Global evaluation of mass transfer effects: In-duct injection flue gas desulfurization

Cole, Jerald A.; Newton, G.H.; Kramlich, John C.; Payne, R.

doi:10.2172/6192018

Cited by 4 publications

(3 citation statements)

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“…The slurry droplet moisture content vs. time profile, shown in Figure 2, is thought to be similar to that calculated from classic spray-drying theory (Cole et al, 1990). Depending on the atomization method, slurry droplet diameters can range from 20 to 150 pm.…”

Section: Spraydrying Evaporation Stagessupporting

confidence: 65%

“…2 requires the estimation of January 1996 AICbE Journal several physical properties of the gas and liquid phases. All of these parameters were estimated from correlations based on theory and/or experimental data (Cole et al, 1990;Ranz and Marshall, 1952); a complete description of these correlations has been given (Neathery, 1993).…”

Section: Overall Sulfur Capture Equationmentioning

confidence: 99%

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Model for flue‐gas desulfurization in a circulating dry scrubber

Neathery

1996

AIChE Journal

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A simple model was developed to describe the absorption of SO, in a circulating d y scrubbing (CDS) process, which is a semidy, lime-based, flue-gas desulfurization (FGD) process that utilizes a circulating fluidized bed arrangement for contucting a sorbent with SO, -laden flue gas under "coo1side"conditions. The reaction chemisty is thought to be similar to that of spray-dying absolption. The liquid-phase mass-transfer coeficient was successfully modeled as a function of the sorbent particle spacing on the wetted surfaces. Gas-phase mass-transfer resistances were assumed to be insignificant. Due to the high surface area available in a CDS reactor, the evaporation rate of water @om the slury was modeled as "constant-rate "dying according to classic spray-dryer theory. However, the "falling-rate 'jand "difision "evaporation stages were negligible in CDS since sorbent particle bunching at the surface of the sluny is nonexistent. IntroductionWet flue-gas desulfurization (FGD) processes were the first SO, control systems to be developed on a commercial scale in the United States. These systems were initially plagued by reliability problems due to a combination of the early status of development at the time, poor design, and questionable operating procedures. In addition, most electric utility plant operators had no previous experience with "chemical plant" operation. By the late 1980s, most of these problems were overcome and some technological advances were made in the scrubbing area that improved wet FGD reliability. However, wet FGD systems remain costly to operate due to large work force requirements, the generation of large quantities of solid waste by-products that must be disposed, and high parasitic energy requirements.Wet scrubber systems are characterized by high liquid-togas ratios (L/G) of liquid sorbent slurry to flue gas. The L/G ratios, ranging from 5,400 to 13,400 1 Nm-3 (40 to 100 gal/std. kft3), are high enough to completely saturate the treated flue gas with water vapor. Typically, some untreated flue gas is bypassed around the scrubber modules to reheat the scrubbed gas and prevent troublesome condensation in the duct and stack.Because of the many shortcomings with wet FGD systems, the power utility industry is continually seeking new processes that will lower the capital, operating, and disposal costs associated with these conventional SO, control systems. in the early 1980s, pilot studies of semidry FGD processes, such as spray-drying absorption, were conducted to determine their potential as SO, control technologies. Many semidry FGD technologies have reached commercial scale in the last decade. As a result, a large number of studies have been performed to research and further develop these processes.As a contrast to wet FGD systems, semidry systems operate with low L/G ratios (about 28 to 40 1 Nm-3 or 0.2 to 0.3 gal/std. kft3) as compared to 5,400 to 13,400 1 Nm-3 or 40 to 100 gal/kSCF or higher for wet FGD systems). Since massive slurry pipe circuits and the associated pumps are not require...

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Section: Spraydrying Evaporation Stagessupporting

confidence: 65%

Section: Overall Sulfur Capture Equationmentioning

confidence: 99%

Model for flue‐gas desulfurization in a circulating dry scrubber

Neathery

1996

AIChE Journal

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“…The sulfur capture module described here is coupled with a detailed one-dimensional model of the duct injection process (Cole et al, 1990). The duct injection model considers changes in the volocity of droplets when injected into the duct, droplet temperature, evaporation, gas temperature, gas humidity, and scavenging of particulate matter (ash or sorbent) from the gas phase.…”

Section: Model Descriptionmentioning

confidence: 99%

Modeling the SO₂‐slurry droplet reaction

1990

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A model of the reaction between SO, and calcium-based slurries is presented. The model is coupled with an extensive model of the evaporation process and considers external SO, mass transfer and liquid-phase mass transfer of dissolved sulfur and calcium species in both the film surrounding the calcium particles and the bulk liquid phase. The model assumes that particles do not circulate within slurry droplets and that evaporation results in an accumulation of particles at the droplet surface that causes a shift in the controlling mechanisms. Agreement between the model and data available in the literature is excellent.

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