1,721,067 research outputs found
Modeling and Design of Membrane Process Recovery of HCl and Metals from Pickling Solutions
No full textAbstract
Hydrochloric acid pickling is one of the key steps in the hot-dip galvanizing process. It is a process widely used as a chemical pre-treatment method for cleaning, where metal surfaces with oxides are immersed into an acid solution. During the pickling process, the acid concentration decreases with time while the metal is accumulated. Thus, the efficiency of the pickling solution decreases and fresh solution must be used. Continuous regeneration of pickling solutions enhances pickling rate and process performance, but also minimises industrial wastewater disposal and chemicals consumption. The recovery and recycling process of valuable substances (e.g. acid and metals) can be accomplished by coupling diffusion dialysis (DD) and membrane distillation (MD) technologies [1,2].
The integrated process is based on a recovery of more than 80% of the free acid exiting from the pickling bath by passing through a selective anionic exchange membrane (in the DD), and then, its concentration by water evaporation through a hydrophobic membrane (in the MD) in order to be recycled in the pickling tank. The outlet stream from the diffusion dialysis, concentrated of metal salts, is fed to a reactive precipitation unit to recover iron as valuable product (iron hydroxide) by adding an alkaline reactant, whereas zinc salt is kept in the solution to be reused.
In the present work, a steady state process simulator for the integrated process has been developed, in order to analyze and predict performances of a small pilot-scale unit to be installed and operated within a hot-dip galvanizing plant. A parametric analysis of the model is performed varying hydrochloric acid and iron concentration in the pickling tank. In this way, usual operations of withdrawing of partially exhausted solutions and refilling with fresh acid is avoided allowing to continuously operating under the optimal pickling conditions
Effective recovery of HCl and metals from pickling solutions by cutting-edge membrane technologies
Full text linkThe pickling process is an essential step in the hot-dip galvanizing process.It is performed by immersing manufacturedsteel pieces inacid bathsin order todissolve the oxidized layers. During the pickling process, acid attacks metal oxides on the surface, dissolving them in the pickling bath. Thus, the efficiency of the pickling liquor decreases due to the accumulation of metal salts and the consumption of free acid in the solution. When hydrochloric acid is used,ferrous chloride is producedduring the pickling treatment, reaching concentrations up to 250 g/l, while the acid concentration decreases by 75-85%. A pickling bath in this condition is considered spent [1] due to thevery low picklingrate, hence it needs to be replaced. In common industrial practice,part of the exhausted solution is withdrawn and replaced with fresh acid orwitha more concentrate solution to prolong the pickling bath life, while spentsolution is disposed asa waste.Disposal of the spentpickling solution strongly affects the hot-dip galvanizing industries footprintand costs, thus the recovery of acid is one of the most beneficial steps to reduce the environmental and economic impact.In particular, continuous regeneration of pickling solutions can enhance pickling rate and process performance, butalso reduce industrial wastewater disposal and chemicals consumption. The recovery and recycling of valuable compounds (e.g. acid, metals and water) can be accomplished by coupling two cutting-edge membrane technologies: diffusion dialysis (DD) and membrane distillation (MD) [2,3]. Membrane techniques are considered simple, effective and sustainable [1]and can be easily scaled from small to medium side installations.In the present work, a case study is presented, relevant tothe hot-dip galvanizing plant of TecnoZinco(Palermo, Italy).The site has a capacity of 20,000 tons per yearof treated steel. Starting from an accurate data mining, a Process Flow Diagram(PFD)of an integrated process that provides a continuous regeneration of pickling solution is proposed, within the framework of the EU-funded ReWaCEM project(www.rewacem.eu), with the final aim of buildinga pilot plant to be installedand operated in real environment. Asteady state process simulator for the integrated process has been developed, aiming to design, analyze and predict performance of the pilot unit. A parametric analysis of the model is performed varying hydrochloric acid in the stream going out from the pickling tank. Results presents the perspective operation of such plant, indicating the technical feasibility of the novel developed process
Potential applications of Salinity Gradient Power-Heat Engines for recovering low-temperature waste heat in cogeneration plants
