JP2013203760A - Dehydration system of low-grade coal and power plant using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dehydration system of low-grade coal, capable of reducing the amount of a used dehydrating agent.SOLUTION: A dehydration system of low-grade coal has a chemical dehydration system (C) for bringing the low-grade coal into contact with a liquefied product of a dehydrating agent to allow the water contained in the low-grade coal to be dissolved in the dehydrating agent to afford a mixture of the water with the dehydrating agent, and to dehydrate the low-grade coal, recovering the dehydrating agent in a gas state by subjecting the mixture to gas-water separation to separate the mixture into the dehydrating agent in a gas state and the water, liquefying the recovered gas-state dehydrating agent by one method of pressurizing, cooling or both of the pressurizing and cooling, and reusing the liquefied dehydrating agent for the dehydration of the low-grade coal, and a mechanical dehydration system (B) installed in the upstream side of the chemical dehydration system, mechanically dehydrating the whole or a part of the bulk water included in the low-grade coal, and feeding the dehydrated low-grade coal to the chemical dehydration system.

Description

  The present invention relates to a system for chemically dehydrating low-grade coal (subbituminous coal, lignite or lignite) and a power plant using the dehydration system.

  Low-grade coal is dehydrated by evaporating the water contained in the low-grade coal with water vapor or high-temperature gas to dehydrate from the low-grade coal (evaporation method), maintaining the liquid state without evaporating moisture There is a method (non-evaporation method) of dewatering from low-grade coal. The non-evaporation method does not require heat corresponding to the latent heat of vaporization of water, so the non-evaporation method requires less energy than the evaporation method.

  Typical examples of the evaporation method include a steam fluidized bed method, a band fluidized bed method, and a rotary tube method. On the other hand, typical examples of the non-evaporation method include a miller process, a mechanical thermal dewatering (MTE) method, and a solvent replacement method.

  Regarding the solvent replacement method, for example, the technique described in Patent Document 1 is known. The solvent replacement method described in Patent Document 1 is a chemical dehydration method using a dehydrating agent. As the dehydrating agent, a substance that is a gas at 25 ° C. and 1 atm (that is, normal temperature and normal pressure), for example, dimethyl ether (hereinafter abbreviated as “DME”) is used. The dehydrating agent is pressurized to form a liquefied product, and the liquefied product and the low-grade coal are brought into countercurrent contact to dehydrate the moisture contained in the low-grade coal. The liquefied product is phase-changed to gas by decompression, and the gas and water are separated. The gas is circulated in the system and used again for dehydration. An expander that is coaxially connected to the compressor (first stage) is installed in the system. The work that the expander performs on the outside environment is recovered and used as part of the compressor power to pressurize the dehydrating agent that has become a gas. In Patent Document 1, the compressor (second stage) is installed on the downstream side of the compressor (first stage) because the pressure of the gas is insufficient only with the compressor (first stage). .

Japanese Patent No. 4,291,772

  When a predetermined amount of water is dehydrated from low-grade coal only by chemical dehydration as in the prior art, a dehydrating agent corresponding to the amount of dehydration is required. That is, if the target dehydration amount is large, the amount of dehydrating agent to be used increases. For example, since liquefied DME is a polar substance, the solubility of water is larger than that of a nonpolar substance, but the solubility of water in liquefied DME is still about 0.07 wt%. The amount of DME required to dehydrate 1 kg of water from low-grade coal is 1 / 0.07 = 14.3 kg. DME can be circulated and reused, but there is a problem that the initial cost increases according to the amount of DME used and the required power of the compressor increases.

  In addition, the prior art requires an expander, multiple compressors, a heat exchanger that connects a condenser that liquefies the dehydrating agent and an evaporator that vaporizes it, and there are many devices that make up the system, resulting in high initial costs. There is also a problem of becoming.

  In addition, in a power plant using low-grade coal as fuel, fuel pretreatment is performed using a system that dehydrates low-grade coal. The same applies to the case where chemical dehydration is used for this fuel pretreatment. There is a problem. Further, in power plants, effective utilization of energy and improvement of the thermal efficiency of the entire plant are permanent issues.

  The present invention has been made to solve the above-described problems, and a first object of the present invention is to provide a low-grade coal dehydration system capable of suppressing the amount of dehydrating agent used and a power plant using the same. There is to do. Furthermore, the second object is to provide a low-grade coal dewatering system with a simple configuration and low cost. In addition, the third object is to improve the thermal efficiency of the power plant using the low-grade coal dehydration system while making effective use of energy.

  In order to achieve the above object, the present invention discloses a low-grade coal dewatering system comprising first to seventh means and a power plant comprising eighth to sixteenth means.

  First, in order to achieve the above object, the first means of the present invention is to bring a low-grade coal into contact with a liquefied product of an organic compound (hereinafter referred to as “dehydrating agent”) that is gaseous at normal temperature and pressure. The low-grade coal is dehydrated by dissolving the water contained in the grade coal in the dehydrating agent to obtain a mixture of water and the dehydrating agent, and the mixture is separated into the dehydrating agent and water in a gaseous state. The gaseous dehydrating agent is recovered, and the recovered gaseous dehydrating agent is liquefied by any one of pressurization, cooling, or a combination of pressurization and cooling, and the liquefied dehydrating agent is recycled. A chemical dehydration system that dehydrates low-grade coal by using it, and is installed upstream of the chemical dehydration system, and mechanically dehydrates all or part of the bulk water contained in the low-grade coal and dehydrates it. For supplying the treated low-grade coal to the chemical dehydration system Dehydration and systems, a low rank coal dewatering system with a.

  According to the first means, since the low-grade coal dehydrated by the mechanical dehydration system is dehydrated by the chemical dehydration system, the amount of the dehydrating agent used can be reduced. Moreover, according to the first means, since the amount of the dehydrating agent used can be reduced, the power for driving the dehydrating system can be suppressed.

  According to a second means of the present invention, in the first means, the chemical dehydration system includes a chemical dehydration apparatus that dehydrates the low-grade coal and the liquefied product of the dehydrating agent in contact with each other, and the chemical dehydration system. An air-water separation device having a dehydrating agent vaporization means for vaporizing the dehydrating agent in the mixture generated by the device; a receiver tank for collecting and storing the dehydrating agent vaporized by the air-water separating device; A compressor that pressurizes a gaseous dehydrating agent stored in the receiver tank, a cooler that cools and liquefies the dehydrating agent pressurized by the compressor, and is vaporized by the steam separator. A blower for transporting the dehydrating agent to the receiver tank, and a pump for discharging water separated from the mixture by the steam separator to the outside of the system. According to this second means, the configuration of the dehydration system can be simplified and low cost can be realized.

