•The mixing ratios of 1:1 showed the better performance in terms of solid yield, carbon and organics retention.•The nitrogen fractions in the solid were increased.•The hydrothermal co-carbonization increased the amount of the surface functional group density of hydrochar by synergism.The aim of this study is to explore the synergistic effects of hydrothermal co-carbonization of sewage sludge and pinewood sawdust on hydrochar production. Firstly, the effects of mixing ratios on hydrothermal carbonization were investigated, and then, the hydrochar was characterized by diverse analytical techniques. The mass balance results indicated that a significant synergistic enhancement occurred in terms of the increased hydrochar yield, organic and carbon retentions. By combining sewage sludge and pinewood sawdust at the mass ratio of 1:1, 58.11 ± 0.91% of hydrochar yield was obtained with high synergistic coefficients (8.41% for hydrochar yield, 13.09% for carbon retention, and 14.92% for organics retention). The hydrochar properties of nutrients, such as nitrogen and phosphorus, and surface functional groups were improved by hydrothermal co-carbonization approach. The FT-IR spectra, CP-MAS 13C NMR and SEM results further indicated that hydrothermal co-carbonization promoted the development of aromaticity and surface structure. Our findings suggested that hydrothermal co-carbonization is a promising strategy to tailor high-performance hydrochar for different applications.

A pyrolysis study of oil sludge with and without oil sludge ash and quartz sand as solid heat carriers was conducted using a laboratory-scale reactor and thermogravimetric analyzer. The effects of the pyrolysis temperature and solid heat carrier on the product distribution and oil quality were investigated. The results of the oil sludge ash addition case were compared to those of the quartz sand case to evaluate the possibility of using oil sludge ash as a solid heat carrier in the oil sludge pyrolysis process. The chemical characterization of the oil products was performed by FT-IR (Fourier transform infrared spectroscopy) and NMR analyses. Finally, the possible catalytic effect of oil sludge ash and the sulfur transformation pathway were proposed. The results of the experiment demonstrate that the presence of oil sludge ash can increase the oil yield and reduce the optimal reaction temperature from 500 to 450 °C. Oil sludge ash can reduce the coke yield and the carbon residue of the oil product and increase the light oil/heavy oil ratio of the oil product to a greater degree than quartz sand. The presence of pyrrhotite in the oil sludge ash was inferred to be the reason why oil sludge ash is able to reduce the coke yield and carbon residue of the oil product. The results of this study indicate that oil sludge ash is a potential alternative to quartz sand as a solid heat carrier in the pyrolysis process of oil sludge for oil production.

•NiO/ceramic foam catalyst was employed for tar reforming.•The maximum hydrogen yield reached 105.28 g H2/kg tar at 700 °C and S/C = 1.•High ratio of S/C was in favor of hydrogen yield, and the increase of ER caused the hydrogen yields decrease.•The catalyst was activated in situ and the carbon deposition can be removed by regular in situ oxidization.In this study, the catalytic steam reforming of biomass tar for hydrogen production was carried out in a fixed-bed reactor with NiO/ceramic foam catalyst. The ceramic foam used as catalyst carrier was a three-dimensional porous material with high porosity and high specific heat capacity. The effects of reaction temperature, steam to carbon ratio (S/C) and equivalence ratio (ER) on gas quality parameters were investigated. And the fresh, coked and regenerated NiO/ceramic foam catalysts were characterized by SEM and XRD analyses. It was found that, when the temperatures varied from 500 to 900 °C and S/C ratio from 0 to 4, H2 yields were in the range of 28.29–105.28 g H2/kg tar. With increasing ERs, the concentrations of H2 decreased from 63.13 to 18.96%. SEM and XRD analyses showed that the catalyst was in situ activated by reducing nickel oxide to the active nickel metal during a reducing atmosphere in steam reforming process.

