by Alexander GRECHKO, Dr. Sc. (Tech.), leading researcher, GINTSVETMET Research Center of the Russian Federation
It is wonderful indeed how many kinds of stoves and furnaces have been invented by humankind during its history. There are Russian and Dutch stoves, metal makeshift stoves for everyday use, stone and Finnish stoves for steam baths, heating and welding stoves, and what not! Even more of them are employed in the technical sphere: heating furnaces, heat-treatment, fuse, burning, casting, glass-making furnaces and the like. Their designs are also numerous, such as chamber, drum, ring, multiple- hearth furnaces: boiling-layer, cyclone, shaft, electric and plasmic things as well as converters. And so on down the line.
The furnace - heating technology is closely connected with hydroaerodynamic processes. This was proved by great Russian scientists, such as Academician Alexei Krylov (1863-1945), the creator of the shipbuilding theory and the author of books on mechanics and mathematics; Nikolai Zhukovsky (1847-1921), Corresponding Member of the Petersburg Academy of Sciences, the father of aerodynamics theory, who contributed greatly to hydrodynamics and hydraulics, and Konstantin Tsiolkovsky (1857-1935), an outstanding researcher in aerodynamics and rocket dynamics, who chartered effective ways of space exploration.
Russia saw the first prototype of modem blast furnaces for ferrous metallurgy in 1630. Nonferrous metallurgy got a similar furnace somewhat later. A reverberatory furnace - equipped with a smoke chimney - was invented in Britain (Wales) in 1698. It was designed to fuse lead-ores using coal. For the last 300 years such furnaces have evolved according to their bottom area from 5 up to 300 sq. m and even more.
True, furnace building and use were the art for the few initiated, that is for those self-taught persons wise in this art's secrets. There existed no theory explaining the principles of furnace design and operational characteristics. Moreover, the following curious incident is reported: as there were no regulations on building heating systems under Peter I (1672-1725), he imposed stove-building standards and banned building in the capital and other cities "black izbas" heated by stoves without chimneys.
Change came only in the beginning of the 19th century when the accumulated knowledge in the physics and chemistry of various processes spurred theoretical and experimental research in the field of gas aerodynamics and heating engineering. One of the major achievements in this sphere was made by Vladimir Grum-Grzhymailo (1864-1928), Corresponding Member of the USSR Academy of Sciences and a prominent Soviet metallurgist and chemist, who worked out a theory of furnaces. Besides scientific intuition he also showed good managerial skills. Therefore, at his initiative a government authority was set up in 1924 under the auspices of the USSR Supreme Council of National Economy to take charge ofmetallurgic and heating-engineering structures. This authority
changed its name several times, but since 1934 it has been known as Stalprojekt ("Steel Project").
The fundamental scientific achievement of Vladimir Grum-Grzhymailo was a hydraulic theory of gas movement in furnaces published in 1910. In 1925 his coverall work Burning Furnaces, was off the press. Interestingly, he used the dissertation of Ms outstanding compatriot Mikhail Lomonosov (1711-1765), Free Air Movement in Mines, as a basis for his own works. Lomonosov was the first to explain a very important phenomenon-the fire action in natural- draft furnaces. The great Russian savant explained gas movement in natural- draft furnaces by the warm (light) smoke being ousted by the surrounding heavy (cold) air.
Yet despite the unquestionable authority of the first Russian Academician, Ms theory was shelved for quite some time. His time, the 18th century, was marked by a tendency to explain all phenomena and processes from the point of view of mechanics; this applied to furnaces as well. The concept of draft, rather odd to a contemporary scientist, was introduced at that time. The draft allegedly helped remove combustion products out of the chimney. One thought: the taller the chimney, the more drafty and effective the furnace. Yet, if we look into the process, we will see that owing to their nature, gases are unable to draw anything. They just transmit pressure, they are ousted-but there is no mechanical action in them.
The false idea of the chimney's draft hampered solution of the furnace problem and sidetracked the development of an appropriate theory for as long as 150 years. Be that as it may, the Lomonosov theory on the cause of gas movement staged a comeback. Overcoming the conservatism of reputable scientists of the day (an important consideration!), Vladimir Grum-Grzhymailo managed to cope with the problem. From the art of a few masters heating engineering turned into a science (a theoretically substantiated approach to furnace designing and building).
All major tasks in this area were fulfilled, it seemed. However, the accepted hydraulic theory concealed flaws which came to light in the 1930s. Then, in the period of the Stakhanovite movement, one was prone to set objectives that were unrealistic technically because some furnaces operated on natural draft, or natural gas movement. The intensification of these regimes by structure modifications and forced gas movement inside furnaces prodded scientists to further search.
Therefore, numerous publications came out, where we can single out certain ideas - specific, general and composite. However, all these ideas had one flaw in common - they considered either a group of concrete furnaces, or separate processes (aspects) of their work. Thus, certain specialists based their theories on forced gas movement in furnaces, and they focused exclusively on convection in what concerned external heat transfer. Other scientists proceeded from the heat-and-power engineering of furnaces as the key factor of their operation. And, eventually, the third group regarded science as an adjunct to this or that technology and left out a general theory relative to furnace processes. But here the works of our compatriot Mikhail Glinkov (1906-1975) can be considered most preferable, summing up as they did all knowledge accumulated by the time (technical physics, hydroaerodynamics, theory of heat transfer, etc.) and its possible application to different furnaces.
Mikhail Glinkov gave a detailed classification (which is a must for a general theory) of both the heating devices and their working regimes. According to him, the major and determining factor for all furnaces is their heating regime. It includes a considerable rise in temperature, heat and mass exchange and mechanics of interactive environments to ensure higher heat and its distribution in the operational zone. As far as these numerous regimes are concerned, only four are of practical use-the radiation, convection, mass exchange and electric regimes. Thus each furnace, depending on its structure and designation, can work both in one or in several regimes.
This approach makes it possible to solve a lot of problems for most furnaces of different designation. However, we cannot say that a complete vigorous theory has been developed. Besides, the existing empiric formulas do not always give a one-to-one answer to certain problems. This applies to some extent to widespread autogenous smelting furnaces for metals from the sulfide raw material and bubbling furnaces for ferrous and non-ferrous metallurgy*, and to some trends in pyrometallurgy**, as well.
Today there is an intensive flow of experimental and statistical data on the work of various furnaces. The achievements in related sciences (named above), experiments on furnaces and test benches as well as the results of physical and mathematical modeling set the stage for further theoretical studies. The point is that R&D methods are based on the principle: analogy - formalization - mathematical apparatus-modeling. A new qualitative leap, we hope, is in the offing.
* See: A. Grechko, "Copper Smelter of the Future", Science in Russia, No. 3, 1998. - Ed.
** See: A. Grechko, "Pyrometallurgy: Contact Heat Exchange", Science in Russia, No. 6, 2000. - Ed .
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