Showing papers on "Fouling published in 1988"

Fouling Science and Technology

Abstract: 1. Fundamentals and Economics.- General Fouling Problems.- General Thermal Fouling Models.- The Economics of Fouling.- 2. Monitoring Equipment.- Liquid Fouling Monitoring Equipment.- Gas-Side Fouling Monitoring Equipment.- Monitoring Fouling using a Novel Technique.- 3. Adhesion.- Adhesion and Removal of Particles - I.- Adhesion and Removal of Particles - II.- Aspects of Cell Adhesion.- 4. Particulate Fouling.- Particulate Fouling of Heat Transfer Surfaces: Mechanisms and Models.- Stochastic Model for the Induction Step on Particulate Fouling.- Fouling by Aqueous Suspensions of Kaolin and Magnetite: Hydrodynamic and Surface Phenomena Effects.- Gas Side Fouling.- 5. Biological Fouling.- Biological Fouling: Basic Science and Models.- Effect of Design and Operating Variables on Biofouling.- Surface Bound Biocides - A Novel Possibility to Prevent Biofouling.- Experimental Investigation of Marine Biofouling and Corrosion for Tropical Seawater.- 6. Crystallisation Fouling.- Crystallisation Fouling - Basic Science and Models.- Deposition of Hardness Salts.- Crystallisation of Organic Materials.- Fouling of Cryogenic Liquids.- 7. Chemical Reaction Fouling.- Basic Science and Models of Reaction Fouling.- Chemical Reaction Fouling of Heat Exchangers.- Fouling from Light Hydrocarbons on Metal Surfaces.- Fouling of Catalysts: Industrial Examples.- The Fouling of Catalysts by Deposition of Filamentous Carbon.- Droplets and Filaments: on the Fouling of Metal Surfaces by Carbonaceous Material from Hydrocarbon Gases above 850K.- Carbon Limits in Steam Reforming.- Carbon Deposition in Steam-Cracking.- 8. Design and Operation of Heat Exchangers.- Basic Relationships for Heat Exchangers and Impact of Fouling on Design.- Selection of Heat Exchangers.- General Design of Heat Exchangers for Fouling Conditions.- Basic Concepts in Heat Exchanger Network Modelling.- The Fouling of Heat Exchanger Networks.- Compensating for Fouling in Heat Exchanger Networks.- 9. Food Processing Fouling.- Fouling by Milk and Dairy Product and Cleaning of Heat Exchange Surfaces.- On-Line Measurement of Fouling and Cleaning of Industrial UHT Exchangers.- 10. Fouling in Industrial Water Systems.- Effectiveness of Biocides.- Case Study-Clean-up of a Coke Oven Cooling System.- Corrision Fouling: Liquid Side.- Avoiding Fouling and Corrosion in Water Cooled Heat Exchangers: The Expert System Approach.- Fouling of Geothermal Energy Systems.- Geothermal Water Scaling in Heat Exchangers.- 11. Fouling in Furnaces.- High Temperature Fouling: The Nature of Deposits.- High Temperature Gas-Side Fouling Case Study.- 12. Discussions.- Cooling Water Fouling - Summary of Discussion.- Debate: Food Processing Fouling.- Cleaning of Fouled Surfaces: A Discussion.- Chemical Reaction Fouling Debate.- Debate on Gas-Side Fouling.

Particulate Fouling of Heat Transfer Surfaces: Mechanisms and Models

Abstract: In the present context particulate fouling is defined as the accumulation of solid particles suspended in a fluid onto a heat transfer surface. Some of the mechanisms which occur are similar to those which govern the fouling of membranes or filters. Unlike filtration surfaces, however, heat transfer surfaces are more often parallel than perpendicular to the flow. Furthermore, the presence of temperature gradients near a heat transfer surface can perturb the isothermal fouling mechanisms as well as introduce additional particle transport mechanisms, thereby drastically modifying the rate and extent of fouling.

Behaviour of 90–10 cupronickel in sea water

Abstract: During the past 50 years, the 90–10 iron modified cupronickel alloy (CA706) has been developed extensively for marine and offshore applications It has proved to have good corrosion, erosion–corrosion, and fouling resistance to sea water The behaviour and protection mechanism of the alloy in these environments has been the subject of many detailed studies under various conditions, ie differing flow velocities, temperatures, pH values, compositions of sea water, and many other factors This review has been compiled by consulting hundreds of references on the properties and behaviour of this alloy It provides a sufficient and unique guide for materials specialists, corrosion technologists, and engineers in the evaluation and use of this alloy in marine environments: it is fully referenced to allow a quick access to the relevant literature

Study of the fouling of a mineral microfiltration membrane using scanning electron microscopy and physicochemical analyses in the processing of milk

Abstract: Soluble proteins and Ca and P salts in the fouling deposit on a mineral microfiltration membrane obtained in static conditions were analysed and compared with those found using dynamic filter conditions in a laboratory pilot installation for milk processing. The serum milk proteins were retained by the porous micellar deposit under both static and dynamic conditions, resulting in progressive fouling of the dynamic micellar membrane, enabling milk to be processed with a mineral microfiltration membrane. Ca and P salts increased fouling probably by allowing better adsorption of casein micelles on the alumina and by acting as intermicellar bonds in the deposit. Fat globules modified porosity, permeability and resistance to matter transfer of the deposit. The dynamic conditions gave a deposit of the same type and structure as with the static conditions although made thinner by the velocity effect.

