CN104745757A - Microwave-fuel combined heating-type coal-based direct reduction method and rotary hearth furnace - Google Patents
Microwave-fuel combined heating-type coal-based direct reduction method and rotary hearth furnace Download PDFInfo
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- CN104745757A CN104745757A CN201310740483.4A CN201310740483A CN104745757A CN 104745757 A CN104745757 A CN 104745757A CN 201310740483 A CN201310740483 A CN 201310740483A CN 104745757 A CN104745757 A CN 104745757A
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Abstract
The invention discloses a microwave-fuel combined heating-type coal-based direct reduction method and a rotary hearth furnace. The method comprises the following steps of drying and pre-heating materials, reducing the materials by a fuel combustion method, and further reducing the materials by a microwave radiation method, wherein a reducer for reducing the metal oxide into metal is fixed carbon in the materials. The rotary hearth furnace is used by the above method. The rotary hearth furnace has the advantages of simple structure, low cost, high metallization rate, and realization and popularization easiness.
Description
Technical field
The present invention is mainly concerned with coal-based direct reduction rotary hearth furnace field, refers in particular to a kind ofly to adopt the microwave fuel combined heat formula coal-based direct reduction method of fuel and microwave and the rotary hearth furnace based on the method.
Background technology
Coal-based direct reduction rotary hearth furnace technology take coal as reductive agent, the metal oxide back in ore materials become a kind of method of metal under non-soft heat situation.The method does not rely on coking coal resource, compares traditional Steel Production Flow Chart, can greatly reduce the discharge of pollutent, and its product can replace steel scrap as the raw material of electrosmelting high-quality steel.Therefore, this technique wide market is one of Main way of following smelting iron and steel development.
Direct-reduction produces conventional method gas-based shaft kiln method, coal-based grate kiln method, coal-based rotary hearth furnace method.Gas-based shaft kiln method take Sweet natural gas as reductive agent, if for natural gas source scarcity and expensive area, direct-reduction production cost is too high.In addition this technological investment is excessive, and equipment performance requires higher, promotes and receives extreme influence.Coal-based grate kiln method take coal as reductive agent, have very large magnetism to the area that coal resource enriches, but this technology requires to temperature control precision, very easily ties kiln, operating rate is lower in production higher, cause frequent stopping production, its promotion and application stay cool.Coal-based rotary hearth furnace Direct Reduction Technology, because of advantages such as rotary hearth furnace simple in equipment, maximization difficulty are little, do not tie kiln, maintenance of the equipment is simple, investment is relatively less, is widely used in the industries such as metallurgical and building materials.As Steel Plant are used for heating the rotary heating furnace of steel billet, its structure is close with rotary hearth furnace, just thermal regulation and principle of work difference to some extent.
Based on the above advantage of rotary hearth furnace, recent domestic for rotary hearth furnace process Steel Plant zinc-containing dust, separation of iron, zinc, lead element; Process loess nickel minerals, extracts nickel metal; Process vanadium titano-magnetite, extracts vanadium, titanium valuable metal etc. and conducts extensive research, and achieve some breakthrough progress.Metallurgical boundary unanimously thinks that rotary hearth furnace method is the good method of existing process Steel Plant zinc-containing dust, effectively can be separated iron, zinc, the lead and other elements in dust, solve zinc enrichment well and cause furnace nodulation, shorten the problem of blast furnace campaign, solve the problem that dust stores up a large amount of land occupation, contaminate environment, solve the problem that valuable metal in dust is difficult to recovery and reuse.But still there is the technical problem of the keys such as such as resultant metal rate is low, quality product is uneven in rotary hearth furnace process implementation process, if can capture above problem, its development prospect will be more wide.
