Alebachew Demoz

Natural Resources Canada | NRCan · CanmetENERGY

Reclamation of fluid fine tailing (FFT) storage facilities to their pre-disturbance equivalent landforms is hampered because micrometer size fines, whose surface-area-to-volume ratio is remarkably high, are occupied with siloxane and hydroxy groups, which bind water strongly. The purpose of this study is to differentiate the forms of water physical...

Only grams or kilograms of valuable resources are extracted for each tonne of ore processed, generating immense amounts of tailings. Returning tailings-containment dams to their equivalent pre-disturbance landscape state is many stakeholders’ acceptable management strategy. The depositing of thickened fluid fine tailings (FFT), which the industry h...

Fluid fine tailings (FFT) comprising clayey-silt solids pose environmental and financial challenges. Currently, mining operators are depositing thickened FFT in deep-pits counting on self-weight consolidation to form stable ground. The motivation of this study is to model the long-term prospects of such deposits utilizing consolidation and direct s...

Industrial scroll decanter centrifuge (SDC) separation of the solids in fluid fine tailings (FFT) which have particles 10 μm and smaller in size require flocculant addition. Accordingly, the mechanism in the centrifuge is flocculation of the fine solid particles followed by sedimentation. Thus, feeding preflocculated material obviates the flocculat...

Operations to reclaim mature fine tailings (MFT) ponds involve flocculation using high-molecular-weight polymers, for which inline static mixers are suited. Three different commercial static mixers were utilized to determine mixing parameters corresponding to optimal dewatering performance of flocculated MFT.MFT was treated with polymer solution un...

High-molecular-weight polymer flocculants are used for accelerated dewatering of mature fine tailings (MFTs) to reclaim the land occupied by containment ponds. Two anionic polymers were used to flocculate an MFT sample containing 98% by weight of fines smaller than 44 μm in diameter, with 85% of this fraction being clay minerals. The polymer soluti...

A wide range of non-intrusive measurement techniques are available, each with strengths and weaknesses. It is important to analyze various techniques with respect to their accuracy, cost benefits, user-friendliness, remote monitoring, and limitations so that the results obtained can be effectively used in integrity management programs. This paper p...

Large numbers of soil samples are routinely analyzed using methylene blue (MB) titration to determine clay content. Although, the MB filter paper spot test titration is simple, it is labor-intensive, subjective, and leaves no record for subsequent re-examination. Preliminary thermometric monitoring of the titration indicated a switch from endotherm...

of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Experiments were conducted in six operating oil and gas production pipelines over four years to determine internal pitting corrosion rates under realistic operating conditions. - Pitting corrosion rates were similar when the compositions of surface layers were similar. - When a compact layer of single species formed, the surface was protected from...

Corrosion potential is a fundamental electrochemical parameter critical to understanding the thermodynamic aspects of corrosion. Many corrosion theories are based on corrosion potentials. Corrosion potential is routinely and easily measured in the laboratory. In order to transfer this scientific knowledge from the laboratory to the field, it is nec...

In order to relate a shear stress controlled-corrosion at the impinged jet wall to that in a pipe the pressure drop along a jet tube and the mass transfer rate at eight locations on the jet-impinged wall were measured concurrently using microelectrodes. The shear stress on the impinged jet wall increased radially giving stagnation and jet wall regi...

Hydrogen is among the emerging energy vectors that are being developed to replace nonrenewable hydrocarbon energy sources. The preferred method to produce hydrogen without generating greenhouse gases is the electrolysis of water using renewable energy. The reduction of energy during the water electrolysis process is a desirable goal regardless of t...

Corrosion potential is a fundamental electrochemical parameter critical to understanding the thermodynamic aspects of corrosion. Many corrosion theories are based on corrosion potentials. Corrosion potential is routinely and easily measured in the laboratory. In order to transfer this scientific knowledge from the laboratory to the field, it is nec...

Impressed current cathodic protection using uniformly distributed ribbon anodes has proven to be effective in controlling the corrosion of soil-side aboveground storage tank bottoms. Parallel and concentric ribbon anodes are two of the most common patterns of laying anode beds some distance underneath tank bottoms. At the design stage, the rule-of-...

