Freeze Desalination Research Articles

Freeze desalination of seawater using LNG cold energy

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 was found that the optimal freezing duration per batch was 1 h for an iron crystallizer and 1.5 h for a glass crystallizer. The optimal coolant temperature should be around −8 °C. The optimal amount of washing water to clean the raw ice was about 50 wt% of the raw ice. Over 50 wt% of the feed could be recovered as raw ice within 1 h, which means an overall ice recovery rate of higher than 25% (of the original seawater), considering the consumption of washing water. Both artificial and real seawater were tested under the optimized conditions. The total dissolved solid in the product ice was around 300 ppm, which met 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.

Investigation of Hydrate-induced Ice Desalination (HIID) and its application to a pretreatment of reverse osmosis (RO) process

In this study, freeze desalination which utilizes CO2 gas hydrate itself as a refrigerant (referred to as Hydrate-induced Ice Desalination, HIID) was systematically investigated and evaluated as a pretreatment method for seawater reverse osmosis (RO) process. To the best of the authors' knowledge, the HIID is the first approach to use the hydrate dissociation energy to freeze seawater in an instant for desalination. The endothermic energy related to hydrate dissociation was the most dominant factor in the freezing of seawater. Using the HIID technique, the rejection of ions with 3.5wt% NaCl was about 67%. Increasing the concentration of salts enhanced rejection of component ions. However, humic acid organic rejection decreased due to agglomeration of organics in presence of salts. The HIID process showed similar levels of cation rejections-approximately 65% of seawater, except boron and potassium. The rejection of cations might be determined by the solubility of salts at various brine concentration. Using HIID as a pretreatment of seawater at 225psi, the RO process showed ~14 LMH and about 99% cation rejections except boron. This study shows that HIID can be utilized as a pretreatment of seawater desalination and further development might make HBID technology run on its own.

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

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.

Application of freeze desalination for chromium (VI) removal from water

Chromium (VI) is a highly toxic metal ion found in the priority list of pollutants, which is also often abundant in areas having low access to high-tech solutions for chromium (Cr) removal. This study was initiated to investigate the capacity of home-use refrigerators to generate fresh water free from Cr(VI) by melting ice produced from Cr(VI) polluted water. Simulated tap water samples as well as deionized water to which different concentrations of Cr(VI) were added were frozen in a closed freezer unit. The effects of initial concentration, time of ice nucleation, fraction of ice volume, and influence of co-occurring ions were evaluated in relation to the quality of the produced ice. The physicochemical characteristics of the produced ice cubes were also evaluated. A high total water recovery of up to 85% was achieved. Chromium removal ranged from 57.4 to 80% for simulated tap and from 93 to 97% for deionized water spiked with Cr. The energy consumption estimation basing form the refrigerator amounted to 0.076kWh. Freeze desalination was found to be relatively viable desalination technology in terms of quality of water produced, easiness for safe water production, and amount of energy consumed, especially where high-tech solutions for Cr(VI) removal are not available.

Laboratory freezing desalination of seawater

Freeze desalination of samples of seawater from Umluj beach, Red Sea, in Saudi Arabia, was investigated by laboratory experiments using nondirect freezing. The influence of kinetic parameters including degree of crystallization, freezing–melting cycles, and gradual melting on the total dissolved solids (TDS) and salt rejection was examined. The melted ice water produced by partial crystallization of single-stage freezing has two times less salt concentration than the feed seawater (TDS, 40,916 mg/l). Continuous cycling of the freezing–melting process reduced the dissolved salts to 1.5% with TDS 610 mg/l, in the level of drinking water. The TDS of the melted ice decreased with gradual melting time and reached 693 mg/l after 6 h. The results indicated that the laboratory freezing desalination could decrease sea ice salinity from 4.1 to 0.06% without using chemical additives.

