BE456198A - - Google Patents

Description

       

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  "PROCESS FOR EXTRACTING ZINO IN A TANK OVEN BY REDUCTION OF ZINCIFEROUS ORES ETC. BY BLOWING IN THE PRESENCE OF A FUEL".



   The present invention relates to a process for extracting zinc in a shaft furnace by reduction of zinc ores or zinc-bearing metallurgical products by blowing in the presence of a fuel. The extraction of metallic zinc from the shaft furnace has been carried out. often tried. but has never been carried out successfully * The cause is that the zinc vapor contained in a large quantity of gas does not allow itself to liquefy into metallic zinc and can only be precipitated in the form of zinc dust at about 40% ZnO (Figure 1).

     This is why we tried to obtain the zino in the form of zino dust and then transform this zinc dust by remelting or by redistillation into metallic zinc.

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 EMI2.1
 However, the remelting process in use s.ujourq'hu1.ne gives a sufficient yield and production only in the case where the zinc dust is of a corresponding constitution. According to the experiment, one can extract by fusion of the dust of zino
 EMI2.2
 formed as a by-product in the retort process to 95% of its zino metal content. But with zinc dust from other sources, for example high-furnace zino dust, this does not lead to an economic return by smelting.

   Extensive tests at, background have shown that zinc dust is of a different nature depending on the method of its obtaining
To obtain a good performance of the extraction by fusion it is necessary to try to obtain!
I) a high content (over 75%) of metallic zinc in zinc dust;
3) as heavy as possible zinc dust.



   For obtaining metallic zinc from dust of
 EMI2.3
 zino I is also the reiqt3lla.tian Which comes into play, and in this way it suffices to produce a thin or specifically light zinc segment (with a bulk weight of less than 2) (see figure 2 ), which must however also have a high metallic zinc content.



   Heavy dust (figure 3), which at the same time has a high content of metallic zinc, appears under the microscope clearly as a plurality of metallic grains and has a high bulk weight, i.e. 1 liter weighed, after having been shaken
 EMI2.4
 for an hour, 2 é. 4 kg. Its density rises, at a pressure of 25 atmospheres to more than 3.5, on average about 5. This zino dust has the most value when it comes to obtaining by the process of extraction by. melting a maximum possible metal yield.



   The main cause of the decrease in the value of zinc dust is carbon dioxide which partially oxidizes
 EMI2.5
 zinc vapor. Therefore it was necessary to recognize

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 first the sources of carbon dioxide formation in the oven process and suppress as much as possible the formation of co2.
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  In the reduction of zinc ores oxidized or oxidized by carbon following the normal process in the open furnace, i.e., when blowing the combustion air through nozzles with oxygen from the air burns with the carbon contained in the charge and in this way supplies the heat necessary for the endothermic reduction of zinc oxide * The following important reactions occur within the charge through which the combustion gases and reduction gases pass
 EMI3.2
 I) 0 + 02 li! I Ctd + 97.8 small calories.



   This reaction is the heat source for the whole process. '
 EMI3.3
 ) 002 + 0 III S 00 - 38.4 small calories.



   This reaction provides the main acting carbon monoxide in the process of - following reduction * -
 EMI3.4
 3) Zn0 + 00 - Zn + 002 - T4; g small calories.



   This reaction is the main reaction, because it releases the zinc vapor from the ore.
 EMI3.5
 4) Zn + 0 s * Zn + t0. 53.5 small calories. '
This reaction is a secondary reaction, because it can only occur in direct contact of the zinc oxide found on the surface of the ore grains with the solid carbon *
 EMI3.6
 s) a C0 * CC + 0 + 38.4 small calories.!
This reaction (Boudouard effect) is the reversal of reaction 2) and it occurs to an increasing extent at
 EMI3.7
 relatively low temperatures between 1050 and 400c'e 6) Zn + 00 = * ZnO + 00 + 14.9 small calories.



   This reaction is the reversal of reaction 3) at relatively low temperatures * !, It is reactions 5) and 6) which are of the utmost importance for the constitution of the zinc dust obtained in the open furnace. The equilibrium of the reaction 5) shifts under

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 its positive thermal effect, at a decreasing temperature, more and more on the side of 00 * For the reaction 6) the equilibrium moves, at decreasing temperatures, on the side of the ZnO, for the marl reasons that in the case of the reaction 5). The sensitivity of Zn vapor to CO2 is increasing rapidly * So at decreasing temperature, an enhanced transformation of zinc to ZnO corresponds to an increased formation of 00 (see Figures 4 and 5).

   Since already during the rise of the reaction gases in the furnace of the hot zone, with a temperature of 1000, in colder zones which have temperatures below 900, a reoxidation by CO2 of the reduced zinc, it is necessary, in order to avoid deterioration or depreciation of the zinc, respectively of the zinc dust, to avoid as much as possible the presence of carbon dioxide in its environment; at too low a temperature carbon dioxide can no longer be reduced by carbon.

   On the other hand, carbon dioxide is formed by the Boudouard effect (reaction 5) at a low temperature also in the presence of coke * On the other hand, the oxidation reaction of Zn by carbon dioxide, being a markedly exothermic reaction, it also occurs at decreasing temperature. In order to obtain zinc dust with a high metallic content, it is therefore necessary first of all to suppress the formation of carbon dioxide in the bottom furnace.



