MXPA99009435A - Method for the recovery of group ia salts during treatment of industrial process waste streams - Google Patents

Abstract

A method for the production of Group IA salts during a process for the recycling of industrial waste streams containing Group IA compounds and iron and/or zinc compounds, by heating the waste stream in a reducing atmosphere, treating the exhaust fumes from the heating step with an ammonium chloride leaching solution resulting in a Group IA salt containing precipitate, and recovering the Group IA salts from the precipitate.

Description

METHOD FOR THE RECOVERY OF SALTS FROM THE LA GROUP DURING THE PROCESS OF TREATMENT OF WASTEWATER INDUSTRIAL BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a process for the recovery of economically useful valuable products from industrial wastewater typically comprising zinc compounds and iron compounds. The present invention relates specifically to a process for recovering Group IA salts from wastewater comprising Group IA compounds together with zinc compounds and iron compounds, in a general process in which a relatively strong iron is produced. pure or a directly reduced iron product feed and a very pure zinc oxide product.

The specific improvement of the present invention is an additional process for the recovery of sodium chloride and potassium chloride from a block of waste material that results after wastewater has been treated wastewater from industrial processes related to metals to extract a significant portion of any iron and zinc compounds. 2. Prior Art Industrial wastewater typically contains components that have economic value if they can be recovered in an economical manner. For example, U.S. Patent No. 3,849, 121 to Burrows now expires, but to which it was assigned to a cession director of the present invention, discloses a method for the selective recovery of zinc oxide from of industrial waste The Burrows method involves leaching a waste material with an ammonium chloride solution at elevated temperatures, separating iron from the solution, treating the solution with zinc metal and cooling the solution to precipitate zinc oxide. The Burrows patent discloses a method for taking EAF powder which is mainly a mixture of iron oxides and zinc and, in a series of steps, separating and disposing of iron oxides and residual metals, so that the solution rich in zinc compounds The resultant can be treated later to recover the zinc compounds.

The waste metal process powder typically has various amounts of other compounds, in various forms, such as the elements of group IA including sodium and potassium, contained in the powder. The Burrows patent does not teach the treatment or recovery of any value of discarded iron oxide containing precipitates and does not discuss any method of recovering Group IA salts, such as sodium chloride and potassium chloride, from the process.

Patent No. 4,071,357 to Peters discloses a method for recovering valuable metals including a vapor distillation step and a calcination step to precipitate zinc carbonate and to convert zinc carbonate to zinc oxide, respectively. Peters still discloses the use of a solution containing approximately equal amounts of ammonium and carbon to leach chimney dust at room temperature, resulting in the removal of only about half the zinc in the dust, almost 7% of the iron, less of 5% of lead and less than half of cadmium. However, Peters does not disclose a method for treating the extracted components that do not contain zinc compounds later, nor for the recovery of Group IA salts from the process. As can be seen, there is a need for a method that allows the continuous treatment of gases and fumes from reduction furnaces or the like to recover the valuable salts of Group IA. This need is addressed by the present invention.

BRIEF SUMMARY OF THE INVENTION The present invention satisfies this need in a method that recovers the salts of Group IA in conjunction with the recovery of a relatively pure iron product from a waste material or a combination of waste materials from industrial processes, such as wastewater from electric arc furnaces, typically containing zinc or zinc oxide and iron or iron oxide and flue gas from reduction furnaces, which are typically poor in iron. The solids without iron and the solutions of foods and products used and / or produced in the general process can be recycled in such a way that the process has minimum solid or liquid residues. Other solids can be recovered by treating other compounds in the waste materials, for example zinc oxide, zinc, valuable metals, and other residues, all of which can be used in other processes. As an alternative example, iron-rich waste products, such as factory scales and used batteries, can also be added to the wastewater of the present process.

Residual water waters are subjected to electric arc furnace dust (EAF) or chimney dust disclosed herein in Table I, to a combination of steps for the process, ultimately resulting in the recovery of certain Group IA salts.

