ISSN:0145-7632    

DOI:10.1080/014576300270834

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

An analysis was performed to determine the effects of fouling of the preheat train on the energy efficiency of a typical crude-distillation unit with a capacity of 100,000 bbl/day. A spreadsheet analysis was developed to calculate the thermal duty for each of the heat exchanger groups that heat the crude oil from ambient conditions to the distillation temperature. A fouling-rate model developed in a previous study was applied to calculate the fouling resistance as a function of time. Improvements in the energy efficiency were analyzed for different mitigation scenarios. The analysis shows economic incentives for new and improved techniques for mitigating fouling of the preheat train.

ISSN:0145-7632    

DOI:10.1080/014576300270843

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Petroleum stability effects on heat exchanger fouling were studied using mixtures of heavy oil containing asphaltenes, and carrier fluids consisting of a fuel oil cut with varying amounts of added aliphatic or aromatic fluid. Fouling was measured in a recirculation loop using an annular, electrically heated probe. The effects of carrier fluid composition, dissolved oxygen, and heteroatomic species additions were investigated. Insolubles formed in the mixtures, measured by hot filtration, and deposits on the probe had compositions similar to asphaltenes. Fouling rates were correlated with instability indices, and with the concentrations of suspended asphaltenes.

ISSN:0145-7632    

DOI:10.1080/014576300270852

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Crude oil fouling in a laboratory fouling unit was investigated. The study focused on the preheat-train heat exchangers located just before the crude unit furnace and operating at temperatures in excess of 200C. A fouling rate model developed using laboratory data from crude blends was used to predict the threshold conditions where negligible fouling was expected under refinery conditions. The results from the model were compared to actual data from a fouling unit located at a refinery. The article discusses factors that may explain the performance of the model and the observed discrepancies between fouling data obtained in the laboratory and the field.

ISSN:0145-7632    

DOI:10.1080/014576300270861

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Though it is of great importance, the majority of predictive models tend not to incorporate water chemistry in their formulations. The ionic diffusion model which was developed for CaCO3, is based purely on crystallization, and is one of the few models that incorporates water chemistry. This model does not provide satisfactory predictions for CaSO4fouling. In this article, a new model is proposed for CaSO4fouling which takes into account the effect of both crystallization and particulate fouling and is capable of predicting the fouling resistance during the cleaning cycle as well as the fouling cycle. A removal term is incorporated into the model, as the occurrence of particulate fouling for CaSO4tends to weaken its crystalline structure and makes it more prone than CaCO3to removal. Properties of the electrolyte were evaluated using MINTEQA2 computer code, which is approved by the U.S. Environmental Protection Agency. In this model, particulate fouling is estimated using the physical mechanism for particle transport and adherence, crystallization is estimated by ionic diffusion, and the removal term is approximated using hydrodynamics of flow and deposit properties. The inclusion of both crystallization and removal terms incorporates the effects of both water chemistry and hydrodynamics of the flow and provides a relationship which not only can predict fouling but also can predict dissolution, by change of water quality and/or stopping the operation, or removal by shear stress. The proposed model was assessed using published experimental data. The results indicate that this model provides good predictions: the slope of predicted rates as a function of the experimental rates is 1.05. The experimental results, though limited in number, suggest that crystallization is not the main or only mechanism contributing to CaSO4fouling. Particulate fouling seems to be a major contributor. Further experimentation is in process to confirm the degree of particulate fouling and to substantiate or to modify the model accordingly.

ISSN:0145-7632    

DOI:10.1080/014576300270870

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Recent research on fouling where composite fouling in aqueous media may be present is reviewed. In practical industrial applications, usually several types of fouling occur simultaneously; however, due to the complexity of fouling, various types of fouling are studied in isolation. Crystallization (precipitation) fouling is the most-studied type of fouling. Other types of fouling are studied in various degrees. Not much attention has been paid to the relative significance and the interactive effects of these processes when they occur simultaneously. This is specifically the case for composite inorganic (precipitation and particulate) and biological fouling. In general, there is lack of attention to the presence, mechanism, modeling, and mitigation of composite fouling.

ISSN:0145-7632    

DOI:10.1080/014576300270889

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Experiments have been carried out on a small-scale simulated cooling water system using a monoculture of Pseudomonas fluorescens to represent the slime-forming microbial community, to examine the opportunities for control using ultrasound. Glass tubes (18mm I.D. x 1m long) through which contaminated water flowed at 1 m/s were ?dosed? with ultrasound along the tube axis. Glass tubes were employed to facilitate the use of infrared absorbance for biofilm accumulation assessment. The preliminary results demonstrate that control of biofilm formation and the removal of established biofilms on the inside of tubes may be achieved by the technology, but there may be some limitations with respect to removal.

ISSN:0145-7632    

DOI:10.1080/014576300270898

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The objective of the present study was to examine the effectiveness of four cleaning methods for the removal of tube-side fouling in a double-pipe heat exchanger. The four cleaning methods are (1) hydrolazing with 10,000-psi head pressure, (2) hydrolazing with 20,000-psi head pressure, (3) chemical cleaning, and (4) brush punching. Fouled tubes were prepared using water from a cooling tower. Each test started with a brand new tube. When the overall heat transfer coefficient dropped by 40% from the initial peak value, scales in the fouled tubes were removed using one of the above four methods. Both the overall heat transfer coefficient and inside diameter were measured before and after fouling, by which the effectiveness of a particular cleaning method was evaluated. The chemical cleaning method was found to be most effective, whereas the brush punching was least effective. When a fouled tube was kept dry, brush punching completely removed scales, indicating that surface wetness plays an important role in scale removal.

ISSN:0145-7632    

DOI:10.1080/014576300270906

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

ISSN:0145-7632    

DOI:10.1080/014576300270915

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

ISSN:0145-7632    

DOI:10.1080/014576300270924

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor