JP6724381B2 - Drying system - Google Patents

Description

The present invention relates to a drying system for drying a water-containing solid substance such as a water-containing solid fuel.

Coal has a useful life of about 150 years, which is more than three times that of petroleum, and because reserves are not unevenly distributed compared to petroleum, it is a natural resource that can be stably supplied for a long time. Is expected as. Coal is classified into peat, lignite, lignite, subbituminous coal, bituminous coal, semi-anthracite, and anthracite in order of low carbon content.Peat, lignite, lignite, subbituminous coal (hereinafter referred to as hydrous solid fuel) is bituminous coal, Has a higher water content (water content) than semi-anthracite and anthracite (hereinafter referred to as anthracite).

Among the hydrous solid fuels, lignite is said to account for half of the world's coal reserves, so effective utilization of lignite is being studied. However, as described above, the water-containing solid fuel such as brown coal has a higher water content than that of anthracite, so that the calorific value per unit weight is low and the energy efficiency as a fuel for transportation cost is low.

Therefore, a technique has been developed in which the hydrous solid fuel is crushed and put into a fluidized bed chamber, and a fluidized bed of particles of the hydrous solid fuel is formed and dried in the fluidized bed chamber (for example, Patent Document 1). However, since the hydrous solid fuel is relatively soft, it is difficult to make the particle size uniform during the crushing process, and the particle size distribution of the crushed particles becomes wide. For this reason, when the crushed water-containing solid fuel is put into the fluidized bed chamber, if the fluidized bed is formed by adjusting the velocity of the fluidizing gas to the relatively large particles, the relatively small particles are scattered. On the other hand, if the fluidized bed is formed by adjusting the velocity of the fluidizing gas to the relatively small particles, the relatively large particles do not fluidize but stay.

Therefore, the fluidized bed chamber is divided into two, and the crushed hydrous solid fuel (particles of hydrous solid fuel) is put into the first chamber, and the velocity of the fluidized gas in the first chamber is made higher than that in the second chamber. Has been developed (for example, Patent Document 2). In the technique of Patent Document 2, a fluidized bed of coarse particles is formed in the first chamber and dried, and at the same time, fine particles are overflowed from the first chamber to the second chamber to form a fluidized bed of fine particles in the second chamber. And dried.

International Publication No. 2012/141217 JP, 2011-214817, A

However, since particles of the water-containing solid fuel are crosslinked by water (hereinafter referred to as “water bridge”), in the technique of Patent Document 2 described above, a fluidized bed of coarse particles is formed in the first chamber. It will take a long time to get there. In addition, depending on the water content, there is a problem that due to water crosslinking, a plurality of coarse particles aggregate to impair the fluidity of the particles, making it impossible to fluidize.

The present invention has been made in view of the above problems, and an object thereof is to provide a drying system capable of suppressing a decrease in fluidity of particles of a hydrous solid substance such as a hydrous solid fuel.

In order to solve the above-mentioned problem, the drying system of the present invention is a drying system for drying a water-containing solid matter, wherein a first accommodating portion for accommodating a particle group of the water-containing solid matter and a gas flow rate A first gas supply unit that supplies gas from the bottom surface of the first storage unit by alternately and periodically switching between a flow velocity and a second flow velocity that is higher than the first flow velocity, and the water content discharged from the first storage unit. A gas is supplied in a pulsed manner from the bottom surface of the second container by switching the gas flow velocity at a frequency that is higher than the frequency at which the second gas container that stores solid particles and the first gas supply unit switches the gas flow velocity. And a second gas supply unit that does.
In order to solve the above-mentioned problems, another drying system of the present invention is a drying system for drying a water-containing solid matter, wherein a first accommodating portion for accommodating particles of the water-containing solid matter and a gas flow rate A first gas supply part for supplying gas from the bottom surface of the first accommodating part by periodically and alternately switching between a first flow velocity and a second flow velocity higher than the first flow velocity. Part derives the force of water bridge between two particles based on the water content of the water-containing solids and the particle size of the particles of the water-containing solids, the mass density and particle size of the particles of the water-containing solids, and the pulse shape. Based on the diameter of the bubbles generated by supplying gas to the buoyancy, buoyancy exceeding the force of the water bridge is derived, and the first flow velocity and the second flow velocity, the mass density and kinematic viscosity of the gas, and the water content. Based on the water content of the solid matter, the frequency that gives the water bridge a buoyancy exceeding the force of the water bridge is derived, and the gas is supplied at the derived frequency.

Further, the first flow velocity may be equal to or higher than the minimum fluidization velocity of the particles of the water-containing solid substance having the average particle diameter.

Further, the first gas supply unit may switch the gas flow rate at a predetermined frequency within the range of 1 Hz to 10 Hz.

In addition, an extraction unit for extracting the particles of the hydrous solid matter segregated in the inner lower portion of the first accommodating section and a crushing unit for crushing the particles of the hydrous solid matter extracted by the extraction unit are provided. The water-containing solid particles crushed by the crushing unit may be introduced into the storage unit.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress the fall of the fluidity of the particle|grains of hydrous solids, such as hydrous solid fuel.

It is a figure for demonstrating free water and bound water. It is a figure which shows the schematic of a drying system. It is a figure explaining the opening/closing timing of a regulating valve, and a pulse flow and a steady flow. It is a figure which shows the model of the bubble and particle at the time of setting a frequency. It is a figure explaining the relationship between a frequency and a fluidization rate.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the invention unless otherwise specified. In this specification and the drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to omit redundant description, and elements not directly related to the present invention are omitted. To do.

