CN111363598B - Method for producing clean coal - Google Patents
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- CN111363598B CN111363598B CN201811604931.7A CN201811604931A CN111363598B CN 111363598 B CN111363598 B CN 111363598B CN 201811604931 A CN201811604931 A CN 201811604931A CN 111363598 B CN111363598 B CN 111363598B
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- 239000003245 coal Substances 0.000 title claims abstract description 376
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 27
- 239000007789 gas Substances 0.000 claims abstract description 190
- 238000006243 chemical reaction Methods 0.000 claims abstract description 93
- 239000012535 impurity Substances 0.000 claims abstract description 83
- 238000001816 cooling Methods 0.000 claims abstract description 68
- 239000003546 flue gas Substances 0.000 claims abstract description 62
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 61
- 239000000571 coke Substances 0.000 claims abstract description 48
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000010438 heat treatment Methods 0.000 claims abstract description 14
- 238000002485 combustion reaction Methods 0.000 claims description 53
- 238000000034 method Methods 0.000 claims description 53
- 238000000197 pyrolysis Methods 0.000 claims description 36
- 239000002918 waste heat Substances 0.000 claims description 23
- 230000008569 process Effects 0.000 claims description 18
- 230000009471 action Effects 0.000 claims description 14
- 239000003077 lignite Substances 0.000 claims description 7
- 239000002245 particle Substances 0.000 claims description 6
- 238000005695 dehalogenation reaction Methods 0.000 claims description 3
- 239000002994 raw material Substances 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 16
- 239000011269 tar Substances 0.000 description 9
- 239000003034 coal gas Substances 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 5
- 235000011114 ammonium hydroxide Nutrition 0.000 description 5
- 238000003763 carbonization Methods 0.000 description 5
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 4
- 229910052753 mercury Inorganic materials 0.000 description 4
- 150000003568 thioethers Chemical class 0.000 description 4
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- 229910052785 arsenic Inorganic materials 0.000 description 3
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 3
- 239000003054 catalyst Substances 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 229910052717 sulfur Inorganic materials 0.000 description 3
- 239000011593 sulfur Substances 0.000 description 3
- 239000004484 Briquette Substances 0.000 description 2
- 238000003915 air pollution Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000009740 moulding (composite fabrication) Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000012216 screening Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 206010028980 Neoplasm Diseases 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 201000011510 cancer Diseases 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000011280 coal tar Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
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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
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B53/00—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
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Abstract
The invention relates to the field of clean production of fire coal, in particular to a method for producing clean coal. The method for producing clean coal comprises the following steps: (1) directly heating raw coal by using a heat source at 750-1200 ℃ in a conversion reactor to perform coal conversion to obtain raw coke oven gas and converted coal; (2) introducing the converted coal, the raw coke oven gas and combustion-supporting air into a impurity removal reactor to obtain impurity removed coal and high-temperature tail gas; (3) exchanging heat between the high-temperature tail gas and water to obtain cooling flue gas and steam, and returning at least part of the cooling flue gas to the step (1) to be used as a heat source for directly heating raw coal; (4) and (5) carrying out dry cooling on the impurity-removed coal to obtain clean coal. The production system provided by the invention can produce qualified clean coal, and simultaneously, the high-temperature tail gas of the impurity removal reactor is used as a heat source for the conversion reaction of the raw material coal, so that the production and operation cost of the clean coal is reduced, and the pollution to the environment caused by the discharge is reduced.
Description
Technical Field
The invention relates to the field of clean production of fire coal, in particular to a method for producing clean coal.
Background
In energy consumption structures in China, coal consumption is the main position, but most of coal is directly combusted at present, coal burning is one of the main causes of air pollution and is also a very important factor of haze, and the coal burning is known as 'cancer' which is difficult to cure in the field of air pollution treatment. Therefore, the scattered coal is urgently cleaned. The civil scattered coal is cleaned by removing volatile components, sulfides, mercury and arsenic in raw coal through pyrolysis, the pollutant emission of the cleaned coal after pyrolysis during combustion can be obviously reduced, and the cleaned coal is used for replacing the original poor scattered coal, so that the method is an effective path for solving the pollution caused by scattered combustion of the coal in China.
CN106398732A describes a process and a device for the poly-generation quality improvement of low-quality coal, the process is that the low-quality coal is sent into a dry distillation furnace through a receiving device and a receiving metering device for heating and dry distillation, after coal gas (including coal tar and moisture) is separated out, the remaining solid material is cooled by a dry quenching device to obtain clean coal with low volatile component and is continuously sent out, wherein the coal gas is purified by a coal gas outlet device. The dry distillation furnace is provided with a plurality of carbonization chambers, combustion chambers and regenerator nozzles, coal is continuously and uniformly distributed to different carbonization chambers in the dry distillation furnace, the combustion chambers generate heat through the combustion of heat accumulating nozzles to continuously supply heat to the carbonization chambers, the dry-distilled material is uniformly heated to 800 ℃, is cooled through heat exchange between a dry quenching device and a film type cooling wall, is discharged through a vibration feeder and is conveyed to a goods yard through a belt, and the generated coal gas is cooled through an ascending pipe on the carbonization chamber by ammonia water through a bridge pipe, is collected with tar ammonia water and is conveyed to a coal gas treatment system for further treatment. The method has the main defects that: 1) in the dry distillation furnace, the combustion chamber generates heat through the combustion of the heat accumulating type nozzle to continuously supply heat to the carbonization chamber, and the structure is complex; 2) the tar ammonia water is collected by cooling the coal gas by the ammonia water, a large amount of tar ammonia water can be generated by the process, and the wastewater treatment method is difficult.
In view of the above, a new civil clean coal production process system needs to be found.
Disclosure of Invention
The present invention has been made to overcome the above problems occurring in the prior art, and an object of the present invention is to provide a novel method for producing clean coal.
