CN111620573A - Four-hearth shaft kiln for calcining dolomite and dolomite calcining method thereof - Google Patents
Four-hearth shaft kiln for calcining dolomite and dolomite calcining method thereof Download PDFInfo
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- CN111620573A CN111620573A CN202010701748.XA CN202010701748A CN111620573A CN 111620573 A CN111620573 A CN 111620573A CN 202010701748 A CN202010701748 A CN 202010701748A CN 111620573 A CN111620573 A CN 111620573A
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- 229910000514 dolomite Inorganic materials 0.000 title claims abstract description 111
- 239000010459 dolomite Substances 0.000 title claims abstract description 111
- 238000001354 calcination Methods 0.000 title claims abstract description 70
- 238000000034 method Methods 0.000 title claims abstract description 12
- 238000001816 cooling Methods 0.000 claims abstract description 30
- 238000007599 discharging Methods 0.000 claims abstract description 17
- 239000000463 material Substances 0.000 claims abstract description 16
- 239000000446 fuel Substances 0.000 claims abstract description 11
- 230000007246 mechanism Effects 0.000 claims abstract description 11
- 239000011819 refractory material Substances 0.000 claims abstract description 5
- 239000002994 raw material Substances 0.000 claims description 39
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 34
- 239000007789 gas Substances 0.000 claims description 26
- 239000001569 carbon dioxide Substances 0.000 claims description 18
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 18
- 239000000428 dust Substances 0.000 claims description 11
- 238000003860 storage Methods 0.000 claims description 10
- 230000000694 effects Effects 0.000 claims description 8
- 238000012216 screening Methods 0.000 claims description 5
- 239000002912 waste gas Substances 0.000 claims description 5
- 230000036571 hydration Effects 0.000 claims description 4
- 238000006703 hydration reaction Methods 0.000 claims description 4
- 230000014759 maintenance of location Effects 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 2
- 239000011707 mineral Substances 0.000 claims description 2
- 238000000746 purification Methods 0.000 claims 1
- 239000011257 shell material Substances 0.000 abstract description 5
- 238000009776 industrial production Methods 0.000 abstract description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 10
- 229910052749 magnesium Inorganic materials 0.000 description 9
- 239000011777 magnesium Substances 0.000 description 9
- 238000002485 combustion reaction Methods 0.000 description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 239000003034 coal gas Substances 0.000 description 5
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 4
- 238000009837 dry grinding Methods 0.000 description 4
- 239000003546 flue gas Substances 0.000 description 4
- 238000005338 heat storage Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 239000003345 natural gas Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 238000003723 Smelting Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 239000000292 calcium oxide Substances 0.000 description 2
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000003203 everyday effect Effects 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000024121 nodulation Effects 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 238000007363 ring formation reaction Methods 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2/00—Lime, magnesia or dolomite
- C04B2/10—Preheating, burning calcining or cooling
- C04B2/12—Preheating, burning calcining or cooling in shaft or vertical furnaces
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2/00—Lime, magnesia or dolomite
- C04B2/10—Preheating, burning calcining or cooling
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/16—Sintering; Agglomerating
- C22B1/214—Sintering; Agglomerating in shaft furnaces
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
- C22B26/20—Obtaining alkaline earth metals or magnesium
- C22B26/22—Obtaining magnesium
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Metallurgy (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Structural Engineering (AREA)
- Geochemistry & Mineralogy (AREA)
- Furnace Details (AREA)
Abstract
The invention provides a four-chamber shaft kiln for calcining dolomite and a dolomite calcining method thereof.A shaft kiln body comprises a kiln body shell and refractory materials, the shaft kiln body is provided with four kiln cylinders, the four kiln cylinders surround into a circle, and the four kiln cylinders are mutually communicated through connecting channels at the lower positions of respective calcining zones; a feeding bin is arranged at the center of the top of the shaft kiln body, a rotary distributor and four feeding pipes are arranged at the bottom of the feeding bin, and outlet ends of the four feeding pipes are respectively positioned in the four kiln cylinders; the top of each kiln cylinder is also provided with an exhaust cylinder, a compressed air nozzle and a fuel nozzle; the bottom of each kiln cylinder is connected with a cooling fan, and the bottommost part of each kiln cylinder is provided with a discharging mechanism. The four-chamber shaft kiln provided by the invention controls the feeding of the kiln cylinder, the airflow is reversed upwards, the heat is transferred to the cold material, the space utilization rate is high, the heat utilization rate is high, the loss is low, the calcination is uniform, the overburning and under-burning phenomena are avoided, the product quality is high, the investment cost is low, and the four-chamber shaft kiln is suitable for large-scale industrial production and application.
