Orexin A but not orexin B regulates lipid metabolism and leptin secretion in isolated porcine adipocytes

It is well known that orexins are involved in the metabolism and endocrine function of rodent adipocytes, but there are no data on other animal species, including pigs. Therefore, in this study, we tested the hypothesis that orexin A (OxA) and orexin B (OxB) modulate the metabolism and endocrine functions of isolated porcine adipocytes and adipose tissue explants. Moreover, we characterized the possible mechanism of OxA action in porcine adipocytes. According to the results, both orexin receptor 1 and orexin receptor 2 were expressed in the porcine adipose tissue. We found that OxA suppressed the release of glycerol from porcine adipocytes both in the absence (basal lipolysis; P < 0.05) and in the presence (stimulated lipolysis; P < 0.05) of isoproterenol. Orexin A increased basal and insulin-stimulated glucose uptake (P < 0.05), as well as it enhanced the rate of glucose incorporation into lipids with insulin (stimulated lipogenesis; P < 0.01) or without insulin (basal; P < 0.05). We have also shown that OxA stimulated the mRNA expression of glucose transporter 4 (P < 0.05) and its translocation into the plasma membrane (P < 0.01). Moreover, OxA upregulated the mRNA expression of leptin in isolated porcine adipocytes (P < 0.05) and increased the secretion of leptin (P < 0.05). We have also demonstrated one of the possible mechanisms of OxA action in adipocytes. In the presence of extracellular-signal-regulated kinase 1 and 2 (ERK1/2) inhibitor, the effect of OxA was not detectable in porcine adipocytes, which indicates that this peptide increased cell viability via ERK1/2 pathway (P < 0.05). However, OxB did not show any effect on the metabolism and endocrine functions of porcine adipocytes. In summary, we have shown for the first time that OxA has a significant impact on the intensity of lipolysis, glucose uptake, lipogenesis, as well as on the expression and secretion of leptin. Therefore, we conclude that OxA but not OxB regulates lipid metabolism in porcine adipose tissue and that this regulation is partly mediated via ERK1/2 pathway. The action of orexins should be further explored to better understand their role in the regulation of adiposity in pigs.

Laboratory and Pilot Experience in the Development of a Conventional Water-Based Extraction Process for the Utah Asphalt Ridge Tar Sands

Abstract

The belief that the Utah tar sands deposits are oil-wet has led to a focus on solvent-based bitumen extraction processes, or some form of solvent assisted water-based extraction process for these types of materials. However, under certain conditions, this ore is in fact amenable to a conventional water-based extraction process. The thermal, mechanical and chemical environments necessary to make the Asphalt Ridge ore behave like an Alberta Athabasca oil sand are outlined, along with the typical criteria which must be satisfied for a novel extraction process to be viable. Laboratory-scale demonstrations of the efficacy of a Clark-style hot water extraction process for the Asphalt Ridge tar sands were subsequently confirmed on a twenty tonne per hour pilot scale. In addition, the scarcity of water at the mining and extraction operation in Utah led to the development of an aggressive tailings treatment process, which also offers lessons for tailings handling in the surface-mined oil sands in Alberta.

Introduction

The CANMET Energy Technology Centre in Devon, Alberta, became involved in the Asphalt Ridge tar sands project when it was a solvent-based extraction operation hampered by a significant emulsion buildup in the recycle water. In working to develop a solution to the emulsion buildup, it became apparent that, using the solvent-based extraction process, solvent losses associated with clay mineral-solvent interactions would be unacceptably high. As a result, a series of standard tests(1, 2) were applied to Asphalt Ridge tar sand samples in order to assess the potential for a solvent-free, water-based extraction process(3, 4). Surprisingly, some of these nominally oil-wet tar sands performed very well, indicating that the Asphalt Ridge tar sand bitumen could be extracted using commercially proven technology developed over the last 40 years in Alberta(5–10). In order to achieve bitumen recoveries similar to those for Athabasca oil sands, significantly higher mechanical energy levels were required, along with high temperatures. Since the early 1990s, the operating temperature used in commercial processing of Athabasca oil sands has been reduced from about 80 °C to less than 50 °C while increasing the mechanical energy input(1, 2, 11, 12). By maintaining both mechanical and thermal energy inputs at high levels, the ‘difficult to process’ Asphalt Ridge tar sand showed bitumen recoveries of approximately 90%; similar to the Athabasca commercial operations.

