S.N. Upadhyay

Biofiltration of toluene using wood charcoal as the biofilter media.

A laboratory scale biofilter inoculated with Pseudomonas putida (MTCC 102) was used for degradation of toluene present in air. Wood charcoal was used as the filter media and a layer of glass beads (6mm) was used for improved air distribution. The biofilter was operated continuously for a period of 5months at four different flow rates - 0.06, 0.12, 0.18, and 0.24m(3)h(-1), with inlet concentration of toluene ranging from 0.04 to 4.5gm(-3). Air having toluene vapor was fed to the biofilter at various loadings ranging from 30.6 to 1104.5gm(-3)h(-1). The removal efficiency was obtained in the range of 70-99.5%. The maximum elimination capacity of 872.5gm(-3)h(-1) was observed at the inlet load of 1104.5gm(-3)h(-1). Wood charcoal was found to an effective biofilter media for toluene biodegradation.

A mechanistic theory for heat transfer between fluidized beds of large particles and immersed surfaces

Abstract A mechanistic theory for the heat transfer between an immersed surface and a fluidized bed of large particles is developed by adopting the well accepted concept that in the absence of radiation the total heat transfer coefficient is the sum of conductive ( h cond ) and convective ( h conv ) components. The solids are assumed to be distributed around the heat transfer surface in an arrangement of unit orthorhombic cells. h cond is then computed by considering a composite infinite layer of gas and solid and by solving the unsteady state heat conduction equations under well defined boundary and initial conditions. h conv is evaluated by assuming that the turbulent boundary layer on the heat transfer surface is disrupted at the front half of the particle and is reformed in its wake. The theoretical model predictions for the total heat transfer coefficient are in good agreement with the available experimental data on large particle systems. The proposed theory is considered a good predictive and design tool.

Biodegradation of trichloroethylene (TCE) by methanotrophic community

Laboratory incubation experiments were carried out to assess the potential of methanotrophic culture for degrading TCE. Measurements of the growth rate and TCE degradation showed that the methanotrophs not only grew in presence of TCE but also degraded TCE. The rate of TCE degradation was found to be 0.19 ppm h(-1). The reverse transcriptase-PCR test was conducted to quantify expression of pmoA and mmoX genes. RT-PCR revealed expression of pmoA gene only. This observation provides evidence that the pmoA gene was functionally active for pMMO enzyme during the study. The diversity of the methanotrophs involved in TCE degradation was assessed by PCR amplification, cloning, restriction fragment length polymorphism and phylogenetic analysis of pmoA genes. Results suggested the occurrence of nine different phylotypes belonging to Type II methanotrophs in the enriched cultures. Out of the nine, five clustered with, genera Methylocystis and rest got clustered in to a separate group.

Fluid—particle heat transfer in fixed and fluidized beds

Abstract Fluid-particle heat transfer in fixed and fluidized beds is re-examined. The heat transfer factor depends not only on the particle Reynolds number but also on the void fraction of the bed. The available experimental data has been correlated to yield a non-linear relationship between ϵ J h and the particle Reynolds number. The resulting expression is: .

On the mass transfer in non-newtonian fluids I. Transfer from spheres to power law fluids

Abstract Mass transfer from a soluble solid cylinder placed in a co-axially flowing stream of non-Newtonian fluids has been investigated. Compressed cylinders of benzoic acid of 2.0 and 2.5 cm diameter and 1.0 to 4.031 cm length have been used as test specimens and demineralized water and 1.0 and 3.0% aqueous solutions of carboxy methyl cellulose (CMC) as the test fluids. It has been shown that the results for both Newtonian and non-Newtonian fluids can be correlated together by using an effective viscosity for power law fluids based on the rheological constants established in a capillary tube viscometer.

