JPH086883B2 - Exhaust heat recovery boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is used in a gas turbine cogeneration system, and is used for an exhaust heat recovery boiler for recovering exhaust gas heat from a gas turbine. It is about improvement.

(Prior art) Combining a gas turbine power generation facility and an exhaust heat recovery boiler,
Various so-called combined heat and power generation facilities that simultaneously supply electric energy and steam energy have been proposed with various system configurations. FIG. 3 shows a typical example thereof, in which high pressure combustion air pressurized by the compressor 1 is supplied to the combustor 2
Introduce into the inside, inject fuel F into this, generate high temperature and high pressure combustion gas, and supply this to the gas turbine 3,
The rotating shaft power causes the generator 5 to rotate via the reduction gear 4. The exhaust gas G from the gas turbine 3 is sent to the exhaust heat recovery boiler C through the exhaust gas duct 7, and the boiler C
After the heat is recovered by the economizer 9, etc., it is discharged from the chimney 10 into the atmosphere.

On the other hand, when it is necessary to increase the amount of steam generated in the exhaust heat recovery boiler C due to the request from the steam load side, the auxiliary combustion device 11
Is operated to perform burner auxiliary combustion using the exhaust gas G as a substitute for combustion air. The exhaust gas G from the gas turbine 3 has an O ₂ amount of about 15% remaining and a dust content of about 0.05 gr / Nm ³ which is relatively small and can be sufficiently utilized as an auxiliary combustion air. .

On the contrary, when a constant electric output is required but the amount of steam generation is small, the openings of the damper 12 and the damper 13 are controlled, and the surplus exhaust gas G ′ is bypassed through the bypass line 14. Emitted from 15 into the atmosphere.

By the way, the temperature of the exhaust gas from the gas turbine 3 is about
500 ° C, in which about 250ppm (kerosene fuel, O ₂
The combustor 2 contains NOx with a concentration of 4% (converted value).
Even if low NOx countermeasures such as steam injection and water injection are adopted, about 100 ppm of NOx exists. Therefore,
If pollution control is strict, it is necessary to install a denitration device in the exhaust gas line to further reduce NOx. Normally, a catalytic reduction type dry denitration device 16 that uses ammonia as a reducing gas recovers exhaust heat. It is installed in the boiler C, and NOx is removed by this.

The dry denitration device 16 uniformly mixes ammonia gas (NH ₃ ) into the exhaust gas G and allows it to pass through the catalyst layer to cause so-called NOx reduction reaction (reactable temperature: about 250 ° -40 ° C.) as described below.
0 ° C.) in are those that decompose and remove Yotsute NOx, in order to increase the denitration _{efficiency, 4NH 3 + 4NO + O 2} → 4N 2 + 6H 2 O 8NH 3 + 6NO 2 → 7N 2 + 12H 2 O gas temperature 300 ° C. to 400 It is an indispensable requirement to keep the temperature around ℃.

However, in the conventional exhaust heat recovery boiler of the combined heat and power generation facility, when the auxiliary combustion device 11 is operated to increase the amount of steam generated, the temperature of the exhaust gas flowing into the dry denitration device fluctuates greatly. However, there is a problem that the denitration efficiency remarkably deteriorates.

On the contrary, when the surplus exhaust gas G ′ is discharged from the bypass chimney in order to suppress the steam generation amount, untreated exhaust gas is discharged, which causes a problem such as environmental pollution. There is.

(Problems to be Solved by the Invention) The present invention has the above-mentioned problems in the conventional cogeneration system using a gas turbine, that is, (a) the temperature of exhaust gas to be subjected to denitration treatment due to fluctuations in steam load, etc. That is, the denitration efficiency is likely to deteriorate, and (b) when the steam generation amount is suppressed, the untreated exhaust gas emission amount increases, and environmental pollution is likely to occur. Therefore, even when performing auxiliary combustion by replacing exhaust gas with combustion air, or even when only reducing the amount of steam generated on the exhaust heat recovery boiler side, the exhaust gas temperature that constantly flows into the denitration device The present invention provides an exhaust heat recovery boiler that can keep the exhaust gas in an optimum range and can constantly denitrate all the exhaust gas from the gas turbine.

