JPH08503025A - How to maintain a fluxing bath in a galvanizing line - Google Patents

Abstract

(57) [Summary] Consumption of a fluxing bath consisting of an aqueous NH ₄ Cl solution and an aqueous ZnCl ₂ solution is used by reacting a used pickling solution or a used dezincification solution with zinc ash or dross to obtain a high zinc concentration and HCl. Was added to the aqueous NH ₄ Cl and ZnCl ₂ aqueous solution produced by making a solution exhausted, and at the refining station, iron was precipitated in the form of Fe (OH) _{3 in} the form of Fe (OH) ₃ to separate it out. It is supplemented by adding hydrogen oxide and an aqueous ammonia solution. The fluxing bath is circulated to the refining station as the concentration of iron in the fluxing bath increases.

Description

DETAILED DESCRIPTION OF THE INVENTION A method of maintaining a fluxing bath of a galvanizing line The present invention comprises a fluxing zo station of a hot-dip galvanizing line consisting of an aqueous solution of NH ₄ Cl and ZnCl _2. A method of maintaining the used fluxing bath; this line is used upstream of the fluxing station to produce a spent pickling solution containing HCl, FeCl ₂ and possibly ZnCl _2. Downstream of the washing station, and thus the spent dezincification solution containing H Cl, FeCl ₂ and ZnCl ₂ , and downstream of the fluxing station, ZnO-rich zinc ash and Zn-rich zinc dross are provided. A galvanizing station that produces; At least a portion of the consumption of Gubasu are, NH ₄ Cl and of ZnCl ₂ solution (hereinafter, the addition is referred to as a solution) is compensated by adding to them, and this additive solution is spent pickling solutions or spent de It is prepared by starting from either a zinc solution or a mixture of the two. Such a method is described in document DE-B-2,663,872. According to this known method, in a galvanizing line, a steel fixing element (for a dezincification station is used for pickling stations where hydrochloric acid is used for pickling before suspending a new filling of the galvanized components). securing elements) are provided, which serve to hold the galvanized components throughout the entire galvanizing process and are therefore unavoidable to accept and dip each dip in the zinc bath and each dip. Get pickled every time. At this dezincing station, poorly plated products to be reprocessed are also pickled. The above procedure is carried out in order to obtain a spent dezincing solution having a high zinc content and a very low hydrochloric acid content, for example a solution having 170 g / l Zn, 70 g / l Fe and 0.5 g / l HCl. Spent dezincing solution is neutralized with ammonia, therefore iron hydroxide precipitates, it is obtained a solution of isolated and ZnCl ₂ and of NH4Cl are by, ZnCl ₂ or NH, CE is added to it. Therefore, this known method requires not only the presence of a dezincification station, but also 100% operation of this station. However, working without a dezincification station, or performing only part of the dezincification operation at the dezincification station, for example dezincing rejected components, and remaining dezincification operations, such as pickling There may be situations where it is more convenient to dezincify the fixing element with pickling of the new component to be galvanized at the station. Therefore, this known method lacks adaptability. Another drawback of this known method lies in the fact that the composition of the solution of ZnCl ₂ and NH ₄ Cl obtained after neutralization is strictly related to the composition of the used dezincification solution used, so that the addition solution If it is necessary to adjust the ZnCl ₂ / NH ₄ Cl ratio in it, the only available means is to add ZnCl ₂ and NH ₄ Cl to the above neutralized solution. The object of the present invention is not only to avoid the drawbacks of the known methods, but also to use zinc ash and dross, by-products which today's zinc megglers have to sell to zinc refiners at a very low price. It is to provide a method as defined above, which enables. For this purpose, according to the invention, the preparation of the solution to be added comprises the following steps: (a) a used solution containing a substance containing zinc oxide and / or