Hot Washing Research Articles

Environmental impacts and decarbonization pathways of oily sludge pyrolysis based on life cycle assessment

Oily sludge is a major hazardous waste generated in the petroleum and petrochemical industry. The increasing accumulation of oily sludge necessitates safe and sustainable management. In recent years, pyrolysis has gained great attention as an effective treatment method for oily sludge. However, a comprehensive environmental assessment of industrial-scale oily sludge pyrolysis remains limited. Based on the life cycle assessment (LCA) method, this study employs data collected from oily sludge treatment plants to investigate the environmental impacts of the whole pyrolysis system, specifically its carbon footprint. The utilization and final disposal of pyrolysis products are in accordance with the real industrial operations. The contributions of each unit process in the pyrolysis treatment of oily sludge to global warming potential (GWP), as well as the decarbonization pathways, are explored in detail. Results indicate that, in general, pyrolysis has lower adverse environmental impacts than incineration does. Within the pyrolysis system, processes such as pyrolysis, flue gas purification, and hot washing are major contributors to GWP. The recycling and utilization of pyrolytic oil and solid residues can significantly mitigate the adverse environmental impacts of oily sludge pyrolysis. Given the combined applications of co-pyrolysis, green electricity, and other low-carbon technologies, the carbon footprint of oily sludge pyrolysis could be reduced from 635.9 to 31.8 kg CO2-eq in the most ideal scenario.

The methods for improving the biodegradability of oily sludge: a critical review.

Biological degradation method, as an environmentally friendly, low-carbon, and clean pollution treatment technology, is widely used for the harmless disposal of oily sludge. The biodegradability of oily sludge with stable emulsification system, high oil, and water content is poor. Therefore, it is necessary to pre-treat the oily sludge to improve its biodegradability, including recover the petroleum resources and remove heavy metals and bio-toxic organic matters. This review systematically summarizes five oily sludge treatment methods and their influences on sludge biodegradability, including pyrolysis, chemical hot washing, solvent extraction, chemical oxidation, and hydrothermal. Pyrolysis at temperatures above 750 °C produces high molecular weight polycyclic aromatic hydrocarbons, chemical hot washing and chemical oxidation would cause secondary pollution, solvent extraction method could not be applied due to the high cost and high toxicity of the extractant, and the oil removal of hydrothermal method is inefficient. Additionally, the principles, advantages, and disadvantages of those treatments and the factors affecting microbial degradation were analyzed, which provide the development direction of pretreatment technology to improve the biodegradability of oily sludge.

Feasibility study on the production of low melt flow rate recycled polypropylene from postconsumer waste

AbstractPolypropylene (PP) recyclates face limitations in their use due to lower qualities compared with virgin PP, resulting from contaminations and the mixing of different PP grades. In particular, their high melt flow rate (MFR) hinders their suitability for applications requiring low MFR, such as pipes. This study investigates the feasibility of producing low MFR PP recyclates from packaging waste. For this purpose, recyclates were produced exclusively from manually sorted extrusion blow molding grades and compared with a recyclate derived from a conventional PP waste stream. Different washing temperatures and recyclate production processes were used to study their effects on the properties of the recyclates. The main objective was to determine the lowest achievable MFR and the rheological, mechanical, and thermal properties of the recyclates from improved sorting. The results are intended to serve as reference points for the evaluation of future automatic sorting trials. The enhanced sorting resulted in an 80% reduction in the MFR and improved ductility, thereby extending the potential applications of the recyclate. The different washing and production processes did not have a significant effect on the investigated properties, except for a slight decrease in the MFR with hot washing and the omission of the pelletizing step.

