Crystal morphology is known to be of great importance to the end-use properties of the crystal product and affect the down-stream processing such as in filtration and drying, but was previously regarded as too challenging to achieve automatic closed-loop control. As a consequence, previous work has focused on control the crystal size distribution (CSD) where the size of a crystal is often defined as the diameter of a sphere that has the same volume of the crystal. This paper reviews very promising new advances made in recent years in morphological population balance models for modelling and simulation of crystal shape distribution (CShD), measurement and estimation of crystal facet growth kinetics, as well as in 2D and 3D imaging for on-line characterisation of crystal morphology and CShD. A framework is presented integrating various components in order to achieve the ultimate objective of model-based closed-loop control of CShD. The knowledge gaps and challenges that require further research are also identified.

High efficiency and compact design of the desulfurization technology is necessary to meet the strict emission requirement of the marine environment. A rotating packed bed (RPB), having high mass transfer efficiency and small size, is an excellent choice for SO2 removal from the exhaust gas in ships. In this work, SO2 removal in a laboratory and a pilot RPB with sodium sulfite solution were investigated. Experimental results show that the SO2 concentration at the gas outlet of the RPB can decrease sharply and it has no obvious scale up effect. A correlation of the mass transfer coefficient (K y a) was proposed and the predicted K y a agrees with the experimental data with a deviation within ±15%. Compared with the spray tower, the RPB has a higher SO2 removal efficiency and a quarter volume, which displays a bright future for the offshore application of SO2 removal.

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A B S T R A C TStart-up experiments were carried out using a constructed a pilot-scale biofilter in a water supply plant to purify iron (Fe), manganese (Mn), and ammonia (NH 3 -N) from low-temperature groundwater (3-4˚C throughout the year). The results of the biofilter operation indicated that the simultaneous removal of these contaminants could be obtained with a one-stage biofilter, while the operational parameters such as aeration and backwashing strength (BWS) should be optimized during the start-up operation period. Removal of Fe was most likely dominated by chemical oxygen oxidation since the biofilter exhibited high removal efficiency at the initial running period and the start-up time was not required. Higher levels of aeration (that corresponds to higher dissolved oxygen concentration) helped to transform the water redox environment and increase Mn removal. Nitrification effects were irrelevant with the extra aeration. A weaker BWS was helpful in avoiding biomass loss during the initial operation of the biofilter; however, the BWS should be improved to eliminate excess amounts of metal oxide accumulation after a long operation time, since it could enhance the overall removal. Using high-throughput sequencing technology, the functional bacteria genera were identified. It was demonstrated that the corresponding functional oxidizing bacteria could be acclimated sufficiently in low-temperature water.

The performance of an iodine radio ion thruster with a 4 cm diameter (IRIT4) was studied experimentally in this paper. Regulation of the mass flow rates of the iodine propellant is achieved by using a temperature control method of the iodine reservoir. Performance of the thruster using iodine as propellants is obtained at different total thruster powers of 40.6-128.8 W, different grid voltages of 1000-1800 V and the iodine flow rate of 100 μg s −1 . Results show that thrust and specific impulse increase approximately linearly with the increasing total thruster power and the screen grid voltage. The thrust of 2.32 mN and the specific impulse of 2361 s are obtained at the nominal total thruster power of 95.8 W and the screen grid voltage of 1800 V. It is also indicated that performance of the iodine propellant is comparable to that of the xenon propellant; and a difference between them is that the iodine thrust is slightly higher than xenon when the total thruster power is more than 62 W. At the nominal 95.8 W total thruster power, the thrust values of them are 2.32 mN and 2.15 mN respectively, and the thrust-to-power ratios of them are 24.2 mN kW −1 and 23.5 mN kW −1 , respectively.

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