Freeze Desalination Process Research Articles

Oilfield Brine as a Source of Water and Valuable Raw Materials—Proof of Concept on a Laboratory Scale

Oilfield brine is the largest byproduct stream generated during the extraction of crude oil and natural gas and may be considered a resource for the production of potable water and valuable raw materials. The high salinity of such waters limits the application of typical membrane-based techniques. In most oilfields, waste cold energy from the process of the low-temperature separation of natural gas is available and may be used as a source of cold for the freezing desalination (FD) of brine. As a result of the FD process, two streams are obtained: partially desalinated water and concentrated brine. The partially desalinated water may be suitable for non-potable applications or as a feed for membrane desalination. The concentrated brine from the FD could be used as a feed for the recovery of selected chemicals. This paper focuses on verifying the above-described concept of the freezing desalination of oilfield brine on a laboratory scale. The brine from a Polish oilfield located in the Carpathian Foredeep was used as a feed. Four freezing–thawing stages were applied to obtain low-salinity water, which subsequently was treated by reverse osmosis. The obtained permeate meets the criteria recommended for irrigation and livestock watering. The concentrated brine enriched with iodine (48 mg/L) and lithium (14 mg/L) was subjected to recovery tests. Ion exchange resin Diaion NSA100 allowed us to recover 58% of iodine. Lithium recovery using Mn- and Ti-based sorbents varies from 52 to 93%.

Productivity Prediction for the Progressive Freeze Desalination Process Using Heat and Mass Transfer Modeling

AbstractPredicting the productivity of the freeze desalination process is of key importance. This paper describes an analytical method to predict the productivity for the progressive freeze desalination process utilizing the rectangular channel crystallizer design. The mass of ice produced during the process is considered a measure of productivity. The model was developed using heat and mass transfer modeling. The effect of coolant temperature (from −8 to −16 °C), liquid flow rate (4400–6000 mL min−1), and initial salt concentration of the liquid (1.5–7 wt%) on the mass of ice produced was investigated. The analytical results of the mass of ice produced were compared with the experimental data. A plausible match was found between the analytical and experimental results, with an error range between 6 % and 9 %. The model can predict the mass of ice produced for given values of the initial salt concentration of the liquid, initial mass of the liquid, salt concentration of thawed ice, liquid flow rate, and coolant temperature.

A gravity-induced desalination technology effectively improving the freshwater production efficiency of freeze desalination

Low desalination efficiency and water production efficiency limit the commercial application of freeze desalination (FD) technology. In this study, three freezing temperatures were set to carry out single-stage progressive freezing desalination of brackish water in southern Xinjiang, China. The ice were melted using conventional methods and gravity-induced desalination (GD), and the salt migration law during the icing and melting process was studied. The effect of GD technology on the improvement of the output of frozen desalinated produced water was quantitatively analyzed using scenario simulation. Experimental results showed that salts accumulated towards concentrated water during FD process. The ice total dissolved solids (TDS) increased with decreasing freezing temperature, which was linearly and positively correlated with the raw water TDS. GD efficiency was significantly affected by the salt concentration of ice crystals. In the first stage (the first 450 mL), ice-melt water was salt explosive dissolution, with salt drained mass accounted for more than 85% of the total salt mass. During GD process, exponential decay of ice-melt water TDS (TDSI) was observed with increasing ice-melt water amount. Through the simulation of the two exponential equation scenarios, it was found that Scenario II (mixed water TDSI as the target value) had significantly higher water yield and production rate than Scenario I (TDSI as the target value), with an increase of more than 23%. The algebraic relationship between TDSI of mixed water and the amount of ice-melt water was derived. GD technology can effectively improve the freshwater output efficiency of the FD process, which is manifested by the fact that the ice crystals of the FD process cannot produce freshwater using conventional melting. Scenario II can produce freshwater as high as 69.83% of the total amount of the GD ice-melt water. The GD technology performed increased multiplicatively in WPdv (decrease in water production) and WPRdv (decrease in water production rate) when the TDSI of the mixed water demanded by the user was low. When FD and GD are combined to desalinate salt water, lowering the freezing temperature can significantly increase the freshwater yield, breaking the limitation of freezing temperature for FD. Therefore, an automated, energy-saving freeze desalination-gravity desalination device capable of realizing the collection of the product water according to the users' needs was conceptualized. This study provides new ideas and algorithms for accurately assessing the efficiency of water production in the combined desalination of saltwater by FD and GD.

