Paper-based packaging is a complex multi-material composed of paper (fibers), plastics, and metals, making efficient material recycling complicated. Currently, most of the fibers are recycled into new paper products while the residual material is commonly incinerated. Therefore, to improve the circularity and reduce the fossil dependency chemical recycling is needed. In this study, recycling of the residual materials was evaluated by thermal and catalytic pyrolysis. First, screening tests were performed using five reject materials and four catalysts in an analytical scale and then, a selection of catalyst and reject materials were evaluated in lab-scale followed by a techno-economic assessment. Experimental results indicated that the conversion was more efficient if the reject had high content of plastics compared to fibers, leading to products with increased heating value, higher hydrocarbon yield and less reactive oxygenates compared to the rejects with low plastic ratio. In the thermal pyrolysis 54 % of the weight of the feedstock and 70 wt% of the carbon in the feedstock ended up in a solid organic product (wax) which contained hydrocarbons and alcohols. In the analytical catalytic pyrolysis, HZSM-5 gave the best result in terms of cracking, deoxygenation, and aromatization. Ex-situ catalytic pyrolysis using HZSM-5 resulted in an improved quality of organic liquid with reduced hydrocarbon length as well as deoxygenated and aromatic compounds. The yield of the organic liquid was up to 19 wt% and contained mainly monoaromatics. The techno-economic evaluation showed, for processing 100,000 tons year−1 residual material, the total plant investment and the annual profit are about 29 and 12 million Euros, respectively, if no incentive for treating the residual material.

The greenhouse gas emissions from the boiler of pulp and paper industries can be minimized by adapting chemical looping combustion (CLC) technology. This work aims to analyze the energy, exergy, economic, and exergoeconomic performance of an industrial scale CLC plant for district heat and electricity generation using waste bark from the paper and pulp industry. The CLC plant with one natural ore and one industrial waste oxygen carrier (OC) is modeled using Aspen Plus. The performance of the CLC plant has been compared to Örtofta combined heat and power plant without CO2 capture and with post-combustion CO2 capture as the reference cases. Results showed that the CLC-based power plant is energetically, exegetically, and economically efficient compared to the reference cases. The circulating fluidized bed boiler unit contributes the highest exergy destruction (about 50–80%). Among the CO2 capture plants, the CLC plant with ilmenite has the lowest levelized cost of district heat (4.58 € GJ−1), and a payback period (9.69 years) followed by the CLC plant with LD slag (5.91 € GJ−1 and 11.84 years), and the plant with PCC (6.94 € GJ−1 and 13.58 years). The exergoeconomic analysis reveals that the CLC reactors have the highest cost reduction potential, followed by the steam turbine. 

The second-generation bio aviation fuel production via Chemical Looping Gasification (CLG) of biomass combined with downstream Fischer-Tropsch synthesis is a possible way to decarbonize the aviation sector. Although CLG has a higher syngas yield and conversion efficiency compared to the conventional gasification processes, the fraction of biogenic carbon which is converted to biofuel is still low (around 28%). To increase carbon utilization and biofuel yield, incorporation of two types of electrolyzers, Polymer Electrolyte Membrane (PEM) and Molten Carbonate Electrolysis Cell (MCEC), for syngas conditioning has been investigated. Full chain process models have been developed using an experimentally validated CLG model in Aspen Plus for Iron sand as an oxygen carrier. Techno-economic parameters were calculated and compared for different cases. The results show that syngas conditioning with sustainable hydrogen from PEM and MCEC electrolyzers results in up to 11.5% higher conversion efficiency and up to 8.1 % higher biogenic carbon efficiencies in comparison to the syngas conditioning with water gas shift reactor. The study shows that the lowest carbon capture rates are found in the configurations with the highest biogenic carbon efficiency which means up to 14% more carbon ends up in FT crude compared to the case with conventional WGS conditioning. Techno-economic analysis indicates that syngas conditioning using PEM and MCEC electrolyzers would result in an increase of the annual profit by a factor of 1.4 and 1.7, respectively, when compared to using only WGS reactors. 

