JPS6325045B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Despite the fact that coal is the most abundant and cheapest raw material for energy production, it has hitherto been used to a very limited extent as a reducing agent in the production of sponge iron. . This situation exists despite the favorable relationship between price and energy content for coal.

Conventional methods for producing sponge iron in which coal is used as the reducing agent include:

(a) Rotary furnace method. In this, coal is used together with the ore to be reduced in an inclined rotary furnace. The difficulty of this process, primarily due to the kinetic energy, is that it has to be carried out at relatively high temperatures, preferably 1000°C, at which temperatures there is significant clogging and deposition of material in the reaction chamber. A problem arises.

(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 CO2.
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. A reducing agent along with water is injected into the hot gas stream leaving the plasma generator, causing the water to react with the reducing agent, primarily
A mixture consisting of CO and _H2 is formed. The temperature level of the produced gas is maintained such that the ash contained within the solid reducing agent forms a slag. The hot CO—H ₂ gas mixture leaving the gas generator is mixed with at least some of the remaining flow rate portion of the purified recycle gas, the proportion of which is such that the temperature of the final gas mixture is suitable for the reduction process. chosen to be the chosen one.

According to one embodiment of the invention, the temperature level of the generated gas in the gas generating blast furnace is adjusted to a temperature range of 1300-1500<0>C. Before the final gas mixture is provided to the lower part of the blast furnace, the mixture is
700~1000℃ by mixing with the flow part of
It is also preferable to set the range of .

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

The apparatus for carrying out the process for producing sponge iron according to the invention comprises a cleaning device for the reducing gas leaving the reaction chamber and a gas generator connected thereto for receiving a portion of the cleaned reducing gas thus obtained. It has a reducing gas generation system including.
The gas generating furnace includes a plasma generating device and a supply device for controlling and introducing a reducing agent and water into the plasma gas generated within the device. An adjustable mixer is provided downstream of the gas generating furnace for mixing the reducing gas portion exiting the furnace with a second untreated portion of the cleaned reaction gas. The lower section of the reaction chamber is also provided with a blowing device for introducing the final gas mixture thus obtained.

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

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

The gas thus removed from blast furnace 1 is 50% to 70%
% of unreacted CO and H ₂ as well as reaction products CO ₂ and
Contains _H2O . This gas still contains relatively high percentages of CO and _H2 and can therefore be reused in the process. however,
In order for the gas to be reusable as a reducing gas, the content of CO ₂ and H ₂ O must be reduced to below 5%. This is achieved by passing the gas through a cleaning device (CO ₂ /H ₂ O cleaning) 7. When the gas passes through this cleaning device, it is not only liberated from the reaction products of CO ₂ and H ₂ O, but also allows for a balance of gas quantities during the actual cleaning process.
Combustion of gas may be prevented. Said cleaning device 7 can contain, for example, monoethanolamine as active substance, in which case the CO ₂ concentration in the gas can advantageously be reduced to below 2% during passage through the cleaning device.

After passing through the cleaning device 7, the gas is passed through the compressor 8.
, the pressure increase required for the process is achieved, and then at least two flow sections 9, 1
Divided into 0.

Said flow section 9, which is at room temperature, is passed into a gas generator 11, where the necessary surplus gas is produced from a solid reducing agent, preferably coal, and water. Said gas stream 9 is used as a plasma gas in a gas generator 11 and the amount of energy required for the gas generation process is provided in a plasma burner 12 . The main energy source, which is coal dust, is treated with an oxidizing agent, preferably water, and is fed through a jet 13 to the gas generator 11, with which the oxidizing agent reacts and generates CO and
H ₂ enters the hot gas stream leaving the plasma burner 12 to form H 2 . In order to ensure a sufficient degree of reaction and to ensure proper handling characteristics, the coal dust preferably has a particle size of less than 20 meshes, preferably less than 100 meshes.

Energy is supplied into the gas generator 11 by melting the ash present in the coal dust as slag 14, and supplying energy to the gas generator 11 in liquid or solid form.
It is timed so that it can be removed from the lower part of the.
Because of the ash content, the temperature is preferably selected in the range 1300-1500°C.

The reducing gases produced in this device are CO and _H2
In addition to containing sulfur, it may also contain sulfur contained in coal. This intermediate gas mixture is then passed through a sulfur filter 15 (e.g. a dolomite filter), where the sulfur content is preferably at a level acceptable in the sponge iron process.
reduced to levels below 75ppm.

The gas leaving said sulfur filter 15 is at a temperature substantially above that required for the sponge iron process, which temperature therefore causes the gas to mix within a suitable portion of the cold scrubbed gas in flow section 10. This results in a temperature suitable for the process, for example 750-1000°C, preferably 825°C.

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.

Substantial technical advantages are obtained by utilizing the method according to the invention. In this regard, the production of the gas is carried out at a temperature at which the ash forms a slag that is easy to handle and can be poured out without causing clogging problems during the process. The hydrogen concentration in the reducing gas can be adjusted to an appropriate level by injecting water into the gas generator after the cleaning process. Moreover, the combination of gas scrubbing and gas generation at high temperatures greatly increases the possibility of balancing the amount of gas in the system and regulating the reduction temperature. At the same time, energy efficiency also increases. This is because the energy supplied by the plasma generator is utilized almost entirely during the process (i.e. temperature regulation is not done by removing heat from the system, but rather by recycling it to a cooler temperature). (This is because this is achieved by adding a reducing gas.)

