JPS5833195B2 - refractory - Google Patents

Description

[Detailed Description of the Invention] [Technical Scope of the Invention] The present invention provides oxides, carbides, nitrides,
The present invention relates to a pourable refractory made by adding a dispersant and a flocculant to a refractory raw material made of one or more known refractory raw materials such as silicides, borides, and carbonaceous materials.

[Technical background of the invention]

As raw materials for these refractories, examples of oxides include alumina, beryllia, calcium oxide, magnesia, zirconia, zircon, silica, chromium oxide (chromite),
Dolomite, forsterite, spinel, cermet, etc.; carbides include titanium carbide, zirconium carbide, tantalum carbide, vanadium carbide, tungsten carbide, silicon carbide, etc.; nitrides include titanium nitride, zirconium nitride, vanadium nitride, boron nitride, Silicon oxynitride, silicon nitride, aluminum nitride, molybdenum nitride, etc., carbonaceous refractories include graphite, amorphous carbon, etc. In addition to the above, all refractory raw materials such as borides and silicides can be used as the refractories of the present invention. can be used.

In general, large amounts of alumina cement, high alumina cement, sodium silicate, and phosphate are used as binders for pouring refractories, but these are all expensive, and depending on the material, the binder and refractory aggregate may be mutually exclusive. There are major drawbacks such as the refractory material being unable to fully demonstrate its inherent fire resistance due to the reduction in heat resistance due to the reaction.

In addition, slip casting, vibration molding, etc. have traditionally been used as pour molding methods, but these materials do not have self-hardening properties, and a plaster frame or the like is used as a formwork for the purpose of hardening by moisture absorption. Things are difficult to dry and require drying under special conditions and for a very long time.

In order to improve these drawbacks, we are developing a pourable refractory by adding a dispersant and a coagulant to a refractory material made by adding fireclay to the refractory aggregate in order to give the refractory material fluidity and hardening properties. JP 50-127907),
Although the purpose was achieved, there are disadvantages in that the volume stability, fire resistance, and corrosion resistance are poor due to the use of fireclay.

[Purpose of the invention]

In order to improve these problems, the present invention eliminates the use of clay minerals in order to strengthen the matrix, and instead adds ultrafine refractory particles of the same material as the refractory aggregate, that is, an originally non-plastic refractory. It is used as a binder for pourable refractories.

In other words, even if a non-plastic refractory aggregate has a particle size on the order of a single micron or less, the particle surface becomes active, and naturally it has fluidity properties in an aqueous system, but its plasticity is also similar to that of clay. - In addition to exhibiting behavior very similar to aqueous systems, they discovered that when used for pouring, they have excellent sintering properties, and can be used without the use of binders, with a low amount of water, and with excellent sinterability. As a result of research into pourable refractories that exhibit fluidity and hardenability, the refractories according to the present invention have been completed.

[Structure of the invention]

The technical concept of the present invention basically applies the theory of dispersion and aggregation, and even if the raw material is a non-plastic refractory material, if it becomes extremely fine particles on the order of a single micron, it will be difficult to solve the problem in a plastic clay mineral-water system. The present invention is based on the discovery that similar dispersion and agglomeration properties can be obtained by applying the same properties.

That is, refractory powder such as the pourable refractory of the present invention -
The relationship between water and particles in an aqueous low-water dispersion system is divided into free water surrounding particles and included water existing within aggregated particles, depending on the dispersion state of the particles.

Free water exists, for example, as free water in a completely dispersed state of particles and is involved in fluidity.

On the other hand, encapsulated water exists as encapsulated water contained within aggregated grains, such as water in an agglomerated state, and does not contribute to fluidity.

Ultrafine particles of refractories are colloidal particles, and when dispersed in water, they have an electric charge, creating an electrical double layer on the surface of the particles, and their dynamic potential is MLill.
er and Abramson (1950), it is assumed that there is a zeta potential expressed by the following equation.

f=4"ed (where e is the surface density of charge, d is the thickness of the double layer, and D is the conductivity constant of the dispersion medium (water in this case).

) and When such ultrafine particles exist in water as colloidal particles, their properties are divided into hydrophilic sols and hydrophobic sols, and refractory particles are considered to be hydrophobic colloids, and suspended particles in a particle-water system. have charges on their surfaces and prevent particle collisions through mutual repulsion.

