Refinery Oily Sludge Research Articles

Bio-oil production from refinery oily sludge using hydrothermal liquefaction technology

This study investigates direct hydrothermal liquefaction (HTL) of refinery oily-sludge (ROS) to produce bio-oil (BO). Optimum operating conditions of HTL were experimentally determined by response surface methodology (RSM). Experiments were implemented in a tube-bomb reactor at various temperatures (275–350°C), reaction time (30–75min) and ROS content (10–40wt%) in feed. BO yield reached to 45.52wt% on dry ash-free basis at optimum conditions (290°C, 65min and 16wt% of ROS). GC/MS analysis showed that BO mainly contained aliphatic, saturated and unsaturated fatty acids, monoaromatic and polyaromatic compounds. Moreover, it was found that by increasing temperature, small compounds were converted into heavier molecules via repolymerization reactions. With increasing reaction time at low temperatures, the amount of nitrogen-containing compounds increased, emphasizing the undesired effect of very long reaction time. Results also indicated that catalytic upgrading is required for dehydrogenation, oxygen removal and new CH bonds creation.

Investigation of waste biomass co-pyrolysis with petroleum sludge using a response surface methodology

The treatment of waste biomass (sawdust) through co-pyrolysis with refinery oily sludge was carried out in a fixed-bed reactor. Response surface method was applied to evaluate the main and interaction effects of three experimental factors (sawdust percentage in feedstock, temperature, and heating rate) on pyrolysis oil and char yields. It was found that the oil and char yields increased with sawdust percentage in feedstock. The interaction between heating rate and sawdust percentage as well as between heating rate and temperature was significant on the pyrolysis oil yield. The higher heating value of oil originated from sawdust during co-pyrolysis at a sawdust/oily sludge ratio of 3:1 increased by 5 MJ/kg as compared to that during sawdust pyrolysis alone, indicating a synergistic effect of co-pyrolysis. As a result, petroleum sludge can be used as an effective additive in the pyrolysis of waste biomass for improving its energy recovery.

Oil recovery from petroleum sludge through ultrasonic assisted solvent extraction

ABSTRACTThe effect of ultrasonic assisted extraction (UAE) process on oil recovery from refinery oily sludge was examined in this study. Two types of UAE treatment including UAE probe (UAEP) system and UAE bath (UAEB) system were investigated. Their oil recovery efficiencies were compared to that of mechanical shaking extraction (MSE). Three solvents including cyclohexane (CHX), ethyl acetate (EA), and methyl ethyl ketone (MEK) were examined as the extraction solvents. The influence of experimental factors on oil and solvent recovery was investigated using an orthogonal experimental design. Results indicated that solvent type, solvent-to-sludge (S/S) ratio, and treatment duration could have significant effects on oil recovery in UAE treatment. Under the optimum conditions, UAEP treatment can obtain an oil recovery of 68.8% within 20 s, which was higher than that (i.e., 62.0%) by MSE treatment after 60 min’ extraction. UAEB treatment can also obtain a promising oil recovery within shorter extraction duration (i.e., 15 min) than MSE. UAE was thus illustrated as an effective and improved approach for oily sludge recycling.

English

Ecotoxicological effects of the discharge of Nigerian petroleum refinery oily sludge on biological sentinels were examined. The ecotoxicological effects examined included acute toxicity tests on Nitrobacter sp., fresh water shrimp (Desmoscaris trispinosa) and brackish water shrimp (Palaemoneles africanus) from the aquatic environment. It also covered chronic toxicity tests on microbial nitrogen transformation activity in soil and the growth of the terrestrial fauna, earthworm (Apporectoda longa) in pristine soils spiked with predetermined concentrations of the sludge. Analysis of the Nigerian petroleum refinery oily sludge used in this study indicated that the sludge is slightly acidic with a high total petroleum hydrocarbon (TPH) content of 340,000 mg/kg made up mainly between 10-40 carbon unit compounds. The sludge reduced the growth of Nitrobacter sp. in aqueous medium and also caused chronic effect on microbial nitrogen transformation activity in soil because it exceeded the 25% inhibition limit for chemicals with the potential to cause chronic effects on soil microbial activities. Similarly, the sludge exhibited toxicity on fresh and brackish shrimp. The freshwater shrimp was however more affected with an LC50 of 1097.375 ± 0.62 mg/kg when compared with an LC50 of 1590. 37±0.92 mg/kg obtained for the brackish water shrimp. It also reduced the growth rate of the earthworm (A. longa) progressively as the sludge concentration increased.   Key words: Toxic effects, petroleum refinery oily sludge, biological sentinels.

