An effective modeling tool for studying erosion

doi:10.1016/j.wear.2011.01.016

Wear

Volume 270, Issues 9–10, 4 April 2011, Pages 598-605

https://doi.org/10.1016/j.wear.2011.01.016 Get rights and content

Abstract

Visual erosion examples based on that occurred in the minerals and oil and gas industries are illustrated by a paint modeling technique. The visual paint patterns were used to illustrate erosion damage “hot spots”. This provided an insight into the underlining fluid dynamics process involved with erosion damages. This insight allows design changes to be made to reduce erosion, illustrated by examples in this paper. The patterns of erosion damages on paints were found to be similar to that occurred with metal materials. This was supported by a similarity in measured erosion angular erosion distribution with cylindrical samples. Error analysis suggested that spatial variations in velocity across a material surface accounted for most of the error in the paint modeling technique.

Due to its low cost and rapidity, the technique is particularly suitable for developing and optimizing the design of flow geometries to reduce erosion, without the need to change the materials used.

Research highlights

► Many practical erosion case examples presented. ► Paint modelling applications illustrated, showing underlining mechanisms, and solution success. ► New data to show and consolidate knowledge on the paint erosion behaviour, in comparison with metal data. ► Analysis equations on the paint modelling error provided, for the first time. ► Finally, this is paper summarizing the extensive experience, success story at CSIRO, Australia on this topic, serving the minerals processing industry.

Introduction

Particulate erosion on material surfaces is common in many process industries, particularly in the minerals processing industry. To reduce erosion due to solid particle impact on the surfaces of materials in multiphase flow equipment, it is general practice to use wear-resistant materials or coatings/surface hardening treatments. This paper focuses on research aimed at reducing the surface erosion of materials through flow geometry modification, without changing the materials used or their properties. As erosion rate is a function of particle velocity and particle impingement angle [1], [2], [3], [4], [5] for any given material and physical properties of particles, this fluid dynamics-based approach can be effective for erosion reduction.

Erosion is often found to be unevenly distributed, and localized deep material loss or holing can lead to functional failure, even if most of the equipment remains undamaged. Fig. 1 shows typical examples of equipment erosion experienced in the minerals industry. It is reasoned that the geometry of an equipment can be modified to alter the flow field so that erosion is more evenly distributed, thereby reducing local maximum erosion rates and thus extending the functional life of equipment.

To achieve erosion reduction via a fluid-dynamics approach, it is essential to model or simulate changes in both erosion rate and distribution as a function of any geometrical modifications. To this end, a computational fluid dynamics (CFD) erosion modeling technique has been developed [6] that incorporates experimentally measured erosion data for cylinders in-pipe flow. However, it is clear from our work thus far that it remains a major challenge to reliably predict erosion patterns via CFD alone, particularly for highly complex multiphase flows such as those with time-dependent vortices, and therefore physical experiments to assess any new design concept are still required to validate CFD predictions.

Materials are often characterized as either ductile or brittle, according to their differing erosion rate versus angle of attack curves [3]. For ductile materials, the erosion rate reaches a maximum value at impact angles of 10–30° (defined as the acute angle between particle impingement direction and material surface), whereas hard, brittle materials experience maximum wear at greater impact angles. For example, the maximum erosion rate of a brittle alumina-based ceramic material is in the range of 70–90°.

Erosion of metals is the major problem addressed by this paper, as metals are widely used in the mineral processing industry. Metals such as mild steels, aluminum and titanium often exhibit ductile or mixed ductile/brittle behavior [1]. Thus it is reasonable to consider using paint as a model material for visualizing the erosions on metals, as paint exhibits similar ductile behavior [7].

Wu et al. [8] and Noui-Mehidi et al. [9] have shown the feasibility of using the multilayer paint technique to produce accelerated and highly visible erosion damage in various flow geometries, to assist in the development of improved geometrical designs that minimize erosion. This paper expands on these previous results, and provides a summary of the basic technical procedures and an error assessment of the paint modeling technique, as well as further examples of its use in developing improved designs.

