CN111412483B - Medium-speed mill pulverizing system for grinding high-moisture lignite - Google Patents
Medium-speed mill pulverizing system for grinding high-moisture lignite Download PDFInfo
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- CN111412483B CN111412483B CN202010341320.9A CN202010341320A CN111412483B CN 111412483 B CN111412483 B CN 111412483B CN 202010341320 A CN202010341320 A CN 202010341320A CN 111412483 B CN111412483 B CN 111412483B
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- 239000003077 lignite Substances 0.000 title claims abstract description 17
- 238000010298 pulverizing process Methods 0.000 title claims abstract description 14
- 238000000227 grinding Methods 0.000 title description 7
- 239000003245 coal Substances 0.000 claims abstract description 178
- 239000000779 smoke Substances 0.000 claims abstract description 65
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 43
- 239000003546 flue gas Substances 0.000 claims abstract description 43
- 238000001035 drying Methods 0.000 claims abstract description 23
- 239000007789 gas Substances 0.000 claims abstract description 18
- 238000003801 milling Methods 0.000 claims abstract description 17
- 239000002893 slag Substances 0.000 claims abstract description 12
- 238000007599 discharging Methods 0.000 claims abstract description 11
- 230000001105 regulatory effect Effects 0.000 claims abstract description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000001301 oxygen Substances 0.000 claims abstract description 8
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 8
- 239000000428 dust Substances 0.000 claims description 20
- 239000002817 coal dust Substances 0.000 claims description 11
- 238000000605 extraction Methods 0.000 claims description 4
- 230000002093 peripheral effect Effects 0.000 claims description 2
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 abstract description 21
- 238000000034 method Methods 0.000 description 9
- 239000000843 powder Substances 0.000 description 6
- 238000010248 power generation Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 2
- 239000002956 ash Substances 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000004200 deflagration Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000010881 fly ash Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000010977 unit operation Methods 0.000 description 2
- 238000007605 air drying Methods 0.000 description 1
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 1
- 239000003830 anthracite Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 238000005338 heat storage Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
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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
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/006—Layout of treatment plant
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23K—FEEDING FUEL TO COMBUSTION APPARATUS
- F23K3/00—Feeding or distributing of lump or pulverulent fuel to combustion apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L1/00—Passages or apertures for delivering primary air for combustion
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L13/00—Construction of valves or dampers for controlling air supply or draught
- F23L13/02—Construction of valves or dampers for controlling air supply or draught pivoted about a single axis but having not other movement
- F23L13/04—Construction of valves or dampers for controlling air supply or draught pivoted about a single axis but having not other movement with axis perpendicular to face
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L15/00—Heating of air supplied for combustion
- F23L15/02—Arrangements of regenerators
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
- F26B17/12—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed solely by gravity, i.e. the material moving through a substantially vertical drying enclosure, e.g. shaft
- F26B17/14—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed solely by gravity, i.e. the material moving through a substantially vertical drying enclosure, e.g. shaft the materials moving through a counter-current of gas
- F26B17/1408—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed solely by gravity, i.e. the material moving through a substantially vertical drying enclosure, e.g. shaft the materials moving through a counter-current of gas the gas being supplied and optionally extracted through ducts extending into the moving stack of material
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Air Supply (AREA)
Abstract
The invention discloses a medium-speed milling system for milling high-moisture lignite, which comprises a medium-speed coal mill, a raw coal drying unit and a primary air temperature regulating unit. And extracting medium-temperature flue gas of the boiler to exchange heat with hot primary air, and drying raw coal by the medium-temperature flue gas after heat exchange and furnace bottom air, wherein a stream of cold flue gas is led out from an outlet of the induced draft fan and used for adjusting the temperature and oxygen content of the mixed gas. The raw coal drying unit can solve the problems of insufficient output, high primary air rate and the like of the dried high-moisture lignite of the traditional medium-speed coal mill pulverizing system; meanwhile, the problems of high emission of nitrogen oxides, high exhaust temperature, low thermal efficiency of the boiler and the like caused by low air leakage of the dry slag discharging system furnace can be solved. The primary air temperature regulating unit utilizes excessive negative pressure to the coal bin to extract intermediate temperature furnace smoke of the boiler, and exchanges heat with hot primary air in the tubular heat exchanger to improve the primary air temperature.
