Staged Pyrolytic Conversion of Acid-Loaded Woody Biomass for Production of High-Strength Coke and Valorization of Volatiles

Abstract

Lignocellulosic biomass is an attractive resource for metallurgical coke. The hot pelletization of powdered biomass followed by carbonization produces a high-strength biocoke. However, the fate of a major portion of biomass after carbonization is the production of low-value volatiles. Here, we enabled the valorization of woody biomass as valuable chemicals, such as anhydrosugars and phenols, and strong coke by loading mineral acid over wood and staged conversion consisting mainly of torrefaction, pelletization, and then carbonization. The loading of H2SO4 or H3PO4 at an amount equal to or slightly less than that of metals inherent in the wood, having catalysis for promoting the formation of valueless light oxygenates from carbohydrates, was effective for passivating those metals and drastically improving the anhydrosugar yield in torrefaction at 300–320 °C. The total yield of anhydrosugars from wood and the yield of levoglucosan, a dominant anhydrosugar, from cellulose in the wood reached 12.1 and 25.3 wt %, respectively. It was noteworthy that torrefaction altered the composition of components in wood and positively influenced the strength of coke prepared by pelletization and carbonization. In particular, torrefaction in the presence of H2SO4 led to a remarkable densification of pellets during carbonization. The resulting coke had a strength (tensile strength) of up to 24.2 MPa, which was much higher than that of coke directly pelletized and carbonized from wood (9.0 MPa). Moreover, the lignin-enriched torrefied wood selectively produced phenols and combustible gas with H2 as the major component in the carbonization. Under the most optimal conditions examined in this work, 45.7 wt % of the wood was converted into the desired products with the remainder being water and heavy condensable volatiles, while the yield of light oxygenates was greatly reduced.

High-Strength Formed Coke from Torrefied Biomass and Its Blend with Noncaking Coal

“…This work has demonstrated preparation of formed coke from noncaking coal and torrefied cedar over the entire range of mixing ratio with S t,C greater than conventional blast furnace coke of 5–6 MPa . Although not measured in this work, cokes from TC–coal mixtures as well as TC are expected to have higher reactivities with CO 2 than those from the coals alone, according to previous studies. − Such high reactivity is arisen primarily from inherent metallic species (alkali and alkaline earth metallic species; AAEMs and transition metals such as Fe). − Influence of the carbon structure of biomass-derived coke on the reactivity is, if any, much less important than the catalytic roles of metallic species. , The present cedar sample in fact retained K, Ca, and Fe with contents of 0.19, 0.29, and 0.06 wt %-dry, respectively …”

“…46,47 The present cedar sample in fact retained K, Ca, and Fe with contents of 0.19, 0.29, and 0.06 wt %-dry, respectively. 48 Use of highly reactive coke in BF could be unfavored under conventional operations. The main reason for this arises from a general trend of CSR and CRI, that is, coke with greater CRI has smaller CSR.…”

Hot Strength of Coke Prepared by Briquetting and Carbonization of Lignite

“…Details for the preparation of lignite-coke by briquetting and carbonization can be found elsewhere. 6,[9][10][11][12][13]19) Briefly, 2.0 g of acid-washed lignite was loaded in a mold having the diameter of 14 mm, heated to 130 ºC, and then pressed at 64 MPa for 8 min. The briquetting produces a briquette having the diameter and height of 14.0 mm and 8.0 mm, respectively.…”

“…The result of TGA was kinetically analyzed with a random pore model 19) described by the following equation:…”

Catalytic Upgrading of Lignite Pyrolysis Volatiles to Aromatics over Urea-Modified HZSM-5: Study on Desilication of Preserved Micropores

“…Clean coal technology, particularly pyrolysis, has received worldwide attention as a platform because of the inexpensive routes to efficiently convert solid carbon into pyrolysis-based products being tar-rich in condensable valuable chemicals as well as solid carbon materials (char) and non-condensable gas, which are particularly suitable for low-rank coal with high volatiles. − Products from direct pyrolysis, however, have the drawbacks of high instability, complex composition, low selectivity of valuable compounds, etc. , Catalytic upgrading has been successfully used for the conversion of pyrolytic volatiles into value-added chemicals and/or fuels. ,, Zeolite-based catalysts have been extensively studied in pyrolysis as a result of their high-temperature resistance, stable physical properties, unique pore structure, large specific surface area, and abundant acidic centers. − In particular, HZSM-5 (HZ5) exhibits unparalleled selectivity for light aromatics (LAs) and is considered as the ideal catalyst for the preparation of LAs. For example, Wei et al investigated the catalytic upgrading of pyrolytic volatiles from sewage sludge.…”