Formation Of Organic Deposits Research Articles

Factors affecting deposit formation in foul condensate stripping systems

In kraft pulp mills, foul condensates are often steam-stripped to produce clean condensate for use as process water. The formation of organic deposits in the stripped condensate is a common problem. A systematic study was conducted to examine the deposit composition and the most likely operating parameters responsible for stripped condensate contamination experienced at a kraft mill in Brazil. Daily averaged data of 170 operating parameters over a 15-month period were analyzed by means of multivariate discriminant analysis and random forest classification analysis. The results showed that the deposit formation is related to high temperature, pressure, and dry solids operations in various evaporator effects. These conditions, combined with the poor demisting efficiency in these effects, may have increased black liquor carryover mist in the vapor. Deposit formation also appeared to be related to increased throughput of the foul condensate stripping system and increased pressure in the stripper. Results of Fourier transform infrared spectroscopy (FTIR) and pyrolysis-gas chromatography mass spectrometry (Py-GCMS) analyses show that the deposit consists of mostly organic matter that likely originated from wood extractives and lignin.

Influence of mechanical impurities composition on formation of organic deposits

Relevance. The need to study the effect of solid particles in the oil stream on formation, composition and structure of deposits. Modern models of formation of asphalt-resin-paraffin deposits, based on correlation dependencies or empirical data, do not take into account the influence of the content of solid particles in oil to the proper extent. Recent studies show that various solid particles in oil can affect both the critical velocity and the structure of the formed deposits, but the effect of various particles on the intensity of formation of asphalt-resin-paraffin deposits remains unexplored. Aim. To study the effect of various sand fractions on the intensity of formation, composition and structure of asphalt-resin-paraffin deposits Methods. Modeling of formation of asphalt-resin-paraffin deposits at the laboratory installation “Cold Finger” when adding various sand fractions to oil; studying composition and structure of deposits after the conducted investigations using a microscope. Results. According to the research results, there is a significant increase in the intensity of formation of asphalt-resin-paraffin deposits when large fractions of sand are added to oil at a concentration of 5% or higher. It is worth noting that small fractions have almost no effect on the amount of deposits formed. Also, if various fractions are added to oil in equal proportions, there is almost no effect on the intensity of formation of asphalt-resin-paraffin deposits. When analyzing the deposits images from a microscope, it can be concluded that paraffin molecules, when interacting with sand particles of a dimension greater than 0.05 mm, form homols, and with an increase in the fraction, their structural strength grows. Conclusions. The study of modern models of formation of asphalt-resin-paraffin deposits and current articles made it possible to understand that the issue of studying the factors of formation of asphalt-resin-paraffin deposits, in particular the effect of the presence of solid particles in oil, remains open. The results of this article can be aimed at improving existing technologies in the field of modeling paraffin formation, as well as contribute to the further work of researchers in this direction.

Formation of Organic Deposits in Model Petroleum Systems

The formation of organic deposits in model petroleum-containing systems of various compositions has been studied. Introduction of asphaltene–resin substances into a model paraffin system reduces the amount of precipitated wax deposit to 40 wt %; significantly changes the ratio of liquid and solid hydrocarbons in the n-alkane composition of the deposits, shifting the distribution maximum towards a lower molecular weight; and substantially reduces the mechanical strength. In the model paraffin system in the presence of resins and asphaltenes, which contain a greater amount of condensed aromatic structures and a smaller amount of paraffin structures, a precipitate is formed with an increased proportion of the liquid phase. The deposits are characterized by lower strength of the crystal lattice and, hence, a decreased value of ultimate shear stress.

