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Patent Analysis of

Coal upgrade plant and method for manufacturing upgraded coal

Updated Time 12 June 2019

Patent Registration Data

Publication Number

US10151530

Application Number

US14/641780

Application Date

09 March 2015

Publication Date

11 December 2018

Current Assignee

MITSUBISHI HEAVY INDUSTRIES ENGINEERING, LTD.

Original Assignee (Applicant)

MITSUBISHI HEAVY INDUSTRIES, LTD.

International Classification

F26B5/00,F26B5/16,B01D53/00,C10B53/04,C10L5/38

Cooperative Classification

F26B5/16,B01D53/00,C10B53/04,C10L5/38,C10L9/083

Inventor

HONJO, SHINTARO,KUNIMUNE, KIYOTAKA,ITO, MOTOFUMI,ASAHARA, JUNJI

Patent Images

This patent contains figures and images illustrating the invention and its embodiment.

US10151530 Coal upgrade plant 1 US10151530 Coal upgrade plant 2
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Abstract

A coal upgrade plant includes a dryer 1 that heats and dries coal before pyrolyzing the coal, and a scrubber 32 that treats a carrier gas discharged from the dryer 1 while catching a desorbed component desorbed from the coal when the coal is dried by the dryer 1. The coal upgrade plant further includes a carrier gas circulation path 22 that guides the carrier gas treated by the scrubber 32 to the dryer 1. A cyclone 28 is also provided on the upstream side of the scrubber 32. Thus, mercury and/or mercury-based substances generated in the dryer 1 can be removed.

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Claims

1. A coal upgrade plant comprising:

a dryer that heats and dries coal before pyrolyzing the coal; a gas feed path configured to supply the dryer with gas for indirectly heating and drying the coal; a carrier gas circulation path configured to supply the dryer with a carrier gas; a carrier gas discharge path configured to discharge the carrier gas catching a desorbed component desorbed from the coal when the coal is dried by the dryer; a cooler provided on the carrier gas discharge path and configured to condense steam contained in the carrier gas; and a scrubber provided at a downstream side of the cooler on the carrier gas discharge path and configured to treat the carrier gas by using an absorber, wherein the absorber is recycled water separated in a waste water treatment equipment, and the carrier gas treated by the scrubber is guided to the dryer via the carrier gas circulation path.

2. The coal upgrade plant according to claim 1, further comprising a dust collector that is provided on the carrier gas discharge path and an upstream side of the scrubber.

3. A method for manufacturing upgraded coal comprising:

a drying step of heating and drying coal; a pyrolyzing step of pyrolyzing the coal dried in the drying step; a gas supply step of supplying a gas for indirectly heating and drying the coal in the drying step; a carrier gas supply step of supplying a carrier gas to the coal in the drying step; a carrier gas discharge step of discharging the carrier gas catching a desorbed component desorbed from the coal when the coal is dried; a cooling step of cooling the carrier gas discharged in the carrier gas discharge step and condensing steam contained in the carrier gas; and a carrier gas treating step of treating, by a scrubber using an absorber, the carrier gas discharged in the carrier gas discharge step and after the cooling step, wherein the absorber is recycled water separated in a waste water treatment equipment, and the carrier gas treated by the scrubber in the carrier gas treating step is supplied in the carrier gas supply step to the coal in the drying step.

4. The coal upgrade plant according to claim 1, wherein

the gas having a temperature of 150° C. to 200° C. is supplied to the dryer, and the scrubber reduces at least one of mercury and mercury-based substances from the carrier gas.

