Theory and Practical Use of Modular-Pouring Electric Furnaces for Firing Vermiculite

Abstract

Results are presented from theoretical and experimental studies of modular-pouring electric furnaces. The process of the absorption of heat energy by vermiculite was examined and the optical-geometric parameters of the firing modules were determined. Efficient values were found for the temperature and duration of the firing of vermiculite concentrates. It is shown that the existing modular-pouring electric furnaces can be improved and new, energy-saving furnaces of this type can be developed.Products based on expanded vermiculite occupy an important place among the wide range of refractory materials that are made. They have good heat-insulating properties thanks to their porous layered structure, which allows them to be used to line different types of high-temperature equipment. Vermiculite is also an effective heat-insulating material and serves as a porous filler for lightweight concretes. It can be used to prepare dry mixes, including mixes with fireprotection properties. Vermiculite is employed in the acoustic insulation of buildings, the casting of steel, and other applications [1,2].The idea of creating a modular-pouring electric furnace for firing vermiculite was conceived in 2003 [2 -4], and refinements were made to the original concept during the ensuing decade of practical use of such furnaces. Improvements were made to the furnaces on the basis of results obtained not only from their operation but also studies of analytical models of their working processes.The goals of the studies were to analyze the process by which heat energy is absorbed by vermiculite, determine the optical-geometric parameters of the firing modules, find efficient temperature-time regimes for the firing operation, and determine the efficiency and unit energy content of the firing process.Modular-pouring electric furnaces can be used as a basis for the construction of small production units designed to obtain different fractions of high-quality expanded products from vermiculite concentrates (including concentrates that have already undergone preliminary beneficiation) and conglomerates with a high content of inert material [2]. Figure 1 shows a block diagram of the process of obtaining an expanded product from high-purity concentrates with a vermiculite content of 94 -96%. Charging the raw material into the furnace in different fractions makes it possible to obtain vermiculite of any desired granulometric composition. If

Electric Modular-Trigger Kiln with an Energy Recuperation System for Firing Vermiculte Concentrates

“…The deficiency in heat determined by expression (3) for the kiln analog adopted with three electrified modules and constant time 2.72 sec [5] Thermal exergy (430.6 kJ) is almost 300% greater than the energy (144.5 kJ) lacking for completing vermiculite dehydration and expansion.…”

“…In contrast to the standard heat assimilation model [7,8] in this scheme there is an additional channel A -B for transformation of vermiculite dry particle heat into mechanical work for expansion. Presence of an additional channel provides a possibility of improving the efficiency of mechanical transformation of vermiculite with values inherent for the standard model (0.544) [5].…”

“…(1) is 1209 kJ/kg. As noted in [5], heat q d does not participate in vermiculite mechanical transformation and is accumulated within grains. A small proportion of this vermiculite energy goes into water vapor and gases heated during expansion, and the rest goes into heating a bunker, kiln metal structure, and is dissipated into the environment.…”

Energy Efficiency of the Electric Kilns With Movable Floor for the Various Size Groups Vermiculite Concentrate's Burning

“…Модульно-спусковые электрические печи для термообработки вермикулитового сырья и других сыпучих материалов [1][2][3] из-за большой стоимости электроэнергии во многих регионах страны до недавнего времени не могли конкурировать с пламенными печами, несмотря на низкую энергоемкость процесса: 150-160 против 235-260 мДж/м 3 [4]. Новые печи с подвижной (вибрационной) подовой платформой [5] способны принципиально изменить эту ситуацию, так как аналитические расчеты [6,7] и экспериментальные результаты [8] показывают возможность достижения удельной энергоемкости 45-65 мДж/м 3 на концентратах Ковдорского месторождения.…”

Dynamics of the First Platform of the Oven for Burning Vermiculite With Vibration Feeding of Raw Material

“…Предшественниками рассматриваемых печей были электрические модульно-спусковые печи [1,2,3] с уже десятилетним опытом их производственной эксплуатации. Но даже в наиболее совершенных из нихпечах с неэлектрическим «нулевым» модулем, не удалось достигнуть удельной энергоемкости обжига 160 МДж/м 3 [4].…”