Layers Of Cake Research Articles

X-ray Computed Tomography (CT) to Scan the Structure and Characterize the Mud Cake Incorporated with Various Magnetic NPs Concentration: An Application to Evaluate the Wellbore Stability and Formation Damage

The X-ray computed tomography method has provided unrivalled data about the characterization and evolution of the internal/external structure of materials by analyzing CTN and non-destructive imaging approach. Applying this method on the appropriate drilling-fluid ingredients plays a significant role in generating proper mud cake quality to stabilize wellbore, and avoid formation damage and filtration loss by preventing drilling fluid invasion into the formation. In this study, smart-water drilling mud containing different concentrations of magnetite nanoparticles (MNPs) was used to assess the filtration loss properties and formation impairment. Conventional static filter press, non-destructive X-ray computed tomography (CT) scan images and high-resolution quantitative measurement of CT number method were used to estimate the filtrate volume and characterize the filter cake layers, hence evaluating the reservoir damage through hundreds of merged images. The CT scan data were combined with the HIPAX and Radiant viewer digital image processing. The variation in CT number of mud cake samples under different concentrations of MNPs and without MNPs concentration were analyzed, and hundreds of 3D images as a cross-sectional profile were used. This paper highlights the importance of MNPs property in terms of minimizing filtration volume and improving mud cake quality and thickness, and hence improving the wellbore stability. From the results, a notable reduction of filtrate drilling mud volume and mud cake thickness to 40.9% and 46.6%, respectively, were recorded for drilling fluids incorporated with 0.92 wt.% of MNPs. However, this study asserts that optimal MNPs should be implemented to guarantee the best filtration property. As confirmed from the results, increasing the MNPs concentration beyond the optimal value (up to 2 wt.%) increased the filtrate volume and mud cake thickness by 3.23 and 33.3%, respectively. CT scan profile images show two layers of mud cake produced from water-based drilling fluids possessing 0.92 wt.% MNPs. The latter concentration was found to be the optimal additive of MNPs as it caused a decrease in filtration volume, mud cake thickness, and pore spaces within the structure of the mud cake. Using the optimum MNPs, the CT number (CTN) shows a high CTN and density material, and uniform compacted thin mud cake structure (0.75 mm). The produced thin mud cake layer reveals the precipitation or exchange of elemental/mineral composition during fluid-solid interaction. These results confirm that MNPs could help in avoiding or reducing the formation damage, driving away drilling fluid from the formation, and improving borehole stability.

Thermal and non-thermal mechanism of microwave irradiation on moisture content reduction of municipal sludge

Both huge volume and high moisture content of municipal sludge have brought great troubles and attracted extensive concerns in the world. The bound water of sludge and pore clogging in the process of pressure filtration dewatering are two key factors influencing the deep-dewatering effect of municipal sludge. The results of this study suggest that microwave irradiation (MI) can be used to synchronously evaporate water, reduce the bound water of sludge and solve the blockage of sludge pore channels during the process filtration dewatering, which can greatly reduce the moisture content of municipal sludge. Low-field nuclear magnetic resonance, carbon dioxide gas absorption and desorption, and scanning electron microscope were synthetically used to detect the pore structure of sludge cakes. Thermogravimetric differential scanning calorimetry was used to detect binding energy to calculate moisture distribution. Thermal mechanism was revealed by dielectric constant, thermal conductivity, fractal dimensions, water saturation and porosity in different layers of sludge cake. The results showed that the bound water in sludge samples after MI was reduced by 19.4%, the pore fractal dimension was reduced from 2.955 to 2.867, the surface fractal dimension increased from 2.099 to 2.362 with the conditions of microwave power (700 w) and treat time (5 min). When the water saturation was close to 1, the dielectric constant of middle and outer layers was the main factor of heating, while the water saturation was close to 0, the main factor became the difference of thermal conductivity in middle and outer layers. Moreover, after MI, moisture content of sludge was greatly reduced from 68.4% to 40.1% for its thermal effect, further reduced to 34.1% by the continuous mechanical dewatering for its non-thermal effect which change the pore structure and moisture distribution. These conclusions are helpful to understand microwave thermal and non-thermal mechanism and shed light on new dewatering-drying integrated techniques of municipal sludge.

