US2192108A - Steel smelting furnace - Google Patents

Description

Feb. 27, 1940. A. scHAcK STEEL sMETING FURNACE Filed July 30, 1938 Patented Feb. 27, 1940 PATENT oF-FICE STEEL SMELTING` FURNAoE Alfred Schack, Meerbusch, near Dusseldorf, Germany, assigner to Rekuperator Gesellschaft mit beschrnkter Haftung, Dusseldorf, Germany, a

rbody corporate of Germany Application July 30, 1938, Serial N0. 222,073 In Germany August 28, 1935 1 Claim.

The invention relates to a steel smelting furnace lay-out, in which the combustion air is heated by a recuperator that is heated by means of the exhaust gases from the smelting furnace and in which a steam boiler heated by the exhaust gases that ow to the recuperator is provided between the recuperator and the smelting furnace. The steam boiler stands according to the invention inv such relation to the recuperator l with respect to the ow of the exhaust gases that the loss of pressure in the exhaust gases flowing through the steam boiler is only a fraction of the loss of p-ressure in the exhaust gases flowing through the recuperator. Therefore the resistance to flow in the boiler isdetermined so as to be less than half the resistance to ow in the recuperator. Generally the relationship is such that the resistance in the boiler amounts to only7 about one-tenth of the resistancev in the recuperator. The determination of the resistances in accordance with the invention is based on the following facts: v

The particles of dust that are carried by the exhaust gas from the Siemens-Martin furnace are in a liquid state at temperatures between` 1250 C. and about 1350 C. When these liquid particles of scale strike against heating surfaces, they solidify on the surfaces and form deposits that are diicult to remove. Consequently the stream of exhaust gas that carries these liquid particles of scale must be so thoroughly cooledas far as possible without any considerable disturbance to flow, such as without causing change in direction of flow and so on-that the temperature is considerably below thev melting point of the particles, for example 1l00 C. Numerous and considerable changes in direction and the like are factorsin the ow of the gas attended by loss of pressure in the stream of exhaust gas. Hence according to the invention the boiler is made so large in its cross-sectional dimensions of passage that the resistance to ow oiered to the exhaust gases is only a fraction of the resistance to flow which the. exhaust gases subsequently experience in the recuperator, where the temperature of the dust is ,considerably below the melting point and therefore the deposits of dust are not objectionable.

In order to avoid in the recuperator the accumulation of the constituents of the dust that melt at a low temperature, and whose sintering vpoint lies near to the temperature ofthe tubes the coefficient of heat transmission in the tubes of the recuperator on the air side in according to the invention, when, also, use is made of a steel recuperator, raised considerably higher than is often the case in ceramic heat exchangers, regenerators as well as recuperators, that is to say, to about 40 k. cal./m2h C.

This increase in the coecient of heat transmission can be secured in known manner by correspondingly raising the speed of flow ofthe air stream or by the use of members built into the path of the air. In this way the temperature of the walls of the tubes is reduced and accordingly there is a cooling of the dening layer between the heating gas and the wall of the tube and consequently a reduction of the sintering point of the dust. The dust can then be blown off from these tubes by compressed air or like means. In consequence of the reduction in the danger due to dust in the heating system, the possibility is thus afforded of working the steel smelting furnace with coal clust which hitherto has been difficult owing to the higher content of dust in the hot exhaust gas, combined with the relatively low melting point of the dust.

A smelting furnace system constructed accord; ing to the invention is diagrammatically illustrated by way of example in the accompanying drawing in which: v

Fig. 1 is an elevational view of the smelting furnace system; and' Fig. 2 is a sectional view taken on the section line 2-2 of Fig. 1.

The smelting furnace, which may be a Siemens- Martin furnace, bears the reference numeral I. The gas discharge passage 3 which is opposite to the burner openings 2 of the furnace opens into a steam boiler 4 having the Water tubes 'I4 connecting the upper and lower drums I3, I2, as shown. The waste gases pass from the steam boiler 4 through a recuperator 5. The gases pass into the recuperator 5 through the pipe 6 into the spaces between the pipes I5 and pass out at the bottom of the recuperator through the pipe 1.

The recuperator serves to heat the combustion air that is supplied to the burners. The cold air is fed into the recuperator 5 at the bottom by a fan 9 through a pipe I0, which extends into the distributing part of the system of tubes of the recuperator which is impinged upon by the gases, but is not shown in the drawing. The hot air passes out at the top of the recuperator through the hot air pipe Il that is connected to the co1- lecting member of the system of tubes of the recuperator, the pipe Il leading to the burners of the smelting furnace which are not illustrated.

I claim:

A steel smelting system comprising a sm'elting furnace,'a fuel burner connected to said furnace, a Water-tube steam generator and an air-heating recuperator, said Water-tube steam generator being interposed in the direct path of,flow of combustion gases from the said furnace'to the said recuperator, said recuperator being connected to said furnace to supply air heated by said combustion gases for the combustion `oil-fuel supplied to 4said fuel burner, the cross-sectional area for thepassage of combustion gases between the tubes of said 4water-tube steam generator being proportioned in relation to the corresponding free area for the passage of combustion gases in the said recuperator, so that the resistance to` the flow of said combustion gases through the space spanned by the tubes of the said steam generator is less than half that of the said free area in the recuperator, wherebythe said combustion gases are cooled in passage through the l is reduced below the melting point thereof, thereby avoiding corrosion on the heating surfaces of- 1 the recuperator.

ALFRED sorteer;`

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