JPH0743081A - Control method of internal pressure of self-fluxing furnace - Google Patents

Abstract

PURPOSE:To provide the control method of internal pressure of a self-fluxing furnace, which is effective for the factor of external disturbance generated suddenly. CONSTITUTION:A self-fluxing furnace is provided with a waste heat recovery boiler, connected to the flue of the automatic balst furnace, and a control valve, provided at the outlet port of the waste heat recovery boiler, while the opening degree of the control valve is regulated based on the value of a difference between the measured value and the specified value of the outlet port pressure of the waste heat recovery boiler and the specified value is regulated based on a difference between the measured value and the set value of the internal pressure of the self-fluxing furnace. According to this method, the response of the outlet port pressure of a boiler with respect to the change of opening degree of the control valve is quickened. As a result, a response speed of internal pressure of the self-fluxing furnace with respect to the opening degree of the control valve is quickened. Further, pressure fractuation in the waste heat recovery boiler, which is generated mainly upon soot blowing, can be detected soon whereby the internal pressure of the self-fluxing furnace can be controlled nicely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a flash smelting equipment, and more particularly to a method for controlling the pressure inside the flash furnace.

[0002]

2. Description of the Related Art One of non-ferrous metal smelting methods using sulfide concentrate as a raw material is a flash smelting method. This method uses a flash furnace basically composed of a reaction tower, a settler having one end connected to the lower end of the reaction tower, and a flue gas duct provided at the other end of the settler, Usually, a waste heat recovery boiler is installed on the downstream side of the flue gas, a dust collector is installed on the lower side thereof to remove the smelting waste gas, and then this smelting waste gas is sent to the sulfuric acid factory by a waste gas fan. Then, in the sulfuric acid factory, for example, a tower, a washing tower, a mist cotrel, etc. are used to remove dust and SO ₃ from the smelting waste gas, and the SO ₂ in the smelting waste gas is converted to SO ₃ through the drying tower. Waste gas is being introduced into the converter.

The pollution problem caused by waste gas discharged from non-ferrous metal smelters has been a serious social problem from the past, and SO _{2 and the} like are generated in the process from the furnace where the gas is generated, such as a flash smelting furnace, to the outlet of the gas treatment facility. Leakage of gas, including gas, will result in immediate shutdown. Therefore, it is no exaggeration to say that how to prevent the leakage of waste gas is a life and death problem in non-ferrous metal smelters. Therefore, it is strictly prohibited to make the gas pressure in the device and the flue gas positive in the entire waste gas system. However, it is inevitable that the gas pressure in each device and flue will fluctuate due to various factors during operation, and the leaked waste gas is collected by the environmental smoke collector to make it harmless. It is the actual situation.

By the way, in order to prevent the waste gas from leaking out of the system without relying on the environmental smoke collection, it is necessary to constantly make the gas pressure in each device and the flue gas to be an excessive negative pressure. It is necessary to install sulfuric acid production equipment, or as a result of excessive negative pressure, it is necessary to install desulfurization equipment that can process gas whose SO ² concentration has become extremely low due to the large amount of air that has flowed into the system. And even the survival of the company may be jeopardized.
Therefore, there is always a demand for the development of an operating method for preventing the leakage of waste gas in the system while minimizing the inflow of free air into each device.

By the way, as a method of controlling the pressure in the flash furnace to a desired value, a control damper is provided at the entrance of the dust collector provided on the downstream side of the flash furnace, and the opening of the control damper is continuously changed. It is generally adjusted according to the measured internal pressure of the flash furnace.

However, according to this method, there is a waste heat recovery boiler between the detection unit of the furnace pressure and the control damper, and the time constant is large and the response of the furnace pressure to the change of the opening of the control damper is delayed. It is easy to occur. In addition, during operation of the soot blower provided to remove the smoke ash attached to the surface of the water pipe in the waste heat recovery boiler,
A large amount of air is temporarily and rapidly blown into the waste heat recovery boiler to blow off the smoke ash from the surface of the water pipe. For this reason, the pressure in the flash furnace undergoes a very rapid pressure fluctuation. Since such a rapid pressure fluctuation cannot be absorbed by the entire waste gas treatment system, the waste gas leaks from the flash furnace to the outside of the furnace. The waste gas that leaks to the outside of the flash furnace must be collected by an environmental smoke collector to prevent it from leaking outside the building, and the capacity of the environmental smoke collector must be excessive. Such problems become more serious and more serious as the operating rate increases.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for controlling the internal pressure of a furnace which is effective against such a sudden disturbance factor.

[0008]

A method of controlling the internal pressure of a flash furnace of the present invention which solves the above-mentioned problems is a reaction tower having a concentrate burner at the top thereof, and one end of which is connected to the lower end of the reaction tower. A settling furnace, a flash furnace basically composed of a smoke exhaust path provided at the other end of the settler, a waste heat recovery boiler connected to the waste smoke path of the flash furnace, and a control valve for the waste heat recovery boiler. In a method for controlling the internal pressure of a flash furnace of a flash smelting equipment that is basically composed of dust collectors connected via a cascade, the internal pressure of the flash furnace is primary and the outlet pressure of the waste heat recovery boiler is secondary The opening of the control valve is adjusted by control, and more specifically, the opening of the control valve is adjusted based on the size of the difference between the measured value of the waste heat recovery boiler outlet pressure and the specified value. The measured value is the measured value of the internal pressure of the flash furnace. And adjusts on the basis of the difference between the value.

