JPH0331996B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for spraying refractories to improve adhesion to objects to be sprayed and to obtain sprayed objects having excellent hot strength and corrosion resistance. [Prior art] Refractory powder spraying is applied to steelmaking furnaces such as converters, electric furnaces, and open hearths, ladles, tundishes, DH furnaces, and RH furnaces.
Various linings for steelmaking furnaces and coke ovens such as furnaces and immersion tubes, hot blast furnaces, blast furnaces, tap-holes, gutter covers, iron-making furnaces such as pig iron mixers, scorching furnaces, chimneys, flues, boilers, and other industrial furnaces. Used for construction and construction. Normally, lining construction, such as spraying for repairs, is done by mixing powdered refractories pumped from a refractory tank with water at the tip of a gun nozzle while the furnace is still cool, which saves labor. From the standpoint of energy conservation, the frequency of hot repairs has increased significantly. Compared to cold spraying, this hot spraying has problems in that the adhesive force to the furnace wall decreases and the structure deteriorates more significantly due to the rapid volatilization of moisture. To solve this problem, for example, as described in Japanese Patent Publication No. 46-23608, various combinations of binders and combinations of hardening agents have been proposed. A dry method is used in which the mixed dry formulation is pumped through a dry gun, water is added at a spray nozzle, and spray repair is performed in the mixed state. However, when applying this dry method,
The time from when the compound and water are mixed until they reach the target furnace wall is very short (estimated to be less than 1 second, for example), and the spray repair is performed before the added binder is sufficiently dissolved. In addition, there are disadvantages in that the mixture is often mixed with water, and adding more water than necessary leads to tissue deterioration and generates dust during operation. In addition, in order to prevent these drawbacks of the dry method, there is a method in which the spraying material in the tank is made semi-wet, so-called semi-wet, but as in the case of the present invention, a curing agent and a binder are used together. In the case of sprayed materials, conventional semi-wet methods cannot be applied as they react in the tank. FIG. 1 is a diagram showing the dissolution time of the binder in the refractory into added water. The figure is from Japanese Patent Application Publication No. 1973-
This shows the dissolution rate of condensed phosphates (e.g. powdered sodium hexametaphosphate) used as a binder in converter hot spray refractories as in Publication No. 99109. Powdered sodium hexametaphosphate added to 50 ml of water. The vertical axis shows the dissolution amount in g, and the horizontal axis shows the dissolution time. In the figure, curve 1 shows the concentration change over time of room temperature water, 2 shows the hot water at 50°C, and 3 shows the 25% concentration sodium hexametaphosphate solution. In this way, when spray repair is performed using the conventional method of simply adding water to the gun refractory formulation,
Since the binder is sprayed without being sufficiently dissolved in the solution, the adhesion to the furnace wall is reduced and peeling is facilitated. Furthermore, in the case of cold water, a large amount of water is added to the formulation to promote dissolution, resulting in deterioration of the spray body structure. Also,
Even when hot water is used, it is not sufficient to increase the solubility of the binder used. Therefore, to compensate for the solubility of the binder,
The binder or curing agent is added in excess of what is necessary, which reduces the fire resistance of the sprayed body and causes deterioration in its durability. [Problems to be Solved by the Invention] The purpose of the present invention is to solve the problems of the spraying method, which involves adding water at the tip of the spray nozzle, and to reduce the amount of water used for conventional dry formulations. An object of the present invention is to provide a method for spraying gun refractories to improve the adhesion and structure of gun refractories to objects to be sprayed. [Means for Solving the Problems] The present invention utilizes the fact that the pH of sodium hexaphosphate is in a high range of 6 to 8, making it possible to use mixed raw materials in a semi-wet state in a tank. A semi-wet preliminary mixture of refractory material and slaked stone with particle size control is conveyed to a spray nozzle, and at the spray nozzle, sodium hexametaphosphate is added at a concentration of 5 to 50% and a viscosity of 5 to 50%.
This is a method for spraying gun refractories, characterized by spraying the refractory in a molten state of 15 cp or less by mixing it with the conveying mixture. The sodium hexametaphosphate solution used here will not be sufficiently effective unless its concentration is 5% or more, and if the solution concentration exceeds 50%, the viscosity of the solution will increase and sufficient mixing will not be possible. In order to achieve instantaneous mixing when the spray mixture is semi-wet, the viscosity of the sodium hexametaphosphate solution used must be below 15 cp, i.e. 15 cp x g/g.
Requires viscosity below cm ² . Furthermore, by using a combination of slaked lime as a hardening agent and sodium hexametaphosphate solution as a binder for the pre-prepared semi-wet refractory material, it is possible to improve the adhesion to objects to be sprayed such as furnace walls. , and its effect is fully exhibited even when added in a small amount. Figure 2 shows MgO-
Apply a thin layer of molten slag to the surface of the CaO brick.
The graph shows the hot bonding shear strength (Kg/cm ² ) measured after heating at ℃, spraying, raising the temperature to 1500℃ again, and holding for 15 minutes. This is a graph showing the amount (converted to powder amount) in weight %. Curve 1 in the figure shows the change in shear strength when various amounts of sodium hexametaphosphate at a concentration of 20% are added to a powdered refractory made by mixing refractory material powder whose particle size has been adjusted and slaked lime as a hardening agent. This shows a case where a mixture of powdered refractory material, powdered sodium hexametaphosphate, and powdered slaked lime is mixed with water at the spray nozzle part and sprayed by the conventional method, and the sprayed refractory of the present invention is used. Shows excellent effects,
Since it is effective in small amounts, it does not reduce the fire resistance of the spray body. Moreover, a structurally strong spray body can be obtained without adding more water than necessary from the melting surface. Therefore, it goes without saying that it can be applied to all types of lining construction, whether cold or hot. The powdered refractories in the pre-prepared tank are not combined with a binder and a curing agent that promotes curing of this binder, so semi-wet powder is used to reduce spray moisture and improve mixing. It became possible to Sodium hexametaphosphate is a substance added to increase the bond strength of the sintered or formed product, and slaked lime is an additive that accelerates the hardening of this sodium hexametaphosphate. The effects of the present invention will be specifically explained below using Examples. [Example] Example 1 A composition used for converter spraying containing water (2 to 3 parts by weight) using slaked lime as a hardening agent
An example is shown in which the mixture is conveyed to a spray nozzle, and a sodium hexametaphosphate solution is added as a binder in the same spray nozzle. Indicates the value of As a comparative example, the values of apparent porosity, compressive strength, and adhesive shear strength in the case of a conventional method containing refractory material, slaked lime, and sodium hexametaphosphate and mixing water at the nozzle tip are given.

