Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Sulfate reduction in a hydrogen fed bioreactor operated at haloalkaline conditions
    Sousa, J.A.B. ; Plugge, C.M. ; Stams, A.J.M. ; Bijmans, M.F.M. - \ 2015
    Water Research 68 (2015). - ISSN 0043-1354 - p. 67 - 76.
    gas-lift reactor - sp-nov. - reducing bacteria - high salinity - soda lakes - uasb reactors - waste-water - gen. nov. - sp. nov - bed
    Biological sulfate reduction is used as a biotechnological process to treat sulfate rich streams. However, application of biological sulfate reduction at high pH and high salinity using H2 was not thoroughly investigated before. In this work the sulfate reduction activity, biomass growth, microbial community and biomass aggregation were investigated in a H2-fed gas lift bioreactor at haloalkaline conditions. The process was characterized by low sulfate reduction volumetric rates due to slow growth and lack of biomass aggregation. Apparently, the extreme conditions and absence of organic compounds prevented the formation of stable aggregates. The microbial community analysis revealed a low abundance of known haloalkaliphilic sulfate reducers and presence of a Tindallia sp. The identified archaea were related to Methanobacterium alcaliphilum and Methanocalculus sp. The biomass did not attach to metal sulfides, calcite and magnesite crystals. However, biofilm formation on the glass bioreactor walls showed that attachment to glass occurs.
    River scale model of an training dam using lightweight granulates
    Vermeulen, B. ; Boersema, M.P. ; Hoitink, A.J.F. ; Sieben, J. ; Sloff, C.J. ; Wal, M.F. van der - \ 2014
    Journal of Hydro-environment Research 8 (2014). - ISSN 1570-6443 - p. 88 - 94.
    sediment transport - spur dikes - bed
    Replacing existing river groynes with longitudinal training dams is considered as a promising flood mitigation measure in the main Dutch rivers, which can also serve to guarantee navigability during low flows and to create conditions favourable for ecological development. Whereas the bed response in the streamwise uniform part of a river trained by a longitudinal dam can be readily predicted, the bed response at the transition zones is unclear. In the present study, we investigate the local morphological effects resulting at the intake section of a longitudinal training dam, where the flow is distributed over the main channel and a side channel in between the dam and the river shore. A sediment recirculating model with a nearly undistorted geometry with respect to the prototype was setup. Lightweight polystyrene granulates were used as a surrogate for sediment, to properly scale the Shields parameter without compromising Froude scaling, and reach dynamical similarity. A laser scanner allowed collecting high-resolution bed elevation data. Results obtained under typical low flow and high flow conditions show a general deepening of the bed in the area adjacent to the training dam, in response to narrowing of the main channel. Scour at an upstream river groyne embedded in the model showed a scour hole which was deeper than realistic. Throughout the entire domain, bedforms developed featuring geometrical properties that reproduced the prototype conditions appropriately. Based on a comparison with characteristics from the River Waal, regarded as the prototype without a longitudinal dam, lightweight sediments were considered to be a proper choice for this study, in which bedload is the main sediment transport mode. The main conclusion regards the absence of significant morphodynamic developments at the intake section, both during the high flow experiment and during the low flow experiment, which can be attributed to the alignment of the dam with the local streamlines.
    Improving dryer energy efficiency and controllability simultaneously by process modification
    Atuonwu, J.C. ; Straten, G. van; Deventer, H.C. van; Boxtel, A.J.B. van - \ 2013
    Computers and Chemical Engineering 59 (2013). - ISSN 0098-1354 - p. 138 - 144.
    desiccant adsorption - optimization - design - integration - model - bed
    This work establishes a relationship between dryer energy performance and controllability using energy balances and process resiliency analysis. It is shown that using the process gain matrix, the dryer energy efficiency can be reliably calculated with conditions for simultaneous controllability improvement established. By incorporating a drying rate modifying system such as a desiccant dehumidifier as an add-on, these conditions are shown to be achievable due to the extra dehumidification which can be manipulated using the additional degrees of freedom introduced by the sorption system. Due to the adsorbent regulation properties which are enhanced by high-temperature regeneration, the resilience of energy performance to disturbances is significantly improved compared to conventional dryers. Also, a desiccant system performance indicator, the “adsorber–regenerator net energy efficiency ARNEE” is introduced and it is shown that energy efficiency improvement is possible only if the ARNEE is greater than the energy efficiency of the stand-alone dryer.
