JP2005226464A - On-line flushing method of blast furnace gas compressor in blast furnace gas mono-fuel combustion gas turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an on-line flushing method of a blast furnace gas compressor in a blast furnace gas mono-fuel combustion gas turbine enabling to appropriately remove dust by dry ice particles during operation of the gas turbine for suppressing drop of adiabatic efficiency of a blast furnace compressor and enabling long term stable operation of the gas turbine. <P>SOLUTION: Dry ice particles of average particle diameter of 0.15 mm or more and 1.0 mm or less are injected from a casing of a compressor of a blast furnace provided on an inlet side of the turbine during operation of the blast furnace gas mono-fuel combustion gas turbine burning highly pressurized blast furnace gas as fuel to exfoliate dust adhering to a blade and/or an inner wall of the compressor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for cleaning a blast furnace gas compressor on-line in a blast furnace gas-only-fired gas turbine that recovers retained energy of the blast furnace gas by burning high-pressure blast furnace gas as fuel.

In steelworks, various by-product gases are generated from coke ovens, blast furnaces, converters, etc., and are used as fuel in steam generating boilers and slab heating furnaces. As an effective use of blast furnace gas with a small calorific value, operation of a blast furnace gas-only fired gas turbine is performed. That is, power is generated by operating a gas turbine using blast furnace gas, which is a by-product gas having a low calorific value, discharged from the blast furnace as fuel, and energy stored in the blast furnace gas is recovered.
Such a blast furnace gas-only fired gas turbine is operated under the system shown in FIG. 1, for example. That is, after being discharged from the blast furnace 1, the blast furnace gas which has been removed by the electric dust collector 3 through the dry dust collector 2 is heated by the gas heater 4, compressed by the gas compressor 5, and then burned by the combustor. By doing so, the gas turbine 6 is driven.

Here, since the blast furnace gas has undergone wet dust removal, the gas contains a considerable amount of moisture. In addition, even if the wet or dry dust removal process is performed several times, about 1.1 mg / Nm ³ of dust is still contained. As a result of analyzing the components in these dusts, it was found that ammonium chloride (NH ₄ Cl) was mainly precipitated.
It is considered that this is because, in recent blast furnace operations, pulverized coal injection and furnace top watering for lowering the furnace top temperature are performed. In other words, pulverized coal contains nitrogen (N) and chlorine (Cl), and iron ore also contains chlorine. Together with the water sprayed from the top of the furnace, these coals are mixed with ammonia and chloride. It is considered that hydrogen is generated.

  These substances remaining after the dust removal process react under certain conditions in the blast furnace gas compressor, and as a result, adhere to the blades of the compressor and reduce the heat insulation efficiency of the compressor. Therefore, the gas turbine must be periodically stopped to clean and remove the ammonium chloride adhering to the stationary and moving blades and the inner wall of the compressor.

As a countermeasure against deposits on the turbine, Patent Document 1 proposes to inject dry ice particles toward the blades of the turbine. This method makes it possible to remove dust adhering to the blades and the like without stopping the gas turbine.
Japanese Patent Laid-Open No. 10-220251

  However, simply spraying dry ice particles may not remove the dust sufficiently, and the dry ice may be relatively hard, which may cause damage to the blades in particular. The problem remained in the place where it was difficult to realize processing stably.

  In view of this, the present invention suppresses the decrease in the heat insulation efficiency of the blast furnace gas compressor and enables the gas turbine to be stably operated for a long time. The purpose is to propose an on-line cleaning method for a blast furnace gas compressor in a blast furnace gas-only gas turbine.

  The inventors have found that in order to clean a blast furnace gas compressor in a gas turbine online with dry ice particles, it is necessary to use dry ice particles having an appropriate diameter. The diameter range was found and the present invention was completed.

That is, the gist configuration of the present invention is as follows.
(1) During operation of a blast furnace gas-burning gas turbine that burns high-pressure blast furnace gas as fuel, the (average particle) diameter is 0.15 mm or more and 1.0 from the casing of the blast furnace gas compressor provided on the inlet side of the turbine. An on-line cleaning method for a blast furnace gas compressor in a blast furnace gas-only fired gas turbine, characterized by injecting dry ice grains of mm or less and separating dust adhering to the blades and / or inner walls of the compressor.

