WO2015053011A1 - 低品位炭の乾燥方法及び乾燥設備 - Google Patents
低品位炭の乾燥方法及び乾燥設備 Download PDFInfo
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- WO2015053011A1 WO2015053011A1 PCT/JP2014/073018 JP2014073018W WO2015053011A1 WO 2015053011 A1 WO2015053011 A1 WO 2015053011A1 JP 2014073018 W JP2014073018 W JP 2014073018W WO 2015053011 A1 WO2015053011 A1 WO 2015053011A1
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L9/00—Treating solid fuels to improve their combustion
- C10L9/08—Treating solid fuels to improve their combustion by heat treatments, e.g. calcining
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L5/00—Solid fuels
- C10L5/02—Solid fuels such as briquettes consisting mainly of carbonaceous materials of mineral or non-mineral origin
- C10L5/04—Raw material of mineral origin to be used; Pretreatment thereof
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K1/00—Preparation of lump or pulverulent fuel in readiness for delivery to combustion apparatus
- F23K1/04—Heating fuel prior to delivery to combustion apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B11/00—Machines or apparatus for drying solid materials or objects with movement which is non-progressive
- F26B11/02—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles
- F26B11/04—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis
- F26B11/0404—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis with internal subdivision of the drum, e.g. for subdividing or recycling the material to be dried
- F26B11/0418—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis with internal subdivision of the drum, e.g. for subdividing or recycling the material to be dried the subdivision consisting of a plurality of parallel tubes, e.g. through which the material to be dried is conveyed in single or multi-pass fashion
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B11/00—Machines or apparatus for drying solid materials or objects with movement which is non-progressive
- F26B11/02—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles
- F26B11/04—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis
- F26B11/0445—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis having conductive heating arrangements, e.g. heated drum wall
- F26B11/045—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis having conductive heating arrangements, e.g. heated drum wall using heated internal elements, e.g. which move through or convey the materials to be dried
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B23/00—Heating arrangements
- F26B23/02—Heating arrangements using combustion heating
- F26B23/028—Heating arrangements using combustion heating using solid fuel; burning the dried product
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
- C10L2290/06—Heat exchange, direct or indirect
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
- C10L2290/08—Drying or removing water
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
- C10L2290/58—Control or regulation of the fuel preparation of upgrading process
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K2201/00—Pretreatment of solid fuel
- F23K2201/20—Drying
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying good
Definitions
- the present invention relates to a technique for drying low-grade coal, particularly low-grade coal containing a lot of moisture, and suppressing spontaneous ignition of the dried coal.
- low-grade coal which has a large reserve and is less expensive, such as low-cost lignite, sub-bituminous coal, and lignite
- low-grade coal has a high moisture content
- low-grade coal is sufficiently used because of its high transportation cost per energy and because it tends to spontaneously ignite when low-grade coal is dried.
- the use of low-grade coal was limited to the vicinity of the coal mine.
- Factors that promote the reaction between oxygen and active groups include specific surface area, water content, presence of FeS, oxygen partial pressure, temperature, and the like.
- Patent Document 1 In order to suppress spontaneous ignition of low-grade coal, briquetting after drying has been performed (Patent Document 1).
- Patent Document 2 That is, most of the active groups that easily react with oxygen react with oxygen to suppress spontaneous ignition.
- Patent Document 2 actually requires two steps of heat treatment at 100 to 350 ° C. in an inert gas and oxidation treatment under an oxygen concentration of 1 to 10% by volume, resulting in a long treatment time. Not practical.
- conventional low-grade coal drying methods have been mainly drying by direct heating of hot air, such as flash dryer or hot air rotary drying.
- the oxygen concentration can be increased, but since the coal temperature does not increase, the chemical structure that easily binds to oxygen near the coal surface is less likely to bind to oxygen, so spontaneous ignition There is no suppression effect.
- the coal temperature can be increased, but since there is no oxygen, there is no effect of suppressing spontaneous ignition. Therefore, in the conventional drying method, dry charcoal is cooled with a cooler after drying, and the temperature rise due to spontaneous ignition is delayed to suppress spontaneous ignition.
- the present invention has been made to solve the above-described problems, and is to dry low-grade coal, particularly low-grade coal having a high water content, and to suppress spontaneous ignition.
- the present invention that has solved the above problems is as follows.
- the low-grade coal of the present invention is meant to include lignite such as Victoria coal, North Dakoda coal, and Belga coal, subbituminous coal such as West Bagon coal and Vinungan coal, and lignite.
