JPH05340501A - Metallurgical furnace exhaust gas sensible heat recovery power generation facility combined with gas turbine - Google Patents

Abstract

PURPOSE:To supply superheated steam with a high-thermal efficiency by a method wherein an intermittent flow of saturated steam generated from a boiler is turned into a continuous flow of saturated steam, which fluctuates in flow rate and pressure, through an accumulator, and the saturated steam is converted to superheated steam by a gas turbine waste heat recovery heat exchanger. CONSTITUTION:A high-temperature gas intermittently discharged from a metal processing furnace 1 is sent to a waste gas treatment apparatus 2 where saturated steam is generated, and the saturated steam enters an accumulator 5 after passing through a steam drum 3. When the valve-lift of an inlet pressure regulating valve of a steam turbine 12 is kept constant, the steam discharged from the accumulator 5 enters a gas turbine waste heat recovery heat exchanger 6 with its flow rate fluctuating in proportion to the internal pressure of the accumulator 5, and is turned in to superheated steam which drives the steam turbine 12 to generate power. Thus, as the waste heat of the gas turbine 7 is utilized, the thermal efficiency is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention collects high-temperature exhaust gas sensible heat from a metallurgical furnace such as a converter operating intermittently by combining with a gas turbine to recover high thermal efficiency regardless of the operating conditions of the metallurgical furnace. It relates to a power generation facility that can generate power under

[0002]

2. Description of the Related Art High-temperature heat energy generated intermittently from a metallurgical furnace such as a converter causes saturated steam to be generated by an exhaust gas treatment device,
There is an example of storing heat in an accumulator and sending it to a customer at a low constant steam pressure of about 10 to 15 bar, but it is not yet fully utilized as a high-value-added effective energy such as electric power by a steam plant. ..

That is, when the saturated steam having a pressure of 10 to 15 bar is used as it is for power generation, the amount of generated electric power is small, while on the other hand, it is generally generated from a converter exhaust gas cooling / removing device (eg, OG device). Steam pressure 40 bar
Of steam to the accumulator, which results in a pressure of 36
bar If a constant continuous vapor is taken out, an enormous capacity accumulator is required. For example, when the blowing process = non-blowing process = 15 minutes and the generated steam amount is 100 ton / h, the required accumulator capacity is about 1,100 m ³ .

If the amount of steam taken out from the accumulator is changed, the accumulator becomes small (in the above example, it is changed from 22 barg to 35 barg and 39 to
If steam of 60 ton / hr is taken out from n / hr, the accumulator capacity will be 200 m ³ . ), It is conceivable to supply steam from the accumulator to the steam turbine in a saturated steam state to drive the turbine generator. (The inventors of the present application filed an application for Japanese Patent Application No. 3-230945.)

[0005]

As described above, also in the above-mentioned conventional technique, steam is generated by utilizing high temperature thermal energy generated intermittently from the metallurgical furnace, thereby driving the turbine to generate power. Was possible. However, the above-mentioned conventional technique still has the following problems.

First, in the power generation equipment based on the method described in the above-mentioned prior art, (i) the recovered power is small because of saturated steam. (Ii) Since high-pressure saturated steam enters the turbine, it is necessary to take measures against drain erosion in the upstream stage of the turbine. (Iii) Since the steam wetness at the exit of the last stage of the turbine greatly exceeds the allowable value, it is necessary to take out steam in the middle of the turbine, separate the moisture with a mist separator, etc., and re-introduce it into the turbine. Etc.

In addition to the methods described in the above-mentioned prior art, several methods have been announced as methods for converting saturated steam generated from a metallurgical furnace exhaust gas treatment apparatus such as a converter into superheated steam. Install a superheater in the exhaust gas treatment device,
A heat storage device such as an accumulator is separately provided, and the purpose is to prevent burnout of the superheater in the initial stage of blowing by sending saturated steam from the heat storage device to the superheater (described in JP-A-61-125502). ) Or

A means for effectively utilizing unstable steam at the beginning and end of blowing (described in Japanese Patent Publication No. 3-22525), or a means for continuously supplying superheated steam by incorporating a heat storage technology using molten salt (Described in JP-A-60-212101),

Further, a fuel-fired boiler is additionally provided, and superheated steam is generated from the boiler during non-blowing (Japanese Patent Laid-Open No. 1-25
No. 2890), it is a complicated system such as switching the steam line between non-blown and blown, and requires a close relationship with the metallurgical furnace exhaust gas treatment device.

