RU2069701C1 - Method and aggregate for direct reduction of iron oxide material - Google Patents

Abstract

FIELD: methods and aggregates for direct reduction of iron oxide materials. SUBSTANCE: in process of oxidation conversion-reduction gas is produced with temperature below 950 C and oxidation degree ((n_o)) up to 0.07. Then it is mixed with heated up to 650 - 950 C oxygen bearing gas producing partially oxidized gas with temperature of at least 1100 C and oxidation degree of 0.10 - 0.17. Then it is subjected to additional reforming in furnace by addition of natural gas in amount providing ratio:

= 0.5 - 0.7, with CH₄ - molar ratio of CH₄ in gas mixture, n_o - oxidation degree of partially oxidized reducing gas defined by formula:

, with CO₂,H₂O,H₂,CO - shares of corresponding components in gas. Traditional aggregate of direct reduction heater is mounted between existing outside aggregates of reforming and reactor for preliminary heating of source of oxygen mixed with reducing gasses produced in outside aggregates of reforming before their introduction in reactor. Besides traditional aggregate is to be reequipped so, that to provide excess of natural gas as raw material fed in reactor together with partially oxidized reducing gas. EFFECT: improved process. 4 cl, 4 dwg

Description

 The invention relates to the steel industry and can be used for direct reduction of iron oxide material, which consists in external reforming of natural gas to produce a reducing gas for the direct reduction process.

A known method of direct reduction of iron oxide material, including the oxidative conversion of natural gas, in external reformers to produce a reducing gas containing at least 90 volume H ₂ and CO, mixing it with heated gaseous reagents and feeding the resulting reducing gas to a direct reduction reactor of iron oxide material [1]
The objective of the invention is the development of a method for increasing the productivity of a known direct recovery installation without the need to increase the performance of external reforming plants existing inside the installation, while reducing energy consumption in the installation.

где CH₄ молярное соотношение СH₄ в газовой смеси;
n_o степень окисления частично окисленного восстановительного газа, определяемая по формуле

где CO₂, H₂O, H₂, CO содержание соответствующих компонентов в газе.The essence of the invention lies in the fact that in the process of oxidative conversion receive reducing gas below 950 ^o With and the degree of oxidation (n _o ) to 0.07, then it is mixed with heated to 650 950 ^o With an oxygen-containing gas to obtain a partially oxidized gas with a temperature at least 1100 ^o C and a degree of oxidation of 0.10 0.17, after which it is subjected to additional reforming in the furnace by adding natural gas in an amount that provides a ratio

where CH _{4 the} molar ratio of CH ₄ in the gas mixture;
n _{o the} degree of oxidation of the partially oxidized reducing gas, determined by the formula

where CO ₂ , H ₂ O, H ₂ , CO the content of the corresponding components in the gas.

 Natural gas is fed into the reactor in an amount equal to 2 4 of the volume of partially oxidized gas. As the oxygen-containing gas, pure oxygen, air or a mixture thereof is used.

 In order to convert an existing conventional direct reduction unit to an improved method of the invention, it is only necessary to install a heater between the existing external reforming units and the reactor to preheat the oxygen source mixed with the reducing gases obtained in the external reforming units before introducing them into the reactor. In addition, the installation should be re-equipped in such a way as to provide an excess of natural gas as a feed to the reactor along with a partially oxidized reducing gas. Natural gas can be fed into the reactor with either a partially oxidized reducing gas or, preferably, directly into the reaction reduction zone of the reactor as a separate feed stream from the oxidized reducing gas.

By using a modified method and refitting the installation, as indicated above, the productivity of existing direct reduction plants can be increased by at least 25 without the need to increase the size of existing external gas reforming. In addition, the cost of refitting the installation is much lower than the cost of increasing the recovery gas productivity of existing reforming plants. Finally, direct recovery units refitted in accordance with the present invention significantly reduce energy consumption by about 30
1 schematically shows a conventional direct reduction installation for external reforming of a reducing gas for use in a vertical direct reduction shaft furnace.

 Fig. 2 is a diagram similar to that of Fig. 1, showing modifications made to an existing direct reduction plant for carrying out a modified direct reduction method for iron ore, in which the productivity of the plant is increased without the need for an increase in the productivity of external reforming plants.

Figure 3 is a graph illustrating the increase in productivity obtained in accordance with the invention, and
4 is a graph illustrating a reduction in energy consumption based on natural gas produced in accordance with the present invention.