Ultrasonic oil recovery and salt removal from refinery tank bottom sludge

The oil recovery and salt removal effects of ultrasonic irradiation on oil refinery tank bottom sludge were investigated, together with those of direct heating. Ultrasonic power, treatment duration, sludge-to-water ratio, and initial sludge-water slurry temperature were examined for their impacts on sludge treatment. It was found that the increased initial slurry temperature could enhance the ultrasonic irradiation performance, especially at lower ultrasonic power level (i.e., 21 W), but the application of higher-power ultrasound could rapidly increase the bulk temperature of slurry. Ultrasonic irradiation had a better oil recovery and salt removal performance than direct heating treatment. More than 60% of PHCs in the sludge was recovered at an ultrasonic power of 75 W, a treatment duration of 6 min, an initial slurry temperature of 25°C, and a sludge-to-water ratio of 1:4, while salt content in the recovered oil was reduced to <5 mg L−1, thereby satisfying the salt requirement in refinery feedstock oil. In general, ultrasonic irradiation could be an effective method in terms of oil recovery and salt removal from refinery oily sludge, but the separated wastewater still contains relatively high concentrations of PHCs and salt which requires proper treatment.

Oil recovery from refinery oily sludge using a rhamnolipid biosurfactant-producing Pseudomonas

In this study, a rhamnolipid biosurfactant-producing strain, Pseudomonas aeruginosa F-2, was used to recover oil from refinery oily sludge in laboratory and pilot-scale experiments. The optimum values of carbon to nitrogen ratio, temperature, sludge–water ratio and inoculum size for oil recovery were determined as 10, 35°C, 1:4 and 4%, respectively. An oil recovery of up to 91.5% was obtained with the equipping of draft tubes during the field pilot-scale studies. The results showed that strain F-2 has the potential for industrial applications and may be used in oil recovery from oily sludge.

Bioremediation of Petroleum Refinery Oily Sludge in Topical Soil

Bioremediation of Petroleum Refinery Oily Sludge in Topical Soil

Oil recovery from refinery oily sludge via ultrasound and freeze/thaw

The effective disposal of oily sludge generated from the petroleum industry has received increasing concerns, and oil recovery from such waste was considered as one feasible option. In this study, three different approaches for oil recovery were investigated, including ultrasonic treatment alone, freeze/thaw alone and combined ultrasonic and freeze/thaw treatment. The results revealed that the combined process could achieve satisfactory performance by considering the oil recovery rate and the total petroleum hydrocarbon (TPH) concentrations in the recovered oil and wastewater. The individual impacts of five different factors on the combined process were further examined, including ultrasonic power, ultrasonic treatment duration, sludge/water ratio in the slurry, as well as bio-surfactant (rhamnolipids) and salt (NaCl) concentrations. An oil recovery rate of up to 80.0% was observed with an ultrasonic power of 66 W and an ultrasonic treatment duration of 10 min when the sludge/water ratio was 1:2 without the addition of bio-surfactant and salt. The examination of individual factors revealed that the addition of low concentration of rhamnolipids (<100 mg/L) and salt (<1%) to the sludge could help improve the oil recovery from the combined treatment process. The experimental results also indicated that ultrasound and freeze/thaw could promote the efficiency of each other, and the main mechanism of oil recovery enhancement using ultrasound was through enhanced desorption of petroleum hydrocarbons (PHCs) from solid particles.

Leaching and Immobilization Behavior of Zn and Cr from Cement-Based Stabilization/Solidification of Ash Produced from Incineration of Refinery Oily Sludge

In this paper, stabilization/solidification of ash derived from real refinery oily sludge samples was applied using two types of cement (CEM I42.5N and II42.5N) in various additions. Leaching behavior of Cr and Zn was investigated, by means of a five-point sequential Toxicity Characteristic Leaching Procedure (TCLP) test. Sequential TCLP extractions of incinerated refinery sludge samples resulted in very low leachability ( < 0.2 mg/L at 8.6 < pH < 11.6) of heavy metals (Ni, Pb, Co, Cd, Cu, and Fe) after stabilization/solidification with cement, except for Cr (< 40 mg/L at 8.6 < pH < 12.1) and Zn (< 6 mg/L at 8.6 < pH < 12.1). Furthermore, the leaching behavior of Cr and Zn was modeled using the chemical equilibrium program Visual MINTEQ. For that purpose the Diffuse Layer Model (DLM) coupled with 2-pK formalism was employed to model the suspected formation of CaCrO4(s), Cr(VI)-ettringite and zinc hydroxide. The results showed that Cr leachability was mainly controlled by the speciation of Cr(VI) in the al...

