LD Slag Research Articles

Effect of the Conversion Degree on the Apparent Kinetics of Iron-Based Oxygen Carriers.

The role of the oxygen carrier is important in energy conversion processes with fluidized beds, particularly chemical looping technology. It is necessary to establish the relevant kinetics of oxygen carriers that can be applicable for various chemical looping processes. In this study, we analyzed the apparent kinetics of three iron-based oxygen carriers, namely, ilmenite, iron sand, and LD slag, during the conversion of CO, H2, and CH4 in a fluidized bed batch reactor. The effect of both the oxidation degree, presented as the mass conversion degree, and temperature was considered. The results show that the changing grain size (CGS) model is generally applicable in predicting the apparent kinetics of reactions between the investigated iron oxygen carriers and gaseous fuels even at lower oxidation degrees (3-5 wt % reduction). The activation energies of the investigated materials in the conversions of CO, H2, and CH4 obtained from the fittings of the CGS model are about 51-92, 55-251, and 72-211 kJ/mol, respectively. Both the mass conversion degree and temperature influence the reactivity of oxygen carriers in a directly proportional way, especially at temperatures higher than 925 °C. The results of this study are useful for reaction engineering purposes, such as designing a reactor, in chemical looping units, or in any other processes that use oxygen carriers as a bed material.

Effect of oxidation degree of iron-based oxygen carriers on their mechanical strength

Iron-based oxygen carriers are currently one of the most popular choices for chemical looping processes. In order to minimize losses of oxygen carrier materials in the system, it is important to assess attrition characteristics. Furthermore, in chemical looping gasification where the oxygen transfer capacity needs to be limited, a higher reduction degree of oxygen carriers can be expected. As different oxidation degrees lead to different phase compositions, this study aimed to investigate the correlation between mechanical strength of iron-based oxygen carriers and the phase composition, which is the result of oxidation degree change. Our findings demonstrate that how the phase composition may affect the attrition rate of oxygen carriers depends largely on the type of the material itself. In this study, the presence of Fe-Ti and Fe-Si combinations contribute to a generally stable attrition rate, while Fe-Ca system exhibits a decreasing attrition rate. Furthermore, attrition rate shows a more conclusive trend compared to crushing strength. Among the investigated materials, both ilmenite ore and iron sand showed a robust, stable mechanical stability with an attrition rate of approximately 0.5–1 wt%/h, which is on par with that of sand (0.5 wt%/h). The attrition rates of LD slag and mill scale are lower, about 1–3 wt%/h.

Energy, Exergy, Economic and Exergoeconomic Analyses of Chemical Looping Combustion Plant Using Waste Bark for District Heat and Power Generation with Negative Emissions

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.

Thermal Behaviour of Epoxy Composites Filled with Micro-sized LD Slag Particulates

Thermal Behaviour of Epoxy Composites Filled with Micro-sized LD Slag Particulates

Effect of Weathering on Steel Converter Slag Used as an Oxygen Carrier.

Steel converter slag, also called LD slag, is a material that has been suggested for use as a low-cost oxygen carrier for chemical looping applications. Low-cost oxygen carriers are especially relevant for the conversion of solid fuels, which may contain large amounts of reactive ashes. Ash may limit the lifetime of the bed material, which is why a high-cost oxygen carrier will likely not be competitive. Applying LD slag on an industrial scale as an oxygen carrier makes the storage properties of the material highly interesting. LD slag has been known to be affected by weathering, thus limiting the possibilities of the material to be used in construction, e.g., as fillers in concrete. In this study, pretreated LD slag for use as an oxygen carrier was weathered outdoors for roughly 1.5 years in southwest Sweden. Afterward, the particles were characterized and used in a laboratory batch fluidized bed reactor system to evaluate the effects of storage on the oxygen carrier properties. It was found that the reactivity with the fuel of the weathered LD slag was similar to that of the original sample when used in a laboratory fluidized bed. However, the physical properties were severely degraded due to weathering. Dissolved CaO formed CaCO3, agglomerating the top layer of the sample. The particles in the bulk of the sample were found to have decreased density and increased attrition rate. This suggests that LD slag particles for use as oxygen carriers should be stored dry to avoid weathering of the particles.

