Showing papers on "Fouling published in 1980"

Factors affecting the mechanism of flux decline during ultrafiltration of Cottage cheese whey.

Abstract: The mechanism of fouling of ultrafiltration membranes during the processing of cheese whey was studied. Attempts were made to develop a mathematical model of the flux decline and to determine the contribution of individual proteins and the aqueous environment to fouling. In general, proteins dissolved in a salt-free system resulted in higher flux than in whey dialysate systems, implicating the salts as a major contributor to flux decline. Statistical analysis and evaluation of the parameters of the model indicated that fouling could be considered in two time periods. In the initial period of operation, α-lactalbumin appeared to cause greater flux decline and bovine serum albumin the least. After 10 min of operation, β-lactoglobulin was the major contributor to fouling. The native whey gave the most rapid rate of flux decline. These differences could be due to variations in protein structure or differences in the nature of the deposit on the membrane.

Cooling Water Fouling in Plate Heat Exchangers

Abstract: Heat exchangers using cooling water are designed with fouling resistance applicable to tubular equipment, in most cases TEMA recommended values. Plant experiences indicate that plate heat exchangers produce substantially lower fouling rates due to turbulence induced by the plate corrugations. Furthermore, plate exchangers are more severely penalized by fouling resistance than tubular exchangers because of the high heat transfer coefficients typical of plate exchangers. To supply reliable folding data to the designer, APV Company. Ltd. sponsored a research project to study fouling in plate exchangers with Heat Transfer Research. Inc. (HTRI). The test fluid was a typical, treated cooling-tower water. Results of these experiments, described in this paper, show that at typical operating conditions the fouling resistances for plate exchangers are substantially lower than those used for tubular equipment.

Process and apparatus for testing fluids for fouling

Abstract: There is disclosed a novel mobile apparatus and process therefor including a heat transfer test assembly and related conduit and valve assemblies for connection in fluid flow communication to a heat transfer apparatus for in-situ testing of the fluid passing therethrough and including monitoring and recording apparatus. The heat transfer test assembly includes a heating member for controlled heat input and thermocouples to measure the surface temperature of the heating member to permit fouling deteminations at varying flow rates with simultaneous monitoring and recording thereof together with data, such as corrosion, pH, conductivity, and the like.

Fluidized beds as turbulence promoters in the concentration of food liquids by reverse osmosis

Abstract: Fluidized beds offer a potential improvement of reverse osmosis processes for food liquids, less fouling of the membrane, and reduced energy consumption. Our experiments were concerned with tubular systems in which fluidized beds of glass, steel, and lead beads were used. Glass beads appeared to be preferable, since they caused little damage to the membrane. Only with the larger glass beads (3 mm) did the membrane skin become corrugated, so that the rejection decreased. The permeate flux for Gouda cheese whey was almost equal to that of an empty tube for which the velocity was about thirty times higher. The erosive action of the glass beads on the fouling layer was partially responsible for this effect. For reverse osmosis of skim milk and potato fruit water the bed did not reduce the fouling layer to a sufficient extent and, therefore, had a lower permeate flux than an empty tube.

Biofouling control with ozone at the Bergen Generating Station

Abstract: The results of a study designed to evaluate the effectiveness of ozone as an alternative to chlorine for condenser biofouling control in a once-through cooling system are reported. Tests were conducted at PSE and G's Bergen Generating Station using a pilot-scale condenser system to simulate plant condenser operations. Three model condensers were operated under identical conditions with only the biocide treatment differing. Comparisons of ozone and chlorine were made and the minimum effective levels of each were determined by daily measurements of the heat transfer coefficient across the model condenser tubes and/or the water side pressure drop. Final evaluation was based on the mass of biofouling material collected from the tubewalls. Test results indicate that chlorine is capable of effective biofouling control when applied for 2 hours/day at a level as low as 0.1 mg/l. Ozone, applied on the same schedule, requires 0.5 mg/l for effective control. The results of this study are representative of only the Bergen site. Water quality at each particular site will influence the development of the biofouling organisms, the chemical reactions of the biocides, and therefore, the effectiveness of the treatment methodology. The results suggest that further examination of ozonation for biofouling control is warranted.more » Although much more costly than chlorine, its effects on indigenous ecosystems may prove ozone to be better suited for application at selected power plants. It must be emphasized, however, that much more information is necessary before ozone can be recommended as an environmentally acceptable alternative to chlorine.« less

Installation to purify and cool domestic effluent etc. - uses cooling vessel with upflow injection to avoid fouling heat transfer surface