  For this purpose it is necessary to maintain the temperatures in the open oven at a height such that reactions 5) and 6) cannot take place, that is to say care must be taken to eliminate them by operating the oven. conditions of storage and formation of carbon dioxide.

   When, under these conditions, all the zinc has been released in the form of vapor, the gases in the furnace must be refrigerated to a low temperature (below 100) with such rapidity that all the harmful reactions which may occur at a temperature relatively low can no longer occur *
During the blowing of air through the nozzles of the shaft furnace, anhydride is formed, as has already been mentioned above.

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 oarbonic by the combustion of oxygen with the car,., bone content of the load.

   There is thus simultaneously a release of the total thermal energy of the oarbone and the latter heats the environment through which the combustion gases pass, to high temperatures * The CO2 formed is therefore immediately reduced to 00 by glowing carbon (coke), so that the carbon dioxide content at 1000 and above goes down to. below 1%. The CE? formed and, to an extent, solid carbon reduces the charge zinc oxide and metallic zinc is released as a vapor and mixed with the gases.



  Carbon dioxide (formed by the reduction of ZnO is immediately retransformed into CO by the glowing coke. So as long as the temperature is above 100,000, the released zinc can no longer be reoxidized in the presence. of carbon * Since these reactions are all the more lively as the temperature is high, it is advisable to operate the furnace in a hot blast.

   In addition it is advantageous to subject the wind to pre-drying, because the water vapor behaves towards the zino vapor in a detrimental manner similar to that of carbon dioxide * However, if the the zinc vapor entrained by the furnace gases would be allowed to pass through the charge, becoming colder upwards and enclosing air, the carbon dioxide formed would no longer be transformed quickly enough into 00 by the incandescent carbon, so that the carbon dioxide content of the gases would increase * With a subsequent lowering of the temperature of the gases by the cold charge, the Boudouard effect following reaction 5) would occur below 1000 C,

   then taking large proportions at decreasing temperatures from 800 C. It follows that, in order to obtain zinc dust with as high a metallic content as possible, the gases from the furnace must %% not be evacuated at temperatures above 800 ° C. and be cooled immediately quickly, usefully below 100 ° C., or else the zino dust must be removed from the gas by rapid mechanical separation (for example using a cy-

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 clone) and 'be cooled away from air. This zino dust is a light zinc dust, with a bulk weight of less than 2.

   The dust and fly ash content varies between 4% and 10% of the amount of zinc dust * The metallic zinc content of the dust and fly ash free product is greater than 75%.



   When it is desired to obtain zinc dust in a heavy form (with a bulk weight greater than 2) and simultaneously with a high content of metallic zinc, it is necessary to avoid, during condensation, sudden cooling of the zinc vapors from too high a temperature; because the higher the temperature at which the condensation of the zinc vapor into zinc dust by cooling is carried out, the finer the grain and hence the lower the bulk weight. It has been found that in order to obtain a high percentage of heavy zino dust, the starting temperature for the sudden cooling of the gases containing the zinc vapor must be 650, 80,000, on average 700 C.



   The results can be further improved by interposing between the oven and the separator a direct or indirect electrically heated zinc dust regenerator. The purpose of such a regenerator is the following: I) to re-vaporize the zino dust already. forced; 2) to reduce again already formed zinc oxide;

   3) to prevent if possible the displacement of the Boudouard equilibrium on the CO2 side and to move it, if possible, on the CO side, which must be done by adding heat from the outside *
In order to re-vaporize already formed zinc dust it would in itself be sufficient to pass the gases through a chamber filled with chamotte pieces and heated from the outside, which has been confirmed by tests. However, if goals 2 and 3 are to be fulfilled simultaneously, it is advisable to charge the regenerator with coke or a fuel of an even higher reactivity, to its view.

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   semi-aoke or charcoal.

   Because of the poor thermal conductivity of carbon it is useful, in order to save heat, to admit fuel heated to high temperature into the regenerator dust and to evacuate from the regenerator a corresponding quantity. of the load.

   The temperature which must prevail in the regenerator is preferably around 700 C. It is also possible to work at a lower temperature, for example at 650 0, but in this case the danger of obstruction by dust of zinc ,, On the other hand, if the temperature of the incoming gases is allowed to exceed 800 C, the dust regenerator can no longer fulfill its mission.
In the tests which led to the present invention, the content of the zinc vapor output gases was 4.4 to 5% by volume. As can be seen from Figure 6, zinc vapor can only condense at such dilution below 675.

   In addition, at temperatures above .800 ° C there is only a little CO2, so that the dust regenerator fails at all to fulfill its intended purpose. say to lower the quantity of CO2. With a working regime at temperatures above 800 0, the dust regenerator would only have to carry out the reduction of any ZnO present * '
Therefore, the action of the dust regenerator consists in first line of lowering as much as possible the CO2 content of the outlet gas shortly before the final condensation, and this at a temperature of 700 C at which a lot of CO2 would be formed following the Boudouard effect according to figure 4.

