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Basim, Gul Bahar Jr. "Fine Coal Dewatering." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/35680.
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Fine coal constitutes a relatively small portion of a product stream in a coal cleaning plant. However, its processing cost is approximately three times higher than the cost of processing coarse coal. Therefore, many coal companies chose to discard the fines to refuse ponds, causing a loss of profit and creating environmental concerns. This problem can be solved by developing more efficient fine coal dewatering processes, since bulk of the cost associated with processing fine coal is due to dewatering. For this reason, Virginia Tech has developed new chemicals that can increase the efficiency of mechanically dewatering coal fines.
To determine the performance of the novel reagents on fine coal dewatering, laboratory vacuum filtration and centrifugation tests were conducted. The utilization of the novel dewatering aids in the dewatering systems decreased the final moisture contents of the filter cakes to sufficiently low values. There was approximately 50% reduction in the cake moisture of many coal samples with the usage of the novel dewatering aids. The tests were performed on various coal samples from different coal preparation plants. This gave the advantage of testing the novel dewatering aids at many different conditions since each sample had its own characteristics.
The vacuum filtration tests were extensively used to compare the efficiency of each novel reagent in dewatering. The best performing dewatering aids were determined and they were further utilized to analyze the effects of operational variables, such as; drying cycle time, cake thickness, vacuum pressure level and slurry temperature on dewatering. A statistical analysis was also performed to observe the effect of each factor quantitatively. The analyses were very useful in terms of determining the synergistic effects of these factors in dewatering of fine coal.
The centrifuge tests were conducted to examine the efficiency of the novel reagents in a different dewatering application. The experimental results showed a significant improvement in centrifuge dewatering with the usage of proper coal sample. The moisture contents of fairly thick cakes decreased down to 5-10%. This outcome was very satisfactory since most of the dewatering aids commonly used in the coal industry were observed to increase the final cake moisture in centrifuge dewatering instead of decreasing it.
Finally, surface chemistry analyses were performed on the coal samples and slurries to analyze the changes in the chemistry of the dewatering system in the presence of the novel dewatering aids. It was observed that there was a favorable improvement in the system chemistry, which was helpful in terms of decreasing the cake moisture content. These observations were also consistent with the results of the dewatering tests. The combined effect of the novel additives in decreasing the surface tension of the slurry and increasing the contact angle of the coal surface at the same time was concluded to be the reason for their significant performance as dewatering aids.Master of Science
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Smyth, Ian Charles. "Cyclonic dewatering of oil." Thesis, University of Southampton, 1988. https://eprints.soton.ac.uk/411627/.
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Åslund, Peter. "On Suction Box Dewatering Mechanisms." Doctoral thesis, KTH, Fiber- och polymerteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4780.
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In previous studies on suction box dewatering, three mechanisms were identified that determine the dry content of a web, viz. web compression, displacement of water by air and rewetting. In the present work, the relative importance of the three mechanisms was investigated through direct measurement of the web deformation, the dry content changes during and after the suction pulse, the air flow through the fibre network and the saturation of the web after the suction pulse. Suction pressure, suction time and rewetting time were varied. The experiments were done with chemical and mechanical pulp webs of various grammages. It was found that a large web deformation took place during the suction pulse, particularly at its beginning. Compression dewatering was found to be the most dominant dewatering mechanism. Displacement dewatering started after most of the web compression had occurred. Its contribution to the increase in dry content was most pronounced for higher suction pressures, longer suction times and for chemical pulp webs. A surprisingly large expansion of the web was observed immediately after the suction pulse. This expansion was the effect of rewetting. This rewetting strongly reduced the dry content of the web if the web had not been immediately separated from the forming fabric at the end of the suction pulse. Under the conditions studied, the decrease in dry content amounted to the order of 3 to 6 %. Rewetting was smaller for longer suction times and higher suction pressures. A considerable air flow through the web occurred under these conditions. This air flow apparently moved water from the forming fabric into the suction box, thus making less water available for rewetting. Rewetting for mechanical pulp webs was more pronounced and took place faster than for chemical pulps. The use of a membrane on top of the web during suction box dewatering proved to be advantageous for reducing the air flow through the web. However, under the conditions investigated, the dry content could not be improved. Although the web compression was increased when using a membrane, especially at a higher suction pressure, rewetting after the suction pulse had an even larger negative impact on the dry content, which, as a result, was lower.QC 20100924
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Usher, Shane Patrick. "Suspension dewatering : characterisation and optimisation /." Connect to thesis, 2002. http://eprints.unimelb.edu.au/archive/00000972.
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Ju, Shuohui. "Electroosmotic dewatering of bentonite suspensions." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59868.
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Electroosmotic dewatering of Bentonite suspensions under conditions of constant DC voltage and constant DC current was investigated experimentally in a column 5 cm in diameter. The suspensions were prepared with CaCl$ sb2$ in distilled water with concentrations up to 1 M. The initial solid content was between 9.1 wt% and 26 wt% and the initial bed height ranged from 1.0 cm to 5.2 cm. Constant voltages from 4.0 V to 8.0 V and constant currents from 90 mA to 110 mA were used.Electroosmosis removed 20-60% of the water with energy expenditures well below the energy required to vaporize the water. Higher voltages or currents removed more water. Removal rates were increased by the addition of CaCl$ sb2$. The lowest bed height (1 cm) gave the lowest energy of dewatering, but the final water removal was low. For constant voltage experiments with an initial field strength of 2.8 V/cm, bed heights around 2 cm gave the highest water removal. The initial solid content had little effect on the final solid content. The Helmholtz/Smoluchowski theory did not predict correctly the effects of electrolyte concentration, solid content and bed height on the rate of electroosmotic dewatering.
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Neeson, S. J. N. "New technologies in sludge dewatering." Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546397.
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Bevan, Marc A. "Geoenvironmental impacts of construction dewatering." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431942.
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Zhang, Yi. "Suspension dewatering with aggregate densification." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/suspension-dewatering-with-aggregate-densification(7599d818-8f26-4e2d-b80f-b4fa243dba52).html.
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This thesis concerns design of two pieces of suspension dewatering equipment (i.e. transient batch settlers and steady state continuous gravity thickeners). In a transient batch settler, very slow densification of aggregates within the suspension is considered whilst the drag on the solids in the suspension is assumed to be negligible. The interface of the suspension is then determined by a balance between gravity and the gradient of the compressive yield stress of the gelled suspension. The compressive yield stress functional form in general could be either a weakly gelled formula, or a strongly gelled formula. These formulae differ in the way they behave for solids concentrations in the neighbourhood of the suspension gel point. The effects of the above two gel formulae, the evolution of the compressive yield stress functional form over time during aggregate densification, different initial suspension heights, and different initial feed solids volume fractions upon the predictions of consolidated bed structures and solids volume fractions obtained at the bottom of a batch settler, and upon the evolution of the heights of the suspension and the consolidated bed have been explored. A sufficiently tall initial suspension height might lead to insignificant increases in the solids volume fractions obtained at the bottom of batch settlers after time-dependent aggregate densification. The interfaces of the suspension and the consolidation zone coincide after aggregate densification if the gel point, which increases with time, is larger than the initial feed solids volume fractions. Moreover, the maximum permitted underflow solids fluxes predicted from steady state thickeners have been investigated and compared. Pre-shearing of aggregates which densifies aggregates to have smaller diameters upon entering the thickener is necessary if large underflow solids fluxes and small underflow solids volume fractions are specified. The solids volume fraction at the top of the consolidated bed which is the densified gel point is influenced by the extent of pre-shearing of aggregates. An algorithm for determining this densified gel point has also been developed. In reality, thickeners contain not just a consolidating bed, but also a hindered settling region above it. When the hindered settling region is considered in a thickener, the effects of the extent of aggregate densification that has occurred in the hindered settling region and how that impacts upon thickener performance and sludge rheological properties have been explored in this thesis. A new algorithm for predicting the densified gel point obtained at the top of the consolidated bed has been developed when the hindered settling region is present. The effects of underflow solids volume fractions, aggregate densification rate parameters and pre-shearing of aggregates upon the predictions of maximum permitted underflow solids fluxes, sludge rheological properties, and thickener performance have been explored. The predictions of thickener performance using both the weakly and strongly gelled formulae have also been achieved. In cases where it is possible to neglect the hindered settling region, substantial increases in the maximum permitted underflow solids fluxes, and substantial decreases in the consolidated bed heights and the total solids residence times have been achieved after aggregate densification for a comparatively small underflow solids volume fraction. The benefits arising from aggregate densification are more modest if the underflow solids volume fraction is larger. On the other hand, when the hindered settling region is included, more densification of aggregates occurring in the hindered settling region might lead to taller consolidated bed heights for a specified suspension flux and a specified aggregate densification rate parameter due to higher underflow solids volume fractions.
