JPH04161702A - Waste heat recovery heat exchanger - Google Patents

Abstract

PURPOSE:To prevent obstruction to heat transfer performance and an output drop of a gas turbine by providing a water injection grid for removing ammonium sulfate which is attached to a group of heat exchanger tubes, in a region where an exhaust gas temperature is in a specific range. CONSTITUTION:Exhaust gas 5 from a gas turbine for which fuel containing sulfur is used passes in order through a high-pressure superheater 9, a high- pressure evaporator 7, a high-pressure economizer 6, a low-pressure evaporator 4, and a low-pressure economizer 2 arranged in a waster heat recovery heat exchanger 1 and is discharged from a smoke stack 10. In this case, the low- pressure economizer 2 is divided into two sections, and a water injection grid 16 is provided in a space opened by division i.e., in a region where an exhaust gas temperature is 150-300 deg.C. When water is regularly injected, ammonium sulfate attached to a group of heat exchanger tubes can be easily removed. Accordingly, it becomes possible to avoid corrosion of the heat transfer tubes, obstruction to heat transfer performance, and an output drop of the gas turbine caused by an increase in a draft loss.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a combined cycle power generation plant that includes:
The present invention relates to an exhaust heat recovery heat exchanger that generates steam using the heat of exhaust gas discharged from various heat generating means such as gas turbines.

(Conventional technology) Conventional power generation equipment generally used a single steam turbine or a single gas turbine as the prime mover, but recently, combined cycle power generation, which skillfully combines the advantages of both, has been used. It has become to.

This combined cycle power generation plant sends the exhaust gas from the gas turbine to an exhaust heat recovery heat exchanger to generate steam, and sends the generated steam to the steam turbine to extract electricity. It is convenient in that it can be used effectively, and startup, load change, and stop times can be significantly shortened.

Liquefied natural gas (LNG), which is said to be a clean fuel, has traditionally been used as fuel for gas turbines, which are one of the components of combined cycle power generation plants, but in recent years gas turbine fuels have diversified. As a result, fuels containing sulfur (for example, naphtha and kerosene) are increasingly being used. When using fuel containing this sulfur content.

Sulfur oxides, so-called SOx, are produced in the exhaust gas of the gas turbine.

On the other hand, in the exhaust heat recovery heat exchanger, there is an ammonia injection grid (hereinafter referred to as AIa) and an AIG that injects ammonia into the gas turbine exhaust gas in order to reduce nitrogen oxides, so-called NOx, in the gas turbine exhaust gas.
A denitrification catalyst device (hereinafter referred to as DeNOx) is installed downstream of the denitrification catalyst.

FIG. 4 shows an example of a conventional exhaust heat recovery heat exchanger.

This figure shows a double pressure natural circulation type exhaust heat recovery heat exchanger 1 equipped with two steam generation systems.

Feed water supplied from a low-pressure water pump (not shown) exchanges heat with the exhaust gas 5 of the gas turbine while sequentially passing through a low-pressure economizer 2, a low-pressure steam drum 3, and a low-pressure evaporator 4, and part of it evaporates while the rest It is returned to the low pressure steam drum 3. The steam generated during this time is guided to the low pressure steam turbine via the low pressure main steam pipe.

In addition, part of the water that has exited the low-pressure economizer 2 is separated from the main route midway and is boosted in pressure by the high-pressure water pump.
While successively passing through the high-pressure evaporator 7, it exchanges heat with the exhaust gas 5, and a part of it is evaporated, and after the moisture is separated in the high-pressure steam drum 8, it further passes through the high-pressure superheater 9 and becomes superheated steam. 6 led to the high pressure steam turbine via the high pressure main steam pipe
The high pressure evaporator 7 and the high pressure steam drum 8. In each loop of the low-pressure evaporator 4 and the low-pressure steam drum 3, water in the downcomer tube that supplies canned water from each steam drum 8, 3 to the heat transfer tube in each evaporator 7, 4, and water in the evaporator heat transfer tube. A natural circulation system is realized in which water is circulated by obtaining circulation force from the difference in density of water.

