Continuous Pyrolysis Technology for Oily Sludge Treatment in the Chain-Slap Conveyors

Homogenizing microwave pyrolysis of oily sludge using nano-Fe3O4: volatile gas product analysis

To improve the homogeneity of heating, the magnetic absorbing material Fe3O4 is considered to use in microwave pyrolysis of oily sludge. Therefore, the effect of Fe3O4 on the microwave pyrolysis of oily sludge is investigated based on gas volatile products. Thermogravimetric mass spectrometry result certifies that Fe3O4 will increase the weight-loss ratio from 13.0% to 14.1%. Also, the characteristic peak intensity of CO in gas products decreases from 5.41 × 10-10 A/g to 1.95 × 10-10 A/g, while H2O increases from 3.57 × 10-10 A/g to 7.32 × 10-10 A/g and CO2 increases from 6.87 × 10-10 A/g to 8.92 × 10-10 A/g. This is caused by the esterification of alcohols and esters and the reduction of Fe3O4 by CO. Based on the decrease in activation energy and enthalpy values of Stage II and IV, it infers that Fe3O4 catalyzes the pyrolysis process of oily sludge to some extent. Similarly, gas chromatography-mass spectrometry results show that Fe3O4 can make the types of gas products increase. Especially, the number of molecular species increases from 5 to 46 under 200-300 °C. Finally, a simple molecular dynamics simulation model is conducted, and the results are in agreement with the experimental results. This study shows that Fe3O4 improves the pyrolysis homogeneity and the pyrolysis efficiency also improves.

Production of Mesoporous Magnetic Carbon Materials from Oily Sludge by Combining Thermal Activation and Post-Washing

In this work, the oily sludge (OS) from a local waste oil recycling plant was reused as a precursor for producing porous magnetic carbon composites (CC) by pyrolysis, followed by carbon dioxide activation. Based on the thermogravimetric analysis (TGA) of the OS feedstock, the preparation experiments were performed at 800−900 °C. From the pore analysis of the CC products, it indicated an increasing trend, as the BET surface area greatly increased from about 1.0 to 44.30 m2/g. In addition, the enhancement effect on the pore properties can be consistently obtained from the acid-washed CC products because the existing and new pores were reformed due to the leaching-out of inorganic minerals. It showed an increase from 32.27 to 94.45 m2/g and 44.30 to 94.52 m2/g at 850 and 900 °C, respectively, showing their mesoporous features. These porous and iron-containing features were also observed by the scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). In addition, the adsorption removal of total organic carbon (TOC) in the raw wastewater, by the CC product, showed its high performance (>80%).

A review of application and development of combustion technology for oil sludge

Oil sludge is a typical hazardous waste in the petrochemical and electric power industry. It has complex components and special properties, and has serious hazards to humans, plants, water, and soil. Therefore, how to realize the effective disposal of oil sludge has become an urgent issue to be solved worldwide. Among the existing oil sludge treatment approaches, combustion has been considered to be a promising technology to realize the large-scale industrial application. In the present work, the characteristics of oil sludge were described in detail. The application and development of oil sludge combustion technology were critically summarized and discussed, including factors affecting combustion, drying process, combustion characteristics, synergistic treatment technology, and formation and control of secondary pollution. Besides, the development of combustion equipment, and integrated thermal treatment technology for oil sludge were prospected. This work can be used for guiding the industrial disposal of oil sludge.

Materials and energy recovery from oily sludges removed from crude oil storage tanks (tank bottoms): A review of technologies

Sludge and solids accumulating in crude oil storage tanks (referred as tank bottoms) reduces tank volume and requires periodic removal and disposal. Effective management of tank bottoms require considerations to reduce the toxicity of wastes and reduce potential environment impacts. This review compares alternative technologies for economical and environmentally beneficial management of oily sludges for recovery of hydrocarbons and energy with and without oil recovery. Management options with oil recovery include solvent extraction, centrifugation, surfactant oil recovery, and pyrolysis. Management options without oil recovery include incineration and anaerobic co-digestion. The selection of the appropriate technology depends on the characteristics of oily sludge, treatment capacity, as well as operation and maintenance costs. An efficient treatment can involve integration of different technologies for recovery of different oil fractions and to reduce energy demand. Technologies that utilize renewable energy (e.g., solar pyrolysis) can offset the high energy demand of pyrolysis process while recovering marketable products.

Products distribution and hazardous elements migration during pyrolysis of oily sludge from the oil refining process

Oily sludge is a hazardous waste due to the enrichment of nitrogen, sulfur, PAHs, and heavy metals. In this work, an oily sludge from oil refining factory was pyrolyzed at various temperatures of 250-850 °C in a fixed bed reactor focusing on product distribution and migration of hazardous compounds of PAHs, sulfur, nitrogen-containing compounds, and heavy metals. The mechanism of PAHs formation and migration of nitrogen, sulfur, heavy metals were elucidated by comprehensive analysis of the solid, liquid, and gas products. The distribution and risk analysis of heavy metals were also conducted. The pyrolytic products distribution was markedly affected by pyrolysis temperatures. A maximum oil yield was observed at 500 °C, which can further crack into gas due to secondary reaction. The pyrolytic gas was enriched in the order of CO₂ > CO > CH₄ > H₂. At lower temperatures, CO₂ was largely generated due to the elimination of oxygen-containing functional groups, while H₂ was mainly formed above 450 °C due to the recombination reaction. Higher temperatures promoted more N-/S-containing compounds into tar and gas phases. The N-/S-containing compounds mainly included NH₃, HCN, H₂S, SO₂, COS in the gas phase and amines, indoles, pyridines, nitriles, thiophenes in liquid phase. PAHs with 2-ring to 5-ring were mainly generated due to the secondary reaction at higher temperatures. Moreover, Pyrolysis caused the accumulation of heavy metals in chars. Cd presented a high potential risk while the other heavy metals in chars presented a low risk.