На фиг.1 газ риформинга, полученный в установках риформинга 5 и имеющий указанные выше характеристики, охлаждают в кондиционирующей установке 6 до температуры ниже 850^oC перед вводом газа риформинга в восстанавливающую зону 3 вертикальной печи шахтного типа 10. Для известных процессов, описанных здесь, является критическим охлаждение газа риформинга до температуры максимум 850^oС, чтобы обеспечивать поддержание максимальной температуры в зоне восстановления в интервале между 800 и 830^oС, чтобы избежать агломерации ПВЖ в восстанавливающей зоне.In FIG. 1 is a diagram of a conventional direct reduction installation for external reforming of reducing gases for use in a vertical direct reduction shaft furnace. Referring to FIG. 1, a starting iron oxide having an iron content of between 60 and 70 masses is fed into the reduction reactor 1 through a pipe 2. The reactor is a vertical shaft type furnace having a reducing zone 3, in which metal oxides are in contact with the reducing iron oxides. The reducing gases used in the reduction practice inside the reducing zone are obtained outside the reduction zone using a continuous catalytic reforming process carried out in external reforming units 5 where a hydrocarbon, such as natural gas or any other volatile hydrocarbon, is in contact with heated indirect heating loem catalyst in the presence of an oxidant to get a hot reducing gas which consists mainly of CO and H _2, and CO and H ₂ are in an amount greater than or equal to 90 by volume. In accordance with known commercial direct reduction processes, the reforming gas is in the reforming unit at a temperature of about 950 ^° C. The oxidation rate of the reforming gas formed in the reforming unit can be as large as 0.07 in ideal situations. Typically, the oxidation state of the reforming gas is between 0.04 and 0.07. The oxidation state is defined as

In figure 1, the reforming gas obtained in reforming units 5 and having the above characteristics is cooled in an air conditioning unit 6 to a temperature below 850 ^° C. before introducing the reforming gas into the reducing zone 3 of the shaft type vertical furnace 10. For the known processes described herein, it is critical that the reforming gas is cooled to a temperature of a maximum of 850 ^{° C.} to ensure that the maximum temperature in the reduction zone is maintained between 800 and 830 ^{° C.} to avoid agglomeration of the DRI in the reducing zone .

 The metallized product obtained in the known method described above in FIG. 1, restored at least 95 i.e. contains at least 85 Fe.

 Until now, in order to improve the performance of an existing direct recovery unit of the type described above, in Fig. 1, in order to increase production of DRI, it was necessary to increase the performance of external reforming units, i.e. increase the amount of reducing gas produced in external reformers. This can only be done by introducing additional catalytic reforming plants outside the direct reduction reactor. The costs of additional catalytic reforming units are very high due to the nature of the catalytic layer and the reforming reaction.

Figure 2 shows a modified method and installation to improve the performance of existing direct recovery installations without the need to introduce additional external reforming installations in a common installation. In Fig.2, the existing direct reduction unit and method are modified in such a way as to provide a preheater 7 after an external reforming unit 5 for preheating an oxygen source that is supplied from the preheater 7 via line 8 to the feed line from external reforming units 5 to the reactor 1 for mixing a preheated oxygen source with a reducing gas leaving the reforming unit. In accordance with the invention, the oxygen source, which may also be air, or pure oxygen, or mixtures thereof, is preheated in a preheater to 650 - 900 ^o C, preferably 750 850 ^o C. After that, the preheated oxygen source is mixed with a reforming gas, exiting the reforming unit at 950 ^° C. If necessary, an air-conditioning unit can be used to heat the reforming gas from the reforming unit, however, additional heating is not required under normal operating conditions. Since the preheated oxygen source is mixed with the reducing gas, partial burning of the oxygen source occurs. Partial combustion raises the temperature of the supplied partially oxidized reducing gas to at least 1100 ^° C. This temperature increase is controlled by the amount of a preheated oxygen source and the supply of a reducing gas to the stream. In addition to increasing the temperature, the partially oxidized reducing gas feed stream has a higher oxidation state than the reforming gas obtained in the reforming unit, so that the oxidized partially oxidized reducing gas feed is between 0.10 and 0.17.

 The partially oxidized reducing gas stream, as described above, is then fed to the reactor reforming-recovery zone 3 and contacted with the DRI in the presence of natural gas inside the reforming-reducing agent zone. In accordance with the present invention, natural gas is introduced, preferably directly into the reforming-reduction zone via line 9 for contacting a partially oxidized reducing gas with a feed stream inside the reforming-reduction zone, wherein the DRI acts in this zone as a catalyst for the interaction of oxides in the supplied partially oxidized reducing gas with natural gas with the formation of additional reducing gas for the reaction with metal oxides in the recovery zone Inga to regenerate the metal oxide fed into DRI. As noted above, in accordance with the present invention, it is preferable that natural gas is supplied directly to the reduction zone, however, it should be noted that the natural gas can be mixed with the stream of partially oxidized reducing gas before entering it into the reducing zone of the reactor.

