Showing papers on "Fouling published in 1991"

Albumin denaturation during ultrafiltration: effects of operating conditions and consequences on membrane fouling.

Abstract: Ultrafiltration of high-purity grade bovine serum albumin has been carried out under various temperature between 5 and 30°C and at various cross-flow velocities, pressures, and concentrations with the aim of studying protein denaturation and its consequences on the process. Three different pump heads have been tested. Denaturation of proteins in solution has been monitored by laser light scattering and size exclusion chromatography. The rate of protein denaturation increases with temperature, cross-flow, and time. It is observed that membrane fouling is different whether denaturation has occurred or not. Under high-concentration polarization, denaturation can occur in the boundary layer if the wall concentration exceeds 400 g/L. It is shown how the residence time, operating temperature, and pressure play an important part in membrane fouling. This can provide guidelines for process design and control.

Some observations on biofouling in the cooling water conduits of a coastal power plant

Abstract: Biofouling of cooling water conduits is a problem common to all coastal power stations using seawater as a heat sink. Madras Atomic Power Station has been facing the problem of fouling induced flow resistance of cooling water in its submarine tunnel leading to a drop in water level beyond design limits in the forebay. Inspection of the tunnel system by a diving team with the help of a Remotely Operated Vehicle (ROV) revealed severe fouling by the green mussel, Perna viridis in the tunnel. This paper reports qualitative and quantitative data on the fouling within different areas of the tunnel system.

Study of the fouling of inorganic membranes by acidified milks using scanning electron microscopy and electrophoresis. II. Membrane with pore diameter 0·8 μm

Abstract: The fouling of an inorganic microfiltration membrane with an average pore diameter of 0·2 μm obtained in static conditions with milk, acidified milk and acid coagulum was examined using scanning electron microscopy. The structure and porosity of external fouling related to the pH of the milk accounts for the performance and efficiency obtained in microfiltration. Electrophoretic analysis of permeate, characterized by lack of casein, shows that the deposit plays a fundamental role in mass transfer through filter layers. Variations in the physicochemical properties of casein as a function of pH at 50 °C were used to account for the development of the structure of fouling, which comprised three main states: (i) dense deposit of juxtaposed micelles, (ii) loose network formed by chains made up of bonded protein aggregate, (iii) irregular protein aggregate leading to high-porosity deposits. The presence of a protein film strongly adsorbed on the membrane layer of alumina particles is demonstrated.

Method for the prevention of fouling and/or corrosion of structures in seawater, brackish water and/or fresh water

Abstract: A device and method for preventing fouling and/or corrosion of the exposed surfaces of a structure which is in contact with seawater, brackish water, fresh water, or a combination of these. The system includes using a structure having an exposed zinc-containing surface. At the exposed surface water interface a negative capacitive charge or an asymmetric alternating electrostatic is induced and maintained.

Biofouling and its control in a tropical coastal power station: A case study

Abstract: Macrofouling in the cooling circuits of coastal nuclear power stations is an important problem from the operational and safety viewpoints. However, comprehensive studies on settlement, biomass build‐up and response of settled organisms to control measures are very few. This paper presents data on the biofouling problems encountered in the precondenser section of the cooling circuit of a tropical coastal power station and the control measures adopted to alleviate them. In the Madras Atomic Power Station, development of severe, mussel‐dominated biofouling was noticed in the cooling water intake tunnel, in spite of intermittent chlorination used as a fouling control measure, resulting in serious pressure drop in the cooling water circuits. Switching over to shock dose chlorination, followed by continuous low dose chlorination helped removal of a large quantity of sessile biomass from the tunnel, leading to satisfactory flow performance. The data also indicate the effectiveness of continuous low level chlorin...

Hydrocarbon treating process

Abstract: Cracked hydrocarbon gases are treated to remove contaminating compounds that react in caustic wash to form the reaction products which cause equipment fouling. The treating of the cracked hydrocarbon gases includes the contacting of a cracked hydrocarbon stream with an aqueous amine solution, prior to caustic washing, to remove carbonyl compounds contained in the cracked hydrocarbon gases. By treating the cracked hydrocarbons with an amine compound prior to caustic washing, the formation and deposition of fouling compounds upon the internal components of caustic treating equipment is inhibited.

