JPS63153206A - Method for temperature control in smelting reduction process of chromium ore - Google Patents

Abstract

PURPOSE:To reduce the consumption of raw material and the corrosion of refractory by performing assumption and prediction of metal temp. based on data of exhaust gas information, blowing O2 flow rate and raw material charging quantity and controlling the metal temp. according to the difference between the prediction value and the aimed value. CONSTITUTION:In smelting reduction process for chromium ore by a top-bottom blowing refining furnace, the data of the exhaust gas information (composition, flow rate), the blowing O2 flow rate and the raw material charging quantities (chromium ore, coke, etc.) are used and reaction velocity is found by material balance for reaction in the furnace and heat balance, to assume the metal temp. at every moment. On the other hand, the metal temp. is measured by a sub-lance at every set time. By comparison between the actual measured value and the above assumption value, a feedback operation is executed and in case the operational condition assumed to be held constant, the subsequent metal temp. is predicted. Based on the difference between the prediction value and the aimed value, the necessary blowing O2 flow rate to hold the metal temp. constant and the raw material charging velocity are calculated. Based on the calculated values, the operational condition is decided and the suitable metal temp. is stably held.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method of controlling metal temperature in a smelting reduction process of chromium ore using a top-bottom blowing smelting furnace, which smoothly promotes the reduction reaction of chromium ore with a carbon source such as coke. ,
The present invention also relates to a method of controlling the temperature of metal during refining to a constant level in order to suppress the heat load on refractories in a refining furnace and reduce melting loss of the refractories.

Conventional technology and its problems Conventionally, stainless steel has been manufactured using ferrochrome produced by reducing chromium ore with carbon in an electric furnace. The cost of stainless steel is high, and as a result, the cost of stainless steel increases and spare parts are eliminated.

For this reason, in recent years, a method has been developed in which chromium ore or its pre-processed products are reduced with carbon using coke or the like without consuming electricity in a top-down blowing smelting furnace to melt ferrochrome and produce stainless steel. Law (Japanese Patent Publication No. 5
5-91913 etc.) have been attempted.

However, in the conventional smelting reduction process of chromium ore, if the metal temperature during reduction refining is too low, the reduction reaction of the chromium ore with coke etc. cannot be carried out smoothly, leading to an increase in the amount of raw materials used. If the temperature is too high, the heat load on the refractories on the inner wall of the smelting furnace will increase, resulting in significant melting and loss of the refractories. Therefore, it is necessary to stabilize the metal temperature during reduction refining to a predetermined level, but until now there have been no reports on controlling this metal temperature, and the metal temperature has been controlled only by the intuition of operators. is the actual situation.

Purpose of the Invention This invention was made to solve the above-mentioned conventional problems. By properly controlling the metal temperature during melt reduction, the carbon reduction reaction of chromium ore is smoothly promoted and the amount of raw material used is reduced. The purpose of this paper is to propose a method for reducing the heat load on refractories in smelting furnaces and reducing corrosion of the refractories.

Means for Solving the Problems The present invention solves the above-mentioned conventional problems by providing exhaust gas information (components, flow rate), blowing 02 flow rate, and raw material input amount when chromium ore is melted and reduced in a top-bottom blowing smelting furnace. Using each data, the momentary metal temperature is estimated based on the material balance and heat balance related to the reaction in the furnace, and the actual measured value of the metal temperature and the estimated value are compared and feedback calculation is performed. Blow 02 to predict the metal temperature at a future time assuming that the flow rate and raw material input rate are held constant, and to maintain the metal temperature constant based on the difference between this predicted value and the target value. By calculating the flow rate and raw material input speed and controlling the metal temperature based on these calculated values, the carbon reduction reaction is smoothly promoted to reduce the amount of raw material used, and the heat load on the refractory of the smelting furnace is suppressed. It is necessary to reduce the corrosion damage of refractories.