Influence of elevated temperature on compressive strength of LD slag aggregate concrete

PurposeThis study aims to investigate the compressive strength of concretes incorporating Linz-Donawitz slag (LD slag) as partial replacement for natural fine and coarse aggregates and compare them with traditional concrete.Design/methodology/approachThe natural fine and coarse aggregates were replaced by weight simultaneously up to 100% with LD slag aggregates at an incremental increase of 20%. Concrete of grades M20, M25, M30, M35 and M40 were cast, cured and tested with standard cube specimens to study the density and compressive strength of reference and LD slag aggregate concretes (LDSACs). The concrete specimens were exposed to elevated temperatures, i.e. 100 to 900 °C at an equal interval of 100 °C and tested to study the variation in density and residual compressive strength.FindingsThe results from the experiments reveal that the LDSAC yields a higher density than that of the reference concrete and also undergo less density variation when exposed to elevated temperatures. In addition, the residual compressive strength of LDSAC specimens was significantly higher than that of the reference concrete.Research limitations/implicationsLD slag is believed to be stronger and more durable than locally available limestone aggregates or blast furnace slag. Moreover, it is necessary to study its strength and other properties to determine whether it can be successfully used as an aggregate in concrete universally.Practical implicationsUse of LD slag as aggregates in concrete will convert LD slag into a value added product and as an alternative to the existing natural aggregates which will help in maintaining ecological balance and save valuable lands.Social implicationsThe economically weaker section of the society may now use LDSAC as waste utilization will bring down the overall cost and hence it will benefit people on large scale.Originality/valueUse of LD slag as aggregate in concrete can help find an alternative to the existing natural aggregates which will save the ecosystem and at the same time help in reducing the industrial waste on a large scale.

Sustainably produced concrete using weathered Linz-Donawitz slag as a fine aggregate Substitute: A comprehensive study with Artificial intelligence approach

Continuous consumption of natural resources such as river sand and coarse aggregates due to increased industrialization and urbanization has impeded the movement towards green concrete in construction, i.e., utilizing waste materials in its production, steel slag waste being one of them. Accumulation of Linz-Donawitz slag (LD slag) has become cumbersome in India, posing a problem of landfills and environmental degradation, i.e., abating soil and water quality due to the leaching of toxic metals. Fewer experimental studies have examined whether weathered fine LD Slag can substitute for fine aggregates in concrete. Additionally, the research has yet to compare the behavior of concrete comprising weathered fine LD slag in Normal Strength Concrete (NSC) and High Strength Concrete (HSC) containing Metakaolin. The current study aims to establish an optimum replacement quantity for fine aggregates with fine LD slag. The slag replaced fine aggregates by volume at 25, 50, 75 and 100%. The findings that examined the effects of using LD slag on the mechanical behaviour, durability and microstructure of concrete are presented in this study. Furthermore, taking a total of 180 experimental data points, the compressive strength of concrete was predicted using artificial intelligence (AI) methods such as Artificial Neural Networks (ANNs), Decision Trees (DT) and Random Forests (RF). Coefficient of determination R2, Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were computed to assess the performance of generated models. Besides, a sensitivity analysis technique was employed to determine the most influential parameter among cement, Metakaolin, Fine Aggregate, Coarse Aggregate, LD slag, Superplasticizer, water content and testing age on the compressive strength results. Experimental investigation showed that adding LD slag up to 50% for NSC and 25% for HSC was optimal and showed better results for tested properties than conventional concrete mixes. Among proposed AI techniques, the DT technique was the best-performing model with an R2 value of 0.973 and the least for MAE (3.534 MPa) and RMSE (4.409 MPa). Sensitivity analysis performed on the DT model showed that testing age was the most critical parameter for the prediction of compressive strength.

