scholarly journals Calculations of Complex Chemical Reaction Equilibria using Free Energy Minimization and Arc-Length Continuation

2021 ◽  
Author(s):  
Housam Binous ◽  
Ahmed Bellagi
Keyword(s):  
Energy Minimization ◽  
Sensitivity Analyses ◽  
Arc Length ◽  
Lagrangian Multipliers ◽  
High Pressure And Temperature ◽  
Chemical Equilibria ◽  
Temperature And Pressure ◽  
Reacting Systems ◽  
Process Simulator ◽  
Continuation Technique

In the present paper, we determine the chemical equilibrium compositions for two combustion reactions involving either hydrazine or propane at fixed high pressure and temperature values using several computational approaches. Then, we compute the chemical equilibria for reacting systems under a multitude of temperature and pressure conditions and various initial system compositions. These sensitivity analyses are based on a combination of the method of Lagrangian multipliers and the arc-length continuation technique. Indeed, three industrially relevant case studies are elucidated: (1) the synthesis of ammonia using the Haber process, (2) the gasification of a typical biomass surrogate: glucose using steam and (3) the gasification of cellulose using steam. For all the above reacting systems, our results are benchmarked against their counterparts obtained either from the ubiquitous process simulator: ASPEN-Plus® or from data available in the open literature.

Sensitivity Analysis of Cable Parameters on Tension of a Suspended Cable under Combination Resonances

2019 ◽  
Vol 19 (03) ◽  
pp. 1950025 ◽  
Author(s):  
Kyu Won Kim ◽  
No-Cheol Park ◽  
Weon Keun Song ◽  
Moon Kyum Kim ◽  
Manukid Parnichkun
Keyword(s):  
Sensitivity Analysis ◽  
Time Domain ◽  
Damping Coefficient ◽  
Sensitivity Analyses ◽  
Phase Portraits ◽  
Arc Length ◽  
Cable Tension ◽  
Suspended Cable ◽  
Direct Integration Method ◽  
The Time Domain

This paper studies the vibration of a suspended cable with small sag excited by a second excitation (normal) mode causing combination resonance in the three modes, i.e. tangent, normal and bi-normal modes. The displacement response spectra in the time domain and phase portraits are provided as evidence of the transition from the unstable steady-state motion to the stable one for nonlinear cable oscillation. A nondimensional equation for the cable tension is established with its variation evaluated for the unstable zone. The half-normalized sensitivity analysis of cable parameters, such as damping coefficient, excitation amplitude, arc length parameter and initial conditions, for their influence on cable tension is conducted in the time domain by a direct integration method. Also, the characteristics of the dynamic sensitivity of cable tension to the parameters are discussed. As a result, a sensitivity ranking chart is prepared based on the sensitivity analyses for the parameters considered. It is clearly revealed that cable tension is very sensitive to tangent and normal initial displacements in spite of their small values, whereas the same is not true for the arc length parameter and bi-normal damping coefficient. To verify the sensitivity analysis algorithm, a forced Rayleigh oscillator is introduced. A feasibility study using the oscillator shows that the numerical results obtained are in good qualitative agreement with the analytical predictions, implying that the associated algorithm works well.

Thermodynamic Models for the Temperature and Pressure Variations Within Adiabatic Caverns of Compressed Air Energy Storage Plants

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
R. Kushnir ◽  
A. Ullmann ◽  
A. Dayan
Keyword(s):  
Energy Storage ◽  
Storage Temperature ◽  
Pressure Ratio ◽  
Pressure Fluctuations ◽  
Compressed Air ◽  
Plant Performance ◽  
Sensitivity Analyses ◽  
Compressed Air Energy Storage ◽  
State Equations ◽  
Temperature And Pressure

The temperature and pressure variation limits within the cavern of a compressed air energy storage (CAES) plant affect the compressor and turbine works, the required fuel consumption and therefore the overall plant performance. In the present work, the thermodynamic response of adiabatic cavern reservoirs to charge/discharge cycles of CAES plants are studied. Solutions for the air cavern temperature and pressure variations were derived from the mass and energy conservation equations, and applied to three different gas state equations, namely, ideal, real, and a self-developed simplified gas models. Sensitivity analyses were conducted to identify the dominant parameters that affect the storage temperature and pressure fluctuations. It is demonstrated that a simplified gas model can adequately represent the air thermodynamic properties. The stored air maximal to minimal temperature and pressure ratios were found to depend primarily on, both the ratio of the injected to the initial cavern air mass, and the reservoir mean pressure. The results also indicate that the storage volume is highly dependent on the air maximum to minimum pressure ratio. Its value should preferably be in between 1.2 and 1.8, where the exact selection should account for design and economic criteria.