【table】

[Table] Example 2 A water-containing mixture (2 to 3 parts by weight) of a composition used for blast furnace stamp troughs using slaked lime as a hardening agent was conveyed to a spray nozzle, and a binder was added to the spray nozzle. In the method of the present invention in which a sodium hexametaphosphate solution is added as
An example of spraying onto a blast furnace stamp material set in a °C furnace is shown, and the values of its apparent porosity, compressive strength, and adhesive shear strength are shown. In addition, as a comparative example, the values of porosity, compressive strength, and adhesive shear strength in the case of a conventional method containing fireproofing material, slaked lime, and sodium hexametaphosphate and mixing water at the tip of the nozzle are shown.

[Table] Example 3 A water-containing mixture (2 to 3 parts by weight) containing slaked lime as a hardening agent, which is a composition used for spraying on waxite bricks lining a ladle, was sprayed. An example is shown in which the method of the present invention is used in which a sodium hexametaphosphate solution is added as a binder in the same spray nozzle, and the values of the apparent porosity, compressive strength, and adhesive shear strength are show. In addition, as a comparative example, the values of apparent porosity, compressive strength, and adhesive shear strength in the case of a conventional method containing refractory material, slaked lime, and sodium hexametaphosphate and mixing water at the tip of the nozzle are given.

【table】

〔Effect of the invention〕

As is clear from the results of the above examples, the spraying method of the present invention has good adhesion, requires only a small amount of binder and sprayed water, and has good mixing. Compared to the method, a product with a better composition and far superior compressive strength and adhesive shear strength can be obtained.

[Brief explanation of drawings]

Figure 1 is a graph showing changes in concentration over time of sodium hexametaphosphate used as a binder for sprayed refractories at room temperature 1, warm water at 50°C 2, and 25% concentration product 3; Figure 2 is a refractory material whose particle size has been adjusted; A case 1 in which the method of the present invention is applied to a powder refractory consisting of slaked lime as a powder hardening agent using a sodium hexametaphosphate solution as a binder, and a case 1 in which the particle size is adjusted using a conventional method, a refractory, a powder binder, and a powder hardening agent. 2 is a graph showing the relationship between the amount of binder added and the hot bonding shear strength of the sprayed refractory in case 2 when water is mixed with the powdered refractory made of the sprayed refractory.

Claims (1)

[Claims] 1 Prepare a wet mixture by adding water to a mixture of refractory material whose particle size has been adjusted in advance and slaked lime as a hardening agent, and mix the wet mixture with a binder solution at the spray nozzle and spray it. Then, as the binder solution, the concentration is 5 to 50%,
A method of spraying gun refractories using a sodium hexametaphosphate solution with a viscosity of 15 cp or less.