(364e) Mechanisms Of High-Temperature (900°C – 1000°C) In-Flight Sequestration Of Mercury In Coal Combustion And Gasification Systems

Authors: 
Biermann, J., MinPlus, BV.


Data from a laboratory scale entrained-flow quarts reactor (180cm in length; 4.7 mm I.D) were used for to elucidate the mechanisms of reaction between elemental mercury and a specially mass produced non-carbon based sorbent. The sorbent, denoted as MinPlus, consists of CaO, CaCO3, and Al2O3-2SiO2 and is manufactured from paper recycling residues. In this experimental study, it is indroduced at rates of 2-6 g/h, into a quartz reactor by a vibration forced sorbent feeding system, details of which will be described. Nitrogen and compressed air at 3.5 slpm are used as carrier gases to simulate flue gas at temperatures ranging from 600°C to 1100°C. Effects of addition of other gases, such as CO/CO2, HCl, SOx, and NOx, will also be reported.. Elemental mercury vapor (25 µg/m3) was produced by Hg calibrator and monitored by 2537A Tekran Hg monitor through SnCl2-NaOH impinging system.

Preliminary results indicated that Hg removal efficiency increases with both sorbent feeding rate and reactor temperature. At temperatures between 900-1000°C, about 83% Hg removal efficiency was achieved. At temperatures below and above this range, sorption was decreased, suggesting that both activation and de-activation mechanisms came into play Other fixed packed bed test results agree well with this optimal temperature zone for Hg adsorption.

To explain and identify the reaction paths between elemental mercury and sorbent as well as mineral transition of sorbents at high temperature, XRD, TGA, and SEM-EDS analysis were performed on both raw and spent sorbents. MinPlus sorbent has been shown to be very effective for mercury sequestration at high temperatures (900-1000°C). This high temperature sorbent injection process could yield enhanced energy efficiencies in coal combustion and gasification processes and provide enhanced fly ash utilization for cement manufacturing.