Description
Technical Field
The invention belongs to the technical field of coal-fired power generation, relates to a medium-speed coal mill pulverizing system matched with a dry slag discharging unit boiler, and particularly relates to a medium-speed coal mill pulverizing system for grinding high-moisture lignite.
Background
Currently, coal mills commonly used in coal-fired power plant boiler pulverizing systems mainly have three main types: steel ball coal mill, medium speed coal mill and fan coal mill. The steel ball coal mill mainly grinds anthracite and lean coal with low grindability, the medium-speed coal mill mainly grinds coal with a scour and wear index Ke less than or equal to 5.0 and a total moisture Mt less than or equal to 35%, and the fan coal mill mainly grinds coal with a scour and wear index Ke less than or equal to 3.5 and a total moisture Mt more than 35%. The traditional generator set for burning high-moisture (Mt > 30%) lignite is usually provided with a fan mill direct-blowing pulverizing system, and most of drying mediums are high-temperature furnace smoke, hot air and cold furnace smoke. Actual operation finds that the fan coal mill has the problems of easy abrasion of the impeller impact plate, large overhaul workload, high maintenance cost and the like. In addition, the current domestic electric coal market is tense in supply, the power generation cost is high, and the power plant increases the purchase of lignite to ensure the long-term stable supply of electric coal and reduce the operation cost. However, the medium speed coal mill matched with many power plant boilers in China is designed with low-moisture and high-heat value coal, and the lignite with high-moisture and low-heat value has to be combusted at present, so that the coal which is ground by the fan coal mill is finally ground by the medium speed coal mill, and the problems of low temperature of a grinding outlet of the coal mill, insufficient drying output, overlarge primary air rate, high emission of nitrogen oxides at an outlet of an economizer and the like are caused.
In order to solve the above problems, the methods currently in common use mainly include the following methods:
1. The primary air quantity is increased. The method mainly increases the primary air rate to improve the drying output of the coal mill, has limited effect, and when the water content of the coal is large (such as more than 40%), the increase of the primary air rate still cannot meet the requirement of the primary air drying output, and when the primary air rate is increased to a certain value, the proportion of the secondary air is seriously deviated from a design value, the combustion working condition in the furnace can be influenced, and the problems of central upward movement of the flame of a hearth, overtemperature of a heating surface of a boiler, increase of the quantity of water reduction, increase of the carbon content of fly ash, increase of nitrogen oxide emission, increase of the exhaust gas temperature and the like occur.
2. And the primary air temperature is improved. It is common practice to reverse the air preheater or raise the air preheater inlet primary air temperature. The hollow pre-heater is inverted by adopting a method of inverting the side of the first air pre-heater and the side of the second air pre-heater, namely, the primary air passes through the heat storage element before the secondary air so as to achieve the purpose of improving the primary air temperature, but the method has limited primary air temperature improvement range, and is generally between 20 and 30 ℃. The low-temperature flue gas is led to the inlet of the primary air fan from the outlet of the induced draft fan by the air cooler to improve the temperature of the primary air inlet of the air preheater, so that the temperature of the hot primary air at the outlet of the air preheater is properly improved, but the range of the primary air temperature is limited.
3. And (5) preparing powder by using high-temperature furnace smoke. The method is that the high-temperature furnace smoke fan is used for extracting the high-temperature furnace smoke from the boiler and is introduced into the coal mill after being mixed with primary air, and the medium-speed coal mill pulverizing system belongs to the positive pressure pulverizing system, so that the high-temperature furnace smoke fan can stably operate for a long time under the severe environment with high temperature and high pressure of about 500 ℃ and 12Kpa and high dust content, and the requirement on the high-temperature furnace smoke fan is higher.
