Shannan Xu

TG–FTIR–MS analysis of the pyrolysis of blended seaweed and rice husk

Pyrolysis of seaweed (Enteromorpha clathrata), rice husk, and five kinds of samples of blended Enteromorpha clathrata and rice husk (at different mass ratios as 3:1, 2:1, 1:1, 1:2, and 1:3) was investigated with thermogravimetric–infrared–mass spectrometry analysis. The results indicated that the pyrolysis of seaweed and rice husk can be divided into four stages: evaporation, depolymerization, devolatilization, and carbonization. However, due to the major pyrolysis component differences between seaweed and rice husk, the pyrolysis characteristics between them varied significantly. Through differential scanning calorimetry analysis, seaweed showed a special exothermic reaction during the stage of precipitation of main volatiles, while the rice husk showed mainly an endothermic reaction in that process. But it appeared to be an exothermic process during pyrolysis of the seaweed and rice husk mixture. We can infer that there was mutual promotion between the seaweed and rice husk, and energy coupling was realized. Meanwhile, it can be concluded that the experimental value of thermal mass loss rate turns out to be higher than that of theoretical value in the process of the main stage of pyrolysis through the comparison between the experimental data and the theoretical data for calculated DTG curves in the pyrolysis of blended sample of different proportions of seaweed and rice husk. The FTIR analysis indicated that with the increasing proportion of the rice husk, the volatile gas, sulfurous gas, and nitrogen gas are decreasingly released from the process of pyrolysis. Judging from the thermogravimetric–mass spectrometry, the pyrolysis of the blended mixture of seaweed and rice husk has been affected because of the increasing amount of rice husk. This reduced the emission of NO, NO2, and SO2 gases which are released from the above process of pyrolysis. Therefore, for the pyrolysis of mixed seaweed and rice husk, there was actually a synergistic effect rather than the simple sum of the characteristics of the pyrolysis of different components.

A comparative study on the quality of bio-oil derived from green macroalga Enteromorpha clathrata over metal modified ZSM-5 catalysts

The green macroalga Enteromorpha clathrata was pyrolyzed with or without catalysts at the temperature of 550 °C for producing high-quality bio-oil. The ZSM-5 and 1,2,3 mmol Mg-Ce/ZSM-5 catalysts were introduced to investigate the yields and components distribution of bio-oil. Increase of bio-oil production was obtained with the use of ZSM-5 and 1,2,3 mmol Mg-Ce/ZSM-5 catalysts. The 1 mmol Mg-Ce/ZSM-5 catalyst exhibited more promising property for promoting the relative content of C5-C7 compounds, and decreasing the relative content of acids in bio-oil. The results suggested that E. clathrata had potential as pyrolysis feedstocks for producing the high-quality bio-oil with large amounts of C5-C7 compounds and low relative content of acids when the 1 mmol Mg-Ce/ZSM-5 catalyst was used. Furthermore, the physicochemical properties of ZSM-5 and 1 mmol Mg-Ce/ZSM-5 catalysts were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and temperature-programmed desorption of ammonia.

Combustion mathematical simulation of single seaweed particle in a bench-scale fluidized bed

In this study, combustion experiments of green algae granulations (Enteromorpha clathrata) (EN) were carried out in a bench-scale fluidized bed. The particle diameter was kept constant during the combustion process and combustion model was described as a shrinking core model. Model was divided into water ball, volatile-matter ball, and carbon ball. Ash ball radius was assumed to be the same during the combustion and carbon ball was burned layer by layer. Simulation of single-particle combustion process consists of process of water evaporation, release of volatile matters and combustion, and the process of char combustion. Finally, a mathematical model was established for the combustion of EN single particle in the fluidized bed, validated by the experiment data. The model can be applied for the design of the combustion devices for the combustion of seaweed particles with high content of ash.

Study of pyrolytic mechanisms of seaweed based on different components (soluble polysaccharides, proteins, and ash)

The pyrolysis mechanisms of the main components of seaweed (soluble polysaccharides, proteins, and ash) were investigated in this study using characterization analysis and thermogravimetric analysis–mass spectrometry. XPS analysis indicated that most of the metal ions existed in the ash, while substituents of Na and K ions were found in polysaccharides. Oxygen-containing functional groups in Enteromorpha were found to exist mainly in the following forms: -OH/C-O in polysaccharides, COO- in proteins, and inorganic oxygen in the ash. Pyrolysis thermogravimetric (TG) curves of the components of Enteromorpha indicated that the thermogravimetric analysis ranges of polysaccharides and proteins were 175–310 °C and 300–350 °C, respectively. During the pyrolysis process, due to the effects of metal ions, the maximum thermal weight loss rate was found to increase, while the pyrolysis temperature also increased. CO2 was generated from the decarboxylation of uronic acids and the decomposition of inorganic carbonates ...

Comparative Study of Combustion Properties of Two Seaweeds in a Batch Fluidized Bed

ABSTRACT In the present study, combustion of two seaweeds, Enteromorpha clathrate and Sargassum natans, was carried out in a bench-scale fluidized bed. According to the shrinking core model, combustion of E. clathrate particles resulted in dehydration and release of volatile components first, followed by char combustion. While combustion of S. natans particles resulted in scraps formation due to the rapid release of large amounts of volatiles, followed by expansion and fragmentation. The cross sections of E. clathrate particles and the cokes collected after different combustion durations were analyzed with a scanning electron microscope. Some micro-pores were generated with a rougher surface after being burned for 30 s. When combustion continued for 3 min, a cotton wool-like structure was obtained due to complete release of volatiles. After 4 min of burning, internal surface of the ash particle became cohesive, due to partial melting of ash particles. In addition, the released gases were studied during the combustion process. Results showed that SO2, NOx, and other gases emitted spontaneously as soon as seaweed particles were fed into the fluidized bed, indicating that both pyrolysis and oxidation reactions rapidly take place within the seaweed particles. In general, the heat transfer rate was accelerated by increasing bed temperature and led to an earlier release of volatile components with shortened burnout time. Moreover, increasing air velocity and raising the bed height also enhanced, to some extent, the combustion and shortened the burnout time.

Study on Pore Structure of Seaweed Particles After Combustion

In this work, the particles of two seaweeds, Enteromorpha clathrata (E. clathrata) (EN) and Sargassum natans (S. natans), were combusted in a fluidized bed. It was found that while combustion of EN particles was stable, there was a substantial slagging period during the combustion of S. natans particles. Seaweed and its bottom ash samples were collected, and their pore structures were determined with both mercury intrusion method and N2 adsorption–desorption method. The structural analysis revealed that the number of porosity, pore volume, and specific surface area was all increased and the internal pore in ash samples was expanded after combustion. Fractal analysis showed that while the surface of original seaweed was smooth, it became irregular and rough after combustion. This study has suggested that the ash of seaweeds with porous structure can be valuable for comprehensive utilization.