The Asphalt Ridge tar sand samples that did not perform well in bench-top laboratory assessments were found to be weathered or oxidized; conditions that also inhibit extractability in the Athabasca oil sands in Alberta(13–17). The difficulties encountered by earlier researchers in using Canadian technology, or a modified water-based extraction process for the Asphalt Ridge tar sand (without pre-treatment with an organic diluent before ore conditioning), may have been due to improper handling of cores or bulk samples resulting in bitumen oxidation or weathering(18–24). In referring to the differences between the Utah tar sands and those in the Athabasca deposit, "These differences preclude the direct application of the Canadian mining and recovery technology to Utah's tar sands and to other United States tar sands(18)."

The Potential for Carbon Dioxide Sequestration in Oil Sands Processing Streams

Abstract

The consolidated tailings (CT) process involves chemical amendments to combine the clays and fines in oil sands mature fine tailings or thickened tailings with the coarser sand components to create a nonsegregating tailings (NST) mixture that will rapidly consolidate. Over the years, several amendment chemicals have proved useful in controlling the fluid tailings properties so that they may support sand loading and remain non-segregating. Suncor has several years of commercial-scale operating experience with gypsum as the CT process aid and in the years leading up to the commercialization of the CT process at Suncor, carbon dioxide was also investigated as a CT process aid. With the concerns over carbon dioxide related to the Kyoto Protocol, the extent to which carbon dioxide is trapped and chemically sequestered in the CT process has been investigated. The mechanism by which carbon dioxide addition affects the strength of the mature fine tailings or fluid tailings componentas been investigated, and the potential for carbon dioxide sequestration has been quantified. Depending upon the availability of gypsum as a CT or NST additive, carbon dioxide could beuseful alternative.

Introduction

Water-based extraction of bitumen from the Athabasca oil sands deposit results in the generation of a large amount of waste tailings. The tailings comprise slow settling fine clays with release water that is recycled for bitumen extraction, and a sand component that is generally used to create containment for the fluid fine ailings waste streams. The accumulated slowly settling fine claysare termed mature fine tailings (MFT) and settle to 30 to 45 wt﹪ after several years. Since approximately one barrel of fine tailings is generated from the production of 1 barrel of crude oil equivalent, over 1B m3 of MFT are currently impounded in containment ponds. Government regulations mandate that the containment ponds eventually be reclaimed to a natural landscape.

The poor settling behaviour of fine tailings is a consequence of high concentrations of bicarbonate ion in the water, residual bitumen, and fine clays. Viable reclamation options that have been investigated in the industry involve some form of chemical manipulation using coagulants or polymeric flocculants to increase the dewatering rate, leaving behind a geotechnically stable deposit(1). The most successful strategy to date is the consolidated tailings (CT) process, which has been implemented by Suncor Energy Inc. using gypsum (CaSO4.2H2O) as a coagulant. The CT process can not only help deal with the accumulated MFT but, with thickeners to create an MFT analog at the end of pipe, it can also be used to prevent accumulation of fluid fine tailings or MFT. The making of a suitable CT mixture involves creation of a nonsegregating mixture of sand, clay, and water; rapid initial settling (water release) of the mixture; and ultimate consolidation of the mixture. Extensive studies by Scott et al.(1) have demonstrated that there is a wide range of sand-to-fines ratios, solids contents, and gypsum addition levels where these criteria are met.

Characterization of Bitumen Properties Using Microscopy and Near Infrared Spectroscopy: Processability of Oxidized or Degraded Ores

Abstract

Oxidized or degraded oil sands can exhibit poor processability, which is often not correlated with the fines or clay contents in the ore. Chemical markers (such as low pH and high soluble iron and calcium) for oil sands oxidation are sometimes not present even though significant changes in bitumen properties may have occurred. In these cases, changes in bitumen chemistry have been successfully quantified using microscopic techniques developed at CANMET. More recently, an on-line tool using near infrared (NIR) spectroscopy, which correlates with the CANMET microscopic method, has been developed with Suncor Energy Inc. An on-line technique based on NIR that can quantify the amount of degraded ore coming to the extraction plant from Suncor Energy Inc.'s Steepbank mine will be useful in effectively controlling additions of process aids for treating oxidized or degraded ores.

This paper discusses the processability of oxidized or degraded ores along with a microscopic method for identifying oxidized ore and its correlation with the NIR spectroscopic technique.

Introduction

Oil sands processing efficiency is dependent upon many factors, including the quality of the ore. The operating companies have developed correlations between extraction recovery and bitumen and fines content in the ore. These correlations generally fit observed processability, but often ores are encountered with recoveries that fall well outside these simple relationships. These are variously known as bad ores, problem ores, type X ores, or ores with a high misery factor (the misery due to the loss in recovery or to the "difficult to settle" tailings). Detailed characterization can reveal the reasons for such poor processing behaviour and they can sometimes be traced to unusual water chemistries or unusual clay properties. Often, however, changes in bitumen chemistry can be the source of the problem, and this is the focus of the present discussion. Bitumen oxidation and its negative impact on processability has been extensively studied, mostly on stockpiled or stored samples(1–7). Experience at Suncor Energy Inc.'s Steepbank mine has shown that bitumen changes that may have occurred in geological time frames can also be important in determining processability(8–10).