  According to a third means of the present invention, in the second means, between the pressure gate valves respectively provided at the inlet and the outlet of the chemical dehydration system, and between the receiver tank and the suction port of the compressor. A pressure control valve provided; a path through which the liquid dehydrating agent flows in the chemical dehydration system; and a path through which the gaseous dehydrating agent flows in the chemical dehydration system. Pressure measuring means for measuring the pressure of the pressure, and a control device for switching the opening / closing operation of the pressure gate valve and adjusting the opening of the pressure control valve based on the measurement by the pressure measuring means. It is a feature.

  When the water from the low-grade coal is dehydrated, the dehydrating agent needs to be present in a liquid state, and when the water dehydrated from the low-grade coal is separated from the dehydrating agent, the dehydrating agent needs to be present in the gaseous state. Thus, in a chemical dehydration system, the dehydrating agent will exist in either a liquid state or a gaseous state. Although the presence state of the dehydrating agent greatly depends on the operating pressure, according to the third means of the present invention, the control device switches the opening / closing operation of the pressure gate valve and the pressure control valve based on the measurement by the pressure measuring means. Since the opening degree is controlled to be adjusted, the dehydrating agent can be maintained in a liquid state or a gas state by a chemical dehydration system.

  At this time, it is preferable to use a polar organic compound for the dehydrating agent from the viewpoint of affinity with water. For example, formaldehyde, acetaldehyde, dimethyl ether (DME), ethyl methyl ether, or the like can be used. Further, these organic compounds may be used singly or in combination as a dehydrating agent.

  According to a fourth means of the present invention, in the second means, the chemical dehydration apparatus sprays the liquefied product of the dehydrating agent onto the belt conveyor unit for conveying the low-grade coal and the low-grade coal being conveyed. It has the spraying part and the storage part which stores the said mixture, It is characterized by the above-mentioned.

  According to a fifth means of the present invention, in the second means, the dehydrating agent vaporizing means vaporizes the dehydrating agent by heating.

  According to a sixth means of the present invention, in the first means or the second means, the mechanical dehydration system is provided with a screw feeder that has a tapered outlet and conveys low-grade coal therein. And a mechanical dehydrator. According to the sixth means, since the outlet of the mechanical dehydrator is tapered, the low-grade coal can be pressurized at the outlet and drained (dehydrated).

  According to a seventh means of the present invention, in the second means, a deaeration tower for degassing the dehydrating agent contained in the water separated by the steam separator, and a deaeration in the deaeration tower And a path for returning the dehydrating agent returned to the receiver tank. According to the seventh means, the recovered amount of the dehydrating agent can be increased.

Next, the operation of the present invention according to the first to seventh means will be described.
When a substance that is a gas at 25 ° C. and 1 atm is liquefied by pressurization and used as a dehydrating agent for low-grade coal, the conditions required for the dehydrating agent are high affinity with water, environmentally hazardous substances ( It contains no heavy metals, sulfur, halogens, etc., is a flammable organic compound (can be burned in a boiler), has known physical properties (specific heat, density, saturated vapor pressure, etc.), has low toxicity That is, it is cheap. For example, DME is one of the dehydrating agents that satisfies these requirements. When DME is used as a dehydrating agent, the boiling point of DME is −25 ° C. Therefore, if the mixture of dehydrated water and DME is depressurized at normal temperature, the DME is easily vaporized (no energy equivalent to latent heat of vaporization is required) to be evaporated. And separate.

  FIG. 1 shows an example of the moisture content ratio of low-grade coal and the moisture content ratio in low-grade coal. Although depending on the production area of the low-grade coal, in this example, the moisture content of the low-grade coal is 60 wt%. Of the total water content of low-grade coal, 60% is physically adsorbed on the surface of low-grade coal, water is retained in relatively large cracks, so-called bulk water, and 30% is pore water. 10% exists as chemically bonded water that is hydrogen-bonded to oxygen-containing functional groups (carboxyl group, hydroxyl group, etc.) of low-grade coal. If bulk water and pore water are dehydrated, the moisture content will be the same as that of high-grade coal even for low-grade coal.

  The ease of dewatering of the water contained in the low-grade coal is in the order of bulk water → pore water → bonded water, and dewatered in this order. Compared with a chemical dehydration system, it takes time to dehydrate pore water and bound water in a mechanical dehydration system. Therefore, a part of bulk water that can be dehydrated relatively easily is dehydrated in the mechanical dehydration system. Depending on the target dehydration amount, after the dehydration by the mechanical dehydration system, the remaining bulk water and pore water are dehydrated by using a dehydrating agent in the chemical dehydration system. Thereby, the quantity of a dehydrating agent can be reduced.

  FIG. 2 shows an image of dehydration according to the prior art and an image of dehydration according to the present invention. In conventional dehydration, the surface of low-grade coal is covered with bulk water. First, after contacting the bulk water with a dehydrating agent (for example, DME), part of the bulk water is dissolved in the dehydrating agent. After the dehydration, a two-stage dehydration is generated, in which a fresh dehydrating agent is brought into contact with the water in the pores, and a part of the water in the pores is dissolved and dehydrated in the dehydrating agent. On the other hand, in the dehydration according to the present invention, when about half of the bulk water is dehydrated by a mechanical dehydrator, a part of the surface of the low-grade coal appears and the pores and the dehydrating agent can be easily contacted. Since simultaneous dehydration (one-stage dehydration) of the bulk water and the water in the pores can be performed, the dewatering efficiency of the low-grade coal in the chemical dehydration system is improved as compared with the prior art.

  The dehydrating agent substituted with water in the pores of the low-grade coal is difficult to vaporize even if the atmosphere is at room temperature and normal pressure due to the surface tension in the pores. Will contain a dehydrating agent. The calorific value of the low-grade coal increases by the amount of the dehydrating agent adhering to the low-grade coal (for example, in the case of DME, the calorific value: 14143 kcal / kg).

  Next, in order to achieve the above object, the eighth means of the present invention includes an exhaust gas system for flowing combustion exhaust gas discharged from a boiler in the order of a denitration device, an air heater, a dust collector, and a desulfurization device, and the boiler. A steam turbine that drives a steam turbine with the steam generated by the steam, supplies steam to the condenser after driving the steam turbine, and a water supply system that supplies water condensed by the condenser to the boiler, A low-grade coal dehydration system that dehydrates low-grade coal and supplies it to the boiler as a fuel, wherein the low-grade coal dehydration system is a low-grade coal dehydrated at room temperature and normal pressure. By contacting a liquefied product of a gaseous organic compound (hereinafter referred to as “dehydrating agent”), water contained in the low-grade coal is dissolved in the dehydrating agent to obtain a mixture of water and the dehydrating agent. Dehydrated carbon , Separating the mixture into a gaseous dehydrating agent and water to recover the gaseous dehydrating agent, and pressurizing, cooling, or pressurizing and cooling the recovered gaseous dehydrating agent. A chemical dehydration system that liquefies by any of the methods in combination and reuses the liquefied dehydrating agent to dehydrate low-grade coal, and is provided upstream of the chemical dehydration system and is included in the low-grade coal And a mechanical dehydration system that mechanically dehydrates all or a part of the bulk water and supplies the dehydrated low-grade coal to the chemical dehydration system.

