High-temperature gases thermodynamics

The thermodynamic properties of gases, liquids, solids and aqueous solutes of interest for desulfurization processes are tabulated for temperatures from 298 K to temperatures as high as 1000 K when possible. Major emphasis has been placed on aqueous lime or limestone scrubbing, but the data can also be used for high temperature gas processes and for N0 processes. 

For the analysis heat and mass transfer in concrete samples at high temperatures, the numerical model has been developed. It describes concrete, as a porous multiphase system which at local level is in thermodynamic balance with body interstice, filled by liquid water and gas phase. The model allows researching the dynamic characteristics of diffusion in view of concrete matrix phase transitions, which was usually described by means of experiments. 

Nitridoborates of lanthanum and the lanthanides were obtained from reactions of lanthanide metal or lanthanide metal nitride with layer-like (a-)BN at elevated temperatures (3>1200°C). These reactions require elaborated techniques in the inert gas sample-handling and the use of efficient heating sources, such as induction heating. Only some compounds remain stable in this high-temperature segment, and the yields of such reactions are often limited due to the competing stability of binary phases, allowing only the most (thermodynamically) stable compounds to exist. 

Special synthetic routes are necessary to gain access to the metastable monohalides of A1 and Ga, since they are thermodynamically unstable at room temperature toward disproportionation into A1 metal and A1X3 or Ga metal and GaX3. First, the gaseous MX species, that are thermodynamically stable at high temperatures,22 have to be synthesized. A variety of methods are available for their preparation, some of which are shown in equations (a)-(c) of Scheme 2. 

No tar generated More release of trace metals into gas phase due to higher temperatures Higher thermodynamic losses due to inherent high temperature operation... 

The reformate gas contains up to 12% CO for SR and 6 to 8% CO for ATR, which can be converted to H2 through the WGS reaction. The shift reactions are thermodynamically favored at low temperatures. The equilibrium CO conversion is 100% at temperatures below 200°C. However, the kinetics is very slow, requiring space velocities less than 2000 hr1. The commercial Fe-Cr high-temperature shift (HTS) and Cu-Zn low-temperature shift (LTS) catalysts are pyrophoric and therefore impractical and dangerous for fuel cell applications. A Cu/CeOz catalyst was demonstrated to have better thermal stability than the commercial Cu-Zn LTS catalyst [37], However, it had lower activity and had to be operated at higher temperature. New catalysts are needed that will have higher activity and tolerance to flooding and sulfur. 

As discussed above, the pyrolysis of biomass at high temperature (>1000 °C) results in the formation of synthesis gas, a valuable mixture of CO and H2. The decomposition of carbohydrate to synthesis gas is an endothermic reaction since the heating value of product is —125% of that of the feedstock (Reaction 1). The reaction becomes nearly thermo-neutral upon burning about 1/4 of the products. Since the thermodynamics favors the combustion of H2 over CO, the gasification reaction resemble the theoretical Reaction (2). Indeed numerous gasification processes feed 02 or air to drive the gasification reaction. 

Thermochemical data are also available from the Internet. Some examples are the NIST Chemical Kinetics Model Database (http //kinetics.nist. gov/CKMech/), the Third Millennium Ideal Gas and Condensed Phase Thermochemical Database for Combustion (A. Burcat and B. Ruscic, ftp //ftp. technion.ac.il/pub/supported/aetdd/thermodynamics/), and the Sandia National Laboratory high-temperature thermodynamic database (http //www.ca.sandia. gov/HiTempThermo/). 

Binary Systems and Related Compounds.—Halides. The thermodynamics of gas-phase equilibria in the W-F2 and W-F2-H2 systems at high temperatures have been described.The Raman spectrum of solid MoF exhibits Mo—F stretching bands at 746, 722, and 690 cm These results suggest that the compound has a similar structure to NbF4, with each molybdenum co-ordinated to six fluorine atoms.The Raman spectrum of crystalline M0F5 has also been reported and interpreted in terms of the crystal structure.The electronic spectrum of liquid M0F5 has been determined and shown to be consistent with a trigonal-bipyramidal molecular unit. ... 

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