CN1132255A

CN1132255A - Safety working method for remained converter slag

Info

Publication number: CN1132255A
Application number: CN 95110987
Authority: CN
Inventors: 王虎
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-03-28
Filing date: 1995-03-28
Publication date: 1996-10-02
Anticipated expiration: 2015-03-28
Also published as: CN1048284C

Abstract

A safe slag-laving job for steelmaking in converter features that carbon-contained reducer such as coal powder, coke, or graphite is added to surface of molten slag in converter before or during tapping for reducing FeO in molten slag and increasing slag viscosity, so ensuring the safety of slag-leaving job. Its advantages are simple process and low cost.

Description

Converter slag-remaining safe operation method

The invention relates to a method for safely remaining slag of a converter.

The high-alkalinity oxidizing slag generated after the refining in the converter has high dephosphorization performance, and contains a large amount of sigma (FeO), MFe, CaO and other components with recovery value and a large amount of sensible heat. The slag remaining operation is implemented, so that the steel-making operation cost can be greatly reduced. In the sixties and the seventies, the slag reserving operation of the converter is implemented in the steel industry in China, but the slag reserving operation is only forced to be abandoned due to the fact that sigma (FeO) in the final slag is high, especially sigma (FeO) in low-carbon steel slag is higher and the fluidity is good, and slag spraying accidents occur frequently when the converter mixes molten iron to cause injury to people.

The reasons for slag spraying during molten iron mixing in the converter slag retaining operation are as follows: during the reaction, a large amountof CO bubbles are generated instantly and float upwards, and carry a large amount of slag to be sprayed outwards to cause accidents. The key to inhibit slag spraying is to inhibit (FeO) - [ C]during molten iron mixing]The reaction between them. Research shows that the key point of inhibiting the reaction is to control the diffusion speed of (FeO) under the smelting condition of the converter. Because of (FeO) - [ C]]The reaction is a first-order reaction, and the reaction speed V is equal to K_D(C_FeO°-C_FeO′)＝C/η(C_FeO°-C_FeO' (because of K)_Dη ═ C) where K is_DDiffusion constant of (FeO) in slag, η slag viscosity, C_FeODegree is the concentration of (FeO) in the slag, C_FeO' is (FeO) - [ C]]The interfacial reaction concentration at the interface (FeO), C is a constant. As can be seen from the products of the reaction, the partial pressure P of CO in the furnace gas is increased_coCan inhibit (FeO) - [ C]]In the reaction ofFrom the reaction rate equation, it can be seen that increasing the slag viscosity η decreases the concentration C of (FeO) in the slag_FeOThe reaction can be inhibited. Since slag viscosity depends on slag composition and slag temperature. Increasing the melting point of the slag or reducing the temperature of the slag, and adding dispersed solid particles into the slag can effectively increase the viscosity of the slag. According to the analysis of the FeO-SiO-CaO ternary phase diagram and relevant research data, the slag alkalinity (CaO/SiO) is constant, the Sigma (FeO) in the slag is reduced by 10 percent, and the melting point of the slag is increased by 200-350 ℃. As can be seen from FIG. 1, when the basicity R is 4, T.Fe is reduced from 18% to 15%, and the melting point of slag is increased from 1400 deg.CTo 1600 ℃; when the T.Fe is reduced to 10% from 15%, the melting point of the slag is increased from 1600 ℃ to 1760 ℃. Therefore,if sigma (FeO) in the slag can be effectively reduced, the dual effects of increasing the slag melting point, increasing the slag viscosity, and reducing sigma (FeO) in the slag can be achieved. (FeO) - [ C]M-reaction rate V ═ K_D(C_FeO°-C_FeO') then is K_D、C_FeOThe product amplitude of the reduction value is greatly reduced, and the effect is far greater than the effect of simply reducing the temperature of the slag. For this reason, several manufacturers have recently organized tests to add coke powder to the slag residue to reduce the content of FeO in the slag. As mentioned in the discussion of "converter slag-remaining steelmaking" of Yangxinglin of the fifth Steel works (the fifth period of 26 in Steel&lt/EN&gt 1991, 5 months) and "converter steelmaking slag-remaining operation" of Zhang Yi of Nanjing Steel works (the Steel&lt/EN&gt 1991), and in the summary of the Tang Steel steelmaking 30T converter slag-remaining steelmaking test of Mingkui et al (the Tang Steel science&lt/EN&gt 1989), the method of reducing the final slag (FeO) by coke powder is proposed, but the reduction effect of (FeO) is not ideal, the reduction amount of (FeO) in most of the furnace slag tests is 2-3%, and the individual furnace times is 5-6%. So that the above-mentioned techniques have not been practically applied so far. The aluminum-containing waste material is used for reducing sigma (FeO) in the slag abroad, but the cost is higher.