Description
Technical Field
The invention discloses a four-hearth shaft kiln for calcining dolomite and a dolomite calcining method thereof, belonging to the technical field of kiln calcination.
Background
In recent years, the yield of raw magnesium in China is over 90 ten thousand tons, which accounts for over 90 percent of the total yield of the raw magnesium in the world, and the consumption of dolomite is over 800 ten thousand tons. In the silicothermic magnesium smelting, the calcination of the raw material dolomite is a very important link, which determines the quality of calcined dolomite and directly influences the reduction rate of magnesium. The prior dolomite calcining equipment mainly comprises a rotary kiln and a shaft furnace, wherein the rotary kiln can meet the requirements of dolomite on various calcining conditions, but has the defects of high operation cost, low heat utilization rate, easy ring formation and frequent maintenance; the shaft kiln has uneven calcination temperature and low calcined dolomite activity, and greatly influences the yield of magnesium in the reduction process. The double-barrel shaft kiln newly developed in the dolomite calcination at present shows great superiority, the heat utilization rate is improved, the calcined dolomite activity is high, the yield is still low, a large amount of heat is still not utilized, the loss is lost and needs to be further enhanced and utilized, and in addition, carbon dioxide is directly discharged outside, so that the atmospheric pollution and the greenhouse gas effect are caused.
Disclosure of Invention
The invention provides a four-chamber shaft kiln for calcining dolomite and a dolomite calcining method thereof, aiming at solving the heat loss of the existing magnesium smelting raw material dolomite calcining equipment, increasing the productivity, improving the quality of calcined dolomite and recycling carbon dioxide.
The specific technical scheme is as follows:
a four-chamber shaft kiln for calcining dolomite comprises a shaft kiln body, wherein the shaft kiln body comprises a kiln body shell and refractory materials, the shaft kiln body is provided with four kiln cylinders, the four kiln cylinders are enclosed into a circle, and the four kiln cylinders are mutually communicated through connecting channels at the bottom positions of respective calcining zones; a feeding bin is arranged at the center of the top of the shaft kiln body, four feeding pipes are arranged at the bottom of the feeding bin, and the outlet ends of the four feeding pipes are respectively positioned in the four kiln cylinders;
the top of each kiln cylinder is also provided with an exhaust cylinder, a compressed air nozzle and a fuel nozzle; the exhaust funnel is sequentially connected with the dust remover and the carbon dioxide gas storage cabinet;
the bottom of each kiln cylinder is connected with a cooling fan, and the bottommost part of each kiln cylinder is provided with a discharging mechanism.
The kiln barrel is internally provided with a preheating zone (about in the section 1/3 at the upper part of the barrel), a calcining zone (in the section 1/3 in the middle of the barrel) and a cooling zone (in the section 1/3 at the lower part of the barrel) from top to bottom in sequence. The dolomite raw material is heated in a preheating zone and calcined in a calcining zone, the lower part is a cooling zone, and a calcined dolomite product sinks in the cooling zone; the cooling fan is connected with the cooling area; the four connecting channels are positioned at the bottom of the calcining zone.
The charging pipe is provided with a charging control gate for controlling the charging amount of the dolomite raw material.
And a high-temperature radar level gauge is also arranged in the kiln cylinder for measuring the position of the dolomite raw material.
Dolomite is firstly processed into blocks of 30-90 mm by a crusher and is calcined on a four-hearth shaft kiln, and the four-hearth shaft kiln is characterized in that the dolomite cannot be over-burnt or under-burnt, and the used combustion is natural gas or coal gas. Sieving the calcined product to obtain calcined dolomite, wherein the undersize product is a combined product of aluminum oxide, silicon oxide, calcium oxide and magnesium oxide, the carbon dioxide generated by calcination is dedusted by a deduster arranged at the top of the furnace, and the purified carbon dioxide is stored in a gas storage cabinet and further purified and compressed for industrial drive oil extraction, biogas fertilizer, refrigerant, chemical raw materials and the like.
