Method for controlling content of silicon and sulfur in molten iron of blast furnace

Abstract

The invention discloses a blast furnace molten iron silicon and sulfur content control method which comprises the following steps: detecting the silicon content and the sulfur content of molten iron in a molten iron groove in the production process from a blast furnace tap hole to a molten iron ladle; and then oxygen is blown from the top of the molten iron in the molten iron groove and / or sulfuric acid slag is added for treatment, so that the silicon content of the molten iron is smaller than or equal to 1% and the sulfur content is larger than or equal to 0.015%. According to detection feedback of the molten iron in the molten iron groove, top blowing of oxygen is performed on the molten iron to control the silicon content of the molten iron, sulfuric acid slag is added into the molten iron to control the sulfur content of the molten iron, the silicon content of the molten iron in the molten iron groove is smaller than or equal to 1%, the sulfur content of the molten iron is larger than or equal to 0.015%, and the fluidity of the molten iron is guaranteed; the situation that graphite precipitation affects and pollutes the working environment is reduced, the situation that bonding substances need to be cleaned by operators when the molten iron channel is bonded can be reduced, the labor intensity of the operators is reduced, and the working risk is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking, and in particular to a method for controlling silicon and sulfur content in molten iron in a blast furnace. Background Art

[0002] Producing molten iron of qualified quality is one of the important goals of blast furnace ironmaking. The silicon and sulfur content in molten iron is not only an important indicator to test whether the molten iron is qualified, but also reflects the state of the blast furnace and its changes.

[0003] At present, during the start-up, shutdown or abnormal condition of the blast furnace, molten iron with a high silicon content is easily produced, and the silicon content and sulfur content of the blast furnace molten iron are in a corresponding relationship. Under the same smelting conditions, the high silicon content of the molten iron is usually accompanied by the low sulfur content of the molten iron, that is, the high silicon and low sulfur molten iron is formed. However, the high silicon and low sulfur molten iron has poor ductility and is easy to form adhesion in the molten iron ditch before the blast furnace is discharged, and it will also cause a large amount of graphite precipitation. Graphite is easy to float and pollute the working environment. At the same time, in order to avoid the increase in the amount of adhesion and the overflow of the molten iron from the molten iron ditch, the operator needs to use the support rod to scrape and clean the adhesion in the molten iron ditch, which is labor-intensive and has high operating risks. Summary of the invention

[0004] The object of the present invention is to provide a method for controlling the silicon and sulfur content in molten iron of a blast furnace, which is easy to operate, can reduce the silicon content in the molten iron and increase the sulfur content in the molten iron, and ensure the fluidity of the molten iron.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A method for controlling silicon and sulfur content in molten iron in a blast furnace is provided, comprising the following steps:

[0007] S10, in the production process from the blast furnace tap hole to the iron ladle, detecting the silicon content of the molten iron in the iron ditch and the sulfur content of the molten iron;

[0008] S20, top blowing oxygen and / or adding slag sulfate to the molten iron in the molten iron ditch to treat the molten iron so that the silicon content of the molten iron is ≤1% and the sulfur content of the molten iron is ≥0.015%.

[0009] As a preferred solution for controlling the silicon and sulfur content in blast furnace molten iron, the composition requirements of the sulfate slag are: Fe2O3: 20-50%, SiO2: 15-65%, Al2O3: 10%, CaO: 5%, MgO: 2-5% and S: 3-5%.

[0010] As a preferred solution for the method for controlling the silicon and sulfur content in molten iron of a blast furnace, the proportion of the sulfate slag having a particle size D1≤1 mm is greater than 80%.

[0011] As a preferred scheme of the method for controlling the silicon and sulfur content of blast furnace molten iron, when the silicon content of the molten iron is detected to be greater than 1.25% and the sulfur content of the molten iron is greater than or equal to 0.015%, a metal pipe is inserted into the molten iron ditch, and the oxygen is gradually introduced into the metal pipe, and the molten iron in the molten iron ditch is treated by blowing oxygen to reduce the silicon content of the molten iron, so that the silicon content of the molten iron is gradually reduced until the silicon content of the molten iron is detected to be ≤1%, wherein the diameter D2 of the metal pipe is 30mm≤≤50mm.

