Crystallisation Fouling Of Mixed Salts During Convective Heat Transfer And Sub-Cooled Flow Boiling Conditions

The mechanisms of mixed salt crystallisation fouling on heat transfer surfaces have been investigated for convective and sub-cooled flow boiling heat transfer. Effects of various operating parameters such as solution composition and hydrodynamics of the system, on crystallisation fouling of mixtures of calcium sulphate and calcium carbonate have been studied experimentally. The results of the experiments were used to develop a mechanistic model for prediction of fouling resistances. Model predictions were compared with the measured experimental data when calcium sulphate and calcium carbonate form and deposit on the heat transfer surface, simultaneously. Deviations ranging from 6% to 25% were observed which confirm the suitability of the model. Finally, the crystalline samples were analysed using Scanning Electron Microscopy, X-Ray Diffraction and Ion Chromatography techniques. Fractal analysis performed on Scanning Electron Microscopy photographs of the deposits was used to quantify deposit characteristics by introducing the fractal dimension as a new characteristic quantit

Heat Exchanger Fouling in Phosphoric Acid Evaporators - Evaluation of Field Data -

Multistage evaporators are frequently used in phosphoric acid plants to increase the concentration of dilute phosphoric acid to 52-55 wt% P2O5. The concentrated phosphoric acid solution is supersaturated with respect to calcium sulfate. As a result, part of the calcium sulfate in the liquor deposits on the heat exchanger tube walls. Since the thermal conductivity of these scales is very low, thin deposits can create a significant resistance to heat transfer. Therefore, regular cleaning of heat exchangers is required, frequently at less than biweekly intervals. As the major costs in modern phosphoric acid plants are the cost of energy, a thorough understanding of the fouling kinetics and of the effects of various operational parameters on the behavior of calcium sulfate is required to improve operation and design of the shell and tube heat exchangers, which are extensively used. In this investigation, a large number of heat exchanger data were collected from shell and tube heat exchangers of the phosphoric acid plant of the Razi Petrochemical Complex (Iran) and the fouling deposits were analyzed with respect to appearance and composition. The overall heat transfer coefficients and fouling resistances were evaluated at different times and a kinetic model for the crystallization fouling was developed. It is shown that the crystallization rate constant obeys an Arrhenius relationship with activation energy of 57 kJ/mol. The predictions of the suggested model are in good agreement with the plant data

SCALE DEPOSITS IN POROUS MEDIA AND THEIR REMOVAL BY EDTA INJECTION

Formation damage has been observed in several oil reservoirs and production equipment in Iranian oil fields. Laboratory and field testing confirmed that the primary cause of damage was the build-up of calcium carbonate, calcium sulfate and strontium sulfate scale either in the perforation tunnels or in the formation sandstone nears the wellbore. Conventional acid treatments could dissolve this scale, but scale precipitation from the spent acid caused rapid productivity decline. A scale removal treatment with Na2H2EDTA has been developed that can effectively dissolve scale and chelate the dissolved metal ions. Chelation of the dissolved scale prevents scale reprecipitation. This study describes the results of an experimental and theoretical study on the removal of formation damage resulting from scale formation in porous media. An experimental investigation was undertaken to look into the possible causes of the injectivity loss in a typical Iranian oilfield. Sets of experimental investigations were undertaken with different objectives in mind. Glass and sand bead packs were used to test the experimental set up and to observe the general behaviour of scale formation and removal by ethylene diamine tetra acetic acid (EDTA) to determine its possible effects on the permeability of the porous medium

Obesity and Insulin Resistance: A Review of Molecular Interactions

The prevalence of insulin resistance and diabetes mellitus is rising globally in epidemic proportions. Diabetes and its complications contribute to significant morbidity and mortality. An increase in sedentary lifestyle and consumption of a more energydense diet increased the incidence of obesity which is a significant risk factor for type 2 diabetes. Obesity acts as a potent upstream event that promotes molecular mechanisms involved in insulin resistance and diabetes mellitus. However, the exact molecular mechanisms between obesity and diabetes are not clearly understood. In the current study, we have reviewed the molecular interactions between obesity and type 2 diabetes

Protective role of nutraceuticals against myocarditis

Myocarditis is an inflammatory disease of the myocardium that mostly affects young adults. The disease is commonly caused by viral infection, medications, autoimmune disorders, and inflammatory conditions. Nearly 50% of the cases of myocarditis are due to post-viral immune response in a setting of an identifiable or non-identifiable infection. The clinical manifestation is nonspecific ranging from asymptomatic courses to sudden death in infants and young patients. This review describes the properties of phytochemicals as plant-derived active ingredients which can be used in the prevention and treatment of myocarditis and its associated risk factors. Meanwhile, it has illustrated epidemiological analyses, mechanism of action, and the metabolism of phytochemicals in animal and human clinical trials. We also mentioned the precise mechanism of action by which phytochemicals elicit their anti-viral, anti-inflammatory, antioxidant, and immunomodulatory effects and how they regulate signal transduction pathways. Nevertheless, comprehensive clinical trials are required to study the properties of phytochemicals in vivo, in vitro, and in silico for a proper management of myocarditis. Our findings indicate that phytochemicals function as potent adjunctive therapeutic drugs in myocarditis and its related complications

Anti-inflammatory potentials of incretin-based therapies used in the management of diabetes

GLP-1 receptor agonists (GLP-1RA) and dipeptidyl peptidase 4 inhibitors (DPP-4i) are two classes of antidiabetic agents used in the management of diabetes based on incretin hormones. There is emerging evidence that they have anti-inflammatory effects. Since most long-term complications of diabetes have a background of chronic inflammation, these agents may be beneficial against diabetic complications not only due to their hypoglycemic potential but also via their anti-inflammatory effects. However, the exact molecular mechanisms by which GLP-1RAs and DPP-4i exert their anti-inflammatory effects are not clearly understood. In this review, we discuss the potential molecular pathways by which these incretin-based therapies exert their anti-inflammatory effects