Performance analysis and multi-objective optimization of the offshore renewable energy powered integrated energy supply system

Offshore renewable energy technologies offer a promising prospect for energy supply on offshore islands. However, traditional wind and solar energy sources exhibit strong variability and cannot fully meet the energy demands of users. At the same time, the energy demand of users also has great volatility, so the supply side and demand side of energy cannot match well. Existing renewable energy systems often utilize thermal power generation as a stabilizer for the system, however, this approach is difficult to apply in offshore conditions. This study introduces an innovative multi-energy complementary system that integrates seawater freezing desalination, refrigeration and power-hydrogen-ammonia co-generation, driven by ocean thermal energy, wind energy, and solar energy. The system incorporates the use of a new developed small temperature difference ejector refrigeration cycle to stabilize the entire system and produce low-temperature refrigeration. By utilizing the seawater freezing desalination process to minimize energy conversion losses and balancing fluctuations in multiple energy inputs and user demands through ammonia-hydrogen co-production, this approach effectively minimizes energy waste, enhances energy utilization efficiency, and reduces excess power handling. The purpose is to optimize the configuration of the energy conversion subsystem within the multi-energy complementary multi-effect co-generation system, thus improving the economic feasibility and reliability of the system in providing energy and freshwater supply, ultimately achieving the goals of reducing energy waste, achieving high conversion efficiency, and minimizing equipment investment. This study conducts an economic analysis and optimization of a multi-energy complementary system, utilizing a 2 MW-level OTEC subsystem as a stabilizer. Both equipment investment and operating costs are considered in the economy analysis. The carbon emission reduction performance of this system is evaluated. The performance optimization results show that the system achieves an energy storage efficiency of 65.96 %, and the curtailment rate of this system is only 3.99 %, significantly lower than the 10 % curtailment rate in traditional system. The proposed system can meet the annual electricity demand of 33.09 million kWh, as well as a cooling demand of 546.81 million kWh. Under typical conditions, the ocean thermal energy conversion cycle exhibits a power efficiency of 0.85 % and a refrigeration efficiency of 29.10 %. Meanwhile, it annually reduces CO2 emissions by 2.54 million tons, demonstrating significant environmental benefits. This proposed system is mainly applicable to tropical waters with high surface water temperatures and depths of no less than 600 m worldwide. This study offers a practical and economically beneficial solution for energy and freshwater supply on offshore islands.

Towards spatiotemporal-resolved spectroscopic measurement of freezing desalination using femtosecond laser filaments

Freezing desalination can produce freshwater from seawater or industrial wastewater by ice crystallization with low energy consumption and less corrosion, and is promising for alleviating current stress on the world's water supply. However, the salt rejection dynamics during the freezing process is less understood due to the lack of real-time, high spatiotemporal-resolved detection methods. Here we present a proof-of-principle, quantitative, and simultaneous multi-salt detection approach for the measurement of salt rejection dynamics in salt-contaminated water at the ppm level using an ultrashort-pulsed femtosecond laser propagating in the filamentation regime. We show that this approach of filament-induced plasma spectroscopy possesses the abilities for both monitoring the change of salt concentration in the remaining unfrozen water during the freezing process and imaging the spatial concentration distributions of metal contaminants on the resultant ice surface. With this approach, we find that the initial salt concentration in water plays an essential role in the efficiency of the freezing desalination process, which shows a metal-species-dependent characteristic. Our results pave the way towards real-time, online, and high spatiotemporal-resolved detection of salt rejection dynamics of freezing desalination by ultrashort-pulsed lasers.