4. Steam heats primary air or dries raw coal. The method mainly adopts steam turbine to extract steam to heat primary air or dry water in raw coal, and the method has the problems of high extraction quantity, low unit operation efficiency and the like.
Researches show that the lignite after combustion, drying and upgrading can reduce the carbon content of fly ash and slag, reduce the exhaust gas temperature, improve the thermal efficiency of a boiler, reduce the emission of nitrogen oxides by burning coal with high volatile components, reduce the energy consumption of auxiliary machines of power stations such as induced draft fans, coal mills and the like, and reduce the power generation coal consumption. Therefore, the drying and upgrading of the coal quality of the inlet of the medium-speed coal mill can be carried out, the output of the medium-speed coal mill can be improved, the economical efficiency and the environmental protection of the unit operation can be improved, and the method has important application value.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a medium-speed milling system for milling high-moisture lignite.
The above object of the present invention is achieved by the following technical scheme:
the medium-speed milling system for milling the high-moisture lignite comprises a medium-speed coal mill, a raw coal drying unit and a primary air temperature regulating unit; wherein:
the raw coal drying unit comprises an excessive coal feeding bin for feeding coal to the medium-speed coal mill, a furnace bottom air pipeline for conveying extracted furnace bottom air of the boiler to the excessive coal feeding bin, a medium-temperature smoke pipeline for conveying medium-temperature smoke extracted from the boiler to the excessive coal feeding bin, a cold smoke pipeline for conveying cold smoke extracted from an outlet of a draught fan to the excessive coal feeding bin, a spent air fan for providing extraction power for the furnace bottom air, the medium-temperature smoke and the cold smoke and conveying the extraction power back to the boiler, and a coal dust separator arranged between the excessive coal feeding bin and the spent air fan; the furnace bottom air pipeline, the medium-temperature smoke pipeline and the cold smoke pipeline are communicated with a coal dropping port of the excessive coal feeding bin, the exhaust gas fan is communicated with a smoke outlet of the excessive coal feeding bin through a coal dust separator, and the coal dust separator is communicated with a medium-speed coal mill;
The primary air temperature regulating unit comprises a hot primary air pipeline for feeding hot primary air extracted from an outlet of an air preheater of the boiler into the medium-speed coal mill for pulverizing, and a hot primary valve and a cold primary valve which are arranged on the hot primary air pipeline and used for regulating the temperature of the hot primary air;
The flue gas heat exchanger is used for exchanging heat between the flue gas in the medium-temperature flue gas pipeline and the flue gas in the hot primary air pipeline, and the dust remover is arranged on the medium-temperature flue gas pipeline and between the boiler and the heat exchanger.
Further, the excessive coal feeding bin comprises a bin body, wherein the bin body is provided with a coal inlet positioned at the upper part of one side of the bin body, a coal dropping opening positioned at the lower part of the other side of the bin body, and a smoke outlet; the bin body is internally provided with a coal conveying belt for conveying the coal falling from the coal inlet to the coal falling inlet.
Further, a conical plate for receiving and dispersing the coal falling from the coal conveying belt and a smoke inlet pipe for feeding smoke are arranged at the coal falling port of the excessive coal feeding bin, the smoke inlet pipe is arranged below the conical plate, and a plurality of smoke inlet holes are formed in the peripheral wall of the smoke inlet pipe.
Further, a roller for adjusting the thickness of the coal bed and/or a rake board for turning the coal bed are arranged on the inner wall of the bin body above the coal conveying belt.
Further, an air cannon is arranged on the bin wall at the coal dropping port of the excessive coal feeding bin.
Further, the boiler bottom air comprises air leakage of a dry slag discharging system and part of bottom smoke.
Further, the heat exchanger for exchanging heat between the flue gas in the medium-temperature flue gas pipeline and the hot primary air pipeline is a tubular heat exchanger.