5. The coal upgrade plant according to claim 4, wherein the gas is steam.

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Claim Tree

  • 1
    1. A coal upgrade plant comprising:
    • a dryer that heats and dries coal before pyrolyzing the coal
    • a gas feed path configured to supply the dryer with gas for indirectly heating and drying the coal
    • a carrier gas circulation path configured to supply the dryer with a carrier gas
    • a carrier gas discharge path configured to discharge the carrier gas catching a desorbed component desorbed from the coal when the coal is dried by the dryer
    • a cooler provided on the carrier gas discharge path and configured to condense steam contained in the carrier gas
    • and a scrubber provided at a downstream side of the cooler on the carrier gas discharge path and configured to treat the carrier gas by using an absorber, wherein the absorber is recycled water separated in a waste water treatment equipment, and the carrier gas treated by the scrubber is guided to the dryer via the carrier gas circulation path.
    • 2. The coal upgrade plant according to claim 1, further comprising
      • a dust collector that is provided on the carrier gas discharge path and an upstream side of the scrubber.
    • 4. The coal upgrade plant according to claim 1, wherein
      • the gas having
  • 3
    3. A method for manufacturing upgraded coal comprising:
    • a drying step of heating and drying coal
    • a pyrolyzing step of pyrolyzing the coal dried in the drying step
    • a gas supply step of supplying a gas for indirectly heating and drying the coal in the drying step
    • a carrier gas supply step of supplying a carrier gas to the coal in the drying step
    • a carrier gas discharge step of discharging the carrier gas catching a desorbed component desorbed from the coal when the coal is dried
    • a cooling step of cooling the carrier gas discharged in the carrier gas discharge step and condensing steam contained in the carrier gas
    • and a carrier gas treating step of treating, by a scrubber using an absorber, the carrier gas discharged in the carrier gas discharge step and after the cooling step, wherein the absorber is recycled water separated in a waste water treatment equipment, and the carrier gas treated by the scrubber in the carrier gas treating step is supplied in the carrier gas supply step to the coal in the drying step.
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Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coal upgrade plant which pyrolyzes coal after drying the coal, and a method for manufacturing upgraded coal.

2. Description of Related Art

Since low ranking coal such as sub-bituminous coal and lignite has a lower carbonization degree and a higher water content than high ranking coal, a calorific value per unit weight is lower. However, since there are abundant deposits of low ranking coal, the low ranking coal is desired to be effectively used. Thus, various coal upgrading techniques have been studied in which the calorific value of the low ranking coal is increased by performing pyrolysis after drying the low ranking coal, and upgraded coal is deactivated so as to prevent spontaneous combustion during transportation or storage (e.g., Japanese Unexamined Patent Application, Publication No. 2014-31462 (hereinafter referred to as JPA 2014-31462)).

JPA 2014-31462 discloses that pulverized coal is fed into a pyrolysis furnace, and mercury-based substances (HgS, HgCl2 or the like) contained in a pyrolysis gas generated when coal is pyrolyzed are adsorbed to the pulverized coal and discharged outside of a system in order to prevent an increase in the concentration of mercury in pyrolyzed coal with the mercury-based substances being re-adsorbed to the pyrolyzed coal.

A temperature of pyrolyzing coal is 300° C. or more to 500° C. or less, and an evaporating temperature of mercury is about 400° C. Thus, it can be said that it is technically appropriate to take into consideration the generation of the mercury-based substances in a pyrolyzer as described in JPA 2014-31462. Under such understanding, since a dryer used before the pyrolysis heats the coal to 150° C. or more to 200° C. or less to remove moisture in the coal, it has been considered that the generation of the mercury and/or the mercury-based substances is small enough to be negligible.

However, as a result of earnest study, the present inventors confirmed that there is a possibility that a non-negligible amount of mercury and/or mercury-based substances is generated in the dryer used for removing the moisture in the coal.

The present invention has been made in view of such circumstances, and an object thereof is to provide a coal upgrade plant and a method for manufacturing upgraded coal capable of removing mercury and/or mercury-based substances generated in a dryer.

BRIEF SUMMARY OF THE INVENTION

To achieve the above object, a coal upgrade plant and a method for manufacturing upgraded coal of the present invention employ the following solutions.

