Pyrolysis of palm kernel shell with internal recycling of heavy oil

E-waste management, treatment options and the impact of heavy metal extraction from e-waste on human health: Scenario in Vietnam and other countries

Ho Chi Minh (HCM) City is the most important urban region of Vietnam, Southeast Asia. In recent times, the quantity of electronic waste (e-waste) has been growing by several thousand tonnes every year. In this research, some of the existing and developing technologies being employed for the recycling of e-waste have been reviewed. Accordingly, the paper has been divided into three sections namely, e-waste treatment technologies in Ho Chi Minh City, the effect of heavy metals on human health and the extraction of metals from e-waste using pyrolysis, hydrometallurgy, bioleaching, mechanical, and air classifier methods, respectively. The extraction of precious metals and heavy metals such as Cd, Cr, Pb, Hg, Cu, Se, and Zn from e-waste can be hazardous to human health. For example, lead causes hazards to the central and peripheral nervous systems, blood system and kidneys; copper causes liver damage; chronic exposure to cadmium ends up causing lung cancer and kidney damage, and mercury can cause brain damage. Thus, this study examines the key findings of many research and review articles published in the field of e-waste management and the health impacts of metal pollution.

Integrated Leaching and Thermochemical Technologies for Producing High-Value Products from Rice Husk: Leaching of Rice Husk with the Aqueous Phases of Bioliquids

It remains challenging to develop a techno-economically feasible method to remove alkali and alkaline earth metal species (AAEMs) from rice husk (RH), which is a widely available bioresource across the world. In this study, the AAEMs leaching effect of aqueous phases of both bio-crude prepared by hydrothermal liquefaction (AP-HT) and bio-oil prepared by pyrolysis (AP-Pyro) of RH were systematically investigated. The results indicated that although the acidity of AP-HT and AP-Pyro are much lower than that of HCl, they performed a comparable removal efficiency on AAEMs (Na: 56.2%, K: 96.7%, Mg: 91.0%, Ca: 46.1% for AP-HT, while Na: 58.9%, K: 96.9%, Mg: 94.0%, Ca: 86.3% for AP-Pyro) with HCl. The presence of phenolics in bio-oil could facilitate the penetration of water and organic acids into the inner area of RH cells, thus enhancing the AAEMs removal via chelate reactions. The thermal stability of leached RH during thermochemical conversions was studied via TG and Py-GC-MS. The results showed that the heat conduction efficiency in leached RH was enhanced with a high pyrolysis rate, resulting in a narrow carbon chain distribution (C5–C10) of derived chemical compounds.

Biomass pyrolysis with alkaline-earth-metal additive for co-production of bio-oil and biochar-based soil amendment

The alkaline-earth-metal (AEM) has a good performance on modification of both bio-oil and biochar during biomass pyrolysis. In this work, the pyrolysis of rice husk (RH) in the presence of CaO, CaCO₃, MgO and MgCO₃ was comparatively studied for selecting an appropriate AEM additive to balance the qualities of pyrolytic products. Pyrolysis of RH with the AEM additives could decrease the acids content and increase the hydrocarbons content in bio-oil. Compared with the Ca-additives (i.e., CaO, CaCO₃), the Mg-additives (i.e., MgO, MgCO₃) were more beneficial for enhancing the hydrocarbons production. The addition of biochar to soil can significantly enhance the water retention. RHC-MgCO₃ had a maximum water retention capacity, while RHC-MgO had a minimum water retention capacity due to its lowest specific surface area. Additionally, the Mg-modified biochar had a much higher nutrient (i.e., K⁺, PO₄^3-) adsorption capacity. In particular, RHC-MgO with a lowest specific surface area had a highest PO₄^3- adsorption capacity, which was evidenced by the adsorption of PO₄^3- onto biochar mainly controlled by the chemisorption process. PO₄^3- adsorbed in the RHC-MgO released rapidly indicating its low PO₄^3- retention capacity. In general, MgCO₃ would be an appropriate candidate that is used in pyrolysis of biomass for co-production of bio-oil and biochar composite with high capacities of water/nutrient adsorption and retention for soil amendment.