Water-containing solids such as brown coal contain free water and bound water. Free water is water existing on the surface of a water-containing solid material and in macroscopic voids inside the water-containing solid material, and exhibits the same thermophysical properties as bulk water. Bound water is water condensed in the capillaries of the hydrous solid, adsorbed water having a multi-layer or single layer on the surface of the hydrous solid, and bound water bonded to hydrogen on the surface of the hydrous solid. Bound water is less likely to evaporate than free water, and thus requires more heat energy than free water to evaporate bound water.

FIG. 1 is a diagram for explaining free water and bound water. In FIG. 1, the horizontal axis represents the proportion of water contained in brown coal (water content of brown coal), and the vertical axis represents the temperature (° C.) of water vapor contacting the brown coal. As shown in FIG. 1, when steam at 100° C. is brought into contact with brown coal and heated at normal pressure, the water content of the brown coal decreases to about 30%. Thus, of the water contained in brown coal, the water that vaporizes at about 100° C. is free water.

On the other hand, when steam having a temperature of more than 100° C. and less than 200° C. is brought into contact with brown coal and heated, the water content of the brown coal decreases to about 3%. As described above, among the water contained in the brown coal, the water that is vaporized at more than 100° C. and less than 200° C. is the bound water.

That is, free water requires less heat energy (vaporization heat, heat of vaporization) for vaporization than bound water. Therefore, in the drying system 100 of the present embodiment, first, free water is vaporized and removed from the water-containing solid matter, and subsequently, bound water is vaporized and removed from the water-containing solid matter from which the free water is removed. Here, the thermal energy is the energy (kJ/mol) required to vaporize the water contained in the hydrous solid.

(Drying system 100)
FIG. 2 is a diagram showing a schematic view of the drying system 100. In FIG. 2, the flow of lignite is shown by a dashed-dotted line arrow, the flow of gas such as steam and exhaust gas is shown by a solid line arrow, and the flow of signals is shown by a broken line arrow. Also, in order to facilitate understanding, in FIG. 2, relatively large particles are indicated by black circles that are larger than they actually are. In the present embodiment, a case where brown coal is dried as a water-containing solid will be described as an example.

As shown in FIG. 2, the drying system 100 includes a water-containing solids introduction unit 110, a first drying furnace 210, a second drying furnace 310, a cooling unit 410, and a flow velocity setting unit 510. ..

In the drying system 100 of the present embodiment, undried brown coal is introduced into the first drying furnace 210 by the hydrous solids introducing unit 110, and in the first drying furnace 210, free water contained in the brown coal is vaporized and removed, In the second drying furnace 310, the bound water contained in the brown coal from which the free water has been removed is vaporized and removed, and in the cooling unit 410, the brown coal dried in the second drying furnace 310 is cooled.

Hereinafter, specific configurations of the water-containing solids introduction unit 110, the first drying furnace 210, the second drying furnace 310, the cooling unit 410, and the flow velocity setting unit 510 will be described.

(Hydrous solids introduction part 110)
The water-containing solids introduction unit 110 includes a main communication pipe 112, a crushing unit 114, a conveyance unit 116, and a return pipe 118.

The main communication pipe 112 is a pipe that communicates a brown coal supply source with a later-described first accommodating portion 212 that constitutes the first drying furnace 210. The crushing unit 114 is provided in the main communication pipe 112 and crushes lignite introduced from a supply source or a return pipe 118 described later. The transport unit 116 is, for example, a screw feeder, is provided on the downstream side of the crushing unit 114 in the main communication pipe 112 (between the crushing unit 114 and the first accommodating unit 212), and the brown coal crushed by the crushing unit 114. Are conveyed to the first drying furnace 210.

The return pipe 118 is a pipe that connects an inner lower portion of the first accommodating portion 212 (a discharge port opened at the lower portion of the side wall) and an upstream side of the crushing portion 114 in the main communication pipe 112. As will be described later in detail, when the lignite crushed by the transport unit 116 is transported to the first storage unit 212, the brown coal (large particles) segregated in the lower inside of the first storage unit 212 is crushed through the return pipe 118. It will be pushed out to the portion 114.

(First drying furnace 210)
The first drying furnace 210 includes a first accommodating part 212, a first gas supply part 220, a first heat transfer part 230, and a gas-liquid separating part 240. The first accommodating section 212 accommodates the brown coal particle group introduced by the hydrous solids introducing section 110.

The first gas supply unit 220 includes a wind box 222, blowers 224 and 226 for sending the first fluidizing gas into the wind box 222, and an adjusting valve 228 for adjusting the flow rate of the first fluidizing gas supplied by the blower 226. The gas is supplied in a pulsed manner from the bottom surface of the first accommodating portion 212.

The wind box 222 is provided below the first accommodating section 212, and when the drying system 100 is operated, the wind box 222 is first fluidized from the bottom surface of the first accommodating section 212 into the first accommodating section 212 through the wind box 222. Gas will be supplied. More specifically, the upper part of the wind box 222 also functions as a bottom surface of the first accommodating portion 212, and is formed of a dispersion plate 222a that is permeable to air. The dispersion plate 222a is, for example, a plate provided with a plurality of openings having a diameter smaller than that of brown coal (particles having the smallest particle size among brown coal particles) or an opening having a diameter smaller than that of brown coal. It is composed of a plate on which a nozzle provided with is installed.