Development of low heavy metal − Linz-Donawitz slag for safe spinach cultivation

Linz-Donawitz Slag is regarded as a soil conditioner and can be exploited for its mineral and nutritional value in agriculture, however, it is necessary to check the Potentially Toxic Elements (PTEs) which could impact the soil rapidly and crop production adversely. Environmental hazards associated with mounting piles of Linz-Donawitz slag emanating from the steel producing industry and its sustainable management are a major challenge. A research study was carried out using different chemical chelating agents to achieve reduction in PTEs' concentration in Linz-Donawitz slag and to study the effect of transfer of PTEs’ from the treated and untreated LD Slag applied to the spinach. Optimization was done using response surface methodology, and the highest extraction efficiency for Cadmium (Cd) and Lead (Pb) removal was observed using a concentration of 10 mM, liquid-to-solid ratio of 5:1, and shaking time of 60 min to obtain Low heavy metal Linz-Donawitz slag (Low HM-LD Slag). The highest chelation was observed while using the chelating agent Ethylene diamine-N, N'-Di succinic acid (EDDS) followed by Ethylene diamine tetra acetic acid (EDTA) then Diethylene triamine penta acetate (DTPA), and the least extraction was observed using the Citric acid (CA). The Low HM-LD Slag so obtained was assessed for its response on Spinach under the varied level of Recommended Dosage of Fertilizer (RDF) under field soil in pot culture. A significant difference in the growth of spinach was observed between 100% RDF treated Low HM-LD Slag and 50% RDF treated Low HM-LD Slag derived using different chelating agents The PTE analysis of soil and plant showed an undetectable level of Cd, Pb in both the shoot and root samples Under Low HM-LD Slag treatments @ 100% and 50% RDF condition. The present work advocates the use of chemical chelators reducing PTEs' load in Linz-Donawitz slag before using it for application in agriculture as a soil conditioner or as a fertilizer.

Utilization of Linz-Donawitz slag and brick bat for the production of sustainable paver blocks

Due to the unplanned and uncontrolled exploitation of mineral resources and the massive production of industrial trash, waste is now being reused and recycled for sustainable development. The production of cement and concrete in the building industry has been enhanced by the recycling and reuse of waste. Construction provides a lot of opportunities for recycling. These by-products can produce better outcomes and can raise concrete quality. There are about 120,000 brick kilns in India. Each year, 250 billion bricks are manufactured, of which 5% are waste. On the other hand, the buildup of Linz-Donawitz slag (LD slag) in India has become problematic, leading to a problem with landfills and environmental deterioration. Nowadays, paver blocks have become quite popular and are utilized to pave vacant spots in front of homes as well as parking lots, businesses, and enterprises. One of its key advantages is that damaged individual blocks can be replaced. The current study concentrates on utilizing these waste materials to create Paver Blocks that can be used by pedestrians. Paver blocks comprising LD slag at a replacement level of 50% for fine aggregate and brick bat at a maximum replacement of 30% with coarse aggregate were tested for properties such as compressive strength, flexural strength, water absorption and abrasion resistance. Out of the proposed mixes, the mix with 20% Brick Bat and 50% LD Slag is the best as it qualifies the necessary quality and strength requirements.

Metal impregnation on steel converter slag as an oxygen carrier

AbstractOxygen carriers used in chemical looping processes operated with biofuel are affected by the inorganic matter of the fuel. It is therefore expected that the lifetime of the oxygen carrier is limited, and preferably low‐cost oxygen carriers should be used. Oxygen carriers based on iron ore or steel manufacturing waste products are available in significant quantities at low cost. However, it is common for these types of materials that their reactivity is low. This study investigates the effect of adding small amounts of more reactive elements into steel converter slag, also called LD slag.Slag particles were wet impregnated with 2 or 5 wt.% of Ni, Cu, Mn, or Ce. The new material's morphology was evaluated using X‐Ray Diffraction and SEM‐EDS. Changes in reactivity towards CO, CH4 and the model tar molecule benzene were evaluated using a bench‐scale laboratory fluidized bed reactor.It was observed that even small amounts of either Ni, Cu, or Mn could increase reactivity toward CO. Both Cu and Mn formed phases with LD slag that released oxygen via CLOU (chemical looping with oxygen uncoupling) and increased the conversion of methane and benzene. Ni and Ce doping also increased methane conversion but had only a minor effect on the benzene conversion. © 2023 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

Interaction behavior of sand-diluted and mixed Fe-based oxygen carriers with potassium salts