   However, this is prevented by the new heat input, thanks to which the reaction is moved to the 00 side, this reaction being endothermic (reaction 3). In the second line it is a question of reducing the zinc oxide enveloping dust particles, to promote the growth of dust particles by the addition or adhesion of metallic zino. Thirdly, for the new vaporization of the zinc dust already partially condensed, a concentration

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 higher zinc vapor, which also contributes to the magnification of the zinc dust particles during the subsequent sudden cement cooling.

   Dust regenerators of this reread have been tried in the most diverse embodiments ?! and it was found that with a larger surface the proportion of heavy zinc dust increased. Figures 7 to. 9 represent some possible constructive forms of dust regenerators.



   A zinc regenerator generally consists of a tank-shaped chamber made of heat-resistant iron or another material which is a good conductor of heat and coolant, heated from the outside. Heating of the regenerator can also be achieved in part by subjecting the filling material employed to applied blast heating outside of the regenerator; and that the material thus heated is introduced into the latter.



  For the filling the best is to use a material in Pieces not too small, namely, of a size of about 60 to 80 mm, because otherwise the resistance offered by the zinc dust deposits increases too quickly and the filling must be renewed too quickly during work. In calculating the cross section of a regenerator care must be taken that the working temperature can be kept as uniform as possible up to the center. Therefore the dimensions must be adapted in each case to the material of construction used for the filling chamber.



   As soon as the airways leave the dust regenerator, they are cooled as quickly as possible from the hazardous temperature zone by driving them along cold surfaces or by throwing the dust mechanically against the cold surfaces and separating it from the gas.

   As already mentioned, the proportion of heavy dust can be increased voluntarily by enlarging the dust regenerator. For economic reasons, however, it is not advisable to bring all the dust to the heavy form if possible, provided that the residual dust remaining lighter contains very little ZnO

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 after treatment with the dust regenerator and is heavier than without this treatment, so that during remelting it can be relegated to the heavy dust obtained *
The resulting total, mixed dust still meets the requirements set above for heavy dust.



   The relatively fine dust can be separated in multioyolones and the residue which remains is usefully washed out or collected by means of filter bags *
The ways which have led to the solution of the problem of preparing zinc dust with a high content of metallic zinc are described in the working examples below which are subdivided as follows:

   I) preparation of a light zinc dust with a high metallic content, with a bulk weight of less than 2; 2) preparation of heavy zinc dust with a high metal content, with a bulk weight greater than 2; 3) a) preparation of a heavy zinc dust with a high metallic content, with the intercalation of a dust regenerator (r.p.) b) increase in the quantity obtained of heavy dust by the enlargement of the dust regenerator; o) increase in the amount of heavy dust obtained by the kind of filling of the dust regenerator.



   I) Preparation of a light zinc dust with a high metallic content with a bulk weight of less than 2.



   The filler consists, for example, of roasting blende agglutinated with limestone, with a lump size of 8 to 20 mm, and coke or semi-coke with lump sizes of 10 to 30 mm. , mixed in a ratio of I: 1. For an ash content of 10% in charge 1.6 kg of coke per 1 kg of Zn. The components of the load are subjected, if necessary, to drying before loading and are admitted into the bottom oven at outside temperature or slightly preheated.



   A shaft furnace for testing had a height of 1.10 m, measured from the top to the plane of the nozzles. He had a section

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 quadrangular transverse of 28 x 28 cm. For industrial purposes these dimensions may of course be enlarged in such a manner that the uniform passage of air through the load is ensured.



  The quantity of air admitted was 6 m3 N / kg of Zn; the amount of charge passed through the furnace in the tempe unit was 250 kg coke / m 2 at the plane of the nozzles and -car hour.



   The air was admitted by three nozzles arranged in the plane, after having preheated the latter to 600 C. The gas was evacuated at the height of the throat and the CO2 content was 0.6%.



   In a second test we worked with cold air, instead of preheated air, and it was necessary to have the gas discharge a little lower to reach a temperature of 1000 C of the discharge gases.



   The process is usefully carried out under pressure, because it is necessary to avoid anyway the inflows of sucked air, because of the danger of explosions and the possibility of an oxidation afterwards of the zinc vapor. The overpressure of the air admitted into the furnace ranged from 200 to 400 mm. To avoid aspiration? air also in the separating device, the shutter register before the chimney was adjusted so that there was still an overpressure of 7 1 ::. 20 mm.



   The charge can also be put in the oven in a briquetted or coked form, obtaining in this case, from the point of view of the ZnO content, somewhat better results, as shown in Table I) below. The resistance of the briquettes does not have to undergo great efforts because the load column is not very high.



   The diversion can '' be carried out at. liquid or dry state; in the case of using a shaud wind tunnel, a complete melting of the components of the slag cannot be avoided. If you want to have a liquid diversion from the non-preheated wind, it is advisable to shrink the furnace 0. open to its lower part (coke load at least 500 kg per square meter at the plane of the nozzles and per hour) or if necessary provide additional heating, for example heating by resistances in the furnace structure.

   /

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To separate the entrained fly ash and dust beforehand (coke ash from the charge), it is recommended to have a preliminary separator downstream of the gas outlet of the oven%, which retains the ash and fly dust *
In a test, in which the gas was evacuated at a temperature of 9760 and where one worked without prior separator, the content of the Zn dust in total zinc was, because of the dilution by the ash and fly dust, of only 83 , 85% and 77.4% in metallic zinc.

