Construction of economical linings of production equipment

Abstract

Effective utilization of material and energy resources is an important problem of the national economy to which much attention is being devoted at present. The problem of optimization of production linings installed in furnaces and other equipment, which are important technical, thermal engineering, and constructional functions, is one of its aspects. The lining must eliminate uncontrolled gas exchange of the furnace with the atmosphere, possess the necessary strength and chemical resistance at the working temperatures and under constant and variable thermal and mechanical loads, and have a high thermal resistance. In the final analysis these factors are integrated into the index of economy of the lining, the total combination of capital and operating costs related to it.Problems of optimization of a lining may be solved by minimization of some target function reflecting the influence of the primary production factors on costs. Depending upon the specific approach and assumptions the structure of the target function is not the same for different authors, which naturally leads to a difference in the results obtained.In [i] the target cost function I I in rubles/m 2 is taken as the sum of the cost of the energy lost during the period of the interrepalr campaign and the construction costs for thermal insulation:where q is the heat flow in W/m z tg--t a q= ; (2)is the length of the interrepair campaign, sec; Cq, Cin , and Cin , costs of heat, rubles/J, of thermal insulation, rubles/m s, and of installation of it, rubles/mZ; 61n, thickness of the thermal insulation layer, m; t s and ta, temperatures of the furnace gases and the surrounding air, ~ as, coefficient of convective heat exchange from the furnace gases to the wall, W/(m2"K), and a s -f(Cs, As, Ws, deq); ~w, coefficient of heat exchange from the wall to the surrounding medium, W/(m2"K); Cs, As, and Ws, specific heat, J/(mS'K); the thermal conductivity, W/(m'K); and the velocity, m/sec, of the furnace gases; d.q, equivalent diameter for the channel of gases, m; As thermal conductivity of the i-th layer of the lining, W/(m'K); and n, number of layers in the wall.From the condition dL =0 with constant thermophysical characteristics was determined u6i n the optimum thickness of thermal insulation ~opt in m: In the method of optimization considered the cost of the lining is taken into consideration insufficiently fully and the temperature factor, the minimized function, is decreased as the result of both positive and negative factors (for example, a decrease in q and r).