Chemical Science and Engineering

There is global interest in utilization of biomass energy through thermochemical processes such as gasification. The crucial step in many gasification processes is the upgrading of the produced gas, removing for example problematic components, such as tar, preferably with a flexible solution that adapts to several feedstock compositions, gasification technologies, and conditions. The present work focuses on the underpinning modeling for the development of a burner for partial combustion in an autothermal tar reformer. A design and modeling study considering the effect of the burner geometry and inlet locations on flame stability was performed. The model and the constructed burner is verified and validated against experimental results, displaying a successful operation of the combustion zone, verifying and validating the developed model against specific requirements. The verified model was finally applied for an extended process window.

Surface tension driven capillary flow from a pendant droplet into a horizontal glass capillary is investigated in this paper. Effect of the droplet surface on dynamic behavior of such capillary flow is examined and compared with surface tension driven capillary flow from an infinite reservoir. In the experiment, capillaries of 300-700 lm in diameter were used with glycerol-DI water mixture solutions having viscosities ranging from 80 to 934 mPa s. It is observed that compared to the capillary flow from an infinite reservoir, the capillary flow from a droplet exhibits higher rates of meniscus displacement. This is due to an additional driving force resulted from change in droplet surface area (or curvature). The two main parameters influencing the flow are the dimensionless droplet geometry parameter (k) and the dynamic contact angle (h D ). The molecular kinetics theory of Blake and De Coninck's model [Adv Colloid Interface Sci 96(1-3): 21-36, 2002] is used to interpret the dynamic contact angle. This theory considers a molecular friction coefficient (f) at the liquid front flowing over a solid surface. Moreover, three models are proposed to describe the shape of the pendant droplet during capillary action. It is found that the egg-shaped model provides a more realistic model to compute the shape of the pendant droplet deformed during the capillary action. Thus the predictions by the egg-shaped model are in good agreement with the experimental data.

This article presents an investigation into the effects of pneumatic pressure of trapped air on the dynamics of capillary filling. Controlled experiments were carried out in horizontal closed-end capillaries with diameters of 200-700 lm. Glycerol-DI water mixture solutions having viscosities ranging from 8 to 80 mPa s were used as the filling liquids. The pneumatic air backpressure is built up as a result of the air compressed at the closed end of the capillary. A model is presented based on the conventional theory of capillary filling (i.e., Washburn's equation) with consideration of the effect of air backpressure force on the advancing meniscus. The molecular kinetics theory of Blake and De Coninck's model (Adv Colloid Interface Sci 96:21-36, 2002) is also incorporated in the model to account for the dependence of dynamic contact angle on wetting velocity. The model predictions agree reasonably well with the experimental data. It is observed that due to the presence of air backpressure, the smaller the capillary diameter, the longer the length that the liquid fills the capillary, regardless of the liquid viscosity. It is also shown that the increased pneumatic air backpressure reduces the equilibrium contact angle (h 0 ). A relation is then proposed among liquid penetration, capillary length and radius, and contact angle. In addition, a dimensionless analysis is performed on experimental data, and the power law dependence of dimensionless meniscus position on dimensionless time is obtained.

This paper presents an investigation into spreading dynamics and dynamic contact angle of TiO 2 -deionized water nanofluids. Two mechanisms of energy dissipation, (1) contact line friction and (2) wedge film viscosity, govern the dynamics of contact line motion. The primary stage of spreading has the contact line friction as the dominant dissipative mechanism. At the secondary stage of spreading, the wedge film viscosity is the dominant dissipative mechanism. A theoretical model based on combination of molecular kinetic theory and hydrodynamic theory which incorporates non-Newtonian viscosity of solutions is used. The model agreement with experimental data is reasonable. Complex interparticle interactions, local pinning of the contact line, and variations in solid-liquid interfacial tension are attributed to errors.

We describe a method, correlation force spectrometry (CFS), which characterizes fluids through measurement of the correlations between the thermally stimulated vibrations of two closely spaced micrometer-scale cantilevers in fluid. We discuss a major application: measurement of the rheological properties of fluids at high frequency and high spatial resolution. Use of CFS as a rheometer is validated by comparison between experimental data and finite element modeling of the deterministic ringdown of cantilevers using the known viscosity of fluids. The data can also be accurately fitted using a harmonic oscillator model, which can be used for rapid rheometric measurements after calibration. The method is non-invasive, uses a very small amount of fluid, and has no actively moving parts. It can also be used to analyze the rheology of complex fluids. We use CFS to show that (non-Newtonian) aqueous polyethylene oxide solution can be modeled approximately by incorporating an elastic spring between the cantilevers.

