Modeling of limestone dissolution for flue gas desulfurization with novel implications

solid-liquid dissolution is a central step in many industrial applications such as pharmaceutical, process engineering, and pollution control. Accurate mathematical models are proposed to improve reactor design and process operations. Analytical methods are significantly beneficial in the case of iterative methods used within experimental investigations. In the present study, a detailed analytical solution for the general case of solid particles dissolving in multiphase chemical reaction systems is presented. In this model, the authors consider a formulation that considers the particles' shape factor. The general case presented could be utilized within different problems of multiphase flows. These methods could be extended to different cases within the chemical engineering area. Examples are illustrated here in relation to limestone dissolution taking place within the Wet Flue Gas Desulfurization process, where calcium carbonate is dissolving in an acidic environment. The method is the most common used technology to abate SO2 released by fuel combustion. Limestone dissolution plays a major role in the process. Nevertheless, there is a need for improvements in the optimization of the WFGD process for scale-up purposes. The mathematical model has been tested by comparison with experimental data from several mild acidic dissolution assays of sedimentary and metamorphic limestone. We have found that R2 c 0.92 ± 0.06 from dozens of experiments. This fact verifies the model qualifications in capturing the main drivers of the system.Fil: De Blasio, Cataldo. Abo Akademi; FinlandiaFil: Salierno, Gabriel Leonardo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Quimicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Quimicos.; ArgentinaFil: Sinatra, Donatella. Abo Akademi; FinlandiaFil: Cassanello, Miryan. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Quimicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Quimicos.; Argentin

Analysis of operational issues in hydrothermal liquefaction and supercritical water gasification processes: a review

Biomass is often referred to as a carbon–neutral energy source, and it has a role in reducing fossil fuel depletion. In addition, biomass can be converted efficiently into various forms of biofuels. The biomass conversion processes involve several thermochemical, biochemical, and hydrothermal methods for biomass treatment integration. The most common conversion routes to produce biofuels include pyrolysis and gasification processes. On the other hand, supercritical water gasification (SCWG) and hydrothermal liquefaction (HTL) are best suitable for converting biomass and waste with high moisture content. Despite promising efficiencies, SCWG and HTL processes introduce operational issues as obstacles to the industrialization of these technologies. The issues include process safety aspects due to operation conditions, plugging due to solid deposition, corrosion, pumpability of feedstock, catalyst sintering and deactivation, and high production costs. The methods to address these issues include various reactor configurations to avoid plugging and optimizing process conditions to minimize other issues. However, there are only a few studies investigating the operational issues as the main scope, and reviews are seldomly available in this regard. Therefore, further research is required to address operational problems. This study reviews the main operational problems in SCWG and HTL. The objective of this study is to enhance the industrialization of these processes by investigating the operational issues and the potential solutions, i.e., contributing to the elimination of the obstacles. A comprehensive study on the operational issues provides a holistic overview of the biomass conversion technologies and biorefinery concepts to promote the industrialization of SCWG and HTL.Fil: Ghavami, Niloufar. Abo Akademi; FinlandiaFil: Özdenkçi, Karhan. Abo Akademi; FinlandiaFil: Salierno, Gabriel Leonardo. Abo Akademi; Finlandia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Björklund Sänkiaho, Margareta. Abo Akademi; FinlandiaFil: De Blasio, Cataldo. Abo Akademi; Finlandi

Comparison of the fluidized state stability from radioactive particle tracking results

Currently, various industrial processes are carried out in fluidized bed reactors. Knowing its internal dynamics is fundamental for the intensification of these processes. This work assesses the motion of fluidized calcium alginate spheres under the influence of an upward fluid flow within a 1.2 m high and 0.1 m inner diameter acrylic column. The liquid–solid fluidized bed was compared with a gas–liquid–solid fluidized bed operation mode in terms of mixing behavior. The radioactive particle tracking technique is a proper methodology to study the internal dynamics of these kinds of equipment. Data gathered were analyzed with Shannon entropy as a dynamic mixing measure. Mixing times were found to be between 1 and 2.5 seconds for both fluidization modes. The liquid– solid fluidized bed presents a rather smooth mixing time profile along the column. On the other hand, the gas–liquid–solid fluidized bed showed high sensitivity of entropy production with height, reaching a sharp tendency break at the second quartile of the column. The Glansdorff–Prigogine stability measure can accurately capture flow regime transitions of the gas–liquid–solid fluidized bed, allowing it to be used to construct reliable operative windows for fluidization equipment.Fil: Salierno, Gabriel Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: Gradizek, Anton. Joef Stefan Institute; EsloveniaFil: Maestri, Mauricio Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: Picabea, Julia Valentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cassanello, Miryan. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: De Blasio, Cataldo. Åbo Akademi University; FinlandiaFil: Cardona, Maria Angelica. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Tecnologías Emergentes y Ciencias Aplicadas. - Universidad Nacional de San Martin. Instituto de Tecnologías Emergentes y Ciencias Aplicadas; ArgentinaFil: Hojman, Daniel Leonardo. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Somacal, Héctor Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Tecnologías Emergentes y Ciencias Aplicadas. - Universidad Nacional de San Martin. Instituto de Tecnologías Emergentes y Ciencias Aplicadas; Argentin

