Improving Flue Gas Mercury Removal in Waste Incinerators by Optimization of Carbon Injection Rate

Abstract

This study tested the mercury emission characteristics of six municipal solid waste incinerators (MSWIs) and recommended future mercury control via adjusting operational parameters. The results indicated that over 99% of the mercury in solid wastes ended in fly ash and flue gas, of which 3.3-66.3% was emitted to air through stack gas. Mercury in the stack gas was mainly in the form of oxidized mercury (Hg), the proportion (65.4-89.0%) of which was far higher than previous estimation (15%). Mercury removal efficiencies (MRE) of the tested incinerators were in the range of 33.6-95.2%. The impact of waste incineration capacity, gas flow, fly ash yield, and activated carbon (AC) injection on MRE were analyzed. We found that the MRE was significantly linearly correlated to the ratio of AC injection and fly ash yield (correlation coefficient = 0.98, significance <0.01). AC injection value is determined based on the control of dioxin emissions without considering mercury control in traditional design. To increase MRE of MSWIs, the AC injection should increase from around 100 mg·Nm to 135 mg·Nm for grate furnace combustor and 170 mg·Nm for circulation fluidized bed combustor, so as to reach a MRE of 90%.

New insights on mercury abatement and modeling in a full-scale municipal solid waste incineration flue gas treatment unit

“…Likewise, for the analyzed process conditions, the simulation results showed that mercury removal efficiencies higher that 95% can be obtained with activated lignite injection rates above 8 kg/h. These results are also in accordance with several reported studies, which showed that the adsorbent amount available for mercury capture is directly correlated to the mercury removal efficiency in both laboratory-scale and industrial-scale facilities (Ghorishi and Gullett, 1998;Li et al, 2018;Scala, 2001b). In fact, higher adsorbent concentrations in the flue gases are associated to a greater collision probability between the solid reactant and the pollutant, and also a greater surface area available for adsorption.…”

The myth and the reality of energy recovery from municipal solid waste

“…Incineration leads to emissions of metals like mercury [108] and organics like dioxins [18,84,109,166] which are highly toxic. They not only put the people living in the vicinity of incinerators to great risk [28,110] but also cause dispersion of these pollutants far and wide [54].…”

Mercury adsorption in the gas phase by regenerable Au-loaded activated carbon foams: a kinetic and reaction mechanism study

“…This problem is being addressed through the development of specific sorbents. [5][6][7] By using regenerable sorbents, the mercury that is retained may be desorbed and condensed to be confined and isolated. The sorbents studied so far for this purpose are mainly metal oxides and porous solids impregnated with noble metals such as gold, silver, palladium and platinum.…”