Products distribution and interaction mechanism during co-pyrolysis of rice husk and oily sludge by experiments and reaction force field simulation

In this work, the co-pyrolysis behavior of rice husk (RH) and oily sludge (OS) was investigated by combining experiments and simulation. The thermogravimetric-derivative thermogravimetric (TG-DTG) and Reaction force field (ReaxFF MD) results indicate that synergetic effects exist in co-pyrolysis. Compared with the single component pyrolysis, the activation energy of RH and OS in co-pyrolysis was decreased by 15.97% and 17.14% shown by kinetic analysis, respectively. The Pyrolysis-gas chromatography/mass spectrometry (PY-GC/MS) experiments, and simulation products analysis reveal that more bio-oil and molecules with low molecular weight were produced during the co-pyrolysis process. The synergetic effect mechanism was studied by detecting the variation of free radical intermediates. The results show that hydroxyl radicals from RH pyrolysis reduced cracking temperature of OS, and the hydrogen radicals from OS pyrolysis increased the degree of ring-splitting of RH. The study explores an approach to identify the synergetic effect and reveal the mechanism of co-pyrolysis.

Hazardous elements flow during pyrolysis of oily sludge

Oily sludge (OS) is a hazardous waste and pyrolysis is a promising technology to achieve energy recovery and non-hazardous disposal simultaneously. However, the distribution of hazardous elements, including N/S/Cl and heavy metals, in pyrolytic products possibly causes secondary pollution. This study conducted a systematic research on hazardous elements flow during OS pyrolysis under variant temperature. Results showed that N/S/Cl in OS were distributed 44.77-15.51 wt%, 83.29-80.22 wt%, and 78.59-73.41 wt% into the solid residues after pyrolysis, respectively. Elevating pyrolysis temperature facilitated more N/S/Cl flowing into pyrolytic oil and gas. The macromolecular N-/S-/Cl-containing compounds, including amides, amines, nitriles, sulfonates, chloroalkanes, etc., were widely distributed in pyrolytic oil and gas products. The micromolecular N-/S-/Cl-containing pollutants released between 200 and 400 °C included HCN, NH₃, NO_x, H₂S, CH₄S, CS₂, SO₂, and HCl, which originated from the decomposition of the amine N, organic sulfide and sulfone-S, and inorganic Cl, respectively. The main pollutants released at above 400 °C included NH₃, HCN, NO_x, CS₂, and SO₂, which were derived from the decomposition of heterocyclic N and inorganic pyritic-S and sulfate-S. Moreover, the solid residues intercepted more than 60.0 wt% of total heavy metals, which should be concerned in the future.

A critical review on energy recovery and non-hazardous disposal of oily sludge from petroleum industry by pyrolysis

This review systematically reports the pyrolysis of oily sludge (OS) from petroleum industry in regards to its dual features of the energy recovery potential and the environmental risks. The petroleum hydrocarbons are the nonbiodegradable fractions in OS that possess hazardous properties, i.e. ignitability and toxicity. Besides, complicated hazardous elements (i.e. N, S and Cl) and heavy metals inherently existing in OS further aggravate the environmental risks. However, the high oil content and heating value of OS contribute to its huge energy resource potential. Considering the energy demand and the environmental pressure, the ultimate purposes of the OS management are to enhance the oil recovery efficiency to minimize the oil content as well as to stabilize the hazardous elements and heavy metals into the solid residue. Among various OS management technologies, pyrolysis is the most suitable approach to reach both targets. In this review paper, the pyrolysis principle, the kinetics and the product distribution in three-phases are discussed firstly. Then the effects of operating parameters of the pyrolysis process on the quality and the application potential of the three-phase products, as well as the hazardous element distribution are discussed. To further solve the dominant concerns, such as the oil content in the solid residue, the pyrolytic oil quality and the migration of hazardous elements and heavy metals, the potentials of the catalytic pyrolysis and the co-pyrolysis with additives are also summarized. Also, the typical pyrolysis reactors are then presented. From the perspective of the energy efficiency and the non-hazardous disposal, the integrated technology combining the pyrolysis and the combustion for the OS management is recommended. Finally, the remaining challenges of OS pyrolysis encountered in the research and the industrial application are discussed and the related outlooks are itemized.

Anaerobic Co-Digestion of Oil Sludge with Corn Stover for Efficient Biogas Production

The feasibility of anaerobic co-digestion for the utilization of oil sludge was verified using corn stover, to assess the influence of different raw material ratios and inoculum volumes on the properties of the generated gas. The anaerobic co-digestion method is a novel treatment technology, which may help to solve the problem of pollution by hazardous waste oil sand from the oil exploitation and smelting process. Results showed that single-oil sludge was not suitable for gas production as a digestive substrate due to the lack of organic materials and possible hazardous materials. With the increase in the quality of exogenous organic matter (corn stover), the cumulative gas production volume was proportional to the amount of corn stover material added. It was established that when the mass ratio of corn stover to oil sludge was 4:1, the gas production performance was optimal, with a cumulative gas yield of 1222.5 mL using an inoculum volume of 30 mL. The results of this study provide a fundamental parameter baseline for the treatment of oil sludge and the improvement of gas production efficiency.