JP2000336419A - Method for setting and switching flow rate of bottom blown gas in converter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To minimize tuyere pressure in a converter at a level that does not hinder operation, to extend the life of tuyere and to reduce the service cost for bottom blown gas. SOLUTION: The flow rate setting of the bottom blown gas is performed by using the bottom blow gas control results such as the flow control valve opening results and the tuyere pressure results, and considering the minimum necessary tuyere pressure without operation trouble. Find the value and the valve opening setting at gas switching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for setting and switching a flow rate of a bottom blown gas in a converter, and more particularly, to a method for controlling the flow rate of a bottom blown gas from a furnace bottom tuyere and the tuyere pressure without hindering operation. The present invention relates to an optimization control method that can be minimized.

[0002]

2. Description of the Related Art Conventionally, in controlling the flow rate of a bottom-blown process gas (referred to as bottom-blown gas) and gas switching control of a converter, sequence control is performed using a preset flow rate and a valve opening degree setting at the time of switching. Was implemented.

For example, Japanese Patent Application Laid-Open No. 61-284514 discloses that
By feeding back the measured gas flow rate to the control valve and controlling the gas flow rate to be the set flow rate, by constant flow rate control,
When controlling the flow rate of gas blown into the refining furnace (converter) from the tuyere, when controlling the flow rate of the blown gas in the refining furnace, when changing the flow rate of the gas in a stepwise manner or changing the gas type When increasing the gas flow rate, first, the constant flow rate control is performed by switching the flow rate set value to an excessive flow rate set value higher than the changed flow rate set value, and when decreasing the gas flow rate,
First, the flow rate set value is switched to the lower flow rate set value lower than the flow rate set value after the change, and the constant flow rate control is performed.
When the pressure set value set in relation to the changed flow set value based on the flow pressure characteristic curve is reached, the flow rate is changed from the excessively large or small flow set value to the changed flow set value and the constant flow control is performed. In the case where the set value of the gas blowing flow rate is largely changed stepwise or the type of the blowing gas is switched, the rise or fall of the gas flow rate actually blown from the tuyere into the molten metal is increased. It describes that the transient response characteristics are remarkably improved and the accuracy of the flow rate measurement is ensured.

Japanese Patent Application Laid-Open No. Sho 62-274015 discloses a shut-off valve, a flow meter, and a flow control valve, each of which is provided with a plurality of gas supply lines provided in parallel. When supplying, first, the shut-off valve of the preceding gas supply line is opened, so that the flow rate of the preceding gas measured by the flow meter of the preceding gas supply line becomes the desired set flow rate at the blowing tuyere. The feedback control of the flow control valve of the preceding gas supply line, while maintaining the flow control valve of the subsequent gas supply line at a preset opening close to close, and closing the shut-off valve of the subsequent gas supply line. In a state of waiting for the supply of the following gas, the preceding gas is supplied from the preceding gas supply line to the blowing tuyere, and then the gas supply line is switched to change the supplied gas from the preceding gas to the following gas. To At the same time, the shut-off valve of the following gas supply line is opened, and the supply of the following gas is started via the flow control valve of the following gas supply line held at the preset opening. The starting gas is supplied to the trailing gas while controlling the flow rate control valve to be gradually opened at a constant speed, and the flow rate of the trailing gas is measured by a flow meter. But,
The opening degree of the flow control valve of the preceding gas supply line is cascaded so as to be the difference between the desired set flow rate and the measured subsequent gas flow rate. At the same time as the set flow rate or a flow rate in the vicinity thereof is reached, the shut-off valve of the preceding gas supply line is closed, and the flow rate control valve of the supply line is maintained at a preset opening close to close to supply the preceding gas. By stopping, the transition period ends, and when the transition period ends, the opening degree of the flow control valve of the trailing gas supply line is adjusted so that the flow rate of the trailing gas becomes the desired set flow rate. It is described that by switching the control to feedback control, it is possible to prevent an excessive amount of gas from being ejected in a transition period when the gas supply line is switched, and to smooth the gas switching.

Japanese Patent Application Laid-Open No. 2-87710 discloses that when a process gas supplied to a molten metal of a metallurgical furnace (converter) through a tuyere is switched from a preceding gas to a succeeding gas, a process gas is not changed. Classify the combination of leading gas and trailing gas into the required number of units according to the type of tuyere and process gas,
For each categorized unit, how to change the flow rate of the process gas when switching the process gas
4 for "continuation", "end of sink", and "irrelevant to switching"
The slave sequence for performing process gas switching control is defined for each unit based on the content of the change in the flow rate of each recognized pattern, and the defined slave sequence is defined as a tuyere and a tuyere. By switching the process gas under the control of the master sequence according to the type of the process gas, the switching logic for switching the process gas can be centralized and simplified, and a free combination of process gases can be set. It is described.

[0006]

However, in any case, when molten steel is charged into the converter, the bottom blow gas is always supplied at such a pressure that the molten steel does not flow back to the bottom tuyere. There must be. Therefore, in order to prevent operation troubles, the flow rate is increased, and the opening of the flow control valve (hereinafter, also simply referred to as a valve) at the time of gas switching is slightly open.