Originally hydrophilic sols are not affected much by the addition of small amounts of electrolytes and exhibit amphoteric properties depending on the pH in an electric field, whereas hydrophobic sols have a unilateral charge and exhibit only unilateral charge in an electric field. migrate and precipitate as influenced by the addition of small amounts of electrolyte.

The clay particles disclosed in JP-A-127907-1987, which the inventor previously filed, are essentially hydrophilic colloidal and are mostly negatively charged, and have the property of reacting sensitively to the addition of a small amount of electrolyte. are doing.

This is also the reason why the refractory ultrafine particles of the present invention, which is a hydrophobic sol, can be used as a pourable refractory with added dispersant and flocculant as in the present invention, similar to clay, which is a hydrophilic sol. Thoughtful.

Specifically, the raw materials used for the pouring refractories of the present invention include raw materials containing the compounds mentioned above in the form of oxides, such as silica stone, silica sand, siliceous materials such as fused silica, mullite, bauxite, sillimanite, and kyanite. , alumina materials such as sintered alumina and fused alumina, lowite, chamotte,
Alumina such as pottery stone, silica, zircon, zirconia, basic properties such as magnesia, spinel, chromium oxide,
Chromium such as chromite, carbides such as silicon carbide,
Carbides such as aluminum carbide and zirconium carbide, silicon nitride, etc.Nitrides include zirconium nitride, boron nitride,
Carbonaceous raw materials include nitrides such as aluminum nitride, carbonaceous materials such as coke, natural graphite, calcined anthracite, carbon bricks and electrode scraps, and all refractory materials such as borides and silicides. Use at least one or more of the following.

The refractory aggregate used in the present invention is prepared by adjusting the above-mentioned various raw materials to the required particle size, but as the binder, ultrafine particles of these refractories are used, and in order to determine the particle size of the ultrafine particles, The most common alumina and magnesia were selected as the refractories used as raw materials in the present invention, and the particle size at which they were dispersed in water to form a sol was tested.
The practical thickness of ordinary colloid particles is 0.2μ.
However, as a result of tests on the two representative types of ultrafine particles of the present invention, 100μ or less, IOμ or less, and 1μ or less, ultrafine particles of IOμ or less are considered to be the bond of the present invention. It has been confirmed that the particles can be used as a sol for drugs, and ultrafine particles with a size of 10μ or less are used in all the following experiments.

The essence of the flocculant that is added to the sol of these refractories to cause agglomeration and the dispersant that is used to disperse them is that in the electric double layer at the particle boundary in the particle-water system mentioned above, the effect of the dispersant is primarily to increase the particle ζ Increase the potential, expand the electrical double layer,
The second effect is to increase the interparticle rupture force and to make the coagulated ions present into insoluble salts.On the other hand, the effect of a flocculant is in contrast to that of a dispersant (lower the electric potential and reduce the electrical double layer that has been formed). By compressing the particles, the attractive force between the particles is increased and the particles coagulate.

The refractory of the present invention uses water as a medium to disperse refractory particles by adding a dispersant to maximize free water.
It provides fluidity with a minimum amount of water, delays the effect of a flocculant added separately, causes the particles to coagulate, and incorporates water into the aggregated particles as included water, thereby imparting hardenability to the material.

The refractory ultrafine particle sol used as the refractory binder of the present invention is a hydrophobic sol, so its surface tension is the same as that of water, which is a dispersant, and clay is almost the same as water. Since fluidity is created by adding water, clay is not required as a dispersant, but it is a characteristic of pourable refractories that it is necessary to provide fluidity by adding as little water as possible.

The dispersant of the present invention is added for this purpose,
Provides fluidity with a small amount of added water, giving it the ability to easily pour into the gap between the furnace shell and frame material.

However, this method alone cannot remove the frame due to the fluidity of the refractory composition.

For this purpose, we give cohesiveness to the dispersed refractory raw material sol,
In order to form a refractory lining by coagulating the refractory composition, a flocculant is added at the same time or after construction to give the refractory raw material sol both fluidity and plasticity.

Therefore, the dispersant and flocculant used in the present invention only play an auxiliary role, and the refractory composition is only combined with the refractory raw material to form a refractory lining, and when used in a furnace, it becomes a refractory plastic. Similarly, when a bonded refractory is sintered, the structure changes continuously from the heated side to the cold end, and it is necessary to form a refractory structure such as a castable refractory without a weak zone. There should be no additives or amounts used that inhibit, ie reduce, fire resistance.

Regarding the effects of dispersion and agglomeration in this case, the so-called Hofmeister series (Hofmeister series)
es).

