CN101067160A - MgO-based desulfurizer and preparation method thereof - Google Patents

Abstract

The present invention relates to external desulfurization technology, and is especially MgO-base desulfurizer as one new kind of molten iron and steel desulfurizing material and its production process. The MgO-base desulfurizer consists of MgO, graphite or charcoal, reaction promoter SiO2, pH regulator of lime, limestone, dolomite or silica, and adhesive comprising asphalt, tar and resin. It is produced through drying the material, crushing, grinding, mixing, palletizing stoving and packing. The present invention has the advantages of lowered desulfurizing cost, effective suppression of magnesium vapor explosion, high desulfurizing efficiency, etc.

Description

MgO-based desulfurizer and preparation method thereof

Technical field: The present invention relates to the technical field of desulfurization outside the furnace, and mainly relates to a new type of desulfurizer material and manufacturing process for desulfurization of molten iron or molten steel.

Background technology: Today's iron and steel industry is still dominated by the blast furnace-converter long-flow process, and the steel output accounts for about 70% of the total output. The three stages of pretreatment, converter smelting, and refining outside the furnace decompose the various chemical reactions of steelmaking from the past in a converter to three stages to complete, and various chemical reactions are carried out under their optimal conditions. The result is increased productivity, lower production costs, and a purer quality steel that meets the higher demands placed on steel by various industries.

In addition to special requirements for desiliconization and dephosphorization or extraction of some special elements, the pretreatment of molten iron is mainly to desulfurize the molten iron. The desulfurization of molten iron before entering the converter smelting has the best reaction conditions, because: 1) The molten iron contains a large amount of elements with good reducibility such as Si, C, Mn, etc., and its reducibility is beneficial to the desulfurization reaction, (strong desulfurizers Ca, Mg less burning loss); 2) C and Si in molten iron can greatly increase the activity coefficient of S in molten iron, making it easier to remove sulfur to a low level; 3) the oxygen content in molten iron is low, and the distribution coefficient of sulfur is correspondingly reduced 4) During the desulfurization process of molten iron pretreatment, the change of molten iron composition has less influence on the final steel grade than the change of molten steel composition during steelmaking or molten steel treatment; 5) The temperature of molten iron treatment is low, It is beneficial to the life of the processing device.

In addition, desulfurization outside the molten iron furnace can reduce the load of the blast furnace, reduce the coke ratio, reduce the amount of slag and increase productivity. The experience of some foreign iron and steel plants proves that: the desulfurization of blast furnace hot metal outside the furnace can reduce the basicity of blast furnace slag from 1.25 to 1.06, the coke ratio can be reduced by 36kg/t iron, and the productivity can be increased by 13%. 83% of the cost saved, the cost is about 3.65 US dollars / ton of iron, saving 0.8 US dollars per ton of iron.

With the development of industrial technology, the requirements for steel quality are getting higher and higher, especially for the sulfur content in steel. The performance of steel is an inflection point at the sulfur content of 0.013%, and some high-performance pure steel requires the sulfur content to be reduced. To below 0.01%-0.001%, this desulfurization task is mainly completed by molten iron pretreatment. Due to technical and economic reasons, in today's traditional blast furnace converter smelting process, hot metal pretreatment desulfurization has generally become an indispensable process. The proportion of molten iron pretreatment in the long process of the world's major steel-producing countries has already reached 90%-100%, but there is a big gap between my country and developed countries. Since the 1960s and 1970s, the former Soviet Union and Eastern Europe began to use magnesium-based desulfurizers for hot metal desulfurization, and Western Europe and North America successively cited and redeveloped them. By the 1990s, desulfurization outside the furnace had become a key technology for reducing sulfur content in steel.

There are two main methods of desulfurization outside the molten iron furnace: the first method is the method of feeding the cored wire, inserting the cored wire into the molten iron to achieve desulfurization of the molten iron; the second method is to inject a powdery desulfurizer into the molten iron for desulfurization. There are four main desulfurizers for desulfurization outside the hot metal furnace: soda Na ₂ CO ₃ , lime CaO, calcium carbide CaC ₂ based desulfurizer and magnesium Mg based desulfurizer.

