JPS5820908B2 - Fire-resistant mixture composition and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to a dry refractory blend composition having a long shelf life of 18 months or more and a process for making the same, and more particularly to a single package phosphate-binding composition. The present invention relates to a high intensity mixing method for producing dry refractory mixed compositions and mixtures thereof.

The term "refractory specialty" is often used to describe a wide range of unbonded refractories, ie, those that are not preformed, such as molded bricks.

Refractory special products are typically used in unitary refractory structures where the refractory is provided in situ to form an integral, seamless structure.

Many refractory specialty products are commonly manufactured, packaged, and shipped as mixtures (ie, blends of materials formulated in a certain manner).

These mixtures may be used in a substantially wet or plastic state requiring no further processing for use, or in a dry state requiring conditioning and mixing with a liquid, or with or without the addition of a liquid prior to use. Two packages (one dry, one wet) that require mixing of packaging ingredients without
It can be manufactured and transported as a system.

Thus, refractory specialty mixtures used for integral refractory structures can be modified in one of two ways: by the conditions in which they are transported (e.g., plastic, dry and wet); can be further differentiated by the technique of application (e.g., driving, spraying, pouring, and troweling) or both.

Wet refractories are substantially wet to the touch; conversely, dry refractories are substantially dry to the touch.

Plastic refractories are refractory materials generally prepared with water to a strong plasticity that can be extruded and have the desired consistency without further preparation to form a unitary structure. be.

Plastic refractories are often cast in place.

The driving (or tamping) mixture may be limited to:
The crushed and sized refractory aggregates are made more substantial with an amount of other materials added to promote processability and cohesion and cannot be extruded, but a single It has suitable properties to allow it to be driven in place to form a structure.

Therefore, the casting mixture is usually transported in a wet state and does not require further addition of liquid for the application technique.

In contrast, pouring mixtures generally consist of refractory granules that, after addition of a suitable liquid, are poured into place to form a refractory shape or structure that becomes hard through chemical action. is defined as a combination of a suitable binder and a suitable binder.

Pouring compositions are generally poured or filled into place.

Refractory blend compositions using high percentages of various inert refractory aggregates, particularly alumina, and containing phosphoric acid or phosphates are known in the art.

When using phosphoric acid or phosphates to generate chemical bonds, premature hardening and loss of processability often occur and these limit the shelf life of the mixture.

The premature and uncontrolled pre-curing of these phosphate-binding mixtures is believed to be caused by a complex series of chemical reactions between the phosphate component and the alumina-containing material in the mixture.

There are currently phosphate-binding refractory mixture products sold as two-package (each with multiple components) systems.

A typical two-package product includes a package with a wet mix component containing platelet alumina and a phosphoric acid-based equilibrium mixture, and a package with a dry mix component containing platelet alumina, calcined alumina, water conserve alumina, and calcium aluminate cement. Package included.

Curing of the mixture is initiated by mixing the components of the two packages with water to obtain the desired consistency.

Because the wet and dry packages cannot be mixed until just before the mixture is to be applied, each package must be manufactured, packaged, and maintained separately.

Additionally, the shelf life of wet packages is limited by the reaction of its components with acid and alumina.

Such reactions can be accelerated if the wet ingredient package is contaminated, poorly sealed, or exposed to excessive heat.

The limited shelf life of wet-temperature ingredient packages can create warehousing and/or manufacturing scheduling problems.

Additionally, the use of two-package mixtures can lead to errors, for example when weighing and mixing each component, which can result in lower quality product and waste as well as increased preparation time for the user. There is sex.

Clearly, a one-package mixture with a long shelf life can provide improved economics.

Techniques for extending the shelf life of one- or two-package phosphate-binding formulations generally include the use of sequestrants or inhibitors to retard premature reactions between alumina and phosphoric acid. includes.

For example, U.S. Pat. No. 3,622,360 discloses an alumina-phosphoric acid implant mix composition.

The casting mixture of U.S. Pat. No. 3,622,360 is said to have a long shelf life and processability, especially due to the addition of an inhibitor selected from the group consisting of nitrilotriacetic acid and ethylenediaminetetraacetic acid, which promotes the aging retardation of the mixture. Are listed.

