JPS6154743B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composition that provides an acid- and water-resistant refractory material, and more particularly, the present invention relates to a composition that provides a refractory material that is resistant to acids and water, and more particularly to a composition that, upon curing, produces a refractory material suitable for use in contact with hot gases containing acidic corrosive gases such as sulfur oxides. The present invention relates to a composition for providing. Heating furnaces, hot blast furnaces, oil cracking furnaces, ceramic firing furnaces, incinerators, etc. usually use heavy oil containing sulfur as fuel, and as a result, various parts of the furnace are exposed to combustion gas containing sulfur oxides. The Rukoto. For this reason, for the inner walls of furnaces, steel shells lined with acid-resistant refractories have conventionally been used. In addition, recently, for the purpose of energy saving,
Ceramic fiber insulation modules are installed and constructed on the inner wall of a furnace by various methods. For example, such a ceramic fiber insulation module can be attached directly to the steel shell using a fire-resistant adhesive, or it can be bonded to a wire mesh using a fire-resistant adhesive to form an integrated product and then attached to the steel shell. It is attached to the inner wall of the furnace by fixing it to the skin with studs, etc. As mentioned above, fire-resistant adhesives used for such applications include acidic or neutral adhesives such as silica, waxite, syamoto, mullite, and alumina, considering that they will be used in an acidic gas atmosphere. An acid-resistant refractory composition has been used, which is composed of an acid-resistant refractory raw material and a binder whose main component is sodium silicate. In addition, in order to improve its acid and water resistance, hardening agents used with sodium silicate include sodium silicate, aluminum phosphate,
Zinc oxide, organic acids, organic esters, etc. have been used or proposed. However, there is one major problem with attaching ceramic fiber insulation modules using refractory adhesives as described above. That is, since the ceramic fiber insulation material has an extremely excellent insulation effect, the temperature of the iron skin underneath it often drops to below the dew point of the sulfur oxide in the atmospheric gas. As a result, strongly acidic sulfur oxides such as sulfuric acid condense on the fire-resistant adhesive layer that joins the iron skin and the ceramic fiber insulation module.
As a result, the fire-resistant adhesive layer eroded and became brittle, resulting in problems such as the ceramic heat-insulating module bonded with the fire-resistant adhesive falling off. In addition, the fire-resistant adhesive used for this purpose must have the property of maintaining fluidity suitable for the application for a relatively long time when mixed with water, that is, it must have good workability. Conventional fire-resistant adhesives have had problems in this respect as well. In view of the above-mentioned circumstances, an object of the present invention is to provide an acid- and water-resistant fireproof composition that exhibits durability even against strong acid aqueous solutions and has excellent suitability as a fireproof adhesive. As a result of research for the above-mentioned purpose, the present inventors have discovered that a hard fire can be achieved by using a binding medium consisting of a water-soluble alkali borosilicate or an equivalent mixture thereof, and a combination of silicon polyphosphate and alkali silicate in a specific ratio. It was later discovered that a composition that provides a refractory with excellent acid and water resistance can be obtained. In addition, a composition made of a combination of this binding medium and a refractory raw material has good workability when mixed with water. The acid-resistant and water-resistant refractory composition of the present invention is based on the above-mentioned knowledge, and more specifically, the acid-resistant and water-resistant refractory composition is based on the above-mentioned knowledge, and more specifically, it contains 100 parts by weight of a refractory raw material and 10 to 10 parts of a binding medium made of a combination of the following components (A) to (C). It is characterized in that it consists of 100 parts by weight. (A) 35 to 60% by weight of an aqueous alkali borosilicate or an aqueous alkali borosilicate equivalent consisting of a combination of an aqueous alkali silicate and an alkali borate soluble in an aqueous alkaline solution; (B) 10 to 25% by weight of a silicon polyphosphate; % by weight, and (C) 10-45% by weight of alkali silica. Components (A) to (C) constituting the binding medium in the composition of the present invention are characterized by containing a silicic acid content or a silicon content, which improves the acid resistance of the cured composition.・It is thought that this contributes to improved water resistance. The composition of the present invention is a composition in which the above-mentioned components are mixed with water and cured during the process of coating and drying the mixture on the inner wall of a furnace, for example, to form a cured composition.
(A), such as alkali borosilicate, is used as a main binder, and component (B), silicon polyphosphate, is used as a curing agent.
Ingredient (C), alkali silicate, is used as a curing aid.