The invention aims to provide a method for inhibiting the reaction between (FeO) - [ C]and preventing slag spraying in the process of charging molten iron in the slag reserving operation of a converter.

The safe slag remaining operation method of the invention comprises the following steps: after the converter steelmaking is stopped blowing, a jet machine is used for jetting a carbonaceous reducing agent to the surface of slag liquid in the converter before or in the tapping process, and after slag is pre-reduced; according to the slag condensation condition of the slag, secondary carbon supplement can be carried out on the surface of the slag before or after tapping is finished, and then partial lime is added into the furnace to carry out slag retention operation.

The carbonaceous reducing agent is one of powdered graphite, coke and coal, the diameter of the powdered particles is less than 5mm, and the amount of the carbonaceous reducing agent injected each time is 0.5-2 Kg per ton of steel.

FIG. 1 is a graph showing the relationship between slag basicity R and melting point.

Example (b): the converter does not immediately tap steel after blowing is stopped, but coal, graphite, coke and other powdery carbonaceous reducing agents are firstly added into the converter, the addition amount of the carbonaceous reducing agents is 0.5 to 1.5Kg per ton of steel, the interface area of C powder and FeO is greatly increased because the converter body is positioned at the steel tapping position, the slag spreading area is large, the slag layer is thin, and the C powder is uniformly sprayed, meanwhile, the physical temperature reduction generated by the slag is small because the sprayed C powder is small (0.5 to 1.5Kg per ton of steel), and the viscosity of the slag is small,since the diffusion rate of (FeO) is high and the generated CO bubbles are easily released, the reaction between C- (FeO) is sufficient, and the amount of (FeO) in the slag can be greatly reduced. And C is used for reducing FeO, the molten steel is not carburized, and P is contained in slag₂O₅) Nor reduced. In addition, the dispersed C powder can effectively improve the viscosity of the slag, and simultaneously can play a role in mechanically breaking the CO bubbles once formed during molten iron mixing and maintain a certain P in the furnace_COAnd the ability of eating scrap steel can be increased. Therefore, before the tapping is finished, reducing agents containing C, such as coal, coke or graphite, are secondarily added to the surface of the slag, the addition amount is close to the first injection amount, and then 10% of lime is added to carry out slag retention operation. The change in slag composition before and after slag reduction by spraying reducing agent containing C before tapping is shown in Table 1.

TABLE 1 composition change before and after reduction of slag injected with reducing agent C before tapping.

The content of slag is%	CaO	SiO₂	Al₂O₃	MnO	FeO	P₂O₅	S
The content of slag is%	CaO	SiO₂	Al₂O₃	MnO	FeO	P₂O₅	S	Before slag reduction	53	13	2.0	2.2	26	2.1	0.09
After slag reduction	58	14	2.2	2.0	15	2.2	0.10	Before slag reduction	53	13	2.0	2.2	26	2.1	0.09

The invention has simple process, simple equipment and low cost; can fully ensure the safeslag retention operation of the converter, thereby obviously reducing the steel-making operation cost of the converter and having great economic benefit.

Claims

1. A converter safe slag remaining operation method is characterized in that: after the converter steelmaking is stopped blowing, a jet machine is used for jetting a carbonaceous reducing agent to the surface of slag liquid in the converter before or in the tapping process, and the slag is pre-reduced and then tapped; and then adding part of lime into the furnace to carry out slag retention operation.

2. The safe leaving operation method according to claim 1, characterized in that: after the converter stops blowing, a jet machine is used for jetting a carbonaceous reducing agent to the surface of slag liquid in the converter before or in the process of tapping, the slag is pre-reduced, carbon is secondarily supplemented to the surface of the slag before or after the tapping is finished, and then partial lime is added into the converter to carry out slag remaining operation.

3. The safe slag remaining operation method according to claim 1, characterized in that: the reducing agent is a carbon-containing reducing agent containing graphite, coke, coal and the like, the diameter of powdery particles of the reducing agent is less than 5mm, and the amount of the carbon-containing reducing agent injected each time is 0.5-2 Kg per ton of steel.