A steel slag from the Linz-Donawitz process, called LD-slag, having significant calcium and iron-fractions, was investigated as an oxygen carrier in a recently developed 10 kWth chemical-looping combustor with three high-volatile biomass fuels. In order to improve operability, the LD-slag was found to require heat-treatment at high temperatures before being used in the unit. In total, operation with the biomasses was conducted for more than 26 h at temperatures of 870–980 °C. The fuel thermal power was in the range of 3.4–10 kWth. The operation involved chemical looping combustion (CLC), chemical looping gasification (CLG) and oxygen carrier aided combustion (OCAC). Around 12 h was in CLC operation, 13.3 h was conducted in CLG-conditions, while the remaining 0.7 h was OCAC. Here, the results obtained during the CLC part of the campaign is reported. Increased temperature in the fuel reactor and higher airflows to the air reactor both lead to better combustion performance. Steam concentration in the fuel reactor has little effect on the performance. The LD-slag showed higher oxygen demand (31.0%) than that with ilmenite (21.5%) and a manganese ore (19.5%) with the same fuel and normal solids circulation. However, with the LD-slag, there is possibility to achieve a lower oxygen demand (15.2%) with high solids circulation. © 2023 The Author(s)

Iron sand as an industrial by-product has a reasonable iron content (35 wt% Fe) and low economical cost. The reactivity of iron sand as an oxygen carrier was examined in a bubbling fluidized bed reactor using both gaseous and solid fuels at 850–975 °C. Pre-reductions of iron sand were performed prior to fuel conversion to adapt the less-oxygen-requiring environment in chemical looping gasification (CLG). Based on the investigations using CO and CH4, iron sand has an oxygen transfer capacity of around 1 wt%, which is lower than that of ilmenite. The conversion of pine forest residue char to CO and H2 was higher when using iron sand compared to ilmenite. Depending on the mass conversion degree of iron sand, the activation energy of pine forest residue char conversion using iron sand was between 187 and 234 kJ/mol, which is slightly lower than that of ilmenite. Neither agglomeration nor defluidization of an iron sand bed occurred even at high reduction degrees. These suggests that iron sand can be utilized as an oxygen carrier in CLG. Furthermore, this study presents novel findings in the crystalline phase transformation of iron sand at various degrees of oxidation, altogether with relevant thermodynamic stable phases. 

The second-generation bio aviation fuel production via Chemical Looping Gasification (CLG) of biomass combined with downstream Fischer-Tropsch (FT) synthesis is a possible way to decarbonize aviation sector. The CLG process has the advantage of producing undiluted syngas without the use of an air-separation unit (ASU) and improved syngas yield compared to the conventional gasification processes. This study is based on modelling the full chain process of biomass to liquid fuel (BtL) with LD-slag and Ilmenite as oxygen carriers using Aspen Plus software, validating the model results with experimental studies and carrying out a techno-economic analysis of the process. For the gasifier load of 80 MW based on LHV of fuel entering the gasifier, the optimal model predicts that the clean syngas has an energy content of 8.68 MJ/Nm3 with a cold-gas efficiency of 77.86%. The optimized model also estimates an aviation fuel production of around 340 bbl/day with 155 k-tonne of CO2 captured every year and conversion efficiency of biomass to FT-crude of 38.98%. The calculated Levelized Cost of Fuel (LCOF) is 35.19 $ per GJ of FT crude, with an annual plant profit (cash inflow) of 11.09 M$ and a payback period of 11.56 years for the initial investment.

Tar management is one of the key components to achieve high energy efficiency and low operational costs connected to thermal gasification of biomass. Tars contain a significant amount of energy, and unconverted tars result in energy efficiency losses. Also, heavy tars can condense downstream processes, resulting in increased maintenance. Dual fluidized beds for indirect gasification operated with active bed material can be a way to better convert and control the tar generated in the process. Using an active material to transport oxygen in an indirect dual reactor gasification setup is referred to as chemical-looping gasification (CLG). A higher oxidative environment in the gas phase, in addition to possible catalytic sites, could mean lower yields in comparison to normal indirect gasification. This paper investigates the effect of using Steel converter slag (LD slag), a byproduct of steel manufacturing, as an oxygen-carrying bed material on tar species generated in a 10 kWth dual fluidized bed biomass gasifier. The results are compared to the benchmark oxygen carrier ilmenite and conventional silica sand. Three different solid biofuels were used in the reactor system: steam exploded pellets, pine forest residue and straw. Tar was absorbed from the raw syngas using a Solid Phase Adsorption (SPA) column and was analyzed using GC-FID. Bench-scale experiments were also performed to investigate benzene conversion of LD slag and ilmenite at different oxidation levels. The findings of this study suggest that oxygen carriers can be used to decrease the tars generated in a dual fluidized bed system during gasification. Phases in LD slag possess catalytic properties, resulting in a decreased ratio of heavy tar components compared to both ilmenite and sand. Temperature and fuel load showed a significant effect on the tar generation compared to the circulation and steam ratio in this reactor system. Increased temperature generated lower tar yields and lower ratios of heavy tar components for LD slag in contrast to sand.