Robust downstream technologies in polystyrene waste pyrolysis: Design and prospective life-cycle assessment of pyrolysis oil reintegration pathways

Chemical recycling of polystyrene waste to virgin styrene by fluidized bed pyrolysis and purification of pyrolysis oil in a distillation sequence is investigated. It is shown experimentally that pre-treatment of expanded polystyrene (EPS) waste by hot washing does not improve styrene yields and thus styrene content in the pyrolysis oil, suggesting that no elaborate waste pre-treatment is necessary for polystyrene chemical recycling. Based on experimental results, pyrolysis oils with styrene content from 30 wt.-% to 80 wt.-% are considered in an Aspen Plus® downstream simulation. Process robustness is evaluated in terms of operating parameter sensitivity such as reflux and distillate-to-feed ratio. It is shown that for the purification of highly variable feed compositions trade-offs such as more columns or higher RR must be made. Prospective LCA reveals that chemical recycling is preferable to incineration of polystyrene waste, although to varying degrees depending on critical impurities present in the pyrolysis oil.

Analysis of Wax Formation Mechanism and Anti Wax Effect of Oil Well Tubing in a Certain Oilfield

During the production process of oil wells, wax deposition is caused by factors such as temperature reduction and dissolved gas precipitation. Severe wax deposition in oil wells can cause tubing blockage, leading to a decrease in oil well production and even stopping production due to wax blockage, affecting normal oil well production. Therefore, wax deposition can have a serious impact on the wellbore and even oilfield production. This article takes a certain oilfield block as an example to analyze the mechanism of wax deposition in oil wells and compares the effectiveness of commonly used wax removal and prevention measures such as different hot washing processes, adding wax removers, running acoustic viscosity reduction and wax prevention devices along with the oil pipe, and hot washing packers for sealing wells. The results show that superconducting hot washing, adding wax remover, and using acoustic wave viscosity reducing and wax preventing devices can effectively slow down wax deposition in oil wells. The use of hot washing packers effectively solves the problem of long-term inability to hot wash sealed wells, and it is recommended to promote their use.

Suitability of silver birch bark as a natural source for cotton dyeing

Suitability of silver birch bark as a natural source for dyeing cotton. The study was carried out on dyeing cotton fabric with silver birch bark extract without a mordant and with the use of mordants - oxalic acid and inorganic salts of aluminum, tin, iron and copper. The color of the fabric was determined in the CIE L*a*b* system. Pale orange to salmon shades were obtained. In the case of iron and copper, a significantly different color was obtained, dark grayish and rusty, respectively. Color fastness tests were carried out using hot water, mineral acid, mild and hot washing, dry cleaning and natural exposure to sunlight. Excellent resistance to dry cleaning and mild and hot washing was found, as well as good resistance to mineral acid. The dyed fabric had the weakest, although still quite good, resistance to sunlight.

Process for the Reduction of High Water Content from Oily Sludge and Scum by Hot Washing

The reduction of oily sludge and scum with high water content by hot washing and analysis of the main factors that affect the reduction and oil recovery rate of oily sludge and scum in hot washing were investigated. Best process conditions for the reduction of tank bottom sludge, refining sludge, and oily scum were carried out, which can make the oil recovery rate and reduction rate of tank bottom sludge after reduction reach 96.30% and 93.00%, respectively, the oil recovery rate and reduction rate of refining sludge after reduction reach 95.36% and 92.60% respectively, and the oil recovery rate and reduction rate of oily scum after reduction reach 95.92% and 93.60% respectively. After treatment, the oil content of the residue is reduced to below 5.1%, and the water content is reduced to below 59.0%. Oil content in the separated water is lower than 200 mg.L-1, and the water content in the separated oil is lower than 0.2%, far below the requirement of 0.5% in the oilfield’s crude oil gathering and transportation standard.

Suitability of apple tree bark as a natural source for cotton dyeing

Suitability of apple tree bark as a natural source for cotton dyeing. The study of dyeing cotton fabric with apple bark extract with the use of mortars - inorganic aluminum, tin, iron and copper salts, moreover oxalic acid and without mortar. The color of the fabric was determined using the CIE L*a*b* system. The result was a yellow color of varying shades, ranging from lemon to warm, intense yellow. In the case of iron and copper, a significantly different color was obtained, dark khaki and rusty brown respectively. Color fastness tests were carried out using hot water, mineral acid, mild and hot washing, dry cleaning and natural exposure to sunlight. It has been found to have excellent resistance to dry cleaning and good to a gentle wash. Dyed fabric showed the weakest resistance to sunlight and to mineral acid.

