Removal and melting of zinc powder formed in an electrowinning cell

Abstract

The invention provides methods of using concentrated zinc chloride to protect zinc powders formed by electrowinning from oxidation during collection and removal from an electrowinning cell, during periods of prolonged storage and during melting. The invention provides a means of flushing zinc powders from all surfaces of an electrowinning cell and transporting and storing the zinc powders under a concentrated zinc chloride solution. The same concentrated solution can be used with ammonium chloride in a flux solution to melt the zinc powders prior to shaping the molten zinc into briquettes, pellets and the like.

What is claimed is:  
     
         1 . A method of removing zinc metal from an electrowinning cell comprising flushing said zinc metal from said electrowinning cell with a concentrated zinc chloride solution.  
     
     
         2 . The method of  claim 1  wherein said electrowinning cell is an EMEW cell.  
     
     
         3 . The method of  claim 1  wherein said zinc metal is flushed from the surfaces of said electrowinning cell.  
     
     
         4 . The method of  claim 1  wherein the concentration of said concentrated zinc chloride solution is greater than about 250 grams of zinc chloride per liter.  
     
     
         5 . The method of  claim 1  wherein the concentration of said concentrated zinc chloride solution is greater than about 500 grams of zinc chloride per liter.  
     
     
         6 . The method of  claim 1  wherein the concentration of said concentrated zinc chloride solution is greater than about 1000 grams of zinc chloride per liter.  
     
     
         7 . The method of  claim 1  comprising the additional step of recycling said concentrated zinc chloride solution to flush an electrowinning cell.  
     
     
         8 . The method of  claim 7  wherein said recycling step comprises adjusting the concentration of said concentrated zinc chloride solution.  
     
     
         9 . A method of recovering zinc metal powder formed in an electrowinning cell comprising: 
 a. flushing said zinc metal powder from said electrowinning cell with a concentrated zinc chloride solution; and,    b. removing excess concentrated zinc chloride flush solution from said zinc powder.    
     
     
         10 . The method of recovering zinc metal powder of  claim 9 , wherein the zinc metal powder formed is protected from oxidation by residual concentrated zinc chloride solution from previous operations performed on the zinc metal powder.  
     
     
         11 . The method of recovering zinc metal powder of  claim 9 , comprising the additional step of pressing the recovered zinc metal powder into a desired shape, wherein the zinc metal powder recovered is protected from oxidation by concentrated zinc chloride solution added to the pressing operation used to form desired shape zinc metal particles.  
     
     
         12 . A method of storing zinc metal comprising contacting said zinc powder with a concentrated zinc chloride solution for the duration of storage.  
     
     
         13 . The method of  claim 12 , wherein the concentration of said concentrated zinc chloride solution is greater than about 250 grams of zinc chloride per liter.  
     
     
         14 . The method of  claim 12 , wherein the concentration of said concentrated zinc chloride solution is greater than about 500 grams of zinc chloride per liter.  
     
     
         15 . The method of  claim 12 , wherein the concentration of said concentrated zinc chloride solution is greater than about 1000 grams of zinc chloride per liter.  
     
     
         16 . The method of  claim 12 , wherein the zinc metal is in a form selected from the group consisting of powder, ingot, bar, pellet, briquette, brick and plate.  
     
     
         17 . A method of protecting zinc metal from oxidation comprising contacting said zinc metal with a concentrated zinc chloride solution.  
     
     
         18 . The method of  claim 17 , comprising the additional step of removing excess concentrated zinc chloride solution from said zinc metal.  
     
     
         19 . The method of  claim 17 , wherein said contacting step comprises adding concentrated zinc chloride solution to a mixture of zinc metal in water or other dilute solution.  
     
     
         20 . The method of  claim 18 , wherein said contacting step comprises; 
 a. dewatering said zinc metal; and,    b. contacting said dewatered zinc metal with a concentrated zinc chloride solution.    
     
     
         21 . The process of  claim 20 , wherein the dewatering step comprises complete dewatering.  
     
     
         22 . The process of  claim 20 , wherein the dewatering step comprises partial dewatering.  
     
     
         23 . A method of melting zinc powder comprising; 
 a. dewatering zinc powder previously in contact with a concentrated zinc chloride solution,    b. adding to the dewatered zinc powder a flux comprising ammonium chloride,    c. heating the zinc powder and flux to a temperature between about 200° C. to about 700° C.    
     
     
         24 . The method of  claim 23 , wherein the flux additionally comprises zinc chloride.  
     
     
         25 . The method of  claim 23 , wherein the zinc powder is first dried in an oven in the presence of added flux components zinc chloride and ammonium chloride.  
     
     
         26 . The method of  claim 23 , wherein the flux is first placed in a melting furnace and the dewatered zinc powder is added to the flux before melting occurs.  
     
     
         27 . The method of  claim 23 , wherein the dewatered zinc powder is added to flux in contact with a molten metal phase.  
     
     
         28 . The method of  claim 23 , wherein the zinc powder is first pressed into a shape selected from the group consisting of pellets, briquettes, ingots, bars, plates and bricks to assist in the melting process.  
     
     
         29 . The method of  claim 28 , wherein all or part of the flux is added to the zinc powder during the pressing process and the balance is added to the zinc pellets or other desired shapes in the melting furnace.