Ash deposition and fusion during the incineration of high-concentration organic wastewater rich in salt is complicated by various issues, resulting in severe operational problems, such as fouling, slagging, and even unscheduled shutdown. The fusion characteristics and melting kinetics of ash samples collected from an industrial-scale wastewater incineration plant were determined by ash fusion temperature tests, simultaneous thermal analysis, and X-ray powder diffractometry. The results showed that the ash fusion characteristics depended upon not only ash compositions but also mineralogy transformation and evolution. The major melting process of ash sample 1 was within the range of 1158–1196 K. Because of the existence of the low-temperature eutectic compounds Na3Fe(SO4)3 and Na2Ni(SO4)2·4H2O, the temperature ranges of melting processes of ash samples 2–4 were 200–300 K lower than that of ash sample 1. Weight loss processes in ash sample 5 continued over the whole furnace temperature range. The Coats–Redfern equation was used to approximately evaluate the ash melting kinetics. Ash sample 1 had the highest activation energy for an ash melting process (3125.31 kJ mol–1). Ash samples 2 and 5 had relatively moderate activation energies (729.15–1338.93 kJ mol–1). Ash samples 3 and 4 had the lowest activation energies (374.00 and 375.68 kJ mol–1), which indicated that Na2SO4 melting required more energy than the melting of low-temperature eutectic compounds. The most probable reaction model for all of the melting processes was f(α) = (1 – α)2. The most probable reaction model for the melting process at 1163.0–1284.9 K in ash sample 3 was f(α) = (1 – α)4.

•Pyrolysis behavior of dried sewage sludge was investigated by thermogravimetric analysis and a tubular pyrolyzer.•The activation energies for two temperature ranges of 186–296 °C and 296–518 °C were 82.28 kJ mol−1 and 48.34 kJ mol−1, respectively.•The main gaseous products identified by the FTIR were CH4, CO2, CO and organic volatile compounds such as aldehydes, acids, alcohols and phenols.•The maximum oil yield of 46.14% was obtained at the temperature of 550 °C under the fast pyrolysis condition.Pyrolysis behavior of dried sewage sludge was studied by thermogravimetric–Fourier transforms infrared analysis (TG–FTIR) and differential scanning calorimetry (DSC) to investigate thermal decomposition and kinetics analysis. A tubular pyrolyzer was used to explore the production distribution of dried sewage sludge pyrolysis under different runs. The results showed that two weight loss peaks were presented in pyrolysis reaction in the ranges of 186–296 °C and 296–518 °C, and the activation energy of each stage was 82.284 kJ mol−1 and 48.342 kJ mol−1, respectively. The main gases identified by FTIR analysis were CH4, CO2, CO and organic volatile compounds such as aldehydes, acids, alcohols and phenols. Under fast pyrolysis of dried sewage sludge, the maximum tar yield obtained was 46.14% at the temperature of 550 °C. The concentrations of all gases increased steadily with increasing pyrolysis temperature from 450 °C to 650 °C except for CO2.

•A flash pyrolysis of oilfield sludge was carried out in a rotary kiln reactor.•The maximum oil yield was achieved at temperature of 550 °C and MR of 1:2.•Functional group of pyrolytic oils are similar as extraction oils.•The pyrolytic oils are the major linear chain hydrocarbons in the range C13–C25.In this work, an experimental study of flash pyrolysis of oilfield sludge in different operation conditions was carried out under inert condition in a rotary kiln reactor. The effects of pyrolysis temperature, mixture ratio (MR) of sludge and solid heat carrier on the characteristics of product distribution were investigated. The composition of oils obtained from extraction and pyrolysis process were analyzed by Fourier transform infrared spectroscopy (FT-IR) and gas chromatography–mass spectrometry (GC–MS), respectively. The results indicated that, the maximum oil yield was achieved at temperature of 550 °C and MR of 1:2, which was 28.98% (wt% of sludge oil) and oil recovery rate was 87.9% basing on the oil content in the sludge. High fraction of saturates (72.5%) was obtained at 550 °C. The increasing temperature and solid heat carrier favor of pyrolysis gases increase. FT-IR analysis of pyrolytic oils shows that the oils have similar IR features as extraction oils. The pyrolytic oil was also found to contain the major linear chain hydrocarbons in the range of C13–C25.