(2) The on-line cleaning method for a blast furnace gas compressor in a blast furnace gas-only fired gas turbine as described in (1) above, wherein the average particle size of the dry ice particles is 0.2 mm or more and less than 0.5 mm.

In order to solve the above-mentioned problems, the inventors conducted an experiment using an actual machine in order to select an optimum dry ice diameter for effective online cleaning.
That is, in the experiment, dry ice grains are injected from the casing of the compressor 5 when the heat insulation efficiency in the compressor 5 is reduced to 80% due to dust accumulation under the system shown in FIG. At that time, the dry ice particle size was changed variously, and the recovery rate (%) of the heat insulation efficiency of the gas compressor and the dry ice residual degree (mg / Nm ³ ) were investigated for each particle size. The injection pressure of dry ice grains was 0.25 to 0.35 MPa.

Here, the recovery rate of the heat insulation efficiency of the gas compressor is the value obtained by dividing the heat insulation efficiency of the blast furnace gas compressor after injecting dry ice particles and operating for a certain period of time by the heat insulation efficiency of the blast furnace gas compressor immediately after the previous cleaning. It is displayed as a percentage. From this ratio, the cleaning effect of the blast furnace gas compressor can be evaluated.
On the other hand, dry ice residual degree shows the result of having analyzed the gas by sampling the gas of the blast furnace gas compressor exit side. From this residual degree, the amount of injection can be evaluated.

  The results of these investigations are shown in FIG. In FIG. 2, when the average particle size of the dry ice grains exceeds 0.07 mm to 0.08 mm, the recovery rate increases, and when it exceeds 0.15 mm, the recovery rate increases to 88% or more. It can be seen that the recovery rate increases and the dry ice residual degree decreases in the range where the average particle size of the dry ice particles is 0.15 mm or more and 1.0 mm or less. Therefore, by injecting dry ice having an average particle size of 0.15 to 1.0 mm into the blast furnace gas compressor, online cleaning of the blast furnace gas compressor can be reliably realized.

  Further, in FIG. 2, the recovery rate is greatest especially when the average particle size of the dry ice particles is around 0.2 to 0.8 mm, while the dry ice residue is lowest when the average particle size of the dry ice particles is around 0.3 to 0.8 mm. Become. Furthermore, when the average particle size of the dry ice particles is 0.3 to 0.4 mm and reaches a peak (maximum value) of 0.5 mm or more, the recovery rate tends to decrease. The problem that the recovery rate decreases when the average particle size is 0.5 mm or more is considered to be a decrease in efficiency due to damage to the blades of the compressor blades. For this reason, in order to realize more efficient online cleaning in combination with preventing the blade damage of the compressor, it is preferable that the average particle size of the dry ice particles is 0.2 mm or more and less than 0.5 mm. More preferably, the recovery rate is in the range of 0.2 mm or more and less than 0.4 mm, where the recovery rate tends to increase. Within this range, there is no risk of blade damage, and online cleaning of the blast furnace gas compressor can be realized with certainty.

  According to the present invention, the dust inside the gas compressor is appropriately removed by the dry ice particles, so that it is possible to suppress a decrease in the heat insulation efficiency of the compressor and realize a long-term stable operation of the gas turbine.

Next, an embodiment of the present invention will be described based on FIG. 3 showing a blast furnace gas compressor.
In FIG. 3, 7 is a casing of a blast furnace gas compressor, 8 is a rotor, 9a and 9b are blades of a blast furnace gas compressor, 10 is a stationary blade of a blast furnace gas compressor, and 11 is a nozzle for spraying dry ice particles. It is.

  This nozzle 11 has a special structure that can efficiently inject dry ice grains onto the first stage stationary blade 9a to which a large amount of ammonium chloride adheres and that can produce dry ice grains with a particle diameter of 0.15 to 1.0 mm. ing. For example, a structure in which a cutter is attached to the tip of the nozzle 11 and dry ice is crushed to a predetermined diameter with the cutter is appropriate.

  Reference numeral 12 denotes a dry ice production apparatus. The dry ice produced here is stored in a dry ice storage tank 13. It is also possible to pulverize the dry ice extruded from the tank 13 to the above-mentioned diameter with a pulverizer. Further, the dry ice in the tank 13 is sent to the nozzle 11 through the extruder 14 and is jetted from the nozzle 11 by the compressed air from the air compressor 15. The pressure in the air compressor 15 is appropriately 0.4 to 0.5 Mpa.

