G. Sh. Ashkinadze

Burning clinker for high-alumina cement in a rotary kiln

ConclusionsWe prepared clinker for high-alumina cement in a rotary kiln and determined the material balance in firing when preparing the raw mixtures with two methods: granulation in a plate granulator and briquetting on a roller press. It is shown that much less dust removal (4%) is ensured by firing the briquets obtained on the roller press. The aluminous cement obtained with this technology has a high graded strength.

Investigating sintering of magnesia obtained by chemical beneficiation

ConclusionsA study was made of the sintering behavior of samples of magnesium oxide obtained by chemical purification. The magnesia obtained by the nitrate method is a low sinter-active material. The density of the material after firing at up to 2400°C equals about 3.0 g/cm3. Partial hydration of the material improves the sintering results. The magnesia obtained by the ammonium-sulfate technology is an active material which when fired yields a densely sintered product with a density of 3.3–3.4 g/cm3.

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.

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.

Furnace truck with channeled base

ConclusionsChanneled furnace truck linings have been devised and industrially tested; they greatly reduce the vertical temperature drop in the furnace channel and improve the annealing quality of the refractories.

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.

Firing difficult-to-sinter high-purity dolomite with oxygen

ConclusionsA technology was developed for firing difficult-to-sinter dolomites in the crushed state which yields an adequately dense powder not contaminated to an appreciable degree with fusing agent.It was established that the life of the converter linings at the NLMP increased by 12.2% when made of tar-bound refractories from high-purity powder processed from Bosnin dolomite.

Heat engineering tests on high-temperature tunnel kilns with setting heights of 700 and 1100 mm

ConclusionsRoof refractories can be fired in a setting 600–700 mm high; increased height of the setting leads to the development of substantial loss of products (fusion and deformation) in the lower courses. High-grade firing of roof products is achieved in a high-temperature tunnel kiln with a working space 0.75 m high.The low tunnel kiln designed by the All-Union Institute of Refractories compared with the standard tunnel kiln for firing single-grade settings of roof refractories gives better uniformity of product firing, close control of the process of improved cooling of the products, and lower loss. The specific consumption of heat for firing the goods in the low kiln is higher than in the standard.Improvements in the low tunnel kiln should be continued so as to permit the injector devices for feeding low-pressure air to the burners and intermediate burners to be cut off and to develop a lining for the cars and the kiln roof with higher thermal shock resistance, as well as improved systems of sealing the kiln.

Convective heat exchange in tunnel kilns

ConclusionsIn calculating the coefficients of heat transfer by convection in tunnel kilns for the longitudinal surfaces of the setting with a latticed column structure Eq. (1) is recommended, for the longitudinal surfaces of the setting with solid columns Eq. (9); and for transverse surfaces in the setting Eq. (14). The resulting coefficients of heat transfer can be made more accurate by multiplying them by the value η, determined from Eq. (2).