CATALYTIC GAS PLATING WITH NICKEL CARBONYL

Hydrogen sulfide reformation in the presence of methane

Steels used in coal gasification vessels and piping (externals) can be exposed to mixtures of hydrogen, water vapor (steam), hydrogen sulfide, methane, carbon monoxide, carbon dioxide, and other gases at temperatures and pressures up to 600°K and 10 MPa. Such mixtures, under certain operating conditions, can either enhance or inhibit crack growth in these steels. As a part of a program to identify thermodynamic conditions for this enhancement or inhibition, fatigue crack growth experiments have been carried out on a 2-1/4Cr-1 Mo (ASTM A542, Class 2) steel in hydrogen, water vapor, and hydrogen sulfide at low pressures (below 133 kPa). The results indicate considerable enhancement of fatigue crack growth by some of these environments and also indicate that the apparent immunity of this material to stress corrosion cracking does not imply the same immunity to corrosion fatigue. The results will be discussed in terms of the influences of temperature, gas pressure and loading variables, and will be interpreted in terms of chemical reaction kinetics.

Although there have been many studies of erosion‐corrosion of alloys involving impact by solid particles in air or oxygen at high temperatures, there have been very few, if any, in gases of high‐sulphur, low‐oxygen activities. As these environments are pertinent in processes such as coal gasification and catalytic cracking of oil, there is a need for some basic studies of the interactions of erosion and corrosion in oxidizing/sulphidizing gases. Thus, a whirling‐arm rig has been designed and constructed; it can operate under a range of erosion conditions (velocities to 30 m s−1, particles fluxes to 1 g m−2 s−1) in gaseous environments consisting of mixtures of nitrogen, hydrogen, hydrogen sulphide and water vapour as necessary, at temperatures to 800°C.Some preliminary tests have been carried out using 310 stainless steel and Alloy 800HT at 500 and 700°C and Fe‐2.25Cr‐1 Mo and 410 stainless steel at 500°C. Erosion particles were 25 μm alumina, with impact velocities of 10 to 25 m s−1 and fluxes of 0.06 to 0.16 g cm−2 s−1. The gaseous environment was a mixture of hydrogen, hydrogen sulphide and nitrogen; this caused sulphidation of all the alloys at both temperatures. The extents of erosion‐corrosion damage were determined by thickness‐change measurements taken every 5 h and overall metal‐recession measurements taken at the end of the full test period of 35 h.The extents of damage were increased significantly with increasing impact velocity for the austenitic alloys at 700°C; similar trends were observed at 500°C for Fe‐2.25Cr‐ 1 Mo and 410 stainless steel, although the presence of impacting particles had only a small effect on the austenitic alloys at the lower temperature. These initial results are discussed in terms of the interactions of growth of the sulphide scale and removal of scale by the particles.

Experts have long projected that in the future solid oxide fuel cells (SOFCs) could provide a viable path for the replacement of existing power sources and the production of clean, secure, and sustainable energy. Today, not only have SOFCs matured as a technology with a proven ability to provide high density, high efficiency power with long term stability at low cost and environmental impact, but with the theoretical capacity to utilize a variety of naturally sourced fuels. This theoretical capacity makes their potential use attractive in many additional applications and positions SOFCs to be the technology which can bridge the gap between current hydrocarbon fueled technologies and future hydrocarbon fueled electric technologies. That said, there remains many technical hurdles associated with the incorporation of naturally sourced fuels, to include thermal stress cracking and catalyst coarsening, delamination, and poisoning. Catalyst poisoning, specifically arising from sulfur impurities in naturally sourced fuels, remains one of the largest SOFC technical challenges, since their presence, even at low concentrations, have now shown permanent performance degradation. As the U.S. Army begins to investigate SOFCs to enable additional capabilities like silent watch, advanced radios, and exportable power in their fleet, catalyst poisoning from sulfur impurities presents a concerning technology gap which must be addressed, as the entire fleet operates on JP-8 kerosene-based fuel, which by specification can contain up to 3000 ppm of sulfur, via AR-70 single fuel policy.As SOFC technologies migrate to lower temperature operation to resolve physical degradation issues, the development catalysts materials with greater sulfur tolerance are being explored to resolve issues of chemical degradation related to sulfur poisoning. In this study, a previously reported, high temperature, sulfur tolerant SOFC catalyst, La0.7Sr0.3VO3.86-⸹ (LSV), was further experimentally investigated via Optical Microscopy, X-ray Diffraction, Scanning Electron Microscopy and Energy Dispersive Spectroscopy for its sulfur tolerance at currently targeted SOFC intermediate operating temperatures (400-600°C) in wide range of hydrogen sulfide (30ppm, 300ppm and 10vol%) balance hydrogen gas environments for up to 100 hours. When compared against the industry standard Ni-YSZ anode, LSV was observed to have significantly lower (287x) sulfur adsorption rates, with the lowest rates observed between 600-700°C. This behavior is attributed the cubic structure the material presents in this temperature range. Higher adsorption rates were observed in the monoclinic/tetragonal structure the material presents at temperatures between 400-500°C. This study was further supplemented by a theoretical investigation of hydrogen sulfide adsorption on low index LSV surfaces via periodic Density Functional Theory. When compared against Ni-YSZ, which is known to accumulate sulfur from hydrogen sulfide via two-step dissociative adsorption, LSV was observed to accumulate sulfur through weak chemisorption (0.43 eV max) of undissociated molecular hydrogen sulfide only. The weak chemisorption behavior is attributed to structural surface changes due to oxygen vacancies near strontium defects, wherein the strongest adsorption energies were observed, and in direct contrast to similar calculations of hydrogen sulfide adsorption with low index surfaces of LVO3, wherein no adsorption was observed.Since it is likely SOFCs will operate on hydrocarbon fuels, as well as compressed hydrogen gas in the future, this study is also currently experimentally investigating sulfur accumulation under the same operating conditions above with hydrogen sulfide mixtures in methane gas. Methane is a small hydrocarbon chain, which will help minimize the accumulation of carbon deposition. Initial comparisons of sulfur adsorption between hydrogen and methane gas mixtures, using low hydrogen sulfide concentrations, show they are statistically similar, although methane gas exposure was observed to result in the formation of two activation energies, which was not observed with hydrogen mixture previously. The methane gas was also observed to promote LSV to take the monoclinic/tetragonal structure at lower operating temperatures than hydrogen mixtures. This observation may lead to elevated sulfur adsorption rates at higher hydrogen sulfide concentrations. Finally, it was originally observed during experimental exposure experiments with hydrogen sulfide/hydrogen gas balance mixtures that higher concentrations of lattice oxygen, present at lower temperatures, had a positive correlation with sulfur accumulation in the LSV material. This study is therefore currently theoretically investigating the effect of lattice oxygen content on the LSVs structure via Density Functional Theory, which could lead to further derivation from optimal cubic configuration, which may lead to configurations which increase sulfur adsorption. Figure 1