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Astorsdotter, Jennifer. "Dewatering Cellulose Nanofibril Suspensions through Centrifugation." Thesis, KTH, Skolan för kemivetenskap (CHE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215079.
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Cellulose nanofibrils (CNF) is a renewable material with unique strength properties. A difficulty in CNF production is that CNF suspensions contain large amounts of water. If CNF suspension volume can be decreased by dewatering facilitated by centrifugation, then transportation costs and storage costs can be reduced. The aim of this thesis is to investigate the impact various parameters have on CNF centrifugation dewatering and identify optimal conditions for maximal water removal. A laboratory study was conducted using four materials; 2.0 w% enzymatically treated CNF (CNF1), 1.9 w% carboxymethylated CNF (CNF2) and two commercial samples (1.9 w% CNFA and 1.8 w% CNFB). The main method was analytical centrifugation up to 2330 g. Parameters tested were initial concentration before centrifugation, temperature, NaCl addition, pH, and applied solid compressive pressure (g-force and surface weight). In addition to centrifugation experiments the four materials were characterized with laser diffraction, UV-vis absorption, Dynamic light scattering, and dry weight measurements. Analysis of the experimental data collected show that increase in initial concentration give a higher final concentration, but less water is removed. Furthermore, temperature changes have no effect on separation of CNF and water. At an applied solid compressive pressure of 3 kPa and initial concentration at 1.5 w% the concentrations 5.5 w%, 1.5 w%, 4.0 w%, and 4.3 w% can be reach for CNF1, CNF2, CNFA, and CNFB respectively. After extrapolation of polynomial functions fitted to experimental data an applied solid compressive pressure of 22 kPa and initial concentration at 1:5 w%, the concentrations 9.1 w%, 1.5 w%, 6.9 w%, and 7.9 w% are predicted for CNF1, CNF2, CNFA, and CNFB respectively. The thickening of CNF suspensions achieved and predicted in this thesis implies possibilities for large amounts of water removal, e.g. the water content in a CNF1 suspension is reduced from 65.7 litres/kg CNF to 10.0 litres/kg CNF at the solid compressive pressure 22 kPa. The concentrations at 22 kPa are determined by extrapolation from experimental data <3 kPa solid compressive pressure. The carboxymethylated CNF2 can not be dewatered unless it is diluted or if salt or pH is adjusted. This is directly correlated to the electrostatic forces in the suspension and the Debye length. Addition of salt or lowered pH also eliminate any concentration gradients in diluted and centrifuged CNF2 suspensions.Cellulosa nanofibriller (CNF) är ett förnybart material med unika styrkeegenskaper. En svårighet med produktion av CNF är att CNF suspensioner innehåller stora mängder vatten. Om volymerna av CNF suspensioner kan minskas med avvattning genom centrifugering, då kan transport- och lagerkostnader sänkas. Målet med det här examensarbetet är att undersöka vilken inverkan olika parametrar har på CNF-avvattning genom centrifugering och identifiera optimala förhållanden för maximalt avlägsnande av vatten. En laboratoriestudie utfördes på fyra olika material. De fyra materialen är 2 w% enzymatiskt behandlad CNF (CNF1), 1.9 w% karboxymetylerad CNF (CNF2) och två kommersiella prover (1.9 w% CNFA och 1.8 w% CNFB). Den huvudsakliga metoden var analytisk centrifugering upp till maximalt 2330 g. De testade parametrarna var initial koncentration innan centrifugering, temperatur, NaCl tillsats, pH, och applicerat fast kompressionstryck (g-kraft och ytvikt). Förutom centrifugeringsexperimenten så karaktäriserades the fyra mmaterialen med laser diffraktion, UV-vis absorption, dynamisk ljusspridning och vägningar av torrhalt. Analys av den experimentella data som insamlats visar att en ökad initial koncentration ger en högre slutkoncnentration, men mindre vatten kan bortföras. Temperaturförändringar har ingen effekt på separation av CNF och vatten. Vid ett applicerat fast kompressibelt tryck på 3 kPa och en initial koncentration 1.5 w% kan koncentrationerna 5.5 w%, 1.5 w%, 4.0 w%, och 4.3 w% nås för CNF1, CNF2, CNFA, och CNFB. Efter extrapolering av polynoma funktioner passad till experimentell data förutspås att koncentrationerna 9.1 w%, 1.5 w%, 6.9 w%, och 7.9 w% kan nås för CNF1, CNF2, CNFA, and CNFB vid 22 kPa och en initial koncentration på 1.5 w%. Förtjockningen av CNF suspensioner som kan, eller förutspås kunna nås genom centrifugering i det här examensarbetet innebär att det är möjligt att avlägsna stora mängder vatten, till exempel kan vatteninnehållet i CNF1 minskas från 65.7 liter/kg CNF till 10.0 liter/kg CNF vid 22 kPa fast kompressionstryck. Koncentrationerna vid 22 kPa fast kompressionstryck är extrapolerade från exprimentell data <3 kPa fast kompressionstryck. Den karboy- metylerade CNF2 kan inte avvattnas om den inte späds ut eller om salt eller pH justeras. Detta är direkt kopplat till de elektrostatiska krafterna i suspensionen och Debye längden. Tillsats av salt eller sänkt pH eliminerar också de koncentrationsgradienter som kan förekomma i utspädda centrifugerade CNF2 suspensioner.
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Grant, Christine Sharon. "Electro-osmotic dewatering of mineral ultrafines." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/12117.
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Rios, Andrea. "DEWATERING OF BIOSOLIDS BY SODIUM FERRATE." Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2887.