It is also possible to produce, from the general process, an enriched iron compound (an enriched iron block or EIC) that can be used as feed for steel mills and other valuable products, and disclosed in and / or covered for other patent applications and patents assigned to the Metal Recycling Technologies Corporation of Atlanta, Georgia, United States, the cession of this invention. The EIC is typically rich in directly reduced iron (DRI). Preferably, the precipitate containing iron oxides is extracted from a process for the recovery of zinc oxide and zinc metal from industrial wastewater. During the recovery process, the carbon compounds can be added to the wastewater and produce a block of the product from undissolved iron and carbon compounds, which can also be used as feed for the steel mills.

In a preferred specimen of the process, the wastewater material is heated in a reduced atmosphere in a reduction furnace, resulting in the reduction of iron compounds within DRI and the production of combustion products. The DRI can be fed directly to the steel mill as a feed resource and the combustion products, typically in the form of dust gases and fumes, are recovered in a filtering medium, such as a vacuum cleaner or a wet scrubber. The gas and fume powders comprise the majority of the constituents of the JA Group salt and the iron-free compounds, such as zinc, cadmium, copper, lead and calcium compounds.

EAF powder, either alone or in combination with iron rich waste materials; Factory scales, used batteries or other iron-rich or iron-poor waste materials can be used as the initial feed for the process. These combined wastes are first heated in a reduced atmosphere, reducing any iron oxide present for the usable DRI. Vapor gases from the DRI process are condensed and compressed mainly in oxides of zinc, lead, cadmium and in Group IA chlorides. These waste materials are then leached with an ammonium chloride solution resulting in a solution of the product (leached) and undissolved materials (precipitate). In a stable state, Group IA species reach saturation in the ammonium chloride solution and therefore do not dissolve, remaining with the solids in the filter block. In the leaching step, the constituents of Group IA salts reach their saturation concentration in the ammonium chloride solution and precipitate. The leachate comprises metal oxides contained in the waste material, such as lead oxide and cadmium oxide, zinc and / or zinc oxide. The solution of the product and the undissolved materials are separated, the solution of the product and the undissolved materials being later treated to recover the salts of Group IA and other valuable components, as is appropriate. For example, the remaining product solution can be treated to produce a zinc oxide product of 99% or higher purity. Alternatively, the solution of the remaining product can be subjected to electrolysis on zinc metal plates on the cathodes of the electrolysis cells. Any solution of the remaining product after crystallization or electrolysis can be recycled again to treat the residual input material.

When the EAF powders are processed, the residues that contain zinc and fumes from rotating hearth furnaces reach the stable state; The filter block obtained after the first leaching step contains sodium chloride and potassium chloride since these have reached their saturation concentration in the ammonium chloride solution. The filter block comprises true insolubles, which are mainly silicates and water soluble salts, which are mainly sodium chloride and potassium chloride. The salts can be recovered by: 1. Washing the filter block with water, dissolving all water-soluble salts; 2. Optional foundation of heavy metals such as lead using pulverized zinc; and 3. Crystallization of sodium chloride and potassium chloride salts either alone or mixed by selective evaporative crystallization or vaporization drying. The salts can be dried, put in bags and sold.

Therefore, it is an object of the present invention to provide a waste material for the recovery process that recovers valuable chemicals including the salts of the LA Group from industrial wastewater, recycling fumes gases from furnaces such as arc furnaces. electric, recycling fumes gases from industrial processes such as the iron and steel production process and recycling other waste materials, including rich and poor iron waste materials, to produce valuable products.

Another object of the present invention is to provide a method for recovering Group IA salts from the precipitate of a leached ammonium chloride used to recover zinc oxide.

These and other objects, features and advantages of the present invention will be apparent to those skilled in the art after reading the following Detailed Description of a Preferred Sample.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic of a representative process including the present invention. Where A is iron, B is waste, C is slag, D is steel, E is the water cooling step F is liquid PIG, G is the valuable chemical, H is the gas outlet, I is the packing step and J is the step where it is covered with water.

