Reprinted from Pollution Equipment News, October 2005
MERCURY CONTROL CASE STUDY
Background
Federal and state regulators have been increasing the focus on mercury air emissions from all sources, including wastewater treatment plant sludge incinerators; municipal, medical, and hazardous waste incinerators; small coal-fired boilers and power plants; waste-to-energy plants; certain refineries; coal gasifiers; and other industrial exhaust streams.
Alternatives
Alternatives for mercury control include the following control technologies:
- Activated carbon adsorption bed;
- Activated carbon injection;
- APC Technologies’ Hg Ultra-High Efficiency Filter (UHF™) system.
APC Technologies’ UHF™ system utilizes proprietary technology to achieve mercury compliance with a simpler, more cost-effective design – that is particularly advantageous for treating gas streams with particulate or wet/saturated conditions present. UHF™ can simultaneously control other heavy metals.
Comparison of Alternatives
Activated carbon beds can provide the necessary control efficiency required to meet compliance levels, but are often subject to disadvantages including plugging by ultra-fine particulate and aerosols, high carbon usage rates, and excessive downtime, resulting in very high costs and maintenance attention. These problems are especially prevalent following a wet particulate control system (e.g., wet scrubber). In dry systems, spray injection of activated carbon followed by a particle control device can provide adequate control efficiency but typically requires a very high ratio of activated carbon to mercury (i.e., a very high carbon usage rate) and is very expensive.
The UHF™ system presents the activated carbon on an substrate surface and provides both high-efficiency particulate filtration, where necessary, as well as mercury emission control. APC custom-designs the UHF™ system to comply with applicable mercury emission limits. The system avoids the plugging and operational problems associated with carbon beds, and requires no process downtime at all for carbon media changeout.
The UHF™ utilizes much less activated carbon than the amount required by activated carbon injection, or comparable or less than an activated carbon bed.
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