JP2002517607A - Sustained iron production and solid waste minimization by enhanced direct reduction of iron oxide - Google Patents

Abstract

(57) Abstract: A method for treating iron oxide, which comprises heating a composite mass formed from iron oxide and a solid carbonaceous reducing agent on a grate 27 in a furnace 20; Thereby involving the mass forming a moving bed on the grate. The hot gas is passed through the first region 21 of the furnace 20 as the mass passes through the first region 21 to dry and / or preheat the mass of the bed through the grate and mass bed. Oriented (down and / or upward). Cold or preheated air and / or oxidant is directed upwardly through the grate 27 and the preheated mass in the second region 23 of the furnace 20. Reduction of the agglomerate iron oxide is performed in the second region 23 to form a directly reduced iron product, whereby the upwardly directed air and / or oxidant is reduced. Volatile substances including carbon monoxide generated from the lump are effectively burned in the gaps of the bed.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD [0001] The present invention relates generally to iron and steel making, and more particularly to producing an iron product such as steel, steel cast iron, or pig iron in an environmentally advantageous manner. Reduction of iron oxide (DR
The process incorporating I). More favorable environmental performance preferably includes minimizing energy consumption and maximizing the benefits derived from by-product production.

BACKGROUND OF THE INVENTION The prereduction and treatment of untreated or refined iron ore in a range of furnaces, particularly furnaces for producing sponge iron and pig iron to be melted in electric arc furnaces, is diverse. Processes have been proposed. One example is Midrex C
Orporation) has developed a process called Midrex DRI, in which pellets of iron ore concentrate are directly reduced using modified natural gas to produce direct reduced iron, which is then converted to blast furnace and electric Used as a direct feed to a variety of melting furnaces, including arc furnaces. Similarly, the process using pellets is described in Hill III (
Hyl III). In another process, the fine iron ore concentrate is pre-reduced in a fluidized or circulating fluidized bed. In both types of processes, the products are:
It may be transferred directly to the melting furnace, or may be made into a hot briquette that can be transported and stored without oxidation or self-heating.

The Fastmet ™ process developed by Midrex Corporation
For example, "Metallurgical Plant and Technology International", February 1991 (Metallurgical Plant and Technology International 2/1)
991), p. 36, and "Steel Times", 1994, 1
Described on February 91, p. 91, is a DRI process whose product has been proposed as a direct feed to a variety of melting furnaces, including blast furnaces and electric arc furnaces. In this process, composite raw pellets formed from iron ore concentrate, pulverized coal or similar solid reducing agent, and a binder pass through a rotary hearth furnace in a layer one pellet deep. I do.

[0004] This layer is heated mainly by radiation from the hot combustion gases. The average heat transfer coefficient is around 130 kW / m ^{2 of} hearth and a typical production rate is 100 kg / hr · m ² of DRI product for hearth surface area. Therefore, fast-met furnaces are large in relation to most melting furnaces. The metallization rate of the product (expressed as a percentage of the total amount of iron converted to metallic iron) can be varied to suit the end use. The product is either hot briquetted (to obtain hot briquetted iron (HBI)) or transferred to an adjacent steel or steelmaking furnace as a high temperature DRI. According to the references mentioned above, this furnace may be a blast furnace or an electric arc furnace (E
AF), submerged arc furnace (SAF), or energy optimization furnace (E
OF). In a particular development of such an integration, the melting furnace is a submerged arc furnace, followed by an EAF.

[0005] The International Metals Reclamation Company (The International Me
In the Inmetco (TM) process developed by the tals Reclamation Company, the finely divided waste of coal and stainless steel mills is processed into untreated pellets and pre-reduced in a rotary hearth furnace. The product in this furnace is removed as hot DRI pellets and carried into an electric arc furnace via a transfer vessel. This process has many similarities to the FastMet process.

[0006] The SL / RN ™ process developed by Lurgi does not pelletize ore fines and pulverized coal to produce DRI products that are also transferred to a range of melting furnaces. It involves a process of feeding directly to a rotary kiln.

[0007] A more specific variant of the SL / RN process is the WAELTZ kiln. It is used to reprocess high zinc content scraps, in particular these scraps are produced from electric arc furnaces with scrap from galvanized steel products. The iron shavings are filled into the kiln as composite untreated pellets.
While heated from 1000 ° C. to 1250 ° C., the zinc volatilizes and is captured as zinc oxide, which is further processed to produce zinc metal or highly concentrated zinc dust. The iron component in the iron swarf is converted to high iron-containing slag or DRI, which can be further reduced and melted to produce a liquid iron product using a blast furnace and a range of furnaces including BOF. it can.

