JP2018039697A - Heat insulation monolithic refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat insulation monolithic refractory capable of uniformly dispersing gaps (pores) into a refractory without using a foam agent.SOLUTION: Provided is a heat insulation monolithic refractory obtained by adding water to a blend of a refractory material and an additive. As the additive, a material eluting lignin is added by 0.3 to 5 mass% to the refractory material, a surfactant is added by 0.001 to 0.2 mass% to the refractory material, the addition amount of water is controlled to 35 to 60 mass% to the blend, and its bulk density when being cured at ordinary temperature for 24 hr and dried at 110°C for 24 hr is 1.6 or lower.SELECTED DRAWING: None

Description

  The present invention relates to a heat insulating amorphous refractory.

  Conventionally, a heat-insulating amorphous refractory has been used in a part that requires not only fire resistance but also heat insulation, such as a steel pipe heating furnace and a soaking pipe of a soaking furnace.

  As a technique for imparting heat insulation to an amorphous refractory, a technique for forming voids (pores) inside the refractory by burning (burning out) a combustible substance such as sawdust is known. For example, Patent Document 1 describes the use of sawdust as a heat insulating aggregate (left column of page 2), and Patent Document 2 describes the use of sawdust as a pore-imparting agent (paragraph 0038). ). Patent Document 3 describes that an aqueous peroxide solution is used as a foaming agent and sawdust is used as a pore forming material (paragraph 0035).

  However, in the technology of forming voids (pores) inside the refractory by adding sawdust and burning (burning) it, the sawdust is uniformly dispersed in the refractory material due to the difference in specific gravity between sawdust and refractory material. As a result, it is difficult to uniformly disperse voids (pores) inside the refractory.

  On the other hand, if a foaming agent is used as in Patent Document 3, it is possible to uniformly disperse voids (pores) inside the refractory. However, since the foaming agent generates gas, an explosion or the like may occur depending on the type of gas. There is a risk. For example, oxygen, which is an auxiliary combustion gas, is generated from the peroxide aqueous solution exemplified in Patent Document 3, and therefore there is a risk of explosion if there is a fire type in the vicinity. There are also foaming agents that generate hydrogen, and the use of such foaming agents increases the risk of explosion.

Japanese Patent Publication No.58-9066 JP 2006-290656 A JP 2010-242992 A

  The problem to be solved by the present invention is to provide a heat-insulating amorphous refractory that can uniformly disperse voids (pores) inside the refractory without using a foaming agent.

  In order to solve the above problems, the present inventors have repeatedly studied the action of sawdust used in heat-insulated amorphous refractories. As a result, when lignin eluted from sawdust coexists with a surfactant, the mutual action It has been found that an excellent foaming effect is obtained by the action, and an effect of stabilizing the foam is also obtained.

That is, according to one aspect of the present invention, the following heat insulating amorphous refractory is provided.
"It is a heat-insulating and unshaped refractory made by adding water to a blend of refractory materials and additives,
As the additive, containing a material that elutes lignin and a surfactant,
The material for eluting the lignin is contained in an amount of 0.3 to 5% by mass with respect to the refractory material, and the surfactant is contained in an amount of 0.001 to 0.2% by mass with respect to the refractory material.
The amount of water added is 35% by weight to 60% by weight with respect to the blend,
A heat insulating amorphous refractory having a bulk specific gravity of 1.6 or less when cured at room temperature for 24 hours and dried at 110 ° C. for 24 hours. "

  Since the heat-insulating amorphous refractory of the present invention contains a material that elutes lignin as an additive and a surfactant, it was eluted when water was added to the blend of the refractory material and the additive and kneaded. The lignin and the surfactant exhibit an excellent foaming effect due to the interaction and stabilize the foam. As a result, the bulk density when the voids (pores) are uniformly dispersed inside the refractory without using a foaming agent, cured at room temperature for 24 hours, and dried at 110 ° C. for 24 hours is as low as 1.6 or less. A heat-insulating amorphous refractory having high specific gravity and high heat insulation can be obtained.

  The heat-insulating amorphous refractory of the present invention can be obtained by adding water to a blend of a refractory material and an additive and kneading it in the same manner as a normal amorphous refractory (castable refractory).

