KR20000011107A - Process for the treatment of particulate matter by fluidisation, and vessel with apparatus to carry out the treatment - Google Patents

Abstract

PURPOSE: A process and a vessel for reduction treating particulate matters by fluidisation is required not to generate sticking or fouling and to minimize the consumption of reduction treatment gas. CONSTITUTION: Particulate matter containing iron oxide, with a wide ranging grain size distribution and a relative large content of fines, preferably with a size being 50-150 micrometer of that of the largest particle, is used in the treatment. The empty pipe flow rate of the reducing gas in the fluidised bed(2) is kept smaller than, for example 0.25-0.75 Vmin/Dmax of the flow rate required for the fluidising of the larger particles of the particulate matter, the particulate matter is held and treated in a fluidised bed (2) with the reducing gas flowing from the bottom to the top, and all the larger particles thereof move to the top with the particulate and are released from the upper part of the fluidised bed (2). The vessel comprises a cylinder-type fluidized bed section (3) for supplying and distributing a reducing gas; a corn-type upper section (9) where the empty pipe flow rate of the reducing gas is decreased homogeneously and continuously; and a calming section (15). A cyclone (21) for separating dust is placed in a cylinder-type section of the calming section (15), a recycling pipe of dust (22) from the cyclone (21) comes down vertically to be connected into the fluidized bed (2), and a gas releasing pipe (23) of the cyclone (21) is connected into a space (24) placed between a ceiling (16) and a ceiling of the vessel (17).

Description

Reduction method of particulate matter by fluidization and reduction furnace with device for same

Methods of this kind are known, for example, from US Pat. No. 2,909,423, WO 92/02458 and EP-A-0 571 358. In this method, iron oxide-containing materials, such as spectroscopy, are maintained by the reducing gas inside the fluidized-bed reduction reactor which is fed into the fluidized-bed reduction reactor via a nozzle grate while penetrating the reduction reactor from the lower side to the upper side. While the iron oxide-containing material is charged to the reduction reactor with reducing gas flow and approximately countercurrent. To maintain the fluidized bed, a specific velocity of reducing gas inside the fluidized bed is required, which is a function of the charge particle diameter.

In the known method, since the velocity of the reducing gas is relatively high, not only the fine particles of the iron oxide-containing material are discharged considerably but also the already reduced iron oxide-containing material is discharged from the fluidized bed in the preliminary stage of the reduction process, and the fine particles are then discharged. It is contained in reducing gas. In order to remove the particulates from the reducing gas, ie using partially oxidized reducing gas, for example further use for a previously arranged reduction reactor, or of iron oxide-containing or already reduced materials that may be lost. Recoverable-The reducing gas containing particulates is passed through a dust separator, such as a cyclone, and the separated dust is recycled into the fluidized bed. The dust separator or cyclone is preferably arranged inside the reactor, respectively (see US-A-2,909,423), but may also be installed outside the reactor.

The present invention relates to a process for treating particulate matter by a fluidized bed method, preferably to reducing, in particular, to reducing spectroscopy, and to a reducing furnace for carrying out the method, wherein the particulate matter is fluidized by a reducing gas flowing from the lower side to the upper side. Is maintained at and processed.

1 is a cross-sectional view of a reduction furnace according to the present invention,

Figure 2 is a process chart for reducing iron ore that can be used in accordance with the present invention,

3 is a diagram showing several particle size distributions of iron ore fines to be treated according to the present invention.

Indeed, it is evident that the partially reduced or completely reduced particulate iron oxide-containing material tends to stick or solidify to each other and / or to the walls of the reactor or cyclone and to the connecting or conveying tubes. This phenomenon is called "sticking" or "fouling". Sticking or fouling is a function of the reduction temperature and the degree of reduction of the iron oxide containing material. Partially or completely reduced iron oxide-containing material that adheres or adheres to the walls of the reduction reactor or to other parts of the plant may cause failures, making it impossible to operate the plant for a long time without interrupting operation. . I found it almost impossible to keep it running for more than a year.

The removal of deposits or coagulants requires a considerable amount of work, which entails a large amount of costs, ie workers' wages and costs resulting from loss of equipment production. Often, these deposits spontaneously fall, resulting in deposits that fall into the fluidized bed, disrupting the reduction process, or-if the deposits fall from the cyclone-blocking the dust recirculation channel from the cyclone to the fluidized bed to remove dust from the reducing gas. Further separation is completely impossible.

