Experience in feeding coal into a liquefaction process development unit

A system for preparing coal slurry and feeding it into a high pressure liquefaction plant is described. The system was developed to provide supporting research and development for the Bureau of Mines coal liquefaction pilot plant. Operating experiences are included

Influence of strain on anisotropic thermoelectric transport of Bi2_2Te3_3 and Sb2_2Te3_3

On the basis of detailed first-principles calculations and semi-classical Boltzmann transport, the anisotropic thermoelectric transport properties of Bi$_2$Te$_3$ and Sb$_2$Te$_3$ under strain were investigated. It was found that due to compensation effects of the strain dependent thermopower and electrical conductivity, the related powerfactor will decrease under applied in-plane strain for Bi$_2$Te$_3, while being stable for Sb$_2$Te$_3$. A clear preference for thermoelectric transport under hole-doping, as well as for the in-plane transport direction was found for both tellurides. In contrast to the electrical conductivity anisotropy, the anisotropy of the thermopower was almost robust under applied strain. The assumption of an anisotropic relaxation time for Bi$_2$Te$_3$ suggests, that already in the single crystalline system strong anisotropic scattering effects should play a role

Lorenz function of Bi2_{2}Te3_{3}/Sb2_{2}Te3_{3} superlattices

Combining first principles density functional theory and semi-classical Boltzmann transport, the anisotropic Lorenz function was studied for thermoelectric Bi$_{2}$Te$_{3}$/Sb$_{2}$Te$_{3}$ superlattices and their bulk constituents. It was found that already for the bulk materials Bi$_{2}$Te$_{3}$ and Sb$_{2}$Te$_{3}$, the Lorenz function is not a pellucid function on charge carrier concentration and temperature. For electron-doped Bi$_{2}$Te$_{3}$/Sb$_{2}$Te$_{3}$ superlattices large oscillatory deviations for the Lorenz function from the metallic limit were found even at high charge carrier concentrations. The latter can be referred to quantum well effects, which occur at distinct superlattice periods

Thermoelectric transport in Bi2Te3/Sb2Te3\text{Bi}_2\text{Te}_3/\text{Sb}_2\text{Te}_3 superlattices

The thermoelectric transport properties of $\text{Bi}_2\text{Te}_3/\text{Sb}_2\text{Te}_3$superlattices are analyzed on the basis of first-principles calculations and semi-classical Boltzmann theory. The anisotropy of the thermoelectric transport under electron and hole-doping was studied in detail for different superlattice periods at changing temperature and charge carrier concentrations. A clear preference for thermoelectric transport under hole-doping, as well as for the in-plane transport direction was found for all superlattice periods. At hole-doping the electrical transport anisotropies remain bulk-like for all investigated systems, while under electron-doping quantum confinement leads to strong suppression of the cross-plane thermoelectric transport at several superlattice periods. In addition, insights on the Lorenz function, the electronic contribution to the thermal conductivity and the resulting figure of merit are given

The Tri-Party Repo Market before the 2010 Reforms

This paper provides a descriptive and quantitative account of the tri-party repo market before the reforms proposed in 2010 by the Task Force on Tri-Party Repo Infrastructure (Task Force 2010). We provide an extensive description of the mechanics of this market. We also use data from July 2008 to early 2010 to document quantitative features of he market. We find that both the level of haircuts and the amount of funding were surprisingly stable in this market. The stability of the margins is in contrast to evidence from other repo markets. Perhaps surprisingly, the data reveal relatively few signs of stress in the market for dealers other than Lehman Brothers, on which we provide some evidence. This suggests that runs in the tri-party repo market may occur precipitously, like traditional bank runs, rather than manifest themselves as large increases in margins

Atomic Energy Commission Report NYO-2978-34

From abstract: The concept of using high intensity beta radiation from an isotopic source, Sr-90, inside a high temperature, high pressure chemical reactor has been developed for potential radiation chemical processes. Distinct advantages include high utilizable intensity from a relatively small source with a minimum of shielding against external radiation

BETA RADIATION PROCESSING AT RIGOROUS CONDITIONS

An investigation was conducted on the impossible use of beta radiation to promote chemical reactions at high temperatures and pressures. The advantages of beta sources over other radiation sources are enumerated. A radiation processing apparatus is described which allows operations to 10,000 psi and 500 deg C and uses 90 C of Sr/sup 90/-Y/sup 90/. The dosimetry of the source was accomplished with an iodineheptane system, and the mean dose rate within the chemical reactor was determined to be 0.98 x 10/sup 6/ rad/hr. The radiation utilization efficiency in the dosimetry measurements was determined to be 34.7%. Results of runs on hydrogenation of coal extract indicate that radiation does not increase the extent of hydrogenation, but that radiation reduces the content of hetero atoms N and S in the 100 x 400 deg C boiling oil products. The use of beta radiation in the hydrorefining of oils is suggested. (D.L.C.

HEAT TRANSFER CHARACTERISTICS OF TWO-PHASE FLOW THROUGH PACKED BEDS

The effective thermal conductivity (K//e) and wall heat transfer coefficient (H//w) were determined in a packed bed reactor model. Two flow regimes are described. The entrance effects for the low liquid flow regime seem to be limited to about ten diameters, while the entrance effects for the high liquid flow seem to extend the entire length of the column

HEAT TRANSFER CHARACTERISTICS OF TWO-PHASE FLOW THROUGH PACKED BEDS.

The effective thermal conductivity (K//e) and wall heat transfer coefficient (H//w) were determined in a packed bed reactor model. Two flow regimes are described. The entrance effects for the low liquid flow regime seem to be limited to about ten diameters, while the entrance effects for the high liquid flow seem to extend the entire length of the column

Heat transfer studies of packed bed coal liquefaction reactors

The effective thermal conductivity (K/sub e/) and wall heat transfer coefficient (H/sub w/) were determined in a packed bed reactor model over a range of gas mass velocities from 0 to 15,000 kg/m/sup 2/ hr, liquid mass velocities from 5000 to 65,000 kg/m/sup 2/ hr, and pressures that simulate coal liquefaction pressures from 1000 to 4000 psig. A correlation for K/sub e/ and H/sub w/ was developed for the range of study. Several mathematical models for one and two dimensions, and for one and two parameters, were derived to describe two-phase flow in packed beds. Two flow regimes are described. The entrance effects for the low liquid flow regime seem to be limited to a length of about ten diameters, while the entrance effects for the high liquid flow seem to extend through the entire length of the column