Quantifying material flow of oily sludge in China and its implications

Role of municipal solid waste incineration fly ash components in co-pyrolysis of oily sludge: Pyrolysis products and catalytic mechanism

The co-pyrolysis of oily sludge (OS) and municipal solid waste incineration fly ash (IFA) is a promising strategy for sustainable waste management. This study delves into the distinct catalytic roles of individual IFA components during co-pyrolysis and assesses their impact on the inherent Fe species in OS, highlighting their contributions to overall catalytic activity. Notably, in comparison to IFA, CaCl2 and KCl significantly enhance pyrolysis oil upcycling, while IFA components collectively exhibit a positive catalytic effect on pyrolysis gas and coke production. Ca(OH)2 notably boosts H2 yield by 137.16 %. Alkali chlorides facilitate gaseous hydrocarbon formation and convert oxygen-containing compounds to CO and CO2 which are subsequently consumed and absorbed by CaO and Ca(OH)2. CaCl2 and KCl promote heavy compound decomposition and alkane aromatization, reducing coke formation and increasing light aromatic production. Conversely, NaCl increases alkane proportions. However, CaSO4 and CaCO3 hinder catalytic reactions, promoting carbon conversion to coke. Importantly, IFA compounds aid the dispersion of inherent Fe-based species from OS on char surface, enhancing in-situ catalytic pyrolysis. Additionally, the augmented H2 production accelerates the reduction of Fe-based species. The findings expand waste utilization possibilities and provide insights for co-processing solid wastes.

Characterization and treatment of oily sludge: A systematic review

Oily sludge is a prevalent hazardous waste generated in the petroleum industry, and effectively treating it remains a key challenge for the petroleum and petrochemical sectors. This paper provides an introduction to the origin, properties, and hazards of oil sludge while summarizing various treatment methods focused on reduction, recycling, and harmlessness. These methods include combustion, stabilization/solidification, oxidation and biodegradation techniques, solvent extraction, centrifugation, surfactant-enhanced oil recovery processes as well as freezing-thawing procedures. Additionally discussed are pyrolysis, microwave radiation applications along with electrokinetic method utilization for oily sludge treatment. Furthermore explored are ultrasonic radiation techniques and froth flotation approaches. These technologies have been thoroughly examined through discussions that analyze their process principles while considering influencing factors as well as advantages and disadvantages associated with each method. Based on the characteristics of oily sludge properties and treatment requirements, a selection methodology for choosing appropriate oily sludge treatment technology is proposed in this study. The development direction of processing technology has also been explored to provide guidance aimed at improving efficiency by optimizing existing processing technologies. The paper presents a comprehensive treatment method for oily sludge, ensuring that all the parameters meet the standard requirements.

Investigation of Catalytic Co-Pyrolysis Characteristics and Synergistic Effect of Oily Sludge and Walnut Shell

The co-pyrolysis of oily sludge and walnut shell is a reliable method for solid waste treatment and waste recycling. In this paper, a thermogravimetric analysis was used to study the thermodynamics and synergy effect of oily sludge (OS) and walnut shell (WS) at four heating rates (10, 20, 30, and 40 °C/min) in the temperature range from 50-850 °C. Two model-free methods (FWO and KAS) were used to calculate the activation energy. The results showed that the heating rate had no significant effect on the pyrolysis process. The addition of walnut shell improved the pyrolysis process of the samples. Mixture 1OS3WS had a synergy effect, while other blends showed an inhibitory effect. The synergy effect of co-pyrolysis was strongest when the mass ratio of oily sludge was 25%. The activation energy of the Zn-ZSM-5/25 catalyst was the lowest, and the residual substances were the least, indicating that the Zn-ZSM-5/25 was beneficial to the co-pyrolysis of oily sludge and walnut shell. The analysis of catalytic pyrolysis products by Py-GC/MS found that co-pyrolysis was beneficial to the generation of aromatic hydrocarbons. This study provided a method for the resource utilization of hazardous waste and biomass waste, which was conducive to the production of aromatic chemicals with added value while reducing environmental pollution.

Experimental study on alkali catalytic gasification of oily sludge in supercritical water with a continuous reactor

Realizing the harmless resource utilization of oily sludge is urgent for petroleum industry and of great significance for environmental management. The treatment of oily sludge was investigated using supercritical water gasification (SCWG) with a continuous fluidized bed reactor. The effect of operating parameters on gasification efficiency and gas yield without catalyst was tested, and then the influences of catalyst type (K₂CO₃ and Na₂CO₃) and concentrations (1-8 wt%) were systematically studied. The results indicated that a medium mass flow ratio and low feedstock concentration were beneficial for gas production. Alkali catalyst improved carbon gasification efficiency (CE) prominently, and Na₂CO₃ showed better performance due to its better stability. A maximum CE of 95.87% was achieved when 5 wt% Na₂CO₃ was added at 650 °C, 23 MPa with 5 wt% oily sludge concentration. Besides, according to XRD patterns of solid residues, Na₂CO₃ was more stable than K₂CO₃ during SCWG. SEM-EDX results also revealed that more K was migrated into solid residues than Na. The analysis of pore structure demonstrated that alkali catalyst promoted the evolution of pore structure, resulting in higher specific surface areas and total pore volumes. Na₂CO₃ has a more substantial destructive effect on solid matrix, causing the matrix structure to collapse and inhibiting pore structure development. The FTIR spectra of solid products exhibited a lower content of carbohydrates and aromatic structures than the initial oily sludge. NH₄-N results demonstrated that SCWG was a potential green treatment process for oily sludge. This work can not only give an insight into the reaction mechanism of alkali catalytic gasification of oily sludge, but also help to guide the optimal design of reactor and the regulation of operating parameters.