The specific dolomite calcination method adopting the four-hearth shaft kiln for dolomite calcination comprises the following steps:
s1, crushing and screening the mined dolomite with a crusher, conveying the dolomite with the bulk density of 30-90 mm into an underground receiving bin with a forklift, conveying the dolomite to a storage bin in front of a kiln through an electromagnetic vibrating feeder and a large-inclination-angle belt conveyor to carry out screening through a single-layer vibrating screen, screening out the crushed materials in the dolomite, and conveying the crushed materials with the undersize of less than 30mm into the crushed material bin to be transported.
S2, the qualified dolomite raw material is put into the elevator hopper, the hoist lifts the dolomite to the feeding bin, then the rotary distributor at the bottom of the feeding bin rotates at a certain speed, the discharging thickness is fixed, the discharging weight can be weighed) and evenly arranges the feeding pipes, and the feeding is controlled by the feeding control gate on each kiln feeding pipe.
S3, after preheating, calcining and cooling the dolomite raw material in a four-hearth shaft kiln, unloading the dolomite raw material into a kiln bottom material bin by an unloading mechanism (14) arranged below the kiln, and entering the next procedure; in four kiln barrels of a four-hearth shaft kiln, one kiln barrel is used for blanking, refueling and pressing compressed air, the kiln belongs to a calcining kiln, an exhaust barrel is closed, the other three kiln barrels are used for enabling waste gas to flow through from bottom to top, the kiln belongs to an exhaust kiln, and the exhaust barrel is opened for exhaust at the time.
In the calcining kiln, the airflow flows from top to bottom and is consistent with the descending of the mineral aggregate. The dolomite raw material firstly reaches the preheating stage of the kiln cylinder, the temperature is 300-800 ℃, and the dolomite raw material absorbs the heat radiated in the kiln cylinder at the stage. The preheated dolomite raw material further descends to the calcining stage of the kiln cylinder, the temperature reaches 1200-1350 ℃ in the stage, a large amount of carbon dioxide gas is discharged, and the gas enters other three exhaust kilns through connecting channels. And (3) continuously reducing the calcined dolomite product (CaO and MgO) to a cooling stage, wherein the calcined dolomite temperature reaches 120-150 ℃, conveying the calcined dolomite product from a bin at the bottom of the kiln to a large-inclination-angle belt conveyor by a vibrating feeder, conveying the calcined dolomite product to a dry grinding workshop for ore blending and dry grinding, then blending a reducing agent and a catalyst, and entering a magnesium extraction reduction furnace for extracting magnesium metal after ball pressing.
The four-cylinder shaft kiln calcined dolomite reaches the standard index: the retention time of the dolomite raw material in the four-chamber shaft kiln is 18-20 hours, the burnt loss of the calcined dolomite product is less than or equal to 0.5 percent, and the hydration activity is 25-30 percent;
s4, exhausting gas in the kiln, allowing the carbon dioxide gas flow to rise to meet the dolomite raw material in the kiln barrel, absorbing heat by the dolomite raw material, reducing the temperature to below 300 ℃ when reaching the exhaust barrel, discharging to a dust remover, further purifying, and allowing to enter a carbon dioxide gas storage cabinet.
The invention provides a four-hearth shaft kiln for calcining dolomite and a method for calcining the dolomite, which are novel dolomite calcining equipment. The equipment has the advantages of full utilization of heat, uniform calcination, high calcined dolomite product activity, reasonable occupied area, high space utilization rate, high yield, low investment cost and suitability for large-scale industrial production and application.
Drawings
FIG. 1 is a schematic top view of a four-chamber shaft kiln of the present invention.
FIG. 2 is a schematic sectional view of a four-chamber shaft kiln A-A according to the present invention.
Fig. 3 is a schematic top view of the rotary distributor of the present invention.
In fig. 1 and 2: 1-shaft kiln body; 2-a feeding bin; 3-rotating the distributing device; 4-a feed pipe; 5-a charging control gate; 6-compressed air nozzle; 7-high temperature radar level gauge; 8-an exhaust funnel; 9-a dust remover; 10-carbon dioxide gas holder; 11-a fuel nozzle; 12-upper cover of kiln body; 13-connecting the channels; 14-a discharge mechanism; 15-a cooling fan; 16-a wrought white product; 17-a refractory material; 18-kiln body shell; 19-dolomite raw material.
