Sedimentation Of Aqueous Coal Slurry In Presence Of Sodium-PDF Free Download

Sedimentation of Aqueous Coal Slurry in presence of Sodium
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International Journal of Engineering Technology Management and Applied Sciences. www ijetmas com April 2017 Volume 5 Issue 4 ISSN 2349 4476. about 1000 10 3 was found The two states could be reversed or a mixture of the two could be obtained by. appropriate changes in the suspending medium They came across an identical phenomenon of the same two. sedimentation rates but unrelated in this instance to the presence of calcium In a media more acidic than pH. 5 8 the more rapidly sedimenting component alone was observed while above this pH region only the slower. one was seen, Robert 1949 observed that the rate of sedimentation dH dt decreases linearly with the difference between its. height at any time t and ultimate height H which would be achieved after infinite time of settling. Thus dH dt k H H 1, Where k is a constant, On integration dH dt k H HL 2. Therefore exp kt H H Hc H 3, Where t Time of the start of the experiment. H Height of the interface at time t, Hc Initial height corresponding to t the critical height at which the constant settling rate gives way to a. diminishing rate, Casassa et al 1984 in their experiments measured a variety of properties of dry coal powders and of coal.
water slurries for ten bituminous coals some available as both ROM and beneficiated samples Slurry. rheology maximum solids content and stability towards sedimentation are in general related to the. electrophoretic mobility measured in concentrated suspensions rather than to the microelectrophoretic. mobility determined in very dilute suspensions of the coals They also discussed the influence of coal particle. median size BET surface area with nitrogen as adsorbate ash content and soluble ashcontent and degree of. oxidation on slurry properties At the end of the series of experiments it was observed that median particle. size particle size distribution width and particle internal volume accessible to water have a strong influence. upon coal water slurry viscosity and stability At a given median size size distribution and surface area slurry. properties can be predicted from the electrophoretic mobility of concentrated suspensions The effects upon. surface charge and therefore upon slurry viscosity and stability of oxidation beneficiation and slurry ionic. strength can also be predicted although slurry viscosity is less sensitive to ionic strength than slurry stability. toward sedimentation, Bueno et al 1990 carried out batch sedimentation tests with coal mining wastes in a wide range of. concentrations and flocculant dosages in an original prototype of photo sensible sedimentograph In spite of. the peculiarities of the slurries studied the experimental procedure and the way the data have been fitted to an. empirical equation can be extended to any suspension as a useful tool in the preliminary design of settlers. whatever the nature and complexity of the slurry may be. Evangelou and Karathanasis 1991 through their research article provided an insight on the importance of. coal sedimentation from an environmental point of view Colloidal particle settling experiments were. conducted in the laboratory to test the influence of pH and dissolved solids on the kinetics of settling of. suspended solids in a coal mine spoil sample obtained from western Kentucky Potentiometric titrations. suggested that the pH range of colloid co flocculation for the sample tested was around 4 2 Repulsive diffuse. double layers at pH above 4 2 appeared to control suspended solid behavior The rate of settling of suspended. solids decreased as the pH of the suspension increased The ratio was highly influenced by the ionic strength. sodium adsorption rate SAR and type of divalent cation Ca or Mg With Ca as the saturating cation and. SAR values below 1 the suspended solids dropped below the required 35 mg L limit within a 2 h period At. SAR values above 4 and pH near and or above 7 suspended solids exceeded those required by the law When. the divalent cation was Mg the coal mine spoil solids appeared to be less dispersive For sedimentation ponds. neutralized with NaOH this type of kinetic information is necessary to improve sediment trapping efficiency. and design ponds with appropriate water detention times Gregory 1998 studied the effect of structure of. flocscan greatly influence the flocculation in solid liquid separation process Latsa et al 1999 through their. research study presented a two phase model for the simulation of sedimentation processes The model solves. the continuity and momentum equations for the pure clear liquid and the sludge phases and it is verified. against a well known benchmark problem for which analytical solutions exist Numerical simulations of a. typical 1 D batch sedimentation process for mono dispersed particles are carried out and results are found to. 36 Edwin Gomes Koheli Modak Gurupada Mondal Shraboni Chakraborty. Deepshikha Datta Bimal Das, International Journal of Engineering Technology Management and Applied Sciences. www ijetmas com April 2017 Volume 5 Issue 4 ISSN 2349 4476. be in satisfactory agreement with experimental data and model predictions of other researchers A further. expansion of the model to two dimensions leads to predictions of the dynamic behavior of settling tanks and. the effect of the inclination angle on the sedimentation process Font and Laveda 2000 studied a batch test of. sedimentation with flocculated suspension to obtain the design parameters for continuous gravity thickeners. However they concluded that the design procedure was only approximate because the surface height was. measured by virtual observation of the sediment, Ganguly and Saha 2001 carried out experimental investigation to find the value of n in the generalized. relationship, dH d k0 H Heq n 4, On integration yields. 1 1 n H Heq 1 n H Heq 1 n k0 for n 1 0 5, There observation was when n 0 1 a better result is obtained as compared to that when n 1 0.
