Fundamental Thermodynamic Equations Research Articles

A new model for predicting pressure traverse in two phase flow geothermal well

The complexity associated with the two phase or multiphase flow system have been a long-time challenge in the modelling of the flowing pressure in the production channel which includes geothermal well. The flow of hot water and its vapour ensued all throughout the geothermal system producing from the reservoir source to the wellbore and later to the surface. The performance of geothermal system is primarily dependent on the ability to accurately predict the flowing pressure in the production well. Several models derived from the fundamental thermodynamic energy equation to handle the complexity of two-phase flow in geothermal well have demonstrated diverse discrepancy when compared with real time measurement. It has been conceived in the study that the inclusion of pressure drop due to accumulation in the thermodynamic energy equation reduces the discrepancy between the predicted pressure and the field measurement. It is pertinent to the geothermal energy industry to assess the accurate model that consider all constituent terms that impact the two-phase flow behaviour in a geothermal production well. A more exact numerical model for evaluating the flowing pressure in geothermal has been derived in this study where the right constituent terms that practically impact the two-phase flow behaviour in a geothermal vertical well are considered. The present model has the capacity to predict flowing pressure accurately as the flow transit from one regime to another. Likewise, the present model was able to capture the transient period that usually occurs when the geothermal well is put to production. The present model was validated using data from KE1-22 and Mesa 6-1 wells reported in literature. The present model gave the least mean absolute relative error of 0.033 when applied to measured field data from KE1-22 Well while Hassan and Kabir, Ansari, Orkiszewski and Homogenous models gave errors of 0.12, 0.33, 0.41 and 0.38 respectively. Similarly, relative to data from Mesa 6-1 the present model gave a mean absolute relative error of 0.052 while Hassan and Kabir, Ansari, Orkiszewski and Homogenous models gave errors of 0.17, 1.46, 1.37 and 2.53 respectively. The newly derived model is reliable for assessing the performance of the geothermal system and evaluating flowing pressure at every difference transition period.

Structural Realism About the Free Energy Principle, the Best of Both Worlds

AbstractThere are realist and antirealist interpretations of the free energy principle (FEP). This paper aims to chart out a structural realist interpretation of FEP. To do so, it draws on Worrall’s (Dialectica 43(1–2): 99–124, 1989) proposal. The general insight of Worrall’s paper is that there is progress at the level of the structure of theories rather than their content. To enact Worrall’s strategy in the context of FEP, this paper will focus on characterising the formal continuity between fundamental equations of thermodynamics—such as Boltzmann’s equation and Gibbs’s equation—on the one hand, and Friston’s characterisation of FEP on the other. Lack of a universal consensus on the physical character of entities that feature in thermodynamics, information theory and FEP notwithstanding, I argue that there is structural continuity and unity at the level of mathematical equations that regiment entropy, information and free energy. The existence of such structural continuity and unity provides grounds for structural realism about FEP.

Quantum non-Markovianity, quantum coherence and extractable work in a general quantum process.

A key concept in quantum thermodynamics is extractable work, which specifies the maximum amount of work that can be extracted from a quantum system. Different quantities are used to measure extractable work, the most prevalent of which are ergotropy and the difference between the non-equilibrium and equilibrium quantum free energies. Using the latter, we investigate the evolution of extractable work when an open quantum system undergoes a general quantum process described by a completely-positive and trace-preserving dynamical map. We derive a fundamental equation of thermodynamics for such processes as a relation between the distinct sorts of energy change in such a way that the first and the second law of thermodynamics are combined. We then identify the contributions from the reversible and irreversible processes in this equation and demonstrate that they are respectively responsible for the evolution of heat and extractable work of the open quantum system. Furthermore, we show how this correspondence between irreversibility and extractable work has the potential to provide a clear explanation of how the quantum properties of a system affect its extractable work evolution. Specifically, we establish this by directly connecting the change in extractable work with the change in standard quantifiers of quantum non-Markovianity and quantum coherence during a general quantum process. We illustrate these results with two examples.