The invention provides a method for producing clean coal, which comprises the following steps:
(1) directly heating raw coal by using a heat source at 750-1200 ℃ in a conversion reactor to perform coal conversion, wherein the final conversion temperature of the coal conversion is 500-640 ℃, and the conversion time is 10-60 min, so as to obtain raw coke oven gas and converted coal;
(2) introducing the converted coal, the raw coke oven gas and combustion-supporting air into a impurity removal reactor, so that the converted coal and the raw coke oven gas run in a countercurrent mode, and in the running process, the raw coke oven gas and pyrolysis gas generated by impurity removal of the converted coal are combusted under the action of the combustion-supporting air and provide heat for impurity removal of the converted coal;
the final impurity removal temperature of the impurity removal reactor is 650-750 ℃, and the impurity removal time is 10-60 min, so that impurity removed coal and high-temperature tail gas are obtained;
(3) exchanging heat between the high-temperature tail gas and water to obtain cooling flue gas and steam at the temperature of 750-1200 ℃, and returning at least part of the cooling flue gas to the step (1) to be used as a heat source for directly heating raw coal;
(4) and (5) carrying out dry cooling on the impurity-removed coal to obtain clean coal.
The production method provided by the invention fully utilizes high-temperature tail gas generated by impurity-removing pyrolysis incineration of raw coal as a heat source of coal conversion reaction from the aspect of overall utilization efficiency; in the impurity removal reactor, pyrolysis gas generated by raw coke oven gas, converted coal and combustion-supporting air are subjected to self-balancing combustion (mainly the raw coke oven gas and the pyrolysis gas are combusted, and only a small amount of converted coal is locally combusted), so that the raw coke oven gas with low calorific value can be burnt, tar is prevented from being accumulated in a downstream system to block a pipeline and a fan, impurities can be further removed from the converted coal, heat is provided for recarburization, qualified clean coal is produced, and meanwhile, high-temperature tail gas of the impurity removal reactor is used as a heat source for conversion reaction of raw coal, so that the production and operation cost of clean coal is reduced, and the pollution to the environment caused by external discharge is reduced.
Drawings
FIG. 1 is a schematic flow diagram of one embodiment of a method for producing clean coal according to the present invention.
FIG. 2 is a schematic flow diagram of another embodiment of a method for producing clean coal according to the present invention.
Description of the reference numerals
1: a conversion reactor; 2: an induced draft fan; 3: a de-impurity reactor; 4: a waste heat boiler; 5: and (7) drying and cooling.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a method for producing clean coal, which comprises the following steps:
(1) directly heating raw coal by using a heat source at 750-1200 ℃ in a conversion reactor to perform coal conversion, wherein the final conversion temperature of the coal conversion is 500-640 ℃, and the conversion time is 10-60 min, so as to obtain raw coke oven gas and converted coal;
(2) introducing the converted coal, the raw coke oven gas and combustion-supporting air into a impurity removal reactor, so that the converted coal and the raw coke oven gas run in a countercurrent mode, and in the running process, the raw coke oven gas and pyrolysis gas generated by impurity removal of the converted coal are combusted under the action of the combustion-supporting air and provide heat for impurity removal of the converted coal; the final impurity removal temperature of the impurity removal reactor is 650-750 ℃, and the impurity removal time is 10-60 min, so that impurity removed coal and high-temperature tail gas are obtained;
(3) exchanging heat between the high-temperature tail gas and water to obtain cooling flue gas and steam at the temperature of 750-1200 ℃, and returning at least part of the cooling flue gas to the step (1) to be used as a heat source for directly heating raw coal;
(4) and (5) carrying out dry cooling on the impurity-removed coal to obtain clean coal.
According to the invention, the main function of the step (1) is to remove water, volatile components, sulfides and other light substances in the raw coal. The conversion reactor used for the coal conversion may be a rotary kiln, a fluidized bed, a tower moving bed, a rake moving bed, an entrained flow bed, or preferably a rotary kiln, as long as the high-temperature flue gas can be directly contacted with the raw coal, and the raw coal and the high-temperature flue gas may be operated in a counter-current or co-current manner. Optionally, in one embodiment of the invention, the configuration and throughput of the dehazing reactor and the conversion reactor are substantially the same.
The method for producing clean coal belongs to a continuous process, and in the stable implementation process of the whole process, the heat source in the step (1) is mainly provided by the cooling flue gas generated after heat exchange in the step (3). It should be understood that prior to starting up the process, the conversion reactor and the dehairing reactor are brought to their respective temperatures by providing a heat source for start-up of the overall system for producing clean coal. The heat source for start-up in the present invention is not particularly limited, and may be any of various heat sources known in the art, such as flue gas.
In the present invention, the ratio is 10000Nm3The cooling flue gas, the feed rate of raw coal can be 6000 ~ 12000kg, preferably 8000 ~ 10000 kg.
In the invention, the raw coal conversion in the step (1) and the coal impurity removal in the step (2) are mutually matched, so that the quality of clean coal can be ensured, and the yield of the clean coal can be improved. When the final conversion temperature in the step (1) is too low, the content of light components in the converted coal is high, the temperature required by the impurity removal of the converted coal in the step (2) cannot be realized, and the quality of clean coal is difficult to ensure; and when the final conversion temperature in the step (1) is too high, on one hand, the consumption of a heat source required in the same conversion time is higher, the consumption of induced air power is improved, on the other hand, the content of the generated raw gas is too high, the yield of clean coal is reduced, and the inflammability of the clean coal is influenced. And the final conversion temperature of the coal conversion is ensured to be 500-640 ℃ and the final impurity removal temperature of the impurity removal reactor is ensured to be 650-750 ℃, so that the whole process can be ensured to stably and reliably run, and the requirement on the adopted equipment is low.