The blower 224 sends the first fluidizing gas (for example, water vapor) into the wind box 222 at a predetermined first flow rate. Here, the first flow velocity is equal to or higher than the minimum fluidization speed of particles having an average particle size of brown coal, and is set to the minimum fluidization speed of particles having an average particle size of brown coal in the present embodiment.

The blower 226 uses the first fluidized gas at the third flow rate so that the flow rate of the first fluidized gas passing through the first storage portion 212 (wind box 222) is switched from the first flow rate to the second flow rate. Is sent to the wind box 222. More specifically, when the blower 226 sends the first fluidizing gas having the third flow rate to the wind box 222, the blower 224 mixes the first fluidizing gas with the first fluidizing gas having the first flow rate to the second flow rate. Becomes the first fluidizing gas of. Here, the second flow velocity is set based on the first flow velocity and the minimum fluidization velocity of the largest particles of the lignite introduced into the first accommodation portion 212. The second flow velocity is set such that the average flow velocity with the second flow velocity is the minimum fluidization velocity of the largest particle.

The adjusting valve 228 is formed of, for example, an open/close valve, and is provided between the blower 226 and the wind box 222. The adjustment valve 228 periodically switches between the open state and the closed state, so that the flow velocity of the first fluidizing gas sent from the blower 226 to the wind box 222 is zero (0) and the third flow velocity. It alternates periodically. In the present embodiment, the ratio (duty ratio) of the time when the adjustment valve 228 is in the open state and the time when the adjustment valve 228 is in the closed state is 1:1. Further, the frequency at which the adjusting valve 228 switches the flow rate of the first fluidizing gas (the switching frequency of the first fluidizing gas by the adjusting valve 228) is set by the flow rate setting unit 510. The frequency setting by the flow velocity setting unit 510 will be described in detail later.

Therefore, the first fluidizing gas is constantly supplied from the blower 224 to the first housing portion 212 (wind box 222) at the first flow rate, and the first fluidizing gas is intermittently supplied from the blower 226 at the third flow rate. Gas will be supplied. That is, the first gas supply unit 220 periodically and alternately switches the flow rate of the first fluidizing gas between the first flow rate and the second flow rate so that the first fluidizing gas (hereinafter, the flow rate is periodic). The flow of gas that is switched alternately is referred to as a "pulse flow").

Due to the configuration in which the first gas supply unit 220 supplies the first fluidizing gas in a pulsed flow, the particle size of the brown coal is relatively large compared to the case where the first fluidizing gas is supplied in a steady flow. Alternatively, it is possible to shorten the formation time of the fluidized bed of particles having a large mass (hereinafter referred to as “large particles”).

FIG. 3 is a diagram for explaining the opening/closing timing of the adjusting valve 228 and the pulsed flow and the steady flow. In FIG. 3, the opening/closing timing of the regulating valve 228 is shown by a thick line, the pulse flow is shown by a solid line, and the steady flow is shown by a chain line. As described above, the particles of brown coal are crosslinked with water. In the steady flow, if the first fluidizing gas is supplied at a flow rate suitable for fluidizing large particles (for example, the second flow rate), the water bridge can be broken by the bubbles of the supplied first fluidizing gas. Although it is possible to form a fluidized bed of large particles, there is a problem that particles having a relatively small particle size or a small mass (hereinafter referred to as “small particles”) are scattered. Therefore, conventionally, the flow velocity of the steady flow has been set between the minimum fluidization velocity (first flow velocity) of particles having an average particle diameter of brown coal and the second flow velocity to prevent scattering of small particles. Therefore, in the conventional steady flow, there is a problem that it takes a long time to form a fluidized bed of large particles. Also, because the flow rate is set to prevent the scattering of small particles, the fluidity of large particles becomes low, and depending on the water content of brown coal, large particles aggregate due to water bridges, resulting in fluidity of large particles. May be impaired, and it may become impossible to fluidize.

However, as shown in FIG. 3, when the opening/closing of the regulating valve 228 is switched in a pulsed manner and the first fluidizing gas is supplied in a pulsed flow in which the first flow velocity and the second flow velocity are alternately switched periodically, The period during which the first fluidizing gas is supplied at the second flow rate is intermittent. That is, since the first fluidizing gas is not continuously supplied at the second flow rate, it is possible to efficiently form a fluidized bed of large particles while preventing scattering of small particles. For example, assuming that the average flow velocity of the pulse flow is equal to the flow velocity of the steady flow, the flow of the large particles is larger when the first fluidizing gas is supplied by the pulse flow than when the first fluidizing gas is supplied by the steady flow. It is possible to reduce the layer formation time to about 1/2. Note that, as shown in FIG. 3, even if the opening/closing of the adjusting valve 228 is switched in a pulse shape, a delay occurs, so that the flow velocity of the pulse flow is not in a pulse shape.

Further, the pulsed flow can improve the fluidity of lignite (large particles), and can avoid the situation where lignite agglomerates.

Furthermore, in steady flow, there is almost no difference between the response speed that fluidizes large particles and the response speed that fluidizes small particles, but in pulsed flow, the response speed that fluidizes small particles fluidizes large particles. It is faster than the response speed. Therefore, in the pulsed flow, the small particles can move upward faster than in the steady flow, and the separation (segregation) of the large particles and the small particles can be performed in a short time.