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This study was conducted to evaluate the effectiveness of the liquid form of ferrate for dewatering of biosolids from wastewater treatment facilities. Two different ferrate products prepared using calcium hypochlorite and sodium hypochlorite were used. Samples of anaerobic digested sludge and waste activated sludge with solids content of 2.1% and 0.95 %, respectively were conditioned with both products to evaluate and compare their effectiveness. Centrifugation and filtration of the sludge after conditioning were used. For centrifugation the volume reduction and the turbidity of the supernatant after centrifugation were evaluated. For filtration, the Capillary Suction Time test was used. The optimum doses and conditions for dewatering of the sludge using ferrate were determined for each type of sludge. The centrifugation and filtration results were compared with those obtained for polymer doses currently used at the wastewater treatment plants where the samples were collected and with ferric coagulants as well. The results of this research indicated that optimum pH was 7.0. The time required to achieve mechanical equilibrium defined as the time at which the volume occupied by the solids was no more than one percent of the preceding reading was 1800 seconds for both types of sludge. The optimum rotational speeds were 800 and 2400 for waste activated sludge and anaerobic digested sludge, respectively. The optimum ferrate dose for anaerobic digested sludge for centrifugation and filtration was 5000 mg/l. For waste activated sludge a dose of 10 mg/l was found to be effective for filtration and centrifugation. The results indicated that the ferrate product prepared using calcium hypochlorite provides better results for the waste activated sludge than the ferrate prepared using sodium hypochlorite, while for anaerobic digested sludge no significant difference was observed. Finally, the results show that ferrate is a cost-effective alternative for the conditioning and disinfection of waste activated sludge, but not for the conditioning of anaerobic digested sludge.M.S.Env.E.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environmental Engineering
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Mok, Chi Kit. "Design and modelling of electroosmotic dewatering." Thesis, University of Newcastle Upon Tyne, 2006. http://hdl.handle.net/10443/746.
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Many previous studies have demonstrated that electroosmotic dewatering is an effective technique to dewater sewage sludge. However, the technology has not yet been successfully applied in industry. This is because there are several technological barriers to the commercial exploitation of the technology that are yet to be resolved. One of these barriers is a scientifically robust design methodology. This aim of this study is to establisha qualitative and quantitative understanding model of electroosmotic dewatering of sewage sludge and from this produce a robust design methodology. This study is divided into three parts: The first part evaluates the feasibility of electroosmotic dewatering under constant voltage for range of sludge types. A number of experiments with four different sewage sludges were undertaken to examine the dewatering efficiency in terms of rate of dewatering, final solid concentration and energy consumption. The results showed that electroosmotic dewatering of sludge is both feasible and potentially economic. It is also shown that the use of the Helmholtz-Smolucowski flow eqPation, together with the assumptions of no electrochemical reaction and a constant electroosmotic permeability, to predict the dewatering process is not sound. The second part of this thesis presents an integrating framework for electroosmotic dewatering under constant voltage and constant current, founded on the mathematics of simple electricalc ircuits and demonstrated by laboratory experimentation. The derived equations and experimental results showed that electroosmotic flow rate decreases with time when dewatering with constant voltage and is constant when dewatering with constant current. Having a linear relationship between flow and time, electroosmotic dewatering with constant current not only enhances the sludge dewatering efficiency, but also has the advantage of simplifying design procedures. The third part explores in further detail each of the design parameters of electroosmotic dewatering under constant current, including sample thickness, current, time over which constant current could be maintained, power supply, pressure and type of electrodes. A detailed design methodology, including design equations to predict final solid content and treatment time, design requirements for each parameter and design procedures, is presented.
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Keles, Serhat. "Fine Coal Dewatering Using Hyperbaric Centrifugation." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/37807.
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The solid-solid separation processes employed by modern coal preparation plants require large amounts of process water that must be removed from the surfaces of particles using mechanical dewatering equipment. Unfortunately, the existing processes that are used to dewater fine particles are inefficient in terms of moisture reduction and/or solids recovery. Many coal preparation plants are forced to discard fine coal particles because of the inability of existing technologies to reduce the moisture content of this product to an acceptable level. In light of this problem, a new ultrafine dewatering process called hyperbaric filter centrifugation (HFC) has been developed. This novel method combines centrifugation and pressure filtration within a single process to substantially reduce moistures over what can be achieved using conventional dewatering systems.
In the current study, steady-state and dynamic dewatering models were developed in order to be able to simulate the behavior of the HFC technology. The steady-state model, which was based on grain-size properties, used empirical expressions to predict product moistures. On the other hand, the dynamic model was based on fundamental theories of filtration and centrifugation. Although the dynamic model provided a better understanding of the working principles of the process, the steady-state grain model produced more accurate equilibrium moisture predictions. Therefore, the steady-state model was used to further investigate the effects of several parameters on cake moistures. As such, the steady-state model was useful for scale up and design purposes.
The steady-state dewatering model was also used to perform an economical analysis of potential applications of the HFC technology. The model was used to investigate a variety of new circuit designs that have the potential to be commercially applied in the coal industry. The results clearly showed that this new technology would allow coal companies to process difficult-to-dewater ultrafines using the HFC process, while coarser solids would be more appropriately dewatered using conventional technologies such as vacuum filters or screenbowl centrifuges. This â split dewateringâ concept would provide substantially higher profitability due to lower moistures and higher recoveries of ultrafine solids than could be achieved using a single dewatering process.
Laboratory- and pilot-scale versions of this technology has been constructed and tested at the facilities of Mining & Minerals Engineering Department of Virginia Tech. Results of this testing program showed that 30-50% lower moisture values than the ones obtained using conventional mechanical dewatering processes could be achieved with the HFC technology. Based on these promising results, a pilot-scale prototype unit, which was tested successfully at several commercial U.S. coal plants, was also constructed by Decanter Machine, Inc. Finally, the process of developing of this novel technology was successfully completed with the sale of the first full-scale commercial unit by Decanter Machine, Inc. to a major U.S. coal producer.Ph. D.
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Buckley, Margaret M. "Conditioning for shear in sludge dewatering." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09052009-040620/.
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Satyamurthy, Ranjan. "Experimental investigations of geotextile tube dewatering." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.
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Paterson, Daniel Thomas. "Understanding rapid dewatering of cellulose fibre suspensions." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58195.
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Rapid dewatering of cellulose fibre suspensions is a fundamental process in many unit operations in the production of pulp and paper. Understanding dewatering behaviour can be applied to optimizing designs of industrial equipment. In this project, we assess the suitability of a well-established modeling approach, referred to as the base model, at capturing the one dimensional dewatering behaviour of cellulose fibre suspensions seen experimentally. This modeling approach requires two closure relationships determined experimentally, i.e. compressive yield stress and permeability. Experimental equipment has been designed, constructed, and operated to obtain the closure relationships and collect dewatering results for validation of the model. Two experimental techniques, with close agreement, have been developed for the collection of compressive yield stress. Permeability results are obtained through Darcian permeation experiments. Two approaches, neglecting and accounting for flow induced compaction, were developed. Results were found to fall within values seen in the literature. The base model provided good representation of ideal nylon fibre suspension trials. These solid fibres are representative of the base models constitutive equation for an infinite solid phase rearrangement rate constant. The base model poorly represents the cellulose fibre suspensions' dewatering behaviour. The suggested source of discrepancy is the further dynamic due to the dewatering of the individual porous cellulose fibres which results in a finite solid phase rearrangement rate constant. The base model is expanded upon in hopes of capturing this rate dependent behaviour. This extended model, with the determined closure relationships, captured load versus solid volume fraction profiles at varying dewatering rates better than the base model for cellulose fibre suspensions. Further improvements in representation were seen through close representation of the solid phase velocity profiles found experimentally during dewatering. Various cellulose fibre suspensions were investigated to begin a catalog of different dewatering behaviours seen through variations in pulp production variables. Investigations included varying fibre species, pulping processes, levels of low consistency refining, and impacts of dewatering chemical additives.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Gopalakrishnan, Sridhar. "Electroosmotic and combined field dewatering of sludges." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23367.