It is thought that each of them works. The present invention will be explained in more detail below. In the following description, "%" and "part" are based on weight unless otherwise specified. The refractory raw materials used in the present invention are those that are acidic or neutral and are used as ordinary refractory raw materials, such as silica, silica, silica, mullite, alumina, etc. used in or as a mixture. In addition, the maximum particle size of refractory raw materials is 3 mm or less, and the average particle size is 0.3 mm.
The following powder form is preferable in order to provide a fire-resistant adhesive with good workability. The refractory composition of the present invention comprises such a refractory raw material and a binding medium consisting of the three components (A) to (C) above. Binding medium component (A) consists of a water-soluble alkali borosilicate or its equivalent. This water-soluble alkali borosilicate provides a superior binding effect when combined with the curing agent component (B) described below, compared to conventional alkali silicate/binder base ingredients, and when made into a water-miscible composition, It has the function of preventing early gelation or partial gelation of the composition and maintaining a highly fluid state (that is, providing a water-miscible composition with a suitably long pot life). Alkali borosilicate _{is SiO2} : _M2O : _B2O3
(M is alkali metal) molar ratio is 1:0.55~
0.80: Preferably in the range of 0.03 to 0.3.
When the M ₂ O/SiO ₂ molar ratio is outside the above range, the adhesive strength when using the composition of the present invention as an adhesive tends to decrease. Also, the B ₂ O ₃ /SiO ₂ molar ratio is
If it is less than 0.03, the water resistance of the cured composition will decrease and the stability of the water-miscible composition will also become poor.
On the other hand, even if the B ₂ O ₃ /SiO ₂ molar ratio exceeds the above range, no particular advantage will be obtained and it will be economically disadvantageous. A more preferable B ₂ O ₃ /SiO ₂ molar ratio is 0.05
~0.25. If the water-soluble alkali borosilicate is obtained in advance as a single substance, it may be used, but in the composition of the present invention, it is formed in situ when forming the water-miscible composition. That's fine. Therefore, in the composition of the present invention, a combination powder of a water-soluble alkali silicate and an alkali borate soluble in an aqueous alkali solution can be used instead of the water-soluble alkali borosilicate, and is even more preferable. By using this combination, all the components can be blended in powder form in one package, and just before use, only the required amount of water can be added to form a water-miscible composition and ready for use immediately. That is, there is an advantage that measuring and mixing of each component is not necessary upon final use. Any alkali silicate and alkali borate can be used as long as they provide water-soluble and alkaline aqueous solution-soluble powders and provide the above-mentioned SiO ₂ :M ₂ O:B ₂ O ₃ molar ratio. for example,
An alkali silicate having a M ₂ O/SiO ₂ molar ratio of 0.38 to 0.77 and an alkali tetraborate may be combined so that the B ₂ O ₃ /SiO ₂ molar ratio is 1:0.03 to 1:0.3. As the alkali metal species, Na is preferred, but K can also be used. Further, the alkali silicate and the alkali borate may be powders that contain water in the form of hydration water or crystallization water to the extent that they are powders. The particle size of these powders is preferably 100 μm or less for ease of dissolution. Next, silicon polyphosphate as the second component (B) of the binding medium is a compound in which the silica component is bonded to the condensed phosphoric acid component in the form of a cation, and among various phosphates, the phosphoric acid component is It is known to have particularly excellent sustained release properties (US Pat. No. 4,018,616). In the present invention, this water-soluble borosilicate alkali component is used as a curing agent component.
