LU86054A1 - PROCESS FOR TREATING METALLURGICAL DAIRY FROM A TANK OVEN - Google Patents

Description

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Method for treating metallurgical slag from a shaft furnace.

The present invention relates to a method of treating metallurgical slag from a shaft furnace! in a plant comprising a multi-stage granulation head for the formation of superimposed water jets, a filtration station for separation! the granulated slag from the filtration water which is collected in an underlying hopper from which it is sent to a cooling tower, a condensing hood 1 to collect and condense the gases | 10 exhaust polluted with recovery water! from the cooling tower.

Although not limited to the process targeted (by the invention, more particularly relates to the treatment of slag in an installation of the type i. 15 described in the Luxembourg patent Ko 79466, that is to say a installation in which filtration is carried out by means of a rotary drum provided with internal buckets The granulation head is preferably similar to that described in Luxembourg patent 20 No. 82585, that is to say a granulation head in in which superimposed water jets are formed and in which the upper water jets are essentially used for granulation proper, while the lower water jets are used primarily for discharging the slag and cooling the walls of the channel i through which the evacuation of the pulp which is made up of granulating water and granulated slag is carried out!

Regulations aimed at defending the environment impose increasingly stringent rules on steelmakers regarding the discharge of polluted vapors and gases from steel treatment processes. This is the case, for example, with the liquid granulation of slag from blast furnaces.

. 35 To answer some of this? ecological criteria— 'gigues, it is known to be received: 11: - ceo gas emanating from ψ ί' Ί I -2-! j granulation of slag in a hood, in the existing one; j at least part of the gases and vapors are condensed by means of cold water nozzles. On the other hand, it is well known that granulating slag with cold water is much more environmentally friendly! i gic that that carried out with hot water, that is to say i i j pollution by gases and vapors from j 'granulation with cold water is much! i less important than in the case of granulation with 10 hot water. However, the use of cold water both in the granulation head and in the condensation hood increases the water consumption. As an illustration, if a consumption of 4000 m ^ per hour is planned for the granulation head, 3

j 15 provide about 2000 m per hour in the hood of I

. condensation, resulting in huge consumption | 6000 m ^ per hour. On the other hand, if recovery water is to be used, provision must be made for cooling installations designed to be able to treat this body of water and reduce its temperature to an acceptable value. The object of the present invention j is to provide a new process for granulating dairy i which makes it possible to comply with ecological criteria with reasonable water consumption.

! : 25 To achieve this objective, the method according to the present invention is essentially characterized 1 in that the condensation water is recovered at the bottom; j from the condensation hood and is sent to the

• bottom of the granulation head to serve essen- I

i 30 tally for the transport of slag and in that the upper part of the granulation head essentially serving: granulation itself, is fed! in water from the cooling tower. .

i i

The advantage provided by the process according to the present invention is that all of the water used in the condensation hood is recovered for the benefit of this granulation. This means that because.? 1 euem-pls quoted above r you only have to treat 411: ir-1 r * \ ________ -, r - i -3- cooling water compared to 6000 m ^ which had to be treated before when the water recovered from the condensation hood was returned to the cooling tower through the recovery hopper 5 of the filtration water.

Despite the heating of the water undergone in the condensing hood, granulation can be carried out with cold water thanks to the separation of the functions of granulation and transport in the granulation head 10 , since the heated water collected in the condensation hood is injected into the part! bottom of the granulation head and it is used only for the evacuation of the granulated slag.

Another significant advantage of the proposed process is that the solid constituents from! precipitation and condensation in the hood, like! for example the slag filaments also called "angel hair" are recycled in the granulation station instead of being sent, as before, in the water recycling circuit in which they risked '' damage pumps and valves.

Other features and characteristics will emerge from the detailed description of an embodiment presented below, by way of illustration, with reference to the single figure which shows schematically; ment a granulation installation of the kind proposed in the Luxembourg patent No 79466. This.! installation comprises a head of Granulation 10 of the cenrej; * - i

! described in Luxembourg patent No 82585, that is I

! I

’* | 30 to say, a device in which one forms several! superimposed jets, or the upper jets are mainly used for granulation, while the jets! interiors are mainly used for the evacuation of! granulated slag and cooling the walls of the discharge channel. The pulp 12, made up of the mixture of water and more or less solidified slag particles, flows through a slop inclined in a

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distribution channel yes, it opens out inside a filtration valve 16. In this drum 16 separation takes place between the solidified slag particles and the granulation water. The granulated slag is evacuated by means of a conveyor belt 18, while the filtered granulation water is collected in a hopper; | of the underlying settling tank 20. j The filtration water is recovered from the hopper j v 20 and sent through a line 22 to a cooling tower j for subsequent reuse! 10 after cooling. This reuse consists in sending the cooled water through a pipe \ 26 to the granulation head 10.!

Above the installation there is a hood 28 in which is provided a series of nozzles 30 \ 15 also supplied with cooled water recovered from the tower 24 through a pipe 32. In this hood 28 the precipitation of the solid particles and the condensation of gases and vapors from the granulation of the slag. In accordance with the present invention, the water is collected at the bottom of the condensation hood 28 and sent with the particles! solids precipitated through a pipe 34 in the j I granulation head 10. Thanks to the separation of the j j functions in this granulation head 10 this water! 1. 25 recovery is used primarily for pulp disposal purposes 12 so that the heater! ment suffered in hatte 28 remains without influence in! granulation process. This can, on the contrary, be carried out with cold water coming from the granulation tower 24 so that these can be used. advantages, from an ergological point of view, of a granuia-! tion with cold water. On the other hand, the water consumption is reduced, since the cooling water! this the condensation hood is fully recovered.

I On the other hand, the solid constituents recovered! tees with the water at the bottom of the hood 28 are again mixed with the liquid slag precipitated in front of the granulation head and remain, in part, enclosed in the slag particles which are solidifying, j _ - Φ v ί * iii! i j! ! i

Claims (1)

1.- Method for treating metallurgical slag from a shaft furnace in an installation comprising a multi-stage granulation head for the formation of superimposed jets, a filtration station for separating the oranulated slag from the filtration water which is recovered in an underlying hopper from which it is sent to a cooling tower, a condensation hood to collect and condense the polluted exhaust gases using recovery 10 from the cooling tower, characterized in that the condensation water is recovered at the bottom of the condensation hood and is sent to the part; bottom of the granulation head to be used mainly for the transport of slag and in that the part i *! j 15 upper of the granulation head serving essential-; | The actual granulation is supplied with water from the cooling tower. v '^ \ y 1 J i i i. J j I: ”, i i i f i i i