Formation of organic deposits on low-preassure reverse osmotic membranes in treating water from surface sources

Introduction. In this paper, we investigate the interaction of organic pollutants with nanofiltration and reverse osmosis membranes in natural water on the basis of experimental data and available literature information. The rates of formation of various organic deposits (humic acids changing the water colour and forming low-molecular organic compounds characterised by an oxidation index) on membranes during purifying river and pre-treated water are presented.
 Aim: To determine the required efficiency of removing organic substances from surface waters at the pre-treatment stage prior to water treatment by reverse osmosis on the basis of measuring the rates of adsorption of organic substances on membranes and predicting the amount of as-formed organic deposits.
 Methods and materials. Methods for determining the adsorption rate of organic pollutants using gas-liquid chromatography and total carbon determination are described. The advantages of spectrogram analysis in assessing water quality are specified. The formation rates of high- and low-molecular organic substances, which produce colouring and characterise water oxidisability, respectively, were determined using a membrane test unit.
 Results. According to the rates of forming organic deposits on membranes both during the processing of river water with a colour of 60 PCU and purified (tap) water with a colour of 18 PCU, organic substances adsorbed on membranes are shown to have little effect on the efficiency of the reverse osmosis process. In addition, the rate of depositing organic substances on the membranes under study is established to be significantly lower than that using sparingly soluble salts (calcium carbonate).
 Conclusion. Our results demonstrate that organic deposits formed on the membranes under study have an insignificant effect on the membrane performance. Therefore, pre-treatment aimed at removing organic substances when purifying natural waters with colour indices of up to 60 PCU is not required.

Effect of electroconvection and its use in intensifying the mass transfer in electrodialysis (Review)

The modern concepts on the origin of electroconvection (EC) are surveyed briefly and the known mechanisms of this phenomenon are classified. Factors that influence the EC character and intensity at the surface of ion-exchange membranes are analyzed, such as electrical and geometrical heterogeneity of the membrane surface, its degree of hydrophobicity, and the surface charge. The EC mechanism is shown also to depend on the applied potential difference and the rate of solution flow between membranes. The mechanism of the EC-induced gain in the mass transfer is elucidated, the possible gain in the mass transfer is estimated, and the prospects for using the EC for reducing the membrane fouling caused by sedimentation and formation of organic deposits are assessed.

Laboratory Investigation of Organic-Scale Prevention in a Russian Oil Field

Summary The objective of this research is a definition of wax-precipitation conditions in waxy oil (a kind of oil that intends to produce high-molecular-weight paraffins during production) at various thermobaric conditions taking place in oil wells, and also proposing a method for the determination of the potential wax-formation depth in a well. In most cases in Russia, many reservoirs are producing oil with high asphaltenes, resins, and wax content that causes the formation of organic deposits in downhole equipment. It reduces the workover period of wells and decreases their productivity. The oil-production system represents the sensitive hydrodynamic system, so any changes in well operational parameters, thermobaric conditions, and oil composition lead to wax and asphaltenes precipitation in oil. Natural surfactants (asphaltenes) stabilize water-in-oil emulsions and change rheological properties of the borehole flow. It demands additional energy consumption for raising reservoir fluid to the surface and for transporting it to gathering and oil-treatment systems. All laboratory experiments are conducted by use of conventional (standard) techniques. The grain-size-analysis microscopy was performed under high-pressure conditions. Also, a light-scattering method and viscometric analysis were performed, and functional wax-appearance temperature (WAT) vs. the pressure of live and degassed oil are carried out during experimental studies. The results of our experiments showed that, when the pressure drops below the bubblepoint pressure and the gas starts coming out from the oil, the WAT increases. A significant increase in the viscosity of a live-oil sample with a decrease in temperature and pressure in the range of downhole conditions that can become the reason of decline in the performance of an electrical submersible pump (ESP) is noted. The most technological methods directed on drop in the presented risks—among which are offered (1) the change of well-operation conditions allowing the regulation of the waxing of tubings and (2) the application of inhibitors that demonstrated high efficiency during the laboratory investigations—are mentioned. Mathematical analysis showed that the increase in well flow rate promotes a considerable decrease in potential wax-formation depth in an oil well. The proposed assessment technique of wax-precipitation depth that has been performed in this work can be useful for selecting the well-operation system. Among the studied inhibitors, the experiments showed that Inhibitor A has the highest efficiency in the slowing of the wax-formation process in the borehole conditions.