The present invention has been made in view of such a situation, and has a simple structure and an independent system regardless of the operating conditions of the metallurgical furnace such as blowing and non-blowing.
It is an object of the present invention to provide a metallurgical furnace exhaust gas sensible heat recovery power generation facility capable of supplying superheated steam with high thermal efficiency.

[0011]

The above object can be achieved by a metallurgical furnace exhaust gas sensible heat recovery power generation facility combined with a gas turbine described in the claims. That is, (1) in a plant having an intermittent operation metallurgical furnace, a gas turbine, and a steam turbine driven generator, a saturated steam boiler for metallurgical furnace exhaust gas, an accumulator, a gas turbine waste heat recovery heat exchanger, and a condenser. , A boiler water supply means, and converts saturated steam generated intermittently from the boiler into continuous saturated steam with variable pressure and flow rate through an accumulator and takes it out, and the continuous saturated steam heat recovery heat recovery of gas turbine Metallurgical furnace exhaust gas sensible heat recovery power generation facility combined with a gas turbine that generates superheated steam by a steam generator and drives a steam turbine with the superheated steam. (2) Intermittent operation When the metallurgical furnace is a converter, the time between converter blowing processes (non-blowing process time) is longer than expected, and the amount of continuously generated saturated steam from the accumulator decreases, the gas turbine Combined with the gas turbine described in (1), the condensate flowing out of the condenser is heated by the energy of the excess gas turbine waste heat from superheated saturated steam in the waste heat recovery heat exchanger and is fed into the accumulator. Metallurgical furnace exhaust gas sensible heat recovery power generation facility. Is. Hereinafter, the operation and the like of the present invention will be described based on Examples.

[0012]

1 to 10 are views for explaining an embodiment in the case where a metallurgical furnace is a converter, FIG. 1 is a system diagram showing a main constitution of the present invention, and FIG. 2 is a steam drum-generated steam. FIG. 4 is a diagram showing a state, FIG. 3 is a diagram showing a state of the internal pressure of the accumulator and the amount of steam flowing out of the accumulator, FIG. 4 is a steam turbine expansion diagram,
FIG. 9 is a diagram showing a state at each equipment inlet and outlet in the saturated steam turbine cycle, FIG. 5 is a diagram showing a state at each equipment inlet and outlet in the flow chart of the cycle of the present invention, FIG.
FIG. 7 is a diagram for explaining a difference in thermal efficiency between a superheated steam turbine, a saturated steam turbine, and a normal combined cycle.
Is a system diagram of a normal gas turbine combined cycle in which low pressure steam is mixed in the steam turbine among the generated high pressure and low pressure steam by using a gas turbine, and FIG. FIG. 10 is a diagram showing the relationship between the heat exchange amount and the temperature of the heat recovery heat exchanger, and FIG. 10 is a diagram showing the relationship between the heat exchange amount and the temperature of the gas turbine waste heat recovery heat exchanger in a normal gas turbine combined cycle.

First, in FIG. 1, a high temperature gas of about 1500 ° C. is discharged from a metallurgical furnace 1 during a blowing period, and the heat causes a saturated steam to be generated from an exhaust gas processing device 2 and enter a steam drum 3. Blowing time is generally about 15 minutes, and the time until the next blowing depends on the operating conditions, but is usually about 15 minutes.

The steam pressure from the steam drum 3 is controlled to a constant pressure (usually about 40 bar) by a pressure regulating valve 20. Therefore, the state of the steam at the outlet of the steam drum 3 becomes a step like that shown in FIG.