Analysis of the Performance of a Hybrid Thermal Power Plant Using Adaptive Neuro-Fuzzy Inference System (ANFIS)-Based Approaches

The hybridization of conventional thermal power plants by the incorporation of renewable energy systems has witnessed widespread adoption in recent years. This trend aims not only to mitigate carbon emissions but also to enhance the overall efficiency and performance of these power generation facilities. However, calculating the performance of such intricate systems using fundamental thermodynamic equations proves to be both laborious and time-intensive. Nevertheless, possessing accurate and real-time insights into their performance is of utmost significance to ensure optimal plant operation, facilitate decision making, and streamline power production planning. This paper explores the novel application of machine learning techniques to predict the performance of hybrid thermal power plants, specifically the integrated solar combined cycle power plant (ISCCPP). These plants combine conventional thermal power generation with renewable energy sources, making them crucial in the context of carbon reduction and enhanced efficiency. We employ three machine learning approaches: the adaptive neuro-fuzzy inference system (ANFIS), ANFIS optimized via particle swarm optimization (ANFIS-PSO), and ANFIS optimized through a genetic algorithm (ANFIS-GA). These methods are applied to the complex ISCCPP, comprising steam and gas turbine sections and a concentrated solar power system. The results highlight the accuracy of ANFIS-based models in evaluating and predicting plant performance, with an exceptional overall correlation coefficient of 0.9991. Importantly, integrating evolutionary algorithms (PSO and GA) into ANFIS significantly enhances performance, yielding correlation coefficients of 0.9994 for ANFIS-PSO and 0.9997 for ANFIS-GA, with ANFIS-GA outperforming the others. This research provides a robust tool for designers, energy managers, and decision makers, offering valuable support in assessing the performance of hybrid thermal power plants. As the world transitions to cleaner energy sources, the insights gained here are poised to have a significant impact on the growing number of these thermal power plants globally.

Plasma-Assisted Abatement of Per- and Polyfluoroalkyl Substances (PFAS): Thermodynamic Analysis and Validation in Gliding Arc Discharge

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic organofluorine surfactants that are resistant to typical methods of degradation. Thermal techniques along with other novel, less energy-intensive techniques are currently being investigated for the treatment of PFAS-contaminated matrices. Non-equilibrium plasma is one technique that has shown promise for the treatment of PFAS-contaminated water. To better tailor non-equilibrium plasma systems for this application, knowledge of the energy required for mineralization, and in turn the roles that plasma reactive species and heat can play in this process, would be useful. In this study, fundamental thermodynamic equations were used to estimate the enthalpies of reaction (480 kJ/mol) and formation (−4640 kJ/mol) of perfluorooctanoic acid (PFOA, a long-chain legacy PFAS) in water. This enthalpy of reaction estimate indicates that plasma reactive species alone cannot catalyze the reaction; because the reaction is endothermic, energy input (e.g., heat) is required. The estimated enthalpies were used with HSC Chemistry software to produce a model of PFOA defluorination in a 100 mg/L aqueous solution as a function of enthalpy. The model indicated that as enthalpy of the reaction system increased, higher PFOA defluorination, and thus a higher extent of mineralization, was achieved. The model results were validated using experimental results from the gliding arc plasmatron (GAP) treatment of PFOA or PFOS-contaminated water using argon and air, separately, as the plasma gas. It was demonstrated that PFOA and PFOS mineralization in both types of plasma required more energy than predicted by thermodynamics, which was anticipated as the model did not take kinetics into account. However, the observed trends were similar to that of the model, especially when argon was used as the plasma gas. Overall, it was demonstrated that while energy input (e.g., heat) was required for the non-equilibrium plasma degradation of PFOA in water, a lower energy barrier was present with plasma treatment compared to conventional thermal treatments, and therefore mineralization was improved. Plasma reactive species, such as hydroxyl radicals (⋅OH) and/or hydrated electrons (e−(aq)), though unable to accelerate an endothermic reaction alone, likely served as catalysts for PFOA mineralization, helping to lower the energy barrier. In this study, the activation energies (Ea) for these species to react with the alpha C–F bond in PFOA were estimated to be roughly 1 eV for hydroxyl radicals and 2 eV for hydrated electrons.

