JPH01203277A - Castable refractories for hot application to blast furnace trough - Google Patents

Abstract

PURPOSE:To provide castable refractories for a blast furnace which are suitable for application in a high-temp. atmosphere by adding petroleum pitch which is specified in softening point, grain size, fixed carbon content, and volatile content respectively as well as a curing retarder, exothermic agent, coagulating agent, and decoagulating agent, etc., to a refractory raw material which is adjusted in grain size. CONSTITUTION:The above desired refractories are obtd. by adding 1-6wt.% petroleum pitch having 150-250 deg.C softening point, <=3mm particle size, >=55wt.% fixed carbon content, and <=40wt.% volatile component as well as the curing retarder, exothermic agent, coagulating agent, and decoagulating agent, etc., to the refractory raw material which consists of alumina, etc., and is adjusted in the grain size. Tannic acid, etc., are used as the above-mentioned curing retarder, Al powder, etc., as the exothermic agent, calcium alminate as the coagulating agent and sodium phosphate, etc., as the decoagulating agent, respectively. The above-mentioned refractories compare favorably with a cold applied material and are the applied material having excellent structural stability and the excellent corrosion resistance and wear resistance to molten iron and slag.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a castable refractory used for lining or repairing blast furnace gutters.

[Conventional technology]

In small blast furnaces, etc., there are only one or two tap holes, and gutter lining or repair is always carried out under high temperature conditions.
Even in medium and large-sized blast furnaces, emergency repairs, etc. immediately after removal of residual pig iron must be carried out at high temperatures affected by the residual heat of the base metal.

In the case of construction under such high temperatures, the hardening of the construction material is accelerated and the pot life is extremely shortened. For this reason, the amount of cross-conducting water used during construction at room temperature is increased considerably to utilize the specific heat of the water bodies and the latent heat of water evaporation, in order to extend the pot life.

In addition, there are restrictions on the construction time for lining or repairing blast furnace gutters, and it is necessary to dry the constructed structure within a short period of time after construction is completed before it can be used. Therefore, it is necessary to take measures to prevent explosions during drying. There is.

JP-A-53-66917, JP-A-59-3354
Publication No. 9.

JP-A-61-38154, JP-A-61-4062
Publication No. 2 and other publications propose technologies to prevent explosions during rapid heating and drying, but all of these technologies are designed with room-temperature construction in mind, and are subject to the bubbling phenomenon and pot life during high-temperature construction mentioned above. It is insufficient to solve problems such as securing

On the other hand, the gutters attached to blast furnaces are subject to repeated thermal shock and wear due to tapping and slag, so unlike the castable refractories used in open-air furnaces, they have volumetric stability that does not shrink during hot temperatures, and It is necessary to have excellent spalling resistance against thermal stress caused by impact, erosion resistance and abrasion resistance against high-temperature hot metal and slag, and structural stability so that the construction body is completely integrated. Various refractories have been proposed in the past to meet these demands, but castable refractories are currently being widely used due to their ease of construction, labor savings, and long service life. - However, pitch-containing castable refractories are commonly used.

In this case, the pitch is softened, melted, and dispersed during drying, heating, or heating during use, and is then carbonized to obtain a refractory structure through carbon bonding. In addition, carbon produced through carbonization is difficult to wet with hot metal and slag, has high thermal conductivity, and has excellent oxidation resistance, so it is effective in improving corrosion resistance and thermal and structural spalling. be. Also,
Compared to other hydrocarbon resins, pitch also has the advantage of being inexpensive and having a high afterflame rate.

Focusing on this point, we have developed castable refractories for blast furnace gutters.
JP-A No. 60-215581 discloses that 80 to 250°C
Two or more pitches with different softening points within the range of 0.5
It is disclosed that the addition amount is 10% by weight.

[Problem to be solved by the invention]

However, the castable refractories for blast furnace troughs disclosed in the same publication still have unresolved issues in terms of countermeasures against smoke generation during high-temperature construction, securing of pot life, and explosion resistance during rapid heating.

This type of pitch-based castable uses coal tar-based pitch, which emits smoke during high-temperature construction and drying, and
-4 Emit harmful substances such as benzpyrene. Furthermore, if the fuming substance adheres to the skin, it may cause inflammation, which poses environmental hygiene problems that need to be resolved.