- the surface temperature of the low-grade coal at the outlet of the dryer is 0 ° C. to 5 ° C. higher than the dew point of the carrier gas discharged from the dryer, and 70 Low in temperature, characterized in that the drying condition of the indirect heating dryer is such that the oxygen concentration in the carrier gas discharged from the dryer is over 10% to 15% on a wet gas basis.
- the meaning of “the drying condition of the indirect heating dryer” means that the carrier gas amount is adjusted, the steam amount of the indirect heating dryer is adjusted indirectly, as long as the first half conditions specified in the present invention are satisfied.
- the manipulated variable may be fixed to the set value in advance, and of course, the fluctuation value is taken in so that the first half conditions specified in the present invention are satisfied. It is also possible to control the operation amount so as to achieve the target value by adjusting the carrier gas amount, adjusting the steam amount of the indirect heating dryer, adjusting the rotation speed of the indirect heating dryer, and the like. In practice, the latter control method is desirable. This also applies to the invention of claim 2.
- the low-grade coal is dried by the indirect heating dryer in the constant rate drying section until reaching the limit water content point. Since the drying is performed by an indirect heating dryer, the product temperature of the low-grade coal can be increased by adjusting the dew point of the carrier gas (adjusting the amount of carrier gas). It can be raised to 95 ° C. In addition, since it is dry-treated in a dry atmosphere with a high oxygen concentration of over 10% to 15% on a wet gas basis, the active groups of low-grade coal can be reacted well with oxygen, which has a high spontaneous ignition suppression effect. It can be modified to the low-grade coal shown.
- the upper limit of the drying temperature is 95 ° C., and if it exceeds 95 ° C., the drying is performed in the reduced rate drying section. In the reduced rate drying section, the coal temperature may rise above the dew point, and the carrier gas enriched with oxygen may ignite. On the other hand, the reason why the lower limit of the drying temperature is set to 70 ° C. or more is that the oxidation reaction is slowed below 70 ° C.
- the surface temperature of the low-grade coal at the outlet of the dryer is 0 ° C. to 5 ° C. higher than the dew point of the carrier gas discharged from the dryer, and 80
- the drying of the indirect heating dryer in which the oxygen concentration in the carrier gas exhausted from the dryer is more than 10% to 15% on a wet gas basis when oxygen is enriched in the carrier gas.
- the carrier gas discharged from the indirect heating dryer has a low O 2 concentration (wet gas base) compared to air because it contains a large amount of moisture evaporated from the coal, and the same temperature as the dry coal surface temperature. It is. Therefore, by supplying such a carrier gas as a carrier medium for an air slide type conveyor, spontaneous combustion is suppressed (it is difficult to ignite due to low oxygen concentration), and the oxidation reaction on the dry coal surface is promoted (the temperature of the supply gas is reduced). The reaction proceeds because it is high).
- the 1 / 2 ⁇ mu 3 is 30 to 200, where the gas blowing speed from the aperture of the deflectable perforated plate is u m / s, the aperture ratio of the nozzle is m, and the gas density is ⁇ kg / m 3. 3.
- a practical transport amount per unit width can be obtained with respect to a certain amount of gas blown from the aperture of the perforated plate.
- a preferable range of 1 / 2 ⁇ mu 3 is 40 to 100.
- ⁇ Invention of Claim 6> Indirect heating dryer for drying low-grade coal, measuring means for measuring the temperature of the dry coal at the outlet of the dryer, dew point measuring means for measuring the dew point of the carrier gas discharged from the dryer, and oxygen concentration of the carrier gas Oxygen concentration measuring means for measuring A means for adjusting the surface temperature of the dry coal at the outlet of the dryer in association with the dew point measured by the dew point measuring means, and a means for adjusting the oxygen concentration in the carrier gas discharged from the dryer on a wet gas basis;
- a low-grade coal drying facility characterized by comprising.
- a dust collector that removes dust in the carrier gas discharged from the indirect heating dryer in a dry manner.
- Pulse air must be N2 gas with low oxygen concentration to prevent dust explosion during cleaning.
- the required N 2 gas is desirably obtained by a nitrogen-containing gas production apparatus.
- a PSA Pressure Swing Adsorption
- oxygen adsorption in this case, exhaust gas is nitrogen-rich
- nitrogen adsorption in this case, desorption gas is nitrogen-rich
- the adsorbed nitrogen-rich gas is used as pulse air, and the unnecessary oxygen-rich gas is used as a carrier gas for the steam tube dryer (STD), thereby suppressing ignitability without providing extra equipment.
- the necessary carrier gas can be obtained.
