Showing papers on "Fouling published in 1987"

Fouling of heat transfer surfaces

Abstract: Fouling and/or scaling of heat transfer surfaces causes serious problems in industry. Prevention of fouling is therefore essential for technical (considerable deterioration of heat transfer) and also economic reasons (increased costs). In order to provide successful countermeasures, it is, however, necessary to obtain more detailed information on the physical, chemical and biological processes which produce fouling. Based on the already known fouling mechanisms, it is shown that a satisfactory prediction of fouling behaviour of heat exchangers is not yet possible. This contribution presents a physical model for the description of fouling, caused by sedimentation and crystallization. It is assumed that, during fouling, deposition and removal processes overlap. In order to verify the theoretical considerations, experiments were carried out on a test rig, which could also be used for field experiments. Aqueous CaSO4 solutions served as experimental liquids. A comparison of experimental and calculated fouling factors shows a satisfactory agreement.

Method for controlling fouling of hydrocarbon compositions containing olefinic compounds

Abstract: Fouling of equipment used for processing of organic feed streams containing olefinic compounds is controlled by inhibiting polymerization of the olefinic compounds by carrying out the processing in the presence of from about 20 ppb to less than 1000 ppb of a stable free radical, such as a nitroxide.

Fouling of a heat exchange surface by whey, milk and model fluids. An analytical study

Abstract: Summary Fouling caused by sweet whey, milk, artificial ultrafiltrate, phosphate and calcium solution and prote in solutions was studied in weil defined hydrodynamic (flow rate: 0.096 m.s -1) and thermal conditions (temperatures ranging from 25 to 88 "C with a standard value of 72 "C ; temperature difference with the heat carrier fluid : 0, 5 or 10 "C) using a laboratory fouling deviee. Deposits were assessed quantitatively by weighing and qualitatively by Auger electron spectrocopy, X photoelectron spectroscopy and infrared spectroscopy. These spectra gave evidence for three main groups of compounds: proteins, phosphates and lipids as weil as the corresponding atoms (calcium, phosphorus, nitrogen and carbon). These findings suggest a fouling mecha- nism based on calcium phosphate building-up, with various structures ranging from simple weil crystallized phases «

Fouling Due to Corrosion Products Formed on a Heat Transfer Surface

Abstract: This paper is concerned with a type of fouling that has received very little attention int eh past in spite of its importance to designers and operators of heat trasnfer equipment, namely, the foulilng due to corrosion products that form on heat trasnfer surfaces exposed to flowing water. The lack of previous interest probably arises from uncertainty about the importance of this type of fouling. For this reason it is the objective of the research described in this paper to obtain quantiative information on the thermal resistance associated with corrosion fouling, and to compare it to thermal resistance values reported for other categories of fouling. The tests were made with the following conditions comparable to those found in industrial heat transfer equipment: the temperature of the heat transfer surface, material of the heat transfer surface, and the following properties of the water: oxygen content, pH, and temperature.

A novel fouling monitor

Abstract: A tapered tube device is described which allows the influence of a range of shear stresses on the formation of a wall fouling layer to be examined in the same experiment. The device is demonstrated for fouling from reconstituted skimmed milk over a range of surface shear stresses and temperatures. The shear stress required to maintain a clean surface, the critical shear stress, is shown to a function of temperature, with an activation energy of 150 ± 10Kj/mol. A mechanism for the early stages of fouling is proposed, based on a simple application of turbulent burst theory, which explains the form of the experimental results. The fouling from reconstituted skimmed milk is shown to be a two-stage process. Suggestions for the modelling of such processes are given. The further development of the tapered tube device is outlined.

Fouling and Flux Restoration of Ultrafiltration of Passion Fruit Juice

Abstract: Fouling phenomena of passion fruit juice in tubular ultrafiltration (UF) system were studied. The membrane deposit was found to be composed of pectin, sugars, citric acid, hemicellulose, and cellulose. Rinsing behaviour of the fouled membrane indicated that the deposit might be in the form of gel. Scanning electron microscopic examinations showed slime-like deposit on the fouled membrane. Intermittent on-off operation was able to restore the flux effectively. Rebounding of the gel layer at sudden release of pressure may explain the effect of on-off operation on flux restoration.

Effect of chlorination on materials for sea water cooling systems: a review of chemical reactions

Abstract: The electrode and the chemical reactions likely to occur on electrochlorination of sea water are reviewed. The levels of chlorine required to control fouling and the effects of pressure are also discussed. The reactions of chlorine with both common pollutants and chemical additions present in sea water are reviewed, as are the effects of chlorinated sea water on the corrosion of copper and ferrous alloys.

Fouling From Vaporizing Kerosine

Abstract: Fouling rate data have been obtained by passing kerosine at a low flow rate through a small horizontal tubular furnace. Substantial circumferential variations in surface temperature and fouling rate occurred during vaporization, the highest rates being at the bottom of the tube where surface temperatures were the lowest. Fouling rates generally increased as pressure increased from 1 to 2.5 bar, but were reduced markedly either by decreasing the feedstock oxygen content or by raising the wall superheat. All the observations are consistent with fouling occurring predominantly via autoxidation and cracking-synthesis mechanisms for the liquid and vapor phases, respectively.