Anion Leaching from Refinery Oily Sludge and Ash from Incineration of Oily Sludge Stabilized/Solidified with Cement. Part II. Modeling

This paper presents the modeling of anion leaching (SO4(2-) and CrO4(2-)) from refinery oily sludge and ash produced by incineration of oily sludge, stabilized/solidified (s/s) with two types of cement, 142.5 and 1142.5. Anion leaching was examined using a sequential toxicity characteristic leaching procedure (TCLP) test. To elucidate the mechanisms of sulfate and chromate leaching, we employed Visual MINTEQ, incorporating a multiple-problem setup. Specifically, 10-14 different problems, depending on the pH range of the leachates, were connected together in the same run. Each problem corresponded to one pH value of the leachate and the model run covered the pH range of the five sequential TCLP extractions. This modeling approach was tested using chemical equilibrium with or without sorption onto ferrihydrite. Good agreement between experimental and modeling results was obtained for sulfate leaching from solidified oily sludge and ash, considering surface complexation onto ferrihydrite on top of chemical equilibrium controlled by gypsum at pH <11 and ettringite at pH >11. Chromate leaching was described by chemical equilibrium, controlled by CaCrO4(s) (at pH <11) and Cr(VI)ettringite (at pH >11).

Anion Leaching from Refinery Oily Sludge and Ash from Incineration of Oily Sludge Stabilized/Solidified with Cement. Part I. Experimental Results

This paper presents the leaching behavior of anions (SO4(2-) and CrO4(2-)) from refinery oily sludge and ash produced by incineration of oily sludge, stabilized/solidified (s/s) with two types of cement, 142.5 and 1142.5. Anion leaching was examined using a 5-step sequential toxicity characteristic leaching procedure (TCLP) test. A single TCLP extraction resulted in limited sulfate release (<50 mg/L) for s/s ash and significant sulfate release (<850 mg/L) for s/s oily sludge. Chromate release was <1 mg/L for s/s ash and nondetectable for s/s oily sludge. The sequential TCLP tests resulted in increased leaching for both sulfate and chromate. In general,the increase of liquid-to-solid ratio (TCLP leachant-to-waste ratio) resulted in increased leaching of sulfate from solidified samples compared to untreated oily sludge, ash and cement. In contrast, chromate leaching decreased by s/s process. A qualitatively similar leaching behavior for SO4(2-), even for radically different wastes such as oily sludge and ash, solidified with two different types of cement was observed.

Characterization of stabilized/solidified refinery oily sludge and incinerated refinery sludge with cement using XRD, SEM and EXAFS

Solidification/stabilization (S/S) of refinery oily sludge and incinerated oily sludge (ash) with cement type I42.5 and II42.5 was investigated using, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectroscopy (EDS) and Extended X-ray Absorption Fine Structure (EXAFS). The results showed that delayed ettringite formation (DEF) and major cement hydration reactions occurred. XRD analysis of S/S oily sludge samples revealed cement-bearing solid phases, such as portlandite, calcite, C3S, C2S and C4AF. SEM analysis, confirmed ettringite at solidified oily sludge samples. Solidified ash samples contained ettringite substituted by chromates. However, solid phases found in solidified ash samples with I42.5 cement showed minor variation in type and structure compared to those observed in solidified ash samples with II42.5 cement. Fe K edge EXAFS analysis revealed the presence of iron oxides in both S/S wastes. The comparison between spectra of the S/S resulting materials and the ones of their original components, showed that the first sphere Fe–O distances were longer than in the pure iron oxide thereby providing evidence that the resulting materials were not simple mixtures, but products of a reaction that modified the local environment of iron.