In this way, the first gas supply unit 220 supplies the first fluidizing gas in a pulsed flow, so that a fluidized bed of large particles is formed in the lower inner portion of the first storage unit 212 in a shorter time than the steady flow. In addition to (segregation), a fluidized bed of small particles can be formed (segregated) in the upper portion inside the first housing portion 212 (above the large particles).

Therefore, as compared with the case where a steady flow is supplied, the formation time of the fluidized bed and the time required for segregation can be shortened, and the first accommodating portion 212 can be made compact.

In this way, the first fluidizing gas supplied to the first accommodating part 212 by the first gas supplying part 220 causes the brown coal to flow in the first accommodating part 212 to form a fluidized bed, and at the same time, the first fluidizing gas. Is contacted with brown coal to vaporize part of the free water contained in the brown coal. The first fluidizing gas supplied to the first storage portion 212 is adjusted to a temperature (for example, 120°C) at which free water is efficiently evaporated.

Returning to FIG. 2, the first heat transfer section 230 is composed of, for example, a pipe through which a heat medium flows, and is disposed in an upper portion inside the first accommodation section 212 (a region where a fluidized bed of small particles is formed). To be done. The 1st heat transfer part 230 heats a brown coal (small particle) with the heat which a heat medium has in the distribution process of a heat medium. In the present embodiment, steam is supplied to the first heat transfer section 230 as a heat medium by the blower 232. The steam (heat medium) supplied to the first heat transfer section 230 by the blower 232 is adjusted to a temperature (for example, 120° C.) and a flow rate at which free water of brown coal is efficiently evaporated.

With the configuration including the first heat transfer section 230, heat exchange is performed between the heat medium and the first fluidized gas in the first accommodation section 212, and the first fluidized gas moving upward is further heated. can do. Therefore, the drying (vaporization of free water) of brown coal (small particles) by the first fluidizing gas is further promoted.

In addition, when heat is exchanged between the heat medium and the first fluidizing gas in the first heat transfer section 230 (the outer surface of the tube forming the first heat transfer section 230), a part of the heat medium is transferred to the first heat transfer section. It will be condensed in the heat part 230. Therefore, the gas-liquid separation unit 240 is provided, and the heat medium sent from the first heat transfer unit 230 is separated into the gas-liquid by the gas-liquid separation unit 240. In this way, the separated and condensed heat medium (liquid water) is delivered to the outside.

As described above, in the first drying furnace 210, the undried brown coal is introduced into the first storage portion 212, and the brown coal (small particles) is heated by the first gas supply unit 220 and the first heat transfer unit 230. Free water is vaporized and removed. On the other hand, describing the flow of lignite, when undried lignite is introduced into the first accommodating portion 212 by the transport unit 116, the volume of the introduced lignite and the volume of the fluidized bed increase. Then, the brown coal (small particles) from which the free water has been removed overflows (is discharged) from the outlet of the first accommodating part 212, and the first accommodating part 212 and the second accommodating part 312 of the second drying furnace 310 are separated. The lignite (large particles), which is introduced into the second container 312 through the communicating pipe and segregated in the lower inner portion of the first container 212, is pushed out to the crushing unit 114 through the return pipe 118.

That is, the transport unit 116 functions as an extraction unit that extracts the large particles segregated in the lower inside of the first storage unit 212. Then, the extracted large particles are crushed by the crushing unit 114, reintroduced into the first accommodating unit 212, and dried. Therefore, although the large particles that have been fluidized in the first storage portion 212 are not dried, the large particles can be dried by extracting and crushing them again and introducing them into the first storage portion 212.

The free water (steam of about 103° C.) vaporized in the first drying furnace 210 is sent again to the wind box 222 by the blowers 224 and 226, or is supplied to the first heat transfer section 230 by the blower 232. It will be.

(Second drying furnace 310)
The second drying furnace 310 includes a second accommodating section 312, a second gas supply section 320, a second heat transfer section 330, and a gas-liquid separation section 340. The second storage unit 312 stores the brown coal from which the free water has been removed by the first drying furnace 210.

The second gas supply unit 320, like the first gas supply unit 220 constituting the first drying furnace 210, has a wind box 322, blowers 324 and 326 for sending the second fluidizing gas to the wind box 322, and a blower 326. And a regulating valve 328 that regulates the flow rate of the second fluidized gas supplied by the above, and supplies the gas in a pulse form from the bottom surface of the second accommodating portion 312.

The wind box 322 is provided below the second storage portion 312, and when the drying system 100 is operated, the air box 322 is second fluidized from the bottom surface of the second storage portion 312 through the wind box 322 into the second storage portion 312. Gas will be supplied. More specifically, the upper part of the wind box 322 also functions as a bottom surface of the second accommodating portion 312, and is formed of a breathable dispersion plate 322a. The dispersion plate 322a is, for example, a plate provided with a plurality of openings having a diameter smaller than that of brown coal (particles having the smallest particle size among brown coal particles), or an opening having a diameter smaller than that of brown coal. It is composed of a plate on which a nozzle provided with is installed.

The blower 324 sends the second fluidizing gas (for example, steam) into the wind box 322 at a predetermined fourth flow rate. Here, the fourth flow velocity is equal to or higher than the minimum fluidization speed of particles of the average particle size of the brown coal introduced into the second storage portion 312, and in the present embodiment, the fourth flow velocity of the brown coal introduced into the second storage portion 312 is Set to the minimum fluidization rate of particles of average size.