[0008] Another special variant of the SL / RN process is that of Lurgi and Mannesmann.
Combismelt developed by Mannesmann Demag
It is a process and "SEAISI Quarterly Journal" (SEAISU Quart
erly Journal) October 1986, page 29. This process uses a SL / RN kiln to produce pellets or fine-grained DRIs that are melted in a submerged arc furnace. 80% to 9% for submerged arc furnaces
Either high-temperature DRI or low-temperature DRI with a reduction rate of 0% (oxygen removal rate from iron oxide present in the ore) can be supplied. This is equivalent to a metallization ratio of 70% to 80%. When filling with hot DRI, this DRI is transferred to the submerged-arc furnace by skipping or hopper.

[0009] The Hismelt ™ process uses coal as the primary energy source and reducing agent. This process requires that the melter and pre-reduction tower or circulating fluidized bed configuration be integrated together and the top gas from the smelter vessel against the iron ore descending to fill the pre-reduction unit. Rises. According to this arrangement, the pre-reduction of iron ore from the pre-reduction unit is approximately 30
%, Resulting in relatively low rates of reduction, whereby the melting furnace must be operated with a high energy input. This requires a high degree of post-combustion of the melt (expressed as a percentage of carbon monoxide to burn to carbon dioxide), which requires a large amount of injected air and a highly turbulent environment. At the temperatures required in the gas space of the melting vessel and the melt vessel, serious difficulties can arise with regard to the deterioration of the refractory properties, the slag of which has a higher FeO content compared to blast furnaces or melting furnaces with higher pre-reduction. (Iron monoxide). The high level of FeO in the slag prevents direct processing by grinding large quantities of slag produced to replace cement, and provides both economic and environmental benefits from by-product slag. Will decrease.

In the McDowell-Wellmann process, an approach disclosed in US Pat. No. 2,806,779 was developed, and US Pat.
Further improvements have been made as described in US Pat. Nos. 64092, 3304168 and 3495971. The bed of coal-ore-limestone composite pellets is heated on a moving grate to produce DRI for the melting furnace with a metallization rate of 90%. In this process, hot gas from the combustion hood is 125 to 25
It is guided down through a bed of 0 mm deep pellets. This process involves 3
There are two areas. The first is the drying zone, in which hot gas,
It is guided down through a bed of pellet layers at a temperature of 150 to 300 ° C. for a few minutes. These hot gases are obtained by mixing the recycled hot gases from beneath the adjacent carbonized region with the ambient air. In the carbonized region, the hot combustion gases are drawn through the bed, causing the bed to 980-120.
Heat to about 0 ° C. U.S. Pat. No. 3,264,092 suggests that for this flow any direction is preferred except downward.
Later refinements reverse this flow at the end of the bed to achieve a more uniform treatment.

In general, since the 1970s, it has been important to develop steelmaking processes that are less capital intensive than traditional integrated steelmaking, require no coke, and allow for the direct use of fine iron ore. There was a profit. More recently, some steelmakers have found that steel as a product is environmentally unfavorable because its production consumes more energy and emits greenhouse gases compared to competing materials. It is gradually being recognized.

At present, the most successful low capital cost steel production process uses an electric arc furnace. These are usually known as minimills and are supplied with scrap iron and, increasingly, DRI and HBI from DRI plants. EAF minimills require electricity, scrap, and high quality feed including highly reduced DRI or HBI (typically 87-95% reduction or 87-94% metallization). Has disadvantages. Meanwhile, DRI
And HBI plants require large quantities of low-cost natural gas, a source of energy that is more expensive than coal, and are more flexible because natural gas is not as easy to transport and store as coal. Inferior. This makes it more difficult to improve efficiency through the integration of DRI and steelmaking (particularly hot filling of the EAF). In addition, natural gas has an energy reserve of 10% less than coal. As the proportion of scrap used in electric arc furnaces increases, steel products can contain high levels of harmful residual elements such as copper, arsenic and tin, which are transmitted to the steel products and Detrimentally affects the mechanical properties of steel. To control such contamination,
It is required to dilute the scrap with a sufficient amount of DRI and HBI produced from iron ore. However, the production of DRIs and HBIs is capital intensive, with only slight improvements in energy consumption and overall greenhouse gas emissions for producing steel. The EAF process with high levels of DRI and HBI has the further disadvantage of producing large amounts of slag. This slag is high in FeO content (generally greater than 10%) and, due to the presence of free or undissolved flux, is generally unsuitable for direct treatment by grinding to replace cement. This material is commonly used as a low value road aggregate after prolonged exposure in open air. The use of slag as a cement replacement reduces effective greenhouse gas emissions by 0.8 to 1.2 tonnes of CO2 per tonne of slag.

<< Disclosure of the Invention >> In addressing these problems, the present invention includes two important concepts. (I) A grate-type furnace is used in the drying and preheating area, and high-temperature furnace gas is extracted through the grate. Then, low temperature or preheated air is blown up through the grate in the pre-reduction region to maximize heat transfer along the grate. (Ii) applying a separated layer to the hearth of a grate furnace. In one variation, a separate bed of fuel (e.g., coal, coke, charcoal, or wood chips or chips) is provided at the bottom of the grate, and a coal-ore composite mass, e.g., pellets Is placed on the top layer. Other options include a relatively unreactive layer on the grate and a top layer, such as flux, on the pellet bed.