Experimental investigation of freezing desalination using silicon oil for ice production

Because of its potential benefits in lowering process energy consumption, freezing desalination as a seawater desalination method has attracted a lot of attention. However, significant mass loss caused by extensive washing is a fundamental problem preventing the development of freezing desalination technologies. For freezing desalination technology to be widely adopted, the washing process must be eliminated. In this study, a fluid-layer-based method for separating ice is introduced. The density differences between the generated ice and the silicon oil intermediate fluid layer facilitate the separation of the product water without the need of conventional crushing or washing processes. The aim of this work is to study the feasibility and applicability of using silicon oil as an intermediary fluid layer in ice separation during the freezing desalination process. The outcomes show promise for a feasible freezing desalination technique utilizing silicon oil as an intermediate separation layer. It was also observed that as feed salinity decreases, the desalination rate increases. For instance, the distillation rate is 50.89 % and 67.3 % at an initial feed salinity equal 45,000 and 10,000 ppm, respectively. Overall, the initial feed salinity and COP are found to have an impact on specific energy usage.

Thermodynamic assessment of a new PTC operated polygeneration system for fresh water, cooling, electricity and hydrogen production for a residential community

The current study aims to design a new parabolic trough collector (PTC) operated polygeneration system to produce freshwater, hydrogen, cooling, and electricity in a residential society. Dowtherm A (a heat transfer fluid) is used to transfer the heat from PTC to the Organic Rankine Cycle, which is used to produce electrical power. The produced electrical power is utilized in three different ways, namely, to run the home appliances, to produce hydrogen (via water electrolysis), and to produce cooling (through a vapor compression cycle). The cooling produced by the vapor compression system is utilized to preserve the food, milk, and to operate the freezing desalination process. Effects of several factors, such as direct normal irradiance, evaporator temperature, and seawater inlet temperature, have been analyzed on the overall system behavior. Thermodynamic study results show that for a PTC area of 2000 m2, an electrical output obtained is 72 kW, the cooling rate is 112 kW, and the mass flow rate of fresh water produced is 18.4 l/day and 10.8 kg/day of hydrogen for mean solar irradiation of 700 W/m2. The energy efficiency of the system is found to be 17.5%, and the exergy efficiency of the system is around 10.9%.

Design of a multistage hybrid desalination process for brine management and maximum water recovery.

Hypersaline brine production from desalination plants causes huge environmental stress due to the untenable conventional discharge strategies. Particularly, brine production is expected to drastically increase in the coming few decades due to the increasing desalination capacity in attempts of forestalling water scarcity. Thereby, zero liquid discharge (ZLD) is a worth-considering solution for strategic brine management. ZLD or minimal liquid discharge (MLD) systems provide maximum water recovery with least or zero liquid waste generation and valuable salt production. In this work, a theoretical design of ZLD/MLD system is proposed for reverse osmosis (RO) brine management. Different scenarios are investigated utilizing multistage freeze desalination (FD) and its hybridization with multistage direct contact membrane distillation (DCMD), and eutectic freeze crystallization (EFC) technologies. The design is based on the experimental assessment of the indirect FD process at different feed salinities, i.e., 2g/L to 155g/L. FD experiments showed that ice quality is reduced at greater crystallinity levels and initial concentration. Moreover, a computational fluid dynamics (CFD) model is utilized to assess the performance of DCMD. A single DCMD module could produce 53kg/(m2.h) of pure water operating with 69% thermal efficiency. Eventually, water recovery, water quality, as well as specific energy consumption (SEC) are evaluated for the whole system. Based on different configurations of the hybrid ZLD system, the proposed design can achieve water recovery between 40 and 93% with SEC range of 28-114 kWh/m3. Results also showed that the produced water quality exceeds drinkable water standards ( 500mg/L). This work has provided great evidence in the practicality of ZLD/MLD systems for sustainable brine management.

