JPS6325046B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Conventional processes for the production of sponge iron in which a solid reducing agent such as coal is used as the reducing agent include the following.

(a) Rotary furnace method. In this method, coal is used together with the ore to be reduced in a tilted rotary furnace. The difficulty of this method, primarily due to the kinetic energy, is that it must be operated at relatively high altitudes, preferably 1000°C, and at this temperature there is a significant problem of clogging and deposition of material in the reaction chamber. A dot appears.

(b) A method using a blast furnace combined with a device for vaporizing coal on the basis of partial combustion. The disadvantage of this known method is that the investment cost of the vaporizer is very high and the energy consumption is very high.

(c) A method of directly vaporizing coal in solid form using a plasma generation device, such as the method described in Swedish Patent No. 7304332-5. The disadvantages of this method are that the coal supply must be very precisely regulated and, depending on the quality of the coal, problems arise in handling the ash. There is also the problem that the gas produced has a lower hydrogen concentration than is ideal for reduction purposes.

It has been found that the aforementioned difficulties and drawbacks with respect to known methods can be substantially obviated by the present invention. The present invention is directed to a method for producing sponge iron by continuous reduction of iron oxide in a blast furnace. The reducing gas is passed in countercurrent to the iron oxide, and is mainly
Consists of CO and _H2 . This reducing gas is made not only from the recirculated gas, i.e. the reducing gas leaving the blast furnace, but also from the surplus gas produced from coal, preferably a solid reducing agent such as coal, with the aid of a plasma generator. The recirculating gas is initially _CO2 and
The H ₂ O is substantially removed and the thus purified gas is divided into two parts and one part is passed to the plasma generator. The plasma generating device consists of a gas generating furnace substantially filled with a solid reducing agent such as coke or the like. A plasma burner is arranged in the lower part of the generator, and water and/or oxygen gas is injected into the hot gas stream leaving the plasma burner, so that the water and/or oxygen gas is injected into the stream of hot gas leaving the plasma burner. is reacted with a reducing agent to form a mixture consisting primarily of CO and _H2 . The temperature level of the produced gas is maintained within a range such that the ash contained within the solid reducing agent forms a slag. Said hot CO—H ₂ mixture leaving the gas generator is mixed with at least some of the other stream portion of the scrubbed recycle gas, the mixing ratio being such that the temperature of the final gas mixture is suitable for the reduction process. has been selected.

According to one embodiment of the present invention, the temperature level of the gas produced in the gas generator is between 1300 and 1500.
Adjusted to a temperature range of ℃. by mixing the gas mixture with said second flow section before the final gas mixture is provided to the lower part of the blast furnace.
It is also preferred to carry it within the temperature range of 700-1000°C.

According to another embodiment of the invention, the recycle gas is scrubbed so that its CO ₂ concentration is preferably below 2%.

The apparatus for carrying out the method for producing sponge iron according to the present invention has a reducing gas generation system,
The generation system includes a cleaning device for the reducing gas leaving the reaction chamber and a gas generating furnace connected thereto for containing a portion of the cleaning reducing gas thus obtained. The gas generating furnace is provided with a plasma burner in its lower part,
The burner is substantially filled with a solid reducing agent such as coke. A feeding device is provided for the controlled introduction of water and/or oxygen gas as well as optionally additional reducing agent in powder form into the plasma gas produced in the burner. A regulated mixer is provided downstream of the gas generating furnace to mix a portion of the reflux gas from the furnace with a second untreated portion of the scrubbed reactant gas. A blowing device is also provided for introducing the final gas mixture thus obtained into the lower section of the reaction chamber.

The present invention will be described in more detail below with reference to the accompanying drawings.

Reduction of the iron oxide lump is carried out in a reduction furnace 1. The iron oxide mass 2 is fed into the furnace 1 via the tuyere valve 3 and treated by a countercurrent of hot reducing gases, mainly carbon monoxide and hydrogen gas, introduced in the lower section of the furnace 1. be done. The sponge iron product is removed through an outlet 5 provided in the bottom 4 of the blast furnace 1. The reducing gas, of which 30% to 50% has been reacted, is removed from the upper part of the blast furnace 1 via the outlet 6.

Thus, the gas removed from blast furnace 1 ranges from 50% to 70%.
% unreacted CO and _H2 plus reaction products _CO2
and H ₂ O. Since this gas still contains a relatively high percentage of CO and _H2 , it can be reused within the process.

