This article reports the application of a new method in identifying the accumulated sludge deposits (e.g., oily sludge, water sludge, and filter sludge). The method is an excellent approach for identifying the inorganic materials found in sludge deposits generated in refineries and gas plants. The phase identification and quantification on inorganic material in the form of corrosion products are important to facilitate chemical cleaning and prevent the reoccurrence to stop the generation of sludges. Therefore, the authors developed a new method to separate the inorganic materials from the hydrocarbon of the as-received sludge samples from the fields. When the sample preparation was taken with great care, the results revealed that this method is fast and can accurately identify very small quantities (>0.5 wt%) of sludge deposits present in the sample. Additionally, if the color of the dichloromethane soluble part collected is changed, it indicates the presence of hydrocarbon in the sludge. Thermal gravimetric analysis results revealed that the sludge contained approximately 3 wt% of inorganic compound, 25 wt% of water, and 72 wt% of hydrocarbon. Subsequently, gas chromatography mass spectrometry analysis results revealed that the type of hydrocarbon was diesel with the C10–C27.
Sludge deposits are the semisolid mixture and formed by the combination of liquid (e.g., oil and water), hydrocarbon (e.g., grease and lubricant), and nonhydrocarbon or inorganic compounds of solids [
The schematic diagrams of the sludge samples used in this study are (a) oily sludge, (b) soft sludge, (c) water sludge, (d) dry oily sludge, (e) filter sludge, and (f) dry soft sludge.
In this paper, a new method was developed in separating the nonhydrocarbon or inorganic materials from the hydrocarbon parts of the accumulated sludge deposits (e.g., oily sludge, water sludge, and filter sludge) in refineries and gas plants. For example, a known quantity of sludge deposits was taken in a beaker and dried in a fume hood for 2 to 3 days for water-based sludge. Figure
(a) The schematics of dichloromethane, filtration assembly, mortar pestle, filter paper, beaker, spatula, and container. (b) Phase identification results of sludge deposit collected from the NG line, where the methylene chloride was insoluble.
XRD peaks are produced by constructive interference of a monochromatic beam of X-rays scattered at specific angles from each set of lattice planes in a sample [
When all the phases are identified accurately, the Rietveld method [
The main objective of this laboratory-based study was to develop a method that can identify precisely the sludge deposits that align with the need of XRD applications in refinery and gas plants. When the sample preparation was taken with great care, this new method is fast and accurate to identify more than 40 samples from the refineries and gas plants, which are very small quantities (>0.5 wt%) of corrosion products, scale deposits, inorganic additives, and so forth, in sludge deposits.
To fulfill the above objectives, in the present study, the authors developed the new method and assessed it experimentally on the various sludge samples, Figure
Listed here are the new methods in sample preparation to identify the accumulated sludge deposits from refineries and gas plants and assessed it for each of the as-received sludge samples: For the water-based sludge, a known quantity of sludge was taken in a beaker and dried in a fume hood for 2 to 3 days. For sulfur analysis, it is a must to analyze samples without any pretreatment. For oil-based sludge, it was treated with dichloromethane and then filtered in the filtration assembly, Figure The dichloromethane insoluble part (i.e., inorganic materials or nonhydrocarbon) was analyzed by XRD for inorganics, Figure The dichloromethane soluble part (i.e., hydrocarbon) was analyzed by gas chromatography mass spectrometry, Figure
The treated samples previously described in the sample preparation procedures were manually ground by an agate mortar and a pestle for several minutes to achieve a fine particle size [
In this article, the authors used the software package PANalytical High Score Plus (X’Pert High Score Plus Version 2.2c PANalytical Inc.), combined with the ICDD of the PDF-4+ database of the standard reference materials to determine the phase identification of the XRD data of the crystalline materials at the treated sludge samples. Subsequently, the Rietveld method was used to refine whole XRD patterns for the phase composition analysis [
To assess further the new method, the authors particularly investigated the unknown black sludge deposit that was found in the diesel oil tank in a refinery, a case study. Figure
The schematic of the unknown black sludge deposit that was found in the diesel oil tank in a refinery: (a) the as-received sample, (b) dichloromethane insoluble, and (c) dichloromethane soluble.