Oxygen carriers, in the form of metal oxide particles, are bed materials that transport oxygen in solid form in fluidized bed applications, such as in chemical-looping applications. In biofuel applications, it is well known that alkali from the fuel ash can react with the bed material and cause, among other operation issues, agglomeration. When using oxygen carriers in a fluidized bed, it is likely that the bed material is either a mixture of different metal oxide materials or partly diluted with sand. This is to improve or combine the chemical properties of the materials used or simply for economic reasons.This work investigates how three potassium salts K2CO3, K2SO4 and KH2PO4 interact with the oxygen carriers: Steel converter slag (LD slag), ilmenite, mixtures of the two and each carrier diluted with silica sand. The salts were used as model compounds that can occur in biofuel ash. The set-up used was a fixed bed where a small sample of bed material is mixed with a potassium salt equivalent to 4 wt-% of potassium. The mixture was then exposed to reducing (H2 in steam) conditions at 900 °C during several hours in a tubular furnace. This provides a worst-case scenario for solid–solid interaction in a fluidized bed. If a solid–solid reaction does not take place in this setup, it will most likely never occur in a fluidized bed.When LD slag and ilmenite were combined, the potassium from the salts would prefer to accumulate in the ilmenite rather than the LD slag. Ca from LD slag interacted with KH2PO4 resulting in a less severe agglomeration than when ilmenite was used separately with the same salt. When the oxygen carriers were diluted with silica sand, potassium salt interaction resulted in agglomeration for both the oxygen carriers with all potassium salts. K2CO3 and K2SO4 formed potassium silicates, while KH2PO4 formed a phosphorus-containing melt. When LD slag was present, phosphorus was located in a K-Ca-P phase that was not present if ilmenite was present.

Synthesis and characterization of ladle furnace slag on the mechanical properties of self-compacting concrete

The current study examines the use of industrial wastes in the construction industry. Slag from ladle furnaces (Ld) is a solid waste product of the steel industry. Primary and secondary steel-making processes are used in the production of steel from iron or scrap. Ladle furnace slags are steel slags created during the secondary steel-making process. In this study, conventional and self-compacting M25 grade concrete mixtures were made with Ld slag in place of some of the cement. It is also utilised as a filler ingredient in self-compacting concrete (SCC), where the content of Ld slag is 99 kg/m3. In concrete mixtures, Ld slag was used to substitute cement to varying degrees (0 %, 5 %, 10 %, 15 %, 20 %, 25 %, and 30 %). Self-compacting concrete (SCC) was tested for workability in its fresh form as well as for filling, passing, and viscosity. The hardened state of these mixes was also studied, and compressive and split tensile strengths were determined. This slag had its cementitious qualities improved by activating it mechanically for application in concrete mixing. The results show that substitution of up to 10 % of the Ld slag can increase concrete strength, but it also provides good strength that is on par with that of regular concrete. However, when SCC was generated, it provided the best strength of all. SCC can be formed by replacing up to 15 % of the cement with Ld slag and still get the desired results.

Tar characteristics generated from a 10 kWth chemical-looping biomass gasifier using steel converter slag as an oxygen carrier

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.

Physical, mechanical, and sliding wear behavior of micro‐sized Linz‐Donawintz slag filled epoxy composites

AbstractLinz‐Donawintz (LD) slag is a solid waste produced during the basic oxygen furnace process of steel making and is more often disposed of on nearby land causing a disturbance in vegetation and human health. Hence, judicial management of LD slag is a need for an hour. For this purpose, the usability of LD slags as a reinforcement material in epoxy composites was investigated in the present work. In this investigation, the physical properties (density, void content, water absorption rate), mechanical properties (tensile properties, flexural properties, compressive strength, hardness), and tribological properties (sliding wear behavior) are reported. From the experimental investigation, it is found that the density, void content, and water intake capacity increase with LD slag loading. The maximum voids present in the composite is 1.92% for epoxy/40 wt. % LD slag composite. Similarly, maximum water uptake of only 0.6% is observed for composite with maximum filler content and for maximum immersion time. Further, it is observed that the strength of composite under tensile and flexural loading was compromised slightly. At 40 wt. % of LD slag, the measured tensile and flexural strength are 20.8 MPa and 28.78 MPa respectively. The strength of composites under compressive loading increases with filler content and reaches a maximum of 108 MPa for epoxy/40 wt. % LD slag composite. The high hardness of filler assists in increasing the hardness of the composites. The hardness of neat epoxy is Shore‐D number 75 which increases to Shore‐D number 84. With increased hardness, ultimately the specific wear rate under dry sliding conditions reduces. Taguchi's L25 orthogonal array having four factors, each at five different levels is implemented to conduct the sliding wear tests. A forecast model is built on an artificial neural network (ANN) which successfully envisages the sliding wear performance of the composite under investigation inside and outside the experimental domain.