That is, a coal upgrade plant according to one aspect of the present invention includes: a dryer that heats and dries coal before pyrolyzing the coal; and a scrubber that treats a carrier gas discharged from the dryer while catching a desorbed component desorbed from the coal when the coal is dried by the dryer.

The above coal upgrade plant reduces a water content of the coal by heating and drying the coal by the dryer before pyrolyzing the coal.

The carrier gas is caused to flow through the dryer so as to discharge the desorbed component desorbed from the coal when the coal is dried. Steam and pulverized coal are discharged as the desorbed component together with the carrier gas. As a result of earnest study, the present inventors found that a non-negligible amount of mercury and/or mercury-based substances is contained. The scrubber removes the mercury and/or the mercury-based substances generated in the dryer.

The coal upgrade plant according to one aspect of the present invention further includes a carrier gas circulation path that guides the carrier gas treated by the scrubber to the dryer.

By guiding the carrier gas treated in the scrubber to the dryer by the carrier gas circulation path, the carrier gas is circulated and reused. The consumption of the carrier gas can be thereby reduced.

Since the mercury and/or the mercury-based substances are concentrated in the dryer when the carrier gas is circulated without removing the mercury and/or the mercury-based substances, it is particularly effective to remove the mercury and/or the mercury-based substances by the scrubber.

The coal upgrade plant according to one aspect of the present invention further includes a dust collector that is provided on an upstream side of the scrubber.

The pulverized coal accompanying the carrier gas is separated by the dust collector provided on the upstream side of the scrubber. However, when the pulverized coal cannot be sufficiently separated by the dust collector, the pulverized coal can be separated from the carrier gas by the scrubber that is provided on the downstream side of the dust collector.

A method for manufacturing upgraded coal according to one aspect of the present invention includes: a drying step of heating and drying coal before pyrolyzing the coal; and a carrier gas treating step of treating, by a scrubber, a carrier gas discharged in the drying step while catching a desorbed component desorbed from the coal when the coal is dried in the drying step.

The method for manufacturing upgraded coal according to one aspect of the present invention reduces a water content of the coal by heating and drying the coal in the drying step before pyrolyzing the coal.

The carrier gas is caused to flow in the drying step so as to discharge the desorbed component desorbed from the coal when the coal is dried. For instance, steam and pulverized coal are discharged as the desorbed component together with the carrier gas. As a result of earnest study, the present inventors found that a non-negligible amount of mercury and/or mercury-based substances is contained. In the carrier gas treating step, the scrubber removes the mercury and/or the mercury-based substances generated in the drying step.

The mercury and/or the mercury-based substances generated in the dryer can be removed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram illustrating the entire configuration of a coal upgrade plant according to one embodiment of the present invention.

FIG. 2 is a configuration diagram schematically illustrating a drying step shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In the following, one embodiment according to the present invention is described by reference to the drawings.

FIG. 1 shows a coal upgrade plant according to one embodiment of the present invention. The coal upgrade plant includes a dryer 1 that heats and dries coal, a pyrolyzer 3 that heats and pyrolyzes the dried coal dried in the dryer 1, a quencher 5 that cools the pyrolyzed coal pyrolyzed in the pyrolyzer 3, a finisher 7 that deactivates the pyrolyzed coal cooled in the quencher 5, and a briquetter 9 that briquettes the upgraded coal deactivated by the finisher 7 into a predetermined shape.

A coal hopper 12 that receives raw coal 10 is provided on the upstream side of the dryer 1. The raw coal is low ranking coal such as sub-bituminous coal and lignite, and has a water content of 25 wt % or more to 60 wt % or less. The coal guided from the coal hopper 12 is crushed to a particle size of, for example, about 20 mm or less in a crusher 14.

