Water is essential to the hydrolysis and conversion of lignocellulosic materials as it is both the medium through which enzymes diffuse to and products diffuse away from the reaction sites and a reactant in the hydrolysis reaction of the glycosidic bonds within the polysaccharides. However, little is known about how water interactions with the biomass change with solids content and how this affects mass transfer resistances during high solids saccharification. Nuclear magnetic resonance spectroscopy measurements of the T 2 relaxation times of water in cellulose suspensions were used to demonstrate that increases in solids content led to increases in the physical constraint of water in the suspensions. Moreover, the addition of either glucose (a monosaccharide which end-product inhibits b-glucosidase) or mannose (a stereoisomer of glucose that does not end-product inhibit b-glucosidase) further increased water constraint at all solids contents. The presence of either monosaccharide constrained water and inhibited saccharification rates to similar extents. This observation, coupled with the absence of cellobiose produced in the reactions, demonstrated that the presence of soluble sugars can negatively impact saccharification efficiency simply by increasing water constraint in cellulose suspensions before impacting enzyme activity. Furthermore, results are presented that demonstrate strong correlations between water constraint in cellulose suspensions with diffusivities of enzyme and monosaccharides within the system. These results are discussed in the context of increased viscosity of the aqueous fraction in the suspension resulting from increased watercellulose and water-solute interactions that ultimately increases diffusion resistances and decreases saccharification rates.

With increasing pressure on project costs, accepting uncertainty is increasingly less viable for offshore field developments. An urgent issue that affects conventional and novel technologies across the production landscape is that of the kinetics of fluid phase behavior changes. Be it pressure boosting using electrical submersible pumps (ESPs) or separation with novel compact separators, the rates of gas dissolution and evolution are a critical uncertainty. PVT laboratories today report fluid properties at equilibrium points, with a prevailing unwritten assumption that the system can achieve the new phase equilibrium either instantaneously or at a time scale that is negligible when compared with production system residence time scales. However, even anecdotally, many in the industry understand this assumption to be optimistic and recognize there is a kinetic process that must occur to achieve the new equilibrium state. Fluid property measurements – kinetics included – are highly valuable to a variety of disciplines: research engineers, process engineers, flow assurance engineers, and more. To effectively apply fluid property measurements to field development activities, each engineer must have a quantitative understanding of the data uncertainties. The kinetics of fluid phase behavior changes are, however, often overlooked; nearly all industrial process simulators apply equilibrium models, regardless of whether the system has achieved the equilibrium state. As the industry drives towards more challenging offshore fields and focuses on simplifying designs, reducing size, and reducing costs, the result is an increasing risk of consequences due to incomplete evolution or dissolution of gas. Engineers currently have no tools available to predict or estimate the rate at which the gas will evolve from or dissolve into solution. This unknown propagates to potential issues in a variety of applications, including design and optimization of artificial lift systems, design and operation of electrical submersible pumps, subsea or topsides pumping, compact separations, and more generally gas-liquid separations. In this paper the authors share insight and information about challenges in design, development, operation and troubleshooting with regards to the uncertainty in the kinetics of fluid phase behavior. Discussion also covers the value in developing an alternative fluid property measurement for quantifying and predicting the rates of gas evolution and dissolution.

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In the petroleum industry, emulsions are encountered in nearly every stage of oil production, transportation, and operation. An understanding of the mass transfer rates during gas evolution from supersaturated solutions is critical for enabling better design and operation of gas−liquid separators. The objective of this work was to elucidate the influence of surfactant and water droplet sizes present in water-in-oil emulsions on the rate of gas evolution (volumetric mass transfer coefficient) from supersaturated systems. The volumetric mass transfer coefficient during gas evolution at elevated pressure (3.45 ± 0.00689 MPa) was determined using a batch stirred tank system. The volume of the liquid phase (0.0005 m 3 ), the initial saturation pressure (3.45 ± 0.00689 MPa), the liquid-phase temperature (298.15 ± 0.5 K), and the mixing speed during gas evolution (250 rpm) were kept constant during the experiments. Ultrahigh purity methane was used as the gas phase. Pure model oil (Tech 80) and water-in-oil emulsions (30 wt % water) were used as the liquid phases. Water-in-oil emulsions with two different droplet sizes with average droplet sizes of 6.6 ± 2.6 and 21.7 ± 7 μm were used to investigate the influence of the droplet size on gas evolution rates. We hypothesize that the presence of water droplets in the continuous oil phase increases the diffusional path length, which would result in a decrease in the volumetric mass transfer coefficient. At the investigated emulsion concentrations, our results showed that the presence of the surfactant (Span 80 at 0.1 wt %) did not affect the volumetric mass transfer coefficient of methane leaving the model oil. However, the volumetric mass transfer coefficient decreased with a decrease in the initial droplet size. The decrease in the volumetric mass transfer coefficient results in an increased time required for gas evolution. Based on our data set, one can infer that a decrease in the initial droplet size might increase the time required for the solution gas to exit the liquid in a gas−liquid separator. In addition, our results showed that gas evolution from supersaturated water-in-oil emulsions led to the destabilization of the water-in-oil emulsions. We hypothesize that this increase in the droplet size is due to the coalescence of the emulsion droplets during gas evolution.