Microwave catalytic co-pyrolysis of chlorella vulgaris and oily sludge: Characteristics and bio-oil analysis

Interaction Effects between the Main Components of Protein-Rich Biomass during Microwave-Assisted Pyrolysis

The interaction effects between the main components (proteins (P), carbohydrates (C), and lipids (L)) of protein-rich biomass during microwave-assisted pyrolysis were investigated in depth with an exploration of individual pyrolysis and copyrolysis (PC, PL, and CL) of model compounds. The average heating rate of P was higher than those of C and L, and the interactions in all copyrolysis groups reduced the max instant heating rate. The synergistic extent (S) of PC and PL for bio-oil yield was 16.78 and 18.24%, respectively, indicating that the interactions promoted the production of bio-oil. Besides, all of the copyrolysis groups exhibited a synergistic effect on biochar production (S = 19.43-28.24%), while inhibiting the gas generation, with S ranging from -20.17 to -6.09%. Regarding the gaseous products, apart from H2, P, C, and L primarily generated CO2, CO, and CH4, respectively. Regarding bio-oil composition, the interactions occurring within PC, PL, and CL exhibited a significantly synergistic effect (S = 47.81-412.96%) on the formation of N-heterocyclics/amides, amides/nitriles, and acids/esters, respectively. Finally, the favorable applicability of the proposed interaction effects was verified with microalgae. This study offers valuable insights for understanding the microwave-assisted pyrolysis of protein-rich biomass, laying the groundwork for further research and process optimization.

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.

Progress in thermochemical co-processing of biomass and sludge for sustainable energy, value-added products and circular economy

To achieve the main goal of net zero carbon emission, the shift from conventional fossil-based energy/products to renewable and low carbon-based energy/products is necessary. Biomass has been perceived as a carbon-neutral source from which energy and value-added products can be derived, while sludge is a slurry waste that inherently contains high amount of minerals and organic matters. Hence, thermochemical co-processing of biomass wastes and sludge could create positive synergistic effects, resulting in enhanced performance of the process (higher conversion or yield) and improved qualities or characteristics of the products as compared to that of mono-processing. This review presents the current progress and development for various thermochemical techniques of biomass-sludge co-conversion to energy and high-value products, and the potential applications of these products from circular economy's point of view. Also, these technologies are discussed from economic and environmental standpoints, and the outlook towards technology maturation and successful commercialization is laid out.

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.

Trend in Research on Characterization, Environmental Impacts and Treatment of Oily Sludge: A Systematic Review

Oily sludge is a hazardous material generated from the petroleum industry that has attracted increasing research interest. Although several review articles have dealt with specific subtopics focusing on the treatment of oily sludge based on selected references, no attempt has been made to demonstrate the research trend of oily sludge comprehensively and quantitatively. This study conducted a systematic review to analyze and evaluate all oily sludge-related journal articles retrieved from the Web of Science database. The results show that an increase in oily sludge-related research did not take place until recent years and the distribution of the researchers is geographically out of balance. Most oily sludge-related articles focused on treatment for harmfulness reduction or valorization with limited coverage of formation, characterization, and environmental impact assessment of oily sludge. Pyrolytic treatment has attracted increasing research attention in recent years. So far, the research findings have been largely based on laboratory-scale experiments with insufficient consideration of the cost-effectiveness of the proposed treatment methods. Although many methods have been proposed, few alone could satisfactorily achieve cost-effective treatment goals. To enable sustainable management of oily sludge on a global scale, efforts need to be made to fund more research projects, especially in the major oil-producing countries. Pilot-scale experiments using readily available and affordable materials should be encouraged for practical purposes. This will allow a sensible cost-benefit analysis of a proposed method/procedure for oily sludge treatment. To improve the treatment performance, combined methods are more desirable. To inform the smart selection of methods for the treatment of different oily sludge types, it is suggested to develop universally accepted evaluation systems for characterization and environmental risk of oily sludge.

Microwave catalytic co-pyrolysis of Chlorella vulgaris and high density polyethylene over activated carbon supported monometallic: Characteristics and bio-oil analysis

Activated carbon (AC) has attracted much attention owing to its low cost and abundant sources. In this paper, three monometallic supported catalysts were prepared using AC as support (Ce/AC, Fe/AC, Ni/AC), and the effects of three catalysts on the microwave co-pyrolysis of Chlorella vulgaris (C. vulgaris) with high density polyethylene (HDPE) were studied. The results showed that the co-pyrolysis characteristics of C. vulgaris/HDPE = 1:1 (C1HP1) were significantly improved by three catalysts at high additions (>20 %). Among them, the C1HP1 group with 50 % Fe/AC addition had the shortest co-pyrolysis reaction time (2901 s). Besides, Ce/AC and Fe/AC have a promoting effect on bio-oil yields, while Ni/AC has an inhibiting effect. The maximum bio-oil yield (25.6 %) was obtained under 40 % addition of Fe/AC. Moreover, Ce/AC obtained the highest hydrocarbons content (66.68 %), while Fe/AC obtained the highest aromatic hydrocarbons content (36.64 %). Additionally, Ce/AC had the highest deoxygenation efficiency (47.33 %) and denitrification efficiency (42.28 %).