- low-grade coal in particular, low-grade coal having a high water content can be dried and spontaneous ignition can be suppressed. Therefore, inexpensive low-grade coal can be used, and the energy situation can be improved.
- steam tube dryer steam tube dryer
- the overall drying process of the low-grade coal of the present invention can be carried out, for example, in the form shown in FIG. And as a drying processor, the steam tube dryer (STD) 3 can be used suitably.
- STD steam tube dryer
- a steam tube dryer 3 shown in FIG. 2 has a plurality of heating pipes 31 arranged between both end plates in parallel with the axis in a rotary cylinder 30 that is rotatable around the axis. Heating steam as a heat medium is supplied to the heating pipes 31 through the attached heat medium inlet pipes 51 and is distributed to the respective heating pipes 31, and then drains of the heating steam K through the heat medium outlet pipes 52. Is discharged.
- the steam tube dryer 3 is provided with a charging device 33 having a screw or the like for charging the workpiece into the rotary cylinder 30.
- Low-grade coal (LRC) introduced from one end side into the rotary cylinder 30 through the charging port 53 of the charging device 33 is brought into contact with the heating pipe 31 heated by the heating steam K and dried.
- LRC Low-grade coal
- the rotary cylinder 30 is installed with a downward slope, it is moved smoothly in the direction of the discharge port 54, and this dry charcoal (DC) is continuously discharged from the other end side of the rotary cylinder 30.
- the rotating cylinder 30 is installed on a base 36, and the tire 34 is mounted by two sets of support rollers 35 that are spaced apart from each other in parallel with the axis of the rotating cylinder 30. It is supported through.
- the width between the two sets of support rollers 35 and the inclination angle in the longitudinal direction thereof are selected in accordance with the downward gradient and the diameter of the rotating cylinder 30.
- a driven gear 40 is provided around the rotating cylinder 30, and the drive gear 43 meshes with the driven gear 40, and the rotational force of the prime mover 41 is transmitted via the speed reducer 42.
- a carrier gas is introduced into the rotary cylinder 30 from a carrier gas inlet 61, and these carrier gases are accompanied by vapor evaporated of moisture contained in low-grade coal (LRC) from a carrier gas outlet 62. Discharged.
- LRC low-grade coal
- the whole structure of the said steam tube dryer 3 is an example, and this invention is not limited by the said structure.
- the drying process can be performed as follows.
- low-grade coal crushed to about 10 mm or less by the crusher 33A in advance is supplied to the charging device 33 and then supplied to the indirect heating dryer 3.
- the supplied low-grade coal is indirectly heated by steam supplied to the indirect heating dryer 3 and dried, and is discharged from the dryer outlet 54 as dry coal (DC).
- a temperature measuring device 21 for measuring the temperature of the dry coal is installed.
- the temperature measuring device is not limited as long as it is a thermometer capable of measuring the product temperature of dry coal, but a dry coal surface temperature measuring device 21 such as a non-contact type thermometer is installed.
- the product temperature of the dry coal to be measured may be either the internal temperature or the surface temperature.
- a temperature measuring device that measures the surface temperature is used. The measured value is sent to the drying condition adjusting means (not shown) by the temperature measuring device 21.
- the carrier gas is pressurized by the push-in fan 22 and air and oxygen are monitored from the carrier gas inlet 61 of the charging device 33 while the oxygen concentration is monitored by an oxygen concentration meter (O 2 meter) 23A so as to obtain a predetermined oxygen concentration.
- oxygen enriched in air may be adsorbed by an oxygen PSA device (Pressure Swing Adsorption) (not shown) provided separately or exhaust gas after adsorbing nitrogen by a nitrogen PSA device. it can.
- an oxygen-containing gas discharged from a nitrogen PSA device that generates nitrogen for nitrogen purge used in the thermal power plant.
- the carrier gas is discharged together with water vapor evaporated from low-grade coal (LRC) and some coal dust in the indirect heating dryer 3 and is removed by a dry dust collector (dust collector) 24.
- the dry dust collector 24 is provided with a pulse gas supply device (not shown) for removing the coal dust, and a pulse gas is supplied according to a constant interval or a pressure difference before and after the filter medium.
- the carrier gas discharged from the dry dust collector 24 is discharged from the exhaust fan 25 while the oxygen concentration is measured by an oxygen concentration meter (O 2 meter) 23B.
- the oxygen concentration is calculated on a wet gas basis. Specifically, for example, a zirconia oxygen concentration meter can be used.