Further, a dust remover arranged on the medium-temperature flue pipe and between the boiler and the heat exchanger is a dust removing bellows. The flow equalizing plate is arranged in the dedusting air box, so that the flue gas can uniformly enter the air box, the air speed of the flue gas can be rapidly reduced, and dust contained in hot flue gas can be deposited at the bottom end of the air box. The dust discharging port is arranged at the bottom end of the dust removing bellows, and operators can regularly discharge dust in the bellows.
Further, a valve and a flowmeter are respectively arranged on the furnace bottom air pipeline, the medium temperature smoke pipeline and the cold smoke pipeline.
Further, the furnace bottom air pipeline, the medium temperature smoke pipeline and the cold smoke pipeline are respectively provided with an oxygen meter.
The beneficial effects are that:
the invention provides a medium-speed grinding powder making system for grinding high-moisture lignite, which mainly comprises two parts, namely a raw coal drying unit and a primary air temperature adjusting unit, wherein the raw coal drying unit is used for pre-drying raw coal, and the primary air temperature adjusting unit is used for improving primary air temperature. And extracting medium-temperature flue gas of the boiler to exchange heat with hot primary air, and exhausting air from the medium-temperature flue gas after heat exchange and a dry slag discharging system, and drying raw coal by partial furnace bottom flue gas, wherein a stream of cold flue gas is led out from an outlet of a draught fan and used for adjusting the temperature and oxygen content of mixed gas. The raw coal drying unit can solve the problems of insufficient output, high primary air rate and the like of the dried high-moisture lignite of the traditional medium-speed coal mill pulverizing system; meanwhile, the problems of high emission of nitrogen oxides, high exhaust temperature, low thermal efficiency of the boiler and the like caused by low air leakage of the dry slag discharging system furnace can be solved.
The primary air temperature regulating unit utilizes excessive negative pressure to the coal bin to extract medium temperature furnace smoke of the boiler, and exchanges heat with hot primary air in the tubular heat exchanger so as to improve the primary air temperature. In addition, as the primary air temperature is increased, the required primary air quantity can be reduced, and the problems of low furnace efficiency, high nitrogen oxide emission and the like caused by increasing the primary air quantity are fundamentally solved.
Drawings
FIG. 1 is a schematic diagram of a medium-speed milling system for milling high-moisture lignite;
FIG. 2 is a schematic diagram of the internal structure of the overfeeding bin;
Wherein 1 is a raw coal bin; 2 is a coal feeder; 3 is an air lock; 4 is an excessive coal feeding bin; 5 is a medium-speed coal mill; 6 is a burner; 7 is a boiler; 8 is a denitration device; 9 is an air preheater; 10 is a dust remover; 11 is a draught fan; 12 is a chimney; 13 is a dry slag discharging system; 14 is a hot primary air pipeline; 15 is a hot primary valve; 16 is a cold primary valve; 17 is a dust removal bellows; 18 is a tubular heat exchanger; 19 is a medium temperature flue valve; 20 is a furnace bottom air pipeline valve; 21 is a flowmeter; 22 is a cold smoke pipeline valve; 23 is a pulverized coal separator; 24 is a powder return pipeline; 25 is a exhaust fan; 26 is a exhaust gas nozzle;
4-1 is a bin body; 4-2 is a coal inlet (a cylindrical coal dropping pipe); 4-3 is a coal conveying belt; 4-4 is a conical plate; 4-5 is an annular coal dropping port; 4-6 are cylindrical smoke inlet pipes; 4-7 are annular smoke outlets; 4-8 are rollers; 4-9 are rake plates; 4-10 is a motor; 4-11 are air cannons.
Detailed Description
The following describes the essential aspects of the invention in detail with reference to the drawings and examples, but is not intended to limit the scope of the invention.