In fig. 3: 3-1-rotating the distributor housing; 3-2-rotating disc; 3-3-a feed opening; 3-4-scraper; 3-5-a feed inlet; 3-6-rotation axis.
Detailed Description
The specific technical scheme of the invention is described by combining the embodiment.
As shown in fig. 1, 2 and 3, the four-chamber shaft kiln for calcining dolomite comprises a shaft kiln body 1, wherein the shaft kiln body 1 comprises a kiln body shell 18 and an alumina refractory material 17, the shaft kiln body 1 is provided with four kiln cylinders, the four kiln cylinders surround into a circle, and the four kiln cylinders are communicated with each other through connecting channels 13 at the bottom positions of respective calcining zones; a kiln body upper cover 12 and a feeding bin 2 are arranged at the center of the top of the shaft kiln body 1, a rotary distributor 3 is arranged at the bottom of the feeding bin 2, a feed opening 3-3 of the rotary distributor 3 is connected with four feeding pipes 4 at the tops of four kiln cylinders, and the outlet ends of the four feeding pipes 4 are respectively positioned in the four kiln cylinders;
the top of each kiln barrel is also provided with an exhaust barrel 8, a compressed air nozzle 6 and a fuel nozzle 11, the exhaust barrel 8 is connected with a dust remover 9, and pure carbon dioxide gas is compressed and stored in a gas storage cabinet 10 for industrial application;
the bottom of each kiln cylinder is connected with a cooling fan 15, and the bottommost part of each kiln cylinder is provided with a discharging mechanism 14.
A preheating zone and a calcining zone are sequentially arranged in the kiln cylinder from top to bottom, the dolomite raw material 19 is heated in the preheating zone and calcined in the calcining zone, the lower part is a cooling zone, and the calcined dolomite product 16 sinks in the cooling zone; the cooling fan 15 is connected with the cooling area; the connecting channels 13 are located at the bottom of the calcining zone.
The charging pipe 4 is provided with a charging control gate 5.
And a high-temperature radar level gauge 7 is also arranged in the kiln cylinder. The high-temperature radar level gauge is ZYHC-100, and has stable performance and low failure rate. The ZYHC-100 level gauge has an advanced signal processing technology, has a measuring range as high as 70 meters, and is suitable for severe environments with dust and steam at high temperature (300 ℃ and 600 ℃). The device has the characteristics of disassembly and maintenance under pressure, self cleaning, double purging, adjustment of the antenna aiming direction according to the angle of the material, and double cooling systems, and is the best solution for the high-temperature material level at present. The 26G high-frequency radar level gauge antenna emits narrow microwave pulses, and the pulse microwaves are transmitted in space at the speed of light, reflected back on the surface of a measured medium and received by the same antenna. The time interval between the transmission of the pulse microwave and the reception of the microwave is proportional to the distance from the antenna to the surface of the measured medium. The radar level gauge adopts a special related demodulation technology, and can accurately identify the time interval between the transmission of microwaves and the reception of microwaves, so that the distance from the antenna to the surface of a measured medium is further calculated. The distance hl from the top of the cylinder to the material level can be obtained by processing the instrument, the cylinder height H is preset by a user, the cylinder height H is subtracted from hl, so that the material level height H is H-hl, and the instrument directly displays the material level height (H). The system is controlled by a PLC.