Abstract: Appts. for the purificn. and cooling of domestic effluent etc. by removal of grease, detergent scum etc. and by recuperation of heat for re-use, is described. The recuperative heat exchanger comprises cooling surfaces inside a vessel into which the effluent is injected upwards from the base. The upflow of effluent prevents the settlement of impurities as cooling proceeds. Pref. flow through the heat exchanger is controlled to produce laminar flow which entrains the impurities and carries them to an overflow discharge. This discharged effluent is pref. passed through a grease trap comprising filtration and decantation in series. Appts. is for purifying and cooling hot, domestic effluent etc., before discharging it to drainage systems. Heat is recovered for domestic use, e.g. hot water systems as the effluent is cooled. The upflow through the heat exchanger vessel prevents fouling of the heat transfer surfaces. The system is equipped with in place cleaning.

Ammonium phosphate recovery from urban sewages by selective ion exchange

Abstract: Some practical aspects of the process for nutrient recovery from secondary effluents by ion exchange are investigated in detail. These aspects comprise ion speciation, production, resin regeneration and resin fouling. Fouling by bio-resistant organic pollutants appears to affect the anion resin performances in the absence of a properly designed scavenging section.

Effect of marine biofouling on the heat transfer performance of titanium condenser tubes

Abstract: The fouling of the sea water side surfaces of condenser tubes lowers their heat transfer and affects the efficiency of thermal and nuclear power stations. Recently, with the rise of energy cost, the economical and technical interests on this problem have increased. Titanium tubes have very excellent corrosion resistance in sea water, but are apt to undergo biofouling since they are non-poisonous. In this study, titanium tubes and aluminum brass tubes were compared regarding biofouling, and as the countermeasures, the effect of the frequent cleaning with Carborundum balls was compared with other methods. On the basis of these results, the heat transfer performance of the titanium tubes cleaned frequently with Carborundum balls was examined. A model condenser in the Atsumi Power Station, Chubu Electric Power Co., Inc., was used for the experiment. The experiment was commenced on November 6, 1976, and finished on April 5, 1979. The tubes tested, the test conditions, and the measurement of the coefficient of overall heat transmission and the calculation of the fouling factor are explained. For the prevention of the biofouling of titanium tubes, the frequent cleaning with Carborundum balls was very effective, and these titanium tubes showed the same coefficient of overall heat transmission as the aluminum brass tubes cleaned with sponge balls.

Predictive test method for coking and fouling tendency of used lubricating oil

Abstract: A short, reliable test has been developed to measure the coking and fouling tendency of used lubricating oils undergoing thermal stress. The technique utilizes commercially available instrumentation and requires only 200 mL of sample and three hours analysis time. Correlations based on oils of known quality demonstrate good qualitative predictive abilities, while reproducibility studies demonstrated quantitative reliability. It is shown that ash content alone may not always be a reliable measure of fouling potential.

Fouling and the inhibition of salt corrosion

Abstract: In an attempt to reduce fouling while retaining the beneficial effects of alkaline earth inhibitors on the hot corrosion of superalloys, the use of both additives and the intermittent application of the inhibitors were evaluated. Additions of alkaline earth compounds to combustion gases containing sodium sulfate were shown to inhibit hot corrosion. However, sulfate deposits can lead to turbine fouling in service. For that reason, dual additives and intermittant inhibitor applications were evaluated to reduce such deposit formation. Silicon in conjunction with varium showed some promise. Total deposition was apparently reduced while the inhibition of hot corrosion by barium was unimpaired. The intermittant application of the inhibitor was found to be more effective and controllable.

Effect of microfouling on heat-transfer efficiency

Abstract: Field experiments, performed at Keahole Point, Hawaii and in the Gulf of Mexico, were designed to determine the relationship between decreased heat transfer efficiency and the accumulation of corrosion and/or biofouling films on heat exchanger surfaces. The sample tubes were maintained under conditions simulating those of an Ocean Thermal Energy Conversion (OTEC) system and data from the two sites have been compared. Seawater flowed through 2.54 (internal diameter) metal tubes at approximately 1.8m sec/sup -1/. Four types of tubes were used: 5052 Aluminum (A1), Grade 2 titanium (Ti), 90-10 copper-nickel (Cu-Ni) and Allegheny-Ludlum 6X stainless ssteel (SS). All surfaces were colonized by microorganisms, though colonization of the Cu-Ni surface was initially retarded. Total film weight was greatest for the Al and Cu-Ni surfaces which were characterized by corrosion as well as microbial fouling. The total organic carbon: total nitrogen ratios of the fouling films from Ti, Al, SS and Cu-Ni, 4.2, 4.0, 4.8 and 7.9 respectively, remained constant throughout the experiment. The degradation of heat transfer efficiency due to the formation of fouling layers on Ti and SS is neither linear nor a simple exponential function. A microfouling model is proposed for corrosion-resistant surfaces that is consistent with field observations.

