JPH0638034B2 - Exhaust heat recovery device and method for metallurgical furnace - Google Patents

Description

The present invention relates to an exhaust heat recovery device for a metallurgical furnace for recovering the heat of exhaust gas generated intermittently from a metallurgical furnace such as a smelting reduction furnace, a converter, a blast furnace, and the like. Regarding the method.

[Conventional technology]

Exhaust gas generated in large quantities in metallurgical furnaces, such as converters, has a high temperature and retains a large amount of heat. Therefore, it has been conventionally practiced to recover this retained heat and use it effectively for power generation, for example. It is being appreciated.

In the case of a converter, for example, in the case of a converter, a boiler tube is arranged in an exhaust gas duct above the CO and H ₂ gas in the exhaust gas to combust the exhaust gas by combusting the exhaust gas. A typical method is to recover the retained heat of the combustion gas as steam using water flowing in the boiler tube as a medium.

FIG. 3 shows an example of equipment configuration for implementing the exhaust heat recovery method in the case of this conventional converter. That is, the exhaust gas duct 2 is arranged above the furnace opening of the converter 1.
An evaporator 3 is provided in the inside, and water is supplied to this evaporator 3 to be vaporized by heat exchange and guided to a steam / water separation drum 6, where it is separated into steam and water, and the steam / water separation drum 6 The water vapor therein is passed through a superheater SH provided in the exhaust gas duct 2.
Here, this steam is further heated by the heat of the exhaust gas, and is sent as an overheated steam to an energy converter (not shown) such as a steam turbine for power generation so that it can be recovered as, for example, electric power. . (See Iron and Steel No. 13 (1978) No. 13, pp. 1865-1868).

[Problems to be Solved by the Invention]

In general, not only in this converter but also in metallurgical furnaces such as smelting reduction furnaces, the generation of exhaust gas is intermittent, and the steam that passes through the superheater when the exhaust gas is generated and flows in the duct and when it is not. The amounts and temperatures of the are extremely different.

For example, when the exhaust gas from the metallurgical furnace is flowing through the duct, the water supplied to the evaporator is sufficiently heated by the heat retained in the exhaust gas, and the required amount and temperature of steam are passed through the steam separation drum. can get. After passing through the superheater, this steam can be supplied to, for example, a steam turbine as superheated steam by the heat retained in the exhaust gas by the superheater provided in the exhaust gas duct. However, when the exhaust gas is not generated or is small in the metallurgical furnace, the water supplied to the evaporator is insufficiently heated and the amount of generated steam is significantly reduced. or,
Since the superheat capacity of the superheater is also significantly reduced, the amount of heated steam obtained from the mood water separation drum through the superheater is greatly reduced,
For example, it becomes impossible to continuously operate the steam turbine for power generation.

Moreover, when a large amount of exhaust gas is generated in the metallurgical furnace from such a state and the exhaust gas flows through the duct, the superheater is rapidly overheated,
In addition, a so-called water hammer phenomenon occurs and a large thermal and mechanical shock is applied to the superheater. As a result, not only the life of the pipes constituting the superheater is shortened, but also troubles such as water vapor leakage occur.

Therefore, it is conceivable that the exhaust gas generated intermittently will be recovered by saturated steam and the fluctuation will be averaged by incorporating an accumulator. However, in this case, when the exhaust gas is used, it becomes low-pressure saturated steam, and driving the steam turbine for power generation lowers efficiency and results in loss.

Further, an auxiliary fuel-burning burner is attached to the exhaust gas duct, and when exhaust gas is not generated from the metallurgical furnace, the combustion gas obtained by this auxiliary fuel-burning burner is supplied to the superheater provided in the exhaust gas duct. It is possible. But,
Exhaust gas generated by the combustion of auxiliary fuel is mixed in the gas generated from the metallurgical furnace.Therefore, the gas generated in the metallurgical furnace is burned as in the case of the conventional technology, and the sensible heat of the gas is added. And, even the latent heat as the chemical energy, there is no problem in the case of recovering as the heat energy of the steam, but only the sensible heat of the metallurgical furnace generated gas is recovered as the heat energy of the steam, and the latent heat of the chemical energy is When recovering this exhaust gas for separate use, there is a problem such as a decrease in recovery utility.