Figure 2 is a flow diagram of the process of the present invention. Where A is the zinc containing feed, B is ammonium chloride, C is the wastewater containing zinc and / or iron, D is the heating and reduction step, E is the leaching step, F is the first materials without dissolve, G, is washed, H is the salt solution I is the cementation (optional), J is the crystallization step, K is the salts of Group IA, L is the iron-containing feed, M is carbon, (optional ), N is the first solution of the product, OR is the solids without dissolving, P is the recovery step of heavy metals), Q is the recovery step of zinc and other metals and / or valuable chemicals, R is the recovery step of iron and other metals and / or valuable chemicals.

Figure 3 is a flow diagram of an alternate process of the present invention. Where A is the zinc-containing feed (optional), B is water, C is wastewater containing zinc and / or iron, D is the dissolution step of the salts of the Group IA, E is the salt solution, F is the cementing step (optional), G is the crystallization step, H are the salts of Group IA, I is the iron-containing feed (optional), J are the solids Without dissolving, K is the heavy metals (optional), L is the recovery step of zinc and other metals and / or valuable chemicals, M is the recovery step of iron and other metals and / or valuable chemicals.

DETAILED DESCRIPTION OF AN EXEMPLARY OF PREFERENCE The method disclosed herein is carried out in its best way treating the waste material from wastewater from metal fabrication processes, industrial or other processes. These waste materials can be combined with other waste materials recovered from furnace gas waters. Many processes produce poor iron wastewater, such as reduction furnaces and iron and steel manufacturing processes. Many other processes produce a rich iron of wastewater. Other processes extract iron-rich materials before processing. Poor iron materials can be combined with a typical industrial water, which, after treatment, results in a rich iron material suitable for use as a feeder for a steel mill. Iron-rich materials can also be combined with typical industrial wastewater and poor iron wastewater.

Typical industrial wastewater is used as a flue gas where the load contains galvanized steel, which has the composition percentage shown in Table I: TABLE I Analysis of Chimney Dust Component Percent by Weight Zinc Oxide 30 Iron Oxide 40 Lead Oxide and Chloride 6.48 Inert Materials 9.10 Sodium and Chloride Oxide 5.00 Calcium Oxide 2.80 Potassium Oxide and Chloride 3.00 Manganese Oxide 1.29 Tin 1.13 Aluminum Oxide 0.38 Magnesium Oxide 0.33 Chromium Oxide 0.16 Copper Oxide 0.06 Silver 0.05 Unidentified Materials 0.22 A second typical industrial wastewater used is a zinc rich smoke from a rotary hearth furnace used in a steelmaking process or in a steelmaking process, which has the percentage of composition shown in the Table. II: TABLE p Rotary Home Furnace Smoke Analysis Component Percentage Weight Zinc Oxide 70 Lead 6 Sodium 3 Potassium 3 Chloride 11 Insoluble 3 Miscellaneous 4 General Description of the Process Generally, the present process is a new addition to a continuous method for the recovery of valuable chemicals and metals from wastewater. The steps of the basic process for recovering Group IA salts from said method are shown in a flow chart in Figure 2 and comprise: a. Heating of a typical industrial waste water process comprising compounds of Group IA such as metals or metal product processes, in a reduced atmosphere to produce gas waters (typically fumes); b. Treatment of gas waters which can be a combination of waste material comprising other wastewater, with a solution of ammonium chloride at a high temperature to form a product solution and an undissolved precipitate comprising the salts of the Group IA; c. Separation of the product solution from the undissolved precipitate comprising the salts of Group IA; d. Washing the undissolved precipitate to form a salt solution comprising the salts of Group IA and an undissolved solid; and e. Crystallization of Group IA salts from saline by evaporative crystallization or vaporization drying.

An alternative establishment of the steps of the process for recovering Group IA salts from said method is shown as a flow chart in Figure 3 and comprises: a. Add a smoke from a rotary hearth furnace comprising salts of Group IA in water to dissolve the salts of Group IA; b. Filter the components of smoke that do not dissolve in water as solids without dissolving; and c. Crystallize Group IA salts from the saline solution by evaporative crystallization or vaporization drying. The saline solution can be attached to a foundation step to extract other compounds. The undissolved solids can be sent to a leaching solution to recover other valuable chemicals and / or metals.

