JP2003261316A - Method of controlling reaction gas composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling a reaction gas composition in a 1st reaction furnace in a method of manufacturing iron carbide by performing partial reduction in a 1st reaction operation and performing remaining reduction and carbonization in a 2nd reaction operation. <P>SOLUTION: A part of the reduction reaction of an iron-containing raw material is carried out in the 1st reaction furnace 19 and the remaining reduction and the carbonization reaction is carried out in the 2nd reaction furnace 39. The reaction gas composition in the 1st reaction furnace 19 is controlled by adjusting the flow rate of the reaction gas discharged out of the reaction line through a pipe line 25 from the 1st reaction furnace. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a reaction gas composition, and more particularly, to a method for controlling a reaction gas composition in the production of iron carbide, which is suitable as a raw material for steelmaking and steelmaking. It relates to a control method. 2. Description of the Related Art Generally, steel production is performed by converting iron ore into pig iron using a blast furnace and then converting pig iron into steel using a flat furnace or a converter. However, such a traditional manufacturing method requires large amounts of energy, equipment scale, and cost.Therefore, for small-scale steelmaking, iron ore is directly converted into steelmaking furnace raw material by steelmaking. A method of converting the raw material of the steelmaking furnace into steel by an electric furnace or the like is employed. In such direct steelmaking, there is a direct reduction method for converting iron ore to reduced iron, but the reduced iron produced by this method has a strong reaction activity and generates heat by reacting with oxygen in the atmosphere, so that it is transported and stored. Requires a treatment such as sealing with an inert gas. For this reason, the reaction activity is low, it can be easily transported and stored,
Iron carbide containing a relatively high percentage of iron has recently been used as a raw material for steelmaking by electric furnaces and the like. [0003] Further, steel raw materials containing iron carbide as a main component are not only easy to transport and store, but also carbon combined with iron serves as a fuel source for iron making or steel making furnaces.
In a steelmaking furnace, there is also an advantage that it is a source of fine bubbles that promote the reaction. For these reasons, in recent years, raw materials for steelmaking and steelmaking mainly composed of iron carbide have attracted particular attention. [0004] In the conventional method of producing such iron carbide, a powder of iron ore is charged into a fluidized-bed reactor, and a mixed gas of a reducing gas (hydrogen gas) and a carbon gas (for example, methane gas) is mixed with a predetermined gas. By reacting at a temperature, iron oxides (such as hematite (Fe ₂ O ₃ ), magnetite (Fe ₃ O ₄ ), wustite (FeO)) in iron ore can be reduced to a single operation (reduction and addition in one reactor). (Referring to an operation performed by simultaneously introducing a carbonized gas). As this kind of prior art, Japanese Patent Application Laid-Open No. 6-50198 is disclosed.
There is one described in Japanese Patent Publication No. Although the method of performing reduction and carbonization in a single operation has the advantage of system simplicity, the reaction gas composition and reaction temperature are individually flexible so as to be optimal for each of the reduction reaction and carbonization reaction. , The reaction cannot proceed efficiently. Therefore, the present applicant has set the gas used in the first reaction operation to have an optimum composition only for the reduction reaction, and the gas used in the second reaction operation to have the optimum composition for the remaining reduction reaction and carbonization reaction. As possible, `` after the first reaction operation to perform a part of the reduction reaction of the iron-containing raw material for iron production, the method for producing iron carbide characterized by proceeding a second reaction operation to perform the remaining reduction reaction and carbonization reaction and Filed a patent application for the invention relating to "manufacturing equipment" (Japanese Patent Application No. 8-30985).
issue). According to the present invention, various operations can be taken for each operation, which is impossible with the conventional method of manufacturing iron carbide in a single operation, and the process becomes flexible. There is an advantage that the flow rate of the gas can be greatly reduced. Although the method of performing the reaction in two stages as described above has many advantages, the reaction cannot be efficiently advanced unless the degree of progress of the reaction after the first reaction operation is controlled. There is. That is, if the reduction ratio in the first reaction operation is too low or the reduction ratio is too high, there is a disadvantage that the reaction operation time becomes long. [0007] For example, Japanese Patent Application Laid-Open No. Sho 56-98412 discloses a method for adjusting a reaction gas of this kind, as shown in FIG. , The carbon material is introduced from the supply port 73 and the combustion reaction
Inside, the heat medium particles are generated by the carbon material introduced from the supply port 75 and the gas containing oxygen supplied from the nozzle 76, and the heat medium particles are fluidized by the circulating gas supplied from the supply port 77. Is moved to the reduction reaction tower 71 via the connecting pipe 78, and the supply port 79 is provided in the reduction reaction tower 71.