The coal crushed in the crusher 14 is guided to the dryer 1. The dryer 1 is of indirect heating type using steam, and includes a cylindrical vessel 16 that rotates about a center axis, and a plurality of heating tubes 18 that are inserted into the cylindrical vessel 16. The coal guided from the crusher 14 is fed into the cylindrical vessel 16. The coal fed into the cylindrical vessel 16 is guided from one end side (the left side in FIG. 1) to the other end side while being agitated according to the rotation of the cylindrical vessel 16. Steam having a temperature of 150° C. or more to 200° C. or less (more specifically, 180° C.), which is produced in a steam system 20, is fed into each of the heating tubes 18, thereby indirectly heating the coal in contact with the outer periphery of each of the heating tubes 18. The steam fed into each of the heating tubes 18 is condensed after applying condensation heat by heating the coal, discharged from the dryer 1, and returned to the steam system 20.

A carrier gas is fed into the cylindrical vessel 16 through a carrier gas circulation path 22. As the carrier gas, an inert gas is used. More specifically, a nitrogen gas is used. When in shortage, the nitrogen gas is additionally fed from a nitrogen feed path 24 that is connected to the carrier gas circulation path 22. The carrier gas is discharged outside of the cylindrical vessel 16 through a carrier gas discharge path 26 that is connected to the cylindrical vessel 16 while catching a desorbed component (steam, pulverized coal, mercury, mercury-based substances, etc.) desorbed from the coal when passing through the cylindrical vessel 16.

A cyclone (dust collector) 28, a carrier gas cooler 30, and a scrubber 32 are provided in the carrier gas discharge path 26 sequentially from the upstream side of a carrier gas flow direction.

The cyclone 28 mainly removes the pulverized coal (for example, having a particle size of 100 μm or less) that is a solid from the carrier gas by use of a centrifugal force. The pulverized coal removed in the cyclone 28 is guided to the upstream side of a bag filter 34 as indicated by reference character A. The pulverized coal separated in the cyclone 28 may be also mixed into the dried coal dried in the dryer 1.

The carrier gas cooler 30 cools the carrier gas, from which the pulverized coal has been removed, thereby condensing steam guided together with the carrier gas and removing the condensed steam as drain water. The carrier gas cooler 30 is an indirect heat exchanger. Industrial water having a normal temperature is used as a cooling medium. Recycled water separated in a waste water treatment equipment 40 may be also used as the cooling medium. The drain water produced in the carrier gas cooler 30 is guided to a liquid phase section in a lower portion of the scrubber 32.

The scrubber 32 removes the mercury and/or the mercury-based substances (simply referred to as “mercury etc.” below) from the carrier gas, from which the pulverized coal and the steam have been removed. Water is used as an absorber in the scrubber 32. More specifically, the recycled water separated in the waste water treatment equipment 40 is used as the absorber. The mercury etc. in the carrier gas is adsorbed by the water sprayed from above the scrubber 32, and guided to the liquid phase section in the lower portion of the scrubber 32. In the scrubber 32, the pulverized coal that could not be removed in the cyclone 28 is also removed.

An upstream end of the carrier gas circulation path 22 is connected to an upper portion of the scrubber 32. A blower 36 is provided at an intermediate position of the carrier gas circulation path 22. The carrier gas treated in the scrubber 32 is returned to the dryer 1 by the blower 36. Although not shown in the drawings, one portion of the carrier gas treated in the scrubber 32 is guided to a combustor 42.

The waste water treatment equipment 40 is connected to the lower portion of the scrubber 32 through a waste water path 38. The waste water treatment equipment 40 separates sludge 39, which is a solid content such as the pulverized coal and the mercury etc., and the recycled water by a sedimentation tank (not shown) after aggregating and enlarging the mercury etc. by injecting a chelating agent into waste water. The recycled water is reused in various portions of the plant.