[0007] As a result, the tuyere pressure becomes unnecessarily high, so that there is a problem that the refractory of the tuyere is quickly worn and its life is shortened. There is also a problem that the service cost of the bottom blown gas is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is intended to minimize the tuyere pressure at a level that does not hinder the operation, thereby prolonging the tuyere life and reducing the utility cost. To do that.

[0009]

According to the present invention, when setting the flow rate of the bottom blown gas from the bottom tuyere of a converter in a converter, the present invention uses the minimum value of the tuyere pressure of the same gas type in the previous and previous charges. The above-mentioned problem is solved by obtaining the flow rate set value.

According to the present invention, when switching the bottom blown gas from the bottom tuyere in the converter, the tuyere pressure actual maximum value at the time of switching the preceding gas and the succeeding gas in the previous charge of the same gas type, The problem is solved by using the minimum value of the tuyere pressure result and the rise time of the following gas flow to obtain the opening of the flow adjustment valve of the preceding gas and the opening of the flow adjustment valve of the following gas at the time of gas switching this time. It was done.

[0011] In the present invention, the actual flow rate control valve opening degree,
Using the bottom blow gas control record such as the tuyere pressure record, etc., and considering the minimum required tuyere pressure without operation trouble, set the bottom blow gas flow rate and the valve opening at gas switching. By obtaining this, tuyere pressure is minimized (optimized) at a level that does not hinder operation, thereby realizing a longer tuyere life and a minimum service cost for bottom blown gas.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 schematically shows a converter and its bottom blown gas system assumed in the present invention. The tuyere is a double tube of an inner tube and an outer tube, and a process gas is blown from the inner tube and a tuyere cooling gas is blown from between the inner tube and the outer tube. The tuyere pressure means the inner pipe pressure, and the outer pipe pressure is set slightly higher than the inner pipe pressure. Each kind of gas connected to the inner tube and the outer tube of the converter 10 (the inner tube is O ₂ , N ₂ , Ar,
The outer pipe is connected to a piping system 12, 14, 16, 22, 24, 26 of Pr (propane gas), N ₂ , Ar, etc., respectively.
Flow control valve (FCV) 32 and two block valves (SO
A V) 36 and a shutoff valve 34 including a bleed valve (SOV) 38 are provided so that the valve can be automatically opened and closed.

A gas flow meter 60 is provided on the outlet side of each flow control valve (FCV) 32, and a tuyere gas pressure gauge 62 is provided on the tuyere pipe. The gas types are not limited to this example.

FIG. 2 is a block diagram of the bottom blowing gas flow rate and gas switching optimization system devised in the present invention. The bottom blowing gas control device 40 outputs an automatic valve opening / closing command and performs sequence control as in the prior art, whereas the bottom blowing gas flow / gas switching optimization device 50 according to the present invention employs a flow control valve. The actual data such as the flow control valve opening from the nozzle 32, the tuyere pressure from the tuyere pressure gauge 62, and the blow gas flow from the gas flow meter 60 are collected, and the valve opening of the bottom blow gas control device 40 is set based on the actual data. Automatically correct the table so that the pressure is at a level that does not interfere with the operation.

FIG. 3 shows a chart of the gas switching sequence and the flow rate and tuyere pressure results at that time.
The parameters that are automatically changed by this system are: (1) the gas flow rate set value in the steady state where gas switching is not performed; and (2) the valve opening of the preceding gas (step d) in the gas switching state.
own) and the valve opening (regular opening) of the following gas.

The details of the automatic correction method will be described below.

Method (1) for optimizing the gas flow rate in the steady state The minimum value of the tuyere pressure results from the end of the gas switching to the gas to the start of the gas switching to the following gas is defined as Pmin. This Pmin collects the tuyere pressure results of the above period at regular intervals,
The minimum value is obtained.

This Pmin (i) and the current gas flow rate set value SV
Using (i), the flow rate set value SV (i + 1) when the same gas type is blown next is determined as follows.

SV (i + 1) = SV (i) −K × (Pmin (i) −Pset) (1)

Here, K: gain (> 0) Pset: reference tuyere pressure (K and Pset are constants of gas type), and Pset is
The value is determined in consideration of the lower limit pressure (setting for preventing the molten steel from flowing back to the tuyere) at which the bottom blow gas control device 40 performs the abnormality processing and the variation in operation.

In order to reduce the variation in operation, Pmin in the above equation (1) is an average (moving average) Pmin * (i) of past N charges and the following (3) shown in the following equation (2). ) May be a value that has passed through a first-order lag filter shown in the equation.

Pmin * (i) = ΣPmin (j) / (N + 1) (j = iN,..., I) (2) Pmin * (i) = α × Pmin (i) + (1−α) × Pmin * (i-1)… (3)

Here, this optimization method is applied in the following manner.
For oxygen, the blowing time has a margin, and the operation for minimizing the tuyere pressure is realized.

