Composition and chemistry of particulates from the Tidd Clean Coal Demonstration Plant pressurized fluidized bed combustor, cyclone, and filter vessel

In a Pressurized Fluidized Bed Combustion (PFBC)/cyclone/filter system ground coal and sorbent are injected as pastes into the PFBC bed; the hot gases and entrained fine particles of ash and calcined or reacted sorbent are passed through a cyclone (which removes the larger entrained particles); and the very-fine particles that remain are then filtered out, so that the cleaned hot gas can be sent through a non-ruggedized hot-gas turbine. The 70 MWe Tidd PFBC Demonstration Plant in Brilliant, Ohio was completed in late 1990. The initial design utilized seven strings of primary and secondary cyclones to remove 98% of the particulate matter. However, the Plant also included a pressurized filter vessel, placed between the primary and secondary cyclones of one of the seven strings. Coal and dolomitic limestone (i.e, SO{sub 2} sorbent) of various nominal sizes ranging from 12 to 18 mesh were injected into the combustor operating at about 10 atm pressure and 925{degree}C. The cyclone removed elutriated particles larger than about 0.025 mm, and particles larger than ca. 0.0005 mm were filtered at about 750{degree}C by ceramic candle filters. Thus, the chemical reaction times and temperatures, masses of material, particle-size distributions, and chemical compositions were substantially different for particulates removed from the bed drain, the cyclone drain, and the filter unit. Accordingly, we have measured the particle-size distributions and concentrations of calcium, magnesium, sulfur, silicon, and aluminum for material taken from the three units, and also determined the chemical formulas and predominant crystalline forms of the calcium and magnesium sulfate compounds formed. The latter information is particularly novel for the filter-cake material, from which we isolated the ``new`` compound Mg{sub 2}Ca(SO{sub 4}){sub 3}

Measurements of filter-cake properties

The Pressurized Fluidized-Bed Combustion (PFBC) and Integrated Gasification Combined Cycle (IGCC) programs of the U.S. Department of Energy require filtration, at temperatures from about 600 to 900 {degrees}C, of fine particles of coal ash, char, or spent and unreacted sorbent from hot-gas streams. Achieving acceptable filter lifetimes requires solutions to or avoidance of, such problems as incomplete filter cleaning, re-entrainment (i.e., re-filtration) of particles from filter cleaning, and bridging of filter cake between adjacent filters. These and other potential problems may arise from the materials properties of filter cakes, from the filter-bank design, and from the mechanisms of filter cleaning. Avoiding re-entrainment requires that some bonding and agglomeration of particles occur in the cakes (so that the agglomerates from filter cleaning are too large to be re-entrained), but excessive agglomeration can produce poor cleaning or bridging. For both PFBC and IGCC applications, we can form filter cakes at process temperatures, gas compositions, and gas flow rates, and measure the gas-phase permeabilities, porosities, tensile strengths, and deformation coefficients of these filter cakes to determine their dependencies on temperature, reaction time, gas composition, particle compositions, and particle size distributions. Filter-cake shear strengths and flow factors can be measured for powders ``as received,`` for filter cakes that we have heated to process temperatures, or for powders heated in reactive gases to simulate gas-solid reactions in process filter cakes

Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering

We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 = 0.15, 0.25 (GeV/c)^2. The results are inconsistent with calculations solely using the elastic nucleon intermediate state, and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the 2-gamma exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.Comment: 5 pages, 3 figures, submitted to Physical Review Letters; shortened to meet PRL length limit, clarified some text after referee's comment

Strange Quark Contributions to Parity-Violating Asymmetries in the Forward G0 Electron-Proton Scattering Experiment

We have measured parity-violating asymmetries in elastic electron-proton scattering over the range of momentum transfers 0.12 < Q^2 < 1.0 GeV^2. These asymmetries, arising from interference of the electromagnetic and neutral weak interactions, are sensitive to strange quark contributions to the currents of the proton. The measurements were made at JLab using a toroidal spectrometer to detect the recoiling protons from a liquid hydrogen target. The results indicate non-zero, Q^2 dependent, strange quark contributions and provide new information beyond that obtained in previous experiments.Comment: 5 pages, 2 figure

