Letteratura scientifica selezionata sul tema "Laboratory/pilot-Scale fouling"

Pasteurisation was investigated as a process to achieve high microbial quality standards in the recycling of water from unfiltered secondary effluents from a wastewater treatment plants in Melbourne, Australia. The relative heat sensitivity of key bacterial, viral, protozoan and helminth wastewater organisms (Escherichia coli, Enterococcus, FRNA bacteriophage, adenovirus, coxsackievirus, Cryptosporidium, and Ascaris) were determined by laboratory scale tests. The FRNA phage were found to be the most heat resistant, followed by enterococci and E. coli. Pilot scale challenge testing of a 2 ML/day pasteurisation pilot plant using unfiltered municipal wastewater and male specific coliphage (MS2) phage showed that temperatures between 69 °C and 75 °C achieved log reductions values between 0.9 ± 0.1 and 5.0 ± 0.5 respectively in the contact chamber. Fouling of the heat exchangers during operation using unfiltered secondary treated effluent was found to increase the energy consumption of the plant from 2.2 kWh/kL to 5.1 kWh/kL. The economic feasibility of pasteurisation for the current municipal application with high heat exchanger fouling potential can be expected to depend largely on the available waste heat from co-generation and on the efforts required to control fouling of the heat exchangers.

In this study, pilot scale experiments were carried out to examine membrane fouling occurring in membrane bioreactors (MBR) with or without pre-treatment (coagulation/sedimentation). Especially, the influence of suspension viscosity and dissolved organic matter (DOM) on membrane fouling was investigated. The pre-coagulation/sedimentation process improved the performance of a MBR in terms of membrane permeability by controlling irreversible fouling and formation of thick cake layer. The upper limit of MLSS concentration for an efficient operation in MBR without pre-treatment was suggested to be around 10 g/L based on the measurement of suspension viscosity. In this study, it was difficult to directly relate membrane fouling to DOM detected in the membrane chamber. A series of laboratory scale dead-end filtration experiments was carried out to investigate which fractions in biomass suspension would be the most influential in the deterioration of membrane permeability. Based on the dead-end tests, it was shown that the deterioration of membrane permeability was mainly caused by the colloidal particle fraction in the biomass suspension.

The feasibility of reverse osmosis (RO) for treating coking wastewaters from a steel manufacturing plant, rich in ammonium thiocyanate was assessed. DOW FILMTECTM SW30 membrane performance with synthetic and real thiocyanate-containing solutions was established at the laboratory and (onsite) pilot plant scale. No short-term fouling was observed, and the data followed the known solution-diffusion model and the film theory. Those models, together with non-steady state mass balances, were used in simulations that aided to design a full scale two-stage RO plant for thiocyanate separation.

Abstract Fouling indices for evaluating fouling propensity of secondary effluents (SEF) as feed of ultrafiltration (UF) systems are important parameters for the design and operation of the UF process. However, limited fouling indices have been developed and applied for UF feedwater. This study (i) established a modified UF fouling index (MFI40) by raising operating pressure from 30 psi in a traditional MFI test to 40 psi. Standard deviation of MFI40 tests was lower than that of traditional MFI by 68.6%, indicating better stability and repeatability of MFI40. It (ii) investigated the combined effects of UF feedwater characteristics on MFI40. Biopolymers and turbidity played a dominant and secondary positive role in the MFI40, respectively. The effect of conductivity on MFI40 changed from positive to negative with a turbidity increase. It also (iii) validated the MFI40 in both laboratory- and pilot-scale UF membrane units, and UF fouling rates were linearly correlated to the MFI40 of their feeds, and (iv) explored the practical use of the MFI40. It was applied to determine the maximum allowable UF feedwater quality (MFI40max), which could be used to select an appropriate pre-treatment process. A fouling predicting model was established based on the feedwater MFI40 and the operating flux, with an average predicting error of 26.8%.