Preferably, the ratio of the conversion time to the impurity removal time is (1-2): 1, thus further improving the quality of clean coal.
In the step (2), the converted coal and the raw gas run in a countercurrent mode in the impurity removal reactor. In the operation process, the raw gas is firstly combusted under the action of combustion-supporting air, the heat generated by combustion enables the converted coal to be subjected to impurity removal, so as to generate impurity-removed coal and pyrolysis gas, the pyrolysis gas is also combusted, and the high-temperature tail gas is generated by the combustion of the raw gas and the pyrolysis gas. In the step, the raw coke oven gas and the pyrolysis gas are incinerated, so that tar in the raw coke oven gas and the pyrolysis gas can be prevented from accumulating in a downstream system to block pipelines and fans. It will be appreciated that the present invention is directed to obtaining a clean coal product having a high economic efficiency, whereby the pyrolysis gas (raw gas) produced in the conversion step is directly sent to the dehairing reactor for combustion after leaving the conversion reactor without any tar extraction treatment such as cooling or condensation, and the heat is provided for the dehairing reaction by burning the pyrolysis gas (including the pyrolysis gas produced during the dehairing process).
In the step (2), the adding amount of the combustion-supporting air is controlled by raw coke oven gas burning reaction, and can be specifically determined according to the required clean coal product index or the temperature of the impurity removal reactor. Generally, relative to 10000Nm3The consumption of the combustion-supporting air can be 3000-4500 Nm3. In order to further improve the quality of clean coal, it is preferable to use 10000 Nm/Nm3The consumption of the combustion-supporting air is 3500-4000 Nm3Therefore, the reduction of the content of C in the clean coal product (the excessive combustion of C in the converted coal) caused by the excessive consumption of the combustion air can be further avoided, and the content of other components (such as ash) is increased; and can further avoid the problem that the content of the volatile components in the clean coal product is too high due to too low consumption of the combustion-supporting air (the combustion-supporting air only can meet the requirements of pyrolysis gas and a very small amount of converted coal to cause that the generated heat can not raise the temperature of the whole system, so that the volatile components in the converted coal can not be decomposed at a sufficient temperature).
The present invention is not particularly limited to the above-mentioned impurity removal reactor, and may be selected from any conventional reactors capable of achieving the above-mentioned functions, for example, a rotary kiln reactor. In view of the present invention, generally, the rotary kiln reactor for impurity removal treatment comprises a solid feed port (also referred to as an introduction port of the converted coal herein), a gas feed port, a solid discharge port, and a gas discharge port, wherein the number of the gas feed ports is at least two, and the gas feed ports are used for introducing raw coke oven gas and combustion air respectively. The solid feeding hole and the gas feeding hole for introducing raw coke oven gas (also referred to as raw coke oven gas introducing hole) are respectively positioned at the front part and the rear part of the rotary kiln reactor, and the solid discharging hole and the gas discharging hole are respectively positioned at the rear part and the front part of the rotary kiln reactor, so that the converted coal and the raw coke oven gas run in a countercurrent way, and the impurity-removed coal and the high-temperature tail gas generated by impurity-removing combustion are respectively discharged from the rear part and the front part of the reactor. The number of gas feed openings for introducing said combustion air (also referred to herein as introduction openings for combustion air) may be one or more.
In the present invention, "front" and "rear" of the rotary kiln reactor are relative concepts, and are defined specifically according to the flow direction of the converted coal. The introduction port of the converted coal may be provided in a front partial region of not more than 30% of the length of the reactor, and the introduction port of the raw coke oven gas may be provided in a rear partial region of not more than 30% of the length of the reactor.
According to one embodiment, as shown in fig. 1, the number of said inlets for the combustion air is one and close to the inlets for the raw gas. In this case, the combustion-supporting air is introduced into the rotary kiln reactor from the same position of the rotary kiln reactor, and the axial distance between the introduction port of the combustion-supporting air and the introduction port of the raw coke oven gas accounts for 0-10% of the length of the rotary kiln reactor.
According to another preferred embodiment, as shown in fig. 2, the number of the combustion air feed ports is three, and the three combustion air feed ports are respectively arranged at the front, middle and rear portions of the rotary kiln reactor, so that the combustion air is introduced from different positions and provides oxygen necessary for the combustion of the raw coke oven gas and the pyrolysis gas generated by the removal of impurities from the reformed coal. In this case, the combustion air may be introduced into the rotary kiln reactor from the front, middle and rear positions thereof, the axial distance between the introduction port of the front part and the introduction port of the converted coal accounts for 0 to 10% of the length of the reactor, the axial distance between the introduction port of the middle part and the introduction port of the converted coal accounts for 20 to 50% of the length of the reactor, and the axial distance between the introduction port of the rear part and the introduction port of the raw coke oven gas accounts for 0 to 10% of the length of the reactor. In this context, the axial distance is the distance between the radial cross sections of the two inlets of the rotary kiln reactor, and an axial distance of "0" means that the inlets for combustion air are on the same radial cross section as the inlets for raw gas or reformed coal.
More preferably, the proportion of the combustion air entering the front part, the middle part and the rear part is respectively 10-30%, 20-30% and 40-70% by taking the total consumption of the combustion air as a reference.
In this context, it should be noted that the terms "rotary kiln" and "rotary kiln reactor" have different meanings and refer to different rotary kilns for the conversion reactor and the impurity removal reactor, respectively, wherein the main difference between the "rotary kiln reactor" and the "rotary kiln" is that the rotary kiln reactor needs to be provided with the inlet for the combustion air.