In addition, in order to prevent blocking during storage and to increase the amount of fixed carbon after carbonization, its softening point is 80 to 130.
Pitches in the °C range are widely used. Therefore, in castables that use this type of pitch, during rapid heat drying after construction, the pitch melted by heating fills the pores on the surface of the refractory and impedes air permeability, which prevents the moisture remaining inside from escaping. , the disadvantage is that cracks and explosions occur on the refractory surface.

These explosions and internal cracks occur when the internal temperature of the construction body when dry is 1
It is known that the maximum internal vapor pressure occurs between 10 and 130°C. Furthermore, this temperature range is the temperature range in which this type of pitch softens and melts and disperses inside the construction body, and the more refractory ultrafine powder is added and the construction is performed at a lower moisture content, the more likely this explosion or internal cracks will occur. The problem becomes more pronounced as the refractory structure becomes denser, the pore size becomes smaller, and the air permeability becomes lower.

Furthermore, during pouring construction of such castables, the water boils due to residual heat, and the reaction of the exothermic agent is accelerated by elution of soluble alkali components from the coagulant, etc., and a bubbling phenomenon occurs, causing separation of fine powder and coarse particles. The construction structure becomes fragile with high porosity and low strength, and its lifespan is short and requires frequent repairs.

An object of the present invention is to solve the above-mentioned problems of castable refractories for blast furnace gutters constructed in a high-temperature atmosphere.

[Means to solve the problem]

The castable refractory for blast furnace gutters of the present invention was completed based on the knowledge that the use of petroleum-based pitch as a pitch material can solve the above problems without impairing the advantages of pitch-based castable in any way, Softening point: 150-250°C based on 100% by weight of refractory raw material with particle size adjustment;
1 to 6 petroleum pitches with a particle size of 3 u or less, a fixed carbon content of 55% by weight or more, and a volatile content of 40% by weight or less
% by weight, and appropriate amounts of curing retarder 1, exothermic agent, flocculant, and peptizer are added.

Pitch with a low softening point generally has a low amount of fixed carbon, and because it softens and melts at low temperatures, it is more likely to crack or explode when it dries rapidly. Moreover, those with a softening point exceeding 250° C. have poor fluidity after thermal softening and poor dispersibility into the refractory structure, so they do not contribute to carbon bond formation and also deteriorate corrosion resistance. The coal-based pitch traditionally used is usually 15
Evaporation and decomposition begin at around 0°C, peak at around 400°C, and almost complete at 600°C, so those with a softening point of 150°C or higher have undergone some kind of thermal modification, have low volatile content, and are fixed. Although the amount of carbon is large, the viscosity when softened and melted increases, and it is not sufficiently dispersed inside the construction object, resulting in insufficient carbon bond formation and corrosion resistance.

This results in poor strength and wear resistance.

On the other hand, the petroleum-based pitch used in the present invention is made from asphalt, which is heat treated and near-blown to make it reformed and heavier, so it contains a lot of aliphatic hydrocarbons and has a high softening point. have characteristics. In addition, compared to coal-based pitch, less colored gas is generated during heating, and 3-
It has the advantage that the amount of 4-pentupyrene is 1710 to 1/20 and does not cause inflammation even if it adheres to the skin.

The petroleum pitch used in the present invention has a fixed carbon content of 55% by weight or more, a volatile content of 40% by weight or less, and generally has an H/C ratio in the range of 0.45 to 0.55 and a benzene-based pitch. Insoluble content 55-65%, quinoline soluble content 15-34%
Preferably. As described above, a large amount of fixed carbon and a large amount of penzole and quinoline soluble components generate less smoke and are advantageous for carbon bond formation.

There are two types of pitch used: powder and granular.
A spherical shape is preferable from the viewpoint of prevention of dust generation and fluidity of the refractory during kneading with water. From the viewpoint of dispersibility, the particle size is 3 ++
The temperature should be less than 100 yen to prevent dust generation.

From the viewpoint of preventing clogging of the refractory surface, it is better not to contain fine powder of 0.1+nm or less.

The amount of pitch used is 1 to 6% by weight based on the refractory raw material. If the amount is less than 1% by weight, sufficient carbon bonds cannot be formed, resulting in insufficient effects such as thermal shock resistance and corrosion resistance. If it exceeds 6% by weight, the explosion resistance during rapid heating will decrease due to the influence of volatile content, the porosity of the constructed body will increase during use, tissue defects such as shrinkage will easily occur, and the carbon content will increase. If the temperature is too high, the oxidation resistance of the refractory will deteriorate.

