Treatment and Utilization of Spent Acid that Used in Galvanizing ( Pickling )

                                

                                      1-       6 HCl + Fe2O3 ----- 2 FeCl3 + 3 H2O 

2-            Fe + HCl  -------- Fe Cl2 + H2

 

The main concentration of pickling tank is 16% wt/ wt .

The performance of the tank can't be effective when it reaches 5  wt/ wt .

At this point the iron content is 150 gr / lit . it means you have  ore or iron mine .

There is more than one option to treat this consumed acid :

·        Acid Regeneration : it can be used on or off line by using special type of resins in order to get rid of iron then concentrate  it to reach crystal stage as FeCl3 and it is necessary to keep Fe content within 10 gr/ lit to reduce dipping time in pickling or acid tank . the second option to treat the consumed acid off line by evaporation or treat it with sulfuric acid as below

3 H2SO4 + 2 FeCl3 ------ 6 HCl +   Fe2( SO4)3

  H2SO4 +  FeCl2 ------  2 HCl +   Fe SO4

The value of ferric sulfate or ferrous sulfate is very high in water treatment Plant (domestic water treatment or as fertilizer ).

·        The critical issue is the polluted  of consumed acid : it should not contain other metal such as zinc or pickling additive which cant be evaporated by simple purification  .





  

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