  According to the eighth means, since the low-grade coal dehydrated by the mechanical dehydration system is dehydrated by the chemical dehydration system, the amount of the dehydrating agent used can be reduced. According to the eighth means, since the amount of the dehydrating agent used can be reduced, the power for driving the dehydrating system can be suppressed.

  According to a ninth means of the present invention, in the eighth means, the chemical dehydration system comprises a chemical dehydration apparatus for dehydrating by bringing low-grade coal and a liquefied product of the dehydrating agent into contact with each other, and the chemical dehydration system. An air-water separator having a heat exchanger for vaporizing the dehydrating agent in the mixture produced by the apparatus; a receiver tank for collecting and storing the dehydrating agent vaporized by the air-water separator; and A compressor that pressurizes a dehydrating agent in a gas state stored in a receiver tank, a cooler that cools and liquefies the dehydrating agent pressurized by the compressor, and vaporized by the steam separator A blower that conveys the dehydrating agent to the receiver tank, and a pump that discharges water separated from the mixture by the steam separator to the outside of the system. According to the ninth means, the configuration of the power plant can be simplified and low cost can be realized.

  A tenth means of the present invention is characterized in that, in the ninth means, a path is provided for flowing the combustion exhaust gas extracted from the outlet of the air heater to the dust collector via the heat exchanger. It is said. According to the tenth means, the heat source of the combustion exhaust gas from the boiler can be effectively used as energy for separating the dehydrating agent from the water, leading to an improvement in the thermal efficiency of the power plant.

  The eleventh means of the present invention is characterized in that, in the ninth means, a path is provided for flowing the combustion exhaust gas extracted from the outlet of the dust collector to the desulfurization device via the heat exchanger. It is said. According to the eleventh means, the heat source of the combustion exhaust gas from the boiler can be effectively used as energy for separating the dehydrating agent from the water, leading to an improvement in the thermal efficiency of the power plant.

  A twelfth means of the present invention is characterized in that, in the tenth means or the eleventh means, a gas gas heater is provided in the exhaust gas system.

  According to a thirteenth means of the present invention, in the ninth means, after the heat medium having obtained the latent heat of vaporization by exchanging heat with steam in the condenser is guided to the heat exchanger, the condensate is again formed. It is characterized by providing a route to return to the vessel. According to the thirteenth means, the heat source of the steam of the condenser can be effectively used as energy for separating the dehydrating agent from the water, which leads to an improvement in the thermal efficiency of the power plant.

  The fourteenth means of the present invention is characterized in that, in the thirteenth means, water or air is used as the heat medium.

  According to a fifteenth means of the present invention, in the ninth means, the steam extracted from the steam turbine is guided to the water supply system to the heat exchanger, and heat exchange with the dehydrating agent is performed in the heat exchanger. The steam is recovered as condensed water, and a path for supplying the condensed water to the boiler is provided. According to the fifteenth means, the heat source of the steam extracted from the steam turbine can be effectively used as energy for separating the dehydrating agent from the water, leading to an improvement in the thermal efficiency of the power plant.

  According to a sixteenth means of the present invention, in the ninth means, a deaeration tower for degassing the dehydrating agent contained in the water separated by the steam separator, and a deaeration in the deaeration tower And a path for returning the dehydrating agent returned to the receiver tank. According to the sixteenth means, the recovery amount of the dehydrating agent can be increased.

  According to the low-grade coal dehydration system of the present invention, the low-grade coal dehydrated by the mechanical dehydration system is dehydrated by the chemical dehydration system, so that the amount of dehydrating agent used can be reduced. Further, as the amount of the dehydrating agent is reduced, the power of the compressor can be reduced. Moreover, according to the power plant according to the present invention, an unused heat source can be effectively used as energy for separating the mixture of water and a dehydrating agent into air and water, leading to an improvement in the thermal efficiency of the power plant. Further, as compared with the above-described conventional technology, an expander is not required, and the number of compressors and a vaporization heat recovery facility are not required. Therefore, the system can be simplified and the cost can be reduced.

It is a figure which shows the content rate of the water | moisture content contained in a low grade coal, and the ease of dehydration. It is a figure which shows the difference in the mechanism of dehydration of the low grade coal of this invention and a prior art. 1 is a system diagram showing a first embodiment of a low-grade coal dewatering system according to the present invention. It is a figure which shows the detail of the chemical dehydration apparatus shown in FIG. It is a figure which shows the operating conditions of the dehydration system of the low grade coal shown in FIG. It is a systematic diagram which shows 2nd Example of the dehydration system of the low grade coal which concerns on this invention. 1 is a system diagram showing a first embodiment of a power plant according to the present invention. It is a figure which shows the modification of the exhaust gas system | strain of the power plant shown in FIG. It is a systematic diagram showing a second embodiment of the power plant according to the present invention. It is a figure which shows the modification of the exhaust gas system | strain of the power plant shown in FIG. It is a systematic diagram which shows 3rd Example of the power plant which concerns on this invention. It is a systematic diagram which shows 4th Example of the power plant which concerns on this invention. It is a systematic diagram which shows 5th Example of the power plant which concerns on this invention.

"First embodiment of low-grade coal dewatering system (SYS1)"
The contents of the present invention will be described in detail in the following examples, but the present invention is not limited to these examples. First, a first embodiment of a low-grade coal dehydration system according to the present invention will be described with reference to FIGS. The low-grade coal dehydration system SYS1 according to the first embodiment includes a low-grade coal supply unit A, a mechanical dehydration system B, a chemical dehydration system C, and a low-grade coal storage unit D from the upstream side of the low-grade coal flow. They are connected by piping in order. Further, the operations of various devices, valves, etc. constituting this dehydrating system are controlled by a control device 70. In the first embodiment, dimethyl ether (DME) is used as the dehydrating agent.

