JP3126705B1 - Exhaust gas energy recovery equipment - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide an exhaust gas energy recovery facility capable of greatly improving the recovery efficiency by enabling recovery of an exhaust gas generated from a smelting reduction plant using a blast furnace combined cycle power plant that has already been developed and put into practical use. I do. SOLUTION: This is a facility for recovering energy from exhaust gas generated in a smelting reduction plant 1 through a combined cycle power plant 10 for a blast furnace. Is adjusted so as to have an optimal gas energy amount and supplied to the combined cycle power plant 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas energy recovery for recovering a large amount of flammable exhaust gas containing CO and H ₂ gas, which is generated in a metallurgical furnace plant, particularly in a smelting reduction plant. It concerns equipment.

[0002]

2. Description of the Related Art Conventionally, a combustion boiler is generally used as an energy recovery system for exhaust gas generated in a metallurgical furnace plant, but the energy recovery efficiency is extremely low at about 35%.

[0003] In recent years, a combined cycle power plant (CCPP) having excellent power generation efficiency has been applied to exhaust gas generated from a blast furnace in place of a combustion boiler. This combined cycle power plant
Developed a single-shaft powertrain with gas turbine (GT), fuel gas compressor (FGC), steam turbine (ST), and generator (GENO) as main components, which can be operated using exhaust gas from blast furnace as fuel Have been. When the combined cycle power plant is used, the recovery efficiency is improved to about 45%.

The prior art is disclosed in Japanese Patent Laid-Open No. 2-29863.
No. 3 discloses a coal gasification combined cycle power plant. This coal gasification combine cycle gasifies coal, uses the coal gas as fuel to drive a gas turbine to operate a generator, recovers the exhaust gas from the gas turbine, and uses the steam generated by this heat to generate steam from the steam turbine. Is a cycle for driving the generator by driving the power generator.

The smelting reduction plant (smelting reduction method) according to the present invention for generating exhaust gas for energy recovery is a plant for reducing iron ore or the like in a molten state, and is an alternative to the blast furnace method or the like. This is a plant (method) for obtaining ore and ferroalloy by reducing ore containing a metal oxide such as iron ore (iron oxide) in a molten state. There are various types of smelting reduction methods. Some methods use only a smelting reduction furnace, and others use a combination of a preliminary reduction furnace and a smelting reduction furnace. In a smelting reduction furnace, ore, coal, etc. are charged into the furnace and oxygen is blown into the furnace to reduce the ore in a molten state. At this time, CO
Since a high-temperature gas with a reducing power consisting mainly of (carbon monoxide) and H ₂ (hydrogen) is generated, the ore is preliminarily reduced in a solid state using this gas. It is a combined plant. In this case, there is an advantage that the heat and reducing power of the gas generated in the smelting reduction furnace can be effectively used, and therefore, the use of the preliminary reduction furnace is becoming the mainstream of the smelting reduction method. As the preliminary reduction furnace, a fluidized bed reactor in which powdered ore forms a fluidized bed (fluidized) and contacts / reacts with the above gas is widely used.

[0006]

However, when the combined cycle power plant for blast furnace described above is used in combination with a smelting reduction plant, the following disadvantages occur.

That is, even if an attempt is made to apply the method to a smelting reduction plant, the energy amount of the exhaust gas is different from that of the exhaust gas generated from the blast furnace. Will be huge.

More specifically, since the blast furnace exhaust gas has a lower heating value (LHV) of 740 to 840 kcal / Nm ³ , the lower heating value (LHV) of the exhaust gas usable in the blast furnace CCPP is 750 to 980 kcal / Nm ^3. Before and after, the total LHV of the exhaust gas was 320 MJ / sec (275, 150,
592 kcal / h). In this case, for example, when the LHV is set to 900 kcal / Nm ³ , the gas flow rate at the gas turbine inlet becomes 305,720 Nm ³ / h.

On the other hand, the exhaust gas generated from the smelting reduction plant has a considerably high LHV of 1,000 to 1,400 kcal / Nm ³ and a gas flow rate of 200,000 to ³ kcal / Nm ^3.
There is a variation of 00,000 Nm ³ / h.

Therefore, the LHV of the exhaust gas from the smelting reduction plant cannot be used because it is too high compared to the LHV of the exhaust gas applicable to the CCPP for the blast furnace. Also, the total LHV needs to be substantially the same, but it is considerably different from the exhaust gas generated from the smelting reduction plant.