According to the invention, in the step (2), the temperature of the obtained high-temperature tail gas is generally 1000-1500 ℃. And (3) recovering the heat value of the high-temperature tail gas in the system through heat exchange to obtain the cooling flue gas and steam at the temperature of 750-1200 ℃. The heat exchange may be performed using a waste heat boiler and the boiler feed water may be any source of water that enables the heat exchange, for example, the boiler feed water may be water from the water produced by a power plant boiler feed water system. Generally, the temperature of the steam obtained after heat exchange is 300-500 ℃. The temperature of the temperature-reducing tail gas is preferably 850-1000 ℃, namely the temperature of the conversion reaction in the step (1) is preferably 850-1000 ℃. The high-temperature tail gas belongs to inert gas after combustion and mainly comprises CO2、N2And H2O and the like, and does not have adverse effect on the preparation of clean coal from raw coal.
According to the invention, the raw coke oven gas and the cooling tail gas can be respectively and correspondingly treated by providing power through the induced draft fan.
According to the invention, in the step (4), the clean coal can be obtained by cooling the deduplicated coal from the deduplicated reactor to 90-110 ℃ in a dry cooler. According to the actual need, optionally, the method may further include: and forming the clean coal to obtain the clean coal. Preferably, the clean coal briquette meets the standard of DB13-2081-2014 civil coal briquette.
In the invention, the impurity-removed coal refers to uncooled coal obtained by drying and removing impurities from raw coal in the method provided by the invention.
In the present invention, the raw coal may not be particularly limited. Preferably, the raw coal is at least one of lignite with the particle size of 1-100 mm, long flame coal and non-caking coal.
In the invention, the quality of the obtained clean coal can meet the standard of DB 13-2081-2014. Wherein the content of volatile matters in the clean coal is less than or equal to 12 weight percent and more than or equal to 6 weight percent, and the content of ash is less than or equal to 16 weight percent. Preferably, the content of volatile components in the clean coal is more than or equal to 8 weight percent and less than or equal to 10 weight percent. In addition, the clean coal has a total sulfur content of 0.4 wt% or less.
Of the three raw coals listed above, lignite has a relatively low carbon content and a relatively high volatile content, and therefore the yield of clean coal produced in accordance with the present invention with lignite produced of satisfactory quality is relatively low, typically less than 70%. The clean coal which meets the requirements in quality and is obtained by processing the long flame coal or the non-sticky coal has the yield of 70-75%. In addition, in the case that the final conversion temperature of the step (1) is higher than 640 ℃ and/or the final impurity removal temperature of the step (2) is higher than 750 ℃, the yield of clean coal produced from the raw coal is lower than the value due to the generation of excessive raw gas.
The method of the invention is implemented in a clean coal production system comprising: the conversion reactor, the impurity removal reactor, the waste heat boiler, the induced draft fan and the dry cooler; wherein,
the waste heat boiler is respectively communicated with the impurity removal reactor and the conversion reactor so as to ensure that the high-temperature tail gas from the impurity removal reactor exchanges heat with boiler feed water to obtain cooling flue gas and steam, and at least part of the cooling flue gas is returned to the conversion reactor to be used for directly heating raw coal;
the induced draft fan is used for feeding the raw coke oven gas generated by the conversion reactor into the impurity removal reactor and providing power for feeding the cooled flue gas into the conversion reactor;
the dry cooler is used for cooling the impurity-removed coal from the impurity-removing reactor by a dry cooling method to obtain clean coal.
In the present invention, the dry cooler may use an existing dry quenching method apparatus.
Fig. 1 and 2 show the flow of two different embodiments of the method for producing clean coal according to the present invention.
As shown in fig. 1 and 2, the system provided by the present invention mainly includes: the device comprises a conversion reactor, an induced draft fan, a impurity removal reactor, a waste heat boiler and a dry cooler, wherein the impurity removal reactor is a rotary kiln reactor. Wherein, the gas discharge mouth of conversion reactor with the entry intercommunication of draught fan, its solid discharge mouth with the mouth intercommunication is introduced to the conversion coal of rotary kiln reactor, the export of draught fan with the mouth intercommunication is introduced to the raw coke oven gas of rotary kiln reactor, the gas discharge mouth of rotary kiln reactor with waste heat boiler's entry intercommunication, waste heat boiler's export and conversion reactor's gas feed inlet intercommunication, the solid discharge mouth of rotary kiln reactor and the entry linkage of dry cold ware.
In addition to the above-described equipment, the system may include other equipment known in the art for producing clean coal systems. These devices will be described below in connection with fig. 1 and 2 to illustrate the method of the present invention.
According to the embodiment shown in fig. 1, the method for producing clean coal provided by the invention comprises the following steps:
(1) sending the cooled flue gas (750-1200 ℃) from the waste heat boiler into a conversion reactor to be used as a heat source for converting raw coal (namely the raw material coal in the figure 1); lifting raw coal with the particle size of 1-100 mm to a raw coal buffer bin, enabling the raw coal to enter the conversion reactor from the buffer bin, directly heating the raw coal to 500-640 ℃ by cooled flue gas for conversion reaction, and removing part of volatile components, sulfides, mercury, arsenic and the like in the raw coal to obtain converted coal and raw coke oven gas;
(2) introducing the converted coal from the conversion reactor from the front part of the rotary kiln reactor, introducing the raw gas and combustion-supporting air from the rear part of the rotary kiln reactor together, so that the raw gas and the converted coal run in a countercurrent mode, burning the raw gas under the action of the combustion-supporting air and the converted coal, removing tar in the raw gas, providing heat for impurity removal of the converted coal to generate pyrolysis gas, burning the pyrolysis gas, and obtaining impurity removal coal and high-temperature tail gas, wherein the final impurity removal temperature in the reactor is 650-750 ℃, and the impurity removal time is 10-60 min;
(3) recovering the heat value of the high-temperature tail gas from the rotary kiln reactor through a waste heat boiler, exchanging heat with boiler feed water to obtain the cooling flue gas (750-1200 ℃) and steam, and returning the cooling flue gas (namely the hot flue gas in the figure 1) to be used as a heat source for raw coal conversion in the step (1);
(4) and (3) reducing the temperature of the miscellaneous coal discharged from the rotary kiln reactor to 90-110 ℃ in a dry cooler, sending the miscellaneous coal into a clean coal bunker for storage, or preparing a clean bulk coal product through the processes of screening, grinding, forming and the like.