Large Decrease in the Melting Point of Benzoquinones via High-n Eutectic Mixing Predicted by a Regular Solution Model.

Decreasing the melting point (Tm) of a mixture is of interest in cryopreservatives, molten salts, and battery electrolytes. One general strategy to decrease Tm, exemplified by deep eutectic solvents, is to mix components with favorable (negative) enthalpic interactions. We demonstrate a complementary strategy to decrease Tm by mixing many components with neutral or slightly positive enthalpic interactions, using the number of components (n) to increase the entropy of mixing and decrease Tm. In theory, under certain conditions this approach could achieve an arbitrarily low Tm. Furthermore, if the components are small redox-active molecules, such as the benzoquinones studied here, this approach could lead to high energy density flow battery electrolytes. Finding the eutectic composition of a high-n mixture can be challenging due to the large compositional space yet is essential for ensuring the existence of a purely liquid phase. We reformulate and apply fundamental thermodynamic equations to describe high-n eutectic mixtures of small redox-active molecules (benzoquinones and hydroquinones). We illustrate a novel application of this theory by tuning the entropy of melting, rather than the enthalpy, in systems highly relevant to energy storage. We demonstrate with differential scanning calorimetry measurements that 1,4-benzoquinone derivatives exhibit eutectic mixing that decreases their Tm, despite slightly positive enthalpies of mixing (0-5 kJ/mol). By rigorously investigating all 21 binary mixtures of a set of seven 1,4-benzoquinone derivatives with alkyl substituents (Tm's between 44 and 120 °C), we find that the eutectic melting point of a mixture of all seven achieves a large decrease in Tm to -6 °C. We further determine that the regular solution model shows improvement over an ideal solution model in predicting the eutectic properties for this newly investigated type of mixture composed of many small redox-active organic molecules.

Ideal quantum gases: A geometrothermodynamic approach

We derive the fundamental thermodynamic equation for Fermi-Dirac and Bose-Einstein quantum gases, which contains the first order contribution due to the quantum nature of the gas particles. Then, we analyze the fundamental equation in the context of geometrothermodynamics. Although the corresponding Hamiltonian does not contain a potential, indicating the lack of classical thermodynamic interaction, we show that the curvature of the equilibrium space is non-zero and can be interpreted as a measure of the effective quantum interaction between the gas particles. In the limiting case of a classical Boltzmann gas, we show that the equilibrium space becomes flat, as expected from the physical viewpoint. In addition, we derive a thermodynamic fundamental equation for the Bose-Einstein condensation and, using the Ehrenfest scheme, we show that it can be considered as a first order phase transition which in the equilibrium space corresponds to a curvature singularity. This result indicates that the curvature of the equilibrium space can be used to measure in an invariant way the thermodynamic interaction in classical and quantum ideal gases.

General adsorption isotherm for polyoxyethylene alkyl ethers CnEOm adsorbed at the water/air surface

An empirical adsorption isotherm model is presented based on fundamental thermodynamic equations of adsorption for the homologous series of the nonionic surfactants polyoxyethylene alkyl ethers (CnEOm) at the aqueous solution surface to determine the surface tension and surface pressure isotherms, surface equation of state, and molar characteristics for the adsorbed surfactant molecules. The new model describes the surface properties of CnEOm much better than the original Langmuir adsorption model used as thermodynamic basis. The analysis of the results shows that the increase of the alkyl chain length n (hydrophobic part) leads to an increase in the adsorption activity, while the increase of hydrophilic head group given by the number of EO units m, leads to a better solubility in water, and hence, to a smaller adsorbed amount. The results also show that the ethylene oxide group mainly influences the molar surface area.