    On the controllability and energy sensitivity of heat-integrated desiccant adsorption dryers
    Atuonwu, J.C. ; Straten, G. van; Deventer, H.C. van; Boxtel, A.J.B. van - \ 2012
    Chemical Engineering Science 80 (2012). - ISSN 0009-2509 - p. 134 - 147.
    structure selection - design - optimization - systems - bed - efficiency - kinetics - recycle - model
    This work studies the controllability of heat-integrated zeolite adsorption dryers. Mean product moisture content, temperature and vitamin C concentration (representative of product quality) are considered as controlled variables. Set-point tracking and disturbance rejection controllability metrics are considered in addition to energy performance sensitivity. In adsorption dryers, the adsorption system introduces extra degrees of freedom of which some input-output pairs are promising. For corresponding inputs, adsorption dryers are shown to have higher steady-state gains than equivalent conventional dryers due to correlation between dehumidification, adsorption heat and the controlled variables. They also show improved resilience to ambient air disturbances due to adsorbent subsystem-induced self-regulation properties. The encouraging mechanisms of the self-regulation are adsorption heat, kinetic and equilibrium properties of the adsorbent. Due to the high correlation between product moisture content and temperature, improved controllability is observed when vitamin C concentration is used as an output variable instead of product temperature. It is thus proposed that on the availability of reliable soft sensors or state estimators, instead of product temperature, vitamin C or some other temperature-dependent quality measure should be controlled in addition to product moisture in decentralised drying system control. Under perfect rejection of unfavourable disturbances like ambient temperature drop and humidity rise, the energy performance of adsorption dryers is not significantly degraded, whereas, it is for conventional systems.
    Hydraulic and sedimentary processes causing anastomosing morphology of the upper Columbia River, British Columbia, Canada
    Makaske, B. ; Smith, D.G. ; Berendsen, H.J.A. ; Boer, A.G. de; Nielen-Kiezebrink, M.F. van; Locking, T. - \ 2009
    Geomorphology 111 (2009)3-4. - ISSN 0169-555X - p. 194 - 205.
    rhine-meuse delta - predicting channel patterns - avulsion frequency - geomorphology 40 - load transport - brewer 2001 - netherlands - bed - classification - hydrology
    The upper Columbia River, British Columbia, Canada, shows typical anastomosing morphology - multiple interconnected channels that enclose floodbasins - and lateral channel stability We analysed field data on hydraulic and sedimentary processes and show that the anastomosing morphology of the upper Columbia River is caused by sediment (bedload) transport inefficiency, in combination with very limited potential for lateral bank erosion because of very low specific stream power (90% of the sediment in the cross-valley transect studied. Because of very low sediment transport capacity, the morphological evolution of most secondary channels is slow. Measurements and calculations indicate that much more bedload is sequestered in the relatively steep upper anastomosing reach of the upper Columbia River than in the relatively gentle lower anastomosing reach. With anastomosing morphology and related processes (e.g., crevassing) being best developed in the upper reach, this confirms the notion of upstream rather than downstream control of upper Columbia River anastomosis.
    Process Integration for Food Drying with Air Dehumidified by Zeolites
    Djaeni, M. ; Bartels, P.V. ; Sanders, J.P.M. ; Straten, G. van; Boxtel, A.J.B. van - \ 2007
    Drying Technology 25 (2007)1. - ISSN 0737-3937 - p. 225 - 239.
    pinch analysis - plant - bed - performance - dryer
    Zeolites have potential to increase efficiency of medium-temperature drying in the food industry. This work concerns the comparison between conventional dryers and dryers using air dehumidified by zeolite. Steady-state mass and energy balances have been used and the work concerns drying temperatures ranging from 52 to 70°C. Process integration based on pinch analysis has been applied and nine different heat exchanger networks for energy recovery are compared. Results indicated that dryers using air dehumidifier by zeolites are 10-18% more efficient than conventional dryers.
    Heat and water transfer in a rotating drum containing solid substrate particles
    Schutyser, M.A.I. ; Weber, F.J. ; Briels, W.J. ; Rinzema, A. ; Boom, R.M. - \ 2003
    Biotechnology and Bioengineering 82 (2003)5. - ISSN 0006-3592 - p. 552 - 563.
    state fermentation - scale-up - model - simulation - bed - bioreactors - design
    In previous work we reported on the simulation of mixing behavior of a slowly rotating drum for solid-state fermentation (SSF) using a discrete particle model. In this investigation the discrete particle model is extended with heat and moisture transfer. Heat transfer is implemented in the model via interparticle contacts and the interparticle heat transfer coefficient is determined experimentally. The model is shown to accurately predict heat transfer and resulting temperature gradients in a mixed wheat grain bed. In addition to heat transfer, the addition and subsequent distribution of water in the substrate bed is also studied. The water is added to the bed via spray nozzles to overcome desiccation of the bed during evaporative cooling. The development of moisture profiles in the bed during spraying and mixing are studied experimentally with a water-soluble fluorescent tracer. Two processes that affect the water distribution are considered in the model: the intraparticle absorption process, and the interparticle transfer of free water. It is found that optimum distribution can be achieved when the free water present at the surface of the grains is quickly distributed in the bed, for example, by fast mixing. Alternatively, a short spraying period, followed by a period of mixing without water addition, can be applied. The discrete particle model developed is used successfully to examine the influence of process operation on the moisture distribution (e.g., fill level and rotation rate). It is concluded that the extended discrete particle model can be used as a powerful predictive tool to derive operating strategies and criteria for design and scale-up for mixed SSF and other processes with granular media.
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