Flame guniting is based on the principle of interaction of the high-temperature refractory particles with the surface of the lining, the temperature of which is significantly lower than the temperature of the particles being applied and the gunited coating being formed. In such a process the temperature state of the coating--lining system satisfies the inequality to<~
The method of torch guniting is based on the creation of a high-temperature flame in the cavity of the converter in jet mixing and combustion of coke fines in a flow of oxygen. However, in such a method of combustion complete mixing of the components does not occur in the flame, as the result of which the guniting flow does not contain a stoichiometric mixture of fuel and oxygen.To provide complete combustion of the fuel, it is necessary to add an additional quantity of oxygen.Determination of the necessary quantity of oxygen to maintain rational guniting conditions in relation to the capacity of the guniting equipment, the chemical compositions of the guniting mixture and the coke fines, and the ratio of the initial velocities of the coke fines and oxygen is a complex and pressing problem.
At present questions of the protection and repair of refractories in service in oxygen converters are inseparably related to the use of torch guniting.
The technology for applying guncrete is now extensively used. The protection of furnaces using such concretes, as well as industrial buildings and plant using various cement-sand compositions or ash-slag mixtures, is possible by employing a highly effective method and equipment which produce guncrete of the desired properties and which make the best possible use of the raw materials.The extensive introduction of guncreting requires the investigation of the parameters that affect the movement of the mortar-air mixture. The effectiveness of guncreting is largely determined by the parameters of the movement of these mixtures in the channel of the mixing nozzle of the g~an, since it is a closed design element in the production chain in which the mixture is created and from which it then flows.The parameters influencing the flow cycle are: the velocity of the mortar-air mixture in the channel; the volume of air consumed, and the density of the mixture. The flow rate is selected taking account of the optimum consumption of air and nozzle diameter. Regulation of the flow rate is done by using mixing nozzles of different diameters and by maintaining the necessary air consumption. Ensuring the given velocity of the mortar-air mixture in the channel is effected by the choice of the cross sectional area of the material duct feeding in the air for pneumatic transporting of the dry (up to 2% moisture) material at a fixed pressure.To determine the parameters for the mortar-air flow we specify conditions satisfying the inequalities:where %r is the critical velocity of the dry material in' the duct for which there is no clogging, m/sec; %, velocity of the mortar in the channel of the mixer nozzle, m/sec; COa.w, velocity of the mixture in the channel for which rapid abrasive wear is absent, m/sec; Pu.m, pressure of the guncrete jet for which the maximum efficiency of material use is achieved. MPa; pg, pressure of the guncrete jet for which there is rapid breakdown of the freshly applied guncrete coating, MPa; Qa, volume consumption of 3 * air in m /sec; Qmin, minimum permitted air consumption ensuring pneumatic transportation of the dry material in m3/sec. The critical velocity of the material at the end of the material duct before reaching the nozzle is determined by the expressionwhere c is an experimental constant taking account of the tendency of the material to caking, the presence of moisture, and the complexity of the trace (for easily aerated mixtures c = 0:.075 [1]), ,%1 is the mass concentration of material, kg/kg; ,a N *Calculations were made with air parameters in normal conditions (p = 0.1013 MPa, T = 273 K).
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