(Means for Solving Problems) The present invention is, in an exhaust heat recovery boiler of a cogeneration system using a gas turbine, in order to achieve the above object, in particular, a boiler heat transfer part A primary evaporator provided in the exhaust gas duct and a secondary evaporator downstream thereof, and an auxiliary combustion device located upstream of the primary evaporator and a dry denitration device located between both evaporators in the exhaust gas duct. And the first and second bypass ducts that bypass the respective evaporators and communicate with the inlet side exhaust gas duct portion and the outlet side exhaust gas duct portion of each evaporator, and connect the inlet side exhaust gas ducts of the primary evaporator. First and second in the part and the first bypass duct
A damper device is provided, and the third and fourth damper devices are provided at the inlet side exhaust gas duct portion and the second bypass duct of the secondary evaporator, and the exhaust gas temperature detector is provided at the inlet side exhaust gas duct portion of the dry denitration device. The exhaust heat recovery boiler is provided with a gas temperature control device for controlling the first and second damper devices based on the temperature detected by the temperature detector so as to maintain the temperature of the exhaust gas flowing into the denitration device at an appropriate temperature for denitration treatment. A steam pressure detector is provided in the main steam pipe of the third and fourth damper devices based on the pressure detected by the steam pressure detector so that the amount of steam generated by the exhaust heat recovery boiler becomes an appropriate amount according to the steam load. It is proposed to provide a steam load control device for controlling the auxiliary burner.

(Operation) Exhaust gas from the gas turbine is sent to the inside of the primary evaporator through the exhaust gas duct and treated by the dry denitration device.
Heat is recovered in the order of the secondary evaporator and economizer, and then discharged from the chimney to the outside.

The exhaust gas temperature at the inlet side of the dry denitration device is detected by the temperature detector and is input to the gas temperature control device. An open / close control signal is sent from the gas temperature control device to the damper device, whereby the amount of exhaust gas flowing through the bypass duct of the primary evaporator (that is, the amount of exhaust gas flowing through the primary evaporator) is adjusted. By doing so, the temperature of the exhaust gas flowing into the denitration device is maintained at the set value.

On the other hand, the steam pressure in the main steam pipe is detected by the steam pressure detector and is input to the steam load control device. A control signal is sent from the steam load control device to the damper device and the auxiliary fuel control valve, and the amount of exhaust gas flowing through the bypass duct of the secondary evaporator (that is, the amount of exhaust gas flowing through the secondary evaporator, economizer, etc.). ) And the operation of the auxiliary combustion device, the amount of steam generated corresponding to the desired steam load is controlled.

Can water is naturally circulated to the secondary evaporator through a steam drum, a downcomer pipe, a water drum, etc., and to the primary evaporator, can water is forcedly circulated from the steam drum by a circulation pump. Has been done.

(Examples) Examples of the present invention will be described below with reference to FIGS. 1 and 2. The parts common to those in FIG. 3 are designated by the same reference numerals.

FIG. 1 is a schematic system diagram of a cogeneration power generation facility to which an exhaust heat recovery boiler according to the present invention is applied. The cogeneration power generation facility A includes a gas turbine power generator B and an exhaust heat recovery boiler C in an exhaust gas duct 7 It is configured by connecting via.

The gas turbine power generation facility B includes an air compressor 1, a combustor 2, a gas turbine 3, a speed reducer 4, a generator 5, and the like.

In the exhaust heat recovery boiler C of this embodiment, as shown in FIG. 1, in the exhaust gas duct 7 led from the gas turbine 3 to the chimney 10, the auxiliary combustion device 11 and the primary evaporation are sequentially arranged from the upstream side. The reactor 17, the dry denitration device 16 and the secondary evaporator 18 are arranged in parallel, and the boiler heat transfer section is composed of both evaporators 17 and 18. Further, the exhaust gas duct 7 is provided with each evaporator 17,18.
The exhaust gas duct part 17 on the inlet side of each evaporator 17, 18
First and second bypass ducts 19 and 20 communicating with a and 18a and outlet side exhaust gas duct portions 17b and 18b are connected. Further, the economizer 9 is provided at the outlet side exhaust gas duct portion 18b of the secondary evaporator 18.

In this embodiment, the end of the bypass duct 20 for the secondary evaporator 18 is connected to the downstream side of the economizer 9, but it is connected to the upstream side of the economizer 9. Alternatively, a superheater (not shown) may be arranged on the exhaust gas upstream side of the primary evaporator 17.

Further, in the present embodiment, the auxiliary combustion device 11 is constituted by a so-called induct burner in which an auxiliary combustion burner is provided in the exhaust gas duct and the exhaust gas G is used as a substitute for combustion air, but any auxiliary combustion device can be used. Of course, you can pay attention.

A so-called natural circulation type water supply system is adopted for the secondary evaporator 18, and a space between the steam drum 21 and the water drum 22 is provided.
By connecting the secondary evaporator 18 and the downcomer group 23, a natural circulation path is formed, which has the steam / water drum 21 → downcomer tube 23 → water drum 22 → secondary evaporator 18 → steam / water drum 21 as a normal path. .

A so-called forced circulation type water supply system is used for the primary evaporator, and water is supplied from the steam drum 21 through the circulation pipe line 24 by the forced circulation pump 25.