Example 1:
The object of the embodiment is a 600MW supercritical front and rear wall opposed firing boiler, pi-shaped arrangement, a dry slag discharging system and a positive pressure direct blowing powder system matched with 6 medium speed coal mills, wherein the total moisture of coal is 8.14%, lignite with the total moisture of more than 40% is designed to be mixed and fired, and the phenomenon of insufficient drying output of the coal mill powder making system exists.
The medium-speed milling system for milling the high-moisture lignite comprises a medium-speed coal mill 5, a raw coal drying unit and a primary air temperature adjusting unit.
As shown in fig. 1, raw coal in a raw coal bin 1 enters an excessive coal feeding bin 4 through a coal feeder 2 to be dried, the dried coal enters a medium-speed coal mill 5 to be ground, ground coal powder enters a boiler 7 through a combustor 6 to be combusted, and flue gas in a hearth passes through a denitration device 8, an air preheater 9, a dust remover 10 and an induced draft fan 11 and is finally discharged to a chimney 12.
In the raw coal drying unit, furnace bottom wind is extracted from the upper part of the dry slag discharging system 13, namely the lower part of the slag well, and the furnace bottom wind comprises air leakage of the dry slag discharging system and part of furnace bottom smoke, and the temperature is about 450 ℃; simultaneously, medium-temperature flue gas is extracted from the boiler 7, the temperature is about 600 ℃, the medium-temperature flue gas exchanges heat with hot primary air at the outlet of the air preheater 9 in the tubular heat exchanger 18, the temperature of the flue gas after heat exchange is about 400 ℃, and the flue gas is mixed with furnace bottom air and sent into the excessive coal feeding bin 4 through a pipeline to dry raw coal; in order to eliminate the risk of excessive coal feeding bin deflagration, a stream of cold flue gas is led out from the outlet of the induced draft fan 11, the temperature is about 115 ℃, and the cold flue gas is mixed with the mixed gas again to be used for adjusting the temperature and the oxygen content of the mixed gas, and finally, the oxygen content volume concentration in the excessive coal feeding bin is controlled to be lower than 16 percent so as to prevent deflagration. The exhaust gas after drying the raw coal is sent into the boiler 7 through the exhaust gas nozzle 26 by the exhaust gas fan 25 after passing through the coal dust separator 23, and the coal dust separated by the coal dust separator 23 is returned to the medium-speed coal mill 5 through the return pipe 24. The furnace bottom wind, medium-temperature flue gas and cold flue gas power are extracted from the raw coal drying unit and are sourced from the exhaust gas fan 25, and the exhaust gas passing through the exhaust gas fan 25 is subjected to excessive cooling and dust removal for the coal bin 5 and the coal dust separator 23, so that the working environment is greatly improved, and the fan can stably run. The furnace bottom air pipeline, the medium temperature smoke pipeline and the cold smoke pipeline are respectively provided with a furnace bottom air pipeline valve 20, a medium temperature smoke pipeline valve 19, a cold smoke pipeline valve 22 and a flowmeter 21, the flow of each path of gas can be regulated, and when the coal variety changes and does not need to be dried, the valve can be fully closed. While each pipe is provided with an oxygen meter (not shown) to control the oxygen amount of the system.