For cations H+〉A13+〉Ba2+〉Sr2+〉Ca2+〉Mg
2+ aggregation>Cs ”>Rb +>NH4+>K +>N a +
For L i + dispersed cations 804'>F>NO3>cl>Br>I>large cohesive force CN5->PO43->P 2074->CO3" -
> Low OH cohesive force As can be seen from the above permutation, dispersants containing monovalent cations are effective, and these phosphates, silicates, carbonates, etc. alone or in combination can be used in fireproof compositions. The amount used varies depending on the properties of the refractory raw material used and the type of dispersant used.

In this case, if the amount added is 0.5% or more, the fire resistance of the fire resistant composition may be affected depending on the content, resulting in a disadvantage in terms of durability.

For example, as a dispersant, one or two types of well-known dispersants such as acidic and alkali phosphates such as lithium, sodium, potassium, and ammonium, inorganic salts such as silicates, carbonates, organic acid salts, and surfactants are used. Mixtures of the above can be used.

In an ultrafine particle-water system of a non-plastic raw material, the particle interface is positively or negatively charged depending on the raw material used, and it is necessary to select a dispersant depending on the raw material constituting the ultrafine particle.

In some cases, hydrogen chloride or organic acids may be used as dispersants.
Acidic phosphoric acid may also be used effectively as a dispersant in some cases.

The amount of dispersant used is determined by the amount of ultrafine particles used (at which the potential becomes extremely thick).

As the flocculant to be added, the cations are Ca,
As divalent and trivalent ions such as Mg and A1, and anions, inorganic flocculants such as SO4, NO3, and Cl and other organic flocculants can be used, and generally these have low solubility in water. Since it is large, sufficient care must be taken in the addition method.

Proteins with a high dissolution rate in water, such as gelatin and casein, should be treated with flocculants.

Plant rubbers such as gum arabic, cellulose pastes such as CMC, PVA, etc. are coated as a film, and the fireproof composition and dispersant are mixed in a dry state, and when used, water is added and mixed to coagulate. It is possible to take measures to delay the action of the agent.

In addition, materials such as calcium aluminate and calcium sulfate, which dissolve gradually in water and require time to ionize, are mixed with the fireproof composition and dispersant in a dry state, and then mixed with water by pouring water at the time of use. As a result, it is effective to allow the dispersant to function as a flocculant after pouring without inhibiting the function of the dispersant during pouring, and this is the most effective method for implementing the present invention.

Like the dispersant, the amount of flocculant used varies depending on the characteristics of the refractory material used and the type of dispersant used.

Now, taking the use of calcium aluminate as an example,
When mixed with water, calcium aluminate becomes C.
It takes time for a2+ to elute, and the pouring work of the refractory composition can be completed with sufficient time without being affected by calcium ions eluted during dispersion.

Ca0A1203+naq-+Ca2++A1203n
H20 (sol) After that, after a sufficient amount of calcium ions have been eluted from the construction body,
This causes the refractory composition to become highly viscous and lose its fluidity, making it possible to remove the frame.

In this case, the amount of calcium aluminate added must be within a range that does not affect the properties of the refractory composition, as described above.

That is, the flocculant needs to dissolve gradually after construction without impeding the fluidity of the material during construction, and to impart cohesiveness to the material when necessary.

〔Effect of the invention〕

In the pouring process, water is added to the above-mentioned mixture to give it fluidity, and the refractory is poured into the frame provided in the furnace shell and the space inside the furnace shell to fill it.

The water-added mixture has good fluidity with a low amount of water due to the action of a dispersant that is uniformly added and mixed into the mixture, which makes pouring work easy, and the mixture has good fluidity with a low amount of water. , it is possible to obtain a structure with a uniform, close-packed structure.

After pouring, the lining material still has fluidity, so
The flocculant that is uniformly added and mixed into the compound gradually dissolves over time, causing a flocculating effect, causing the construction material to gradually flocculate, and finally having sufficient curing properties to allow the frame to be removed. It gives

In addition, when applying vibration to the construction body using a vibrator during casting construction, construction can be performed with an even lower amount of water.

Although the refractory of the present invention has been described above as an example of a monolithic refractory, it goes without saying that the refractory of the present invention can be applied not only to this but also to shaped refractories such as large blocks, ordinary bricks, etc. It is.

〔Example〕

Experiments of the present invention and their results are described below.

<Example 1> Sintered alumina was used as the refractory aggregate.