[0012] As a preferred scheme for controlling the silicon and sulfur content in blast furnace molten iron, when the oxygen blowing and silicon reduction treatment using the metal tube cannot reduce the silicon content of the molten iron to ≤1%, and the sulfur content of the molten iron is detected to be <0.015%, the oxygen blowing and silicon reduction treatment is maintained, and the sulfuric acid slag is gradually added to the molten iron ditch to increase the sulfur content of the molten iron until the sulfur content of the molten iron is detected to be ≥0.015% and the silicon content of the molten iron is reduced to ≤1%.

[0013] As a preferred solution of the method for controlling the silicon and sulfur content of molten iron in a blast furnace, before the operation, the operator divides the pile of the evenly mixed sulfuric acid slag into at least 1 weight part, 2 weight parts, 4 weight parts, 10 weight parts, and 20 weight parts of the sulfuric acid slag, and packages them separately in plastic bags;

[0014] During the addition operation of the sulfuric acid slag, 1 weight part of the sulfuric acid slag is added to the molten iron ditch per minute to increase the sulfur content of the molten iron; if the sulfur content of the molten iron is still less than 0.015% after 5 minutes, 2 weight parts of the sulfuric acid slag is added to the molten iron ditch; if the sulfur content of the molten iron is still less than 0.015% after another 5 minutes, 4 weight parts of the sulfuric acid slag is added to the molten iron ditch.

[0015] As a preferred solution of the method for controlling the silicon and sulfur content of blast furnace molten iron, when the silicon content of the molten iron is detected to be ≤1% and the sulfur content of the molten iron is <0.015%, the sulfuric acid slag is gradually added to the molten iron ditch to increase the sulfur content of the molten iron until the sulfur content of the molten iron is detected to be ≥0.015%.

[0016] As a preferred solution of the method for controlling the silicon and sulfur content of molten iron in a blast furnace, during the production process from the blast furnace tap hole to the molten iron ladle, it is also necessary to detect the temperature of the molten iron in the molten iron ditch to meet the following requirements: the blast furnace body capacity C≤1000m 3 When 1450℃≤the temperature of the molten iron T≤1480℃; 1000m 3 <Blast furnace capacity C≤2000m 3 When the temperature of the molten iron is 1480℃<T≤1510℃; the capacity of the blast furnace C>2000m 3When the temperature of the molten iron is T>1510°C.

[0017] As a preferred scheme of the method for controlling the silicon and sulfur content of molten iron in a blast furnace, the molten iron in the blast furnace body flows into the molten iron ditch from the blast furnace tapping port, the molten iron ditch includes a main ditch and a dragon ditch, the main ditch is connected to the blast furnace body, the end of the main ditch away from the blast furnace body is connected to the dragon ditch, the end of the dragon ditch away from the main ditch is guided to the molten iron ladle through a swinging spout, and the sulfuric acid slag is added to the main ditch and a position adjacent to one end of the blast furnace tapping port.

[0018] As a preferred solution of the method for controlling the silicon and sulfur content in blast furnace molten iron, the molten iron ditch also includes a slag ditch and a slag skimmer. The slag skimmer is provided at one end of the main ditch adjacent to the dragon ditch, and the slag ditch is connected to one end of the main ditch adjacent to the dragon ditch. The slag ditch is used to discharge the slag intercepted by the slag skimmer, and the oxygen is added into the main ditch and is located at the front end of the slag skimmer.

[0019] The beneficial effects of the present invention are as follows: according to the detection feedback of the molten iron in the molten iron ditch, oxygen is top-blown into the molten iron to control the silicon content of the molten iron, and sulfuric acid slag is added to the molten iron to control the sulfur content of the molten iron, so that the silicon content of the molten iron in the molten iron in the molten iron ditch is ≤1% and the sulfur content of the molten iron is ≥0.015%, so as to ensure the fluidity of the molten iron, reduce the situation where graphite precipitation affects the pollution of the working environment, and can reduce the situation where the molten iron ditch is sticky and needs operators to clean up the sticky materials, thereby ensuring the quality of the molten iron and the safety of transportation, and the operation is simple, reducing the labor intensity of operators and effectively reducing the operating risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described in detail below based on the accompanying drawings and embodiments.