According to the embodiment shown in fig. 2, the method for producing clean coal provided by the invention comprises the following steps:
(1) sending the cooled flue gas (750-1200 ℃) from the waste heat boiler into a conversion reactor to be used as a heat source for converting raw coal (namely the raw material coal in the figure 2); lifting raw coal with the particle size of 1-100 mm to a raw coal buffer bin, enabling the raw coal to enter the raw coal conversion reactor from the buffer bin, directly heating the raw coal to 500-640 ℃ by cooled flue gas for conversion reaction, and removing part of volatile components, sulfides, mercury, arsenic and the like in the raw coal to obtain converted coal and raw coke oven gas;
(2) introducing the converted coal from the conversion reactor from the front part of the rotary kiln reactor, introducing the crude gas from the rear part of the rotary kiln reactor, so that the crude gas and the converted coal run in a countercurrent mode, introducing combustion-supporting air from the front part, the middle part and the rear part of the rotary kiln reactor, burning the crude gas under the action of the combustion-supporting air and the converted coal, removing tar in the crude gas, providing heat for removing impurities of the converted coal to generate pyrolysis gas, burning the pyrolysis gas, controlling self-balancing combustion by controlling the air intake of the combustion-supporting air at different positions, controlling the final impurity removal temperature in the reactor to be 650-750 ℃, and controlling the impurity removal time to be 10-60 min, so as to obtain the impurity removal coal and high-temperature tail gas;
(3) recovering the heat value of the high-temperature tail gas from the rotary kiln reactor through a waste heat boiler, exchanging heat with boiler feed water to obtain the cooling flue gas (750-1200 ℃) and steam, and returning the cooling flue gas (namely the hot flue gas in the figure 2) to be used as a heat source for raw coal conversion in the step (1);
(4) and (3) reducing the temperature of the miscellaneous coal discharged from the rotary kiln reactor to 90-110 ℃ in a dry cooler, sending the miscellaneous coal into a clean coal bunker for storage, or preparing a clean bulk coal product through the processes of screening, grinding, forming and the like.
In the invention, the raw gas and the converted coal are subjected to the impurity removal reaction of the converted coal and the combustion reaction of the raw gas and the pyrolysis gas generated by impurity removal in the rotary kiln reactor, on one hand, qualified clean coal can be produced, on the other hand, the phenomenon that tar components in the gas are accumulated in a downstream system to block a pipeline and a fan can be effectively avoided, and the heat generated by combustion is used as a heat source for the impurity removal reaction, so that the production and operation cost of the clean coal can be reduced, and the environmental pollution can be reduced. In addition, the heat of the miscellaneous coal can be recovered through a dry cooler to generate steam, and the overall energy utilization efficiency is improved. The invention can balance the manufacturing cost, the running cost and the product cost of the whole system by the overall design of the process flow and the reasonable selection of the process parameters of each step, so that the whole set of process and the corresponding system have very good industrial application value.
The present invention will be described in detail below by way of examples.
The clean coals obtained in the examples and comparative examples were measured for sulfur content, ash sulfur content and volatile matter content according to the DB13-2081-2014 standard.
The method for producing clean coal and the system to which the method is applied according to the present invention will be described with reference to fig. 1 and 2. Unless otherwise indicated, the flow specific operations are as described above.
The following examples 1 to 4 and comparative examples 1 to 2 each produced clean coal according to the flow shown in fig. 1, in which the introduction port of combustion air and the introduction port of raw gas were on the same radial section of the rotary kiln reactor.
Example 1
(1) 14000Nm3The temperature-reduced flue gas (900 ℃) is directly contacted with 13000kg of raw coal (lignite, the grain diameter is 20mm) in a countercurrent mode in a rotary kiln, coal conversion is carried out for 50min, and the final conversion temperature is 600 ℃, so that raw coke oven gas and converted coal are obtained;
(2) respectively feeding raw gas, converted coal and combustion-supporting air into a rotary kiln reactor, so that the raw gas and the converted coal are directly contacted in a countercurrent mode, the raw gas is combusted under the action of the converted coal and the combustion-supporting air, pyrolysis gas generated by the converted coal is combusted, coal impurity removal is carried out for 35min, and the final impurity removal temperature is 650 ℃, so as to obtain impurity-removed coal and high-temperature tail gas; relative to 10000Nm34500Nm of raw gas and combustion-supporting air3/h。
(3) Dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas (900 ℃) and water vapor (450 ℃), and returning the cooling flue gas to the rotary kiln in the step (1) through an induced draft fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 1.
Example 2
(1) 10000Nm3The temperature-reduced flue gas (900 ℃) is directly contacted with 7000kg of raw coal (non-caking coal, the grain diameter is 1mm) in a countercurrent mode in a rotary kiln, the coal is converted for 40min, and the final conversion temperature is 580 ℃, so that raw coke oven gas and converted coal are obtained;
(2) respectively feeding the raw gas, the converted coal and combustion air into a rotary kiln reactor to enable the raw gas and the converted coal to run in a countercurrent mode, burning the raw gas under the action of the converted coal and the combustion air, burning pyrolysis gas generated by the converted coal, removing impurities from the coal for 35min, and finally, removing impurities at 700 ℃ to obtain the impurity-removed coalCoal and high temperature tail gas; relative to 10000Nm3The consumption of raw gas and combustion air is 3500Nm3；
(3) Dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas (900 ℃) and water vapor (400 ℃), and returning the cooling flue gas to the rotary kiln in the step (1) through an induced draft fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 1.