Influence of an Oxygen Carrier on the CH4 Reforming Reaction Linked to the Biomass Chemical Looping Gasification Process.

A major challenge in biomass chemical looping gasification (BCLG) is the conversion of CH4 and light hydrocarbons to syngas (CO + H2) when the goal is the use for bioliquid fuel production. In this work, tests were performed in a batch fluidized bed reactor to determine the catalytic effect on the CH4 reforming reaction of oxygen carriers used in the BCLG process. Three ores (ilmenite, MnGB, and Tierga), one waste (LD slag), and five synthetic materials (Fe10Al, Fe20Al, Fe25Al, Cu14Al, and Ni18Al) were analyzed. These results were compared to those obtained during ∼300 h of continuous biomass gasification operation in a 1.5 kWth BCLG unit. The low-cost materials (ores and waste) did not show any catalytic effect in the CH4 reforming reaction, and as a consequence, the CH4 concentration values measured in the syngas produced in the continuous prototype were high. The synthetic oxygen carriers showed a catalytic effect in the CH4 reforming reaction, increasing this effect with increasing temperature. With the exception of the Ni-based oxygen carrier (used as a reference), the Cu-based oxygen carrier, working at 940 °C, showed the best catalytic properties, in good agreement with the low CH4 concentration values measured in the syngas generated in the continuous unit. The tests performed in a batch fluidized bed reactor were demonstrated to be very useful in determining the catalytic capacity of oxygen carriers in the CH4 reforming reaction. This fact is highly relevant when a syngas with a low CH4 content is desired as a final product.

Comparison of slag-based gypsum with commercial gypsum as a nutrient source on soil properties, nutrient uptake and yield of rice (Oryza sativa L.) under aerobic and wetland conditions

ABSTRACT Slag-based gypsum (SBG) is produced from LD slag (Linz-Donawitz slag) which is a byproduct of the steel industry. As the constituents of SBG are almost similar to the commercial gypsum (CG), two field experiments on acidic and alkaline soil under aerobic and wetland conditions were conducted to know their performance on rice. The treatments included recommended dose of fertilizer (RDF) as control, 300, 450, 600 and 750 kg ha−1 of SBG and CG along with RDF. Application of 750 kg SBG ha−1 recorded higher grain (6.15 and 9.22 t ha−1, respectively) and straw yield (10.80 and 12.71 t ha−1, respectively) in acidic and alkaline soils. The application of 750 kg SBG ha−1 increased the pH of acidic soil from 4.56 to 5.00 and from 9.04 to 9.37 in alkaline soil. Available nutrients in the post-harvest soil increased with the increase in the application rates of SBG and CG in soil. There was an increase in total uptake of the nutrients by the rice crop with an increase in application rates of SBG and CG. Application of a graded levels of SBG recorded higher grain and straw yield, nutrient uptake and nutrient availability in comparison to CG.