The blower 326 uses the second fluidized gas at the sixth flow rate so that the flow rate of the second fluidized gas passing through the second storage portion 312 (wind box 322) switches from the fourth flow rate to the fifth flow rate. Is sent to the wind box 322. More specifically, when the blower 326 sends the second fluidizing gas having the sixth flow rate to the wind box 322, it is mixed with the second fluidizing gas having the fourth flow rate by the blower 324 to form the fifth flow rate. Becomes the second fluidizing gas of. Here, the fifth flow velocity is set based on the fourth flow velocity and the minimum fluidization velocity of the largest particles of the lignite introduced into the second accommodating section 312, and for example, the fourth flow velocity The fifth flow velocity is set such that the average flow velocity with the fifth flow velocity is the minimum fluidization velocity of the largest particle.

The adjusting valve 328 is formed of, for example, an open/close valve, and is provided between the blower 326 and the wind box 322. The adjustment valve 328 periodically switches between the open state and the closed state, so that the flow velocity of the second fluidizing gas sent from the blower 326 to the wind box 322 is zero (0) and the sixth flow velocity. It alternates periodically. In the present embodiment, the ratio (duty ratio) of the time when the adjustment valve 328 is in the open state and the time when the adjustment valve 328 is in the closed state is 1:1. Further, the frequency at which the adjusting valve 328 switches the flow rate of the second fluidizing gas is higher than the frequency at which the adjusting valve 228 switches the flow rate of the first fluidizing gas, and is set by the flow rate setting unit 510. The frequency setting by the flow velocity setting unit 510 will be described in detail later.

Therefore, the second fluidizing gas is constantly supplied from the blower 324 to the second housing portion 312 (wind box 322) at the fourth flow rate, and the second fluidizing gas is intermittently supplied from the blower 326 at the sixth flow rate. Gas will be supplied. That is, the second gas supply unit 320 supplies the second fluidizing gas by periodically and alternately switching the flow rate of the second fluidizing gas between the fourth flow rate and the fifth flow rate.

With the configuration in which the second gas supply unit 320 supplies the second fluidizing gas in a pulsed flow, it is possible to shorten the formation time of the fluidized bed of brown coal as compared with the case where the second fluidizing gas is supplied in a steady flow. It will be possible.

In this way, the second fluidizing gas supplied to the second accommodation portion 312 by the second gas supply portion 320 causes the brown coal to flow in the second accommodation portion 312 to form a fluidized bed, and at the same time, the second fluidization gas. Is contacted with brown coal to vaporize a part of the bound water contained in the brown coal. The second fluidizing gas supplied to the second container 312 is adjusted to a temperature (for example, 115° C.) at which the combined water is efficiently evaporated.

The second heat transfer section 330 is, for example, a pipe through which a heat medium flows, and is arranged in the second accommodating section 312, similarly to the first heat transfer section 230 configuring the first drying furnace 210. The 2nd heat transfer part 330 heats brown coal with the heat which a heat medium has in the distribution process of a heat medium. In the present embodiment, the second heat transfer section 330 is supplied with water vapor (for example, 200° C.) as a heat medium.

With the configuration including the second heat transfer section 330, heat exchange is performed between the heat medium and the second fluidized gas in the second accommodation section 312, and the second fluidized gas moving upward is further heated. can do. Therefore, the drying of the brown coal (vaporization of bound water) by the second fluidizing gas is further promoted.

In addition, when heat is exchanged between the heat medium and the second fluidizing gas in the second heat transfer section 330 (the outer surface of the tube forming the second heat transfer section 330), a part of the heat medium is transferred to the second heat transfer section. It will be condensed in the heat section 330. Therefore, the gas-liquid separating section 340 is provided, and the heat medium sent from the second heat transfer section 330 is separated into the gas-liquid by the gas-liquid separating section 340. In this way, the separated and condensed heat medium (liquid water) is sent to the outside.

As described above, in the second drying furnace 310, the brown coal from which the free water has been removed in the first drying furnace 210 is introduced into the second accommodating section 312, and the brown coal is removed by the second gas supply section 320 and the second heat transfer section 330. Upon heating, the bound water is vaporized and removed from the brown coal. On the other hand, describing the flow of lignite, when lignite from which free water has been removed is introduced from the first drying furnace 210 to the second storage unit 312, the volume of the introduced lignite and the volume of the fluidized bed increase. Then, the brown coal (fluidized bed) from which the bound water has been removed overflows from the outlet of the second storage unit 312, and the third storage unit 312 is connected to the third storage unit 412 of the cooling unit 410 through a pipe that communicates with the third storage unit. It will be introduced into the section 412. In addition, the combined water (water vapor at about 115° C.) vaporized in the second drying furnace 310 is fed again to the wind box 322 by the blowers 324 and 326, or is supplied to the second heat transfer section 330 by the blower 332. Will be done.

(Cooling unit 410)
The cooling unit 410 includes a third accommodating unit 412 and a cooling gas supply unit 420. The third storage unit 412 stores the brown coal from which the bound water has been removed by the second drying furnace 310. Like the first gas supply unit 220 and the second gas supply unit 320, the cooling gas supply unit 420 includes a wind box 422 and a blower 424 that sends cooling gas (for example, air) to the wind box 422. It The wind box 422 is provided below the third accommodation unit 412, and when the drying system 100 is operated, the cooling gas is supplied from the bottom surface of the third accommodation unit 412 through the wind box 422 into the third accommodation unit 412. Will be done.

