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Microwave assisted pyrolysis (MWAP) is an alternative heating approach to convert biosolids into value-added products, such as biochar, biogas and bio-oil. Studying the dielectric properties of biosolids is fundamental to understand the behaviour of this material under microwave irradiation and to design microwave assisted pyrolysis systems. This study examined the dielectric properties of biosolids with changes in moisture content and applied microwave frequency. Results demonstrated that the dielectric constant decreases with decreasing moisture content and with increasing microwave frequency, but the dielectric loss factor of dry biosolids is almost zero. Simulations demonstrated that moisture content of biosolids impacts on the distribution and intensity of electromagnetic field. Because of the poor dielectric properties of dry biosolids, a microwave susceptor must be added to the biosolids to attract microwave energy so that the materials can reach temperatures required for pyrolysis. Therefore, this study also investigated the impact of four microwave susceptors (activated carbon, charcoal, biochar and glycerol) on biosolids pyrolysis and on biochar properties produced from biosolids via microwave assisted pyrolysis at 600 °C. The choice of microwave susceptor influences the heating rate of biosolids and the specific surface area of the resultant biochar. Results show that activated carbon favours the heating process, increases surface area, and the biochar produced with activated carbon has the highest carbon stability and energy value.

The contamination of water with silver has increased due to the widespread applications of products with silver employed as antimicrobial agent. Adsorption is a cost-effective method for silver removal from aqueous solution. In this study biochar, produced from the microwave assisted pyrolysis of biosolids, was used for silver removal from an aqueous solution. The adsorption kinetics, isotherms and thermodynamics were investigated to better understand the silver removal process by biochar. X-ray diffraction results demonstrated that silver removal was a combination two consecutive mechanisms, reduction and physical adsorption. The Langmuir model fitted the experimental data well, showing that silver removal was predominantly a surface mechanism. The thermodynamic investigation demonstrated that silver removal by biochar was an exothermic process. The final nanocomposite Ag-biochar (biochar plus silver) was used for methylene blue adsorption and photodegradation. This study showed the potential of using biochar produced from biosolids for silver removal as a promising solution to mitigate water pollution and an environmentally sustainable approach for biosolids management and re-use.

The amount of biosolids increases every year, and social and environmental concerns are also rising due to heavy metals and pathogen contamination. Even though biosolids are considered as a waste material, they could be used as a precursor in several applications, especially in agriculture due to the presence of essential nutrients. Microwave assisted pyrolysis (MWAP) is a promising technology to safely manage biosolids, while producing value-added products, such as biochar, that can be used to improve soil fertility. This study examined the impact of pyrolysis temperature between 300 °C and 800 °C on the chemical and physical properties of biochar obtained from biosolids via MWAP. Preliminary phosphorus adsorption tests were carried out with the biochar produced from biosolids. This research demonstrated that pyrolysis temperature affects biochar specific surface area, ash and volatiles content, but does not impact heavily on the pH, chemical composition and crystalline phases of the resultant biochar. Biochar yield decreases as the pyrolysis temperature increases. Phosphorus adsorption capacity of biochar was approximately around 15 mg/g of biochar. Biochar resulting from MWAP is a potential candidate for land application with an important role in water and nutrient retention, due to the high surface area.

Dedicated studies performed for toroidal Alfvén eigenmodes (TAEs) in ASDEX-Upgrade (AUG) discharges with monotonic q-profiles have shown that electron cyclotron resonance heating (ECRH) can make TAEs more unstable. In these AUG discharges, energetic ions driving TAEs were obtained by ion cyclotron resonance heating (ICRH). It was found that off-axis ECRH facilitated TAE instability, with TAEs appearing and disappearing on timescales of a few milliseconds when the ECRH power was switched on and off. On-axis ECRH had a much weaker effect on TAEs, and in AUG discharges performed with co- and counter-current electron cyclotron current drive (ECCD), the effects of ECCD were found to be similar to those of ECRH. Fast ion distributions produced by ICRH were computed with the PION and SELFO codes. A significant increase in T e caused by ECRH applied off-axis is found to increase the fast ion slowing-down time and fast ion pressure causing a significant increase in the TAE drive by ICRH-accelerated ions. TAE stability calculations show that the rise in T e causes also an increase in TAE radiative damping and thermal ion Landau damping, but to a lesser extent than the fast ion drive. As a result of the competition between larger drive and damping effects caused by ECRH, TAEs become more unstable. It is concluded, that although ECRH effects on AE stability in present-day experiments may be quite significant, they are determined by the changes in the plasma profiles and are not particularly ECRH specific., This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053 and from the RCUK Energy Programme [grant number EP/P012450/1]. The views and opinions expressed herein do not necessarily reflect those of the European Commission., Peer Reviewed, Postprint (author's final draft)