Abstract Soft acidic waters are often treated for drinking water purposes by using limestone filters to attain chemical equilibrium. The present study investigated the process parameters of a relatively new process combination in which powdered calcium carbonate (CaCO3) was added prior to an ultrafiltration (UF). In order to reach the targeted pH value (≥7.8), dosing concentration, type of material and retention time were evaluated in pilot-scale experiments. The deacidification followed the same kinetics as for limestone filtration and yielded similar filtrate characteristics with dosing concentrations of 20 and 40 g/L CaCO3. No significant increase in transmembrane pressure was observed during the operation of a pilot-scale UF module at low flux (34 L m−2 h−1). Critical flux was determined in a laboratory scale to evaluate the potential impact of CaCO3 particles on the UF operation. Stepping-flux experiments revealed the presence of fouling only at high-dosing concentrations, resulting in a critical flux of 55 L m−2 h−1. At a higher flux, a CaCO3-fouling layer was formed, which decreased the membrane's permeability by 20% over 5 h. Considering that effective air-enhanced backwash and acidic chemical cleanings will be implemented in large-scale applications, the investigated process combination promises to be an appropriate treatment technology for turbid and soft acidic waters.

A two-step forward osmosis (FO) desalination process combining both FO and reverse osmosis (RO) systems has been developed by the Centre for Osmosis Research and Applications at the University of Surrey and commercialised by Modern Water plc. In the FO + RO process seawater was used as feed water (FW) and a concentrated aqueous solution was used as a draw solution (DS). By taking advantage of natural osmosis, pure water is transferred from the FW to the DS and then recovered from the DS by the RO process utilising low resistance membranes, and hence lower specific energy consumption (SEC). This paper presents results of FO experiments conducted on flat sheet membrane using a bench-scale rig. The osmotic agent investigated in this study was magnesium sulphate, which is non-toxic, and highly soluble in water. Furthermore experiments were carried out on the RO pilot in order to regenerate the DS for reuse in the FO process and produce clean water. This paper also presents some pilot plant results and data from commercial plants in Oman and Gibraltar. The data demonstrates the efficiency of the FO + RO compared with the conventional RO process in terms of SEC and membrane fouling performance.

Few investigations have attempted to connect the mechanism of dairy fouling to the chemical reaction of denaturation (unfolding and aggregation) occurring in the bulk. The objective of this study is to contribute to this aspect in order to propose innovative controls to limit fouling deposit formation. Experimental investigations have been carried out to observe the relationship between the deposit mass distribution generated in plate heat exchangers (PHE) by a whey protein isolate (WPI) mainly composed ofβ-lactoglobulin (β-Lg) and the ratio between the unfolding and aggregation rate constants. Experiments using a PHE were carried out at a pilot scale to identify the deposit distribution of a model fouling solution with different calcium contents. In parallel, laboratory experiments were performed to determine the unfolding/aggregation rate constants. Data analysis showed that (i)β-Lg denaturation is highly dependent on the calcium content, (ii) for each fouling solution, irrespective of the imposed temperature profile, the deposit mass in each channel and the ratio between the unfolding and aggregation rate constants seem to be well correlated. This study demonstrates that both the knowledge of the thermal profile and theβ-Lg denaturation rate constants are required in order to predict accurately the deposit distribution along the PHE.

The past decade has seen a rise in the importance of the ultrafiltration (UF) technique in the separation of various complex solutions. However, the fouling phenomenon is the main limitation to faster process development. To the best of the authors’ knowledge, the present paper is the first to aim to identify the role of corrosion fouling in long-term UF. For this purpose, polyvinylidene fluoride (PVDF) and polyethersulfone (PES) membranes were used. The investigations were carried out with the use of both pilot-scale and laboratory-scale units. Results obtained in the present study have clearly demonstrated that the oil concentration has a significant impact on the process performance. Indeed, it has been noted that a reduction in oil concentration from 160 to 100 mg/L resulted in an increase in the PVDF membrane flux from 57 to 77 L/m2h. In addition, it has been shown that the feed temperature has a significant influence on the UF performance. Importantly, it has been shown that corrosion fouling is of vital importance in UF membranes. Indeed, corrosion products such as iron oxides contaminated the membrane surface leading to an irreversible decrease in the UF process performance. In addition, it has been found that repeating the chemical cleaning of the membrane units significantly reduced the intensity of the fouling phenomenon. However, the complete elimination of its effects was not achieved. Therefore, it has been indicated that cleaning agents recommended by membrane manufacturers do not remove corrosion products deposited on the membrane surface. Undoubtedly, the obtained results can be used in the design of UF units leading to the extension of membrane installation lifetime.