Material flow analysis and recycling performance of an improved mechanical recycling process for post-consumer flexible plastics

Increasing the recycling rates for post-consumer flexible plastics (PCFP) waste is imperative as PCFP is considered a difficult-to-recycle waste with only 17 % of PCFP effectively recycled in Europe. To tackle this pressing issue, improved mechanical recycling processes are being explored to increase the recycling rates of PCFP. One interesting option is the so-called quality recycling process (QRP) proposed by CEFLEX, which supplements more conventional mechanical recycling of PCFP with additional sorting, hot washing, improved extrusion, and deodorization. Material flow analysis (MFA) model is applied to assess the performance of QRP. Four performance indicators related to quantity (process yield and net recovery) and quality (polymer grade and transparency grade) are applied to measure the performance of three PCFP mechanical recycling scenarios. The results are compared against the conventional recycling of PCFP, showing that QRP has a similar process yield (64 % – 66 %) as conventional recycling (66 %). The net recovery indicator shows that in QRP higher recovery rates are achieved for transparent-monolayer PCFP (>90 %) compared to colored-multilayer PCFP (51 % – 91 %). The quality indicators (polymer and transparency grades) demonstrate that the regranulates from QRP have better quality compared to the conventional recycling. To validate the modeling approach, the modeled compositional data is compared with experimental compositional analyses of flakes and regranulates produced by pilot recycling lines. Main conclusions are: (i) although yields do not increase significantly, extra sorting and recycling produces better regranulates’ quality (ii) performing a modular MFA gives insights into future recycling scenarios and helps in decision making.

Quality evaluation and economic assessment of an improved mechanical recycling process for post-consumer flexible plastics

Packaging represents the largest fraction of plastic waste in Europe. Currently, mechanical recycling schemes are mainly focused on the recovery of rigid packaging (like bottles), while for flexible packaging, also called films, recycling rates remain very low. Existing mechanical recycling technologies for these films are quite basic, especially in the case of complicated post-consumer flexible plastics (PCFP) waste, leading to regranulate qualities that are often subpar for renewed use in demanding film applications. In this study, the technical and economic value of an improved mechanical recycling process (additional sorting, hot washing, and improved extrusion) of PCFPs is investigated. The quality of the four types of resulting regranulates is evaluated for film and injection molding applications. The obtained Polyethylene-rich regranulates in blown films offer more flexibility (45–60%), higher ductility (27–55%), and enhanced tensile strength (5–51%), compared to the conventional mechanical recycling process. Likewise, for injection molded samples, they exhibit more flexibility (19–49%), enhanced ductility (7 to 20 times), and higher impact strength (1.8 to 3.8 times). An economic assessment is made between the obtained increased market value and the capital investment required. It is shown that the economic value can be increased by 5–38% through this improved recycling process. Overall, the study shows that it is possible to increase the mechanical recycling quality of PCFP in an economically viable way, thus opening the way for new application routes and overall increased recycling rates.

Investigation of the Dyeability Behaviors of Cotton Surfaces with Natural Dyes Extracted from Rubia Tinctorum and Reseda Luteola L. Plants