Development and experimental validation of a mechanistic chamber model of a novel peristaltic compressor

This work presents the novel peristaltic compressor, which has the potential to improve compressor efficiency by eliminating losses due to valves and over/under compression. This compressor operates by means of a progressively actuated diaphragm that compresses vapor and stimulates flow through a cylindrical chamber. In this study, we present a mechanistic chamber model of the compressor. A geometric model is developed along with the fundamental thermodynamic equations that describe compression as well as sub-models describing mass flow, leakage, and heat transfer. Additionally, validation of the model is presented using data from a reconfigurable prototype compressor using air as the working fluid. The reconfigurable prototype is operated with volume ratios ranging from 1.5 to 9 at pressure ratios ranging from 1 to 2.1. Each test is repeated 6 times and the experimental uncertainty of each test is within 5%. The mechanistic chamber model of the peristaltic compressor predicts the experimental mass flow rate and volumetric efficiency within 10% MAPE.

Liquid-Phase Speed of Sound and Vapor-Phase Density of Difluoromethane.

Difluoromethane (HFC-32, DFM), with a global warming potential (GWP) of 677, is of interest as a pure refrigerant and as a component in low-GWP refrigerant mixtures. Additionally, difluoromethane has recently been identified as a safe, liquefied-gas electrolyte material in batteries. Using state-of-the-art instruments for measurements, this paper presents new liquid-phase speed of sound and vapor-phase density data for difluoromethane. Two hundred and nine liquid-phase speed of sound values were measured using a dual-path pulse-echo instrument at temperatures from 230 to 345 K and pressures from 2.1 to 70 MPa. Accounting for all sources of uncertainty, the relative expanded combined uncertainty (k = 2) in the speed of sound ranged from 0.035 to 0.17%. One hundred and thirty-eight vapour-phase density values were measured using a two-sinker densimeter at temperatures from 240 to 340 K and pressures from 0.1 to 1.61 MPa with an uncertainty of 0.011 to 0.12%. These experimental data will be valuable in the ongoing development of a new fundamental thermodynamic equation of state for difluoromethane.

Predicting Solubility Limits of Organic Solutes for a Wide Range of Solvents and Temperatures.

The solubility of organic molecules is crucial in organic synthesis and industrial chemistry; it is important in the design of many phase separation and purification units, and it controls the migration of many species into the environment. To decide which solvents and temperatures can be used in the design of new processes, trial and error is often used, as the choice is restricted by unknown solid solubility limits. Here, we present a fast and convenient computational method for estimating the solubility of solid neutral organic molecules in water and many organic solvents for a broad range of temperatures. The model is developed by combining fundamental thermodynamic equations with machine learning models for solvation free energy, solvation enthalpy, Abraham solute parameters, and aqueous solid solubility at 298 K. We provide free open-source and online tools for the prediction of solid solubility limits and a curated data collection (SolProp) that includes more than 5000 experimental solid solubility values for validation of the model. The model predictions are accurate for aqueous systems and for a huge range of organic solvents up to 550 K or higher. Methods to further improve solid solubility predictions by providing experimental data on the solute of interest in another solvent, or on the solute's sublimation enthalpy, are also presented.

Solution-State Hydrostatic Pressure Chemistry: Application to Molecular, Supramolecular, Polymer, and Biological Systems

