Techno-Economical Method for the Removal of Alkali Metals from Agricultural Residue and Herbaceous Biomass and Its Effect on Slagging and Fouling Behavior

Abstract

Nowadays, it is widely recognized that biomass combustion processes can contribute to the mitigation of greenhouse gas emissions, and thus, these processes have become a viable option as an alternative energy source for the power industry. Among various biomasses, the herbaceous biomass is regarded as an abundant and relatively inexpensive fuel. However, it contains high ashes (especially high levels of alkali metals), leading to operation troubles such as slagging and fouling inside a heat exchanger or deterioration in efficiency. Accordingly, we herein propose an economical method to remove the inherent ashes in the biomass using 16.6 M acetic acid pretreatment at 60 °C for 10 min. Seven different biomasses were investigated to validate the effects of method. The Kenaf shows the total mineral rejection of 93.48%. In particular, the potassium and sodium elements in the Kenaf, which are major factors influencing fouling and slagging in a boiler, were removed up to 99.46 and 100%, respectively. Furthermore, the proposed wet treatment was more effective for biomass with higher surface areas.

Energy Recovery of Agricultural Residues: Incorporation of Vine Pruning in the Production of Biomass Pellets with ENplus® Certification

“…Another way of assessing the impact of ash fusion was described in several studies, which resorted to the transposition of analysis methodologies that are common in coal science through the adaptation of indices that relate the different constituents to each other, allowing a qualitative assessment of the potential for the occurrence of fouling or slagging phenomena. [31][32][33][34][35]. The results obtained in the determination of fouling and slagging prediction indices in the present study, described in Section 2.8, indicated a severe tendency for the occurrence of slagging processes, both for vine pruning and for wood pellets of Pinus pinaster.…”

Characteristics of Miscanthus Fuel by Wet Torrefaction on Fuel Upgrading and Gas Emission Behavior

“…In addition, the indicators of the effects of slagging and fouling on the effects of alkali-based minerals are shown in Table 5. All of these items such as the B/A ratio, silica percentage, fouling, and alkali index are all affected by alkali-based minerals, especially Na 2 O and K 2 O [26,27]. As described above, the WT sample was found to increase only the silica percentage and the remaining items decreased as the alkaline minerals were extracted.…”

Comparing the Physicochemical Properties of Upgraded Biomass Fuel by Torrefaction and the Ashless Technique

“…The second procedure used was the ashless method, which involves removing the alkaline mineral matter content in ash [14]. A. PSD and A. Kenaf were produced by the ashless process with acetic acid (CH 3 COOH).…”

“…Another pretreatment method to improve biomass quality is the ash rejection process developed by Korea Institute of Energy Research (KIER). This acetic acid-based pretreatment method has been used to extract the alkali mineral inside biomass and may contribute to a significant reduction in chloride-induced corrosion and slag/fouling caused by the deposition of the boiler during combustion [14]. Lee et al [14] proposed that the optimal pretreatment conditions for maximum ash rejection were a pH of 1.76, temperature of 60 • C, and a residence time of 10 min, at which point the losses of hemicellulose, cellulose, and lignin were minimized and investigated for several kinds of biomass.…”