Sensor prototypes for measurement of ammonium, nitrate and phosphate in wastewater treatment plants are described together with the results obtained in laboratory and pilot scale wastewater treatment plants. A functional description of the sensor principles is presented together with the installation and operation procedures. Basically the measurements are done using membrane technology in combination with semi-micro Continuous Flow Analysis (μCFA) with classic colorimetry. Because of this the sensors can be installed directly in the aeration tanks without any need for sampling, filtration, etc. Furthermore, the semi-micro scale is used in such a way, that handling of chemicals and waste is a closed loop in a package to be changed once a month. The sensors have been tested thoroughly in a pilot scale waste water treatment plant (recirculation) using real raw wastewater as well as artificial wastewater. The sensors have been placed directly in the aeration tank or in the anoxic tank of the pilot plant. The tests show very little, if any, fouling problems due to the membrane material used. The test results show a good reproducibility and most important, compared to other available sensors/analyzers on the market, very low response times, less than 5 minutes. Owing to these low response times, experiments with direct measurement of nitrification and denitrification rates were carried out.

Le présent travail est une contribution pour mieux comprendre l’influence des micelles de caseine sur l’encrassement de solutions de protéines sériques. En particulier, des approches expérimentales et numériques ont été réalisées, à des tailles laboratoires et pilotes, pour décrire les phénomènes de dénaturation et mieux cerner le rôle du calcium dans les mécanismes d’encrassement. Tout d'abord, l'effet du ratio massique caséine / lactosérum sur les performances d'encrassement des protéines de lactosérum a été étudié dans un échangeur à Plaques à l'échelle pilote. La masse totale du dépôt d'encrassement chute d’abord de manière significative avec l'augmentation de la concentration en caséine, atteignant un minimum quand le ratio vaut 0,2. Au-delà de cette valeur, la masse de dépôt réaugmente. La chute de la masse du dépôt, pour un ratio ≤ 0,2, ne semble pas être corrélée à la dénaturation thermique du BLG mais plus probablement due à la modification des interactions minérales introduites par la caséine. L'augmentation de la masse de dépôt, pour un ratio ≥ 0,2, semble être liée à une co-précipitation du complexe BLG-caséine qui augmente l'encrassement. Il est suggéré que la présence de caséine micellaire modifie profondément l'équilibre calcique en solution et que la teneur en nanocluster de Ca-P modifie fortement les interactions entre les espèces protéiques et les minéraux (calcium ionique, Ca-P) affectant ainsi la dénaturation des protéines et la précipitation des minéraux. Un nouveau modèle cinétique concernant le dépliement thermique et l'agrégation de BLG a été établi. Ce modèle est en mesure de justifier la rupture de pente dans le diagramme d'Arrhenius et de fournir des informations thermodynamiques détaillées pour les processus de dépliement et d'agrégation. Sur la base de ce modèle, il a été confirmé que le calcium ionique avait un rôle protecteur sur le dépliement thermique du BLG à basse température. En revanche, à des températures plus élevées, le calcium favorise l'agrégation et la formation d'espèces BLG dépliées. Un dispositif d'encrassement à l'échelle laboratoire a été construit et tester avec des protéines de lactosérum en régime laminaire. Un modèle CFD 3D réaliste a été implémenté simulant à la fois les réactions au cœur du fluide et en surface. Les résultats ont montré une relation linéaire entre le facteur pré-exponentiel et la concentration de calcium, ce qui suggère que l'encrassement nécessite qu’une seule molécule de calcium soit associée à une protéine de BLG. Il est confirmé que le calcium est essentiel à l'encrassement avec des effets significatifs à la fois sur les processus de dénaturation thermique et sur la croissance du dépôt. Enfin, l'effet du ratio caséine / lactosérum sur l'encrassement a été étudié avec un dispositif d'encrassement de laboratoire. Les résultats laboratoires montrent que la caséine réduit l’aptitude à l’encrassement comme déterminé précédemment avec l’installation pilote. Cependant, dans