Environmental Engineering Reference
In-Depth Information
Figure 5.3: Stages of total catalyst management system [From ref. 329 . Reprinted with
permission].
(1) Characteristics, which can be defined in terms of physical and chemical properties, cause
the waste to be hazardous.
(2) Properties defining hazardous characteristics must be measurable and quantified by testing
protocols and must be detectable by hazardous waste generators (e.g., petroleum
refineries).
Potentially hazardous constituents that are relevant to spent catalysts, listed User's Guide, are
shown in Table 5.2 [306] . The list includes all metals that are considered by EPA as hazardous
(e.g., Pb, Cd, Hg, Cr, Se, Ba, Ag, and Cu). The constituents in Table 5.2 can be divided into
two groups, such as those present in the fresh catalysts as well as those present in spent and
regenerated catalysts. Other possibilities are to classify the constituents either as inorganic and
organic or combustible and non-combustible. It is believed that Mo and W, which are the
principal active metals in hydroprocessing catalysts, should also be added to the list in
Table 5.2 in anticipation that most of the heavy metals might be regulated in a near future.
The efforts to develop more active and stable catalysts may require the addition of other
constituents to the list.
Table 5.2 [306] covers all metals that are included in the NPDWS listed in Table 5.1 [296] . The
organic constituents listed in these tables, i.e., benzene, toluene, PAHs, etc., may be of a
 
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