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Four type of suspensions were dewatered by electroosmosis alone or by electroosmosis combined with other methods: (1) Clay (Bentonite or hydrocol)--electroosmosis with constant voltage continuous DC or square wave interrupted power. In the interrupted mode, a constant voltage was applied for t$ sb1$ seconds (the on-time) followed by a short circuit for t$ sb2$ seconds (the off-time). (2) Food waste--electroosmosis (continuous DC only) alone or in combination with expression (pressure of 207 kPa). (3) Titanium oxohydrate slurry--electroosmosis (similar to (1)) alone or in combination with a vacuum (absolute pressure of 89 kPa). (4) Pyrite slurry--electroosmosis (similar to (1)) in combination with vacuum (similar to (3)). The major independent variables were applied voltage, t$ sb1$ and t$ sb2,$ and initial bed height. The dependent variables were the amount of water removed and the electric current.For clay and titanium oxohydrate there was an optimum off-time for a fixed on-time. For $ rm t sb1=30$ s, the most water was removed from clay with $ rm t sb2=0.1$ s while for titanium oxohydrate the most water was removed for $ rm t sb2=3.5$ s. For suspensions (2), (3) and (4), the combination of electroosmotic dewatering with vacuum or expression increased the amount of water removed. In general, interrupted power removed more water than continuous power electroosmosis. For suspensions (3) and (4), only the combined modes were able to achieve dewatering targets set by industry.
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Murthy, Sudhir N. "Predicting dewatering equipment performance from laboratory tests." Thesis, Virginia Tech, 1992. http://hdl.handle.net/10919/43976.
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Asmatulu, Ramazan. "Advanced Chemical-Mechanical Dewatering of Fine Particles." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26604.
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In the present work, novel dewatering aids and a novel centrifuge configuration were developed and applied for the purpose of dewatering fine particles. Three different types dewatering reagents were tested in different filtration and centrifugation units. These chemicals included low-HLB surfactants, naturally occurring lipids, and modified lipids. Most of these reagents are insoluble in water; therefore, they were used in solutions of appropriate solvents, such as light hydrocarbon oils and short-chain alcohols. The role of these reagents was to increase the hydrophobicity of the coal and selected mineral particles (chalcopyrite, sphalerite, galena, talc, clay, phosphate, PCC and silica) for the dewatering. In the presence of these reagents, the water contact angles on the coal samples were increased up to 90o. According to the Laplace equation, an increase in contact angle with the surfactant addition should decrease the capillary pressure in a filter cake, which should in turn increase the rate of dewatering and help reduce the cake moisture. The use of the novel dewatering aids causes a decrease in the surface tension of water and an increase in the porosity of the cake, both of which also contribute to improved dewatering.
A series of batch-scale dewatering tests were conducted on a variety of the coal and mineral samples using the novel dewatering aids. The results obtained with a Buchner funnel and air pressure filters showed that cake moistures could be reduced substantially, the extent of which depends on the particle size, cake thickness, drying time, reagent dosage, conditioning time, reagent type, sample aging, water chemistry, etc. It was determined that use of the novel dewatering aids could reduce the cake formation time by a significant degree due to the increased kinetics of dewatering. At the same time, the use of the dewatering aids reduced the cake moistures by allowing the water trapped in smaller capillaries of the filter cake. It was found that final cake moistures could be reduced by 50% of what can be normally achieved without using the reagents. However, the moisture reduction becomes difficult with increasing cake thickness. This problem can be minimized by applying a mechanical vibration to the cake, spraying a short-chain alcohol on the cake and by adding a small amount of an appropriate coagulant, such as alum and CaCl2 to the coal and mineral slurries.
The novel dewatering aids were also tested using several different continuous filters, including a drum filter, disc filter and horizontal belt filter (HBF). The results obtained with these continuous filtration devices were consistent with those obtained from the batch filters. Depending on the coal and mineral samples and the type of the reagent, 40 to 60% reductions in moisture were readily achieved.
When using vacuum disc filters, the cake thickness increased substantially in the presence of the novel dewatering aids, which could be attributed to the increased kinetics of dewatering. A dual vacuum system was developed in the present work in order to be able to control the cake thickness, which was necessary to achieve lower cake moistures. It was based on using a lower vacuum pressure during the cake formation time, while a full vacuum pressure was used during the drying cycle time. Thus, use of the dual vacuum system allowed the disc filter to be used in conjunction with the novel dewatering aids. Its performance was similar to that of HBF, which is designed to control cake thickness and cake formation time independently.
The effectiveness of using the novel dewatering aids were also tested in a full-continuous pilot plant, in which coal samples were cleaned by a flotation column before the flotation product was subjected to the disc filter. The tests were conducted with and without using novel dewatering aids. These results were consistent with those obtained from the laboratory and batch-scale tests.
The novel centrifuge developed in the present work was a unit, which combined a gravity force and air pressure. The new centrifuge was based on increasing the pressure drop across the filter cake formed on the surface of the medium (centrifuge wall). This provision made it possible to take advantage of Darcy s law and improve the removal of capillary water, which should help lower the cake moisture. A series of tests were conducted on several fine coal and mineral particles and obtained more than 50% moisture reduction even at very fine particle size (2 mm x 0).
Based on the test results obtained in the present work, two proof-of-concept (POC) plants have been designed. The first was for the recovery of cyclone overflows that are currently being discarded in Virginia, and the other was for the recovery of fines from a pond in southern West Virginia. The former was designed based on the results of the plant tests conducted in the present work. Cost vs. benefit analyses were conducted on the two POC plants. The results showed very favorable internal rates of return when using the novel dewatering aids.
Surface chemistry studies were conducted on the coal samples based on the results obtained in the present investigation. These consisted mainly of the surface characterization of the coal samples (surface mineral composition, surface area, zeta potential, x-ray photoelectron microscopy (XPS)), acid-base interactions of the solids and liquids, dewatering kinetic tests, contact angle measurements of the coal samples and surface force measurements using AFM. In addition, carbon coating on a silica plate using palsed laser deposition (PLD) and Langmuir-Blodgett (LB) film deposition tests were conducted on the sample to better understand the surfactant adsorption and dewatering processes. The test results showed that the moisture reductions on the fine particles agree well with the surface chemistry results.Ph. D.
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Eraydin, Mert Kerem. "Scale-up of Using Novel Dewatering Aids." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/27990.
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Coal preparation plants use large quantities of water for cleaning processes. Upon cleaning, the spent water must be removed such that the final product moisture level meets market constraints. However, removal of free water from the surface of fine particles is difficult and costly, and often the results are less than desirable. Fine particles inherently have very large surface areas, and hence retain large amounts of water. Increased amounts of fines also cause denser particle packing, which creates relatively small capillaries in filter cakes and, thus, cause slower dewatering kinetics. As a result, dewatering costs for fine particles are much higher than for dewatering coarse particles. Considering the technical and economic issues associated with dewatering coal and mineral fines, an extensive matrix of laboratory- and pilot-scale dewatering tests have been conducted to evaluate the use of novel dewatering aids. The reagents are designed to lower the surface tension of water, increase the hydrophobicity of the particles to be dewatered, and increase the capillary radius by hydrophobic coagulation. All of these are designed to lower the moisture of the filter cakes produced in mechanical dewatering processes. Laboratory-scale dewatering tests confirmed that using the novel dewatering aids can lower the final cake moisture of coal by 20-50%, while increasing the dewatering kinetics. Several on-site, pilot-scale tests were conducted to demonstrate that the process of using the novel dewatering aids can be scaled.