  The low-grade coal supply unit A includes a low-grade coal supply hopper 11 that stores low-grade coal, a low-grade coal supply pipe 31 connected to the inlet of the low-grade coal supply hopper 11, and a low-grade coal supply hopper 11. A communication pipe 32 connected to the outlet, a low-grade coal supply valve 22 provided in the low-grade coal supply pipe 31, and a rotary valve 21 provided in the communication pipe 32 are provided. The low-grade coal 1 before dehydration is supplied from the low-grade coal supply pipe 31 to the low-grade coal supply hopper 11 and stored. The low-grade coal stored in the low-grade coal supply hopper 11 is cut out by the rotary valve 21 and then supplied to the mechanical dehydration system B.

  The mechanical dehydration system B has a mechanical dehydration device 12 that mechanically dehydrates low-grade coal. The mechanical dehydrator 12 is connected to the low-grade coal supply hopper 11 via a communication pipe 32 and is connected to a chemical dehydrator 13 described later via a communication pipe 33. The mechanical dehydrator 12 has a configuration in which a screw conveyor 12c that conveys low-grade coal is provided inside a substantially cylindrical body 12a. The screw conveyor 12c is driven by a motor. Moreover, the exit 12b of the trunk | drum 12a is formed in the taper shape. Further, a drain pipe 36 is connected to the body portion 12a, and a drain valve 23 is provided in the drain pipe 36.

  The low-grade coal supplied from the low-grade coal supply hopper 11 is conveyed to the tapered outlet 12b while being mechanically pressurized by the rotation of the screw conveyor 12c of the mechanical dehydrator 12. This pressure dehydrates all or part of the bulk water contained in the low-grade coal. Then, the dehydrated low-grade coal is sent to the chemical dehydrator 13. At this time, the dehydrated water 3 a is drained out of the mechanical dehydration system B through the drain pipe 36. As long as the drain valve 23 is not opened, the dewatered water 3a is maintained in a water-sealed state in the mechanical dehydrator 12.

  The chemical dehydration system C is configured to vaporize DME out of a mixture of water and DME generated by the chemical dehydration apparatus 13 and a chemical dehydration apparatus 13 that dehydrates low-grade coal and DME liquefied material in contact with each other. A steam / water separator 14, a receiver tank 16 that collects and stores the DME vaporized in the steam / water separator 14, a compressor 17 that pressurizes the gaseous DME stored in the receiver tank 16, and a compression The cooler 10 that cools and liquefies the DME pressurized by the machine 17, the blower 20 that transports the DME vaporized by the steam separator 14 to the receiver tank 16, and water by the steam separator 14. And a drainage pump 60 for discharging water separated from the mixture of DME to the outside of the system.

  Furthermore, the chemical dehydration system C includes a chemical dehydrator inlet valve (pressure gate valve) 50 provided at the inlet, a low-grade coal discharge valve (pressure gate valve) 26 provided at the outlet, and a receiver tank. 16 and a pressure transmitter (provided in the chemical dehydrator 13 in the path through which the DME in the liquid state flows) 27 provided between the compressor 17 and the suction port 17a of the compressor 17 Pressure measuring means) 65 and a pressure transmitter (pressure measuring means) 66 provided in a receiver tank 16 (a path through which the gaseous DME flows) through which the gaseous DME flows. Note that the control device 70 uses input signals from the pressure transmitters 65 and 66 to switch the opening and closing operations of the chemical dehydrator inlet valve 50 and the low-grade coal discharge valve 26 and to adjust the opening of the compressor inlet valve 27. Based on.

  As shown in FIG. 4, the chemical dehydrator 13 is driven by a spray nozzle (spraying unit) 13 a that sprays liquefied DME onto low-grade coal to chemically dehydrate the moisture of the low-grade coal, and is driven by a motor. A belt conveyor (belt conveyor unit) 13b that conveys high-grade coal from the inlet to the outlet of the chemical dehydrator 13, and a liquefied DME containing water dehydrated from the low-grade coal (hereinafter referred to as "water-containing liquefied DME") And a liquefied DME tank (reservoir) 13c. The low-grade coal supplied to the chemical dehydrator 13 is dehydrated by DME sprayed from the spray nozzle 13a in the process of being conveyed by the belt conveyor 13b. The low-grade coal dehydrated by the chemical dehydrator 13 is conveyed to the outlet of the chemical dehydrator 13 by the belt conveyor 13b, and is supplied to the low-grade coal reservoir D via the communication pipe 34. On the other hand, the water-containing liquefied DME is stored in the liquefied DME tank 13 c and then supplied to the steam-water separator 14 using the pump 19 installed in the liquefied DME recovery pipe 38. In order to maintain the water sealing state of the chemical dehydrator 13, the liquefied DME recovery pipe 38 is provided with a DME recovery valve 25. In addition, a check valve 28 is provided in the liquefied DME recovery pipe 38 in order to prevent the DME vaporized by the steam separator 14 from flowing back to the chemical dehydrator 13.

  The steam-water separator 14 stores a heat exchanger 18 as a dehydrating agent vaporization means, a steam-water separator 14a that separates the water-containing liquefied DME into gaseous DME and water, and water separated from the water-containing liquefied DME. The internal pressure of the water tank 14b is adjusted by the compressor inlet valve 27 so as to be lower than the internal pressure of the chemical dehydrator 13. The heat exchanger 18 is connected to the combustion exhaust gas pipe 42, and is supplied with the combustion exhaust gas 5a discharged from a boiler (not shown). The water 3b is discharged out of the system through the drainage pipe 37 by driving the pump 60. In addition, in order to maintain the water seal state of the steam separator 14, a drain valve 24 is installed in the drain pipe 37.

  The gaseous DME separated from the water-containing liquefied DME is supplied to the receiver tank 16 using the blower 20 installed in the DME recovery pipe 39 and stored in the receiver tank 16. The DME in the gaseous state is re-pressurized by the compressor 17 installed in the DME supply pipe 41 to become liquefied DME. The liquefied DME is adjusted to a predetermined temperature by the cooler 10 and then supplied to the chemical dehydrator 13 and sprayed from the spray nozzle 13a onto the low-grade coal.

  Part of the DME is not circulated in the system but is attached to the low-grade coal (after dehydration) 2 and discharged out of the system. For this reason, in the first embodiment, DME 4 for replenishment is replenished via the DME replenishment pipe 40 connected to the receiver tank 16 according to the amount of DME discharged to the outside of the system.

  The low-grade coal storage unit D is connected to the chemical dehydrator 13 via the communication pipe 34, and the low-grade coal recovery hopper 15 that stores the low-grade coal dehydrated by the chemical dehydrator 13 is stored. A low-grade coal discharge pipe 35 for supplying low-grade coal to a boiler (not shown).

  The control device 70 is electrically connected to each device of the low-grade coal supply unit A, the mechanical dehydration system B, the chemical dehydration system C, and the low-grade coal storage unit D, and has the following operating conditions. Thus, the operation of the entire low-grade coal dewatering system is controlled.