- the installation position of the oxygen concentration meter 23B is not limited to the outlet side of the dry dust collector 24, and may be provided, for example, in a carrier gas flow path between the indirectly heated dryer 3 and the dust collector 24.
- the measured value of the oxygen concentration meter 23B is sent to a drying condition adjusting means (not shown).
- the measured value that is the measurement result by the temperature measuring device 21 is compared with the preset setting range (or set value) of the temperature of the dry coal, and the measured value is within the set range.
- the flow rate, temperature, and pressure of the steam supplied to the indirect heating dryer 3 and the number of rotations of the indirect heating dryer 3 are adjusted so as to be within (set value). These adjustment items are not limited to one, and can be adjusted in combination as appropriate.
- the measured value sent from the oxygen concentration meter 23B is compared with a preset range (or set value) of the oxygen concentration of the carrier gas, and the carrier is set so that the measured value is within the set range (set value). Adjust the oxygen enrichment to the gas.
- the drying condition adjusting means can be divided into two for adjusting the temperature of the dry coal and for adjusting the oxygen concentration of the carrier gas.
- the drying speed of the dry coal (DC) is adjusted by the steam pressure supplied to the indirect heating dryer 3 or the amount of low-grade coal (LRC) supplied.
- dry charcoal is supplied to an air slide type (mesh) conveyor 26 provided with a perforated plate 26A having an opening 26a that divides the inside of the hollow main body vertically.
- the dry exhaust gas 27 supplied to the air slide type conveyor 26 by the blower 27a keeps the temperature while transporting and promotes the oxidation of the active group of the low-grade coal with oxygen in the gas, thereby suppressing the spontaneous ignition. Is desirable.
- the dry exhaust gas supplied to the air slide type conveyor 26 may be used as it is, but may be used after preheating with steam drain after drying.
- the fine powder discharged from the air slide type conveyor is returned to the dust collector 24 by the flow path 28, and dried dry charcoal (DC) is stored in a bunker (not shown) and supplied as fuel to a fluidized bed boiler, for example.
- DC dried dry charcoal
- the powder is supplied to a combustion burner.
- low-grade coal dust explosion may occur when the oxygen concentration is 16% or more.
- spontaneous ignition of low-grade coal is governed by coal temperature, atmospheric oxygen concentration, and elapsed time.
- the present invention reacts with oxygen in a range of coal temperature and atmospheric oxygen concentration where a rapid oxidation reaction occurs and does not reach a dangerous area when drying coal to a constant rate drying section using an indirect heating dryer. It is intended to suppress spontaneous ignition by gradually oxidizing an active group that is easy to oxidize in advance.
- FIG. 5 shows the relationship between the oxygen concentration (wet gas base; the same applies hereinafter) and the dew point when only air is used as the carrier gas supplied to the indirect heating dryer and dried to the decremental drying section.
- the oxygen concentration in the carrier gas and the dew point are in an inversely proportional relationship, and the oxygen concentration in the gas decreases as the dew point is raised, that is, the product temperature of the coal is raised.
- the atmospheric oxygen concentration (wet gas base; the same shall apply hereinafter) when the coal product temperature is desired to be about 90 ° C. is about 7%. This cannot promote the oxidation reaction.
- the dew point of the dry atmosphere (approximately equal to the temperature of the dry coal) is reduced with oxygen-enriched air as a carrier gas. Control by adjusting.
- the drying temperature is raised, the oxidation reaction can be promoted, contributing to suppression of ignition.
- the oxygen concentration of the wet gas base decreases as the drying temperature increases. Therefore, even if the drying temperature is raised, the oxygen concentration is low, and it becomes difficult to efficiently suppress ignition.
- the atmospheric oxygen concentration should be 12% or less.
- the residence time in the dryer may not have a sufficient spontaneous ignition suppression effect.
- after drying, in the dry charcoal transport process transport in an atmosphere with a high oxygen concentration while maintaining the temperature of the dry charcoal, for example, using an air slide type (mesh) conveyor as described above By doing so, the active group of coal which is easy to react with oxygen is reacted with oxygen.
- the form of the transport facility is not particularly limited to an air ride type (mesh) conveyor, and may be any of a screw conveyor, a belt conveyor, a vibration conveyor, or a combination thereof.
- the operation range of the present invention is as shown in FIG.
- the inventors added that the operation range Z1 (the scope of claim 1) and the operation range Z2 (the scope of claim 2) of the present invention were determined by many experiments in addition to the following experiment. Keep it.
- the oxygen concentration in the dry atmosphere is 16% or less, and practically, the highest possible concentration of 15% or less is preferable in view of the safety factor.