Removal of Methylene Blue by Metal Oxides Supported by Oily Sludge Pyrolysis Residues

As a typical pollutant, methylene blue poses a serious threat to the environment and human health. Oily sludge pyrolysis residue loaded with metal oxides could be used to prepare composite materials, which is not only an effective way to treat oily sludge, but also a possible method to treat methylene blue pollutants. In this paper, composite materials (AC-CuO, AC-ZnO, and AC-TiO2) were prepared by oily sludge pyrolysis residue-loaded CuO, ZnO, and TiO2 directly, and characterized by XRD, SEM, EDS, BET, FT-IR, and XPS, and it was shown that the metal oxides were successfully supported on the pyrolysis residue. Then, the composite materials were applied to the removal of methylene blue solution. The removal effect of composite materials on methylene blue with respect to the impregnation time, impregnation ratio and dosage, and the contact time and number of regenerations were investigated, and the removal parameters were optimized by response surface methodology. The removal process for methylene blue was described by applying Lagergren, McKay, Langmuir isotherm, Freundlish isotherm and intraparticle diffusion models. According to the response surface methodology and the main factors affecting the removal effect of methylene blue, the results indicate that the removal effect of 5 mg/L methylene blue could reach 95.28%, 94.95%, and 96.96%, respectively, and the corresponding removal capacities were 4.76, 4.75, and 4.85 mg/g. In addition, kinetic studies showed that the removal process of methylene blue was mainly constituted by chemical adsorption. The intraparticle diffusion showed that the removal of methylene blue may be controlled by both liquid film diffusion and intraparticle diffusion. The isotherms showed that the adsorption sites of composites for methylene blue were uniformly distributed and had the same affinity. Furthermore, regeneration experiments showed that the composite materials were stable and had relatively reusability.

Novel conditioner for efficient dewaterability and modification of oily sludge with high water content

The oily sludge with high water content (OS) was dewatered, modified, and converted into solid fuel by a novel chemical conditioner (OSO-101). The effect of OSO-101 dosage on the dewaterability of OS was studied, showing that OSO-101 dosage of 15% (wt.) could achieve the best dewaterability efficiency of OS (98.18%). Meanwhile, compared with some conventional conditioners, OSO-101 developed by our team was more effective in improving OS dewaterability efficiency. And OSO-101 may have free radical reaction, polar reaction, and redox reaction with petroleum hydrocarbons in OS, thereby polymerizing and forming condensed solid structures. The calorific value change of OS after conditioning, heavy metal content, and dioxin content of fly ash leached from incinerated product were measured for resource analysis and environmental assessment. Results showed that the resultant OS fuel blocks had extremely low content of heavy metals, dioxins, and other toxic and hazardous substances leached from fly ash. And this process did not require secondary treatment and fully met environmental protection emission standards. Additionally, OSO-101 had certain economic rationality and could effectively recover the calorific value contained in OS. This research is expected to provide new insights for efficient dewaterability and modification of OS, as well as subsequent resource utilization and harmless treatment, bringing potential environmental and economic benefits.

Characterization of heavy metals and oil components in the products of oily sludge after hydrothermal treatment

In this study, the method combining hydrothermal treatment (HT) and in-situ mechanical compression (MC) is used to treat oily sludge. The possible transfer and reaction pathways of different oil components during the process of HT&MC were investigated. In addition, the leaching toxicity, distribution, and risk of heavy metals in oily sludge treated in different temperatures and residence times were evaluated. The results revealed that siloxane and heavy oil components are left in the solid residue, and the light oils and oils with hydrophilic groups are transferred to hydrothermal fluids. The content of Cd, Cr, Pb, and Zn in form of F4 (residual) in the solid residue obtained at a hydrothermal temperature of 240 °C and residence time of 60 min increased by 7.37%, 1.21%, 3.06%, and 9.97%. This reduced the biological availability and environmental risk of heavy metals in the treated oily sludge. Meanwhile, the result of FT-IR illustrated an increase in hydroxyl groups of alcohols, phenols and organic acids, which have a beneficial effect on the adsorption of heavy metals and other pollutants. All results indicated that HT&MC might be a suitable pretreatment method for the stabilization of heavy metals in oily sludge.