Furthermore, by adding a hardening retarder, the castable refractory of the present invention secures a pot life during hot construction, enables construction with an appropriate amount of water, suppresses the reaction of exothermic agents, and prevents bubbling. It is possible to obtain a compact, dense and homogeneous construction structure, and to solve the problems associated with conventional high-temperature hot construction.

A curing retarder that can be used is tannic acid.

Carboxylic acids such as tartaric acid, oxalic acid, malic acid, citric acid,
Alternatively, some additives that normally function as dispersants, such as boric acid, borax, borates, naphthalene sulfonic acid formalin condensate, and sodium phosphate, can be mentioned. Then, one type or a mixture of two or more of them is added at 0.01 to 0.
It is used in a range of 3% by weight. Although it varies depending on the type of curing retarder, if it is less than 0.01% by weight, there is no effect of curing retardation, and if it exceeds 0.3% by weight, it may deteriorate the fire resistance of the refractory, which is not preferable.

Examples of the exothermic agent include metal aluminum powder, metal aluminum-silicon alloy powder, aluminum-magnesium alloy powder, and the like.

The particle diameter of these metal powders should normally be 1 W or less, but from the viewpoint of reaction efficiency and dispersibility, powders of 0.2 W or less are preferable, and in order to not adversely affect fluidity, spherical shapes are preferred. Generally, flakes are not desirable. Further, if the amount added is less than 0.1% by weight, sufficient heat generation cannot be obtained, and the effect of preventing explosion during rapid heat drying is weak. A content of 1% or more is preferable because it promotes the bubbling phenomenon during hot construction, tends to destroy the structure of the constructed body, and also causes blistering or cracking of the constructed body due to the generation of a large amount of hydrogen gas. do not have.

As the coagulant, lime aluminate such as alumina cement is used. The appropriate amount of addition is 0.1 to 5% by weight based on the refractory aggregate. The amount used varies depending on the type of coagulant and refractory raw material used, but if it is less than 0.1%, the curing time becomes long, which causes problems in operation and tends to result in insufficient strength of the construction body. Moreover, if it exceeds 5% by weight, depending on the type of flocculant, the fire resistance and corrosion resistance of the refractory will deteriorate, and the curing time during hot construction will become shorter, causing operational problems.

The peptizer improves the dispersibility of the refractory fine powder and contributes to the fluidity of castable refractories in a shrub-like manner. In addition, the amount of soluble alkaline components eluted from the coagulant is suppressed, and the pot life is secured by suppressing coagulation. The types include, for example, one of the well-known deflocculants, such as inorganic salts such as sodium phosphate, sodium borate, and sodium carbonate, and organic salts such as sodium citrate, sodium tartrate, sodium polyacrylate, sodium sulfonate, and sodium humate. seeds or a mixture of two or more.
It is used in a range of 0.01 to 0.3% by weight. Outside this range, depending on the type of deflocculant used, the fire resistance of the refractory may deteriorate, which is not preferable.

Refractory raw materials include oxide refractory raw materials such as alumina, alumina-magnesia spinel, high alumina, zirconia, zircon, zircon chamotte, rockstone, silica, and fused silica, or silicon carbide, silicon nitride, and silicon nitride. One or more types selected from non-oxide refractory raw materials such as bare iron, carbon, and other carbides. The maximum particle size of the refractory raw material is about 5 to 10ml11, and it can be coarse, medium, fine,
Adjust to fine powder as appropriate.

In addition, when the amount of pitch added is reduced, scaly graphite, earthy graphite, artificial graphite, coke powder, carbon black, etc. can be used to supplement the carbon source. Furthermore, various fibers may be added to reinforce the construction structure.

〔Example〕

Example 1 An experiment was conducted to examine the effects of the type and amount of pitch on the structure of the constructed body during high-temperature construction and on the explosion resistance during subsequent rapid heat drying.

For refractory raw materials containing 20% by weight of silicon carbide of 1 mm or less, 10% by weight of ultrafine refractory powder, and the remainder consisting of coarse, medium, fine, and fine powder of fused alumina with a maximum particle size of 8 mm or less. , 0.5% by weight of metallic aluminum powder on the outside,
2% by weight of high alumina cement, 0.1% by weight of an organic dispersant, and 0.1% by weight of boric acid and borax were added. Coal-based pitch and petroleum-based pitch are added to the above blend.