ce cas, l'encrassement reste à un niveau faible y compris pour des ratios élevés (jusqu'à 4). La présence de caséines individuelles dans la phase sérique a été considérée comme responsable de cette atténuation de l'encrassement, probablement par leurs activités de type chaperon. Cependant, quand le pH de la solution d'encrassement est fixé à 6,6, il est démontré que la caséine perd son effet d'atténuation de l'encrassement pour des ratios plus élevés. Ce comportement est lié à sa faible capacité de micelle de caséine à contrôler le calcium ionique dans la phase sérique à un pH plus bas, entraînant une concentration plus élevée en calcium facilitant la dénaturation de la BLG et l'accumulation de dépôts. Une quantité plus faible de caséines dissociées dans la phase sérique à pH 6,6 pourrait aussi expliquer l'augmentation de la masse d'encrassement car elles ne sont pas en concentration suffisantes pour remplir des fonctions de type chaperon
The present work is a contribution to better understand the influence of casein micelles on the fouling of serum whey protein solutions. In particular, experimental and numerical approaches have been carried out, at laboratory and pilot scales, to describe denaturation phenomena and better understand the role of calcium in fouling mechanisms. First of all, the effect of casein/whey mass ratio on the whey protein fouling performance was investigated in a pilot-scale PHE. The total fouling deposit mass drop significantly with the addition of casein, resulting in a minimum value located at Casein/WPI of 0.2. Exceeding this critical ratio, fouling deposit increased with elevated casein concentrations. The deposit mass drop (Casein/WPI ≤ 0.2) is unlikely to be linked to the thermal denaturation of BLG and is more probably due to the change in mineral interactions introduced by casein. The increased fouling mass (Casein/WPI ≥ 0.2) was attributed to a co-precipitation of BLG-casein complex that enhances the fouling. It is proposed that micellar casein change deeply the calcium balance and the content of CaP nanocluster modifies sharply the interactions which occur between protein species (BLG, caseins) and mineral elements (ionic calcium, Ca-P) thereby affecting the protein denaturation and fouling behavior. A novel kinetic model concerning thermal unfolding and aggregation of BLG was established. This model interprets mathematically the break-slope behavior in the Arrhenius plot and provides detailed thermodynamic information for both unfolding and aggregation processes. Based on this model, it was confirmed that ionic calcium has a protective role on the thermal unfolding of BLG at low temperature. In contrast, at higher temperatures, calcium promotes aggregation and the formation of unfolded BLG species. A bench-scale fouling rig was built to perform whey protein fouling experiments in a laminar regime. A realistic 3D CFD model was achieved to simulate both the bulk and surface reactions. Results showed a linear relationship between the deposition pre-exponential factor and calcium concentration, suggesting the fouling is built in such a pattern that only one calcium ion per BLG molecule is involved. Calcium was confirmed to be essential to fouling growth with significant effects both on the thermal denaturation and deposition processes. Finally, the effect of casein/whey ratio on the whey protein fouling was investigated in the laboratory-scale fouling device. Results revealed a similar effect of casein on fouling mitigation as those found in the pilot plant. However, in this case, the fouling was suppressed and maintained at a low extent even at high Casein/WPI ratios (up to 4). The presence of individual caseins in the serum phase was considered to be responsible for this fouling mitigation probably through their chaperon-like activities. However, when the pH of the fouling solution is set at 6.6, casein is shown to lose its fouling-mitigating effect at higher ratios. This behavior is related to its weak ability of casein micelle to control ionic calcium in the serum phase at lower pH, resulting in higher calcium concentration facilitating BLG denaturation and deposition accumulation. A lower amount of dissociated caseins in the serum phase at pH 6.6 could also explain the increase in fouling mass because they are not in sufficient concentration to perform chaperone-like functions