Performance comparison of hydraulic and gravitation HybridICE filters in freeze desalination of mine waters

HybridICE is an emerging freeze desalination technology for treating complex mine wastewaters. The technology works on the principle that growing ice crystals reject impurities during freezing. The bottleneck in the freeze desalination processes may be the separation of ice from the ice slurry generated in the freeze engine. Two types of HybridICE filter have been developed to effect ice separation from ice slurry. The two types differ in the design of the filter elements, mode of feeding the slurry into the filter, and the mechanism of separation of ice from the slurry. In both types of filter, an extruded continuous ice column is formed around the filtering element, which has some openings to allow excess concentrated process water to flow out of the filter. However, the driving force in the gravitation filter is buoyancy, while in the hydraulic filter the ice column is driven by the pressure generated from the flow of the slurry. Salt removal and ice yield from each of the filter types was evaluated when a solution of approximately 4% m/m NaCl solution, prepared by dissolving 25.1 kg of NaCl in 674 litres of water, was treated in a HybridICE freeze crystallisation pilot plant. The objective was to describe the operation of the two types of filter and compare their performance. Salt removal and ice yield were found to be higher with the gravitation filter than the hydraulic filter.Keywords: freeze, desalination, filter, yield, salt removal, ice

Theoretical approach of freeze seawater desalination on flake ice maker utilizing LNG cold energy

In this work, a novel concept in freeze desalination (FD) was introduced. Nowadays the total liquefied natural gas (LNG) production capacity has reached 290Mt/year. Its enormous cold energy released from re-gasification can be used in the freeze desalination process to minimize the overall energy consumption. A process of FD on flake ice maker utilizing LNG cold energy was designed and simulated by HYSYS software. An ice bucket on flake ice maker was chosen as seawater crystallizer mainly due to its continuous ice making and removing ice without heat source. A dynamic model of the freezing section has been developed and simulated through gPROMS software. The results show that the consumption of 1kg equivalent LNG cold energy can obtain about 2kg of ice melt water. In addition, it is shown that the power consumption of this LNG/FD hybrid process is negligible.

HybridICE® filter: ice separation in freeze desalination of mine waste waters.

Freeze desalination is an alternative method for the treatment of mine waste waters. HybridICE(®) technology is a freeze desalination process which generates ice slurry in surface scraper heat exchangers that use R404a as the primary refrigerant. Ice separation from the slurry takes place in the HybridICE filter, a cylindrical unit with a centrally mounted filter element. Principally, the filter module achieves separation of the ice through buoyancy force in a continuous process. The HybridICE filter is a new and economical means of separating ice from the slurry and requires no washing of ice with water. The performance of the filter at a flow-rate of 25 L/min was evaluated over time and with varied evaporating temperature of the refrigerant. Behaviours of the ice fraction and residence time were also investigated. The objective was to find ways to improve the performance of the filter. Results showed that filter performance can be improved by controlling the refrigerant evaporating temperature and eliminating overflow.

Process optimization of freeze desalination of brine using HybridICETM pilot plant

Freeze desalination of synthetic brines prepared from sodium chloride was investigated. Brine solutions of levels between 2.3% to 10% sodium chloride were used as feed to the plant operated in a batch and continuous mode. The effects of pump, gear motor speed, and differential temperatures on ice formation and purity were investigated. The HybridICE process produced ice of quality levels between 80–96% purity. It was observed that the pump speed was directly proportional to the effluent flow rate coming out of the heat exchangers. Generally, it was observed that the quality of product ice was higher at low to medium flow rates of feed. The gear motor speed variation was inversely proportional to effluent flow rate from the heat exchangers. The HybridICE was found to be a viable desalination technology in terms of quality of water produced, energy consumption, and its easiness to be incorporated into existing refrigeration systems.

Application of progressive freeze-concentration for desalination

There is a demand for new and effective desalination technologies, as water shortage is expected to spread all over the world in the future. Among many methods, the freeze desalination process has some advantages such as high energy efficiency, corrosive resistance, and easy operation. In this study, a progressive freeze-concentration, currently used in food processing, was applied for desalination. The progressive freeze-concentration is a method to concentrate impurities into a liquid phase and obtain a pure solid phase by controlling an ice front one-dimensionally. The effect of three parameters (the advance speed of the ice front (U), the circumferential velocity of the stirrer (Ur), and initial concentration (C0)) were investigated by conducting the laboratory experiments. In order to evaluate the efficiency of the desalination process, effective partition constant (K), and intrinsic partition constant (K0) were introduced by adopting the concentration gradient model. The results showed the effect of three parameters on desalination successfully. Furthermore, at a certain Co, K can be expressed as a function of U, Ur and K0. This function is useful for scaling up the system.