К ВОПРОСУ ОПРЕДЕЛЕНИЯ ТЕМПЕРАТУРНОГО РЕЖИМА ТРУБОПРОВОДОВ СИСТЕМЫ НЕФТЕСБОРА

The relevance of the task of examining such characteristics of protective coatings, as sedimentation, corrosion and heat resistance, is demonstrated. Protective coatings must be selected considering the temperature that affects their thermal resistance, so that the costs of carrying out various activities in order to remove organic sediments are reduced. The results of constructing a computer program to determine the temperature change of oil along a specified length of pipeline, for the sake of selecting the optimum type of protective coating to prevent corrosion and formation of organic sediments, are presented. The results of calculating the temperature distribution under given conditions and the length of the pipeline using the computer application “Automated system for calculating thermodynamic flow parameters” developed at the department “Development and operation of oil and gas fields” of the Almetyevsk State Oil Institute show the reasonability of applying protective coatings not only for the purpose of protection from corrosion and formation of organic deposits, but also to reduce the cooling rate of pumped oil products through the pipelines of oil-gathering system. The developed computer program allows to model the temperature conditions of pipelines in order to select the optimal coating system, taking into account the aspects that complicate transportation of oil and oil products.

Effect of pressure on the performance of poly(ethylene‐vinyl acetate) as wax deposition inhibitors by calorimetric method

AbstractChemical inhibition is one of the traditional methods used by the petroleum industry to prevent or correct the problems caused by the formation of organic deposits. In this work, three samples of poly(ethylene‐co‐vinyl acetate)s (EVAs) were added at different concentrations to three different Brazilian crude oils, and their effect on the wax appearance temperature (WAT) and crystallization enthalpy of the oils was evaluated as a function of increasing pressure and the type of saturation gas, using high‐pressure microcalorimetry (HPμDSC). The results show that different copolymer compositions present dissimilar performance in reducing WAT, and, in some cases, an optimum concentration was observed. When rising pressure, a positive influence on the WAT is observed, but the performance of organic deposition inhibitors that are ineffective at atmospheric pressure is not enhanced at higher pressures. On the other hand, additives able to modify the crystallization kinetics of waxes at atmospheric pressure show a synergy when evaluated in the presence of light fractions and under high pressures. HPμDSC analysis is an important tool to optimize the additive concentration to be used in oil fields. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Holocene vegetational and coastal environmental changes from the Lago Crispim record in northeastern Pará State, eastern Amazonia

Vegetational and coastal environmental changes have been interpreted from a 600 cm long and 7640 14C yr B.P. old sediment core from Lago Crispim located in the northeastern Pará State in northern Brazil. The radiocarbon dated sediment core was studied by multi-element geochemistry, pollen and charcoal analysis. Holocene Atlantic sea-level rise caused an elevation of local water table, which allowed the formation of organic deposits in a probably former inter-dune valley. Dense, diverse and tall Amazon rain forest, and some restinga (coastal vegetation) covered the study area at the beginning of the record at 7640 14C yr B.P. Mangrove vegetation developed along rivers close to the core site at that time. Subsequent decrease in less mangrove vegetation near the study site indicates a sea-level regression, beginning since around 7000 14C yr B.P. Lower sea-levels probably favoured the formation of a local Mauritia/Mauritiella palm swamp at 6620 14C yr B.P. Oscillations of higher and lower sea-level stands probably changed the size of the local palm swamp area several times between 6620 and 3630 14C yr B.P. Sea-level transgression at around 3630 14C yr B.P., caused marked coastal environmental changes: the development of mangroves near the site, the replacement of the local palm swamp by a Cyperaceae swamp, the substitution of the surrounding former Amazon rain forest and some restinga vegetation mainly by salt marshes. High amount carbonised particles suggest a strong human impact by burning on the coastal ecosystems during this late Holocene period. Highest concentrations of NaCl and also Ca, Mg and K in the upper sediment core indicate that the Atlantic was close during the late Holocene period. The core site, which is today 500 m from the coastline and only 1–2 m above modern sea-level, was apparently never reached by marine excursions during the Holocene. Less representation of mangrove since ca. 1840 14C yr B.P., may be related due to a slightly lower sea-level or to human impact in the study region. The modern shallow lake seems to be formed recently by road construction, forming an artificial dam.