Theoretical approach for enhanced mass transfer effects in-duct flue gas desulfurization processes. Volume 1, Dry sorbent injection: Final report

This report presents the results of fundamental mass transfer testing for in-duct removal of SO{sub 2}. Following this initial part of an experimental program, it became clear that the amount of initial moisture on the sorbent strongly affected the extent of Ca(OH){sub 2} conversion. Novel techniques aimed at increasing sorbent utilization were investigated and are described. Major novel technique investigated and reported on here was the reaction with SO{sub 2} of sorbents with initial free moisture (damp sorbents). The duct injection process using damp solids has the following steps: preparation of sorbent as a slurry, blending of the slurry with dry recycle materials to create damp solids, injection of the solids into the duct, reaction and drying of the solids with flue gas in the duct, collection in particulate control equipment, and finally recycle of dry solids with some bleed to disposal. The moisture content of the solids at each step affects system performance. Various factors favor high moisture whereas others favor low moisture. (VC

Theoretical approach for enhanced mass transfer effects in-duct flue gas desulfurization processes. Volume 2, Duct spray drying: Final report

Removal of sulfur dioxide (SO{sub 2}) from the flue gas of coal- burning power plants can be achieved by duct spray drying using calcium hydroxide [Ca(OH){sub 2}] slurries. A primary objective of this research was to discover the aspects of mass transfer into Ca(OH){sub 2} slurries which limit SO{sub 2} absorption. A bench- scale stirred tank reactor with a flat gas/liquid interface was used to simulate SO{sub 2} absorption in a slurry droplet. The absorption rate of SO{sub 2} from gas concentrations of 500 to 5000 ppm was measured at 55{degrees}C in clear solutions and slurries of Ca(OH){sub 2} up to 1.0 M (7 wt percent). Results are reported in terms of the enhancement factor, {O}. This research will allow prediction of conditions where the absorption of SO{sub 2} in Ca(OH){sub 2} slurries can be enhanced by changes to liquid phase constituents (under which SO{sub 2} absorption is controlled by liquid film mass transfer). Experiments in the stirred tank have shown that SO{sub 2} absorption in a 1.0 M Ca(OH){sub 2} slurry was completely dominated by gas film mass transfer with a large excess of Ca(OH){sub 2} but becomes controlled by liquid film resistance at greater than 50 percent Ca(OH){sub 2} utilization. (VC

UNEP Demonstrations of Mercury Emission Reduction at Two Coal-fired Power Plants in Russia

The United Nations Environment Programme (UNEP) partnership area “Mercury releases from coal combustion” (The UNEP Coal Partnership) has initiated demonstrations of mercury air emission reduction at two coal-fired power plants in Russia. The first project has modified the wet particulate matter (PM) scrubber installed in Toliatti thermal plant to allow for addition of chemical reagents (oxidants) into the closedloop liquid spray system. The addition of oxidant resulted in significant improvement of mercury capture from 20% total mercury removal (without the additive) up to 60% removal (with the additive). It demonstrates the effectiveness of sorbent injection technologies in conjunction with an electrostatic precipitator (ESP). ESPs are installed at 60%, while wet PM scrubbers are installed at 30% of total coal-fired capacity in Russia. Thus, the two UNEP Coal Partnership projects address the majority of PM emission control configurations occurring in Russia

Options for mercury reduction from coal combustion

The UNEP coal combustion partnership area has been established to contribute to significantly reduce global mercury emissions mainly though existing multi-pollutant reduction approaches. As part of this, the partnership area has been assisting participating governments in developing mercury inventories and providing technically sound information on cost effective approaches for enhancing reductions of mercury emissions. Guidance material has been produced for developing nations and countries with economies in transition. Activities are ongoing in China, India, Russia and South Africa, and new projects are being planned in Southeast Asia

Options for mercury reduction from coal combustion

The UNEP coal combustion partnership area has been established to contribute to significantly reduce global mercury emissions mainly though existing multi-pollutant reduction approaches. As part of this, the partnership area has been assisting participating governments in developing mercury inventories and providing technically sound information on cost effective approaches for enhancing reductions of mercury emissions. Guidance material has been produced for developing nations and countries with economies in transition. Activities are ongoing in China, India, Russia and South Africa, and new projects are being planned in Southeast Asia