   Since the remainder is formed by entrained fly ash and dust and that this portion is not uniform, all the results indicated below are referred to pure zinc dust, therefore after deduction of the fly ash and dust. From this we obtain a certain basis of comparison. The aforementioned dust contains, according to this calculation, 98.1% of total Zn and 90.5% of metallic Zn, as well as 9.5% of zinc oxide. After shaking it for one hour, the dust re zinc had a bulk weight of 0.67.



   In table 1) below we find the results of various drilling tests carried out with preheated air, at 6500 to 730 C and with exhaust gas temperatures between 960 and 970 C. It is noted that l 'test 1) gave the maximum content of metallic zinc * In test 2) 1st cooling was slowed down a little by a change of the separating device, and an increase in the zinc oxide content was immediately observed. from 9.5% to 14.5%.



   In tests 4 and 5 we worked with cold air and the top temperatures were around 600 C. The high oxide content in these tests shows that it is very disadvantageous to remove the gases from the oven. low temperatures (see also test 3).

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  TABLE 1.
 EMI12.1
 1P: Oarafteristics -ure: Content of the push-Weight
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<tb>: <SEP> of <SEP> test <SEP>: <SEP> of <SEP> wind: <SEP> gas <SEP> Beer <SEP> in, <SEP> in
<tb>
<tb> evacua- <SEP> Zn <SEP>: <SEP> Zn <SEP>: <SEP> Zn0 <SEP>: <SEP> bulk <SEP> *
<tb>
<tb>: tion <SEP> total <SEP> mets.1- <SEP>:
<tb>: <SEP>, ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯liguē¯¯¯¯¯¯¯¯¯¯¯¯
<tb>
 
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 ...... *
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<tb> 1.): <SEP> Air <SEP> hot,
<tb>
<tb>: <SEP> Cooling <SEP>
<tb>
<tb>
<tb> abrupt <SEP> fast <SEP>: <SEP>
<tb>
<tb>: <SEP> of <SEP> gases <SEP> of
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 gu-eulprd: 650 976 98.I: 0.5: 9.5: 0, b7 - !. ¯ ---... "....
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<tb>



  2 .: <SEP> Air <SEP> hot
<tb>
<tb>
<tb> Cooling:
<tb>
<tb>
<tb>
<tb>: <SEP> slightly <SEP> ra-
<tb>
 
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 lenti; ? 30 960: 7: 85.5: 14.5 1.66, .. 'if. III. 11 .....
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<tb> 3 .: <SEP> Air <SEP> hot,
<tb>
<tb>
<tb>: <SEP> Cooling <SEP>: <SEP>
<tb>
<tb>
<tb>: <SEP> in <SEP> a <SEP> oven
<tb>
<tb>
<tb>: <SEP> open <SEP> enhanced
<tb>
<tb>
<tb>
<tb> (1.40m <SEP> at <SEP> place <SEP>: <SEP>
<tb>
 
 EMI12.9
 : 1.10 m): 610 663: 90 * 3; 51.8 48.2 0.75. ¯¯ ### #. #. -.¯¯¯¯¯¯ ¯¯. # ¯¯ ¯¯¯¯ ¯¯¯¯ ¯¯¯¯¯
 EMI12.10
 
<tb> 4 .: <SEP> Air <SEP> cold,
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<tb>: <SEP> Cooling:
<tb>
<tb>: <SEP> to the <SEP> oven <SEP> tank <SEP>.
<tb>
<tb>



  : <SEP> approx. <SEP> 20 <SEP> 567 <SEP>: <SEP> 93.1 <SEP>: <SEP> 65., 6 <SEP>: <SEP> 34.4 <SEP> @
<tb>
 
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 - 1- ..., .- -y.-.
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<tb> 5.,: Cold <SEP> air,
<tb>
<tb>
<tb>: Cooling:
<tb>
<tb>
<tb>: <SEP> to the <SEP> oven <SEP> tank,
<tb>
<tb>
<tb>: Briquettes <SEP> co-
<tb>
<tb>
<tb>: kefied <SEP> of <SEP> mine- <SEP>; <SEP>:
<tb>
<tb>
<tb>
<tb>: spoke <SEP> of <SEP> zino <SEP> and
<tb>
 
 EMI12.13
 : from noke, approx. 20 609: 94.I: 70.1: 29.4: O.E3 * The zinc dust was shaken for 1 hour in a container closed on a vibrating device ,,
 EMI12.14
 2) Preparation of a heavy zinc sludge with a high metallic content of a bulk weight of 2.
 EMI12.15
 The charge etc., were the same as in example I.

   We, - put on, only the height of the tank which saw in all 1.60 m and from the nozzles up to the loading level 1.40 m. In addition, the gas evacuation was no longer placed at the loading level of the tower, but lower, laterally. The center of driving

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 discharge was disposed 0.85 mm above the nozzles. The gases had to. they exit a temperature of about 700 C.