Example 3
Clean coal was produced according to the method of example 1, except that, in the step (2), the amount of the catalyst was changed to 10000Nm3The consumption of raw gas and combustion air is 5000 Nm/h3/h；
(3) Dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas and water vapor, and returning the cooling flue gas to the rotary kiln in the step (1) to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 1.
Example 4
Clean coal was produced according to the method of example 1, except that, in the step (2), the amount of the catalyst was changed to 10000Nm3The consumption of raw gas and combustion air is 3000 Nm/h3/h；
(3) Dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas and steam, and returning the cooling flue gas to the rotary kiln in the step (1) through an induced draft fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 1.
Comparative example 1
(1) 16000Nm3The temperature-reduced flue gas (900 ℃) is directly contacted with 13000kg of raw coal (lignite with the particle size of 20mm) in a rotary kiln in a countercurrent mode for coal conversion for 50min, and the final conversion temperature isThe temperature is 700 ℃, and raw coke oven gas and converted coal are obtained;
(2) respectively feeding raw gas, converted coal and combustion-supporting air into a rotary kiln reactor, so that the raw gas and the converted coal are directly contacted in a countercurrent mode, the raw gas is combusted under the action of the converted coal and the combustion-supporting air, pyrolysis gas generated by the converted coal is combusted, coal impurity removal is carried out for 35min, and the final impurity removal temperature is 910 ℃, so as to obtain impurity-removed coal and high-temperature tail gas; relative to 10000Nm34500Nm of raw gas and combustion-supporting air3/h。
(3) Dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas (900 ℃) and water vapor (550 ℃), and returning the cooling flue gas to the rotary kiln in the step (1) through an induced draft fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 1.
Comparative example 2
(1) 10000Nm3Directly contacting 13000kg of raw coal (lignite with the particle size of 20mm) with high-temperature tail gas at 900 ℃ in a countercurrent mode in a rotary kiln, and carrying out coal conversion for 50min, wherein the final conversion temperature is 430 ℃ to obtain raw coke oven gas and converted coal;
(2) respectively feeding raw gas, converted coal and combustion-supporting air into a rotary kiln reactor, so that the raw gas and the converted coal are directly contacted in a countercurrent mode, the raw gas is combusted under the action of the converted coal and the combustion-supporting air, pyrolysis gas generated by the converted coal is combusted, coal impurity removal is carried out for 35min, and the final impurity removal temperature is 580 ℃, so as to obtain impurity-removed coal and high-temperature tail gas; relative to 10000Nm34500Nm of raw gas and combustion-supporting air3/h。
(3) Dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) returning the high-temperature tail gas to the rotary kiln in the step (1) through an induced draft fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 1.
The following examples 5 to 8 and comparative example 3 each produced clean coal according to the flow shown in fig. 2, in which the front inlet for combustion air and the inlet for converted coal were on the same radial cross section of the rotary kiln reactor, the rear inlet and the inlet for raw gas were on the same radial cross section of the rotary kiln reactor, and the axial distance between the inlet in the middle and the inlet for raw gas was 30% of the reactor length.
Example 5
(1) 10000Nm3The temperature-reduced flue gas (950 ℃) is directly contacted with 7000kg of raw coal (long flame coal, the grain diameter is 5mm) in a countercurrent mode in a moving bed, the coal is converted for 35min, and the final conversion temperature is 570 ℃, so that raw coke oven gas and converted coal are obtained;
(2) respectively feeding raw gas and converted coal into a rotary kiln reactor, and introducing combustion-supporting air into different positions of the reactor to enable the raw gas and the converted coal to run in a countercurrent mode, wherein the raw gas is combusted under the action of the converted coal and the combustion-supporting air, and pyrolysis gas generated by the converted coal is combusted to carry out coal impurity removal for 35min, and the final impurity removal temperature is 700 ℃, so that impurity-removed coal and high-temperature tail gas are obtained;
wherein, relative to 10000Nm3The total consumption of raw gas and combustion air is 4000Nm3Respectively introducing combustion-supporting air into the front part, the middle part and the rear part of the rotary kiln reactor, wherein the consumption of the combustion-supporting air accounts for 20%, 30% and 50% respectively;
(3) dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas (950 ℃) and water vapor (450 ℃), and returning the cooling flue gas to the moving bed in the step (1) through an induced draft fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 2.
Example 6
(1) 14000Nm3The temperature-reduced flue gas (850 ℃) is directly contacted with 12000kg of raw coal (long flame coal, the grain diameter is 3mm) in a countercurrent mode in a rotary kiln, the coal is converted for 50min, and the final conversion temperature is 520 ℃, so that raw coke oven gas and converted coal are obtained;
(2) respectively feeding raw gas and converted coal into a rotary kiln reactor, and introducing combustion-supporting air into different positions of the reactor to enable the raw gas and the converted coal to run in a countercurrent mode, wherein the raw gas is combusted under the action of the converted coal and the combustion-supporting air, and pyrolysis gas generated by the converted coal is combusted to carry out coal impurity removal for 40min, and the final impurity removal temperature is 650 ℃, so that impurity-removed coal and high-temperature tail gas are obtained;
wherein, relative to 10000Nm3The total consumption of raw gas and combustion air is 3500Nm3Introducing combustion-supporting air into the front part, the middle part and the rear part of the rotary kiln reactor respectively, wherein the consumption of the combustion-supporting air accounts for 20%, 20% and 60% respectively;
(3) dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas (850 ℃) and water vapor (400 ℃), and returning the cooling flue gas to the rotary kiln in the step (1) through an induced draft fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 2.
