JPH0638035B2 - Exhaust heat recovery method for metallurgical furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for recovering exhaust heat from exhaust gas intermittently generated from a smelting reduction furnace, a converter, or the like.

[Conventional technology]

In steelmaking facilities such as smelting reduction furnaces and converters, a large amount of thermal energy is released as exhaust gas. It has been conventionally practiced to recover this energy and use it effectively for power generation, for example.

A typical method for recovering the sensible latent heat of the exhaust gas is to arrange a boiler in the flue above the converter and forcibly combust the CO gas to recover the sensible heat as steam.

FIG. 2 shows the equipment configuration used in the conventional exhaust heat recovery method. That is, the duct 22 is connected to the exhaust gas source 21 such as a metallurgical furnace.
Then, water is supplied to the evaporator 23 to be vaporized by heat exchange, and the steam / water separation drum 24 separates it into steam and water, and the steam in the steam / water separation drum 24 is passed through the superheater 25. This steam is further heated to superheated steam by the heat of exhaust gas and sent to an energy converter (not shown) such as a steam turbine for power generation. In this way, the energy in the exhaust gas can be recovered, for example, as electric power (Iron and Steel
978) No. 13, pp. 1865-1868).

[Problems to be Solved by the Invention] However, when exhaust heat is recovered from exhaust gas intermittently generated in a metallurgical furnace such as a converter or a smelting reduction furnace by this method, the exhaust gas passes through a duct. The amount of heat received by the superheater 25 is extremely different between when the exhaust gas does not flow.

For example, when the exhaust gas from the metallurgical furnace is flowing through the duct, the water supplied to the evaporator 23 is sufficiently heated and the required amount of steam is obtained. Therefore, the superheater 25 is filled with this steam, and a predetermined superheat is performed.
On the other hand, if there is no generation of exhaust gas in the metallurgical furnace,
The water in the evaporator 23 is insufficiently heated, and the amount of water vapor separated by the steam separation drum 24 becomes insufficient. In addition, a part of the water vapor in the water / water separation drum 24 may become mist and flow in. When the superheater 25 is in such a state, the exhaust gas generated in the metallurgical furnace in the next step flows through the duct 22, the superheater 25 is rapidly overheated, so-called water hammer occurs, the piping of the superheater 25 Thermal shock is applied to. As a result, not only the life of the pipe is shortened, but also troubles such as water vapor leakage occur.

Therefore, it is possible to incorporate an accumulator in order to average the amount of exhaust gas generated intermittently. However, in this case, when the exhaust gas is used, it becomes low-pressure saturated steam, and the high temperature sensible heat originally possessed by the exhaust gas cannot be used as steam for power generation.

In addition, an auxiliary fuel burning burner is attached to the exhaust gas duct 22,
When the exhaust gas is not generated from the metallurgical furnace, it is possible to supply the superheater 25 with the amount of heat obtained by the auxiliary fuel-burning burner. However, if this is used in, for example, an OG boiler, the exhaust gas generated by the combustion of the auxiliary fuel is mixed in the converter gas, and there is a concern that the recovery amount of the converter gas may be reduced.

Therefore, the present invention, the steam generated in the fuel-fired boiler of another system, by supplying to the superheater corresponding to the presence or absence of exhaust gas generation from the metallurgical furnace, even against high-temperature gas generated intermittently The purpose is to effectively recover heat without damaging the superheater.

[Means for Solving the Problems]

In order to achieve this object, the exhaust heat recovery method of the present invention, for recovering the heat of exhaust gas generated in a metallurgical furnace as superheated steam using a superheater arranged in an exhaust gas duct When the emission of exhaust gas from the furnace is interrupted,
Steam from another fuel-fired boiler is supplied to the superheater.

[Action]

If the exhaust gas is not generated in the metallurgical furnace such as the smelting reduction furnace or the converter, or if the exhaust gas is small in amount, a sufficient amount of steam is supplied to the superheater installed in the exhaust gas duct. Not supplied. Therefore, in the present invention, in such a state, by supplying the steam generated in another fuel-fired boiler to the superheater, the exhaust gas generated in the metallurgical furnace will overheat the superheater. However, make sure that the superheater is not subject to sudden thermal shock. Thereby, heat can be smoothly recovered from the exhaust gas generated intermittently, and superheated steam can be obtained under stable conditions.

In addition, the flue of other fuel-fired boilers has a different system from the duct that guides the exhaust gas generated in the metallurgical furnace. Therefore, the combustion gas generated in the fuel-fired boiler does not mix with the exhaust gas from the metallurgical furnace, and does not affect the components of the exhaust gas.

〔Example〕

Hereinafter, the features of the present invention will be specifically described by way of examples with reference to the drawings.

FIG. 1 shows an exhaust heat recovery facility used in an embodiment in which the present invention is applied to converter gas exhaust heat recovery.

The exhaust gas discharged from the converter 1 is collected by the duct 2. An evaporator 3, a superheater 4, an auxiliary evaporator 5, and an economizer 6 are arranged in the duct 2. Further, reference numeral 7 is a steam separation drum.

A fuel-fired boiler 8 is attached to the exhaust gas / heat recovery system. The fuel-fired boiler 8 vaporizes the water supplied to the evaporator 9 by the combustion heat generated by the combustion of fuel such as coal, oil, natural gas. Further, an economizer 10 is provided downstream of the evaporator 9 in order to efficiently recover the combustion heat. The obtained steam is guided to the steam separation drum 7 described above. The steam discharged from the steam separation drum 7 is adjusted to a predetermined temperature by the superheater 4 and the superheater 11 and then sent to the turbine.