a substance containing metallic zinc, preferably zinc ash and / or Producing a zinc-rich and HCl-depleted solution by reacting with dross; and (b) adding a measured amount of H ₂ O ₂ and NH ₃ or NH ₄ OH to the solution produced in step (a). By means of which the iron contained in the solution is precipitated in the form of Fe (OH) ₃ , the ZnCl ₂ contained in the solution is kept in the solution and the Fe (OH) ₃ precipitate formed is removed there. To produce an iron-free solution of NH ₄ Cl and a solution of ZnCl ₂ . Advantageously, step (a) is carried out by passing the spent solution through a bed of the substance containing metallic zinc or by adding a measured amount of the substance containing zinc oxide to the used solution. In the latter case, in the step (a), iron is added by adding a total amount of H ₂ O ₂ according to the reaction 2 FeCl ₂ + H ₂ O ₂ +2 ZnO + 2 H ₂ O → 2 Fe (OH) ₃ ↓ + ZnCl _2. Part of the iron can be precipitated: In step (b), the remaining iron can be precipitated according to the reaction 2 FeCl ₂ + H ₂ O ₂ +4 NH ₄ OH → 2 Fe (OH) ₃ ↓ + 4 NH ₄ Cl. It is advantageous to keep the fluxing bath at a temperature of 30-80 ° C, preferably at a temperature of 40-50 ° C, in order to cause the evaporation of water in excess of the amount of NH ₄ OH and H ₂ O ₂ added in volume. Is. If the fluxing bath becomes increasingly iron-rich, especially because the components to be impregnated in the fluxing bath carry a small amount of FeCl ₂ with them, the fluxing solution can be run through a refining station. The concentration of FeCl ₂ in the fluxing bath is kept below the limit value, but in the refining station the ZnCl ₂ contained in the fluxing solution is used to precipitate the iron in the form of Fe (OH) ₃ and the ZnCl ₂ contained in it is in solution. H ₂ O ₂ and NH to hold at. Alternatively, a measured amount of NH ₄ OH is added to the flux of fluxing solution and the Fe (OH) ₃ precipitate formed is separated therefrom. It is advantageous to use a single refining station for separating iron from the fluxing solution and for carrying out step (b). Therefore, it is possible to add the solution or valv produced in step (a) to the fluxing solution entering the purification station and carry out purification of the fluxing bath and step (b) in a single operation. Other details and special features of the invention will become apparent from the description of an embodiment of the method according to the invention which is given below by way of non-limiting example and in connection with the drawings attached hereto. In these figures: -figure 1 shows diagrammatically a hot dip galvanizing consisting of stations for maintaining a fluxing bath according to the method of the invention; and-figure 2 shows said maintenance station in more detail. Like reference symbols in the various drawings indicate like elements. The galvanizing line shown in FIG. 1 includes a degreasing station 1, a rinsing station 2 for degreased ingredients, a pickling station 3, a dezincing station 4 for rejected ingredients, a pickled and dezinced station. A rinsing station 5 for different components, a fluxing station 6, a drying station 7, a galvanizing station 8, a cooling station 9 and a station 10 for maintaining the fluxing solution. The components to be galvanized are suspended from a carrier element that deviates from being galvanized in a conventional galvanizing process, as shown by arrows 11 and 12, at stations 1-3 and Pass continuously through 5-9. The failing component is dezinced at 4 and then follows the same route as the component pickled at 3 as shown at 13. In the pickling station 3, a pickling bath containing HCl as a pickling agent is used, and by bleeding the bath at 14 to control the iron content and at 15 to adjust the hydrochloric acid content. By supplementing the bleed with the addition of hydrochloric acid, the HCl and Fe ⁺⁺ contents of the bath are maintained at 30-100 g / l and 65-150 g / l, respectively. This hydrochloric acid addition may consist of concentrated hydrochloric acid and the used rinse water generated in 5. The bleed 14, or in other words the spent pickling solution, typically comprises HCl 50 g / l Fe 110 g / l and Zn 60 g / l. A part of the bleed 14 is sent to the