To apply these concepts effectively, performing pre-reduction in a grate furnace extends the integration between the pre-reduction step and the melting step and provides a relatively high degree of It is recommended to produce at least partly the heat for the pre-reduction step from the sensible heat and combustion of the gas from the melting furnace, while producing the reduced hot material.

Accordingly, in a first aspect, the present invention provides a method for treating iron oxide, comprising the steps of: providing iron oxide and a solid-phase carbonaceous reducing agent on a furnace grate; Heating the composite agglomerate formed from the grate so that the agglomerate forms a moving bed on the grate; and in a first region of the furnace, hot gas is passed through the grate and the bed of the agglomerate. Directing the agglomerates as they pass through a first zone to dry and / or preheat the agglomerates in a second zone of a furnace, through a grate and the preheated agglomerates. Directing the air and / or oxide upwards, reducing the iron oxide of the mass in the second region to form a directly reduced iron product, thereby generating from the mass being reduced Carbon monoxide The non volatile material, effectively combusting the air and / or oxidizing agent is directed to the upward in bed gap.

[0016] Recycled gas or fuel gas discharged from the top of the moving bed may be directed upward through a grate and a preheated mass in a second region of the furnace.

The hot gas is directed in one direction selected from the group consisting of lower, upper, and a combination of lower and upper.

It is preferable that the reduction ratio exceeds 60% (equivalent to a metallization ratio of 65%).

According to one option, to protect the grate from excessive temperatures, a relatively less reactive layer may be provided as an intermediate layer between the bed of mass and the grate. The layer provides a barrier between the grate and the hot bed, improving gas distribution and improving post-treatment product emissions. This layer may include, for example, unburned flux, burned flux, or ore.

Alternatively, and usually preferably, the method comprises providing an intermediate layer of solid carbonaceous fuel disposed between the grate and the pellet moving bed to the mass moving bed. It is to be included. Advantageously, the carbonaceous reducing agent of the mass is then consumed mainly for the reduction of the mass, and
The carbonaceous fuel of the intermediate layer is mainly consumed for the combustion of gaseous substances and volatile components in and below the composite lump bed.

In a second aspect, the present invention provides a method of treating iron oxide, the method comprising: forming a composite agglomerate formed from a solid-phase carbonaceous reducing agent and the iron oxide. Feeding a grate in a furnace along a grate, whereby the mass forms a moving bed through the furnace, and transfers an intermediate layer containing solid carbonaceous fuel to the grate and the mass. Supplying between the mass transfer bed and reducing the iron oxide of the mass so as to obtain a directly reduced iron product at a predetermined reduction rate, wherein the carbonaceous reducing agent of the mass is It is mainly consumed in the reduction of the iron oxide of the agglomerate, and the carbonaceous fuel of the intermediate layer is mainly composed of gaseous substances and volatiles in and below the bed of the composite agglomerate. Consumed for the burning of components.

The agglomerates are preferably composite pellets, but in general the agglomerates may be formed by pelletizing, briquetting, rolling, extrusion or the like.

[0023] The content of the reducing agent in the pellets is preferably about 15 to 30% by weight in the case of water separation. As an option, the pellets may contain a flux.

Suitably, a layer of flux is further provided over the bed of mass. The flux may be unfired (ie, limestone or dolomite) or may be burned (ie, quicklime or burned dolomite). It is believed that this layer has the effect of recovering in situ energy from the hot gas emanating from the top of the pellet bed and also has the effect of absorbing radiant energy from the combustion space above. It is. In the first zone where drying / preheating takes place, a further advantage of this superimposed flux layer is that it moderately relieves hot gases drawn through the bed.

In one particularly advantageous application of the invention, the furnace is a pre-reduction furnace,
The directly reduced iron product is passed to a melting furnace, where the temperature is in the range of 700 to 1300 degrees Celsius, preferably in the range of 800 to 1100 degrees Celsius. Also, the method further includes melting the directly reduced iron product with added oxygen in the melting furnace. This melting forms molten iron containing carbon, slag, and upper gas containing carbon monoxide. Then, the method includes recovering the molten iron from the melting furnace.

The grate furnace is, for example, a travelling type, a rotary type, a tripping type (tr).
ipping) type or fixed type.

Preferably, the heat for the pre-reduction furnace is provided at least in part by combustion of the top gas from the melting furnace using air or oxygen.

Preferably, the gas composition in the pre-reduction furnace minimizes that the reduced pellet is re-oxidized or prevents it from being re-oxidized too much. Has become.

The moisture in the bed in the grate furnace is preferably reduced satisfactorily to control the speed of propagation of the flame tip in the pre-reduction zone or to reduce decrepitation ( decrepitation).

Preferably, off gases from said pre-reduction furnace are recovered in a means for obtaining energy from the off-gas, preferably a waste heat boiler or gas turbine.