Pressure (P), as one of the most inherent state quantities, has become an academic subject of study and has attracted attention for a long time for the minute control of reaction equilibria and rates, not only in the gas phase, based on the gas state equation, but also in the solution state. In the latter case, the pressure applied to the solutions is classified as hydrostatic pressure, which is a type of isotropic mechanical force. For instance, deep-sea organisms are exposed to hydrostatic pressure environments of up to 100 MPa, implying that hydrostatic pressurization plays a role in homeostatic functions at physiological levels. The pressure control of such complicated biological behavior can be addressed by thermodynamics or kinetics. In fact, the spontaneity (ΔG) of a reaction that is governed by weak interactions (approximately 10 kcal/mol), such as electrostatic, van der Waals, hydrophobic, hydrogen bonding, and π-π stacking, is determined by the exquisite balance of enthalpy (ΔH) and entropy changes (ΔS), in accordance with the fundamental thermodynamic equation ΔG = ΔH - TΔS. The mutually correlated ΔH-ΔS relationship is known as the enthalpy-entropy compensation law, in which a more negative enthalpic change (more exothermic) causes further entropic loss based on a more negative entropy change. Namely, changing the temperature (T) as the state quantity, except for P, is highly likely to be equal to controlling the entropy term. The solution-state entropy term is relatively vague, mainly based on solvation, and thus unpredictable, even using high-cost quantum mechanical calculations because of the vast number of solvation molecules. Hence, such entropy control is not always feasible and must be demonstrated on a trial-and-error basis. Furthermore, the above-mentioned equation can be rearranged as ΔG = ΔF + PΔV, enabling us to control solution-state reactions by simply changing P as hydrostatic pressure based on the volume change (ΔV). The volume term is strongly relevant to conformational changes, solvation changes, and molecular recognition upon complexation and thus is relatively predictable, that is, volumetrically compact or not, compared to the complicated entropy term. These extrathermodynamic and kinetic observations prompted us to use hydrostatic pressure as a controlling factor over a long period. Hydrostatic pressure chemistry in the solution phase has developed over the past six decades and then converged and passed the fields of mechanochemistry and mechanobiology, which are new but challenging and current hot topics in multidisciplinary science. In this Account, we fully summarize our achievements in solution-state hydrostatic pressure chemistry for smart/functional molecular, supramolecular, polymer, and biological systems. We hope that the phenomena, mechanistic outcomes, and methodologies that we introduced herein for hydrostatic-pressure-controlling dynamics can provide guidance for both theoretical and experimental chemists working in supramolecular and (bio)macromolecular chemistry, mechanoscience, materials science, and technology.

Holographic thermodynamics requires a chemical potential for color

The thermodynamic Euler equation for high-energy states of large-$N$ gauge theories is derived from the dependence of the extensive quantities on the number of colors $N$. This Euler equation relates the energy of the state to the temperature, entropy, number of degrees of freedom and its chemical potential, but not to the volume or pressure. In the context of the gauge/gravity duality we show that the Euler equation is dual to the generalized Smarr formula for black holes in the presence of a negative cosmological constant. We also match the fundamental variational equation of thermodynamics to the first law of black hole mechanics, when extended to include variations of the cosmological constant and Newton's constant.

A single zone thermodynamic simulation model for predicting the combustion and performance characteristics of a CI engine and its validation using statistical analysis

In this investigation, a single zone thermodynamic model was developed to predict the combustion characteristics such as in-cylinder pressure, rate of pressure rise (ROPR)), ignition delay and combustion duration and performance characteristics such as brake power (BP), brake specific fuel consumption (BSFC), and brake thermal efficiency (BTE) using fundamental thermodynamic equations and various models. The test was performed on a four-stroke 1- cylinder diesel engine fueled with MnP15 and neat diesel fuel at different loading conditions. The success of the thermodynamic model was evaluated by statistical metrics (R2, standard error (S), Pearson’s correlation (r), P-value, and Z-test). The model accurately predicted the numerical results of cylinder pressure and ROPR for diesel fuel and MnP15 blend at all tested loading conditions. The statistical analysis of the predicted data by regression method and Z-test showed strong evidence of significant data by this model. The maximum standard error (S) found for in-cylinder pressure data by regression analysis was 2.47 for the MnP15 blend at 100% load, and the minimum error was 1.336 for the MnP15 blend at 25% load. The mean values of the numerical data lay within 95% confidence interval in Z test analysis, and also calculated value of Z fell less than the tabulated value of Z (=1.96) of 95% confidence interval level, for diesel and MP15 blend at all tested loading conditions. The engine performance output such as BP, BSFC, and BTE computed accurately. The coefficient of determination (R2) for the performance parameters (BSFC and BTE) was above 98%, and Pearson’s correlation (r) was also above 0.9 for both blends, whereas the maximum relative error was 7.58% for the MnP15 blend in BSFC output at 75% load and 6.07 % in BP output in the case of diesel fuel, implying an accurate simulation model for a diesel engine. In conclusion, the model could be used to accurately predict the performance and combustion characteristics of the C.I. engine.