Indeed, one drawback in the known fluidized bed process lies in the separation and supply of the reducing gas stream, i.e. the need and difficulty of separating and feeding the reducing gas stream in the aforementioned prior art processes. Another drawback in the prior art is that in each process step, ie preheating, pre-reduction and final reduction, in most cases two or more product flows leaving the device placed in the process step must be slused, thereby transferring and There is a significant cost to the slurry means. In addition, two gas supply systems have to be adjusted for each process step, which is actually very difficult for hot dust containing gases.

In addition, since the reducing gas flows at a relatively high speed, a large amount of reducing gas is consumed. Significantly more reducing gas is consumed to maintain the fluidized bed than is necessary for the reduction process itself.

The process of reducing metal ores by the fluidized bed method is also known from GB-A-1 101 199. In this patent, by selecting the process conditions such that the materials coagulate together during the reduction process, due to the size of the material, uncured lumps are formed. Thus, the completely reduced material discharged downward from the fluidized bed reactor can be separated from the completely unreduced material remaining in the fluid state. Smaller product particles are recovered at the top of the fluidized bed. Therefore, it is inevitable that there will be two product flows in this process as well, and the apparatus will be expensive.

It is an object of the present invention to avoid these disadvantages and difficulties, and to process the particulate iron oxide-containing material by treating a minimum amount of reducing gas over a period of time without risk of failure due to sticking or fouling. And a vessel for carrying out the method. In particular, both the amount of reducing gas required to maintain the fluidized bed and the flow rate of the reducing gas can be reduced, so that only a minimum amount of fine particles is discharged.

According to the present invention, the object is that the fine particles having a wide particle distribution including a relatively large amount of fine particles and a large portion of the particles are used in the reduction treatment, the surface velocity of the reducing gas in the fluidized bed is a particle It is achieved that it is kept below the speed necessary for the large part of the fluidization, and that larger particles move all up with the particulates and exit from the top region of the fluidized bed.

Even in the case of having a wide particle distribution, the surface velocity of the fluidized bed is maintained within the range of 0.25 to 0.75 of the velocity required for the fluidization of the largest particles in the particulate matter.

It is preferable to use the particulate material of the particle whose particle band has the median particle diameter of 0.02-0.15, preferably 0.05-0.10 of the largest particle diameter among the said particulate matter.

The surface velocity for the reducing gas on the fluidized bed is suitably adjusted to a cut diameter of 50 to 150 μm, preferably 60 to 100 μm, theoretically for the largest diameter of the reduction furnace arranged to receive the fluidized bed. It is preferable that the speed is adjusted in the range of 0.3 m / s to 2.0 m / s to reduce the run of mine spectroscopy.

In a method for directly reducing particulate iron oxide-containing material by the fluidized bed method according to the method disclosed in the present invention, the reformed gas is mixed with the top gas formed in the direct reduction of the iron oxide-containing material as a reducing gas in the fluidized bed reduction zone. Supplied, both saw gas and reformed gas are subjected to CO ₂ scrubbing and the reducing gas formed from the mixture of saw gas and reformed gas is adjusted to a specific H ₂ and CO content.

The reduction furnace for carrying out the process according to the invention is characterized in that the following features are combined.

A cylindrical lower fluidized bed portion for accommodating a fluidized bed and including a gas distribution bottom layer, a reducing gas supply pipe, and a particulate material supply means and a discharge means disposed on the gas distribution bottom layer,

A cone-shaped portion arranged subsequent to the fluidized bed above the fluidized bed portion and widening upwardly in a conical shape, the wall of the cone-shaped portion is inclined at 6 to 15 degrees, preferably 8 to 10 degrees with respect to the central axis of the reactor,

A conical section, closed at the top, and comprising a at least partially cylindrical calming section through which the reducing gas discharge pipe is branched,

The ratio of the cross-sectional area of the cylindrical zone stop to the cross-sectional area of the fluidized bed is ≧ 2.

Reduction furnaces comprising two cylindrical portions of different diameters and very short and distinct cone-shaped portions disposed between the cylindrical portions, carrying out the ore reduction method in a fluidized bed, are known, for example, from EP-A-0 022 098. . However, in this reduction furnace, two gas supply pipes, one under the lower cylindrical part and one conical part are disposed. Fully reduced ore is discharged downwards from this fluidized bed reactor.

Preferably, in the present invention, the cross-sectional area of the stop space in the cylindrical region is large enough for the surface velocity to be adjusted in this region so that particles having a particle diameter of about 50 μm or more can be sufficiently separated from the gas.