Evaporation of liquids with dispersant added

Abstract: A vertical tube evaporation process for the concentration of saline water and other liquids, including the addition of an anionic mono-molecular dispersant thereto which interacts with materials precipitated during concentration and inhibits the formation of scale or fouling depositions on evaporator surfaces, and wherein the additive is incorporated into the precipitated materials and improves their removal during the descaling or defouling of evaporator surfaces by rendering such precipitates redispersable in fresh water or in a non-saturated liquid used for descaling or defouling of evaporator surfaces.

The Economics of Fouling

Abstract: Fouling was for long considered by many to be an ‘act of God’. The simple theological implications of this view are that fouling is (a) beneficial, and (b) unavoidable, while the legal implications suggest that since no mortal can be held responsible, no damages can be sought as a result of losses attributable to fouling. No apology is therefore required for introducing the devil at this stage. Fouling, treated as an unwanted deposition of materials on surfaces, is not beneficial, and although it may not be completely avoidable, both it and its effects can be reduced.

General Design of Heat Exchangers for Fouling Conditions

Abstract: Not all heat exchangers have serious problems with fouling. Many operate satisfactorily for long periods without being cleaned. Garret-Price et al. [1] assembled Table 1 which identifies the kind and typical extent of fouling for fluids in various industry groups. This is useful in determining which heat exchangers must seriously consider fouling when they are being designed.

Fouling by Milk and Dairy Product and Cleaning of Heat Exchange Surfaces

Abstract: Among processes of food engineering, heat transfer plays a key role. The use of heat exchangers is of such frequent occurence that they appeared in every step of industrial transformations and underwent a constant evolution. Different kinds of equipment, corresponding to specific use conditions according to concerned fields of using are available, among which, just to mention the best known ones: tubular exchangers, shell an tubes exchangers, plate heat exchangers, spiralflow exchangers, scraped surface exchangers and platular exchangers. Their function will be to transmit heat flux to one or between two fluids according to a given thermal specification. The principles of heat transmission are conduction, convection, evaporation, condensation and radiation, whatever the state of the involved fluids (gaz or liquid state) or changing phase in course of treatment. However, while flow and heat transmission in exchangers are now well-known phenomena in the simplest cases, fouling of surfaces remains one of the major problems not yet completely solved (47). This is especially true in the case of food liquids containing thermosensitive compounds such as milk, for example. Thus, in dairy industry, special attention and constant care are focused on thermal treatments and especially on sterilization processes.

Asphaltene precipitation primary crude exchanger fouling mechanism

Abstract: Research at Exxon Chemical Co. has shown that asphaltene precipitation and subsequent carbonization is the major mechanism in crude oil heat exchanger fouling. Exchangers that foul frequently must be cleaned on a regular basis. In the worst case, furnace-limited refiners may have to cut crude-charging rates as preheat fouling reduces coil inlet temperatures. To improve operation and control these costs, many refiners invest significant amounts of money in antifoulant programs. A new way to characterize crude oil fouling tendencies, Exxon's AFC fouling index has been developed. Two examples of how refiners can improve the cost effectiveness and performance of their antifoulant programs by using the index are presented in this article, along with the general methods used to control fouling.

Assessment of corrosion and microfouling of several metals in polluted seawater

Abstract: It has been widely acknowledged in the literature that fouling of metal surfaces in contact with seawater is the main cause of several technical problems and economic loss in industry. Corrosion of metal surfaces is one of the principal events affecting the performance of structural metals. Copious literature is available with reference to fouling initiation and progression on metal structures immersed in the marine environment. Nevertheless, the information on the relation of fouling to corrosion is by no means complete. Previous attempts to correlate fouling with corrosion of the metal base have generally been made under conditions when important biomass had already accumulated. It is important to emphasise that corrosion and fouling of metals exposed to seawater occur within the same time scale, beginning immediately after the immersion of the specimens in the aqueous environment. The aim of this paper is to assess comparatively the corrosion behaviour of several metal surfaces in contact with polluted harbour seawater during the early stages of microfouling formation. The effect of the length of exposure of the metal samples, their surface finish, and the degree of water pollution on microbial settlement were examined by scanning electron microscopy (SEM). Corrosion of the metal substrate was studied in the laboratory by means of potentiodynamic polarisation experiments and open circuit records in artificial and natural filtered seawater. In situ measurements of open circuit potentials were made with metal samples placed in the water supply intake of a power plant. In both cases, SEM observations were complemented with energy dispersive x-ray analysis (EDXA) of corrosion products. The results obtained with the different solutions used in this paper may warn against conclusions drawn from laboratory experiments made with membrane-filtered seawater or artificial solutions used to replace in situ measurements with natural seawater.