However, in order for the gas to be reusable as a reducing gas, the concentration of CO ₂ and H ₂ O must be 5%.
Must be reduced to: This is achieved by passing the gas through the scrubber 7 (CO ₂ /H ₂ O scrubber). When the gas passes through this cleaning device, it is mixed with reaction products.
Not only is CO ₂ and H ₂ O released, but the actual cleaning process balances the amount of gas and prevents it from burning. Said cleaning device 7 can contain, for example, monoethanolamine as an activator, suitably reducing the concentration of CO ₂ in the gas to below 2% when it passes through the cleaning device.

After the cleaning device 7, the gas passes through a compressor 8 and is divided into at least two flow parts 9, 10 after achieving the pressure increase required for the process.

Said flow section 9 at room temperature is connected to a gas generator 11
where the necessary excess gas is passed into a solid reducing agent, preferably coke, and water and/or
Or generated from oxygen gas. The gas stream 9 is used as a plasma gas in a gas generation device 11 and the amount of energy required for the gas generation process is provided in a plasma burner 12. Said gas generator 11 is substantially filled with a solid reducing agent, preferably coke. An oxidizing agent, preferably water and/or oxygen gas, is supplied to the gas generator 11 via a jet 13, which oxidizing agent enters the hot gas stream leaving the plasma burner 12. Extra reducing agent, for example in powder form, can optionally be added via the injection device 13a. This additional reducing agent is preferably coal dust, said coal dust having a particle size of less than 20 meshes, preferably less than 100 meshes. The hot gas stream from the plasma burner is thus reacted with the reducing agent to form CO and _H2 .

The supply of energy in said gas generator 11 is such that the ash present in the coal dust is melted into a slag 14 and can be removed from the lower part of the gas generator 11 in liquid or solid form via a pouring device 16. It is regulated as follows. Because of the composition of the ash, the temperature is
The temperature is preferably selected within the range of 1300 to 1500°C.

The reducing gas produced within the generator includes CO and H ₂ as well as potentially sulfur from the reducing agent. This intermediate gas mixture is then passed through a sulfur filter 15 (eg a dolomite filter) where the sulfur concentration is reduced to a level acceptable for sponge iron processes, preferably below 75 ppm.

According to an alternative embodiment of the invention, the sulfur filter 15 can be integrated into the gas generator itself by providing a suitable material in the coke bed.

The gas leaving said sulfur filter 15 is at a temperature substantially above that required for the sponge iron process, which temperature therefore directs the gas to flow section 1.
Mixed into a suitable portion of the cold cleaning gas within 0°C, e.g. 750-1000°C, preferably 825°C
A suitable temperature for the process is created.

Incidentally, if the sulfur content of the coal used is low and therefore desulfurization of the generated reducing gas is not particularly required, the step of passing the gas through the sulfur filter 15 can be omitted.

Gas from the gas generator and the flow section 1
Although a separate mixing device can be used to mix the 0, it is also possible to introduce part or all of the flow section 10 into the top of the gas generator 11 and use the gas generator as a mixing chamber. .

In pilot scale experiments, the following consumption values were obtained per ton of sponge iron produced:

That is, the amount of electricity was 820kWh and the amount of coal powder was 172Kg.

Next, data from the above experiment will be explained in detail.

1 ton of sponge iron manufactured
contains 93% iron (Fe), or 930 kg,
Since 1mol of Fe = 55.8g, this contains 930/55.8 = 16.667kmol Fe. Assuming that the metallization rate of this iron is 95%, 1 ton of sponge iron contains 15.834 kmol of Fe/ton of sponge iron and 0.833 kmol of FeO/ton of sponge iron...(1).

Analysis of the raw materials shows that Fe ₂ O ₃ per ton of sponge iron is 8.334 kmol/ton sponge iron and oxygen (O) is 25.001 kmol/ton sponge iron.
...(2) It was included.

Therefore, the amount of oxygen to be removed by reduction is (2) - (1) = 25.001 - 0.833 = 24.168 kmol/ton sponge iron ... (3).

This oxygen is removed by the following reaction O+CO→CO ₂ or O+HB→H ₂ O.

Next, the reducing gas generated from 1 kg of coal will be described.