Fuel Processing and Combustion: An Extreme Thermodynamic Analysis

1999 ◽  
Author(s):  
Sergei P. Filippov ◽  
Alexandre V. Keiko ◽  
Peter P. Pavlov
Keyword(s):  
Nitrogen Oxides ◽  
Thermodynamic Analysis ◽  
Close Correspondence ◽  
Coal Processing ◽  
Fuel Processing ◽  
Chemical Equilibria ◽  
Intermediate States ◽  
Chemically Reacting Systems ◽  
Chemically Reacting ◽  
Reacting Systems

Abstract The paper concerns application of the extreme thermodynamics approach within the analysis of chemically reacting systems. Some principal techniques of the approach are shown on simplified examples of coal processing and nitrogen oxides formation. The analyses are based on the investigation of incomplete chemical equilibria using the models of extreme intermediate states (MEIS). The close correspondence between the MEIS statement and graphical interpretations is shown and used.

Reaction rates as virtual constraints in Gibbs energy minimization

2011 ◽  
Vol 83 (5) ◽  
pp. 1063-1074 ◽  
Author(s):  
Pertti Koukkari ◽  
Risto Pajarre ◽  
Peter Blomberg
Keyword(s):  
Gibbs Energy ◽  
Energy Minimization ◽  
Reaction Rate ◽  
Reaction Rates ◽  
Free Energy Calculations ◽  
Energy Calculation ◽  
Chemical Equilibria ◽  
Gibbs Energy Minimization ◽  
Physical Chemical ◽  
Work Factors

The constrained Gibbs energy method has been developed for the use of immaterial entities in the formula conservation matrix of the Gibbs energy minimization problem. The new method enables the association of the conservation matrix with structural, physical, chemical, and energetic properties, and thus the scope of free energy calculations can be extended beyond the conventional studies of global chemical equilibria and phase diagrams. The use of immaterial constraints enables thermochemical calculations in partial equilibrium systems as well as in systems controlled by work factors. In addition, they allow the introduction of mechanistic reaction kinetics to the Gibbsian multiphase analysis. The constrained advancements of reactions are incorporated into the Gibbs energy calculation by using additional virtual phases in the conservation matrix. The virtual components are then utilized to meet the incremental consumption of reactants or the formation of products in the kinetically slow reactions. The respective thermodynamic properties for the intermediate states can be used in reaction rate formulations, e.g., by applying the reaction quotients.

scholarly journals Analysis of superheater tubes failure

2019 ◽  
Vol 82 ◽  
pp. 01002
Author(s):  
Łukasz Felkowski ◽  
Jakub Mędrala
Keyword(s):  
Stress Concentration ◽  
Local Stress ◽  
Material Structure ◽  
Creep Equation ◽  
High Pressure And Temperature ◽  
Structure Changes ◽  
Creep Analysis ◽  
Temperature And Pressure ◽  
Two Parameters ◽  
External Loads

Failures of boiler pressure parts, which working in high temperature and pressure conditions are often caused by overheating or corrosion. These two parameters are decisive, but not the only ones. Local stress concentration also depends on the type of headers support and external loads from pipelines. Boiler pressure parts subjected to all loads mentioned before are steam superheaters. Thermal expansion, high pressure and temperature lead to shortening superheaters lifetime. In the places with significant stress caused by all load combinations it is difficult to predict creep strains and material structure changes. This paper shows superheater in which considering external loads from pipeline and their influence on the stress concentration in the superheater tubes. This article also shows steel S304H creep analysis for 100k [h] results and creep equation with experimental developed constants.

scholarly journals Toward Elusive Iodoplumbic Acid HPbI3: High-Energy Isochoric Synthesis of Hydronium Forms of the PbI3- Anion at Elevated Temperature and Pressure

2021 ◽  
Author(s):  
Szymon Sobczak ◽  
Athena M. Fidelli ◽  
Jean-Louis Do ◽  
George P. Demopoulos ◽  
Audrey Moores ◽  
...  
Keyword(s):  
Three Dimensional ◽  
High Energy ◽  
Hydriodic Acid ◽  
X Ray Diffraction ◽  
Lead Iodide ◽  
High Pressure And Temperature ◽  
One Dimensional ◽  
Diamond Anvil ◽  
Temperature And Pressure ◽  
Temperature Crystallization

High-pressure and -temperature crystallization and X-ray diffraction crystallography have revealed hydronium forms of the proposed but never demonstrated iodoplumbic acid HPbI<sub>3</sub>. Depending on the pressure range, the reaction of PbI2 and aqueous concentrated hydriodic acid under isochoric conditions in a diamond anvil cell (DAC) held between 0.11 and 1.20 GPa produces two hydrated hydronium salts with compositions [H<sub>3</sub>O][PbI<sub>3</sub>].<i>n</i>H<sub>2</sub>O (<i>n</i>=3,4). Comprised of polymeric one-dimensional PbI<sub>3</sub><sup>-</sup> anions, these hydronium salts represent the so far best match for the elusive HPbI<sub>3</sub> progenitor of hybrid lead perovskites. We also reveal a new three-dimensional polymorph of lead iodide (PbI<sub>2</sub>), so far known only as a layered structure.<br>

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