Leaching Behavior of Metals Released from Cement-Stabilized/Solidified Refinery Oily Sludge by Means of Sequential Toxicity Characteristic Leaching Procedure

In this study, stabilization/solidification (S/S) of refinery oily sludge was applied using two types of cement (I and II), in cement-to-waste ratio from 0.1 to 0.7. The leaching behavior of heavy metals was investigated, by means of a five-point sequential toxicity characteristic leaching procedure (TCLP) test. Sequential TCLP was used to provide an improved assessment of long-term contaminant potential leachability, because the acidic leachant is renewed, whereas in the single TCLP, contaminant leachability is limited by the pH neutralization of the alkaline binder. Cement-based S/S of real refinery oily sludge resulted in very low leachability of heavy metals. Pb and Cd were not detected in any TCLP leachate. The maximum leachability of Fe, Zn, and Ni occurred in the pH range between 5.5 and 6.5. The leachability of Cu and Cr increased with increasing pH. Maximum cumulative percentage of Fe, Ni, and Zn leaching after five consecutive TCLP extractions (for worst case conditions, i.e., 10% II42.5) were 0.01, 22, and 1.2%, respectively, on the basis of metal content of each solidified sample. Further, the leaching behavior of Zn and Ni was modeled using the chemical equilibrium program Visual MINTEQ. Using several combinations of suspected solid phases of Zn and Ni hydroxides, carbonates and sulfides, and surface complexation onto ferrihydrite the diffuse double layer model did not accurately describe the leaching behavior of Zn and Ni.

Screening of Efficient Hydrocarbon-Degrading Strains and Study on Influence Factors of Degradation of Refinery Oily Sludge

Three kinds of bacterial strains, HJ-1, HJ-2, and HJ-3, were isolated by means of enrichment culture from oily sludge in Shengli oil field. HJ-1 was identified as Bacillus by primary test. The influence of seed age, oil concentration, microbial quantity experimental time, and pH on the degradation ability of the HJ-1 strains was investigated. The results showed that the oil reduction rate was 69.4% for the refinery oily sludge, and the conditions were as follows: 50 mL, pH 9, oil concentration 5 g·L-1 enrichment culture of crude oil, addition of 12 mL of strain HJ-1 at the seed age of 16 h, experimental time 6 days, then evaluate the fermentation of hydrocarbon-degrading strain HJ-1 in a shake flask. The influencing factors of pH, microbial quantity, glucose concentration, salt concentration, rotation speed, and temperature were also studied. The oil degradation rate of HJ-1strains rose from 78.6% to 82.0% for crude oil and from 69.4% to 77.4% for oily sludge from the refinery, as the fermentation bacter...

Leaching of VOCs from Cement-based Stabilized/Solidified Refinery oily Sludge using Solid Phase Microextraction

Cement-based Stabilization/Solidification was applied to refinery oily sludge. Zero Headspace Extraction was employed for the investigation of the leaching behavior of volatile organic compounds from untreated and stabilized/solidified oily sludge in water. A method is described combining zero headspace extraction, solid phase microextraction and gas chromatography with flame ionization detector for determination of volatile organic compounds in aqueous leachates. For stabilization/solidification of the waste, two types of cement were used, I42.5 and II42.5. The I42.5 is a Portland Cement whereas the II42.5 is a Blended Cement, which contains pozzolanic material. In general, the I42.5 cement showed better immobilizing characteristics than the II42.5 cement, but the difference was small. The leaching behavior of toluene, o-xylene, p,m-xylene and ethylbenzene from stabilized/solidified samples was similar for both types of cement. The reduction in the maximum leached amount of stabilized/solidified specimens compared with that of the untreated oily sludge alone, varied from 80% to 98%, for specimens with 10% cement addition (both types). Increased leaching was observed with increasing cement addition. In the case of naphthalene, stabilized/solidified samples leached more than threefold the amount leached from the untreated oily sludge alone.

Influential Factors in Fermentation of Refinery Oily Sludge

In an experiment of one-pass aerobic fermentation, sawdust was used as the amendment and straw was used as the bulking agent. The forced aeration was at the rate of 0.1 m 3 /h while the influence of nitrogen and microbe sources on the process was thus investigated. The oil degradation rate was up to 52.7% after fermentation under the conditions of poultry manure as the nitrogen source and HJ-1 strain as the microbe. Simultaneously, the color of oily sludge changed from black to brown, the stink from the manure disappeared, and the appearance of the sludge changed from a sticky state to loose particles. The analytical results indicated that the amount of saturated hydrocarbons in the refinery sludge was decreased remarkably after fermentation.

Release of Zn, Ni, Cu, SO 42− and CrO 42− as a function of pH from cement-based stabilized/solidified refinery oily sludge and ash from incineration of oily sludge

A framework for the evaluation of leaching behavior of inorganic constituents from stabilized/solidified refinery oily sludge and ash produced from incineration of oily sludge with cement was employed. Metal and anion release as a function of pH was investigated. The leaching test consisted of multiple parallel extractions at pH range from 2 to 12. Remarkably good immobilization >98% was observed for metals of solidified ash at pH > 6 and >93% of solidified oily sludge at pH > 7. Sulfate leaching was high at pH range 2–12. The leaching behavior of metals and anions was simulated by VMINTEQ. The calculations showed that leaching behavior of Zn, Ni and Cu was controlled by chemical equilibrium and surface complexation onto ferrihydrite, at the pH range 2–12. The dominant solid phases that controlled metal leachability were metal hydroxides. The dominant mechanism that described sulfate leaching was found to be chemical equilibrium. Sulfate and also chromate leachability was controlled by Ettringite and Cr(VI)Ettringite as the major minerals affecting their release.