Preferred Sample Referring to Figure 1, a preferred sample of a general wastewater recovery process is shown. Subprocess 100, the digestion and filtration steps, generally comprise the processes disclosed and claimed in U.S. Patent No. 5,464,596. The subprocess 200, the DRI production steps, generally comprise the processes disclosed and claimed in the applications of the United States Series Nos. 08 / 384,446 and 08 / 665,043. The subprocess 300, the recovery steps of valuable chemicals, when combined with the subprocess 100, generally comprise the process disclosed and claimed in the Patent of the States United No. 5,453,111. Subprocess 400, the steps of DRI production increased, when combined with subprocess 200, generally comprise the processes disclosed and claimed in U.S. Patent No. 5,571,306. Each of the subprocesses 200, 300 and 400 must be added to the general process. The patents of the The United States mentioned in this paragraph is incorporated herein by this reference.

The subprocess 200 comprises the leaching steps. The subprocess 500 comprises the feeding process and includes the relevant step for heating the wastewater in a reduced atmosphere. Feeding waters such as wastewater poor in iron from electric arc furnaces 12 and other furnaces such as reduction furnaces or smelters 14 are filtered in a vacuum 16. Other feed waters such as the steel-rich DRI and iron pig, as well as pieces of iron and steel, are subject to the production process of iron or steel. Smoke gases from said processes, which typically include an electric arc furnace or other reduction furnace, are also filtered in a vacuum 16. The constituents filtered in a vacuum 16 comprise the feed of waste water for the subprocess 100.

In subprocess 500, the waste feed waters are heated in a reduced atmosphere, resulting in the reduction of iron compounds within DRI. This typical heating occurs between 500 ° C and 1315 ° C, and preferably between 980 ° C and 1260 ° C. The DRI can be fed directly into the industrial process, like a steelmaking process. The fumes from the heating step are recovered in a capture means, such as a vacuum 16, and then subjected to leachate and other recovery steps of valuable chemicals.

In subprocess 100, the wastewater feed is leached in a digester 18 with ammonium chloride, preferably at about 90 ° C and about 18-23% by weight concentration. The constituents soluble in ammonium chloride go into the solution, while the insoluble constituents in ammonium chloride, such as iron oxides, do not dissolve. In a stable state the salts of Group IA reach their concentration of saturation in the solution and do not dissolve. The precipitates are filtered from the solution in a filter 20. The filtered solution is sent to the cement 22 and is subjected to the sub-process 200 to recover other valuable chemicals. The precipitate, which is typically a filter block, is discussed below to recover the salts of Group IA and / or sent to subprocess 300.

If the precipitate is sent to sub-process 300 before or instead of recovering the salts of the Group LA, the precipitate is dried and triturated in a dryer / shredder 24, the smoke gases derived from the dryer / shredder 24 can be sent to a vacuum cleaner such as vacuum cleaner 16, but is typically sent to an air cleaner, as the scrubber 26 for cleaning, since the smoke gases derived from the dryer / shredder 24 do not significantly have a significant amount of recoverable constituents. The dried and ground precipitates are compacted in a compactor 28 and sent to the reduction or melting furnace 14. In the reduction furnace 14, the dry and crushed iron block is heated between 980 ° C and 1315 ° C, producing a block of enriched iron (EIC) that can comprise the DRI and pig iron, which can be in liquid form. The EIC can be compacted in a second compactor 30 and then cooled by cold water in a cooling conveyor 32, to produce the DRI. The DRI can then be used as the feed for an EAF steel mill and the process cycle begins again.

The fumes from gases derived from the reduction furnaces4 are sent to the scrubber 34, which is preferably a recirculating wet scrubber using water or an aqueous solution of ammonium chloride. Smoke from gases derived from EAFs such as EAF 12 can also be sent to scrubber 34. In scrubber 34, the fumes from the gases are purified and the purified gas is released. The water or the aqueous solution of ammonium chloride containing the constituents derived from the fumes of the purified gases are sent to the cement 22 or to the digester 18, depending on the purity; the purest solutions are typically not sent to the debugger 18, while the less pure solutions are typically sent to the cement 22.