Volatile-char interactions during biomass pyrolysis: Understanding the potential origin of char activity

To understand the potential origin of char activity responsible for volatile evolution during biomass pyrolysis, the interactions between benzyl phenyl ether (BPE, a typical lignin dimer) and pinewood chars prepared under a series of thermal, acidy, and steamy conditions were investigated. The results showed the activity of low-temperature char on BPE conversion was mainly attributed to the surface O-containing functional groups. The BPE conversion decreased as the temperature for char preparation raised, resulting from the elimination of char surface functional groups to a large degree at high temperature. The low activity of high-temperature char on BPE conversion could be recovered by acid-washing to release metal-occupied carbon based active sites (e.g., small aromatic rings), and further promoted by steam activation to modify the surface property and porous structure, finally achieving a full conversion of BPE and high selectivity to the products of phenol and toluene.

Torrefaction at 200 °C of Pubescens Pretreated with AlCl3 Aqueous Solution at Room Temperature

Metal salt soaking-torrefaction conversion technology was investigated. It was found that AlCl₃ pretreatment of pubescens favored observably the yield of liquid and small-molecular products in torrefaction via changing the composition and structure of the raw material. The maximum conversion of pretreated samples, washed (PSW) and Y _liquid were 15.5 and 10.8 wt % (with 0.26 wt % monosaccharides, 0.26 wt % carboxylic acids, 0.38 wt % furan compounds, and 1.28 wt % phenols), where 20.4 wt % hemicellulose, 22.9 wt % cellulose, and 5.7 wt % lignin were converted, respectively. However, for pretreated samples (PS), the maximum conversion and Y _liquid reached 44.2 and 32.1 wt %, respectively, along with 96.0 wt % hemicellulose and 31.8 wt % cellulose converted, yielding 2.39 wt % monosaccharides, 5.14 wt % carboxylic acids, 2.60 wt % furan compounds and 10.52 wt % phenols, indicating obvious catalytic effects of residual AlCl₃ on the decomposition of the three major components in torrefaction. Two-dimensional HSQC and electrospray ionization mass spectrometry (ESI-MS) characterizations further confirmed the dominant formation of oligomers derived from holocellulose, lignin, and cross-linkage involving the lignin-carbohydrate complex, indicating that the catalytic thermal cleavage of β-O-4, C-O-C, β-β, 5-5, 4-O-5, C_α-C_β, and α-O-4 linkages by aluminum species in the samples benefited the yield of liquid as well as monophenols.

Features and Commercial Performance of a System of Biomass Gasification for Simultaneous Clean Heating and Activated Carbon Production

Biomass is a renewable and clean energy. Moreover, clean heating plays a vital role in solving issues related to the heating source structures in northern China. This paper reports on our novel technology: a system of biomass (mainly fruitwood waste, referred to in short as FWW) gasification for simultaneous clean heating and fruitwood activated carbon (FAC) production. In particular, we will discuss the features of our gasification system and product characteristics, as well as energy efficiency, environmental benefits, and economic benefits. The results showed that the energy conversion from FWW gasification was as follows: 48.10% hot gas, 49.08% fruitwood gasified carbon (FGC), and 2.82% energy loss. The NO _x emissions of this system were about 126 mg/Nm³. The iodine adsorption values of the derived FGC and FAC were about 550 and 1000 mg/g, respectively. The system of gasification consumed 36 t of FWW per day, obtained 10 t of FGC, and produced 5 t of FAC. The emissions of CO₂ were neutral during the operation, and the clean heating area was 4100 m²/d in Chengde, Hebei, China, with the payback period under one heating season. These results show that the system is practical, economical, energy-saving, and environmentally friendly.

Volatile-char interactions during biomass pyrolysis: Cleavage of C-C bond in a β-5 lignin model dimer by amino-modified graphitized carbon nanotube

This study investigated the interactions between volatile and char during biomass pyrolysis at 400 °C, employing a β-5 lignin dimer and amino-modified graphitized carbon nanotube (CNT-NH₂) as their models, respectively. The results demonstrated that both -NH₂ and its carrier (CNT) facilitated the conversion of the β-5 dimer, which significantly increased from 9.7% (blank run), to 61.6% (with CNT), and to 96.6% (with CNT-NH₂). CNT mainly favored the breakage of C-O bond in the feedstock to produce dimers with a yield of 55.5%, while CNT-NH₂ promoted the cleavage of both C-O and C-C bonds to yield monomers with a yield up to 63.4%. Such significant changes in the pyrolysis behaviors of the β-5 lignin dimer after the introduction of CNT-NH₂ were considered to be mainly caused by hydrogen-bond formations between -NH₂ and the dimeric feedstock/products, in addition to the π-π stacking between CNT and aromatic rings.