Fouling of heat exchangers in the food industry: a chemical engineering prespective

Abstract: Fouling and cleaning of process plants is a serious industrial problem. Although the chemistry of the process of fouling is understood, the interaction between the chemistry and the fluid mechanics of process plants makes it difficult to deal with the problem. However, it is well suited to a chemical engineering approach.

The Major Developments of the Evolving Reverse Osmosis Membranes and Ultrafiltration Membranes

Abstract: The current status of reverse osmosis and ultrafiltration membranes are reviewed with the view for the future. In the case of reverse osmosis (RO) membranes, as examples, new crosslinked aromatic polyamide membranes exhibited the superior separation performance with the sufficient water permeability, the high tolerance for oxidizing agents and chemicals. Ultrafiltration (UF) membrane based on poly(phenylene sulfide sulfone)(PPSS) also exibited the superior separation performance with the high solvent, heat and fouling resistance.

Method for inhibiting fouling in caustic scrubber systems

Abstract: A method for inhibiting the formation of polymeric based fouling deposits normally formed during the caustic washing to hydrocarbons is disclosed. The method comprises adding an effective amount for the purpose of an acetoacetate ester compound to the caustic wash system.

Biofouling: Effects and Control

Abstract: Biofouling refers to the undesirable accumulation of a biotic deposit on a surface. The deposit may contain micro- and macroorganisms. The focus of this paper is microbial fouling biofilms which consist of an organic film composed of microorganisms embedded in a polymer matrix of their own making. The composite of microbial cells and EPS is termed a biofilm. The surface accumulation is often composed of significant quantities of inorganic materials. Complex fouling deposits, like those found in industrial environments, often consist of biofilms in intimate association with inorganic particles (1), crystalline precipitates or scale (2), and/or corrosion products (3). These complex deposits often form more rapidly and are more tightly bound than biofilm alone. These deposits are difficult to characterize at the microscale, i.e. at the cellular level.

Analytical Modeling of Calcium Carbonate Deposition for Laminar Falling Films and Turbulent Flow in Annuli: Part II—Multispecies Model

Abstract: The present study proposes a multispecies transport model to predict calcium carbonate deposition. The model has been applied to predict the deposition flux, the mean fouling layer thickness, and the profile of local thickness along a heated plate of a laminar falling film. Good agreement is found when comparing with experimental data. Similarly, the model is applied to predict the fouling layer in a turbulent annulus flow system and a good agreement of the predicted results is also found with recent experimental data. Finally, solutions in dimensionless forms are presented to show the effects of various dimensionless parameters on calcium carbonate deposition.

Influence of scaling on the performance of shell-and-tube heat exchangers

Abstract: Fouling in shell-and-tube heat exchangers was modeled by combining Hasson's ionic diffusion model for scaling from CaCO3 solutions with a model for predicting the temperature distribution developed by Gaddis and Schlunder. Using the computed results, clean heat exchanger design rules were tested for fouling conditions. The effects of fouling on the efficiency of heat exchanger configurations were determined.

Comparison of power-plant condenser cooling-water fouling rates for spirally-indented and plain tubes

Abstract: This paper presents the fouling rates for twelve TVA power-plant condensers, nine of which were retubed with an enhanced tube. The overall heat-transfer coefficients were calculated from logged field data taken over periods from one to ten years. The fouling resistances were calculated with the separate-resistance method and with a bundle correction factor to the condensing, single-tube Nusselt prediction. The fouling rates with the enhanced tubes ranged from about the same as to about twice that of the plain tubes. The thermal performance with the enhanced tubes remained superior to that obtained with plain-tubes for more than a year without cleaning. After one year of operation, the enhanced-tube fouling resistance values were less than the minimum value of the TEMA Standards and the plain-tube fouling resistance values were always less than one half of this value. After shutdown cleaning, the thermal performance values for both tubes were restored to essentially the new, clean levels. 28 refs., 9 figs., 2 tabs.

Reverse osmosis treatment process

Abstract: This invention relates to a reverse osmosis treatment process, particularly a stable reverse osmosis treatment process which prevents a lowering in throughput capacity by carrying out treatment while keeping the permeate flux of a reverse osmosis membrane constant through the time of use of a module. The process of this invention can keep the throughput capacity constant, can prevent adhesion and pollution onto membrane surfaces and fouling thereon, and moreover can maintain stable operation in a continuous run.