Steepbank Sampling

During the commissioning of the Suncor Energy Inc. Steepbank mine, areas of ore were identified that created processing difficulties, in particular high froth densities. The high froth densities resulted in problems in downstream facilities where high solids content in the froth resulted in overloading of the froth treatment centrifuges. These effects were quickly identified with certain areas of the mine and a sampling program was undertaken to identify the causes of the poor processability. The ores linked to the poor processability were generally high-grade ores containing in excess of 12% w/w bitumen (occasionally &gt;14% w/w) with low fines content, that do not fit the normal profile for poorly processing ores. Cryogenic sampling of the froths in the commercialscale separation cell was carried out in order to help identify the cause of the high froth densities. Macroscopic observation of the froths from the problem ores included very large bubble sizes and sometimes a distinct reddish froth colour(9,12).

Small Scale Simulation of Pipeline or Stirred Tank Conditioning of Oil Sands: Temperature and Mechanical Energy

Abstract

The oil sands industry is moving away from tumbler conditioning at 80 °C to pipeline conditioning, often at significantly lower temperatures. This lower temperature conditioning can be less efficient, requiring longer conditioning times. Control of conditioning time in a pipeline is difficult and inadequate conditioning can result in either lower recoveries or higher froth densities, depending upon the operating conditions. A bench scale test was developed at CANMET to simulate the mechanical conditioning environment found in a stirred tank or in a pipeline. A small scale extraction test has been used at CANMET to investigate the relationship between the efficiency of oil sands conditioning and various process variables. A shift from relatively high temperature tumbler conditioning to pipeline or hydrotransport conditioning requires a slightly different approach to batch extraction testing. The CANMET test protocol has been compared to pipeline and stirred tank conditioning at a pilot scale and has been used to investigate the effect of several process variables in oil sands extraction. This technology brief discusses the preliminary findings and a potential link to operating experience.

Introduction

Conditioning is conventionally considered to be the separation of bitumen from the mineral matrix, combined with air attachment. At low temperatures, bitumen separation may be complete, but inadequate air attachment can result in poor bitumen recovery. Oxidation or degradation of the bitumen can negatively impact the bitumen separation, but not necessarily reduce the efficiency of air attachment. This can result in poor bitumen froth quality, while maintaining high recovery. In cases where there is a combination of low temperatures and a degraded or oxidized bitumen component in the oil sand, recovery as well as froth quality can be drastically affected(1).

Ordinarily, extraction experiments are carried out in a small scale unit where various stirring, aeration, and water additions are done in an attempt to mimic the commercial extraction process. The froth quality and bitumen recovery determined from these experiments allows for investigation of trends as a function of ore type, water chemistry, temperature, and other process variables. Previous studies have investigated the various factors that impact extraction performance, but limitations in the batch (or small scale) extraction protocol often limits the discussion to impacts on recovery only(2–6). Furthermore, it is often not possible to separate the effects of the bitumen liberation and air attachment, the two key points in conditioning of oil sands.

Recent CANMET work has overcome some of these experimental difficulties and focused on the relationship between temperature, mechanical energy, and process chemicals in the conditioning step and the resulting impact on both recovery and froth quality(7). It was shown that to a certain extent, increasing mechanical energy can substitute for higher extraction temperatures and/or chemical process aids. By far the most important factor is process temperature, largely because of a change in the bitumen- air attachment mechanism as the temperature is reduced.

Characterization of Petroleum Industry Emulsions And Suspensions Using Microscopy

Abstract

Confocal microscopy and cryogenic scanning electron microscopy are common characterization techniques in biological, pharmaceutical, and food sciences. Although these techniques are less common in the petroleum industry, there are many similarities in the samples found there and those in the life sciences. Cryogenic scanning electron microscopy (cryo-SEM) and confocal laser scanning microscopy (CLSM) are ideally suited to elucidate the fundamental interactions that ultimately determine the bulk behaviour of oil emulsions and suspensions. Both water-in-oil and oil-in-water emulsions are found in oil processing and resolving or separating the phases is important for both environmental and economic reasons. Whether or not the dispersed phase is stabilized by solid particles, the nature of the particle surface, and the size distribution of the dispersed phase are all important factors in determining emulsion stability or the degree of difficulty in separating the components. Microscopy is an important first step in determining whether a chemical or physical separation method would be the most efficient.