  The operating conditions of the low-grade coal dewatering system SYS1 according to the first embodiment will be described with reference to FIG. The operating conditions of the chemical dehydrator 13 are a pressure of 0.78 MPaA and a temperature of 30 ° C. Since the boiling point of DME under this pressure is 35 ° C., DME exists as a liquid in the chemical dehydrator 13. Although the pressure is reduced in the steam / water separator 14, since the sensible heat of the combustion exhaust gas is input, the temperature in the steam / water separator 14 is maintained. Therefore, the operating conditions of the steam separator 14 are a pressure of 0.55 MPaA and a temperature of 30 ° C. Since the boiling point of DME under this pressure is 22 ° C., DME exists as a gas in the steam separator 14. Therefore, under this condition, the dehydrated water exists as a liquid, so that water and DME can be separated.

  The separated gaseous DME is re-pressurized by the compressor 17 to a pressure of 0.78 MPaA and a temperature of 38 ° C. Since the boiling point of DME is 35 ° C. under this pressure, DME pressurized by the compressor 17 exists as a gas. The gaseous DME is cooled by the cooler 10 installed on the downstream side of the compressor 17 to become a liquid DME. The operating conditions in this state are a pressure of 0.78 MPaA and a temperature of 30 ° C., which are the same operating conditions as the chemical dehydrator 13. The DME that has become liquid again is used for dehydration of low-grade coal.

(Experimental example 1)
Next, in order to verify the effect of the low-grade coal dehydration system SYS1 according to the first example, the following dehydration test was performed. The low-grade coal used in the dehydration test is Australian brown coal (hereinafter referred to as “AY coal”). Table 1 shows analysis values of AY charcoal (however, fixed carbon and fuel ratio are calculated values). The moisture content of AY coal is 60% or more, and the fuel ratio is 1 or less because coalization is not progressing.

  In the dehydration test, the water content of half of the bulk water (dehydrated amount 0.30 kg / water content in raw lignite 1 kg) was first dehydrated by mechanical dehydration method, and then the moisture content of lignite coal was determined by chemical dehydration method. The procedure was to dehydrate until 10%. The results obtained in this test are shown in Table 2 as Experimental Example 1.

(Comparative Example 1)
Moreover, in order to compare the dehydration effect, the dehydration test of the low grade coal was implemented using the dehydration system based on the chemical dehydration method of patent document 1. FIG. In addition, although the expander is used in patent document 1, in the test of the comparative example 1, the pressure control valve was used instead of the expander. Therefore, although the apparatus configuration is slightly different between Patent Document 1 and Comparative Example 1, the pressure and temperature conditions in the system are not affected by controlling the pressure in the system by the pressure control valve. The low-grade coal used in the test of Comparative Example 1 was AY coal, which was dehydrated by chemical dehydration until the moisture content of the lignite was 10%. The results obtained in this test are shown in Table 2 as Comparative Example 1.

(Comparative Example 2)
Moreover, in order to compare the dehydration effect, a dehydration test of low-grade coal was conducted using a fluidized bed dehydrator. As fluidizing gas, 130 ° C. air was supplied to the wind box at the bottom of the fluidized bed dehydrator. The air also served as a heat source for low-grade coal dehydration. A hot air generator was used for heating and supplying air. The fluidized bed dewatering device was a batch type device. In order to prevent heat dissipation, the surroundings of the fluidized bed dewatering device were insulated with rock wool, and the piping between the hot air generator and the fluidized bed dewatering device was heat traced. The ratio between the weight of the packed coal and the amount of hot air supplied was about 0.1 (kg / kg). The low-grade coal used in the test of Comparative Example 2 was AY coal, which was dehydrated by an evaporation method until the moisture content of the lignite became 10%. The results obtained in this test are shown in Table 2 as Comparative Example 2.

In the dehydration test described above, the calorific value of coal was measured using a thermal test based on JIS M 8814 “Coal and cokes—a method of measuring the total calorific value with a bomb calorimeter and a method of calculating the true calorific value”. A bomb type calorimeter was used.

  In Comparative Example 2, the calorific value increased with the dehydration of moisture in the lignite. The value of the calorific value of the dehydrated lignite in Experimental Example 1 and Comparative Example 1 is larger than the value of the calorific value of the dehydrated lignite in Comparative Example 2. This is because in the lignite after dehydration in Experimental Example 1 and Comparative Example 1, DME has entered the pores, and the amount of heat generated by this amount of DME is added. The amount of DME used in circulation was 5.2 kg / kg-dehydrated amount in Experimental Example 1 and 7.6 kg / kg-dehydrated amount in Comparative Example 1, and the amount of Experimental Example 1 was significantly reduced compared to Comparative Example 1. It became. From this test result, it was possible to demonstrate that the low-grade coal dehydration system according to the first example can significantly reduce the amount of dehydrating agent used compared to the conventional one.

  As described above, according to the low-grade coal dehydration system SYS1 according to the first embodiment, the low-grade coal dehydrated by the mechanical dehydration system B is dehydrated by the chemical dehydration system C. The amount used can be reduced. Moreover, the power of the compressor 17 can also be reduced with a reduction in the amount of the dehydrating agent used. Furthermore, the low-grade coal dehydration system SYS1 according to the first embodiment does not require an expander, a vaporization heat recovery facility, or the like, and the compressor 17 is sufficient, so that the system can be simplified and the cost can be reduced. Can be realized.

"Second example of low-grade coal dewatering system (SYS2)"
Next, a second embodiment of the low-grade coal dehydration system according to the present invention will be described with reference to FIG. The low-grade coal dewatering system SYS2 according to the second embodiment is different from the first embodiment in that it further includes a degassing system E for degassing DME contained in the water separated by the steam separator 14. To do. Therefore, in the following description, this difference will be mainly described, and the same components as those of the low-grade coal dewatering system SYS1 according to the first embodiment will be denoted by the same reference numerals and description thereof will be omitted. To do.

  As shown in FIG. 6, the deaeration system E includes a deaeration tower 8 connected to the air / water separator 14 via a drain pipe 37 and a dimethyl ether recovery pipe 44 connecting the deaeration tower 8 and the receiver tank 16. And a drain pipe 47 for discharging the water separated by the deaeration tower 8 out of the system, and a heat exchanger 48. A dimethyl ether recovery valve 49 is installed in the dimethyl ether recovery pipe 44. Further, a flue gas pipe 45 is connected to the heat exchanger 48, and the flue gas 5b discharged from the boiler (not shown) flows through the flue gas pipe 45, whereby heat is introduced into the deaeration tower 8. Is supplied.