Chemical-Looping Combustion (CLC) of biofuels is a promising technology for cost-efficient CO2 separation and can lead to negative CO2 emissions when combined with carbon capture and storage. A potential challenge in developing CLC technology is the effects of alkali metal-containing compounds released during fuel conversion. This study investigates the interactions between alkali and an oxygen carrier (OC), CaMn0.775Ti0.125Mg0.1O3-δ, to better understand the fate of alkali in CLC. A laboratory-scale fluidized bed reactor is operated at 800–900 °C in oxidizing, reducing and inert atmospheres to mimic CLC conditions. Alkali is fed to the reactor as aerosol KCl particles, and alkali in the exhaust is measured online with a surface ionization detector. The alkali concentration changes with gas environment, temperature, and alkali loading, and the concentration profile has excellent reproducibility over repeated redox cycles. Alkali-OC interactions are dominated by alkali uptake under most conditions, except for a release during OC reduction. Uptake is significant during stable reducing conditions, and is limited under oxidizing conditions. The total uptake during a redox cycle is favored by a high alkali loading, while the influence of temperature is weak. The implications for the understanding of alkali behavior in CLC and further development are discussed. 

Chemical looping gasification (CLG) is an emerging process that aims to produce valuable chemical feedstocks. The key operational requirement of CLG is to limit the oxygen transfer from the air reactor (AR) to the fuel reactor (FR). This can be accomplished by partially oxidizing the oxygen carrier in the AR, which may lead to a higher reduction degree of the oxygen carrier under the fuel conversion. A highly reduced oxygen carrier may experience multiple issues, such as agglomeration and defluidization. Given such an interest, this study examined how the variation of the mass conversion degree of ilmenite may affect the conversion of pine forest residue char in a fluidized bed batch reactor. Ilmenite was pre-reduced using diluted CO and then underwent the char conversion at 850, 900, 950, and 975 °C. Our investigations showed that the activation energy of the char conversion was between 194 and 256 kJ/mol, depending upon the mass conversion degree of ilmenite. Furthermore, the hydrogen partial pressure in the particle bed increased as the oxygen carrier mass conversion degree decreased, which was accompanied by a lower reaction rate and a higher reduction potential. Such a hydrogen inhibition effect was confirmed in the experiments; therefore, the change in the mass conversion degree indirectly affected the char conversion. Langmuir-Hinshelwood mechanism models used to evaluate the char conversion were validated. On the basis of the physical observation and characterizations, the use of ilmenite in CLG with biomass char as fuel will likely not suffer from major agglomeration or fluidization issues.

Alkali release was studied in a 10 kWthchemical looping pilot operated with a Linz-Donawitz (LD) slag oxygen carrier (OC) and three biomass fuels. Experiments were performed at three temperatures and in three operation modes: chemical looping combustion (CLC), chemical looping gasification (CLG), and oxygen-carrier-aided combustion (OCAC). Gas-phase alkali release was measured with a surface ionization detector (SID). Fuel reactor (FR) gas-phase alkali emissions increased with the temperature. This occurred as a result of increased evaporation of KCl and enhanced decomposition of alkali salts during char conversion. Air reactor (AR) alkali emissions were lower than in the FR and independent of the operating temperature. In comparison of operating modes, CLC and CLG modes resulted in similar gas-phase alkali emissions due to the similar extent of char conversion. In contrast, operation of the reactor system in OCAC mode resulted in significantly lower levels of gas-phase alkalis. The difference in alkali emission was attributed to the steam-rich atmosphere of CLC. The effect of steam was further investigated in CLC and OCAC tests. Lowering steam concentrations in CLC operation resulted in lower gas-phase alkali emissions, while introducing steam to the FR during OCAC operation resulted in higher alkali emissions. It was concluded that steam likely enhances gas-phase K release through a reaction of K2CO3within the fuel char with steam to produce KOH(g). Solid sampling and analysis for K content was used along with SID measurements to develop a K mass balance for the reactor system. Mass balance results for the straw pellet fuel tests showed that LD slag OC absorbs approximately 15-51% of fuel K, 2.2% of fuel K is released to the gas phase, and up to 3.4% of fuel K is captured in the AR fly ash. The residual 40-80% of fuel K was determined to leave the FR as K-rich fly ash.