Coal-fired power plants are facing stringent regulations intended to reduce the emissions of mercury, acid gases (such as hydrogen chloride and sulfur oxides), and other major air toxics from chimney stacks, in compliance with two recent U.S. Environmental Protection Agency regulations: the Mercury and Air Toxics Standards and the Clean Power Plan. The ISGS has taken up this challenge by developing and patenting, over the past decade, six sorbent-based technologies that incorporate a unique sorbent activation process (SAP) to control air toxic emissions.
On April 5, the ISGS, through the Office of Technology Management at the University of Illinois at Urbana-Champaign, was awarded a new U.S. patent (US 9,302,218 B2) on technology for the on-site production of chemically modified activated carbon- and calcium-based sorbents. Inventors of the process are Yongqi Lu (ISGS), Massoud Rostam-Abadi (ISGS), and Ramsay Chang (Electric Power Research Institute).
The SAP concept was initially developed to simplify complex activated carbon manufacturing to a simple step. The process involves pulverizing sorbent precursors such as the coal on site at a power plant, using power plant heat or burning coal or gas as a heat source to activate the sorbent, and injecting the produced sorbent directly into the power plant flue gas. An additional benefit of the SAP, as a sorbent production technology, is that it eliminates the need to install a carbon capture unit at an activated carbon or lime plant site. The gaseous and liquid products from the SAP process are recycled to the power plant boiler and can be captured in the power plant’s carbon dioxide capture unit.
These sorbents can potentially be used to simultaneously remove acid gases such as hydrogen chloride, sulfur dioxide or trioxide, and vapor-phase mercury from combustion-generated flue gas streams. Use of the SAP process can greatly simplify, and reduce the cost of, sorbent production at utility sites. The SAP technology has been demonstrated at pilot and full scale at several sites over the past five years, and the Electric Power Research Institute has negotiated licensing agreements with several industries.
