JPS61116289A - Method of preventing trouble of adhesion of mist - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for preventing mist adhesion problems, and in particular, in a high-temperature exhaust gas system, based on the volatilization of moisture, scale-like substances are caused in the system by drying of mist components. The present invention relates to a method for effectively preventing the adhesion of

[Prior art] In a Wf furnace, pig iron is produced by reducing iron ore, and normally, for every 1 ton of pig iron, 0.3 tons of slag and 1,600~ of blast furnace gas are produced as by-products. .

This blast furnace scum contains a large amount of combustible gases such as CO and H2,
It has a calorific value of approximately 800 kcal/NIT+'(7). This corresponds to the energy output of fuel such as coke charged into the blast furnace. To utilize this energy effectively, blast furnace gas is recovered and used as fuel for eight furnaces, coke ovens, heating furnaces, and power generation boilers within the steelworks.

In addition, in recent years, with the generalization of high-pressure operation of blast furnaces, the furnace top pressure has also increased to 2.5 to 3.0 kg/am'. So, does the blast furnace gas of 8 x 105 Nm' per hour generated in a blast furnace with an internal volume of 5,000 rn' be produced by that pressure alone?
, has an energy of 0 to 25,000 kW/h. Therefore, this pressure energy, which was previously wasted in the atmosphere, is used to rotate an expansion turbine and recovered as electrical energy.

Furnace top pressure power generation equipment (T, R, T,) has been introduced.

However, the blast furnace gas discharged from the top of the blast furnace is Ca
It is a high-temperature gas containing large amounts of scale components such as , Mg, and Fe, and if it is used as is, it not only causes scale damage and deteriorates thermal efficiency, but also may damage various equipment. Similarly, even if this blast furnace exhaust gas is fed to the top pressure power generation equipment without any treatment, scale failure will occur in the top pressure turbine blade row.

Therefore, when reusing such blast furnace exhaust gas, it is usually treated by removing dust through wet dust collection, dehumidifying it in a cooling tower, or by sending it to an electrostatic precipitator or wet flue gas desulfurization equipment. As mentioned above, blast furnace exhaust gas is a high-temperature gas that contains a large amount of scale components, so it is not possible to use a packed tower method for dust collection, and it is generally treated by spraying water with a venturi etc. are doing.

However, in this case, the mist in the gas and the mist generated during water spraying adhere to the vessel wall above the water spraying surface of the Venturi, and the water in the adhering mist is evaporated by the high-temperature gas, leaving the remainder to dryness. , the problem of scaling stagnates. Formation of scale causes disturbances in the water spray pattern of the water spray nozzle and disturbances in the gas flow on the wall surface, making it impossible to maintain a specified dust removal rate.

Moreover, when gas containing such mist is supplied to an electrostatic precipitator, the mist will adhere to the electrode surface within the precipitator as well. On the other hand, wet desulfurization equipment uses a venturi to spray an aqueous solution of a calcium compound such as lime instead of water, but mist adhesion still occurs above the spray surface of the venturi.

Such a phenomenon similarly occurs in the blast furnace top pressure power generation device, and mist adheres to the turbine blade row of the furnace top pressure turbine. In a blast furnace top pressure power generation system, water is sprayed onto the turbine blade row, but it is not economical to increase the amount of water because it causes a decrease in power generation efficiency.Mist in the gas and generated during this spraying The mist adheres to the turbine blade rows and scales. Unbalanced adhesion of scale to the turbine blade cascade reduces the power generation efficiency and causes abnormal vibrations in the rotation of the turbine, sometimes resulting in a state in which the original operation becomes impossible. Furthermore, once the scale particles that have adhered and solidified flow into the moving and stationary blades, there is a possibility that the blades will be damaged.

Conventionally, in order to prevent such mist adhesion problems, scale inhibitors used in water systems, such as polyacrylic acid scale inhibitors, were added to the spray water in venturis, blast furnace top pressure power generators, etc. We are trying to prevent scale.

Furthermore, periodic inspections, temporary inspections, and scale removal cleaning are carried out in each facility, and electrodes and the like in electrostatic precipitators and the like are regularly replaced.

[Problems to be Solved by the Invention] However, it is not industrially or economically advantageous to frequently inspect, clean, and replace equipment. In addition, scale inhibitors for water systems are not effective in preventing scale adhesion due to drying of mist components, and even if such scale inhibitors for water systems are added to spray water, a very good effect cannot be obtained.

In other words, scale adhesion in water systems occurs when scale species precipitate due to changes in water temperature and pH, whereas in highly advanced gas systems that contain small particles 4) such as 1-1 silent furnace gas. Unlike water-based systems, scaling occurs due to moisture volatilization and drying of mist components.

Therefore, although polymer-based, inorganic phosphoric acid-based, and organic phosphonic acid-based scale inhibitors for aqueous systems are effective in suppressing scale formation in aqueous systems, scale buildup occurs in high-temperature exhaust gas treatment systems, etc., which have different causes of scale formation. It has almost no suppressive effect on

As described above, no method has been proposed in the past to effectively prevent problems caused by adhesion and drying of mist from high-temperature exhaust gas systems.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned conventional problems. In this system, the drying rate of the mist is slowed down to prevent scale formation, and water added with a polyhydric alcohol compound is sprayed onto high-temperature exhaust gas containing scale components to prevent the mist from drying up. A method for preventing mist adhesion failure W, which is characterized by the following.

The present invention will be explained in detail below.

In the present invention, a polyhydric alcohol compound is added to water that is sprayed onto high-temperature exhaust gas containing scale components.