  Then, the mixture of water and DME absorbs heat from the combustion exhaust gas 5b through the heat exchanger 48, whereby DME is vaporized and water and DME are separated. The vaporized DME is collected in the receiver tank 16 through the dimethyl ether collection pipe 44 by opening the dimethyl ether collection valve 49. On the other hand, the water 3c separated from the mixture is drained from the drainage pipe 47 to the outside of the system. A drain valve 46 is installed in the drain pipe 47 in order to maintain the water sealing state of the deaeration tower 8.

  Thus, in the low-grade coal dehydration system SYS2 according to the second embodiment, the DME recovery rate can be increased by providing the degassing system E. Moreover, the load of the compressor 17 can also be reduced. Explaining this in detail, the DME that can be recovered by the steam separator 14 is determined by the atmospheric pressure (saturated vapor pressure). If the pressure of the atmosphere is lowered in order to increase the recovery rate, the compression work of the compressor 17 increases, so the load on the compressor 17 increases. On the other hand, if the deaeration tower 8 is installed on the downstream side of the steam separator 14 as in the second embodiment, the load on the compressor 17 is not increased and the DME recovery rate can be increased.

“First Example of Power Plant (PP1)”
Next, a first embodiment of the power plant according to the present invention will be described with reference to FIG. The power plant PP1 according to the first embodiment of the present invention is condensed by an exhaust gas system 100a through which combustion exhaust gas discharged from the boiler 102 flows, a steam system 100b through which steam generated by the boiler 102 flows, and a condenser 109. A dewatering system SYS1 for dewatering low-grade coal as fuel for the boiler, and a pulverizer 101 for crushing low-grade coal dehydrated by the low-grade coal dehydration system SYS1. ing.

  The exhaust gas system 100a is a system for guiding combustion exhaust gas generated when low-grade coal is burned in the boiler 102 to a chimney (not shown), and the boiler 102 and the denitration device 103 are connected by a combustion exhaust gas pipe 121a. The denitration device 103 and the air heater (A / H) 104 are connected by a combustion exhaust gas pipe 121b, the air heater 104 and a dry electrostatic precipitator (DESP) 105 are connected by a combustion exhaust gas pipe 121c, and the dry electric dust collector 105 A wet desulfurization apparatus (WFGD) 106 is connected by a combustion exhaust gas pipe 121d, and a combustion exhaust gas pipe 121e is connected to the wet desulfurization apparatus 106. In the course of the combustion exhaust gas discharged from the boiler 102 flowing in the order of the denitration device 103, the air heater 104, the dry electrostatic precipitator 105, and the wet desulfurization device 106, the environmentally regulated substances contained in the combustion exhaust gas are removed to a regulation value or less. And the processed combustion exhaust gas 130 is discharged | emitted from a chimney outside.

  The steam system 100 b is a system through which steam generated by the boiler 102 flows, and includes a steam turbine 107 and a condenser 109. The steam generated in the boiler 102 is guided to the steam turbine 107 through the steam pipe 124, and the steam turbine 107 is driven by the steam. When the steam turbine 107 is driven, the generator 108 rotates to generate power. The steam discharged from the steam turbine 107 is supplied to the condenser 109 for condensing.

  The water supply system 100 c is a system for supplying the water condensed by the condenser 109 to the boiler 102, and is configured by connecting the condenser 109 and the boiler 102 with a condensate pipe 125. Note that the cooling water 131 is supplied to the condenser 109 via the cooling water pipes 126 and 127.

  A pulverization apparatus 101 is provided between the boiler 102 and the low-grade coal dewatering system SYS1, and the low-grade coal subjected to the dehydration process is finely crushed by the pulverization apparatus 101 and then the low-grade coal. It is supplied to the boiler 102 via the supply pipe 120. The low-grade coal dehydration system SYS1 used in the power plant PP1 is the same as the low-grade coal dehydration system SYS1 according to the first embodiment described above. For this reason, the same components are denoted by the same reference numerals, and description thereof is omitted here.

  Further, in the power plant PP1 according to the first embodiment, the heat exchange incorporated in the flue gas piping 121c between the air heater 104 and the dry electrostatic precipitator 105 and the steam separator 14 of the low-grade coal dehydration system SYS1. The exhaust gas exhausted from the outlet of the air heater 104 is connected to the vessel 18 by piping, and a path is provided for the combustion exhaust gas to flow to the dry electrostatic precipitator 105 via the heat exchanger 18. As a result, the water-containing liquefied DME taken into the steam / water separator 14 is vaporized by the heat of the combustion exhaust gas flowing through the heat exchanger 18 and separated from water.

  According to the power plant PP1 configured in this way, the amount of dehydrating agent used can be reduced, and the power of the compressor 17 can also be reduced, so that the power consumption of the power plant PP1 can be reduced. Furthermore, since the DME can be vaporized from the water-containing liquefied DME using the heat of the combustion exhaust gas discharged from the boiler 102, energy is effectively used, and the thermal efficiency of the power plant PP1 is improved.

  In addition, the power plant PP1 can also provide a gas gas heater in the exhaust gas system 100a. In this case, as shown in FIG. 8, a high temperature side gas gas heater (GGH) 132a is provided between the air heater 104 and the dry electrostatic precipitator 105, and a low temperature side gas gas heater (GGH) 132b is provided downstream of the wet desulfurization apparatus 106. . In this way, it is possible to take measures against white smoke in the power plant PP1.

“Second Example of Power Plant (PP2)”
Next, a second embodiment of the power plant according to the present invention will be described with reference to FIG. 9. The power plant PP2 according to the second embodiment of the present invention is the same as the power plant PP1 according to the first embodiment. In comparison, the configuration is the same except that the path connecting the exhaust gas system 100a and the heat exchanger 18 of the steam separator 14 is different. Therefore, in the following description, this difference will be mainly described, and the same components as those of the power plant PP1 will be denoted by the same reference numerals and description thereof will be omitted.

  In the power plant PP2 according to the second embodiment, the heat exchanger 18 incorporated in the flue gas piping 121d between the dry electrostatic precipitator 105 and the wet desulfurization device 106 and the steam separator 14 of the low-grade coal dehydration system SYS1. Are connected by a pipe, and the exhaust gas extracted from the outlet of the dry electrostatic precipitator 105 flows through the heat exchanger 18 to the wet desulfurization device 106. As a result, the water-containing liquefied DME taken into the steam / water separator 14 is vaporized by the heat of the combustion exhaust gas flowing through the heat exchanger 18 and separated from water.