As depicted in figs. 1 and 2, the existing rotary hearth furnace vertical view containing cooling section and stretch-out view is respectively; As shown in Figure 3 and Figure 4, the existing rotary hearth furnace vertical view without cooling section and stretch-out view is respectively.This rotary hearth furnace technology adopts burner 1 combustion fuel to heat the material 3 of the carbon containing on siege 2.This conventional direct-reduction rotary hearth furnace forms primarily of the siege 2 rotated and top bonnet 4.Bonnet 4 covers on the siege 2 of rotation, is sealed between bonnet 4 and siege 2 by the mode of liquid sealing or sand seal, flees and heat losses to prevent air-flow inside and outside stove.Siege 2 is divided into cloth section 101, drying and preheating section 102, fuel combustion reduction section 103, cooling section 105(Fig. 1 successively according to its operation function), discharge zone 106.Between cloth section 101 and drying and preheating section 102 and between discharge zone 106 and cooling section 105, and be equipped with sealed wall 7 between cloth section 101 and discharge zone 106.Burner 1 as heating plant is located on the inside and outside side wall of the bonnet 4 being positioned at fuel combustion reduction section 103, burner 1 combustion fuel produces high-temperature flue gas, meet the heat needed for direct reduction reactor temperature, in stove, minimum temperature is 800 DEG C, and top temperature reaches 1300 DEG C or higher.Flue gas stream direction of motion (the traffic direction direction as shown in Fig. 1, Fig. 3 solid line of material 3 and siege 2 contrary to material 3 traffic direction that stove fuel combustion produces; Flue gas stream traffic direction is as Fig. 1, direction shown in dotted lines in Figure 3), finally discharge from the chimney 6 of bonnet top near cloth section side being arranged on drying and preheating section 102.Material 3(is commonly called as green-ball) be laid on equably by material distributing machine 8 on the siege 2 of rotary hearth furnace rotation, after the processes such as super-dry, preheating, reduction, the moisture in material 3, volatile part are removed, and metal oxide back is become metal by the fixed carbon in material 3.The high temperature reduction product obtained discharges rotary hearth furnace (as Fig. 3) by unloading machine 10, or after the cooling section 105 through being covered with water-cooled tube 9 cools (as Fig. 1), discharges rotary hearth furnace by unloading machine 10, enters water cooler 11 or enter mineral hot furnace to carry out adding hot melt and divide.
The subject matter that this conventional direct-reduction rotary hearth furnace exists has:
1) because the heat be laid on needed for the drying of the material 3 rotated on siege 2, preheating, reduction all comes from the radiant heat of the high-temperature flue gas that burner 1 combustion fuel be positioned on the inside and outside side wall of bonnet 4 of fuel combustion reduction section 103 produces, and material 3 has certain thickness, thus top material 3 is heated soon, bottom material 3 heats slowly.Material 3 is thicker, and this thermograde is more obvious.Meanwhile, after only having the temperature of material 3 to reach certain value, reduction reaction just can be carried out by fast and stable.The reason of above two aspects creates the contradiction that the seed output and quality (mainly reduction ratio) of rotary hearth furnace to its product is difficult to take into account, i.e. bed thickness one timing, output and the residence time of material 3 in stove are inversely proportional to, and reduction ratio was directly proportional to the residence time of material 3 in stove.This contradiction causes the series of problems such as investment, running cost, energy consumption, economy, quality product.With regard to existing some rotary hearth furnace production instances put into operation, the counter investment of its unit capacity is comparatively large, and for guaranteeing that the degree of metalization of product meets the requirement of electric arc furnace smelting, significantly need reduce throughput, this is difficult to allow enterprise accept.Just because of this, make numerous enterprises give up the pursuit of high degree of metalization and guarantee certain processing power, cause the resultant metal rate of coming out of the stove lower, its product can only as blast furnace burden, and less than 3 millimeters pulverulent materials can only return and sinter agglomeration again.Add up according to existing production data, the degree of metalization of product is all lower than 70%, and more than 3 millimeters yield rates only have about 50%, and zinc recovery only has 80%.As can be seen here, also obviously there is numerous problem demanding prompt solution in conventional rotary hearth furnace technology, otherwise by danger on the verge of being replaced.
2) another major issue that conventional rotary hearth furnace technology exists, even if allow material 3 stop the sufficiently long time in stove, guarantees that the metal oxide of lower floor's material 3 obtains sufficiently high reduction ratio, but owing to containing a large amount of CO in the flue gas of fuel combustion
2the gas of class oxidizing atmosphere, can be oxidized again by metal as-reduced in top material 3.This is also under existing rotary hearth furnace thermal regulation, the another reason that resultant metal rate is not high.Further investigation finds, conventional heating means are utilized to be difficult to overcome the above problems, if take the back segment of fuel combustion reduction section 103 not lay the measure of burner, to reduce the oxidizing atmosphere in flue gas, then reduction heat absorption and body of heater heat radiation will make furnace temperature decline fast, cause resultant metal rate still cannot improve further.Therefore, there is fatal defect in conventional rotary hearth furnace technology in thermal regulation, cannot realize output, the two high target of degree of metalization.