Preferably, one or more raw materials for the flux are also passed to the pre-reduction furnace, where they are prepared for melting, and then passed to the melting furnace at an elevated temperature. In one embodiment, the flux comprises raw limestone and / or dolomite, and the step of preparing comprises calcining the limestone and / or dolomite. In certain other embodiments, the flux comprises a baked flux,
The calcined flux was prepared by preliminary calcination at some other plant.

The reduction of the intermediate DRI product is preferably at least 50%, for example 8
A range of 0% to 90% is desirable (corresponding to a metallization of 73% to 86%). By maximizing the degree of pre-reduction, the post-combustion energy requirements required in the melting furnace can be dramatically reduced. In this way, the severe burden, the criticality and the variability of the melting process can be reduced. Also, conventional processes such as "DIOS" and "Hismelt" (Hismel)
A relatively low level of oxygen or air consumption may be required compared to t), or a relatively low level of power consumption if the melting furnace is an oxygen-blown EAF (electric arc furnace). Furthermore, the energy content of the top gas (which is not required to the same extent as supplying heat to the melting furnace for post-combustion treatment) is supplied to the waste heat boiler or gas turbine and the pre-reduction furnace. It can be used for combustion to supply heat. The invention also provides, in a first aspect of the invention, an apparatus for treating iron oxide, the furnace having a traveling or rotating grate, wherein the furnace has a composite mass on the grate. A furnace wherein the pellets formed from the iron oxide and the solid carbonaceous reducing agent can be sent, wherein the mass forms a moving bed on the grate; Directing the grate and the mass bed downward in a first zone of the furnace, thus drying and / or preheating the mass bed as they pass through the first zone Means to cool and preheat air and / or oxidant to the second furnace.
In an upward direction through the grate and the preheated mass, so that the iron oxide contained in those masses is reduced during operation of the furnace to form a direct reduced iron product And thereby, due to the effect of the upwardly directed air and / or oxidizing agent, in the gaps of the bed, volatile constituents (which are evolved from the reducing mass) Means that burns carbon monoxide (containing carbon monoxide).

The present invention also provides, as a preferred application of the first aspect, an integrated apparatus for treating iron oxide to produce an iron product, comprising: A melting furnace having a melting chamber and means for carrying oxygen to the melting chamber; and 700 degrees Celsius for transferring the direct reduced iron product from the pre-reduction furnace to the melting chamber.
Temperature in the range of from 1 to 1400 degrees Celsius, preferably from 800 to 1 degree Celsius.
Means for delivering at a temperature in the range of 100 degrees, wherein the melting furnace may be optionally energized, but with the addition of oxygen, to transfer the direct reduced iron product to the melting chamber. In such a way as to form molten iron containing carbon, slag and a top gas having a carbon monoxide: carbon dioxide ratio of greater than 1.0 on a volume basis. Means for recovering the molten iron from the melting chamber.

Preferably, the integrated device further comprises means for supplying heat for the pre-reduction furnace at least in part from combustion and sensible heat of the top gas from the melting furnace.

Since the iron oxide is supplied to the pre-reduction furnace as a composite mass, for example as pellets, the upper gas of the melting furnace can be used for combustion to supply heat to the pre-reduction furnace, and It is not limited to use as a reducing atmosphere as seen in the prior art process.

The method may include forming the composite mass, for example, pelletizing, briquetting, rolling, or extruding.

[0037] The iron oxide is preferably iron ore concentrate. Alternatively, in another application, the feedstock can be solid waste from steelworks, such as iron oxide containing dust, or dust collected and recycled from the process of the present invention.

[0038] The carbonaceous reducing agent in the solid phase of the pellet is preferably coal or charcoal and / or a biomass material such as wood waste. The carbonaceous fuel of the middle layer may be coal, coke, char, charcoal, petroleum coke, or wood waste or wood or green wastes.

The composite pellets are preferably 15-40% w / w in coal (or equivalent reducing agent), most preferably 20-30% w / w in coal.

The carbon content of the direct reduced iron product is preferably about 5 to 15% w / w. The direct reduced iron product (reduction 80-90%) and, if included, the pretreated flux are preferably passed directly to the melting furnace and the upper gas. The top gas is to be recycled for heating and combustion, it is an integrated facility where the two furnaces are in close proximity to each other, for example bridged by conduit connections or connecting enclosures Is done in Said delivery is typically done in such a way as to feed the reduced iron product directly in the indicated temperature range. Alternatively, the pre-reduced iron product and the pre-treated flux are recovered from the pre-reduction furnace (for operational convenience) and stored, for example in bins. In some cases, it may be transported at a high temperature and then delivered to the melting furnace at a desired time. In this case, some cooling and reheating may be required, but is preferably minimized.

The maximum temperature in the second zone of the mobile grate furnace is preferably 80 degrees Celsius.
Temperatures in the range of 0 to 1300 degrees Celsius, but are typically maintained near 1050 to 1250 degrees Celsius. The required heat is supplied by the combustion and sensible heat of the top gas, and is augmented as needed, for example by a coal or natural gas fueled burner.