The objective of this paper is to present erosion solution cases, developed from applying the paint modeling technical through laboratory or site testing, with validation by error analysis and cylindrical sample measurements.

Section snippets

Erosion test rigs

Two experimental flow loops were set up, as shown schematically in Fig. 2, Fig. 3. The slurry flow test loop (Fig. 2), consisted of a 3000-L agitated slurry holding tank, a Warman 3 × 2 slurry pump, an Emerson magnetic flowmeter. Typically silica sand (Garfield sand) of d₅₀ = ∼200 μm were used as erodent particles. Tap water was used as the liquid phase. A solid concentration of 7% (w/w) was used in the tests. Sand/water slurries were recirculated at typical velocity range of 0–10 m/s. The test

Validating paint erosion modeling technique

Fig. 4(a) shows the results of a test on a rotating cylindrical rod placed horizontally in a slurry pot (Fig. 4(b)). It can be seen that a double-wedge erosion pattern developed along the rod surface. Note that the angular location of the axes (approximately 20–30° from the frontal normal face) of the double-wedge corresponds to where the angles of particle impingement produced peak erosion. It can be estimated, based on CFD particle flow modeling by Lester et al. [6] that this corresponds to

Error analysis

Due originally to Finnie [3], an erosion model of the following form has been widely accepted in the literature: $E = k V^{n} f (a)$ where E is mass eroded divided by total mass of particles impinging on a surface; k is a constant that depends on material properties (e.g. hardness); V is particle impingement velocity; n is an empirical coefficient (n = 1.8–2.3 for ductile material, n = 2.0–4.0 for brittle materials); and α is the particle impingement angle (f(a) is a dimensionless function dependent on

Conclusion

This paper presents extensive case examples and solutions on erosion patterns developed on industrial equipments with assistance of a rapid and low-cost multilayer paint modeling technique. The technical was found suitable for visualizing the erosion distribution on material surfaces exposed to particulate-laden flows. An error analysis and validation of the technique via comparisons with other experimental techniques and full-scale equipment show that the technique is suitable for use in the

Acknowledgements

The authors are grateful for the support of CSIRO Minerals DU Flagship, Alcoa World Alumina, BHP Billiton/Worsley Alumina, Rio Tinto Alcan and Tyco Flow Control, who sponsored this work through the AMIRA International Collaborative Research Project P931 ‘Reduced Erosion in Multiphase Flow Equipment’. We also wish to acknowledge Huping Luo of Chevron for collaboration and support, and Lawrence Cheung of CSIRO for the artwork and photos.

References (11)

I.M. Hutchings
Wear by particulates
Chem. Eng. Sci.
(1987)
J.A.C. Humphrey
Fundamentals of fluid motion in erosion by solid particle impact
Int. J. Heat Fluid Flow
(1990)
I. Finnie
Erosion of surfaces by solid particles
Wear
(1960)
Y. Zhang et al.
Erosion of alumina ceramics by air- and water-suspended garnet particles
Wear
(2000)
L.J.W. Graham et al.
Quantification of erosion distributions in complex geometries
Wear
(2010)

There are more references available in the full text version of this article.

Cited by (19)

