JPS6217003B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an exhaust gas recovery control device for recovering unburned exhaust gas in an oxygen converter, and in particular recovers a larger amount of converter exhaust gas with a high CO concentration by controlling the exhaust gas flow rate. The present invention relates to an exhaust gas recovery control device for a converter.

Generally, in an oxygen converter, oxygen is blown into the steel bath in the furnace from a lance or the bottom of the furnace, or both, and auxiliary materials such as lime are added to reduce C (carbon) in the steel bath.
P (phosphorus) and Mn (manganese) are removed by oxidation. At this time, a large amount of gas rich in CO gas is generated, so a hood is installed above the furnace mouth to collect this gas, thereby cleaning the working environment and preventing danger. Efforts are being made to save energy through reuse. The upper end of this hood is connected to the exhaust gas suction duct, while the lower end of the hood is provided with a skirt that covers the upper part of the furnace mouth. Although this equipment arrangement is for safety reasons, the amount of exhaust gas induced must be appropriate due to the distance between the hood and the converter. In other words, if the amount of suction is too large, the atmosphere will be sucked in between the skirt and the furnace mouth and drawn into the hood, which will not only reduce the calorie content of the exhaust gas, but also cause a combustion reaction between CO in the exhaust gas and atmospheric _O2 . This may cause an accident that may cause damage to the hood, ducts, etc. Furthermore, if the amount of suction is too low, CO-enriched exhaust gas will blow out from between the furnace mouth and the skirt, contaminating the working environment, making it dangerous, and causing energy loss.

Conventionally, in order to solve the above-mentioned problems, a detection end was installed inside the hood, and based on the value of the furnace pressure measured by this detection end, the furnace pressure was set to be the same or almost the same as the atmospheric pressure. The amount of exhaust gas suction is controlled. This control system uses a PI (proportional-integral) control loop based on furnace pressure feedback, and can appropriately control the exhaust gas flow rate by changing the furnace pressure setting based on the operator's empirical judgment.

However, such furnace internal pressure control means has the following problems. One of them is that it cannot adequately cope with sudden changes in the amount of gas generated when adding auxiliary materials or changing the amount of oxygen fed. In other words, when the amount of gas generated in the furnace suddenly changes when adding auxiliary materials or changing the amount of oxygen supplied, and the furnace entrance is sucked into the atmosphere or the exhaust gas is blown out of the furnace, the furnace pressure setting value is changed at the operator's discretion. At that time, there is already a delay in changing the set value, and there is also a delay in measuring the furnace internal pressure that has been changed by operating the control end after changing the set value.In addition to this, there is a delay in the transmission of the control loop, etc. , control loop operation delays are inevitable. Another problem is that the work environment is prevented from being contaminated and the exhaust gas recovery work is kept safe by preventing sudden air entrainment and exhaust gas ejection. This often results in the loss of CO-enriched gas. Furthermore, another problem is that there are large individual differences among operators. That is, since the adjustment is performed manually by the operator, the amount of adjustment varies depending on the work skill level of each operator, and this has a problem in that it directly affects the controllability of the exhaust gas flow rate.

Therefore, in order to improve the above-mentioned problems, three improved techniques as described below have been considered.

(1) Exhaust gas recovery control method using the predicted value of residual O ₂ in the furnace.

This control method calculates the amount of O ₂ remaining in the furnace from time to time based on the difference between the amount of O ₂ injected into the furnace and the amount of O ₂ output from the furnace, and uses the instantaneous value based on this calculation result to The amount of O 2 remaining in the furnace can be calculated by calculating the change in the amount of residual oxygen in the furnace and subtracting the amount of O ₂ spent in oxidizing the steel bath [Si] and remaining in the slab as [SiO _{2 ]} from this integrated value. I am getting . In this case, it is specifically determined by taking into consideration the exhaust gas flow rate, exhaust gas composition, oxygen supply amount, input amount for each brand of auxiliary raw material, etc. Then, the amount of residual O ₂ in the reactor determined as described above is extended over time to predict and estimate the future value. Furthermore, the future amount of gas generated in the furnace is predicted from this estimated value, the scheduled value from the lance, and the amount of O ₂ generated by the auxiliary material decomposition O ₂ model, and the secondary precipitator damper is adjusted based on this predicted gas amount. of
This is an exhaust gas recovery control method that implements DDC (Direct Digital Control).
Publication No. 1 and Japanese Patent Publication No. 56-22927.

However, since this method predicts the amount of O ₂ remaining in the furnace by extending the actual time series, it cannot eliminate the lag time and cannot adequately respond to sudden changes in gas generation conditions that may occur in the future. .

(2) Control method using constant entrainment air rate control using equivalent skirt resistance.

This method uses the actual value of air intake at the furnace mouth, which is calculated from the exhaust gas flow rate and exhaust gas composition, and the furnace internal pressure (expressed as the difference between atmospheric pressure and actual pressure inside the furnace).
This method calculates the equivalent skirt resistance, which is the flow path resistance of the space in the gap between the furnace mouth and the skirt, and controls the amount of air entrained at the furnace mouth so that it approaches a target value. Special Publication No. 58-3004, Special Publication No. 57-58409 and Special Publication No. 57-
Technologies such as those disclosed in Publication No. 45447 fall under some or all of such control methods.

However, in this control method, the equivalent skirt resistance is a quantity based on past performance, and there is a lag in the calculation method itself, and there is also a problem that it cannot demonstrate sufficient adaptability to future changes in circumstances. .

(3) Furnace pressure control method using process characteristic compensation device.