The coal (dried coal) dried in the dryer 1 passes through a dried coal feed path 44 to be guided to the pyrolyzer 3 by use of its weight. The pyrolyzer 3 is an external-heat rotary kiln, and includes a rotating inner cylinder 46, and an outer cylinder 48 that covers the outer peripheral side of the rotating inner cylinder 46. A nitrogen gas as a carrier gas is fed into the rotating inner cylinder 46.

A combustion gas produced in the combustor 42 is guided to a space between the rotating inner cylinder 46 and the outer cylinder 48 through a combustion gas introduction path 50. Accordingly, the inside of the rotating inner cylinder 46 is maintained at 350° C. or more to 450° C. or less (for example, 400° C.)

To the combustor 42, an air feed path 54 that guides combustion air force-fed by a blower 52 into the combustor, a natural gas feed path 55 that guides a natural gas as fuel into the combustor, and a pyrolysis gas collection path 56 that collects a pyrolysis gas generated in the pyrolyzer 3 together with the carrier gas, and guides the gas into the combustor are connected. In the combustor 42, a fire 51 is formed by the natural gas, the pyrolysis gas, and the air fed into the combustor. Since the pyrolysis gas contains a volatile content such as tar and has a predetermined calorific value, the pyrolysis gas is used as fuel in the combustor 42. The natural gas fed from the natural gas feed path 55 is used for adjusting a calorific value of the fuel injected into the combustor 42. A flow rate of the natural gas is adjusted such that the combustion gas produced in the combustor 42 has a desired temperature.

A pyrolysis gas discharge path 58 that is used in emergency is connected to an intermediate position of the pyrolysis gas collection path 56. A flare stack 60 is installed on the downstream side of the pyrolysis gas discharge path 58. A combustible component such as tar in the pyrolysis gas is incinerated by the flare stack 60, and a gas obtained after the incineration is released to the atmosphere.

A combustion gas discharge path 62 through which the combustion gas produced in the combustor is discharged is connected to the combustor 42. An upstream end of the combustion gas introduction path 50 that guides the combustion gas to the pyrolyzer 3 is connected to an intermediate position of the combustion gas discharge path 62. A first medium-pressure boiler 64 is provided in the combustion gas discharge path 62 on the downstream side of a connection position with the combustion gas introduction path 50.

An after-heating gas discharge path 66 through which the combustion gas after heating the rotating inner cylinder 46 is discharged is connected to the outer cylinder 48 of the pyrolyzer 3. A second medium-pressure boiler 68 is provided in the after-heating gas discharge path 66. The after-heating gas discharge path 66 is connected to the combustion gas discharge path 62 on the downstream side. A blower 70 that force-feeds the combustion gas is provided in the combustion gas discharge path 62 on the downstream side of a connection position with the after-heating gas discharge path 66.

The downstream side of the combustion gas discharge path 62 is connected to the bag filter 34. A flue gas, from which combustion ash or the like is removed in the bag filter 34, is released to the atmosphere (ATM).

The steam system 20 includes the first medium-pressure boiler 64 and the second medium-pressure boiler 68. In the second medium-pressure boiler 68, boiler feed water (BFW) fed thereto is heated by the combustion gas flowing through the after-heating gas discharge path 66, thereby producing steam. Medium-pressure steam produced in the first medium-pressure boiler 64 and medium-pressure steam produced in the second medium-pressure boiler 68 are respectively stored in a steam drum (not shown), and fed to various portions of the plant such as the heating tubes 18 of the dryer 1.

The pyrolyzed coal pyrolyzed in the pyrolyzer 3 is guided to the quencher 5 through a pyrolyzed coal feed path 72 by use of gravity. The quencher 5 includes a first cooler 74 that receives the pyrolyzed coal from the pyrolyzer 3, and a second cooler 76 that receives the pyrolyzed coal cooled by the first cooler 74.