In this study, a dynamic model of oil sludge pyrolysis in a rotary kiln with a solid heat carrier was developed. In the proposed model, both the particle motion in the rolling mode and oil sludge pyrolysis were taken into consideration. Saeman’s model and a multiple-reaction model were involved to simulate the bed depth profile inside the rotary kiln based on the solid motion and the volatile evolution, respectively. Furthermore, the temperature profiles of three phases (solid carrier, oil sludge, and gaseous phase) in diverse conditions were predicated by combining pyrolysis kinetics, heat transfer, and motion equations. In the proposed model, the yields of CxHy, H2, CO, and CO2 were successfully stimulated and predicted. The validity of the model was verified from both aspects of solid axial velocity and gas yields by comparing numerical values to literature reports and experimental data, respectively. This simulation practice was expected to provide an alternative approach to obtain helpful parameters for the designing of an industry-scale rotary kiln pyrolyzer.

Challenges including low furfural yield, high energy and fresh water consumption and a high level of pollution have blocked the development of the furfural industry for decades. In this study, a seawater-based furfural process integrated with wastewater recycling was proposed. In this process, acetic acid steam and FeCl3 were used as environmentally friendly catalysts instead of mineral acids. In order to provide supporting data for acetic acid steam-catalyzed furfural production, data on the vapor/liquid components of the water + acetic acid system were experimentally determined. In addition, the effects of acetic acid steam, seawater or/and FeCl3 on corncob hydrolysis were systematically investigated. The results indicated that coexistence of three components resulted in a remarkable increase in furfural yield and delignification efficiency. Maximum furfural yields of 72.93% and 79.53% of lignin removal were obtained at 190 °C in the presence of 60 mM FeCl3 and concentrated seawater (10×) in acetic acid steam. Another special focus was put on exploring the feasibility of reutilizing the furfural wastewater as a steam and acetic acid source. The results showed that comparable furfural yield and lignin removal were obtained when furfural wastewater was used instead of pure acetic acid steam. The seawater-based furfural production integrated with wastewater recycling provides a green and environmentally friendly approach to the furfural or other bio-chemicals industry.

In the present study, an updraft biomass gasifier combined with a porous ceramic reformer was used to carry out the gasification reforming experiments for hydrogen-rich gas production. The effects of reactor temperature, equivalence ratio (ER) and gasifying agents on the gas yields were investigated. The results indicated that the ratio of CO/CO2 presented a clear increasing trend, and hydrogen yield increased from 33.17 to 44.26 g H2/kg biomass with the reactor temperature increase, The H2 concentration of production gas in oxygen gasification (oxygen as gasifying agent) was much higher than that in air gasification (air as gasifying agent). The ER values at maximum gas yield were found at ER = 0.22 in air gasification and at 0.05 in oxygen gasification, respectively. The hydrogen yields in air and oxygen gasification varied in the range of 25.05–29.58 and 25.68–51.29 g H2/kg biomass, respectively. Isothermal standard reduced time plots (RTPs) were employed to determine the best-fit kinetic model of large weight biomass air gasification isothermal thermogravimetric, and the relevant kinetic parameters corresponding to the air gasification were evaluated by isothermal kinetic analysis.Highlights► An updraft biomass gasifier with a porous ceramic reformer for hydrogen-rich gas production was studied. ► The ER values of maximum gas yield were 0.22 and 0.05 in air and oxygen gasification. ► The best-fit kinetic models of air gasification were determined by Reduced time plots (RTPs). ► The activation energy is 34.295 kJ mol−1 and 23.797 kJ mol−1 in the 5 g and 10 g samples thermogravity, respectively.