Aluminum sulfate O,X coated with pyrophosphoric acid Sog O,I weight (outer weight) as a dispersant and glycerin, stearic acid, etc. as a flocculant, in a refractory material containing particles with a particle size of 10μ or less in a range of 3 to 35% by weight. A material is prepared by adding and mixing a weight factor (outer hook), and the construction is carried out using the appropriate amount of water for the pouring method (the amount of water required to create a state of natural flow), and the sintered alumina ioμ or less is made as shown in the drawing. Content rate (
The relationship between the amount of water added (weight %) (horizontal axis) and the amount of added water (weight %) (vertical axis) was obtained.

If the amount of fine powder of 10μ or less in the compound is less than 5% by weight, the target amount of added water for castable refractories is 10%.
Even if heavy, upwind water volume is used, sufficient fluidity cannot be obtained (indicated by ← in the diagram), and if a large amount of water is used, breathing occurs on the surface of the construction object (water oozes out on the surface and the surface becomes unsightly). ) and was defective.

However, all the constructed bodies were firmly cured after 24 hours and were in good condition.

From the above experiments, it was found that the required amount of particles of 10μ or less in the formulation must be at least 5% by weight, and cracks were observed during drying in formulations containing ultrafine powder up to 30kg. (indicated by medium →) was found to be outside the appropriate addition range.

Accordingly, the appropriate amount of the ultrafine particle portion is 5 to 300% by weight, and therefore the amount of the refractory aggregate is 95 to 700% by weight.
Become.

<Example 2> A refractory material prepared by adding 20% by weight of ultrafine powder of sintered alumina containing 700% by weight of 10 μ or less to 80% by weight of sintered alkina whose particle size was adjusted as a refractory aggregate (1% by weight in the blend)
0.1% by weight (outer weight) and 1 and 2% by weight (outer weight) of various dispersants and various flocculants in 0 μ or less (18 weight percent)
Added and mixed materials were prepared (Tables IA1 to IA6), and construction was carried out using an amount of water suitable for the pouring method (moisture necessary to achieve a naturally flowing state), and the results shown in Table 1 were obtained.

All of them showed good fluidity with a low water amount of less than 10 weight range, and after drying of the cured products, dense structures with apparent porosity of 20% or less were obtained.

<Example 3> Refractory aggregate 85-80 made of a combination of one or more of silica stone, chamotte, calcined bauxite, synthetic mullite, magnesia, chromite, fused alumina, zircon, carbon, and silicon carbide whose particle size has been adjusted in advance For the weight officer,
15 each of ultrafine particles of silica, calcined alumina, zircon, chromite, silicon carbide, containing 70-92% by weight of ioμ or less
A material was prepared by adding and mixing 1 and 2% by weight of activated alumina as a coagulant, and 1 and 2% by weight (outer part) of activated alumina as a flocculant. 11) Perform construction with the appropriate amount of water for the pouring method (moisture required to achieve a naturally flowing state), and
The results shown are obtained.

All of them showed good fluidity with a low water amount of less than 10 weight range, and it was possible to obtain a dense structure with an apparent porosity of approximately 20 coefficients or less after drying of the cured product.

As is clear from the results of Experimental Examples 1, 2, and 3, the amount of less than ioμ contained in the formulation is at least 5 ioμ from the viewpoint of fluidity.
% by weight or more is required.

Further, the upper limit of the amount of ultrafine powder of 10 μm or less contained in the composition is 300% by weight, and adding more than that is not preferable because it may cause microcracks to occur during drying after application.

[Brief explanation of the drawing]

The figure is a graph showing the relationship between the weight width of the content of sintered alumina of 10μ or less (horizontal axis) and the weight width of added water amount (vertical axis) in the present invention.

Claims (1)

[Scope of Claims] 1. One or more kinds of oxides, carbides, nitrides, silicides, borides, and carbonaceous substances having a particle size composition containing 5 to 30 by weight of ultrafine powder with a particle size of 10 μ or less, and A pourable refractory characterized by being made by adding a dispersant and a flocculant to a refractory raw material that does not contain binding clay. 2. The pourable refractory according to claim 1, wherein the flocculant is added after the dispersant is added. 3. The pourable refractory according to claim 1, wherein the flocculant is provided with a coating layer that delays the reaction of gelatin, casein, vegetable rubber, cellulose glue, PVA, or the like. 4. The pourable refractory according to claim 1, wherein the dispersant is added as a mixture that has been mixed with the refractory composition in a dry state in advance.