3) in order to provide enough heat, raising resultant metal rates, often require that traditional rotary hearth furnace reduction section temperature is higher than 1300 DEG C.Siege 2 is in rotation process, and the temperature difference constantly between experience high temperature reduction section and subcooling section is impacted, and causes siege reduced lifetime.
Practitioner is had to propose a kind of direct-reduction rotary hearth furnace adopting full microwave mode, as shown in Figure 5 and Figure 6, it utilizes one or more microwave catheter, microwave radiation 12 is imported furnace chamber from microwave generator, by controlling the strength grade of microwave radiation, make the Fe forms material 3 of carbon containing be heated to moderate moisture and carry out autoreduction, avoid the reduction of phosphorus, sulphur and silicon oxide.But the method has no the report of relevant further investigation and practice at present.By known to the in-depth analysis of which, its subject matter being difficult to put into practice is caused to have:
1) when material 3 is lower than certain temperature, the coupling between microwave radiation 12 and material 3 is more weak, and the radiation heating speed of microwave radiation 12 pairs of metal oxide materials 3 is comparatively slow, and thermo-efficiency is very low.But at high temperature, not only microwave self radiation capacity is strengthened, and can strengthen the activity of metal oxide, accelerates the gasification reaction of fixed carbon, makes the reduction temperature of metal oxide reduce, and rate of reduction is accelerated.Therefore, material 3 is not be all applicable under all temperature conditions adopting carry out microwave radiation heating.Result illustrates that full microwave mode is when furnace temperature is lower, and efficiency is very low, and this will cause products production cost to uprise.
2) the rotary hearth furnace device of full microwave mode heat supply, its cost of investment will exceed tens times of even hundred times than the cost of investment of conventional fuel combustion heat supply rotary hearth furnace device, particularly when current HIGH-POWERED MICROWAVES heating unit price is very expensive, its investment cannot can bear for enterprise.And the life-span of microwave device and maintenance cost can produce great impact to production run and economy, be also that full ripple is slightly difficult to realize industrialized another reason.
3) current full microwave mode is a blank, provide only a conception of species, do not match, can industrialized complete design, all unprecedented any research of technology such as fume emission, controling of the pressure of the oven wherein under a lot of technical problem such as microwave reduction.
Summary of the invention
The technical problem to be solved in the present invention is just: the technical problem existed for prior art, the invention provides that a kind of structure is simple, investment and production cost is low, degree of metalization is high, easy realization and the microwave fuel combined heat formula coal-based direct reduction method applied and the rotary hearth furnace based on the method.
For solving the problems of the technologies described above, the present invention by the following technical solutions:
A kind of microwave fuel combined heat formula coal-based direct reduction method, material enters restore job through super-dry and preheating; First utilize the mode of fuel combustion to reduce to material, then adopt the mode of microwave radiation to reduce further to material; The reductive agent of metal oxide back needed for metal comes from the fixed carbon in material.
Further improvement as the inventive method: when adopting fuel combustion mode to reduce, utilize the heat supply of burner combustion fuel, the high-temperature flue gas of generation heats described material and reduces, and reduction temperature is 900 ~ 1250 DEG C; When adopting microwave radiation mode to reduce, by microwave radiation heat supply, heat and catalytic reduction described material, reduction temperature is 950 ~ 1300 DEG C.
The present invention further provides a kind of microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace, comprise siege and the bonnet of rotation, it is characterized in that, the turning direction along described siege forms cloth section, drying and preheating section, fuel combustion reduction section, microwave radiation reduction section and discharge zone successively; Be provided with burner in described fuel combustion reduction section, in described microwave radiation reduction section be provided with for produce microwave radiation) microwave radiation assembly.
Further improvement as apparatus of the present invention: the side near microwave radiation reduction section in described discharge zone is provided with furnace pressure control device, the reducing gas flow direction of described microwave radiation reduction section is identical with the turning direction of siege, and the reducing gas that described microwave radiation reduction section place produces is discharged from furnace pressure control device.
Further improvement as apparatus of the present invention: be provided with chimney near the side of cloth section in drying and preheating section, the flue gas of described fuel combustion is discharged from chimney.
Further improvement as apparatus of the present invention: be equipped with sealed wall between fuel combustion reduction section and microwave radiation reduction section, between microwave radiation reduction section and discharge zone.
Further improvement as apparatus of the present invention: along the turning direction of described siege, arranges cooling section between microwave radiation reduction section and discharge zone.
