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Abstract Pyrolysis tar and char yields were measured at atmospheric pressure between 400–800 °C in three reactors with significantly different design characteristics: a fluidized bed; a wire-mesh reactor; and a ‘hot-rod’ fixed bed reactor. Ranges of conditions under which results were generally in good agreement were identified using a common sample of Linby (low rank British bituminous) coal. Differences highlighted important non-ideal characteristics in the behaviour of all three systems. The causes of these non-idealities and their implications for the interpretation of pyrolysis data from the three types of reactors are discussed in detail.

Abstract Pyrolysis tar and char yields were measured at atmospheric pressure between 400–800 °C in three reactors with significantly different design characteristics: a fluidized bed; a wire-mesh reactor; and a ‘hot-rod’ fixed bed reactor. Ranges of conditions under which results were generally in good agreement were identified using a common sample of Linby (low rank British bituminous) coal. Differences highlighted important non-ideal characteristics in the behaviour of all three systems. The causes of these non-idealities and their implications for the interpretation of pyrolysis data from the three types of reactors are discussed in detail.

Abstract In this study, a methodology is developed to assess the feasibility of a reverse osmosis (RO) desalination system powered by a stand-alone salinity driven pressure retarded osmosis (PRO) technology. First, the proposed hybrid RO–PRO system is analysed as a thermodynamic cycle and its feasibility is mathematically interpreted using a feasible condition (FC) number, several dimensionless operational variables and a number of constraints to represent the objective of zero brine discharge. Then, a study of the stand-alone feasibility of a hybrid seawater RO–PRO system is carried out. The results show that lower RO water recovery and higher dimensionless flow rate improve the stand-alone feasibility of the system. A subsystem, a look inside the PRO, is developed to study the applied pressure and the required membrane area to achieve the operations with optimum FC numbers. It is found that the optimum applied hydraulic pressure is inversely proportional to the dimensionless flow rate in the feasible range of stand-alone operations and more area of membrane is required by a larger FC number. Finally, a case study of a selected operation is presented based on its energy performance, and two influencing factors, the inefficiency of the components and the salinity concentration of the feed water.

Abstract In this study, a methodology is developed to assess the feasibility of a reverse osmosis (RO) desalination system powered by a stand-alone salinity driven pressure retarded osmosis (PRO) technology. First, the proposed hybrid RO–PRO system is analysed as a thermodynamic cycle and its feasibility is mathematically interpreted using a feasible condition (FC) number, several dimensionless operational variables and a number of constraints to represent the objective of zero brine discharge. Then, a study of the stand-alone feasibility of a hybrid seawater RO–PRO system is carried out. The results show that lower RO water recovery and higher dimensionless flow rate improve the stand-alone feasibility of the system. A subsystem, a look inside the PRO, is developed to study the applied pressure and the required membrane area to achieve the operations with optimum FC numbers. It is found that the optimum applied hydraulic pressure is inversely proportional to the dimensionless flow rate in the feasible range of stand-alone operations and more area of membrane is required by a larger FC number. Finally, a case study of a selected operation is presented based on its energy performance, and two influencing factors, the inefficiency of the components and the salinity concentration of the feed water.

This study aims to systematically evaluate the detrimental effects, namely concentration polarization (CP) and reverse solute permeation (RSP), and search for the optimum performance of a scale-up osmotic power assisted reverse osmosis (RO) desalination plant. The simulation clearly shows the performance reductions of the hybrid RO-PRO plant due to the CP and RSP effects. However, in both the co-current and counter-current PRO configurations, when the overall dimensionless flow rate decreases, these performance reductions become less significant. In addition, the counter-current PRO has high effectiveness because of the low theoretical net specific energy consumption (SEC) of RO-PRO. It is observed that more severe reduction due to the CP and RSP effects at high overall dimensionless flow rate shrinks the advantageous performance. Furthermore, PRO feed solutions with different concentrations are studied to evaluate the overall performance of the hybrid system. The results indicate that the advantageous performance can be achieved in a range of the concentration of the PRO feed. And with the increase on the PRO feed concentration, the osmotic energy generation reduces but the un-extracted energy due to the detrimental effects is also reduced.

This study aims to systematically evaluate the detrimental effects, namely concentration polarization (CP) and reverse solute permeation (RSP), and search for the optimum performance of a scale-up osmotic power assisted reverse osmosis (RO) desalination plant. The simulation clearly shows the performance reductions of the hybrid RO-PRO plant due to the CP and RSP effects. However, in both the co-current and counter-current PRO configurations, when the overall dimensionless flow rate decreases, these performance reductions become less significant. In addition, the counter-current PRO has high effectiveness because of the low theoretical net specific energy consumption (SEC) of RO-PRO. It is observed that more severe reduction due to the CP and RSP effects at high overall dimensionless flow rate shrinks the advantageous performance. Furthermore, PRO feed solutions with different concentrations are studied to evaluate the overall performance of the hybrid system. The results indicate that the advantageous performance can be achieved in a range of the concentration of the PRO feed. And with the increase on the PRO feed concentration, the osmotic energy generation reduces but the un-extracted energy due to the detrimental effects is also reduced.

This paper proposes a method to obtain the optimal placement of wind turbines (WTs) in an offshore wind farm (WF). The optimization objective is to minimize the levelized average cost per net electric power generated by a WF with a fixed number of WTs while the distance between WTs is not less than the allowed minimal distance in the far wake region. The WT wake losses have been taken into account, with the Frandsen-Gaussian (F-G) wake model and the optimization problem is subsequently solved by the hybrid grey wolf optimization (HGWO) algorithm. Synthesis methods that contain a special WT ranking strategy for multiple WTs are described in detail. Both the F-G model and Jensen's model are applied in the offshore WF optimization simulation platform for comparison. Simulation results demonstrate that the F-G model is more consistent with real wakes and thus the optimization result is more accurate than the commonly used Jensen's model.

This paper proposes a method to obtain the optimal placement of wind turbines (WTs) in an offshore wind farm (WF). The optimization objective is to minimize the levelized average cost per net electric power generated by a WF with a fixed number of WTs while the distance between WTs is not less than the allowed minimal distance in the far wake region. The WT wake losses have been taken into account, with the Frandsen-Gaussian (F-G) wake model and the optimization problem is subsequently solved by the hybrid grey wolf optimization (HGWO) algorithm. Synthesis methods that contain a special WT ranking strategy for multiple WTs are described in detail. Both the F-G model and Jensen's model are applied in the offshore WF optimization simulation platform for comparison. Simulation results demonstrate that the F-G model is more consistent with real wakes and thus the optimization result is more accurate than the commonly used Jensen's model.

The behaviour, in a moderator, of the neutron density wave propagating from a modulated thermal neutron source is studied. The Boltzmann equation, in the diffusion approximation, is solved numerically to obtain a complete set of complex eigenfunctions whose amplitudes are obtained from the oscillating source condition. By introducing an effective (complex) wave parameter the detector response as a function of time, and position is examined. The feasibility of measuring asymptotic values of the wave parameters, particularly when critical values of frequency and buckling have been exceeded, is investigated, and the effect of various source energy distributions demonstrated. The calculated values of the fundamental wave parameters α0, ξ0 are compared directly with the measured values of Perez and Booth, for a graphite system with B⊥2 = 000596 cm−2.