The described casting mixtures are also adjusted with water to obtain the desired plasticity.

U.S. Pat. No. 3,197,315 discloses the formulation and use of a typical high alumina content wet refractory composition using 85% phosphoric acid and packaged in a paper container suitable for shipping.

As an additional requirement, the alumina particles are precoated with a heated fatty acid such as palmitic acid or stearic acid or mixtures thereof to produce a lubricated, free-flowing gunning composition.

The composition disclosed in No. 5 also contains an amount of boric acid used in combination with phosphoric acid as a binder.

The addition of small amounts of boric acid to such compositions is known to retard the alumina-phosphoric acid reaction.

The composition is prepared by heating the fatty acid mixture components above the melting point of the fatty acid mixture and adding to the premixed batch of remaining ingredients and mixing the entire mixture.

U.S. Patent No. 3,303,034 discloses the use of phosphoric acid, plate alumina, bauxite, and kyanite.
) and diaspores, and are described as being suitable for provision by the driving technique after a storage period of up to 6 months.

The improved shelf life is due to the presence of bentonite as a plasticizer, which is less reactive with phosphoric acid than the plasticizers previously used.

U.S. Pat. No. 2,852,401 teaches a high humidity phosphate binding refractory composition in the form of ununited particles that are substantially dry to the touch.

The composition of U.S. Pat. No. 2,852,401 incorporates phosphoric acid into a refractory batch having a small percentage of refractory aggregates and a small percentage of alumina material that is chemically reactive with the phosphoric acid at room temperature; It is produced by drying the mixture at a temperature not exceeding about 125°F (52°C).

Therefore, the refractory aggregates, upon addition of the acid, reduce the batch temperature to the critical 125° on which the desired properties of the composition depend.
It should be sufficiently inert that it does not generate enough heat of reaction to rise above 52°C.

Conventional techniques for the preparation of binary mixtures typically include
It relies on mixing each component separately and thoroughly.

At the time of use, the ingredients are mixed with water and again subjected to further mixing.

Thus, the development of a dry, alumina-based, phosphate-binding, single-package refractory blend composition that exhibits a long shelf life and does not require inhibitors is highly desirable.

Moreover, it adds a simplified method of manufacturing the composition that eliminates prior art process steps required for mixture preparation, such as drying or precoating the aluminous material with a combination of fatty acids under controlled conditions. provide a unique appeal.

The composition of the present invention is a single package dry refractory mixture that exhibits a substantially improved shelf life and preferably has properties comparable to prior art two package mixtures.

Preferred compositions of the present invention include platy alumina, calcined alumina, water-containing alumina, calcium aluminate cement, and an amount of acid to provide an amount of PO equivalent to that provided by 85% concentration phosphoric acid from 3 to 19%. Contains mixtures of ingredients.

Preferred mixtures include formulating a mixture of dry ingredients in a mixer, mixing the dry ingredients to a homogeneous state, introducing a liquid acid component to the homogeneous mixture of dry ingredients, and subjecting the entire mixture to a high-intensity mixing step for a scheduled period of time. to produce a single-package refractory mixture that is substantially dry to the touch and has an acid phase well dispersed throughout the mixture.

The resulting mixture is characterized as a dry, single-package, alumina-based, phosphate-binding, refractory blend composition with a long shelf life.

The various features of novelty which characterize the invention are pointed out with particularity in the claims.

For a better understanding of the invention, its operational benefits and the particular objects achieved by its use, reference is made to the following description of preferred embodiments of the invention.

The compositions of the present invention, as described above, are dry alumina-based, phosphate-bonded, refractory blend compositions that have particular use in preparing refractories by pouring, spraying, and troweling techniques. It can be described as a thing.

This is a variant of chemically cured refractory specialty products that are generally heated after application.

Preferred compositions include sized platelet alumina, calcined alumina, hydric alumina, calcium aluminate cement, and dispersed phosphoric acid.

Each component is blended within certain composition ranges described below and is characterized by a significantly longer shelf life than existing competitive products and has comparable modulus of rupture, cold compressive strength, abrasion resistance and A dry single-package mixed composition having a dimensional change rate is produced.

All dimensions or mesh designations herein are in accordance with the standard Tyler series.