In a pilot scale experiment, 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=16.667kmolFe. If the metallization rate of this iron is 95%, then 1 ton of sponge iron contains 15.834 kmol/ton of FeO/0.833 kmol/ton of sponge iron (1).

Analysis of the raw materials revealed that each ton of sponge iron contained 8.334 kmol of Fe ₂ O ₃ / ton sponge iron and 25.001 kmol of oxygen (O) / ton of sponge iron (2).

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

This oxygen is removed by the following reaction O+CO→CO ₂ or O+H ₂ →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/Kg coal C 75.9 63.250 ……(4) H 4.3 43.000 O 9.4 5.875 ……(5) The carbon content of coal is removed by the following reaction with water: C+H ₂ O→C+(H ₂ +O)→CO+H ₂ Oxidized. 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 spongeiron...(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 spong 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 x 63.250 + 42.5 x 100.375) x 147.366 = 1048.095 MJ/ton sponge 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 heat balance (H) is (H)=(9)+(10)+(11)-(12) =2620.400MJ/ton sponge iron It is.

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 as well as Miderex
in the EDR 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.

Moreover, the process according to the invention is much easier to regulate and control than conventional processes. That is, by pre-mixing coal dust and added water in an appropriate ratio, preferably in a stoichiometric ratio,
A simpler and more efficient overall process control for plasma gas generation is achieved. This premixing of coal dust and water also makes the mixture easier to inject in the form of a coal-water emulsion.

If it is difficult to combine the ash from the solid reducing agent into the slag phase, use additives that influence the properties of the slag (e.g. melting point, sulfur adsorption capacity, etc.), such as alkaline compounds and silica. I can do it. Preferably, these additives are mixed with a solid reducing agent. It is possible to add a suitable gel former to stabilize the coal-water mixture, and oxygen in the form of oxygen gas can be supplied to the gas generator 11 instead of water.

[Brief explanation of the drawing]

The accompanying drawings schematically illustrate one embodiment of the invention. 1: blast furnace, 2: iron oxide, 7: cleaning device, 8: compressor, 9, 10: two flow sections of gas,
11: Gas generator, 12: Plasma burner, 1
3: Jet, 14: Slag, 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 and directing the reducing gas upward into the blast furnace; (b) removing the reduced iron from the blast furnace; (c) removing the reactive gas from the blast furnace; and (d) removing the reactive gas from the blast furnace. Substantially all _CO2 and
(e) dividing the reactant gas into at least two flow portions, (f) including a plasma burner and further injecting a solid reducing agent _and an oxidizing agent. passing one of said flow sections through a gas generator comprising an apparatus, heating said reactant gas in said plasma burner, injecting a solid reducing agent and an oxidizing agent into the heated gas, and injecting a solid reducing agent and an oxidizing agent into the heated gas; forming an intermediate gas mixture consisting of H ₂ ; (g) maintaining said intermediate gas mixture at a temperature such that ash contained within said solid reducing agent forms a slag; mixing said intermediate gas mixture with at least one portion of another portion of said flow section in a ratio such 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, comprising: 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. A method according to claim 3, wherein the intermediate gas mixture is mixed with the at least one other flow portion in a ratio that is equal to or lower than that of the reducing gas before being injected into the blast furnace. A method for producing sponge iron, characterized in that the temperature is selected to be between approximately 700°C and 1000°C. 5. The method for producing sponge iron according to claim 4, wherein the temperature of the reducing gas before being injected into the blast furnace is about 825°C. 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 coal. 8. The method for producing sponge iron according to claim 7, wherein the reducing agent is coal dust. 9. A method for producing sponge iron according to claim 8, wherein the reducing agent is pit coal dust. 10. The method for producing sponge iron according to claim 8, wherein the reducing agent is coal dust having a particle size of 20 meshes or less. 11. The method for producing sponge iron according to claim 10, wherein the reducing agent is coal dust having a particle size of 100 mesh or less. 12 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, passing the reducing gas upward through the blast furnace; (b) removing reduced iron from the blast furnace; (c) removing reactant gas from the blast furnace; and (d) removing substantially all of the CO from the reactant gas. ₂ and
(e) dividing the reactant gas into at least two flow portions, (f) including a plasma burner and further injecting a solid reducing agent _and an oxidizing agent. passing one of said flow sections through a gas generator comprising an apparatus, heating said reactant gas in said plasma burner, injecting a solid reducing agent and an oxidizing agent into the heated gas, and injecting a solid reducing agent and an oxidizing agent into the heated gas; forming an intermediate gas mixture consisting of H ₂ ; (g) maintaining said intermediate gas mixture at a temperature such that ash contained within said solid reducing agent forms a slag; passing said intermediate gas mixture through a sulfur filter; (i) mixing said intermediate gas mixture with at least one portion of the other portions of said flow section in a proportion, thereby reducing the temperature of the resulting reducing gas; A method for producing sponge iron, comprising the steps of: making the sponge iron suitable for reducing iron oxide in a blast furnace.