Yanqin Huang

Effects of metal catalysts on CO2 gasification reactivity of biomass char

The effects of five metal catalysts (K, Na, Ca, Mg, and Fe) on CO(2) gasification reactivity of fir char were studied using thermal gravimetric analysis. The degree of carbonization, crystal structure and morphology of char samples was characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The CO(2) gasification reactivity of fir char was improved through the addition of metal catalysts, in the order K>Na>Ca>Fe>Mg. XRD analysis indicated that Na and Ca improved the formation of crystal structure, and that Mg enhanced the degree of carbon structure ordering. SEM analysis showed that spotted activation centers were distributed on the surface of char samples impregnated with catalysts. Moreover, a loose flake structure was observed on the surface of both K-char and Na-char. Finally, the kinetic parameters of CO(2) gasification of char samples were calculated mathematically.

The transformation pathways of nitrogen in sewage sludge during hydrothermal treatment

Hydrothermal treatment (HT) has been proved as a significant pretreatment in decreasing emissions of NOX pollutants from thermochemical utilization of sewage sludge (SS) derived solid fuel. This study aims to investigate the denitrification of HT and the redistribution of nitrogen (N) in different products so as to speculate the comprehensive pathway of N transformation during hydrothermal process. Results found that only 20% of N remained in hydrochar, whereas the rest of N (nearly 80%) was transformed into other phase. A majority of amino-N in SS was enriched in liquid phase in the form of Org-N at first, then further decomposed to NH4+-N. The remaining amino-N converted to pyrrole-N, pyridine-N and quaternary-N as temperature progresses. Meanwhile, amine-N derived from protein-N formed heterocyclic-N in oil phase via Diels-Alder reaction. NH3, the major nitrogenous gas, was dissolved in liquid as NH4+-N immediately after producing, but increased with prolonged reaction time.

Characteristics of NO x precursors and their formation mechanism during pyrolysis of herb residues

Abstract Based on two herb residues-herbal tea waste (HTW) and penicillin mycelial waste (PMW), characteristics of NOx precursors during their pyrolysis were investigated in a horizontal tubular reactor with the help of XPS and TGA technologies. Effects of thermal conditions and physicochemical properties of fuels were discussed and compared. The results demonstrate that protein-N is the main nitrogen form for both HTW and PMW, determining the dominance of NH3 among NOx precursors at any operational conditions. Thermal conditions would still change the ratio and total yield by intrinsically influencing their formation pathways. Subsequently, the effects could be sequenced as follows: high temperatures with rapid pyrolysis > high temperatures with slow pyrolysis > low temperatures with rapid pyrolysis ≈ low temperatures with slow pyrolysis. Moreover, at high temperatures with rapid pyrolysis, increase in particle size or decrease in moisture content would result in reduction of total yield by 5%–11% and 4%–6%, respectively. In addition, NH3 yield is produced at low temperatures or slow pyrolysis with sequence of PMW > HTW and vice versa, depending on components in the fuels. Consequently, analyses on nitrogen forms in char and nitrogen distribution indicate that total yield of 20%–45% is observed to be independent of fuel type under typical pyrolysis conditions, which may provide helpful guidance for the clean reutilization of herb residues.

Structure and Pyrolysis Characteristics of Lignin Derived from Wood Powder Hydrolysis Residues

Physicochemical characteristics of wood powder acid hydrolysis residue (WAHR) were studied firstly in this study, and WAHL (lignin derived from WAHR) was separated successfully from WAHR based on an improved isolating method. The content of functional group such as phenolic hydroxyl group of guaiacyl, syringyl, and hydroxyl–phenyl units in WAHL were identified by 31P-NMR and DFRC (derivatization followed by reductive cleavage) method. Thermal degradation experiments were carried out on a thermogravimetric (TG) analyzer to show pyrolysis characteristics of WAHL. The compositions of pyrolysis products of WAHL were also studied throughout a pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) analyzer. It was shown that the pyrolysis of WAHL took place in a wide temperature range and there were two obvious peaks in the differential thermogravimetric diagram. Results of Py–GC–MS analysis indicated that pyrolysis products were mainly formed through cleavage of the β-O-4 connection and multiple pyrolysis.