Example 7
(1) 14000Nm3The flue gas per hour (1150 ℃) is directly contacted with 11000kg of raw coal (long flame coal, the grain diameter is 3mm) in a countercurrent mode in a rotary kiln, coal conversion is carried out for 40min, and the final conversion temperature is 600 ℃, so that raw coke oven gas and converted coal are obtained;
(2) respectively feeding raw gas and converted coal into a rotary kiln reactor, and introducing combustion-supporting air into different positions of the reactor to enable the raw gas and the converted coal to run in a countercurrent mode, wherein the raw gas is combusted under the action of the converted coal and the combustion-supporting air, and pyrolysis gas generated by the converted coal is combusted to carry out coal impurity removal for 60min, and the final impurity removal temperature is 650 ℃ to obtain impurity-removed coal and high-temperature tail gas;
wherein, relative to 10000Nm3The total consumption of raw gas and combustion air is 4000Nm3Introducing combustion-supporting air into the front part, the middle part and the rear part of the rotary kiln reactor respectively, wherein the consumption of the combustion-supporting air accounts for 20%, 20% and 60% respectively;
(3) dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas (1150 ℃) and water vapor (300 ℃), and returning the cooling flue gas to the rotary kiln in the step (1) through an induced draft fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 2.
Example 8
Clean coal was produced according to the method of example 6, except that, in the step (2), the amount of the catalyst was changed to 10000Nm3The consumption of raw gas and combustion air is 3000 Nm/h3/h；
(3) Dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas and water vapor, and returning the cooling flue gas to the step (1) through a draught fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 2.
Comparative example 3
(1) 18000Nm3The temperature-reducing tail gas (850 ℃) is directly contacted with 12000kg of raw coal (long flame coal, the grain diameter is 5mm) in a countercurrent mode in a rotary kiln, the coal is converted for 50min, and the final conversion temperature is 670 ℃, so that raw coke oven gas and converted coal are obtained;
(2) respectively feeding raw gas and converted coal into a rotary kiln reactor, and introducing combustion-supporting air into different positions of the reactor to enable the raw gas and the converted coal to run in a countercurrent mode, wherein the raw gas is combusted under the action of the converted coal and the combustion-supporting air, and pyrolysis gas generated by the converted coal is combusted to carry out coal impurity removal for 40min, and the final impurity removal temperature is 800 ℃, so that impurity-removed coal and high-temperature tail gas are obtained;
wherein, relative to 10000Nm3The total consumption of raw gas and combustion air is 3500Nm3Introducing combustion-supporting air into the front part, the middle part and the rear part of the rotary kiln reactor respectively, wherein the consumption of the combustion-supporting air accounts for 20%, 20% and 60% respectively;
(3) dry cooling the impurity-removed coal to obtain clean coal;
(4) and (3) sending the high-temperature tail gas to a waste heat boiler, exchanging heat with boiler feed water to obtain cooling flue gas (850 ℃) and water vapor (500 ℃), and returning the cooling flue gas to the step (1) through an induced draft fan to be used as a heat source for coal conversion.
The quality of the clean coal was determined and the results are shown in table 3.
Comparative example 4
(1) 14000Nm3The flue gas (850 ℃) of per hour directly contacts 12000kg of raw coal (long flame coal, the grain diameter is 3mm) in a countercurrent mode in a rotary kiln, the coal is converted for 90min, and the final conversion temperature is 620 ℃, so that raw coke oven gas and coal products are obtained;
(2) and (5) carrying out dry cooling on the coal product by using air to obtain clean coal.
The quality of the clean coal was determined and the results are shown in table 3.
Comparative example 5
(1) 14000Nm3The flue gas (850 ℃) of/h directly contacts 12000kg of raw coal (long flame coal, the grain diameter is 3mm) in a countercurrent mode in a rotary kiln, the coal is heated for 120min, and the final heating temperature is 750 ℃, so that raw coke oven gas and coal products are obtained;
(2) and (5) carrying out dry cooling on the coal product by using air to obtain clean coal.
The quality of the clean coal was determined and the results are shown in table 3.
TABLE 1
1: comparative example 2 refers to high temperature tail gas;
2: the ratio of conversion time to dehalogenation time.
TABLE 2
TABLE 3
In tables 2 and 3, 1: the expression "×/×" denotes the proportion of combustion air introduced from the front, middle and rear of the rotary kiln reactor;
2: the ratio of conversion time to dehalogenation time;
3: comparative examples 4 and 5 refer to flue gases.
From the results of examples 1 to 8, it can be seen that the clean coal obtained by the method of example had a volatile content of < 11% by weight and > 6% by weight and an ash content of < 15% by weight.
Compared with the comparative example 1, the coal conversion temperature of the comparative example 1 is higher, so that on one hand, more cooling flue gas needs to be adopted in the same conversion time, so that the energy consumption of a fan is higher, on the other hand, the final impurity removal reaction temperature at the downstream is higher, the generated raw gas is too much, the yield of clean coal is low, the volatile content is too low (less than 6 wt%), and the combustibility is poor; in addition, the low conversion temperature of comparative example 2 resulted in a lower final dehairing temperature for the same dehairing time, failing to produce acceptable clean coal.
Comparing example 6 with comparative example 3, the final conversion temperature of comparative example 6 was higher, resulting in low clean coal yield and poor combustibility.
Comparing example 6 with comparative examples 4-5, it can be seen that the present invention can ensure the production of clean coal meeting the quality standards and the substantial reduction of mercury content by sequentially performing coal conversion and impurity removal on raw coal under different operating conditions.
Comparing examples 1-2 with examples 5-6, it can be seen that the quality of the clean coal produced can be further improved by introducing different proportions of combustion air at different locations in the rotary kiln reactor.
Comparing the two groups of examples 1 and 3-4, and 6 and 8, respectively, it can be seen that the quality of the clean coal produced is not as good as that of examples 1 and 6 when the amount of combustion air introduced is not within the most preferable range.
