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A dry sorbent post-combustion CO 2 capture process using a circulating fluidized bed (CFB) was developed to a 10 MWe scale. Particle attrition is a major challenge for many CFBs owing to the loss of particles and increased operating costs. Furthermore, predicting and alleviating the rate of particle attrition in an entire CFB is difficult owing to limited information on attrition in the riser and cyclone. This study experimentally investigated particle attrition in risers and cyclones and the effect of system scale-up using CO 2 adsorbent particles used in a 10 MWe scale CFB. Experiments were conducted in two types of CFBs to measure the attrition rate in the riser and cyclone for 22 and 12 h for each experimental condition. To verify the scaled-up effect, internals were added to the riser to measure the effect of the surface-area-to-volume ratio. Correlations for the attrition rate of CO 2 adsorbent particles in riser and cyclone were proposed, and a model for the scale-up effect was suggested. In the 10 MWe scale system, particle attrition mainly occurred in the cyclone (58.0 %) and riser (37.3 %) according to the calculation, and the calculated overall attrition rate reasonably matched the operational data. Figure: (a) Calculated attrition rate of CO 2 adsorbent particles in the circulating fluidized bed of 10 MWe scale CO 2 capturing process, and (b) effect of cyclone inlet gas velocity on the particle attrition rate in cyclone. [Display omitted] • Particle attrition mainly occur in the cyclone and riser of a CFB. • Attrition rate in cyclone was proportional to the square of the gas velocity. • The top size of fines formed by attrition in riser increased with gas velocity. • Attrition rate in the riser increases by increasing surface area. • Correlation for particle attrition rate in the riser and cyclone are proposed. [ABSTRACT FROM AUTHOR]

Attrition rate R a,j versus new stirring factor α new. • The new stirring factor α new was a key factor for jet attrition. • The α new fit well the effect of bed height on jet attrition. • The top size of fines formed by attrition increased with α new. • The attrition rate increased linearly with α new. Particle attrition is a major challenge when handling bulk solid materials with fluidized beds due to its ability to cause particle loss. Herein, the particle attrition induced by the gas jets on a perforated plate distributor in a bubbling fluidized bed was investigated for CO 2 adsorbent particles. An attrition tube, which used air as the fluidizing gas, was used as the fluidized bed. At a constant fluidizing velocity, the initial static bed height and orifice gas velocity were considered as variables. It was confirmed that abrasion dominated the particle attrition. The trend indicating the change in the maximum size of the particles (d pm,a) formed by attrition followed that of the attrition rate (i.e., the formation rate of fine particles via attrition). A new stirring factor that combined the model developed by Werther and Xi with the original stirring factor adequately explained the effect of the static bed height on both the attrition rate and d pm,a when the initial static bed height was greater than the length of the orifice gas jet that penetrated the bed. The attrition rate increased linearly with the new stirring factor. However, d pm,a increased exponentially with the new stirring factor. Relationships were successfully proposed to enable the estimation of the attrition rate and d pm,a for the CO 2 adsorbent particles. This study provided the evidence indicating the significance of the effect of bed height on particle attrition induced by the gas jet on the distributor. Moreover, proper models for correlating the attrition rate and the maximum size of the fine particles formed by attrition in the bubbling fluidized bed were provided. [ABSTRACT FROM AUTHOR]

