IMPROVEMENT OF

STOVE

HOT

OF T H E BLAST

V. M, Pryadko, V. S. M a g a l a ,

SERVICE

LIFE AND

EFFICIENCY

VALVES

K. I . K o t o v , A . M. Z h a k , M. I . D i k , a n d V. M. L u k i a n e t s

The a c c e l e r a t i o n of the iron melting process has a considerable damaging effecr on blast furnace plants and has placed special emphasis on the problems of service life and efficiency of thi~ type of equipment. An investigation into the operation of the hot blast valves, carried out a t the Petrovski[ pIant in 1965-1969, showed that the average life of these valves is 8 months. A similar conclusion was drawn at the VNIImetmazh (AI1-Union Scientific-Research Institute of Local industries) and the Giprostal' Institute, which carried out inv'estigations at other m e t a l l u r g i c a l plants. Unsatisfactory l i f e of valves increases blast furnace stoppages causing considerable cuts in production and subsequent financial losses. Calculations carried out by the VNIImetmash showed that an increase in the valve life by three times (the valve is replaced during the 3rd class furnace overhaul) would result in a total yearly saving in iron production and equipment repair costs throughout the USSR of at least 635,000 rubles~ The increase in iron o u t p u t resulting from a reduction of stoppages in the entire USSR, would be approximately 97,500 tons per year. The most frequent cause of valve failure in the bottom part of both wails and cylinders. source) wall where it join~ the side wall on the usualty some transverse cracks, the main cause a nonuniform heating.

is the d a m a g e to discs and rings. W a i l - t o - w a l l cracks are formed Both valve rings usuatly fail in the internal (nearer to the blast circumference. In addition to the longimdinaI cracks there are of a short l i f e of rings being the variable internal stresses due to

The Laboratory of Heat-Resistant Concretes and of Increasing the Life of Metallurgical Equipment and Structures at the Dnepropetrovsk Civil-Engineering Institute and the MChM UkrSSR ('Minista3r of Ferrous Metaliurgy of the UkrSSR) carried out, in cooperation with the Petrovskii Plant, a project involving the protection of valve surfaces facing the hot flow by heat-resistant concrete. This protection has e l i m i n a t e d sharp thermai shocks on rings and reduced the h e a t loss through cooling water. This protection method becomes even m e i e i m p o r t a n t in view of the planned increase in blast temperature. It is intended to increase the hot blast temperature a t the v a l v e to 15000C. When lining rings, no change was m a d e in the d i a m e t e r of the m e t a l structure of the hot blas~ duct. But the lining reduced the ring d i a m e t e r (Fig. 1) from 1100 to 960 ram. The hot air stop dampers, which have been previously faced with firebrick, were reduced to the same diameter. The flanges of the hot blast valve now have variable diameters: from 960-1100 mm, which made possible a smooth transition from the heat-resistant c o n crete portion to the duct with asbestos insulation and firebrick lining ' In the lining the heat-resistant concrete works under severe conditions. Because of a local narro~.eing of the cross-sectional area its thermal loading increases, as does its exposure to t h e r m a l erosion. Neverthe!ess, ::the performance of heat-resistant concrete lining was found to be good. For use in hot blast valves a heat-resistant concrete has been developed in which fireclay mixed with water glass is used as the filler. Dnepropetrovsk Civil-Engineering Institute. Petrovskii Plant. A pril, 1971.

Translated from MetaIturg, N 0 . 4 , pp, 8-10,

9 1971 Consultants Bureau, a division of Plenum Publishing Corporation, 227 [(lest 17th Street, New ] York, N. Y. I001I. All rights reserved.. This article cannot be reproduced for any purpose whatsoever I without permission of the publisher. A copy of this article is available from the publisher for ~15.00. t

