(693d) Sustainable Materials for Mercury Control

USA Environmental Protection Agency recently signed a Clean Air Act rule that will reduce the allowable mercury emissions for electric power plants.  Here, we present results obtained from laboratory studies of mercury uptake from a simulated flue gas using unactivated biochars made from agriculture and biorefinery residues. The residues were pyrolyzed at four different temperatures (350, 500, 650, and 800°C). The results show that biochars made from almond shells and cotton seed hulls had very little affinity for mercury. The performance of lignin-based biochar showed clear dependence on pyrolysis temperature, with the biochars made at either 500 or 650°C performing the best. The same was true for biochars created from chicken manure (containing lignocellulosics), and biochars created at higher temperatures out-performed those made at lower temperatures. Overall, the best performance was seen with chicken-manure-based biochar created at 800°C. This material removed 80-98% of the mercury from the simulated flue gas.

Steam activation of the manure-based biochar improved the performance and 100% of the mercury was routinely removed; however, the source of the manure was found to be important.  Manure from turkeys did not have the same affinity as manure from chickens.  The presence of chicken house bedding material in the manure had an effect on surface area properties but not on the mercury uptake.