Based on the laboratory- and pilot-scale tests conducted, a scale-up model for the process of using the novel dewatering aids has been developed. It can predict the final cake moistures as a function of vacuum pressure, filtration time and specific cake weight. The model can be useful for the scale-up of vacuum disc filters (VDF) and horizontal belt filters (HBF). Simulation results indicate that dewatering aids can be very effective, especially when used in conjunction with HBF due to its ability to control cake thickness and drying cycle time independently.
In light of the promising laboratory- and pilot-scale test results, an industrial demonstration of the novel dewatering aids has been conducted at the Smith Branch impoundment site, which contains 2.9 million tons of recoverable coal. When the reagent was used for dewatering flotation products using a VDF, the moisture content was reduced from 26 to 20% at 0.5 lb/ton of reagent addition and to 17.5% at 1 lb/ton. The use of the dewatering aid also improved the kinetics of dewatering, increased the throughput, and reduced the power consumption of vacuum pumps by 30%.
The novel dewatering aids were also tested successfully for dewatering of kaolin clays. In this case, the mineral was treated with a cationic surfactant before adding the dewatering aids. This two-step hydrophobization process was able to reduce the cake moisture and also increase the throughput.Ph. D.
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Eraydin, Mert Kerem. "Evaluation of Novel Fine Coal Dewatering Aids." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/34182.
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The costs of cleaning fine coal are substantially higher than those of cleaning coarse coal. Therefore, many many coal companies in the U.S. choose to discard fine coal (150 micron x 0) by means of 6-inch diameter hydrocyclones. The cyclone overflows are stored in fine coal impoundments, which create environmental concerns and represent loss of valuable national resources. The major component of the high costs of cleaning fine coal is associated with the difficulty in fine coal dewatering. Therefore, the availability of efficient of fine coal dewatering methods will greatly benefit companies.
In the present study, three different novel dewatering aids have been tested. These include Reagents W (RW), Reagent U (RU), and Reagent V (RV). These reagents are designed to increase the contact angles of the coal samples to be dewatered, which should help decrease the Laplace pressure of the water trapped in filter cake and, hence, increase dewatering rate. They were tested on i) the fresh coal samples from Consolidation Coal Corporation's Buchanan Preparation Plant, ii) a composite drill core sample from the Smith Branch Impoundment, Pinnacle Mine Mining Company, and iii) a blend of coals from the Smith Branch Impoundment, thickener underflow, and thickener feed.
The coal samples were used initially for laboratory-scale tests using a 2.5-inch diameter Buchner vacuum filter. The results showed that the use of the novel dewatering aids can reduce the cake moisture up to 50% over what can be achieved without using any dewatering aid. The use of the dewatering aids also increased the kinetics of dewatering by up to 6 times, as measured by cake formation times.
On the basis of the laboratory test results, pilot-scale continuous vacuum filtration tests were conducted using a 2-feet diameter Peterson vacuum disc filter. The cake moistures obtained in the pilot-scale test work were similar to those obtained in the laboratory tests, while the fast dewatering kinetics observed in the laboratory tests was manifested as higher throughput. It was found that high-shear agitation is essential for achieving low cake moistures and high throughput.Master of Science
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Agarwal, Saurabh. "Conditioning and Dewatering Behavior of ATAD Sludges." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/31480.
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Autothermal thermophilic aerobic digestion (ATAD) of sludge has been used to produce class A biosolids. With stringent EPA guidelines, more and more municipalities are looking to use this process for digestion of sludge. However the large polymer costs associated with dewatering these sludges has made the use of this technology unfavorable. Several studies have been conducted in the past which have looked into the mechanism leading to such a poor dewatering of sludge. Some of these studies have attributed the release of protein and polysaccharide during the high temperature digestion to be responsible for the poor dewatering. However the exact mechanism leading to the poor dewatering is still not totally clear. Laboratory scale studies were conducted to evaluate the mechanism leading to the poor dewatering of these sludges and also to be able to economically condition these sludges. ATAD sludge samples were collected from ATAD processing facilities in Ephrata, PA, Cranberry, PA, Titusville, FL and College Station, TX. The research included experiments evaluating the protein and polysaccharide concentrations in solution, cations and anions, iron and aluminum, zeta potential and capillary suction time. It was found that during digestion large amounts of protein and polysaccharide were released which were in the colloidal range, and the dewatering of each of these sludges became poorer as the amount of protein and polysaccharide in the solution increased. The release of protein and polysaccharide was related to the monovalent to divalent cation ratio and the iron and aluminum concentration in the sludge. Also during the digestion process, the pH of the sludge increased appreciably and the divalent cations precipitated out. The zeta potential of the ATAD digested sludge was also found to be positive. Different chemical coagulants were used to condition the sludge, but even with high polymer doses the dewatering of the sludge was not satisfactory. A combination of iron (or cationic polymer) followed by anionic polymer was found to improve the dewatering to a desired level. The use of this combination of sludge conditioning also provides an economical solution to the problem of dewatering. The role of iron in improving the dewatering of the sludges was found to be important, with the sludge dewatering being better for sludges with a high iron content. The combination of high pH, divalent cation precipitation, iron deficiency and biopolymer release all contribute to the poor dewatering of ATAD sludge.Master of Science
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Liao, Kaixia. "Dewatering of natural sediments using geotextile tubes." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.
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Myers, William Scott Elton David J. "Dewatering rock crushing fines using geotextile tubes." Auburn, Ala., 2010. http://hdl.handle.net/10415/2033.
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Shih-Yun, Liu. "Slurry dewatering in the pipe jacking industry." Thesis, University of Leeds, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619040.
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Lobosco, Vinicius. "On the Modelling of Mechanical Dewatering in Papermaking." Doctoral thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3702.
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Most of the water fed into a paper machine is removedmechanically in the forming and press sections. One of thefactor which has an important influence on mechanicaldewatering, i.e. in both forming and pressing, is thestress-strain behaviour of the fibre network.
The focus of this thesis is on the development of improvedmathematical descriptions of the stress-strain behaviourexhibited by fibre networks in the forming and press sections.The first part of the thesis presents a physically based modelof the forming and densification of fibre mats in twin-wireformers. The model can calculate the ecect of the applicationof a varied load through the forming section. It was developedfrom mass and momentum balances of the fibre and liquid phases,the fibre mat stress-porosity relation and an expression forthe permeability as a function of the porosity. The fibre-matstress-porosity relation used is rate-independent and presentshysteresis. Simulations have been conducted to study theeffects of roll pressure, blade pulses, wire tension andbeating. The effect of sequential blade pressure pulses afterthe forming roll on the dewatering and the concentrationgradients could be characterised. The simulations alsoexhibited rewetting by expansion when the fibre mats left theforming roll. Increasing wire tension resulted in increaseddewatering, but the rate of increase diminished rapidly withincreasing tension. The simulation results also indicated thatbeating has a large influence on dewatering.
The second part of the thesis presents two models of therate-dependent stress-strain behaviour of the fibre networkthat is observed in wet pressing. The first model was based onthe approach pioneered by Perzyna (1966) for strain-ratedependent plasticity and was quite satisfactory for calculatingthe stress-strain behaviour of the fibre network in singlepress nips. It was successfully applied for studyingdensification and dewatering in both normal wet pressing andhigh temperature wet pressing. However, the first model onlyincludes rate dependence in the compression phase of thecompressionexpansion cycle; the expansion phase is treated asbeing rate independent
The second model of the stress-strain behaviour of the fibrenetwork treats both compression and expansion as being ratedependent, according to experimental observations. It is basedon the idea that the wet fibre web may be conceived as alayered network of restricted swelling gels. A swollen fibre isa restricted gel, the inner swelling pressure in a swollenfibre wall being balanced by the stresses in the fibre wallstructure. The observed rate dependence of wet webs in bothcompression and expansion phases was attributed to the flow ofwater out of and into the fibre walls. The second model gavepredictions that are in good agreement with results fromuniaxial experiments using pressure pulses of arbitrary shapefor both a single pulse and a sequence of pulses. It maytherefore be used as a general model for the rheologicalbehaviour of the wet fibre network in wet pressing, providedthe model parameters are estimated from experimental data withsmall experimental error.