The polyhydric alcohol compounds used in the present invention include:
Specific examples include dihydric alcohols such as ethylene glycol, trihydric alcohols such as glycerin, tetrahydric alcohols such as eltrit, and adducts of these with ethylene oxide or propylene oxide. The molecular weight of these polyhydric alcohol compounds is preferably IO,000 or less.

In the present invention, it is also possible to use a commonly used scale inhibitor together with such a polyhydric alcohol compound. The scale preventive agent is not particularly limited, and known scale preventive agents for aqueous systems can be used. Specifically, polymerized phosphoric acids or their salts such as tripolyphosphoric acid and hexametaphosphoric acid, phosphonic acids such as aminotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylphosphonic acid, phosphonobutanetricarboxylic acid, phosphonocarboxylic acids, or Salts thereof, carboxylic acid-based polymer compounds, and the like can be mentioned.

Carboxylic acid-based polymer compounds include homopolymers or salts thereof such as polyacrylic acid, polymethacrylic acid, polymaleic acid, and polyitaconic acid, or acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and other polymerizable monomers. Examples include copolymers with acrylamide, isobutyne, butene, hydroxymethacrylate, styrene, styrene sulfonic acid, etc., or salts thereof. The molecular weight of these polymer compounds is 500-100,000
degree, preferably in the range of i, ooo-to, ooo.

The amount of the polyhydric alcohol compound and the aqueous scale inhibitor to be used is appropriately determined depending on the type of exhaust gas to be treated, the scale of the equipment, and other conditions such as the treatment temperature. The amount added is usually 0.1 to 2.000 mg/i, especially 0
．． It is sufficient to select between 5 and 1,000 mg/l.

In the method of the present invention, water to which the above-mentioned polyhydric alcohol or polyhydric alcohol-based compound and the above-mentioned scale anti-chalking agent are added is sprayed onto high-temperature exhaust gas containing scale components such as blast furnace exhaust gas.

The spraying location and spraying means may be those conventionally used for water spraying, but are not particularly limited thereto.

According to the method of the present invention, the mist adhering to the wall surface etc. is prevented from drying and becoming scaled. Moreover, the sprayed polyhydric alcohol compound-containing water is also absorbed by the mist components that have already adhered and dried, and has the effect of moistening the mist components and allowing them to fall naturally.

[Function] According to the method of the present invention, an excellent scale adhesion prevention effect is achieved by adding a polyhydric alcohol to the spray water. Because it is strongly bound to water through hydrogen bonds, solutions containing polyhydric alcohol compounds are difficult to dry up, especially in environments with high water vapor pressure, and are also difficult to form dry solids even in systems that repeatedly wet and dry. .

In addition, the polyhydric alcohol compound forms a moist film on the wall surface, etc., and this, together with the drying-out prevention effect, allows the mist adhering to the wall surface, etc. to flow off. Therefore, the attached mist is prevented from remaining on the wall surface and becoming scaled.

It is surmised that the effects of preventing dryness and accelerating the run-off of adhering mist, etc., act alone or in combination to provide an excellent scale adhesion prevention effect.

[Example] The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 The method of the present invention was carried out on a system for supplying Takaatsu cypress gas to a furnace top pressure generator.

Blast furnace exhaust gas contained oxides such as zinc, iron, calcium, and silica, and high-temperature gas at 150°C was introduced into the generator. In the wet dust collection process of this system, chemical-free water was sprayed into the blast furnace exhaust gas and the system was operated for 19 days.

Similarly, the generator was operated for 17 days by spraying water to which 50 mg/kg of glycerin propylene oxide adduct (molecular weight 3.000) had been added.6 In each case, the generator was The differential pressure after the first stage static E in of the turbine was measured, and the differential pressure rise was determined, and the rate of increase in the differential pressure was determined.

The results are shown in Table 1.

Table 1 From Table 1, the method of the present invention shows a rate of increase in differential pressure that is 1/3 to 1/4 of that without drugs, and it is recognized that scale adhesion is significantly suppressed.

Furthermore, when the turbine was disassembled, it was found that hard scale had adhered to the blades without chemical injection, and it took considerable effort to remove it. On the other hand, when the method of the present invention was adopted, the scale adhering to the turbine was soft and could be easily peeled off with pressurized water.

[Effects] As detailed above, the method for preventing mist adhesion failure of the present invention is to spray water to which a polyhydric alcohol compound has been added to high-temperature exhaust gas containing scale components. Due to its high hydrophilicity, the adhesion of mist and drying out is effectively prevented, and the adhesion of scale due to adhesion of mist and drying out is significantly reduced. As a result, scale failures such as blockages in piping, abnormal vibrations in turbines, and falling cooling tower filler accidents are prevented, and equipment inspections, cleaning equipment replacement, etc. need to be performed less frequently. . (
Incidentally, with the adoption of the method of the present invention, it is no longer necessary to open and clean the blast furnace top pressure generator every 40 days for as many as 90 days. Furthermore, in the case of conventional electrostatic precipitators that required approximately 100 electrodes to be replaced every year, by adopting the method of the present invention, the number of electrodes to be replaced was reduced to less than 30 per year. ) Moreover, even if deposits occur, they can be easily removed because they are significantly softened.

Therefore, the method of the present invention is extremely industrially and economically advantageous.

Claims (1)

[Claims] (1) A method for preventing mist adhesion failure, which comprises preventing mist from drying out by spraying water added with a polyhydric alcohol compound to high-temperature exhaust gas containing scale components.