Anodically polarized surface for controlling biological soilage and scale deposition

Abstract: BBiofouling and scale control in conductive aqueous systems is effected on metal surfaces, particularly valve metal surfaces such as titanium, on which such fouling normally occurs, by applying thereto a stable electrocatalytic coating and anodically polarizing the metal or the coating on it such that only oxygen is evolved at the surface thereof, preferably at a rate of at least 4.66 millimoles per hour per square metre, without the evolution of any chlorine taking place.

Measurement of Thermal Resistance Due to Fouling on Heat Exchanger Surfaces

Abstract: Fouling which occurs on power plant heat exchangers, particularly Ocean Thermal Energy Conversion plants, is a problem since these deposits reduce heat tranfer efficiency. An apparatus to quantify the thermal resistance due to fouling, including low levels of fouling, has been developed and operated to acquire experimental data. The heat transfer monitor device developed utilizes a stable heat flux applied by direct electric heating to a circular tube in order to simulate flow characteristics of a shell and tube heat exchanger. The device serves to evaluate heat exchanger materials and antifouling or cleaning treatments in power plant applications. Several series of experiments were performed at a San Diego Bay location to determine the effect of materials, velocity, and low level chlorination on the fouling rate. Each experiment was run for a period of 6-10 weeks. The most dramatic reduction in fouling observed was afforded by chlorination dosed at 0.1 mg/l. Traditional control of fouling by chlorination may present toxicological problems to aquatic organisms in the receiving water. Minimizing the environmental impact of biofouling without delays and high costs as a result of the trial and error approach can be accomplished by measurement of the status of biofouling, or its effect on lowering heat transfer. The heat transfer monitor described herein seeks to provide this capability.

A technique for prevention or removal of biofouling from surfaces exposed to the marine environment

Abstract: Direct electrolytic hypochlorination of surfaces exposed to the marine environment is an effective technique for prevention or removal of biofouling. The surfaces to be protected or cleaned are first coated with a thin platinum film and made the anode in an electrochemical circuit using seawater as the electrolyte. Tests demonstrated that an electrical current density as low as 0.022 mA/cm square applied continuously to a surface exposed in ocean water for seven months prevented biofouling from occurring on that surface. Initial test results indicate that intermittent energizing of the electrochemical circuit for short periods on an 8 or 24 hours cycle is also effective in preventing biofouling. Removal of existing fouling using this technique was demonstrated on several specimens, including one with a three-month accumulation of micro- and macrofouling. The biofouling was completely removed within a 24-hour peiod using a current density of 0.5 mA/cm square.

Combined Cycle Steam Generator Gas Side Fouling Evaluation.

Abstract: : Liquid-fueled gas turbines can produce serious steam generator fouling in gas turbine combined cycle applications and other waste heat recovery systems as a result of combustion system generated soot particles. In addition, standard soot blowing practices are not always compatible with the advanced, compact matrix designs sometimes required for minimum package size applications. In Phase I, an experimental program was conducted on both test rigs and engine hardware designed to evaluate the effects on gas side soot fouling rates of various operational parameters such as soot loading, temperature, and velocity. Results showed that the self-cleaning concept, whereby soot deposits are removed by curtailing steam generator water flow and raising fin/tube temperatures to that of the prevailing exhaust gas, is a viable alternative to standard soot-blowing practice. The results, however, also showed inconsistencies in the self-cleaning threshold temperature between the various rigs. Phase II of this program was conducted to resolve these inconsistencies and, more specificaly, to define a cleaning schedule for a LM-2500 combined cycle. The results lend further support to the self-cleaning concept and show that at full load a LM-2500 combined cycle system would be expected to clean itself within an hour after dryout. (Author)

The Effect of a Synthetic Flocculant on Ion-Exchange Resin

Abstract: Experiments were conducted to determine if a synthetic flocculant would foul ion-exchange resin used in deionization plants. It was found that unreacted flocculant fouled the surface of cation-exchange resin, restricting mass transfer, but that total capacity was not significantly affected. Several samples of used resin from a deionization plant did not show evidence of surface fouling, but did have less capacity than new resin. This indicated that unreacted flocculant had not been present in the plant feed water.