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Production oxygen blowing decarburization process is a low carbon manganese iron reduction furnace or blast furnace of high-carbon ferromanganese raw material liquid, to heat against the converter, by blowing oxygen lance, carbon oxide, carbon ferromanganese; added simultaneously a suitable amount of slagging or coolant, when carbon alloy removal of the standard requirements, i.e. low-carbon ferromanganese.
In a 1.2t hour oxygen top-blown converter, a plant uses liquid blast furnace ferromanganese as raw material to blow medium carbon ferromanganese. The main parameters of the blowing are: the oxygen gun nozzle is 400mm away from the metal surface, the blast furnace ferromanganese w(Mn) is >73%, w(P)<0.2%, and the oxygen supply system adopts the "low one high one low" type, ie the early stage The oxygen supply pressure is 0.6 MPa, the medium-term 0.85 MPa, and the reducing agent (manganese-silicon alloy) is added in an amount of about 25% and 20% to 21% of the liquid high-carbon ferromanganese. The final slag basicity is controlled at 1.1.
U.S. Union Carbide Corporation began mass production of medium carbon ferromanganese by converter oxygen top-blowing decarburization in 1976. After the liquid high-carbon ferromanganese is fed into the converter, the production begins to blow oxygen decarburization until the carbon content of the alloy is qualified. This method can produce medium carbon ferromanganese containing 80% manganese and 1.3% carbon. The energy consumption of the contract is half of the electricity consumption of the electrothermal method. The production cost is low, but the volatile loss of manganese during the blowing process. Larger, high carbon manganese ferromanganese recovery rate of about 80%. After the end of the oxygen decarburization, the German electric metallurgical company added MnO in the ferrosilicon and lime reducing slag to the furnace, so that the recovery rate of manganese reached 91.8%.
South Africa cooperated with France to blow with two fuel-protected oxygen lances on the 61-bottom converter, blowing at temperatures ranging from 1650 to 1750 °C. The first stage of oxygen blowing, the carbon from 6% ~ 7.5% to 2% ~ 3.2%, the melt temperature is 1650 ~ 1720 ° C, the second stage is added a mixture of oxygen and water vapor, the temperature remains unchanged, the carbon It is reduced to 1.6%; the third stage is blown with argon to catch hydrogen, and then manganese oxide is added to the slag. The manganese recovery rate produced by this method is 91.5%.
Japan Metals and Chemicals Co., Ltd. uses a combination of top and bottom composite blowing technology, blowing oxygen in the upper part of the converter, and blowing inert gas (Ar, N 2 , CO 2 ) at the bottom. After being blown to carbon, the top is sprayed with ferrosilicon. , silicon manganese, aluminum powder and flux reduction slag MnO, high-carbon ferromanganese in the recovery rate of 88% manganese.
The advantage of producing low-carbon ferromanganese by oxygen decarburization method is that blast furnace ferromanganese can be utilized to broaden the way of production of medium and low carbon ferromanganese. However, due to the higher smelting temperature required by the method, the volatile loss of manganese is large, especially for the production of low-carbon ferromanganese. The smelting temperature needs to be controlled above 1950 °C, and the volatile loss of manganese is greater. Therefore, how to improve the recovery rate of manganese is the key to solving the production of this method.
A factory in Japan installed the converter on the cradle. When the oxygen was decarburized to 2%, the shaking equipment was started, and the oxygen was diluted at 40% (inert gas, (oxygen + inert gas)). At a rate of 16 to 20 r/min, the recovery of manganese increased from 85% without shaking to 92%.
It is found in the production that lime is added to the converter during the blowing process, and the desulfurization effect is obvious. The sulfur content of the product can be reduced to 0.02% from 0.13% without lime.
The production of medium and low carbon ferromanganese by oxygen blowing decarburization method adopts the hot-packing production process, which eliminates the processes of casting, finishing, transportation and crushing of intermediate products, simplifies the process, replaces the electric furnace with a converter, and replaces it with oxidation. Electricity, energy saving, simple equipment, easy to realize mechanization. This method has short production period, high output, low production cost, and can fully utilize the production of lean manganese ore resources. It is a production method with obvious superiority. [next]
Note on smelting operations:
(1) Filling the furnace. When blowing slag serious erosion of the lining, the furnace after completion of the required magnesium sand, brine fettling mixing materials, high-temperature rapid fettling to do.
