Removal of VOCs from air by absorption and stripping in hollow fiber devices

Large volumes of exhaust air streams contaminated with volatile organic compounds (VOCs) such as toluene, xylene, acetone etc. are discharged into the atmosphere by various industrial facilities. Common technologies for VOC emission abatement e.g., activated carbon adsorption, absorption in a liquid, incineration and catalytic oxidation, have many strengths as well as considerable limitations. In this study, a regenerative absorption-based removal of VOCs from N2 in an inert, nonvolatile, organic liquid flowing in compact hollow fiber devices has been developed. The process eliminates flooding, loading and entrainment encountered in conventional absorption devices. Contaminated air/N2 stream was fed through the tube side of the hollow fiber module; a suitable inert absorbent liquid having a high solubility for the VOCs and extremely low vapor pressure was pumped countercurrently over the outside (shell side) of the fibers. The absorbent liquid was regenerated by vacuum in a separate hollow fiber membrane-based stripper. Two types of hollow fiber membranes were studied: one having microporous wall and the other having a nonporous VOC-permeable coating on the outer surface of a microporous hollow fiber. Criteria for nondispersive operation have been developed for each case. Experiments were conducted for the absorption of acetone, methylene chloride, toluene and methanol from the respective VOC-N2 gas mixture using two different inert absorbent liquids, silicone oil and Paratherm™. Theoretical models have been developed from first principles to simulate the behavior of absorption as well as the combined absorption-stripping process. Highest mass transfer coefficient was obtained for toluene absorption followed by methylene chloride, acetone and methanol absorption. Studies with multicomponent VOCN2 gas mixtures also showed that percent toluene removal was highest followed by methylene chloride, acetone and methanol. The behaviors of VOC mass transfer coefficients have been illustrated as a function of the gas and liquid flow rates. A comprehensive characterization of different resistances making up the overall resistance in VOC absorption has been carried out to develop a predictive capability and compare two types of fibers. Relative absorption performance between the two types of fiber for a given VOC was dependent on the diffusivity of the VOC in the absorbent liquid used. VOC absorption characteristics were determined and compared for the two absorbents used. The absorbent-filled porous membrane was found to contribute significantly to the total mass transfer resistance. Continuous absorption-stripping experiments employing recycling of the absorbent liquid via regeneration in a hollow fiber stripper were also accomplished. The overall performance of the combined process appears to be controlled by stripping due to the low temperature and lower membrane surface area in the stripper. The difference between only absorption and combined absorption-stripping results was more pronounced for VOC-absorbent system having higher Henry\u27s law constant and diffusivity. Simulated results obtained from the mathematical models agree well with the experimental results for absorption as well as for combined absorption-stripping

Complexes of Ethylene-1,2-bis-diphenylarsine with Pt(II & IV), Pd(II) & Ru(III)

174-17

Probing R-parity violating models of neutrino mass at the LHC via top squark decays

It is shown that the R-parity violating decays of the lighter top squarks (${\widetilde t}_1$) triggered by the lepton number violating couplings $\lambda^{\prime}_{i33}$, where the lepton family index i = 1-3, can be observed at the LHC via the dilepton di-jet channel even if the coupling is as small as 10$^{-4}$ or 10$^{-5}$, which is the case in several models of neutrino mass, provided it is the next lightest supersymmetric particle(NLSP) the lightest neutralino being the lightest supersymmetric particle(LSP). We have first obtained a fairly model independent estimate of the minimum observable value of the parameter ($P_{ij} \equiv BR(\widetilde t \to l_i^+ b) \times BR(\widetilde t^* \to l_j^- \bar b$)) at the LHC for an integrated luminosity of 10fb$^{-1}$ as a function of \mlstop by a standard Pythia based analysis. We have then computed the parameter $P_{ij}$ in several representative models of neutrino mass constrained by the neutrino oscillation data and have found that the theoretical predictions are above the estimated minimum observable levels for a wide region of the parameter space.Comment: 19 pages, 1 Figure and 11 Table