A variety of materials are suitable for use as inert (not active in causing primary bonding reactions) refractory aggregates in the practice of this invention.

Examples of these include plate alumina, calcined bauxite, and calcined kaoline.
) and synthetic mullite.

The use of a particular aggregate or combination of two or more aggregates and particle sizing will depend on the particular application technique and the desired properties of the unitary structure being formed.

Plate alumina is preferred because of its high fire resistance and abrasion resistance.

Plate-shaped alumina contains a trace amount of S io2. It is a relatively pure form of sintered calcined alumina containing Fe203 and Na2O.

This form of alumina has well-developed alpha-alumina crystals with a Mohs hardness reading of 9.

For use in accordance with the present invention, particles larger than 6 meshes generally have an adverse effect on the processing properties of the resulting mixture.

Therefore, the plate-like alumina aggregates should be ground into 16 meshes in order to obtain the desired particle loading.

Plate alumina is generally available commercially in sizes greater than 100 mesh, but aggregates sized at -100 mesh are preferred.

Aluminum Company of America (“Alc
oa”) by “Tabular Al umina
Appropriate plate-shaped alumina is manufactured and sold under T-61''.

Other sources of aggregates may be used in place of platelet alumina, but the selection of the dimensions of the substitute aggregates will be based on availability and end use.

The preferred calcined aluminas are all sized as a -100 mesh.

This alumina phase is characterized by crystallite sizes smaller than 5 microns and exhibits relatively little shrinkage.

A suitable commercially available calcined alumina is Alcoa”
Manufactured by and Calcined Aluminum
It is sold as "naA-2".

Calcined bauxite or kaolin calcined product may also be substituted.

To produce one of the required binders, a reactive alumina compound such as water-containing alumina is used in combination with a suitable distribution of phosphorus pentoxide in the acid.

Irrigated alumina is a granular white crystalline material commonly designated as Al(OH)3.

Purified forms generally contain a small amount (less than 1%) of S io2. Contains Fe203 and Na2O.

Hydra manufactured by “AI coa”
tedAlumina C-31'' is a commercially available material suitable for use in the present invention.

Also, naturally hydrated common impure bauxite is also satisfactory for the compositions of this invention.

It has been found that the size of the water-containing alumina component has a significant effect on the processing time and hardening of the mixture.

Equal weight finer forms of alumina hydrate result in shorter processing times in that finer grades expose more surface to reaction.

Calcium aluminate cement is a composition having calcium aluminate (CaO-8203) as the main component.

"Refcon", an impact sintered pelletized calcium aluminate cement manufactured by the Universal Atlas Cement Division of United States Steel Corporation, is a binder for refractory condensates such as those described above. One of these has been found to provide satisfactory performance in the compositions of the present invention.

"Fucon" is supplied as a ground powder.

In the selection of refractory cement binders as well as the selection of aggregates, attention must be paid to the temperature requirements of the final refractory product.

If temperatures approaching 3.000'F (1,649C) are anticipated, suitable commercial alternatives to "Refcon" may be used.

Polyphosphoric acid (PPA) as an anhydrous supersaturated solution containing orthophosphoric acid and P2O distributed as condensed acids is the preferred P2O5 derived acid component.

PPA has strong dehydration properties and has a variety of uses due to its catalytic and sequestering abilities.

The following is a typical composition of polyphosphoric acid manufactured by FMC Corporation of Philadelphia, Pennsylvania, USA, and used to successfully prepare the refractory mixture of the present invention described herein. Listed in Table 1.

Table 1 Concentration, %H3PO4115 Viscosity at 25°C, centipoise 28.0001
Viscosity at 00°C, centipoise 510 Composition P2O6, % 83.2P
205 Distribution Orthophosphoric acid, % 5 Pyrophosphoric acid, % 16 Triphosphoric acid, %
17 Tetraphosphoric acid, %
16 Higher polymeric acid, %
46 Because of the high viscosity of PPA at low temperatures, it is preferred to use PPA within the temperature range of 160-200°F (71-93°C) to facilitate addition to dry ingredients as described below. , but not required.

The preparation of the mixture using the method described below is 85%
It has been found that the substitution of PPA by phosphoric acid is tolerated.