Associations between depressive symptoms and disease progression in older patients with chronic kidney disease: results of the EQUAL study

Background Depressive symptoms are associated with adverse clinical outcomes in patients with end-stage kidney disease; however, few small studies have examined this association in patients with earlier phases of chronic kidney disease (CKD). We studied associations between baseline depressive symptoms and clinical outcomes in older patients with advanced CKD and examined whether these associations differed depending on sex. Methods CKD patients (>= 65 years; estimated glomerular filtration rate <= 20 mL/min/1.73 m(2)) were included from a European multicentre prospective cohort between 2012 and 2019. Depressive symptoms were measured by the five-item Mental Health Inventory (cut-off <= 70; 0-100 scale). Cox proportional hazard analysis was used to study associations between depressive symptoms and time to dialysis initiation, all-cause mortality and these outcomes combined. A joint model was used to study the association between depressive symptoms and kidney function over time. Analyses were adjusted for potential baseline confounders. Results Overall kidney function decline in 1326 patients was -0.12 mL/min/1.73 m(2)/month. A total of 515 patients showed depressive symptoms. No significant association was found between depressive symptoms and kidney function over time (P = 0.08). Unlike women, men with depressive symptoms had an increased mortality rate compared with those without symptoms [adjusted hazard ratio 1.41 (95% confidence interval 1.03-1.93)]. Depressive symptoms were not significantly associated with a higher hazard of dialysis initiation, or with the combined outcome (i.e. dialysis initiation and all-cause mortality). Conclusions There was no significant association between depressive symptoms at baseline and decline in kidney function over time in older patients with advanced CKD. Depressive symptoms at baseline were associated with a higher mortality rate in men

Reactive dissolution of sedimentary rocks in flue gas desulfurization : modeling and experimental investigation

Svavel förekommer i kol och olja och oxideras vid förbränning till svaveldioxid (SO2). Årligen utsläpps stora mängder svaveldioxid som åstadkommer sura regn, minskning av stratosfäriskt ozon och sjukdomar. Av dessa orsaker är det nödvändigt att minska utsläppen av svaveldioxid. Den teknologi som rör planering av reaktorer och processer för rökgasavsvavling (FGD) har utvecklats kraftigt och idag använder man olika typer av lösningar. De vanligaste alternativen för FGD är våtskrubber- och semitorra skrubbersystem (Spray Dry Scrubbers, SDS) och injektionsprocesser för absorbenter. SDS-processer har studerats bland annat av Ahlbeck [4] och Klingspor [5] och injektionsprocesser av Alvfors [6]. Kalksten, som i huvusak består av kalciumkarbonat, används i rökgasavsvavling på grund av sin förmåga att binda svavel i form av sulfatsalter. Den vanligaste rökgasavsvavlingsmetoden är våtskrubbning, där det sedimentära stenmaterialets upplösningshastighet är en av de faktorer som påverkar resultatet mest. Utvärdering av kalkstensreaktivitet är därför speciellt viktig vid planering och drift av anläggningar för rökgasavsvavling. Målsättningen med detta arbete var att modellera upplösningen av olika typers kalksten för att få en kvantitativ utvärdering av kvaliteten på de analyserade proverna. Därtill testades även karbonatbiprodukter från stålindustrin för att utvärdera möjligheter att använda andra råmaterial. Det transienta förloppet har analyserats, varvid upplösningshastigheten modellerades bl.a. i avseende på tid och pH. Under arbetets gång har antalet empiriska korrelationer minskats till fördel för fysikaliska modeller av diffusiva och konvektiva masstransportfenomen. En målsättning var att skapa en effektiv och snabb metod för att testa olika absorbenter för rökgasavsvavling under transienta förlopp. I arbetet användes PSD-analys, gjordes pH-mätningar och andra utvärderingar av de fysikaliska parametrar som ingår i beräkningarna. On-line mätningar för de icke-stationära variablerna tid och pH ger möjlighet att eliminera osäkerheter. Vissa modeller kan vara komplicerade. En modell för upplösningshastigheten med mer detaljerad utvärdering av parametrar och färre approximationer är därför nödvändig då man vill utvärdera reaktionshastigheten för fasta partiklar i sur miljö. Arbetet utfördes under fyra år och fem peer review-artiklar ingår i avhandlingen

