Effects of Briquetting and High Pyrolysis Temperature on Hydrolysis Lignin Char Properties and Reactivity in CO-CO2-N2 Conditions

Abstract

Carbonaceous reductants for pyrometallurgical applications are usually obtained from fossil-based sources. The most important properties of the reductants greatly depend on the application and the feeding of the reductant into the process. However, the mechanical strength, calorific value, fixed carbon content, and reactivity of the reductant are the properties that usually define the applicability of the reductant for different processes. The reactivity of the biochars is usually high in comparison to metallurgical coke, which may restrict the applicability of the biochar in reduction processes. One cause of the higher reactivity is the higher surface area of the biochars, which can be suppressed with agglomeration treatment, e.g., briquetting. In this work, hydrolysis lignin was used for slow pyrolysis experiments to produce biochars. The biochars were pyrolyzed in briquetted form and in as-received form at various temperatures. The reactivity values of the biochars were tested in dynamic reactivity tests in a CO-CO2-N2 gas atmosphere at temperatures of up to 1350 °C. It was found that the yield of the hydrolysis lignin char only decreased by 3.36 wt% when the pyrolysis temperature was elevated from 600 to 1200 °C, while a decrease in yield of 4.88 wt% occurred when the pyrolysis temperature was elevated from 450 to 600 °C. The mass loss of hydrolysis lignin biochar in the reactivity experiment in CO-CO2-N2 atmosphere was significantly decreased from 79.41 wt% to 56.80 wt% when the hydrolysis lignin was briquetted before the slow pyrolysis process and the temperature of the pyrolysis process was elevated from 600 to 1200 °C. This means that the mass loss of the material was suppressed by 22.61 wt% due to the higher pyrolysis temperature and briquetting process.

The Reduction Reaction Behavior of Steelmaking Dusts with Lignin under Different Atmospheres

“…During this temperature range, mass spectra curves belonging to H2O and CO2 appeared to have high fluctuation. The identified reaction phenomena for these reductions were the thermal decomposition of carbohydrates, leading to the breakdown of complex structures into simpler compounds [31,50]. This process involved the release of water vapor, carbon dioxide, and other volatile byproducts such as methane, which perfectly match to the TG, DSC, and MS data.…”

A Crucial Step Toward Carbon Neutrality in Pyrometallurgical Reduction of Nickel Slag

“…The use of biochar is beneficial from an industrial point of view, as it requires a shorter reduction time and results in lower CO 2 emissions compared to coke. Issues related to low volume density, high moisture content, high transportation and storage costs, and poor grindability reported by [25] can be addressed by briquetting and pyrolysis of biomass [45] in order to facilitate the adoption of biochars in industrial applications.…”

The Application of Lignocellulosic Biomass Waste in the Iron and Steel Industry in the Context of Challenges Related to the Energy Crisis

“…The enormous surface area and very porous structure of biocarbon cause an unfavorable increase in CO 2 gasification reactivity [130]. However, according to Koskela et al [131], pyrolysis temperature as well as briquetting, i.e., agglomeration, can change the gasification reactivity of biocarbon. The structural features of biocarbon are changed by high pyrolysis temperatures and briquetting which result in a denser and smaller surface area.…”