This finding is unexpected in view of the fact that no inhibitor is required as in the prior art.

Although products with long shelf lives were produced when replacing PPA with 85% phosphoric acid, the mechanical properties of products using PPA are poor in petroleum catalytic crackers where high wear resistance is required. It appears to be excellent for certain industrial applications such as

Although the physicochemical properties of the resulting bond are not completely understood, phosphoric acid readily reacts with water-containing alumina in the presence of water to form hydrated aluminum phosphate and is associated with the bonding reaction of calcium aluminate cement. It is believed that the combination is responsive to the curing of the mixture.

In the composition of the present invention, the PPA and phosphoric acid provide the phosphate component needed to ultimately form the aluminum phosphate bond, but the acid is removed while the suitably prepared mixture is kept dry. Dispersion prevents bond formation.

The mixtures of the invention have broad and preferred compositions within the ranges shown in Table 2 below.

Table 2 Components Wide range Preferred range (W10*) (W10*) Plate alumina 40-70 50-60 Calcined alumina 15-35 22-32 Irrigation alumina 2-
102-6 Cal aluminate 1-101-5 Providing sium cement P2O6 equivalent 3-195-9 Acid component providing (85%H3P04) (85%H3P
04) *W/〇-wt% Irrigated alumina present in amounts greater than 10 wt% promotes expansion of the refractory when wet, thus making it undesirable for use as a casting mixture. .

Difficulties arise in curing when the mixture contains less than 2% hydric alumina.

Also, the presence of between 0 and 1% calcium aluminate cement retards the hardening of the mixture upon application.

However, with an amount of calcium aluminate cement greater than 10%, the mixture tends to harden instantly;
This makes it extremely difficult to apply it to the surface and process it in situ.

Additionally, it has been found that PPA (the preferred acid component) must be present in the range of 3-15% in order for the mixture to develop the necessary curing properties when water is added.

However, amounts of PPA exceeding 15%, especially in the presence of high calcium aluminate contents, cause instant hardening of the mixture and thus have an adverse effect on the processability of the mixture.

In this regard, 15%
An upper limit on PPA is mandatory.

When using 85% phosphoric acid, the upper limit is 19%.

The shrinkage of products made from quantities greater than 19% will be unacceptably high.

The remainder of the materials used to make up the mixture, the platy alumina and the calcined alumina, are in preferred embodiments adjusted as known in the art to provide suitable processability and the like.

In use, water is added to the mixture in an amount sufficient to obtain the consistency required for the application technique to be used for the particular mixture, such as driving, spraying, or troweling.

A preferred embodiment binder system is believed to include a phosphate component, an hydric alumina, and a calcium aluminate cement.

The complex reaction sequence and the physicochemical properties of the resulting bonds are not completely understood.

However, the reaction is highly exothermic and the final bond is characterized as an aluminate-phosphate bond.

No subsequent heating or curing of the bond is required, so the bond is essentially a cold bond.

It has been found that the desired properties achieved by the mixture cannot be obtained in the absence of the calcium aluminate cement, which is clearly essential due to the highly exothermic nature of the binding reaction.

Therefore, the presence of calcium aluminate cement is essential.

Moreover, the use of calcium aluminate cement in combination with other components of the binder system is
The result is a mixture that produces a unitary refractory structure that has advantages over conventional calcium aluminate cement structures in that excellent properties are obtained within a temperature range of (538-1.093°C).

The method of making the mixture consists of formulating the dry (non-acid) ingredients in a mixing pot and then mixing it to a homogeneous state.

It is not essential to achieve homogenization of the dry ingredients prior to addition of acid.

PPA is then added in an amount such that the composition of the composition falls within the ranges indicated above for each component.

The mixture is then subjected to a high intensity mixing step for a scheduled time (this will vary based on the size of the batch being prepared)
give

For the production of improved product mixtures, it is essential that the mixing operation be characterized as high strength, as described below.

Although the exact reason for this is not understood, it is believed that the high intensity mixing action breaks up and disperses the acid droplets, thus allowing the acid to be coated by the alumina fines.

This coating and separation of acid particles is believed to prevent their reaction and thus suppress the aluminum phosphate and cement watering reactions that harden the mixture.

Moreover, although the acid component was added as a liquid, the resulting mixture is substantially dry to the touch.

