Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Measurement of Ore Concentration in Multilayer Flexible Pipe Based on Ultrasonic TechniqueMengran Wei1),2),

Yijun Shen 2),*

1) School of Information and Communication Engineering, Hainan University，Haikou, China
2) State Key Laboratory of Marine Resources Utilization in South China Sea, Hainan University, Haikou, China

can measure high concentration suspensions as well as various particle
size concentrations, and the ultrasonic system is simple and stable andcan provide real-time measurement information, and in general,
ultrasonic techniques are very suitable for two-phase flow measurements(Murai et al., 2010).

ABSTRACTUltrasonic-based particle measurement is developing rapidly, but noresearch has been conducted on the measurement of ore particles insidemultilayer flexible pipes. In this paper, based on theoretical analysis andsimulation, the measurement of ore particles inside multilayer flexible
pipes is investigated. Based on various attenuation models, the ECAH
model, UA model, HT model and BLBL model are compared, and theultrasonic attenuation mechanisms at different frequencies, particle sizes
and concentrations are analyzed. The multilayer model was established
by COMSOL Multiphysics to obtain the attenuation coefficients ofultrasonic waves in multilayer pipes, and the particle size andconcentration of ore particles were obtained by inversion of the particle
size using the regularization method. The results show that the BLBL
model is applicable to the inversion of the particle size and concentrationof ore particles by ultrasonic attenuation method.

Ultrasonic method is to install the transmitting transducer and receiving
transducer on both sides of the object to be measured, due to the different
attenuation coefficients of ultrasonic waves at different concentrations,according to the different attenuation coefficients can calculate theconcentration and particle size information of the particles in thesuspension to be measured. The classic EACH model (Epstein, Carhart,Allegra and Hawley's model) is a milestone in ultrasonic propagation
research. This is a theoretical model proposed by Epstein to describe theinteraction between ultrasonic waves and spherical particles, which not
only takes into account the viscosity of the liquid medium and the elastic
effect of the solid, but also considers the effect of thermal conduction.
Later, for this theoretical model, Epstein and Carhart jointly derived adetailed theoretical solution and used it to illustrate the important effectsof viscosity and thermal conduction in the process of acoustic attenuation(Epstein et al., 1953). This model was further developed by Allegra andHawley based on the work of Epstein and Carhart by considering theabsorption and scattering effects of solid particles on acoustic waves, andfinally the ECAH model was developed (Allegra et al., 1972). Since theECAH model considers the interaction between individual sphericalparticles and ultrasonic waves, the model is only applicable to solutions
with low concentrations, and when the solution concentration isrelatively high, the calculated results have large errors with thetheoretical values. Urick and Ament established a coupled model
considering only the effect of viscous action on the decay process, andverified this model through mercury-in-water and bromoform-in-water
experiments with non-uniform particle sizes. (Urick et al., 1949). The
HT model is a viscous resistance equation proposed by Harker andTemple based on hydrodynamic analysis of the mass and energy
conservation in the flow process of liquid-solid two-phase flow,
combined with the study of viscous force, so this model mainly considers
the viscous decay pair The effect of ultrasound (Harker et al., 1988). The
BLBL model ignores thermal and viscous losses, and considers that

KEY WORDS: Particle size inversion; Concentration measurement;
BLBL model; Ultrasonic attenuation

INTRODUCTION
Deep-sea mineral resources are abundant and have high development
value. Hydraulic lifting is the most practical and potential way of ore
transportation at present. In the transmission of ore in multi-layer flexible
pipelines, real-time monitoring of ore particle concentration is one of thetechnologies that need to be solved in the design of deep-sea mining
systems. Typical phase holdup measurement methods include: OpticalTechnique, Conductivity Technique, X-ray Technique, etc. However,each of these methods has its own drawbacks, for example, optical-based
methods require fluid transparency, conductivity-based methods require
the measured object to be magnetic, and x-ray technology-based
methods are not only expensive but also harmful to the environment andhuman body (Chaouki et al., 1997). Compared to the above methods,
ultrasonic methods have the advantages of being more penetrating, noninvasive, can provide real-time information, and have a widemeasurement range (Povey, 2000). This means that ultrasonic techniques

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