Continuous Flocculation Research Articles

Research Progress in Nanoparticle Inhibitors for Crude Oil Asphaltene Deposition.

Currently, the alteration of external factors during crude oil extraction easily disrupts the thermodynamic equilibrium of asphaltene, resulting in the continuous flocculation and deposition of asphaltene molecules in crude oil. This accumulation within the pores of reservoir rocks obstructs the pore throat, hindering the efficient extraction of oil and gas, and consequently, affecting the recovery of oil and gas resources. Therefore, it is crucial to investigate the principles of asphaltene deposition inhibition and the synthesis of asphaltene inhibitors. In recent years, the development of nanotechnology has garnered significant attention due to its unique surface and volume effects. Nanoparticles possess a large specific surface area, high adsorption capacity, and excellent suspension and catalytic abilities, exhibiting unparalleled advantages compared with traditional organic asphaltene inhibitors, such as sodium dodecyl benzene sulfonate and salicylic acid. At present, there are three primary types of nanoparticle inhibitors: metal oxide nanoparticles, organic nanoparticles, and inorganic nonmetal nanoparticles. This paper reviews the recent advancements and application challenges of nanoparticle asphaltene deposition inhibition technology based on the mechanism of asphaltene deposition and nano-inhibitors. The aim was to provide insights for ongoing research in this field and to identify potential future research directions.

The impacts of high salinity and polymer properties on dewatering and structural characteristics of flocculated high-solids tailings

In seeking to better understand the inline flocculation technique for enhanced water recovery from concentrated fine-particle suspensions, polymers of different molecular weight (MW) and chemistry were used to treat a synthetic tailings slurry in a low-shear mixer for continuous flocculation under controlled conditions. The effects of dissolved salts in the slurry and polymer solution make-up water on dewatering performance were evaluated for conventional acrylamide/acrylate copolymers (BASF Magnafloc® products) and an alternative functional chemistry polymer (BASF Rheomax® DR 1050). The properties of the separated liquid and solid phases were examined to understand the impacts of salinity and polymer type on the formation of rapidly dewatering flocculated material. Higher concentrations of NaCl (0.006–0.6 M) and CaCl2 (0.006–0.06 M) salts in the unflocculated slurries formed larger coagulated structures, with focussed beam reflectance measurement (FBRM) showing greater pre-aggregation for the divalent salt. NaCl slurries show edge-to-edge (EE) and edge-to-face (EF) inter-particle associations that are open and easily disrupted while more compact face-to-face (FF) contacts are observed in CaCl2 slurries. For concentrated NaCl slurries, the dosing of medium-to-high MW polymers is generally preferred to maximise net water recovery, with the implication being that bridging mechanisms are still at play in high solids applications. In calcium-enriched slurries, the lower MW conventional copolymer gave comparatively better water returns than the other polymers when applied under low shear conditions, highlighting quite distinct aggregation processes compared to low solids flocculation. These results provide insight on the fundamental complexity of the ionic strength dependence of high solids-high dosage tailings flocculation, towards informing reagent polymer dosing and offering greater flexibility for end-of-pipe dewatering schemes.

Effect of hydrodynamic breakage on floc evolution and turbidity reduction in flocculation and sedimentation processes

Abstract Coagulation and sedimentation process is one of the most popular processes in drinking water treatment. Hydrodynamic breakage has a significant impact on the evolution of floc characteristics and the efficiency of turbidity removal. In this work, the effects of hydrodynamic breakage on floc size, fractal dimension, and floc morphology were investigated with an in-situ recognition system. The experiments were conducted in a continuous flocculation and sedimentation reactor equipped with perforated plates to provide different hydrodynamic breakage conditions. The experimental results indicated that the hydrodynamic conditions significantly influenced the floc destabilization and restructuring processes. A low hydrodynamic shear force provided by P1 led to the increase of both bigger sized flocs but accompanied with small particles (0–10 μm). Excessive velocity gradient provided by P3 produced smaller and looser flocs. An appropriate velocity gradient (i.e., the flow velocity through the perforated plate P2 at 18.9 × 10−3m s−1) was conducive for the formation of larger and more compact structures, with higher average floc size and fractal dimension. This flocculation condition in turn resulted in effective improvements in the turbidity removal efficiency. Floc evolution models were described based on the mechanism of the breakage and restructuring process.