In this study, the pigment obtained from Rubia Tinctorum plants growing around Central Anatolian Region (Konya) and the Reseda Luteola L plant extract collected from Black Sea Region, have been used as natural dye sources. The 100% cotton, single pique knitted surfaces with 190 g / m2 weight are used as a material to be dyed. Prior to the dyeing process, the samples were mordanted with 1% potassium aluminum sulphate and copper sulphate in a laboratory dyeing machine (Thermal). Following the mordant process, the samples were dyed in the laboratory dyeing machine at boiling temperature for 60 minutes according to the exhaustion method. The samples were left to be cooled in the dyeing liquor and 12 hours later, cold overflow washing, hot washing, boiling soaping and cold rinsing were performed additionally. After the drying process, color measurements were carried out with a spectrophotometer (Machbeth 2 180 V) using Color office Textile program to create color coordinates according to the CIE Lab system under D65 illuminate and 10° standard observer. As a conclusion, the samples mordanted with potassium aluminum sulphate and then dyed with natural dye obtained from Rubia Tinctorum plant is considered the standard for color measurement, it has been determined that copper sulphate mordant is effective in the change of (ΔE*) total color difference (ΔE*=7.93). The samples with Rubia Tinctorum have a lighter color than the standard, the green and blue nuance is more, and the color is more matte as well. The samples mordanted with potassium aluminum sulphate and then dyed with natural dye obtained from Reseda Luteola L plant is considered the standard for color measurement, it has been determined that copper sulphate mordant is effective in the change of (ΔE*) total color difference (ΔE*=24). On the lightness axis (ΔL*), the dyed sample is darker than the standard. The color of Reseda Luteola L. dyed the samples is darker than standard, more red and blue; the nuance is more, also the color is more matte. When the Color Strength (K / S) values of the samples dyed with the dyestuffs obtained from Rubia Tinctorum and Reseda Luteola L plants were compared; in both dyestuffs, the highest Color Strength Value (K / S) was obtained in samples dyed after mordant process with copper sulphate (Rubia Tinctorum: K / S= 3,336; Reseda Luteola L: K / S= 10,649). The washing fastness results are lower than the staining fastness for all performed dyeing process. Both the color change in washing and staining rates are between the values accepted by the industry. Likewise, the dry rubbing fastness and wet rub fastness of all dyeing are similar. Light fastness values of samples dyed with natural dye obtained from Rubia Tinctorum plant are higher than samples dyed with Reseda Luteola L.

Determining the efficiency of cleaning a milk line made from different materials from contaminants

While moving along the milk-conducting systems in a milking machine, milk is in contact with the inner surface whose area exceeds 20 m2. That leads to the formation of protein-fat biofilms of contamination, which are a nutrient medium for the development of microorganisms. With insufficiently effective cleaning of these contaminants, in the periods between milking, the number of microflorae located in milk-conducting systems increases by tens of thousands of times. When cleaned with ineffective cleaning agents, mineral elements from milk are adsorbed on the surface of a protein-fat bio-film, which are subsequently compacted, changed, and converted into milk stone. In this case, the technical implementation of milk conducting systems is of critical importance. It has been established that a milk line made from any material is better cleaned with a hot washing solution than a cold one. Thus, with an increase in the temperature of a washing solution from 60 °C to 85 °C, the cleaning time of the milk line is reduced from 9.5 minutes to 1.5 minutes, or by 6 times. It was established that during the washing phase of a milk line there is a significant decrease in the temperature of the washing solution (≈30 %), which reduces the effectiveness of cleaning the parts of the system. Therefore, there is a need to maintain the solution temperature throughout the entire cleaning process. It is proved that the specific energy of adhesion of pollution in water is 2 times higher than that in a washing solution. With an increase in the temperature of the solution for every 10 °C, the decrease in the specific energy of pollution adhesion is on average 13 %. With an increase in the period after the end of milking before washing the milk line, the specific energy of its purification increases. The study reported here could lead improve the productivity of milking machines and the quality of the resulting product. That involves designing milking and dairy equipment from innovative materials.

Factors affecting chemical heat washing efficiency of oily sludge and Demulsification Mechanism

Oily sludge belongs to the hazardous waste specified in the national hazardous waste list. It will directly or indirectly threaten the ecological environment and human health. This paper introduces the advantages of chemical hot washing of oily sludge. This paper discusses the main factors affecting the treatment effect, Demulsification Mechanism and research progress in the treatment of oily sludge by chemical thermal washing, and puts forward some suggestions on the future research and development direction of oily sludge utilization and disposal.