The iron ore and the heat medium particles are fluidized by the circulating gas supplied from the furnace, the reduced iron particles generated after the reaction for a certain period of time are discharged from the lower outlet 80, and the heat medium particles are communicated with the connecting pipe 81 and the cyclone 82. And returned into the combustion reaction tower 74,
Adjusting the amount of steam introduced from the nozzle 83 into the combustion reactor 74 to change the ratio of H ₂ to CO in the circulating gas.
Is described. At first glance, the publication described in this publication consists of two reactors.
Group (only the reduction reaction tower 71), and only promotion of the reduction reaction may be considered. In contrast, in the present invention, when two reactions, a reduction reaction and a carbonization reaction, are performed in a two-step operation, the reduction and the carbonization are partially performed in the first reaction operation and the remaining reduction and carbonization are performed in the second reaction operation. To provide a method of controlling the reaction gas composition of the first reactor in a method of obtaining iron carbide having a target composition by performing the above. In order to achieve the above object, the gist of the present invention is to convert gas components in a first reactor into a gas necessary for the reaction, a gas generated by the reaction, and an impurity gas. When divided, the gas density obtained from the gas composition at the inlet and the outlet of the reactor is kept constant, and the impurity gas ratio at the inlet and the outlet of the reactor is A and A ', respectively. The impurity gas amount D to be mixed into the reactor is obtained based on the impurity gas ratio B in the supply gas and the gas amount C consumed in the reaction, and the impurity gas amount D is obtained by dividing the impurity gas amount D by the impurity gas ratio A ′. The amount of bleed gas discharged to the outside of the system is referred to as E, and the amount of gas circulating in the reaction loop passing through the reactor is referred to as the circulating gas amount F. And controlling the reaction gas composition in the first reactor by feeding to the reactor, with it, reducing to a predetermined reduction ratio under a predetermined reaction gas composition in the first reactor. Thereafter, in the second reactor, the remaining reduction and carbonization are performed to produce iron carbide having a target carbonization ratio. [0010] That is, the present invention provides an iron carbide in which a first reaction operation for partially performing a reduction reaction of an iron-containing raw material is followed by a second reaction operation for performing the remaining reduction reaction and carbonization reaction. A method for controlling the reaction gas composition by making the gas density at the inlet and outlet of the first reactor performing the first reaction operation in the production of the first reactor, gas components in the first reactor required for the reaction When the gas and the gas generated by the reaction are divided into impurity gases, the gas density obtained from the gas composition at the inlet and the outlet of the reactor is kept constant, and the impurity gas ratio at the inlet and the outlet of the reactor is A, respectively.