The G0 Experiment: Apparatus for Parity-Violating Electron Scattering Measurements at Forward and Backward Angles

In the G0 experiment, performed at Jefferson Lab, the parity-violating elastic scattering of electrons from protons and quasi-elastic scattering from deuterons is measured in order to determine the neutral weak currents of the nucleon. Asymmetries as small as 1 part per million in the scattering of a polarized electron beam are determined using a dedicated apparatus. It consists of specialized beam-monitoring and control systems, a cryogenic hydrogen (or deuterium) target, and a superconducting, toroidal magnetic spectrometer equipped with plastic scintillation and aerogel Cerenkov detectors, as well as fast readout electronics for the measurement of individual events. The overall design and performance of this experimental system is discussed.Comment: Submitted to Nuclear Instruments and Method

A Study of Cosmic Ray Secondaries Induced by the Mir Space Station Using AMS-01

The Alpha Magnetic Spectrometer (AMS-02) is a high energy particle physics experiment that will study cosmic rays in the $\sim 100 \mathrm{MeV}$ to $1 \mathrm{TeV}$ range and will be installed on the International Space Station (ISS) for at least 3 years. A first version of AMS-02, AMS-01, flew aboard the space shuttle \emph{Discovery} from June 2 to June 12, 1998, and collected $10^8$ cosmic ray triggers. Part of the \emph{Mir} space station was within the AMS-01 field of view during the four day \emph{Mir} docking phase of this flight. We have reconstructed an image of this part of the \emph{Mir} space station using secondary $\pi^-$ and $\mu^-$ emissions from primary cosmic rays interacting with \emph{Mir}. This is the first time this reconstruction was performed in AMS-01, and it is important for understanding potential backgrounds during the 3 year AMS-02 mission.Comment: To be submitted to NIM B Added material requested by referee. Minor stylistic and grammer change

Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at \sqrt{s} = 189 GeV

A search for the lightest neutral scalar and neutral pseudoscalar Higgs bosons in the Minimal Supersymmetric Standard Model is performed using 176.4 pb^-1 of integrated luminosity collected by L3 at a center-of-mass energy of 189 GeV. No signal is observed, and the data are consistent with the expected Standard Model background. Lower limits on the masses of the lightest neutral scalar and pseudoscalar Higgs bosons are given as a function of tan(beta). Lower mass limits for tan(beta)>1 are set at the 95% confidence level to be m_h > 77.1 GeV and m_A > 77.1 GeV

Search for Extra Dimensions in Boson and Fermion Pair Production in e+e- Interactions at LEP

Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to be of the same order as the electroweak scale. A sizeable interaction between gravitons and Standard Model particles is then predicted. Effects of these new interactions in boson and fermion pair production are searched for in the data sample collected at centre-of-mass energies above the Z pole by the L3 detector at LEP. In addition, the direct production of a graviton associated with a Z boson is investigated. No statistically significant hints for the existence of these effects are found and lower limits in excess of 1 TeV are derived on the scale of this new theory of gravity

Measurement of the Probability of Gluon Splitting into Charmed Quarks in Hadronic Z Decays

We have measured the probability, n(g->cc~), of a gluon splitting into a charm-quark pair using 1.7 million hadronic Z decays collected by the L3 detector. Two independent methods have been applied to events with a three-jet topology. One method relies on tagging charmed hadrons by identifying a lepton in the lowest energy jet. The other method uses a neural network based on global event shape parameters. Combining both methods, we measure n(g->cc~)= [2.45 +/- 0.29 +/- 0.53]%

Measurement of Triple-Gauge-Boson Couplings of the W Boson at LEP

We report on measurements of the triple-gauge-boson couplings of the W boson in e+e- collisions with the L3 detector at LEP. W-pair, single-W and single-photon events are analysed in a data sample corresponding to a total luminosity of 76.7 pb^{-1} collected at centre-of-mass energies between 161 GeV and 183 GeV. CP-conserving as well as both C- and P-conserving triple-gauge-boson couplings are determined. The results, in good agreement with the Standard-Model expectations, confirm the existence of the self coupling among the electroweak gauge bosons and constrain its structure