Recycling of printed circuit board (PCB) waste is an important subject not only for the protection of environment but also for the recovery of valuable materials. A preliminary study of the possibilities of pyrolysis for recovering valuable products and energy from PCB waste was presented. Pyrolysis of PCB waste was performed on a fixed-bed reactor. The properties of the pyrolytic oil and residue were investigated. The oil was characterized by various chromatographic and spectroscopic techniques. Chromatographic and spectroscopic studies on the pyrolysis oil showed that it contained significant concentrations of phenol, as well as 4-(1-methylethyl)-phenol and could potentially be recycled into phenolic resin. The oil was then polymerized with formaldehyde under basic conditions to synthesize pyrolysis oil-based resin. FT-IR and 1H NMR analysis revealed that the aromatic nuclei in the oil were linked by ether linkages or methylene bridges after polymerization. The pyrolysis residues obtained from PCB waste were very friable, prone to delamination and could be easily liberated for carbon, glass fiber, and metallic fractions. A controlled combustion of the solid phase allowed the formation of glass fibers unaltered, which could be recycled.

This paper investigates the hydrogen-rich gas produced from biomass employing an updraft gasifier with a continuous biomass feeder. A porous ceramic reformer was combined with the gasifier for producer gas reforming. The effects of gasifier temperature, equivalence ratio (ER), steam to biomass ratio (S/B), and porous ceramic reforming on the gas characteristic parameters (composition, density, yield, low heating value, and residence time, etc.) were investigated. The results show that hydrogen-rich syngas with a high calorific value was produced, in the range of 8.10–13.40 MJ/Nm3, and the hydrogen yield was in the range of 45.05–135.40 g H2/kg biomass. A higher temperature favors the hydrogen production. With the increasing gasifier temperature varying from 800 to 950 °C, the hydrogen yield increased from 74.84 to 135.4 g H2/kg biomass. The low heating values first increased and then decreased with the increased ER from 0 to 0.3. A steam/biomass ratio of 2.05 was found as the optimum in the all steam gasification runs. The effect of porous ceramic reforming showed the water-soluble tar produced in the porous ceramic reforming, the conversion ratio of total organic carbon (TOC) contents is between 22.61% and 50.23%, and the hydrogen concentration obviously higher than that without porous ceramic reforming.

•OSFA is recycled as a secondary material to produce value-added glass–ceramics.•The increase of basicity promotes the crystallization and densification of samples.•The properties of glass–ceramics are improved when increasing the basicity.•Based on the results, the glass–ceramics possess good properties and are safe to use.Recently, various solid wastes such as sewage sludge, coal fly ash and slag have been recycled into various products such as sintered bricks, ceramics and cement concrete. Application of these recycling approaches is much better and greener than conventional landfills since it can solve the problems of storage of industrial wastes and reduce exploration of natural resources for construction materials to protect the environment. Therefore, in this study, an attempt was made to recycle oil shale fly ash (OSFA), a by-product obtained from the extracting of shale oil in the oil shale industry, into a value-added glass–ceramic material via melting and sintering method. The influence of basicity (CaO/SiO2 ratio) by adding calcium oxide on the performance of glass–ceramics was studied in terms of phase transformation, mechanical properties, chemical resistances and heavy metals leaching tests. Crystallization kinetics results showed that the increase of basicity reduced the activation energies of crystallization but did not change the crystallization mechanism. When increasing the basicity from 0.2 to 0.5, the densification of sintering body was enhanced due to the promotion of viscous flow of glass powders, and therefore the compression strength and bending strength of glass–ceramics were increased. Heavy metals leaching results indicated that the produced OSFA-based glass–ceramics could be taken as non-hazardous materials. The maximum mechanical properties of compression strength of 186 ± 3 MPa, bending strength of 78 ± 6 MPa, good chemical resistances and low heavy metals leaching concentrations showed that it could be used as a substitute material for construction applications. The proposed approach will be one of the potential sustainable solutions in reducing the storage of oil shale fly ash as well as converting it into a value-added product.Graphical abstractDownload high-res image (102KB)Download full-size image