No full textSalinity Gradient Power-Heat Engine is an innovative technology able to convert very low-temperature heat into electricity. Energy and economic benefits could be achieved by integrating this technology into cogeneration plants, where the exploitation of waste heat available during the operation could increase the revenues arising from “High-Efficiency” labels. For the first time, this paper proposes two potential applications in this field, and three illustrative case studies are purposely investigated. In the first case study, a salinity gradient-heat engine converts the waste heat available from a cogeneration plant serving an industrial process. In the second case study, a salinity gradient-heat engine is integrated into a cogeneration plant coupled to a district network. In the third case study, the possibility to reduce the size of a cogeneration plant by coupling this engine with a heat pump is investigated. The analysis relied on simplified models of the integrated systems which were numerically solved. Results for the first case study show an increase of 10.6% in revenues from the high-efficiency support mechanism and electricity selling. In the second case study, the primary energy saving increases from 8.7% up to 10.1%, thus achieving the threshold value for “High-Efficiency” eligibility. In the third case study, the heat engine allows to reduce up to 12.1% the nominal capacity of the prime mover. A prospective analysis of the integration of salinity gradient-heat engine in cogeneration plants is thus presented, and it poses a fundamental reference for future integration of this novel technology into these energy systems
Center for research and care of aging : a strategy for an integrate approach
No full textThe effects of longevity, real revolution of this century, are producing significant impact on social and public health programs, on family life, economy, job placements and training of health care employees. Center for
Research and Care of Aging is an organical structure which tries to face up to preventive medicine with a close connection with Family Medicine, through a broad range of innovative and comprehensive programs in clinical care and education, closely related to biomedical research. The structure
is an University Training Center for junior faculty of Medicine, Nursing, Biotechnology and for Postgraduate students in Geriatric Medicine. Continuing Medical Education (CME) program in Geriatric Medicine and in Geriatric Rehabilitation is yearly planned.
The organical stucture extends for 30.000 sq.m. downtown in Milan, provides at the ground floor a variety of clinical services, radiology, an ambulatory care center with over 3000 patients weekly (80% are over 65 years old; at the first floor are simmetrically located a 12-bed inpatient Acute Care for the Elderly Unit and 4-bed and DH 18-bed inpatients Rehabilitation Unit
and 15-bed DH.Long-term care services are provided three floors up, in a 160-bed teaching nursing home with high standard of medical care. Patients with requiring intensive care can be admitted to Coronary Care Unit and Stroke Unit in the same hospital. This structure also provides 4000 sq.m. of laboratories dedicated to diagnostic assays and to research on neurobiology, endocrinology and metabolism, cardiovascular diseases, immunological disesases and longevity linked to both a clinical department and a basic science
department, to promote our goal of building a strong basic science program devoted to the study of clinically-relevant issues related to aging. Clinical geriatric researchers are working on search adequate tools for a good management of older patients with multiple chronic conditions, to better define diagnostic and therapeutic courses of a given individual. Electronic health records (EHR) are being developed to improve communication as health information follows patients from one care setting to another (Acute care and Rehabilitation Unit, Nursing home) reducing fragmentation of services for seniors transitioning from one level of care to another and from one
health care system to another. EHR systems must accommodate information germane to a senior frail population, including, but not limited to, functional assessments, cognitive assessments, and information on advance directives to correctly choose location and practice setting of patients. The EHR should provide prompts on prevention relevant to seniors and on potential errors, e.g. drug-drug interactions or excessive dosing, specific for older adults
Recovery of zinc from spent pickling solutions by liquid–liquid extraction using TBP
No full textIn this paper, recovery of zinc from real spent pickling solutions by liquid–liquid extraction with
tributyl phosphate (TBP) was studied. In particular, the effects of some parameters were investigated,
such as the volume ratio between the organic phase and real spent pickling liquor (O/A) (1:2, 1:1, 2:1,
4:1), the stirring time (5–20–30 min) and the TBP concentration (10%–55%–100%), in order to determine
the conditions leading to higher zinc extraction efficiency, as well as selectivity in relationships
to other metals such as iron. After zinc extraction, TBP was successfully regenerated. Among several
tested solutions, water allows zinc recovery higher than 90%, especially at 10% diluted TBP solution.