On the other hand, the exhaust gas 5 from the gas turbine sequentially passes through the high-pressure superheater 9, high-pressure evaporator 7, high-pressure economizer 6, low-pressure evaporator 4, and low-pressure economizer 2 of the exhaust heat recovery heat exchanger 1, and passes through the chimney lO more excreted.

In order to reduce NOx in the gas turbine exhaust gas 5, an AIGII is provided on the downstream side of the high-pressure superheater 9 in this figure, and the exhaust gas temperature is set at 300, which is considered to be the optimum level for the denitrification reaction.
DeN Ox 12 is installed in a region of ~400°C (in this figure, it is shown downstream of the high-pressure evaporator 7).

) FIG. 5 shows a general viscosity diagram of DeNOx12.

One row of catalyst layers 14 is formed by incorporating a large number of 1 m square catalyst baskets 13, and generally consists of two to three rows of catalyst layers 14. This catalyst basket 13
is width 150w11, height 150w111, length 100
It is made up of 15 unit catalysts of about 0.0 cm.

(Problems to be Solved by the Invention) In the conventional 3L DeNOx12, sufficient consideration has been given to the gas seal structure so that the denitrification performance will not deteriorate due to ammonia leakage, but as mentioned above, the unit catalyst 1
5, a catalyst basket 13 is formed by the collection of catalyst baskets 13, and a row of catalyst layers 1 is formed by the collection of catalyst baskets 13.
4, it is impossible to completely cover the duct cross section, and it cannot be denied that there are some flow path gaps. Therefore, ammonia sprayed from A I Gll leaks at DeNOx12, and DeNC)x1
It will flow downstream from 2.

Additionally, as the catalyst performance gradually declines due to deterioration over time due to the operation of a combined cycle power plant, AI
Ammonia erupted from GII is DeNOx12
DeNOx as unreacted ammonia without 00% reaction
It will flow downstream from No. 12.

When such leaked ammonia and SOx in the gas turbine exhaust gas 5 reach a temperature of about 300° C. or lower, they react to form ammonium sulfate salt. Since the melting point of this ammonium sulfate salt is about 150°C,
In the temperature range below ℃, it melts into a corrosive and highly sticky liquid substance.

In other words, if the gas turbine exhaust gas temperature is 150°C or higher
Heat exchanger tubes installed in areas below 0°C (in the case of the double pressure natural circulation type exhaust heat recovery heat exchanger 1 shown in Figure 4,
If this ammonium sulfate salt adheres to heat transfer tubes and the like that constitute the low-pressure evaporator 4 and low-pressure economizer 2 (the temperature range falls within this temperature range), the constituent materials will corrode.

Furthermore, since each tube group of the exhaust heat recovery heat exchanger 1 is composed of finned tubes, the ammonium sulfate salt and dust in the exhaust gas 5 adhere between the fins.
This not only impedes the heat transfer effect of the heat transfer tubes, but also increases the draft loss of the exhaust heat recovery heat exchanger 1, resulting in a decrease in the output of the gas turbine.

Therefore, the purpose of the present invention is to reduce the gas turbine exhaust gas temperature to 15
This prevents the ammonium sulfate salt produced by the reaction between SOx in the exhaust gas and leaked ammonia in the range of 0 to 300°C from adhering to the heat exchanger tubes installed in this temperature range, and also prevents the adhering ammonium sulfate salt from adhering to the heat exchanger tube group installed in this temperature range. Exhaust heat recovery can avoid corrosion of heat transfer tubes, inhibition of heat transfer by deposits caused by the combination of ammonium sulfate salts and dust contained in gas turbine exhaust gas, and reduction in gas turbine output due to increased draft loss. Our purpose is to provide heat exchangers.

[Structure of the Invention] (Means for Solving Problem A) In order to solve the above problems, the present invention provides a denitrification device that reduces nitrogen oxides by injecting ammonia into the exhaust gas of a gas turbine that uses sulfur-containing fuel. This exhaust heat recovery heat exchanger is characterized in that a water injection grid for removing ammonium sulfate salt adhering to the heat exchanger tube group is provided in the region where the exhaust gas temperature is 150 to 300°C.

(Function) Since ammonium sulfate salt has the property of being easily soluble in water, ammonium sulfate salt can be easily removed by periodically spraying water from this water injection grid.