Further improvement as apparatus of the present invention: the side near cooling section in described discharge zone is provided with furnace pressure control device, the described reducing gas flow direction stating microwave radiation reduction section is identical with the turning direction of siege, and the reducing gas that described microwave radiation reduction section produces is discharged from furnace pressure control device.
Further improvement as apparatus of the present invention: between described fuel combustion reduction section and microwave radiation reduction section, be equipped with sealed wall between microwave radiation reduction section and cooling section.
Further improvement as apparatus of the present invention: the further improvement as apparatus of the present invention: be provided with chimney in described drying and preheating section near the side of cloth section, the flue gas that fuel combustion produces is discharged from chimney.
Further improvement as apparatus of the present invention: in described drying and preheating section, the material on siege is heated to 600 ~ 900 DEG C by the fume afterheat of gentle fuel combustion more than siege; At described fuel combustion reduction section, by the heat supply of described burner combustion fuel, the high-temperature flue gas of generation heats material and reduces, and reduction temperature is 900 ~ 1250 DEG C; At described microwave radiation reduction section, by microwave radiation heat supply, heat and catalytic reduction described material, heat-processed produces reducing gas, and reduction temperature is 950 ~ 1300 DEG C; The flow of flue gas direction of described fuel combustion is contrary with the rotation direction of siege.
Further improvement as apparatus of the present invention: the length of described microwave radiation reduction section is that corresponding central angle accounts for 10/360 ~ 60/360 of whole rotary hearth furnace one week.
Further improvement as apparatus of the present invention: between described cloth section and discharge zone, between cloth section and drying and preheating section, between discharge zone and microwave radiation reduction section, between discharge zone and cooling section, all sealed wall is set.
Compared with prior art, the invention has the advantages that: microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace of the present invention, structure be simple, investment and production cost is low, degree of metalization is high, easy realization and applying; Rotary hearth furnace of the present invention is when material is in low-temperature condition, adopt burner combustion fuel to carry out heating and reducing, thus avoid and occur the problems such as coupling between microwave radiation and low-temperature material is more weak, microwave radiation is comparatively slow to the radiation heating speed of metal oxide material, thermo-efficiency is very low.Meanwhile, after temperature of charge rising acquires a certain degree, then by microwave radiation, it is heated and catalytic reduction, this enhances the activity of metal oxide, accelerate the gasification reaction speed of fixed carbon, and the reduction temperature of metal oxide is reduced, rate of reduction is accelerated.Final raising whole rotary hearth furnace equipment high-effect in ensure that all the period of time that material runs in rotary hearth furnace, reduce running cost.From another one angle, be the mode of local microwave due to what adopt, so also greatly reduce cost of investment, reduce the difficulty of rotary hearth furnace manufacture assembling, be conducive to realizing industrialization and marketing application.
Accompanying drawing explanation
Fig. 1 is the plan structure schematic diagram containing traditional rotary hearth furnace of cooling section in prior art.
Fig. 2 is the deployed configuration schematic diagram containing traditional rotary hearth furnace of cooling section in prior art.
Fig. 3 is the plan structure schematic diagram without traditional rotary hearth furnace of cooling section in prior art.
Fig. 4 is the deployed configuration schematic diagram without traditional rotary hearth furnace of cooling section in prior art.
Fig. 5 is the plan structure schematic diagram of full microwave mode rotary hearth furnace in prior art.
Fig. 6 is the deployed configuration schematic diagram of full microwave mode rotary hearth furnace in prior art.
Fig. 7 is the plan structure schematic diagram of the present invention without cooling structure multistage heat-supply type rotary hearth furnace.
Fig. 8 is the deployed configuration schematic diagram of the present invention without cooling structure multistage heat-supply type rotary hearth furnace.
Fig. 9 is the plan structure schematic diagram that the present invention contains cooling structure multistage heat-supply type rotary hearth furnace.
Figure 10 is the deployed configuration schematic diagram that the present invention contains cooling structure multistage heat-supply type rotary hearth furnace.
Figure 11 is the iron ore concentrate change in dielectric constant trend schematic diagram along with temperature raises.
Figure 12 is the iron ore concentrate magnetic permeability variation tendency schematic diagram along with temperature raises.
Marginal data:
1, burner; 2, siege; 3, material; 4, bonnet; 5, wheel; 6, chimney; 7, sealed wall; 8, material distributing machine; 9, water-cooled tube; 10, unloading machine; 11, water cooler; 12, microwave radiation; 13, furnace pressure control device; 101, cloth section; 102, drying and preheating section; 103, fuel combustion reduction section; 104, microwave radiation reduction section; 105, cooling section; 106, discharge zone.