The apparatus for directly reducing particulate iron oxide-containing material by the fluidized bed method comprises at least one fluidized bed reactor for accommodating iron oxide-containing material, the reducing gas supply pipe and the reduction gas supply pipe communicating with the fluidized bed reactor. A saw gas discharge pipe discharged from the fluidized bed reactor, the reformer, a reformed gas pipe branched from the reformer and merged with the saw gas discharge pipe, and a CO ₂ scrubber, and the reducing gas formed of the reformed gas and the saw gas is reduced. The gas supply pipe enters the fluidized bed reactor, and both the reformed gas pipe and the top gas discharge pipe are passed through the CO ₂ scrubber and the reducing gas supply pipe is passed through the CO ₂ scrubber to the fluidized bed reactor.

Next, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a view showing a fluidized bed reactor, in particular a reduced reactor 1 composed of a reduction reactor, in which a gas distribution lowermost layer accommodating a fluidized bed 2 and composed of nozzle grate 4 is disposed at a predetermined height level to reduce gas. It comprises a lower fluidized bed portion 3 for supplying and evenly distributing. The reducing gas starts from the nozzle grate 4 and passes through the reduction reactor from the lower side to the upper side. Above the nozzle grate 4 in the cylindrical fluidized bed part 3, the transfer pipes 5 and 6, that is, the spectroscopy supply pipe and the discharge pipe, are disposed. The fluidized bed 2 represents the bed height 7 from the nozzle grate 4 to the level of the spectroscopic discharge pipe 6, ie the opening 8.

The cylindrical fluidized bed portion 3 is connected with a cone-shaped portion 9 which flares upward, and the inclination with respect to the central axis 11 of the reaction path of the wall 10 of the cone-shaped portion 9 is at most 6-15. °, Preferably it is 8-10 degrees. In this region, the cross section 12 of the cone 9 continues to increase so that the surface velocity of the reducing gas flowing upwards steadily and continuously decreases.

Since the wall 10 of the cone portion 9 is only slightly inclined, even when the cross section 12 is enlarged, turbulence and unseparable flow from the wall 10 can be obtained in the cone portion 9. have. This prevents turbulence that can locally increase the rate of reducing gas. Thus, the surface velocity of the reducing gas over the cross section 12 is uniformly and reliably reduced throughout the entire height of the cone 9, ie at all levels of the cone.

At the upper end 13 of the cone 9, a cylindrical wall 14 is disposed, the upper end of which is closed by a ceiling 16 which is leveled (or partially spherical in shape) ( calming section 15 is connected. A reducing gas discharge opening 18 is arranged in the center of the reactor ceiling 17 arranged above the ceiling 16. The cross-sectional area of the cone 9 is designed so that the ratio of the cross-sectional area 19 of the stop 15 to the cross-sectional area 20 of the fluidized bed 3 is ≧ 2.

Inside the reduction reactor 1, a cyclone 21 for dust separation of reducing gas is disposed in the cylindrical section of the stop 15. The dust recirculation pipe 22 branched from the cyclone 21 passes vertically downward into the fluidized bed. The gas discharge pipe 23 of the cyclone 21 passes into the space 24 located between the ceiling 16 and the reactor ceiling 17.

According to the present invention, spectroscopy having a wide particle distribution containing a relatively large amount of fine powder is treated in a reduction reactor (1). For example, an example of this type of particle distribution may be as follows.

Mass ratio

100% up to 4 mm

72% up to 1 mm

55% up to 0.5 mm

33% up to 0.125 mm

In general, it has been found that the spectroscopy having the above-described particle distribution can be fluidized without separation in the fluidized bed 2, and it is essential in the present invention that the surface velocity V _super is always lower than the lowest fluidization rate of the largest particles of the spectroscopy.

The optimum operating range of V _super is found to be the following ratio.

V _super = 0,25-0.75V _min (d _max )

V _super -surface velocity of the fluidized bed (2) above the lowest distributed bed (4)

V _min (d _max )-lowest fluidization rate of the largest particles of the charged fraction

As mentioned above, spectroscopy having a wide particle distribution is essential in the present invention. This particle distribution is characteristic of crushed spectroscopy, i.e., spectroscopy that has not been screened after crushing small. 3 shows particle distributions of some examples of crushed iron ore. These particle distributions of crushed iron ore are always so small that they are too small as fine particle fractions that do not remain in the fluidized bed and are discharged with the gas and recycled via cyclones. Particulate classification needs to ensure that very large particles only fluidize at the surface velocity of the relatively slow reducing gas.