KEYWORDS:Paper, modelling, dewatering, forming, wetpressing, fibre network stress, rheology, hysteresis,intra-fibre water, compressibility, structural stress,stress-strain, restricted gels, swelling.
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Mao, Songqin. "High water content sludge dewatering via freeze-thaw." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21188.pdf.
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Silva, Marvin Jose. "Plant dewatering and strengthening of mine waste tailings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0015/NQ46918.pdf.
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Krishnamurthy, Shivakumar. "Dual-chemical conditioning for dewatering municipal wastewater sludges." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60230.pdf.
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Grant, Christine Sharon. "Surfactant enhanced electro-osmotic dewatering of mineral ultrafines." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/11704.
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Rabie, Hamid Reza. "Continuous and interrupted electroosmotic dewatering of clay suspensions." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56987.
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Suspensions of Bentonite, kaolin and red clay were dewatered electroosmotically under continuous and interrupted DC voltage and current. The suspension was held in a vertical 5-cm diameter column between two platinum mesh electrodes, an upper anode and a lower cathode. Suspensions were prepared with CaCl$ sb2$ in distilled water at concentrations up to 10$ sp{-2}$ M. The initial solid content was between 9.1 and 15 wt% for Bentonite and between 25 and 45 wt% for kaolin and red clay. The initial bed height ranged from 0.5 to 2 cm. Constant voltages from 2.75 to 5.0 V and constant currents from 30 to 90 mA were used. In the interrupted regime the off-time ranged from 0.5 to 20 s with the on-time fixed at 30 s. A short circuit or an open circuit was applied during the off-time. The interrupted process with a short circuit was also applied at the end of a DC run when dewatering had stopped.Electroosmosis removed 20-70% of the water with an energy expenditure well below the heat of vaporization. The water removal rates were increased by the addition of CaCl$ sb2$. Beds of 0.5 cm thick were dewatered faster and with less energy consumption than thicker beds. Interruption with a short circuit applied during a 0.5 s off-time removed about 20-40% more water than DC for equal energy consumption. Interruption at the end of a DC run removed nearly the same amount of water as interruption applied from the beginning of a run. Relative motion between the electrodes in the form of rotation of the upper electrode at 40 or 70 rpm had no significant effect on dewatering. The Helmholtz/Smoluchowski theory did not agree with the experiment results for the effects of interruption in power and electrolyte content.
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Ng, Yue-hang, and 伍宇鏗. "Dewatering and treatment of sewage sludge before landfill." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31253222.
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Marklund, Stefan. "Dewatering of wastewater sludge by natural air drying." Licentiate thesis, Luleå tekniska universitet, 1997. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18524.
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Reitz, Daniel D. "Municipal sludge dewatering using a belt filter press." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53178.
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Experiments were performed on alum, anaerobically digested and aerobically digested sludges to determine the optimum polymer conditioning for a belt filter press The optimum polymer dosages for all three zones of a belt filter press were compared with each other to determine the best overall conditioning. The requirements of all three zones of a belt filter press were the same. However, the gravity rate of drainage seems to under predict the dosages for optimum belt filter press performance. In addition the total mixing energy, G (the shear) and t (the mixing time), that represents the laboratory belt filter press was found to be approximately 45,000. Using a mixing energy input of 45,000 and a standard Buchner funnel apparatus the correct polymer dose for the belt filter press can be predicted.Master of Science
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Smith, Kara E. "Cleaning and Dewatering Fine Coal using Hydrophobic Displacement." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/33416.
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A new processing technique, known as hydrophobic displacement, was explored as a means of simultaneously removing both mineral matter and surface moisture from coal in a single process. Previous thermodynamic analysis suggests that coal moisture will be spontaneously displaced by any oil with a contact angle greater than ninety degrees in water. Based on these results, six methods of hydrophobic displacement were evaluated: hand shaking, screening, air classification, centrifugation, filtration, and displacement. In the first five methods hydrophobic displacement took place during the cleaning stage. A recyclable non-polar liquid (i.e. pentane) was used to agglomerate coal fines followed by a physical separation step to remove the coal agglomerates from the mineral-laden slurry. Bench-scale tests were performed to identify the conditions required to create stable agglomerates. Only the last method, displacement, did not utilized agglomeration and performed hydrophobic displacement during dewatering, not cleaning. A procedure was also developed for determining moisture content from evaporation curves so that the contents of water and pentane remaining in a sample could be accurately distinguished.
Two primary coal samples were evaluated in the test program, i.e., dry pulverized 80 mesh x 0 clean coal and 100 mesh x 0 flotation feed. These samples were further screened or aged (oxidized) to provide additional test samples. The lowest moisture, 7.5%, was achieved with centrifugation of the pulverized 80 mesh x 0 clean coal sample. Centrifugation provided the most reliable separation method since it consistently produced low moisture, high combustible recoveries, and high ash rejections. Hand shaking produced the next lowest moisture at 16.2%; however, the low moistures were associated with a drop in combustible recovery. There was also a great deal of error in this process due to its arbitrary nature. Factors such as oxidation, size distribution, and contact angle hysteresis influenced the concentrate moistures, regardless of the method utilized.
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McInnis, Jeffrey A. "Biodegradation and Dewatering of an Industrial Waste Oil." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/41440.
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Waste oil generated from industrial operations at a diesel locomotive maintenance facility was investigated to establish its treatability and potential volume reduction. The waste oil and water mixture separated into four distinct layers; free oil, emulsified oil, weathered oil, and wastewater. The research was conducted in a series of three batch experiments and focused on the emulsified and weathered oils. The waste oil was aerobically treated in nutrient amended, 55 gallon (208 L) drums for 38 to 42 days in 10 and 20 % mixtures with sufficient air for mixing and oxygen. Biodegradation, and the role of a synthetic surfactant in promoting biodegradation, was measured using chemical oxygen demand (COD), fluorescein diacetate (FDA), and gas chromatography (GC) analyses with extractable material. Dewatering of biodegraded oil was measured using capillary suction test (CST), time to filter (TTF), and percent cake solids.
Batch 1 examined the role of bioaugmentation by comparing a 10% waste oil mixture that was augmented with a mixture of hydrocarbon degraders to a 10 % mixture of waste oil with no bioaugmentation. Final COD reductions were 59 (± 9) and 38 (±3) % for the bioaugmented and non-bioaugmented reactors, respectively. Chromatographs showed significant reduction in the abundance of peaks by the end of the experiment for both reactors. Overall results suggested that there was no significant difference in biodegradation capabilities between the amended and native microorganisms.
Batch 2 was conducted to determine if a synthetic surfactant (Tween-80) could enhance biodegradation of a 10 % waste oil mixture. The surfactant-amended reactor showed COD reduction 3 days before the non-surfactant-amended reactor. Chromatographs showed similar results for both reactors with the non-surfactant-amended reactor showing slightly better degradation by the end of the experiment. The total COD reduction by the end of the experiment was the same in both (R1: 85 ± 20%, R2: 84 ± 16 %), suggesting that exogenous surfactant addition did not have a long-term impact in the biodegradation of the waste oil.
