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In this study, a two-section pyrolysis reactor was used for the pyrolysis of corn straw at 550°C. The pyrolysis of corn straw was performed in the first section, while a biochar sample (untreated biochar, acid-washed biochar, or biochar loaded with NaCl, KCl, MgCl2, or CaCl2) was placed in the second section. The effects of the biochar and the metal salts it contained on corn straw pyrolysis were researched. The results showed that acid-washing pretreatment removed most of the metal ions (99.1% of K, 95.2% of Ca, 94.3% of Na, and 95.3% of Mg) in biochar. As the amount of acid-washed biochar added raised from 0 to 3 g, the bio-oil yield declined from 51.2% to 45.3%, the gas yield raised from 21.9% to 27.1%, and volume fraction of CO and H2 increased from 33.5% and 10.8% to 35.6% and 13.1% respectively. In addition, the acid-washed biochar promoted the decomposition of acid substances in the pyrolysis volatiles and the formation of phenolic substances. After loading with various metal salts in biochar, the bio-oil yield is further reduced while gas yield is further increased. Among the metal salts, KCl exhibited the strongest effects on the enrichment of phenolics and decomposition of acids. In addition, MgCl2 clearly promoted CO formation. The results in this study confirm that both biochar and its constituent metal ions play important roles in the secondary cracking of pyrolysis volatiles, and thus biochar has potential for application as a catalyst in biomass pyrolysis. [ABSTRACT FROM AUTHOR]

Pyrolysis is the first step of gasification and combustion. The pyrolysis process of biomass is complicated, which is generally considered to consist of the pyrolysis of the three major components (i.e., cellulose, hemicellulose, and lignin). Understanding the pyrolysis behavior and product of each component holds a key to understanding the biomass pyrolysis mechanism. In this work, the pyrolysis behavior, pyrolysis kinetics, volatile evolution, and product characterization of the three major components are investigated. Results showed that pyrolysis characteristics and thermal stability of the three components were closely related to their unique chemical structures. During pyrolysis, the main pyrolytic volatiles of hemicellulose appeared first, followed by cellulose and then lignin volatiles in the 3D FTIR spectra. In term of pyrolysis products, gases were generated by the cracking of specific functional groups. Hemicellulose had the highest CO 2 yield, whereas lignin had the highest CH 4 yield due to the aromatic rings and methoxy groups in lignin structure. Whereas cellulose demonstrated the highest CO yield at high temperatures (above 550 °C). With increasing temperature, the carbon structures of carboxylic-C and O-alkyl-C in biochar decreased, while aryl-C was enhanced. This was due to the deoxygenation reactions such as dehydroxylation, decarboxylation, decarbonylation, and demethoxylation, resulting in a reduction in the number of oxygen-containing functional groups (such as –OH, –C=O, –COOH, and –OCH 3), as well as the polycondensation reactions that formed more polycyclic aromatic hydrocarbon units during pyrolysis. The major components of cellulose bio-oil included anhydrosugars and furans. Whereas the bio-oils derived from hemicellulose and lignin showed the highest relative content of acids and phenols, respectively. Based on this analysis, the thermal decomposition pathways of cellulose, hemicellulose, and lignin were proposed. [ABSTRACT FROM AUTHOR]

• Solar torrefaction and solar pyrolysis of cotton stalk were performed. • Deoxygenation was the key for preparing high quality biomass sample. • Torrefaction had a significant effect on the subsequent catalytic pyrolysis. • Selective yield of benzene, toluene, and xylene increased markedly by torrefaction. • Torrefaction pretreatment inhibited the formation of coke deposited on the catalyst. Solar pyrolysis of biomass is a novel method for bio-fuels production. In this study, cotton stalks were first subjected to solar torrefaction at 200–300 °C, and then subjected to solar catalytic pyrolysis at 550 °C. The effects of torrefaction deoxygenation pretreatment and HZSM-5 zeolite on the bio-fuels (gas, biochar, and bio-oil) upgradation was investigated. Results showed that the elements of cotton stalks removed via torrefaction follow the order of deoxygenation > dehydrogenation > decarbonization. Torrefaction pretreatment has a remarkably influence on the subsequent catalytic pyrolysis. The bio-oil and gas yields were considerably reduced while the biochar yield increased with increasing torrefaction temperature. The primary pyrolytic volatiles cracked under the HZSM-5 catalyst, followed by a series of deoxygenation and aromatization reactions to form H 2 O, CO 2 , CO, alkanes, olefins, and aromatic hydrocarbons. Consequently, the oxygen-containing functional groups were removed to generate hydrocarbons that were rich in bio-oil, meanwhile the selective yield of benzene, toluene, and xylene (BTX) increased remarkably. Moreover, the torrefaction pretreatment inhibited the formation of coke deposited on the catalyst and promoted the carbon yield in the biochar. Considering the benefits of electricity savings, the approach proposed herein is a potential way to improve the competitiveness of biomass-derived products. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]