LU81330A1 - PROCESS AND PLANT FOR THE RECOVERY OF IRON, ZINC AND LEAD CONTAINED IN DUST AND SLUDGE FROM BLAST FURNACES, AS WELL AS CONVERTERS AND ELECTRIC STEEL FURNACES - Google Patents

Description

A 572

8- | ΐ — T AiRAND-DUCHÉ DE LUXEMBOURG

I 0 ù y 3 0MAM979 du —.......................................... ..... Minister of National Economy

Title issued ................................. [5¾¾¾ Industrial Property Service,

__BftS LUXEMBOURG

. —Tl · —— Application for Patent

30, M W

I. ARBED request. ..HER............................................. .................................................. .................................................. ................................................ <1 >

Avenue de la ..Liberté, LUXEMBOURG ......................

represented by ... Mon. rené NEYEN, engineer .................................. ...................... (2) deposits ....... this ... thirty May 1900 seventy-nine .... ............................... ..... (3) to ../ jß ...... ............ hours, at the Ministry of National Economy, in Luxembourg: 1. this request for obtaining an invention patent concerning: • Process and installation for recovery iron, ..... zinc ........ (4) and ... du. lead contained in high dust and sludge ................

furnaces./ as well as converters ... e.t. of ... ovens..electrical .......

d1aciéries declares, assuming responsibility for this declaration, that the inventor (s) is (are): ........................ ............ Sir. Paul METZ_____________________ ______ _____________ ________ ___________________________ (5) engineer 18 / rue JP Brasseur ................................... ................ LUXEMBOURG ................................. .................................................. .................................

2. the delegation of power, dated ... Luxeinbourç on May 29. 1.979 .______ 3. the description in French of the invention in two copies; 4. ...... 1________ drawing boards, in two copies; 5. the receipt of the taxes paid to the Luxembourg Registration Office, .30 May 1979 ............................ ... .................

claims for the above patent application the priority of an idea (s) of (6) ............... ........ ..... ..... ... deposited in (7) on __________________________ / ................................ .................................................. ................................................ .. ..................................... (8) on behalf of ....... ......... ......................................... ........... ¢ 9) takes up residence for him '' and, if appointed, for his representative, in Luxembourg

Central Administration of ARBED, PO Box 1802 dO) requests the issuance of a patent for the object described and represented in the abovementioned appendices, - with adjournment of this issuance to the 1st month.

The agent IL Priteês-verfcü de Dépôt

The aforesaid patent application has been filed with the Ministry of National Economy, Industrial Property Service in Luxembourg, eri date: 3 Q HAl î8? 8

Pr- k Minister of National Economy, at .............. hours // f ^ '\ n. d.

/ / £ * ke.Chef ôu Service dsTfe pfipriété Industrielle, 'z' f; t r A, "V: J} V '' * A 572 * Patent application A R B E D S.A.

Avenue de la Liberté LUXEMBOURG

Process and installation for the recovery of iron, zinc and lead contained in dust and sludge from blast furnaces, as well as from converters and electric furnaces from steelworks * ·

The present invention relates to a process and an installation for the recovery of iron, zinc and lead contained in dust and sludge from blast furnaces, as well as from converters and electric furnaces from steelworks.

5 Blast furnaces can produce up to 100 tonnes of dust and sludge per 1,000 tonnes of pig iron depending on their market. Considerable amounts of dust are also collected during the purification of gases from refining furnaces.

10 Depending on the quality and composition of the ores, agglomerates or scraps sent in the oven and the operation of the installations, the dust and sludge may contain variable amounts of iron, zinc, lead and alkali metals present in the dust. and sludges in the form of complex oxides.

So we are faced with waste that cannot be recycled directly. In fact, direct recycling would lead to a concentration of zinc, lead and alkalis inside the various installations, which could pollute the products produced, as well as considerable discomfort during the flows by the formation of harmful fumes.

Furthermore, it would obviously be desirable to be able, on the one hand, to isolate the iron contained in this waste to reintegrate it into the production processes and, on the other hand, to recover the zinc and lead for specific uses.

A lot of research has been done in this direction and has resulted in processes, most of which fall into the field of chemistry, resp. electrochemistry.

Thus a process, developed by the applicant and described in the Luxembourg patent no. 73.039, consists in subjecting dust to leaching with water saturated with CO2 and in separating the water which contains the dissolved zinc. The latter is precipitated by removing the CO2. This process gives excellent results with regard to the isolation of zinc.

