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Materials Selection in the Oilsands Industry
Based on Materials Degradation Mechanisms
a report by
Juan F Flores
1
and Anne Neville
2
1. Marie Curie Fellow; 2. Director, Institute of Engineering Thermofluids, Surfaces and Interfaces (iETSI), University of Leeds
Containing nearly 180 billion barrels of oil, the oilsands deposits in University of Leeds in the UK, Syncrude Ltd Research Laboratories in
Engineering & Construction
Northern Alberta in Canada are among the world’s largest Canada, the National Research Council of Canada (NRC) and the
hydrocarbon reservoirs and have positioned Canadian oil reserves as Alberta Research Council (ARC), among others.
5–9
Surface engineering
the second biggest in the world, behind Saudi Arabia. The current methods improve the materials and equipment performance and make
production of oil from oilsands is approximately 1.32 million barrels the oilsands extraction process economically viable. The purpose of this
per day and is likely to reach about 6 million barrels per day by article is to briefly describe a materials selection methodology based on
2020.
1
Oilsands are mainly composed of quartz sand, silt and clay, the understanding of the degradation mechanisms in the oilsands
water and bitumen, which occupies the pore spaces between the industry and to discuss the application of alternative materials based on
grains. The bitumen is extracted from the ground using two major surface engineering techniques.
techniques: mining operation and in situ thermal recovery. In 2007,
approximately 59% of oilsands production was obtained from open Degradation of Materials in the Mining Process
pits, with the rest through in situ techniques.
1
The oilsands extraction process involves five steps: mining operation,
crushing and separation process, hydrotransport and conditioning,
In mining operations, the tar sand is dug using electric or hydraulic bitumen separation and tailings transportation.
5
In each process the wear
shovels in an open-pit facility and transported on trucks to crushers, mechanisms are intimately related to the ore’s physical and mechanical
where the rocks and big particles are broken apart. After mining, the properties (size, hardness and abrasivity), mechanical interactions between
extracted material is combined with warm water to create a slurry, particles and surfaces (applied forces, angles and impinging velocities) and
which is then transported to the separation facilities using centrifugal corrosion effects (temperature, dissolved oxygen, solvents and pH). Figure
pumps and pipelines.
1
The materials currently employed in the oilsands 1 is a schematic representation of the oilsands extraction process and
industry are hardened carbon steel (HCS), austenitic and martensitic some of the material degradation mechanisms that take place within it.
stainless steels (ASS and MSS, respectively), chromium white irons
(CWIs) and chromium carbide (CrC) overlays; under severe degradation In mining, high forces are used in the digging operations and the
conditions the use of alternative materials such as tungsten carbide shovels are subjected to impact and gouging processes.
4,5
After
metal matrix composites (WC-MMCs) should be considered.
2
excavation, the mined material is transported to crushers, where it is
broken up to a specific particle or aggregate diameter (<100mm).
10
In
Materials and equipment in the oilsands industry are exposed to several the ore emptying process (see Figure 1), the surfaces are subjected to
degradation processes: abrasion, impact, erosion–corrosion, low-impact impact and gouging, whereas in the crushing process – where the
erosion, sliding abrasion and corrosion, among others.
3
For example, the mined ore is compressed between the counter-rotating rolls – high-
ore is composed of granulated material (oilsands, rocks and aggregates) stress abrasion (three-body abrasion) is the main wear process.
4
that produces grooving and abrasive wear on the surface of the shovels Taking into account the wear mechanisms, the surface of the crusher
and digging equipment during extraction and excavation. In pure teeth must have good abrasion resistance and certain ductility to
abrasion, the materials must have a very high surface hardness to overcome ploughing and indentation; ploughing results in the
withstand grooving and cutting processes. When severe impact occurs, formation of grooves, which can be removed by subsequent
for example in the crushing process, the surface of the crushers requires abrasion.
11
After the crushing process, the material is conveyed to the
certain ductility and work hardenability to avoid fracture and failure.
4
After cyclofeeder (see Figure 1), where hot recycled water (~55°C) and
crushing, the ore is combined with warm water and caustic soda to create caustic soda are added to create a slurry.
12
This slurry is one of the
a slurry and conditioned to extract the bitumen in separation vessels.
5
In most complex multiphase flows in industry; the combination of a
the transportation of the slurry (hydrotransport process), erosion– corrosive carrier fluid and the presence of solid particles diminishes
corrosion is the main wear process for the piping, pumping and screening the durability of the materials.
equipment; therefore, the equipment surface should withstand the
removal mechanisms due to the impact of sand particles on the surface Degradation of Materials in the Hydrotransport Process
(good impact resistance and ductility) and the corrosive action of the When the slurry flows, an erosion–corrosion process degrades the
carrier fluid (corrosion resistance). The oilsands industry has a special inner surface of the pipelines, leading to wall thinning; a similar
interest in acquiring a better understanding of the materials degradation occurs on elbows, flow measurement devices and
degradation mechanisms in the extraction and hydrotransport valves.
8
The removal of material occurs by a combination of
processes. This knowledge will help to develop new abrasion-, mechanical actions such as microcutting (material separated from the
corrosion- and erosion–corrosion-resistant materials and a surface, forming debris or chips), ploughing and cracking,
3,5,11
as well
comprehensive materials selection methodology to withstand wear. as corrosive actions (dissolution of the hardened layer and corrosion
Applied research in these areas is being successfully conducted by the of the surface), among others.
3
When materials are subjected to more
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© TOUCH BRIEFINGS 2009
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