The melting furnace may be any suitable furnace equipped with oxygen addition equipment. A variety of conventional furnaces are suitable. For example, oxygen injection type electric arc furnaces (EAF, el
ectric arc furnace, submerged arc furnace (SAF), blast furnace, energy optimized furnace (EOF), basic oxygen steelmaking (BOS) processing vessel, and ROMELT furnace . Of these, those which may be particularly suitable include the EOF style side blown hearth furnace or the ROMELT furnace. The last-mentioned extended configuration of the melting furnace has two problems in terms of components and temperature.
By allowing two melting zones, it would be suitable for the production of liquid steel. Most of the slag is removed from the high C end, ensuring a lower amount of slag iron (<5% FeO). In addition, the melting furnace provides additional reducing agent in bulk and / or
Alternatively, it may be allowed to be added by an injection type.

The molten iron may be steel, cast iron (semi-steel), or pig iron (pig iron).

Preferably, the slag from the melting furnace has a Fe content of 5% in the form of FeO.
Less than 1.5%, and preferably less than 1.5%, measured in the form of FeO, thereby being suitable for being cemented. To this end, in its preferred embodiment, as an integrated steelmaking process, the present invention preferably further comprises recovering and treating or transporting said slag. The processing steps typically required include graining or rapid cooling to ensure a high glass (ie, amorphous) content and then milling. The slag preferably has a Fe content of FeO
Less than 5%, most preferably less than 1.5%, measured in the form Preferably, this is partly due to the carbon content in the bath, the relative intensity of stirring and oxygen blowing between the molten metal phase and the slag phase, and, if necessary, in the slag phase. By controlling the injection of the carbon reducing agent into the

In a preferred embodiment, as an integrated steelmaking process, the method preferably further comprises withdrawing the melt and passing it, preferably, to a further plant nearby.
This plant is for further refining by additionally using oxygen and flux as needed. Preferably, the slag waste of such a further plant is fed back to the melting furnace, which leads to a "zero" generation of solid waste.

Preferably, the overhead gas emissions of such further plants are also fed back to said reduction furnace or waste heat recovery system.

In certain other embodiments, one or more melting furnaces are used, all of which are directly connected to the pre-reduction furnace. Each melting furnace will operate as a two stage cycle. The first stage is loaded with high temperature DRI (direct reduced iron) and carbon content 1
Smelting to form 4.5% liquid metal. Then, the second stage removes the slag from the first stage, and then the liquid metal is refined and decarbonized. This is done by adding flux and injecting oxygen. During this second stage, the pre-reduction furnace continues to produce high temperature DRI, which is transferred to either another melting vessel or some high temperature holding vessel.

Preferably, the apparatus further comprises a gas turbine or a waste boiler for generating power or generating mechanical power using off-gas from the pre-reduction furnace. This is to generate oxygen for the melting furnace and also to caster
It would be possible to supply enough power for all relevant plants up to The hot gas may be supplied directly from the rotary furnace and / or the preheated grate furnace.

<< Exemplary Embodiment >> Hereinafter, the present invention will be further described by way of example only with reference to the accompanying drawings. The drawings are block diagrams of an integrated coal-based iron ore processing plant according to embodiments of both aspects of the invention.

The integrated coal-based iron ore processing plant 10 illustrated in FIG. 1 comprises a preheating and pre-reducing furnace in the form of a tilted, mobile grate furnace 20 having a generally conventional configuration and a side furnace. And a melting furnace provided by a square-blowing hearth furnace 30. The two furnaces are directly connected by a connecting enclosure 25 between the lower discharge end 22 of the furnace 20 and an upper feed port 32 in the center of the melting furnace.

The pellets of the composite type are subjected to iron ore concealment in the pelletizer 40.
ntrate), coal, binder and, optionally, flux from about 15% to 40%, preferably 20% to 30%, coal by product.
%. The pellets are supplied to the furnace 20 along with unrefined flux, such as limestone, and are passed over a movable grate 27 as a bed 28 of pellets. Disposed between the bed and the grate is an intermediate layer 29 of solid carbonaceous fuel.

The furnace 20 has two distinct areas. In the first preheating zone 21, hot furnace gas is passed downward through the pellet bed and grate, as indicated by arrow 50, to preheat the pellets as they traverse zone 21. Is drawn to In the second pre-reduction zone 23, where the temperature of the pellets reaches about 250 ° C., i.e., the point where the coal just begins to volatilize, the iron ore is substantially reduced to form a direct reduced iron (DRI) product. Air 52 is blown upwards through the grate and the bed of pellets. Several individual wind boxes may be used. The reduction rate is about 80 to 90%,
~ Equal to 86%) the carbon content is about 12%. This D at about 1050 ° C
The RI product is discharged from the furnace 20 and dropped into the melting furnace 30 via the connecting enclosure 25. Limestone flux is also calcined in the furnace 20 and sent to the melting furnace.