Numerical investigation on the melting characteristics of wax for the safe and energy-efficiency transportation of crude oil pipelines

Wax precipitation affects the normal transportation of crude oil pipeline. Wax is generally removed by hot washing. Reducing energy of hot washing is the key to the security and energy-saving operation. It is necessary to reveal the heat transfer characteristics of the process. The melting characteristics of paraffin in the gathering and transportation pipeline are studied by numerical simulation in this paper. Mathematical model is established. Melting and flow characteristics of paraffin in gathering pipelines are researched. The effects of water temperature, size of spherical paraffin, and initial temperature on the central temperature and liquid phase ratio of the ball are analyzed. The melting stage is divided into informal melting stage and formal melting stage. The correlations between the dimensionless time Fo number, Ste number, Ra number, and subcooling degree Ci are proposed based on the dimensionless analysis. The correlation can be used to predict the complete melting time of paraffin in natural convection flow field. It is of guiding significance for hot washing.

Post-consumer PET Bottle Recycling: Chemical Dose Optimization

Polyethylene terephthalate (PET) bottles are being used in our daily life and consequently go to the landfills after their use. Additionally, virgin PET resins are produced from nonrenewable resources, such as fossil fuels, whose reserves are depleting continuously. Therefore, to maintain ecological and environmental balances as well as for sustainable development, post-consumer PET (pcrPET) bottles should be recycled. Among many recycling processes, mechanical recycling of pcrPET is attractive due to lower cost involvement. One of the most crucial and important processes of mechanical recycling is hot washing for contaminants removal. Hot washing uses a cleaning solution made of caustic soda (NaOH) and detergent at elevated temperature. In this paper, caustic soda and FORYL LFO (FLO) detergent doses were changed gradually to investigate effective contaminants removal through colorimetric study. Finally, concentration vs. absorbance graphs from colorimetric study suggests that 2% NaOH and 2% FLO detergent is the optimum chemical dose at hot washing for pcrPET recycling.

Odorant composition of post-consumer LDPE bags originating from different collection systems

The establishment of recycling systems aiming at high-quality recyclates from post-consumer plastic waste are essential to avoid the waste of resources. One main impediment for introducing recyclates into the market is their unwanted odor. For this reason, this study aimed at determining if the collection strategy affects the odor profile of post-consumer LDPE bags. Furthermore, the effect of hot water washing, inspired by the conventional mechanical recycling procedure, on the odor of post-consumer LDPE bags was screened. More than 60 odorants were detected in LDPE bags collected in a separate plastic fraction as well as in LDPE bags from the non-separated collection by means of gas chromatography-olfactometry, and 37 of them were unequivocally identified using two-dimensional gas chromatography-mass spectrometry/olfactometry. The sensory results revealed that the type of collection affects the overall odor intensity, the hedonic tone of the odor and the odor profile. Namely, cheesy and fecal smelling odorants were predominant in the waste that had not been separated at source, whereas odorants with earthy and moldy smells showed mostly higher intensity ratings in the waste separated at source. Short chain carboxylic acids, likely originating from microbial spoilage of organic waste, were found with higher dilution factors in the mixed fraction, and could, accordingly, contribute to the observed differences. Additionally, we could show that the hot washing procedure, applied to the LDPE sample from the separate collection system, significantly reduced the overall odor intensity from 8 to 6.3 (0–10 scale). However, the washed waste still showed high smell intensity ratings.