Experiments with the new neutral beam injection source of TCV have been performed with high fast-ion fractions (>20%) that exhibit a clear reduction of the loop voltage and a clear increase of the plasma pressure in on- and off-axis heating configurations. However, good quantitative agreement between the experimental data and TRANSP predictions is only found when including strong additional fast-ion losses. These losses could in part be caused by turbulence or MHD activity as, e.g. high frequency modes near the frequency of toroidicity induced Alfvén eignmodes are observed. In addition, a newly installed fast-ion D-alpha (FIDA) spectroscopy system measures strong passive radiation and, hence, indicates the presence of high background neutral densities such that charge-exchange losses are substantial. Also the active radiation measured with the FIDA diagnostic, as well as data from a neutral particle analyzer, suggest strong fast-ion losses and large neutral densities. The large neutral densities can be justified since high electron temperatures (3–4 keV), combined with low electron densities (about 2 X 1019 m−3) yield long mean free paths of the neutrals which are penetrating from the walls.

A Poiseuille flow reactor (PFR) is examined for the continuous production of struvite seed crystals. Feed phosphorus concentration was 0.02 M and Mg:N:P molar ratio was 1.5:1:1. Non-equilibrium feed saturation index (SI) was varied from 0.8 to 1.4. A Roughton (R) style vortex mixer was compared to the more common impinging jet (IJ) mixer to assess differences in mixing performance. Particle size distribution (PSD) was measured either in-line (without sonication) or after filtration and sonication. All particles produced in this work were within the range of those used for previous struvite seeding studies. Increased feed SI led to an increased in-line volume median particle diameter (D[50]) and PSD width, while sonicated samples produced much smaller PSD variation with increasing SI. At a feed condition of SI = 0.8, the R mixer produced similar PSDs for in-line and sonicated samples, whereas the IJ mixer produced D[50]s and distribution widths which were larger in-line than after sonication. At SI = 1.0 and 1.4, PSD deviation between in-line and sonicated samples was caused by weakly-bound aggregates that were easily disrupted by sonication. Scatter in PSD data at higher SIs indicated incomplete mixing in both mixers. This calls into doubt the applicability of the induction time and mixing models utilized in this study. Improved mixer design models should incorporate mixer aspect ratios. A viscous sub-layer of 0.2 mm of fluid spent longer than crystal induction time in the R mixer, which is expected to have caused scale formation. Discrepancies between particle mass measurements and predictions at the reactor outlet, suggest that between 5% and 13% of particle mass was likely retained within the reactor.

The measurement of dielectric properties of materials is critical to understanding the electromagnetic field distribution in the materials. Reliable knowledge of the dielectric constant is also important when designing a microwave pyrolysis unit for effective pyrolysis of materials of interest. The dielectric probe technique was used to evaluate the dielectric properties of biosolids. Biosolid samples were collected from various sources and the dielectric properties were measured across the microwave frequency range of 1.0 GHz to 10.0 GHz. The dielectric constant of the materials varied in the range from 80 to 2 and depended mainly on the origin of the sample, the electrical conductivity and the moisture content of the material. A mathematical model was developed to accurately predict the values of complex permittivity. This model was verified using the measured data.