Charge Neutralization Mechanism Efficiency in Water with High Color Turbidity Ratio Using Aluminium Sulfate and Flocculation Index

Most of the water supplied in Brazil comes from water streams that may have higher values for apparent color than turbidity. Treatability trials were performed for color and turbidity removal to evaluate the advantages of coagulation during the charge neutralization mechanism when compared to sweep flocculation for water with those characteristics. There were three types of trials: conventional Jar Test with raw water, with and without filtration, and in a pilot Water Treatment Plant, direct downward filtration, with synthetic water. Auxiliary equipment such as Continuous Flocculation Monitoring Equipment (CFME) and image analysis were used to evaluate the growth of flocs. In the Jar Tests experiments, similar levels of color (61.49%) and turbidity (61.30%) removal were observed, with a lower dosage of coagulant (46 mg/L) in the charge neutralization mechanism compared to the ones with sweep flocculation (58.22% for color and 54.73% for turbidity removal with 52 mg/L of aluminium sulfate). Similar results were found on pilot plant. At filtration rates of 180 and 300 m3 m−2 day−1, sweep flocculation mechanism had shorter filtration cycle (<5 m3) compared to other mechanisms. Therefore, a change in the operation of Water Treatment plants that use a coagulant dosage associated with sweep flocculation can bring advantages such as the reduction of coagulant consumption and sludge productions, as well as the increase of chlorine disinfection and filtration cycles.

Using focused beam reflectance measurement (FBRM) to monitor aggregate structures formed in flocculated clay suspensions

The shear sensitivity of fragile, low-density aggregates formed in particle suspensions by polymer-bridging flocculation makes characterisation methods needing sampling or dilution problematic. Focused beam reflectance measurement (FBRM) probes can readily monitor such structures in real-time, but interpretation of resulting chord length data can be superficial, often missing detail within the distributions. However, the potential for deeper insights can’t be realised if flocculating with poor control of applied shear conditions (intensity and duration). In this study, continuous flocculation was achieved in a Couette mixing device with a vertical flow-through arrangement, acquiring operator-independent settling rate and FBRM chord data. The performance of a series of anionic flocculants (same charge density but different molecular weights) was investigated when applied to kaolin suspensions, with the introduction of 10 or 20% bentonite used to induce ‘bad’ flocculation responses. Size-density relationships in selected samples were determined separately by image analysis of free-settling aggregates.Following well controlled flocculation, distinct relationships between settling rate and mean volume-weighted chord length were attributed to variations in both substrate mineralogy and applied mixing intensity impacting on aggregate density. No such distinctions could be drawn from variations in flocculant molecular weight. Unweighted chord length distributions offered sensitivity to inefficiencies in fines capture and aggregate breakage under higher shear, which were both impacted by flocculant molecular weight. The unweighted chord counts <10 µm for the unflocculated clay slurries better anticipated dosage demand than conventional (volume-based) particle sizing, showing the potential of FBRM feed monitoring for flocculation control.

Pilot study of in-line continuous flocculation water treatment plant

Human consumption of groundwater without treatment is not safe and can cause water-borne diseases and other kinds of illnesses. Usually, groundwater extracted through boreholes may be acidic and contains impurities such as organic and inorganic contaminants, microbes, and heavy metals. Hence, it becomes imperative to treat groundwater to make it potable for human consumption. This pilot study was conceptualized based on a simple and the most economical technological approach in groundwater treatment. It employed the basic concepts and working principles of essential unit operations such as coagulation, sedimentation, filtration, and adsorption to ensure potable water for human consumption based on WHO standard specifications. The plant specifically treats groundwater of pH 6.30-6.50. The average flow rate of the plant is 12,570 cm3/min (0.7542 m3/hr) and a centrifugal pump of 0.5 HP and a pipe size of 20 mm diameter were selected for this design. Equipment used were determined, sized and selected as required and the treated water quality is ensured through laboratory routine tests carried out in the course of the continuous operation of the pilot plant. Sand filter and carbon purifier are inevitable and a turbidity sensor is proposed for the filters to optimize the backwash operation. Capital cost evaluation was carried out using the percentage of delivered equipment cost method and the total capital cost for this pilot plant was estimated as One Thousand, Seven Hundred and Eighty-Two-Ringgit (RM 1,782.00 ≈ USD445.50). Thus, with this successful pilot study for a continuous treatment operation, a plant scale-up is feasible for groundwater purification to ensure potable water security in both rural and urban communities.

Continuous cell flocculation for recombinant antibody harvesting.