As the refractory material, for example, heat insulating aggregates mainly composed of CaO.6Al ₂ O ₃ (calcium hexaaluminate, hereinafter referred to as “CA6”), alumina, magnesia, chamotte, silica, titania, zircon, spinel. One or more selected from sillimanite group minerals such as vermiculite, perlite, pumice, heat-insulated brick scrap, kyanite, mullite, and the like can be used. In addition, as a refractory material, it is preferable to use the heat insulation aggregate which makes CA6 the main mineral composition. CA6 is light in weight, has a low thermal conductivity, and is excellent in scale erosion resistance, and can further improve the heat insulating property of the heat insulating amorphous refractory.

  As additives, a material that elutes lignin and a surfactant are used. Examples of materials that elute lignin include those containing plant fibers such as sawdust, rice bran, wheat flour, and buckwheat husks, but readily available and low-cost sawdust is preferred, and among others, the results of our tests. According to, coniferous sawdust is preferred. The material that elutes lignin is added in an amount of 0.3% by mass to 5% by mass with respect to 100% by mass of the refractory material. That is, the heat insulation amorphous refractory of this invention contains 0.3 mass% or more and 5 mass% or less of the material which elutes lignin with respect to a refractory material. When the content is less than 0.3% by mass, a sufficient foaming effect cannot be obtained, and the heat insulating property becomes insufficient. On the other hand, when the content exceeds 5% by mass, the fluidity necessary for the amorphous refractory cannot be obtained, and the strength is insufficient. The content of the material that elutes lignin is preferably 1% by mass to 3% by mass with respect to the refractory material.

  Examples of the surfactant include one or more selected from alkylbenzene sulfonic acid, sodium phthalene sulfonate fatty acid salt, alkyl sulfate ester salt, polycarboxylate, and detergent. The surfactant is added in an amount of 0.001% by mass to 0.2% by mass with respect to 100% by mass of the refractory material. That is, the heat insulation amorphous refractory of this invention contains 0.001 mass% or more and 0.2 mass% or less of surfactant with respect to a refractory material. If the content is less than 0.001% by mass, a sufficient foaming effect cannot be obtained, and the heat insulating property becomes insufficient. On the other hand, when the content exceeds 0.2% by mass, the fluidity necessary for the amorphous refractory cannot be obtained, and the strength is insufficient. The content of the surfactant is preferably 0.005% by mass or more and 0.1% by mass or less with respect to the refractory material.

  As an additive, in addition to the material that elutes lignin and the surfactant, a binder, a dispersant, a thickener, a curing time adjusting agent, an explosion prevention agent, and the like may be appropriately included.

  As the binder, alumina cement, Portland cement, phosphate, silicate, hydraulic transition alumina, etc. can be used, but cohesive like a combination of fine magnesia and evaporated silica among refractory raw materials. It is also possible to substitute a raw material for forming the joint.

  As the dispersant, one or more selected from alkali metal phosphates, alkali metal polyphosphates, polycarboxylates, alkyl sulfonates, aromatic sulfonates, and the like can be used.

  As the thickener, one or more selected from yam starch, taro starch, carboxymethylcellulose, methylcellulose, sunzan gum, karaya gum, locust bean gum, welan gum, arabic gum, and sodium alginate can be used.

  The curing time adjusting agent includes a curing accelerator and a curing retarder. As the curing accelerator, one or more selected from slaked lime, calcium chloride, sodium aluminate, lithium carbonate, and the like can be used. As the retarder, for example, one or more selected from boric acid, citric acid, sodium carbonate, sugar and the like can be used.

  As the explosion preventing agent, one or more selected from organic fibers such as soot and vinylon fibers, and metal powder can be used.

  In the heat insulating amorphous refractory of the present invention, the amount of water added is 35% by mass or more and 60% by mass or less with respect to the blend of the refractory material and the additive (total amount of the refractory material and the additive). When the amount of water added is less than 35% by mass, the viscosity becomes high and the fluidity required for the amorphous refractory cannot be obtained. On the other hand, if the amount of water added exceeds 60% by mass, bubbles generated by the interaction between the above-described material for eluting lignin (eluting lignin) and the surfactant are lost and unstable.

  As described above, the bulk specific gravity when cured at room temperature for 24 hours and dried at 110 ° C. for 24 hours by satisfying all the requirements for the content of lignin-eluting material and surfactant and the amount of water added is as follows. A heat insulating amorphous refractory having a low bulk specific gravity of 1.6 or less and a high heat insulating property can be obtained.

