Letteratura scientifica selezionata sul tema "Reconcentration"

An active brine reconcentration system has been incorporated into the design of the University of Illinois half-acre salt gradient solar pond facility. An important feature of the system is its ability to keep precipitation from diluting the brine. Experimental data presented is in good agreement with a numerical simulation model of the evaporation process. The “film”-type evaporation process used in the system efficiently collects solar energy for evaporating water from brine. Parasitic electrical energy requirements for the evaporation system are 1.2 watts per square meter of evaporation surface area.

Application of small molecular inhibitor in reconcentration of iron ore tailing by direct flotation are discussed. From the results, it can be seen that organic inhibitors are more effective than inorganic inhibitors. When sodium hexametaphosphate and sodium silicate are used as inhibitor, iron grade in concentrates is no more than 30%. However, when organic inhibitors are used as used, iron grade in concentrate are more than 30%. And 2,4-dibydroxy-benzoic acid is the most effective inhibitor to depress quartz. When it is used, iron grade in concentrate is more than 35%. Measurement results of infrared spectrum show that hydrogen bonding adsorption occur between inhibitor and quartz surface.

This paper is to analyse the reconcentration of Seoul Metropolitan Area(SMA)'s population to become clear after 2015, and trace back the background of the phenomena. SMA's population has been over 50% since December 2019, and it came from the outstanding rise of SMA – non SMA population gap in the end of 2015. The high tide of SMA in 2015 is linked directly with two things. One is the big growth of semiconductor and display products in SMA around 2015, and the other is the development of 2nd Dongtan Newtown which the first dwellers moved in 2015. The background factors of the two things are polices that allow industrial complex at Pyeontaek, a southern city of SMA, esp, acceptance of new large semiconductor campus of Samsung Electronics, and create new big city at southern SMA for stabilizing housing price. Throughout this process, our state, S. Korea government had done as if she was an civil affair clergy for giant conglomerate, so called Jaebul. This kind of state is called a neoliberalist state, or Schumpeterian workfare state, which S. Korea takes the form of after the shocks from IMF crisis in 1998. Under that kind of state, the government has become inferior to global multinational conglomerates less and less including Samsung and LG, and her policies for regional equality have been stepped back further and further.