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1

Fig. 1. Hot blast valve, air duct, air duct stop dampers, and flanges lined with heat-resistant concrete, and their connection to the hot air duct; 1) hot blast valve; 2) stop dampers on hot air duct; 8) flanges; 4) heat-resistant concrete lining; 5) hot air duct; 6)asbestos insulation; 7) firebrick lining. A good combination of the physicomechanical properties in the heat-resistant concrete makes possibIe its use for lining hot blast valve rings and the adjoining w a t e r - c o o l e d hot air duct elements (valve flanges and air duct stop dampers). For lining, the v a l v e is placed horizontally (Fig. 2) onto a level surface. Now, the metal frame is placed inside the v a l v e and secured in position by a crossbar bolted to the ring and valve body. A small platform welded to the crossbar takes a S-412A vibrator. To f a c i l i t a t e the removal of equipment after lining,the disc and the internal surface of the molding gear are first given a coat of melted c o m m e r c i a l - g r a d e ceresin. The air duct stop damper (Fig. 3) and valve disc are bolted onto a m e t a l plate. The metal parts of the molding gear Le., a ring for the damper and a truncated cone for the flange, change the lining d i a m e t e r from 960 to 1100 ram. The molding elements were boIted to the bottom plate using previously welded angles. The stability o f t h e i n t e r n a l gear, was increased by a crossbar carrying a S-412A vibrator. After the m o l d i n g gear has been assembled, thering, stop damper, and flange are lined with the heat-resistant concrete prepared in a f o r c e d - m i x i n g concrete mixer with gravity feed. Dry components are mixed for 3 min (adding first fillers and then cement). Next, water glass is added to the dry mixture which is again mixed for 5 rain. The h e a t - r e s i s t a n t concrete thus prepared is poured into the gap between the mold and body while the vibrators are in operation until the emission of air bubbles ceases and a thin liquid l a y e r appears on the lining surface. Thereupon the lined elements are held for 8-4 h air-dry condition at+17~ Then the molding gear is heated from inside until the ceresin melts sufficiently to allow the lined elements to be removed and dried in air for a t least 24 hours. Now the hot blast valve can be turned for lining the other ring. After brief storage in air-dry conditions the elements were dried by a gas burner at a t e m p e r a t u r e gradually increased to 800~ a rate of 50-75~ for 6-7 h. A gradual temperature increase is necessary to ensure a correct formation of the concrete structure.

223

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7

f 7"I

4 2 3

1

'

~-

"

-

t

Hole axis 7

-

O

~0.

Fig. 2. Molding gear for the lining of valve rings by heat-resistant concrete: 1) hot blast valve; 2) disc; 3) m e t a l gear; 4) crossbar; 5) m e t a l platform; 6) S-412A vibrator; 7) heat-resistant concrete lining. After drying, the elements are mounted in the duct. During the operation of the newly lined elements, a test was carried out involving ~ e m e a surement of the cooling water ~emperamre and its consumption. The measurements were taken in an adjacent stove.

Fig. 3. Gear for lining stop dampers for the hot blast duct: 1) stop damper; 2) metal plate; 3) bolts; 4 ) m e t a l lining gear; 5) crossbar; 6) S-412A vibrator.

Repeated measurements of the temperature and consumption of the cooling water flowing through the freshly lined hot blast zing, flanges, and stop dampers of the No. 1 stove at the Petrovskii Plant No. 3 btast furnace showed that at a stove t e m p e r ature of 1000-1200~ the average y e a r l y saving is 55, 000 k c a l / h during the "heating ~ and 850. 000 kcal/during the ~blast." Since only part of the coke carbon heat is utilized in the furnace, a reduction of the heat loss through hot blast improves the blast furnace process and reduces coke consumption. The y e a r l y saving per stove of a 1033 m 3 blast furnace is 26,000 rubies.

The operation of the stove with rings, flanges, and stop dampers lined with the heat-resistant concrete for over a y e a r and the experience gained earlier in lining other items showed that this material is suitable for lining hot-blast duct elements. The heat-resistant e'oncrete can be used at hot blast temperatures now in c o m m o n use, and with the furore blast temperatures o f 1200-1250~ Since the lining gear is easy to m a k e and can be used repeatedly, the lining of the existing stove elemen~:s for existing plants can be organized without an additional c a p i t a l investment. The fact that the duct elements are monolithic improves service life and effieiendy. The service life of a valve working under "blast" conditions can be increased further by protecting the disc seat and the bottom disc parts. In this case the bottom blast flow will be everywhere in contact with the heat-resistant lining.

224

In the future, when using hot blast valves and adjoining elements lined with heat-resistant concrete, measures should be taken to avoid internal cross-section contractions. For this purpose the design of valves and other elements should be revised with the view of increasing the metal structure diameter. The new heat-resistant concrete composition has successfully passed tests in the steel making plants of Petrovskii and Krivoi Rog Metallurgical Plants, where it has been used for Iining lost head parts of molds. The use of this material will increase the average mold life by 60 times and reduce the size of the lost heat compared with heads obtained in molds lined with refractory compound and fire brick.

225