As shown in fig. 2, raw coal in a raw coal bin 1 falls onto a coal conveying belt 4-3 in an excessive coal feeding bin 4 from a coal inlet (a cylindrical coal dropping pipe) 4-2 through a coal feeder 2, a roller 4-8 is arranged above the coal conveying belt, so that the raw coal can be uniformly spread on the coal conveying belt, the roller 4-8 is fixed on the inner wall of a bin body 4-1 by a spring, the thickness of a coal bed can be adjusted, a ceramic rake plate 4-9 is arranged behind the roller 4-8, and the coal bed can be turned over, so that the surface area of the coal bed is larger. The coal conveying belt 4-3 conveys raw coal from one end of the excessive coal feeding bin 4 to the other end, the raw coal falls on the conical plate 4-4 to be dispersed and falls down, the furnace bottom wind, the medium-temperature flue gas after heat exchange and the cold flue gas are mixed and then enter the excessive coal feeding bin 4 through the cylindrical smoke inlet pipe 4-6, wherein the cylindrical smoke inlet pipe 4-6 is fully provided with smoke inlet holes, the flue gas enters the excessive coal feeding bin body 4-1 from the smoke inlet holes, the raw coal is reversely conveyed, the falling raw coal is dried, the total moisture of the raw coal is reduced to be less than 30%, the dried raw coal enters the medium-speed coal mill 5 through the annular coal falling port 4-5 to be ground, and the exhaust gas after the raw coal is dried enters the coal dust separator 23 through the annular smoke outlet 4-7. In addition, the motor 4-10 of the coal conveying belt 4-3 can automatically adjust the running speed of the coal conveying belt 4-3, and the wall of the bin body 4-1 at the coal dropping port 4-5 of the excessive coal feeding bin 4 is provided with an air cannon 4-11, and the air cannon 4-11 can clean the bin or prevent blockage.
Meanwhile, medium-temperature flue gas with the temperature of about 600 ℃ is extracted from a boiler by utilizing the negative pressure of the excessive coal feeding bin 4 in the primary air temperature adjusting unit, enters the tubular heat exchanger 18 after being dedusted by the dedusting bellows 17, and the air preheater 9 is connected with the other end of the tubular heat exchanger 18 through the hot primary air pipeline 14, so that the medium-temperature flue gas with the temperature of about 600 ℃ exchanges heat with the hot primary air with the temperature of about 290 ℃ output by the air preheater 9 in the tubular heat exchanger 18, the hot primary air with the temperature after heat exchange and temperature rise is fed into the medium-speed coal mill 5 through the pipeline for pulverizing, and meanwhile, the hot primary air temperature entering the medium-speed coal mill 5 can still be adjusted by the hot primary valve 15 and the cold primary valve 16 on the pipeline according to the grinding temperature of the medium-speed coal mill 5. The dust removal bellows 17 is arranged in front of the tubular heat exchanger 18, so that the amount of ash entering the tubular heat exchanger can be reduced, the abrasion to the tubular heat exchanger is reduced, the flow equalizing plate is arranged in the dust removal bellows 17, the flue gas can uniformly enter the bellows, the flue gas wind speed can be rapidly reduced, and dust contained in hot flue gas can be deposited at the bottom end of the bellows. The bottom end of the dust removal bellows 17 is provided with an ash discharge port, and operators can regularly discharge dust in the bellows. The primary air temperature regulating unit utilizes excessive negative pressure to the coal bin (4), does not need a medium-temperature furnace smoke blower, and reduces investment cost.
Because the raw coal is subjected to primary drying in the excessive coal feeding bin, the moisture of the raw coal is reduced, and the primary air temperature does not need to be increased too much, compared with the total flue gas amount, the extracted medium-temperature flue gas amount is small, and meanwhile, the exhaust gas of the dried raw coal is fed into the boiler, so that the convection heating surface of the boiler is hardly influenced. As the primary air temperature is increased, the required primary air quantity can be reduced, and the problems of low furnace efficiency, high nitrogen oxide emission and the like caused by increasing the primary air quantity are fundamentally solved.
The above-described embodiments serve to describe the substance of the present invention in detail, but those skilled in the art should understand that the scope of the present invention should not be limited to this specific embodiment.
