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

Abstract

Biomass chemical looping gasification (BCLG) uses lattice oxygen from an oxygen carrier instead of gaseous oxygen for high-quality syngas production without CO 2 emissions. In this work, the effect of the main operating variables, such as oxygen/biomass ratio (λ), gasification temperature, and steam/biomass ratio (S/B), was investigated using two low-cost materials: a Fe ore and a Mn ore. Oxygen fed to the air reactor for oxidation was used as an effective method for controlling the amount of lattice oxygen used for syngas production. The main variable that affected the process performance and the syngas quality was λ, while the fuel reactor temperature and the S/B ratio had a minor effect. Small performance differences found between the ores can be attributed to different degrees of CH 4 and light hydrocarbons reforming in the process. The CO 2 content in the syngas was high (40 −43%) under autothermal conditions because the gasification reactions required the heat to be generated by combustion. CH 4 contents of around 10% were found in syngas, coming from the unburned or unreformed volatiles. Syngas yields around 0.60 Nm 3 /kg of dry biomass were found for both ores. Additionally, high biomass conversions ( X b > 94%) and carbon conversion efficiencies (η cc > 95%) were obtained in all cases, showing the capability of the process of avoiding CO 2 emissions to the atmosphere. No agglomeration was found in the bed during the BCLG process, although attrition rates were high, leading to lifetimes of 160 and 300 h for the manganese and iron ores, respectively. Migration of Fe or Mn to the external part of the particle, generating a metal concentrated shell, was observed. Its detachment was responsible for the decrease in the oxygen transport capacity ( R OC ) of the material with the operating time and the reduced lifetime. The results obtained here allowed the iron ore to be considered as an oxygen carrier suitable for the BCLG process.

MP-PIC Simulation of Biomass Steam Gasification Using Ilmenite as an Oxygen Carrier

“…The influence of the reactor temperature and steam-to-biomass ratio is investigated and compared with experimental data given by Song et al [6]. Second, the gasification of biomass is coupled with the reaction kinetics of ilmenite as an oxygen carrier proposed by Abad et al [37], and the influence of the reactor temperature and the oxidation degree is investigated and compared with experimental data obtained by Condori et al [5] in a lab-scale fluidized bed. The separation in two steps is performed to distinguish the deviations of the simulations compared to the experiments resulting from the two different reduced reaction networks.…”

“…The resulting syngas (which is mainly composed of H 2 , CO, CO 2 und CH 4 ) from biomass gasification is versatile and can be used for the production of synthetic fuels or the generation of heat as well as electricity, for instance [1][2][3][4]. By applying the principle of chemical looping, the emissions and costs can be further reduced compared to other gasification processes [5]. The biomass chemical looping gasification (BCLG) is based on the circulation of an oxygen carrier (OC) between two interconnected reactors.…”

“…The two reactors are separated using loop-seals, which prevents the dilution of the syngas produced in the fuel reactor with flue gas from the air reactor and, thus, a high quality syngas is obtained. Furthermore, a low tar content in the syngas is obtained due to the presence of oxygen carriers underlining the advantage of BCLG compared to other processes for syngas production [5][6][7][8].…”

“…A schematic representation of the chemical looping gasification (CLG) principle is shown in Figure 1 and a detailed description of the CLG process is given in the work of Ge et al [11]. Several experimental studies regarding BCLG have been performed [5,[11][12][13][14][15], but there is no consensus in the literature regarding the influence of the main operating parameters on syngas composition [5]. Furthermore, the harsh conditions in CLG reactors only allow the measurement of mascroscopic quantities [16].…”

“…BCLG is hence expected to work with an oxygen carrier at lower oxidation degrees. Therefore, Condori et al [5] developed a novel method for controlling the oxidation of the OC ilmenite in the air reactor. Their results also showed the effectiveness of ilemnite.…”