That is, the present invention estimates and predicts the metal temperature based on data on exhaust gas information, blow 02 flow rate, and raw material input amount, and determines the operation amount necessary for temperature control based on the difference between the predicted temperature and the target temperature. This is a method to appropriately control the metal temperature during melt reduction.

FIG. 1 is a diagram showing the smelting reduction process and metal temperature transition when chromium ore is smelted and reduced using a top-bottom blowing smelting furnace. In Figure 1, (1) is 02 blowing lance, (2)
is the raw material input port for chrome ore, coke, etc., (3) is 02
Inlet, (4) is bottom blowing nozzle, (5) is metal, (
6) is slag, (sword is coke).

That is, first, the metal temperature is raised to a predetermined temperature by such means as introducing FeSj into the dephosphorized hot metal, and then during the smelting and reduction period, the metal in the furnace is heated through the raw material inlet (2).
), and while stirring with bottom-blown N2 gas etc. from the bottom-blowing nozzle (4), 02 blowing lance (1)
The chromium ore is melted and reduced by top-blown and side-blown acid from the O2 inlet (3). The present invention is based on a method for controlling the metal temperature during this melting and reduction period to keep it constant. Five types of reactions shown in Table 1 below are considered to occur in the furnace during this smelting and reduction period.

Table 1 (Table 1) The reaction rates R1 to R5 can be measured indirectly as described below.

First, from the overall oxygen balance and carbon balance, equations (11 and (21) are established.

<02 balance> RI +R2+3R3+ R4=(Co)c +2(C
Oz) c...(1) Formula C balance> R1+3R3+R4=(CO)c + (CO2) c
...(2) Formula % Formula % Since the blown oxygen is consumed in the combustion of coke and CO, L (R, + R2) = RO□ 2 ...
(3) Formula R02: Blowing 02 flow rate (kmo//m1n)
Assuming that the FaO component in chromium ore is reduced according to the input rate, R4''RFe○ ・(4) Formula RFe○ The input rate of FsO in nichrome ore (kmo, j
/m1n) Since the charged coke is considered to be consumed for reduction of chromium ore, combustion by blown oxygen, and carburization, R+ + 3R3+R4+R5=Rc ・(1-a)・
...(5) Formula Rc knee injection speed (kmol/min) a:
The residual ratio of the charged coke in the slag From the above formulas (1) to (5), R1-R5 can be summarized as shown in Table 2 below.

Table 2 Also, based on the heat balance, the following regarding metal temperature (6)
The formula is obtained.

...(6) Equation W: Metal weight (kg) CP = Metal specific heat (kcaUkg °C) T: Metal temperature ('C) Rj: Reaction rate of reaction j (kmo57min)△Hj
: Reaction heat of reaction j (kcad/kmo (1) Pj:
Heat transfer efficiency of reaction j Ta: atmospheric temperature ('C) Hw: furnace wall heat transfer coefficient (kca 1hIf-'C m
i n ) Aw: Furnace wall surface area (m2) hw: Coefficient By solving the above equation (6), it is sometimes possible to estimate the metal temperature T.

Next, in order to predict the metal temperature at a future time, of the reaction rates R1-R5, if R2 and R3 can be predicted, the second
As can be seen from the table <R+, R4.

R5 can also be predicted. Therefore, by changing the blowing 02 flow rate in steps and examining the response characteristics, R2-R
3 can be formulated as a function of the blow 02 flow rate. The predicted values of R1-R5 obtained by this method are R+, R2, R
3. Let R↓, Rs. At this time, the metal temperature T at a future time is predicted as shown in equation (7) below.

T = T + δT ・-<7) Formula, where T is the value of the metal temperature obtained by substituting the predicted reaction rate values R1 to R5 into the above formula (6), and 6th is the sub-balance at fixed time intervals during reduction refining. This is an adaptive correction term that is a moving average of the difference between the actual measured value and the estimated value.

Calculate the predicted metal temperature value TV after 2 minutes using the above method,
This value is compared with the lower target value, and based on the difference, the following equation is used to calculate the value required to keep the metal temperature constant.