[0021] Figure 1 It is an operation flow chart of a method for controlling silicon and sulfur content in molten iron in a blast furnace according to an embodiment of the present invention;

[0022] Figure 2 Schematic diagram of the structure of the blast furnace of the embodiment of the present invention Figure 1 ;

[0023] Figure 3 Schematic diagram of the structure of the blast furnace of the embodiment of the present invention Figure 2 .

[0024] In the figure:

[0025] 1. Blast furnace body; 11. Blast furnace taphole; 2. Hot metal ladle; 3. Hot metal ditch; 31. Main ditch; 32. Dragon ditch; 33. Slag ditch; 34. Slag skimmer; 4. Swinging spout. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0027] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0029] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0030] like Figures 1 to 3 As shown, the method for controlling the silicon and sulfur content in molten iron in a blast furnace according to an embodiment of the present invention comprises the following steps:

[0031] S10, in the production process from the blast furnace tap hole 11 to the molten iron ladle 2, detecting the silicon content and the sulfur content of the molten iron in the molten iron ditch 3;

[0032] S20, top blowing oxygen and / or adding sulfuric acid slag to the molten iron in the molten iron ditch 3 to treat the molten iron so that the silicon content of the molten iron is ≤1% and the sulfur content of the molten iron is ≥0.015%.

[0033] It can be understood that the method for controlling the silicon and sulfur content in molten iron in blast furnace of the present scheme is simple to operate. It is only necessary to top-blow oxygen into the molten iron to control the silicon content of the molten iron according to the detection feedback of the molten iron in the molten iron ditch 3, and add sulfuric acid slag to the molten iron to control the sulfur content of the molten iron, so that the silicon content of the molten iron in the molten iron ditch 3 is ≤1% and the sulfur content of the molten iron is ≥0.015%, so as to ensure the fluidity of the molten iron, reduce the situation where graphite precipitation affects the pollution of the working environment, and can reduce the situation where the molten iron ditch 3 is sticky and the operator needs to clean the sticky materials, thereby ensuring the quality of the molten iron and the safety of transportation. It is simple to operate, reduces the labor intensity of the operators and effectively reduces the operating risks.

[0034] Optionally, the composition of the slag is as follows: Fe2O3: 20-50%, SiO2: 15-65%, Al2O3: 10%, CaO: 5%, MgO: 2-5% and S: 3-5%. The cost of slag is low. Slag is a waste generated in the process of sulfuric acid production. By utilizing slag, the waste can be recycled, and the composition is coordinated to strictly control the sulfur content in the slag to be 3-5%. For example, the sulfur content in the slag is 3%, 3.5%, 4%, 4.5% or 5%. If the sulfur content in the slag is too high, it is easy to mix unevenly, resulting in the phenomenon that the sulfur content of the local molten iron is too high and the sulfur content of the local molten iron is too low when adding slag for adjustment. If the sulfur content in the slag is too low, it is difficult to adjust the sulfur content and it is easy to increase the content of other elements. The sulfur content in the slag is moderate and easy to adjust.

[0035] Further, the proportion of the particle size D1≤1mm of the sulphuric acid slag is greater than 80%. For example, the particle size D1 of the sulphuric acid slag is 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1.0mm, etc. The proportion of the sulphuric acid slag with a particle size D1≤1mm to the whole sulphuric acid slag is 82%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98% or 100%, etc. The reducing atmosphere in the iron water ditch 3 will reduce the sulfur to free sulfur, and the free sulfur can react with the iron in the molten iron to generate iron sulfide. The reaction process needs to absorb a certain amount of heat in the molten iron. The preheating baking temperature of the finer-grained sulphuric acid slag is lower, and the energy consumption is also lower. By controlling the fineness of the sulphuric acid slag, the influence of the sulphuric acid slag on the molten iron temperature when it is added to the iron water ditch 3 can be reduced.

[0036] In this embodiment, the detection element detects the molten iron in the iron ditch 3 once every 5 minutes. When the silicon content of the molten iron is greater than 1.25% and the sulfur content of the molten iron is greater than or equal to 0.015%, a metal pipe is inserted into the iron ditch 3, and oxygen is gradually introduced into the metal pipe to blow oxygen and reduce silicon in the iron ditch 3, so that the silicon content of the molten iron is gradually reduced until the silicon content of the molten iron is detected to be ≤1%, wherein 30mm≤the diameter D2 of the metal pipe≤50mm. Oxygen combustion is used to cause the silicon molecules in the molten iron to react with oxygen molecules to form silicon dioxide, which will form slag and be intercepted by the subsequent slag skimmer 34, effectively reducing the silicon content in the molten iron.

