A. G. Luzin

Drying magnesia refractories with the flue gas of the tunnel kiln

ConclusionsExperiments at the Magnezit Plant confirmed the feasibility of drying magnesia refractories with the flue gas in the first positions of a tunnel kiln. Drying the refractories in the section where the flue gas is tapped off does not result in more rejects or in degradation of the properties of the fired products.Compounding the processes of drying and firing magnesia refractories in a single unit, viz., the tunnel kiln, makes it possible to dispense with the driers the freed floorspace of which can be used for installing equipment for mechanizing the loading of the products on the kiln trucks.

A modernized tunnel kiln for firing magnesia and magnesia-spinellide refractories at 1850°C

ConclusionsA low high-temperature tunnel kiln was rebuilt, including increasing the length of the firing zone, supplying hot air to the burners, supplying air to the cooling zone through the roof, and providing a system of aerodynamic sealing of the subhearth space of the kiln.Reconstruction of the kiln and the firing method developed made it possible to obtain a stable firing temperature of 1850°C and a hold of up to 6 h at a temperature above 1800°C, to decrease the temperature differential across the kiln channel cross section, to reduce scrap, to increase the quality of magnesia and magnesia-spinellide parts and the kiln productivity, and to improve the car serivce conditions and the working conditions of the operating personnel.

Influence of the size of voids, impregnation with bakelite, and heat treatment of periclase plates on their properties and life in steel pouring ladle valves

ConclusionsThe relationship of the properties, the quality of the ground surface, and the wear resistance in service of the refractory plates in the gates of steel teeming ladles to the size and form of the voids, impregnation, and heat treatment of periclase plates was established.

Operation of gas-burner devices with increased jet aperture angle for heating rotary furnaces

ConclusionsAn increase in the aperture angle of high-velocity gas jets intensifies the mixing of fuel with oxidizer in the accompanying flow as a result of the growth in the transverse pulsation constituent of the velocity and the surface of the flame front.Tests of the gas-burner device with an increase in the angle in a rotary kiln 50 m long firing raw magnesite showed that, as a result of the intensification of the fuel combustion using the new burner design, we can obtain an increase in the kiln output of 6.5%, with a simultaneous improvement in the quality of the powder being fired. To ensure the optimum working conditions in the kiln and get complete combustion of the natural gas, its pressure in front of the burner should be not less than 0.2 MPa.

Change in the structure and properties of magnesia goods fired in industrial kilns

The p r o p e r t i e s of r e f r a c t o r i e s and the i r behavior in s e rv i ce a r e se r ious ly affected by the p r o c e s s e s that occur in f ir ing [1]. To d i scover means of improving the qual i t ies of magnes ia r e f r a c t o r i e s it i s impor tan t to know how the s t ruc tu re and p r o p e r t i e s a l t e r during heat t r ea tmen t in the va r ious zones of the industr ia l ki lns used to f i re them.

Tunnel kiln for firing refractories at 1850°c

ConclusionsThe refractories industry of the Soviet Union has designed and is now operating a tunnel kiln for firing refractories at 1850–1900°C. The kiln works with high cost-benefit indices and is used for firing high-grade magnesite-spinel goods on the basis of fused and sintered materials.

Gas-burner design as a factor in the performance of rotary kilns

ConclusionsAn investigation of the thermal performance of a rotary kiln 4.5 m in diameter and 170 m in length used for firing raw magnesite showed that the principal performance indices of the kiln varied with the type of burner (“tube” type, GRTs, and GDG-1).The performance of the kiln is better with GDG-1 burners than with either of the other two types.

Combustion of natural gas in high-temperature tunnel kilns

ConclusionsThe positions in the firing zone of a tunnel kiln can be divided into transfer, principal, and fume-laden types in accordance with the characteristics of the combustion of gaseous fuel. Each type of position requires its own system of heating in which account is taken of the characteristics of the heating process. The GTP-3-type burner can be used to advantage in the principal positions because it permits the fuel distribution across the kiln space to be regulated.

The grain-size distribution of the raw magnesite and the rotary speed of the kiln as factors in the kiln performance and the quality of the powder

ConclusionsThe current of the drive and consequently the power consumption of rotary kilns 4.5 m in diameter and 170 m in length decrease with an increase in the rotary speed of the kiln. The open porosity of the sintered magnesite powder decreases only slightly in this case but the grain-size distribution of the powder undergoes a change.A decrease in the grain size of the raw magnesite results in more rapid dissociation and sintering and in a significant improvement in the cost-effectiveness indices of the performance of rotary kilns: the productivity increases and dust entrainment, the coefficient of raw material consumption, and specific fuel consumption decrease without a decrease in the density of the sintered powder.In a rotary kiln 3.5 m in diameter and 90 m in length, when firing the magnesite 0–15-mm fraction in place of the usual 0–40-mm fraction, the productivity of the kiln increases by 5–8% and the coefficient of raw material consumption and the specific fuel consumption decreases by 5–7 and 5–8%, respectively, in addition to which the sintered powder contains 4–5% more of the 3–0.5-mm fraction, which is used for refractories production.For firing magnesite in the form of the 0–15-mm fraction in place of the usual 0–40-mm fraction on a large scale, the crushing-beneficiation mills (the third crushing stage) must be modified with a view to utilizing mainly magnesite grades 1 and 2 as well as magnesite enriched in heavy suspensions.

Performance analysis of gas-burner equipment of rotary kilns for calcining magnesite

ConclusionsThe performance of diffusion-type gas burners of various designs was investigated under comparable conditions in 170-m-long kilns 4.5 m in diameter at the Magnezit Plant.It was established that the medium-pressure regulatable diffusion-type GRTs and GDG burners possessed significant advantages over the nonregulatable “pipe”-type burners used hitherto.For a given gas flow rate the GDG-type burner produces a maximum flame power and gives a rigid, high-temperature flame which can be regulated within extensive limits to meet the requirements for magnesite calcination.For a given kiln charge of raw magnesite and a given quantity of heat admitted to the kiln the GDG type burner gives a higher yield of calcined powder at lower specific fuel consumption without adverse effect on the quality of the powder.