Abstract Fouling of heat exchanger equipment through the formation and attachment of hard scale, microbially induced corrosion (MIC) products, or particulate erosion is a serious challenge to reliable production in the oil and gas industry. Exchangers which become fouled in this way perform 15-30% worse than their rated ability, requiring either constant intervention to clean away biofilms, continuous injection of biocides and corrosion inhibitors, or the regular plugging of tubes to prevent leaks, representing a significant operating expense and billions of dollars in lost production time. When an exchanger is unable to provide sufficient heat due to tube fouling, additional sources of heating must be utilized to make up for this deficit and to ensure that facility processes remain within design allowances. This need for supplemental heating is a significant source of carbon emissions in the industry and represents a significant obstacle towards decarbonization efforts. However, it also represents an economically attractive way to simultaneously lower emissions while also lowering a producer's cost per barrel. This work describes an alternate strategy to control and prevent fouling in heat exchangers, through the one-time application of an omniphobic (water- and oil-repelling) nano-surface treatment. Once applied to a heat exchanger, the extremely smooth and low-surface energy material greatly reduces the ability of MIC-causing bacteria to deposit and adhere to the surface. Because it imparts functionality to the surface itself, rather than simply function as a physical barrier, it enables long lasting protection which was validated under laboratory conditions in a pressurized autoclave, as well as two pilot demonstrations. Results from both the laboratory and field evaluations of the treatment's promise showed that treated surfaces showed a corrosion rate over 36-times lower when compared to untreated surfaces, while also completely arresting the formation of corrosion pitting, tube fouling, and erosion of the tube interior. These field-validated results were then applied to the observed heating deficit of a proposed deployment site, resulting in calculated carbon emissions savings of up to 17,000 Tons CO2 per year.

Abstract Kinetic hydrate inhibitors (KHIs) offer an alternative to traditional thermodynamic hydrate inhibitors (THIs) for the prevention of gas hydrates. KHIs have several advantages over THIs, such as lower required volumes, easier logistics and reduced CAPEX. However, KHIs are once through chemicals leading to increased OPEX, are mostly non-biodegradable and therefore cannot be discharged to sea or disposal wells in fear of aquifer pollution. KHIs can also lead to fouling of process equipment, especially at elevated temperatures. To resolve these issues, a new KHI polymer removal method using a solvent extraction-based technique has been developed. In this approach, an immiscible extraction fluid is mixed into the KHI containing aqueous phase where the KHI polymer partitions into the extraction fluid, which can then be separated from the aqueous phase. In some cases, the KHI separated this way can be re-used. This process has the potential to solve problems with KHI produced water treatment/disposal, including where KHI is used in combination with MEG, reducing the costs and process fouling and protecting the environment. A new joint industry project (JIP) is underway with the aim of developing the concept into a commercial process for removal and possible re-use of KHIs upstream of PW treatment or MEG Regeneration systems. The first phase of this project is lab scale evaluation of the solvent extraction method for simulated removal and re-use of two commercial KHI formulations for a real gas-condensate field case. Both the removal efficiency and hydrate inhibition performance of 4 cycles of re-injected/re-used KHI has been successfully demonstrated. Removal of KHI from a real MEG system case was also successfully demonstrated. In the second phase of the JIP, lab scale tests were used to screen extraction and separation equipment and identify optimum process conditions. The upcoming third phase of this JIP is dedicated to demonstrating the selected process concept(s) on pilot scale in a flow loop. In this proceeding we will give highlights of the early laboratory test results from a produced water case where two field qualified KHIs are removed from PW and reused 4 times, still showing adequate hydrate inhibition performance. Successful pilot tests will confirm the operability of this process in the field.

When moving towards CO2 neutral bio fuels and waste derived fuels, new challenges are set for combustion facilities and technical boiler solutions. A common feature for both bio- and waste fuels is a big variety in composition, often high levels of alkali metals, chlorine and moisture which make these fuels difficult to burn in facilities designed for conventional fuels such as coal, peat and wood. The problems that might occur due to high alkali and chlorine levels in the fuels, are slagging, fouling, corrosion and bed sintering. The Fortum BioMAC BFB boilers are designed especially for difficult, unconventional fuels such as rice husk, olive waste, straw, construction residue, de-inking sludge, etc. The design of each individual boiler is made based on advanced theoretical prediction tools and extensive fuel testing in laboratory and in pilot scale combustion facilities. The theoretical tools consist of a multi-phase multi-component chemical equilibrium model that estimates the slagging/fouling, sintering and corrosion propensity of the fuels/fuel mixtures and of a computational fluid dynamics part. CFD calculations are used to optimize the flow pattern and the temperature of the boiler in order to avoid hot temperatures in the vicinity of refractory linings and cooled surfaces. The chemical equilibrium calculations predict the melting behavior of the fuel ash, which is used as an indicator for the placement of the superheaters. The bottom ash removal is controlled for efficient removal of coarse material, screening and recirculation. The ash related problems of important bio and waste fuels, the analytical procedure of the evaluation of the usability of the fuels and the adaptation of the boiler design are discussed in the paper.