Le latex naturel d’hévéa (LCN) est une dispersion colloïdale aqueuse de caoutchouc naturel de polyisoprène (PI). Après concentration, le LCN (1,2 Mt/an) a de nombreuses applications (gants chirurgicaux, préservatifs) grâce aux propriétés de son composant principal, le PI. La centrifugation, méthode de concentration généralement utilisée, donne un co-produit (skim) pauvre en particules de caoutchouc (5 % massique) mais riche en composés non caoutchouc. Sa récupération actuelle (coagulation par H2SO4) conduit à un caoutchouc de basse qualité et l’effluent final est polluant pour les rivières (H2S). Des essais antérieurs de filtration avaient montré la faisabilité du concept, mais présentaient une faible productivité, des problèmes de coagulation, de colmatage.La thèse vise un procédé de concentration du skim par ultrafiltration (UF), récupérant le PI de qualité et réduisant la charge de l’effluent, destiné à l’application industrielle, dans le cadre du projet Filtexcol (ADEME). L’optimisation du procédé a inclus la caractérisation chimique et physicochimique des skims au-delà des seuls paramètres hydrodynamiques en unité pilote. La composition chimique (espèces non caoutchouc) des skims étudiés est variable (taux de lipides, protéines, tensioactifs (TA) anioniques, non ioniques). Leur stabilité au cisaillement est mesurée via un test rapide mis au point pour être utilisable en usine, adapté à la faible charge du milieu (PI ~3-5 %, non-PI ~2 %). L’aptitude d’un skim à l’UF peut être estimée via sa stabilité sous forte contrainte de cisaillement, paramètre principal limitant.La stabilité augmente avec le taux de protéines extractibles et de TA non ioniques. Elle est améliorée par des additifs à des taux précis sous peine d’obtenir l’effet inverse. Par contre, la stabilité n’est pas liée au potentiel Zêta. L’effet des TA non ioniques (mono-, diacylglycérols) formés par hydrolyse des lipides indique une stabilisation par répulsion stérique, mais la corrélation observée aussi avec les protéines, combinée aux TA anioniques (savons) en forte concentration et au pH optimal supérieur à 9,5, peut impliquer aussi la répulsion électrostatique. Nos résultats montrent une structure complexe différente de celle du LCN concentré. Ces résultats relatifs à la physicochimie contrôlant la stabilité du skim, combinés à la granulométrie, ont permis de choisir en pilote 10 L le type de pompe (équipement critique en raison du risque de fort cisaillement) et de membrane (ZrO2), de réaliser un pilote de 100L équipé d’un module membranaire multicanal pour l’industrie, de déterminer le domaine critique d’UF (pression transmembranaire, vitesse tangentielle, taux de retour rétentat) vis-à-vis du flux de perméat J (flux critique, flux limite) et les conditions partiellement optimisées via un plan d’expérience combiné à la simulation par réseau de neurones artificiels. Le contrôle du pH durant le nettoyage et le conditionnement de la membrane assure un J élevé dès le début de l’UF. Mais même hors du domaine critique, J initial est très inférieur J-eau (1/20), l’interaction rapide skim-membrane introduit la principale résistance hydraulique puis J reste stable, témoignant de l’absence d’interactions ultérieures. Le fait de concentrer le PI (rétentat) augmente proportionnellement la résistance jusqu’au facteur de concentration volumique ~3, au-delà elle évolue peu. J se stabilise à 20 L/h.m² après 20 h d’UF. Le régime de filtration recherché via la loi des puissances est de type SBM : faible colmatage de la membrane durant la concentration (bouchage partiel à l’intérieur de pores). La totalité du PI et les non-PI (protéines et lipides) associés aux particules sont retenus et concentrés en pilote 100 L jusqu’à ~40 % de matière sèche ; la demande chimique en oxygène du nouvel effluent (perméat) est divisée par 4. Ces performances ouvrent la voie à des essais à plus grande échelle et à des applications prometteuses
Natural rubber latex (LCN) is an aqueous colloidal dispersion of polyisoprene (PI) natural rubber. After concentration, LCN (1,2 Mt/an) has many applications (surgical gloves, condoms) thanks to the properties of its main component, PI. Centrifugation concentration is mainly performed, producing a co-product (skim) with low rubber particle content (5% weight) but rich in non-rubber compounds. Its current recovery (H2SO4 coagulation) leads to low-quality rubber and the final effluent is hazardous for rivers (H2S). Previous filtration tests have proven the feasibility of the concept, but showed low productivity, coagulation problems and clogging.The thesis aims for a skim concentration process by ultrafiltration (UF), recovering the valuable PI and reducing the load of the effluent - for industrial application – within the Filtexcol project (ADEME). The process optimization included chemical and physicochemical characterization beyond only hydrodynamic parameters with a pilot plant. The chemical composition (non-rubber compounds) of the studied skims varies (lipid content, protein, anionic and nonionic surfactants (TA)). Their shear stability is measured with a rapid test developed to be factory use compatible, adapted to low load medium (PI ~3-5% ; non-PI ~2%). The UF suitability of the skim can be estimated via its high shear stability, the main limiting factor. The stability increases with the extractible protein and the non-ionic TA content. It is improved by precise additive amounts otherwise leading to the opposite effect. However stability is not related to the Zeta potential. The effect of nonionic TA (mono and diacylglycerol) formed by lipid hydrolysis indicates stabilization by steric repulsion, but the correlation also observed with proteins combined to anionic TA (soaps) in high concentration and optimal pH above 9,5 can also involve electrostatic repulsion.Our results show a complex structure different from the concentrated LCN’s. These results related to physcochemistry controlling the stability of the skim, combined with granulometry, allowed to choose through a 10L pilot the pump type (critical equipment due to the risk of high shear) and the membrane (ZrO2), to build a 100L pilot with a multicanal industrial membrane module, to determine a critical UF area (transmembrane pressure, tangential speed, retentate return rate) regarding the permeate flux J (critical flux, limit flux) and the partially optimized conditions via an experimental plan combined with artificial neural network simulation.PH control during cleaning and membrane conditioning ensures high J since early UF operation. But even outside of the critical area, initial J is very inferior to J-water (1/20), the rapid skim-membrane interaction introduces the main hydraulic resistance then J remains stable, reflecting the absence of subsequent interactions. Concentrating PI (retentate) increases proportionally the resistance to the volume concentration factor ~3 after which it decreases only slightly.J stabilizes at 20 L/h.m² after 20h of UF. The filtration state searched by the power law is SBM : low membrane fouling during concentration (partial blockage inside the pores). The entire PI and the particle-associated non-PIs (proteins and lipids) are retained and concentrated into the 100L pilot until ~40% dry matter; the chemical oxygen demand of the new effluent is divided by 4. These performance open the way to larger-scale trials and promising applications