[0037] In addition, for example, the diameter D2 of the metal pipe is 30mm, 32mm, 34mm, 36mm, 38mm, 40mm, 42mm, 44mm, 46mm, 48mm or 50mm, etc. The diameter D2 of the metal pipe is too small to meet the mixed contact surface of oxygen and molten iron, and the oxidation reaction space is small. The diameter D2 of the metal pipe is too large to be easy to hold and balance the oxygen delivery rate, which easily causes the molten iron to splash. The diameter D2 of the metal pipe is reasonably designed to effectively ensure the mixing of oxygen and molten iron. It should be noted that when oxygen is introduced, the oxygen valve needs to be opened slowly to control the molten iron without water splashing. When the flow rate of oxygen introduction reaches the point where iron flowers splash, the oxygen introduction amount should be appropriately reduced.

[0038] Furthermore, when the oxygen blowing and silicon reduction treatment using a metal tube cannot reduce the silicon content of the molten iron to ≤1%, and the sulfur content of the molten iron is detected to be <0.015%, the oxygen blowing and silicon reduction treatment is maintained, and sulfuric acid slag is gradually added to the molten iron ditch 3 to increase the sulfur content of the molten iron, until the sulfur content of the molten iron is detected to be ≥0.015% and the silicon content of the molten iron is reduced to ≤1%. Since the silicon content in the molten iron is inversely proportional to the sulfur content, when the oxidation reaction of oxygen and molten iron is no longer sufficient to control the silicon content in the molten iron, sulfuric acid slag is added to increase the sulfur content in the molten iron and reduce the silicon content in the molten iron. In practical applications, when the metal tube is used to blow oxygen and silicon reduction to reduce the silicon content in the molten iron to between 1% and 1.25%, the sulfur content in the molten iron will be reduced to below 0.012%, so adding sulfuric acid slag at this time can effectively increase the sulfur content in the molten iron and reduce the silicon content in the molten iron.

[0039] Of course, when the initial contact detection component detects that the silicon content of the molten iron is greater than 1.25% and the sulfur content of the molten iron is less than 0.015%, oxygen is directly introduced through the metal pipe and sulfuric acid slag is added into the molten iron groove 3 for simultaneous treatment.

[0040] Furthermore, when the silicon content of the molten iron is detected to be ≤1% and the sulfur content of the molten iron is <0.015%, sulfuric acid slag is gradually added to the molten iron ditch 3 to increase the sulfur content of the molten iron, until the sulfur content of the molten iron is detected to be ≥0.015%. At this time, the silicon content in the molten iron is qualified, and only sulfuric acid slag needs to be added to control the sulfur content of the molten iron.

[0041] In some embodiments, before the operation, the operator divides the pile of sulfuric acid slag that has been evenly mixed into at least 1 weight part, 2 weight parts, 4 weight parts, 10 weight parts, and 20 weight parts of sulfuric acid slag, and packages them individually with plastic bags; when adding the sulfuric acid slag, 1 weight part of sulfuric acid slag is added to the iron water ditch 3 per minute to increase the sulfur content of the molten iron; if the sulfur content of the molten iron is still less than 0.015% after 5 minutes, 2 weight parts of sulfuric acid slag is added to the iron water ditch 3; if the sulfur content of the molten iron is still less than 0.015% after another 5 minutes, 4 weight parts of sulfuric acid slag is added to the iron water ditch 3.

[0042] It can be understood that, taking 1 part by weight as 50g as an example, the mixed pile of sulfuric acid slag is divided into multiple parts of 50g sulfuric acid slag, 100g sulfuric acid slag, 200g sulfuric acid slag, 500g sulfuric acid slag and 1000g sulfuric acid slag, etc. and packaged independently in plastic bags. During the sulfuric acid slag addition operation, within 5 minutes of the first stage, 50g of sulfuric acid slag is placed in the iron water ditch 3 every minute using a support rod, and the plastic bag melts at the high temperature of the molten iron to allow the sulfuric acid slag to be melted into the molten iron for mixing. According to the second test result after 5 minutes, if the sulfur content of the molten iron is still less than 0.015%, 100g of sulfuric acid slag is added at one time, and the sulfur content in the molten iron is ≥ 0.015%. Gradually add to effectively control the sulfur content of the molten iron in the iron water ditch 3, and avoid the situation where the sulfur content is too high and the silicon content is too low due to excessive addition.

