C.E. Schwarz

Phase equilibrium of propane and alkanes: Part I. Experimental procedures, dotriacontane equilibrium and EOS modelling

Abstract In order to study the equilibria of long-chain alkanes and supercritical fluids, a high-pressure phase equilibrium cell has been designed, constructed, commissioned and tested against reliable literature data. Phase equilibrium data for propane-dotriacontane (nC32H66) have been measured between 378.2 and 408.2 K. Emphasis was placed on measuring equilibrium data in the mixture critical region. Ten cubic and five non-cubic equations of state have been applied to the phase equilibrium data at 408.2 K. The modified Patel–Teja (MPT), as a cubic EOS, and statistical associating fluid theory (SAFT), as a non-cubic EOS, give the best-fit of the data at 408.2 K. The phase equilibrium predictions of the SAFT EOS significantly deteriorated as the critical point of the solvent was approached.

Thermodynamic modelling of supercritical water gasification: investigating the effect of biomass composition to aid in the selection of appropriate feedstock material.

A process model developed in Aspen Plus®, was used for the thermodynamic modelling of supercritical water gasification (SCWG) using a wide variety of biomass materials as feedstock. The influence of the composition of the biomass material (in terms of carbon, hydrogen and oxygen content) on various performance indicators (such as gas yields, cold gas efficiency, calorific value of product gas and heat of reaction), were determined at various temperatures (600, 700 and 800°C) and biomass feed concentrations (5, 15 and 25wt.%). Generalised contour plots, based on the biomass composition, were developed for these performance indicators to provide the thermodynamic limits at various operating conditions. These plots can aid in the selection or screening of potential biomass materials and appropriate operating conditions for SCWG prior to conducting experimental work.

Phase equilibrium of propane and alkanes part II: hexatriacontane through hexacontane

Abstract In this work phase equilibrium measurements for binary systems of supercritical propane with the n-alkanes C 36 H 74 , C 38 H 78 , C 40 H 82 , C 44 H 90 , C 46 H 94 , C 54 H 110 and C 60 H 122 , in the temperature range 378.2–408.2 K, are reported. In this temperature range the isopleths can be approximated as straight lines. A plot of the phase transition pressure as a function of carbon number at constant temperature and mass fraction yields a linear relationship. These linear relationships can be used for interpolation and limited extrapolations. The equilibrium data indicate that propane can be used for the fractionation of alkane mixtures. The SAFT EOS, using two binary interaction parameters, can be used to describe the equilibrium data provided that the temperature is not too close to the critical temperature of the solvent. The binary interaction parameters tend towards constant values for high carbon number alkanes.

Catalytic supercritical water gasification of primary paper sludge using a homogeneous and heterogeneous catalyst: experimental vs thermodynamic equilibrium results.

H2, CH4, CO and CO2 yields were measured during supercritical water gasification (SCWG) of primary paper waste sludge (PWS) at 450°C. Comparing these yields with calculated thermodynamic equilibrium values offer an improved understanding of conditions required to produce near-equilibrium yields. Experiments were conducted at different catalyst loads (0-1g/gPWS) and different reaction times (15-120min) in a batch reactor, using either K2CO3 or Ni/Al2O3-SiO2 as catalyst. K2CO3 up to 1g/gPWS increased the H2 yield significantly to 7.5mol/kgPWS. However, these yields and composition were far from equilibrium values, with carbon efficiency (CE) and energy recovery (ER) of only 29% and 20%, respectively. Addition of 0.5-1g/gPWS Ni/Al2O3-SiO2 resulted in high H2 and CH4 yields (6.8 and 14.8mol/kgPWS), CE of 84-90%, ER of 83% and a gas composition relatively close to the equilibrium values (at hold times of 60-120min).

Supercritical water gasification of Eucalyptus grandis and related pyrolysis char: Effect of feedstock composition.

Eucalyptus grandis (E. grandis) wood and char products derived from pyrolysis of E. grandis wood, were gasified in supercritical water at 450°C - with and without the use of a homogeneous (K2CO3) and heterogeneous (Ni/Al2O3-SiO2) catalyst. Gas yields and gasification efficiencies were measured experimentally and compared to calculated thermodynamic equilibrium values, specifically considering the effects of the O/C ratio and volatile matter content of the feed material. Thermodynamically, feed material with lower O/C ratios (0.22) typically resulted in higher CH4 yields (30mol/kgfeed,dry) and gasification efficiencies (188%). However, experimentally, feed material with lower O/C ratios and lower volatile matter resulted in the lowest CH4 yields and gasification efficiencies. Furthermore, a linear relationship between the carbon efficiency (CE) and both the volatile matter content and O/C ratio of the feed material was found to hold true in both catalytic and non-catalytic experiments.

High Pressure Phase Equilibria of the CO2/Saturated Ethyl Esters Homologous Series

A systematic study on the phase behavior of saturated ethyl esters with supercritical CO2 is presented. High pressure phase behavior measurements for the systems CO2/ethyl decanoate, CO2/ethyl dodecanoate, CO2/ethyl tetradecanoate, and CO2/ethyl hexadecanoate were conducted in a static synthetic view cell in the temperature range 308–358 K. Phase transition pressures were measured in the range 5.86–23.01 MPa for ethyl ester mass fractions in the range 0.0174–0.657 and complement existing literature data. Throughout the temperature and compositional range measured, which encompassed the liquid phase, mixture critical region, and vapor phase, an increase in temperature leads to an increase in phase transition pressure with no temperature inversions or three phase regions observed. Additionally, an increase in hydrocarbon backbone length leads to an ever-increasing phase-transition pressure, suggesting fractionation of ethyl esters according to molecular mass with supercritical CO2 is possible. Finally, the ...