BACKGROUNDIntegrated continuous production technology is of great interest in biopharmaceutical industry. Efficient, flexible and cost effective methods for continuous cell removal have to be developed, before a fully continuous and integrated product train can be realized. The paper describes the development and testing of such an integrated continuous and disposable set‐up for cell separation by flocculation combined with depth filtration.RESULTSScreening of multiple flocculation agents, depth filters, and conditions demonstrated that the best performance was obtained with 0.0375% polydiallyldimethylammonium chloride (pDADMAC; a polycationic flocculation agent) in combination with Clarisolve® depth filters. Using this set‐up, a 4‐fold decrease of filtration area was achieved relative to standard filtration without flocculation, with yields of ≥97% and DNA depletion of up to 99%. Continuous operation was accomplished using a simple tubular reactor design with parallelization of the filtration. The reactor length was selected to allow a 13.2‐min residence time, which was sufficient to complete flocculation in batch experiments. Continuous flocculation performance was monitored on‐line using focused beam reflectance measurement. Filter switch cycles based on upstream pressure were controlled by in‐line pressure sensors, and were stable from one filter to the next.CONCLUSIONIt was demonstrated that stable and efficient continuous flocculation associated with depth filtration can be easily accomplished using tubular reactors and parallelization. Continuous cell separation is essential for the development of fully continuous integrated process trains. This cost‐efficient disposable design run in continuous mode significantly reduces facility foot print, process costs and enables great flexbility. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Variations in the molecular weight response of anionic polyacrylamides under different flocculation conditions

The influence of applied mixing (intensity and duration), solids concentration, and liquor chemistry on the molecular weight (MW) response of seven anionic (30%) polyacrylamides was investigated in the flocculation of standard kaolin slurry at pH 8. Continuous flocculation was achieved in a Couette mixing device (CSIRO Shear Vessel) with a vertical flow-through arrangement allowing operator-independent settling rate measurements to be made under tightly controlled mixing conditions. It was found that the relative performance of the flocculants was strongly dependent on the hydrodynamic conditions prevailing during flocculation. The lower MWs gave a more dosage-effective response under mild mixing, producing denser, faster-settling aggregates than equivalent sizes produced with the higher MWs. Conversely, the larger sizes created by the higher MWs gave access to faster settling rates under intense mixing, except in the instance where polymer size and concentration led to chain entanglements. Sodium cations (<0.01 M) in the slurry favoured some degree of particle coagulation, whereas calcium cations had an adverse effect on settling rates even at low concentrations (<0.002 M), with the effects of a reduced bridging capacity most apparent in the lower MWs. The results advance the fundamental understanding of how chain length can substantially alter inter-particle bridging behaviour under different conditions, and thus provide a more robust basis for enhanced dewatering of clay suspensions through flocculant MW selection.

Principles and performance of a submerged internal-circulation membrane coagulation reactor

Coagulation has been the most successful pretreatment for the mitigation of membrane fouling, the improvement of permeate quality, and the extension of membrane service life. Membrane coagulation reactor (MCR), which is a coupled coagulation and membrane filtration process, is a promising technology for surface water purification. In order to decrease footprint, promote flocculation efficiency, and mitigate efficiently membrane fouling, a submerged internal loop MCR with in-line coagulation, sludge thickening, and air sparging was developed. In the MCR, the internal loop flow induced by air lift through a flocculation region can cause a continuous flocculation of raw water and consequently avoid the accumulation of fine flocs prone to blocking membrane pores and forming a compact cake layer. Furthermore, the flocs with a large size and a fast settling velocity can consecutively settle into the sludge thickening region and then are discharged for controlling sludge concentration. The MCR with hollow fiber microfiltration membranes and with polyaluminium chloride (PACl) as coagulant exhibited excellent performance in removing the turbidity, total organic carbon (TOC), and dissolved organic carbon (DOC) of surface water at bench-scale test. The turbidity and TOC of the permeate met the needs of centralized water supply set by “Standards for Drinking Water Quality” (GB 5749–2006) of China, below 1 NTU and 5 mg/L, respectively. The water flux above 55 L/(m2 h) was achieved at the transmembrane pressure of 0.025 MPa. Air sparging could effectively control membrane fouling of the MCR and continuous air sparging was more favorable than intermittent air sparging. The observations by scanning electron microscope showed that the cake layer on membrane surface was loose and irregular and easily cleaned by air sparging, but CaCO3 was difficult to be removed compared to other precipitates, such as those of Al, Si, and Fe. The experimental results indicated that the MCR has a promising application in treating surface water for drinking.

Study of a Novel Honeycomb Continuous Flocculator

The continuous flocculator described in this article refers to a kind of continuous flocculation device designed to flocculate fermentation liquid. The honeycomb continuous flocculator is composed of a vessel and built-in trapezoid subassemblies, which divide the space within the vessel into multiple honeycomb channels. The length ratio between the longest diagonal of the regular hexagon and the axial length of the channel is within the range 0.01–0.04; and the internal surface roughness (Ra) of the channels should be 0 &lt; Ra ≤ 0.2 μm. In contrast to current flocculator designs, the channels of the honeycomb continuous flocculator could control the floc grain size, grain fineness distribution in the fermentation liquid and flocculating time and decrease the flow resistance of the flocculating fermentation liquid and increase handling capacity. These capabilities improve solid-liquid separation efficiency for fermentation liquids. The flocculator could be used either for purification of industrial fermentation liquids or sewage treatment.