Therefore, the present inventors provided a fuel-fired boiler in a system different from the exhaust gas duct of the metallurgical furnace, provided a superheater in the combustion gas passage thereof, and provided a heat recovery device to generate steam from the metallurgical furnace. Exhaust gas generation amount, that is, depending on the amount of steam generated from the heat recovery device of the exhaust gas duct, by supplying the required amount to the superheater, even if the exhaust gas generation from the metallurgical furnace is intermittent, the superheater For the purpose of enabling stable supply of superheated steam to a steam turbine for power generation, the invention of Japanese Patent Application No. 63-78367 was previously proposed. However, in the present invention, since the superheater is arranged in the exhaust gas duct of the metallurgical furnace, the exhaust gas from the metallurgical furnace is subject to intermittent fluctuations during the generation of the exhaust gas, which shortens the life as described above. Various problems remain, such as problems, difficulty in controlling the temperature of superheated steam, and maintenance measures.

The present invention provides an exhaust heat recovery apparatus and method for a metallurgical furnace that also solves these problems.

[Means for Solving the Problems]

A first aspect of the present invention is to provide a heat recovery device using water as a medium in an exhaust gas duct of a metallurgical furnace, convert water into steam by the heat retained by the exhaust gas of the metallurgical furnace, and pass this steam through a steam separation drum and a superheater. In a device for recovering as superheated steam, a superheater is not provided in the exhaust gas duct of the metallurgical furnace, a combustion furnace is provided outside the system, and a heat recovery device using a superheater and water as a medium is provided in the combustion gas passage, A heat recovery device for a metallurgical furnace, wherein a steam passage is formed between the heat recovery device and the steam separation drum, and a steam recovery circuit from the steam separation drum is connected to the superheater. According to a second aspect of the present invention, in the exhaust heat recovery apparatus for a metallurgical furnace according to the preceding paragraph, the heat recovery apparatus for the exhaust gas duct of the metallurgical furnace is supplied to the superheater in accordance with the amount of water vapor supplied to the steam separation drum. So that the steam amount is within the set range Combustion conditions in serial metallurgical furnace, an exhaust heat recovering method of metallurgical furnace, characterized by controlling the amount of injected water superheater.

A third invention provides a heat recovery device using water as a medium in an exhaust gas duct of a metallurgical furnace, and a first steam separation drum for separating steam from the heat recovery device into steam. No superheater is provided in the exhaust gas duct of the furnace, a combustion furnace is provided outside the system, a superheater is provided in the combustion exhaust gas passage, and a heat recovery device using water as a medium is provided to vaporize steam from this heat recovery device. It is led to a second steam / water separation drum for separating it into water, and a steam recovery circuit from the second steam / water separation drum and the first steam / water separation drum is connected to a superheater in a combustion gas passage of the combustion furnace. An exhaust heat recovery device for a metallurgical furnace characterized by the above.

A fourth aspect of the present invention is the exhaust heat recovery device for a metallurgical furnace according to the third aspect, wherein the heat recovery device for the exhaust gas duct supplies the heat to the superheater in accordance with the amount of water vapor supplied to the first steam separator. By controlling the combustion conditions of the combustion furnace and the amount of water supplied to the heat recovery device of the combustion furnace so that the superheated steam is within a set range, and controlling the amount of steam generated from the heat recovery device of the combustion furnace. It is characterized in that it is mixed with the steam from the first steam / water separation drum through a second steam / water separation drum and supplied to a superheater, and the amount of water injection is controlled in the superheater to recover a predetermined superheated steam. The heat recovery method of the metallurgical furnace.

[Action]

In the present invention, exhaust gas is not generated in the metallurgical furnace,
Alternatively, if the amount of steam generated from the heat recovery device of the exhaust gas duct is small, even if it is generated, if the amount of steam generated from the heat recovery device of the exhaust gas duct is small, an appropriate amount of the steam obtained from the heat recovery device of the separate combustion furnace is mixed into the superheater. The superheated steam amount and temperature obtained by supplying and superheating can be stably maintained in an optimum range for continuous operation of a steam turbine, for example. Further, the superheater is provided in the combustion gas passage of the combustion furnace in which stable combustion is performed in a system separate from the exhaust gas duct of the metallurgical furnace, and the fluctuation range of the amount of water vapor supplied to the superheater can be reduced. Therefore, it is possible to maintain a state in which no sudden mechanical or thermal shock is applied to the superheater of the combustion furnace, and especially the life of the superheater is extended, its maintenance is easy, and the controllability of the temperature of superheated steam and the like is good.