Thermochemical conversion of biomass volatiles via chemical looping: Comparison of ilmenite and steel converter waste materials as oxygen carriers

Two oxygen carriers were tested with respect to chemical looping combustion (CLC) and chemical looping gasification (CLG). Ilmenite, a natural ore composed mainly of iron–titanium oxide, and LD Slag, an iron-based industrial waste, were investigated at 850 and 900 °C in a continuous operation in a 0.3 kW chemical-looping reactor system using synthetic biomass volatiles as fuel. CLC and CLG conditions were simulated in the fuel reactor by changing the fuel flow rates. In the case of ilmenite the syngas yield and methane conversion increased with fuel flow rate. Consequently, the syngas to hydrocarbon ratio was higher for ilmenite. Methane conversion improved for both tested oxygen carriers with increasing the operating temperature. Oxygen release was observed in the case of LD Slag. The H2/CO ratio was between 0.7 and 0.8 for both oxygen carriers at the higher fuel flows. With respect to CLC, ilmenite showed higher gas conversion than LD slag. Analysis of the particles revealed that ilmenite possessed better mechanical properties and formed less dust compared to LD Slag during the continuous operation with fuel.

Modification of microstructure of LD slag for recovery of hybrid flux material

The Basic Oxygen Furnace steel making process produces BOF slag (LD slag) at a rate of about 125 kg/t. The LD slag contains about 18% Fe in wustite and dicalcium ferrite and about 45% CaO. These minerals are an excellent source of alternative flux material for the steel industry. Through slag modification and in-depth characterization studies, investigations were carried out to develop a material that could be utilized as an alternative flux material. Detailed characterization studies were conducted using SEM-EPMA and XRD to identify the changes in the crystal structure, phase distribution, grain size and liberation size of minerals. The grain size of phases was found to be between 10-150 ­­­­­µm for normally cooled slag and 20-250 µm for slowly cooled slag. It was also shown that slow cooling promotes the formation of an additional phase which is essentially the dicalcium silicate phase (C2S) with some amounts of FeO and MgO in the crystal lattice. Overall, it was observed that about 50% of the LD slag could be recovered as alternative flux material containing approximately 30% CaO and 30% Fe content. This alternative flux material is an excellent source of material for use in steel industries because of its low melting slag formation.

Biomass chemical looping gasification for syngas production using LD Slag as oxygen carrier in a 1.5 kWth unit

Biomass Chemical Looping Gasification (BCLG) is an autothermic gasification process that provides pure syngas for many applications, including liquid biofuels production. Finding low-cost materials that can be used in the process is a key issue, especially when they come from waste. In this sense, LD Slag is a by-product of the steel industry used as an oxygen carrier in Chemical Looping Combustion with good results. This work investigates the use of LD Slag as oxygen carrier in a continuous 1.5 kWth BCLG unit. The effect of the main operational variables (temperature, oxygen-to-fuel and steam-to-biomass ratios) and the use of CO2 instead of steam as gasification agent were analysed. LD slag allowed the process with high biomass conversions, Xb > 90%, carbon conversion efficiencies, ηcc > 90%, and syngas yields, Y ≈ 0.66 Nm3/kg of dry biomass, at conditions corresponding to autothermal operation. A lifetime of 300 h under reducing conditions was inferred and agglomeration problems were never detected. LD slag can be considered a suitable material for BCLG since it is possible to obtain high-quality syngas at autothermal conditions from different types of biomass with low tar generation and CO2 emissions.

Study of defluidization of iron- and manganese-based oxygen carriers under highly reducing conditions in a lab-scale fluidized-bed batch reactor

Oxygen carriers play an important role in chemical looping processes to transport oxygen for fuel conversion. In this study, the defluidization phenomena of oxygen carriers were examined under highly reducing conditions in a fluidized-bed batch reactor. This is highly relevant to chemical-looping gasification, where oxygen carriers could be reduced to a significant extent compared to that in chemical-looping combustion. Only a few studies have reported the physical phenomena in a fluidized bed system under highly reducing conditions. Three iron- and two manganese-based oxygen carriers were investigated at 900 °C at several degrees of reduction in this study. Some oxygen carriers that have been exposed to several hours of operation in a 300 W chemical-looping reactor unit were also included in this study to provide a comparison to the fresh-calcined materials. Defluidization of particle beds occurred with the iron-based oxygen carriers, except for LD slag, which has a low content of iron. The defluidization was caused by the formation of elemental iron on the oxygen carriers' surface at high degree of reduction. All defluidizations occurred at a mass-based conversion (∆ω) between 3.2–5.0%. The manganese-based materials were found to be less prone to defluidization.