[0043] Furthermore, during the production process from the blast furnace tap hole 11 to the ladle 2, the temperature of the molten iron in the molten iron channel 3 needs to be detected to meet the following requirements: the capacity C of the blast furnace body 1 is ≤ 1000m 3 When 1450℃≤molten iron temperature T≤1480℃; 1000m 3 <Blast furnace body 1 capacity C≤2000m 3 When 1480℃<molten iron temperature T≤1510℃; blast furnace body 1 capacity C>2000m 3 When the temperature of the molten iron is T>1510℃. Too high a tapping temperature may lead to excessive oxidation and increased heat loss, affecting the quality of the molten iron. By ensuring that the temperature of the molten iron is moderate, the viscosity of the molten iron can be reduced, the flow of the molten iron can be promoted, and the impurity content in the molten iron can be reduced, so as to balance the smelting efficiency and product quality.

[0044] Furthermore, if Figure 2and Figure 3 As shown, the molten iron in the blast furnace body 1 flows into the iron water ditch 3 from the blast furnace tapping hole 11, and the iron water ditch 3 includes a main ditch 31 and a dragon ditch 32. The main ditch 31 is connected to the blast furnace body 1, and the end of the main ditch 31 away from the blast furnace body 1 is connected to the dragon ditch 32, and the end of the dragon ditch 32 away from the main ditch 31 is guided to the iron ladle 2 through the swinging nozzle 4, and the sulfuric acid slag is added to the main ditch 31 and the position of one end adjacent to the blast furnace tapping hole 11. The molten iron in the main ditch 31 and the end adjacent to the blast furnace tapping hole 11 has a large rolling fluctuation, and at the initial end of the molten iron flow, so after the sulfuric acid slag is added to the main ditch 31 and the end adjacent to the blast furnace tapping hole 11, the mixing effect of the sulfuric acid slag and the molten iron can be improved, and the operation process of manual stirring can be reduced. Preferably, the sulfuric acid slag is added to the landing point where the blast furnace body 1 flows out from the tapping hole in a parabola, and the molten iron flow and rolling effect at this position is the best.

[0045] Optionally, the molten iron ditch 3 further includes a slag ditch 33 and a slag skimmer 34. The slag skimmer 34 is provided at one end of the main ditch 31 adjacent to the dragon ditch 32, and the slag ditch 33 is connected to one end of the main ditch 31 adjacent to the dragon ditch 32. The slag ditch 33 is used to discharge the slag intercepted by the slag skimmer 34. Oxygen is added to the main ditch 31 and is located at the front end of the slag skimmer 34. With the addition of sulfuric acid slag, the temperature of the molten iron in the molten iron ditch 3 is partially absorbed, but the oxidation reaction of oxygen will release corresponding energy. Therefore, oxygen is inserted into the front end of the slag skimmer 34 in the main ditch 31 by using a metal pipe, so that the silicon dioxide formed by oxygen and molten iron can be intercepted by the slag skimmer 34. At the same time, the temperature of the molten iron before the main ditch 31 flows to the dragon ditch 32 can be increased to ensure the fluidity of the molten iron.

[0046] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for controlling silicon and sulfur content in molten iron of a blast furnace, characterized in that: The following steps are involved: S10, in the production process from the blast furnace tap hole to the iron ladle, detecting the silicon content of the molten iron in the iron ditch and the sulfur content of the molten iron; S20, top blowing oxygen and / or adding slag sulfate to the molten iron in the molten iron ditch to treat the molten iron so that the silicon content of the molten iron is ≤1% and the sulfur content of the molten iron is ≥0.015%.

2. The method for controlling silicon and sulfur content in molten iron of a blast furnace according to claim 1, characterized in that: The composition requirements of the sulfate slag are: Fe2O3: 20-50%, SiO2: 15-65%, Al2O3: 10%, CaO: 5%, MgO: 2-5% and S: 3-5%.

