Yingquan Chen

Biomass-based pyrolytic polygeneration system on cotton stalk pyrolysis: influence of temperature.

To study the process of biomass-based pyrolytic polygeneration and its mechanism in depth, the pyrolysis of cotton stalk was investigated in a packed bed, with focus on the evolution of the chemical and physical structures of the solid, liquid and gaseous products. The evolution of product characteristics could be good explaining the process mechanism of biomass pyrolysis. A relationship between the pore distribution of solid products and the fused aromatic rings system revealed by Raman analysis might be exist and need to quantify in further study. Regarding the optimum conditions for obtaining high-quality pyrolytic products from the polygeneration system, the optimum temperature is 550-750°C, with a higher calorific value of the obtained charcoal (≈ 28 MJ/kg) and a higher surface area (>200 m(2)/g). Meanwhile, the calorific value of the gas reaches 8-9 MJ/m(3) and the liquid oil would be used as a platform product in biorefinery.

Torrefaction of agriculture straws and its application on biomass pyrolysis poly-generation

This study investigated the properties of corn stalk and cotton stalk after torrefaction, and the effects of torrefaction on product properties obtained under the optimal condition of biomass pyrolysis polygeneration. The color of the torrefied biomass chars darkened, and the grindability was upgraded, with finer particles formed and grinding energy consumption reduced. The moisture and oxygen content significantly decreased whereas the carbon content increased considerably. It was found that torrefaction had different effects on the char, liquid oil and biogas from biomass pyrolysis polygeneration. Compared to raw straws, the output of chars from pyrolysis of torrefied straws increased and the quality of chars as a solid fuel had no significant change, while the output of liquid oil and biogas decreased. The liquid oil contained more concentrated phenols with less water content below 40wt.%, and the biogas contained more concentrated H2 and CH4 with higher LHV up to 15MJ/nm(3).

Application of biomass pyrolytic polygeneration technology using retort reactors

To introduce application status and illustrate the good utilisation potential of biomass pyrolytic polygeneration using retort reactors, the properties of major products and the economic viability of commercial factories were investigated. The capacity of one factory was about 3000t of biomass per year, which was converted into 1000t of charcoal, 950,000Nm(3) of biogas, 270t of woody tar, and 950t of woody vinegar. Charcoal and fuel gas had LHV of 31MJ/kg and 12MJ/m(3), respectively, indicating their potential for use as commercial fuels. The woody tar was rich in phenols, while woody vinegar contained large quantities of water and acetic acid. The economic analysis showed that the factory using this technology could be profitable, and the initial investment could be recouped over the factory lifetime. This technology offered a promising means of converting abundant agricultural biomass into high-value products.

Transformation of Nitrogen and Evolution of N-Containing Species during Algae Pyrolysis

Transformation and evolution mechanisms of nitrogen during algae pyrolysis were investigated in depth with exploration of N-containing products under variant temperature. Results indicated nitrogen in algae is mainly in the form of protein-N (∼90%) with some inorganic-N. At 400-600 °C, protein-N in algae cracked first with algae pyrolysis and formed pyridinic-N, pyrrolic-N, and quaternary-N in char. The content of protein-N decreased significantly, while that of pyrrolic-N and quaternary-N increased gradually with temperature increasing. Pyridinic-N and pyrrolic-N formation was due to deamination or dehydrogenation of amino acids; subsequently, some pyridinic-N converted to quaternary-N. Increasing temperature decreased amides content greatly while increased that of nitriles and N-heterocyclic compounds (pyridines, pyrroles, and indoles) in bio-oil. Amides were formed through NH3 reacting with fatty acids, that underwent dehydration to form nitriles. Besides, NH3 and HCN yields increased gradually. NH3 resulted from ammonia-N, labile amino acids and amides decomposition, while HCN came from nitrile decomposition. At 700-800 °C, evolution trend of N-containing products was similar to that at 400-600 °C. While N-heterocyclic compounds in bio-oil mainly came from pyrifinic-N, pyrrolic-N, and quaternary-N decomposition. Moreover, cracking of pyridinic-N and pyrrolic-N produced HCN and NH3. A mechanism of nitrogen transformation during algae pyrolysis is proposed based on amino acids decomposition.

Fast pyrolysis of cotton stalk biomass using calcium oxide

We herein investigate the various roles of calcium oxide in the pyrolysis of biomass at a variant temperatures. The evolution of pyrolysis products was examined to propose the various roles of Ca at a range of temperatures and CaO addition ratios with cotton stalk on a fixed-bed reactor. We found that upon the addition of CaO, the content of ketones produced increased, while that of acidic compounds decreased. Under similar conditions, the concentration of evolved H2 and CH4 increased, while that of CO2 decreased. Thus, variation in the CaO/biomass (Ca/B) mass ratios and pyrolysis temperatures indicated that CaO could act as a reactant, an absorbent, and a catalyst at Ca/B ratios of <0.2, >0.2, and >0.4, respectively. Moreover, at temperatures >600°C, the roles of CaO as an absorbent and a reactant were less apparent, while its role as a catalyst was enhanced.

