Negative emissions of carbon dioxide through chemical-looping combustion (CLC) and gasification (CLG) using oxygen carriers based on manganese and iron

Abstract

Carbon capture and storage (CCS) is an economically attractive strategy for avoiding carbon dioxide (CO 2) emissions from, e.g., power plants to the atmosphere. The combination of CCS and biomass combustion would result in a reduction of atmospheric CO 2 , or net negative emissions, as plant growth is a form of sequestration of atmospheric carbon. Carbon capture can be achieved in a variety of ways, one of which is chemical looping. Chemical-looping combustion (CLC) and chemical looping gasification (CLG) are two promising technologies for conversion of biomass to heat and power or syngas/methane with carbon capture. There have been significant advances made with respect to CLC in the last two decades for all types of fuel, with much less research on the gasification technology. CLG offers some interesting opportunities for production of biofuels together with carbon capture and may have several advantages with respect to the bench mark indirect gasification process or dual-bed fluidized bed (DFBG) in this respect. In CLG, an oxygen carrier is used as a bed material instead of sand, which is common in indirect gasification, and this could have several advantages: (i) all generated CO 2 is present together with the syngas or methane in the fuel reactor outlet stream, thus in a concentrated stream, viable for separation and capture; (ii) the air reactor (or combustion chamber) should largely be free from trace impurities, thus preventing corrosion and fouling in this reactor; and (iii) the highly oxidizing conditions in the fuel reactor together with solid oxide surfaces should be advantageous with respect to limiting formation of tar species. In this study, two manganese ores and an iron-based waste material, LD slag, were investigated with respect to performance in these chemical-looping technologies. The materials were also impregnated with alkali (K) in order to gauge possible catalytic effects and also to establish a better understanding of the general behavior of oxygen carriers with alkali, an important component in biomass and biomass waste streams and often a precursor for high-temperature corrosion. The viability of the oxygen carriers was investigated using a synthetic biogas in a batch fluidized bed reactor. The conversion of CO, H 2 , CH 4 , and C 2 H 4 was investigated in the temperature interval 800-950°C. The reactivity, or oxygen transfer rate, was highest for the manganese ores, followed by the LD slag. The conversion of C 2 H 4 was generally high but could largely be attributed to thermal decomposition. The K-impregnated samples showed enhanced reactivity during combustion conditions, and the Mangagran-K sample was able to achieve full conversion of benzene. The interaction of the solid material with alkali showed widely different behavior. The two manganese ores retained almost all alkali after redox testing, albeit exhibiting different

Syngas Production in a 1.5 kWth Biomass Chemical Looping Gasification Unit Using Fe and Mn Ores as the Oxygen Carrier

“…Previous investigations have shown that the BCLG process represents a good option for syngas production with low tar generation, because the presence of an oxygen carrier in the system helps its reduction. 5 , 12 , 16 It was observed that the operational variables with the greatest impact on the tar content were the fuel reactor temperature and the steam/biomass ratio.…”

“…If CO 2 formed during combustion is captured and then stored [bioenergy with carbon capture storage (BECCS) technologies], it is possible to achieve net-negative CO 2 emissions into the atmosphere. 4 , 5 …”

“…Biomass is an abundant renewable energy source on Earth that removes CO 2 from the atmosphere during its growth through photosynthesis. If CO 2 formed during combustion is captured and then stored [bioenergy with carbon capture storage (BECCS) technologies], it is possible to achieve net-negative CO 2 emissions into the atmosphere. , …”

“…If CO 2 formed during combustion is captured and then stored [bioenergy with carbon capture storage (BECCS) technologies], it is possible to achieve netnegative CO 2 emissions into the atmosphere. 4,5 Biomass gasification is a thermochemical conversion process, which converts biomass into high-energy fuel gas using steam, CO 2 , air, or O 2 as gasifying agents. 6,7 This fuel gas produced is usually a mixture of carbon dioxide (CO 2 ), hydrogen (H 2 ), carbon monoxide (CO), and methane (CH 4 ).…”

Characteristic Evaluation and Process Simulation of CuFe2O4 as Oxygen Carriers in Coal Chemical Looping Gasification

“…Nowadays, the utilization of fossil fuels has been considered as one of the biggest problems to the increasing emission of CO 2 . Chemical looping has emerged as a promising technology for coal utilization as it decreases the irreversible entropy production to increase the energy utilization efficiency. , It takes advantage of the redox behavior of oxygen carriers (OCs) between two individual reactors to realize initial CO 2 separation and NO x emission control without the enrollment of pure oxygen. − In situ gasification chemical looping combustion (CLC) is known as a typical strategy for coal utilization for complete oxidization between the fuel and the OC in the reducer. , Conversely, chemical looping gasification (CLG) − was proposed to achieve plenty of syngas (H 2 and CO) through partial oxidization, as is shown in Figure .…”