An empirical model was previously developed to predict internal pitting corrosion of oil and gas pipelines. This model is based on experiments carried out in the laboratory at high pressure and high temperature under the operating conditions of the oil and gas pipelines. The inputs are of two kinds: construction (pipe diameter, pipe wall thickness,...

The design of coatings must be adequate to protect pipelines under long-term, severe environmental conditions, including the extreme climatic conditions that will apply in the North before the pipe is installed and operation begins. Practices and standardised methodologies for evaluating and qualifying pipeline coatings for application in northern...

A grid of concentric circular ribbons is one of the two most common patterns used in laying an anode bed below the bottom of a large aboveground storage tank. The authors considered the design of such a grid by taking a simplified approach, which is based only on the diameter and height of the tank bottom from the plane of the bed, the ribbon anode...

A new high-pressure, high-temperature submerged impinging jet device is described. The experimental results of its flow characteristics are summarized. The device generates well-developed steady flow in the jet tubes with laminar flow up to Reynolds numbers (Re) of 1,980 and turbulent flow above Re = 2,800. Lacal mass transfers were measured on a p...

Impressed current cathodic protection using grid pattern ribbon anodes has proved to be effective in controlling the corrosion of soil-side aboveground storage tank bottoms. At the design stage, rule-of-thumb approaches and historical data are employed to determine the spacing between ribbon anodes. This article presents equations that enable one t...

Addition of corrosion inhibitors is one of the common methods to control both general and pitting corrosion of oil and gas pipelines. Development of an integrity management program to control internal corrosion of such pipelines depends on our ability to monitor the efficiency of the inhibitor performance. Monitoring in an oil and gas pipeline is a...

Experiments were carried out using a loop in three fields (gassy-oil, oily-gas, and oil-transmission pipes) under 17 operating conditions, using six inhibitors (three continuous and three batch). Laboratory experiments were carried out under field conditions using the same inhibitors at the same concentrations. Four types of data were used to compa...

Multi-phase flow achieved in a relatively short distance at a custom-designed testing facility.

Internal pitting corrosion is the predominant failure mechanism of gathering pipelines. To screen inhibitors, their effectiveness in controlling pitting corrosion rates must be evaluated. In this article, the pit depths of coupons exposed in the field are compared with pit depths on the inside wall of an experimental pipe loop.

Based on the literature database and information from pipeline companies, the methodologies used to select inhibitors were critically reviewed. Round robin tests were carried out in three laboratories to assess reproducibility of the wheel test. In total, twelve (12) laboratory methodologies were evaluated. Field monitoring was carried out in Alber...

Laboratory methodologies to evaluate corrosion inhibitors are reviewed. Flow patterns and hydrodynamic parameters of the rotating cage are presented.

A multi-purpose instrumented loop in line with an oil producing well is described. The loop has several ports for coupons which were replaced periodically. Some of the coupons were used for electrochemical monitoring in addition to weight loss and visual inspection. Weight loss, pit rate and all the electrochemical methods used gave corrosion rates...

The ac impedance characteristics of an ion-selective membrane|insulator|semiconductor (MIS) structure designed for chemical sensing applications have been modelled quantitatively for a frequency range from about 5 Hz to 40 kHz. When plasticized poly(vinylchloride)-based K+-selective membranes, nominally 100 μm thick, are used with 45 nm of Si3N4 an...

Hexadecanethiol (HDT) forms self-assembled monolayers on static Hg drop electrode (SMDE) surfaces. Films are formed in less than 1 min and are extremely impermeable, indicating the absence of defects. The onset of Hg oxidation at about 0.4 V vs SCE on a bare SMDE in 0.1 M NaF is shifted anodically by 1 V on an HDT-coated SMDE. The current for Ru(NH...

The endeavors of a number of academic labs to address the difficulties associated with ion-sensitive field effect transistors (ISFETs) are examined. The focus is entirely on these devices, since most others, such as enzyme FETs, extended gate, and diode devices, are all based on the same principles. The focus is on several of the more troublesome a...