между 0,5 и 0,7, где n_o определяется следующим образом:

На установке, которая была модифицирована, что составляет подачу природного газа в зону риформинга-восстановления, равную примерно 2 4 объемн. по отношению к подаче газового потока. При поддержании соотношения H₂ к СО в подаваемом газовом потоке больше 1,3, обеспечивающем избыток тепла от потока частично окисленного восстанавливающего газа, и подаче избытка природного газа в зону риформинга-восстановления реактора в определенном количестве, сохраняется термическое равновесие, так что проходит риформинг газа внутри зоны восстановления и сохраняется реакция восстановления оксидов металла.In accordance with the invention, in order to ensure the necessary thermal equilibrium between the stream of partially oxidized reducing gas and metal oxides in order to maintain the reduction process, methane gas is fed to the reactor reforming-reduction zone in relation to the partially oxidized reducing gas in an amount sufficient to maintain the ratio of natural gas to the oxidation state of the supplied gas stream, i.e.

between 0.5 and 0.7, where n _o is defined as follows:

At the installation, which was modified, which is the supply of natural gas to the reforming-recovery zone, equal to about 2 4 vol. in relation to the gas flow. By maintaining the ratio of H ₂ to CO in the feed gas stream greater than 1.3, providing an excess of heat from the partially oxidized reducing gas stream, and supplying an excess of natural gas to the reactor reforming-recovery zone in a certain amount, thermal equilibrium is maintained, so that gas reforming takes place inside the reduction zone, the metal oxide reduction reaction is maintained.

 When modifying the DRI processes and plants, as described above, the productivity of the installation increases by more than 25 without the need to increase the performance of external reforming plants. In addition, the total energy consumption is reduced. All this is done with capital investments that are significantly lower than those that might be required to obtain a similar increase in productivity with the addition of increased additional external reforming plants.

 The well-known direct recovery installation, built in accordance with the prior art described above, and in a commercial operation at the CVG industrial complex in Puerto Ordaz, Venezuela has been modified and refurbished in accordance with the invention. The modified process in accordance with the invention led to an increase in productivity on average in the first three months of operation up to about 20 tons of DRI / hour. Figure 3 graphically presents the results of the installation for the first three months of operation. In addition to this, energy consumption in the form of natural gas consumption per ton of DRI is significantly reduced, as shown in FIG.

 The invention can be implemented in other ways, without going beyond the essential features. Therefore, the present embodiment is considered as in all respects an illustrative and non-limiting scope of the invention shown in the claims, and all changes that fall within the meaning and range of equivalence are covered by the invention.

Claims (4)

1. A method for the direct reduction of iron oxide material, comprising the oxidative conversion of natural gas in external reformers to produce a reducing gas containing at least 90 vol. H ₂ and CO, mixing it with heated gaseous reagents and feeding the resulting reducing gas to a direct reduction reactor of iron oxide material, characterized in that during the oxidative conversion process, a reducing gas is obtained with a temperature below 950 ^° C. and an oxidation state of n _° to 0.07, then it is mixed with the preheated to 650 950 ^o C to obtain an oxygen-containing gas is partially oxidized gas with a temperature of at least 1100 ^o C and the degree of oxidation 0.10 0.17, after which it was subjected to further reforming in ne and by the addition of natural gas in an amount providing a ratio of CH ₄ / n _o 0,5 0,7, wherein the molar ratio of CH ₄ in the gas mixture, n _o oxidation state partially oxidized reducing gas, which is determined by the formula
n _o (CO ₂ + H ₂ O) / (CO ₂ + H ₂ O + H ₂ + CO),
where CO ₂ , H ₂ O, H ₂ , CO the content of the corresponding components in the gas.  2. The method according to p. 1, characterized in that the natural gas is fed into the reactor in an amount of 2 to 4% of the volume of partially oxidized gas.  3. The method according to p. 1, characterized in that as the oxygen-containing gas using pure oxygen, air or a mixture thereof.  4. Installation for direct reduction of iron oxide material, comprising a direct reduction reactor and a reducing gas preparation system including sources of natural and oxygen-containing gases, a device for converting natural gas and a gas mixer connected to the pipeline of converted natural gas, characterized in that it is equipped with a heater, an input which is connected to a source of oxygen-containing gas, and the output to a gas mixer, and located after the mixer and connected to regular enrollment gas means to provide additional mixing of natural gas and the resulting reducing gas in the reactor.

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