This control method determines the amount of change in the furnace pressure setting value when adding auxiliary materials and changing the amount of oxygen fed using a predetermined time compensation formula and a generation amount compensation formula that corresponds to the amount of input and the amount of change. For example, Tokukaisho
The technology related to Publication No. 58-1011 falls under this category.

In this control method, the same auxiliary raw material input amount and
Even when the oxygen feed rate is changed, the reproducibility of the change in the furnace pressure set value is restricted depending on the reaction situation in the furnace, so the amount of change in the furnace pressure set value only for the feed forward element cannot be set to a sufficiently optimal value. There are issues that cannot be decided.

Therefore, to summarize the above control methods, improved techniques (1) and (2) both make predictions by extending a time series with a past delay, so they are effective against sudden changes that cannot be predicted from past trends. Prediction accuracy has not been improved sufficiently. Next, improved technology (3) only makes predictions based on feed forward control, so the reaction situation inside the reactor is not reflected. Therefore, each control method has fatal drawbacks, and it is difficult to say that any of them is a perfect control method. Furthermore, in order to realize improved technologies (1) and (2), it is necessary to modify the equipment by converting the secondary precipitator damper to DDC, which also increases the cost.

The present invention was made in order to solve the problems of the conventional technology as described above, and the present invention corrects the estimated amount of gas generated in the furnace obtained by estimating it from the metallurgical reaction in the furnace using the actual value of the amount of gas generated in the furnace. The predicted value of the amount of gas generated in the furnace is calculated, and based on this predicted value, the optimal set value of the furnace pressure is determined from the pressure balance of the furnace mouth hood. Based on this set value, advance control of the exhaust gas flow rate is possible. Therefore, an object of the present invention is to provide a converter exhaust gas recovery control device that can recover a larger amount of converter exhaust gas with a higher CO concentration in a converter under the same refining operation as the conventional one.

An embodiment of the present invention will be described below. FIG. 1 is a diagram showing the overall configuration of the device. In the figure, reference numeral 1 indicates a converter, and reference numeral 2 indicates a steel bath.The converter 1 is disposed so that the tip of an exhaust gas duct 3 extending in a predetermined direction is located above the converter 1. A hood 4 and a skirt 5 are attached to the tip of the exhaust gas duct 3 to suck in the gas generated in the furnace. A furnace internal pressure detection transmitter is attached to the hood 4, and a skirt height transmitter 7 is attached to the skirt 5. Further, an oxygen supply lance 8 for blowing oxygen is inserted into the converter from the upper part of the converter, while an auxiliary raw material inlet 9 for inputting auxiliary raw materials is provided at the rear end of the hood 4. 10 is an auxiliary raw material input amount transmitter, 11 is an input chute, and 12 is an auxiliary raw material input device. 13 is an oxygen flow meter that detects the flow rate of oxygen sent into the furnace through the feed lance 8. The exhaust gas duct 3 has an inverted U shape from the top of the converter.
They are arranged in a letter shape, with the lower end of the other end extending in parallel. An exhaust gas analyzer 14 is attached to the top of the inverted U-shape of the exhaust gas duct 3, and a secondary precipitator damper drive device 15 is disposed on the outside of the duct 3 going downward from the top. An exhaust gas induction device 16 is provided in the parallel portion of the exhaust gas induction device 16 . A three-way valve 17 is inserted into the duct 3 extending rearward from the exhaust gas induction device 16, and the valve 17 sends exhaust gas to the chimney 18 and the rear end of the duct. 19 is a recovery valve, and 20 is a gas holder. 21 is an exhaust gas flow rate transmitter that detects the flow rate of exhaust gas flowing in the duct 3 located on the input side of the exhaust gas induction device 16;
22 is a main raw material information collection device.

23 is a calculation unit for estimating the amount of gas generated in the furnace;
Based on the information from the main raw material information collection device 22 and the like, an estimated value X ^M of the amount of gas generated in the furnace is determined by the calculation formula (1).

X ^M = (M _A

Claims (1)

[Claims] 1. Attach a hood and a skirt to the tip of the exhaust gas duct and place them above the oxygen converter furnace mouth to control the collection of exhaust gas generated from the oxygen converter during blowing when the exhaust gas is sucked through the duct. In a converter exhaust gas recovery control device, an in-furnace generated gas amount estimation calculation unit that takes main raw material information as an initial value and calculates an estimated value of in-furnace generated gas amount from momentary auxiliary raw material information and lance information; An in-furnace gas amount actual calculation unit that calculates the actual value of the in-furnace gas amount from the exhaust gas flow rate and composition of flowing exhaust gas, and an estimated value and actual value of the in-furnace gas amount obtained by both of these calculation units. The statistical properties of the deviation time series are calculated from the time series up to the point of the latest actual value, and the deviation at the prediction time is predicted from the statistical properties of the deviation time series obtained by this calculation. a calculation means for predicting the amount of gas generated in the furnace for calculating the predicted value of the amount of gas generated in the furnace by correcting the estimated value of the gas amount generated in the furnace at the time of the prediction, and a furnace pressure calculation formula derived from the pressure balance at the mouth of the converter. In addition to modifying the parameters from time to time based on the ratio of the target entrained air amount to the actual entrained air amount, the above parameters are adjusted based on the predicted value of the amount of gas generated in the furnace obtained in advance, the target optimum amount of entrained air, and the skirt height. 1. An exhaust gas recovery control device for a converter, comprising means for determining the furnace internal pressure using a correction parameter and supplying this as a furnace internal pressure set value to a control system that controls an exhaust gas control damper.