RU2252973C1 - Chip melting method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method is realized by charging chips into melting space of furnace through metallic tube and melting chips. Before charging chips, on furnace hearth melt metal bath is provided whose volume consists 0.2 - 0.25 of volume of melting space of furnace. Chips are charged into melting space of furnace through metallic tube having area of its inner cross section consisting 0.03 - 0.05 of bath surface area with use of metallic pusher directly into melt metal under slag layer coated with carbon-containing material. Then chips are melted in melt metal bath.

EFFECT: enhanced efficiency of process, lowered metal losses.

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Description

The proposed method relates to the field of processing non-ferrous metal and alloy waste and can be used in the smelting of shavings in enterprises of secondary processing of metals and engineering enterprises having waste of their own production.

A known method of remelting (see V.Ya. Konyukh “Oxidizing metal smelting”, Kiev, “Naukova Dumka”, 1979, p. 87), in which the chips are uniformly and continuously loaded on top of a layer of charcoal, over which a reducing atmosphere is maintained due to burning fuel with a lack of air.

The disadvantage of this method is that due to the significant number of fine fractions, the supply of chips into the furnace over a layer of charcoal towards the flow of exhaust gases leads to significant entrainment and oxidation of the metal.

In addition, the slag formed on the surface of the metal bath has a high viscosity and high surface tension, which does not allow chips having a low bulk density to penetrate into the melt. Thus, the process of melting the chips proceeds in a layer of charcoal above the surface of the slag bath, and drops of molten metal pass through a layer of charcoal and slag, partially precipitated in them in the form of “kings”, which leads to an increase in metal losses.

до температуры плавления металла

и непосредственно плавление самой стружки. Все эти процессы приводят к увеличению времени переплава, т.е. снижают производительность. Кроме того, мелкие капли расплава, проходя через слой шлака, осаждаются в виде “корольков”, что приводит к увеличению потерь металла.Of the known closest in technical essence is the method of smelting metal shavings directly in a slag bath (see V.Ya. Konyukh “Oxidative smelting of metals, Kiev,“ Naukova Dumka ”, 1979, p.93), according to which the shavings are loaded into the furnace through a steel pipe directly into the slag bath, while the entrainment of the charge from the working space by exhaust gases is significantly reduced. However, when particles of shavings, the melting temperature of which are higher than the pour point of the slag, are immersed in the slag melt, the slag crust freezes on them as a result of intense heat absorption by the cold shavings. The heat generated during crystallization of the slag is completely used to heat the chips. The freezing process ceases when thermal equilibrium sets in, when heat fluxes are equal on the inner and outer surfaces of the frozen layer. From this moment begins the melting of frozen slag, and then subsequent periods: heating of the chips from the melting point of the slag

to the melting point of the metal

and directly melting the chips themselves. All these processes lead to an increase in remelting time, i.e. reduce productivity. In addition, small drops of the melt, passing through the slag layer, are deposited in the form of “kings”, which leads to an increase in metal losses.

The technical result of the proposed method is to increase the productivity of the process of remelting chips and reduce metal loss.

The essence of the proposed method lies in the fact that prior to loading the chips onto the hearth of the furnace, the metal melt is pre-welded with a volume of 0.2-0.25 of the volume of the furnace melting space, the chips are loaded into the furnace melting space through a metal pipe with an internal cross-sectional area of 0, 03-0,05 surface area of the bath, using a metal pusher directly into the metal melt under a layer of slag coated on top with carbon-containing material, and the chips are melted in the melt.

This combination of new features with the known allows you to increase the productivity of the process of remelting chips compared with the prototype, as it increases the speed of its melting, and reduce metal loss, since less “kings” are deposited in the slag.

The method is as follows. First, a “swamp” is created on the bottom of the melting unit from a metal melt with a volume of 0.2-0.25 of the volume of the furnace’s melting space, which is covered with a layer of carbon-containing material on top of which a reducing atmosphere is maintained due to lack of air. Then, through a metal pipe, the lower end of which is immersed in a metal melt below the slag level using a metal pusher, the chips are loaded directly into the metal melt under the slag layer.