Here, oxygen is blown in laterally at spaced apart locations 31 on the outer circumference, and DRI is performed in the form of a liquid iron melt or steel cast iron having a carbon content of less than 5% and FeO as FeO. It is dissolved to form a slag having an iron content of less than 5% as measured. Oxygen is blown from the side into the melt. Melting furnace 3
Due to the high rate of pre-reduction of the DRI feed to zero, the amount of oxygen injected is correspondingly reduced and the post-combustion can be controlled to a relatively low 20-30%.
The top gas, including carbon monoxide, is supplied to furnace 20 (eg, at about 1600 ° C.) via connecting enclosure 25. In this furnace the gas is burned with air.
This is to provide some of the heat for maintaining the furnace temperature and to provide additional reducing properties.

In region 21, by pulling the hot gas downward through grate 27,
At the cooler end of the furnace 20, the most efficient heat transfer from the melting furnace off-gas is provided, while also facilitating drying and preheating of the entire bed. In zone 23, the CO generated from the hot pellets in the upper bed and coal volatiles and char in the lower bed is burned by blowing air through the preheated bed. In-situ heating in this position greatly supplements the transfer of radiant and convective heat to the top of the bed by burning the hot gases of the melting furnace in the free space above the bed. This additional (inset) heating helps to maintain control of the temperature and oxygen, fuel and humidity content of the air rising through the grate. This ensures that the different levels of the bed have the appropriate time at a certain temperature to achieve the required reduction rate and the required degree of sintering or agglomeration, as well as reducing agent / fuel consumption and grate. This is for minimizing excessive temperature of the battery. For example, the addition of a small amount of steam or steam is very effective in lowering the temperature of the grate and controlling the firing of coal deposited on the grate.

The average heat absorption by the bed is believed to be significantly higher than radiant and convective heating only to the top of the bed as in the FastMet method described above,
It can reach as ^high as 0 kWh / m ² . This significantly reduces the scale of the process and improves thermal efficiency and greenhouse gas generation by reducing energy loss from the walls.

Additional preheat air may be blown over the bed at low speed and low turbulence. CO
And a region for burning volatile substances is formed directly above the bed. Such a measure also suppresses dust from adhering to the enclosure 25.

An important advantage of the rising gas in region 23 is that the most metallized products in the lower layer at the top of the pellet bed are in contact with less oxidizing gases.

The composition of the bed is such that approximately 20 to 30% by weight of the approximate carbon and water fractionation is added to the pellets in order to satisfy the reduction to the required metallization ratio. The remaining carbon is added directly to the grate as an intermediate layer 29. This allows combustion of the volatiles and gasified char to occur within and below the overlying composite pellet bed 28.

The carbonaceous material remaining on the grate falls into the melting furnace together with the reduced pellets (DRI).

Such properties include the advantages of pellets of coal and ore composites, including increased process strength, reduced process scale, improved process thermal efficiency, and greenhouse effect. This is combined with reducing gas generation and increasing fuel flexibility. (The fuel layer covers a wide range of coal, char,
It can also include dry wood. ) Not all carbon required for reduction and melting furnaces is required in the pellets. This makes it possible to more easily use charcoal, which is difficult to produce strong pellets.

Further, the advantages of this process include: 1. The pellets need not be very strong. This is because the physical environment of a mobile grate is not as demanding as some other types of furnaces. Therefore, there is less decrepitation and less dust, and a smaller amount of binder is required. 2. The coke layer protects the grate from the elevated temperatures of the pellet layer and prevents any slagging reactions that occur in the pellet layer. 3. The fuel layer is a bed that is thicker than, for example, a single thickness layer required in a rotary hearth. Again, this results in a significantly reduced fuel bed travel capacity.

A suitable melting furnace 30 has a diameter of 8 m. The slag is collected and transported to a grinding / grinding plant 50 for conversion to cement clinker. The melt is optionally taken as hot metal or steel cast iron for further refining. Slag waste from such further refining plants is recycled to the melting furnace 30 and exhaust gases are recycled to either the pre-reduction furnace 20 or the waste heat recovery unit 60. Instead, slag waste is used by value-added applications, such as soil conditioners and slow-release fertilizers.

The molten products that can be used from the melting furnace 30 include steel cast iron (2% carbon),
Includes low silicon hot melt (3.5% carbon) or steel (0.1% carbon). However, if a two-zone ROMELT configuration is used or the melting furnace is operated as a two-step process as described above, the latter is preferably manufactured in the best condition.

The invention disclosed and defined herein may cover any combination of two or more, alternatively combined, individual features as set forth in, or apparent from, the description or drawings. Understood. All these different combinations constitute various alternative aspects of the invention.

[Brief description of the drawings]

FIG. 1 is a block diagram of an integrated coal-based iron ore processing plant according to an embodiment of both aspects of the present invention.