dezincification unit 4 at 16, another part is sent to the maintenance station 10 at 17 and also another part is a station for storing the spent solution at 18. Sent (not shown). In the dezincification station 4, a dezincification bath or groups of baths containing HCl as dezincification agent are used, by bleeding the bath at 19 to adjust the Zn ⁺⁺ content and adding hydrochloric acid at 20 The HCl and Zn ⁺⁺ contents of the dezincing solution are kept below 5-20 g / l and 250 g / l, respectively, by adding and / or supplementing the spent dezincing solution 16, to make up for the bleed. Bleed 19, a so-called spent dezincing solution, typically comprises 20 g / l HCl, 150 g / l Zn and 50 g / l Fe. This bleed is sent to the station for storing the spent solution. The fluxing bath used in 6 contains 200 g / l ZnCl _{2 and} 200 g / l NH ₄ Cl, the consumption of which is 2-20 liters per ton of treated steel. The components rinsed in 5 entering the fluxing bath carry with them a small amount of FeCl ₂ , HCl, and ZnCl ₂ · rinse solution. As a result, the fluxing bath gradually increases the FeCl ₂ and HCl concentrations. Therefore this bath must be purified and refilled. For this purpose, the fluxing bath is bleed at 21 to the maintenance station 10 and the consumption of the bleed and bath is compensated by the solution produced at 10. At the galvanizing station 8 where the components are immersed in a bath of zinc or zinc alloy, the reaction between iron and zinc results in the formation of zinc dross, which is an iron-zinc compound typically containing 96% zinc. Most often at the end it collects at the bottom of the bath, so reaction of the bath with oxygen in the air produces zinc ash containing 50% ZnO. A portion 23 of the zinc dross produced in 8 is used in 10. The station 10 for maintaining the fluxing station shown in FIG. 2 is a ZnCl ₂ regeneration container 24, a neutralization container 25 with a stirrer 26, a hydrogen peroxide tank 27, an ammonia water tank 28, and a coagulant dissolving agent. The container 29 with the stirrer 30, the aggregator 31 with the variable speed stirrer 32, the decanter 33, the filter 34, and the heater 35. Spent pickling solution 17 is delivered into the bottom of container 24, from which it rinses the bed of dross 23 carried by perforated plate 36. As described above, most of the acid contained in the solution 17 reacts with the draft 23 as in the formula 2HCl + Zn → ZnCl ₂ + H ₂ ↑. While passing through the dross bed, the solution 17 is converted into the zinc-rich and hydrochloric acid-depleted solution 37 represented thereby. The solution 37 is fed to the neutralization container 25 via the pipe 38. In the neutralization vessel 25, the iron contained in the solution 37 and the bleed 21 of the fluxing bath is selectively precipitated as in the formula 2 FeCl ₂ + H ₂ O ₂ +4 NH ₄ OH → 4 NH 4 Cl + 2 Fe (OH) ₂ ↓. The pH therein is measured by a conventional apparatus, which is shown in the figure, and is adjusted to a set value of 3-3.6 by adding NH ₄ OH. The redox potential, which is not shown, was similarly measured by a conventional apparatus and was adjusted to 0 .. by adding H ₂ O ₂ . It is adjusted to a set value corresponding to a divalent iron concentration of less than 5 g / l. The pulp produced in the neutralization vessel 25 is fed via pipe 39 into the bottom of the agglomerator 31, where it is produced at 29 and also fed via pipe 40 into the bottom of the agglomerator. It is mixed with a solution of a polyacrylamide type flocculant. The pulp left in the agglomerator is conveyed via tube 41 to decanter 33, where it is fed through central box structure 42 into a bed of agglomerated sludge. The decanter is fitted with a peripheral groove 43 into which the decanted liquid overflows and enters. The decanted liquid is conveyed through pipe 44 to heater 35, where the fluxing bath is thereby kept at a temperature of 40-50 ° C. The heated liquid suspension is recombined through 22 into the fluxing bath. The sludge formed in the decanter is placed directly or in an intermediate storage container (not shown) for a certain period of time and then filtered at 34. The filtrate is reinjected into the decanter through the pipe 45. It will be apparent that numerous modifications can