Comparing example 6 with example 7, it can be seen that when the conversion and dehairing time ratio is not in the most effective range, clean coal of acceptable quality can be produced, but the quality of clean coal is not as good as that of example 6.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (22)
1. A method of producing clean coal, the method comprising:
(1) directly heating raw coal by using a heat source at 750-1200 ℃ in a conversion reactor to perform coal conversion, wherein the final conversion temperature of the coal conversion is 500-640 ℃, and the conversion time is 10-60 min, so as to obtain raw coke oven gas and converted coal;
(2) introducing the converted coal, the raw coke oven gas and combustion-supporting air into a impurity removal reactor, so that the converted coal and the raw coke oven gas run in a countercurrent mode, and in the running process, the raw coke oven gas and pyrolysis gas generated by impurity removal of the converted coal are combusted under the action of the combustion-supporting air and provide heat for impurity removal of the converted coal;
the final impurity removal temperature of the impurity removal reactor is 650-750 ℃, and the impurity removal time is 10-60 min, so that impurity removed coal and high-temperature tail gas are obtained;
(3) exchanging heat between the high-temperature tail gas and water to obtain cooling flue gas and steam at the temperature of 750-1200 ℃, and returning at least part of the cooling flue gas to the step (1) to be used as a heat source for directly heating raw coal;
(4) and (5) carrying out dry cooling on the impurity-removed coal to obtain clean coal.
2. The method according to claim 1, wherein in the step (1), the feeding amount of the raw coal is 6000-12000 kg relative to 10000Nm3 of cooling flue gas.
3. The method according to claim 1, wherein the ratio of the conversion time to the dehalogenation time is (1-2): 1.
4. the method according to claim 1, wherein in the step (2), the combustion air is used in an amount of 3000 to 5000Nm3 relative to 10000Nm3 of raw coke oven gas.
5. The method according to claim 4, wherein in the step (2), the combustion air is used in an amount of 3500Nm to 4500Nm3 relative to 10000Nm3 of the raw coke oven gas.
6. The method according to any one of claims 1, 4 and 5, wherein in the step (2), the impurity removal reactor is selected from rotary kiln reactors, the combustion air is introduced into the rotary kiln reactor from the same position of the rotary kiln reactor, and the axial distance between an introduction port of the combustion air and an introduction port of the raw coke oven gas is 0-10% of the length of the rotary kiln reactor.
7. The method according to any one of claims 1, 4 and 5, wherein in the step (2), the impurity removal reactor is selected from rotary kiln reactors, the combustion air is introduced into the rotary kiln reactor from the front part, the middle part and the rear part of the rotary kiln reactor, the axial distance between an introduction port of the front part and an introduction port of the converted coal accounts for 0-10% of the length of the rotary kiln reactor, the axial distance between an introduction port of the middle part and an introduction port of the converted coal accounts for 20-50% of the length of the rotary kiln reactor, and the axial distance between an introduction port of the rear part and an introduction port of the raw coke oven gas accounts for 0-10% of the length of the rotary kiln reactor.
8. The method according to claim 7, wherein the ratio of the combustion air entering from the front, middle and rear parts is 10-30%, 20-30% and 40-70% respectively, based on the total amount of the combustion air used.
9. The method according to claim 1, wherein in the step (3), the temperature of the cooled flue gas is 850-1000 ℃.
10. The method according to claim 1 or 9, wherein in the step (3), the heat exchange is carried out so that the temperature of the obtained steam is 300-500 ℃.
11. The method according to claim 1, wherein the raw coal is at least one of lignite, long flame coal and non-caking coal having a particle size of 1 to 100 mm.
12. The method of any of claims 1-5, 9, 11, wherein the clean coal has a volatile content of 12 wt.% or less and 6 wt.% or more; the ash content in the clean coal is less than or equal to 16 wt%.
13. The method of claim 12, wherein the clean coal has a volatile content of 8 wt.% or more and 10 wt.% or less.
14. The method of claim 6, wherein the clean coal has a volatile content of 12 wt.% or less and 6 wt.% or more; the ash content in the clean coal is less than or equal to 16 wt%.
15. The method of claim 14, wherein the clean coal has a volatile content of 8 wt.% or more and 10 wt.% or less.
16. The method of claim 7, wherein the clean coal has a volatile content of 12 wt.% or less and 6 wt.% or more; the ash content in the clean coal is less than or equal to 16 wt%.
17. A process as claimed in claim 16, wherein the clean coal has a volatile content of 8% by weight or more and 10% by weight or less.
18. The method of claim 8, wherein the clean coal has a volatile content of 12 wt.% or less and 6 wt.% or more; the ash content in the clean coal is less than or equal to 16 wt%.
19. The method of claim 18, wherein the clean coal has a volatile content of 8 wt.% or more and 10 wt.% or less.
20. The method of claim 10, wherein the clean coal has a volatile content of 12 wt.% or less and 6 wt.% or more; the ash content in the clean coal is less than or equal to 16 wt%.
21. The method of claim 20, wherein the clean coal has a volatile content of 8 wt.% or more and 10 wt.% or less.
22. The method of claim 1, wherein the method is implemented in a clean coal production system comprising: the conversion reactor, the impurity removal reactor, the waste heat boiler, the induced draft fan and the dry cooler; wherein,
the waste heat boiler is respectively communicated with the impurity removal reactor and the conversion reactor so as to ensure that the high-temperature tail gas from the impurity removal reactor exchanges heat with boiler feed water to obtain cooling flue gas and steam, and at least part of the cooling flue gas is returned to the conversion reactor to be used for directly heating raw coal;
the induced draft fan is used for feeding the raw coke oven gas generated by the conversion reactor into the impurity removal reactor and providing power for feeding the cooled flue gas into the conversion reactor;
the dry cooler is used for cooling the impurity-removed coal from the impurity-removing reactor by a dry cooling method to obtain clean coal.
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