•Glass ceramic composite is prepared from oil shale fly ash and MSWI bottom ash.•A novel method for the production of glass ceramic composite is presented.•It provides simple route and lower energy consumption in terms of recycling waste.•The vitrified slag can promote the sintering densification process of glass ceramic.•The performances of products decrease with the increase of oil shale fly ash content.Oil shale fly ash and municipal solid waste incineration bottom ash are industrial and municipal by-products that require further treatment before disposal to avoid polluting the environment. In the study, they were mixed and vitrified into the slag by the melt-quench process. The obtained vitrified slag was then mixed with various percentages of oil shale fly ash and converted into glass ceramic composites by the subsequent sintering process. Differential thermal analysis was used to study the thermal characteristics and determine the sintering temperatures. X-ray diffraction analysis was used to analyze the crystalline phase compositions. Sintering shrinkage, weight loss on ignition, density and compressive strength were tested to determine the optimum preparation condition and study the co-sintering mechanism of vitrified amorphous slag and oil shale fly ash. The results showed the product performances increased with the increase of sintering temperatures and the proportion of vitrified slag to oil shale fly ash. Glass ceramic composite (vitrified slag content of 80%, oil shale fly ash content of 20%, sintering temperature of 1000 °C and sintering time of 2 h) showed the properties of density of 1.92 ± 0.05 g/cm3, weight loss on ignition of 6.14 ± 0.18%, sintering shrinkage of 22.06 ± 0.6% and compressive strength of 67 ± 14 MPa. The results indicated that it was a comparable waste-based material compared to previous researches. In particular, the energy consumption in the production process was reduced compared to conventional vitrification and sintering method. Chemical resistance and heavy metals leaching results of glass ceramic composites further confirmed the possibility of its engineering applications.Download full-size image

Municipal solid waste incineration (MSWI) fly ash is classified as a hazardous waste due to its high content of leachable heavy metals. Currently, cement-based stabilization process before landfill has attracted much attention since it can transform the hazardous waste into non-hazardous waste. It is known that MSWI fly ash in China has high-level of soluble chlorides, which has a negative effect on the stabilization of the solidified matrix. In this study, therefore, a water washing pre-treatment process was applied to remove chlorides as much as possible. Experiments were conducted at the conditions of liquid-to-solid (L/S) ratio of 10, 20, 30, 40 and 50 and washing time of 0.5, 1, 2, 3 and 4 h for the washing process. Based on the analysis, the MSWI fly ash with L/S ratio of 10 and washing time of 2 h was selected for the subsequent experiment. The washed fly ash and raw fly ash were then mixed with different amounts of cement and placed into the mould for 7, 14 and 28 days, respectively. The results showed that cement-based solidification process exhibited the maximum compressive strength of 7.87 MPa when the addition of cement was 67% and the maintenance period was 7 days. Besides, toxic characteristic leaching procedure (TCLP) tests showed that the solidified matrix can meet the requirement of landfill.

The purpose of this study is to explore the possibility of long-term sustainable anaerobic digestion of food waste in semi-continuous single-stage reactors by supplementing trace elements. Compared with the failure of anaerobic digestion of food waste after prolonged operation, a clearly enhancement of process performance was observed by supplementing a model trace element solution. Although the sustainable continuous anaerobic digestion of food waste could not be achieved by supplementing a model trace element solution, the correlation of process performance and trace element profile during continuous operating period revealed that the declining performance was highly likely due to the decreasing trace element concentrations, especially Co, Mo, Ni and Fe. This finding was expected to provide a promising strategy for sustainable anaerobic digestion of food waste.