Tarnishing layers grown on copper exposed to air contaminated by traces of sulfur dioxide and/or hydrogen sulfide were detected by a coulometric and characterized by a chemical method. Depending on the nature of the corrosive gas, or on the use of a gas mixture, it was found that sulfate, sulfide, oxides or a mixed oxide‐sulfide compound could be formed in these conditions. The same tarnishing products were found, either in hydrogen sulfide or in a sulfur dioxide + hydrogen sulfide mixture, and the same linear growth law of the copper (I) sulfide was also found, within the limits of the duration of the corrosion test, in the two gaseous environments.

Solubilities of ethane, carbon dioxide, and hydrogen sulfide have been measured in propylene carbonate, N‐methyl‐2‐pyrrolidone and tetramethylene sulfone (sulfolane); and in mixtures of these physical solvents with monoethanolamine and diglycolamine, in the range −10 to 100°C. Thermodynamically consistent equations are given for gas absorption with chemical reaction at equilibrium. Henry's law describes physical equilibrium between the acidic gas in the vapor phase and free acid solute in the liquid phase. Equilibrium constants describe chemical equilibria for the absorbed gas and the chemical solvent.Preliminary design calculations for sweetening natural gases by absorption with mixed solvents suggest that, under some circumstances, mixed‐solvent absorption may be more economical than using conventional aqueous alkanolamine.

The principal purpose of this investigation was to make clear the oxidation behavior at 1200° to 1400°C of silicon carbide bodies containing 15% bonds in the system K2O-Al2O3-SiO2.The oxidation resistance was determined using a small plate specimen 14mm in diameter and about 8mm thick. For most of work the specimen was oxidized at 1200° and 1400°C in a flowing atmosphere with controlled amounts of oxygen and water vapor. The weight gain, volume change, and porosity of the specimen were determined. The results obtained are summarized as follows:(1) The bonds containing large amounts of K2O and Al2O3 retarded the oxidation of silicon carbide. At 1200°C K2O was more effective on reduction of the oxidation than Al2O3, but at 1400°C the effect of Al2O3 on the oxidation resistance became somewhat high.(2) Silicon carbide was oxidized very strongly by the mixture of water vapor and oxygen when heated above 1200°C. It was observed that at such a high temperature the specimen swelled and cracked and permitted oxidation.(3) The presence of Al2O3, K2O in the bodies and water vapor in the atmosphere caused the formation of cracks, which had also been found in ceramic bonded silicon carbid refractories. The mechanism of formation of cracks was explained on the basis of reactions in the system K2O-Al2O3-SiO2-H2O.(4) After heating the specimen in air at 1400°C for 10 hrs the rate of oxidation by water vapor at 1200°C diminished considerably.