In the dry denitration device 16, a so-called dry catalytic reduction method in which ammonia gas is used as a reducing gas, NOx is decomposed and removed by uniformly mixing this gas in the exhaust gas G and passing it through the catalyst layer. The denitrification equipment according to the above is used, and the heat resistant temperature of the catalyst layer is 420 ° to 430 ° C, and the optimum temperature of the reduction reaction is 300 to 400 ° C. Further, it goes without saying that the denitration device 16 may be a device having any structure as long as it is a dry denitration device.

In FIG. 1, reference numeral 26 is a first damper device provided at the inlet side exhaust gas duct portion 17a of the primary evaporator 17, and 27 is a first damper device.
The second damper device provided in the bypass duct 19, 28 is a third damper device provided in the inlet side exhaust gas duct portion 18a of the secondary evaporator 18, and 29 is a fourth damper device provided in the second bypass duct 20.

Reference numeral 30 denotes a gas temperature control device, which inputs the temperature of the exhaust gas G in the exhaust gas duct portion 16a on the inlet side of the denitration device 16 from a temperature detector 31 provided on the inlet side of the dry denitration device 16, and Open / close drive signals for the damper devices 26, 27 are output to respective damper drive devices (not shown).

Further, 32 is a steam load control device, which inputs the steam pressure in the main steam pipe from a steam pressure detector 34 provided in the main steam pipe 33, and opens / closes drive signals to the damper devices 28, 29 and Open / close control signals are output to the auxiliary fuel adjusting valve 35 of the auxiliary combustion device 11, respectively.

Next, the operation of the exhaust heat recovery boiler C will be described.

Exhaust gas G discharged from the gas turbine 3 through the exhaust gas duct 7 has a temperature of about 500 ° C. and a NOx concentration of about 250 ppm (kerosene fuel, O ₂ 4% conversion value), a primary evaporator 17, a dry denitration device.
16, passing through the secondary evaporator 18 and the economizer 9, and discharged from the chimney 10 to the outside.

At this time, the exhaust gas G flowing into the dry denitration device 16 is subjected to denitration treatment by controlling the first and second damper devices 26 and 27 by the gas temperature control device 30 based on the temperature detected by the temperature detector 31. It is kept at a proper temperature.
That is, the exhaust gas temperature at the inlet side of the dry denitration device 16 is set to about 380 to 400 ° C. from the viewpoint of denitration efficiency, and the gas temperature control device 30 is set so that the exhaust gas temperature becomes the set value. Both damper devices 26, 27 are controlled to be opened / closed via.

The exhaust gas G that has passed through the primary evaporator 17 and the bypass duct 19 is denitrated by the denitration device 16 to a desired NOx concentration,
It is cooled to about 180 to 190 ° C. (when the pressure is 7 kg / cm ² G) by the secondary evaporator 18, further cooled by the economizer 9, and then released to the atmosphere.

At this time, the amount of steam generated by the exhaust heat recovery boiler C is controlled by controlling the third and fourth damper devices 28, 29 and the auxiliary combustion device 11 by the steam load control device 32 based on the pressure detected by the steam pressure detector 34. , It is adjusted to an appropriate amount according to the steam load. That is, when the steam load increases / decreases and the steam pressure in the main steam pipe 33 changes, the steam load control device 32
Open / close control of both damper devices 28, 29 and auxiliary burner 1 via
The start / stop of 1 and the opening / closing control of the auxiliary fuel adjusting valve 35 are performed, and the amount of steam commensurate with the steam load is generated.

The heat transfer area ratio between the primary evaporator 17 and the secondary evaporator 18 was calculated by measuring the exhaust gas amount of the gas turbine: 40,000 Nm ³ / H, the exhaust gas temperature: 500 ° C,
The exhaust gas temperature at the outlet of the primary evaporator: 380 ° C, the exhaust gas temperature at the outlet of the secondary evaporator: 185 ° C, and the pressure of the steam / water drum: 7 kg / cm ² G.

That is, the exhaust gas temperature in the denitration device 16 is set in the optimum range 380
In order to adjust the temperature to 90 ° C to 390 ° C, it is necessary to install a primary evaporator corresponding to about 12% of the total heat transfer area on the upstream side of the denitration device 16, and the absorbed heat amount is about 39% of the total evaporator. Become. Therefore,
The forced circulation pump is used by combining the primary evaporator 17 with the forced circulation type and the secondary evaporator with the natural circulation type.
The capacity of 25 can be reduced, the required power is reduced, and
The advantage is that the steel frame supporting the steam drum etc. can be omitted.

FIG. 2 is a schematic system diagram of an exhaust heat recovery boiler according to the second embodiment of the present invention, in which the primary evaporative air 17 and the secondary evaporator 18 are entirely of a forced circulation type. That is, the point that the feed water flowing through both evaporators 17 and 18 is forcedly circulated by the forced circulation pump 25 is different from the case of the first embodiment, and the other configurations are exactly the same.

