Vapor-liquid activity coefficients for methanol and ethanol from heat of solution data: application to steam-methane reforming

This paper presents equations and curves to calculate vapor-liquid phase eq uilibria for methanol and ethanol in dilute aqueous solution as a function of temperature, using activity coefficients at infinite dilution. These the rmodynamic functions were originally derived to assess the distribution of by-product contaminants in the process condensate and the steam-system deae rator of a hydrogen plant [Paper ENV-00-171 presented at the NPRA 2000 Envi ronmental Conference, San Antonio, TX, 10-12 September 2000], but have gene ral applicability to other systems as well. The functions and calculation m ethod described here are a necessary piece of an overall prediction techniq ue to estimate atmospheric emissions from the deaerator-vent when the proce ss condensate is recycled as boiler feed water (BFW) make-up. Having such an estimation technique is of particular significance at this t ime because deaerator-vent emissions are already coming under regulatory sc rutiny in California [Emissions from Hydrogen Plant Process Vents, Adopted 21 January 2000] followed closely elsewhere in the US, and eventually world wide. The overall technique will enable a permit applicant to estimate envi ronmental emissions to comply with upcoming regulations, and a regulatory a gency to evaluate those estimates. It may also be useful to process enginee rs as a tool to estimate contaminant concentrations and flow rates in inter nal process streams such as the steam-generating system. Metallurgists and corrosion engineers might be able to use the results for materials selectio n. (C) 2001 Elsevier Science B.V All rights reserved.