In one example, the furnace 12, 14 expels gases comprising ZnO and other particulate impurities. If the exhausted gases are cleaned in the scrubber 34, the water balance is maintained using a temperature control such as the heat exchanger 36. In addition, the concentration of ZnO and other soluble in the liquid scrubber can be controlled by the addition of water W to cement 22, or ammonium chloride to scrubber 34. If an ammonium chloride solution is used as the scrubbing liquid, it is preferred to keep the solution at about 90 ° C and at 23% NH 4 Cl.

Heating in a Reduction Atmosphere The heating step can be carried out before the initial leaching step and also optionally between a first and second leaching step, the wastewater is heated to temperatures higher than 500 ° C, but typically not more of 1315 ° C. This temperature causes a reaction that causes a decomposition of the stable franklinite phase contained in the wastewater within the zinc oxide and other components. The resulting zinc oxide can be extracted by sublimation or extraction with a solution of ammonium chloride, as it is following the steps detailed above in the general process. The material resulting after the extraction can be reduced using many conventional processes, such as direct or indirect heating and the passage of hot gases through the powder. For example, non-explosive mixtures of reduced gases, such as hydrogen gas and nitrogen or carbon dioxide, can be passed through the waste material. Hydrogen gases are not the only species that can be used for the reductive decomposition of franklinite. It is possible to use species that contain carbon or simple coal, including reduced gases that contain carbon and elemental carbon. The heterogeneous gas phase reductions are faster than the reductions of solid states at low temperatures and therefore the use of carbon monoxide is suggested. The carbon monoxide can be generated in situ by mixing the franklinite powder with carbon and heating it in the presence of oxygen at elevated temperatures. The concentration of oxygen is controlled to optimize CO production. Carbon monoxide can be introduced as a separate resource to more clearly separate the rate of preparation of carbon monoxide from the decomposition rate of franklinite. Then the prepared zinc oxide can be extracted by extraction of ammonium chloride or sublimation.

Leaching Treatment The outflow of the reduction step (typically fumes) and, optionally a part of the waste material, is subjected to a leaching of ammonium chloride. A solution of ammonium chloride in water is prepared in known amounts and concentrations. If the two-stage leaching process is used, the feed material, such as the exhaust stream and chimney dust of waste material described in Table I combined with any other source of feed material containing iron oxide, is Add to the ammonium chloride solution. Otherwise, the first feed material is heated in a reducing atmosphere. Most of the waste mixture, including any zinc and / or zinc oxide, lead oxide, cadmium oxide and other metal oxides, are dissolved in the ammonium chloride solution. The iron oxide does not dissolve in the ammonium chloride solution. In a continuous state, the Group IA salts reach their saturation concentration in the solution and do not dissolve.

It has been found that 18% -23% by weight of the ammonium chloride solution in water at a temperature of at least 90 ° C, provides the best solubility for a waste mixture. Concentrations of ammonium chloride below this range do not dissolve the maximum amount of zinc oxide from the waste mixture, and concentrations of ammonium chloride above this range tend to precipitate the ammonium clone along with zinc oxide when the solution is cooled. Therefore, 18-23% has been chosen as the preferred concentration of the ammonium clom solution. Iron oxide and inert materials such as silicates will not dissolve in the preferred solution.

Ammonium sulfate can be added to the leaching solution to reduce and / or eliminate excess calcium accumulated during the process. The calcium sulfate that forms will be filtered with the iron cake and returned to the oven to make steel. Calcium is calcined in calcium oxide when heated during the steelmaking process. This method can also be used when using a rotary center oven in the first step.

The powder enriched in this process contains small amounts of calcium, so treatment will be necessary on a smaller scale. The calcium sulfate precipitated together with the solids without leaching, will be returned to the rotating center oven. Calcium sulfate will form calcium oxide and will return to the iron units for steel making.

The zinc oxide, as well as the lower concentrations of lead or cadmium oxide, will be removed from the waste mixture by the solution in the ammonium chloride solution. The remaining solid after this leaching step contains the salts of G IA, iron oxide, and some impurities including zinc, lead, cadmium and possibly some other impurities. By subjecting the leaching to evaporation, the leaching product can be concentrated, thereby precipitating the salts of Group IA. As the concentration of ammonium chloride increases, the solubility of group A salts decreases, causing additional precipitation.