As is clear from these results, by using petroleum-based pitch in Yanagawa Castable, which can be constructed with a low amount of water by adding refractory ultrafine powder, it is possible to prevent cracks in the construction body during high-temperature construction and to prevent rapid heat generation. It was possible to prevent drying defects.

Table 1 Test piece preparation conditions were as follows: Okegawa castable refractory was cast into a cast iron mold with a diameter of 100n++n and a depth of 200mm, filled with a protrusion rod, and then cured in an air bath at 300°C for 4 hours. The amount of kneading water was 5.0% external to the refractory material, and the flow value was 140-160 mm.

The rapid heat drying conditions were such that the above test piece was placed in a propane gas oven heated to 800°C, and after being left for 30 minutes, the presence or absence of explosions and internal cracks was observed.

Table 2: Quality Example 2 of Test Pinch Regarding the effect of adding exothermic agent and curing retarder, silicon carbide 1
mm or less 20% by weight, refractory ultrafine powder 10% by weight, petroleum pitch 1mm or less 3%, high alumina cement 2% by weight
To a refractory raw material consisting of coarse, medium, fine, and fine powder of fused alumina with the remainder having a maximum particle size of 8 mm or less, 0.1% of an organic dispersant was added as an extra layer. 0 to 0.5% by weight of metallic aluminum powder and 0 to 0.1% by weight of boric acid and borax are added to the above formulation. As is clear from these results, the addition of a heat-generating agent improves the explosion resistance during rapid heating, and the addition of a curing retarder secures pot life during high-temperature construction and prevents structural defects such as swelling and cracks in the constructed body. The preventive effect was confirmed.

Table 3 Test piece preparation conditions are 100mff1. Okegawa castable refractories were cast into a cast iron mold with a depth of 200 m, filled with protrusions, and then cured in an air bath at 150°C for 4 hours.

The amount of kneading water was 5.0% external to the refractory material, resulting in a flow value of 140-160 mm. The curing time was checked by poking the cast surface with a metal rod every 5 minutes.

The rapid heat drying conditions were as follows: The above test piece was placed in a propane gas oven heated to 800°C, and after being left for 30 minutes, the presence or absence of explosions and internal cracks were observed.

Example 3 The results of using the product of the present invention in the gutter of a medium-sized blast furnace are shown.

In the case of conventional products, during high-temperature construction with residual heat of 300°C or higher, smoke was generated severely, the amount of kneading water was required to be about 9%, about 2% more than during normal construction, and explosions sometimes occurred when drying.

In addition, the amount of iron passed between repairs was low at 30,000 to 40,000 tons, and there was a large amount of spraying repairs and a large amount of dismantling.

The product of the present invention did not emit smoke when applied under the same conditions, the amount of kneading water was only about 6%, and there was no explosion during rapid drying. In addition, the amount of iron passed between repairs was high at 40,000 to 50,000 tons, and the amount of spraying repairs and demolition was also reduced. As a result, the refractory unit consumption is expected to be reduced by about 30%.

〔Effect of the invention〕

The castable refractory for hot construction of blast furnace gutters of the present invention ensures a usable life during construction, uses an appropriate amount of water for construction, prevents bubbling, prevents skin irritation caused by pitch adhesion, prevents smoke generation, and generates harmful substances. It has excellent structural stability and corrosion resistance against hot metal and slag, which is comparable to cold-constructed structures.

A construction body with excellent wear resistance can be provided.

As a result, the useful life of the construction body is extended and the number of repairs is reduced. In addition, the amount of construction per time is reduced, making it possible to reduce the basic unit of refractories and the basic unit price. Furthermore, because the structure of the construction body is dense, it has superior oxidation resistance compared to conventional products and can be used as a base material for a long time. Therefore, the amount of dismantling is reduced, and the unit price of refractories is further reduced.

Claims (1)

[Claims] 1. 1 to 6 petroleum pitches having a softening point of 150 to 250°C, a particle size of 3 mm or less, a fixed carbon content of 55 weight % or more, and a volatile content of 40 weight % or less, based on 100 weight % of the refractory raw material whose particle size has been adjusted. A castable refractory for hot construction of blast furnace gutter, which is made by adding a curing retardant, a heat generating agent, a flocculant, a peptizer, etc.