  This power plant PP2 can also vaporize DME from the water-containing liquefied DME using the heat of the combustion exhaust gas discharged from the boiler 102, so that the energy can be used effectively and the thermal efficiency of the power plant PP2 is improved. To do.

  The power plant PP2 can also be provided with a gas gas heater in the exhaust gas system 100a. In this case, as shown in FIG. 10, a high temperature side gas gas heater 132a is provided between the air heater 104 and the dry electrostatic precipitator 105, and a low temperature side gas gas heater 132b is provided downstream of the wet desulfurization apparatus 106. In this way, it is possible to take measures against white smoke in the power plant PP2.

"Third embodiment of power plant (PP3)"
Next, a third embodiment of the power plant according to the present invention will be described with reference to FIG. The power plant PP3 according to the third embodiment of the present invention is characterized in that the cooling water flowing through the condenser 109 is guided to the heat exchanger 18 of the steam separator 14. Therefore, in the following description, the description will be focused on this feature point, and the same components as those of the power plants PP1 and PP2 will be denoted by the same reference numerals and description thereof will be omitted.

  In the power plant PP3 according to the third embodiment, the cooling water pipe 127 provided at the outlet of the condenser 109 and the heat exchanger 18 incorporated in the steam separator 14 of the low-grade coal dehydration system SYS1 are provided. The cooling water connected by piping and having absorbed heat by the condenser 109 flows through the heat exchanger 18 and returns to the cooling water piping 127. The cooling water flowing through the condenser 109 exchanges heat with steam in the condenser 109 to obtain latent heat of evaporation. When the cooling water having obtained latent heat of vaporization is passed through the heat exchanger 18, the water-containing liquefied DME taken into the steam-water separator 14 is vaporized by the latent heat of vaporization and separated from water.

  Thus, according to the power generation plant PP3, DME can be vaporized from the water-containing liquefied DME using the latent heat of vaporization of the cooling water flowing through the condenser 109, so that energy can be effectively used, and the power plant The thermal efficiency of PP3 is improved.

  In addition, although the power plant PP3 uses cooling water as a heat medium flowing through the heat exchanger 18, for example, air may be used in addition to the cooling water.

"Fourth embodiment of power plant (PP4)"
Next, a fourth embodiment of the power plant according to the present invention will be described with reference to FIG. The power plant PP4 according to the fourth embodiment of the present invention is characterized in that the steam extracted from the steam turbine 107 is guided to the heat exchanger 18 of the steam separator 14. For this reason, in the following description, the description will focus on this characteristic point, and the same components as those of the power plants PP1, PP2, PP3 will be denoted by the same reference numerals and description thereof will be omitted.

  In the power plant PP4 according to the fourth embodiment, the steam turbine 107 and the heat exchanger 18 incorporated in the steam separator 14 of the low-grade coal dehydration system SYS1 are connected by a turbine extraction pipe 135 to perform heat exchange. The condenser 18 and the condensate pipe 125 are connected to the turbine bleed condensate return pipe 136 so that the steam extracted from the steam turbine 107 flows into the heat exchanger 18 and then returns to the condensate pipe 125. . Steam flowing through this path exchanges heat with the water-containing liquefied DME taken into the steam separator 14 by the heat exchanger 18 to become condensed water. This condensed water is returned to the condensate pipe 125 and supplied to the boiler 102. On the other hand, the water-containing liquefied DME taken into the steam separator 14 is absorbed by the heat exchanger 18 and vaporized.

  Although not shown in detail, the steam turbine 107 includes a low pressure turbine, an intermediate pressure turbine, and a high pressure turbine. In the power plant PP4, the steam extracted from the low pressure turbine or the intermediate pressure turbine is guided to the heat exchanger 18. I am doing so. Further, the boiler 102 is provided with a economizer (not shown), and the steam exchanged with the water-containing liquefied DME by the heat exchanger 18 is supplied to the economizer as condensed water.

  As described above, according to the power generation plant PP4, DME can be vaporized from the water-containing liquefied DME using the heat of the steam extracted from the steam turbine 107, so that energy can be effectively used, and the power generation plant PP4. The thermal efficiency of is improved.

"Fifth embodiment of power plant (PP5)"
As shown in FIG. 13, the power plant PP5 according to the fifth embodiment includes a low-grade coal dewatering system SYS2 having a deaeration tower 8 instead of the low-grade coal dewatering system SYS1 in the configuration of the power plant PP1. Applicable. With this configuration, the recovery rate of DME can be increased.

  In addition to this, in the power plants PP2-4, the low-grade coal dewatering system SYS2 according to the above-described second embodiment can be applied instead of the low-grade coal dewatering system SYS1. Thereby, the recovery rate of DME can be increased.

1: low-grade coal (before dehydration), 2: low-grade coal (after dehydration), 3a to c: water, 4: dimethyl ether (DME), 5a, 5b: combustion exhaust gas, 6: cooling water, 8: deaeration tower , 9: electric motor, 10: cooler, 11: low-grade coal supply hopper, 12: mechanical dehydrator, 12a: fuselage, 12b: outlet, 12c: screw conveyor (screw feeder), 13: chemical dehydrator 14: Steam separator, 15: Low-grade coal recovery hopper, 16: Receiver tank, 17: Compressor, 17a, compressor inlet, 18: Heat exchanger (dehydrating agent vaporization means), 19: Pump, 20 : Blower, 21: Rotary valve, 22: Low grade coal supply valve, 23, 24: Drain valve, 25: Dimethyl ether recovery valve, 26: Low grade coal discharge valve (pressure gate valve), 27: Compressor inlet valve (pressure) Control valve), 28: check valve, 1: low-grade coal supply piping, 32-34: communication piping, 35: low-grade coal discharge piping, 36, 37: drainage piping, 38: liquefied dimethyl ether recovery piping, 39: dimethyl ether recovery piping, 40: dimethyl ether supply piping, 41 : Dimethyl ether supply pipe, 42: combustion exhaust pipe, 43: cooling water pipe, 44: dimethyl ether recovery pipe, 45: combustion exhaust pipe, 46: drain valve, 47: drain pipe, 48: heat exchanger, 49: dimethyl ether recovery valve 50: Chemical dehydrator inlet valve (pressure gate valve), 60: pump, 65: pressure transmitter (pressure measuring means), 66: pressure transmitter (pressure measuring means), 70: control device 101: grinding device, 102: Boiler, 103: Wet denitration device (denitration device), 104: Air heater, 105: Dry type electric dust collector (dust collection device), 106: 107: steam turbine, 108: generator, 109: condenser, 120: low-grade coal supply piping, 121a to e: combustion exhaust gas piping, 122: combustion exhaust gas extraction piping, 123: combustion Exhaust gas return pipe, 124: steam pipe, 125: condensate pipe, 126, 127: cooling water pipe, 130: combustion exhaust gas (treated), 131: cooling water, 132a: gas gas heater (high temperature side), 132b: gas gas heater (Low-temperature side) 133: Condenser heat exchange medium extraction piping, 134: Condenser heat exchange medium return piping, 135: Turbine extraction piping, 136: Turbine extraction condensate return piping, SYS1, 2: Low-grade coal Dehydration system, PP1-5: Power plant