In the above equipment, a coolant such as cooling water is first supplied to the economizer 6. When the exhaust gas generated in the converter 1 is flowing in the duct 2, the cooling by the water causes the duct 2 to cool.
The heat of the exhaust gas is recovered as warm water. The warm water is then supplied to the evaporator 3 and the auxiliary evaporator 5, where it is heated to about 300 ° C. to form a steam-water mixture. Then, the steam-water mixture is sent to the steam-water separation drum 7 and separated into steam and water.

The steam separated by the steam separation drum 7 is sent to the superheater 4 via the steam supply pipe 12. On the high temperature side of the superheater 4, the exhaust gas generated in the converter 1 at a temperature of about 1500 ° C flows through the duct 2 and the temperature of the gas is lowered to about 1000 ° C. Supplied.
As a result, the steam supplied to the superheater 4 becomes superheated steam heated to 400 ° C. or higher. This superheated steam is
It is sent to the superheater 11 via the steam discharge pipe 13.

The superheated steam is maintained at a predetermined temperature by being further heated by the superheater 11 or being cooled by the water injected from the water injector 16. It is also possible to send the superheated steam obtained in the superheater 4 directly to the turbine without passing through the superheater 11.

Next, the superheated steam heated to a predetermined temperature by the superheater 11 is sent to the turbine and consumed as energy for power generation.

On the other hand, when no exhaust gas is generated in the converter 1, the heat of the exhaust gas is not given to the superheater 4. At this time, in order to increase the heat recovery efficiency of the fuel-fired boiler 8, the water circulated through the economizer 10 is supplied to the evaporator 9 to partially vaporize the steam-water mixture, and the steam-water pipe 14 is used. Send to the steam separation drum 7. Then, the steam is separated from the steam mixture by the steam separation drum 7. This water vapor is
Similarly, it is sent to the turbine through the superheater 4, steam discharge pipe 13, and superheater 11.

In this way, the duct 2 that guides the exhaust gas flowing out of the converter 1
The fuel-fired boiler 8 is disposed separately from the superheater 4 provided in the above, and when the exhaust gas is not flowing through the duct 2, the superheater 4 is passed from the evaporator 9 of the fuel-fired boiler 8 via the steam separation drum 7. Is supplying steam to. Therefore, the superheater 4 can always be maintained at a constant pressure and temperature regardless of whether exhaust gas is generated in the converter 1. Therefore,
The superheater 4 generates a predetermined superheated steam without receiving a sudden temperature change or thermal shock. When the temperature of the superheated steam is insufficient, the superheater 11 raises the temperature of the superheated steam to a required temperature. As a result, superheated steam having a constant pressure and temperature is sent to the turbine, and the power generation device is driven under stable conditions to recover heat.

The switching of the steam supply path for the steam separation drum 7 is performed based on the detection result of the exhaust gas generated in the converter 1 detected by an appropriate means. Alternatively, converter 1
It is also possible to switch the steam supply path according to the operation schedule of. The superheater 4 and the superheater 11 are provided with water injectors 15 and 16 each having a temperature detector. The water injectors 15 and 16 detect the internal temperature of the corresponding superheater 4 or the superheater 11 by the temperature detector, and control the amount of water injected to the superheater 4 or the superheater 11 based on the detected value. As a result, the superheater 4 and the superheater 11 are maintained under constant conditions, and the temperature and pressure of the generated superheated steam are made constant.

In the above embodiment, the steam-water separation drum 7 of the system that recovers the sensible heat of the exhaust gas is also used as the steam-water separation drum of the fuel-fired boiler 8. However, without being restricted by this, it is possible to provide a steam separation drum dedicated to the fuel-fired boiler 8 separately from the steam separation drum 7. Further, the converter has been described as an equipment for intermittently generating exhaust gas, but it is needless to say that the invention can be similarly applied to other metallurgical furnaces such as a smelting reduction furnace.

〔The invention's effect〕

As described above, in the present invention, when recovering exhaust heat from exhaust gas intermittently generated in a metallurgical furnace operated in a batch system, when exhaust gas is not generated, the exhaust heat recovery system overheats. The steam is supplied from the evaporator to the fuel-fired boiler. As a result, the superheater is always maintained under a predetermined temperature condition, the thermal shock to the piping of the superheater is reduced, and troubles such as damage and water leakage of the superheater are suppressed. Further, it is possible to smoothly absorb the exhaust heat even when the exhaust gas is generated next time. Then, by sending steam that retains the heat generated in another series to the piping of the superheater, heat is replenished to the superheater when exhaust gas is not generated, so it is the same as in the case of conventional auxiliary fuel firing. It is also possible to recover latent heat from CO, H _{2 and the} like contained in the exhaust gas after recovering the sensible heat without changing the components of the exhaust gas.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment in which the present invention is applied to exhaust heat recovery of converter gas, and FIG. 2 is a diagram for explaining problems of a conventional exhaust heat recovery system. 1: Converter, 2: Duct 3,9: Evaporator, 4,11: Superheater 5: Auxiliary evaporator, 6,10: Economizer 7: Steam separation drum, 8: Fuel-fired boiler 12: Steam supply pipe , 13: Steam discharge pipe 14: Steam pipe, 15, 16: Water injector

Claims (1)

[Claims] 1. When exhaust gas emission from the metallurgical furnace is interrupted when heat retained in exhaust gas generated in the metallurgical furnace is recovered as superheated steam using a superheater arranged in an exhaust gas duct, A method for recovering exhaust heat of a metallurgical furnace, comprising supplying steam from another fuel-fired boiler to the superheater.