Factors affecting fouling of an inorganic membrane during sweet whey ultrafiltration

Abstract: Summary The effect of sweet whey concentration and composition on fouling was studied during ultrafiltration at 50 "C through an inorganic membrane (Carbosep M4 type). The experimental variations in the course of time of flux, protein rejection and membrane resistance were analysed for several solutions and operating conditions. It is likely that protein adsorption and convective deposition of particles of solid matter are involved in membrane fouling by whey. Both phenomena occured at the very beginning of the ultrafiltration run. Their respective extent and kinetics depended on whey composition and concentration as weil as on operating conditions. The effect of several whey components on membrane fouling was also shown : soluble proteins, suspended particules, residual fat, calcium salts precipitating during ultrafiltration. Moreover, protein rejection was related to fouling type and operating conditions. The results obtained with concentrated wheys should lead to an improvement of operating conditions in a three-stage ultrafiltration plant. A compromise solution between high fluxes and high protein rejection must be choosen to limit protein losses since the membrane is only partly retentive for whey proteins.

Blending of hydrocarbon liquids

Abstract: Crude oil (one of which is a high fouling crude oil) are blended to maintain the incompatible asphaltene thereof below a predetermined level thereby reducing the fouling tendency of the high fouling crude oil. Paraffinic liquids, LPG's, and condensates may also be blended with crude oil, while monitoring and controlling incompatible asphaltenes thereof.

Crystallisation Fouling — Basic Science and Models

Abstract: One of the common ways in which heat exchangers, or other pieces of equipment for that matter, become fouled is through the process of crystallisation. It usually involves aqueous solutions of soluble salts, which are either being heated or cooled. For this reason cooling water systems are often prone to crystal deposition, due to hardness salts, the problem being more acute where the dissolved solids content is high.

General Thermal Fouling Models

Abstract: If we describe the progress of a thermal fouling process by a plot of thermal fouling resistance, Rf, against time, t, then the three upper curves of Figure 1 represent the most common and primitive, though not the only, configurations observed in practice. These are designated linear, falling rate (non-asymptotic) and (falling rate) asymptotic, respectively. A delay period, tD, is often, but not always and not consistently, observed before any appreciable fouling is recorded after starting an experiment or a process with an apparently clean heat transfer surface. The delay period is frequently much less reproducible than the subsequent fouling curve. The cleanliness of the initial heat transfer surface can be a crucial factor. Thus the presence of a measurable delay period in Figure 2 for the upper heater but none for the spare heater is probably related to the fact that the former was reported by the operator to be in a cleaner condition than the latter at time zero [1].

Comparison of indices for the scaling and corrosion tendency of water

Abstract: Three commonly used fouling indices to characterize the scaling and corrosion tendencies of water, namely the Saturation Index, the Langelier Saturation Index and the Ryznar Stability Index, have been compared and checked for consistency. While the first two indices give similar results, major deviations between the predictions of saturation and stability indices were found.

Method and apparatus for conducting fouling tests

Abstract: This invention relates to a laboratory device which produces a fouling deposit, under controlled temperature and pressure, which reproduces actual plant conditions, and accurately measures the deposit of foulant accumulated during the deposition process. The device is utilized for testing the fouling tendencies of a wide variety of fluids which change on contact with a hotter surface, forming a solid or semisolid deposits which stick to the surface. The apparatus has the capability of calibration and measurement of the probe temperature and temperature measurement changes with fouling, and may be advantageously related to the amount of fouling present. The apparatus includes multiple probes each removably supporting test wires which are electrically heated to selected temperatures for simultaneous multiple fouling tests by a constant heat flux or to a constant temperature.

Non-fouling liquid nitrogen cooled polymerization process

Abstract: A non-fouling economical liquid cooled cryogenic polymerization process is disclosed for essentially olefinic monomers. The heat of cooling and polymerization is removed by evaporation of the liquid nitrogen and the nitrogen vapors eliminate the need for moisture traps and drying agents to block the in flow of said moisture.

Biofouling in oilfield water systems - a review

Abstract: The literature on biofouling in oilfield water systems is reviewed and the implications of such fouling considered. The currently available methods for the detection and control of the causative organisms are also discussed.

Non-biocidal Anti-fouling Coatings

Abstract: The dry weight of fouling on raft panels coated with silicone elastomers (low energy surfaces) has been measured at two-monthly intervals for one year A flow cell is described for testing the adhesion of slimes to raft panels: Results on removal of slimes from silicone elastomers and formica are discussed

Silica Fouling of Heat Transfer Equipment—Experiments and Model

Abstract: Silica fouling of heat transfer equipment in geothermal energy systems is studied. The effects of temperature, pH, and salinity on silica solubility and silica polymerization are reviewed. Experimental fouling data are presented for geothermal brines with different pH values, chemical compositions, and thermal-hydraulic conditions. The effects of supersaturation, pH, Reynolds number, and the concentration of ions in the brine solution on the formation of silica scale in the heat exchanger tube are discussed. A silica deposition model is proposed that accounts for supersaturation, pH factor, salinity, and thermal-hydraulic effects. Results based on the analytical model are compared with silica fouling data are obtained in the laboratory as well as from two geothermal fields.