Claims (16)

  A low-grade coal is brought into contact with a liquefied organic compound (hereinafter referred to as “dehydrating agent”) that is a gas at normal temperature and normal pressure, and the water contained in the low-grade coal is dissolved in the dehydrating agent so that water and the dehydrating agent are dissolved. The low-grade coal is dehydrated by obtaining a mixture with the agent, and the mixture is separated into the gas dehydrant and water to recover the gas dehydrant, and the recovered gas state A chemical dehydration system in which the dehydrating agent is liquefied by pressurization, cooling, or a combination of pressurization and cooling, and the low-grade coal is dehydrated by reusing the liquefied dehydrating agent; and the chemical dehydration A mechanical dehydration system provided upstream of the system for mechanically dehydrating all or part of the bulk water contained in the low-grade coal and supplying the dehydrated low-grade coal to the chemical dehydration system; , Equipped with low-grade coal dehydration system. In the description of claim 1,
The chemical dehydration system is configured to vaporize the dehydrating agent in the chemical dehydration apparatus that contacts and dehydrates low-grade coal and the liquefied product of the dehydrating agent, and the mixture generated by the chemical dehydrating apparatus. An air / water separator having a dehydrating agent vaporization means, a receiver tank for collecting and storing the dehydrating agent vaporized by the air / water separating device, and pressurizing the gaseous dehydrating agent stored in the receiver tank A compressor, a cooler that cools and liquefies the dehydrating agent pressurized by the compressor, a blower that conveys the dehydrating agent vaporized by the steam separator to the receiver tank, and the steam A low-grade coal dehydration system comprising: a pump for discharging water separated from the mixture by a separation device to the outside of the system. In the description of claim 2,
A pressure gate valve provided respectively at an inlet and an outlet of the chemical dehydration system; a pressure control valve provided between the receiver tank and a suction port of the compressor; and a liquid state in the chemical dehydration system A pressure measuring means for measuring the pressure of the dehydrating agent, and a measurement by the pressure measuring means, which are respectively provided in a path through which the dehydrating agent flows and a path through which the dehydrating agent in the gaseous state flows in the chemical dehydration system. And a control device for switching the opening / closing operation of the pressure gate valve and adjusting the opening degree of the pressure control valve based on the above. In the description of claim 2,
The chemical dehydration apparatus includes a belt conveyor unit that conveys low-grade coal, a spray unit that sprays a liquefied product of the dehydrating agent onto the low-grade coal being conveyed, and a storage unit that stores the mixture. A low-grade coal dehydration system characterized by In the description of claim 2,
The dehydrating system for low-grade coal, wherein the dehydrating agent vaporizing means vaporizes the dehydrating agent by heating. In the description of claim 1 or 2,
The mechanical dehydration system includes a mechanical dehydration apparatus having a tapered outlet and a screw feeder that transports low-grade coal therein. In the description of claim 2,
A degassing tower for degassing the dehydrating agent contained in the water separated by the steam separator, and a path for returning the dehydrating agent degassed by the degassing tower to the receiver tank. This is a low-grade coal dehydration system. A flue gas exhausted from the boiler flows in the order of a denitration device, an air heater, a dust collector, and a desulfurization device, and a steam turbine is driven by steam generated by the boiler, and then condensate after driving the steam turbine. A steam system for supplying steam to the steam generator, a water supply system for supplying the water condensed by the condenser to the boiler, and dewatering the low-grade coal supplied to the boiler by dehydrating the low-grade coal A power plant comprising a system,
The low-grade coal dehydration system contacts low-grade coal with a liquefied product of an organic compound (hereinafter referred to as “dehydrating agent”) that is gaseous at normal temperature and normal pressure, and dehydrates the moisture contained in the low-grade coal. The low-grade coal is dehydrated by dissolving in an agent to obtain a mixture of water and the dehydrating agent, and the mixture is separated into the gas dehydrating agent and water to recover the gaseous dehydrating agent. Then, the recovered dehydrating agent in the gaseous state is liquefied by any method of pressurization, cooling, or a combination of pressurization and cooling, and the liquefied dehydrant is reused to dehydrate low-grade coal. A mechanical dehydration system and an upstream side of the chemical dehydration system, mechanically dehydrating all or part of the bulk water contained in the low-grade coal, and dehydrating the low-grade coal A mechanical dehydration system that supplies the system Power plant, characterized in that was. In the description of claim 8,
The chemical dehydration system is configured to vaporize the dehydrating agent in the chemical dehydration apparatus that contacts and dehydrates low-grade coal and the liquefied product of the dehydrating agent, and the mixture generated by the chemical dehydrating apparatus. A steam separator having a heat exchanger, a receiver tank for collecting and storing the dehydrating agent vaporized in the steam separating apparatus, and a compression for pressurizing the gaseous dehydrating agent stored in the receiver tank , A cooler that cools and liquefies the dehydrating agent pressurized by the compressor, a blower that conveys the dehydrating agent vaporized by the steam separator to the receiver tank, and the steam separator A power plant comprising: a pump for discharging water separated from the mixture by an apparatus to the outside of the system. In the description of claim 9,
A power plant comprising a path for flowing the combustion exhaust gas extracted from an outlet of the air heater to the dust collector through the heat exchanger. In the description of claim 9,
A power plant comprising a path for flowing the combustion exhaust gas extracted from an outlet of the dust collector to the desulfurization device via the heat exchanger. In the description of claim 10 or 11,
A power plant comprising a gas gas heater in the exhaust gas system. In the description of claim 9,
A power plant comprising: a heat medium that has exchanged heat with steam in the condenser to obtain latent heat of evaporation, the heat medium being guided to the heat exchanger, and then returned to the condenser again. In the description of claim 13,
Water or air is used as the heat medium. In the description of claim 9,
The steam extracted from the steam turbine is guided to the heat exchanger to the water supply system, and the steam is recovered as condensed water by heat exchange with the dehydrating agent in the heat exchanger, and the condensed water is supplied to the boiler. A power plant having a supply path. In the description of claim 9,
A degassing tower for degassing the dehydrating agent contained in the water separated by the steam separator, and a path for returning the dehydrating agent degassed by the degassing tower to the receiver tank. A power plant characterized by that.