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Claims (57)

[Claims] 1. A method for treating iron oxide, comprising heating a composite mass formed from iron oxide and a solid carbonaceous reducing agent on a grate of a furnace, wherein the mass is heated. Forming a moving bed on the grate, and in the first region of the furnace, passing hot gas as the mass passes through the first region through the grate and the bed of mass; Directing for drying and / or preheating, in a second region of the furnace, directing cold or preheated air and / or oxidant upward through the grate and the preheated mass; Reducing the iron oxide of the mass in a region to form a directly reduced iron product, thereby removing volatiles, including carbon monoxide, evolving from the mass being reduced, in the crevice of the bed at the upper Direction Which method comprises to effectively combusted by air and / or oxidant. 2. The method according to claim 1, wherein the reduction ratio of the iron oxide exceeds 60%. 3. The method according to claim 1, further comprising providing an intermediate layer between the mass bed and the grate. 4. The method of claim 3, wherein the intermediate layer comprises unburned flux, burned flux, or ore. 5. The method of claim 3, wherein the mass bed is provided with a solid phase carbonaceous fuel intermediate layer disposed between the grate and the mass bed. . 6. The mass of carbonaceous reducing agent is consumed primarily to reduce the mass, and the carbonaceous fuel of the intermediate layer comprises volatile material under and within the bed of the composite mass. The method according to claim 5, wherein the gas is consumed mainly for burning gaseous substances. 7. The method of any preceding claim, wherein the hot gas is directed in a direction selected from the group consisting of lower, upper, and a combination of lower and upper. 8. Recycled gas or fuel gas discharged from the top of the moving bed is directed in a second region of the furnace upward through a grate and preheated mass to any of the preceding. The method according to the claim. 9. Passing a composite mass formed from iron oxide and a solid carbonaceous reducing agent along a grate of the furnace such that the mass forms a moving bed through the furnace; Providing an intermediate layer of solid phase carbonaceous fuel between the grate and the moving bed of the lump, reducing the iron oxide of the lump to form a directly reduced iron product having a predetermined reduction rate Wherein the carbonaceous reducing agent of the mass is consumed primarily to reduce the iron oxide of the mass, and the carbonaceous fuel of the intermediate layer is volatilized under and inside the bed of the composite mass. A method for treating iron oxide, which is mainly consumed by burning volatile and gaseous substances. 10. The carbonaceous fuel of the intermediate layer is coal, coke, char, charcoal, petroleum coke, or wood, or untreated waste.
The method according to any of the above. 11. A method according to any preceding claim, wherein the solid carbonaceous reducing agent of the pellet is a biomass material such as coal or charcoal and / or woody waste. 12. The method according to any of the preceding claims, wherein the agglomeration is performed by pelletizing, briquetting, rolling, extrusion or the like. 13. The method of any preceding claim, further comprising forming the composite mass by, for example, pelletizing, briquetting, rolling, or extruding. 14. The method of any preceding claim, wherein the agglomerates are composite pellets. 15. The method according to claim 14, wherein the reducing agent component of the pellets is about 15 to about 40 weight percent. 16. The method of claim 15, wherein the reducing agent component of the pellets is about 20 to about 30 weight percent. 17. The method according to claim 14, wherein the pellet contains a flux.
7. The method according to any one of the above items 6. 18. The method of any preceding claim, comprising superimposing a layer of flux on the bed of mass. 19. The method according to claim 17, wherein the flux is unburned. 20. The flux according to claim 17, wherein the flux is combusted.
9. The method according to 8. 21. The method of any preceding claim, wherein the grate furnace is a mobile, rotary, trip, or fixed furnace. 22. Any of the preceding wherein the moisture in the grate furnace bed is sufficiently reduced to control the propagation speed of the flame tip in the pre-reduction zone and substantially prevent decrepitation. The method according to the claim. 23. The method of any preceding claim, wherein the furnace is a pre-reduction furnace. 24. The direct reduced iron product has a temperature of 700 ° C. to 1300 ° C.
24. The method of claim 23, wherein the method is conveyed to a melting furnace at a temperature in the range of: 25. The direct reduced iron product may have a temperature between 800 ° C. and 1100 ° C.
The method according to claim 24, wherein the material is conveyed to a melting furnace at a temperature in the range of: 26. The melting furnace, wherein the directly reduced iron product is melted by adding oxygen in the melting furnace to form an iron melt containing carbon, slag, and an upper gas containing carbon monoxide. 26. The method of claim 24 or 25, further comprising recovering the iron melt from. 27. The method of any of claims 24 to 26, wherein heat for the pre-reduction furnace is provided by burning the top gas from the melting furnace using at least partially air or oxygen. The described method. 28. A method according to any of claims 23 to 27, wherein the composition of the gas in the pre-reduction furnace minimizes or prevents excessive re-oxidation of the reduced pellets. 29. The method according to claim 23, wherein the exhaust gas from the pre-reduction furnace is recovered in a means for generating energy from the exhaust gas. 30. The method according to claim 29, wherein said energy generating means is a waste heat boiler or a gas turbine. 31. A method according to claim 23, wherein one or more flux raw materials are also conveyed to the pre-reduction furnace, where they are prepared for melting and sent hot to the melting furnace. Method. 32. The flux material comprises raw limestone and / or dolomite, and the preparing comprises calcining the limestone and / or dolomite.