According to the present invention, the effect of the pulse transfer of the fine particles having a wide particle distribution to the larger fine particles takes place. Therefore, even when the surface velocity of the reducing gas is less than or equal to the surface velocity required for larger fine particles, fluidization of large fine particles is possible. According to the invention, it is possible to use spectroscopic particles of natural particle distribution (in the crushed state) without any prior screening, where d _max preferably represents up to 12 mm and up to 16 mm.

By using a reduction reactor designed according to the above-mentioned features and using a relatively fine particle spectroscopy, the following advantages are obtained for fluidization properties.

Flexible system in that solid density and particle size distribution change according to the change of charged raw materials

Insensitivity to the decomposition of the particles, ie the change of the particulate fraction occurring between the feed stream and the product stream

The reduction furnace 1 can be used with the same advantages as the preheating and preliminary reduction and final reduction reduction reactors.

The installation in which the reduction furnace 1 of the above-described type constructed in accordance with the present invention is preferably arranged is described in detail with reference to FIG.

The facilities for producing pig iron or steel semi-finished products are four fluidized-bed reactors (1, 1 ', 1 ", 1"') having a generally similar configuration, which are continuously connected in series and which characterize the above-described reduction furnace (1). It includes. Iron oxide-containing material such as crushed spectroscopy is charged to the first fluidized bed reactor 1, which is a preheating step in which the preheating and possibly preliminary reduction of the spectroscopy takes place via the ore supply pipe 5, and then the transfer pipe 5, 6) are transferred from the fluidized bed reactor 1 to the fluidized bed reactor 1 'or from the fluidized bed reactor 1' to the fluidized bed reactor 1 ". Inside the second fluidized bed reactor 1 '. In the preliminary reduction stage, a preliminary reduction stage occurs, and a wider reduction occurs in the continuously connected fluidized bed reactor (1 "). In the last arranged fluidized bed reactor (1" '), iron ore, the final reduction stage, Final reduction.

The fully reduced material, i.e., spongy iron, is briquetted at high or cold temperatures in a briquetting plant 25. If necessary, reduced iron is prevented from reoxidation during briquetting operations by an inert gas system, not shown.

Prior to feeding the spectroscopy into the first fluidized bed reactor 1, the spectroscopy is subjected to ore preparation such as drying and sieving, not shown in detail.

The reducing gas is transferred from the fluidized bed reactor (1) to the fluidized bed reactor (1 ') to the fluidized bed reactor (1 "') in the ore flow and backflow, and in the direction of gas flow through the top gas discharge pipe (26). It is discharged as top gas from the fluidized bed reactor 1 arranged in the above, and cooled and scrubbed in the wet scrubber 27. The reducing gas is supplied through the pipe 28 and desulfurized in the desulfurizer 29. By reforming the gas, it is generated in the reformer 30. It is essential that the reformed gas formed from natural gas and steam consists of H ₂ , CO, CH ₄ , H ₂ O and CO _2. The reformed gas is a reformed gas pipe 31. Is supplied to several heat exchangers 32 where it is cooled to ambient temperature whereby water condenses from the gas.

The reformed gas pipe 31 is in communication with the top gas discharge pipe 26 after the top gas is compressed by the compressor 33. The obtained gas mixture is passed through the CO ₂ scrubber 34 to be used as a reducing gas after the CO ₂ is removed. The reducing gas passing through the reducing gas supply pipe 35 is heated to a reducing temperature of approximately 800 ° C. in the gas heater 36 connected to the CO ₂ scrubber 34 and then connected to the fluidized bed reactor 1 '′ first connected in the gas flow direction. And the directly reduced iron is produced by re-reacting with the spectroscopy. In the fluidized bed reactor (1 "'), the fluidized bed reactor (1) is connected in series, and is connected to the reducing gas via a connecting pipe (37). Is passed from the fluidized bed reactor (1 "') to the fluidized bed reactor (1") and the like.

Some of the top gas is sloshed from the gas cycles 26, 35, 37 so that there are not many inert gases such as N2. The sawed top gas is supplied to the gas heater 36 via the branch pipe 38 to heat the reducing gas and burn it there. Energy that may be lacking is replenished with natural gas supplied via supply pipe 39.