Calorimetry based temperature and specific enthalpy measurements associated with ice-water phase change in saline systems for freeze desalination

Ice based Freeze Desalination (FD) offers a potential alternative to recover fresh water from seawater. However, ice-water phase change data in saline water in the range of practical interest and of importance in FD process design is limited. In this study, reliable and accurate measurements related to ice–water phase change temperatures and specific enthalpies have been carried out using a Micro–Differential Scanning Calorimeter (μ–DSC). The runs were carried out using pure water, synthetic salt water (0.5 to 5 wt% NaCl) and seawater. The NaCl concentrations covered a range of values of practical interest in FD. In the case of pure water, the specific enthalpy value was found to be in excellent agreement to within ± 0.51% of the value reported in literature, i.e. 333 J/g which validated the experimental protocols adopted in this study. Phase change temperature and specific enthalpy values for salt water were found to decrease with an increase in salt concentration. Test runs conducted subsequently using seawater were consistent with the results obtained from the synthetic salt water test runs. The experimental protocol adopted and data presented in this study can be used in design of an ice based FD process.

Heat and mass transfer analysis and optimization of freeze desalination utilizing cold energy of LNG leaving a power generation cycle

Freeze desalination (FD) works upon the separation of impurities from pure water during ice crystals formation. The required cold source could be supplied by the cold energy of liquefied natural gas (LNG). In the current study, freeze desalination of seawater is explored by directly exploiting the cold energy of LNG within an appropriate range of temperature after producing work in a power generation cycle. A detailed discussion has been given on the inlet temperature of LNG to the FD unit for the first time. The direct utilization has the privilege of eliminating the addition of a secondary refrigerant and its refrigeration cycle to the FD process. A multi-objective optimization is conducted to specify the optimal conditions to acquire the highest ice mass with lowest salinity. Results show that decreasing LNG inlet temperature from −10 to −60 °C improves the ice mass production from 60.9 to 977.6 g, whereas diminishing its quality by 90%. Also, increasing Reynolds number of LNG from 4000 to 32,000 leads to the production of 492 g more ice and increment of ice salinity from 1.22 to 1.56%. Finally, conducting multi-stage freezing reveals that for Reynolds numbers below 16,000, potable water is achievable after three-stage desalination.

Ice crystal growth in the freezing desalination process of binary water-NaCl system

In this study, ice crystal growth in the freezing desalination process of binary water-NaCl system is investigated. The phase field method is used to conduct simulation and predict dendrite growth behaviour during the crystallization of sea ice. An experimental setup focusing on the directional crystallization of binary water-NaCl solutions on the horizontal wall is established to verify the e theoretical model. The results show that the crystal with single nucleus obtains obvious six-fold symmetry, while in the competitive crystallization of multiple crystal nuclei, spindle growth is inhibited. Brine channels and salt cells are formed in the directional crystallization, seawater consists of higher Mg2+and SO42− get more difficult in freezing desalination. The degree of subcooling significantly affects the salt cell concentration at the roots, the solid phase ratio, and the height of the planar crystal, while the heat flux significantly affects dendrite growth rate. The experimental average tip growth rate is 9.15 × 10−5 m/s, and the experimental average tip radius is 5.16 × 10−6 m. Peclet number of both simulation and experiment have the same order of magnitudes, with 0.1–0.2 and 0.3–0.6, respectively, which suggests the three-field coupling model established is reasonable for desalination simulation.