35 However, the leaching residues still contain almost all of the lead and some of the alkalis, so that recycling at the expense of a blast furnace is hardly recommended.

Other processes are essentially based on the calcination of pelletized dust and the volatilization of zinc, lead being very difficult to vaporize. Thus it is for example known to treat according to the Waelz process pelletized dust together with a carboniferous reducer inside „5 of a rotary kiln where the reduction of metal oxides takes place, in concert with the reaction of Boudouard, while in the gas phase there is oxidation of the vaporized zinc.

Another method provides for the calcination of dust pelletized together with coke fines in a closed enclosure 10, excluding oxygen, at temperatures of 1050-1150 ° C. During this treatment, the zinc is almost 100% volatilized and the lead about 15%. To further reduce the lead levels in the residue, it is proposed to practice the same process several times.

The methods based on the calcination of pelletized dust are very slow and do not solve the problem of recovering lead-free iron in a satisfactory manner. Chemical and electrochemical processes on the other hand require expensive reagents resp. large amounts of electricity and are further confronted with the problems of disposal of liquid residues.

The object of the invention is therefore to propose a process which makes it possible to recover the iron, zinc and lead contained in the dust and sludge and which avoids the disadvantages of the conventional processes described above.

This object is achieved by the process according to the invention which is characterized by the fact that the zinc is volatilized by continuously introducing the dried or ground dust or sludge into an iron bath, which is introduced at the same time. continuously in said bath carbonaceous materials in sufficient quantity to maintain therein a carbon content greater than 1%, which is added to the bath of the formers of a slag with a basic character and which means are provided for heating to compensate for the heat losses in the said bath. content and constantly added in the iron bath and on the other hand a selective volatilization of the reduced zinc, the reduced lead having a very high evaporation temperature, and finally a fusion of the reduced iron. Lead, which hardly oxidizes at the temperature of liquid iron in the presence of small amounts of oxygen, is found in the bottom of the bath, in metallic form.

Furthermore, by maintaining a layer of slag on the bath, preferably having a basicity index close to 1.4, it is possible to retain the sulfur contained in the treated dust and sludge. This constitutes a considerable advantage over conventional methods based on reductive calcination, the products of which are polluted by sulfur and therefore cannot be used directly without additional purification.

A first embodiment of the process according to the invention provides that the materials to be treated, the fuel additives and the slag formers are blown below the surface of the bath. The present embodiment can be carried out either by means of a plunging lance and using a reducing or neutral carrier gas, or in analogy to any method of steel refining by blowing from the bottom.

According to a second embodiment, the materials to be treated, the fuels and the slag formers are introduced into the bath by blowing from above, in analogy with the LDAC process and intense agitation is supported in the bath by blowing into it. gas through a porous brick. The gas is still neutral or reducing gas.

A third embodiment provides for side blowing combined with gas blowing through a porous brick.

According to a particularly advantageous embodiment of the process according to the invention, the blowing gas consists of the fumes of an oxygen converter, taken during the blowing phases when they have a high content of carbon monoxide. carbon and a very low oxygen content. These converter fumes are normally burned.

The role which falls to the blowing gas consists first of all of transporting the dust and the additions inside the bath and of causing inside the latter a stirring

1 day

intense and then to support the rapid volatilization towards the surface of the bath.

The zinc fumes released are oxidized according to Zn + CX ^ · * ZnO + CO in the gas phase to be evacuated and collected continuously / while part of the metal bath or liquid slag which is formed is withdrawn intermittently during the treatment according to the invention and which contains sulfur. The cast metal is generally subjected to granulation, preferably to water granulation. These granules 10 can then be integrated into the charge of a blast furnace. The slag drawn off can also be granulated.

For the execution of the process, it must be ensured that the freshly baked iron bath, as well as the slag formers contain only a minimum of silicon, since zinc 15 and lead very easily form complex compounds with l 'silicon oxide, which complexes are extremely stable.

A preferred embodiment of the installation used for implementing the method according to the invention is characterized in that it comprises in particular a metallur-2o container (1 °) r a lance (23) provided with a refractory lining (26), the head (25) of which is located near the bottom of the bath (15) and the inlet of which is connected to a cellular metering device (20) located outside the container, as well as a pipe ( 14) which extends inside the container and which is connected to a dust collector (30).

The use of a honeycomb dispenser of the type described by the applicant in Luxembourg patent no. 80.692 is particularly advantageous in the present context, since it is possible to maintain inside its piping and in the lance a constant gas pressure, sufficient to impart intense agitation to the bath and add a adjustable amount of dust, fuel or flux.