Evaluation of frost heave in clay soils

Frost heaving in clayey soils with a low coefficient of permeability raises a lot of questions regarding the cryosuction, surface tension forces, and accompanying phase transfer of water. The freeze-thaw laboratory test results were considered in this work in terms of temperature and volumetric parameters change, dry density, and water mass transfer. The article presents a model for calculating the mass transfer of water (vapour) in the gas state under the influence of cryogenic forces. Findings include the improved understanding of the heat and mass transfer phenomenon during the unidirectional freezing of soils in an open system. Most of the tests for engineering properties registered a slight reduction in relation to strength, cohesion, and angle of internal friction. However, there was a significant increase in the coefficient of permeability after the freeze-thaw cycles with initially dense compacted soil samples, which was due to loosening and moistening of the soil samples during the heave at sub-zero temperatures. The conceptual model for frost heave in soils was developed based on the vapour mass transfer. There was presented algorithm of vapour flow calculation in unsaturated soils using fundamental thermodynamic equations.

The Stoichiometric Uniqueness of Multiple Chemical Reaction Systems in Chemical Thermodynamics, Kinetics and Catalysis – Contributions of Professor Ilie Fishtik

The main scientific achievements of great significance accomplished by Professor Ilie Fishtik at the University of Iowa and the Worcester Polytechnic Institute, in several fields of the physical chemistry as chemical thermodynamics, kinetics and heterogeneous catalysis were revealed and briefly analysed. Fundamental equations of chemical thermodynamics within the De Donder (stoichiometric) approach were reformulated in terms of a special class of chemical reactions, called as response reactions. Using this approach, the unusual behaviour of chemical equilibrium systems, to interpret the apparent contradictions to Le Chatelier principle and to discover hitherto unnoticed thermodynamic identities, was rationalised. The stabilities of chemical species were formulated in terms of a certain class of stoichiometrically unique chemical reactions and their thermochemical characteristics. A completely new approach for the generation and simplification of kinetic mechanisms for complex reaction systems was developed and applied. Based on a new type of reaction networks, referred to as reaction route graphs, a systematic method of analysis and reduction of a microkinetic mechanism was established and employed.

Entropy of higher-dimensional charged Gauss–Bonnet black hole in de Sitter space

The fundamental equation of the thermodynamic system gives the relation between the internal energy, entropy and volume of two adjacent equilibrium states. Taking a higher-dimensional charged Gauss–Bonnet black hole in de Sitter space as a thermodynamic system, the state parameters have to meet the fundamental equation of thermodynamics. We introduce the effective thermodynamic quantities to describe the black hole in de Sitter space. Considering that in the lukewarm case the temperature of the black hole horizon is equal to that of the cosmological horizon, we conjecture that the effective temperature has the same value. In this way, we can obtain the entropy formula of spacetime by solving the differential equation. We find that the total entropy contains an extra term besides the sum of the entropies of the two horizons. The corrected term of the entropy is a function of the ratio of the black hole horizon radius to the cosmological horizon radius, and is independent of the charge of the spacetime.