Embodiment
Below with reference to Figure of description and specific embodiment, the present invention is described in further detail.
Electromagnetic performance is the internal cause embodying material and microwave coupling ability to function, and the electromagnetic performance of material determines the micro-wave heating characteristic of material, is that can material basic by microwave heating.From the electromagnetic performance of material itself, go to study the ability of absorbed microwave of affect, mainly examine or check because of have material complex permittivity (real part of permittivity ε '
rwith imaginary part ε "
r), because in microwave electromagnetic field, affect the mainly dielectric loss of material warms.But also very large variation can be there is along with the change of the factors such as the change of temperature, thing phase and structure in the electromagnetic performance of material.The result that studies for a long period of time shows (as shown in figure 11), when magnetite concentrate put into microwave field heat time, below 400 DEG C, the real part of permittivity ε ' of magnetite concentrate
rwith imaginary part ε "
rchange is little, and after exceeding this temperature, ε '
rwith ε "
rrapid increase.Known according to formula (1), along with temperature raises, the heat-up rate of material is accelerated, and the functioning efficiency of microwave improves.
ε=ε
0·ε″
eff=ε
0(ε′-jε″) （2）
μ=μ
0·μ″
eff=μ
0(μ′-jμ″) （3）
In formula, f represents frequency (Hz), and ε ' represents real part of permittivity, ε, and " represent imaginary part of dielectric constant, E represents strength of electric field size, and H represents magnitude of field intensity, ε
0permittivity of vacuum, ε "
effeffective dielectric loss factor relatively, μ "
effbe effective magnetic loss factor relatively, ρ is density of material, and C is sample specific heat capacity, q
damageit is the thermosteresis caused due to radiation, convection current and conduction.
As shown in figure 12, when magnetite concentrate put into microwave field heat time, before 550 ~ 600 DEG C, magnetic permeability (the real part μ ' of magnetic permeability
rwith imaginary part μ "
r) change not quite, after 600 DEG C, magnetic permeability is close to null value, and the magnetic of material disappears.For magnetite concentrate material, after temperature is more than 600 DEG C, dielectric loss becomes the major way that microwave heating heats up.
Based on above theory, a kind of microwave fuel combined heat formula coal-based direct reduction method of the present invention, step is: material enters restore job through super-dry and preheating, the mode of fuel combustion is first utilized to reduce to material, then adopt the mode of microwave radiation to carry out the reduction of a step to material, finally utilize the fixed carbon in material that metal oxide back is become metal.
In embody rule example, when adopting fuel combustion mode to reduce, utilize the heat supply of burner combustion fuel, the high-temperature flue gas of generation heats material and reduces, and reduction temperature is 900 ~ 1250 DEG C; When adopting microwave radiation mode to reduce, by microwave radiation heat supply, heat and catalytic reduction described material, reduction temperature is 950 ~ 1300 DEG C.
Further, as shown in Figure 7 and Figure 8, the present invention proposes a kind of microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace, siege 2 rotates clockwise direction (in Fig. 7 solid arrow direction) or turning direction (in Fig. 8 solid arrow direction) from left to right in Fig. 8 in Fig. 7, successively by cloth section 101, drying and preheating section 102, fuel combustion reduction section 103, microwave radiation reduction section 104, discharge zone 106 forms, burner 1 is provided with in fuel combustion reduction section 103, burner 1 is installed in the bonnet 4 in corresponding region, on outer side wall, the microwave radiation assembly for producing microwave radiation 12 is provided with in microwave radiation reduction section 104 place, in other words, the whole reduction section of rotary hearth furnace forms by two sections, the heat-supplying mode of every section is different, in the side near drying and preheating section 102 by the heat supply of burner 1 combustion fuel, in microwave radiation 12 heat supply that the side near discharge zone 106 is produced by microwave radiation assembly, microwave radiation 12 also has the effect of catalytic reduction simultaneously.