The present invention has been made in view of the above points,
Exhaust gas generated from the smelting reduction plant can be recovered by using a blast furnace combined cycle power plant that has already been developed and put into practical use, thereby greatly improving the recovery efficiency compared to the conventional combustion boiler. It is another object of the present invention to provide an exhaust gas energy recovery facility that can operate the entire plant at low cost and with flexibility.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, an exhaust gas energy recovery system according to the present invention is an equipment for recovering energy from exhaust gas generated in a smelting reduction plant through a combined cycle power plant for a blast furnace. Wherein the exhaust gas is blown into the smelting reduction plant.
Oxygen production equipment that produces oxygen used during production
Nitrogen, which is generated as a substance, is passed through the
Gas energy required for bind cycle power plants
Volume (LHV (lower heating value) and total LHV (lower heating value)
The total amount of nitrogen is adjusted so that
After being combined, it is characterized by being preheated by an exhaust gas preheating device and supplied to a combined cycle power plant.

[0013] According to the exhaust gas energy recovery equipment of the present invention having the above-described configuration, the blast furnace combined cycle power plant that has already been put into practical use is used for energy recovery of exhaust gas generated from a smelting reduction plant. This eliminates the need for a new development cost and development period for developing a power plant specifically for the smelting reduction plant. Then, when using a combined cycle power plant for blast furnaces, just by continuously mixing an appropriate amount of nitrogen as an inert gas into the exhaust gas from the smelting reduction plant,
The power plant can be used smoothly. Moreover,
Nitrogen is produced as a by-product when producing oxygen required for operation in a smelting reduction plant, particularly in a smelting reduction furnace, using air as a raw material. It is a target. Also,
LHV of smelting reduction plant exhaust gas is converted to blast furnace CCPP
It is too high compared to the applicable exhaust gas LHV,
Can not be used as is, and CCPP for blast furnace
LHV totals need to be roughly matched to apply to
Will be able to use the exhaust gas for CCPP for blast furnaces.
As a result, exhaust gas energy from conventional combustion boilers
The collection efficiency can be greatly improved compared to the collection of Further
In addition, the nitrogen mixed in the exhaust gas is also
Exhaust gas and nitrogen are heated and the fuel gas is
Into a combined cycle power plant for blast furnaces
Supplied.

According to a second aspect of the present invention, the smelting reduction plant includes a smelting reduction furnace and a preliminary reduction furnace that uses the exhaust gas of the smelting reduction furnace .
LHV is 1,300kcal / Nm ³ and discharge flow rate is 212,300N
m ³ / h, and the nitrogen generated from the oxygen production apparatus is 94,
360 Nm ³ / h continuously mixed with the exhaust gas
Supply to unbound cycle power plants.
The LHV of the exhaust gas is 900 kcal / Nm ³ and the introduced flow rate is 30
LHV and unit of exhaust gas to be 6,660 Nm ³ / h
Before adjusting the introduction amount per hour (introduction flow rate)
Total LHV required by the power plant (275,150,592k
cal / h) can be satisfied.

According to the exhaust gas energy recovery system of the second aspect , the LHV of the exhaust gas discharged from the preliminary reduction furnace is reduced.
1,300 kcal / Nm ³ and discharge flow rate 212,300 Nm ³ / h
Is required for combined cycle power plants.
Reduce the LHV of the exhaust gas to the required LHV, and
The total LHV required for the runt can be secured.

[0016]

[0017]

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an exhaust gas energy recovery system according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the overall outline of an exhaust gas energy recovery system according to an embodiment of the present invention in which a combined cycle power plant is combined with a smelting reduction plant having a smelting reduction furnace and a preliminary reduction furnace.

As shown in FIG. 1, a smelting reduction plant 1
Is a method for reducing iron ore using a preliminary reduction furnace and a smelting reduction furnace, 2 is a smelting reduction furnace, and 3 is a preliminary reduction furnace.

The smelting reduction furnace 2 is a furnace for reducing iron ore in a molten state to obtain pig iron. Iron ore (preliminarily reduced iron described below), coal, oxygen, and quick lime described below are contained in the furnace as raw materials and auxiliary materials. Is charged. The high-temperature gas (exhaust gas) generated by the reduction reaction contains a large amount of CO and H ₂ and has a reducing power, and is thus introduced below the preliminary reduction furnace 3 through the hood and the duct 4.

