The Wheeler–Jonas equation: a versatile tool for the prediction of carbon bed breakthrough times

Lodewyckx, Peter; Wood, Gerry O.; Ryu, Seung‐Kon

doi:10.1016/j.carbon.2004.01.016

Cited by 64 publications

(30 citation statements)

References 16 publications

(18 reference statements)

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“…When using the model to predict breakthrough times, this introduces a supplementary problem, as one needs the breakthrough time in order to calculate the mean value of the inlet concentration between the donning of the mask and the breakthrough time. This means the model will need a loop on the linked values of t b and , but this does not constitute a major problem, as in all tested cases this loop quickly (2-3 iterations) reached a solution and no cases of instability were detected [13].…”

Section: Non Constant Inlet Concentrationmentioning

confidence: 98%

“…5), whereas for carbon fibres the determining parameter would be the (average) length of the fibres, their diameter having a negligible contribution to the external surface. These assumptions have been proven experimentally for non-spherical particles [17], activated carbon monoliths (ACM) [18] and activated carbon fibres (ACF) [13].…”

Section: Non Granular Activated Carbonsmentioning

confidence: 99%

See 1 more Smart Citation

Estimating the Service Life of Activated Carbon Filters for Air Purification

Lodewyckx

Fernandez-Velasco

Boutillara

2019

Eurasian Chem. Tech. J.

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It is very important to be able to predict the breakthrough time of gas mask filters under real life circumstances. This article describes the use of a very simple predictive equation, the Wheeler-Jonas equation, that yields excellent predictions but only within a very restrictive set of boundary conditions. In order to make this model work in a more realistic environment, it has been gradually adapted to take into account a number of parameters related to this environment: a non-constant inlet concentration, a breather flow, new physical forms of activated carbon, the relative humidity and temperature of the ambient air, chemisorbed gases and mixtures of organic vapours. As (nearly) all of these parameters can be calculated independently of each other, based on data that are either readily available or that can be measured, their influence on the complexity of the model stays low. This makes this combined model both easy to use and powerful in predicting breakthrough times of gas mask filters under real-life conditions.

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Section: Non Constant Inlet Concentrationmentioning

confidence: 98%

Section: Non Granular Activated Carbonsmentioning

confidence: 99%

Estimating the Service Life of Activated Carbon Filters for Air Purification

Lodewyckx

Fernandez-Velasco

Boutillara

2019

Eurasian Chem. Tech. J.

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“…A widely used semi-empirical model for the adsorption of organic vapours on activated carbon (a common application) is the Dubinin-Radushkevich equation [3].…”

Section: Introductionmentioning

confidence: 99%

“…where is the effective mass transfer coefficient of the contaminant on carbon. Although the Wheeler-Jonas equation provides a good estimate of breakthrough times in large carbon beds, it has some limitations [3]. In small beds, the assumption of plug flow will be followed less closely, as the effect of no-slip at the wall becomes more significant.…”

Section: Introductionmentioning

confidence: 99%

A numerical model for predicting adsorption behaviour in small activated carbon beds

Wood¹,

Chakraborty²,

Smith³

et al. 2019

Proceedings of the 6th International Conference on Fluid Flow, Heat and Mass Transfer (FFHMT'19)

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A Reynolds-Averaged Navier-Stokes (RANS) model to describe the adsorption of volatile organic compounds on activated carbon beds was developed, using the Dubinin-Radushkevich adsorption isotherm with a Linear Driving Force (LDF) kinetic model. The model was validated using experimental breakthrough data for cyclohexane. The model was then used to predict the impact of adsorption kinetics in small activated carbon beds. The adsorption showed two distinct phases: an initial period where contaminant very rapidly penetrated into the bed, followed by a period where the contaminated front advanced at a slow, constant pace. The initial distance penetrated into the bed was shown to be inversely proportional to the LDF kinetic constant, a trend the same as that predicted using a common plug-flow mass-balance model. The velocity distribution after this initial phase showed some small variations with kinetic constant. This suggests that the kinetic constant may have an impact on the speed of the advance of the contaminated front, an effect not seen in plug-flow models.