In the present embodiment, material distributing machine 8 is provided with in cloth section 101, green-ball is commonly called as containing the fixed carbon particulate matter of charcoal (namely containing) and the material 3(of metal oxide (i.e. the particulate matter of containing metal oxide) after mixed pelletizing) be evenly laid on the siege 2 of rotary hearth furnace by material distributing machine 8, rotate clockwise (as Fig. 7 solid arrow direction) or rotation (as Fig. 8 solid arrow direction) from left to right with the siege 2 driven by wheel 5.Material 3 enters drying and preheating section 102, is heated to 600 ~ 900 DEG C by the fume afterheat of the gentle fuel combustion of siege more than 2, and moisture, volatile part are progressively removed.Enter fuel combustion reduction section 103, adopt traditional combustion fuel mode heat supply, heat and reduce to material 3 by burner 1, under the reduction temperature condition of about 900 ~ 1250 DEG C, the fixed carbon in material 3 starts gasification and metal oxide back is become metal.Enter microwave radiation reduction section 104, microwave radiation 12 heat supply produced by microwave radiation assembly, the metal oxide in material 3 is all reduced, and reduction temperature is 950 ~ 1300 DEG C.Under this reduction temperature condition, not only the radiation heating ability of microwave self strengthens, and the activity of metal oxide in material 3 in microwave radiation 12 scope can be strengthened, accelerate the gasification reaction speed of fixed carbon in material 3, and the reduction temperature of metal oxide is reduced, rate of reduction is accelerated, and makes microwave radiation 12 have the effect of catalytic reduction.After material 3 goes through fuel combustion reduction section 103 and microwave radiation reduction section 104, degree of metalization is up to more than 92%.Material 3 after reduction finally discharges rotary hearth furnace by the unloading machine 10 of discharge zone 106, enters water cooler 11 or enter mineral hot furnace to carry out adding hot melt and divide.
By adopting said structure of the present invention, when material 3 is in low-temperature condition, the heat-supplying mode of burner 1 combustion fuel is adopted to carry out heating and reducing, thus the problem that phenomenon produces such as the coupling radiation heating speed that is more weak, microwave radiation 12 pairs of metal oxide materials 3 under cryogenic between microwave radiation 12 and material 3 of avoiding is comparatively slow, thermo-efficiency is very low.Material 3 enters fuel combustion reduction section 103, and temperature raises further, partial fixing carbon gasification, produces reduction reaction, then enters microwave radiation reduction section 104, then continues heating and catalytic reduction by microwave radiation 12 to it.This not only increases the activity of metal oxide, accelerates the gasification reaction speed of fixed carbon, and the reduction temperature of metal oxide is reduced, and rate of reduction is accelerated.Finally ensure that the high-effect of whole rotary hearth furnace equipment in all the period of time that material 3 runs in rotary hearth furnace, reduce the running cost of rotary hearth furnace.From another one angle, due to adopt be local microwave mode, so also greatly reduce cost of investment, reduce manufacture assembling difficulty, the needs of marketing can be met.
In the present embodiment, the length of microwave radiation reduction section 104 need be determined according to the different qualities of material 3, and be generally that corresponding central angle accounts for whole rotary hearth furnace one week 10/360 ~ 60/360, this is the prioritization scheme obtained by experiment.
In another embodiment, as shown in Figure 9 and Figure 10, can also further along the turning direction of siege 2, cooling section 105 is set between microwave radiation reduction section 104 and discharge zone 106, complete the material 3 after microwave radiation reduction after cooling section 105 cooling being equipped with water-cooled tube 9, finally discharge rotary hearth furnace by unloading machine 10, enter water cooler 11 or enter mineral hot furnace and carry out adding hot melt and divide.Water-cooled tube 9 is laid in the bonnet 4 corresponding to cooling section 105.
In the present embodiment, further except being provided with sealed wall 7 in cloth section 101 rear end and discharge zone 106 front end, the effect of sealed wall 7 herein prevents the flue gas at cloth section 101 place from running helter-skelter to discharge zone 106, allows atmosphere and temperature between cloth section 101 and discharge zone 106 not interfere with each other as far as possible.Outside, and in microwave radiation reduction section 104 front and back end, namely between fuel combustion reduction section 103 and microwave radiation reduction section 104, between microwave radiation reduction section 104 and cooling section 105 (during without cooling section 105, for between microwave radiation reduction section 104 and discharge zone 106) be equipped with sealed wall 7, to prevent air or oxidizing gas from entering microwave radiation reduction section 104, reoxidizing of reducing metal is avoided to leak with microwave.The object preventing microwave from leaking has two: the first to be allow microwave action at microwave radiation reduction section 104 as far as possible, improves micro-wave energy utilising efficiency; Second is after preventing microwave leakage to fuel combustion section, continues to leak into (because fuel combustion reduction section 103 is communicated with chimney 6 and cloth section 101) stove from chimney 6 and cloth section 101, causes safety problem.
