Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
1999-12-30
2001-12-25
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S325000, C075S500000, C266S160000, C266S176000
Reexamination Certificate
active
06332911
ABSTRACT:
The invention relates to a method for the production of liquid metal, in particular liquid pig iron or liquid steel pre-products, from metal carriers, in particular partially reduced or reduced sponge iron, in a melter gasifier in which with supply of a carbon-containing material at least partially formed of fine coal and coal dust and supply of oxygen or oxygen-containing gas the metal carriers are melted in a bed of the carbon-containing material at the simultaneous formation of a reducing gas, optionally upon previous final reduction, and a plant for carrying out the method.
One problem arising in the charging of fine-particulate carbon-containing material, such as fine coal and coal dust, to a melter gasifier is that the fine-particulate carbon-containing material due to the gas velocities existing in the melter gasifier is instantly carried out of the same again. This also applies to fine-particulate ore to the same degree. To prevent this, it has f.i. been proposed in AT-B-401 777 to charge carbon carriers to the melter gasifier together with fine ore and/or ore dust by means of dust burners, namely to the lower region of the melter gasifier. With this process, substoichiometric combustion of the charged carbon carriers takes place. One disadvantage of this is that the carbon carriers cannot contribute to the formation of a bed made up of solid carbon carriers in the melter gasifier.
It is internally known to charge fine-particulate coal to a melter gasifier in the upper region thereof, wherein the fine-particulate coal is reacted to coke, the coke is carried out along with reducing gas and is separated and together with fine-particulate material is subsequently supplied to a melter gasifier via a burner. However, this also does not contribute to the formation of a bed of carbon-containing material.
Such as bed is usually formed from lumpy coal which has to have a high thermal stability. Due to the development of the coal market, which is governed by the demands of the operators of coal-fired power stations, the situation may arise that fine coal is preferentially offered, for the coal dust burners that are customary today. Grate firings, which were formerly the practice and which necessitated the charging of lumpy coal, now only play a minor role in the market of coal consumers. As a consequence thereof, the fines portion of the coals offered in the market may assume considerable proportions, ranging in the order of up to 50 to 70%.
When charging such coals to a melter gasifier, the coal fines usually must be screened out first, so that only the coarse fraction, i.e. the lumpy coal, will be available for charging to the melter gasifier. The fines are put to use elsewhere.
The invention has as its object to also utilize the fines in a useful manner in that they contribute to the formation of a bed of carbon-containing material in the melter gasifier, thus making it possible to reduce the cost of charging lumpy carbon-containing material.
According to the invention, this object is achieved in that, after undergoing a drying operation, fine coal and coal dust which are being charged are mixed with bitumen in the hot state and subsequently are cold-briquetted, and that the briquettes thus formed are charged to the melter gasifier in the cold state and in the melter gasifier are subjected to shock-heating.
Surprisingly, it has been found that the briquettes so produced exhibit an excellent thermal stability that even exceeds the thermal stability of lumpy carbon-containing material. The briquettes show very slight disintegration at the shock-like action of the temperatures of the melter gasifier of about 1000° C. This is due to the properties of the bitumen used as a binding agent, which melts rapidly at the indicated high temperature and thus occasions a beneficial bridging effect between the coal particles. What is essential here is that the bitumen does not evolve gas at the indicated temperature and besides retains its doughy consistence and its binding power.
From DE-A-24 07 780 it is known to charge pit-coal briquettes made from a mixture of treated high-grade, in particular anthracite and/or nonbituminous fine coal or fine coal as the charging coal and high-vacuum bitumen as a binding agent, with the briquettes thus produced serving for firing, f.i. in domestic stoves, or optionally, if they are subjected to a thermal process such as oxidation, low-temperature carburization or coking, being even suitable for charging to a blast furnace. Yet, these briquettes fulfil different requirements than the briquettes produced according to the invention, the more so since with the briquettes of the present invention it is thermal stability that matters, that is to say, the briquettes should not burst even at sudden temperature shocks in the case of charging to a melter gasifier, whereas according to DE-A-24 07 780 it is important that the briquettes exhibit a high stability, that is a high resistance to pressure, to enable charging them to the blast furnace. In accordance with the known method, the high-vacuum bitumen is heated to 200° C. and after mixing with the fine coal is briquetted at a temperature of about 85° C. Due to the high portion of coke formers in the known briquettes there is formed a coke network, whereby a high stability results.
According to a preferred embodiment, fine coal and coal dust are separated during and/or after drying of the carbon-containing material being charged and are further treated in the hot state.
Lumpy carbon-containing material arising in the separation of the fine coal and of the coal dust according to a preferred embodiment of the method of the invention is charged to the melter gasifier directly.
Preferably, fine coal with a particle size smaller than or equal to 8 mm is separated from the carbon-containing material.
From EP-B-0 315 825 there is known a method of the type initially described, in which fine coal after grinding is mixed with a binding agent, for example lime, molasses, pitch or tar, and is granulated, whereupon it is introduced into a melter gasifier. However, according to the invention, not a granulating but a briquetting operation is carried out, with the briquettes exhibiting a higher thermomechanical stability as compared to the granulates. A further disadvantage arising in accordance with EP-B-0 315 825 is the substantial expenditure of energy necessary for grinding the fine coal. According to the invention, this disadvantage is avoided in that the carbon-containing material being charged is not ground, but the fine coal and the coal dust are separated.
From AT-B-376 241, a method is known according to which the solids made up of dust-like carbon which have been entrained out of a melter gasifier by the reducing gas are separated from the reducing gas and agglomerated and the thus-formed agglomerates, in particular shaped coke, are recycled to the melter gasifier. Yet, unlike with the invention, the carbon-containing material being charged is not agglomerated here, and fine coal cannot be charged on a larger scale. With the method according to AT-B-376 241, a further disadvantage arises in that the agglomerating means is arranged directly after the hot cyclone serving for separating the dust-like carbon, which necessitates considerable expenditures in terms of construction.
According to the invention, the fine coal or the coal dust separated from the carbon-containing material being charged is mixed with bitumen and briquetted, with the briquetting being arranged downstream of the drying of the carbon-containing material. In doing so, the heat content of the fine coal and the coal dust after drying is suitably made use of in the mixing with the bitumen and in briquetting. No additional thermal energy has to be expended for briquetting.
According to a preferred embodiment of the method, the fine coal and the coal dust are mixed with the bitumen at a temperature below 100° C., preferably at a temperature between 75 and 80° C. Advantageously, bitumen with a softening point below 80° C., preferably below 75° C., is cha
Schrey Gunter
Zahedi Parviz
Andrews Melvyn
Deutsche Voest-Alpine Industrieanlagenbau GmbH
Ostrolenk Faber Gerb & Soffen, LLP
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