   The gas was therefore evacuated very early from the furnace and consequently no longer came into contact with the charge containing air, because the latter had undergone, at the point indicated, a preheating to such a point that air y content was already consumed by combustion *
By the advanced evacuation of the gases it was above all the stay of the latter in the shaft furnace which was greatly shortened * Table 2 shows the results which were obtained by these tests.



   TABLE 2.
 EMI13.1
 
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  N <SEP> Characteristics <SEP> Temperature <SEP> of <SEP> Content <SEP> of <SEP> the <SEP> dust <SEP> Weight <SEP>
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<tb> from <SEP> test <SEP> gas <SEP> evacua- <SEP> in <SEP> in <SEP> bulk
<tb>
<tb>
<tb> yours <SEP> Zn <SEP> Zn <SEP> ZnO <SEP> after
<tb>
<tb> total <SEP> metal <SEP> shakes- <SEP>
<tb>
<tb>: <SEP> pic: <SEP> ment
<tb>
 
 EMI13.2
 j '' 1 1 1 1 6 Cold air 705 95.3 81.3 18.7 3.04
 EMI13.3
 7. Cold air 744 97.3 88.2 11.8 3.06 drier.



   The test gave a ZnO content of 18.7% and a bulk weight of 3.04. This content is considerably higher than that of test 1, which results from the procedure with cold air and the resulting low temperatures, as well as from the cooling.
 EMI13.4
 dement at 700 0 in the oven a auve, Lean that the results of test 6) clearly show that thanks to the advanced evacuation, b, higher temperatures than in tests 4 and 5 (Table I) the formation of ZnO was lower * But what is most surprising is the bulk weight which was 5-6 times higher as a result of the rapid abrupt cooling of the exhaust gas withdrawn from the furnace to optimum temperatures.

     As it has already been mentioned above, it is not all the dust that is obtained in this heavy form, but 40% in the oocurence. The dust obtained in the following contains even less ZnO, but it is a little lighter *

 <Desc / Clms Page number 14>

   % of total Zn 94.3% of metallic Zn ......... 89.8% of ZnO .................... 5.7
 EMI14.1
 Bulk weight (rough) shaking) ....... 3 * 1
This dust may also be referred to as heavy dust.



     In test 7) the air, which on the day of the test contained 10 g of H2O / m 3, was previously dried by means of silica gel to a water content of less than 2%.



   The above table clearly shows that following the described procedure the ZnO content can be considerably lowered by the removal of H2O. In this test we also obtained about 40 heavy dust of the composition indicated, while the remainder contained:% of total Zn ............... 99.3% of metallic Zn .... ....... 96.3% ZnO .................... 3.7 3 a) Preparation of heavy dust, with a high metallic content. with use of a dust regenerator.



   In tests 8 to 13 according to Table 3, these are tests carried out without and with dust regenerator, in order to bring out the influence of the dust regenerator. As the dust regenerator (test II) a regenerator filled with coke with a hoop size of 60 to was used. 80 mm and having the shape of an iron tube, the dimensions of which appear in figure 7.



   The composition of the charge was as usual; namely, 1 kg of ore per 1 kg of coke, or, reported the zinc content, of 1 kg of Zn per 1.6 g of coke. Only in trial 10 was this ratio changed. The height of the tank varied from case to case and is indicated for each oas in the section of test characteristics. For the rest, the test conditions from the point of view of the blown air, the cross section of the tank, the size

 <Desc / Clms Page number 15>

 of grain of the load, etc * ,, were the marls as in the previous tests; any deviations are indicated in the test characteristics. In all the tests, except test 12, cold air was blown.



   TABLE 3.
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  ============ - =
 EMI15.2
 NO: 7th cctéris: zqtes: emperature of. Zinc contents Weight in: of the top test in 0 "ZS 1 Zn bulk zoo after total metal - shaking: nique: * .... 11 ..



  : 8i: Height of :::; : or + e. "1.4 w JSO: 9 * 55: 6'7, ': 3ûi3: 0.81,,. TI. It' .... <1- 9. i: .GiI.Ü. ' 8uIx't, from tank;;:: 1.1 m Preload4: c: .2t, ißée. 400 0 800; J3 * 0 "I: 6v.9i 1: 64. 4: I.66 w 10.:Tank height ::::: 1.4m; 1 kg of t t:: ore on: 2 lc .e coke. : 456: 86.5: 364: 63.6: 0 * 18 d,; ......: Temperature: ûans le r * pt Inlet Outlet 1 tttit 1 ¯¯¯¯ t :::::: II ..: Tank height ::::: II mm r.1 '.. .1: 808: 633; 94.4: 73.6 36.4 .S8 ........ a ...----. L 18: Opening height: 0.66 mi Air: hot 5b5 Ù, t: r .. p..1. : 883: 720: 97.0: S5.2: 14.8 1.83 ......



  ........



  .... 181., .. ####. ####### - ############ I3.: Bowl height ::::: 1.'1 rn; J :: '. P.1. : 650,700: $ 9 8. : D * 8a: 9.15 3. or # 1 1 â
Table 3 clearly shows that without the characteristics of the invention it is necessary to count on obtaining an ordinary zinc dust, of poor quality, of 35% to 60% ZnO; compare trials 8 to 10.