In addition, the combustion gas passage of the combustion furnace is a separate system from the exhaust gas duct of the metallurgical furnace, so that the combustion exhaust gas does not mix with the exhaust gas of the metallurgical furnace and does not affect the components of the exhaust gas of the metallurgical furnace. After recovering the heat, the effective components of this exhaust gas can be efficiently recovered.

〔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 outline of exhaust heat recovery equipment in an example in which the present invention is applied to exhaust heat recovery of converter exhaust gas.

The exhaust gas discharged from the converter 1 is collected by the exhaust gas duct 2. The exhaust gas duct 2 is provided with a heat recovery device including an evaporator 3, an auxiliary evaporator 4, an economizer 5, and the like, and above the exhaust gas duct 2, steam for separating steam from the heat recovery device into steam. A separation drum 6 is provided.

Further, outside the system of the exhaust gas duct 2, a fuel-fired boiler 7 is attached as a combustion furnace, and the fuel-fired boiler 7 is provided with a heat recovery device using water as a medium. The fuel-fired boiler 7 uses the heat of combustion of fuel such as coal, oil or natural gas to steam the water supplied to the evaporator 8. In addition, in order to efficiently recover the combustion heat, the evaporator 8
Auxiliary evaporator 9 and economizer 10 are additionally provided near the steam generator, and the steam obtained by these heat recovery devices is guided to the steam / water separation drum 6 provided on the side of the exhaust gas duct 2 described above. The steam separated by the steam / water separation drum 6 is adjusted to a predetermined temperature by a superheater 11 provided in a fuel-fired boiler 7, and then sent to a steam turbine (not shown) to generate energy for power generation. Consumed.

The water separated by the steam separation drum 6 is supplied to the water supply pipe W0.
Alternatively, it is supplied to the heat recovery device on the exhaust gas duct 2 side and the fuel-fired boiler 7 side via W1 and used as a heat recovery medium.

In the above-mentioned exhaust heat recovery equipment, in the heat recovery device on the side of the exhaust gas duct 2, water as a medium for heat recovery is first supplied to the economizer 5. During operation of the converter in which the exhaust gas generated in the converter 1 is flowing in the duct 2, this water cools the exhaust gas duct 2 to thermally protect the exhaust gas duct 2 and to retain the heat of the exhaust gas from the converter 1. Becomes hot water and is supplied to the auxiliary evaporator 4 and the evaporator 3.
It is heated to about ℃ and becomes a steam-water mixture. Then, the steam-water mixture is sent to the steam-water separation drum 6 through the steam pipes P0 and P1 and separated into steam and water.

On the other hand, also on the combustion furnace side, that is, on the side of the fuel-fired boiler 7, water as a medium for heat recovery is similarly supplied to the economizer 10, and becomes hot water due to the heat of combustion gas held in the fuel-fired boiler 7 and becomes the auxiliary evaporator. 9. It is supplied to the evaporator 8 and heated here to about 300 ° C. to form a vapor-water mixture.

This steam-water mixture is sent to the steam-water drum 6 provided on the side of the exhaust gas duct through steam pipes P3 and P4, where it is mixed with the steam-water mixture from the side of the exhaust gas duct 2 to separate steam and water. To be done.

The steam separated by the steam separation drum 6 is sent to the superheater 11 provided on the fuel-fired boiler 7 side via the steam recovery circuit P5. Combustion gas of about 1000 ° C generated in the fuel-fired boiler 7 flows through the superheater 11, and the steam supplied from the steam separation drum 6 to the superheater is 400 ° C.
It becomes superheated steam at the above temperature. The steam / water separation drum 6 is provided with a pressure gauge 12, and the superheater 11 is provided with a temperature adjusting water injector 13. The pressure in the steam / water separation drum 6 and the thermometer on the outlet side of the superheater 11 are provided. If the temperature (pressure) of the superheated steam from the superheater 11 is supplied to the steam turbine as a heating steam recovery device by adjusting the amount of water and the amount of water injected in the superheater 11 so that the temperature by 14 falls within an appropriate range. Keep within acceptable limits.

As described above, the generation of exhaust gas from the converter 1 is not constant and varies considerably.

In the present invention, for example, even when there is no exhaust gas generation in the converter 1, the capacity of the heat recovery device attached to the superheater 11 necessary for the steam turbine, the capacity of the superheater, that is, the generation and combustion heat recovery device of the combustion gas Of the steam generation amount, the control range of the superheated steam generation amount, and the combustion conditions of the fuel-fired boiler 7 and the amount of water supplied to the heat recovery device according to the fluctuations of the exhaust gas generation amount from the converter.
It controls the amount of water injected into the superheater.

