Search

This article proposed an original comprehensive thermal treatment coupled with gasification and combustion (CGC) of oil sludge (OS), which was designed to produce hydrogen-rich syngas. Based on the experimental results of OS gasification with steam, the combustion characteristics of char from OS gasification were analyzed by thermogravimetric experiments under different heating rates of 10, 20 and 30 °C/min. The combustion process of OS gasification char can be divided into three stages, including water evaporation, volatile combustion and heavy component combustion. The average values of activation energy (E) obtained by Friedman, FWO and Starink methods were 89.98 kJ/mol, 147.61 kJ/mol and 143.09 kJ/mol, respectively. According to OS gasification and OS gasification char combustion experiments, the comprehensive thermal treatment process CGC of OS was simulated by Aspen Plus. The simulation results showed that increasing both gasification temperature and the mass ratio of steam to OS (SOS) could promote the hydrogen production. Considering energy consumption, the recommended OS gasification temperature, SOS and char combustion temperature were 800 ∼ 900 °C, 0.3 ∼ 0.5, and 900 ∼ 1000 °C, respectively, which could ensure full burning of char and reduce the generation of pollutants. The CGC process could reduce CO2 emissions by 44.2% from carbon flow analysis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Combustion of High-sulfur oil sludge (OS) blended with CaO can significantly reduce the emission of sulfur gas pollutants, but its combustion and kinetic characteristics need to be further studied. TGA experiments showed the combustion characteristics of OS were significantly changed after adding CaO. As reflected by comprehensive combustion index (S), the combustion performance of OS decreased after adding CaO, and significantly improved with the increase of heating rate. The kinetic parameters of the main combustion process of OS with CaO were calculated by the iso-conversion methods of Friedman, FWO, and Starink, respectively. Kinetic analysis results indicated the energy required for OS combustion with CaO first increased and then decreased with deepening of reaction degree. The thermodynamic parameters of ΔH, ΔG and ΔS were determined on the basis of kinetics. The negative ΔH, positive ΔG, and negative ΔS validated the combustion of OS with CaO was an exothermic and nonspontaneous process. [ABSTRACT FROM AUTHOR]

Recycling of waste biomass energy has attracted more and more attention. Oil sludge char (OS char) combustion blended with microalgae residue (MR) is a clean, effective method for recycling energy. The co-combustion and kinetics analysis were conducted on a thermogravimetric analyzer (TGA). The simulation calculation and potential toxicity of heavy metals in the co-combustion process were investigated. Results showed that adding MR could improve the combustion performance of OS char. The average activation energy of OS char, MR and the mixture was 121.28 kJ mol−1, 153.43 kJ mol−1, and 142.24 kJ mol−1, respectively. The KAS and Starink methods were more accurate than the FWO method. Besides, the risk assessment results indicated the risk index (RI) values of MR and fly ash at 1100 °C were at a considerable risk level of 140.33 and 109.50, respectively. Simulation results demonstrated that the synergistic removal of arsenic (As) and nitrogen (N) could be achieved by moderately controlling temperature. Furthermore, MR addition could significantly reduce the content of chlorine (Cl) in the mixture, decreasing the generation of gaseous ZnCl 2 and PbCl 2. The results will supply essential data and theoretical support for the high-value utilization and low heavy metal emissions of biomass waste. • OS char combustion mixed with MR is a promising method for energy recovery. • Simulation calculation of heavy metals migration was studied by FactSage. • MR addition improve the combustion characteristics and stability of OS char. • A moderate MR addition could significantly reduce the heavy metals ecotoxicity. • The synergistic removal of As and N elements can be achieved above 1000 °C. [ABSTRACT FROM AUTHOR]

Experimental study on combustion and emission characteristics of microalgae (M) and the extraction residue (MR) was carried out on a coupled thermogravimetric and mass spectrometer system (TG-MS). TG results showed that combustion process of M and MR can be divided into three stages, including water volatilization, the release and combustion of proteins, carbohydrates and lipids, and minerals decomposition. As the heating rate increased, thermal hysteresis was occurred during combustion of M and MR, especially for M. Friedman method, FWO method and Starink method were used to calculate the apparent activation energy during combustion of M and MR. As the conversion rates increased, the apparent activation energy of M and MR showed different trends. The average apparent activation energy of M and MR in the main combustion stage was 183.41 kJ mol−1 and 144.41 kJ mol−1, respectively. MS results demonstrated that the release of nitrogen-containing compounds of M was more than MR while the release of sulfur-containing compounds was similar during M and MR combustion. • Combustion of microalgae and the residue was carried out on a TG-MS system. • The average apparent activation energy of M and MR was 183.41 and 144.41 kJ mol−1, respectively. • Nitrogen-containing compounds released during the combustion in M were more than MR. • The release of sulfur-containing compounds were similar during combustion of M and MR. [ABSTRACT FROM AUTHOR]