The first cooler 74 is a shell-and-tube heat exchanger, and includes a first cylindrical vessel 78 that rotates about a center axis, a first water spray tube 79 that is inserted into the first cylindrical vessel 78, and a plurality of first cooling tubes 80 that are inserted into the first cylindrical vessel 78. The first water spray tube 79 is installed in a stationary state with respect to the rotating first cylindrical vessel 78. The pyrolyzed coal having a temperature of 300° C. or more to 500° C. or less (for example, about 400° C.), which is guided from the pyrolyzer 3, is fed into the first cylindrical vessel 78. The pyrolyzed coal fed into the first cylindrical vessel 78 is guided from one end side (the left side in FIG. 1) to the other end side while being agitated according to the rotation of the first cylindrical vessel 78.

Industrial water having a normal temperature is guided to the first water spray tube 79. The water is sprayed on the pyrolyzed coal and thereby brought into direct contact with the pyrolyzed coal to cool down the pyrolyzed coal. The first water spray tube 79 is provided on the upstream side (the left side in FIG. 1) of the pyrolyzed coal moving within the first cylindrical vessel 78. The recycled water separated in the waste water treatment equipment 40 may be used as the water fed to the first water spray tube 79.

Boiler feed water having a temperature of 50° C. or more to 100° C. or less (for example, about 60° C.) is fed into each of the first cooling tubes 80, thereby indirectly cooling the pyrolyzed coal in contact with the outer periphery of each of the first cooling tubes 80. Each of the first cooling tubes 80 is provided on the downstream side (the right side in FIG. 1) of the pyrolyzed coal moving within the first cylindrical vessel 78. Each of the first cooling tubes 80 cools the pyrolyzed coal cooled by the first water spray tube 79 to about 150° C. that is equal to or higher than a condensation temperature of water.

The second cooler 76 has substantially the same configuration as the first cooler 74. The second cooler 76 is a shell-and-tube heat exchanger, and includes a second cylindrical vessel 81 that rotates about a center axis, a second water spray tube 82 that is inserted into the second cylindrical vessel 81, and a plurality of second cooling tubes 83 that are inserted into the second cylindrical vessel 81. The second water spray tube 82 is installed in a stationary state with respect to the rotating second cylindrical vessel 81. The pyrolyzed coal cooled to about 150° C. in the first cooler 74 is fed into the second cylindrical vessel 81. The pyrolyzed coal fed into the second cylindrical vessel 81 is guided from one end side (the left side in FIG. 1) to the other end side while being agitated according to the rotation of the second cylindrical vessel 81.

Industrial water having a normal temperature is guided to the second water spray tube 82. The water is sprayed on the pyrolyzed coal to adjust the water content of the pyrolyzed coal to a desired value (for example, 8 wt %). The second water spray tube 82 is provided over substantially the entire second cylindrical vessel 81 in an axial direction. The recycled water separated in the waste water treatment equipment 40 may be used as the water fed to the second water spray tube 82.

Industrial water having a normal temperature is guided into each of the second cooling tubes 83, thereby indirectly cooling the pyrolyzed coal in contact with the outer periphery of each of the second cooling tubes 83. Each of the second cooling tubes 83 cools the pyrolyzed coal to about 50° C. The recycled water separated in the waste water treatment equipment 40 may be used as the water fed to each of the second cooling tubes 83.

The pyrolyzed coal cooled in the quencher 5 is guided to the finisher 7 through a cooled pyrolyzed coal feed path 84.

The finisher 7 includes a first deactivator 86 that receives the pyrolyzed coal cooled in the quencher 5, and a second deactivator 88 that receives the pyrolyzed coal from the first deactivator 86.

An oxidation gas having an oxygen concentration of about 0.5 to 3.0% is guided into the first deactivator 86 from a first oxidation gas feed path 90. Although not shown in the drawings, oxygen (more specifically, air) is fed to the first oxidation gas feed path 90 so as to adjust the oxygen concentration to a desired value.