A model of a mixed-mode nutrient recovery reactor is developed for a urine feed, incorporating complex solution thermodynamics, dynamic conservation relations and a power-law kinetic expression for crystal growth from seed crystals. Simulations at nominal operating conditions predict phosphorus recoveries greater than 99%, based on existing process kinetic parameters and operating conditions employed in previously published studies. The overall rate of nutrient recovery depends on the saturation index of the precipitating solid, the available surface area for mass transfer and the feed rate of the limiting constituent ion. Under the conditions considered, the nutrient feed rate appears to be the limiting factor for precipitation. Simulations demonstrate that diurnal feed flow variations of ±50% have a small effect on the rate of nutrient recovery. Overall, the study shows that valuable insights are gained in relation to process performance predictions, which should lead to more confident process design, operation and control.

The ASDEX Upgrade programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. After the finalization of the tungsten coating of the plasma facing components, the re-availability of all flywheel-generators allowed high-power operation with up to 20 MW heating power at Ip up to 1.2 MA. Implementation of alternative ECRH schemes (140 GHz O2- and X3-mode) facilitated central heating above ne = 1.2 × 1020 m−3 and low q95 operation at Bt = 1.8 T. Central O2-mode heating was successfully used in high P/R discharges with 20 MW total heating power and divertor load control with nitrogen seeding. Improved energy confinement is obtained with nitrogen seeding both for type-I and type-III ELMy conditions. The main contributor is increased plasma temperature, no significant changes in the density profile have been observed. This behaviour may be explained by higher pedestal temperatures caused by ion dilution in combination with a pressure limited pedestal and hollow nitrogen profiles. Core particle transport simulations with gyrokinetic calculations have been benchmarked by dedicated discharges using variations of the ECRH deposition location. The reaction of normalized electron density gradients to variations of temperature gradients and the Te/Ti ratio could be well reproduced. Doppler reflectometry studies at the L–H transition allowed the disentanglement of the interplay between the oscillatory geodesic acoustic modes, turbulent fluctuations and the mean equilibrium E × B flow in the edge negative Er well region just inside the separatrix. Improved pedestal diagnostics revealed also a refined picture of the pedestal transport in the fully developed H-mode type-I ELM cycle. Impurity ion transport turned out to be neoclassical in between ELMs. Electron and energy transport remain anomalous, but exhibit different recovery time scales after an ELM. After

The effect of crystallization conditions on the dextran partition coefficient between impure syrup and sugar crystal has been investigated in a batch crystallizer. The crystallizer is operated isothermally at temperatures of 30, 40, and 50 °C, at constant relative supersaturations of 0.05, 0.07, and 0.09, and with mother liquor dextran concentrations of 1000 and 2000 ppm/Brix. The dextran content has been determined by the CSR method. A 1:1 mass ratio of high-fraction dextran (approximately 250,000 Da) and low-fraction dextran (60,000–90,000 Da) is used to represent a wide range of dextran contamination. It is seen that the dextran partition coefficient in sucrose crystallization increases with both increasing supersaturation and increasing crystallization temperature. However it appears that these are secondary effects, with the partition coefficient strongly correlating with crystal growth rate alone, despite the regressed data having large variations in temperature, mother liquor dextran content, and supersaturation. Dextran incorporation into the sugar crystal results from both dextran adsorption onto the crystal surface and mother liquor inclusions. The explanation for the variation in the dextran content in sugar crystal with respect to the growth rate is due to increased adsorption due to the higher surface roughness of crystals grown at high growth rates. Although the dextran concentration in the solution affects the dextran content in the crystal, it does not strongly affect the dextran partition coefficient.

Discharge of untreated nutrient-rich wastewater is a problematic issue, which may cause root burning and the eutrophication of receiving water. It is also a problematic issue due to the formation of crystalline deposits in waste water systems. The recovery of nutrient using crystallization technique may provide a value added product. The recovered product is struvite, which is chemically known as magnesium ammonium phosphate hexahydrates. The key focus of this paper is the modeling and simulation of struvite growth, incorporating solution chemistry and thermodynamics, growth kinetic and process description of the recovery system. An ensemble of experimental data is combined with the dynamic model to estimate struvite growth kinetics.