In the present embodiment, chimney 6 is provided with in the front end of drying and preheating section 102, the high-temperature flue gas that fuel combustion reduction section 103 produces flows to contrary with the direction that siege 2 rotates, as the dotted arrow direction in Fig. 7, Fig. 8, Fig. 9, Figure 10 corresponding to fuel combustion reduction section 103, after drying preheating section 102, discharge from chimney 6.The high-temperature flue gas that fuel combustion reduction section 103 produces and material 3 counter current contact of rotating with siege 2, heated material 3, make its top layer fixed carbon gasify and make metal oxide back, then continue material 3 counter current contact with drying and preheating section 102, moisture, volatile part are progressively removed.
In the present embodiment, further between cooling section 105 rear end and unloading machine 10 (when without cooling section 105, for between microwave radiation reduction section 104 rear end and unloading machine 10) be provided with furnace pressure control device 13, the reductibility high-temperature gas that microwave radiation reduction section 104 produces flows to identical with the direction that siege 2 rotates, as the dotted arrow direction in Fig. 7, Fig. 8, Fig. 9, Figure 10 corresponding to fuel combustion reduction section 103, through cooling section 105((when there being cooling section 105), after discharge zone 106, from the top discharge of furnace pressure control device 13.The Main Function of furnace pressure control device 13 is reductibility and the reduction reaction speed of guaranteeing atmosphere in microwave radiation reduction section 104.
Remain micro-vacuum state in rotary hearth furnace, prevent from, because of after sealing problem reveals, causing the reducing gas in stove (belonging to inflammable gas) to leak, producing inflammable and explosive safety issue.
One of effect of microwave radiation reduction section 104 reoxidizing reducing metal that be the oxidizing atmosphere of avoiding combustion fuel to produce.When rotary hearth furnace normally works, the gaseous tension in bonnet 4 is micro-vacuum state.By furnace pressure control device 13 provided by the invention, make the gaseous tension absolute value of rotary hearth furnace microwave radiation reduction section 104 a little more than the gaseous tension of the fuel combustion reduction section 103 be adjacent, discharge zone 106 or cooling section 105, prevent the gas of the flue gas of fuel combustion reduction section 103 and discharge zone 106 or cooling section 105 from entering, ensure the reductibility of atmosphere in microwave radiation reduction section 104.In addition, the Direct Reduction of material 3 in rotary hearth furnace reacts (1) by indirect reduction and gasification reaction (2) forms jointly, and reductive agent derives from fixed carbon.The speed of Direct Reduction controls by gasification reaction (2), gasification reaction (2) is an increase-volume reaction, if furnace pressure raises, then the speed that reaction formula (2) carries out to the right declines, CO dividing potential drop in balance gas phase is reduced, and then the speed causing reaction formula (1) to carry out to the right decline.Therefore, make the gaseous tension absolute value of rotary hearth furnace microwave radiation reduction section 104 a little more than the gaseous tension of the fuel combustion reduction section 103 be adjacent, discharge zone 106 or cooling section 105 by furnace pressure control device 13, both can ensure that reacting the gas produced flowed to the rear outer row of furnace pressure control device 13 smoothly, the reduction potential of atmosphere in rotary hearth furnace can be ensured again, also can ensure the speed of whole reduction reaction.
Me
xO
y+yCO=xMe+yCO
2（1）
xC+xCO
2=2xCO （2）
In whole rotary hearth furnace device operation process, the flow of flue gas direction that fuel combustion reduction section 103 produces and material 3 the rotation direction reverse direction of fuel combustion reduction section 103 place respective dashed (in Fig. 7, the Fig. 9), after drying preheating section 102 preheating material 3, discharge from chimney 6.Under the effect of furnace pressure control device 13, the gaseous tension absolute value of microwave radiation reduction section 104 is in a little more than adjacent fuel combustion reduction section 103, when discharge zone 106(is without cooling section 105) or the pressure state of cooling section 105, the gas that microwave radiation reduction section 104 produces is under the effect of furnace pressure control device 13, major part gas flow direction and material 3 rotation direction (Fig. 7 in the same way, direction shown in microwave radiation reduction section 104 place dotted line in Fig. 9), from the top discharge of furnace pressure control device 13, a small amount of gas can enter fuel combustion reduction section 103, discharged by chimney 6 in the lump.
Below be only the preferred embodiment of the present invention, protection scope of the present invention be not only confined to above-described embodiment, all technical schemes belonged under thinking of the present invention all belong to protection scope of the present invention.It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention, should be considered as protection scope of the present invention.