The oxidation gas fed into the first deactivator 86 oxidizes an active spot (radical) generated by the pyrolysis to deactivate the pyrolyzed coal within the first deactivator 86. The oxidation gas discharged from the first deactivator 86 is guided to a first blower 92 through a first oxidation gas outlet tube 91 together with the pulverized coal. The oxidation gas force-fed by the first blower 92 is guided to the first oxidation gas feed path 90 again, and recirculated. The oxidation gas guided not to the first oxidation gas feed path 90, but to an oxidation gas discharge tube 93 is guided to a cyclone 94. The solid content such as the pulverized coal is separated from the oxidation gas guided to the cyclone 94 in the cyclone 94, and the resultant gas is guided to the bag filter 34 and released to the atmosphere (ATM). The solid content such as the pulverized coal separated in the cyclone 94 is fed to a kneader 100.

The pyrolyzed coal is injected from an upper portion of the first deactivator 86, and deactivated in contact with the oxidation gas while descending. The pyrolyzed coal retained in a lower portion of the first deactivator 86 is taken out from the lower portion, and guided to an upper portion of the second deactivator 88.

An oxidation gas having an oxygen concentration of about 8.0 to 12.0% is guided into the second deactivator 88 from a second oxidation gas feed path 95. Although not shown in the drawings, oxygen (more specifically, air) is fed to the second oxidation gas feed path 95 so as to adjust the oxygen concentration to a desired value.

The oxidation gas fed into the second deactivator 88 further deactivates the pyrolyzed coal deactivated in the first deactivator 86. The oxidation gas discharged from the second deactivator 88 is guided to a second blower 97 through a second oxidation gas outlet tube 96 together with the pulverized coal. The oxidation gas force-fed by the second blower 97 is guided to the second oxidation gas feed path 95 again, and recirculated. The oxidation gas guided not to the second oxidation gas feed path 95, but to the oxidation gas discharge tube 93 is guided to the cyclone 94. The solid content such as the pulverized coal is separated from the oxidation gas, and the resultant gas is guided to the bag filter 34 and released to the atmosphere.

The upgraded coal deactivated in the finisher 7 has a particle size of about 1 mm. The upgraded coal passes through an upgraded coal feed path 98 to be guided to the kneader 100. The pulverized coal separated in the cyclone 94 is guided to the upgraded coal feed path 98 through a pulverized coal collection path 99.

A binder guided from a binder feed section 102, the upgraded coal including the pulverized coal, and water are fed to and kneaded in the kneader 100. Examples of the binder include polyethylene oxide and starch. The upgraded coal kneaded in the kneader 100 is guided to the briquetter 9.

The briquetter 9 includes a female mold where a plurality of recessed portions having a shape corresponding to the product shape of the upgraded coal are formed, and a male mold that compresses the upgraded coal fed into the recessed portions by pressing. The upgraded coal briquetted in the briquetter 9 becomes upgraded coal 104 as a product. The upgraded coal 104 has a size of about several cm, and has a water content of 6 wt % or more to 9 wt % or less. Note that the water content of the upgraded coal 104 is based on a dry weight when the water content is in equilibrium with a storage environment, and the water content largely depends on relative humidity of the storage environment, but does not much depend on the temperature. For example, PRB (powder river basin) coal has a water content of about 8 wt % when the relative humidity is 90%.

Next, the features of the present invention are described by using FIG. 2.

FIG. 2 schematically shows the configuration around the above dryer 1. That is, the configuration in which the carrier gas discharged from the dryer 1 passes through the cyclone 28, the carrier gas cooler 30, and the scrubber 32, and is recirculated to the dryer 1 through the carrier gas circulation path 22 is shown.

In the cyclone 28, the pulverized coal contained in the carrier gas discharged from the dryer 1 is removed. The pulverized coal removed in the cyclone 28 is guided to the bag filter (see reference numeral 34 in FIG. 1).

In the carrier gas cooler 30, the steam contained in the carrier gas is condensed and removed as the drain water. The drain water is guided to the liquid phase section of the scrubber 32.