The metallurgical container (10) is closed by means of a removable cover (11) through which the lance * (23) and the heating electrodes (12) pass.

While the lance may be integral with the removable cover, the electrodes are adjustable in height, since only intermittent heating is provided as required.

* - r: _ I The container is also provided with a tap hole (16) for the metal which can lead into a granulation tank (40) and with a tap hole (17) intended for the evacuation slag (18).

5 Other characteristics and advantages emerge from the description given below with reference to the drawing which represents a schematic view of a possible embodiment of the installation according to the invention.

The illustrated metallurgical container (10) is provided with a removable cover (11). The latter is crossed by the lance (23) and by the electrodes (12).

The lance (23) which is here of the submerged type comprises an outer refractory lining (26). By the head (25) of the lance (23) one can thus evacuate the additions in the bottom 15 of the bath (15). The lance is connected at the other end to a cellular metering device (20).

The insufflation gases / under a pressure (P) sufficient to ensure an "intense bubbling of the bath, pass through the alveolar metering device (20) and the lance (23), so that it suffices to adjust the rotation of the 'shaft (22) of the metering device (20) at a determined speed, for injecting into the bath (15) a desired amount of dust which is in the funnel (21).

It is possible to add by the same route or by a separate cellular metering device the necessary quantities of refueling, as well as of slag formers. These products can be mixed beforehand.

The metal dust is treated inside the bath (15) which is kept in a state of constant agitation thanks to the blowing gases.

The ZnO dust, formed during the treatment, is evacuated through the pipe (14) and collected inside * of a cyclone (30) provided with a discharger (31).

A certain quantity of the bath, the volume of which increases continuously due to the quantities of iron recovered from the dust during the treatment, is withdrawn intermittently through the tap hole (16). The cast metal can undergo water granulation inside the tank (40), to be reintegrated at the expense of a blast furnace. Alternatively, the molten metal which is free of sulfur can be put directly into a steelworks converter thanks to the presence of basic slag during the treatment. The separation of lead is particularly easy, since thanks to its high specific weight the metallic lead is assembled at the bottom of the bath.

"

Claims (12)

1. Process for the recovery of iron, lead and zinc contained in dust and sludge from blast furnaces * as well as from converters and electric furnaces from steelworks, characterized in that the zinc is volatilized by introducing into continuously the dust or sludge dried and ground in the bottom of an iron bath, which is simultaneously introduced continuously into said bath carbonaceous materials in sufficient quantity to maintain a carbon content greater than 1%, that 10 are added to the bath formers of a slag with a basic character and that heating means are provided to compensate for the heat losses in said bath. 2. Method according to claim 1, characterized in that the materials to be treated are blown, the recarburants and the slag formers below the surface of the bath using a reducing or neutral carrier gas. 3. Method according to claim 1, characterized in that the materials to be treated, the recarburants and the slag formers are introduced into the bath by blowing from above using a reducing or neutral carrier gas. and that an additional quantity of this gas is blown into the bath through a porous brick. 4. Method according to claim 1, characterized in that the materials to be treated, the recarburants and the slag formers are introduced into the bath by side blowing using a reducing or neutral carrier gas and that l 'an additional quantity of this gas is injected into the bath through a porous brick. 5. Method according to claims 1-4, characterized in that the gas consists of the fumes of an oxygen converter, taken during the blowing phases when they have a high content of monoxide of carbon and a very low oxygen content. 6. Method according to claims 1-5, charac-35 in that it collects continuously the dust formed during treatment. 7. Method according to claims 1-5, characterized in that part of the metal bath and the slag layer are drawn off intermittently. 8. Method according to claims 1-7, characterized in that one integrates the recovered metal treated by granulation at the expense of a blast furnace. * 9. A method according to claims 1-7, charac-5 se in that the untreated molten metal is placed in a steelworks converter. 10. Installation for implementing the method according to claims 1, 2 and 5-9, characterized in that it comprises in particular a metallurgical container (10), a lance (22 10 provided with a refractory lining (26) , whose head (25) is located near the bottom of the bath (15) and whose inlet is connected to a cellular metering device (20) located outside the container, as well as a discharge pipe (14) which extends inside the container and which is connected to a dust collector (30) 15 11) Installation according to claim 10, charac terized in that the metallurgical container (10) has a removable cover (11) through which the lance (23) and heating electrodes (12). 12. Installation according to claim 10, carac-20 terized in that the metallurgical container (10) is provided with a tap hole (16) for the metal and a tap hole (17) for the slag. t