  Here, when the dry ice particles having a diameter of 0.15 to 1.0 mm from the nozzle 11 are injected from the casing 7 to clean the blast furnace gas compressor online, for example, paying attention to the efficiency of the blast furnace gas compressor, this efficiency Is injected below, the dry blast furnace particles are injected, and then the insulation efficiency of the blast furnace gas compressor is increased and restored to a region that sufficiently exceeds the threshold value. Good. The blast furnace gas compressor adiabatic efficiency is the ratio of theoretical power to actual power.

  The efficiency of the blast furnace gas compressor is determined by installing thermometers 16a and 16b and pressure gauges 17a and 17b on the inlet and outlet sides of the casing 7 of the blast furnace gas compressor, and adiabatic efficiency based on the detected temperature and pressure. The adiabatic efficiency is calculated by the calculator 18 and the change in efficiency is measured. This result is monitored by the computer 19, and when the efficiency drops below a threshold value, dry ice particles are injected. For example, if the dry ice injection setting for the computer 19 is set: 83% efficiency for the blast furnace gas compressor and 88% for the efficiency recovery value, the temperature detected by the thermometers 16a, 16b and the pressure gauges 17a, 17b Based on the pressure, the adiabatic efficiency calculator 18 calculates the adiabatic efficiency, and when the efficiency drops to 83%, an operation signal is sent to the extruder 14, and the injection of dry ice particles is started. The efficiency of the blast furnace gas compressor is calculated based on that, and when the efficiency recovery value reaches 88%, the injection of dry ice particles is stopped and the cleaning is completed.

  According to the present invention, by injecting dry ice particles adjusted to an appropriate particle size from the blast furnace gas compressor casing, dust adhering to the wings or inner walls of the compressor can be efficiently separated, and the heat insulation efficiency is reduced. This makes it possible to operate gas turbines for a long period of time. In addition, since the above-described cleaning process is performed online, the blast furnace gas compressor can be cleaned without affecting the power supply in the ironworks.

  In the operation for introducing the blast furnace gas and driving the gas turbine 6 in the system shown in FIG. In the blast furnace gas compressor shown in FIG. 3, when the injection (injection) of dry ice particles was performed for 30 minutes according to the following conditions, the turbine efficiency could be returned to 87%. At this time, there was no damage on the blades of the compressor due to the injection of dry ice grains.

・ Dry ice particle size: 0.2-0.5mm
・ Dry ice grain injection pressure: 0.35-0.45MPa
・ Dry ice particle injection flow rate: 7-15kg / min

  The present invention can be advantageously applied not only to the above-mentioned blast furnace gas-only gas turbine but also to a blast furnace top pressure power generation turbine having the same problem.

It is a figure which shows the introduction system of blast furnace gas. It is a figure which shows the relationship between the recovery rate of the heat insulation efficiency in a gas compressor after a blast furnace gas compressor washing | cleaning, dry ice residual degree, and dry ice particle size. It is a figure which shows the structure of a gas compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Dry type dust collector 3 Electric dust collector 4 Gas heater 5 Gas compressor 6 Gas turbine 7 Blast furnace gas compressor casing 8 Rotor 9a, 9b Rotor blade of blast furnace gas compressor
10 Stator blade of blast furnace gas compressor
11 Nozzle for spraying dry ice grains
12 Dry ice production equipment
13 Dry ice storage tank
14 Extruder
15 Air compressor

Claims (2)

  Dry ice with an average particle size of 0.15 mm or more and 1.0 mm or less from the blast furnace gas compressor casing provided on the inlet side of the blast furnace gas combustion gas turbine that burns high-pressure blast furnace gas as fuel An on-line cleaning method for a blast furnace gas compressor in a blast furnace gas-only fired gas turbine, characterized by injecting grains and separating dust adhering to the blades and / or inner walls of the compressor.   2. The on-line cleaning method for a blast furnace gas compressor in a blast furnace gas-only fired gas turbine according to claim 1, wherein the average particle size of the dry ice particles is 0.2 mm or more and less than 0.5 mm.

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