Batch 3 examined the effect of different oil phases and concentrations on biodegradation and the dewatering characteristics of post-biodegraded waste oil. The 20 % weathered and emulsified waste oil mixture showed a clear delay in COD reduction (no notable reduction until day 24) compared to the 10 % weathered waste oil mixture. The final COD reductions were the same (R1: 48 ± 13%, R2: 49, ± 23 %). Chromatographs showed similar results for both reactors and indicated that degradation of the waste oil occurred in both reactors. The data suggest that the 20 % waste oil mixture can be degraded to the same extent as the 10 % mixture in 38 days.
Dewatering characteristics, as measured by CST, were poor for the 20 % post-biodegraded combined waste oil mixture without conditioning. Conditioning with alum or ferric chloride substantially improved dewatering of the waste oil for the 20 % mixture but was of limited benefit for the 10 % mixture. Percent cake solids for conditioned 10 % post-biodegraded waste oil mixture was 44 (± 0.3) to 50 (± 1.7) % and 34 (± 0.3) to 50 (± 1.8) % for the 20 % mixture. The cake solids for the unconditioned 10 % mixture was 50 to 65 % and 54 to 68 % for the 20 % mixture. The higher percent cake solids for the unconditioned 20 % mixture was countered by the very high TTF (up to 30 min. to filter 50 mL) and the inability to dewater the sludge during the last five sampling events. Conditioning appeared to have a limited effect on the dewatering properties of the 10 % mixture.Master of Science
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Hou, Jing. "ALGEA SUSPENSION DEWATERING WITH AN INCLINED GRAVITY SETTLER." Cleveland State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=csu1328154061.
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Ng, Yue-hang. "Dewatering and treatment of sewage sludge before landfill /." Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B14723232.
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Lightfoot, Dennis G. (Dennis George). "Combined fields (electro-osmosis and pressure) dewatering of kelp." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68202.
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The world's brown marine algae, or kelps, have a great potential for agricultural use. Over 14 million tonnes of kelp are estimated to be available for harvesting every year, but only 6.3% is harvested, mostly for food products or alginate extraction. The inclusion of kelp in an animal's ration has been found by several researchers to have a beneficial effect on the animal's health and productivity. High concentrations of kelp in an animal's ration, however, can have detrimental effects on the animal's health due to toxic levels of certain inorganic salts.By including a dewatering operation in the production of dried kelp meal, much of the soluble salts present in the kelp will be removed with the filtrate. The filtrate would also be valuable as a source of potassium, trace minerals, and phyto-hormones for crops. Energy costs for dewatering are also much lower than for drying. Because kelp is difficult to dewater using conventional methods, a combined fields technique using electro-osmosis and mechanical pressure was investigated.
Electric current and pressure were both found to have a significant positive effect on dewatering. Dewatering resulted in significantly lower ash and available carbohydrate fractions, while having no other significant effect on kelp meal composition. The combined fields dewatering resulted in significant total energy savings over conventional dewatering or drying alone.
The combined fields dewatering process was successfully scaled up to a continuous process using a prototype roller press. The press was able to produce a press cake with up to 32% solids. The continuous process resulted in significantly lower ash content and significantly higher protein. The total energy to produce kelp meal with the roller press was found to be about half of the energy required for drying alone.
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PULGAR, NEIRA HUGO ALEJANDRO. "Inverkan av avvattningshastighet på formation och styrka på ark med låg ytvikt." Thesis, KTH, Skolan för kemivetenskap (CHE), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172445.
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For this thesis project, a method to analyze the dewatering time for the drainage process during laboratory sheet making on a Finnish sheet former was developed. The resulting method proved to deliver very reliable information about the dewatering time and the transient speed of the sheet making process. The method was then used for two studies to find how fiber types, refining and/or slower dewatering conditions affects sheet properties, like formation and tensile strength. The first study compared the difference in formation and strength between softwood and hardwood fibers at three different drainage restrictions. The second study was performed to understand the effect of refining on dewatering time and the connection to resulting sheet properties. The results of both studies showed that at low grammages, the fiber web that was formed did not affect the dewatering time and speed regardless of the type of fibers or refining level. This meant that the drainage for low grammages sheets was solely controlled by the drainage restriction of the draining pipe on the sheet former. In addition, tensile strength and formation of the sheets did not vary significantly between the different dewatering speeds tested and the differences where more related to fiber properties than to the modified conditions of the dewatering of the sheet making process.
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Chu, Wan-bun. "Failure analysis for the conveyor chain at dewatering system." access abstract and table of contents access full-text, 2000. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174131a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2000."Submitted in partial fulfilment of the requirements for the degree of Master of Science in materials technology and management from City University of Hong Kong." Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.
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Rumpus, Josephine Mary. "Scale down of recovery and dewatering in industrial centrifuges." Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287982.
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Bansal, S. P. "Sludge dewatering in terms of structure and hydraulic conductivity." Thesis, University of Strathclyde, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382265.
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Small, Derek Matthew. "A computational and experimental study of the dewatering hydrocylone." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301345.
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Burslem, Rosemary Helen. "The pervaporative dewatering of alcohol using caesium polyacrylate membranes." Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321842.
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MARAZZI, FRANCESCA ALICE. "Growth of microalgal biomass on supernatant from biosolid dewatering." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2017. http://hdl.handle.net/10281/158195.
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Questa tesi è volta a valutare l’integrazione delle microalghe in impianti di depurazione con il duplice scopo di rimuovere azoto e produrre biomassa da convogliare ai digestori anaerobici. In particolare, questa tesi si concentra sulla identificazione dei acque reflue di tipo agricolo e civile (come effluenti, centrati, digestato, e una miscele di loro) più idonee ad essere usate come substrato per la cultura microalghe.
Il capitolo 2 contiene un resoconto che tratta degli attuali approcci per la produzione di biomassa microalgale utilizzando diversi tipi di rifiuti. Il cuore della mia sperimentazione è descritta nei capitoli 3-7; in particolare, il capitolo 3 mostra i risultati di test nei quali il centrato di origine civile è stato usato come substrato per la produzione di biomassa algale. La novità dello studio consiste: (i) nell’uso di centrato tal quale come substrato di crescita, mentre la maggior parte dei dati di letteratura sono stati ottenuti su refluo pretrattato, (ii) nell'uso di un fotobioreattore alimentato in continuo e (iii) nello svolgimento delle prove in condizioni ambientali naturali. Questo lavoro ha dimostrato che le microalghe (Chlorella sp e Scenedesmus sp) sono in grado di crescere facilmente sul centrato e il loro tasso medio di crescita specifico, che varia tra 0,14-0,16 d-1 è comparabile con i dati di letteratura. Anche i test di produzione di biometano (BMP) hanno mostrato buoni risultati: il BMP ottenuto dalla biomassa microalgale è più lento rispetto ai fanghi, ma il suo valore finale è leggermente superiore (208 mLCH4 gVS-1 vs 190 mLCH4 gVS-1).