Use in combination with (A). More specifically, the silicon polyphosphate preferably has a molar ratio of P ₂ O ₅ :SiO ₂ ranging from 1:1.8 to 1:3.6, particularly from 1:2.0 to 1:3.3. That is, if the molar ratio of the phosphoric acid component (P ₂ O ₃ ) is smaller than the above range, the desired curability of the water-miscible composition cannot be obtained, and a cured product with low mechanical strength tends to be obtained. be. Moreover, if this molar ratio is larger than the above range, early gelation or partial gelation of the water-miscible composition will occur. In order to prevent early gelation and partial gelation, and to act on the alkali borosilicate to uniformly and firmly harden the composition, this silicon polyphosphate must be
It is important to have sustained release properties for phosphoric acid. In this regard, the silicon polyphosphate used in the present invention has an initial elution volume (b) of 3 ml or less and an average hydrolysis rate constant (a) of 0.015 ml/min or more, expressed by the following formula: Y=a・t+b (However, in the above formula, Y is 1 g of silicon polyphosphate dispersed in 100 ml of pure water with stirring, and a 1/10 normal NaOH aqueous solution so as to maintain the pH of the dispersion at 10.5. represents the cumulative addition amount (ml) of the NaOH aqueous solution over the elapsed time t (minutes) when the solution is gradually poured, and in the above formula, a and b are the slope and Y-axis intercept, respectively, as a result of plotting Y-t. ). A particularly preferable range is that b is 2.5 ml or less and a is 0.2 to 2.0. Details of the preparation and properties of such sustained release phosphoric curing agents are also described in the aforementioned US Pat. No. 4,018,616. Next, an important feature of the present invention is that an alkali silicate is used as the third component (C) of the binding medium. This alkali silicate is a well-known substance in itself as a curing agent for alkali silicate binders, but in the present invention,
In order to improve the fluidity of the water-miscible composition, it is used as a curing aid in combination with a silicon polyphosphate curing agent. In other words, by using a combination of alkali silicate and silicon polyphosphate as a hardening agent, good fluidity can be maintained not only at the initial stage of mixing with water but also after a considerable period of time has passed after mixing. This makes it possible to significantly improve the workability of coating for joining ceramic fiber modules to the inner wall of the furnace. More specifically, in the present invention, sodium silicate (Na ₂ SiF ₆ ), potassium silicate (K ₂ SiF ₆ ), etc. are used as the alkali silicate, and these are generally fine powders, especially particles with a particle size. is used in the form of a powder of less than 60 microns. It is also important for this silicate to be in the form of an alkali salt from the viewpoint of improving fluidity. For example, when an alkaline earth metal salt such as barium silicate is used, the fluidity when made into a water-miscible composition is rather important. There is a tendency for the performance to decrease significantly. In the binding medium of the present invention, the above components (A) to (C)
, based on dry product at 110℃, alkali borosilicate etc. (A) 35-65%; silicon polyphosphate (B) 10-25%
%, especially 12-20%; alkali silica (C) 10-45
%, particularly preferably 20 to 40%. That is, if the amount of silicon polyphosphate is greater than the above range, the fluidity of the water-miscible composition tends to decrease, and if it is less than the above range, the composition is difficult to solidify, and the strength and acid resistance of the cured product decrease. Also, water resistance tends to decrease. Furthermore, if the amount of alkali silica (C) is less than the above range, the fluidity of the water-miscible composition tends to decrease, while if it is more than the above range, acid resistance and water resistance decrease, resulting in a cured product. There is a tendency for blooming phenomenon to occur. The composition of the present invention is composed of 10 to 100 parts of the above-mentioned refractory raw material and 10 to 10 parts of the binding medium consisting of the above-mentioned components (A) to (C).
It is made by combining 100 parts. If the binding medium is less than the above range, the strength and acid/water resistance of the cured product will be insufficient, and if it is used in excess of the above range, the composition will shrink significantly during curing and heat reception, causing cracks in the cured product. It is also undesirable because it causes a decrease in fire resistance. The refractory composition of the present invention basically consists of the above-mentioned refractory raw material and a binding medium consisting of components (A) to (C), but if necessary, strength reinforcing agents such as aluminum phosphate, Aluminum compounds such as aluminates and alumina cement; various synthetic resins such as phenolic resins, urea resins, and melamine resins can be blended up to 20 parts per 100 parts of refractory raw materials; Inorganic fibers and/or organic fibers such as hemp, rayon, Tetoron, etc. can be added as necessary. The composition of the present invention has the property of curing at room temperature by adding an appropriate amount of water. The amount of water is
It is preferable to add 10 to 50 parts to 100 parts of the refractory raw material from the viewpoint of workability of the resulting water-miscible composition and strength, acid resistance, and water resistance of the cured product. When the amount of water is less than 10 parts, workability is poor, and when it is more than 50 parts, the strength of the cured product is reduced. As mentioned above, the water-miscible composition obtained by adding water to the composition of the present invention has the property of curing at room temperature, but after curing, drying and heat treatment at 100°C or higher can improve acid resistance and water resistance. A cured product with further improved properties can be obtained. As mentioned above, the refractory composition of the present invention has excellent suitability as an inorganic refractory adhesive used for attaching ceramic fiber insulation modules for lining industrial furnaces used in oxidizing gas atmospheres. However, in addition to this, its excellent acid resistance and
It is suitable as a general inorganic adhesive or as a wall coating material due to its water resistance, fire resistance, and workability.