The optimization method at the time of gas switching of the above (2) The tuyere pressure at the time of gas switching, the actual gas flow rate of the preceding gas and the succeeding gas are sampled at high speed, and the maximum tuyere pressure Pcmax at the time of gas switching is obtained. The values of the tuyere pressure minimum value Pcmin and the following gas flow rise time T at the time of gas switching are determined.

Here, Pcmax and Pcmin are the maximum value and the minimum value of the tuyere pressure sampling data, respectively. T is the time from the output of the following gas block valve opening command to the actual gas flow rate reaching the flow rate setting.

In this optimization method, Pcmax is minimized while satisfying the following equation.

Pcmin ≧ Pset (4) T ≦ Tset (5) where Tset is a reference rise time (constant)

Here, the correction (operation amount) is based on the valve opening “SV (head)” (step down) at the time of gas switching of the preceding gas.
And the valve opening "SV (rear)" (specified opening) at the time of gas switching of the following gas, and qualitatively operates as follows. Here, ↓ indicates that the value decreases, and ↑ indicates that the value increases.

Pcmax for reducing "SV (head)"
↓, Pcmin ↓, T ↓ ・ Increase “SV (point)” Pcmax ↑, Pcmin ↑,
T ↑ ・ Decrease “SV (after)” Pcmax ↓, Pcmin ↓,
T ↑ · Increase “SV (after)” Pcmax Ｐ, Pcmincm,
T ↓

The following formulas (6) and (7) are used to correct the valve opening.
Defined by an expression.

[0032] SV (previous) (i + 1) = SV ( previous) (i) -ΔSV _p (previous) -ΔSV _t (earlier) ... (6) SV (after) (i + 1) = SV ( after) (i) -ΔSV _p (after) + ΔSV _t (after) ... (7) where, ΔSV _p (after earlier or) = K _p (after earlier or) × (Pcmax (i) -Pset) (Pcmin (i) ≧ time of Pset) ... (8) = K p ( earlier or later) × (Pcmin (i) -Pset ) (Pcmin (i) < time of _{Pset) ... (9) ΔSV t} ( after the previous or) = 0 ( a T (i) at the time of ≦ Tset) ... (10) = K t ( after the previous or) × (T (i) -Tset) (T (i)> time of Tset) ... (11), K p ( _Kt (before or after), Kt (before or after) is the gain (>
0).

FIG. 4 shows an example in the case of Pcmin (i) ≧ Pset.
FIG. 5 shows an example in the case of cmin (i) <Pset.

Here, the automatic correction of the above setting is performed in advance,
It is classified according to the combination of the following gas types, the preceding and the subsequent gas flow setting levels, and is applied the next time the gas is switched under the same conditions.

As for Pcmax, Pcmin, and T, as in the case of the gas flow rate in the steady state, a moving average result or a first-order lag filter may be used.

In this embodiment, the automatic change of the set value of the gas flow rate and the automatic change of the valve opening of the preceding gas and the valve opening of the following gas in the gas switching state are used together, so that optimization is achieved. be able to. In addition, it is also possible to employ only one of them.

The present invention can be applied to both bottom-blowing converters and top-bottom-blowing converters.

[0038]

According to the present invention, the tuyere pressure can be minimized (optimized) at a level that does not hinder the operation, so that the tuyere life can be prolonged and the service cost for bottom blown gas can be minimized. Can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a converter in which the present invention is implemented and a bottom blown gas system diagram thereof.

FIG. 2 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 3 is a time chart showing an example of a relationship between a control amount and an operation amount at the time of gas switching in the embodiment.

FIG. 4 is a time chart showing an example where the minimum tuyere pressure at the time of gas switching is equal to or higher than a reference tuyere pressure.

5 is a time chart showing an example in which the tuyere pressure minimum value at the time of gas switching is smaller than a reference tuyere pressure, contrary to FIG.

[Explanation of symbols]

 10 converters 12, 14, 16 ... piping to inner pipes 22, 24, 26 ... piping to outer pipes 32 ... flow control valve (FCV) 34 ... shutoff valve 36 ... block valve (SOV) 38 ... bleed valve ( SOV) 40 bottom-blowing gas control device 50 bottom-blowing gas flow / gas switching optimization device 60 gas flow meter 62 tuyere gas pressure gauge

Claims (2)

[Claims] In setting a flow rate of a bottom blown gas from a bottom tuyere in a converter, a current flow rate set value is obtained by using an actual minimum value of the tuyere pressure in a previous charge of the same gas type. A method for setting the flow rate of bottom blown gas in a converter. 2. A tuyere pressure record maximum value and a tuyere pressure record result at the time of switching a preceding gas and a succeeding gas in a previous and previous charge of the same gas type when switching a bottom blown gas from a bottom tuyere in a converter. Bottom-blowing gas in a converter characterized by obtaining the flow control valve opening of the preceding gas and the flow control valve of the following gas at the time of gas switching using the minimum value and the rise time of the following gas flow. Switching method.