The rotary distributor 3 at the bottom of the feed bin 2 is opened according to a starting instruction, an electric switch rotating shaft 3-6 is opened to drive the rotary table 3-2 to rotate, dolomite raw materials are uniformly distributed on the rotary table 3-2 through a feed opening 3-5 on a rotary distributor shell 3-1, the dolomite raw materials 19 respectively enter a feed opening 3-3 through a scraper 3-4, the dolomite raw materials 19 are uniformly added into four kiln cylinders through feed pipes 4, one kiln cylinder supplies heat for calcination, smoke is discharged from the other three kiln cylinders, and the other three kiln cylinders are replaced according to a certain period. In the calcining kiln, fuel and combustion air (primary air) are pressed in by the compressed air nozzle 6 at the upper part of the kiln cylinder, and combustion gas is sprayed into the kiln cylinder through the fuel nozzle 11 and flows downwards in the same direction as the calcined dolomite raw material 19. Meanwhile, cooling air is introduced by bottom cooling fans 15 of the four kiln cylinders. The combustion air and dolomite are calcined in a calcining zone and mixed with cooling air in the lower cooling zone of the kiln drum. The mixed gas enters the other three kiln cylinders through the connecting channel 13 and flows upwards in the opposite direction (opposite to the flow direction of dolomite) to form a preheating zone for preheating the dolomite raw material 19 entering the kiln. The flue gas temperature is reduced while preheating dolomite, the low-temperature waste gas is discharged out of the kiln cylinder through an exhaust cylinder 8, the temperature is not more than 300 ℃, and then the low-temperature waste gas enters a dust remover 9 and is further compressed and stored in a carbon dioxide gas storage cabinet 10. The kiln pressure is released through the action of a hydraulic valve of the exhaust funnel, the position of the flashboard is changed at the same time, the combustion air on the top of the kiln is controlled to be shut down and the gas fuel is controlled to be shut down, the conversion between the calcining chamber and the heat storage chamber is realized, the whole process can be changed in direction every 30-100 min, the flow direction of flue gas and combustion air is reversed, the exhaust funnel in the previous period supplies heat for calcination, and waste gas flows through the calcining funnel in the previous period. The whole four-chamber shaft kiln system is operated by positive pressure.
The production process flow comprises the following steps:
dolomite with the block size of 30-90 mm is transported into an underground receiving bin by a forklift in a dolomite stock yard, transported to a storage bin in front of a kiln through an electromagnetic vibration feeder and a large-inclination-angle belt conveyor to be screened by a single-layer vibrating screen, crushed aggregates in the dolomite are screened, and the crushed aggregates with the size smaller than 30mm below the screen are transported out of the crushed aggregate bin.
Qualified dolomite raw materials 19 are put into the elevator hopper, the hoist engine lifts the dolomite to the feeding bin 2, and then the rotary distributor 3 (the rotary speed of the distributor is certain, the discharging thickness is certain, the discharging weight can be weighed) at the bottom of the feeding bin is uniformly distributed into the kiln top feeding pipe 4, and the feeding is controlled by the feeding control gate 5 on each kiln feeding pipe 4. The dolomite raw material 19 is preheated, calcined and cooled, and is discharged into a kiln bottom bin for storage by a discharging mechanism 14 arranged below the kiln. And (3) conveying the calcined dolomite product 16 from a kiln bottom bin to a large-inclination-angle belt conveyor by a vibrating feeder, conveying the calcined dolomite to a dry grinding workshop for ore blending and dry grinding, then blending a reducing agent and a catalyst, and pressing balls to enter a magnesium extraction reducing furnace to extract metal magnesium. The four-cylinder shaft kiln calcined dolomite reaches the standard index: the retention time of the dolomite raw material 19 in the four-hearth shaft kiln is 18-20 hours, the burnt loss of the calcined dolomite material 16 obtained after calcination is less than or equal to 0.5 percent, and the hydration activity is 25-30 percent.
In the production process, a high-strength electromagnetic iron discharger is designed on the upper part of a feeding belt conveyor for feeding dolomite into a kiln top bin, so that the addition of waste iron in the transportation and transportation process of the dolomite raw materials is prevented, and waste products of calcined dolomite caused by the addition of the waste iron into a kiln are avoided.
An air cannon device is designed outside the four-chamber shaft kiln body, and sufficient compressed air is blown into the kiln body through a compressed air nozzle 6 at regular time, so that the influence of material sticking and nodulation on the inner wall of the kiln body on production is prevented.
Coal gas or natural gas for fuel.
The discharge belt conveyor of the four-chamber shaft kiln adopts a heat-resistant belt conveyor, and the heat-resistant temperature can reach 120 ℃ so as to prevent the belt conveyor from being burnt out when the temperature of a finished product is too high.
Examples
Each shaft kiln with four chambers has the diameter of 6 meters and the height of 15 meters. The yield is 1200 tons/d per day.