Furthermore, if necessary, it can be molded and used as a molded refractory material. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples. Reference Example In this reference example, the coupling medium used in the following examples will be explained. In the following examples, abbreviations are used for the components of the coupling medium as described below. SSB: Water-soluble alkali borosilicate or a combination powder of water-soluble alkali silicate and alkali borate soluble in aqueous alkali solution (Component A) PSP: Powder of silicon polyphosphate (Component B) SAF: Alkali silicate (Component C) ) (A) Preparation of SSB The silicic acid component used as a raw material is a highly reactive silica powder (manufactured by Mizusawa Kagaku Kogyo Co., Ltd.) that has a latent layer structure and is produced by sufficiently acid-treating acid clay. Silton A") was used. The main components of this silica powder (Silton A) on a dry matter basis were as follows. _SiO2 92.5%, _{Al2O3 2.68} %, _{Fe2O3 0.24}
%, MgO0.13%, CaO0.13%, scorching loss 3.38
%. Add 3 kg of water to 1 kg of the silica powder, add 0.6 kg of solid caustic soda (NaOH), a commercially available reagent, and further add 0.2 kg of sodium borate (Na ₂ B ₄ O ₇・5H ₂ O), a commercially available reagent, to give a total When stirred thoroughly and homogeneously, an exothermic reaction occurred, and the whole became a liquid, although slightly opaque. This liquid was separated with a cloth to obtain a transparent liquid, and the liquid was concentrated to dryness at about 60°C to prepare a powdery water-soluble sodium borosilicate (SSB-1). The analytical composition of SSB-1 prepared here was as follows. _SiO2 59.2%, _Na2O32.6
%, _{B2O3 3.1} %. Further _, SSB-2 was prepared in the _{same manner} as above, except that potassium borate ( _K2B4O7.5H2O ) was used instead of sodium borate. Its analytical composition was as follows. _SiO2 59.0%, _Na2O29.9 %,
_K2O2.5 %, _{B2O3 2.9} %. (B) Preparation of PSP As powdered silicon polyphosphate, silicon polyphosphate was prepared by the method shown below in accordance with the method described in the specifications of two patents (Japanese Patent Publication No. 46-40866 and Japanese Patent Publication No. 46-42711). Two types of PSP-1 and PSP-2 were prepared and used. (B)-1 PSP-1 Commercially available industrial sodium silicate (JIS No. 3 product,
Na ₂ O 9.63%, SiO ₂ 28.9%, molar ratio SiO ₂ /
Na ₂ O = 3.1) was selected and first, partial desodification was performed using a cation exchange resin. After diluting the above sodium silicate so that the silicate content (SiO ₂ ) concentration is 0.25 molar, it is brought into contact with a cation exchange resin, and the pH of the sodium silicate solution is 10.0.
Soda ions were removed so that The composition of the recovered sodium silicate solution with a pH of 10.0 was as follows. _SiO2 1.72g/100ml,
Na ₂ O 0.091g/100ml, SiO ₂ /Na ₂ O molar ratio
19.5. Commercially available industrial phosphoric acid (JIS grade 1 85.0% H ₃ PO ₄ ,
(specific gravity 1.69) was mixed with the above SiO ₂ /P ₂ O ₅ molar ratio of 2.2, and then the whole was heated and concentrated with stirring to obtain a dry product. After crushing the dried material obtained here, using a rotary kiln,
The mixture was fired at 950°C for 120 minutes, pulverized, and then classified using a 200 mesh sieve to prepare silicon polyphosphate powder (PSP-1). (B)-2 PSP-2 The easily reactive silica powder (Silton A) used as the raw material for SSB preparation in section (A) was used as the silicic acid raw material. This easily reactive silicic acid (Silton A)
Using the commercially available industrial phosphoric acid mentioned above,
Mix the two so that the molar ratio of SiO ₂ /P ₂ O ₅ is 3.0, granulate them into granules with a diameter of about 0.5 mm to 2 mm while stirring, and then granulate them once using a rotary kiln.