No suitable technique is available to measure the degree of dispersion of acids in mixtures;
A suitable degree of dispersion can be estimated by reference to the specific mixing energy''' or specific energy power.

In preparing the compositions of the present invention, the straw h/
10. It has been found that a specific mixing energy in the range of 100 kg is required.

However, the time variable was found to be essential for preferred mixtures.

This variable appears in the form of mechanical work on the mixture.

Work on the mixture is defined as the product of power [amperes (operating current - free load current) x mixer motor nominal voltage] and mixing time.

Once a suitable specific mixing energy value is obtained, a total mixing time of 1 to 4 minutes ensures a satisfactory product, and for acid formulations a mixing time of 2.5 minutes is the optimal time value. .

The term "high intensity mixing" as used herein refers to batch component 1
This means mixing with a specific mixing energy of 0.4 to 1.4 per 00 kg.

A preferred method of preparing the compositions of the invention is to formulate the dry ingredients in a mixing pot and mix them to a homogeneous state.

The acid is then added to the formulated dry ingredient mixture.

The whole is then mixed for the scheduled time (not to exceed 4 minutes).

The order in Example 1 of starting the mixer at low speed and then increasing speed is not critical to the method and is only one example for the particular equipment used.

Similarly, the rotation of the mixer pan as described in Example 1 is not critical to the present method, but is a feature of the particular mixer.

Additionally, there is no need to stop the mixer prior to adding the acid component.

Alternatively, the dry and acid components can be charged to the mixer at the same time.

The invention will be better understood with reference to Examples 1 and 2 below.

Example 1 °' Eirich Mode with suction type rotor
l D 228 in the pan of an E14″ counter-current powerful mixer.
1b (103 kg) of -6 M/F (-6 mesh or finer) T-61 plate alumina was added.

Also, -14M/F of 4681b (211kg) for bread
T-61 alumina of 361b "Refc
on) ”added together with cement.

In addition, -20 of 501b (23 Yu) is added to the mixer bread.
0 mesh crude ``Dutch Guiana'' bauxite hydrate and! 156 lb of -325 mesh “Alcoa A-2” alumina of 771b (80 kg)
(70 kg) of -325 mesh coarse A-2'' alumina was added.

The mixer was then started and operated at a rotor speed of 880 rpm and rapidly increased to a low speed of 1.76 Orpm.

The rotation of the rotor was counterclockwise, and the pan rotation of the mixer was clockwise.

The mixer pan was rotated for 60 seconds before stopping the mixer.

841b (38 kg) of 115% polyphosphoric acid (p
pA) was added.

The mixer was then energized at a rotor speed of 88 Orpm and rapidly increased to 1,760 rpm while the rotor rotated in a counter-clockwise direction and the pan in a clockwise direction for 90 seconds.

The mixer was then stopped and the material from the pan was packed into polyethylene lined paper bags.

The bag was sealed and stored. After 18 months, the samples were removed from the bag.

The material flowed freely from the bag and no lumps were observed.

Mix the material with 6% water and shape into 2x2x9
Test specimens with dimensions of in (5x5x23CrIl) were made.

This material had a pot life of approximately 20 minutes.

Each sample was air dried overnight, dried at 220°F (104°C) for 24 hours, and baked to the temperatures listed in Table 3 for 5 hours.

Upon cooling to ambient temperature, the samples exhibited the properties listed in Table 3.

Example 2 A mixture was formulated with the following composition:

-6M/F plate alumina 93.5 l b (42
, 1kg)-14M/F plate-shaped alumina 191.5 l
b (86,2kg)-325M calcined alumina 13
6.5 l b (61,4 kg) Irrigation alumina
20.5 lb (9.2 kg) Calcium aluminate cement 14.5 lb (6.5 kg
) Phosphoric acid (85%) 43.5 th (1
9.6 kg) The operation using “Eirich Mod
el DE -12''' countercurrent mixer pan, mixing the batch at 1008 rpm for approximately 35 seconds, adding acid to the batch without stopping the mixer, and mixing for an additional 150 seconds. Was.

Samples were prepared and tested using the method described in Example 1.

The results are reported in Table 3. The mixture was then packed into polyethylene paper bags, sealed and stored for 71 days.