More specifically, the upper part of the wind box 422 also functions as a bottom surface of the third accommodating portion 412, and is formed of a breathable dispersion plate 422a. The dispersion plate 422a is composed of, for example, a plate provided with a plurality of openings having a diameter smaller than that of brown coal, or a plate provided with a nozzle having an opening having a diameter smaller than that of brown coal. ..

With the configuration including the cooling unit 410, the brown coal from which free water and bound water have been removed can be cooled (for example, up to about 50° C.). The brown coal thus cooled is sent to the brown coal utilization facility in the subsequent stage.

(Flow velocity setting unit 510)
The flow velocity setting unit 510 is composed of a semiconductor integrated circuit including a CPU (central processing unit), reads programs and parameters for operating the CPU itself from the ROM, and cooperates with the RAM as a work area and other electronic circuits. Then, the opening/closing frequency (frequency of flow velocity) of the adjusting valves 228, 328 is set. The setting of the frequency at which the adjusting valve 228 switches the flow rate and the frequency at which the adjusting valve 328 switches the flow rate by the flow rate setting unit 510 will be described in detail below.

(Frequency setting)
FIG. 4 is a diagram showing a model of bubbles and particles when the frequency is set. As shown in FIG. 4, when gas is supplied, bubbles are formed in the fluidized bed. Then, assuming that a plurality of lignite particles are arranged around the bubbles, the frequency range in which the fluidized bed can be efficiently formed was derived.

…式（１）
ここで、Ｒは水架橋の長さであり、最大で粒子の半径と同一である。また、ｒは水の表面張力（例えば、３０℃の空気と接触している場合には、０．０７１２Ｎ／ｍ）である。なお、褐炭は、含水率が高いほど水架橋を作りやすく、粒子間の水架橋の力Ｆ_ｌが大きくなる。 As described above, particles of brown coal are cross-linked by water. Therefore, first, the force F ₁ of the water bridge between the particles of the brown coal is derived. The force F ₁ of water bridge between two particles is derived from the following equation (1).

... Formula (1)
Where R is the length of the water bridge and is at most the radius of the particle. Further, r is the surface tension of water (for example, 0.0712 N/m when in contact with air at 30° C.). The higher the water content of lignite, the easier it is to form a water bridge, and the inter-particle water bridge force F _l increases.

…式（２）
ここで、Ｆ_ｂは流動層内に形成される気泡（パルス流によって形成される気泡）の浮力であり、ｎは１の気泡の周囲に配される粒子の粒子数である。 If the particles receive a buoyancy force that exceeds the force F ₁ of the water bridge thus derived, the water bridge between the particles can be broken, and a fluidized bed can be efficiently formed. The buoyancy F _p of the particles is derived from the following equation (2).

... Formula (2)
Here, F _b is the buoyancy of bubbles (bubbles formed by pulse flow) formed in the fluidized bed, and n is the number of particles arranged around one bubble.

…式（３）
ここで、ε_ｍｆは平均粒径の粒子の最小流動化速度時の層内空隙率、ρ_ｐは粒子の質量密度、ｇは重力加速度、Ｖ_ｂは気泡の体積を示す。 The buoyancy F _b of the bubble is derived from the following equation (3).

... Formula (3)
Here, ε _mf is the in-layer porosity at the time of the minimum fluidization velocity of particles having an average particle size, ρ _p is the mass density of the particles, g is the gravitational acceleration, and V _b is the volume of the bubbles.

…式（４）
ここで、Ｄ_ｂは気泡の直径、ｄ_ｐは粒子の直径である。 The number of particles n is derived from the following equation (4).

... Formula (4)
Here, D _b is the diameter of the bubble and d _p is the diameter of the particle.

…式（５）
したがって、下記式（６）の関係となる直径Ｄ_ｂの気泡を生成すれば、水架橋を切断できる浮力Ｆ_ｐを粒子に与えることができ、効率よく流動層を形成することが可能となる。

…式（６）
そこで、下記式（７）、式（８）、式（９）を用いて、上記式（６）の関係となる直径Ｄ_ｂの気泡が生成できる周波数Ｆを導出する。

…式（７）
ここで、Ｕ_ｍｆは平均粒径の粒子の最小流動化速度（第１の流速）であり、Ｕ_ｐは第２の流速の際の流動化ガスの空塔速度であり、ｈは層高である。

…式（８）
ここで、μ_ｇはガスの動粘度であり、Ａｒはアルキメデス数であり、ρ_ｇは流動化ガスの質量密度であり、Ｍは粒子の平均含水率である。

…式（９）
ここで、αは流動化ガスの平均総流量に対するパルス流の流量の比であり、Ｕ_０は流動化ガスの空塔速度であり、Ｆqは流速を切り換える周波数（調整弁２２８、３２８の開閉周波数）であり、ｔは気泡が直径Ｄ_ｂに成長するまでの時間であり、βは１周期における調整弁２２８、３２８の開放割合である。 Therefore, by substituting equations (3) and (4) into equation (2), the particle buoyancy F _p can be expressed by the following equation (5).

... Formula (5)
Therefore, when the bubbles having the diameter D _b satisfying the relationship of the following formula (6) are generated, the buoyancy F _p capable of breaking the water bridge can be given to the particles, and the fluidized bed can be efficiently formed.

... Formula (6)
Therefore, the following formula (7), formula (8), and formula (9) are used to derive the frequency F at which bubbles having a diameter D _b that satisfy the relation of the above formula (6) can be generated.

