Optimizing the multilayer heat-insulating lightweight refractory linings of industrial furnaces and heat-powered units

Abstract

A universal criterion for estimating the service life of the refractory lining in heat-powered units is proposed. An algorithm for optimum choice of the design and thermal engineering properties of multilayer heat-insulating linings is discussed.The state of the fuel and power complex in the early 21st century in Russia and countries of the former Soviet Union dictates implementing a stringent engineering policy in the area of fuel resources, in particular, calcination technologies. Because of the low market cost of energy resources, of late predominant in the Russian Federation, the domestic industry has so far shown little interest in reducing the power supply per unit product. Still, the trends towards a leveling of prices of power resources in the internal and world markets makes the reduction of energy expenditures and, consequently, enhancing competitiveness of domestic products on the world market, an issue of urgent concern.Modern calcination processes are implemented through curtailing the consumption part of the heat balance of a particular furnace or a heat-powered unit. The use of modular high-temperature heat-insulating lightweight materials (MHTLWM) makes it possible to reduce heat losses through the refractory lining of the working chamber of a heat-powered unit to an acceptable level of about 250 W/m 2 [1]. The MHTLWM is thus a set of space-oriented multilayer refractory heat-insulating materials assembled into a module and aimed at solving a multifunctional engineering task in a particular heat-powered unit. The development of a lining for MHTLWM-based furnace and heat-powered units is a challenging task which involves a compromise between the requirements, not infrequently contradictory, placed on the refractories' service [2].It is practically impossible to functionally harmonize parameters for a lining made of a uniform material [3]; a way out of this situation is to use a multilayer refractory lining. In developing such a structure, the designer should take into account a number of parameters, such as: (i) the cost of refractory materials available from domestic and foreign manufacturers; (ii) operating temperature for a particular refractory; (iii) heat conductivity, heat capacity, coefficient of linear thermal expansion (CLTE), and mechanical strength of the lining materials; (iv) resistance of refractories to thermochemical attack of the hot-furnace space; (v) environmental requirements placed on the chemical composition of the refractory; (vi) temperature drop at the layer interface and the associated therewith change in heat conductivity of the material; and (vii) resistance of the hot layer of the lining to abrasive attack of the dust-and-gas furnace space.In this work, we have estimated the MHTLWM service life in terms of a criterion with a value of K = 1.0 which parametrizes the loss of basic operational properties (heat capacity, heat conductivity, and mechanical strength). This criterion has been derived using research data from the literature [2, 4 -7], statistical results of obser...