New signals of a R-parity violating model of neutrino mass at the Tevatron

In a variety models of neutrino masses and mixings the lighter top squark decays into competing R - parity violating and R - parity conserving channels. Using Pythia we have estimated in a model independent way the minimum value of P $\equiv$ BR($\widetilde t_1 \to c \widetilde \chi_1^0$) $\times$ BR($\widetilde t_1 \to l^+_i b$), where $l_i = e^+$ and $\mu^+$, corresponding to an observable signal involving the final state 1$l$ + jets +\met (carried by the neutrinos from the $\tilde \chi_1^0$ decay) at Tevatron Run II. For the kinematical cuts designed in this paper P depends on $m_{\widetilde t_1}$ only. We then compute P for representative choices of the model parameters constrained by the oscillation data and find that over a significant region of the allowed parameter space P is indeed larger than $P_{min}$. This signal is complementary to the dilepton + dijet signal studied in several earlier experimental and phenomenological analyses and may be observed even if BR($\widetilde t_1 \to l^+_i b$) is an order of magnitude smaller than BR($\widetilde t_1 \to c \widetilde \chi_1^0$). The invariant mass distribution of the hardest lepton and the hardest jet may determine $m_{\widetilde t_1}$ and reveal the lepton number violating nature of the underlying interaction. The invariant mass distribution of the two lowest energy jets may determine $m_{\widetilde \chi_1^0}$.Comment: Some minor changes in language are made at pages 1,2,8 and 18 respectivel

A Low-spin Mn(III) Complex

205-20

Scaling of NonOhmic Conduction in Strongly Correlated Systems

A new scaling formalism is used to analyze nonlinear I-V data in the vicinity of metal-insulator transitions (MIT) in five manganite systems. An exponent, called the nonlinearity exponent, and an onset field for nonlinearity, both characteristic of the system under study, are obtained from the analysis. The onset field is found to have an anomalously low value corroborating the theoretically predicted electronically soft phases. The scaling functions above and below the MIT of a polycrystalline sample are found to be the same but with different exponents which are attributed to the distribution of the MIT temperatures. The applicability of the scaling in manganites underlines the universal response of the disordered systems to electric field

Development and evaluation of multi millet thresher

In tribal areas of India, traditional methods of threshing of minor millets like little millet (Panicum sumatrense), M1, kodo millet (Paspalum scrobiculatum), M2, foxtail millet (Setaria italica), M3, proso millet (P. miliaceum), M4, barnyard millet (Echinochloa frumantacea), M5, finger millet (Eleusine coracana), M6 is done of beating by sticks or treading out the crop panicle under the feet of oxen. This operation is most time consuming, labour intensive, drudgery prone, uneconomical, lower output and obtain low quality products. A thresher for these millet crops was developed and optimization of the operating parameters with little millet was done by using Response surface methodology (RSM). The optimized parameters were 7.79% (d.b) moisture content, 105 kgh-1 feed rate, 625 rpm cylinder speed, 5 mm threshing sieve size which gave maximum threshing efficiency of 95.13% and cleaning efficiency of 94.12%. After optimization of parameters the thresher was tested for threshing of all the six minor millets with proper adjustments of sieve. Threshing capacity of M1, M2, M3, M4, M5 and M6 were obtained as 89, 137, 140, 91, 88 and 99 kg/h, respectively with more than 96% threshing efficiency and less than 2% broken grain

Top squark and neutralino decays in a R-parity violating model constrained by neutrino oscillation data

In a R-parity violating (RPV) model of neutrino mass with three bilinear couplings $\mu_i$ and three trilinear couplings $\lambda'_{i33}$, where $i$ is the lepton index, we find six generic scenarios each with a distinctive pattern of the trilinear couplings consistent with the oscillation data. These patterns may be reflected in direct RPV decays of the lighter top squark or in the RPV decays of the lightest superparticle, assumed to be the lightest neutralino. Typical signal sizes at the Tevatron RUN II and the LHC have been estimated and the results turn out to be encouraging.Comment: 20 pages, 4 figures, LaTex,typos corrected and reference added for section 2, a paragraph has been added in the conclusion par