Hydrothermal reaction of phenylalanine as a model compound of algal protein

Abstract The decomposition behavior of phenylalanine, as a model compound of algal protein, in water at high temperature was investigated in a quartz mini-batch reactor. The conversion of phenylalanine at 130–190°C as well as the decomposition pathways and nitrogen transition behavior in the hydrothermal process at 220–340°C with a batch holding time of 5–240 min were determined. The results showed that the conversion of phenylalanine is extremely low at 130–190°C, and that provided a reference for extracting high value-added protein during hydrothermal liquefaction of algae. The major product at 220–280°C is phenylethylamine; however, the yield of styrene is increased with the increase of reaction temperature and holding time. In water at high temperature, phenylethylamine is obtained via decarboxylation of phenylalanine, while styrene is produced via deamination of phenylethylamine under higher temperature and longer holding time; phenylethanol is further formed via the hydration of styrene. Most of nitrogen in phenylalanine is firstly transferred into phenylethylamine via the decarboxylation of phenylalanine, and then further transferred into water-soluble NH 4 + via the deamination of phenylethylamine.

Denitrification and desulphurization of industrial biowastes via hydrothermal modification

In attempt to decrease NOX and SO2 emission from thermochemical utilization, three industrial biowastes (penicillin mycelia waste, sewage sludge and peat waste) contained high nitrogen (N) and sulfur (S) were chosen to investigate the denitrification and desulphurization of hydrothermal modification. The results demonstrated that hydrothermal modification destroyed the structure of N- and S-containing components, thereby altering their existed conformations. Inorganic-N (N-IN) and most of amino-N/polyamide-N (N-A) were enriched by liquid phase in the forms of NH4+-N and soluble organic-N (Org-N), respectively; subsequently, Org-N could further decompose to NH4+-N at higher temperature. Residual N in hydrochars was converted from N-A to heterocyclic-N (pyrrolic-N, pyridinic-N and quaternary-N) via hydrolysis and cyclization. Similarly, over 60% of S was remove form biowastes at 240 °C. In solid phase, part of organic-S was altered to thiophenes-S after modified, while the remainder was transformed to inorganic-S; but the variation of inorganic-S in hydrochars strongly affected by its specific species.

Relevance between chemical structure and pyrolysis behavior of palm kernel shell lignin

Palm kernel shell (PKS) lignin obtained by enzymatic/mild acid hydrolysis (EMAL) was thoroughly elucidated by FTIR (fourier transform infrared), 13C-1H 2D-NMR (nuclear magnetic resonance), quantitative 31P NMR combined with DFRC (derivatization followed by reductive cleavage), and Py-GC/MS (pyrolysis-gas chromatography/mass spectrometry) with and without TMAH (tetramethylammonium hydroxide). Pyrolysis behavior was then characterized by TG-FTIR-MS (thermo-gravimetric-FTIR-mass spectrometry) and Py-GC/MS. The PKS lignin is demonstrated to be a p-hydroxyphenyl-guaiacyl-syringyl (H-G-S) lignin with abundances of p-hydrobenzoates and low S/G ratio of 0.15. 2D-NMR indicated that the main substructures are β-O-4-ethers (~85%), and 31P NMR/DFRC quantified the total β-O-4 content of 2295μmol/g. Py-GC/MS with and without TMAH confirmed that phenol mainly originated from p-hydroxybenzoates units. Thermal-stability, evolution behavior of typical volatiles, and selectivity of phenolic compounds (H-, G-, S-, C-type) during PKS lignin pyrolysis were explored. Relationship between chemical structure and pyrolysis behavior are also obtained. This work will provide a deep insight to the effective utilization of PKS.