Resources
The consumption of water and chemicals depends on the type of residue and the degree of stabilisation that is required.
The quality of the water and chemicals used can be low.
Below is an example of the water and chemicals needed for treatment of 10 000 tonnes of fly ash from waste incineration.
|
Water |
30 000 m3 |
|
FeSO4x7H2O |
700 tonnes |
|
H2SO4 |
0 tonnes |
Fly ash with or without sludge from wet flue gas cleaning requires the least water and chemicals. Dry/Semidry APC-residue requires more water and chemicals including possibly H2SO4.
Leaching and waste water
The Ferrox®-process stabilises the residues, whereby the release of heavy metals and salts are substantially reduced compared to the untreated residues. An example of the reduction in leaching of some critical contaminants from a semidry APC-residue and a fly ash is shown below.
|
Residue |
Semidry APC-residue |
Fly ash |
||||
|---|---|---|---|---|---|---|
|
Untreated |
Treated |
Untreated |
Treated |
|||
|
Cl |
mg/kg |
180000 |
1700 |
85000 |
1400 |
|
|
K |
mg/kg |
27000 |
850 |
32000 |
1500 |
|
|
Na |
mg/kg |
26000 |
1000 |
27000 |
1500 |
|
|
Cd |
mg/kg |
0.012 |
< 0.002 |
0.13 |
< 0.002 |
|
|
Cu |
mg/kg |
3.7 |
< 0.01 |
0.32 |
< 0.01 |
|
|
Pb |
mg/kg |
730 |
0.048 |
450 |
0.068 |
|
The leaching figures in the table are the accumulated release from a two-step batch leaching test (L/S 10, 24 hours).
The process yields 2 – 3 m3 wastewater for each tonne of residue treated.
An example of the composition of the wastewater discharged from stabilising semidry APC-residue and fly ash with the Ferrox®-process is shown below.
|
Semidry APC-residue |
Fly ash |
||
|---|---|---|---|
|
Cl |
mg/l |
52 000 |
28 000 |
|
K |
mg/l |
7 500 |
12 000 |
|
Na |
mg/l |
7 400 |
10 000 |
|
Cd |
mg/l |
0.006 |
0.003 |
|
Cu |
mg/l |
0.007 |
< 0.005 |
|
Pb |
mg/l |
0.07 |
0.03 |
For further information, please contact Babcock & Wilcox Vølund ApS.