The dolomite raw materials enter a charging bin 2 after being screened by an underground feeder, a belt conveyor and a raw material vibrating screen, and then are added into a kiln through a charging pipe 4 by a rotary distributor 3 to be used as a kiln cylinder of a heat storage chamber for heat storage. The four-chamber shaft kiln is provided with four kiln cylinders, and the other kiln cylinder is used for calcining while the three kiln cylinders are used for storing heat in the chambers. Reversing every 30-100 min, releasing kiln pressure through the action of an exhaust barrel hydraulic valve, changing the position of a flashboard, and controlling the shutdown of combustion-supporting air and gas fuel at the top of the kiln to realize the conversion between the calcining kiln and the exhaust kiln. In the calcining chamber, coal gas (or natural gas) is pressed in through a fuel nozzle 11, is fed into the calcining kiln from 66 spray guns, and is mixed with combustion air introduced from the upper part of the kiln for combustion. The flue gas generated by calcination flows to the heat storage chamber through a connecting channel at the bottom of the four-kiln cylinder calcining zone, flows upwards under the action of cooling wind from bottom to top, stores heat of the dolomite raw material 19 which is just added into the exhaust kiln, and enters the flue gas dust remover 9 after the temperature is reduced. The system feeds the exhaust kiln for 3 times in each period, and the system can increase the rotating speed of the dust removal fan to avoid dust raising when the upper cover 12 of the kiln cylinder kiln body is opened every time. And discharging the finished product generated by calcination through the edge of the discharging mechanism, enabling the finished product to enter a kiln bottom product bin, and opening the discharging mechanism during reversing to enable the finished product to enter the finished product bin.
When gas calcined dolomite is used, the gas consumption of each ton of dolomite lump calcined is 700m3On the left and right sides, the yield is calculated by setting the yield of a four-chamber shaft kiln, the calcined dolomite is produced by 1383/0.53 (the amount of stone thrown per day) × 0.46.46/1200 t per day, and the consumed gas flow rate is 1200t × 700m3＝840000m3The reversing time of the four-hearth shaft kiln is 40s, the burnout time is 20s, 98 production periods are carried out every day, the coal gas feeding time is 3600 × 24-98 × (40+20) ═ 80520s every day, and the calculated coal gas flow is 840000 × 3600 ÷ 80520 ═ 37556m3·h－1The four-hearth shaft kiln uses converter gas to calcine dolomite, the air-coal ratio is controlled to be 1.5-1.7, and the combustion-supporting air quantity is controlled to be about 1.5 × 37556-56334 m3·h－1. The retention time of dolomite in a four-chamber shaft kiln is 18-20 hours, the burnt reduction of the calcined dolomite material obtained after calcination is less than or equal to 0.5, and the hydration activity is 25-30%.
Claims (5)
1. A four-chamber shaft kiln for calcining dolomite comprises a shaft kiln body (1), wherein the shaft kiln body (1) comprises a kiln body shell (18) and refractory materials (17), and is characterized in that the shaft kiln body (1) is provided with four kiln cylinders which are enclosed into a circle and are communicated with each other through connecting channels (13) at the bottom positions of respective calcining zones; a feeding bin (2) is arranged at the center of the top of the shaft kiln body (1), a rotary distributor (3) and four feeding pipes (4) are arranged at the bottom of the feeding bin (2), and outlet ends of the four feeding pipes (4) are respectively positioned in four kiln cylinders;
the top of each kiln barrel is also provided with an exhaust barrel (8), a compressed air nozzle (6) and a fuel nozzle (11); the exhaust funnel (8) is sequentially connected with a dust remover (9) and a carbon dioxide gas storage cabinet (10);
the bottom of each kiln cylinder is connected with a cooling fan (15), and the bottommost part of each kiln cylinder is provided with a discharging mechanism (14).
2. The four-hearth shaft kiln for dolomite calcination according to claim 1, wherein the kiln cylinder is provided with a preheating zone, a calcining zone and a cooling zone from top to bottom, wherein the dolomite raw material (19) is heated in the preheating zone and calcined in the calcining zone, the cooling zone is arranged at the bottom, and the calcined dolomite product (16) sinks into the cooling zone; the cooling fan (15) is connected with the cooling area; the connecting channel (13) is positioned at the bottom of the calcining zone.
3. The four-hearth shaft kiln for dolomite calcination according to claim 1, wherein the charging pipe (4) is provided with a charging control damper (5).
4. The four-chamber shaft kiln for dolomite calcination as claimed in claim 1, wherein the kiln cylinder is further provided with a high temperature radar level gauge (7).