The effect of cations on the activity of anionic polyacrylamide flocculant solutions

The conformation of acrylamide/acrylate copolymers' aqueous solutions is known to be affected by the presence of cations to varying degrees. Such effects are expected to be reflected in the flocculation activity of the polymer solutions, but the published literature in this area is far from convincing, particularly on the influence of divalent cations. Part of the problem was believed to stem from the inevitable poor control of the applied shear conditions (both intensity and duration) in conventional batch cylinder or jar tests. To address this, continuous flocculation was achieved in a Couette mixing device that allowed operator-independent settling rate measurements to be made, with much greater control over the residence time under shear and its intensity. A standard calcite (calcium carbonate) slurry was then used as the substrate for comparison between flocculants of increasing anionic character in the presence of selected cations at various concentrations. Rather than shifting the dosage response curve, the divalent cations Ca2+ and Mg2+ were found to limit the settling rates that could be achieved at higher dosages, but this effect could be masked under stronger applied shear conditions that favour some degree of aggregate breakage and also limit settling rates. Such effects increased with the flocculant's anionic character and the cation concentration. In contrast to the conventional anionic products, a flocculant that contained an alternative functional chemistry (BASF Rheomax® 1050) was found to be far less affected by the presence of these cations. Low levels of iron (either as Fe2+ or Fe3+) were sufficient to deactivate dilute flocculant solutions, but had reduced effects when present in stock solutions. The mechanisms by which the different cations affect flocculant solutions are discussed, together with the practical implications for flocculant make-up and application within gravity thickening as practiced in mineral processing.

The preparation and ageing of acrylamide/acrylate copolymer flocculant solutions

The flocculation activity achieved with aqueous solutions of polyacrylamide and acrylamide/acrylate copolymers is shown to be highly dependent upon the solution age. Continuous flocculation with a standard kaolin slurry in a Couette mixing device, giving settling rate and in-line chord length distributions, allows the comparison of different flocculant properties and make-up conditions. The multiple-stage ageing process proposed by Owen et al. [Owen, A.T., Fawell, P.D., Swift, J.D. and Farrow, J.B. (2002), The impact of polyacrylamide flocculant solution age on flocculation performance. Int. J. Miner. Process., 67, 123–144.] for nonionic flocculant stock solutions is found to also apply for the wider range of products, although the relative effects of each stage varies, depending on the flocculant form and molecular weight. For powder-based products, the initial wetting, swelling and dispersion of the solid polymer is influenced by the powder size, such that activity may be extremely poor even after several hours. Emulsion-based flocculants effectively eliminate this stage, but both forms of the high molecular weight flocculants require at least an additional 24 h to achieve maximum activity. This is attributed to the slow disentanglement of highly agglomerated polymer. The practical implications for flocculant make-up and use in mineral processing are discussed.

An integrated anaerobic - physico-chemical treatment concept for wool scouring wastewater

The strong flow wastewater from a wool scouring industry is treated by a combination of anaerobic digestion and physico-chemical postreatment. Based on previous laboratory results (Gutiérrez et al., 1999), three anaerobic baffled reactors (ABR) of 300 m3 each were built, processing 60% of the strong flow of a wool scouring mill for about two years. COD and grease removal in the anaerobic reactors were 47-50% and 50-55% respectively, with an organic load between 8.9 and 6.7 kg COD/m3 d. The effluent of the anaerobic reactors was assayed with additives in an industrial decanter centrifuge. As results of these assays, all the effluent of the three reactors was sent to the decanter centrifuge after dosing additives. Overall COD and grease removal of the integrated system were 87% and 93% respectively. Dosage of coagulation-flocculation additives was optimized in a continuous flocculation device. The proposed treatment is cheaper and easier to control than others alternatives with COD removal higher than 93%.

Comparative analysis of ethanolic fermentation in two continuous flocculation bioreactors and effect of flocculation additive

Two types of bioreactor using a flocculating strain of Saccharomyces cerevisiae and continuous ethanolic fermentation as model were compared in terms of start-up evolution, overall performance and power costs. Also, the effect of adding to the medium a polymer — Magna Floc LT25 — that increases floc porosity was studied.

Comparative analysis of ethanolic fermentation in two continuous flocculation bioreactors and effect of flocculation additive

Comparative analysis of ethanolic fermentation in two continuous flocculation bioreactors and effect of flocculation additive