Recovery of the LA Group Salts When these EAF powders are processed, the zinc-containing waste and the fumes from the rotary center furnaces, upon reaching the continuous state, the filter cake obtained after the first leaching step, contains clomor of sodium and potassium chloride once these have reached their saturation concentration in the solution of ammonium clomro. The filter cake comprises true insolubles, which are mainly silicates, and water soluble salts, which are mainly sodium chloride and potassium chloride. The salts can be recovered by: 1. Washing the filter cake with water, dissolving all the water-soluble salts; 2. Cement optionally heavy metals such as lead using zinc powder; and 3. Crystallize the sodium clomor and potassium chloride salts, either alone or mixed by selective evaporative crystallization or spray drying.

These preferred steps are carried out in combination with a complete wastewater recycling operation as disclosed herein. If the optional cementation step is carried out, the cemented heavy metals are filtered from the aqueous solution and sent to a mixed metal separation step, such as sub-process 300.

The production of the salts of Group IA can be carried out by continuously eliminating the salts of sodium chloride and potassium chloride during each cycle of a wastewater recycling process, such as that disclosed herein, so that the filter cake would not contain any significant amount of these salts. This can be done by taking the recycle stream going to the evaporator condenser and evaporating the water to a concentration of ammonium chloride which results in the precipitation of the sodium chloride and potassium chloride, since the solubility of the salts decreases when the concentration of ammonium clomro increases. The salts of precipitated solids can then be filtered out of the solution, dried and put into bags. The salts can then be further separated into specific salts by another crystallization step.

Optional Step of Addition of Coal The present process can also be operated to produce a high quality cake in iron-carbon as a residual product. The iron oxide contained in the wastewater does not go into the ammonium chloride solution, but is filtered out of the product solution as undissolved material. This iron oxide cake can be used as the feed for an iron mill; however, as discussed previously, it becomes more valuable if it is reduced by the reaction with elemental carbon to produce an iron-carbon or directly reduced product. A preferred method for producing said iron-carbon or reduced iron product directly from the waste material comprises the steps of, after the first heating of the wastewater in a reducing atmosphere: a. Treat the waste material with an ammonium chloride solution at an elevated temperature to form a product solution that comprises dissolving zinc and dissolving zinc oxide so that no residual iron oxide material will go to the solution and salts of the Group AI will rush; b. Add carbon to the product solution so the carbon will not go into the solution; c. Separate the product solution from the undissolved materials present in the product solution including the LA Group salts, any of the iron and carbon oxides; and d. Wash undissolved materials to dissolve and remove salts from the group LA for recovery, leaving iron oxide and carbon as an undissolved solid.

A mixture of iron oxide and carbon is used by the steel industry as power for electric arc furnaces. The iron oxide cake that is removed as the undissolved material from the leaching step, is mainly iron oxide, being a mixture of Fß2? 3 and F3? . The iron oxide cake can be made in the mixture of iron oxide and carbon by adding elemental carbon to the iron oxide cake in various ways. First, carbon can be added to the leach tank at the end of the leach step, but before the undissolved materials are separated from the product solution. Because the carbon is not soluble in the ammonium chloride solution and will not react in the aqueous solution, the iron oxide cake and carbon can be separated from the product solution and made into the hard cake. Different sizes of coal, such as powder, granules or pills, can be used depending on the wishes of those who make the steel. Secondly, coal can be added to iron oxide and coal can be mixed in a separate process. The combination of carbon and iron oxide in a reducing atmosphere and at an elevated temperature, results in the reduction of iron oxide, producing DRI.

Generally, the iron oxide and carbon product is compressed into a cake to facilitate handling and use. The cake typically contains approximately 82% solids but can be in the range of 78% to 86% solids and can be used and handled easily. Although cakes of less than 78% solids can be formed, the other 22% of the material would be product solution which, if the cake is used as a feed for a steel mill, would be reintroduced. It can be filtered in a vacuum cleaner, adding the resulting filtrate to the wastewater of the present process or the resulting filtrate being the main wastewater feed of the present process. The exhaust fumes can also be purified in a wet scrubber, adding the resulting charged scrubbing solution to the leaching of the ammonium chloride of the present process. If an ammonium cloning purification solution is used instead of water, the charged purification solution can be used as the main leaching of the present process.