Influence of binary, ternary and quaternary mixtures on oxidative stability and study of kinetics and thermodynamic parameters of the degradation process of soybean biodiesel

Currently, studies show that plant extracts may exert antioxidant action and have aroused great interest because they have the property of preventing or minimizing the oxidative stress caused by free radicals. This study concerning to the binary, ternary and quaternary mixtures of plant extracts and the natural antioxidant quercetin with soybean biodiesel in concentrations ranging from (500 to 3000 ppm), using the acceletated oxidation techniques (Rancimat and PetroOXY), where the temperatures varied from 90 °C to 140 °C. The stabilizing factor was studied and indicated the existence of an antioxidant effect and not an antagonistic effect. Among the extracts the highest quantitative levels of flavonoids and total carotenoids were obtained in the following decreasing sequence: oregano extract (OE) > basil extract (BAE) > bilberry extract (BE), while for antioxidant activity front the DPPH radical the decreasing sequence was: oregano extract (OE) > bilberry extract (BE) > basil extract (BAE). The activation energies of the antioxidant mixtures were obtained by the Arrhenius equation and followed the ascending order: OEQC (62.69 kJ/mol) < BOBE (65.01 kJ /mol) < BAEQC (77.15 kJ/mol) < BEQC (77.73 kJ/mol) < BOBEQC (81.73 kJ /mol) by the technique Rancimat and BEQC (40.90 kJ/mol) < OEQC (41.82 kJ/mol) < BAEQC (42.32 kJ/mol) < BOBEQC (44.48 kJ/mol) < BOBE (45.31 kJ/mol) by the technique PetroOXY. The thermodynamic parameters ΔH* and ΔS*, were obtained by the Eyring equation and the ΔG* by the fundamental equation of thermodynamics, being evident, by the results shown, the existence of an endothermic and non-spontaneous process. The shelf life of antioxidant mixtures with biodiesel followed the descending order: BAEQC > BEQC > OEQC > BOBEQC > BOBE and OEQC > BAEQC > BEQC > BOBEQC > BOBE in the Rancimat and PetroOXY method, respectively. Therefore, the use of mixtures of these natural antioxidants was very promising and of fundamental importance in the control of the oxidative process of soybean biodiesel.

Optimization of fuel consumption in natural gas city gate station based on gas hydrate temperature (Case study: Abbas Abad station)

A new approach has been presented for optimization of fuel consumption in the natural gas city gate station. In the city gate station, the temperature drops because of pressure drop has been occurred. In this case, the gas temperature may be reached to natural gas hydrates’ temperature and therefore natural gas pipelines are blocked. To avoid this condition, natural gas is preheated. Heating of natural gas should be in the range to avoid the gas hydrated temperature as well as, if possible, lower fuel consumption. For this purpose, the minimum possible temperature regulator output has been defined. The minimum temperature is based on gas hydrate temperature and has been calculated by applying fundamental thermodynamic equations and the equation of state. For validation of proposed method, the results have been compared to the measured temperature of Abbas Abad CGS. The validation shows that the proposed method has reduced fuel consumption by about 35%. The results show the price of reduced fuel consumption and carbon tax has been dropped in a year, also producing carbon dioxide because of incomplete combustion is significantly reduced.

Thermodynamic Derivations of Various Ammonium Salt Deposition Equations Common to the Refining Industry

Ammonium salts represent a common problem for the refining industry. These saltslead to fouling of piping and heat exchangers resulting in loss of duty, underdeposit corrosionwhen wetted, and corrosive sour water solutionsonce sufficient water is available to dissociate these salts into solution. To properly manage fouling and corrosion associated with these salts, knowledge of the temperatures at which these salts will deposit is critical. In this age of process control, these temperatures can be predicted in real-time provided the salt deposition temperature relationships are known. The salt deposition equations for salts most often encountered in refining are not in the public domain. To close this gap, ammonium salt deposition equations were derived for NH4Cl, NH4HS, NH4Br, and NH4Fusing fundamental thermodynamic equations of state with published thermodynamic properties for the individual chemical species/reactions.