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CURATOR
A pinboard by
JIAN CHANG

PhD, National University of Singapore

PINBOARD SUMMARY

With the aid of cold energy from regasification of liquefied natural gas (LNG), freeze desalination (FD) is an emerging technology for seawater desalination because of its low energy characteristics and insensitivities to fouling problems. This work aims to investigate the major operating parameters of FD such as coolant temperature, freezing duration, supercooling, seeding, agitation, crystallizer material and subsequent washing procedure on ice production and water quality. It is found that the optimal freezing duration per batch is 1 hr for an iron crystallizer and 1.5 hr for a glass crystallizer. The optimal coolant temperature should be around -8 °C. The optimal amount of washing water to clean the raw ice is about 50 wt% of the raw ice. The overall ice recovery rate is higher than 25% within 1 hr. Both artificial and real seawater have been tested under the optimized conditions and the results are consistent with the data from the 3.5 wt% NaCl solution. The total dissolved solid in the product ice is around 300 ppm, which meets the World Health Organization (WHO) potable water salinity standard of 500 ppm. Therefore, the process parameters optimized in this study can be directly used for the freeze desalination of seawater.

4 ITEMS PINNED

Efficient suspension freeze desalination of mine wastewaters to separate clean water and salts

Abstract: Abstract Suspension freeze desalination is a promising technique for producing clean water from mine wastewaters. The principle is that growing ice crystals reject impurities during freezing. As a result, pure water is separated from mine wastewaters as clean ice. Actually, there is a need for improved techniques to increase water yield and purity. Here we tested ice formation in complex synthetic solutions during cooling and addition of seed. Solutions included: pure distilled water, 50, 33 g/L NaCl and 17, 50 g/L Na2SO4, 50 g/L NaCl and 50 g/L Na2SO4. Results show that heat of crystallization was the highest with pure distilled water at 8859 J, whereas the lowest heat of crystallization, of 4608 J, was for the solution of 50 g/L NaCl and 50 g/L Na2SO4, indicating that the presence of the salt enhances ice formation. As an application, we designed a new flow diagram, which, in addition to heat exchanger and ice filter, now includes a fluidized bed reactor for salt crystallization and recovery, and a separate heat exchanger for ice crystallization.AbstractSuspension freeze desalination is a promising technique for producing clean water from mine wastewaters. The principle is that growing ice crystals reject impurities during freezing. As a result, pure water is separated from mine wastewaters as clean ice. Actually, there is a need for improved techniques to increase water yield and purity. Here we tested ice formation in complex synthetic solutions during cooling and addition of seed. Solutions included: pure distilled water, 50, 33 g/L NaCl and 17, 50 g/L Na2SO4, 50 g/L NaCl and 50 g/L Na2SO4. Results show that heat of crystallization was the highest with pure distilled water at 8859 J, whereas the lowest heat of crystallization, of 4608 J, was for the solution of 50 g/L NaCl and 50 g/L Na2SO4, indicating that the presence of the salt enhances ice formation. As an application, we designed a new flow diagram, which, in addition to heat exchanger and ice filter, now includes a fluidized bed reactor for salt crystallization and recovery, and a separate heat exchanger for ice crystallization.242424

Pub.: 01 Dec '16, Pinned: 07 Aug '17

Evaluation of the performance of a new freeze desalination technology

Abstract: The use of desalination technologies which produce concentrated brines is acutely limited by inadequate waste brine disposal mechanisms such that the brine does not contaminate fresh water resources. The treatment of highly saline brine using freeze desalination technique trade marked as HybridICE™ technology was investigated at pilot scale. The capacity of the HybridICE™ process to generate fresh water by freeze desalination of brine was investigated in this study. Brine samples to feed into the HybridICE process unit were prepared in tanks with volume capacities between 1.0 and 10.0 m3 by dissolving common salt into tape water. The effects of refrigerant temperature, initial brine concentration, energy consumption were evaluated in relation to product ice quality. Feed brine samples were processed in batches in a closed system where it was continuously re-circulated to generate product ice and more concentrated residual small volume of brine stream. The quality of ice produced could be turned into potable water it terms of its low total dissolved salts and conductivity. The salt removal, based on the average chloride concentration in the ice samples, was 96 %. The energy utilization efficiency amounted to an average of ZAR 10.0/m3 water assuming energy cost of ZAR 0.39/kWh. The HybridICE™ technology was shown to be a better option than other desalination technologies currently in use, in terms of energy utilization and cleaner by-products.

Pub.: 07 Feb '13, Pinned: 07 Aug '17

A conceptual demonstration of freeze desalination-membrane distillation (FD-MD) hybrid desalination process utilizing liquefied natural gas (LNG) cold energy.

Abstract: The severe global water scarcity and record-high fossil oil price have greatly stimulated the research interests on new desalination technologies which can be driven by renewable energy or waste energy. In this study, a hybrid desalination process comprising freeze desalination and membrane distillation (FD-MD) processes was developed and explored in an attempt to utilize the waste cold energy released from re-gasification of liquefied natural gas (LNG). The concept of this technology was demonstrated using indirect-contact freeze desalination (ICFD) and direct-contact membrane distillation (DCMD) configurations. By optimizing the ICFD operation parameters, namely, the usage of nucleate seeds, operation duration and feed concentration, high quality drinkable water with a low salinity ∼0.144 g/L was produced in the ICFD process. At the same time, using the optimized hollow fiber module length and packing density in the DCMD process, ultra pure water with a low salinity of 0.062 g/L was attained at a condition of high energy efficiency (EE). Overall, by combining FD and MD processes and adopting the optimized operation parameters, the hybrid FD-MD system has been successfully demonstrated. A high total water recovery of 71.5% was achieved, and the water quality obtained met the standard for drinkable water. In addition, with results from specific energy calculation, it was proven that the hybrid process is an energy-saving process and utilization of LNG cold energy could greatly reduce the total energy consumption.

Pub.: 12 Jun '12, Pinned: 07 Aug '17