be made to the embodiments described above without departing from the scope of the invention. Therefore, for example, when the NH ₄ Cl / ZnCl ₂ ratio of the fluxing bath becomes very low, it is possible to directly feed the bleed 17 to the neutralization container 25 while avoiding the ZnCl ₂ regeneration container 24. Instead of starting with the used pickling solution, it can be equally good to start with the used dezincing solution or a mixture of the two solutions. Instead of passing the used solution through the bed of dross, adding a measured amount of H ₂ O ₂ oxidizes a portion of the iron contained therein and, at the same time, adds a measured amount of ash to the solution. It is also possible to partially neutralize, for example up to pH 2.5. A partial precipitation of iron is thus obtained. Thus, ZnCl ₂ is produced by precipitating iron, while the precipitation of iron with aqueous ammonia gives NH ₄ Cl. The amount of iron precipitated and the amount of ZnCl ₂ produced thereby is a function of the amount of H ₄ O ₂ added. Therefore, by adjusting the addition of H ₂ O ₂ , it is possible to obtain the desired NH ₄ Cl / ZnCl ₂ ratio of the solution to be treated. Instead of using the decanter 33, it is possible to send the pulp left in the agglomerator directly to the filtration unit, or preferably through an intermediate sludge container, especially if the solids content is high, eg ≧ 50 g / l. is there. The bleed 21 of the fluxing bath can be omitted if the rinsing in 5 is very effective, especially in countercurrent washing, and the surface of the decanter 33 is covered with a cover and / or a covering of floating balls to prevent cooling. It is possible to protect the surface. Instead of decanter 33, it is possible to use any other type of decanter. Instead of reinjecting the filtrate into the decanter, it is also possible to feed it directly or through an intermediate storage container into a fluxing bath or a flocculator. It should be noted that, in general, the solution produced in step (b) is sufficient for a complete compensation for the consumption of the fluxing bath. If it turns out that the addition of NH ₄ Cl and / or ZnCl ₂ is necessary, it is clear that this addition can be done equally well in the fluxing bath as can be done in the solution produced in step (b). The addition can be made to the used solution or even to the solution produced in step (a).

─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Verain, Christian, Paul, Ma             Lee, Gislan             Base 1200 Brussels, Belgium,             Luteodor De Cuipe 155 Ba             Timan 44

Claims (1)

[Claims] 1. A method of maintaining a fluxing bath consisting of an aqueous solution of NH ₄ Cl and ZnCl ₂ and used in the fluxing station of a hot-dip galvanizing line; this line comprising: upstream of the fractionation Managing scan retardation, HCl, FeCl ₂ and pickling stations resulting pickling solution of spent including ZnCl ₂ by, and by, HCl, dezincification of the used including FCl ₂ and ZnCl ₂ A dezincification station for producing a solution, and a galvanization station for producing ZnO-rich zinc ash and Zn-rich zinc dross downstream of the fluxing station; according to the method, at least one of the fluxing bath consumptions The part is a solution of NH ₄ Cl and ZnCl ₂ Liquids) are added to them, the addition solution being either from the used pickling solution or the used dezincification solution or a mixture of the two (hereinafter these various solutions as the used solution). The method comprises the steps of producing the additive solution in the following steps: (a) a spent solution containing zinc oxide and / or a material containing metallic zinc, preferably zinc ash and / or Or reacting with dross to produce a zinc-rich and HCl-depleted solution; and (b) adding a measured amount of H ₂ O ₂ and NH 3 or NH ₄ OH to the solution produced in step (a). By which the iron contained in the solution is precipitated in the form of Fe (OH) ₃ , the ZnCl ₂ contained in the solution is kept in solution and the F formed is separating the e (OH) ₃ precipitate from it to produce an iron-free solution of NH ₄ Cl and a solution of ZnCl ₂ . 