Leach-resistant solid bodies from fly ash and heavy metal sludge

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for treating heavy metal sludges using fly ash.
It has been found that the fly ash produced in the combustion of sub-bituminous coal from the Powder River Basin forms hard, stable products on the addition of water, and that heavy metal sludges can be fixed very satisfactorily in the hardened products when the sludges are added under certain conditions to this fly ash.
The Powder River Basin coal deposits occur in a well-defined region of northern Wyoming and southern Montana.
The coal which is mined from these deposits is sub-bituminous, i.
e.
coal of rank intermediate between bituminous and lignite having caloric values in the range of 8,300 and 13,000 BTU per pound (calculated on a moist, mineral-matter-free basis).
Coal is currently being mined from fields in the Powder River Basin deposits, for instance, in the vicinity of Gillette, Wyo.
, by the Amax Coal Company.
This coal is typically pulverized and burned, for instance, in power plants.
Fly ash is formed and recovered, frequently with the use of electrostatic precipitators in the power plant smokestacks.
When added to water, the fly ash sets in a matter of several minutes to a dense solid.
The fly ash which is appropriate for use in the process and products of the present invention may typically show the following components on analysis:
Table 1
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Components Proportion
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SiO.
sub.
2 20-40 wt.
%
Al.
sub.
2 O.
sub.
3 10-30
Fe.
sub.
2 O.
sub.
3 3-10
MgO .
5-8
SO.
sub.
3 1-8
TiO.
sub.
2 .
5-2
C .
5-2
H.
sub.
2 O .
33-3
CaO 10-32
K.
sub.
2 0 .
5-4
Na.
sub.
2 O .
5-6
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The mineralogy of the fly ash will typically be as follows:
Table 2
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Fraction Peak Height, X-Ray Analysis
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Quartz 10-28
Hematite 1-6
Periclase 1-6
Calcium Oxide 1-10
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The fineness of the fly ash will ordinarily be such that less than about 34% is retained on a 325 mesh sieve (U