After calcination for about 30 minutes at 250-300℃, continue
The mixture was calcined at 950° C. for about 30 minutes, then crushed using a hammer impact type crusher (manufactured by Tokyo Atomizer Co., Ltd.) and classified using a 200 mesh sieve to prepare silicon polyphosphate powder (PSP-2). The physical properties of the silicon polyphosphate prepared above were as follows. PSP-1: SiO ₂ /P ₂ O ₅ molar ratio 2.2, average hydrolysis constant (a) 0.035, initial hydrolysis amount (b) (ml) 1.5, in the Y=at+b formula determined by the method described in the text. PSP-2: SiO ₂ /P ₂ O ₅ molar ratio, 3.0, average hydrolysis constant (a) 0.026, initial hydrolysis amount (b)
(ml) 1.5. (C) SAF SAF is a commercially available reagent, sodium silica
-1) and potassium carbonate (SAF-2)
was used as is. Five types of binding media (Samples 1-1 to 1-5) were prepared by blending the above three components in the proportions shown in Table 1 below.
I got it.

[Table] The inorganic binding media (5 types) shown in Table 1 are
Each component was used and kneaded in a mixer according to the composition shown in Table 2, and the resulting water-miscible composition was mixed at 40×40×
It was poured into a 150mm metal frame. Table 2 shows the properties of cured samples (1 to 8) prepared by unframed and dried at 105°C for 24 hours after curing at room temperature, together with the properties of conventional products (samples 9 to 11). In the water resistance test, the cured product sample was immersed in cold water at 15°C and hot water at 80°C for 24 hours, and then the bending strength was measured and compared with the value before immersion. In addition, for the acid resistance test, the cured product sample was placed in a 0.2 molar sulfuric acid aqueous solution.
It was immersed for 24 hours, and the bending strength after immersion was measured. As shown in Table 2, the products of the present invention have excellent water resistance and sulfuric acid resistance, and show almost no decrease in strength due to immersion. On the other hand, it can be seen that the conventional product has poor water resistance and sulfuric acid resistance, and its bending strength significantly decreases after being immersed for 24 hours.

【table】

[Table] Next, each component was kneaded in a mixer according to the composition shown in Table 3, and the resulting water-miscible composition was mixed at 40×40×
It was poured into a 150mm metal frame. After curing at room temperature,
The properties of a cured sample prepared by removing the frame and drying at 105°C for 24 hours were compared with those of a conventional product, and the results are shown in Table 3. Table 3 shows that the cured samples of the products of the present invention have excellent water resistance, sulfuric acid resistance, and hydrofluoric acid resistance, and have little strength loss due to immersion. On the other hand, it can be seen that the strength of the cured samples of conventional products was significantly reduced by immersion, and especially in the case of hydrofluoric acid, the samples showed a disintegration phenomenon.

【table】

【table】

Claims (1)

[Claims] 1. An acid-resistant and water-resistant fireproof composition comprising 100 parts by weight of a refractory raw material and 10 to 100 parts by weight of a binding medium made of a combination of the following components (A) to (C). . (A) 35 to 60% by weight of a water-soluble alkali borosilicate or a water-soluble alkali borosilicate equivalent consisting of a combination of a water-soluble alkali silicate and an alkali borate soluble in an aqueous alkali solution; (B) silicon polyphosphate 10 ~25% by weight, and (C) 10-45% by weight of alkali silica. 2. The composition according to claim 1, wherein the refractory raw material is an acidic or neutral refractory raw material selected from silica, pyrite, mullite, and alumina. 3 The molar ratio of SiO ₂ :M ₂ O:B ₂ O ₃ (in the formula, M represents an alkali metal) of component (A) is 1:0.55 to
0.80: The composition according to claim 1 or 2, wherein the ratio is 0.03 to 0.3. 4. The composition according to any one of claims 1 to 3 _, wherein the _P2O5 : _SiO2 molar ratio in silicon polyphosphate (B) is 1:1.8 to 3.6. 5 Silicon polyphosphate (B) has an initial elution amount (b) expressed by the following formula Y=at+b of 3 ml or less, and an average hydrolysis rate constant (a) of 0.015 ml/min or more (however, in the above formula, Y is , elapsed time t (minutes) when 1 g of silicon polyphosphate is dispersed in 100 ml of pure water with stirring, and 1/10 normal NaOH aqueous solution is gradually poured in to maintain the pH of the dispersion at 10.5. The above formula represents the cumulative addition amount (ml) of the NaOH aqueous solution in Y-
5. A composition according to any one of claims 1 to 4, having a value of (given as a result of a plot of t).