The steam generated from the steam drum 3 as shown in FIG. 2 enters the accumulator 5 and accumulates heat. The internal pressure of the accumulator 5 fluctuates between p ₁ bar and p ₂ bar as shown in FIG. This fluctuation range varies depending on the volume blowing time t ₁ minutes of the accumulator 5 and the non-blowing time t ₂ minutes.

If the opening degree of the inlet control valve 22 of the steam turbine 12 is kept constant, the amount of steam flowing out from the accumulator 5 is proportional to the internal pressure of the accumulator and is from G ₁ kg / hr to G ₂ kg.
Fluctuates between / hr. G flowing out from the accumulator 5
Saturated steam from ₁ kg / hr to G ₂ kg / hr (pressure p ₁ bar to p
₂ bar) enters the gas turbine waste heat recovery heat exchanger 6.

On the other hand, if the load of the gas turbine 7 is constant, the temperature and flow rate of the exhaust gas 10 are almost constant, so that the superheating temperature range is large when G ₁ kg / hr is low and the steam flow rate is small.
The superheating temperature range becomes small when the steam flow rate is high at G ₂ kg / hr. (See Figure 4)

The output of the steam turbine has a flow rate of G _t kg /
h, adiabatic heat drop of steam from turbine inlet to outlet is H
Assuming that _t kJ / kg and turbine efficiency are η _t , they are represented by respective products (G _t × H _t × η _t ).

The turbine output is shown in Table 1 when the symbols of the subscripts are expressed as follows. s: Saturated steam turbine h: Superheated steam turbine i: Blowing start state e: Blowing completion state

[0020]

[Table 1]

When the saturated steam is used, the wet steam flows through all the internal stages of the turbine, and when the superheated steam is used, only the rear stage of the turbine becomes the wet steam, so that the wet loss is reduced in the case of the superheated steam. Turbine efficiency is η _tsi <η
_thi and η _tse <η _the .

The adiabatic head of the turbine is naturally H _tsi <
H _thi and H _tse <H _the . Therefore, at the start of blowing,
At the time of completion of blowing, if the ratio of the case of using superheated steam and the case of using saturated steam is taken, the flow rate of passage G _si = G _hi , G _se
= G _he , so H _thi η _thi / H _{tsi respectively}
・ Η _tsi , H _the · η _the / H _tse · η _tse . It can be seen that the turbine output is higher when superheated steam is used regardless of the operation of the metallurgical furnace 1.

Next, in the case of using superheated steam and the case of using saturated steam, considering the fluctuation range of the output at the start of blowing and the specific power at the time of completion of blowing, as described above, the overheating at the start of blowing Degree Δ
Since ti is greater than the superheat Δte at the completion of blowing, the adiabatic head drop ratio H _te / H _ti is that when saturated steam is used H _tse / H
H _the / H _thi when using superheated steam is smaller than _tsi .

The ratio of the turbine outlet steam wetness x _hi at the start of blowing when using superheated steam to the turbine outlet steam wetness x _he at the completion of blowing, x _hi / x _he and that when using saturated steam x _si
Compared with / x _se , the former is larger. This means that the turbine efficiency ratio η _thi / η _the becomes larger than η _tsi / η _tse . That is, it can be seen from the description in paragraph 0023 and the above that the fluctuation of the turbine output when using superheated steam is smaller than when using saturated steam.

Next, the case where the non-blowing time (t ₂ minutes in FIG. 2) is extended will be described. In this case, the accumulator internal pressure naturally falls below p _{1 in} FIG. 3 and the accumulator outflow rate also decreases. This means that the exhaust gas temperature at the outlet of the superheater 6-1 rises and the amount of heat applied to the feedwater heater 6-2 increases due to the decrease in the amount of steam passing through the superheater 6-1 in FIG. That is, the temperature of the water supplied from the water heater 6-2 rises and becomes higher than the temperature of the water stored in the accumulator 5.

In this state, if the water supply valve A17 of the system communicating with the pure water tank 4 is closed and the water supply valve B18 of the system communicating with the accumulator is opened to return the water supply to the accumulator, the temperature of the water stored in the accumulator will be As a result, the rate of decrease in the internal pressure is eased and the amount of steam generated is also moderated.