Pointing at the bottom of the melting unit “swamps” of metal melt with a volume of 0.2-0.25 of the volume of the furnace’s melting space and using a metal pusher and pipe with an internal cross-sectional area equal to 0.03-0.05 of the bath surface as a loading device , provides the maximum possible performance of the smelting unit and minimal metal loss during chip remelting.

The decrease in the volume of the “swamp” below the lower limit leads to a cooling of the melt, since the melting of the chips is mainly due to heat transfer from the melt to the hard chips, and exceeding the upper one is unjustified due to performance considerations and is not economically feasible, since the volume of the working space is reduced ovens.

Reducing the internal cross-sectional area of the loading pipe below the lower limit leads to a decrease in the process productivity, since when loading a single dose of chips necessary to ensure maximum productivity of the remelting process, the column of chips in the pipe is so large that clogging occurs and it is impossible to push the chips into the metal melt using a pusher. An increase in the internal cross-sectional area of the loading pipe above the upper limit leads to an increase in the contact area of the metal melt in the loading space with the atmosphere and, as a result, increased metal waste.

An example implementation of the method.

Smelting was carried out in an induction channel furnace type IPRP - 0.25 as follows. A “swamp” with a volume of 0.15–0.3 of the volume of the furnace’s melting space was deposited in the furnace; charcoal with a layer thickness of 15–25 mm was loaded onto its surface. The loading and distributing space of the furnace was closed with a metal arch, in which a metal pipe was fixed, with an internal cross-sectional area equal to 0.02-0.05 of the surface area of the furnace bath, through which crushed brass chips were loaded in metered portions. The loading pipe was installed so that its lower end was immersed in the metal melt 10-15 mm below the surface of the slag bath. Using a metal pusher with an outer diameter of 3-5 mm less than the inner diameter of the loading pipe, the chip portions were pushed directly into the melt, where the chip was melted. The duration of each melting was 60 minutes, and the melting was carried out in such a way that the rate of loading of brass chips in the furnace maintained the temperature of the melt in the range of 940-970 ° C, since with an increase in the speed of loading of chips, when the temperature of the melt dropped below 940 ° C, melt cooling was observed and the chip melting rate decreased, and with a decrease in the loading speed, when the melt temperature exceeded 970 ° C, increased zinc fume was observed. The temperature was measured with a TPR - 571 thermocouple.

The results of the swimming trunks are presented in the table.

As can be seen from the table, the application of the method provides the maximum possible performance of the melting unit and minimal metal loss during remelting of the chips.

The proposed method is comprehensively investigated and accepted for implementation at OJSC "Penza Valve Plant"

Smelting conditions Amount of remelted chips, kg Smelting time, min The volume of the “swamp” in relation to the volume of the melting space of the furnace The internal cross-sectional area of the pipe relative to the surface area of the furnace bath Metal burn,% Metal loss in the form of “kings” in% Extraction of metal (by weight of metal in the charge,)% The productivity of the process, kg / hour Process performance Known method 80 60 0.25 0.04 5.3 3.8 90.9 80 Stable The proposed method 80 60 0.25 0.02 5.3 0.8 93.9 80 There is a constant “clogging of the pipe with chips 115 60 0.25 0,03 4.9 0.6 94.5 115 Stable 120 60 0.25 0.04 4.8 0.5 94.7 120 Stable 120 60 0.25 0.05 4.9 0.5 94.6 120 Stable 120 60 0.25 0.06 5,4 0.6 94.0 120 Stable, but increased fumes 90 60 0.15 0.04 4.9 0.5 94.6 90 In the initial melting period, the melt “cools” 118 60 0.2 0.04 4.9 0.5 94.6 118 Stable 120 60 0.25 0.04 4.8 0.5 94.7 120 Stable 120 60 0.3 0.04 4.8 0.5 94.7 120 Stable but reduced free space

Claims (1)

A method of melting chips, including loading the chips into the melting space of the furnace through a metal pipe and melting it, characterized in that prior to loading the chips onto the hearth of the furnace, a metal melt of 0.2-0.25 of the volume of the furnace melting space is preliminarily deposited, the chips are loaded into melting space of the furnace through a metal pipe with an internal cross-sectional area equal to 0.03-0.05 of the surface area of the bath, using a metal pusher directly into the metal melt under a slag layer covered about the top with a carbon-containing material, and the chips are melted in the melt.