Optional Recovery of Zinc Oxide from the Product Solution.

To recover the zinc oxide from the solution of the product in a sub-process 300, while the filtered zinc oxide and the ammonium chloride solution continue at a temperature of 90 ° or more, powdered zinc metal is finely added to the solution . Through an electrochemical reaction, any lead metal and cadmium in the solution is placed on the surface of the zinc metal particle plate. The addition of sufficient zinc metal powder results in the removal of virtually all of the lead from the solution. Then, the solution is filtered to remove solid lead, zinc and cadmium.

Zinc metal powder can only be added to zinc oxide and the ammonium chloride solution to remove solid lead and cadmium. However, zinc dust typically congregates to form large groups in the solution that sink to the bottom of the flask. Rapid agitation typically does not prevent this congregation from occurring; however, if mixed with high shear forces, it can be achieved. Alternatively, to keep the zinc powder suspended in the zinc oxide and the ammonium cloning solution, any number of water-soluble polymers that act as antiflocculants or dispersants can be used. In addition, several surface active materials will also act to keep the zinc dust suspended, as well as many compounds used in the measurement control will be used. These materials only need to be present in concentrations of 10 - 1000 rpm. Various suitable materials include water-soluble polymer dispersants, measurement controllers and surfactants, such as lignosulfonates, polyphosphates, polyacrylates, polymethacrylates, maleic anhydride copolymers, polymaleic anhydride, phosphate esters and phosphonates. Flocon 100 and other members of the Flocon series of maleic acrylic oligomers in various molecular weights of water soluble polymers produced by the FMC Corporation are also effective. Adding dispersants to a strong, highly ionic solution containing a wide variety of ionic species is anathema to standard practice since dispersants are often not soluble in such strong highly ionic solutions.

In this stage, there is a filtrate that contains zinc compounds, and a precipitate of the salts of Gamma IA, lead, cadmium and other products. The filtrate and the precipitate are separated, further treating the precipitate to capture the salts of group IA and other valuable chemicals. The filtrate can also be cooled resulting in the crystallization and recovery of zinc oxide and / or subjected to electrolysis resulting in the generation and recovery of metallic zinc.

Then, the filtrate can be treated to crystallize the diclomero diamino zinc salt complex. This can be done in a conventional crystallizer by cooling the filtrate to an appropriate temperature, generally between 20 ° C and 60 ° C. Crystallized zinc diamine dichloride is then mixed with water at 25-100 ° C to decompose the diclomer diamine. zinc in zinc oxide and ammonium clomro. The size of the particles can be controlled as described in the related specifications.

Then, the zinc oxide can be dried using a ring dryer or other drying means. Recycle Iron By Product.

The iron-rich products that are produced during the recovery process can be further processed to obtain a final product that can be recycled back into the leaching step of the recovery process of the present invention. The iron-rich products are preferably reduced to DRI in a reduction oven. During the reduction process, the exhaust fumes, which consist mainly of zinc, lead and cadmium, are produced in the reduction furnace.

According to the first issue, the DRI is sent to a steel mill where it is used in steel production. The steel production process results in exhaust fumes that are processed through vacuum cleaners and / or wet scrubbers, either or both of which may be located in the steel mill. The fumes processed through the vacuum cleaner are filtered, and the solid residue captured, together with the added amount of EAF dust, is recycled back into the wastewater where they are returned to the leaching step of the recovery process. The fumes processed through the wet scrubber are purified in a liquid stream and the residual impurities obtained from the scrubbing process are discharged from the wet scrubber directly into an ammonium clom solution from the leaching step.