The detectable heat from the reformer and the reformer fluegases can be detected and used in the recuperator 40 to preheat the natural gas after passing through the desulfurizer 29 to provide steam for reforming. Not only does it generate, but also preheats the combustion air and optionally the reducing gas supplied to the gas heater 36 via the tube 41. The combustion air supplied to the reformer via pipe 42 is also preheated.

Claims (9)

In a method of treating, preferably reducing, in particular, reducing spectroscopy, in a fluidized bed method, a particulate matter held in the fluidized bed 2 by a reducing gas flowing from the lower side to the upper side is reduced. Particles having a wide particle distribution rule containing a relatively large amount of fine particles and a large portion of the particles are used for the reduction treatment, and the surface velocity of the reducing gas in the fluidized bed 2 is fluidized in the larger particles in the particulate matter. Reduction method characterized in that the smaller particles are kept below the speed necessary for the larger particles to move upwards together with the fine particles and are discharged from the upper region of the fluidized bed. 2. A method according to claim 1, wherein the surface velocity of the fluidized bed (2) is maintained within the range of 0.25-0.75 of the velocity required for fluidization of the largest particles of the particulate matter. The reduction method according to claim 1 or 2, wherein the particle band is a particulate material of particles having a median particle size of 0.02 to 0.15, preferably 0.05 to 0.10, of the largest particle size among the particulates. 4. The surface velocity of the reducing gas on the fluidized bed 2 is determined by the largest diameter of the reduction furnace arranged to receive the fluidized bed 2. With respect to the theoretically cut particle diameter of 50 to 150 μm, preferably 60 to 100 μm. 5. A method according to claim 4, characterized in that the fluidized bed (2) has a surface velocity adjusted in the range of 0.3 m / s to 2.0 m / s to reduce run of mine spectroscopy. A method for directly reducing particulate iron oxide-containing material by a fluidized bed method employing the method described in any one of claims 1 to 5, The reformed gas is mixed with the top gas formed in the direct reduction of the iron oxide-containing material and supplied as a reducing gas to the fluidized bed, and both the top gas and the reformed gas are subjected to CO ₂ scrubbing and the reducing gas formed by the mixture of the top gas and the reformed gas. Reduction method characterized in that it is adjusted to have a specific H ₂ and CO content. A cylindrical lower fluidized bed portion containing a fluidized bed 2 and comprising a gas distribution bottom layer 4, process gas supply pipes 35 and 37, and particulate material supply means and discharge means disposed on the gas distribution bottom layer 4 ( 3), The cone-shaped portion 9 which is arranged after the fluidized bed on the fluidized-bed portion 3 and spreads upward in a conical shape, and the wall 10 of the cone-shaped portion 9 are 6 to 15 ° with respect to the central axis 11 of the reactor. , Preferably inclined at 8 to 10 degrees, It includes a at least partially cylindrical stop portion 15 which is connected to the cone-shaped portion 9 and closed at the upper end, and branched to the reducing gas discharge pipes 26 and 37, The ratio of the cross-sectional area of the stop 15 in the cylindrical region to the cross-sectional area of the fluidized bed 3 is ≧ 2. Reduction furnace for carrying out the method according to any one of claims 1 to 6, characterized in that the features are combined. 8. The cross-sectional area 19 of the stationary space 15 in the cylindrical region is large enough for the surface velocity to be adjusted in the region so that particles having a particle size of 50 μm or more can be sufficiently separated from the gas. Reduction furnace characterized in that. At least one reduction furnace according to claim 7 or 8, comprising a fluidized bed reactor (1 to 1 "') containing iron oxide material, and a reducing gas supply pipe communicating with said fluidized bed reactor (1 to 1"'). 35 and 37 and branched from the top gas discharge pipe 26, the reformer 30, and the reformer 30 to discharge the top gas formed in the reduction process from the fluidized bed reactor 1 and the top gas discharge pipe 26. A reformed gas pipe (31) to be joined, and a CO ₂ remover (34), Reducing gas formed of reformed gas and saw gas enters into the fluidized bed reactor (1 to 1 "') through the reducing gas supply pipes 35 and 37, Both the reformed gas pipe 31 and the top gas discharge pipe 26 pass into the CO ₂ remover 34 and the reducing gas supply pipes 35 and 37 are connected to the fluidized bed reactor 1 from the CO ₂ remover 34. ~ 1 "') A facility for directly reducing particulate iron oxide-containing material characterized by the fluidized bed method according to claim 6.