A numerical model was developed, validated with the aid of pilot evaporator tests, and used to assess practical methods of minimizing scaling observed in a mechanical vapour recompression (MVR) plant at Millar’s Western’s Meadow Lake, Saskatchewan pulp mill. On average, 8,000 m3/day of effluent (approximately 7 m3/Bone Dry Tonne product) resulting from bleached-chemi-thermo-mechanical wood processing, are purified and the recovered water is returned to the plant while the effluent is concentrated to 75% TD&SS in a recovery boiler. The evaporators are used in the first stage of the feed concentration process. The system uses a heat pump principle: steam produced during the boiling of the falling liquid film is mechanically compressed and condensed on the outer surface of a vertical tube evaporator. Most of the condensation and compression heat is recovered. Reducing the rate of scale deposition and increasing the interval between two successive cleaning operations of vertical evaporators used in the MVR scheme was identified as an essential component of operation costs and given special attention. To assist the mill in assessing practical methods for achieving this goal an experimental pilot evaporator and a numerical model were developed and used first at the Alberta Research Council in Edmonton, Canada, and then at the mill location. The mill uses a different model for control and supervision of system parameters. The magnitude of the (critical) temperature difference (CTD) across the laminar sub-layer of boiling liquid film is calculated and is recommended in this paper to be used to quantify the fouling tendency. Further to recommendations resulting from previous experimental investigations [1,2] as well as in this study, the mill introduced additional process control parameters to reduce and maintain the temperature drop across the effluent boiling film to a maximum range of 2–4°C. In addition to CTD, the wall (top-bottom) axial temperature difference (ATD) has been identified as another criteria for assessing potential scale deposition during evaporation-concentration. Calculations and experimental measurements performed with the pilot evaporator [3] suggest that increasing the circulation rate of effluent pumped from the sump to feed the liquid film at the top of evaporator tubes has a positive effect on reducing the CTD and the ATD. During four months of laboratory investigations with a pilot evaporator, non-uniform liquid distribution among vertical evaporator tubes of the evaporator was observed and is discussed separately. This paper will present the model and mill observations and summarize the main results and suggested practical strategies for reducing the rate of scale deposition and improving the system economics.

Abstract The Banyu Urip production facility located in East Java, Indonesia; currently produces ca. 30% of the country's daily oil production. Field fluids are sour with high H2S (1.6%) and CO2 (45%) in the gas, which is conditioned prior to it's use as fuel, for Sulphur Recovery, or for reinjection. Gas conditioning takes place in two amine units, the Acid Gas Recovery Unit (AGRU) and the Acid Gas Enrichment Unit (AGE). Both units use aqueous MDEA as the amine solvent, with Wetted Surface Air Coolers (WSAC) used to cool hot lean amine off the regenerator columns. In early operation both conditioning units operated at design case. In the period 2018-2020 however, the WSACs became progressively fouled with scale and algae which led to a decrease in thermal transfer efficiency and a consequential decline in plant performance and reliability. SOx emissions were also impacted negatively. To resolve fouling and its detrimental consequences, a chemical treatment program was developed and implemented. The program involved laboratory qualification of candidate chemicals, including evaluation in a novel pilot skid that accurately simulated WSAC field conditions; followed by extended field trials. System performance was evaluated, which verified the pilot skid test results, and the program was implemented on a continuous basis. Extensive surveillance of multiple chemical and operational parameters was performed, and with critical evaluation of these derived data sets, improvements in operational practices were implemented, and unit performance gains realized. Implementation of the program has improved the reliability of the Fuel Gas Compressors (FGC) reducing monthly Gas Turbine Generator (GTG) diesel consumption rates by a factor of > 6. Secondly, AGE operational improvements reduced net SOx emissions for the facility by ca. 70% (2019 vs 2021) through a reduction in Thermal Oxidizer feed gas H2S content, and in lowering LP flaring.