And A ′, the ratio B of the impurity gas in the replenishment gas supplied to the reactor from outside the system and the gas amount C consumed in the reaction
The amount of impurity gas D to be mixed into the reaction furnace is obtained based on the above formula, and the amount obtained by dividing the amount of impurity gas D by the ratio of impurity gas A ′ is referred to as the amount of bleed gas E discharged to the outside of the system. When the amount of gas circulating in the passing reaction loop is the circulating gas amount F, a supply gas is supplied to the reaction furnace so that the ratio of F to E is kept constant. According to the present invention configured as described above,
When the gas components in the first reactor are divided into a gas necessary for the reaction, a gas generated by the reaction, and an impurity gas, the gas density obtained from the gas composition at the inlet and the outlet of the reactor is kept constant, and the The impurity gas ratios at the inlet and the outlet of the reactor are A and A ', respectively. Based on the impurity gas ratio B in the supply gas supplied to the reactor from outside the system and the gas amount C consumed in the reaction, the reactor is The amount D of the impurity gas to be mixed is determined, and the amount obtained by dividing the amount D of the impurity gas by the ratio A ′ of the impurity gas is defined as the amount of bleed gas E discharged to the outside of the system, and circulates through a reaction loop passing through the reactor. When the gas amount is the circulation gas amount F,
By supplying a make-up gas to the reactor so as to keep the ratio of F and E constant, unnecessary gas components for the first reaction operation are prevented from accumulating in the reaction system, and The reaction gas composition can be kept constant and can be reduced to a predetermined reduction ratio after a certain reaction time. Further, the rate of hydrogen can be changed by adjusting the flow rate of methane in the gas supplied to the reaction system, thereby controlling the reaction rate of the reduction reaction. In this case, as described later, it is necessary to increase the amount of the reaction gas discharged out of the system in order to prevent the accumulation of methane in the circulating gas. Further, by changing the reaction temperature, the equilibrium gas composition and the reaction rate can be controlled. As described later, if the temperature and the pressure are constant, the gas density is uniquely determined in proportion to the molecular weight.
The gas composition can be known by measuring the gas density. Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram of an iron carbide manufacturing apparatus suitable for carrying out the method of the present invention. The apparatus of FIG. 1 includes a first reaction operation section 10 for partially reducing iron ore mainly containing hematite as an iron-containing raw material for iron production, and a second reaction operation section 30 for performing the remaining reduction reaction and carbonization reaction. It is composed of The flow of the reaction gas in the first reaction operation section 10 is
1, pipe 12, compressor 13, pipe 14, heat exchanger 15,
Pipe 16, heater 17, pipe 18, fluidized bed reactor (first reactor) 19, pipe 20, heat exchanger 15, pipe 21,
The scrubber 22 and the conduit 23 form a loop.
That is, the pipe 1 is connected to the bottom gas inlet of the first reactor 19.
2, compressor 13, pipe 14, heat exchanger 15, pipe 16,
A reaction gas is supplied through a heater 17 and a pipe 18 in order,
From the top outlet of the first reactor 19, a pipe 20, a heat exchanger 1
5, a loop is formed in which the reaction gas circulates sequentially through the pipe 21, the scrubber 22, the pipe 23, the pipe 11, and the pipe 12. A gas having a predetermined composition is supplied to the circulation path from a pipe 24 connected to a connection section between the pipes 11 and 12, and a predetermined amount is supplied from a pipe 25 connected to a connection section between the pipe 11 and the pipe 23. Is discharged outside the system. The scrubber 22 includes a hollow main body 26, a pipe 27 that injects water into the gas, and a pipe 28 that discharges water in the main body 26, and cools the gas discharged from the first reactor 19, It condenses and removes water vapor in the gas. Since the flow of the reaction gas in the second reaction operation part 30 is the same as that in the first reaction operation part 10, the common parts are numbered by adding 20 to each number of the first reaction operation part 10. The description is omitted. In the iron carbide manufacturing apparatus configured as described above, when powdered iron ore is supplied to the upper part of the first reaction furnace 19 of the first reaction operation section 10 through the pipe 50, The iron ore reduced to is continuously supplied from the lower part of the first reactor 19 to the fluidized bed reactor (second reactor) 39 of the second reaction operation part 30 via the pipe line 51, and this second reaction After the rest of the reduction and carbonization in the furnace 39, the iron carbide product is continuously removed via line 52. Regarding the composition of the reaction gas used in the above reaction, since only the reduction reaction needs to be considered in the first reaction operation, the first reaction operation is performed using a reducing gas mainly composed of hydrogen, and the second reaction operation considers the reduction reaction and the carbonization reaction. Therefore, a mixed gas mainly composed of hydrogen and methane is used. The reduction reaction which is the basis of the first reaction operation is represented by the following equation, and the remaining reduction and carbonization reaction which is the basis of the second reaction operation is represented by the following equation. 3Fe ₂ O ₃ + 5H ₂ → 6FeO _2/3 + 5H ₂ O 6FeO _2/3 + 2CH ₄ → 2Fe ₃ C + 4H ₂ O As shown in the formula, if the solid content is neglected, In one reaction operation, 5 moles of hydrogen (H ₂ ) supplied to the first reactor becomes 5 moles of steam (H ₂ O), and the gas volume does not change before and after the reaction. For example, the following Table 1 shows an example of the composition (inlet) of the reaction gas supplied to the first reactor and the composition (outlet) of the gas discharged from the first reactor.