Evaluation of the performance of a new freeze desalination technology

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.

Freeze desalination: An assessment of an ice maker machine for desalting brines

Ice maker machines are extensively used in many commercial and residential areas for the purpose of making ice cubes. As the ice forms a certain amount of dissolved salts will be rejected to the remaining residual liquid. However, the degree of separation by freezing, in terms of the salt rejection and water recovery, is dictated by several factors and influences, such as operating conditions and feed quality. In this paper, the potential of an ice maker is investigated for desalting several types of process feed including sodium chloride solutions, Arabian Gulf seawater and reverse osmosis brines. The performance of multi-staging the freeze concentration process was also experimentally assessed. The results show that the process was useful in concentrating reverse osmosis brine and producing a recycle stream for further processing by membrane plant.

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

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.

해수 히트펌프를 이용한 냉동법 담수화시스템 개념설계

해수 히트펌프를 이용한 냉동법 담수화시스템의 개발을 위한 시스템 설계 및 성능 해석을 수행하였다. 해수 히트펌프시스템의 열역학적 모델은 냉동사이클을 이용하였고, 이를 해수 담수화시스템에 적용하였다. 응축기의 유입 해수온도 및 증발기의 얼음 생성 비율에 따른 해수 히트펌프 시스템의 성능을 분석하고, 이에 따른 담수 생산량 및 담수 1㎏ 생산에 대한 소요 에너지 등 냉동법 담수화 시스템의 성능을 비교 · 분석하였다. 압축기 소요동력 및 응축기 용량은 응축기로 유입되는 해수온도가 감소함에 따라 감소하였다. 담수 1㎏ 생산에 따른 소요 에너지는 응축기 유입 해수온도가 8℃일 때가 20℃일 때에 비해 약 28.9% 감소하였다.

An adhesion model of the axial dispersion in wash columns of packed ice beds

Experimental studies on a packed ice bed wash column, which was used for separating ice from ice slurry in the process of freeze concentration or freeze desalination, showed that the transitional mixing zone at the wash front of the ice bed expanded as the ice particle size decreased. It can be interpreted that the smaller the particle size, the greater the axial dispersion coefficient. This conflicts with the general knowledge or understanding of mixing and diffusion in porous media based on current dispersion theory, which predicts an opposite trend. To address this problem, an adhesion model of the axial dispersion coefficient of wash columns is proposed in this work, which correlates the axial dispersion coefficient in liquid phase with the particle size of the ice bed, the bed porosity, the interstitial flow velocity and the viscosity of the liquid. The model gives an analytical perspective of the axial dispersion in operating a packed ice bed wash column.

Freeze desalination using hydraulic refrigerant compressors

Freeze desalination of seawater using direct contact freezing and melting heat transfer has long been known to be very energy efficient. However, practical dificulties and developmental mishaps have blocked commercial success. The unsuitability of conventional refrigerant compressors for use in freeze desalination plants has been a major obstacle. The recent invention and development of the hydraulic refrigerant compressor now provides an excellent solution to the compressor problem, and the advantages are such as to make reconsideration of freeze desalination worthwhile. Herein suitable candidates are described for each of the principal system components including the hydraulic refrigerant compressors, and the characteristics of a resulting freeze desalination system are discussed.

