Features of dense bed movement in a shaft furnace reactor

Abstract

The construction of a shaft furnace reactor is considered with temperature regimes for the working medium, the dense bed and the lining. Attention is drawn to possible changes in the operating reactor channel cross section and profile. Nonisothermal movement of the dense bed in the reactor is analyzed and its features are noted in relation to the ratios of the dense bed and channel cross sections.The main element of a shaft furnace is its reactor whose operating space is a vertical channel of predominantly circular cross section. The reactor construction consists of a refractory lining and a steel case over whose height there are three heat-engineering zones: A, B, C. The product being treated in the reactor channel moves as a dense bed under the action of gravitation in a counterflow with the working medium [1] that in the reactor is combustion products of hydrocarbon fuel, atmospheric air and mixtures of them. The heat treatment of a product in each zone and in the whole reactor is specified by temperature regimes of the working medium and the dense bed. A diagram of a reactor with the temperature regimes is provided in Fig. 1. The dense bed regime is provided by the regime of the working medium as a result of heat exchange in the counterflow between the working medium and the dense bed. Both temperature regimes, working medium and dense bed, are not steady-state. The reactor lining is specified by its temperature regime that is also determined by the working medium regime. In contrast to the working medium and dense bed regimes, the temperature regime of the lining is steady-state and it has an effect on the cross section of the reactor channel.Levels of temperature regimes for the dense bed and the internal surface of the lining in channel cross sections over the whole height of the reactor have almost the same values. The level of the temperature regime for the dense bed is higher than the average value of the level of the temperature regime for the lining, determining temperature changes of the channel cross section. During reactor operation the cylindrical channel with an initial diameter of cross section D 1 , uniform over its whole height, under the action of a steady lining temperature regime may be converted into an expanding or contracting channel, any cross section of which will have a its own fixed dimension, D 2 or D 3 respectively.The expanding channel will consist in zones A and B of conically expanding parts, and in zone C of a conically contracting part in the dense bed movement direction. The sizes of the cross sections of the expanding parts are greater than

Dependence of fuel consumption on the productivity of a shaft furnace during preparation of a magnesium oxide product

“…In refractory technology a shaft furnace may be used for preparing from magnesium oxide three forms of product of different density: porous, dense, and ultra-dense [1]. Each form of product corresponds to the type of heat treatment for the original material in a shaft furnace reactor with individual dependence of heat consumption on its productivity.…”