The pre-reduction furnace 3 is for pre-reducing iron ore in a solid state to obtain pre-reduced iron. In this embodiment, the pre-reduction furnace 3 is of a fluidized bed type and is provided on a dispersion plate 3a provided with a large number of openings. When the iron ore is charged and the above-mentioned gas is introduced from below the dispersion plate 3a, the iron ore is fluidized and comes into contact with the gas, and the preliminary reduction proceeds. The pre-reduced iron reduced in the pre-reduction furnace 3 is charged into the smelting reduction furnace 2 by a charging pipe (not shown).

In the smelting reduction furnace 2, a molten metal (molten metal bath)
A is a process in which pig iron and slag are held as A, and iron ore is charged together with coal, lime, and the like, and oxygen is blown through a lance 5 to reduce the iron ore in a molten state and convert it into pig iron. Is made.
Oxygen is produced in the oxygen production apparatus 6 using air in the atmosphere as a raw material. In the process of producing oxygen by the oxygen production apparatus 6, nitrogen as an inert gas is simultaneously generated.

The exhaust gas discharged from the pre-reduction furnace 3 is passed through a cyclone separator (not shown) through a duct 7 and then sent to a blast furnace combined cycle power plant 10 through a discharge duct 8. In the separator (not shown), the pre-reduced iron in the form of fine powder that has jumped out of the fluidized bed B together with the exhaust gas is collected and returned to the pre-reduction furnace 3 by a charging pipe (not shown).

In the exhaust gas energy recovery facility of this embodiment, a combined cycle power plant 10 developed for blast furnace exhaust gas is used as a main facility for exhaust gas energy recovery. In the middle of the discharge duct 8, an electric exhaust gas wet type dust remover 11 is interposed. Further, the oxygen supply pipe 9 is connected to the lance 5 from the oxygen production apparatus 6, and the nitrogen supply pipe 12 is connected to the dust removal device 11 of the discharge duct 8.
Is connected to the downstream side.

The following Table 1 shows the gas flow rates (Nm ³ / h, 0 ° C. 1.03323 kg) of the exhaust gas generated from the preliminary reduction furnace 3 of the smelting reduction plant 1, the nitrogen to be mixed, and the gas after nitrogen mixing. / Cm ² abs.), Gas composition (% by volume) and lower calorific value (kcal / Nm ³ ).

[0027]

[Table 1] (See attached table)

That is, the exhaust gas discharged from the preliminary reduction furnace 3 has an LHV of 1,300 kcal / Nm ³ and a discharge flow rate of 212,3
00 Nm ³ / h, and cannot be applied to the blast furnace combined cycle power plant 10 as it is. However, the nitrogen generated from the oxygen production apparatus 6 is converted to 94,360 Nm ³ / h (L
Since HV is mixed and introduced at about 0 kcal / Nm ³ ), as a result, the exhaust gas has an LHV of 900 kcal / Nm ³ and an introduced flow rate of 306,660 Nm ³ / h. In other words, the total LHV is 275,
Power plant 1 at 994,000kcal / h (900 × 306,660)
0 satisfies the required total LHV (275,150,592 kcal / h).

In the above embodiment, nitrogen produced as a by-product when oxygen is produced by the oxygen production apparatus 6 attached to the smelting reduction plant 1 is mixed with the exhaust gas generated from the smelting reduction plant 1 and introduced into the power plant 10. Energy is recovered as electric power. As a result, the efficiency of exhaust gas energy recovery reached 45%. Further, in terms of equipment, a combined blast furnace combined cycle power plant 10 which has already been developed and has a proven track record is combined, and connected to the smelting reduction plant 1 by a discharge duct 8 provided with a dust collecting device 11,
This is a configuration in which a nitrogen generation unit of the oxygen production apparatus 6 and a discharge duct 8 are connected by a nitrogen supply pipe 12. In the above embodiment,
A flow control valve (reference numeral 16 in FIG. 2) for controlling the mixing ratio (flow rate) of nitrogen is not interposed in the nitrogen supply pipe 12. It is desirable to be able to adjust the amount of nitrogen contamination via a valve.

Next, FIG. 2 is a configuration diagram showing an outline of the entire exhaust gas energy recovery equipment according to another embodiment.