Bio-filtration of trichloroethylene using diazotrophic bacterial community

Biodegradation of TCE was studied in a biofilter packed with wood charcoal and inoculated with diazotrophic bacterial community isolated from local soil. Steady state TCE removal efficiencies higher than 85% were observed up to inlet load of 2.866 g m(-3) h(-1). The maximum elimination capacity of 5.31 g m(-3) h(-1) was observed at an inlet load of more than 7.90 g m(-3) h(-1). The biofilter was sensitive to fluctuations in the process conditions but could easily recover its performance after 10 days shutdown. Almost constant and small pressure drop per unit length and very negligible compaction was observed during the whole experimental period. The molecular analyses such as RT-PCR and gene sequencing revealed the presence of functionally active Azospirillum species in the biofilm.

Heat transfer between fluidized beds of large particles and horizontal tube bundles at high pressures

Abstract The experimental heat transfer data for horizontal square inline tube bundles (DT = 13.0 mm and pitch values are 19.5, 29.3 and 39.0 mm) immersed in fluidized beds of glass beads ( d p = 1.25 and 3.1 mm) and sands( d p = 0.794 and 1.225 mm) are measured as a function of fluidizing velocity and system pressure (1.1, 2.6, 4.1 and 8.1 MPa). The heat transfer coefficient values are found to increase with particle diameter, system pressure but are almost independent of tube pitch in the range investigated here. The hw values are compared with the predictions of five different theories available in the literature. The two correlations for Numax are also considered and evaluated. Significant conclusions are drawn on the basis of reported hw data for large particles at high pressures.

High pressure heat transfer investigations for fluidized beds of large particles and immersed vertical tube bundles

Abstract The overall heat transfer coefficient, hw, is measured for vertical tube bundles in fluidized beds of glass beads (ƌp = 1.25 and 3.10 mm) and sands (ƌp = 0.794 and 1.225 mm) at pressures of 1.1, 2.6,4.1 and 8.1 MPa and ambient temperature. Tube bundles of three different pitches (19.5, 29.3 and 39.0 mm) are employed and hw is reported as a function of velocity, G. It is found that hw increases with pressure, to a lesser extent with tube pitch, and with an increase in particle diameter. The experimental data are compared with the predictions of four theories for hw and two theories of hw,max. It appears that the theory of Ganzha et al. is most successful in reproducing the experimental data and it is recognized that the knowledge of reliable bed voidage at the heat transfer surface and in the bulk is crucial for its applicability.

Characterization of bacterial isolates from rubber dump site and their use in biodegradation of isoprene in batch and continuous bioreactors

Bacterial isolates from contaminated soil of a waste rubber dumping site were isolated and characterized using biochemical and molecular approaches. Isoprene degradation kinetics in batch mode (isoprene concentration: 100-1000 ppm) revealed the degradation efficiency of isolates as: Pseudomonas sp. (83%)>Alcaligenes sp. (70%)>Klebsiella sp. (68.5%). The most efficient isolate Pseudomonas sp. was finally inoculated in a specifically designed bioreactor system comprising a bioscrubber and a biofilter packed with polyurethane foam connected in series. The bioscrubber and biofilter units when operated in a series showed more than 90% removal efficiency up to the inlet loading rate (IL) of 371.1g/m(3)/h. Maximum elimination capacity (EC) of biofilter was found to be an order of magnitude greater than that for bioscrubber. Oxidative cleavage of the double bond of isoprene has been revealed through IR spectra of the leachate.

Fluidized bed and freeboard heat transfer studies with vertical tube bundles

Abstract Heat transfer coefficients between fluidized sand beds ( d p = 222, 488 and 778 μ m ) and a bundle of six vertical stainless steel tubes ( D T = 25.4 mm ) are measured as a function of air fluidizing velocity in the maximum temperature range of 311–475K. The results are interpreted to infer the dependence of heat transfer coefficient on gas velocity, bed temperature and particle diameter. Freeboard heat transfer is also investigated by employing a bundle of six nested vertical hair-pin tubes ( D T = 12.7 mm ). Heat transfer coefficient is found to decrease to a minimum value as the gas velocity is increased but thereafter increases slowly with increase in gas velocity. The dependence of heat transfer coefficient on temperature in the range investigated here is found to be weak.