Gaseous nitric acid removal by surfaces in experimental systems and in the atmospheric boundary layer is rapid. However, neither the form of HNO3 on surfaces nor its impact on the properties of the thin surface film are known. We report here studies of surfaces that have been exposed at room temperature (295 ± 2 K) to gaseous mixtures of water vapor with HNO3 at concentrations from 46 ppb to 4 × 103 ppm. The surfaces were probed using a combination of Fourier transform infrared spectrometry (FTIR), non-contact atomic force microscopy (AFM), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS). Exposure of borosilicate glass, quartz, and thin Teflon films to mixtures of gaseous HNO3 and water vapor leads to the subsequent uptake of much larger amounts of water than occurs on the corresponding unexposed surfaces. Infrared spectra show evidence for the formation of nitric acid–water complexes on the surface that leads to this enhanced water uptake. On borosilicate glass, exposure to the nitric acid–water vapor mixture results in surface segregation of the trace metal oxides and their nitrates formed from reaction with HNO3. The majority of these oxides can be removed by rinsing with water; however, smaller, segregated regions of ZnO remain on the surface. The implications for heterogeneous reactions in thin films on surfaces in laboratory systems and in the atmosphere are discussed.

Isotopic techniques involving 18O have been used to study of the reactions of potassium superoxide with water vapour and carbon dioxide. The isotopic analyses have been carried out with an analytical mass spectrometer. For the reactions of potassium superoxide with water vapour and with mixture of water vapour and carbon dioxide, tracer experiments prove that all of the oxygen gas liberated by these reactions originated from potassium superoxide. Carbon dioxide did not react with potassium superoxide without water vapour at room temperature.

Dehydration of Acid Gas Prior to Injection

Treatment of alicyclic β‐keto esters with a mixture of hydrogen sulfide and hydrogen chloride gives β‐thioxo esters.In some cases three forms of these products have been characterized a thioketone form, a conjugated enethiol form and a non‐conjugated enethiol form.

To investigate the effect of temperature on the removal of acetaldehyde, ammonia and trimethyl amine gases from N2 using electron attachment reactor. The target gases are malodorous gaseous components emitted at high temperature from a crematory furnace. Since the emitted gases from a crematory furnace consist of CO2, O2 and water vapor, the factors investigated are percentage of coexisting CO2, O2 and the concentration of water vapor in the N2 gas stream. To understand the effect between the target gases, the experiments are carried out both for the separate removal of target gases and the simultaneous removal of 2 and 3 target gases. The experimental results reveal that, it is found that the presence of carbon dioxide does significantly affect the removal efficiency. The higher the CO2 concentration is employed, the higher the removal efficiency become, the presence of oxygen enhances the removal efficiency of the target gases both in the separate removal of target gases and the simultaneous removal of 2 and 3 target gases. The presence of water vapor enhances the removal efficiency of the target gases from N2 at low temperature but slightly retards it at high temperature. The presence of CO2 in nitrogen, oxygen and water vapor mixture has adverse effect on the removal efficiency. The effects between the target gases on the simultaneous removal of 2 and 3 target gases are investigated. It is found that in the case of the simultaneous removal of 3 target gases, the number of acetaldehyde, ammonia and trimethyl amine gas molecules captured by an electron are higher than in the case of simultaneous removal of these 2 target gases. Furthermore, the application of two independently operated corona-discharge reactors in series is shown to have a good and promise for enhancing the removal efficiency and minimizing the generation of byproducts. It is found that the effluent O3 and NOx are removed completely. On the other hand, CO increases, current increases.

Infrared spectra are reported of mixtures of hydrogen sulphide with chlorine or bromine in low-temperature argon or nitrogen matrices. The H2S … Cl2 and H2S … Br2 complexes were identified from the perturbed halogen stretching vibration. Absorptions due to the corresponding hydrogen halides provided evidence that reaction was occurring between the hydrogen sulphide and halogen (despite the use of a twin-jet deposition), and other reaction products were tentatively identified from the observed absorptions.

LITFIRE is a computer code which simulates lithium fires in fusion reactors by generating the time histories of the temperature and pressure profiles occurring in a reactor containment in response to a lithium or lithium-lead eutectic spill and fire. The fire may take place in a single cell connected to an optional second cell, or in an insulated pan in a single cell. The lithium or lithium-lead may react with any mixture of oxygen, nitrogen or water vapor; an inert gas may also be included in the cell atmospheres. Lithium only may be burned in a carbon dioxide atmosphere without oxygen. An option for liquid metal-concrete interaction is available as well as the following options for mitigating the effects of a fire: gas flooding, emergency space cooling, emergency floor cooling, aerosol removal and gas injection. This user's guide includes a brief description of the physics of lithium fires, the workings of the code and the options available to users, and also includes a listing of the code with a complete glossary of variables used in LITFIRE. The present version of LITFIRE is available on the PFCVAX at MIT and on the Crays at the National Magnetic Fusion Energy Computer Center (NMFECC, hereafter referred to as MFE). It is written in FORTRAN 77 and is compatible with the computing facilities at which it is located. The instructions present in this guide will enable a user to execute the code at either location. 4 refs., 5 figs.

Chapter 20 - Air and Water Vapour Mixtures