Rosalie J Durham

Hydrophobic membrane evaluation and cleaning for osmotic distillation of tomato puree

Abstract Membrane hydrophobicity was investigated for the osmotic distillation (OD) of tomato puree and membrane cleaning. Membrane hydrophobicity was measured by two methods: penetrating drop concentration (PDC%) for surface tension greater than 23 mN/m and penetration temperature (PT°C) newly developed for membrane surface tension less than 23 mN/m. Cleaning methods for tomato paste fouled OD membranes were assessed. The membrane surface tension determined the cleaning regime. The most effective cleaner for membranes with a surface tension greater than 23 mN/m was 1% NaOH. The hydrophobic integrity of these membranes was destroyed during repeated fouling/cleaning trials. The most effective cleaner for membranes with a surface tension less than 23 mN/m was P3 Ultrasil 56. Water vapour flux was maintained and there was no salt leakage during repeated fouling/cleaning trials.

Waste management and co-product recovery in dairy processing.

Publisher Summary Dairy processing in major dairy producing countries has undergone rationalization in recent years, with a trend toward larger yet fewer plants operated with less staff. Large processing plants have enabled the use of automated and more efficient equipment – including the use of specialized processes such as membrane filtration, ion exchange, and modern drying processes, thus increasing the opportunity for the recovery of milk solids that were formerly discharged. In addition, sophisticated process control systems have allowed improved processing efficiencies and cost savings. However, large-scale manufacturing increases the environmental burden on to smaller areas, loading the impact of liquid waste disposal, noise and gas emissions in the vicinity of the plant. There are several aspects of waste disposal that continue to be troublesome in the dairy industry, including acid whey, nanofilter permeates, mother liquor from lactose crystallization, clean-inplace waste, and spent ion exchange regeneration brines. Although limited utilization of many of these by-product streams is due to low returns and economies of scale, continued research and process optimization is required to overcome the remaining technological barriers for maximizing the recovery of dairy by-product streams.

Dynamic modelling and optimisation of alpha-lactose monohydrate seeded batch cooling crystallisation

Abstract This work validates the model equations of a seeded batch cooling process to produce α-lactose monohydrate from highly pure syrup. Experiments are conducted in 2L and 20L crystallisers under various seeding and cooling strategies, obtained from solving a dynamic optimisation problem. Using a nonlinear least square method the best curve fitting of experimental data to the model yields k g and n, two constants used in the growth rate equation. The value of n = 2.7 can be fixed regardless of sizes of seeds and crystallisers but k g must be estimated for different seeding weights. The rate of nucleation must be redefined to reflect the variations in crystal median size prediction. The model can be applied to industrial scale crystallisers providing the cooling rate is slow and the seed size range is narrow.

Dynamic modelling and simulation of lactose cooling crystallisation: from batch and semi-batch to continuous operations

Abstract The focus of this work is to revise for semi-batch and continuous operations, the model equations of a seeded batch cooling crystallisation of α-lactose monohydrate. A case study of evaporative semi-batch operation is also included for reference as models of cooling and heating are not much different. In order to achieve the highest yield, dynamic optimisations must be performed on these models to get optimal cooling, feeding and heating (for evaporative mode only) strategies. Applying these strategies in bench scale experiments shows that models of batch and semi-batch work well before the growth becomes slow. Semi-batch is slightly faster than batch and evaporative semi-batch is ten times faster than cooling but is more difficult to control. The performance of a cooling and seeding run in continuous mode is simulated. The system reaches steady state after seven residence times but the predicted particle size could not be stabilised and continued to increase up to one hundred hours. A plug flow reactor is being studied instead of a continuous stirred tank reactor to close the mass and population balances.