As shown in FIG. The gas density (ρ) is proportional to the molecular weight (M) if the temperature (T ° K) and the pressure (Patm) are constant, as shown in the following equation. Ρ = (M / 22.414) × (Patm / 1atm) × (273/273 + T) As apparent from Table 1, the gas composition at the inlet and outlet of the first reactor contains a considerable amount of impurities such as CH ₄ . Originally, since the first reaction process is performed only reduction reaction, CH ₄ is unnecessary elements, mainly including gas _{H 2 (H 2 ≧ 90%} ) is supplied. However, impurities such as CH ₄ are entrained in the circulating gas of the first reactor together with the supplementary gas or mixed with the raw iron ore, and the amount of the impurities increases with time. In order to reduce the accumulation of impurities in the circulating gas as much as possible, if all the gas discharged from the first reactor is discharged out of the system, the contamination of the circulating gas with the impurities can be minimized. However, in this case, the gas consumption becomes enormous and the operating cost becomes extremely large. Therefore, in actual operation, the amount of gas discharged to the outside of the reaction system is reduced to 5% of the circulating gas amount in consideration of economy. % Or less, the gas balance is maintained. Therefore, as shown in Table 1, the bleed gas was set so that the gas density (average molecular weight) at the inlet of the first reactor was 6.26 and the gas density (average molecular weight) at the outlet of the first reactor was 8.34. A trial calculation is made to determine how much the amount (the amount of gas to be removed from the system from the pipe 25 in FIG. 1) should be set to the circulating gas amount. (Calculation of Circulating Gas Amount) As shown in Table 1, as a result of the reaction in the first reactor, H ₂ has decreased by 13% by volume and H ₂ O has increased by 13% by volume. As shown in the above formula, 5 moles of H ₂ are consumed, so 5 moles corresponds to 13% by volume. Therefore, the amount of gas circulating in the circulation loop of the first reaction operation part is 5 / 0.13 = 38.5 mol. (Bleed gas amount calculation) Now, 95% of the gas supplied from outside the system for the sake of simplicity is H _2, when the impurities such as CH ₄ is 5%, H ₂ to be used in the reaction are Since it is 5 moles, the number of moles of impurities mixed in the reaction system is 5 ×
0.05 / 0.95 = 0.26 mol. From Table 1,
The amount of impurities in the first reactor (CH ₄ , CO, CO ₂ , N
₂ ) is 25% by volume, so 0.26 × 1 / 0.25
If 1.04 mol of gas is removed from the system, accumulation of impurities in the circulating gas can be prevented. That is, if 1.04 mol of gas is bleed with respect to 38.5 mol of circulating gas (1.04 / 38.5 = 0.027), the current gas composition can be maintained. If the bleed gas amount is 2.
If less than 7%, impurities accumulate in the circulating gas and the gas density at the inlet will be greater than the values in Table 1. On the other hand, the amount of bleed gas is 2.
If it is more than 7%, impurities accumulated in the circulating gas will be removed more and more out of the system.
Becomes smaller than the value of. As described above, by adjusting the bleed gas amount, it is possible to change the gas density difference or the gas density ratio between the inlet and the outlet of the first reactor. FIG. 2 shows a specific example of the relationship between the bleed gas amount and the ratio of H ₂ and CH _{4 in} the circulating gas. FIG. 2 shows that the reaction temperature of the first reactor is 590.
