# Ice growth on the cooling surface in a jacketed and stirred eutectic freeze crystallizer of aqueous Na_{2}SO_{4} solutions

Tutkimustuotos: Lehtiartikkeli

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**Ice growth on the cooling surface in a jacketed and stirred eutectic freeze crystallizer of aqueous Na _{2}SO_{4} solutions.** / Hasan, Mehdi; Filimonov, Roman; Chivavava, Jemitias; Sorvari, Joonas; Louhi-Kultanen, Marjatta; Lewis, Alison Emslie.

Tutkimustuotos: Lehtiartikkeli

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_{2}SO

_{4}solutions',

*Separation and Purification Technology*, Vuosikerta. 175, Sivut 512-526. https://doi.org/10.1016/j.seppur.2016.10.014

### APA

_{2}SO

_{4}solutions.

*Separation and Purification Technology*,

*175*, 512-526. https://doi.org/10.1016/j.seppur.2016.10.014

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_{2}SO

_{4}solutions. Separation and Purification Technology. 2017 maalis 24;175:512-526. https://doi.org/10.1016/j.seppur.2016.10.014

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TY - JOUR

T1 - Ice growth on the cooling surface in a jacketed and stirred eutectic freeze crystallizer of aqueous Na2SO4 solutions

AU - Hasan, Mehdi

AU - Filimonov, Roman

AU - Chivavava, Jemitias

AU - Sorvari, Joonas

AU - Louhi-Kultanen, Marjatta

AU - Lewis, Alison Emslie

PY - 2017/3/24

Y1 - 2017/3/24

N2 - Eutectic freeze crystallization (EFC) has been pronounced a promising separation technique to recover ice and salt simultaneously in an energy-efficient manner. Alike other freeze concentration methods, the accumulation of an ice layer, commonly known as ice-scaling, on the heat exchanger surface during operation thwarts the commercial application of EFC as the advantage of low energy requirement is outstripped by high investment cost, scaling up and operational complexities associated with the use of a scraper blade to remove the ice-scaling. Therefore, the aim of this research work is to investigate the ice-scaling phenomenon on a subcooled heat exchanger surface in the absence of mechanical scrapping. For a continuous EFC system, the influence of temperature driving force (ΔT) and the degree of agitation on the onset/induction time (tind) of ice-scaling are considered while keeping the other parameters, e.g., solution concentration (4 wt% Na2SO4 (aq) solution), the level of initial undercooling (0.28 °C) and the residence time (30 min) constant. The experimental results show that at a certain level of agitation, tind is inverse proportional to ΔT. At a low level of ΔT (i.e., <2.0 °C), the effect of the degree of agitation on tind declines. Contrary to this, at a high level of ΔT (>6.0 °C), the effect of the degree of agitation on tind becomes substantial. At the eutectic condition, the heat transfer coefficient of the solution (hsol) in the crystallizer prevails over that of mass transfer (kl). In the experimental setup, the overall heat transfer coefficient for a jacketed vessel type crystallizer is restricted by the heat transfer coefficient of the jacket side coolant (hj). The power number (Np) and pumping number (Nq) for a two-blade paddle type impeller and a crystallizer of specific dimensions and orientation are estimated by means of computational fluid dynamics (CFD) modeling and are used to calculate the specific power input (ε) and impeller pumping capacity (Q) at different levels of agitation. Furthermore, CFD simulations of heat transfer from the coolant to the bulk solution are performed to investigate the effect of the agitation level on solution cooling in the non-crystallizing condition.

AB - Eutectic freeze crystallization (EFC) has been pronounced a promising separation technique to recover ice and salt simultaneously in an energy-efficient manner. Alike other freeze concentration methods, the accumulation of an ice layer, commonly known as ice-scaling, on the heat exchanger surface during operation thwarts the commercial application of EFC as the advantage of low energy requirement is outstripped by high investment cost, scaling up and operational complexities associated with the use of a scraper blade to remove the ice-scaling. Therefore, the aim of this research work is to investigate the ice-scaling phenomenon on a subcooled heat exchanger surface in the absence of mechanical scrapping. For a continuous EFC system, the influence of temperature driving force (ΔT) and the degree of agitation on the onset/induction time (tind) of ice-scaling are considered while keeping the other parameters, e.g., solution concentration (4 wt% Na2SO4 (aq) solution), the level of initial undercooling (0.28 °C) and the residence time (30 min) constant. The experimental results show that at a certain level of agitation, tind is inverse proportional to ΔT. At a low level of ΔT (i.e., <2.0 °C), the effect of the degree of agitation on tind declines. Contrary to this, at a high level of ΔT (>6.0 °C), the effect of the degree of agitation on tind becomes substantial. At the eutectic condition, the heat transfer coefficient of the solution (hsol) in the crystallizer prevails over that of mass transfer (kl). In the experimental setup, the overall heat transfer coefficient for a jacketed vessel type crystallizer is restricted by the heat transfer coefficient of the jacket side coolant (hj). The power number (Np) and pumping number (Nq) for a two-blade paddle type impeller and a crystallizer of specific dimensions and orientation are estimated by means of computational fluid dynamics (CFD) modeling and are used to calculate the specific power input (ε) and impeller pumping capacity (Q) at different levels of agitation. Furthermore, CFD simulations of heat transfer from the coolant to the bulk solution are performed to investigate the effect of the agitation level on solution cooling in the non-crystallizing condition.

KW - CFD

KW - Eutectic point

KW - Freeze crystallization

KW - Ice-scaling

KW - Non-scraped and non-baffled crystallizer

UR - http://www.scopus.com/inward/record.url?scp=85006823130&partnerID=8YFLogxK

U2 - 10.1016/j.seppur.2016.10.014

DO - 10.1016/j.seppur.2016.10.014

M3 - Article

VL - 175

SP - 512

EP - 526

JO - Separation and Purification Technology

JF - Separation and Purification Technology

SN - 1383-5866

ER -

ID: 10770057