Implications on feedstock processing and safety issues for semi-batch operations in supercritical water gasification of biomass

Biomass with a large amount of moisture is well-suited to be processed by supercritical water gasification, SCWG. The precipitation of inorganics, together with char formation and repolymerization, can cause reactor plugging and stop the process operations. When plugging occurs, sudden injections of relatively large mass quantities take place, influencing the mass flow dynamics significantly in the process. Reactor plugging is a phenomenon very well observed during SCWG of industrial feedstock, which hinders scale-up initiatives, and it is seldom studied with precision in the literature. The present study provides an accurate evaluation of continuous tubular reactor dynamics in the event of sudden injections of water. An interpretation of the results regarding water properties at supercritical conditions contributes to comprehending mass and heat transfer when plugging occurs. Experiments are then compared to SCWG of a biomass sample aiming to give key insights into heat transfer and fluid dynamics mechanisms that could help develop operational and control strategies to increase the reliability of SCWG. In addition, a simplified model is presented to assess the effect of material integrity on burst-event likelihood, which states that SCWG is safe to operate, at 250 bar and 610◦ C, in tubular reactors made of 0.22 wall thickness-to-diameter ratio Inconel-625 with superficial microfractures smaller than 30 µm. We also suggest improvement opportunities for the safety of SCWG in continuous operation mode.Fil: De Blasio, Cataldo. Abo Akademi; FinlandiaFil: Salierno, Gabriel Leonardo. Abo Akademi; Finlandia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Magnano, Andrea Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Ultrasonic Power to Enhance Limestone Dissolution in the Wet Flue Gas Desulfurization Process. Modeling and Results from Stepwise Titration Experiments

The goal of this work is to assess the application of ultrasonic power to the reactive dissolution of limestone particles in an acidic environment; this would represent a novel method for improving wet Flue Gas Desulfurization industrial systems. In this study a stepwise titration method is utilized; experiments were done by using different particle size distributions with and without the application of ultrasound. The use of ultrasonic power sensibly affected the reaction rate of limestone and its dissolution; a major difference could be observed when samples from the Wolica region in Poland were studied. In this case, the overall dissolution rate was found to increase by more than 70%. The reactive dissolution of limestone does not follow the same mathematical model when sonication is in effect; in this case, an extra Ultrasonic Enhancement Constant was introduced. It was demonstrated that the dissolution is proportional to an Effective Reaction Surface and, therefore, surface interactions should also be taken into consideration. For this purpose, a study is presented here on the Z-potential and electrophoretic mobility of limestone samples measured in aqueous dispersions by means of Laser Doppler Micro-Electrophoresis

Liquid mixing dynamics in slurry stirred tanks based on electrical resistance tomography

In this work, liquid mixing in a solid-liquid baffled stirred tank is investigated experimentally by Electrical Resistance Tomography (ERT). Since the technique works non-intrusively in opaque systems, the limitations of the most widespread experimental methods for the mixing time estimations are overcame. Whole-field data on the homogenization dynamics are collected with liquid only and with a mass ratio of suspended solid to liquid equal to 0.43. The liquid mixing time, which is often adopted as a measure of the intensity of mixing in turbulent stirred tanks, leads to quantitatively assess the significant difference in the scalar mixing process in the agitated slurry with respect to the single-phase systems. Besides, novel definitions for intensity, scale and rate of change of mixing are proposed. With respect to the conventional mixing time estimation, the parameters extracted from the raw ERT data provide a deeper insight into the evaluation of the scalar mixing dynamics in stirred tanks

Ultrasonic enhanced limestone dissolution: Experimental and mathematical modeling

Stricter emission regulations require the improvement of SO2 scrubbing efficiency and energy usage. In this work, the dissolution of two very pure limestone samples under the effect of ultrasound (US) was compared to their dissolution in silent conditions. The aim of this work was to assess experimentally whether this method could be adopted as a process intensification technique for Wet Flue Gas Desulfurization (WFGD) applications. A pH-stat method with vigorous agitation, coupled with in situ particle size distribution measurements was developed for evaluating the effect of US in limestone dissolution. The samples were characterized in detail, the experiments were modeled mathematically and, a chemical reaction constant was determined and used to compare quantitatively the use of US and the silent case. The results indicate that US does enhance limestone dissolution, and that the degree of enhancement depends largely on the type of sample, i.e. the geological origin and the particle size. The developed mathematical model was implemented satisfactorily; the model was able to fit the data with high degrees of accuracy (>94%). The degree of enhancement, quantified in terms of the increase in the estimated chemical reaction constant, ranged from 18% to 150%