According to the second copy, fumes expelled from the reduction furnace used to produce the DRI are processed through the vacuum cleaner and / or the wet scrubber. The fumes processed through the vacuum cleaner are filtered and the captured solid residue is recycled back into the stream of waste materials, so that it is returned to the ammonium chloride solution of the leaching step. In this example, it is not necessary to add EAF powder with the solid residue. The fumes processed through the wet scrubber are purified in a liquid stream and the residual impurities obtained from the filtration process are discharged from the wet scrubber directly onto the ammonium chloride solution of the leaching step.

The detailed description of a preferred specimen is for illustrative purposes only and is not intended to limit the spirit or scope of the invention, or its equivalent, as defined in the appended Claims.

Claims (18)

1. CLAIMS 1. A method for the production of LA group salts during a process for the recovery of valuable zinc and / or iron from wastewater containing the compounds of group LA, iron and zinc, which comprises the steps of: a. Heat the wastewater to an elevated temperature in a reducing atmosphere resulting in the production of fumes comprising the LA Group compounds and zinc; b. Treat the exhaust fumes with an ammonium chloride solution at an elevated temperature to form a product solution comprising loose zinc and an undissolved solid comprising the salts of Group IA and the iron compounds; c. Wash the precipitate without dissolving with water to form a salt solution comprising the dissolved Group IA salts and an undissolved solid; and d. recover the salts of the LA Group from the salt solution.
2. 2. The method as mentioned in claim 1, wherein the fumes are treated in a continuous state, with a solution of ammonium clomro.
3. 3. The method as recited in Claim 2, wherein the compounds of group I A are sodium chloride and potassium clomro.
4. 4. The method as recited in Claim 3, wherein the concentration of the ammonium clom solution is approximately 18-23% by weight.
5. 5. The method as recited in Claim 4, wherein the wastewater is heated in a reducing atmosphere at an elevated temperature of at least 500 ° C.
6. 6. The method as recited in Claim 5, wherein the group salts IA are recovered from the salt solution via crystallization.
7. 7. The method as recited in Claim 6, wherein the crystallization is crystallization by evaporation.
8. 8. The method as recited in Claim 6, wherein the potassium chloride is crystallized from the salt solution prior to the sodium clomro.
9. 9. The method as recited in Claim 5, wherein the salts of group IA are recovered from the salt solution via spray drying.
10. 10. The method as recited in Claim 1, wherein the iron compounds in the wastewater are reduced to direct reduced iron when the wastewater is heated in the reducing atmosphere.
11. 11. The method as recited in Claim 10, wherein the undissolved solid comprises iron compounds in the form of direct reduced iron.
12. 12. The method as recited in Claim 11, wherein the undissolved solid is used as feed for a steel mill.
13. 13. The method as mentioned in Claim 1, wherein the product solution is subjected to a concentration process, thereby affecting the precipitation of a greater amount of salts from Group IA.
14. 14. The method as recited in Claim 6, wherein the salt solution remaining after crystallization is further treated to recover the valuable chemicals.
15. 15. The method as recited in Claim 9, wherein the salt solution remaining after spray drying is further treated to recover the valuable metals.
16. 16. The method as mentioned in Claim 1, further comprises the step of adding zinc metal to the product solution where any of the metal ions that displace the zinc contained within the product solution are displaced by the zinc metal and they are precipitated from the product solution as metals.
17. 17. The method as recited in Claim 16 further comprises the steps of separating the metals from the product solution and decreasing the temperature of the product solution thereby precipitating at least a portion of any zinc component from the product solution. as a mixture of crystallized zinc.
18. 18. The method as mentioned in Claim 17 further comprises the steps of separating the crystallized zinc compounds from the product solution and washing the crystallized zinc compounds with a water wash thereby solubilizing certain of the zinc compounds and separating any crystallized zinc compound remaining from the product solution and drying the remaining crystallized zinc compounds at a temperature between 100 ° C - 200 ° C resulting in the recovery of a zinc oxide product with 99% purity or more . EXTRACT OF THE INVENTION A method for the production of the salts of Group IA during a process for the recycling of industrial waste water containing compounds of Group IA and iron and / or zinc, by heating the wastewater in a reducing atmosphere, treating the exhaust fumes from the heating step with an ammonium chloride leaching solution, resulting in a precipitate containing the salts of Group IA and recovering the salts from group IA of the precipitate.