℃, furnace pressure is 4 atm, replenishment gas amount is 30000N
This is an example in the case of m ³ / hr, and the methane amount decreases as the bleed gas amount increases, and H ₂ increases on the contrary. As a method of changing the gas composition of the first reactor, there is a method of adjusting the amount of gas (CO ₂ + CH ₄ ) to be added to the supply gas into the system as shown in FIG. FIG. 3 shows that the reaction temperature of the first reactor was 590 ° C.
In pressure, in amounts up gas is 30000 nM ³ / hr, bleed gas weight is an example of the case of 300 Nm ³ / hr. As shown in FIG. 3, the amount of (CO ₂ + CH ₄ ) is 50 Nm ³ / h
Above r, the CH ₄ in the circulating gas reaches the equilibrium concentration and does not increase further. Further, as shown in FIG. 4, by changing the reaction temperature, the equilibrium gas composition and the reaction rate of the reduction reaction can be controlled. The reaction gas composition can be controlled as described above. FIG. 5 shows an example of a gas sampling system for measuring the gas density (molecular weight). In FIG. 5, reference numeral 61 denotes an inlet gas line, and 62 denotes an outlet gas line. 63 is a cooler for removing moisture in the gas,
64 is a gas density meter, 65 is a hygrometer, 66 is a filter,
67 is a gas chromatograph or mass spectrometer. The dotted line portion is kept warm to prevent condensation of water. Since the present invention is configured as described above, in the case where the two reactions of the reduction reaction and the carbonization reaction are performed in a two-stage operation, the reduction is performed to a predetermined reduction rate in the first reaction operation. The remaining reduction and carbonization can be performed in the second reaction operation to efficiently obtain iron carbide having a target composition.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing an example of an iron carbide manufacturing apparatus suitable for carrying out the method of the present invention. FIG. 2 H ₂ and C in circulating gas against bleed gas amount
Is a diagram showing the relationship between the ratio of H _4. FIG. 3 is a graph showing the relationship between the amount of CO ₂ and CH ₄ added to the circulating gas and the ratio of H ₂ and CH _{4 in} the circulating gas. FIG. 4 is a diagram showing a relationship between a reaction temperature and a reduction time. FIG. 5 is a schematic configuration diagram illustrating an example of a gas sampling system. FIG. 6 is a diagram showing a schematic configuration of a conventional fluidizing reduction furnace. [Description of Signs] 10 ... first reaction operation part 19 ... first reaction furnace 30 ... second reaction operation part 39 ... second reaction furnace

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yosuke Suezawa             3-1-1 Higashikawasaki-cho, Chuo-ku, Kobe City, Hyogo Prefecture             No.Kawasaki Heavy Industries, Ltd.Kobe Factory (72) Inventor Teruyuki Nakazawa             2-6-3 Marunouchi, Chiyoda-ku, Tokyo 3             Ryosho Corporation (72) Inventor Akio Nioh             2-6-3 Marunouchi, Chiyoda-ku, Tokyo 3             Ryosho Corporation F term (reference) 4G146 MA12 MB25 NA05 NB07 NB14                       NB20                 4K012 DF01 DF05 DF09

Claims (1)

Claims: 1. A first reaction in the production of iron carbide in which a first reaction operation for performing a part of a reduction reaction of an iron-containing raw material is followed by a second reaction operation for performing a remaining reduction reaction and a carbonization reaction. A method for controlling a reaction gas composition by keeping a gas density at an inlet and an outlet of a first reactor for performing a reaction operation, wherein a gas component in the first reactor is generated by a reaction with a gas necessary for the reaction. Gas and impurity gas, the gas density obtained from the gas composition at the inlet and outlet of the reactor is kept constant, and the impurity gas ratio at the inlet and outlet of the reactor is A and A ', respectively. From the amount of impurity gas B in the supply gas supplied to the reaction furnace and the amount C of gas consumed in the reaction, the amount D of impurity gas mixed into the reaction furnace is determined. When the amount obtained by dividing by the gas ratio A ′ is the bleed gas amount E discharged to the outside of the system, and the amount of gas circulating in the reaction loop passing through the reaction furnace is the circulating gas amount F, A method for controlling the reaction gas composition of a first reactor by supplying a make-up gas to the reactor so as to keep the ratio constant.