In addition, a double stripping step with water led to a near complete regeneration of TBP. In the
present work, a process flowsheet is also proposed, where TBP at 10% concentration is used for zinc
extraction from a spent pickling solution and then regenerated in a double-step stripping stage with
water
Effective magnesium recovery via seawater brines mining
Full text linkIn the last couple of decades, a rising interest has been focused on the research of novel and unconventional sources for mining minerals, such as industrial waste brines. As an example, brines are produced by desalination plants and discharged directly, or after being treated, into receiving water bodies possibly causing environmental concerns and renouncing the possibility to recover minerals [1,2]. Within this framework, the Water Mining WU-H2020 project aims at implementing an advanced Zero Liquid Discharge (ZLD) demo systems for the extraction of minerals and valuables products from industrial waste brines through a circular approach. The ZLD demo plant consists of: (i) Nano Filtration, (ii) Multi effect distillation, (iii) Evaporative ponds, (iv) NaCl Thermal crystallizer, (v) Mg-Ca crystallizer and (vi) Electro-Dialysis with Bipolar Membrane (EDBM). This work presents the development, construction and testing of an innovative key technology of such ZLD treatment chain: the Mg-Ca crystallizer. Also called MF-PFR, “Multi Feed – Plug Flow Reactor” [3], the crystallizer is capable of selectively recovering magnesium and removing calcium in the form of hydroxides from real industrial brine or seawater. More specifically, the precipitation of the magnesium hydroxide occurs mixing directly the feed with an alkaline solution (such as Sodium Hydroxide - NaOH) produced within the treatment chain itself by the EDBM unit. The selective recovery of magnesium and calcium as hydroxides is achieved by an accurate control of the reaction pH. An experimental campaign has been carried out via long-run tests to investigate the stability of MF-PFR in terms of pH, which affects the recovery and purity of Magnesium Hydroxide. The results show that a purity higher than 90% with a recovery higher than 90% of magnesium hydroxide can be achieved using industrial waste brine or seawater as the feed to the demo plant
A MULTI-SCALE TOOL FOR SIMULATING ELECTRODIALYSIS WITH BIPOLAR MEMBRANES SYSTEMS
Full text linkIn recent years, the global capacity of the desalination industry has increased to address freshwater scarcity, with reverse osmosis established as the leading technology. Brine disposal is a major issue due to the environmental impacts. However, novel brine management methods are oriented by (near) Zero Liquid Discharge strategies towards waste disposal minimization and resource recovery. In this context, ElectroDialysis with Bipolar Membranes (EDBM) can be utilised to valorise and, thus, repurpose the waste brine, thereby producing valuable chemicals, such as acid and base solutions, and recovering desalted water. However, the EDBM system must be carefully designed to meet the process requirements. In this work, we present a mathematical multi-scale model of the EDBM technology1. Four different scales were integrated in the gPROMS Model Builder environment. The lowest scale predicts the physical properties at the channel level as well as the bipolar membrane transport properties. The middle-low scale simulates the triplets, i.e. the repetitive cells forming the EDBM stack. This level predicts the main electrical variables and the material balances related to transport phenomena. The middle-high scale is devoted to the prediction of shunt currents via manifolds, as well as of the flow distribution and pressure losses across the stack. Finally, the highest scale of simulation integrates the EDBM unit with the external hydraulic circuit including the reservoirs of the electrolyte solutions and other auxiliary components. The model was experimentally validated across varying operating conditions both in the steady-state and dynamic modes of operation, demonstrating a high reliability. The model capability was exploited to conduct a sensitivity analysis of the EDBM performance on the main process variables, computing Specific Energy Consumption, Current Efficiency, and Yield. Favourable process conditions and detrimental phenomena affecting this technology were identified. Finally, this powerful mathematical tool was used to design a pilot-scale EDBM unit
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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