Wall-scaling prevention in cryogenic external cooler of ammonium chloride solution by liquid-solid fluidization--颗粒学报PARTICUOLOGY

Zhu, Y., Ma, Y., & Liu, M. (2024). Wall-scaling prevention in cryogenic external cooler of ammonium chloride solution by liquid-solid fluidization. Particuology, 94, 120-132. https://doi.org/10.1016/j.partic.2024.07.016

Wall-scaling prevention in cryogenic external cooler of ammonium chloride solution by liquid-solid fluidization

Yusu Zhu^a, Yongli Ma^{a *}, Mingyan Liu^{a b}

a School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300350, China
b State Key Laboratory of Chemical Engineering (Tianjin University), Tianjin, 300350, China

10.1016/j.partic.2024.07.016

Volume 94, November 2024, Pages 120-132

Received 25 May 2024, Revised 10 July 2024, Accepted 23 July 2024, Available online 2 August 2024, Version of Record 13 August 2024.

E-mail: mayl@tju.edu.cn

Highlights

• Multiphase flow technology is firstly applied to anti-fouling of external cooler.

• A double-tube cooler with liquid-solid fluidization operation is developed.

• Heat transfer and anti-fouling performance are enhanced after adding particles.

Abstract

A double-tube cooler with liquid-solid circulating fluidization operation and corresponding parameter measuring system are developed to avoid fouling of inner walls of heat exchange tubes in a cryogenic temperature external cooler of ammonium chloride solution in soda ash production. Wall-scaling prevention performance of the cooling process is experimentally evaluated using convection and overall coefficients, enhancement factor, wall temperature and fouling resistance. Effects of different volume fractions of added particles, particle size, superficial liquid velocity, and cooling medium temperature on heat transfer are examined. Under present conditions, convection coefficient of liquid-solid flow inside the tube of external cooler is higher than that of the liquid phase flow, increased by 0.7–2.8 times, enhancing cooling performance obviously. Convection coefficient initially increases and then decreases as the volume fraction of added particles increases, reaching its maximum value at a volume fraction of 2.0%. The wall-scaling prevention effect of glass beads mainly depends on the volume fraction of added particles; optimal anti-fouling effects are achieved when adding particles at a volume fraction of 2.0%, regardless of changes in superficial liquid velocity or cooling medium temperature. This study lays a foundation for industrial applications of this new technique of fluidized bed external coolers.

Graphical abstract

Keywords

Fouling; Liquid-solid circulating fluidized bed; External cooler; Two-phase flow; Ammonium chloride

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