  About the irregular refractories of each example shown in Table 1, bulk specific gravity, thermal conductivity, normal temperature bending strength after curing, and fluidity were evaluated. In addition, as the refractory material shown in Table 1, a heat insulating aggregate having CA6 as a main mineral composition was used. Although not shown in Table 1, alumina cement was used as a binder.

  The bulk density is determined by adding water to a blend of refractory material and additive, kneading, pouring into a 40 × 40 × 160 mm mold, molding at room temperature for 24 hours, and then removing the frame to 110 ° C. The test piece obtained after drying for 24 hours was measured according to JIS R 2205. In Table 1, the bulk specific gravity is represented by ◎ when 1.0 or less, ○ when 1.6 or less and 1.6 or less, and × when 1.6 or more.

  As for the thermal conductivity, the thermal conductivity at a temperature of 800 ° C. was measured by a hot wire method for a test piece obtained by kneading, molding, curing and drying in the same manner as described above. In Table 1, thermal conductivity (W / m · K) is represented by ◎ when 0.35 or less, ◯ when 0.35 or more and 0.6 or less, and × when 0.6 or more.

  The room temperature bending strength after curing was measured based on JIS R 2511 for test pieces obtained by kneading, molding and curing in the same manner as described above. In Table 1, the normal temperature flexural strength (MPa) after curing is represented by ◎, 0.6 or more and less than 0.6 by ○, and less than 0.3 by ×.

  The fluidity was evaluated by the free flow value. The free flow value is the filling of the clay (mixture of the above-mentioned composition and water) poured into the flow cone specified in JIS R 2521, and the flow cone is extracted upward and left for 60 seconds to stand. The spread diameter. Specifically, the free flow value immediately after kneading the formulation of each example shown in Table 1 and water was measured. In Table 1, a free flow value (mm) of 130 or more is indicated by ◎, 110 or more and less than 130 is indicated by ○, and less than 110 is indicated by ×.

  In Table 1, Examples 1 to 6 are examples of the present invention that satisfy the requirements of the present invention, and all evaluations of bulk specific gravity, thermal conductivity, normal temperature bending strength after curing, and fluidity were good.

  On the other hand, Comparative Example 1 is an example in which the content of the material that elutes lignin is lower than the lower limit of the present invention, and the bulk specific gravity increases and the thermal conductivity also increases. Comparative Example 2 is an example in which the content of the material that elutes lignin exceeds the upper limit of the present invention, and the room temperature bending strength after curing is low and the fluidity is also low.

  Comparative Example 3 is an example in which the surfactant content falls below the lower limit of the present invention (an example in which no surfactant is contained), and the bulk specific gravity is increased and the thermal conductivity is also increased. Comparative Example 4 is an example in which the content of the surfactant exceeds the upper limit of the present invention, and the room temperature bending strength after curing was lowered and the fluidity was also lowered.

  In Comparative Example 5, the amount of water added was lower than the lower limit of the present invention, and the fluidity was low. Comparative Example 6 is an example in which the amount of water added exceeds the upper limit value of the present invention, and the normal temperature bending strength after curing is decreased, and the bulk specific gravity and the thermal conductivity are increased.

Claims (3)

A heat-insulating unshaped refractory material obtained by adding water to a blend of a refractory material and an additive,
As the additive, containing a material that elutes lignin and a surfactant,
The material for eluting the lignin is contained in an amount of 0.3 to 5% by mass with respect to the refractory material, and the surfactant is contained in an amount of 0.001 to 0.2% by mass with respect to the refractory material.
The amount of water added is 35% by weight to 60% by weight with respect to the blend,
A heat insulating amorphous refractory having a bulk specific gravity of 1.6 or less when cured at room temperature for 24 hours and dried at 110 ° C. for 24 hours. 1 mass% or more and 3 mass% or less of the material which elutes the said lignin with respect to the said refractory material,
The heat insulating amorphous refractory according to claim 1, wherein the surfactant is contained in an amount of 0.005% by mass to 0.1% by mass with respect to the refractory material.   The heat insulating amorphous refractory according to claim 1 or 2, wherein the material that elutes lignin is sawdust.