Wire feeding method and injection method have good effect on hot metal desulfurization outside the furnace. Among the four desulfurizers, the magnesium-based desulfurizer is most suitable for the application conditions of desulfurization outside the molten iron furnace. Its advantages are strong desulfurization ability; it still has good desulfurization ability at lower molten iron temperature; Small amount, small temperature drop, good desulfurization effect. Since magnesium can react with a variety of impurities in metals to form stable compounds, it has always been one of the first choices for refining agents. Using magnesium powder to desulfurize molten iron outside the furnace, the equilibrium constant of the desulfurization reaction can reach 2.06×10 ¹ , and high-purity, high-clean steel products can be obtained. Mg-based desulfurizer is currently the first choice for desulfurization outside the molten iron furnace, but there are still many deficiencies in the research and application of magnesium-based desulfurizers in molten iron pretreatment: (1) Metal magnesium desulfurizers used in iron and steel enterprises need passivation treatment , the price is higher; (2) the volatilization of magnesium under high temperature is serious, so that the refining reaction efficiency of magnesium is relatively low. 0.030% sulfur needs to consume 0.227kg of magnesium. Recently, in domestic industrial production, about 0.45kg of magnesium is actually needed to remove about 0.030% of sulfur in 1 ton of molten iron. Obviously, the utilization rate of magnesium is less than 50%; (3) Due to the high vapor pressure of magnesium at high temperature, there are potential safety hazards in the use of metal magnesium granular desulfurizers, and its preventive measures and addition methods need to be further studied.

Due to the above shortcomings of magnesium-based desulfurizers, countries all over the world are looking for new desulfurizers to replace magnesium-based desulfurizers. The Japanese Sano et al. proposed a new refining process that uses the aluminothermic reduction reaction of magnesia to generate magnesium vapor and blows it directly into the steel melt for desulfurization. This method uses aluminum as the reducing agent of magnesia. The study found that: by controlling the partial pressure of magnesium in the blown gas to be below 0.2 atm, the refining efficiency of magnesium is greatly improved. It can be seen that MgO-based desulfurizers show great application prospects. If carbon, which is much cheaper than aluminum, can be used as a reducing agent, not only can the cost of desulfurization and refining be greatly reduced, but also the possible explosion hazard of magnesium vapor can be effectively suppressed, and the efficiency of the desulfurizer can be greatly improved.

Summary of the invention: The present invention provides a MgO-based desulfurizer and its preparation method. The desulfurizer has the characteristics of less raw slag, high desulfurization efficiency, high desulfurization rate, no need for special desulfurization equipment, and easy operation. Its purpose is to solve the problems of reducing desulfurization cost, effectively suppressing the possible explosion hazard of magnesium steam, and the efficiency of desulfurizer needs to be greatly improved.

The present invention is achieved through the following technical solutions:

A MgO-based desulfurizer, characterized in that: the desulfurizer is composed of MgO, graphite or charcoal, a reaction accelerator, a pH regulator, and a binder, wherein the mass percentage of MgO plus graphite or charcoal in the desulfurizer is The MgO/C molar ratio is 1:1; _SiO2 is the reaction accelerator, and the mass percentage in the desulfurizer is 2-10%; the pH regulator is lime, limestone, dolomite, A kind of silica, which accounts for 1-5% by mass in the desulfurizer; the binder is asphalt, tar, resin, which accounts for 5-15% by mass in the desulfurizer. MgO and graphite or charcoal are proportioned according to the molar ratio of the chemical reaction equation.

The preparation method of the MgO-based desulfurizer is characterized in that: the various components of the desulfurizer as claimed in claim 1, the raw materials except the binder are dried and pretreated, the moisture therein is completely removed, and the Crushing and grinding into fine powder below -200 mesh, then weighing and batching according to mass percentage, fully stirring and mixing, adding binder, stirring evenly, forming agglomerates into particles of different shapes, drying and packaging finished product.

The desulfurizer provided by the present invention has the following advantages when used in deep desulfurization of molten iron or molten steel: (1), the desulfurization speed is fast, the sulfur concentration can be desulfurized to an ultra-low level in a short time, and the desulfurization efficiency is high; (2), the desulfurization rate can be greatly increased; (3) The amount of slag is small and no slag removal is required. The desulfurizer can be directly added to the ladle or ladle during tapping or steel tapping without spraying equipment Or other related equipment, low investment, easy operation; (4), the temperature drop is small during the desulfurization process, the desulfurization product is stable, and the desulfurization rate is stable.