Co-pyrolysis of lignocellulosic biomass and microalgae: Products characteristics and interaction effect

Co-pyrolysis of biomass has a potential to change the quality of pyrolytic bio-oil. In this work, co-pyrolysis of bamboo, a typical lignocellulosic biomass, and Nannochloropsis sp. (NS), a microalgae, was carried out in a fixed bed reactor at a range of mixing ratio of NS and bamboo, to find out whether the quality of pyrolytic bio-oil was improved. A significant improvement on bio-oil after co-pyrolysis of bamboo and NS was observed that bio-oil yield increased up to 66.63wt% (at 1:1) and the content of long-chain fatty acids in bio-oil also dramatically increased (the maximum up to 50.92% (13.57wt%) at 1:1) whereas acetic acid, O-containing species, and N-containing compounds decreased greatly. Nitrogen transformation mechanism during co-pyrolysis also was explored. Results showed that nitrogen in microalgae preferred to transform into solid char and gas phase during co-pyrolysis, while more pyrrolic-N and quaternary-N generated with diminishing protein-N and pyridinic-N in char.

Co-gasification of coal and biomass: Synergy, characterization and reactivity of the residual char.

The synergy effect between coal and biomass in their co-gasification was studied in a vertical fixed bed reactor, and the physic-chemical structural characteristics and gasification reactivity of the residual char obtained from co-gasification were also investigated. The results shows that, conversion of the residual char and tar into gas is enhanced due to the synergy effect between coal and biomass. The physical structure of residual char shows more pore on coal char when more biomass is added in the co-gasification. The migration of inorganic elements between coal and biomass was found, the formation and competitive role of K2SiO3, KAlSiO4, and Ca3Al2(SiO4)3 is a mechanism behind the synergy. The graphization degree is enhanced but size of graphite crystallite in the residual char decreases with biomass blending ratio increasing. TGA results strongly suggest the big difference in the reactivity of chars derived from coal and biomass in spite of influence from co-gasification.

Physicochemical properties and hygroscopicity of tobacco stem biochar pyrolyzed at different temperatures

The physicochemical properties and hygroscopicity of biochar derived from tobacco stem pyrolysis were investigated to get the effect of pyrolysis temperature (250–950 °C). The chemical composition and structure of biochar were characterized with proximate and ultimate analysis, X-ray fluorescence, and two-dimensional perturbation-based correlation infrared spectroscopy (2D-PCIS) based on Fourier-transform infrared spectroscopy. The physical pore structure was analyzed by Brunauer-Emmett-Teller surface area. Results showed that surface area and pore volumes of biochar increased, while biochar yield, volatile matter, H/C and O/C ratios decreased with the increasing pyrolysis temperature. The 2D-PCIS analysis suggested that the intensity of hydroxyl groups and aromatic skeletal changed greatly with pyrolysis temperature. Tobacco stem biochar was abundant in Ca and K and contained P, Mg, S, and Cl, while N was low and decreased with temperature. Tobacco stem biochar produced at 550 °C has the lowest hygroscop...

Investigation on biomass nitrogen-enriched pyrolysis: Influence of temperature

Biomass (bamboo waste) nitrogen-enriched pyrolysis was carried out in a fixed bed with NH3 atmosphere at 400-800 °C, and formation mechanism of N-containing species was explored in depth. Results showed that N-enriched pyrolysis greatly increased bio-oil and gas yields. H2 yield increased sharply to 130 mL/g (32.93 vol%) and became the main composition at higher temperature, while CH4 and CO yields deceased, and the lower heating value of gas reached ∼14 MJ/Nm3. For bio-oil, the content of phenols (main compositions) and N-containing species increased significantly, and the maximums reached 61.33% and 11.47%, respectively. While that of acetic acid (disappeared), O-containing species (aldehydes/ketones/furans/esters) and aromatics decreased largely accordingly. For biochar, Nitrogen content increased, and it contained abundant pyridininc-N, pyrrolic-N, quaternary-N, and pyridone-N-oxide. Possible reaction pathways of biomass N-enriched pyrolysis was proposed based on products evolution. In conclusion, biomass N-enriched pyrolysis could obtain high-valued N-containing chemical species and functional biochar.

Preparation of nitrogen-doped microporous modified biochar by high temperature CO2–NH3 treatment for CO2 adsorption: effects of temperature

Nitrogen-rich agricultural waste, soybean straw, was used as a raw material to prepare high efficiency CO2 adsorbents (nitrogen-doped porous modified biochars). Three different modification methods for the preparation of these adsorbents were compared, i.e. activation with carbon dioxide, ammonification with ammonia (NH3) and high temperature treatment with the mixture of CO2 and NH3. Effects of modification temperature on physicochemical properties of the modified biochars and influences of adsorption temperature on their CO2 capture performances were both investigated. Activation with CO2 obviously developed the pore structure of modified biochars, especially micropores, while the ammonification with NH3 and modification with the mixture not only developed porosity, but also introduced nitrogen functional groups, and the modification with the mixture was better than the ammonification with NH3. As the modification temperature increased, the micropore surface area and N/C ratio of the modified biochars by the modification with the mixture both increased first, and reached the maximum at 800 °C, and then decreased. Furthermore, at the lower adsorption temperature, the micropore structure played an important role to influence the CO2 capture performance, while at the higher adsorption temperature, the chemical properties, especially the nitrogen functional groups, contributed more to the CO2 capture.