(Effects of the Invention) According to the present invention, the dry denitration device is provided between the primary evaporator and the secondary evaporator, and the first bypass duct is provided in the primary evaporator. Since the second damper device is configured to be opened / closed by the gas temperature control device, by adjusting the amount of exhaust gas flowing through the first bypass duct, the exhaust gas temperature flowing into the dry denitration device is constantly controlled by the denitration reaction. It can be kept in the optimum temperature range. As a result, over a wide range of power and steam loads,
It becomes possible to denitrify all the exhaust gas with high efficiency.

In addition to the control of the exhaust gas temperature, the secondary evaporator is provided with the second bypass duct, and the steam load control device is used to adjust the fuel of the third and fourth damper devices of the secondary evaporator system and the auxiliary combustion device. Since the valve is configured to be controlled, the power generation device side can perform a wide range of steam generation amount control corresponding to the steam load side while performing the operation control according to the power demand.

INDUSTRIAL APPLICABILITY As described above, the present invention remarkably improves the operational flexibility of the cogeneration power generation facility, enables a wide range of load operation over both electric power load and steam load, and efficiently denitrates all the exhaust gas. It can be processed and has excellent practical utility.

[Brief description of drawings]

FIG. 1 is a schematic system diagram of a combined heat and power generation facility to which an exhaust heat recovery boiler according to the present invention is applied. FIG. 2 is a schematic system diagram of an exhaust heat recovery boiler according to the second embodiment. FIG. 3 is a system schematic diagram of a cogeneration power generation facility using a conventional gas turbine. A: Heat and power cogeneration facility, C: Exhaust heat recovery boiler, G:
Exhaust gas, 3 ... Gas turbine, 7 ... Exhaust gas duct, 11
…… Auxiliary burner, 16 …… Dry denitration equipment, 16a …… Inlet side exhaust gas duct of dry denitration equipment, 17 …… Primary evaporator, 17
a …… Exhaust gas exhaust duct on the inlet side of the primary evaporator, 17b …… 1
Exhaust gas exhaust duct part of the secondary evaporator, 18 ... Secondary evaporator, 18a ... Exhaust gas duct part of the secondary evaporator, 18b
...... Exhaust gas exhaust duct part of the secondary evaporator, 19 …… First
Bypass duct, 20 ... Second bypass duct, 26 ... First damper device, 27 ... Second damper device, 28 ... Third
Damper device, 29 ... Fourth damper device, 30 ... Gas temperature control device, 31 ... Exhaust gas temperature detector, 32 ... Steam load control device, 33 ... Main steam pipe, 34 ... Steam pressure detector .

Claims (3)

[Claims] 1. In an exhaust heat recovery boiler (C) of a combined heat and power generation facility (A) using a gas turbine (3), a boiler heat transfer section is provided in an exhaust gas duct (7) of the gas turbine (3). Auxiliary evaporator (11) located in the exhaust gas duct (7) upstream of the primary evaporator (17), which is composed of the primary evaporator (17) and the secondary evaporator (18) downstream thereof. And a dry type denitration device (16) located between both evaporators (17, 18), bypassing each evaporator (17, 18) and each evaporator (17, 18)
Of the primary evaporator (17) by connecting the first and second bypass ducts (19, 20) communicating with the inlet side exhaust gas duct parts (17a, 18a) and the outlet side exhaust gas duct parts (17b, 18b) of The first and second damper devices (26, 27) are provided in the inlet side exhaust gas duct portion (17a) and the first bypass duct (19),
The inlet and outlet of the dry evaporator (16) are provided with third and fourth damper devices (28,29) in the exhaust gas duct portion (18a) and the second bypass duct (19,20) of the secondary evaporator (18). Exhaust gas temperature detector (31) in the side exhaust gas duct (16a)
Is provided, and the first and second damper devices (26, 2) are provided on the basis of the temperature detected by the temperature detector (31) so as to maintain the exhaust gas flowing into the dry denitration device (16) at an appropriate temperature for denitration treatment.
7) is provided with a gas temperature control device (30), a steam pressure detector (34) is provided in the main steam pipe (33) of the exhaust heat recovery boiler (C), and the exhaust heat recovery boiler (C) is used. A steam load that controls the third and fourth damper devices (28, 29) and the auxiliary combustion device (11) based on the pressure detected by the steam pressure detector (34) so that the generated steam amount is an appropriate amount according to the steam load. An exhaust heat recovery boiler having a control device (32). 2. The exhaust heat recovery boiler according to claim 1, wherein the auxiliary combustion device (11) is a combustion burner provided in the exhaust gas duct (7) at an upstream side portion of the primary evaporator (17). . 3. The method according to claim 1, wherein the secondary evaporator (18) is a natural circulation evaporator for can water, and the primary evaporator (17) is a forced circulation evaporator for can water. Exhaust heat recovery boiler described in.