3. The method for controlling silicon and sulfur content in molten iron of blast furnace according to claim 2, characterized in that: The proportion of the sulfuric acid slag having a particle size D1≤1 mm is greater than 80%.

4. The method for controlling silicon and sulfur content in molten iron of a blast furnace according to any one of claims 1 to 3, characterized in that: When the silicon content of the molten iron is detected to be greater than 1.25% and the sulfur content of the molten iron is greater than or equal to 0.015%, a metal pipe is inserted into the molten iron ditch, and the oxygen is gradually introduced into the metal pipe to blow oxygen and reduce the silicon content of the molten iron in the molten iron ditch, so as to gradually reduce the silicon content of the molten iron until the silicon content of the molten iron is detected to be ≤1%, wherein the diameter D2 of the metal pipe is 30mm≤≤50mm.

5. The method for controlling silicon and sulfur content in molten iron of blast furnace according to claim 4, characterized in that: When the oxygen blowing and silicon reduction treatment using the metal tube cannot reduce the silicon content of the molten iron to ≤1%, and the sulfur content of the molten iron is detected to be <0.015%, the oxygen blowing and silicon reduction treatment is maintained, and the sulfuric acid slag is gradually added to the molten iron ditch to increase the sulfur content of the molten iron, until the sulfur content of the molten iron is detected to be ≥0.015% and the silicon content of the molten iron is reduced to ≤1%.

6. The method for controlling silicon and sulfur content in molten iron of blast furnace according to claim 5, characterized in that: Before the operation, the operator divides the piled sulfuric acid slag that has been mixed evenly into at least 1 weight part, 2 weight parts, 4 weight parts, 10 weight parts, and 20 weight parts of the sulfuric acid slag, and packages them independently with plastic bags; During the addition operation of the sulfuric acid slag, 1 weight part of the sulfuric acid slag is added to the molten iron ditch per minute to increase the sulfur content of the molten iron; if the sulfur content of the molten iron is still less than 0.015% after 5 minutes, 2 weight parts of the sulfuric acid slag is added to the molten iron ditch; if the sulfur content of the molten iron is still less than 0.015% after another 5 minutes, 4 weight parts of the sulfuric acid slag is added to the molten iron ditch.

7. The method for controlling silicon and sulfur content in molten iron of a blast furnace according to any one of claims 1 to 3, characterized in that: When the silicon content of the molten iron is detected to be ≤1% and the sulfur content of the molten iron is <0.015%, the sulfuric acid slag is gradually added into the molten iron ditch to increase the sulfur content of the molten iron until the sulfur content of the molten iron is detected to be ≥0.015%.

8. The method for controlling silicon and sulfur content in molten iron of a blast furnace according to any one of claims 1 to 3, characterized in that: In the production process from the blast furnace tap hole to the ladle, it is also necessary to detect the temperature of the molten iron in the molten iron ditch to meet the following requirements: Blast furnace body capacity C ≤ 1000m 3 When 1450℃≤the temperature of the molten iron T≤1480℃; 1000m 3 <Blast furnace capacity C≤2000m 3 When the temperature of the molten iron is 1480℃<T≤1510℃; the capacity of the blast furnace C>2000m 3 When the temperature of the molten iron is T>1510°C.

9. The method for controlling silicon and sulfur content in molten iron of a blast furnace according to any one of claims 1 to 3, characterized in that: The molten iron in the blast furnace body flows into the molten iron ditch from the blast furnace tapping port, the molten iron ditch includes a main ditch and a dragon ditch, the main ditch is connected to the blast furnace body, the end of the main ditch away from the blast furnace body is connected to the dragon ditch, the end of the dragon ditch away from the main ditch is guided to the molten iron ladle through a swinging spout, and the sulfuric acid slag is added to the main ditch and a position adjacent to one end of the blast furnace tapping port.

10. The method for controlling silicon and sulfur content in molten iron of blast furnace according to claim 9, characterized in that: The molten iron ditch also includes a slag ditch and a slag skimmer. The slag skimmer is provided at one end of the main ditch adjacent to the dragon ditch, and the slag ditch is connected to one end of the main ditch adjacent to the dragon ditch. The slag ditch is used to discharge the slag intercepted by the slag skimmer. The oxygen is added into the main ditch and is located at the front end of the slag skimmer.

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