Desalination of seawater by spray freezing in a natural draft tower

The freeze-melting process can be a viable method for the purposes of desalination because of its low energy consumption, ignorable corrosion issues, and without huge pressure or membrane replacement work. Large contact area for heat and mass transfer per unit mass of water between the water and air and low heat resistance results in higher energy efficiency during spray freezing desalination process compared to other freezing desalination methods. A 200 m high desalination tower was proposed in this paper that could generate 27.7 kg/s fresh water in the form of water droplets with 2 mm diameter at an atmospheric temperature of −26°C. This research has founded that the natural convective airflow induced by the heat released by the warm water in the freezing process could generate through the wind turbine mounted in this system approximately one-third of the energy consumed by the water pump of the system. This free energy has never been studied in previous research. The power consumption required to produce 1 m3 fresh water in this system is approximately 1.07 kWh. Compared to traditional desalination methods, the power consumption of our new spray freezing desalination system is much lower than previous systems with the same mass flow rate of fresh water. Only 375.4 kJ cold energy to produce one-kilogram fresh water. Thus, this spray freezing desalination system could be employed in desalination industry if free cold energy (e.g. from the cold atmosphere or the regasification process of LNG) and seawater resources are available.

Cryogenic Energy for Indirect Freeze Desalination—Numerical and Experimental Investigation

Renewed interest in freeze desalination has emerged due to its advantages over other desalination technologies. A major advantage of the freeze desalination process over evaporative methods is its lower energy consumption (latent heat of freezing is 333.5 kJ/kg and latent heat of evaporation is 2256.7 kJ/kg). Cryogenic fluids like LN2/LAir are emerging as an effective energy storage medium to maximise utilisation of intermittent renewable energy sources. The recovery of this stored cold energy has the potential to be used for freeze desalination. Computational Fluid Dynamics (CFD) modelling was developed to simulate the evaporation of liquid nitrogen to simultaneously conduct freeze desalination to investigate the feasibility of using cryogenic energy for freeze desalination. This integrated CFD model was validated using experimental heat exchanger test facility constructed, to evaporate liquid nitrogen to supply the cooling required for freezing. Parametric study on the LN2 flow rate to observe the volume of ice obtained was also examined using CFD, where increasing the velocity of LN2 by 6 times, increased the volume of ice obtained by 4.3 times. A number of freezing stages were required in order to reduce the ice salinity from 1.5% down to 0.1% as regarded by the World Health Organisation (WHO) as safe to drink. In the cryogenic desalination test rig, approximately 1.35 L of liquid nitrogen was required to reduce the ice salinity from 1.5% to less than 0.1%. Furthermore, the above results illustrate the potential of using the cold energy of cryogenic fluids such as Liquified Natural Gas (LNG) and LN2/LAir for freeze desalination applications as most cold energy during LNG regasification has been unexploited today.

Optimization of simplified freeze desalination with surface scraped freeze crystallizer for producing irrigation water without seeding

Freeze desalination (FD) is a promising desalination technology for overcoming the drawbacks of conventional desalination methods. However, the slow production rate and low productivity of FD have hindered its commercialization. This research presents the challenges confronting current FD processes and proposes a new simplified FD, which employs self-nucleation using the surface scraped freeze crystallizer unit. With the simplified FD process, it was found that optimal conditions are 45 or 50% of the washing water percentage at an operational temperature of −12 °C, and 50% of the washing water percentage at an operational temperature of −16 °C for producing irrigation water (<2000 mg/L in terms of total dissolved solids). Furthermore, we applied the cyclic system, which was the reuse of the mixture of brine and washing waste, on the FD process. The results showed that the use of 45% of the washing water percentage for the 1st cycle raw ice products and 50% for the 2nd cycle at an operational temperature of −12 °C enabled the achievement of >40% in the final productivity. Accordingly, this research introduced the feasibility of the FD process without the use of any additional seeding process.

Techno-economic analysis of seawater freezing desalination using liquefied natural gas

This work aims to propose a detailed mathematical model to evaluate the feasibility of a seawater desalination process that is based on the cold energy provided by the regasification of the liquefied natural gas (LNG). Detailed material and energy balance models as well as the basic models for calculation of thermodynamic properties are presented for subsequent Seawater Freezing Desalination (SFD) process optimisation. Current analysis results reveal that the process is affected by multiple variables that need further optimisation. With the assumption of 50 % ice production rate in the ice generator, the SFD system could be able to produce 400 Mt/y of freshwater over the world.

