tII IlIIlII B CONDITIONING AND DETAILED ANALYSIS OF BIOMASS DERIVED FUEL GAS ONGOING AND PLANNED WORK BY BATTELLE

ABSTRACT Gas turbine based power and cogeneration schemes are likely to become more favored as turbine efficiencies improve, but the economics of local power generation may depend on the use of low cost fuels other than natural gas. Opportunities may arise in the application of gas turbines in the pulp and paper industry and the wider use of biomass derived fuels in general. These fuels, as produced, typically contain inorganic impurities originating from ash forming substances and other minor constituents of the feedstock Also, depending on the biomass treatment process, they contain varying amounts of complex organic derivatives, commonly referred to as tars, and some simpler condensable vapors. The Department of Energy is sponsoring work aimed at providing realistic data on low level constituents and impurities in gas derived by indirect gasification of wood, some of which may have disproportionately severe effects on turbine operation, durability, and emissions performance. It is planned to sample gas from both laboratory scale (up to 20 tons/ day) and pilot scale (200 tons/day) installations and to assess the effectiveness of wet scrubbing procedures and catalytic reforming of condensables in cleaning up the gases This paper discusses the rationale for this work, experimental approach, and analytic procedures that will be used. The work will include the operation of a small (220-kWe) gas turbine to provide direct information on the impact of using the final biomass derived gas delivered by the system. The laboratory scale work is currently under way, with a planned completion date in mid 2000. The second phase is dependent on arrangements for integration of the R&D effort with the operation of the pilot plant

Inclusive charged hadron elliptic flow in Au + Au collisions at sNN\sqrt{s_{NN}} = 7.7 - 39 GeV

A systematic study is presented for centrality, transverse momentum ($p_T$) and pseudorapidity ($\eta$) dependence of the inclusive charged hadron elliptic flow ($v_2$) at midrapidity($|\eta| < 1.0$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27 and 39 GeV. The results obtained with different methods, including correlations with the event plane reconstructed in a region separated by a large pseudorapidity gap and 4-particle cumulants ($v_2{4}$), are presented in order to investigate non-flow correlations and $v_2$ fluctuations. We observe that the difference between $v_2{2}$ and $v_2{4}$ is smaller at the lower collision energies. Values of $v_2$, scaled by the initial coordinate space eccentricity, $v_{2}/\varepsilon$, as a function of $p_T$ are larger in more central collisions, suggesting stronger collective flow develops in more central collisions, similar to the results at higher collision energies. These results are compared to measurements at higher energies at the Relativistic Heavy Ion Collider ($\sqrt{s_{NN}}$ = 62.4 and 200 GeV) and at the Large Hadron Collider (Pb + Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV). The $v_2(p_T)$ values for fixed $p_T$ rise with increasing collision energy within the $p_T$ range studied ($< 2 {\rm GeV}/c$). A comparison to viscous hydrodynamic simulations is made to potentially help understand the energy dependence of $v_{2}(p_{T})$. We also compare the $v_2$ results to UrQMD and AMPT transport model calculations, and physics implications on the dominance of partonic versus hadronic phases in the system created at Beam Energy Scan (BES) energies are discussed.Comment: 20 pages, 12 figures. Version accepted by PR

Observation of D0D^0 meson nuclear modifications in Au+Au collisions at sNN\sqrt{s_{_{\mathrm{NN}}}} = 200 GeV

We report the first measurement of charmed-hadron ($D^0$) production via the hadronic decay channel ($D^0\rightarrow K^- + \pi^+$) in Au+Au collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200\,GeV with the STAR experiment. The charm production cross-section per nucleon-nucleon collision at mid-rapidity scales with the number of binary collisions, $N_{bin}$, from $p$+$p$ to central Au+Au collisions. The $D^0$ meson yields in central Au+Au collisions are strongly suppressed compared to those in $p$+$p$ scaled by $N_{bin}$, for transverse momenta $p_{T}>3$ GeV/$c$, demonstrating significant energy loss of charm quarks in the hot and dense medium. An enhancement at intermediate $p_{T}$ is also observed. Model calculations including strong charm-medium interactions and coalescence hadronization describe our measurements.Comment: 7 pages including author list, 4 figures, submit to PRL with revised versio

Measurements of D0D^{0} and D∗D^{*} Production in pp + pp Collisions at s\sqrt{s} = 200 GeV

We report measurements of charmed-hadron ($D^{0}$, $D^{*}$) production cross sections at mid-rapidity in $p$ + $p$ collisions at a center-of-mass energy of 200 GeV by the STAR experiment. Charmed hadrons were reconstructed via the hadronic decays $D^{0}\rightarrow K^{-}\pi^{+}$, $D^{*+}\rightarrow D^{0}\pi^{+}\rightarrow K^{-}\pi^{+}\pi^{+}$ and their charge conjugates, covering the $p_T$ range of 0.6$-$2.0 GeV/$c$ and 2.0$-$6.0 GeV/$c$ for $D^{0}$ and $D^{*+}$, respectively. From this analysis, the charm-pair production cross section at mid-rapidity is $d\sigma/dy|_{y=0}^{c\bar{c}}$ = 170 $\pm$ 45 (stat.) $^{+38}_{-59}$ (sys.) $\mu$b. The extracted charm-pair cross section is compared to perturbative QCD calculations. The transverse momentum differential cross section is found to be consistent with the upper bound of a Fixed-Order Next-to-Leading Logarithm calculation.Comment: 15 pages, 16 figures. Revised version submitted to Phys. Rev.

Effective Rheology of Bubbles Moving in a Capillary Tube

We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capillary tube with varying diameter, finding a square-root relation from mapping the flow equations onto that of a driven overdamped pendulum. The calculation is based on a derivation of the equation of motion of a bubble train from considering the capillary forces and the entropy production associated with the viscous flow. We also calculate the configurational probability of the positions of the bubbles.Comment: 4 pages, 1 figur

Beam-energy dependence of charge separation along the magnetic field in Au+Au collisions at RHIC

Local parity-odd domains are theorized to form inside a Quark-Gluon-Plasma (QGP) which has been produced in high-energy heavy-ion collisions. The local parity-odd domains manifest themselves as charge separation along the magnetic field axis via the chiral magnetic effect (CME). The experimental observation of charge separation has previously been reported for heavy-ion collisions at the top RHIC energies. In this paper, we present the results of the beam-energy dependence of the charge correlations in Au+Au collisions at midrapidity for center-of-mass energies of 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV from the STAR experiment. After background subtraction, the signal gradually reduces with decreased beam energy, and tends to vanish by 7.7 GeV. The implications of these results for the CME will be discussed.Comment: 6 pages, 4 figures, accepted by Phys. Rev. Lett (more model comparisons have been added in version 2