Highlights • Co-combustion of OS char and microalgae residue exhibited a good performance. • High temperature promoted the conversion of N-5 and N-6 to N-X. • NO x emissions reached the minimum value 96 mg/m3 with a MR ratio of 50% • When temperature reached 1100 °C, more S4+ was converted to S6+ and S2− Abstract Integrated thermal treatment (coupled pyrolysis and combustion) has great potential to be a clean and effective method for massive oil sludge (OS) utilization. Produced OS pyrolysis char (OS char) can be effectively utilized through fluidized bed incinerator with auxiliary fuels. A study on co-combustion of OS char and microalgae extraction residue (MR) were conducted with a coupled thermogravimetric-mass spectroscopy system (TG-MS), and a fluidized bed reactor system. Co-combustion process of OS char and MR could be divided into three stages, including water evaporation, volatiles release and combustion, fixed carbon combustion and minerals decomposition. SO 2 emissions decreased with the increase of MR ratio and NO x emissions initially decreased followed by an increase until the MR ratio exceeded 50%. Both NO x and SO 2 emissions initially increased before a decrease with combustion temperature raised. Higher excessive air ratio (α) promoted the pollutants emission. Pyrrole (N-5) content increased with the increase of MR ratio and more N-5 and pyridine (N-6) could be converted to oxidized nitrogen (N-X) in the bottom ash under a higher temperature during OS combustion. Besides, the temperature range (900–1000 °C) was conductive to SO 2 release, and S4+ formation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Proposed an effective way of integrated thermal treatment of OS. • Both OS pyrolysis and OS pyrolysis char combustion were studied in this work. • OS char from lower pyrolysis temperature had better combustion characteristics. • OS char was simpler in composition and more homogeneous in chemical property. Abstract Integrated thermal treatment of OS is a promising method for massive and effective treatment of the waste. The present work investigated the tank OS pyrolysis by a thermogravimetric analyzer and a tube furnace reactor. Pyrolysis char combustion performance was studied with the thermogravimetric analyzer. Results showed that OS pyrolysis mainly occurred between 200 °C and 700 °C. With the increase of pyrolysis temperature, char yield decreased while gas yield increased. When pyrolysis temperature exceeded 600 °C, the oil yield decreased. Simulated distillation showed that oil products properties barely changed when pyrolysis temperature exceeded 600 °C. Light fractions (gasoline and diesel) from OS pyrolysis were more than 28% higher than those of oil from OS extraction. Major components of pyrolysis gas include H 2 , CO, CO 2 , and hydrocarbons (CH S ). CH S content was more than 40% in the pyrolysis gas in all cases. The molar H/C ratio and O/C ratio were lower for OS chars from higher temperature pyrolysis. The surface of OS char was rough with a well-developed pore structure formed during pyrolysis, which was conducive to the combustion reaction. The combustion characteristic of OS char from higher temperature pyrolysis was poorer than that of OS char from lower pyrolysis temperature, resulting from the less volatile content and more carbon crystal degree for OS char from higher temperature pyrolysis. With well-developed pore structure, relative simple composition, good ignition and burnout characteristics, OS char could perform well in actual combustion in CFB boilers. [ABSTRACT FROM AUTHOR]

Integrated thermal treatment (coupled pyrolysis and combustion) is considered to be an effective method for the utilization of oil sludge (OS). Characteristics of OS pyrolysis, OS combustion and OS char combustion were comprehensively investigated with a thermogravimetry-mass spectrum (TG-MS) system in this work. Small molecule hydrocarbons like CH 4 were main components in OS pyrolysis gas. Nitrogen and sulfur containing compounds, H 2 O, and CO 2 were detected out during OS and OS char combustion. The maximum intensities of NH 3 , HCN and NO all appeared in the OS combustion. H 2 S was the main precursor of SO 2 , and the peak of H 2 S occurred earlier with an increase in the pyrolysis temperature between 500 and 700 °C. Besides, with an increase in the pyrolysis temperature, NO 2 and SO 2 emissions increased during OS char combustion. [ABSTRACT FROM AUTHOR]

Experimental and simulation studies on the migration characteristics of heavy metals during the incineration of OS were conducted with a tube furnace reactor and thermodynamic equilibrium calculation software FactSage, respectively. The results showed that when the incineration temperature increased from 800°C to 1100°C, the release rates of heavy metals such as Cr, Pb, Cu, Zn and Ni increased gradually and reached the maximum at 1000°C. When the excess air ratio increased from 1.0 to 1.4, the release rates of heavy metals such as Cr, Pb, Cu, Zn and Ni first decreased and then became steady. The content of gaseous hydroxide of Cr and gaseous chlorides of Pb and Cu increased while the chemical forms of Zn and Ni did not change obviously with the increase of combustion temperature or excess air ratio. [ABSTRACT FROM PUBLISHER]