That is, due to the operating conditions of the metallurgical furnace, even if the non-blowing time is considerably long, the flow rate through the steam turbine 12 does not fall below the no-load flow rate (about 5% of the rating) and the generator motors. There is no fear.

By adopting the system of the present invention, the advantages described in the section of the effects of the invention are exhibited, the fluctuation range of the power generation output during the operation of the metallurgical furnace is reduced, and the risk of motoring is almost eliminated. This will eliminate the need for power generation equipment that recovers the sensible heat of exhaust gas from metallurgical furnaces that has not been recovered as electric power.

Next, the thermal efficiency of the cycle of the present invention and the thermal efficiency in the case of combining the saturated steam cycle and a normal combined cycle for generating steam by the exhaust gas of the gas turbine to drive the condensing turbine will be described.

Saturated steam is generated in steps from the steam drum 3 of the exhaust gas treating apparatus of the metallurgical furnace as shown in FIG. 2, and the steam having a varying pressure and varying amount of steam flows to the steam turbine 12 as shown in FIG. However, for simplicity, the steam turbine (1
2) always has a constant pressure p ₀ (bar) (accumulator 5
The flow rate is g ₀ = (t ₁ / t ₁ + t ₂ ) ×
And _{(G 0/3600) (kg} / s) through those.

FIG. 9 is a flow chart of the saturated steam turbine cycle showing the states at the inlet and outlet of each device. Heat input Q _i0 = g ₀ · (i _S1 in the cycle of FIG. 9
-I _C ), and the amount of heat loss q _sex is the amount of heat released from the condenser 13.

[0032]

[Equation 1]

Therefore, the thermal efficiency η _{sth of} this cycle is
Is expressed by the following equation.

[0034]

[Equation 2]

Rectangle s1-s3 in the center view of FIG.
-S4-s6-s1 is heat input Q _i0 in the cycle of FIG.
S1-s2-s5-s6-s1 is the emitted heat q _sex ,
s2-s3-s4-s5-s2 represents the output P _SST .

FIG. 5 is a flow chart of the cycle of the present invention, showing the state at the inlet and outlet of each device. In the waste heat recovery heat exchanger superheater 6-1, water is supplied from t _C (° C) (enthalpy i _C kJ / kg) to t _f (° C) (enthalpy i _f kJ / k).
It is heated up to g) and enters the exhaust gas treatment apparatus 2. Therefore, the saturated vapor amount generated by the device 2 becomes g (kg / s) which is increased from g ₀ (kg / s) in the case of the cycle of FIG.
Area s1-s3-s4-s6-s1 = in the center diagram of FIG.
The area s1'-s3-s4'-s6'-s1 'in the left figure is obtained.

The area s3-h3-h4-s in the left diagram of FIG.
4'-s3 is heat given by the superheater 6-1, area h1-
s1'-s6'-h7-h1 represents heat provided by the feed water heater 6-2, and has an area h1-h2-h6-h7-h1.
Represents the amount of heat discarded from the condenser 13 of the steam turbine, and is given by the following equation.

[0038]

[Equation 3]

In the system of the present invention, the increase amount Δg of the saturated vapor amount generated from the exhaust gas treatment device 2 is expressed by the following equation.

[0040]

[Equation 4]

Usually, since the steam dryness at the outlet of the steam turbine is set to the allowable limit, i _{hz ≈i sz} is given. That is, the area h1-h2-h8 in the left diagram in FIG.
-S6-h1 is the area s1-s2-s5-s6 in the center figure.
It may be equal to −s1. Therefore, the amount of heat that is discarded from the steam turbine condenser 13 of the system of the present invention is the same as that of the conventional steam turbine condenser 1 of the saturated steam system.
Area s6 in the diagram on the left of FIG. 6 from the amount of heat discarded from 3 ″
It will be increased by -h8-h6-h7-s6.