- the method of supplying the gas having an oxygen concentration of 15% or less to the transport facility may be supplied simply by a nozzle, or a perforated plate of an air slide type conveyor to improve the contact between coal and gas. You may supply via.
- the opening 26a of the perforated plate 26 is upward with a blowing angle ⁇ of 10 to 20 degrees with respect to the horizontal in the dry coal conveying direction.
- a blow of 14 to 16 degrees is preferable because the conveyance power can be further reduced.
- a dust remover that uses pulse gas as the dust collector.
- the pulse gas must be N2 gas having a low oxygen concentration in order to prevent dust explosion during cleaning.
- the required N 2 gas is desirably obtained by a nitrogen-containing gas production apparatus.
- a PSA Pressure Swing Adsorption
- oxygen adsorption in this case, exhaust gas is nitrogen-rich
- nitrogen adsorption in this case, desorption gas is nitrogen-rich
- a nitrogen adsorption PSA 70 having an adsorption filler 70 a is provided, air is taken in, N 2 adsorption is performed, and the adsorbed N 2 is absorbed by a vacuum pump 72.
- the N 2 rich gas is stored in a temporary storage tank 73 and supplied to a bag filter dust collector (dust removing device) 24 equipped with a pulse gas supply device.
- the adsorbed nitrogen-rich gas can be used as pulsed air for backwashing.
- the pulse gas supply 74 is schematically shown.
- Oxygen-rich gas that becomes unnecessary at this time is stored in the temporary storage tank 71 from the upper part of the PSA device 70 and used as a carrier gas for the steam tube dryer (STD) 3 so that it can be ignited without any additional equipment. It is possible to obtain a carrier gas having an oxygen concentration necessary for suppressing the property.
- the adsorbed O 2 is stored in the temporary storage tank 71 as O gas by the vacuum pump 72, and the carrier of the steam tube dryer (STD) 3 Use gas.
- Nitrogen-rich gas that becomes unnecessary at this time is stored in the temporary storage tank 73 from the upper part of the PSA device 70, and when the bag filter dust collector (dust removal device) 24 equipped with the filter cloth 24a using pulse gas is backwashed, nitrogen-rich gas is removed. It can be used as a pulse gas for backwashing.
- the low-grade coal (LRC) used in the experiment is Indonesian lignite with a total moisture of 59.2% and air-dried moisture of 13.2%.
- Australian bituminous coal (hereinafter referred to as BC) was used as a comparative example of spontaneous ignition.
- Example 1 Effect of pyrophoricity of coal product temperature
- the oxygen concentration of the dry exhaust gas was about 15%
- the dry coal moisture was about 22%
- the dry coal surface temperature was 70 ° C. and 92 ° C.
- Example 2 Influence of atmospheric oxygen concentration
- exhaust carrier gas the carrier gas discharged from the dryer
- Example 3 Nozzle blowing angle and last name of deflectable perforated plate
- the blowing angle with respect to the horizontal of the nozzle of the deflecting perforated plate and the transport name of dry coal were investigated.
- the dry coal used was crushed Indonesian lignite to 10 mm or less (the maximum particle size was about 30 mm mixed and dried to 25% moisture. 1 / 2 ⁇ mu 3 was 100 on a horizontally installed air slide. Then, air preheated to 80 ° C. was supplied, and the conveying amount per unit width of the air slide was measured by changing the angle ⁇ of the blowing nozzle, and the result is shown in FIG. To 16 degrees is preferred.
- Example 4 Supply air volume to air slide and last name
- the air slide blowing angle ⁇ was 16 degrees, and the air supply amount per unit area to the air slide was changed (by changing 1 / 2 ⁇ mu 3 ) to measure the transport amount per unit width of the air slide.
- the result is shown in FIG.
- the coal used is the same as in Example 4.
- the conveyance capacity increases almost in proportion to 1 / 2 ⁇ mu 3 .
- 1 / 2 ⁇ mu 3 is preferably 30 or more. Since 1 / 2 ⁇ mu 3 is proportional to the power of the air slide blower, it should be as small as possible, and it will affect the exhaust gas treatment equipment of the air slide.