Figure
XRD data of the sludge sample: (a) as-received (i.e., mix between the amorphous with the small addition of crystalline materials) and (b) after removing the hydrocarbon (i.e., inorganic materials).
(a) The thermal gravimetric analysis and (b) gas chromatography mass spectrometry results.
The hydrocarbon appeared in the sludge deposits because the color of the dichloromethane soluble part collected was changed. Therefore, the wt% of hydrocarbon and water and the type of hydrocarbons were determined by thermal gravimetric analysis and gas chromatography mass spectrometry, respectively. Figures
The application of the new method has been extended to identify 40 sludge samples. Table
Summary of sludge chemical compounds obtained from High Score Plus.
The identified compounds | Nature |
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Barite-BaSO4 | Drilling mud |
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Quartz-SiO2 |
Formation material, normally found in the sandstone or sand |
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Illite-K0.5(AlFeMg)3(SiAl)4O10(OH)2 | Clay minerals normally found with sandstone |
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Magnetite-Fe3O4 |
Corrosion product: at high temperature magnetite corrosion products it will coat the iron/steel to prevent oxygen to reach underlying metal. Mostly, at low temperature lepidocrocite formed and with time it transformed into most stable goethite. Akaganeite formed in marine environments |
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Basanite-CaSO4⋅2H2O |
Sulfate scale |
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Ettringite-Ca6Al2(SO4)3(OH)12 | Cementing material |
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Aluminum Oxide-Al2O3 | Normally from catalyst |
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Gregite-Fe3S4 |
Corrosion products: pyrophoric iron sulfide (pyrrhotite-FeS) results from the corrosive action of sulfur or sulfur compounds (H2S) on the iron (steel) and moisture |
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Sulfur-S | |
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Sodium Iron Oxide-NaFeO2 | |
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Calcite-CaCO3 | Carbonate scale |
Aragonite-CaCO3 | |
Siderite-FeCO3 | |
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Iron Chloride-FeCl3 | Chloride corrosion products |
Iron Chloride Hydrate-FeCl2-4H2O |
Phase identification results of the scale sample from crude booster pump: (a) the as-received and (b) after removing hydrocarbon along with the standard reference minerals for halite (NaCl), thermonatrite (Na2(CO3)H2O), and natrite (Na2(CO3)).
XRD phase identification results along with the standard reference mineral. (a) The as-received, crude distillation column bottom pump consists of halite [NaCl]; (b) the sludge, which shows the hydrocarbon peak. Here hydrocarbon is dissolved in methylene chloride.
Crude distillation column bottom pump
The hydrocarbon materials
XRD phase identification results along with the standard reference minerals of the sulfur from the (a) sludge and (b) recovery unit line.
XRD phase identification results along with the standard reference mineral. (a) The sulfur recovery unit 1 and (b) the residue soft deposit sample after thermal gravimetric analysis along with the identified phases, halite [NaCl], periclase [MgO], silicon oxide [SiO2], and sulfur.
It can be seen from Figure
Figure
Based on the findings from this new sample preparation method, the following conclusions can be drawn: The new method is an excellent technique for identifying the inorganic materials found in sludge deposits generated in refineries and gas plants. When the sample preparation was taken with great care in the present study, this method is fast and can accurately identify very small quantities (>0.5 wt%) of corrosion/scale deposits, inorganic additives, chemicals, catalysts, formation materials, clay minerals, and drilling muds present in the sample. If hydrocarbon appeared in the sludge deposits, the color of the dichloromethane soluble part collected was changed. Thermal gravimetric analysis results revealed that the sludge contained approximately 3 wt% of inorganic compound, 25 wt% of water, and 72 wt% of hydrocarbon. Gas chromatography mass spectrometry analysis results revealed that the type of hydrocarbon was diesel with the C10–C27.
The authors declare that there are no conflicts of interest regarding the publication of this paper.
The authors would like to acknowledge the management of Saudi Aramco for permission to publish this article.