The method described in. 33. The method of claim 31, wherein the flux material comprises burned flux, which has been pre-calcined in another plant. 34. The method according to claim 23, further comprising removing the melt, transferring the melt to another plant, and adding as much flux or oxygen as necessary to further refine the melt.
3. The method according to any one of the above 3). 35. The slag waste of such another plant is a solid waste generation “
35. The method of claim 34, wherein feedback is provided to the melting furnace to achieve "zero." 36. The method according to claim 34 or 35, wherein the upper waste gas of such another plant is also fed back to the reduction furnace or the waste heat recovery system. 37. The method of any of the preceding claims, wherein the iron oxide is a concentrate of iron ore. 38. The method according to claim 1, wherein the iron oxide is a steel mill solid waste containing iron oxide dust. 39. A movable or rotary grate, on which a composite mass such as a pellet formed from iron oxide and a solid phase carbonaceous reducing agent can be passed. A furnace wherein said mass forms a moving bed on a grate; and in a first region of the furnace, hot gas is passed through the grate and the mass bed to dry and / or preheat the mass of the bed. Means for directing the agglomerate as it passes through the first zone; and, in a second zone of the furnace, raising the cold or preheated air and / or oxidant through the grate and the preheated agglomerate. During operation of the furnace to reduce the iron oxide in the mass to form a directly reduced iron product, thereby removing volatiles, including carbon monoxide, evolving from the reduced mass. The gap in the bed Apparatus for processing iron oxide and means to effectively burn the air and / or oxidizing agent is directed to the upward in. 40. The recycled gas or fuel gas discharged from the top of the moving bed is directed upward through a grate and a preheated mass in a second region of the furnace. The device according to claim 39. 41. A pre-reduction furnace including the processing apparatus according to claim 39, a melting furnace having a melting tank and means for feeding oxygen to the melting tank, and a directly reduced iron product from the pre-reduction furnace. Conveying to a melting furnace at a temperature in the range of 700 ° C. to 1300 ° C., the melting furnace melting the directly reduced iron product by adding oxygen and, optionally, electric energy into the melting tank. Means operable to form an iron melt containing carbon, slag, and an upper gas having a volume ratio of carbon monoxide to carbon dioxide greater than 1.0; and Means for recovering iron oxides and treating the iron oxides into iron products. 42. The direct reduced iron product may have a temperature between 800 ° C. and 1100 ° C.
42. The apparatus of claim 41, wherein the apparatus is conveyed to the melting vessel at a temperature in the range: 43. Apparatus according to claim 41 or 42, further comprising means for providing heat for the pre-reduction furnace, at least in part by sensible heat and combustion of the top gas from the melting furnace. 44. The apparatus according to claim 40, wherein the iron oxide is a concentrate of iron ore. 45. The apparatus according to any one of claims 40 to 43, wherein the iron oxide is a steel mill solid waste containing iron oxide dust. 46. The composite pellets may comprise between 15 and 40 weight percent (
An apparatus according to any of claims 40 to 45, comprising a% w / w) reducing agent. 47. The composite pellets may comprise 20 to 30 weight percent (
47. The device of claim 46, comprising (% w / w) a reducing agent. 48. The apparatus of claim 40, wherein the carbon content of the directly reduced iron product is about 5 to about 15 weight percent (% w / w). 49. The maximum temperature in the second region of the mobile grate furnace is 80.
49. Apparatus according to any of claims 40 to 48, wherein the apparatus is in the range 0 ° C to 1300 ° C. 50. The maximum temperature in the second region of the mobile grate furnace is 10
50. The device of claim 49, wherein the device is in a range from 50C to 1250C. 51. The apparatus according to claim 41, wherein the iron melt is steel, cast iron (semi-steel), or pig iron. 52. The apparatus of claim 41, wherein the slag from the melting furnace has an iron content of less than 5 percent in FeO. 53. The apparatus of claim 41, wherein the slag from the melting furnace has an iron content of less than 1.5 percent in FeO and is suitable for a cementing process. 54. Recovering the slag and treating or transporting the slag;
54. The apparatus of claim 53, comprising performing a cementing process. 55. The apparatus of claim 41, comprising one or more melting furnaces, all connected directly to said pre-reduction furnace. 56. Each melting furnace operates in a two-stage cycle, the first stage containing 1 to 4.5% carbon by filling and melting the hot, directly reduced iron product. 56. The apparatus according to claim 55, wherein the liquid metal is produced, the slag from the first stage is removed in the second stage, and then the liquid metal is purified and decarbonized by adding flux and injecting oxygen. 57. The apparatus according to claim 40, further comprising a waste heat boiler or a gas turbine that generates electric or mechanical power using exhaust gas from the preliminary reduction furnace.
An apparatus according to any one of the preceding claims.