Fluid sprinkling – spraying – and diffusing – Processes – Including mixing or combining with air – gas or steam
Reexamination Certificate
2002-01-15
2003-07-15
Evans, Robin O. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Processes
Including mixing or combining with air, gas or steam
C239S009000, C239S010000, C239S398000, C239S418000, C239S427000, C239S427300, C239S427500
Reexamination Certificate
active
06592048
ABSTRACT:
The present invention relates to a novel method for producing sprayed monolithic refractories, which eliminates problems in conventional dry or wet spray method; dispenses with a mixing operation for a refractory composition to be sprayed, and enables a long distance transportation for a spray operation without causing the blocking of the refractory composition in the transporting pipe, whereby the applied monolithic refractories have a high quality.
As an advantageous method for monolithic refractories, a spray method has been known. This method requires no formwork for casting as a casting method does, and allows an easy operation even though the shape is complicated and even where frameworking is difficult. Accordingly, this method has been used widely in many fields in recent years. The spray method is generally classified into a dry spray method using a compressed air delivering system and a wet spray method using a pump-operated delivering system. These methods have the following merits or drawbacks.
In the dry spray method, a powdery refractory material to be sprayed, comprising a refractory powder such as clay which improves adhesively at the time of spraying and a binder such as aluminous cement which cures by adsorbing water, is supplied to a spray gun in the compressed air delivering system so that the refractory material is forcibly fed by compressed air in the transporting pipe. Then, water necessary for the operation, i.e. application water is added to the forcibly fed powdery refractory material at a spray nozzle portion to render the powdery refractory material with the application water to be a highly viscose adhesive state. Then, the wet refractory material is sprayed through the nozzle so that the material adheres and cures on a furnace wall portion, whereby a refractory furnace is fabricated.
In the dry spray method, since the refractory material to be sprayed is forcibly fed by air in a powdery state, there is little possibility of causing the blocking of the transporting pipe, and therefore, the transportation is easy and a long distance transportation is possible. Accordingly, the operation can be conducted by supplying the refractory material to be sprayed from a location where the spray machine is disposed on the ground to a remote place or a height.
However, the dry spray method has such disadvantage that a time of contact of application water with the refractory material to be sprayed is short since the viscose refractory material is produced by mixing the powdery refractory material with the application water in the nozzle. As a result, the application water can not sufficiently uniformly be mixed with the powdery refractory material to be sprayed, whereby the quality of a refractory furnace wall as an applied body is not uniform, the porosity is small, and refractories having a large strength and a high quality may not be obtained.
On the other hand, the wet spray method has been developed in obtaining a furnace wall having more uniform quality and more excellent in physical properties than that produced by the refractories obtained by the dry spray method, and therefore, has often been employed in recent years. In the wet spray method, a mixture called “mixed batch” is produced by mixing previously the refractory material to be sprayed with the application water in a sufficient manner. The mixed batch is produced by mixing them to such an extent that the flow value of flowability (according to JISR5201 with use of a cone) capable of pump-delivering with a mixer indicates about 200 mm, and the mixed batch is supplied to a delivery pump to be fed in the transporting pipe. Then, a rapid setting agent for agglomerating the mixed batch is added to the mixed batch at the nozzle portion, and the mixed batch is sprayed to a furnace wall structure by compressed air. Then, the refractories for the furnace wall can be fabricated by the agglomeration of the mixed batch relatively instantaneously.
In the wet spray method, since it is necessary to mix the refractory material to be sprayed with the application water with the mixer until a sufficient flowability is obtained before the refractory material is supplied to the delivering pump as described above, a large sized mixer and many workers are necessary. Further, in delivering the mixed batch by the pump, it is difficult to control the amount of mixing water in order to obtain a proper flowability. For example, when the flowability is small, the blocking may occur in the pump or the transporting pipe. On the other hand, when an excessive amount of mixing water is added in order to increase the flowability, there would occur separation of refractory aggregates of coarse particle and a fine powdery refractory powder which is contained in the refractory material to be sprayed. This creates problems that the transportation of the material is impossible and a preferred the spray operation can not be carried out. Thus, the wet spray method has many unstable factors in an application field at the time of the application.
In addition, in order to supply the mixed batch to a long distance location by the pump delivering to conduct the operation, the wet spray method requires a large sized pump because the viscosity of the mixed batch is large, and the distance of transportation is shorter, e.g. about 100 m at the maximum, than that in the dry spray method. Further, since a certain amount of the mixed batch remains in the transporting pipe when the operation has been finished, there are problems that the loss of the material is large and many workers and much time are required to remove the remaining mixed batch and to clean the equipment.
As disclosed in JP-A-62-36071, there has been known such a method that an amount of water of ⅕-¾ of the finally required amount of water for conducting the operation is added to a powdery refractory composition to be sprayed; the added water and the refractory composition are mixed previously by a mixer; the mixed refractory composition is forcibly supplied to a dry type spray gun, and a solution comprising the remaining amount of water for the operation and a curing accelerator is added to the refractory composition at a nozzle portion of the gun, whereby monolithic refractories can be formed by spraying the refractory composition.
In the disclosed method, however, it is necessary to add the aqueous solution comprising the curing accelerator and the application water to the refractory composition to be sprayed at the nozzle portion at the final stage, in the same manner as the conventional dry spray method. Accordingly, a time of contacting uniformly the necessary amount of water with the refractory material is too short to obtain a sufficient dispersing state of the refractory material to be sprayed, whereby it is difficult to form a furnace wall having a high quality. As a result, the disclosed method is within the scope of the conventional dry spray method, and can not be a method capable of improving the problems of the ordinary dry spray method. Further, the distance of transportation is short, i.e., 100 m at the maximum, in comparison with the conventional dry spray method, and therefore, there are many restrictions of locations at which the operation is to be conducted.
It is an object of the present invention to eliminate the problems in the conventional dry or wet spray method as described above.
Namely, the present invention is to provide a novel spray method for monolithic refractories, which does not require a mixing work for a refractory material to be sprayed, and permits a long distance transportation of the refractory material without causing the blocking of the transporting pipe, whereby monolithic refractories obtained by the operation have a high quality and uniform characteristics.
The present invention has been made based on new knowledge and idea obtained by analyzing sufficiently the characteristics of the dry and wet spray methods, whereby the above-mentioned object can be achieved.
Namely, the inventors of the present invention have found tha
Motoki Eiji
Nonaka Katsumi
Evans Robin O.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Plibrico Japan Company Ltd.
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