Multiphase slurry flow regimes and its pipeline transportation of underground backfill in metal mine: Mini review
2023, Construction and Building Materials
The underground cemented backfilling of tailings slurry in metal mines is an important guarantee for controlling goaf, reducing tailings storage, and ensuring mining safety. As a typical multiphase flow, the slurry and its pipeline flow transportation are important factors that affects mining efficiency and leads to poor pipeline wear. To better understand the flow regime and its pipeline transportation characteristics, this paper systemically reviews following aspects: 1) the non-full/full pipeline flow regimes, patterns, and key evaluating parameters (distribution of pressure drop, velocity, etc. of slurry flow); 2) the breakthroughs, findings and limitations by using the slurry rheology experimental (loop pipeline test, etc.), or undisturbed detections methods (electrical resistance tomography, magnetic resonance imaging, Micro-CT, etc.) of slurry pipeline transportation; 3) the computational fluid dynamic models and numerical simulations, and 4) the generating mechanism, major modes and its controlling methods of slurry pipeline wear and undesirable erosion are critically summarized. It conducts that the non-full pipeline transportation, slurry composition heterogeneity, coarse particles segregation/sedimentation, pipeline shapes and its layout, and even electrochemical corrosion caused by acidic/alkaline slurry could be key causes for the high resistance and poor effectiveness of slurry pipeline transportation. These discussions in this review paper will contribute to offering good supports to understand slurry pipeline flow behaviour and potential wearing controlling methods.
Effects of artificial impeller blade wear on bubble–particle interactions using CFD (k–ε and LES), PIV, and 3D printing
2022, Minerals Engineering
Wear reduces velocity and turbulence by reducing the volume of impeller blades; yet there is a lack of knowledge on flotation cells. Additionally, there is a lack of knowledge in the literature regarding the effect of blade wear on bubble–particle interactions. Hence, computational fluid dynamics simulations investigated artificial impeller blade wear of a laboratory–scale Denver cell. Simulations of chalcopyrite flotation showed that blade wear increased floatability of 10 μm particles by 1.4 %, but decreased that of 180 μm particles by 3.0 %. Accordingly, it is proposed that curved surfaces due to wear increased ε (volume–averaged ε [m²/s³]: no–wear 20.5 and wear 25.8), increasing collision of fine particles and detachment of coarser particles. These were supported by results from large eddy simulation and particle image velocimetry measurements using three–dimensional (3D) printed impellers. Finally, experimental results from flotation experiments using 3D printed impellers and 250–300 μm methylated quartz confirmed a floatability decrease (2.1 %–3.8 %) due to wear.
Numerical investigation of effects of inner cone on flow field, performance and erosion rate of cyclone separators
2018, Separation and Purification Technology
Gas cyclones have many industrial applications for separation of solids and liquids from gases. The geometry of the cyclone is the most influential parameter for its performance. This study investigates the effect of presence of an inner cone located at the bottom of the cyclone on the performance of the cyclone separator. Several CFD simulations in cyclones with inner cones with different diameters and heights were performed using the Reynolds stress turbulence model (RSM). The collection efficiency of the cyclone was studied using the Eulerian-Lagrangian approach. The results showed that the maximum tangential velocity is 1.6–1.7 times the inlet velocity. On the other hand, in the radial sections crossing the inner cone, the gradients of the axial and tangential velocities are zero. The maximum axial and tangential velocities occurred in the region between the top of the inner cone to the vortex finder. It was found that by increasing the inner cone height at constant diameter, the cyclone collection performance improves. An increase in the diameter of the inner cone, however, leads to a decrease in the cyclone performance. In overall, with an increase in the inner cone height and diameter, the pressure loss decreases. Finally, the erosion study was conducted using the Det Norske Veritas (DNV) erosion model. It was found that the value of coefficient of restitution affects the predicted erosion rate. In addition, the collection efficiency decreases when the erosion effect was included in the CFD model especially for higher velocities.
Laboratory modelling of erosion damage by vortices in slurry flow
2017, Hydrometallurgy
Erosion damage caused by suspended particles in slurries leads to production loss and on-going maintenance costs. Such damage is common in flow equipment used in slurry transport, including processing equipment in alumina refineries.