La reconcentration d'acide par electrodialyse est un procede limite par le phenomene de fuite en protons a travers les membranes echangeuses d'anions. L'objet de cette these est de determiner les proprietes de transport de membranes echangeuses d'anions en contant avec des solutions d'acide chlorhydrique en vue de la reconcentration de ce dernier par electrodialyse. Des mesures de flux d'electromigration, de flux d'autodiffusion, de sorption d'electrolyte realisees par radiotraceurs couplees a des mesures de conductivite electrique permettent de faire l'hypothese de l'existence d'acide chlorhydrique non dissocie au sein de la membrane. Des experiences realisees sur un pilote d'electrodialyse permettent par ailleurs de determiner le transport d'eau a travers chaque membrane, le transport d'acide et d'eau a courant nul et a courant constant ainsi que la densite de courant limite. Les donnees experimentales sont ensuite representees par une loi empirique simple decrivant la variation de la concentration dans le concentrat en fonction du temps

La reconcentration des acides par les techniques electromembranaires est limitee par la fuite en protons a travers les membranes echangeuses d'anions. La societe morgane a synthetise une nouvelle membrane echangeuse d'anions dont la permselectivite est superieure a celle des membranes actuellement sur le marche. L'objet de ce memoire est de presenter les resultats de caracterisation de cette membrane et des procedes electromembranaires l'utilisant dans le but de reconcentrer l'acide sulfurique et de recuperer des metaux. Les resultats de caracterisation de la membrane ara a l'equilibre avec solutions d'acide sulfurique nous ont permis de mieux comprendre le mecanisme de transport a travers la membrane et de proposer un modele la representant. Nous avons mis en evidence les avantages et les inconvenients de l'electro-electrodialyse et de l'electrodialyse appliques a la reconcentration de l'acide sulfurique puis nous avons represente les donnees experimentales par une loi mathematique simple qui nous a permis de determiner les eventuels paliers de concentration. Des experiences d'electro-electrodialyse sur des solutions acides ou neutres de sulfate de metaux ont montre que la membrane ara est particulierement adaptee pour la recuperation de metal sous forme de depot cathodique et pour la reconcentration de l'acide sulfurique dans le compartiment anodique

La reconcentration d'acide par les procedes electromembranaires est limitee par le phenomene de fuite en protons a travers les membranes echangeuses d'anions (mea). Le but de cette etude est de mieux comprendre le mecanisme de transport des protons et des anions quand des mea commerciales separant deux solutions identiques de hcl ou h#2so#4, sont soumises a un champ electrique. Elle est scindee en deux parties, d'une part les proprietes de transport des mea a l'equilibre et d'autre part, l'analyse des flux ioniques transmembranaires des protons et des anions lorsque les mea sont soumises a un champ electrique. Les proprietes a l'equilibre nous ont permis de representer la phase membranaire par le modele a trois phases, et de calculer les mobilites ioniques individuelles dans la membrane. Lorsque les mea sont soumises a un champ electrique, nous avons determine les constantes apparentes du transfert ionique interfacial et montre que l'etape determinante dans le procede electromembranaire est celle du transfert interfacial