A Laboratory Investigation on the Way to Remove the Filter Cake Generated by Ilmenite Water-Based Drilling Fluids

The increasing demand for deeper drilling and more complicated wells fastens the way for improved drilling fluid (mud) technologies and promising additives. Several studies have shown numerous improvements in mud characteristics upon using ilmenite compared to the commonly used weighting materials. This study aims at investigating the removal of filter cake deposited by ilmenite water-based drilling fluid under harsh conditions using low-concentration (7.5 wt%) of hydrochloric acid (HCl) and chelating agent (HEDTA) to prevent iron precipitation during reaction. API filter press was used to conduct the filtration tests and generate the filter cake at a pressure ~ 300 psi and temperature ~ 250°F. Different sandstone cores of 2.5-in. diameter and 1-in. thickness were used to simulate the formation during filtration. Filtrate fluids were collected for 30 minutes as per API procedures and computerized tomography (CT) scan was used to characterize the cores with the deposited filter cakes. The filter cakes were soaked with HCl–chelate solution for six hours. Cores with the remaining filter cakes were CT scanned again. Effluent solutions resulting from the aforementioned soaking process were analyzed using inductively coupled plasma (ICP). Scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) was used to analyze the dried filter cakes and remaining residue. CT scan and SEM-EDS showed two layers of the filter cake with different densities but similar elemental composition. Using 7.5 wt% of HCl can partially remove the filter cake generated by ilmenite water-based drilling fluids. Adding the chelate showed minimal impact on the filter cake removal-efficiency; however, it helped nullify the corrosion issues during the treatment. This study provides a step forward on the way to chemically remove ilmenite-based filter cake using low acid concentration and virtually overcome corrosion issues encountered while acidizing.

Meso-mechanism of mechanical dewatering of municipal sludge based on low-field nuclear magnetic resonance

Both huge volume and high moisture content of municipal sludge have brought great troubles and attracted extensive concerns in the world. In this paper, the mechanical press filtration (MPF) dewatering was performed under ultrahigh pressure in order to improve the dewatering performance of municipal sludge. Low-Field Nuclear Magnetic Resonance (NMR) technique was used to study the effect of MPF parameters on dewatering performance. Based on the pore characteristics of municipal sludge, a capillary bundle model was developed to explore the mesoscopic mechanisms of MPF dewatering. The results indicate that moisture content of sludge cake decreases gradually with the increase of compressed pressure and dewatering time as well as the decrease of sludge weight , and the moisture content of municipal sludge can be reduced to as low as 30% with MPF dewatering. According to the peak and envelope area of relaxation time curve in NMR, it can be found that the size of pores decreases and the percentage of small pores increases during the dewatering process. Therefore, the capillary water cannot be removed by MPF method because the capillary pressure in very small pores increases evidently. Furthermore, the compaction degree of the outmost layer is generally higher than that of the middle layer, and the difference of moisture content between the middle and outmost layers of cake is 25%–28.4%. The present work may be helpful to understand the MPF dewatering mechanism and shed light on the new dewatering techniques of municipal sludge.

Impact of Clay Minerals on the Dewatering of Coal Slurry: An Experimental and Molecular-Simulation Study

The cleaning process of coals is challenging due to the existence of clay minerals. The overall objective of this study is to investigate how the dewatering of coal slurry is impacted by the presence of clay minerals, i.e., kaolinite and montmorillonite. Filtration tests were first conducted to investigate the effect of kaolinite and montmorillonite on the dewatering efficiency of coal. Specifically, we measured the filtration velocity, moisture, average specific resistance, and porosity of filter cakes for six slurry samples, in which different amounts of kaolinite and montmorillonite were contained. Filtration tests show that a small amount of kaolinite and montmorillonite leads to a significant reduction in the filtration velocity and porosity, and a big increase in the average specific resistance and the moisture of the filter cake. We observe that most kaolinite existed in the top and middle layers of the filter cake, while most montmorillonite existed in the top layer; on the contrary, little montmorillonite is observed in the middle and bottom layers of the filter cake. Montmorillonite results in a much more deteriorative effect than kaolinite. Considering that the interactions between clay minerals and water may play a key role, we then further investigate the effect of such interactions using molecular simulations. Simulation results show that water molecules could hardly diffuse into kaolinite from the edge, while they could readily penetrate into the montmorillonite layers from the edge surface. This result can be explained by the hydrated cation in montmorillonite. The adsorption density of water on the octahedral surface of kaolinite is higher than that of water on the tetrahedral surface of kaolinite. Furthermore, the adsorption density of water on the double surfaces of kaolinite is higher than that of water on the montmorillonite surface. This research is expected to provide benefits or contributions to the dewatering of clay-rich coal tailings.