First, 1 kg of coal had the following composition.

% mol/Kgcoal C 75.9 63.250 ……(4) H 4.3 43.000 O 9.4 5.875 ……(5) The carbon content of coal is oxidized with water according to the following reaction C + H ₂ O → C + (H ₂ + O) → CO + H ₂ be done. required for this reaction
The amount of H ₂ O, that is, (H ₂ + O) is equivalent to the above (4), but since the O (oxygen) in it is obtained from the above (5), (4) - (5) = 63.250 - 5.875 = 57.375mol/Kgcoal...(6).

In addition, the reducing gas theoretically generated from 1Kg of coal is CO 63.250mol/Kgcoal ……(i) H ₂ 100.375mol/Kgcoal ……(ii) 163.625mol/Kgcoal (≒0.164kmol/Kgcoal) ……(7) It has the following composition.

Therefore, this reducing gas can remove oxygen equivalent to (7) above, that is, 0.164 kmol per 1 kg of coal. Therefore, to remove the amount of oxygen shown in (3) above, 24.168/0.164 = 147.366 Kgcoal/ton sponge iron ...(8) of coal is required.

In other words, 147.4 kg of coal is required to obtain 1 ton of sponge iron.

Next, the amount of electricity (E) theoretically required to produce 1 ton of sponge iron is calculated as follows.

(A) To decompose and gasify 1 kg of coal
A heat amount of 1.255 MJ/Kgcoal is required, and therefore, the heat amount required to decompose the amount of coal shown in (8) above is calculated as follows.

1.255×147.366=184.944MJ/ton sponge iron ……(9) (B) To decompose 1 mol of water into H and O, it takes 285.9kJ/
Therefore, the amount of heat required to decompose the amount of water shown in (6) above is the amount of heat shown in (8) above.
It is calculated as follows, taking into account:

285.9×57.375×147.366 = 2417.320MJ/ton sponge iron ……(10) (C) To heat 1 mol of CO and H ₂ to 1600℃, each
A calorific value of 45 kJ/mol and 42.5 kJ/mol is required, so the amounts shown in (i) and (ii) above, respectively, are required.
The amount of heat required to heat CO and H ₂ to 1600°C is calculated as follows, taking into account (8) above.

(45×63.250+42.5×100.375)×147.366 =1048.095MJ/tonsponge iron ……(11) (D) By the way, when 1 mol of C (carbon) is oxidized to CO, 110.5 kJ/mol of heat is generated. Therefore, when the amount of C shown in the above (4) is oxidized, the above (8)
Taking into account, the amount of heat calculated as follows can be obtained.

110.5×63.250×147.366 =1029.959MJ／ton sponge iron ……(12) From the above (A) to (D), the calorific balance (H) is (H)=(9)+(10)+(11)−(12) =2620.400MJ/ton sponge iron.

Here, since 1Wh = 3.6kJ, the required amount of electricity (E) is (E) = 2620.400/3.6 = 727.889kWh/ton sponge iron.

In other words, it takes 727.9kWh to obtain 1 ton of sponge iron.
of electricity is required.

From the above, per ton of sponge iron manufactured
It is theoretically calculated that 147.4Kg of coal and 727.9kWh of electricity are required.

However, in actual experiments conducted, some loss of reducing gas and deterioration during the desulfurization step occurs. Furthermore, electric power is required to drive compressors, pumps, etc. For these reasons, the actual consumption value is 820kWh as mentioned above, and the amount of electricity consumed by coal powder is 820kWh.
It became 172Kg.

These values apply to the existing rotary furnace method.
75kWh of electricity and 850Kg of coal, and
in the MidrexEDR method, which is a method that is being further developed and used on a commercial scale.
When compared with values of 970 kWh of electricity and 349 Kg of coal, it can be seen that the method of the invention is advantageous.

Substantial technical advantages are obtained by utilizing the method according to the invention. In this regard, the generation of the gas can be carried out at a temperature such that the ash forms a slag, which is easy to handle and can be poured out without causing clogging problems in the process. It is. The hydrogen concentration in the reducing gas can be adjusted to a level suitable for the reduction process by using the cleaning process and subsequently injecting water and/or oxygen gas into the gas generator. Moreover, by combining gas scrubbing with gas generation at high temperatures, the possibility of balancing the amount of gas in the system and regulating the reduction temperature is greatly increased. At the same time, the energy efficiency is improved. This is because the energy supplied by the plasma generator is used virtually entirely within the process (i.e. temperature regulation is achieved by adding cooler recycled reducing gas rather than removing heat from the system). (achieved).