(2) Alkalinity control. The alkalinity in the early stage of blowing is controlled at n(CaO)/n(SiO 2 )=1.1~1.2, the alkalinity does not exceed 2, and the alkalinity does not exceed 4 in the later stage. After adding reducing agent, the alkalinity of slag is controlled at 1.1~1.2.
(3) Under the premise of ensuring rapid decarburization, in order to reduce the volatilization loss of manganese, the high temperature above 1850 °C should be avoided in the blowing. When the temperature is too high, an appropriate amount of coolant can be added to cool down. The commonly used coolant has lime. , fluorite, medium carbon ferromanganese.
(4) End point judgment. Accurate endpoint judgment is an important means to control product quality and improve product qualification rate. Usually judged by the flame and oxygen consumption:
1 Observe the flue gas flame that escapes from the furnace when oxygen is blown. At a certain temperature, it depends on the length of the flame combustion of CO 2 concentration and CO produced, a concentration of CO 2 and CO, and indirectly reflect the remaining carbon-carbon alloys has been relatively low, the effect is correspondingly reduced oxygen decarburization furnace The mouth flame appears to be swaying, or shrinking within the mouth of the furnace.
2 Oxygen consumption, in practice, it is found that the consumption of oxygen blowing has a strong relationship with the carbon content of hot metal ferromanganese. It is empirically possible to judge whether the residual amount of carbon in the alloy has reached the end of the blowing from the consumption of oxygen. If necessary, a quick analysis can be taken to determine the carbon content.
(5) Adding a manganese-silicon alloy reducing agent, until the end of oxygen blowing, about 20% to 30% of the manganese in the alloy is oxidized into the slag, which increases the loss of manganese. In order to improve the recovery rate of manganese. It is necessary to add a manganese-silicon alloy having a particle size of less than 20 mm to the furnace to reduce MnO in the slag. The amount of manganese-silicon alloy added is calculated according to the amount of molten iron in the furnace, the amount of coolant, and the type of blowing. Usually, the amount of manganese-silicon alloy added is about 20% of the total amount of ferro-manganese and additional ferromanganese, which needs to be preheated to 400-500 ° C before being added to the furnace.
(6) Bake and cast. The manganese-silicon alloy to be used as a reducing agent is completely melted and then discharged. The slag liquid in the furnace is poured into the ladle together with the molten iron, and the MnO in the slag is reduced by the strong stirring action during the pouring. The alloy liquid is left in the casting bag or the calming basin for a certain period of time to cool down, and then the slag casting is carried out to protect the ingot mold from being burnt by the high-temperature molten iron.
Second, oxygen blowing desiliconization
The oxygen-off desiliconization method uses a liquid manganese-silicon alloy as a raw material, and is desiliconized by oxygen in a converter to obtain medium-low carbon ferromanganese. The operating process is similar to the oxygen decarburization process. In 1978, the Shanghai Ferroalloy Plant used manganese-silicon alloy for oxygen and silicon desulfurization to test low-carbon ferromanganese.
Operation method:
(1) producing manganese-silicon alloy in a submerged arc furnace using manganese ore containing about 32% Mn, m(Mn)/m(Fe)≥4, m(P)/m(Mn)≤0.006;
(2) After the liquid manganese-silicon alloy slag is weighed, it is poured into a converter of lining magnesia bricks, and oxygen is desiliconized;
(3) During the blowing process, the oxygen lance should always be inserted into the slag, and at the same time, slag-forming materials such as lime and fluorite should be added one after another;
(4) When the oxygen is near the end point, the silicon content of the sample is tested and tested. After passing the test, it can be baked, cooled and cooled.
The liquid manganese-silicon alloy is used for oxygen desiliconization to refine medium and low carbon ferromanganese. The recovery rate of manganese is above 75%. Compared with the furnace-electric furnace pre-refining method, the following disadvantages exist: the method deoxidizes oxygen, and the free energy of silicon Not being used effectively. The comprehensive energy consumption is high; the oxidation loss of manganese is large during the smelting process, and the manganese recovery rate is low.
First, the oxygen decarburization method