哈密煤温和液化固体产物热解过程中硫的变迁规律

利用固定床反应器研究了哈密煤温和液化固体产物（MLS）在热解过程中含硫气体的释放规律以及不同形态硫的变迁规律，并分析了矿物质对硫变迁规律的影响。结果表明，在实验考察的条件范围内，MLS热解过程中大部分的硫残留在半焦中，仅有不到10%的硫迁移到焦油中或转化为含硫气体逸出。热解生成的含硫气体以H₂S为主，当热解温度为400℃时H₂S的逸出速率达到最大。通过改进方法测定了MLS及其热解半焦中各种形态硫的含量，发现MLS热解过程中以硫化物硫和有机硫的分解和转化为主。随着热解温度的升高，MLS中有机硫逐渐分解并以含硫气体的形式逸出；当热解温度低于600℃时，MLS中硫化物硫逐渐转化为含硫气体、有机硫和少量的黄铁矿硫；当热解温度高于600℃时，MLS中碱性矿物质吸收气相中的H₂S转化为硫化物硫，硫化物硫缓慢增加。醋酸酸洗可以保留MLS中大部分的硫化物硫，且酸洗后MLS热解生成的H₂S逸出速率增大，峰温向低温方向移动；当热解温度高于600℃时，有机硫和硫化物硫的脱硫反应速率降低，并且MLS中的碱性矿物质与H₂S反应生成金属硫化物，导致H₂S逸出速率明显降低。     

Exact calculation of one-dimensional irreducible integrals

One-dimensional irreducible integrals (_k) are computed in the form of Mayerf-function polynomials for a general interparticle potential. Obeisance to the exact specification of the irreducible integral definition produces regularities in the interaction of star graphs with the integration process. Tables of _k fork 5 and test solutions are presented.     

Discretized Boltzmann equation: Lattice limit and non-Maxwellian gases

We continue the study of a discrete model of the Boltzmann equation, in which the spatial variable is replaced by a finite periodic lattice. Using a weak compactness criterion forL ₁, the existence of a lattice limit as the lattice spacing tends to zero is proved. The case of unbounded collision kernels (non-Maxwellian gases) is also treated.This work was supported in part by National Science Foundation grant no. ENG-75 15882.On leave from Mathematisches Institut der Universität München, Federal Republic of Germany     

Low-viscosity lattice gases

A class of lattice gas models are studied which are variants of the FCHC model. The aim is to achieve the highest possible Reynolds coefficient (inverse dimensionless viscosity) for efficient simulations of the three-dimensional incompressible Navier-Stokes equations. The models include an arbitrary number of rest particles and violation of semi-detailed balance. Within the framework of the Boltzmann approximation exact expressions are obtained for the Reynolds coefficients. The minimization of the viscosity is done by solving a Hitchcock-type optimization problem for the fine tuning of the collision rules. When the number of rest particles exceeds one, there is a range of densities at which the viscosity takes negative values. Various optimal models with up to 26 bits per node have been implemented on a CRAY-2 and their true transport coefficients have been measured with good accuracy. Fairly large discrepancies with Boltzmann values are observed when semi-detailed balance is violated; in particular, no negative viscosity is obtained. Still, the best model has a Reynolds coefficient of 13.5, twice that of the best previously implemented model, and thus is about 16 times more efficient computationally. Suggestions are made for further improvements. It is proposed to use models with very high Reynolds coefficients for sub-grid-scale modeling of turbulent flows.     

Nonlinear Couette Flow in a Low Density Granular Gas

A model kinetic equation is solved exactly for a special stationary state describing nonlinear Couette flow in a low density system of inelastic spheres. The hydrodynamic fields, heat and momentum fluxes, and the phase space distribution function are determined explicitly. The results apply for conditions such that viscous heating dominates collisional cooling, including large gradients far from the reference homogeneous cooling state. Explicit expressions for the generalized transport coefficients (e.g., viscosity and thermal conductivity) are obtained as nonlinear functions of the coefficient of normal restitution and the shear rate. These exact results for the model kinetic equation are also shown to be good approximations to the corresponding state for the Boltzmann equation via comparison with direct Monte Carlo simulation for the latter.     

European Minor Constituent Radiometer: A New Millimeter Wave Receiver for Atmospheric Research

EMCOR is a heterodyne receiver for the frequency range of 201 to 210 GHz. It has been designed for ground-based measurements of various minor constituents of the stratosphere involved in ozone chemistry. Since the aim was the detection of faint spectral lines, a superconducting tunnel junction has been chosen as mixer element and special care has been taken in developing the calibration unit of the system. The front-end is completed by a quasi-optical system, a solid state local oscillator with electronic tuning and a HEMT pre-amplifier. In the back-end an acousto-optical spectrometer is employed to analyse the signal. A PC controls the whole system. The instrument has been installed at a high mountain site in the Swiss Alps.     

Heated granular fluids: The random restitution coefficient approach

We introduce the model of inelastic hard spheres with random restitution coefficient α, in order to account for the fact that, in a vertically shaken granular system interacting elastically with the vibrating boundary, the energy injected vertically is transferred to the horizontal degrees of freedom through collisions only, which leads to heating through collisions, i.e. to inelastic horizontal collisions with an effective restitution coefficient that can be larger than 1. This allows the system to reach a non-equilibrium steady state, where we focus, in particular, on the single-particle velocity distribution f (v) in the horizontal plane, and on its deviation from a Maxwellian. Molecular Dynamics simulations and Direct Simulation Monte Carlo (DSMC) show that, depending on the distribution of α, different shapes of f (v) can be obtained, with very different high-energy tails. Moreover, the fourth cumulant of the velocity distribution quantifying the deviations from Gaussian statistics is obtained analytically from the Boltzmann equation and successfully tested against the simulations. Received 24 November 2000 and Received in final form 8 February 2001     

On the ellipsoidal statistical model for polyatomic gases

The aim of this article is to construct a BGK-type model for polyatomic gases which gives in the hydrodynamic limit the proper transport coefficient. Its construction relies upon a systematic procedure: minimizing Boltzmann entropy under suitable moments constraints (Levermore in J Stat Phys 83:1021–1065, 1996; Brull and Schneider in Cont Mech Thermodyn 20(2):63–74, 2008). The obtained model corresponds to the ellipsoidal statistical model introduced in Andries et al. (Eur J Mech B Fluids 19:813–830, 2000). We also study the return to equilibrium of its solutions in the homogeneous case.      

Isotopic Exchange of Hydrogen between the Fluids of the Hydrocarbon Fields

It is presented the isotopic exchange of hydrogen in natural gas, crude oil, and underground water. The general behaviour of the isotopic exchange occuring in a system with a large number of components is given. A good agreement between the calculated and the experimental isotopic distribution factors is obtained in the case of the isotopic exchange of hydrogen between methane and underground water. The deuterium concentration of the crude oil samples inserts between the values obtained for methane and underground water. This fact is due to the presence of the isotopic exchange between these fluids.