Unshaped refractory materials that can be sprayed to the working face by high-speed airflow and adsorbed on the working face are called refractory injection materials. In principle, any kind of castable or any kind of self-flowing material and pumping material can be used as dry spraying material or wet spraying material, only need to adjust its particle size composition and the type and amount of additives. Refractory blasting material is a kind of unshaped refractory material, which is a new type of refractory material with good fluidity after adding water and stirring without firing and pressure forming. Its masonry structure has few joints, strong integrity, good airtightness, and can avoid powder infiltration. At the same time, compared with traditional refractory products, jet refractory material has the following characteristics:
(1) It is easy to anchor and can effectively prevent the wall from protruding.
(2) The construction is convenient, the labor intensity is low, the masonry efficiency is high, and the furnace building mechanization can be realized.
(3) The delivery time is short, and the inventory and cost can be reduced accordingly.
Refractory blasting materials are widely used, which is convenient for comprehensive utilization of resources. Usually, the granular material that constitutes this material is called refractory aggregate, and the powdery material is called admixture (refractory powder or fine powder), as well as binders and additives.
1. Construction method of sprayed refractory material
According to the state of the material sprayed onto the lining body (working face), it can be divided into two categories: cold material injection method and molten or semi-molten material injection method. The latter includes the following methods.
Flame spray method: The material is sprayed onto the working lining with a propane gas flame. During the spraying process, under the action of high temperature, the material is in a molten or semi-molten state, directly sprayed onto the high-temperature lining, and adsorbed on the surface of the lining. In the past, it was used for repairing furnace linings, but it is not commonly used anymore.
Plasma spray method: The material is sprayed in an ionic state, which is rarely used in refractory materials.
Slag splashing method: such as the slag splashing of the converter to protect the furnace, the mixture of refractory material and slag is blown and splashed on the surface of the converter by using a high pressure oxygen lance. It is the key technology to improve the life of converter lining.
The former is the most commonly used spraying method, which includes a dry spraying method and a wet spraying method.
Dry jetting method: An operating process of a dry jetting device. The dry material enters the rotating cloth drum from the silo. The cloth cloth drum rotates at a certain angle. The upper port and the air channel of the compressor are transported to the vicinity of the nozzle to meet the water. After the material is mixed with the water in the nozzle, it is sprayed to the working lining. superior. Most of the ejected material is adsorbed on the working lining, and a part of it rebounds and falls to the ground. The amount of material lost by the rebound is of great significance to the construction of the ejected refractory. Usually, the rebound rate is used to indicate the adsorption performance of the ejected material. The lower the rebound rate, the better. There are many factors affecting the rebound rate: mainly including the amount of water, wind pressure and air volume.
The wet spraying method is a method in which the castable with good fluidity is pumped to the nozzle through the pipeline, and is sprayed onto the working lining by the high-pressure air flow in the nozzle. The process consists of four main stages: mixing, pumping, spraying and solidification. The mixing and pumping process is not very different from ordinary castables and pumping materials, requiring uniform mixing and good pumping performance.
In the past, spray construction was mostly used for repairing furnace linings, while wet spraying can be directly used for lining. It can be directly used to manufacture ladle and furnace linings of various furnaces. Its advantages are simple process, no template, low cost and high speed.
2. Matters needing attention in the spray method
(1) The following matters should be paid attention to when adopting the dry spray method:
The amount of water added should be appropriate: if the amount of water added is too small, the material will not be well wetted, and the dry material will be easily rebounded; if the amount of water added is too large, the coating formed by spraying is prone to flow, which also reduces the adsorption capacity.
The air pressure and air volume of the spray should be appropriate: when the particle is too large, the impact of the particles on the spray surface is too large, and it is easy to rebound; if it is too small, the material has insufficient adhesion to the material and is easy to fall off.
The distance and angle between the nozzle of the spray gun and the sprayed surface should be appropriate: avoid the force of spraying the material to the sprayed surface is too large or too small. The spray gun should be moved up and down, left and right to ensure a uniform thickness of the sprayed layer.
The thickness of each spraying should not be too thick: too thick is easy to peel off, generally not more than 50mm.
Control the plastic and coagulation of the material: the material can be well adsorbed on the spray coating, and can be solidified quickly to obtain a certain strength.
(2) There are many factors that affect the wet jet method. The main ones are as follows:
Composition of spray material First, it should have reasonable particle size composition, ratio of aggregate to matrix and moisture content. With proper coordination, the matrix part can be better adhered to the surface of the particles. The adhesion layer should not be too thick or too thin, so as to ensure that the particles can have good plasticity and adhere to the material layer when they are sprayed onto the material layer. Commonly used flocculants are sodium aluminate, sodium silicate, polysodium chloride, calcium chloride, aluminum sulfate, potassium calcium sulfate, etc.
If the jet pressure and jet air velocity are too small, the particles will not adhere well to the material, and if they are too large, they will easily rebound.
The distance and angle between the spray gun and the sprayed body have a certain influence on the adhesion rate of the material layer.
Post time: Jul-15-2022