Bo Xue and Yan Sun 2003 studied the experimental and theoretical studies of sedimentation of poly. disperse agarose agar agar beads with broad particle size distribution They used a light extinction principle. to measure the variation of solid concentration in the suspension with time and settling distance They also. studied the effect of solid concentration and liquid density and viscosity on the settling behavior of beads. Boylu et al 2003 studied the effects of different chemicals that were used as dispersing agent and stabilizer. on the stability and viscosity of coal water slurries CWS In the experiments anionic type of chemicals. polyisoprenesulphonic acid soda Dynaflow K a derivative of carboxylic acid AC 1320 and. naphthalenesulfonate formaldehyde condensate NSF were used as dispersing agents and the stabilizer was. the sodium salt of carboxymethyl cellulose CMC Na The coal sample used was a bituminous coal thermal. code no 434 of Turkish origin with medium volatile matter The results of the experiments showed that. polymeric anionic dispersing agents such as Dynaflow have much greater effect on the viscosity and the. stability of coal water slurry, Boylu et al 2004 performed experiments to understand the effect of coal particle size distributions on. rheology of coal water slurries CWS Experiments were carried out on coal samples were different in rank. Besides two different Turkish lignite Soma and Istanbul Agacli a bituminous coal from Siberia Russia. were used In addition to the determination of the chemical and physical properties of the coal samples their. zeta potentials were also measured The pulps of different solids percentage composed of coal particles with. d50 sizes of 19 35 and 50 m were used to determine the effect of volume fraction on the viscosity of the. slurry It was found that the effect of particle size distribution and pulp density on the viscosity was in good. agreement with the findings of other investigators Furthermore the effect of volume fraction venation on the. viscosity was investigated for heterogeneous and homogeneous mixtures prepared with different ranks of. coals Coal water slurries prepared with three types of coals having different ranks but similar particle size. distribution and d50 values showed that although they have similar volume fraction values their apparent. viscosities decreased from lower to higher rank coals Therefore coal water slurries prepared using higher. rank coals could contain much higher amount of solids It was also observed that the viscosity increases with. increasing pulp density by weight for various particle size distributions The results can be explained on the. basis of the fact that coals of different ranks exhibit different chemical and physical properties such as. porosity specific surface areas and O C ratio etc Heterogeneous and homogeneous mixtures prepared with. three different ranks of coals showed that volume fraction of heterogeneous mixtures were higher compared to. the homogeneous mixtures In case of a wide range of particle size distribution fine particles fill the gaps. between coarse particles and therefore higher volume fractions can be obtained Higher rank coals give higher. volume fraction values than lower rank coals, Demeler et al 2004 through their research discussed several improvements to deal with sedimentation. coefficient distributions spanning a large range of s values They presented a method which allowed the. inclusion of scans early and late in the experiment that ordinarily would need to be excluded from the analysis. due to ultracentrifuge cell end effects Scans late in the experiment are compromised by the loss of a defined. plateau region and by back diffusion from the bottom of the cell Early scans involve partial boundaries that. have not fully cleared the meniscus In addition a major refinement of the algorithm for determining the. 37 Edwin Gomes Koheli Modak Gurupada Mondal Shraboni Chakraborty. Deepshikha Datta Bimal Das, International Journal of Engineering Technology Management and Applied Sciences. www ijetmas com April 2017 Volume 5 Issue 4 ISSN 2349 4476. boundary fractions is introduced taking into account different degrees of radial dilution for different species. in the system The method retains its desirable model independent properties the analysis of sedimentation. data does not require prior knowledge of a user imposed model or range of sedimentation coefficients and. reports diffusion corrected s value distributions which can be presented either in a histogram format or the. traditional integral distribution format At the end comparisons are made between data analyzed with the. traditional vHW method with those of the improved method to demonstrate the benefit from the added. information in the analysis, Dickey and Parris 2004 studied as a part of the project to develop a low cost method ethanol soluble protein. from corn meal They noted several advantages over industrially proven methods of liquid particle separation. 1 Extract liquid entrained by settling particles dissolves in water from which ethanol can be recovered. by distillation, 2 Less expensive equipments, 3 Particles which settle at different rates can be collected from different outlets.
Boylu et al 2005 carried out experiments to study the effect of carboxymethyl cellulose CMC used as a. stabilizer in the preparation of coal water slurries on the stability Experiments have been executed on the. coal samples which differ in rank Besides two different Turkish Lignite Soma and Istanbul a bituminous. coal Thermal Code No 434 of Turkish origin Zonguldak with medium volatile matter also has been used. The results of the experiments showed that polymeric anionic CMC agent has much greater effect on the. stability of CWS prepared from bituminous coal Also it was found that inorganic mineral matters were able. to be used as a stabilizer for preventing the sedimentation and separation of CWS. Zhang et al 2005 undertook a research to resolve the problems of high concentrations of circulating water. and difficult settlement of coal slurry in coal preparation plant research the influence of pH on flocculation. and sedimentation of coal slurry The results show that neutral or acidic environment help to get better. flocculation and sedimentation effect Nonionic PAM cationic PAM and anionic PAM get different. flocculation and sedimentation effect in coal slurry with different pH The effect is the best when pH is 9 for. non ionic PAM 5 for cationic PAM and anionic PAM, Mosa et al 2008 through their study illustrated the effect of chemical additives or reagents on rheological. characteristics of coal water slurry CWS The power law model was applied to determine the non. Newtonian properties of coal slurries They studied and tested three types of dispersants namely sulphonic. acid sodium tripolyphosphate and sodium carbonate at different concentrations ranging from 0 5 to 1 5 by. weight from total solids Sodium salt of carboxymethyl cellulose Na CMC and xanthan gum were tested as. stabilizers at concentrations in the range of 0 05 to 0 25 by weight from total solids They reported that. apparent viscosity and flow properties of CWS are sensitive to the use of chemical additives dispersants and. stabilizers Among studied dispersing agents sulphonic acid recorded the best performance in modification. and reducing CWS viscosity The best dosage of all tested dispersants was found to be as 0 75 by wt of. solids With regard to studied stabilizers Na CMC recorded better performance than xanthan gum The best

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