Method and apparatus for measuring corrosion current induced by microbiological activities

Abstract: A corrosion measuring device is disclosed for measuring microbiologically duced corrosion using galvanically coupled electrodes exposed in an electrolytically continuous, biologically separated environment. The device consists of two, mirror image, half-cells separated by either a 0.1-μm porous cellulose acetate/cellulose nitrate membrane or a solid disc. The membrane is used when measuring total corrosion current in a chemically continuous environment while the solid disc is used when evaluating individual corrosion mechanisms in chemically isolated environment. Culture medium is pumped through inlets of the half-cells at a constant speed. One of the electrodes is inoculated with viable microorganisms which colonize the electrode surface creating a corrosion current that can be measured with a zero resistance ammeter. If a solid (Teflon) disc is used, an agar salt bridge is inserted through the utility port of each half-cell to maintain electrolytic continuity. In such a chemically separated environment, the biologically controlled mechanisms for corrosion can be evaluated, including, but not limited to differential aeration, acid production, or entrapment of metallic cations.

Biofouling and corrosion studies of a copper-nickel alloy

Abstract: The marine biofouling and corrosion of Kunifer 10 (10% Ni, 1 5% Fe, copper alloy), was studied using a combination of analytical techniques including x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDXA) and electron microscopy Particular emphasis was placed on the very early stages of fouling, although the study continued until a climax community of macrofouling organisms had become established Dissolved organic matter (DOM), was successfully extracted from seawater by ultrafiltration and chloroform-emulsion separation The collected materials were partially characterised using fourier transform infrared spectroscopy (FTIR) and standard chemical analyses Extracted materials were found to be mainly carbohydrate in character, with lesser quantities of protein The FTIR investigations indicated considerable seasonal variation in the extracted DOM XPS proved to be a suitable technique to investigate the development of marine organic and inorganic films that form on the alloy Adsorbed organic macromolecules exhibited a characteristic spectral "fingerprint" The effect of elevated DOM on the corrosion behaviour of the Kunifer 10 alloy was investigated, using DC and AC impedance electrochemistry Studies indicated that a temporary loss of passivation occurred in the presence of DOM under transient oxygen conditions The development of organic layers on the alloy was shown to influence subsequent stages of biofouling, Kunifer 10 coated with elevated levels' of organic extracts was less likely to become fouled by microorganisms, although certain extracts appeared to stimulate the settlement of marine protozoans However, such effects were short lived due to the continual formation of bio/corrosion layers An unusual form of corrosion, not previously documented, is reported and an explanation for the exfoliation of the bio/corrosion films on Kunifer 10 is suggested A range of cupronickel-iron alloys were assessed for their short-term marine biofouling/corrosion performance Of the alloys tested Kunifer 10 showed optimum resistance The study includes a literature review on marine biofouling and corrosion

Inhibition of fouling during washing under basic conditions

Abstract: A method of inhibiting the formation and deposition of fouling materials in a basic solution in the washing of hydrocarbon streams. The method entails adding to the basic wash a sufficient amount of water-soluble sulfite or bisulfite to inhibit fouling due to polymer formation of oxygenated hydrocarbon components.

Method for preventing fouling with marine life

Abstract: PURPOSE: To effectively prevent the fouling with a marine life, by using a bacteriophage having bacteriolytic activity against fouling microorganism, supporting the bacteriophage on a chitosan-based porous formed material and attaching the material to the expected growing part of said microorganism, thereby efficiently contacting the bacteriophage with the microorganism. CONSTITUTION: A bacteriophage having bacteriolytic (bacteriocidal) activity against fouling microorganism is supported on a chitosan having a deacetylation degree of preferably 70W90% and a relatively low molecular weight, i.e. about 10,000W300,000. The obtained chitosan-based porous formed material 3, 4 is attached to a structural member 1 of a seawater-utilizing facility on which the adhesion of a marine life is expected. The microorganism existing in seawater flowing in large volume is made to efficiently contact with said bacteriophage maintained at a high concentration on the expected adhesion surface or thereabout. The fouling with adhesive marine life can be effectively and economically controlled by this process without causing adverse effect on the other microorganisms, animals and plants nor causing secondary pollution such as accumulation in living body. COPYRIGHT: (C)1989,JPO&Japio

Mixed overbase complex antifoulant compositions and use thereof

Abstract: Fouling in oil, gas and petrochemical refining processes is inhibited by adding an effective fouling inhibiting amount of an antifoulant comprising an overbase complex of magnesium oxide, magnesium carbonate, the magnesium salt of a fatty acid and the magnesium salt of sulfonic acids. The invention provides a method of inhibiting fouling in an oil refining process which comprises adding to fouling areas in said process other than the visbreaker unit an effective fouling inhibiting amount of an antifoulant comprising (A) an overbase complex of magnesium oxide and the magnesium salt of a fatty acid and (B) an overbase complex of magnesium carbonate and the magnesium salt of sulfonic acids.

Improved fuel composition

Abstract: An additive package for reducing and/or preventing injector fouling in a multiport fuel injec­tion means is described. The additive package preferably comprises a particularly described amine oxide, one or more particularly described demulsifiers, and a particularly described solvent system.

Improved chromatographic method for determining fouling tendency of liquid hydrocarbons

Abstract: A method for determining the fouling tendency of an asphaltene containing petroleum stream such as crude oil by the use of thin layer chromatography. The chromatogram of a crude oil formed in the presence of an asphaltene antisolvent which exhibit a fouling tendency developed a distinct, dark ring or disk.