Next, the same gas turbine 7 used in the present invention
A cycle in which the gas turbine waste heat recovery heat exchanger 6'reduces the exhaust gas temperature from the same T _i to T _e to generate steam and drives the steam turbine 12 'will be described. Exhaust gas 1
In order to sufficiently utilize the heat of 0, the waste heat recovery heat exchanger 6'generally adopts a method of generating high-pressure and low-pressure steam and mixing the low-pressure steam with the steam turbine 12 '. This flow is shown in FIG.

FIG. 8 shows the relationship between the heat exchange amount and the temperature of the gas turbine waste heat recovery heat exchanger 6 in the cycle of the present invention, and FIG. 10 shows the relationship in the normal gas turbine combined cycle.

The heat transfer equations for the heat exchanger superheater 6-1 of FIG. 5 and the evaporator 6'-2 and superheater 6'-1 of the heat exchanger 6'of FIG. 7 are expressed as follows.

[0045]

[Equation 5]

[0046]

[Equation 6]

[0047]

[Equation 7]

[0048]

[Equation 8]

[0049] In "number 8", if g _h -Δg> 0, condenser 13 in the case of the system of the present invention 'the amount of heat thrown away from the condenser 13 of the conventional gas turbine combined cycle' And less than the amount of heat wasted from the condenser 13 ″ of the saturated steam turbine, which means that the thermal efficiency is improved.

In the curly braces on the right side of "Equation 8", that is,

[0051]

[Equation 9]

## EQU3 ## Since i _s1 is the enthalpy of saturated vapor and i _c is the enthalpy of condensate, i
_s1 -i _c is about 2,500kJ / kg, the ratio of the latent heat r ₁ and superheat .DELTA.i _h1 is 4 even look larger. Therefore

[0053]

[Equation 10]

Is always greater than 500 kJ / kg. On the other hand, even if the water is heated by the water heater 6-2, the maximum water supply enthalpy i _f is about 550 kJ / kg, and _if −i _c <4
It will be 00 kJ / kg.

Numerical calculation for "Equation 9" by changing the saturation pressure is as follows and all are positive. That is, g _h > Δg
Therefore, the thermal efficiency of the cycle of the present invention is higher.

[0056]

[Table 2] However, gas turbine exhaust gas temperature T _i = 500 ° C. heat exchanger pinch point temperature difference Δ = 20 ° C. heat exchanger outlet gas temperature T _e = 100 ° C. steam turbine outlet pressure R _z = 40 mmHg abs superheated steam temperature t _h1 = 450 ° C.

[0057]

As described above, according to the present invention, the following effects are obtained as described in the above embodiment. Even if the condition of the exhaust gas from the metallurgical furnace fluctuates considerably from the planned value in the blowing condition due to the accumulator, the condition of the steam extracted from the accumulator is almost unchanged from the plan. Therefore, it is not necessary to install excessive equipment in advance. The exhaust gas planning conditions of the gas turbine waste heat recovery heat exchanger used as a superheater, that is, matching with the type of the gas turbine and the saturated steam state supplied, can be adjusted by the accumulator capacity. Since there is no need to relate to blowing and non-blowing conditions,
The operation on the metallurgical furnace side and the state on the power plant side can be treated as independent systems. The supply of superheated steam to the turbine improves the thermal efficiency of the steam cycle and does not require a special system or special turbine as in the case of using saturated steam. Since the waste heat of the gas turbine is used, it becomes a so-called combined cycle of the Brainton cycle and the Rankine cycle, and the thermal efficiency can be improved as compared with the method of the separate fuel-fired boiler. The combined cycle thermal efficiency of the present invention obtains a higher value than the thermal efficiency obtained by the sum of a Rankine cycle plant using saturated steam and a conventional combined cycle plant combining a steam turbine for waste heat recovery of a gas turbine. Will be possible.

[Brief description of drawings]

FIG. 1 is a system diagram showing a main configuration of the present invention.

FIG. 2 is a diagram showing a state of steam generated by a steam drum.

FIG. 3 is a diagram showing the states of the internal pressure of the accumulator and the amount of steam flowing out of the accumulator.

FIG. 4 is a steam turbine expansion diagram.

FIG. 5 is a diagram showing a state at each device inlet and outlet in the flow chart of the cycle of the present invention.