Detailed ways:

The desulfurizer of the present invention is composed of MgO, graphite or charcoal, SiO ₂ , a pH regulator, and a binder, wherein the mass percentage and function of each component are:

MgO+C (graphite or charcoal) reacts in situ to generate Mg vapor, which acts as a sulfophile, in which MgO/C is proportioned according to the molar ratio of the chemical reaction equation, and the molar ratio of MgO/C is 1:1. The mass percentage of agent is 70%～90%;

_SiO2 is a reaction accelerator, adding a small amount of _SiO2 solvent can promote the in-situ reduction reaction of MgO, and then promote the desulfurization reaction, and the mass percentage of the desulfurizer is 2-10%;

The pH regulator is one of lime, limestone, dolomite, and silica, and the mass percentage in the sulfur agent is 1-5%;

The binder is asphalt, tar, resin, etc., and the mass percentage in the desulfurizer is 5-15%.

The sum of the contents of each component in the desulfurizer is 100%.

Dry and pretreat the raw materials of the various components of the above desulfurizer, remove the moisture completely, crush and grind them into -200 mesh fine powder, then weigh and batch according to the mass percentage, fully stir and mix evenly, add 5- 15% binder, and then stir evenly to make agglomerates into particles of different shapes, which are put into use after drying and packaging.

In the process of tapping iron or steel, add the desulfurizer prepared according to the above-mentioned process components and manufacturing process into the ladle or ladle, and stir it under the temperature of molten iron or molten steel (above 1350°C) and the flow of molten iron or steel Under the action of the desulfurizer, the desulfurizer is quickly pulverized and melted, and an in-situ reduction reaction occurs to generate high-temperature magnesium vapor. The magnesium vapor first forms bubbles, grows up, and rises in the molten iron, which has a good stirring effect on the molten iron and provides good desulfurization. Under the dynamic conditions, the sulfide slag formed by the reaction of sulfur in molten iron or molten steel with the desulfurizer combines with the reaction product stabilizer in the desulfurizer to form a stable mixture and floats up to the surface of molten iron or molten steel, forming a slag layer and forming The amount of slag is very small, the desulfurization rate is above 70%, and the comprehensive economic benefits can reduce the cost of molten iron by more than 10 yuan/t.

Specific examples:

Embodiment 1: (by mass percentage)

MgO+C (graphite or charcoal): 80%

SiO ₂ : 8%

pH regulator: 5%

Binder: 7%

Dry and pre-treat the raw materials of the various components of the above desulfurizer (except the binder), completely remove the moisture in them, crush and grind them into -200 mesh fine powder, then weigh and mix according to the mass percentage, and fully Stir and mix evenly, add binder, and stir evenly again to make agglomerates into particles of different shapes, which are put into use after drying and packaging.

Embodiment 2: (by mass percentage)

MgO+C (graphite or charcoal): 85%

SiO ₂ : 5%

pH regulator: 2%

Binder: 8%

The manufacturing process is consistent with Example 1.

Embodiment 3: (by mass percentage)

MgO+C (graphite or charcoal): 90%

SiO ₂ : 3%

pH regulator: 1%

Binder: 6%

The manufacturing process is consistent with Example 1.

The desulfurizer obtained in the above examples is directly added into the ladle or ladle during tapping or steel tapping, the amount of slag is small and no slag removal is required, and no injection equipment or other related equipment is required. The medium temperature drop is small, the desulfurization product is stable, and the desulfurization rate is stable.

Claims (3)

1, a kind of MgO base desulfurizer, it is characterized in that: this desulfurizer is made up of MgO, graphite or charcoal, reaction accelerator, pH regulator, binding agent, wherein, MgO adds graphite or charcoal to account for in desulfurizer The mass percentage is 70% to 90%; _SiO2 is a reaction accelerator, and its mass percentage in the desulfurization agent is 2 to 10%; the pH regulator is one of lime, limestone, dolomite, and silica. The mass percentage in the desulfurizer is 1-5%; the binder is asphalt, tar, resin, and the mass percentage in the desulfurizing agent is 5-15%. 2. The MgO-based desulfurizer according to claim 1, characterized in that: MgO is mixed with graphite or charcoal according to the molar ratio of the chemical reaction equation. 3. A method for preparing the MgO-based desulfurizer as claimed in claim 1, characterized in that: the various components of the desulfurizer as claimed in claim 1, the raw materials except the binder are dried and pretreated, Thoroughly remove the moisture in it, crush and grind it into a fine powder below -200 mesh, then weigh and mix according to the mass percentage, stir and mix well, add binder, stir evenly, and form agglomerates into particles of different shapes , dried and packaged to make finished products.