Claims (8)
1. The utility model provides a grind intermediate speed mill pulverizing system of high moisture brown coal, includes intermediate speed coal pulverizer, its characterized in that: the device also comprises a raw coal drying unit and a primary air temperature adjusting unit; wherein:
The raw coal drying unit comprises an excessive coal feeding bin for feeding coal to the medium-speed coal mill, a furnace bottom air pipeline for conveying extracted furnace bottom air to the excessive coal feeding bin, a medium-temperature smoke pipeline for conveying medium-temperature smoke extracted from a boiler to the excessive coal feeding bin, a cold smoke pipeline for conveying cold smoke extracted from an outlet of a draught fan to the excessive coal feeding bin, a spent air fan for providing extraction power for the furnace bottom air, the medium-temperature smoke and the cold smoke and conveying the extracted furnace bottom air and the medium-temperature smoke and the cold smoke back to the boiler, and a coal dust separator arranged between the excessive coal feeding bin and the spent air fan; the furnace bottom air pipeline, the medium-temperature smoke pipeline and the cold smoke pipeline are communicated with a coal dropping port of the excessive coal feeding bin, the exhaust gas fan is communicated with a smoke outlet of the excessive coal feeding bin through a coal dust separator, and the coal dust separator is communicated with a medium-speed coal mill;
The primary air temperature regulating unit comprises a hot primary air pipeline for feeding hot primary air extracted from an outlet of an air preheater of the boiler into the medium-speed coal mill for pulverizing, and a hot primary valve and a cold primary valve which are arranged on the hot primary air pipeline and used for regulating the temperature of the hot primary air;
The flue gas heat exchanger is used for exchanging heat between the flue gas in the medium-temperature flue gas pipeline and the hot primary air pipeline, and the dust remover is arranged on the medium-temperature flue gas pipeline and between the boiler and the heat exchanger;
wherein:
The excessive coal feeding bin comprises a bin body, wherein the bin body is provided with a coal inlet positioned at the upper part of one side of the bin body, a coal dropping opening positioned at the lower part of the other side of the bin body, and a smoke outlet; a coal conveying belt for conveying the coal falling from the coal inlet to the coal falling inlet is arranged in the bin body;
the furnace bottom air comprises air leakage of a dry slag discharging system and part of furnace bottom smoke.
2. The medium speed milling system of claim 1, wherein: the coal dropping mouth of the excessive coal feeding bin is provided with a conical plate for receiving and dispersing coal dropped by the coal conveying belt and a smoke inlet pipe for feeding smoke, the smoke inlet pipe is arranged below the conical plate, and the peripheral wall of the smoke inlet pipe is provided with a plurality of smoke inlet holes.
3. The medium speed milling system of claim 1, wherein: the inner wall of the bin body above the coal conveying belt is provided with a roller for adjusting the thickness of the coal bed and/or a rake board for turning the coal bed.
4. The medium speed milling system of claim 1, wherein: and an air cannon is arranged on the bin wall at the coal dropping port of the excessive coal feeding bin.
5. The medium speed milling system of claim 1, wherein: the heat exchanger for exchanging heat between the flue gas in the medium-temperature flue gas pipeline and the hot primary air pipeline is a tubular heat exchanger.
6. The medium speed milling system of claim 1, wherein: the dust remover arranged on the medium-temperature flue pipe and between the boiler and the heat exchanger is a dust removing bellows.
7. The medium speed milling system of claim 1, wherein: and the furnace bottom air pipeline, the medium temperature smoke pipeline and the cold smoke pipeline are respectively provided with a valve and a flowmeter.
8. The medium speed milling system of claim 1, wherein: and the furnace bottom air pipeline, the medium-temperature smoke pipeline and the cold smoke pipeline are respectively provided with an oxygen meter.
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| CN112024108A (en) * | 2020-08-17 | 2020-12-04 | 上海电力大学 | Grading heating powder making system based on heat pipe technology and control method thereof |
| CN111853846A (en) * | 2020-08-21 | 2020-10-30 | 西安热工研究院有限公司 | A system for pre-drying furnace smoke and increasing the output of a medium-speed coal pulverizer and its working method |
| CN112466417B (en) * | 2020-11-23 | 2023-01-20 | 西安热工研究院有限公司 | Simple method for determining moisture of coal powder |
| CN113819479B (en) * | 2021-11-01 | 2022-09-30 | 西安热工研究院有限公司 | System and method for increasing drying output of medium-speed coal mill based on high temperature furnace smoke |
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