and drying the water in the coal at the same time;
(e) molding said coal through said drying-stabilizing step using a molding machine, and
(f) cooling the coal through the forming step using a cooler;
Stabilizer is transferred to a cyclone to remove pulverized coal and then supplied to a supply pipe for supplying the carrier gas of the mixer, the melting tank, and the drying-stabilizer,
The mixer is thermally insulated, the screw inside the mixer includes a baffle, the screw has a cavity inside which the hot exhaust gas can pass,
Waste heat recovery Coal reforming method.
3. The method according to claim 1 or 2,
Wherein the mixer, the melting tank, and the supply pipe of the transportation gas include a heating jacket, and supply the exhaust gas from which the pulverized coal is removed to the heating jacket,
Waste heat recovery Coal reforming method.
delete The method according to claim 1,
Wherein a plurality of the screws are provided and the direction of rotation with the adjacent screw is opposite,
Waste heat recovery Coal reforming method.
3. The method according to claim 1 or 2,
In the step of homogeneously mixing the palm pan oil with the pulverized coal, the palm pan oil is mixed with 0.5 to 30% by weight of the coal,
Waste heat recovery Coal reforming method.
3. The method according to claim 1 or 2,
The drying-stabilizing step is carried out in a indirect-type heat exchange type drying-stabilizing machine, wherein the drying-stabilizing device has an internal temperature of 100 to 115 ° C., and the coal moves in the drying- Lt; / RTI > to 70 minutes,
Waste heat recovery Coal reforming method.
3. The method according to claim 1 or 2,
The moisture of the dried coal after the drying-stabilization step is dried-stabilized so as to be 5 to 20 wt%
Waste heat recovery Coal reforming method.

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