Method for processing materials containing iron and zinc

Abstract

A method for processing a source material containing zinc ferrite that includes the following step: B. Partially reduce source material using a reducing gas containing hydrogen to form a reduced material; where step B is carried out at below 1000° C. using a reducing gas containing at least 0.25% (by vol.) and up to 70% (by vol.) hydrogen in a carrier gas.

1 . A method for processing a source material containing zinc ferrite that includes the following step:
 B. partially reduce source material using a reducing gas containing hydrogen to form a reduced material; wherein the reducing gas includes water.   
     
     
         2 . The method as claimed in  claim 1  wherein, step B is carried out at or below 1000° C. 
     
     
         3 . The method as claimed in  claim 1  or wherein, the source material is a particulate material that is not pelletised before processing. 
     
     
         4 . The method as claimed in  claim 1  wherein, the source material is Electric Arc Furnace Dust (EAFD). 
     
     
         5 . The method as claimed in  claim 1  wherein, step B is carried out at between 500° C. and 750° C. 
     
     
         6 . The method as claimed in  claim 1  wherein, the method includes a step C, where step C cools the reduced material to a temperature no higher than 350° C. in an inert or reducing gas environment. 
     
     
         7 . The method as claimed in  claim 1  wherein, the hydrogen content of the reducing gas is between 0.25% and 10% by volume. 
     
     
         8 . The method as claimed in  claim 1  wherein, there is a step A preceding step B, where in step A the source material is analysed to determine the total zinc and/or zinc ferrite concentrations, wherein, step A determines proposed processing conditions to be used in step B, including reduction time (Rt), reduction temperature (RT) and reducing gas flowrate (GF). 
     
     
         9 . The method as claimed in  claim 1  wherein, the water is added to the reducing gas at a predetermined time after step B commences. 
     
     
         10 . The method as claimed in  claim 9  wherein, the predetermined time a. is reached before the temperature has reached a value selected from the list consisting of 500° C., 550° C., 600° C. and 650° C., or b. is reached when the temperature has a value within a range selected from the list consisting of 500° C. to 550° C., 550° C. to 600° C., 600° C. to 650° C., 500° C. to 600° C., 550° C. to 650° C. and 500° C. to 650° C. 
     
     
         11 . The method as claimed in  claim 1  wherein, after step C there is a step D, where step D is an acid leaching step. 
     
     
         12 . The method as claimed in  claim 11  wherein, the acid leaching step uses an acid leach which includes one or more acids selected from the list consisting of sulphuric acid, phosphoric acid, hydrochloric acid, hydrofluoric acid, and an organic acid with less than 15 carbon. 
     
     
         13 . The method as claimed in  claim 11  wherein, step D is carried out at a pH of less than 3. 
     
     
         14 . The method as claimed in  claim 13  wherein, step D is carried out at pH 2. 
     
     
         15 . The method as claimed in  claim 12  wherein, the acid leach used contains sulphuric acid. 
     
     
         16 . The method as claimed in  claim 1  wherein, step B is monitored and/or controlled by one or more methods selected from the list consisting of directly or indirectly measuring the extent of reduction by determining the forms of iron present, determining the composition of the reducing gas within the furnace and determining the composition of an exiting gas stream. 
     
     
         17 . The method of  claim 1 , wherein the ratio of water to hydrogen (H 2 O:H 2 ), on a molar basis, is between 1:20 and 7:1. 
     
     
         18 . The method of  claim 1 , wherein the water to hydrogen ratio is between 1:2 and 2:5. 
     
     
         19 . The method of  claim 1 , wherein the method reduces the zinc ferrite to magnetite and zinc oxide whilst substantially avoiding the formation of wustite, iron or zinc. 
     
     
         20 . The method of  claim 1 , wherein the mass loss during step B is controlled to no more than about 2% (2%+/−0.5%).