   According to test 8 the ZnO content is still relatively low, because the ratio of coke to air was exactly measured, so that unnecessary dilution of the zinc vapor in the evaouation gas was avoided. unlike test 10. The bad result

 <Desc / Clms Page number 16>

 of test 9 from the point of view of the ZnO content arises from the increased formation of CO2 in the upper part of the vessel, caused by the preheating.



   However, in order to show the effect produced under these conditions by a complementary treatment of the dust, the dust regenerator (according to figure 7) was operated in tests II to 13 at low, high and medium temperatures and the exhaust gases were then subjected, in the usual manner, µ to a rapid abrupt cooling in a tubular condenser.



   In Test II the dust regenerator was heated only very weakly, which is why the final product still contained 26.4% ZnO. In run 12 a ZnO content of 14.8% was achieved, but in this case also the bulk weight was still relatively low. Test 13 only shows that full action of the dust regenerator occurs when it is not kept in the exact temperature range.



   Zinc dust according to test 13 is of quality, from the point of view of the low ZnO content of 9.15%, and from the point of view of its high bulk weight, which reaches that of zinc dust Obmme it is obtained by the retort procedure.



   3b) Increase in the amount of heavy dust obtained by enlarging the dust regenerator.



   It was evident from Table 3 that the dust regenerator absolutely creates the conditions necessary for the production of heavy zinc dust and poor in ZnO when operated in the exact temperature range. In tests I3, I4 and 15 (compare Table 4) the normal conditions were applied to the work of the furnace from the point of view of the grain size of the filler and of the coke. The height of the furnace was in all cases 1.10 m. We breathed in cold air. The size and dimensions of the dust regenerators employed I, II, III are shown in figures 7,8 and 9.

 <Desc / Clms Page number 17>

 



  TABLE 4.
 EMI17.1
 



  N,: i t3arab tr-: Temperature: Content. zinc Weight: -% in C02 hard p Z & tc3F <* Zn ZnO in 1 to bitter: 11 test: between Sort * met 'vrac f'ú'ûeu-: b le: ::.,., bacon: riO, th .... t.



  I3: r.p.1 t 650 700: 8y.3: 00.85: 9.19y IS 3.0 = 2.'8 3.8 * W * * o o 11,! Y ry f f ry o .. 1 p f r y 14: 113.i 730 7 1 19: .8 89.0 11.0 3.1 3.3 3.3.
 EMI17.2
 
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  : <SEP>: <SEP>: <SEP>: <SEP>: <SEP>: <SEP>: <SEP>: <SEP>:
<tb>
 
 EMI17.3
 41 .........



  15: r.p &: 1I1: 640: 670 97 * 5: 88J3: II.> 8: 2.6: 1.6: 1.4 f 1 f 1 i i
When filling in, the r.p. of coke, the heavy dust yield can be increased by prolonging the stay of the gases containing the zinc dust in the dust regenerator. ' The digital indications (residence time in seconds, corresponding heated outer surface and Zn content) can be seen from
 EMI17.4
 Figure 10 * In this figure it fauvoocaprendre by metallic zinc in heavy dust the ratio of the quantity of zinc
 EMI17.5
 metallic zn nx> xa & 1 to the total quantity of zinc volatilisa in the shaft furnace *
 EMI17.6
 3c) Increase in the Q \ Hmt.1 tee obtained in heavy dust by filling the regenerator with '9otls,

  century
It has been found by tests that higher amounts of heavy zinc dust can be obtained not only by enlargement of the dust regenerator, but also by the kind of filling of the dust regenerator, so that it It is not necessary to employ very large regenerators, but on the contrary, it is possible to establish the optimum conditions in each case by the combination of the two possibilities.



   In the tests considered below we used the same
 EMI17.7
 size of / regenerator ie, each time the smallest type e4p. 1 denoting r6g6n-4r% dust extraction 1 shown in FIG. 7. The other conditions were the same as those in tests 13 to 15.

 <Desc / Clms Page number 18>

 
 EMI18.1
 



  Table 5 shows clearly that with the use of a
 EMI18.2
 suitable nulation and with a filling of a high reactive power a very high bulk weight of the zinc dust can be achieved which greatly exceeds that of the zinc dust.
 EMI18.3
 zinc retorts. Tests 16 and 17 clearly show that it is impossible to obtain particularly favorable bulk weights without the necessary reduction of ZzlO due to L12nq \ 1e or improper granulation of the reducing substance and without a good heating of the regenerator.
 EMI18.4
 



  TABLE 5,
 EMI18.5
 N: Oaractr1ris-: Temperature: Za content: Weight:% eD, 00: ¯-: ticks of ': j¯4zs le ¯¯% ¯z¯: Zn: Zn me-: ZnO: en: au û-ta ra: the e988.1. : Entr. Sort .. tot talt: real bacon: the a-, ore i:: r.p.



  : :::::: ec 0 u-: -9 1 --- - - ----: - -.:. me.l.1 ..- t: - -: I61R.p.re <nDli;
 EMI18.6
 
<tb>: from <SEP> fragments-.
<tb>
 
 EMI18.7
 



  : de ChaL10tte:: de rJ0 t: 80 mm. : b72: $ 6 0:: 97.0: 85.4: 14.6- 2.! : 1.5: - -.............- ---- ¯.t-.