Nel capitolo 4 sono stati studiati diversi reflui agricoli, che potenzialmente potrebbero essere usati come substrato di crescita per le microalghe. Le analisi chimiche e fisiche hanno dimostrato che le frazioni liquide di letame suino potrebbe essere utilizzato a tale scopo. Nel capitolo 5 viene proposto un pre-trattamento con carboni attivi (AC) del centrato di origine suina per facilitare la crescita microalghe. Sono stati testati diversi dosaggi di carbone attivo e il dosaggio di 40 g L-1 e 10 minuti di tempo di adsorbimento sembra essere il più promettente. Nello specifico la riduzione della torbidità del refluo è stata pari all’88%. Gli incoraggianti risultati in scala di laboratorio presentati nel Capitolo 4 e 5 giustificano le successive sperimentazioni su scala pilota, utilizzando reflui di origine agricola come fonte di nutrienti per microalghe. Nel capitolo 6 viene presentato il lavoro in scala pilota, un fotobioreattore è stato installato presso una azienda agricola nel Nord Italia. Durante la sperimentazione, la densità microalghe è rimasta abbastanza costante, intorno al valore medio di 0,55 gTS/l, mentre le efficienze di rimozione dell’azoto totale e di N-NH4+ erano entrambe molto alte (in media 80 e 87%, rispettivamente).
L'obiettivo principale del capitolo 7 è volto a trovare la migliore tecnica di separazione della biomassa algale dal substrato di crescita. In questa sezione sono stati testati tre processi di separazione liquido/solido della biomassa microalgale: (i) sedimentazione per gravità; (ii) centrifugazione, (iii) flocculazione. Le principali conclusioni sono riportate nel capitolo 8: l'integrazione delle microalghe negli schemi di trattamento delle acque reflue offre una strategia economicamente fattibile e ambientalmente sostenibile; la crescita microalgale è fortemente influenzata dalle condizioni ambientali; il pretrattamento del digestato, combinato con i processi di strippaggio e adsorbimento con carbone attivo potrebbe migliorare notevolmente l'efficacia della coltivazione delle microalghe; le microalghe potrebbero essere co-digerite con fanghi di scarto senza effetti negativi sul consorzio anaerobico, nonostante le biomassa microalgale abbia alcuni punti critici come la parete cellulare resistente che limita la sua bioconversione.This thesis deals with the feasibility of including a mixed microalgal community in a real wastewater treatment sequence with the double aim of removing nitrogen and producing biomass to feed the anaerobic digesters. In particular, this thesis focuses on identification of relevant waste streams from agricultural and municipal activities (like effluents, centrates, digestates, and a mixture of them) as a substrate for microalgal culture. Chapter 2 contains a critical review, this manuscript summarizes the current approaches to microalgal biomass production using waste streams, including wastewater, waste or CO2-enriched gas (flue gas and biogas), waste organics (i.e., crude glycerol) and waste heat, as well as the primary common operational challenges and corresponding mitigation strategies involved in culturing approaches. The core of experimentation is described in Chapters 3-7 using wastewater from urban or agriculture activity as a substrate for microalgal culture. In particular, Chapter 3 shows the results of experimentation using municipal centrate to produce biomass to feed the anaerobic digesters removing at the same ammonia nitrogen. The novelty of the study consists in the use of raw centrate from urban wastewater treatment plant as a substrate to grow microalgae, while the majority of literature data were obtained on pre-treated (diluted and/or supplemented and/or furtherly clarified) centrate samples, in the use of a continuously fed PhotoBio Reactor (PBR) operated under natural, uncorrected environmental conditions. This work demonstrates that microalgae (Chlorella sp and Scenedesmus sp) are able to easily grow on the centrate. The average specific growth rate in indoor and outdoor batch tests is satisfactory and comparable with literature data, ranging between 0.14-0.16 d-1. During the continuous test the average biomass production is 50 mgTSS L-1 d-1 and the difference between N-NH4 concentration in the influent and in the effluent demonstrates an important removal. Also BMP tests showed good results: the production of biomethane from algal biomass is slower than from sludge, but its final value is slightly higher than that from waste sludge (208 mLCH4 gVS-1 vs. 190 mLCH4 gVS-1). Wastewaters from agricultural activities are the subject of Chapter 4, chemical and physical analyses showed that the liquid fractions of swine manure and the first effluent could be suitable for algal treatment, while the other samples had unacceptable levels of both solid content and turbidity which would seriously limit light penetration. The papers in Chapter 4 and Chapter 5 report the results obtained in lab-scale tests using the agro wastes which had been shown to be more suitable. In Chapter 5 a new approach is proposed using Activated Carbon (AC) from wood as a pre-treatment to facilitate microalgal growth, without addition of tap water for dilution. The optimal optical density values were obtained with 40 g L-1 of AC dosage and 10 minutes adsorption time, corresponding to 88% of turbidity reduction. Then semi-continuous microalgae culturing were tested using adsorbed and not adsorbed liquid centrate (3 replicates). The encouraging lab scale results presented in Chapter 4 and Chapter 5 justify further pilot-scale experimentation, using agrowastes as the nutrient source for microalgae, presented in Chapter 6. The pilot scale (PBR) was installed at a piggery farm in Northern Italy. During the culturing period, microalgal density remained quite constant, around the average value of 0.55 gTSS/L, and the efficiency of Total Nitrogen and of N-NH4+ removal were both very high (on average 80 and 87%, respectively). The search for the best biomass harvesting technique is the main objective of Chapter 7. In this point, microalgal biomass is processed by three solid/liquid separation processes: gravity settling; centrifugation tests, flocculation tests. The main conclusions are reported in Chapter 8.
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Kalra, Aashish. "Dewatering of fine coal slurries by selective heating with microwaves." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4536.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains xi, 84 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
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Khan, Konika Moushumi Chemical Sciences & Engineering Faculty of Engineering UNSW. "The effect of floc microstructure and shear on dewatering processes." Awarded by:University of New South Wales. Chemical Sciences & Engineering, 2007. http://handle.unsw.edu.au/1959.4/40547.
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This work investigated the effect of floc microstructure (size and fractal structure) and shear forces on dewatering processes, which are crucial for environmental and economical aspects in many industries. Due to limitations inherent In experimental investigations, a numerical code using the discrete element method and including some novel force models (polymer bridging force, elastic bending moment and a modified concept of rolling friction torque) was developed to simulate the consolidation behavior of flocculated systems. The code showed good agreement with experimental results. The elastic behavior of aggregates is known to depend on the backbone structure (stress bearing structure of the aggregate). However, there is little known about backbone structure. It was found that backbone represents a fractal structure with a fractal dimension value close to 1 and increasing with increase of aggregate mass fractal dimension. The dewatering process was characterized by compressive and hindered settling behavior. The numerical study of compressive rheology with different aggregate microstructure showed that the compaction results from a reduction of the correlation length rather than increase in fractal dimension. The compressive behavior is consistent with theoretical models at higher compressive stresses but is not well described at low compressive stresses. A semi- empirical model is presented describing the compressive rheology in both regions via a correction factor derived using dimensional analysis. The hindered settling behavior was in good agreement with the theoretical model based on the assumption of self similar structure. The investigation revealed that shear effect is not due entirely to hydrodynamics and can arise from the particle bonding mechanism alone. The study showed that low shear increases compressibility but high shear is detrimental. At low shear, bond bending at local voids results in solid densification. High shear increases kinetic energy and kinetic repulsion of the particles. The effect of shear is analogous to the anomalous behavior of the water density- temperature function. At low temperature bond breakage increases the density and at high temperature thermal expansion decreases the density. The investigation showed that shear increases the permeability due to bending of the structure in the shear direction, resulting in large pores.
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Maawia, Abdalla Ali. "Numerical simulation of irrigation canal priming and dewatering flow conditions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0002/NQ38488.pdf.
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Dursun, Derya. "Gel-like behavior of biosolids in conditioning and dewatering processes." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 260 p, 2007. http://proquest.umi.com/pqdweb?did=1362540141&sid=7&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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