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Abstract
Description
なお、本発明の低品位炭とは、ビクトリア炭、ノースダコダ炭、ベルガ炭等の褐炭、西バゴン炭、ビヌンガン炭などの亜瀝青炭、亜炭などを含む意味である。
間接加熱乾燥機により、低品位炭を乾燥するに際し、前記乾燥機出口における前記低品位炭の表面温度が前記乾燥機から排出されるキャリヤガスの露点に対して0℃~5℃高く、かつ70℃~95℃であり、かつ前記乾燥機から排出されるキャリヤガス中の酸素濃度が湿りガスベースで10%超~15%となる、間接加熱乾燥機の乾燥条件とすることを特徴とする低品位炭の乾燥方法。
ここで、「間接加熱乾燥機の乾燥条件とする」の意義は、本発明で規定する前半の条件が満たされるのであれば、キャリヤガス量の調整、間接加熱乾燥機の蒸気量の調整、間接加熱乾燥機の回転数の調整などは不要で、予め操作量を設定値に固定しておいてもよいし、もちろん、本発明で規定する前半の条件が満たされるように、その変動値を取込み、キャリヤガス量の調整、間接加熱乾燥機の蒸気量の調整、間接加熱乾燥機の回転数の調整などによって、その目標値になるように操作量を制御するようにすることもできる。実際的には、後者の制御法であるのが望ましい。これは請求項2の発明の場合も同様に当てはまることである。
本発明では、間接加熱乾燥機により、低品位炭を限界含水率時点に至るまでの恒率乾燥区間において乾燥を行う。間接加熱乾燥機による乾燥であるために、低品位炭の品温をキャリヤガスの露点を調整(キャリヤガス量を調整)することで高めることができ、たとえば乾燥機出口の品温が70℃~95℃と高めることができる。加えて、湿りガスベースで10%超~15%の高い酸素濃度の乾燥雰囲気で乾燥処理するので、低品位炭の活性基を酸素と良好に反応させることができ、高い自然発火性抑制効果を示す低品位炭に改質できる。
ここで、乾燥温度上限を95℃とするのは、95℃超では、減率乾燥区間での乾燥となる。減率乾燥区間では、石炭の温度が露点以上に上昇する可能性があり、酸素富加したキャリヤガスでは発火する恐れが生じる。他方、乾燥温度下限70℃以上とするのは、70℃未満では酸化反応が遅くなるからである。
間接加熱乾燥機により、低品位炭を乾燥するに際し、前記乾燥機出口における前記低品位炭の表面温度が前記乾燥機から排出されるキャリヤガスの露点に対して0℃~5℃高く、かつ80℃~95℃であり、かつキャリヤガスに酸素を富化して、前記乾燥機から排出されるキャリヤガス中の酸素濃度が湿りガスベースで10%超~15%となる、間接加熱乾燥機の乾燥条件とすることを特徴とする低品位炭の乾燥方法。
前記間接加熱乾燥機として、スチームチューブドライヤを使用する場合には、キャリヤガスを流通させることができる構造のものが汎用されている。前記低品位炭から乾燥蒸発した水蒸気を搬送するキャリヤガスとして、空気を使用する場合に比較して、酸素富加した空気を使用することとし、このキャリヤガスを前記間接加熱乾燥機の入口側から出口側に向かって移動させるようにすると、乾燥速度が高いものとなる。その結果、同一乾燥時間ながら、効率的に石炭表面の酸化反応を促進でき、発火抑制効果が向上する。
前記乾燥機出口からの前記低品位炭の乾燥炭を搬送するに際し、エアスライド式コンベアを使用し、その偏向性多孔板上を乾燥炭を搬送する過程で、多孔板の開孔を通してエアを吹き出す方向が、乾燥炭搬送方向に向かい、水平に対して10度~20度上方として、低品位炭の表面と酸素とを接触させる請求項1または2記載の低品位炭の乾燥方法。
乾燥炭の微粉を風力分級することにより、自然発火、粉塵爆発の要因の一つである比表面積を低減した乾燥炭を目的個所に向かって搬送することができる。この場合、後に示すように偏向性多孔板上を乾燥炭を搬送するエアスライド式コンベアを使用するのが望ましい。
多孔板の開孔を通してエアを吹き出す方向角度としては、10度~20度、特に14度~16度が、搬送用ブロワの駆動動力が少なくて単位幅当たりの搬送量が多いものとなる。エアスライド式コンベアは、固気の接触が良く、比較的駆動動力が少ない利点を発揮し、最適である。