  17: R.p. filled:
 EMI18.8
 
<tb>: from <SEP> coke <SEP> from <SEP>; <SEP>
<tb>
 
 EMI18.9
 : 30 ç, fi0 r'l1: i 681: 669: 94.5: 'r,? R0: 28.0: Z.1 I.8 Is9 # * * ¯ @ Y O O IB: R; p. filled: ::::: with coke from: ::::: 60 z 80 Illin: 650:? 00: 98.3 90.85 9-e. 3.0. 2 * 8: 2.8 I9: Rprempl1: :::: "de o '.., rbon:: :: :::: 1 .of wood ::::: from 60 to: 80 mi 1.: 664: 665: 97.8: $ 8.? ' ; Il.3: 4.0: 3.95 3.3 4: ...... '1' "
 EMI18.10
 according to the invention cn obtained the results below '1.) By filling certain cnnditlonn we have the. possibility of producing high-grade zinc dust ?: f; a11 doe -oar processing of ores Eu furnace s. tank.



  3.) By an evacuation carried out b. weather and temperatures
 EMI18.11
 determined, as well as by immediate sudden cooling it
 EMI18.12
 is possible to produce zinc dust with a high mediocre content.
 EMI18.13
 tall and at the same time heavy.

 <Desc / Clms Page number 19>

 



   3.) By further treatment of the exhaust gases containing zinc dust from a shaft furnace in a dust regenerator, the production of heavy, high metal content zinc dust is improved. and increased * It is possible to improve at the same time partially oxidized zinc dust in the shaft furnace.



   4.) By applying optimum working temperatures to the dust regenerator, the action of the regenerator is increased.



     The amount of heavy zinc dust produced can be increased by enlarging the dust regenerator or by choosing a suitable granulation and filling it with a fuel of high reactivity.



   6.) The use of previously dried air produces, in combination with all the measures found, a subsequent lowering of the ZnO content of the zinc dust *
7.) The zinc dust produced is suitable due to its chemical and physical characteristics for obtaining crude metallurgical zinc by smelting or for distillation after prior briquetting.



     Se) When mixing dust of different bulk weights within the limits of 2 to 4, it is possible to increase by an increase in temperature the efficiency of the extraction by fusion *
9.) When we want to obtain fine zinc, we can bring the zinc vapor directly into a rectifying column of a known type,
Zinc dust briquettes having good hardness are preferably used for the distillation. It has been found that, for example, zinc dust briquettes with a size of 20 to 50 mm and a height of 20 mm, obtained with a pressure of 300 atmospheres, gave up all of their metallic zinc content.

   

 <Desc / Clms Page number 20>

 



  Figure II shows the preparation of fine zinc
 EMI20.1
 from zinc powder produced in a foil tank * By 1 is denotes a distillation vessel filled with zino dust briquettes 2 * The distillation vessel may be made of any suitable good heat conductor material.

   By 3 is designated the heating or corn ... bustion heat, by 4 the charging device, consisting of a doubtful bell closure and by 5 the residue evacuation device, consisting mainly only of ZnO In ¯6 is shown a connection pipe leading to the distillation vessel and through which the zinc vapor can exit.by 7 is denotes a heat-insulating pipe which connects the distillation furnace to a rectifying column µ of a known type.

   Zinc vapor
 EMI20.2
 rid! 03-? e of lead, iron, tin etc., and runfer :: aan '' T (mtl1cl- lement still a little Od ,, sor ", * by 9 and is subject to. ' (den known at the subsequent refining, while in IO are collected the impurities from 1. otif.cati.onw Both in the extraction of the JC) è, ssiëro zinc by melting as in redistillation or in the direct obtaining of fine zinc from zinc dust briquettes it
 EMI20.3
 is very 1-.i ^ -oort-nt that the content of ZnO is very low, because the whole of the residue must "be reintroduced into the.} l" OoeSS \ 1S in the oven, vat.

   This reintroduction is best realistically by admixing the ZnO during the agglutination of the charge of the µ furnace. tank, in the form of briquettes of ZnO and charcoal, which must be previously entrusted *
In obtaining zinc dust by treatment of
 EMI20.4
 For example, per kg of zino introduced into the shaft furnace, 7.48 m 3 N of exhaust gas containing 34.6% CO and 1.9% 00 were produced by washing in the tank furnace. who had power
 EMI20.5
 calorific 1030 Ca./3.

   Since the vat kiln process consumes very little heat and most of the fuel in the oven ends up as 00 in the flue gas, it

 <Desc / Clms Page number 21>

 It is possible to use this gas, according to the needs of each case, in a purified form, for:
 EMI21.1
 preheating the air from the blower; regenerator heating remove dust
 EMI21.2
 the extraction of crude zinc by smelting; distillation and refining.



   Any excess which may remain, can also be used - if there are no other economic possibilities - for reheating a part of the exhaust gases which are re-blown, in a strongly heated state, in the shaft furnace, thus saving a little fuel.