... Formula (7)
Here, U _mf is the minimum fluidization velocity (first flow velocity) of particles having an average particle size, U _p is the superficial velocity of the fluidization gas at the second flow velocity, and h is the bed height. is there.

... Formula (8)
Here, μ _g is the kinematic viscosity of the gas, Ar is the Archimedes number, ρ _g is the mass density of the fluidizing gas, and M is the average water content of the particles.

... Formula (9)
Here, α is the ratio of the flow rate of the pulsed flow to the average total flow rate of the fluidizing gas, U ₀ is the superficial velocity of the fluidizing gas, and Fq is the frequency at which the flow rate is switched (the opening/closing frequency of the adjusting valves 228, 328). ), t is the time until the bubble grows to the diameter D _b , and β is the opening ratio of the adjusting valves 228, 328 in one cycle.

By deriving the frequency based on the equations (7) to (9), the water bridge of particles having a high water content (for example, a predetermined value in the range of 25 wt% to 30 wt%) can be efficiently cut (efficiency. The frequency F (where a fluidized bed can be well formed) is 1 Hz to 3 Hz, and the frequency F at which the water bridge of particles having a low water content (for example, less than a predetermined value in the range of 25 wt% to 30 wt%) can be efficiently cut is: It was found to be 3 Hz to 10 Hz.

FIG. 5 is a diagram illustrating the relationship between frequency and fluidization rate. In FIG. 5, high water content particles are shown by solid lines, low water content particles are shown by broken lines, and water content 0% particles are shown by dashed lines. As shown in FIG. 5, with particles having a high water content, the fluidization rate increases as the frequency increases up to 2 Hz, and the fluidization rate becomes highest at 2 Hz. When the frequency exceeds 2 Hz, the fluidization rate decreases as the frequency increases, and when it exceeds 3 Hz, the fluidization rate becomes constant. In addition, at a high water content, when it exceeds 3 Hz, the fluidization rate is almost the same as that when gas is supplied in a steady flow, with almost no fluidization.

With particles having a low water content, the fluidization rate increases as the frequency increases up to 3 Hz, and the fluidization rate becomes highest at 3 Hz. When it exceeds 3 Hz, the fluidization rate decreases as the frequency increases, and when it exceeds 4 Hz, the fluidization rate becomes constant. At a low water content, above 4 Hz, the fluidization rate is the same as when gas is supplied in a steady flow.

On the other hand, for particles with a water content of 0%, the fluidization rate increases as the frequency increases up to 6 Hz, and the fluidization rate becomes constant above 6 Hz, which is the same fluidization rate as when gas is supplied in a steady flow. Becomes

That is, in particles having a water content of 0%, since there is no water bridge, the steady flow has a higher fluidization rate than the pulse flow. On the other hand, it can be seen that the hydrous solid such as brown coal has a higher fluidization rate in the pulsed flow than in the steady flow because of the presence of the water bridge.

As described above, the flow velocity setting unit 510 has a frequency range derived based on the water content of the introduced brown coal, and a frequency range capable of efficiently separating large particles and small particles (separating large particles efficiently). The frequency of the adjusting valve 228 and the adjusting valve 328 is set based on

…式（１０）
また、パルス流の周波数が高いと、ガスの瞬間速度ｖ_ｇが増加して加速度も増加するため、大粒子の偏析（大粒子と小粒子との分離）時間を短縮することができる。一方、パルス流の周波数が低いと、パルス流が流動層内に導入される時間が長くなるため、褐炭の粒子の挙動は定常流における挙動に近くなってしまう。同様に、パルス流のパルス周期が高いと、パルス流が流動層内に導入される時間が短くなるため、褐炭の粒子の挙動は定常流における挙動に近くなってしまう。このため、これらを勘案すると、周波数範囲が、１Ｈｚ〜１０Ｈｚである場合に、大粒子を効率よく偏析できると言える。 The frequency range in which large particles can be efficiently segregated is preferably 1 Hz to 10 Hz. Specifically, as shown in the following formula (10), when a pulsed flow is used and the flow velocity of the pulsed flow is equal, the smaller the particle diameter d of the particles, the larger the acceleration (dv _p /dt). Become. Therefore, in a unit time, the moving distance of the small particles is longer than the moving distance of the large particles.

... Formula (10)
Further, when the frequency of the pulse flow is high, the instantaneous velocity v _{g of the} gas increases and the acceleration also increases, so that the segregation time of large particles (separation of large particles and small particles) can be shortened. On the other hand, when the frequency of the pulsed flow is low, the time for which the pulsed flow is introduced into the fluidized bed is long, so that the behavior of the particles of lignite becomes close to the behavior in the steady flow. Similarly, when the pulse period of the pulsed flow is high, the time during which the pulsed flow is introduced into the fluidized bed is short, and therefore the behavior of the particles of brown coal becomes close to the behavior in the steady flow. Therefore, considering these, it can be said that large particles can be efficiently segregated when the frequency range is 1 Hz to 10 Hz.

Here, as described above, the brown coal from which the free water is removed in the first storage portion 212 is introduced into the second storage portion 312. That is, the brown coal in the second storage portion 312 has a lower water content than the brown coal in the first storage portion 212. Therefore, the flow velocity setting unit 510 sets the frequency of the adjusting valve 328 that supplies the second fluidizing gas to the second accommodating unit 312 to be higher than the frequency of the adjusting valve 228 that supplies the first fluidizing gas to the first accommodating unit 212. Set. For example, the flow velocity setting unit 510 sets the frequency of the adjusting valve 228 to 2 Hz and the frequency of the adjusting valve 328 to 3 Hz.