In this case, in order to perform more precise control, for example, a combustion system in the fuel-fired boiler 7 is provided with two main and auxiliary systems, and the main combustion system supplies almost constant combustion gas to the superheater, and It has a heat recovery function that can generate a certain amount of steam and supply it to the steam-water separation drum, and the auxiliary combustion system is located downstream of the superheater and corresponds to the upper limit of the amount of exhaust gas from the converter, for example. Equipped with a heat recovery function that generates combustion gas and can generate steam equivalent to the amount of steam generated when the converter exhaust gas amount is the upper limit, depending on the fluctuation of the steam generation amount due to the fluctuation of the exhaust gas generation amount from the converter. , In particular, by controlling the combustion conditions of the auxiliary combustion system and controlling the amount of steam generated by the heat recovery device, the amount of steam in the steam separation drum is maintained within a predetermined range, and the amount of steam to the superheater is maintained. Stable supply and superheater A predetermined amount of superheated steam can be stably supplied to the steam turbine Te.

In this example, the superheater provided in the combustion gas passage of the fuel-fired boiler raises the temperature of the steam from the steam separation drum to a temperature at which it is supplied to the turbine, and functions to obtain superheated steam at a predetermined temperature. Therefore, in the main combustion system of the fuel-fired boiler, the necessary combustion is always performed.However, in the auxiliary combustion system, combustion occurs depending on whether the converter exhaust gas is generated or not. The thermal efficiency can be increased by changing the conditions according to the fluctuation of the generation of the converter exhaust gas. Therefore, in this case, in the fuel-fired boiler, the main combustion system for the superheater and the auxiliary combustion system for the heat recovery device, that is, the steam generation, are arranged in consideration of thermal efficiency.

As described above, in these Examples, the converter 1 and the exhaust gas duct 2 are not provided with a superheater, the fuel-fired boiler 7 is installed outside the exhaust gas duct system, and the heat recovery device and the superheater are provided in the combustion gas passages. If the exhaust gas generated from the converter is not sufficient, increase the amount of steam generated in the heat recovery device provided in the fuel-fired boiler 7 and supply steam to the superheater via the steam separation drum. Therefore, regardless of whether or not exhaust gas is generated in the converter 1, steam can be stably supplied to the superheater by controlling combustion in the fuel-fired boiler, and compared with the case where it is provided in the converter exhaust gas duct, It is possible to stably generate superheated steam and stably supply it to the steam turbine for power generation without being subjected to such thermal and mechanical shocks, and the steam turbine can be continuously operated by the superheated steam.

In the above embodiment, the steam / water separation drum for steam generated in the heat recovery device on the converter exhaust gas duct 2 side is replaced by the steam / water separation drum for steam generated in the heat recovery device on the fuel-fired boiler side. It is also used as.

However, without being restricted by this, as shown in FIG. 2, separately from the steam / water separation drum 6 (first) on the exhaust gas duct 2 side, the steam / water separation drum 15 (first 2) may be provided to mix the steam from the steam separation drums and supply the mixed steam to the heater 11 via the steam recovery circuit P5.

Further, the fluctuation of the exhaust gas generation amount from the converter is grasped as the fluctuation of the pressure in the steam separation drum, but the invention is not limited to this. For example, the converter exhaust gas duct or the heat of the exhaust gas duct A pressure gauge, a thermometer, a flowmeter, a calorimeter, etc. may be selectively provided in the water vapor flow path from the recovery device to the superheater, and the measurement result may be grasped by these.

Further, the metallurgical furnace is not limited to the converter and is also applicable to a furnace that generates a large amount of high-temperature exhaust gas such as a smelting reduction furnace, a blast furnace, and an electric furnace, which perform an operation accompanied by oxygen injection.

〔The invention's effect〕

As described above, in the present invention, in the case of recovering heat from exhaust gas intermittently generated in a metallurgical furnace operated in a batch system, exhaust heat of a metallurgical furnace exhaust gas duct provided with a superheater in the exhaust gas duct A combustion furnace provided outside the recovery system is equipped with a superheater and a heat recovery device, and in particular, when steam generation from the exhaust heat recovery system of the exhaust gas duct of the metallurgical furnace is not sufficient, it is possible to supply an increased amount of steam from the heat recovery device of this combustion furnace. I am trying. As a result, it is possible to always stably supply a predetermined steam to the superheater and to stably supply the steam as a power generation steam turbine load by the superheater as a superheated steam having a predetermined temperature. The recovery device can be operated continuously.

