FT-IR-cPAS—New Photoacoustic Measurement Technique for Analysis of Hot Gases: A Case Study on VOCs

This article describes a new photoacoustic FT-IR system capable of operating at elevated temperatures. The key hardware component is an optical-readout cantilever microphone that can work up to 200 °C. All parts in contact with the sample gas were put into a heated oven, incl. the photoacoustic cell. The sensitivity of the built photoacoustic system was tested by measuring 18 different VOCs. At 100 ppm gas concentration, the univariate signal to noise ratios (1σ, measurement time 25.5 min, at highest peak, optical resolution 8 cm−1) of the spectra varied from minimally 19 for o-xylene up to 329 for butyl acetate. The sensitivity can be improved by multivariate analyses over broad wavelength ranges, which effectively co-adds the univariate sensitivities achievable at individual wavelengths. The multivariate limit of detection (3σ, 8.5 min, full useful wavelength range), i.e., the best possible inverse analytical sensitivity achievable at optimum calibration, was calculated using the SBC method and varied from 2.60 ppm for dichloromethane to 0.33 ppm for butyl acetate. Depending on the shape of the spectra, which often only contain a few sharp peaks, the multivariate analysis improved the analytical sensitivity by 2.2 to 9.2 times compared to the univariate case. Selectivity and multi component ability were tested by a SBC calibration including 5 VOCs and water. The average cross selectivities turned out to be less than 2% and the resulting inverse analytical sensitivities of the 5 interfering VOCs was increased by maximum factor of 2.2 compared to the single component sensitivities. Water subtraction using SBC gave the true analyte concentration with a variation coefficient of 3%, although the sample spectra (methyl ethyl ketone, 200 ppm) contained water from 1,400 to 100k ppm and for subtraction only one water spectra (10k ppm) was used. The developed device shows significant improvement to the current state-of-the-art measurement methods used in industrial VOC measurements

Kinetic modeling of NH3-SCR over a supported Cu zeolite catalyst using axial species distribution measurements

In this study, a kinetic model is developed for NH3-SCR over a honeycomb-monolith-supported Cu-zeolites using intra-catalyst axial species distribution measurements. An ammonia TPD experiment, together with micro calorimetry data were used for tuning the ammonia adsorption and desorption properties. The spatial distribution for NO oxidation, NH3 oxidation and NH3 "Standard" SCR were modeled between 200 and 400 degrees C. Four-step protocol measurements were employed in order to validate the transient functions of the model. The resulting kinetic model provides good spatiotemporal simulation of the SCR reaction and component reactions throughout the monolith catalyst system

Towards Deeply Reconfigurable, Long-life Internet of Things Platforms

Our world is racing towards a new era of smart applications, examples of which include: Smart Agriculture, Smart City, Smart Manufacturing, and Smart Traffic. These new applications have great potential in contributing the society, industry, and our daily lives. Internet of Things (IoT) provides the necessary technologies to support such smart applications by connecting the digital and physical worlds. According to market predictions, there will be more than 20 billion IoT devices connected by the year 2020. While the potential is clear, developing and deploying an IoT network for an application remains onerous: 1) The development cost is high, and mostly ad-hoc. It is hard to reuse existing systems outside of specific applications. 2) IoT platforms are not flexible. It is costly and time consuming to customise or reconfigure them. 3) IoT end devices suffer from limited battery lifetime. This increases the cost of maintenance and limits the use cases when an application requires long term deployment. This thesis tackles these problems through targeted contributions in this research field at the system software level. The first contribution is μPnP, it tackles the flexible device reconfiguration problem by introducing Plug-and-Play peripheral integrations into IETF class-1 devices. Combined with a low power identification hardware, a platform-independent software driver, and a standard based peripheral data interaction model, μPnP system significantly reduced IoT development effort, and achieved a true Plug-and-Play reconfigurable platform. The second contribution extends μPnP with flexible adoption of a range of low power networks. We selected 2 representative networks: SmartMesh IP and LoRa in our implementation. SmartMesh IP represents a range of meshed network based on Time Synchronous Channel Hopping (TSCH) technique, it forms a meshed network which returns great reliability. LoRa is one of the Low Power Wide Area Networks (LPWAN), it uses star topology, but achieves multi-kilometres of coverage in urban area. Neither of these networks fits in every IoT scenario, and thanks to our contribution, application developers can flexibility choose networks upon usage. The third contribution looks at the power problem of IoT devices. Energy harvesting is considered the most promising technique for extending IoT device lifetime. However, unpredictable environment energy budget, dynamic runtime power consumption, and complicated energy-aware software management together make a unavoidable barrier. This contribution presents AsTAR, a hardware software system supporting developing applications on energy harvesting based platforms. AsTAR uses adaptive scheduler to dynamically control the execution of tasks, in order to always maintain an optimum charge. The technologies developed in this thesis are now being further evaluated in a wide and growing range of industrial applications. Part of the contributions introduced in this dissertation have been commercialised by VersaSense, a KU Leuven spin-off company.status: publishe

OPTI-VFA: Novel monitoring and process control system for efficient production of VFA and biogas in anaerobic digesters (poster)

Water ManagementCivil Engineering and Geoscience

Miniaturized, high numerical aperture confocal fluorescence detection enhanced with pyroelectric droplet accumulation for sub-attomole analyte diagnosis

To meet the growing demand for early fatal disease screening among large populations, current fluorescence detection instruments aiming at point-of-care diagnosis have the tendency to be low cost and high sensitivity, with a high potential for the analysis of low-volume, multiplex analytes with easy operation. In this work, we present the development of a miniaturized, high numerical aperture confocal fluorescence scanner for sub-micro-liter fluid diagnosis. It is enhanced with high-rate analyte accumulation using a pyroelectro-hydrodynamic dispensing system for generating tiny, stable sample droplets. The simplified confocal fluorescence scanner (numerical aperture 0.79, working distance 7.3 mm) uses merely off-the-shelf mass-production optical components. Experimental results show that it can achieve a high-sensitive, cost-efficient detection for sub-micro-liter, low-abundant (0.04 µL, 0.67 attomoles) fluid diagnosis, promising for point-of-care diagnosis.</p

Kinetic modeling of Fe-BEA as NH3-SCR catalyst – Effect of Phosphorous

The focus of this work is to investigate whether a previously developed micro-kinetic deactivation model for hydrothermally treated Fe-BEA as NH3-SCR catalyst can be applied to describe chemical deactivation of Fe-BEA due to phosphorous exposure. The model describes the experiments well for Fe-BEA before and after phosphorous exposure by decreasing the site density, representing deactivation of sites due to formation of metaphosphates blocking the active iron sites, while the kinetic parameters are kept constant. Furthermore, the results show that the activity for low-temperature SCR is very sensitive to loss of active monomeric iron species due to phosphorous poisoning compared to high-temperature SCR. Finally, the ammonia inhibition simulations show that exposure to phosphorous may affect the internal transport of ammonia between ammonia storage sites buffering the active iron sites which results in a lower SCR performance during transient conditions