This paper focuses on struvite (MgNH4PO4.6H2O) crystallization in controlled supersaturation. Struvite can be used as a slow-release fertilizer. Crystallization experiments were conducted using supersaturated solutions. The secondary focus of this paper is the design of a struvite recovery system in fed-batch-controlled supersaturation mode. The design and commissioning of fed-batch struvite crystallization included the determination of operating supersaturation of struvite crystallization, suitable seed materials and the composition of feed solution. Determination of operating supersaturation of struvite crystallization was conducted by two steps including thermodynamic simulation using gPROMS2 (process simulation software) along with a set of batch experiments. Investigation of suitable seed materials was also conducted using set of batch experiments. Two types of seed materials including quartz sand and struvite seeds were used in the investigation of seed materials. Composition of feed solution included the investigation of struvite solution chemistry using PHREEQC3 thermodynamic modeling package. Based on the previously investigated design approach, struvite crystallization in fed-batch system was conducted using a 44-L of reactor with 15-L of initial reactant volume.

The key feature of this paper is the combined removal of magnesium, ammonium and phosphate from a representative synthetic solution of piggery effluent. The byproduct of this recovery process is struvite, commercially used as slow-release fertiliser. A thermodynamic model was developed relating to all the complexes of magnesium, ammonium and phosphate using gPROMS process software. A laboratory-based batch experiment confirmed 80% recovery of phosphate using this crystallization technique. The batch experiment was conducted at constant pH using synthetic solution made up of analytical-grade MgCl2 and NH4H2PO4. Borosilicate glass grindings of 5 g were used as seeds in this batch experiment. Basic solution characteristics of piggery effluent are reported in this paper.

The main feature of this paper was to recognize struvite crystallization in the metastable region of supersaturation. Thermodynamic equilibria of struvite were simulated to identify the minimum struvite solubility limit, thereafter validated by existing thermodynamic modelling packages such as PHREEQC and the derived data from existing struvite solubility curve. Using laser light scattering detection, spontaneous nucleation was identified by the slow increase of pH in a supersaturated solution of struvite. The crystallization experiment, conducted close to the saturation region in metastable zone, initiated struvite growth. The conducted experiment showed that mother crystal (struvite) was more effective as seeds for struvite crystallization.

This paper proposes a simple dynamic solids transport model for flighted rotary dryers, which results by discretising the dryer in the axial direction into a series of equivolume elements. Each resultant element is partitioned into two zones; one active and the other passive. Solids interchange between the active and passive zones is included, leading to a tanks-in-series/parallel approach, traditionally used by reaction engineers. Modelling solids transport in this manner allows the residence time distribution (RTD) characteristics of the rotary dryer to be elucidated. In this work gPROMS is used to simulate the proposed rotary dryer model. Data from a 100 tonne per hour raw sugar dryer is reconciled against the dynamic solids transport model, by estimating overall solids transport coefficients.

An experimental apparatus capable of fluidising sugar under both spouted and standard fluidising regimes was designed and commissioned. The apparatus was operated under spouting conditions using dry raw sugar and dry sand. The general characteristics of the apparatus and the design procedure for sizing this unit have been outlined in the paper. Minimum spouting velocities over a range of dry sugar bed heights (80–220 mm) were determined for dry raw sugar and qualitative examination of the effect of sugar moisture content on fluidisation was undertaken. The advantages of fluidised bed drying have been presented and the potential application of this drying technology has been discussed.

Conductivity-based vacuum pan controllers dominate the Australian sugar industry. A new scheme, based on Brix control of the massecuite and mother molasses is proposed. Multi-loop control of the process is demons trated, whereby the massecuite Brix is controlled by manipulating the liquor/A molasse s feed rate to the pan and the mother molasses Brix is controlled by manipulating the steam flow rate to the pan. A single loop controller is also proposed, which cont rols massecuite Brix by manipulating the feed flow to the pan. The steam flow rate is set manually (i.e. mother molasses Brix is uncontrolled). A gPROMS simulation of a pi vot pan under typical operating conditions demonstrates the efficacy of this approach.