Claims (13)
1. a microwave fuel combined heat formula coal-based direct reduction method, is characterized in that, material (3) enters restore job through super-dry and preheating; First utilize the mode of fuel combustion to reduce to material (3), then adopt the mode of microwave radiation to reduce further to material (3); The reductive agent of metal oxide back needed for metal comes from the fixed carbon in material (3).
2. microwave fuel combined heat formula coal-based direct reduction method according to claim 1, it is characterized in that, when adopting fuel combustion mode to reduce, utilize burner (1) combustion fuel heat supply, the high-temperature flue gas produced heats described material (3) and reduces, and reduction temperature is 900 ~ 1250 DEG C; When adopting microwave radiation mode to reduce, by microwave radiation heat supply, heat and catalytic reduction described material (3), reduction temperature is 950 ~ 1300 DEG C.
3. a microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace, comprise siege (2) and the bonnet (4) of rotation, it is characterized in that, the turning direction along described siege (2) forms cloth section (101), drying and preheating section (102), fuel combustion reduction section (103), microwave radiation reduction section (104) and discharge zone (106) successively; Being provided with burner (1) in described fuel combustion reduction section (103), being provided with the microwave radiation assembly for producing microwave radiation (12) in described microwave radiation reduction section (104).
4. microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace according to claim 3, it is characterized in that, side near microwave radiation reduction section (104) in described discharge zone (106) is provided with furnace pressure control device (13), the reducing gas flow direction of described microwave radiation reduction section (104) is identical with the turning direction of siege (2), and the reducing gas that described microwave radiation reduction section (104) place produces is discharged from furnace pressure control device (13).
5. microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace according to claim 4, it is characterized in that, be provided with chimney (6) in drying and preheating section (102) near the side of cloth section (101), the flue gas of described fuel combustion is discharged from chimney (6).
6. microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace according to claim 3, it is characterized in that, between fuel combustion reduction section (103) and microwave radiation reduction section (104), between microwave radiation reduction section (104) and discharge zone (106), be equipped with sealed wall (7).
7. microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace according to claim 3, is characterized in that, along the turning direction of described siege (2), arrange cooling section (105) between microwave radiation reduction section (104) and discharge zone (106).
8. microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace according to claim 7, it is characterized in that, side near cooling section (105) in described discharge zone (106) is provided with furnace pressure control device (13), the described reducing gas flow direction stating microwave radiation reduction section (104) is identical with the turning direction of siege (2), and the reducing gas that described microwave radiation reduction section (104) produces is discharged from furnace pressure control device (13).
9. microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace according to claim 7, it is characterized in that, between described fuel combustion reduction section (103) and microwave radiation reduction section (104), between microwave radiation reduction section (104) and cooling section (105), be equipped with sealed wall (7).
10. microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace according to claim 7, it is characterized in that, be provided with chimney (6) described drying and preheating section (102) near the side of cloth section (101), the flue gas that fuel combustion produces is discharged from chimney (6).
11. according to the microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace in claim 3 ~ 10 described in any one, it is characterized in that, described drying and preheating section (102), the material (3) on siege (2) is heated to 600 ~ 900 DEG C by the fume afterheat of the remaining gentle fuel combustion of siege (2); Described fuel combustion reduction section (103), by described burner (1) combustion fuel heat supply, the high-temperature flue gas of generation heats material (3) and reduces, and reduction temperature is 900 ~ 1250 DEG C; Described microwave radiation reduction section (104), by microwave radiation (12) heat supply, heat and catalytic reduction described material (3), heat-processed produces reducing gas, and reduction temperature is 950 ~ 1300 DEG C; The flow of flue gas direction of described fuel combustion is contrary with the rotation direction of siege (2).
12. according to the microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace in claim 3 ~ 10 described in any one, it is characterized in that, the length of described microwave radiation reduction section (104) is that corresponding central angle accounts for 10/360 ~ 60/360 of whole rotary hearth furnace one week.
13. according to the microwave fuel combined heat formula coal-based direct reduction rotary hearth furnace in claim 3 ~ 10 described in any one, it is characterized in that, between described cloth section (101) and discharge zone (106), between cloth section (101) and drying and preheating section (102), between discharge zone (106) and microwave radiation reduction section (104), between discharge zone (106) and cooling section (105), sealed wall (7) is all set.
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