Exhaust gas generated from the smelting reduction plant 1 passes through an electric dust collector 11 and an exhaust gas preheating device 13 in order, and is introduced into an axial compressor 14 by a discharge duct 8. Further, the oxygen production apparatus 6 attached to the smelting reduction plant 1
Is introduced into the exhaust duct 8 immediately upstream of the exhaust gas preheating device 13 through the flow control valve 16 by the nitrogen supply pipe 12. Then, with the nitrogen mixed with the exhaust gas at a predetermined ratio (adjusted by the flow control valve 16),
It is preheated by an exhaust gas preheating device 13. In the exhaust gas energy recovery facility of this example, the combined cycle power plant for blast furnace 10 'includes a series of axial compressors 14 and radial compressors 15 as fuel gas compressors. For this reason, the exhaust gas and the nitrogen become a fuel gas in a state of being mixed together, are compressed by the axial compressor 14, are cooled via the gas cooler 17, are introduced into the radial compressor 15, and are further compressed. You. Then, the compressed fuel gas is sent to the inlet of the gas turbine 20 by the fuel gas supply pipe 19 and introduced into the gas turbine 20.

The gas turbine 20 includes an exhaust heat recovery boiler 21
Are integrally connected to each other, and the exhaust gas of the fuel gas introduced into the gas turbine 20 and used to drive the gas turbine 20 is collected by the exhaust heat recovery boiler 21 to generate steam. This steam is supplied to the steam turbine 2 through the steam supply pipe 18.
3, the steam turbine 23 is rotationally driven, and the generator 24 is rotated by this rotational force to generate electric power. The generator 24
Is connected to the gas turbine 20 via a reduction drive mechanism 25 via a single (common) rotary drive shaft 31 across the axial compressor 14 and the radial compressor 15.
5, the frequency (for example, 50 Hz / 60 Hz) of electricity (alternating current) generated by the generator 24 can be changed. The exhaust heat recovery boiler 21 includes a chimney 21a, and after exhaust heat from the gas turbine 20 is recovered, the exhaust gas is discharged from the chimney 21a.

In addition, the steam turbine 23 includes a condenser 23
After the steam used in the steam turbine 23 is condensed in the condenser 23a to form water droplets and is sent from the feed pipe 27 to the gas cooler 17 via the feed pump 26, It is sent to the exhaust heat recovery boiler 21 and exchanges heat with exhaust gas to become steam. Further, a second gas cooler 28 is provided, and this gas cooler 28 has a radial compressor 15.
A part of the fuel gas sent to the gas turbine 20 from the fuel gas is sent by a branch pipe 32 branched from the fuel gas supply pipe 19, cooled, mixed with the fuel gas preheated by the preheating device 13, It is supplied to the compressor 14. Further, the electricity generated by the generator 24 is converted to a high voltage by the transformer 33 and transmitted to a required power consuming area by an electric wire installed between the steel towers 34. The combined cycle power plant 10 ′ of this example is also basically a blast furnace power plant, and differs in that an appropriate amount of nitrogen as an inert gas is mixed into the exhaust gas from the smelting reduction plant 1.
And in the exhaust gas energy recovery equipment of this example, the energy recovery efficiency of the exhaust gas reached 46% as a result. (Other Embodiments) In the above embodiment, nitrogen is used as the inert gas. However, other than nitrogen, for example, argon or helium can be used.

The smelting reduction plant 1 includes a preliminary reduction furnace 3
However, the present invention can be applied to a type having no smelting reduction furnace 2, in other words, a type having only the smelting reduction furnace 2. However, in this case, since the lower heating value of the exhaust gas is very high and the gas discharge flow rate is considerably large, the amount of the inert gas to be mixed is increased, and the total LHV conforms to the CCPP (for example, 277,660,300 It is necessary to adjust the flow rate to around (kcal / h).

The flow rate of the exhaust gas from the smelting reduction plant and the mixed flow rate of nitrogen shown in Table 1 above are merely examples, and it goes without saying that they are not limited. However, even when the lower heating value of the exhaust gas is high, in order to be able to use the combined cycle power plant for a blast furnace, the inert gas is continuously supplied so that the LHV becomes 800 to 1,000 kcal / Nm ^3. Need to mix.

[0036]

As is apparent from the above description,
The exhaust gas energy recovery equipment of the present invention has the following excellent effects.

