Copper-Doped Silica Materials Silanized With Bis-(Triethoxy Silyl Propyl)-Tetra Sulfide for Mercury Vapor Capture

• Published in: Energy & fuels 2008-07, Vol.22 (4), p.2290-2298
• Main Authors: Meyer, D. E, Meeks, N, Sikdar, S, Hutson, N. D, Hua, D, Bhattacharyya, D
• Format: Article
• Language: English
• Subjects: 01 COAL, LIGNITE, AND PEAT; ADSORBENTS; ADSORPTION; Air pollution caused by fuel industries; AIR POLLUTION CONTROL; Applied sciences; CAPTURE; COPPER; Energy; Energy. Thermal use of fuels; Environmental; Exact sciences and technology; FLUE GAS; MERCURY; Pollution reduction; SILANES; SILICA; SORBENT INJECTION PROCESSES
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef8001873

The use of Cu−S sites for Hg capture from the gas phase has been successfully applied to a silica-based platform using an S4 organic polysulfane and copper sulfate. The maximum fixed-bed equilibrium capacity achieved using these materials was 19 789 μg Hg·g−1 sorbent for a material with 2.5 wt % Cu and 6 wt % S. An optimal S level was determined to be around 3 wt % because enhancement of capacity was only 18% when increasing from this 3 to 6 wt %. The rate of adsorption in pure beds ranged from 0.6 to 1.6 μg Hg·min−1 depending on the inlet concentration. Differences in breakthrough times suggest that material deposition is not uniform. When compared to two other platforms, commercially available Darco HG-LH and previously tested Fe−Cu−S4 nanoaggregates, the Si-1 material performed the best in fixed-bed testing. During entrained-flow testing, a steady-state Hg removal of 82% was achieved using Si-1 at injection rates of both 6 × 10−5 and 1.2 × 10−4 g·L−1·h−1. The lack of increase in Hg removal when the injection rate is doubled suggests that pore accessibility is the rate-controlling step during dynamic Hg capture. A calculation of the approximate pore usage based on injection testing helped confirm this observation. During injection testing, the performance of Si-1 was only diminished 10% when exposed to 20 ppm SO3. This is an encouraging result for flue-gas applications where SO3 levels range from 1 to 40 ppm. Testing demonstrated that Si-1 is stable when exposed to leaching conditions after concrete blending and cement impregnation. This is an important aspect to consider for injection because the sale of fly ash for concrete is a key cost-recovery tool for power plants.