間接加熱乾燥機のキャリヤガス中の粉塵を乾式で除塵する集塵装置で処理されたキャリヤガスを、前記エアスライド式コンベアの搬送媒体とする請求項3記載の低品位炭の乾燥方法。
そもそも、間接加熱乾燥機から排出されるキャリヤガスは、石炭から蒸発した水分を多く含むことから空気と比較してO2濃度(湿りガスベース)が低く、かつ乾燥炭表面温度と同程度の温度である。
したがって、かかるキャリヤガスをエアスライド式コンベアの搬送媒体として供給することで、自然発火を抑制しつつ(酸素濃度が低いため発火しにくい)、乾燥炭表面の酸化反応を促進(供給ガスの温度が高いため反応が進む)することができる。
偏向性多孔板の開孔からのガス吹き出し速度をu m/s、ノズルの開孔比をm、ガス密度をρkg/m3としたとき、1/2ρmu3が、30~200である請求項3記載の低品位炭の乾燥方法。
多孔板の開孔からの、あるガス吹き出し量に対し、実用的な単位幅当たりの搬送量を得ることができる。1/2ρmu3の好ましい範囲は40~100である。
低品位炭を乾燥する間接加熱乾燥機と、乾燥機出口の乾燥炭の温度を測定する測定手段と、乾燥機から排出されたキャリヤガスの露点を測定する露点測定手段と、キャリヤガスの酸素濃度を測定する酸素濃度測定手段とを備え、
前記乾燥機出口の乾燥炭の表面温度を、前記露点測定手段で測定した露点と関連付けて調節手段するとともに、前記乾燥機から排出されるキャリヤガス中の酸素濃度を湿りガスベースで調節する手段を備えることを特徴とする低品位炭の乾燥設備。
基本的に請求項1と同様の作用効果を奏する。
<請求項7記載の発明>
前記間接加熱乾燥機から排出されるキャリヤガス中の粉塵を乾式で除塵する集塵装置で処理されたキャリヤガスを搬送媒体として、前記間接加熱乾燥機から排出される低品位炭を搬送するエアスライド式コンベアを備えた請求項6記載の低品位炭の乾燥設備。
請求項4と同様の作用効果を奏する。
<請求項8記載の発明>
前記間接加熱乾燥機から排出されるキャリヤガス中の粉塵を乾式で除塵する集塵装置と、この集塵装置に供給する窒素含有気体を空気から製造する窒素含有気体製造装置とを備え、
前記窒素含有気体製造装置から排出される酸素含有排ガスを間接加熱乾燥機のキャリヤガスとして供給する手段を備えた請求項6または7記載の低品位炭の乾燥設備。
間接加熱乾燥機から排出されるキャリヤガス中の粉塵を乾式で除塵する集塵装置の設置が、環境汚染防止の観点から必要となる。
この場合、集塵装置としては、パルスエアを使用する除塵装置を使用するのが望ましい。パルスエアは、洗浄時の粉塵爆発防止のため酸素濃度が低いN2ガスでないとならない。この必要とされるN2ガスは、窒素含有気体製造装置により得るのが望ましい。
この例として、PSA(Pressure Swing Adsorption:圧力変動吸着)装置を挙げることができ、空気中の酸素吸着(この場合、排ガスが窒素リッチ)、または窒素吸着(この場合、脱着ガスが窒素リッチ)のいずれかの方法で製造する。吸着した窒素リッチのガスは、パルスエアとして使用し、このとき不要となる酸素リッチのガスは、スチームチューブドライヤ(STD)のキャリヤガスとすることで、余計な設備を別途設けることなく発火性抑制に必要なキャリヤガスを得ることができる。
そして、乾燥処理機としては、好適にはスチームチューブドライヤ(STD)3を使用することができる。
乾式集塵機24には、石炭ダストを払い落とすパルスガス供給装置(図示せず)が備えられていて、一定間隔、もしくは濾材前後の圧力差に応じてパルスガスが供給される。
また、酸素濃度計23Bから送られた測定値と、予め設定されたキャリヤガスの酸素濃度の設定範囲(もしくは設定値)とを比較し、測定値が設定範囲内(設定値)となるようキャリヤガスへの酸素富加量を調節する。
なお、乾燥条件調整手段は、乾燥炭の温度調整用とキャリヤガスの酸素濃度調整用の2つに分割することも可能である。
酸素と反応しやすい石炭の活性基を酸素と反応させるためには、温度が高いほど、雰囲気の酸素濃度が高いほど反応が速い。
この例として、PSA(Pressure Swing Adsorption:圧力変動吸着)装置を挙げることができ、空気中の酸素吸着(この場合、排ガスが窒素リッチ)、または窒素吸着(この場合、脱着ガスが窒素リッチ)のいずれかの方法で製造する。