(1) The energy of the exhaust gas generated from the smelting reduction plant can be recovered using a blast furnace combined cycle power plant that has already been developed and put into practical use. As a result, the recovery efficiency can be greatly improved as compared with the recovery of the exhaust gas energy by the conventional combustion boiler. Specifically, the recovery rate is less than 40% to 45 to 46%
To improve. Further, as compared with a case where a dedicated power generation plant is newly developed and combined, development costs and a period required for development are not required at all, and equipment of the entire plant can be provided at a low cost. Moreover, when using a combined cycle power plant for blast furnaces, it is only necessary to continuously mix an appropriate amount of nitrogen as an inert gas into the exhaust gas from the smelting reduction plant, so that it is possible to operate with flexibility and use the power plant smoothly. can do. In addition, since nitrogen required as a by-product when producing oxygen required for operation in a smelting reduction plant, particularly in a smelting reduction furnace, using air as a raw material is used by mixing it with exhaust gas, there is no waste and economical. In addition, exhaust is performed through the flow control valve.
The amount of nitrogen mixed into the gas can be adjusted. In addition, melting
LHV of exhaust gas from reduction plant is applied to blast furnace CCPP
It is too high compared to the possible exhaust gas LHV,
Unable to use for CCPP for blast furnace
In order to use it, it is necessary to roughly match the total LHV,
The exhaust gas can be used for CCPP for blast furnaces.
Exhaust gas energy recovery by conventional combustion boiler
The collection efficiency can be greatly improved as compared with. Sa
In addition, nitrogen mixed with exhaust gas is also used for exhaust gas preheating equipment.
More preheated, the exhaust gas and nitrogen are mixed
Combined cycle power generation blast furnace for blast furnace
Supplied to the client.

(2) In the exhaust gas energy recovery system according to the second aspect, the LHV of the exhaust gas discharged from the preliminary reduction furnace is
Is 1,300 kcal / Nm ³ and the discharge flow rate is 212,300 Nm ³ /
h, the combined cycle power plant
Reduce the LHV of exhaust gas to required LHV and generate electricity
The total LHV required for the plant can be secured.

[0039]

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an overall outline of an exhaust gas energy recovery facility according to an embodiment of the present invention in which a combined cycle power plant is combined with a smelting reduction plant including a smelting reduction furnace and a preliminary reduction furnace.

FIG. 2 is a configuration diagram showing an overall outline of an exhaust gas energy recovery facility according to a second embodiment of the present invention in which a combined cycle power plant is combined with a smelting reduction plant.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Smelting reduction plant 2 Smelting reduction furnace 3 Preliminary reduction furnace 6 Oxygen production device 7 Duct 8 Discharge duct 10 ・ 10 'Combined cycle power plant for blast furnace exhaust gas 11 Dust collection device 12 Nitrogen supply pipe 13 Exhaust gas preheating device 14 Axial compressor 15 Radial compressor 16 Flow control valve 17 Gas cooler 18 Steam supply pipe 19 Fuel gas supply pipe 20 Gas turbine 21 Exhaust heat recovery boiler 23 Steam turbine 24 Generator 25 Reduction mechanism

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-191307 (JP, A) JP-A-9-317499 (JP, A) JP-A-4-321725 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) F02C 3/30 F02C 6/00 F02C 9/00 F27D 17/00

Claims (2)

(57) [Claims] 1. A facility for recovering energy from exhaust gas generated in a smelting reduction plant through a combined cycle power plant for a blast furnace, wherein the exhaust gas is used during blowing in the smelting reduction plant.
Oxygen production equipment that produces
The generated nitrogen is supplied to the combined combiner through a flow control valve.
Gas energy amount (LHV) required for cycle power plant
And the total amount of LHV).
An exhaust gas energy recovery facility characterized in that after being manufactured and mixed, it is preheated by an exhaust gas preheating device and supplied to a combined cycle power plant. 2. The smelting reduction plant includes a smelting reduction furnace and a pre-reduction furnace using the exhaust gas, and the LHV of the exhaust gas discharged from the pre-reduction furnace is 1,300 kca.
In l / Nm ^3, and a discharge flow rate 212,300Nm ³ / h, the nitrogen originating from the air separation unit 94,360Nm ³ / h ho
Continuously mixed with the exhaust gas
By supplying the exhaust gas to the power plant.
HV is 900 kcal / Nm ³ and introduction flow rate is 306,660 Nm ³ / h
LHV of exhaust gas and introduction per unit time
The amount of L required by the power plant
The exhaust gas energy recovery system according to claim 1 , wherein the total HV (275,150,592 kcal / h) is satisfied .