Arsenic and selenium capture by fly ashes at low temperature.

Area of Science:

• Environmental Science
• Chemical Engineering
• Geochemistry

Background:

• Coal conversion processes can release toxic arsenic and selenium compounds into the environment.
• Fly ash properties and process conditions influence the retention of these trace elements.
• Optimizing trace element capture in fly ash is an economical strategy for emission reduction.

Purpose of the Study:

• To evaluate the capacity of two distinct fly ashes (pulverized coal combustion and fluidized bed combustion) to retain arsenic and selenium compounds.
• To investigate the influence of unburned coal particles on the retention of arsenic, selenium, and mercury.
• To understand the mechanisms governing trace element capture by fly ash.

Main Methods:

• Investigated the retention of arsenic and selenium compounds using fly ash from pulverized coal combustion (PCC) and fluidized bed combustion (FBC).
• Assessed the impact of unburned coal particle content on the simultaneous retention of mercury.
• Quantified retention capacities under varying process conditions.

Main Results:

• Both fly ashes demonstrated significant retention capacities for arsenic and selenium compounds, ranging from 2 to 22 mg g(-1).
• The presence of unburned coal particles in fly ash did not substantially alter the retention capacities for the studied trace elements.
• Fly ash from fluidized bed combustion showed comparable or potentially higher retention capabilities for certain trace elements.

Conclusions:

• Fly ash possesses a notable capacity for capturing arsenic and selenium compounds from coal conversion off-gases.
• Optimizing fly ash characteristics and combustion conditions can enhance the retention of toxic trace elements.
• Further research into capture mechanisms can lead to improved emission control technologies for coal conversion processes.