Application of chemical hot washing method for oily solid waste treatment

In this study, five types of chemical hot cleaning agent were screened to evaluate the oil removal efficiency, which was based on the component analysis of an oily solid waste from an oilfield in western China. The best experimental conditions were determined through single-variable and orthogonal tests. The results indicate that pharmacy AST-01 has the best removal efficiency. The optimum treatment conditions were as follows: AST-01 concentration, 20.0 g/L; temperature, 60 °C; stirring speed, 125 rpm; and stirring time 30 min. The oil content decreased to 1.91% under these conditions. The influence order of different factors decreased in the following order: the dosage of pharmacy, stirring speed, and temperature. The results of a combined experiment show that the removal efficiency was improved. The optimum proportion of pharmacies AST-01 and AST-02 was 10:1. The oil content decreased to 0.82%. The field engineering tests showed that the oil content of the residue was less than 2% when the optimum proportion was used. In general, this method decreases the oil content in an oily solid waste significantly and thus reduces the harmfulness of oily solid wastes.

Influencing factors governing paraffin wax deposition of heavy oil and research on wellbore paraffin remover

Wax deposition is harmful to oil wells, especially for waxy heavy oils at low temperature. The influencing factors on wax deposition of heavy oil were studied and a kind of O/W emulsion type wellbore wax remover was investigated. The results showed that the wax deposition rate of Jinghe heavy oil increased with the increasing wax content and asphaltenes content but decreased with the increasing water content. The oil in water emulsion type paraffin remover was prepared and it showed both good wax dissolution and paraffin prevention ability and can save large quantities of solvent. The results of this study provides a possible way for waxy heavy oils to dissolve wax, to prevent wax deposition and reduce the viscosity of heavy oils by emulsification together, which is helpful to reduce the frequency of hot washing and enhance oil recovery for waxy heavy oils.

Synthesis Process Development of Diethylene Tricarbamide as a Starting Material for Wood Composite Binder Diethylene Tricarbamide–Formaldehyde Resins

Abstract A three-step carbamylation reaction of diethylene triamine (DA) with urea was investigated to find an efficient synthesis procedure for large-scale production of diethylene tricarbamide (D), a monomer of D-formaldehyde resin binders for wood composite boards with very low formaldehyde emission potential. n-Butanol, pyridine, and others with minor amounts of polar solvents were investigated as a reaction medium. Urea is added to the solvent in a stirred reactor and heated to the boiling point of the solvent, which is about 110°C to 130°C. This was followed by the gradual addition of DA while allowing evolved ammonia to escape through the condenser. A delicate balance exists between voluminous particles of di-substituted intermediates and the hard fine particles of tri-substituted final product, and an excessive buildup of the former often occurs, resulting in stirring difficulties, reaction stoppage, and low reaction yields, which are minimized by adding some polar solvents and also by programmed addition of DA. Free-flowing microcrystalline particles of D were obtained in yields of 90 to 98 percent based on DA in 6 to 12 hours of reaction by simple filtration, hot washing with solvents, and drying procedures. These organic solvent–based synthesis procedures appear possible to adapt to large-scale production of D. The ammonia that evolves from the reaction needs to be captured, and solvent losses should be minimized. The high current price of DA, the need to reuse ammonia, and the complexity of the reaction indicate that a company that manufactures ammonia, urea, and DA fit to adopt this technology in support of the wood composite board industry.

Temperature field analysis on the highly-deviated wellbore in backwashing condition

Based on the measured borehole trajectory, a prediction model of temperature field of highly-deviated wells in backwashing condition is established. To verify the model, a test instrument to measure the temperature variations in the wellbore is developed and used to measure the temperature of two typical highly-deviated wells in backwashing condition. The comparative analysis shows that the wellbore temperature predicted by the model is close to that measured in field with the relative error less than 8%. The model was further used to analyze the influence of liquid-injection speed and injection time on the temperature distributions of oil pipe, annulus space and radial direction under the backwashing operation with original-temperature and hot washing liquid. It is found that for the backwashing operation with original-temperature washing liquid, the temperature at the lower part of the shaft is most affected by the displacement rate and backwashing time, whereas the curve section and the lower part of the shaft are most affected by the displacement rate and backwashing time in hot washing operation. Along the depth of the borehole, there is a constant temperature section which is almost unaffected by displacement rate and backwashing time. The radial heat transfer analysis shows that the heat exchange range is not large and near the wellbore.