In the scrubber 32, the mercury etc. contained in the carrier gas and the pulverized coal that could not be removed in the cyclone 28 are removed. A large portion of the carrier gas treated in the scrubber 32 is guided to the dryer 1 through the carrier gas circulation path 22. Also, one portion of the carrier gas is guided to the combustor (see reference numeral 42 in FIG. 1). The absorber (waste water) adsorbing the pulverized coal and the mercury etc. in the scrubber 32 is guided to the waste water treatment equipment 40.

In the waste water treatment equipment 40, the solid content such as the pulverized coal and the mercury etc., and the recycled water are separated by the sedimentation tank (not shown) after aggregating and enlarging the mercury etc. by injecting the chelating agent into the waste water.

As described above, the following effects are produced by the present embodiment.

The present inventors found that a non-negligible amount of mercury etc. is generated even in the dryer 1 that operates in a temperature range (150° C. or more to 200° C. or less) falling below about 400° C. that is the evaporating temperature of the mercury. Thus, the scrubber 32 that treats the carrier gas discharged from the dryer 1 while catching the desorbed component desorbed from the coal when the coal is dried by the dryer 1 is provided. Accordingly, the mercury etc. generated in the coal drying step can be removed. The amounts of the mercury released to the atmosphere, and the mercury contained in the upgraded coal can be also reduced.

By guiding the carrier gas treated in the scrubber 32 to the dryer 1 by the carrier gas circulation path 22, the carrier gas is circulated and reused. The consumption of the carrier gas can be thereby reduced. For example, when coal having a water content of 27.5 wt % or less is dried by using N2 as the carrier gas, it is possible to suppress the consumption of N2 to 14% or less.

Since the mercury etc. is concentrated in the dryer 1 when the carrier gas is circulated without removing the mercury etc., it is particularly effective to remove the mercury etc. by the scrubber 32.

After the pulverized coal accompanying the carrier gas is separated by the cyclone 28 that is provided on the upstream side of the scrubber 32, the pulverized coal is further separated by the scrubber 32. Accordingly, it is possible to prevent the pulverized coal from being released to the atmosphere as much as possible.

  • 1 Dryer
  • 3 Pyrolyzer
  • 5 Quencher
  • 7 Finisher
  • 9 Briquetter
  • 10 Raw coal
  • 12 Coal hopper
  • 14 Crusher
  • 16 Cylindrical vessel
  • 18 Heating tube
  • 20 Steam system
  • 22 Carrier gas circulation path
  • 28 Cyclone
  • 30 Carrier gas cooler
  • 32 Scrubber
  • 34 Bag filter
  • 40 Waste water treatment equipment
  • 42 Combustor
  • 46 Rotating inner cylinder
  • 48 Outer cylinder
  • 50 Combustion gas introduction path
  • 74 First cooler
  • 76 Second cooler
  • 78 First cylindrical vessel
  • 79 First water spray tube
  • 80 First cooling tube
  • 81 Second cylindrical vessel
  • 82 Second water spray tube
  • 86 Second cooling tube
  • 86 First deactivator
  • 88 Second deactivator
  • 100 Kneader
  • 104 Upgraded coal

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Citation

Patents Cited in This Cited by
Title Current Assignee Application Date Publication Date
石炭の自然発火防止方法 栗田工業株式会社 29 September 2003 21 April 2005
高效节能带式压滤机 陆汉克 30 December 2012 03 April 2013
Method and apparatus for drying low grade coal WESTINGHOUSE ELECTRIC CORP <WE> 25 April 1986 07 November 1986
流動層乾燥装置、流動層乾燥設備および湿潤原料乾燥方法 MITSUBISHI HEAVY IND LTD 31 March 2011 08 November 2012
反応性コールチャーの不動態化の方法 テック コール パートナーシップ 01 April 1996 18 March 1997
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