The mixture was then tested and found to be loose and the clumps were broken up during mixing.

When the mixture was placed in 7+-% water, it had a pot life of about 15 minutes.

Table 3 lists the properties of the samples measured.

The average specific mixing energies in Examples 1 and 2 were 1.05 and 0.6 kilowatts/100 kg, respectively.

As previously mentioned, high intensity mixing is essential for the production of improved product mixtures.

Example 3 illustrates control results obtained when the mixture was prepared using a low speed, non-intensive mixing technique.

Example 3 The following ingredients were added in corresponding amounts to a standard Bammerer mixer.

Component Amount Ab (kg) -6M/F, plate-shaped alumina 19D86) -14M/
F, Plate alumina 390 (176)-325M, Calcined alumina 278 (125) Irrigation alumina
42 (19) Calcium Aluminate Cement 30 (14) The above ingredients were dry mixed in a Muller mixer for 3 minutes operating at about 3 Orpm.

11 of 691b (31 kg) while dry mixing the mixture.
5% PPA was added continuously.

After all the acid was added, the ingredients were mixed for at least 5 minutes or until the mixture was well mixed.

The mixer was then stopped, opened and the material packed into polyethylene paper bags for storage.

The mixture was substantially dry to the touch, but had a moist feel.

Within one week, the composition was cured.

The following Examples 4-6 describe three additional compositions using the ingredients shown below.

Each composition was prepared as follows: “Eirich Model DE-1
It was prepared by charging the dry ingredients to a 2" countercurrent mixer, mixing the batch at 1,008 rpm for about 35 seconds, adding acid to the batch without stopping the mixer, and mixing for an additional 150 seconds.

6.6 to the mixture of Examples 4, 5 and 6 as in Example 1.
%, 6.4% and 8% water and tested them.

The results are reported in Tables 4 and 5.

Example 4 Ingredients Weight % -6M/F calcined bauxite 19.0-1
4M/F fired bauxite 39゜〇-325
M/F calcined alumina 27.8 Irrigation alumina (Alcoa C-331) 4.2 Calcium aluminate cement 3.0 115% polyphosphoric acid 7.0 Example 5 Component Weight % -6 M/F calcined bauxite 190-14
M/F fired bauxite 39.0-325M
/F Calcined Alumina 27.8 Irrigation Alumina (
Alcoa C-31) 4.2 Calcium aluminate cement 3.0115% polyphosphoric acid 7.0 Example 6 Ingredients Weight %

Claims (1)

[Scope of Claims] l (a) 55-94% by weight of inert refractory aggregates, of which at least 15% by weight is an aluminous material selected from the group consisting of calcined alumina, calcined bauxite and calcined kaolin. (b) 2-10% by weight of hydrated alumina, (c) 1-10% by weight of calcium aluminate cement, and (d) 3-15% by weight of 115% polyphosphoric acid, more essentially It is a one-package dry refractory mixture, in which the dry ingredients are introduced into a mixer, the dry ingredients are mixed,
prepared by a process comprising the steps of adding an acid component to a mixture of dry ingredients and subjecting the mixture of dry ingredients and acid ingredients to high-intensity mixing action for a predetermined period of time not to exceed 4 minutes; A one-pack dry refractory mixture that exhibits a long shelf life under storage conditions and does not require inhibitors, hardens upon addition of water and exhibits high abrasion resistance upon hardening. 2(a) The dry refractory mixture according to claim 1, wherein the inert refractory aggregate is selected from the group consisting of plate-like alumina, calcined bauxite, calcined kaolin, and synthetic mullite. a) 50-60% by weight inert refractory aggregates, of which 22-32% by weight is an aluminous material selected from the group consisting of calcined alumina, calcined bauxite and calcined kaolin;
Claims consisting of: b) 2-6% by weight of hydrated alumina; (c) 1-5% by weight of calcium aluminate cement; and (d) 3-15% by weight of 115% polyphosphoric acid. Dry refractory mixture according to paragraph 1. 4(a) The dry refractory mixture according to claim 3, wherein the inert refractory aggregate is selected from the group consisting of plate-like alumina, calcined bauxite, calcined kaolin, and synthetic mullite.