Numerical investigation of indirect freeze desalination using an ice maker machine

To overcome the water shortage problem, sea water desalination is a prospective answer in order to cater for the escalating demand for fresh water. Freeze desalination is where the freezing of sea water permits the separation of salts from the water in order to produce potable water. The ice formed is of pure water as the ice crystal lattice prevents the inclusion of any salts. The lower energy usage of freeze desalination in comparison to other desalination processes is the key advantage; as the latent heat of fusion (333.5 kJ/kg) is about 1/7th that of the latent heat of vaporisation (2256.7 kJ/kg). CFD ANSYS fluent software has been used to simulate the freeze desalination process; results were compared with experimental tests showing a maximum deviation of 0.93% for the temperature change during the ice forming process and the percentage errors obtained for the salinities of ice and brine were 15% and 10.5% respectively. From parametric analysis study, results showed that, as the freezing temperature reduces, the volume of the generated ice block increases, where at 225 K freeze temperature, 5 times more ice was produced compared to that at 257.15 K, but with a high salinity level of 3.02%. Results also showed that the lowest average salinity achieved was 0.5% at an ice layer thickness of around 4 mm using a freezing temperature of 245 K. This is higher than the 0.1% salinity level recommended by the World Health Organization (WHO) standards as safe to drink water. Therefore, a second stage freezing process was applied to this 0.5% saline water to produce the required salinity level. Results showed that the achieved average ice salinity in the second stage of freezing process was below 0.05% which is regarded as good quality drinking water; also freezing at 225 K temperature produced the largest pure ice volume. These results highlight the potential of using freeze desalination to produce drinking water.

Computational fluid dynamics investigation on indirect contact freeze desalination

With the global increasing demand for fresh water, desalination of sea water is regarded as a potential solution to provide for potable water shortages. Freeze desalination offers the advantage of lower energy consumption, since the latent heat of fusion is approximately one-seventh that of the latent heat of vaporisation. CFD is a powerful technique that enables the effective analysis and investigation of thermodynamic processes. ANSYS Fluent software was used to develop a 3D CFD model of the freeze desalination process using species transport, solidification/melting and energy modules. This CFD model was then validated by conducting experiments using salt water of 35g/L concentration in a container. A freezing temperature of 260K was applied at the container base using a Peltier device for 30min. The measured ice salinities from the experimental work and those predicted from CFD simulations were compared showing a percentage deviation of 2.10. The salt water temperatures were also compared from the experimental work and CFD simulations, giving an average deviation of ±0.495K. The developed CFD model has been used to carry out parametric analysis to predict the effects of freezing temperature, solution salinity and the direction of freezing; on the freezing time, ice production and its salinity.

Indirect contact freeze water desalination for an ice maker machine – CFD simulation

To offer for potable water shortages, sea water desalination is a potential solution for the global rising demand for fresh water. The latent heat of fusion is about one-seventh the latent heat of vaporisation, thus indicating the benefit of lower energy consumption for the freeze desalination process. Limited literature is reported on computational fluid dynamics (CFD) on freeze desalination. Therefore, analysing and investigating thermodynamic processes are easily conducted by the powerful tool of CFD. A single unit of ice formation in an ice maker machine was modelled using ANSYS Fluent software three-dimensionally. Energy, species transport and solidification/melting modules were used in building the CFD model. Parametric analysis was conducted using the established CFD model to predict the effects of freezing temperature and the geometry of the ice maker machine; on ice production and the freezing time. Lower freezing temperatures allowed more ice production and faster freezing. Increasing the diameter and the length of the freezing tube enabled more ice to be produced.

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.