The US Bureau of Reclamation's research programs in water treatment and desalting technologies

This paper discusses a brief history of desalting research within the Department of the Interior, Office of Saline Water and the Office of Water Research and Technology, as well as the current desalting research programs within the Bureau of Reclamation. An overview is provided on the research that has been accomplished under Reclamation's Yuma Desalting Research Program over the past 12 years, as well as its Water Treatment Technology Program over the past 2 years. Information is also presented on specific on-going desalting research projects. These include a report published on “National Desalting and Water Treatment Needs Survey”, an RO pilot plant being tested to recover groundwater while using the reject flow for a wetlands project; cost-shared studies on improved performance and cost of membranes, membrane fouling, biocides, desalting cogeneration systems, nanofiltration systems, freeze desalination, an improved RO pumping and energy recovery system, a mobile water treatment pilot plant, as well as a “Desalting and Water Treatment Membrane Manual” that has been published on the latest state-of-the-art membranes.

A case study of a solar energy transfer and storage system in a freeze desalination project in Yanbu, Saudi Arabia

Performance evaluation studies of Syltherm-800 (a proprietary heat transfer fluid) and Partherm-290 (a proprietary heat storage salt) are reported based on the data collected for a 1-year operation of solar powered freeze desalination pilot plant (200 m 3 capacity), located in Yanbu, Saudi Arabia. In spite of some operational problems, the thermal stability of these heat transfer media has been observed to be good, which ensures their prolonged use in solar power-generation technology.

Total Dissolved Solids Removal From Water Produced During The In Situ Recovery Of Heavy Oil And Bitumen

Abstract Based on a preliminary economic and technical comparison, evaporation, membrane processes and freeze desalination were identified as the most attractive technologies for removing total dissolved solids (TDS) from produced water. Vapour compression evaporation appeared to be the most cost-competitive. Subsequently, laboratory-scale experiments on the evaporation of produced waters were conducted on four produced water samples from various locations in Alberta and Saskatchewan he evaporator consisted of a 4.6 m long titanium tube; 50.8 mm o.d. by 6.3 mm wall thickness, heated by steam to effect evaporation. Feed flow rate was 19 L/h and each run lasted 1.5 days. Feed TDS levels ranged from 12 000 to 64 000 mg/L. Oil and grease concentrations ranged from 10 to 310 mg/L. Depending on the level of scaling components in the produced water, the evaporator was run in a seeded or unseeded mode of operation. Produced water recoveries ranged from 67% to 93%. Heat transfer coefficients observed ranged from 3650 to 4050Im2.K. No operational problems with respect to foaming and fouling were observed. A preliminary cost estimate, based on heat transfer design parameters obtained, indicated that the capital cost would be approximately $8.9 million (1986 Canadian dollars) for a plant treating 3800 m31d 0/ produced water. Estimated annual operating costs ranged from $1.2 to $1.9 million and were dependent on the produced water characteristics and the mode of operation of the evaporator. Introduction The production of heavy oil and bitumen by in situ methods using steam flooding Or steam stimulation generates large volumes of water called "produced water". The most attractive strategy from an environmental viewpoint to handle this water is to reuse it as feed water for steam generation. However, at some locations in Alberta and Saskatchewan, produced water contains very high levels of total dissolved solids (TDS), with concentrations > > 8000 mg/L(1). This water is unsuitable for reuse in oilfield steam generators unless it can be treated to reduce the TDS concentrations to approximately 8000 mg/L or less(2). As part of an ongoing program dealing with the characterization and treatment of produced water, Environment Canada's Wastewater Technology Centre (WTC) is currently evaluating the technologies available for removing TDS from produced water. This paper presents the results of the first two phases of this evaluation:a literature review which identified the most promising processes, based on technical and economic factors, anda laboratory-scale experimental evaluation of vapour compression evaporation-one of the most promising processes. Status of Produced Water Recycling In situ recovery of heavy oil-bitumen by steam stimulation (or steam flooding) can generate 2 to 20 times as much water as oil, although in most cases, this ratio is approximately four(3, 4). Hence, the volume of produced water generated at some of these sites can be substantial. Water requirements for steam generation at these facilities can also be considerable. The water required for this purpose is approximately 5 to 6 times the volume of oil produced(5).

Crystallization of Ice by Butane Gas Agitation in Freezing Desalination Process

Crystallization of Ice by Butane Gas Agitation in Freezing Desalination Process