Introduction

Emulsion separation can be broadly divided into chemical and physical methods, or combinations of the two. Typically, the approach to chemical separation is an empirical one involving many bottle tests to determine demulsifier effectiveness. The purpose of the demulsifier is to destabilize the oil-in-water or water-in-oil emulsion, resulting in coalescence and separation of the dispersed phase. If a significant amount of solids are present, whether they are associated with the oil or water phases has an impact on the effectiveness of the separation, either because of the hindered movement of the dispersed phase, or because of interactions of the solids at the emulsion interface, preventing coalescence.

Physical separation relies on the density differences between the dispersed and continuous phases. Settling vessel or centrifuge performance is a function of this density difference and the size distribution of the emulsion. Combinations of chemical and physical separation methods are most commonly used and these include the use of demulsifiers to enhance free water knock out vessel performance, and/or centrifugation, as well as chemical process aids to separate solids or to enhance flotation.

Microscopic characterization of the emulsion system can be an important first step in determining whether chemical or physical separation techniques are most likely to be successful and to provide guidelines as to their ultimate efficiency. A series of microscopic methods are available to characterize both oil-in-water and water-in-oil emulsions(1–4). The three most common techniques will be discussed with examples of their use in oil industry emulsion separation problems.

Methods

Light microscopy (LM)

This technique has been used extensively at the Fuel Processing Laboratory (FPL) to study a variety of samples, particularly in the reflectance and fluorescence modes. The optical parameters characterizing the organic and inorganic particles are the isotropic or anisotropic character, fluorescence properties, morphology, colour, and reflectivity. Reflected light is more commonly used than transmitted light because of the opaque nature of most oil emulsion samples. Creating a sample thin enough for transmitted light observation usually distorts the original sample and in some cases can even invert a water-in-oil emulsion into an oil-in-water emulsion when it is squeezed between two glass slides.

Correlations Between Oil Sands Minerals And Processing Characteristics

Abstract

The geology and subsequent mineral composition of oil sands deposits have important consequences for their processing behaviour. Differences in oil sands processability and extraction yields can be dependent upon many factors including the composition of the mineral components and the organic complexes that are associated with certain minerals. These mineral-organic associations help provide the bridge which leads to carry over of bitumen with the tailings as well as carry over of water and mineral matter with the product. Characterization of the minerals via various laboratory techniques and the relationship of these measurements to processing behaviour is discussed. Portions of this work were presented at the 1988 annual meetings of The Canadian Institute of Mining and Metallurgy and the Chemical Institute of Canada.

Introduction

Bitumen extraction from oil sands is carried out commercially via the Clark hot water process and involves mixing the raw oil sand with steam and a caustic solution. The bitumen separates from the sand and floats to the surface of the suspension. The amount of water and mineral matter that is carried over with the bitumen product and the amount of bitumen which is lost with the tailings are important parameters in determining the process efficiency.

The recovery of bitumen from oil sands is a complex process With many steps involving the handling of water/oil systems which are often in the form of emulsions. The first stages of the process concentrate on separating the bitumen from the water and mineral matter, whereas later on the main problem is to remove residual water from the bitumen product. In order to facilitate this removal a combination of chemical (demulsifiers) and mechanical (centrifuges) means is often used.

Losses in process efficiency can be due to many factors, several of which are related to the mineralogy of the oil sands feed. Previous studies(1–3) have correlated the amount of fine clay with processing problems; the clays were found to stabilize the water-in- oil emulsions formed in the bitumen product. In addition, clay floes can trap bitumen, carrying it into the tailings stream. Understanding the correlations between the mineralogy of the raw oil sands and the ultimate processability will help develop methods to deal with problem feeds as they reach the extraction plant rather than after they reach the refinery or tailings pond.

The amount and size distribution of the clays has been shown to be important in determining the processability of the oil sands, but equally important is the nature of the mineral matter. Chemical characterization via electron microprobe analysis is a useful tool in determining both the quantity and size distribution of the critical mineral components. Preliminary results have shown the importance of the iron compounds; pyrites appear to be relatively innocuous although iron carbonates and hydroxides seem to provide a bridge for organic-mineral interactions which lead to processing problems, i.e. carry over of water, clays and minerals with the bitumen and loss of bitumen to the tailings.

Direct observation of frozen hydrated samples in the electron microscope has been utilized for evaluation of both the size distribution of the dispersed phase and the chemical composition(4–5).

The size distribution of the dispersed phase is important because centrifugal separation of the emulsions will be more difficult with smaller droplets; as will chemical treatments because surface area is higher per unit volume. The nature of the clays and other minerals which are carried over with the bitumen product also directly affects the bitu