FIG. 6 is a diagram illustrating a difference in thermal efficiency between a superheated steam turbine, a saturated steam turbine, and a normal combined cycle.

FIG. 7 is a system diagram when a low pressure steam of the generated high pressure and low pressure steam is mixed into the steam turbine using the gas turbine according to the present invention.

FIG. 8 is a diagram showing the relationship between the heat exchange amount and the temperature of the gas turbine waste heat recovery heat exchanger of the cycle of the present invention.

FIG. 9 is a diagram showing a state at each equipment inlet and outlet in the saturated steam turbine cycle.

FIG. 10 is a diagram showing a relationship between a heat exchange amount and a temperature of a gas turbine waste heat recovery exchanger in a normal gas turbine combined cycle.

[Explanation of symbols]

1 Metallurgical Furnace 2 Exhaust Gas Treatment Device (Cooling Section) 3 Steam Drum 4 Pure Water Tank 5 Accumulator 6 Gas Turbine Waste Heat Recovery Heat Exchanger 6-1 Superheater 6-2 Water Supply Heater 7 Gas Turbine 8 Air 9 Fuel 10 Exhaust Gas 11 Exhaust stack 12 Steam turbine 13 Condenser 14 Condensate pump 15 Condensate tank 16 Condensate transfer pump 17 Water supply valve A 18 Water supply valve B 19 Boiler water supply pump 20 Pressure control valve 21 Pressure controller 22 Turbine inlet control valve 23 Generator 24 Saturated steam boiler 6'-1 High pressure steam superheater (HP-SH) 6'-2 High pressure steam evaporator (HP-EVA) 6'-3 High pressure economizer (HP-ECO.) 6'-4 Low pressure steam evaporation vessel (LP-EVA.) 6'- 5 low pressure economizer (LP-ECO.) 12 'steam turbine 13' condenser T _i HRSG superheater Mouth gas temperature (℃) T _e HRSG superheater outlet gas temperature (° C.) G Gas turbine exhaust amount (kg / S) i _h1 HRSG superheater outlet superheated steam enthalpy (kJ /
kg) _is1 HRSG Superheater inlet saturated steam enthalpy (kJ /
kg) t _f HRSG feed water heater outlet feed water temperature (° C) t _c HRSG feed water heater inlet feed water temperature (° C) Δ Superheater pinch point temperature difference (° C) T ₁ High pressure evaporator inlet gas temperature (° C) T ₁ 'low pressure evaporator inlet gas temperature (° C.) T ₂ low pressure economizer inlet gas temperature (℃) t _c HRSG inlet feedwater temperature = condensate temperature (° C.) t _s2 low-pressure steam saturation temperature (° C.) i _s2 low saturation enthalpy (kJ / Kg) P ₂ Low pressure steam saturation pressure (bar a) _{ts 1} High pressure steam saturation temperature (° C) P ₀ High pressure steam saturation pressure (bar a)

Claims (2)

[Claims] 1. In a plant having an intermittent operation metallurgical furnace, a gas turbine and a steam turbine driven generator, a saturated steam boiler for metallurgical furnace exhaust gas, an accumulator, a gas turbine waste heat recovery heat exchanger, and a condenser. , A boiler water supply means, and converts saturated steam generated intermittently from the boiler into continuous saturated steam with variable pressure and flow rate through an accumulator and takes it out, and the continuous saturated steam heat recovery heat recovery of gas turbine A metallurgical furnace exhaust gas sensible heat recovery power generation facility combined with a gas turbine, wherein the steam turbine is used to generate superheated steam, and the steam turbine is driven by the superheated steam to generate electric power. 2. When the intermittent operation metallurgical furnace is a converter and the time between converter blowing processes (non-blowing process time) is longer than planned and the amount of continuously generated saturated steam from the accumulator decreases, The gas turbine according to claim 1, wherein the condensate flowing out from the condenser is heated by the energy of the excess gas turbine waste heat obtained by heating the saturated steam in the gas turbine waste heat recovery heat exchanger, and is fed into the accumulator. Combined metallurgical furnace exhaust gas sensible heat recovery power generation equipment.