Polyelectrolyte Flocculation of Waste Activated Sludge in Decanter Centrifuge Applications: Lab Evaluation by a Centrifugal Compaction Test

This article introduces a centrifugal compaction (spin tube) test to thoroughly evaluate polyelectrolyte conditioning on lab scale. In contrast to the well-known and widely applied existing tests (e.g., the beaker, the Jar settling, the free drainage, and the [sheared] capillary suction time test), the proposed spin tube test has a clear relation with the dewatering process taking place in a decanter centrifuge. First, based on the theory of centrifugal compaction, the solids stress of separate layers of sludge cake (obtained after spinning sludge in a lab centrifuge) is calculated. Next, the test was applied to assess in the lab the performance of three different polymers by evaluating the obtained sludge dryness. To verify and/or compare the results obtained with the spin tube tests, sheared capillary suction time tests were conducted and floc size distributions were analyzed. Finally, two of the three polymers evaluated in the lab were applied in the industrial sludge dewatering and drying system used at the wastewater treatment plant of Monsanto Antwerp in Belgium. Observed field performance was in perfect accordance with the spin tube tests.

Interoperability between Semantic Web Layers: A Communicating Agent Approach

The WWW (World Wide Web) containing volumes of web documents developed in HTML and other markup languages does provides us feature of browsing through interlinked documents and exploring the entire WWW. However the entire WWW is appropriate for human consumption, but the other associated features need the WEB to be made Semantic where the web documents are interpreted by the machines and thus minimizing the need for human intervention. Addressing the above need Tim Berners-Lee and W3C consortium has suggested a layered architecture .This paper proposes to critically evaluate the functional aspects of the Semantic Web Layered cake and suggests inclusion of an interface layer to interchange data in an interoperable format amongst the layers of the Semantic Layered cake.

Melt infiltration of SiCp reinforced Al matrix composite by newly designed pressure infiltration technique

Newly designed pressure infiltration technique was developed to clarify the molten metal flow through solid network, aiming to obtain property materials and, simultaneously, the purified matrix as a filtrated metal. An experimental apparatus was constructed to control the microstructure morphology for varied fraction of solid and applied pressure. A sample, Al-7 wt.% Si-20 vol.% SiCp was squeezed on the double layers of semi-solid aluminum alloy cake and alumina porous medium by using argon gas pressure. Permeability values were estimated by Darcy's law in order to know the molten metal flow characteristics through solid network in the semi-solid range. It was found that the permeability suddenly decreased with increasing fraction of solid, and filtration mechanism was changed between depth and cake filtration near fraction of solid 0.25 due to much difference of the flow resistance between the two. Increasing applied pressure decreased the permeability due to the consolidation of solid grains. For pressurized sample on the filter and filtrated metal, SiCp content became to as high as 38 and less than 0.4 in volume percentage depending on fraction of solid, respectively. The pressurized samples with high SiCp content showed low wear rate and high hardness, when compared with original composite sample.

Improved Dewatering of Coal by Steam Pressure Filtration

The use of steam as an over-pressure forming gas phase has the advantage of a combined mechanical and thermal dewatering. Steam pressure filtration can provide an economical and effective technique, whereas conventional solid-liquid separation processes do not lead to a marketable residual moisture content of the product. A condensation front is built at the cold layers of the filter cake, while removing the capillary water from the porous filter cake. Depending on the filter cake resistance as well as the pressure difference, the condensation front displaces a great amount of cold mother liquid from the filter cake. For further economic drying pressurized air should be applied to the filter cake, utilizing the stored latent heat for the evaporation of a part of the remaining liquid. Pre-dewatering and the presence of inert gases in the filter cake should be prevented.

The variance of the properties of pot-spun viscose fibre

Viscose textile yarn is spun mainly by the centrifugal method. The principal direction in which the quality of the fibre can be raised is represented by improvements in the uniformity of its properties across the layers of the cake. The variance of the properties may be caused by irregularities in the parameters of the viscose or may orinate in the spinning process. It was shown elsewhere /1,2/ that the characteristics of the supramolecular structure of the fibre come into being during the spinning and drawing processes and in the finishing and drying operations.

Stabilizing effects in compressible filter cakes

The filtration of polyvinyl chloride particles of 5–12 in water has been investigated under constant pressure and constant rate conditions. The porosity of the cake was measured at different levels by means of the electrical resistance between gauge pins. A form of ‘retarted packing compressibility’ has been found in which the first layers of cake do not compress gradually but only after a critical cake thickness has been reached. This critical cake thickness can be reduced by the addition of a deflocculant.