If difficulties arise in binding the ash from the solid reducing agent into the slag phase, it is possible to use additives that influence the properties of the slag (e.g. melting point, sulfur adsorption capacity, etc.), such as alkali compounds and thiols. I can do it. Preferably, these additives are mixed with the solid reducing agent.

[Brief explanation of the drawing]

The accompanying drawings are diagrams schematically illustrating one embodiment for carrying out the invention. 1: Blast furnace, 2: Iron oxide, 7: Cleaning equipment, 9,1
0: Two flow sections, 11: Gas generator, 1
2: plasma burner, 13: jet, 16: pouring device, 15: sulfur filter.

Claims (1)

[Claims] 1. A method for producing sponge iron by continuously reducing iron oxide in a blast furnace, comprising: (a) injecting reducing gas into the lower part of the blast furnace; (b) removing the reduced iron from the furnace; (c) removing the reaction gas from the blast furnace; d) Substantially all CO ₂ and
(f) _a gas generating furnace substantially filled with a solid reducing agent and a plasma passing one of the flow sections through a gas generator having a burner and a device for injecting an oxidizing agent, heating the reactant gas by the plasma burner, and heating the heated gas from the plasma burner. (g) injecting an oxidizing agent into the solid reducing agent to form an intermediate gas mixture consisting primarily of CO and H ₂ ; (h) mixing said intermediate gas with at least a portion of said other flow portion in such a proportion that the temperature of the resulting reducing gas is suitable for the reduction of iron oxide in the blast furnace; A method for producing sponge iron, further comprising the steps of: 2. The method for producing sponge iron according to claim 1, wherein the oxidizing agent is water or oxygen. 3. A method according to claim 2, including the step of maintaining the intermediate gas mixture at a temperature between about 1300°C and 1500°C. 4. The method according to claim 3, wherein the intermediate gas is mixed with the at least one other flow portion, the mixing ratio being such that the temperature of the resulting reducing gas is such that the temperature of the resulting reducing gas is such that the temperature of the resulting reducing gas is maintained before the injection into the blast furnace. A method for producing sponge iron, characterized in that the temperature is selected to be between about 700°C and 1000°C. 5. The method for producing sponge iron according to claim 4, wherein the temperature of the reducing gas is approximately 825° C. before being injected into the blast furnace. 6. The method according to claim 1, characterized in that the CO ₂ and H ₂ O are removed from the reaction gas by a gas cleaning device until the concentration of CO ₂ is about 2% or less. A method of manufacturing sponge iron. 7. A method for producing sponge iron according to any one of claims 1 to 6, characterized in that the reducing agent is coke. 8. A method for producing sponge iron according to any one of claims 1 to 6, characterized in that an additional reducing agent is injected into the heated gas from the plasma burner. . 9. A method for producing sponge iron according to claim 8, characterized in that the additional reducing agent is coal dust with a particle size of 20 mesh or less. 10. A method for producing sponge iron according to claim 9, characterized in that the additional reducing agent is coal dust with a particle size of 100 mesh or less. 11 A method for producing sponge iron by continuously reducing iron oxide in a blast furnace, comprising: (a) injecting reducing gas into the lower part of the blast furnace, causing the reducing gas to pass upward through the blast furnace; (b) removing reduced iron from the furnace; (c) removing reactive gas from the blast furnace; and (d) removing the reactive gas from the blast furnace. Substantially all _CO2 and
(f) _a gas generating furnace substantially filled with a solid reducing agent and a plasma passing one of the flow sections through a gas generator having a burner and a device for injecting an oxidizing agent, heating the reactant gas by the plasma burner, and heating the heated gas from the plasma burner. (g) injecting an oxidizing agent into the solid reducing agent to form an intermediate gas mixture consisting primarily of CO and H ₂ ; (h) passing said intermediate gas mixture through a sulfur filter; and (li) maintaining the temperature of the resulting reducing gas at a temperature suitable for the reduction of iron oxide in the blast furnace. A method for producing sponge iron, further comprising the step of: mixing said intermediate gas with at least a portion of said other flow portion in proportion.