乾燥排ガスの酸素濃度は約15%、乾燥石炭水分は約22%で、乾燥石炭の表面温度が70℃の場合と92℃の場合、未乾燥品の自然発火性を調査した。
S00:未乾燥品
S70:乾燥石炭の表面温度が70℃
S92:乾燥石炭の表面温度が92℃
BC :オーストラリア産瀝青炭
乾燥石炭水分は約22%、乾燥石炭の表面温度が92℃となる加熱条件において、乾燥機から排出されるキャリヤガス(以下、排出キャリヤガスという)の酸素濃度をそれぞれ約5%、10%、15%に調整した場合の自然発火性を調査した。
S00 :未乾燥品
S5% :排出キャリヤガスの酸素濃度5%
S10%:排出キャリヤガスの酸素濃度10%
S15%:排出キャリヤガスの酸素濃度15%
BC :オーストラリア産瀝青炭
偏向性多孔板のノズルの水平に対する吹き出し角度と乾燥炭の搬送姓を調査した。
エアスライドの吹き出し角度θは、16度を使用し、エアスライドへの単位面積当たりの空気供給量を変えて(1/2ρmu3を変えて)エアスライドの単位幅当たりの搬送量を測定した。
1/2ρmu3はエアスライド用ブロワの動力に比例するのでできるだけ小さい方が良いしエアスライドの排ガス処理設備にも影響する。
Claims (8)
- 間接加熱乾燥機により、低品位炭を乾燥するに際し、前記乾燥機出口における前記低品位炭の表面温度が前記乾燥機から排出されるキャリヤガスの露点に対して0℃~5℃高く、かつ70℃~95℃であり、かつ前記間接加熱乾燥機から排出されるキャリヤガス中の酸素濃度が湿りガスベースで10%超~15%となる、間接加熱乾燥機の乾燥条件とすることを特徴とする低品位炭の乾燥方法。
- 間接加熱乾燥機により、低品位炭を乾燥するに際し、前記間接加熱乾燥機出口における前記低品位炭の表面温度が前記乾燥機から排出されるキャリヤガスの露点に対して0℃~5℃高く、かつ80℃~95℃であり、かつキャリヤガスに酸素を富化して、前記間接加熱乾燥機から排出されるキャリヤガス中の酸素濃度が湿りガスベースで10%超~15%となる、前記間接加熱乾燥機の乾燥条件とすることを特徴とする低品位炭の乾燥方法。
- 前記乾燥機出口からの前記低品位炭の乾燥炭を搬送するに際し、エアスライド式コンベアを使用し、その偏向性多孔板上を乾燥炭を搬送する過程で、多孔板の開孔を通してエアを吹き出す方向が、乾燥炭搬送方向に向かい、水平に対して10度~20度上方として、低品位炭の表面と酸素とを接触させる請求項1または2記載の低品位炭の乾燥方法。
- 間接加熱乾燥機のキャリヤガス中の粉塵を乾式で除塵する集塵装置で処理されたキャリヤガスを、前記エアスライド式コンベアの搬送媒体とする請求項3記載の低品位炭の乾燥方法。
- 偏向性多孔板の開孔からのガス吹き出し速度をu m/s、ノズルの開孔比をm、ガス密度をρkg/m3としたとき、1/2ρmu3が、30~200である請求項3記載の低品位炭の乾燥方法。
- 低品位炭を乾燥する間接加熱乾燥機と、乾燥機出口の乾燥炭の温度を測定する測定手段と、乾燥機から排出されたキャリヤガスの露点を測定する露点測定手段と、キャリヤガスの酸素濃度を測定する酸素濃度測定手段とを備え、
前記乾燥機出口の乾燥炭の表面温度を、前記露点測定手段で測定した露点と関連付けて調節する手段と、前記乾燥機から排出されるキャリヤガス中の酸素濃度を湿りガスベースで調節する手段を備えることを特徴とする低品位炭の乾燥設備。 - 前記間接加熱乾燥機から排出されるキャリヤガス中の粉塵を乾式で除塵する集塵装置で処理されたキャリヤガスを搬送媒体として、前記間接加熱乾燥機から排出される低品位炭を搬送するエアスライド式コンベアを備えた請求項6記載の低品位炭の乾燥設備。
- 前記間接加熱乾燥機から排出されるキャリヤガス中の粉塵を乾式で除塵する集塵装置と、この集塵装置に供給する窒素含有気体を空気から製造する窒素含有気体製造装置とを備え、
前記窒素含有気体製造装置から排出される酸素含有排ガスを間接加熱乾燥機のキャリヤガスとして供給する手段を備えた請求項6または7記載の低品位炭の乾燥設備。
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