[0009]

In the method of the present invention, maintaining the internal pressure of the flash furnace at a predetermined value on the negative side is a prerequisite. Despite the occurrence of pressure fluctuations such as soot blower in the waste gas system, in order to satisfy this condition, it is extremely important to determine at which position the detected pressure is the reference signal that changes the opening of the control valve. . In the present invention, this position is the outlet of the waste heat recovery boiler. This is because the fluctuations between the internal pressure of the furnace and the outlet pressure of the waste heat recovery boiler showed the strongest correlation, assuming a constant time lag. That is, if the outlet pressure of the waste heat recovery boiler fluctuates, the same fluctuation in the internal pressure of the flash furnace will always occur after a certain period of time, and the fluctuation of the outlet pressure of the waste heat recovery boiler and the fluctuation of the internal pressure of the flash furnace will be proportional to each other. This is because there is an extremely strong correlation of 0.911. In addition, when the waste heat recovery boiler is provided with a soot blower, this is also the position where the pressure fluctuation caused by the operation of the soot blower can be detected earliest.

Therefore, in the method of the present invention, the outlet pressure of the waste heat recovery boiler obtained from the above correlation is selected so that the internal pressure of the flash heating furnace becomes a predetermined negative pressure, and this is set as the specified value, and the waste heat recovery boiler is set. Increase or decrease the control valve opening based on the difference between the measured outlet pressure and the specified value. As a control operation for this purpose, various operation methods such as P operation, PI operation, PD operation, and PID operation can be adopted, and the one that most corresponds to the system to be applied may be adopted. Optimal.

As long as the operating state of the flash furnace is constant, the adjustment of the opening of the control valve can be done by an adjusting method that depends only on the outlet pressure of the waste heat recovery boiler. However, the operating conditions do not remain constant over a long period of time because they change according to changes in the mineral species used and fluctuations in the furnace conditions. in this case,
In particular, the coefficient of the relational expression showing the correlation between the boiler outlet pressure and the internal pressure of the flash furnace becomes different as the amount of the reaction gas blown into the reaction tower increases or decreases. The correction for the difference in the coefficient is the correction for the specified value of the outlet pressure of the waste heat recovery boiler based on the difference between the measured value and the set value of the internal pressure of the flash furnace.

[0012]

EXAMPLES Next, examples of the present invention will be described. (Example 1) An operation test was conducted using a flash furnace in which the opening of a control valve provided at the outlet of a waste heat recovery boiler was adjusted by the method for controlling the internal pressure of the flash furnace of the present invention using the control by PID operation. It was When the charging of the smelting raw material into the reaction tower was started (start of operation), the rotation speed of the exhaust gas fan and the opening of the control valve were manually adjusted so that the internal pressure of the flash furnace was -3 mmAq. When the operation became stable, the control of the internal pressure of the flash furnace was switched to automatic control. At this time, the internal pressure of the flash furnace was -3 mmAq, the value of the outlet pressure of the waste heat recovery boiler was approximately -7 mmAq, and the opening of the control valve was approximately 70%.

The operating condition at this time is the amount of copper concentrate charged.
92t / H, blowing amount of heavy oil as auxiliary fuel 155l /
H, the blowing amount of reaction air was 33000 Nm ³ / H. During the operation, the soot blower was operated for 1 minute and 15 seconds with a blowing amount of 3000 Nm ³ / H from one blowing pipe provided in the waste heat recovery boiler. A chart showing fluctuations in the furnace pressure for a total of 9 minutes including the operation time of the soot blower at the center was read at 5-second intervals, and fluctuations in the furnace pressure in the flash furnace were examined. As a result, the average value of the measured values was -2.91 mmAq and σ _N-1 was 0.83 mmAq with respect to the set value of the furnace pressure of -3 mmAq.

(Conventional example) As in the conventional case, the fluctuation of the internal pressure of the flash furnace is controlled in the same manner as in the example except that the control valve is controlled by the PID operation only by the internal pressure of the flash furnace and the outlet pressure of the waste heat recovery boiler is controlled. Examined. As a result, the average value of the measured values was -3.54 mmAq, σ for the set value of the furnace pressure -3 mmAq.
_N-1 was 1.62 mmAq. Further, during soot blower operation, the internal pressure of the flash furnace became positive twice and gas was blown out from the inspection hole of the flash furnace. From the above results, it is clear that the internal pressure of the flash furnace can be stabilized by using the method for controlling the internal pressure of the flash furnace of the present invention.

[0015]

In the method for controlling the internal pressure of the flash furnace of the present invention, the response of the boiler outlet pressure to the change in the opening of the control valve becomes faster, resulting in the response speed of the internal pressure of the flash furnace to the change in the opening of the control valve. Will be faster. Furthermore, pressure fluctuations in the waste heat recovery boiler, which are mainly caused by soot blowers, can be detected quickly, so that the internal pressure of the flash furnace can be well controlled.

Claims (2)

[Claims] 1. A reaction column having a concentrate burner at its top, a settler having one end connected to the lower end of the reaction column, and a flue gas duct provided at the other end of the settler. A self-smelting furnace of a self-smelting and smelting facility basically composed of a self-smelting furnace, a waste heat recovery boiler connected to a waste flue of the self-smelting furnace, and a dust collector connected to the waste heat recovery boiler via a control valve. In the method for controlling the internal pressure of the flash furnace, the internal pressure of the flash furnace is set as the primary and the outlet pressure of the waste heat recovery boiler is set as the secondary to adjust the opening of the control valve by the cascade control. Control method. 2. The opening of the control valve is adjusted based on the difference between the measured value of the outlet pressure of the waste heat recovery boiler and the specified value, and the specified value is the measured value and the set value of the furnace pressure of the flash furnace. The method for controlling the furnace pressure of the flash furnace according to claim 1, wherein the method is adjusted on the basis of the difference.