2. The method of claim 1, wherein step (a) is performed by passing the spent solution through a bed of material containing metallic zinc. 3. The method according to claim 1, wherein step (a) is performed by adding a measured amount of a substance containing zinc oxide to the used solution. 4. The method of claim 3, in step (a) to precipitate a portion of the iron was further added a metered amount of H ₂ O _2, characterized in that to precipitate the remaining iron in step (b) . 5. Method according to any one of claims 1 to 5, characterized in that the fluxing bath is kept at a temperature of 30-80 ° C, preferably at a temperature of 40-50 ° C. 6. The iron concentration in the fluxing bath becomes progressively higher, and the FeCE ₂ concentration in the fluxing bath is kept below the limit value by flowing the fluxing solution through the purification station, where it Measurement of H ₂ O ₂ and NH ₂ or NH ₄ OH in order to precipitate the iron contained in the solution in the form of Fe (OH) ₃ and keep the Zn Cl ₂ contained in the solution in the form of the solution Process according to any one of claims 1 to 5, characterized in that an amount is added to the fluxing solution and the Fe (OH) ₃ precipitate formed is separated therefrom. 7. 7. The method of claim 6, wherein a single refining station is used to separate iron from the fluxing solution and to carry out step (b). 8. 8. The solution or pulp produced in step (a) and the fluxing solution are treated simultaneously in the refining station so that the refining of the fluxing bath and step (b) are carried out in a single operation. The method described in. 9. H ₂ O ₂ and NH ₃ or NH ₄ OH claims 1 and 6 to 8 The method of any preceding claim, characterized in the pulp obtained by the addition of measured quantities adding flocculant. 10. 10. The method according to claim 9, wherein a polyacrylamide type coagulant is used as the coagulant. 11. 11. The method according to claim 9, wherein the agglomerated Fe (OH) ₃ is settled before the filtration. 12. In the first reactor, the measured amounts of H ₂ O ₂ and NH ₃ or NH ₄ OH are added with stirring, and in the second reactor the flocculant is also added with stirring, and Fe (OH) ₃ is added to the decanter, 9. preferably the etc., wherein the keep Come the decanter provided with a feeding device into the bed of the Fe (OH) ₃ was agglomerated through a central box structure, Fe and (O H) ₃ precipitate seat allowed, The method according to 10 or 11. 13. 10. Method according to claim 9, characterized in that the use of a cover and / or a cover of a floating ball prevents the metabolite of the decanter from cooling down. 14. In the pickling station, by bleeding the pickling bath to control the iron content and by adding hydrochloric acid to control the hydrochloric acid content to make up for the bleed, Method according to any one of claims 1 to 10, characterized in that the Fe ⁺⁺ contents are kept at 30-100 g / l and 65-150 g / l respectively. 15. A galvanizing line comprising a rinsing station downstream of the pickling station to generate used rinsing water, and supplementing the bleed of the pickling bath with the addition of concentrated HCl and used rinsing water. Item 14. The method according to Item 14. 16. In a dezincification station, dezincification is carried out by bleeding a dezincification bath or baths to control the Zn ⁺⁺ content and by adding hydrochloric acid to control the hydrochloric acid content to compensate for the bleeding. 16. A method according to any one of claims 1 to 15, characterized in that the HCE and Zn ⁺⁺ contents of the bath or baths are kept below 5-20 g / l and 250 g / l respectively. 17． 17. The method of claim 16, wherein at least a portion of the dezincification bath or baths bleed is supplemented with a spent pickling solution. 18. Characterized by the galvanizing line including a rinsing station downstream of the dezincification station to generate used rinsing water and supplementing the bleed of the dezincification bath with concentrated HCl, used pickling solution and used rinsing water The method according to claim 16 or 17, wherein 19. 19. The method according to any one of claims 1 to 18, characterized in that the surfactant and / or the corrosion inhibitor are added continuously or semicontinuously to the fluxing bath.