5. A dolomite calcination process, characterized by adopting the four-hearth shaft kiln for dolomite calcination as set forth in any one of claims 1 to 4, comprising the steps of:
s1, crushing and screening mined dolomite, screening the dolomite with the block size of 30-90 mm, removing crushed materials in the dolomite, and conveying the crushed materials with the undersize of less than 30mm to a crushing bin;
s2, lifting the qualified dolomite raw material (19) to a feeding bin (2), uniformly distributing the dolomite raw material into a feeding pipe (4) through a rotary distributor (3) at the bottom of the feeding bin (2), and controlling feeding through a feeding control gate (5);
s3, after passing through a preheating zone, a calcining zone and a cooling zone of a four-hearth shaft kiln, discharging the dolomite raw material (19) into a kiln bottom material bin by a discharging mechanism (14) arranged below the kiln, and entering the next procedure;
in four kiln barrels of a four-hearth shaft kiln, one kiln barrel is subjected to blanking, fueling and compressed air pressing, belongs to a calcining kiln, and an exhaust barrel (8) is closed;
the other three kiln cylinders are positioned at the stage of flowing of waste gas from bottom to top and belong to an exhaust kiln, and the exhaust cylinder (8) is opened to exhaust at the time;
in the calcining kiln, airflow flows from top to bottom and is consistent with the descending of mineral aggregate; the dolomite raw material (19) firstly reaches a preheating zone of a kiln cylinder to carry out a preheating stage, the temperature is 300-800 ℃, and the dolomite raw material (19) absorbs heat radiated in the kiln cylinder at the stage; the preheated dolomite raw material (19) further descends to a calcining zone of a kiln cylinder to carry out a calcining stage, the temperature reaches 1200-1350 ℃ in the stage, a large amount of carbon dioxide gas is discharged, and the carbon dioxide gas enters other three exhaust kilns through a connecting channel (13); the calcined dolomite product (16) continuously descends to a cooling area for cooling, the temperature of calcined dolomite reaches 120-150 ℃, and discharging is carried out from a kiln bottom discharging mechanism (14);
the retention time of the dolomite raw material (19) in the four-chamber shaft kiln is 18-20 hours, the burnt loss of the calcined dolomite product (16) is less than or equal to 0.5 percent, and the hydration activity is 25-30 percent;
s4, exhausting gas in the kiln, wherein carbon dioxide gas flow rises to meet dolomite raw materials (19) in the kiln barrel, heat is absorbed by the dolomite raw materials (19), the temperature is reduced to be lower than 300 ℃ when reaching the exhaust barrel (8), the carbon dioxide gas flow is discharged to a dust remover (9), and the carbon dioxide gas flow enters a carbon dioxide gas storage cabinet (10) after further purification.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113233794A (en) * | 2021-06-01 | 2021-08-10 | 山西太钢不锈钢股份有限公司 | Light calcined dolomite and method for reducing calcined powder rate of high-iron aluminum dolomite |
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| CN107324671A (en) * | 2017-06-30 | 2017-11-07 | 上海柯来浦能源科技有限公司 | A kind of pair of bore type lime shaft kiln |
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| CN111302675A (en) * | 2020-04-27 | 2020-06-19 | 垣曲县五龙镁业有限责任公司 | Method and system for calcining dolomite in heat accumulating type energy-saving double-hearth shaft kiln |
| CN212293336U (en) * | 2020-07-21 | 2021-01-05 | 北京欧菲金太科技有限责任公司 | Four-hearth shaft kiln for calcining dolomite |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107324671A (en) * | 2017-06-30 | 2017-11-07 | 上海柯来浦能源科技有限公司 | A kind of pair of bore type lime shaft kiln |
| CN107892493A (en) * | 2017-12-15 | 2018-04-10 | 中冶焦耐(大连)工程技术有限公司 | A kind of electrical heating shaft furnace and based on light calcined magnesia production technology thereon |
| CN111302675A (en) * | 2020-04-27 | 2020-06-19 | 垣曲县五龙镁业有限责任公司 | Method and system for calcining dolomite in heat accumulating type energy-saving double-hearth shaft kiln |
| CN212293336U (en) * | 2020-07-21 | 2021-01-05 | 北京欧菲金太科技有限责任公司 | Four-hearth shaft kiln for calcining dolomite |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113233794A (en) * | 2021-06-01 | 2021-08-10 | 山西太钢不锈钢股份有限公司 | Light calcined dolomite and method for reducing calcined powder rate of high-iron aluminum dolomite |
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