Chemiluminescence (CL) and imaging chemiluminescence (ICL) were used to study the thermo-oxidative stability of polyamide 6 in the temperature range of 100±140 C. The CL intensity time curves (CL curves) for both unstabilised and stabilised polyamide 6 ®lm indicated an initial period at a high intensity level of varying shape followed by a basically sigmoidal increase and a subsequent maximum. This maximum was found to occur at a time corresponding to a drop in strain at break. Polyamide 6, stabilised with the phenolic antioxidant Irganox 1098, showed a similar CL curve although shifted towards lower intensity levels and longer times. The ICL study revealed essentially homogeneous oxidation. Both the ICL study and the CL studies clearly indicated oxidation from the beginning of ageing, also in the presence of the phenolic antioxidant. The CL intensity is not directly related to the rate of oxygen uptake. Instead, the CL intensity in oxygen seems to be related to the content of peroxides. However, other species causing luminescence cannot be excluded. #

Chemiluminescence (CL) and imaging chemiluminescence (ICL) were used to study the thermo-oxidative stability of polyamide 6 in the temperature range of 100±140 C. The CL intensity time curves (CL curves) for both unstabilised and stabilised polyamide 6 ®lm indicated an initial period at a high intensity level of varying shape followed by a basically sigmoidal increase and a subsequent maximum. This maximum was found to occur at a time corresponding to a drop in strain at break. Polyamide 6, stabilised with the phenolic antioxidant Irganox 1098, showed a similar CL curve although shifted towards lower intensity levels and longer times. The ICL study revealed essentially homogeneous oxidation. Both the ICL study and the CL studies clearly indicated oxidation from the beginning of ageing, also in the presence of the phenolic antioxidant. The CL intensity is not directly related to the rate of oxygen uptake. Instead, the CL intensity in oxygen seems to be related to the content of peroxides. However, other species causing luminescence cannot be excluded. #

Chemiluminescence (CL) and imaging chemiluminescence (ICL) were used to study the thermo-oxidative stability of polyamide 6 in the temperature range of 100±140 C. The CL intensity time curves (CL curves) for both unstabilised and stabilised polyamide 6 ®lm indicated an initial period at a high intensity level of varying shape followed by a basically sigmoidal increase and a subsequent maximum. This maximum was found to occur at a time corresponding to a drop in strain at break. Polyamide 6, stabilised with the phenolic antioxidant Irganox 1098, showed a similar CL curve although shifted towards lower intensity levels and longer times. The ICL study revealed essentially homogeneous oxidation. Both the ICL study and the CL studies clearly indicated oxidation from the beginning of ageing, also in the presence of the phenolic antioxidant. The CL intensity is not directly related to the rate of oxygen uptake. Instead, the CL intensity in oxygen seems to be related to the content of peroxides. However, other species causing luminescence cannot be excluded. #

Injection moulded test specimens of polyamide 6,6 have been subjected to ageing in ambient atmosphere at temperatures ranging from 100 to 130°C for different times. Skin-core oxidation was observed and evaluated by infrared spectroscopy in terms of carbonyl index depth profiles and by imaging chemiluminescence as peroxide depth profiles. The oxidation depth profiles determined by the two techniques showed good agreement with respect to ageing time and temperature. The oxidation depth was shown to decrease with increasing aeeine temnerature.

The success of lab-on-a-chip systems may depend on a low-cost device that incorporates on-chip storage and fluidic operations. To date many different methods have been developed that cope separately with on-chip storage and fluidic operations e.g., hydrophobic and capillary valves pneumatic pumping and blister storage packages. The blister packages seem difficult to miniaturize and none of the existing liquid handling techniques despite their variety are capable of proportional repeatable dispensing. We report here on an inexpensive robust and scalable micro-dispenser that incorporates long-term storage and aliquoting of reagents on different microfluidics platforms. It provides long-term shelf-life for different liquids enables precise dispensing on lab-on-a-disc platforms and less accurate but proportional dispensing when operated by finger pressure. Based on this technology we introduce a method for automation of blood plasma separation and multi-step bioassay procedures. This micro-dispenser intends to facilitate affordable portable diagnostic devices and accelerate the commercialization of lab-on-a-chip devices.