An Eco-Effective Soybean Meal-Based Adhesive Enhanced with Diglycidyl Resorcinol Ether

Soybean meal-based adhesive is a good wood adhesive mainly due to its renewable, degradable, and environmentally friendly features. To improve the enhancement efficiency for adhesives, diglycidyl resorcinol ether (DRE) containing a benzene ring and flexible chain structure was used as an efficient cross-linker to enhance the adhesive in the study. The physicochemical properties of adhesives, the dry shear strength, and wet shear strength of plywood were measured. Results suggested that DRE reacted with the functional groups of soybean meal adhesive and formed a cross-linking network during hot press process in a ring-opening reaction through a covalent bond. As expected, compared to adhesive control, the soybean meal adhesive with 4 wt% DRE incorporation showed a significant increment in wet shear strength by 227.8% and in dry shear strength by 82.7%. In short, soybean meal adhesive enhanced with DRE showed considerable potential as a wood adhesive for industrial applications.

Fast pyrolysis behaviors of cedar in an infrared-heated fixed-bed reactor

To explore fast pyrolysis behaviors of cedar biomass, the infrared heating technique with quick heating rate was taken in a fixed-bed reactor. The effects of heating rates (5-30 °C/s) and pyrolysis temperatures (400-600 °C) on pyrolysis products distribution and compositions were discussed, and the reaction mechanism was proposed. The results show that high heating rate can significantly suppress secondary reaction of primary volatiles. GC/FID and GC/MS analyses indicate that higher heating rate is favorable to the generation of glucose derivatives such as acids and furans. However, higher temperature can obviously promote further conversion of guaiacyl-contained structure following demethylation, demethoxylation and H/CH₃ assisted demethoxylation routes, which were proposed to interpret the formation of biphenolic hydroxyl and monophenolic hydroxyl compounds such as phenol, 2-methyl-phenol and 2,4-dimethyl-phenol, respectively. Moreover, the demethylation route exhibits obvious conversion advantage at higher temperature due to lower energy barrier.

A Downdraft Fixed-Bed Biomass Gasification System with Integrated Products of Electricity, Heat, and Biochar: The Key Features and Initial Commercial Performance

Biomass, as a renewable and clean energy resource, plays a vital role in energy security and greenhouse gas reduction across the world. This paper reports on our newly established technology: a downdraft fixed-bed biomass gasification system using nut shells (mainly apricot kernel shells) for electricity generation, heating and partially activated carbon production at the same time. Particularly, the key features of the gasification reactor will be presented in detail. In the commercial plant (3 MW scale) located in Hebei province, China, the typical energy conversion from apricot kernel shell gasification is as follows: 47% syngas, 44% char (partially activated carbon), 5% hot water, and 4% energy loss. The main gasification temperature is 600–800 °C, while the activation zone is 850–900 °C. The commercial system has currently been in operation for 4 years. Considering the partially activated carbon as a stable carbon carrier, the whole system features negative CO2 emissions.

Enhancement of light aromatics from catalytic fast pyrolysis of cellulose over bifunctional hierarchical HZSM-5 modified by hydrogen fluoride and nickel/hydrogen fluoride

Pore structure and accessible active sites of HZSM-5 (Z5) are the key factors for its catalysis. The bifunctional hierarchical Z5 were prepared with leaching agent HF and loading Ni, and their performance for catalytic fast pyrolysis (CFP) of cellulose was investigated in a drop tube quartz reactor. Z5 modified with 0.5 mol/L HF (0.5F-Z5) showed excellent light aromatics (LAs) yield, which can be attributed to the enhancement in the small mesopores (2-10 nm) and the decrease of Brønsted acid sites during dealumination. Simultaneously, the loading of a 1 wt% Ni produced more LAs than 0.5F-Z5, due to the improvement in deoxidation/hydrogenation reactions. The highest LAs yield (31.3%) was obtained over 1%Ni-0.5 mol/LHF-Z5, which increased by 44.9% compared to the parent Z5. In addition, the reaction routes over different active centers and acid-catalyzed reactions were analyzed, based upon the composition of bio-oils and catalyst characterization.