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“…Models developed for calculation of carbon bed service-lives have been continuously evolving since 1969, with significant contributors such as Wheeler, 11 Nelson, 12-14 Jonas, [15][16][17] Yoon and Nelson, [18][19][20][21][22] and Wood. [23][24][25][26][27][28][29][30][31][32][33][34][35] The widely used "Wood Model" is founded from the Reaction Kinetic equation and specifically used in the 3M ® software and MultiVapor ™ software, where breakthrough time (tb) is calculated by 36 :…”

Section: User Determination Of Carbon Bed Service-lifementioning

confidence: 99%

Development of a Cobinamide-Based Optical Sensor for Hydrogen Cyanide and Hydrogen Sulfide

Greenawald¹

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In an occupational or military environment, a personal air-purifying respirator must be provided when breathing-air is contaminated by harmful dust, fumes, gases, aerosols, or vapors. Too often, a respirator user does not have enough information to know when to change his/her cartridge/canister and thus is potentially exposed to toxic gases. Currently, there is no definitive way to determine when respirators' carbon beds have begun to fail. When an end-of-service-life indicator (ESLI) is incorporated into the carbon bed, it informs one, in real-time, when imminent breakthrough is occurring and to replace the cartridge/canister. ESLIs are a more reliable and safer way to determine respirator end-of-service-life. To date, there are no commercially available active ESLIs for inorganic gases. The objective of this research is to develop an inexpensive, optical sensor for the detection of hydrogen cyanide (HCN) and hydrogen sulfide (H2S) gas, which can be used to determine the end-of-service-life of a respirator carbon bed. The sensor relies on diffuse reflectance from a paper substrate fixed with cobinamide, a Vitamin B12 derivative. Cobinamide undergoes a metal-ligand binding interaction with HCN, whereas both a binding and reduction reaction may occur with exposure to H2S. Characteristic and different spectral shifts rapidly occurred after exposure to HCN and H2S, implying a dual ESLI could be developed to simultaneously detect both gases. Upon increasing the relative humidity from 25 to 85%, the sensitivity was found to increase 7x for cobinamide-immobilized cellulose fiber filter paper and 50x for glass fiber filter paper upon exposure to 5.0 parts-per-million (ppm) HCN-the NIOSH recommended exposure limit for HCN. The cobinamide-immobilized paper sensor successfully detected low concentrations of HCN and H2S upon imminent breakthrough of respirator canisters and cartridges (respectively). The breakthrough curves of the cobinamide paper sensor correlated well with commercial electrochemical detectors, implying that cobinamide may be used to detect both gases at a certain location in the respirator carbon bed and inform the user to replace his or her cartridge/canister. Additionally, a low-power, inexpensive 3-color (RGB) sensor was prototyped to actively monitor the total change in color of the cobinamide complex on paper upon HCN exposure. The photodiodes detected, in real-time, a rapid change in the red, green, and blue values of the cobinamide compound upon exposure to HCN at various concentrations and relative humidity levels. Total change in color from initial cobinamide on paper increased as a function of HCN concentration, where faster reaction kinetics were observed at higher relative humidity. Response times at all relative humidity levels were within 20 seconds for 5.0 ppm HCN exposure.

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The Wheeler–Jonas equation: a versatile tool for the prediction of carbon bed breakthrough times

Cited by 64 publications

References 16 publications

Estimating the Service Life of Activated Carbon Filters for Air Purification

Estimating the Service Life of Activated Carbon Filters for Air Purification

A numerical model for predicting adsorption behaviour in small activated carbon beds

Development of a Cobinamide-Based Optical Sensor for Hydrogen Cyanide and Hydrogen Sulfide

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