En electro-electrodialyse, la reconcentration d'acide est limitee par le phenomene de fuite en proton a travers les membranes echangeuses d'anions #(#m#e#a#). L'ensemble des resultats obtenus a permis d'elaborer un modele interpretatif base sur les equations d'electrodiffusion qui rend relativement bien compte des donnees experimentales. Par ailleurs, ce travail, a permis de mettre au point une membrane a faible fuite en proton. En dialyse, le defaut de selectivite de la membrane neosepta afn, a ete exploite pour la recuperation selective des acides en presence de sels. Une etude physico-chimique a permis de determiner les phenomenes qui sont a la base de la selectivite du transport. Enfin, de nouvelles membranes echangeuses d'ions ont ete testees. Des performances interessantes ont ete obtenues pour les trois procedes

Chapter 1 explores the health crisis caused by Spanish reconcentration policies during the final War of Independence, tracing Cuban and United States efforts to provide relief to the city’s reconcentrados as war gave way to the new U.S. military occupation, and as health and welfare work was systematized and centralized by the new Departmento de Beneficencia (Department of Public Charities), which Cuban physicians and health workers saw as a model for the nationalization of health services in postcolonial Cuba.

In Chapters 7 to 11, we have examined a series of recurring themes in the geography of war and disease since 1850 through regional lenses. In this chapter, we conclude our regional–thematic survey by illustrating further prominent themes which, either because of their subject-matter or because of their geographical location, were beyond the immediate scope of the foregoing chapters. In selecting regional case studies for this chapter, we concentrate on wars which have not been examined in depth to this point (the South African War and the Cuban Insurrection) or which, on account of their magnitude and extent, merit examination beyond that afforded in previous sections (World War I and World War II). Four principal issues are addressed: (1) Africa: population reconcentration and disease (Section 12.2), illustrated with reference to civilian concentration camps in the South African War, 1899–1902; (2) Americas: peace, war, and epidemiological integration (Section 12.3), illustrated with reference to the civil settlement system of Cuba, 1888–1902; (3) Asia: prisoners of war, forced labour, and disease (Section 12.4), illustrated with reference to Allied prisoners on the line of the Burma–Thailand Railway, 1942–4; (4) Europe: civilian epidemics and the world wars (Section 12.5), illustrated with reference to the spread of a series of diseases in the civil population of Europe during, and after, the hostilities of 1914–18 and 1939–45. As before, the study sites in (1) to (4) span a broad range of epidemiological environments, from the cool temperate latitudes of northern Europe, through the tropical island and jungle environments of the Caribbean and Southeast Asia, to the warm temperate and subtropical savannah lands of the South African Veld. Diseases have been sampled to reflect this epidemiological range. The South African War (1899–1902) has been described as the last of the ‘typhoid campaigns’ (Curtin, 1998)—a closing chapter on the predominance of disease over battle as a cause of death among soldiers (Pakenham, 1979: 382). From the military perspective, typhoid was indeed the major health issue of the war, accounting for a reported 8,020 deaths in the British Army (Simpson, 1911: 57).

Abstract When monoethylene glycol (MEG) is used to provide hydrate protection for gas condensate production, MEG pre-treatment, reconcentration and reclamation systems are generally employed to recover and reuse the MEG. Prior to reconcentration, low solubility salts of divalent cations such as calcium, iron, strontium and magnesium, that may be present in the Rich MEG, are removed in a MEG pre-treatment process. This process involves the addition of a base, such as NaOH or KOH, to the Rich MEG at elevated temperatures to convert dissolved carbon dioxide to carbonate ions and so precipitate the cations, as their respective insoluble carbonate or hydroxide salts. When enough residence time is available within the process these precipitated salts are removed from the Rich MEG stream through physical separation. For onshore based MEG systems, this is usually accomplished via settling tanks. However, in offshore systems the residence time for crystallization and settling becomes limited due to vessel sizes imposed by facility space limitations so precipitated salts are actively removed using mechanical equipment such as centrifuges. Centrifuges are only effective when crystals reach threshold particle sizes. Contaminants in MEG such as dissolved hydrocarbons and magnesium ions can inhibit crystal growth of calcium and iron carbonate. This study details the development of testing methodologies to screen chemistries to assist in particle agglomeration and led to the identification of a promising class of chemistries that could be applied in MEG Pre-treatment for the flocculation of cation salts.