With such a configuration, the fluidized bed can be efficiently formed in both the first storage portion 212 and the second storage portion 312, and the time required for drying can be shortened.

As described above, in the drying system 100 according to the present embodiment, the flowability of the particles of brown coal is improved by the configuration in which the first fluidizing gas is supplied in the pulsed flow, compared to the case where the first fluidized gas is supplied in the steady flow. Therefore, it is possible to shorten the formation time of the fluidized bed of large particles. Therefore, in the 1st accommodation part 212, brown coal can be efficiently dried. In addition, it becomes possible to shorten the separation time of the large particles and the small particles (segregation time of the large particles).

In addition, the configuration in which the second fluidizing gas is supplied by the pulse flow can improve the fluidity of the brown coal particles as compared with the case where the second fluid is supplied by the steady flow, and efficiently forms a fluidized bed of small particles. Therefore, the brown coal can be efficiently dried in the second storage portion 312.

The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such embodiments. It is obvious to those skilled in the art that various alterations or modifications can be conceived within the scope of the claims, and it should be understood that these also belong to the technical scope of the present invention. To be done.

For example, in the above-described embodiment, brown coal has been described as an example of the water-containing solid matter. However, the drying system 100 can dry water-containing solid fuel such as peat, lignite, and sub-bituminous coal, and other water-containing solids, as long as it contains water.

Further, in the above embodiment, the configuration in which the first flow velocity is set to the minimum fluidization speed of the brown coal particles having the average particle diameter has been described as an example. However, the first flow velocity may be equal to or higher than the minimum fluidization velocity of the brown coal particles having the average particle diameter.

Further, in the above embodiment, the configuration in which the pulse flow is also supplied to the second drying furnace 310 has been described as an example, but a steady flow may be supplied to the second drying furnace.

Further, in the above-described embodiment, the configuration in which the ratio of the time in which the adjustment valves 228, 328 are in the open state and the time in which they are in the closed state is 1:1 is described as an example. However, the ratio of the time of being in the open state and the time of being in the closed state is not limited to 1:1 and is appropriately set. For example, if α in equation (9) is made small, the instantaneous flow velocity can be made large, while if α is made large, it is possible to suppress the change in the operating state of the first drying furnace 210 to be low.

In the above embodiment, the case where the drying system 100 includes two drying ovens (first drying oven 210 and second drying oven 310) has been described as an example. However, the drying system may include only one drying oven.

Further, each of the first drying furnace 210, the second drying furnace 310, and the cooling unit 410 may be configured by one accommodating portion or may be configured by including a plurality of accommodating portions.

INDUSTRIAL APPLICATION This invention can be utilized for the drying system which dries a water-containing solid substance, such as a water-containing solid fuel.

100 Drying System 114 Crushing Section 116 Conveying Section (Extraction Section)
212 first accommodating part 220 first gas supplying part 312 second accommodating part 320 second gas supplying part

Claims (5)

A drying system for drying a water-containing solid,
A first accommodating portion for accommodating the particle group of the water-containing solid matter,
A first gas supply part for supplying gas from the bottom surface of the first accommodating part by periodically and alternately switching the flow velocity of the gas between a first flow velocity and a second flow velocity higher than the first flow velocity. ,
A second accommodating portion for accommodating the particles of the water-containing solid matter discharged from the first accommodating portion;
A second gas supply unit configured to switch the gas flow rate at a frequency higher than a frequency at which the first gas supply unit switches the gas flow rate to supply the gas in a pulsed form from the bottom surface of the second storage unit;
A drying system characterized by having. A drying system for drying a water-containing solid,
A first accommodating portion for accommodating the particle group of the water-containing solid matter,
A first gas supply part for supplying gas from the bottom surface of the first accommodating part by periodically and alternately switching the flow velocity of the gas between a first flow velocity and a second flow velocity higher than the first flow velocity. ,
Equipped with
The first gas supply unit,
Based on the water content of the water-containing solid and the particle size of the particles of the water-containing solid, derive the force of water bridge between the two particles,
Based on the mass density and particle size of the particles of the hydrous solid, and the diameter of the bubbles generated by supplying the gas in a pulsed manner, deriving buoyancy exceeding the force of the water bridge,
A frequency that gives the water bridge buoyancy exceeding the force of the water bridge based on the first flow velocity and the second flow velocity, the mass density and kinematic viscosity of the gas, and the water content of the water-containing solid. And derive
A drying system, characterized in that gas is supplied at the derived frequency . The said 1st flow velocity is more than the minimum fluidization speed of the particle|grains of the said hydrous solid of an average particle diameter, The drying system of Claim 1 or 2 characterized by the above-mentioned. The drying system according to any one of claims 1 to 3, wherein the first gas supply unit switches the gas flow rate at a predetermined frequency within a range of 1 Hz to 10 Hz. An extraction part for extracting the particles of the water-containing solid matter segregated in the inner lower part of the first accommodating part;
A crushing unit for crushing particles of the hydrous solid matter extracted by the extracting unit,
Equipped with
The drying system according to any one of claims 1 to 4, wherein particles of the water-containing solid crushed by the crushing unit are introduced into the first storage unit.

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