   Below is shown the analysis of an agglomerated product which was treated in a shaft furnace, according to the present invention;
ZnO 60. 15
SiO2 3.70
 EMI21.3
 'èn3 Zizis A1203 1.55
 EMI21.4
 Mn: 3 0 4 0.40 CaO 15.73 MgO 0. 63 PbO 2.13 As 0.055 Sb 0.075 Sn 0.02 CuO 0. 82 Cd traces
 EMI21.5
 Bat74 5.j39
S free 0.22
From this agglomerated product, with the use of 1 kg of coke / kg of agglomerated product, a zinc dust was produced which had a bulk weight of 3.30.

   The composition of the dust was as follows:

 <Desc / Clms Page number 22>

 
96.7% of total Zn
83.2% metallic Zn
16.8% ZnO
From this dust was obtained by fusion extraction, with a yield of 95.5% relative to the metallic zinc content, a crude zinc of the following composition:
Zn 96.96%
Pb 2.66%
Fe 0.32%
Cd 0.05%
As traces
Or nothing
Sn nil
In another fusion extraction test the relatively heavy and relatively light dusts were mixed in the proportion in which they were obtained, namely 40% of a bulk weight of 4.0 and 60% of a bulk weight. bulk of 2.81.



  From this mixture it was also possible to obtain, in the form of liquid zinc, more than 90% of the metallic zinc contained in the dust. An increase in the extraction temperature by melting from 500 to 600 C improves from 1 to. 2% the yield obtained with dusts having bulk weights greater, 3, while for dusts less than 3.0 the improvement in the efficiency of the smelting extraction at 600 ° c and approximately 10% compared to that at a temperature of 500 C. It emerges that it is possible, by means of a change in the extraction temperature by fusion, to transform also zinc dust, the bulk weight of which is not located at the upper limit, with a good yield of raw zinc.


    

Claims (1)

R E V E N D I C A T I O N S 1) Process for extracting zinc by reduction of zinc ores or zinc-bearing metallurgical products, by blowing in the presence of a fuel in a shaft furnace, characterized in that <Desc / Clms Page number 23> the zinc vapor content of the exhaust gases is subjected to a treatment such that a dust with a high metallic content and poor in zinc oxide (light zinc dust) is formed by the fact that the gases from 'evacuation of the shaft furnace at a temperature above. 800 C, preferably at 1000 0, and that either their abrupt cooling as fast as possible is carried out to a temperature below 100 C, or a separation of the zinc dust from the gases and its cooling by means of a rapid mechanical separation * 2) An embodiment of the process according to claim I, for the production of a heavy zinc dust with a high metal content, characterized in that the gases containing zinc vapor content are discharged from the furnace at a temperature of 650 to 800 C, preferably 70,000, and subjected to further treatment according to claim 1. 3) An embodiment of the process according to claims 1 and 3, characterized in that the coke and air are adapted to the Zn content given so that aveo optimum dezincification of the load (au- below a Zn content of 3%) a maximum zinc vapor content is obtained in the exhaust gas (for example 4 to 5% by volume of Zn for 58% of Zn in the ore broiler), while continuously removing any excess coke content from the oven. 4) An embodiment of the method according to claims 1 and 3, characterized in that the gases pass, after leaving the shaft furnace, through a preliminary separator, serving for the removal of flying dust. 5) An embodiment of the method according to claim 2, characterized in that the gases are passed through a zinc dust regenerator usefully fueled and heated indi- reclaim or electrically, and they are maintained in the latter. temperatures of 650 to 800 0, preferably 700 C. <Desc / Clms Page number 24> 6) An embodiment of the process according to claims 2 and 5, characterized in that the obtained quantity of heavy zino dust is increased by an increase in the residence time in the zinc dust regenerator, or by 1 'employment EMI24.1 of a li cawbone, high reactive power as a filler in the dust regenerator, or by a suitable grain or chunk size of said filler, or by all these means. 7) An embodiment of the method according to claim 6, EMI24.2 characterized in that the filling substance is subjected, before its introduction into the regenerator of,> oussilre, a preheating for example by a blowing # -, chaild, and that it is renewed continuously or intermittently. 8) An embodiment of the process according to revendjcations 1 and 2. characterized in that the zinc dust obtained is usefully subjected in the form of briquettes to distillation. 9) An embodiment of the method according to claim 6. EMI24.3 cercotérisé in that the distilled zinc vapor is introduced into a rectifying column of a known type, in order to obtain a very pure zinc, for example 9 ± ', Q ± f% of Zn and more. 10) An embodiment of the process according to claim EMI24.4 2, characterized in that the heavy zino powder alone or in mixture with slightly lighter dust, simultaneously obtained, EMI24.5 for example in a report of I: I, is subjected to fusicn extraction in a manner known per se. II) An embodiment of the process according to claim EMI24.6 9, carctr1se in that the yield of the fusion extraction is increased by an increase in the extraction temperature by fualcn (-rôf <'rably to 600 0), especially in the case of the treatment of mixtures of - ocussisrea had bulk weights between 2 and 3. 12) Zinc extraction process by reduction of ores from EMI24.7 zinc or metallurgical products "inert, by blowing, of <Desc / Clms Page number 25> presence of a fuel, in the shaft furnace, in substance as described above with reference to the examples cited and to the accompanying drawings