Also, according to this method, ammonium sulfate salt can be removed without stopping the operation, so there is no possibility of corrosion of the heat transfer tubes due to the attached ammonium sulfate salt.

It is possible to avoid a situation in which the heat transfer effect is inhibited by deposits caused by the combination of the ammonium sulfate salt and the dust contained in the gas turbine exhaust gas, and the gas turbine output is reduced due to an increase in draft loss.

(Example) An example of the exhaust heat recovery heat exchanger according to the present invention will be described with reference to FIGS. 1 and 2.

In the embodiment shown in FIG. 1, the low-pressure economizer 2 is divided into two parts, and the economizer water injection grid 16 is provided in the open space between the two parts.

The structure of the water injection grid 16 is, for example, as shown in FIG. 2, in which pipes 17 are combined in a grid pattern.

Numerous water injection holes 1 in vertical and horizontal pipes 17
8 is provided.

Furthermore, if neutralized water is used as the aqueous solution for water injection, the waste liquid will become a strong acid, and the bottom surface of the exhaust heat recovery heat exchanger duct will be corroded by the acid.

Therefore, in order to make the waste liquid neutral by using an alkaline aqueous solution, the pH of the alkaline aqueous solution for water injection should be adjusted in advance.
Adjust.

According to the above configuration, ammonium sulfate salt can be easily removed by periodically jetting water from the water jetting grid 16.

Therefore, corrosion of heat transfer tubes due to attached ammonium sulfate salts, inhibition of heat transfer effect due to deposits caused by the combination of ammonium sulfate salts and dust contained in gas turbine exhaust gas, and reduction in gas turbine output due to increased draft loss are avoided. It is possible to do so.

FIG. 3 shows another embodiment of the invention. In this embodiment, the tube group of both the low-pressure economizer 2 and the low-pressure evaporator 4 is divided into two parts, and the economizer and evaporator water injection grids 16 and 19 are provided in the spaces created by the respective divisions. Furthermore, an auxiliary water injection grid 20 is also provided between the low pressure economizer 2 and the low pressure evaporator 4.

In this way, the evaporator water injection grid 19 is provided for the low pressure evaporator 4 together with the low pressure energy saver 2, and one or more auxiliary water injection grids 20 that eject water from the opposite direction are provided as necessary. Ammonium sulfate salt can be reliably removed.

〔Effect of the invention〕

As explained above, according to the present invention, ammonium sulfate salt adheres to the fin tubes constituting the heat exchanger tube group in the region where the gas turbine exhaust gas temperature is 150 to 300 °C, without stopping the operation of the combined cycle power plant. This eliminates corrosion of heat transfer tubes due to attached ammonium sulfate salts, inhibits the heat transfer effect due to deposits caused by the combination of ammonium sulfate salts and dust contained in gas turbine exhaust gas, and reduces gas turbine output due to increased draft loss. It is possible to avoid this situation.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of the exhaust heat recovery heat exchanger according to the present invention, FIG. 2 is a configuration diagram showing an example of a water injection grid, and FIG. 3 is a configuration diagram showing another example of the present invention. 4 is a configuration diagram showing an example of a conventional exhaust heat recovery heat exchanger, and FIG. 5 is a perspective view showing a schematic structure of a D e N Oλ. 1...Exhaust heat recovery heat exchanger 2...Low pressure economizer 4...Low pressure evaporator 5...Gas turbine exhaust gas 11...Ammonia injection grid (AI
G) 12...Denitrification catalyst device (DeNOx) 16.19
．． 20...Water injection grid agent Patent attorney Nori Chika
Kensuke Figure 2 Figure 5 Procedure Amendment (Part 1 3.1.11 1989 Month/Day

Claims (1)

[Claims] In an exhaust heat recovery heat exchanger equipped with a denitrification device that injects ammonia into the exhaust gas of a gas turbine that uses sulfur-containing fuel to reduce nitrogen oxides, the exhaust gas temperature reaches 150 ℃.
An exhaust heat recovery heat exchanger characterized in that a water injection grid for removing ammonium sulfate salt adhering to a group of heat exchanger tubes is provided in a region of 300°C to 300°C.