James T. Yeh

Aqua ammonia process for simultaneous removal of CO2, SO2 and NOx

Experimental research work in applying aqueous ammonia solution for the simultaneous reduction of acidic gaseous emission from fossil fuel-fired utility plants is currently being performed at the National Energy Technology Laboratory. The traditional monoethanolamine process for CO2 removal suffers the disadvantages of low carbon dioxide loading capacity, equipment corrosion, amine degradation by SO2 and O2 in flue gas, and high energy penalty during absorbent regeneration. The aqueous ammonia process can simultaneously remove CO2, SO2, NOx, plus HCl and HF that may exist in the flue gas. There could be oxidation of SO2 and NO prior to contacting the aqueous ammonia absorbent. Test results pertaining to the ammonia/carbon dioxide reaction in a semi-continuous reactor system are presented. The parametric effects of sparger design, reaction temperature, and ammonia concentration on gas loadings and absorption rates are discussed. Regeneration test results, including solution-cycling between the regeneration and absorption steps to determine a realistic loading capacity for the ammonia solutions are also presented.

INTEGRATED TESTING OF THE NOXSO PROCESS: SIMULTANEOUS REMOVAL OF SO2 AND NO x FROM FLUE GAS

Abstract Parametric studies with the NOXSO process—a dry, regenerable flue gas treatment system that simultaneously removes SO2 and NOx from flue gas produced by the combustion of coal—were conducted. The reusable sorbent that was tested consisted of sodium carbonate impregnated on a high surface area γ-alumina sphere (1·6- mm nominal diameter). All process steps, including adsorption and regeneration, were integrated into a new 60-KWe-scale Life-Cycle Test Unit so that continuous, long-term operation of the total process could be experimentally evaluated. The effects of sorbent flow rate, temperature, inlet SO2 and NOx, concentrations, and sorbent residence time (fluid bed depth) on pollutant removal efficiencies in the absorption step were determined. Also, the impact of the type of regenerant gas, temperature, steam, excess regenerant gas, and diluent on the regeneration of the sorbent was investigated. Sorbent properties with respect to time on stream (cycles of operation) are also reported.

Life cycle test of the NOXSO SO2 and NOX flue gas treatment process: Process modeling

Abstract The NOXSO process uses a regenerable sorbent that removes SO2 and NOX simultaneously from flue gas. The sorbent is a γ-alumina bead impregnated with sodium carbonate. The process was successfully tested at three different scales, equivalent to 0.017, 0.06, and 0.75 MW of flue gas generated from a coal-fired power plant. These test results were used to develop a mathematical model for the NOXSO fluid-bed adsorber (NOXSO Corp., Library, PA). The model predicts SO2 and NOX removal efficiencies as a function of process conditions and sorbent properties. The spent sorbent was successfully regenerated with either hydrogen or natural gas. The presence of steam during regeneration helps to remove the residual sulfur, but the benefit of steam diminishes when its inlet concentration exceeds 25%. A design equation for a moving-bed regenerator using natural gas as the regenerant was developed from the 0.06 MW results. The adsorber model and the regenerator design equation were used together to determine the optimum residual sulfur content of the regenerated sorbent. It was concluded that the NOXSO LCTU (0.06 MW) would operate at the minimum cycle time of sorption and regeneration if the sulfur content of the regenerated sorbent was controlled at 0.8 wt%.

Control of NOx During Stationary Combustion

Nitrogen oxides (NO x ) and sulfur oxides (SO x ) emissions are primary contributors to acid rain, which is associated with a number of effects including acidification of lakes and streams, accelerated corrosion of buildings, and visibility impairment. Among the various nitrogen oxides emitted from stationary combustion; nitrogen oxide (NO), nitrous oxide (N2O), and nitrogen dioxide (NO2) are stable, and NO predominates (over 90%). In health effects, NO2 can irritate the lungs and lower resistance to respiratory infection. In the area of ozone nonattainment, NO x and volatile organic compounds (VOCs) react in the atmosphere to form ozone, a photochemical oxidant and a major component of smog. Atmospheric ozone can cause respiratory problems by damaging lung tissue and reducing lung function 1.