19 research outputs found
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Laboratory tests of mafic, ultra-mafic, and sedimentary rock types for in-situ applications for carbon dioxide sequestration
Recent tests conducted at the Albany Research Center have addressed the possibility of in-situ storage of carbon dioxide in geological formations, particularly in deep brackish to saline non-potable aquifers, and the formation of secondary carbonate minerals over time within these aquifers. Various rock types including Columbia River Basalt Group (CRBG) drill core samples, blocks of ultra-mafic rock and sandstone were used. A solution formulated from aquifer data, a bicarbonate salt solution, and distilled water were tested. Pressure and temperature regimens were used to mimic existing in-situ conditions, higher temperatures were used to simulate longer time frames, and higher pressures were used to simulate enhanced oil recovery (EOR) pressure. Results are encouraging, indicating mineral dissolution with an increase of desirable ions (Ca, Fe2+, Mg) in solution that can form the carbonate minerals, calcite (CaCO3), siderite (FeCO3), and magnesite (MgCO3)
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Ex-situ and in-situ mineral carbonation as a means to sequester carbon dioxide
The U. S. Department of Energy's Albany Research Center is investigating mineral carbonation as a method of sequestering CO2 from coal-fired-power plants. Magnesium-silicate minerals such as serpentine [Mg3Si2O5(OH)4] and olivine (Mg2SiO4) react with CO2 to produce magnesite (MgCO3), and the calcium-silicate mineral, wollastonite (CaSiO3), reacts to form calcite (CaCO3). It is possible to carry out these reactions either ex situ (above ground in a traditional chemical processing plant) or in situ (storage underground and subsequent reaction with the host rock to trap CO2 as carbonate minerals). For ex situ mineral carbonation to be economically attractive, the reaction must proceed quickly to near completion. The reaction rate is accelerated by raising the activity of CO2 in solution, heat (but not too much), reducing the particle size, high-intensity grinding to disrupt the crystal structure, and, in the case of serpentine, heat-treatment to remove the chemically bound water. All of these carry energy/economic penalties. An economic study illustrates the impact of mineral availability and process parameters on the cost of ex situ carbon sequestration. In situ carbonation offers economic advantages over ex situ processes, because no chemical plant is required. Knowledge gained from the ex situ work was applied to long-term experiments designed to simulate in situ CO2 storage conditions. The Columbia River Basalt Group (CRBG), a multi-layered basaltic lava formation, has potentially favorable mineralogy (up to 25% combined concentration of Ca, Fe2+, and Mg cations) for storage of CO2. However, more information about the interaction of CO2 with aquifers and the host rock is needed. Core samples from the CRBG, as well as samples of olivine, serpentine, and sandstone, were reacted in an autoclave for up to 2000 hours at elevated temperatures and pressures. Changes in core porosity, secondary mineralizations, and both solution and solid chemistry were measured
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Factors affecting ex-situ aqueous mineral carbonation using calcium and magnesium silicate minerals
Carbonation of magnesium- and calcium-silicate minerals to form their respective carbonates is one method to sequester carbon dioxide. Process development studies have identified reactor design as a key component affecting both the capital and operating costs of ex-situ mineral sequestration. Results from mineral carbonation studies conducted in a batch autoclave were utilized to design and construct a unique continuous pipe reactor with 100% recycle (flow-loop reactor). Results from the flow-loop reactor are consistent with batch autoclave tests, and are being used to derive engineering data necessary to design a bench-scale continuous pipeline reactor
Dilepton production in heavy ion collisions at intermediate energies
We present a unified description of the vector meson and dilepton production
in elementary and in heavy ion reactions. The production of vector mesons
() is described via the excitation of nuclear resonances ().
The theoretical framework is an extended vector meson dominance model (eVMD).
The treatment of the resonance decays with arbitrary spin is
covariant and kinematically complete. The eVMD includes thereby excited vector
meson states in the transition form factors. This ensures correct asymptotics
and provides a unified description of photonic and mesonic decays. The
resonance model is successfully applied to the production in
reactions. The same model is applied to the dilepton production in elementary
reactions (). Corresponding data are well reproduced. However, when
the model is applied to heavy ion reactions in the BEVALAC/SIS energy range the
experimental dilepton spectra measured by the DLS Collaboration are
significantly underestimated at small invariant masses. As a possible solution
of this problem the destruction of quantum interference in a dense medium is
discussed. A decoherent emission through vector mesons decays enhances the
corresponding dilepton yield in heavy ion reactions. In the vicinity of the
-peak the reproduction of the data requires further a substantial
collisional broadening of the and in particular of the meson.Comment: 32 pages revtex, 19 figures, to appear in PR
Role of baryonic resonances in the dilepton emission in nucleon-nucleon collisions
Within an effective Lagrangian model, we present calculations for cross
sections of the dilepton production in proton-proton and proton-neutron
collisions at laboratory kinetic energies in 1-5 GeV range. Production
amplitudes include contributions from the nucleon-nucleon bremsstrahlung as
well as from the mechanism of excitation, propagation, and radiative decay of
Delta(1232) and N*(1520) intermediate baryonic resonances. It is found that the
delta isobar terms dominate the cross sections in the entire considered beam
energy range. Our calculations are able to explain the data of the DLS
collaboration on the dilepton production in proton-proton collisions for beam
energies below 1.3 GeV. However, for incident energies higher than this the
inclusion of contributions from other dilepton sources like Dalitz decay of pi0
and eta mesons, and direct decay of rho and omega mesons is necessary to
describe the data.Comment: 22 pages, 7 figures, more details of the calculations added, version
to appear in Phys. Rev
One-loop corrections to omega photoproduction near threshold
One-loop corrections to photoproduction near threshold have been
investigated by using the approximation that all relevant transition amplitudes
are calculated from the tree diagrams of effective Lagrangians. With the
parameters constrained by the data of , , and reactions, it is found that the one-loop effects
due to the intermediate and states can significantly change
the differential cross sections and spin observables. The results from this
exploratory investigation suggest strongly that the coupled-channel effects
should be taken into account in extracting reliable resonance parameters from
the data of vector meson photoproduction in the resonance region.Comment: 19 pages, REVTeX, 14 figures, title changed, revised version to
appear in Phys. Rev.
Near-threshold and meson productions in collisions
Using a relativistic effective Lagrangian at the hadronic level,
near-threshold and meson productions in proton proton ()
collisions, , are studied within the distorted wave
Born approximation. Both initial and final state interactions are
included. In addition to total cross section data, both and
angular distribution data are used to constrain further the model parameters.
For the reaction we consider two different possibilities:
with and without the inclusion of nucleon resonances. The nucleon resonances
are included in a way to be consistent with the
reaction. It is shown that the inclusion of nucleon resonances can describe the
data better overall than without their inclusion. However, the SATURNE data in
the range of excess energies MeV are still underestimated by about a
factor of two. As for the reaction it is found that the
presently limited available data from DISTO can be reproduced by four sets of
values for the vector and tensor coupling constants. Further
measurements of the energy dependence of the total cross section near threshold
energies should help to constrain better the coupling constant.Comment: Latex, 37 pages, 13 figures (14 EPS-figure files), text modified,
version to appear in Phys. ReV.