Biodegradation Kinetics of Hydrocarbons in Soil during Land Treatment of Oily Sludge

This study focuses on the processes influencing hydrocarbon residue persistence in soil, following land treatment of refinery oily sludge. Treating sludge applied to soil resulted in 70% to 90% degradation of total petroleum hydrocarbon (TPH) during 2 months, regardless of their initial concentrations (9 to 60 g/kg soil). Kinetic analyses performed on TPH degradation, in laboratory and field systems, revealed a degradation pattern characterized by two consecutive first-order kinetics reactions in all experimental settings. The first stage lasted about 3 weeks and was characterized by a temperature dependent rate constant of 0.047 day−1 at 24°C. That value was comparable to the rate constant obtained when combining the individual rate constants of the saturated, aromatic, asphaltene and polar fractions. The subsequent slower stage rate constant was 0.012 day−1, insensitive to temperature and to hydrocarbon composition. The transition between the two stages (about 21 days) was independent of the experimental temperature and the biodegradation extent during the first stage. It was concluded that the extent of residual accumulation in the soil was determined by the biodegradation efficiency during the first three weeks of treatment when biological processes dominated. During the following period, abiotic processes leading to reduced bioavailability of the TPH were limiting the degradation rate. Practically, as the first few weeks of treatment determine its efficiency, efforts to enhance the biological activity should be directed to that period.

Azoarcus gen. nov., Nitrogen-Fixing Proteobacteria Associated with Roots of Kallar Grass (Leptochloa fusca (L.) Kunth), and Description of Two Species, Azoarcus indigens sp. nov. and Azoarcus communis sp. nov.

Among the nitrogen-fixing bacteria associated with roots of Leptochloa fusca (L.) Kunth in saline-sodic soils in the Punjab of Pakistan, we repeatedly found yellow-pigmented, straight to curved, gram-negative rods. To group and identify these organisms, we examined morphological, nutritional, and biochemical features and performed polyacrylamide gel electrophoretic analyses of cellular proteins, gas chromatographic analyses of fatty acids, DNA-rRNA hybridizations, and DNA-DNA hybridizations. Our results showed that 11 isolates formed five groups distinct at the species level, with each group containing one to three members. These bacteria constituted a separate rRNA branch in rRNA superfamily III (corresponding to the beta subclass of the Proteobacteria) at a branching Tm(e) level of 67.7°C [Tm(e) is the temperature at which 50% of a hybrid is denatured under standard conditions]. On this branch, the five groups were located in two clusters with Tm(e) values of 79.4 to 80.4°C and around 71.5°C. We propose a new genus, the genus Azoarcus, for these strains. Azoarcus indigens is the type species and has a growth factor requirement; its type strain is strain VB32 (= LMG 9092). A second named species, Azoarcus communis, includes a strain obtained from French refinery oily sludge, strain LMG 5514. Bacteria of this genus have a strictly aerobic type of metabolism, fix nitrogen microaerobically, and grow well on salts of organic acids but not on carbohydrates. Swedish isolates obtained from human sources (E. Falsen group 15 strains LMG 6115 and LMG 6116), as well as “[Pseudomonas] gasotropha” LMG 7583T, were also located on this rRNA branch at a lower Tm(e) level (70.4 to 71.2°C).

Free-Living Dinitrogen-Fixing Bacteria Isolated from Petroleum Refinery Oily Sludge

Dinitrogen-fixing activity (acetylene reduction and N(2) fixation) was found in an oily sludge originating from a petroleum refinery. Two representative dinitrogen-fixing bacterial strains were isolated from this oily waste. Their nitrogenase activity was effective when they were cultivated on sterilized sludge or simple carbon substrates (organic acid salts, sugars). Using the classical methods, these strains could not be unambiguously related to other diazotrophic taxa. The landfarming process is widely used for oily sludge disposal; this study shows that oily sludges are more than a simple carbon input into the soil but that they must also be considered as real sources of dinitrogen-fixing and probably degradative microorganisms.