CSIRO has been conducting research under AMIRA P931 “Multiphase Flow Erosion” projects from 2006 to 2013, under sponsorship funding support from Alcoa, BHP Billiton, Rio Tinto Alcan, Vale and Pentair Valves (Tyco Flow). CSIRO has a continuing focus on building knowledge and methods to improve prediction of the service life of flow equipment under erosion conditions, and to develop strategies to reduce erosion through altered flow design.
Interestingly, none of the case studies requested by the industry partners involved simple impingement erosion or sliding bed erosion. The emphasis has been on solving erosion problems using the principles of the underlying multiphase fluid dynamics, which called for an in-depth treatment of non-uniform flows. Consequently the current study was very different from the usual treatment of erosion (which focuses on direct impingement simply because it is easier to model and measure) and instead addressed the much more common industrial problem of localised erosion.
By using fluid dynamics modelling, experimental visualisation and quantitative measurements of erosion scars, several fluid dynamic mechanisms have previously been identified as causing severe erosion attacks. These included erosion by vortices, by flashing and by various non-uniform flows. Observations of accelerated wear have shown that vortex erosion is present in many flow geometries critically important in sponsors' plants, e.g. pipe work around a valve, protrusions in a pipe and many conventional engineering designs. This paper focuses on vortex erosion in a variety of flow situations and examines the fluid dynamics and consequent erosion.
Experiments and CFD-based erosion modeling for gas-solids flow in cyclones
2017, Powder Technology
Citation Excerpt :
Table 3 shows the erosion models, their parameters and constants. The DNV [26] erosion model has been widely used in the literature [13,17,36,43–48] and it is also known as the general erosion model. The material constant, K, is dependent on the wall and particle properties [1,49].
In this study, CFD-based erosion modeling combined with experimental work was applied to a cyclone operating with Fluid Catalytic Cracking (FCC) particles as solid phase with 64 μm of diameter, and air at room temperature as gas phase. The inlet velocities ranged from 25 to 35 m/s and the solids loading ratios from 105 to 254 g of solid per cubic meter of gas (g/m³), which are typical values for a regime transition between dilute and dense phases. Experimental data for the erosion rate were obtained in a test facility using a cyclone comprised of gypsum to accelerate the erosion phenomenon and make it more prominent. Numerical simulation was performed using the Euler-Lagrange approach with the Reynolds stress model (RSM) for turbulence in the gas phase, with two-way coupling to take into account the gas-solid interaction, and two erosion models (DNV and Oka models). The experiments showed an increase in the erosion with the gas inlet velocity in the cyclone, notably at velocities of 30 and 35 m/s, and a decrease with the solids loading rate for the same velocities (approx. 20 and 40%, respectively). This decrease in the erosion rate is attributed to the cushioning effect promoted by inter-particle collisions. On the other hand, a comparison between the experimental data and numerical calculations conducted using the two erosion models was carried out and the results show satisfactory agreement for both models.
Erosive wear of filled vinylester composites in water and acidic media at elevated temperature
2017, Wear
Due to their good corrosion properties, fibre reinforced polymer composites are often used instead of metals for example in hydrometallurgical processes. However, the erosion performance of polymer composites is rather poor when compared to metals. This study focused on the effect of mineral fillers on the erosion performance of vinylester composites. The erosion rates were tested both in water and in acidic environments at high temperature. To improve the erosion performance of the filled composites in these environments, to increase the filler particle hardness was an effective method. Within similar filler materials, better adhesion to the matrix improved the erosion performance, regardless if it was achieved by adhesion promoters or better mechanical interlocking. The hardness of the matrix was found to be disadvantageous for filled composites, although for pure vinylesters higher hardness decreased erosion rate. At the high service temperature, softer matrix accommodated more deformations and better absorption of energy of the impacting erosive particles. Consequently, improved adherence of the filler particles into the matrix and slower erosion rate was observed.

View all citing articles on Scopus

View full text

An effective modeling tool for studying erosion

Abstract

Research highlights

Introduction

Section snippets

Erosion test rigs

Validating paint erosion modeling technique

Error analysis

Conclusion

Acknowledgements

Chem. Eng. Sci.

Int. J. Heat Fluid Flow

Wear

Wear

Wear