Further, the superheater is provided in the combustion furnace outside the metallurgical furnace exhaust gas duct system, and compared with the case where it is provided in the metallurgical furnace exhaust gas duct, mechanical and thermal shocks to the piping of the superheater are significantly reduced, Problems such as damage to the superheater and water leakage are suppressed. Further, the steam generated in the heat recovery device of the combustion furnace provided in a system different from the exhaust gas duct of the metallurgical furnace is supplied to the superheater, and when the exhaust gas is not generated, the combustion gas of the combustion furnace is used for the superheater. Since the heat is replenished, the components of the exhaust gas do not fluctuate as in the case of the conventional auxiliary fuel burning, and CO and H contained in the exhaust gas after the retained heat is recovered.
It is also possible to recover active ingredients such as ₂ in high purity.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment in which the present invention is applied to exhaust heat recovery of converter gas, and FIG. 2 is an explanatory diagram of another embodiment of the present invention.
The figure is an explanatory view of an example of a conventional exhaust heat recovery equipment. 1 is a converter, 2 is an exhaust gas duct, 3 is an evaporator, 4 is an auxiliary evaporator, 5 is an economizer, 6 is a steam separation drum, 7 is a fuel-fired boiler, 8 is an evaporator, 9 is an auxiliary evaporator, 10 is an economizer, 11 is a superheater, 12 is a pressure gauge, 13 is a water injector,
14 is a thermometer, 15 is the second steam drum, P0, P1, P2
P3, P4 are steam pipes, P5 is a steam recovery circuit, W0,
W1 is a water supply pipe and SP is a water vapor recovery canal.

Claims (4)

[Claims] 1. A heat recovery device using water as a medium is provided in an exhaust gas duct of a metallurgical furnace, and the water is converted into steam by the heat retained in the exhaust gas of the metallurgical furnace, and this steam is converted into superheated steam through a steam separation drum and a superheater. In the exhaust heat recovery device of the metallurgical furnace to be recovered, a heat recovery device using a superheater and water as a medium in a combustion gas passage is provided outside the system without providing a superheater in the exhaust gas duct of the metallurgical furnace. A steam passage is formed between the heat recovery device and the steam separation drum, and a steam recovery circuit from the steam separation drum is connected to the superheated steam recovery device via the inside of the superheater. Exhaust heat recovery device for metallurgical furnace. 2. The exhaust heat recovery apparatus for a metallurgical furnace according to claim 1, wherein the superheater of the exhaust gas duct of the metallurgical furnace against a change in the amount of steam supplied from the heat recovery apparatus to the steam separation drum. Characterized in that the combustion conditions in the combustion furnace of the claim (1), the water supply amount of the heat recovery device of the combustion furnace, the water injection amount of the superheater is controlled so that the amount of steam supplied to Exhaust heat recovery method for metallurgical furnace. 3. A heat recovery device using water as a medium is provided in an exhaust gas duct of a metallurgical furnace, and a first steam separation drum for separating water vapor from the heat recovery device into steam is provided, and The exhaust gas duct is not provided with a superheater, a combustion furnace is provided outside the system, a superheater is provided in the combustion gas passage, and a heat recovery device using water as a medium, and steam from this heat recovery device to steam A second steam / water separation drum for separation is provided, and a steam recovery circuit from the second steam / water separation drum and the first steam / water separation drum is connected to a superheater in a combustion exhaust gas passage of the combustion furnace. An exhaust heat recovery device for a metallurgical furnace characterized by: 4. The exhaust heat recovery device for a metallurgical furnace according to claim 3, wherein the superheated steam to be supplied to the superheater is set according to the amount of supplied steam separated by the first steam separation drum. The combustion conditions of the combustion furnace and the amount of water supplied to the heat recovery device of the combustion furnace are controlled so as to fall within the specified range to control the amount of steam generated from the second steam separation drum. The exhaust of a metallurgical furnace characterized in that the steam is mixed with the steam from the first steam-water separator and supplied to a superheater, and the amount of water injection is controlled in the superheater to generate a predetermined superheated steam. Heat recovery method.