Δ[: Control period (min) Knigain Then, the predicted value of the coke burning rate when using the indicated value RO2 of the blowing 02 flow rate obtained by the above equation (8) is R1
Then, the coke injection speed R2: which should be changed in accordance with the change in the blowing 02 flow rate can be obtained from the following equation (9) based on the value Rco-1 at the previous time.

However, R'+ is the initial value of R1, which is a value indirectly measured using the formula in Table 2 above.

Figure 2 shows the blow 01 required for metal temperature control based on the above method! FIG. 2 is a block diagram showing a procedure for determining the flow rate and coke injection speed.

That is, first, each data of exhaust gas information (component, flow rate), blowing 02 flow rate, and raw material input amount is read moment by moment (for example, every minute), and the reaction rate is estimated moment by moment based on the formula shown in Table 2 above. do. By substituting this reaction rate into the above equation (6), the momentary metal temperature can be estimated.

On the other hand, a feedback calculation is performed by comparing the above estimated value with the actual value of the metal temperature measured by a sublance at regular intervals (for example, every 20 minutes) during reduction refining, that is, (7
), and calculate the value of the adaptive correction term in the equation, and calculate the value of the adaptive correction term in the future time (for example, 3
The metal temperature (0 minutes ahead) is predicted using equation (7). Then, based on the difference between the obtained future time metal temperature prediction @ lower and the target value Y, the blowing 02 flow rate R3 and coke injection rate R color required to keep the metal temperature constant at a predetermined temperature are determined. Calculated using equations (8) and (9) above. This calculation (based on direct stabilization of the metal temperature during reduction smelting).

Example As a result of applying the method of the present invention to a smelting reduction process using a 160-ton top-bottom blowing smelting furnace shown in Fig. 1, the accuracy rate of metal temperature was 92% within the target ±15°C, which was 6% in conventional operation.
A remarkable effect far exceeding 0% was observed.

Note that an example of the melting reduction treatment conditions in this example is shown in the third example.
Shown in the table.

As explained in detail below, the method of this invention provides exhaust gas information, blowing zero
2. This method estimates and predicts the metal temperature based on each data of flow rate and raw material input amount, and determines the amount of operation necessary for temperature control based on the difference between the predicted temperature and the target temperature. The metal temperature can be stably maintained at an appropriate temperature. Therefore, it is possible to smoothly promote the carbon reduction reaction, reduce the amount of raw materials used, and reduce the heat load on the smelting furnace refractories, thereby reducing the refractory unit consumption, which greatly contributes to cost rationalization. This has the following effect.

[Brief explanation of the drawing]

Fig. 1 (a) is a schematic diagram showing the smelting and reduction process of chromium ore using a top-down blowing smelting furnace, Fig. 1 (b) is a diagram also showing the metal temperature transition, and Fig. 2 shows the metal temperature control method of this invention. It is a block diagram. 1...02 injection lance, 2...raw material input port for chromium ore, coke, etc., 3...
・02 blowing port, 4...bottom blowing nozzle, 5...
Metal, 6...Slag, 7...Coke. Applicant: Sumitomo Metal Industries, Ltd. Figure 1 (a) (b)

Claims (1)

[Claims] In the smelting and reduction process of chromium ore in a top-bottom blowing smelting furnace, the metal temperature is determined from moment to moment based on the material balance and heat balance related to the reaction in the furnace, using exhaust gas information (components, flow rate), blown O_2 flow rate, and raw material input data. By estimating the metal temperature and performing feedback calculation using the measured value of the metal temperature and the estimated value, the metal temperature at a future time is predicted assuming that the blown O_2 flow rate and the raw material input speed are held constant. Blow O_ to keep the metal temperature constant based on the difference between the predicted value and the target value
2. A temperature control method for a chromium ore smelting reduction process, comprising calculating a flow rate and a raw material input speed, and controlling a metal temperature based on the calculated values.