This study aimed to provide a design and operational approach for a loop-seal, which is the heart of a circulating fluidized bed (CFB). Thousands of CFB systems use this non-mechanical valve to optimize performance by controlling the solids circulation rate while preventing gas mixing between reactors. Nevertheless, its design and operating guidance remains unclear because of its intricate flow characteristics, causing confusion in design and operation of the entire CFB. This study experimentally investigated the three most important elements while designing and operating loop-seal: conditions for initiating solids flow, the maximum obtainable solids flow rate, and quantitative control of solids flow rate. Experiments were conducted in a CFB, which simulated 3 MWth chemical looping combustion (CLC) system that is currently being developed. The onset of solids flow occurs when the gas drag force in horizontal passage overcomes the resistance force generated by the bed of particles. The maximum solids circulation rate was determined by solids height in the supply chamber and pressure around CFB loop. A correlation for quantitative control of solids flow in loop-seal was proposed by the relationship between the gas drag force and particle velocity. Finally, operational conditions for the loop-seal in 3 MWth CLC were proposed. Operating conditions of the loop-seal in 3 MWth chemical looping combustion system derived in this study. [Display omitted] • Flow characteristics in loop-seal was analyzed and design factors were confirmed. • Solid flow started after overcoming resistance force by solid in horizontal path. • Particle velocity in horizontal path increased linearly by drag force of gas. • Solid height in standpipe determined the maximum solid circulation rate. • 3 Nm3/hr of Q sup,in was required for solid circulation of 15 kg/s in 3 MWth CLC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical porous carbon beads were prepared from K+-exchanged phenolic resin. • Porous carbon beads have interconnected micro- and mesopores. • K 2 CO 3 -treated CPFR beads adsorbed 7.80 wt% CO 2 at 0.15 bar and 298 K. • The ideal CO 2 /N 2 selectivity of K 2 CO 3 -treated CPFR beads at room temperature is 52.6. • K 2 CO 3 -treated CPFR beads selectively adsorb 5.5 wt% of CO 2 over N 2. Excessive CO 2 emissions from increased energy consumption are causing an environmental disaster that threatens humanity. Herein, we report the development of hierarchical porous carbon beads with interconnected micro- and mesopores for selective CO 2 capture. Hierarchical porous carbon beads were prepared by the carbonization of potassium-exchanged phenol formaldehyde resin (PFR) beads obtained from exchange of K+ to the PFR OH groups. Interestingly, the carbonized K 2 CO 3 -treated PFR (CPFRs) exhibited notably high surface areas and total pore volumes with interconnected micro- and mesopores. Based on their high porosities and nitrogen contents, the K 2 CO 3 -treated CPFR beads adsorbed 7.80 wt% CO 2 at 0.15 bar and 298 K, which is an adsorption result that is much higher than those (4.41 wt% and 5.33 wt%) of pristine and KOH-treated CPFR beads, respectively. More importantly, the ideal CO 2 /N 2 selectivity (52.6) of K 2 CO 3 -treated CPFR beads, as determined by Henry's constant at room temperature, is superior to those (24.2 and 28.6) of pristine and KOH-treated CPFR beads, respectively. Breakthrough experiments with 15 % CO 2 in N 2 , which has a similar partial pressure to the CO 2 partial pressure in flue gases from coal power plants, revealed that K 2 CO 3 -treated CPFR beads selectively adsorb 5.5 wt% of CO 2 over N 2. This selective CO 2 capacity is superior to those reported in other porous carbon materials. Therefore, to reduce CO 2 emissions, hierarchical porous carbon beads with interconnected micro- and mesopores can play an important role in CO 2 capture and separation. [ABSTRACT FROM AUTHOR]

• K-based sorbents with α -Al 2 O 3 shows better performance than that with γ -Al 2 O 3. • CO 2 capture efficiency from 60 to 90 wt.% and the dynamic sorption capacity from 3–7 wt.%. • CO 2 removal efficiency was not varied at the condition above H 2 O/CO 2 mole ratio = 1.5. • About 76% of CO 2 removed in mixing zone, highly dependent on solid hold-up. • All the experimental data were used for designing the 10 MWe-scale CO 2 capture plant. Three kinds of K 2 CO 3 -based solid sorbents was tested in a 0.5 MWe-scale test-bed, integrated with a real coal fired power plant. The test-bed, consisting of a fast fluidized-bed carbonator, a bubbling fluidized-bed regenerator and a bubbling fluidized-bed sorbent cooler, was installed beside a Unit #3 in a Hadong coal-fired power plant. The components of K 2 CO 3 -based solid sorbents were an active reaction component of K 2 CO 3 for CO 2 sorption with the supports including Al 2 O 3 for mechanical strength. Three different solid sorbents were differentiated depending on the amount of an active component (35 wt.% or 40 wt.%) and the different composition of Al 2 O 3 (alpha alumina or gamma alumina). CO 2 capture performance was evaluated in a test-bed at the same operating conditions for three kinds of solid sorbents, which showed better CO 2 capture performance with the solid sorbent with 40 wt.% than that with 35 wt.% one. Better performance with alpha alumina as a support was obtained as compared to that with gamma alumina. Additionally, the effect of water vapor to CO 2 mole ratio in a flue gas, solid hold-up in a mixing zone of a carbonator and the regeneration temperature on the CO 2 capture performance was analyzed. The experimental results in a test-bed was confirmed by analyzing the solid samples of after-carbonation and after-regeneration. The CO 2 capture efficiency in the carbonator was varied from 60 to 90% whereas the dynamic sorption capacity of the sorbents from 3–7 wt.% in relation with the kinds of sorbents and the operating conditions. All the experimental data was used to design the 10 MWe-scale pilot plant beside a Unit #8 in a Hadong coal-fired power plant. [ABSTRACT FROM AUTHOR]

The Potassium-based dry sorbent CO 2 capture process can selectively capture CO 2 from flue gas without toxicity. In this study, the optimization of regeneration condition was investigated to pursue economical CO 2 capture process in a circulated fluidized bed reactor as most energy for CO 2 capture is consumed in the sorbent regeneration. One important part for CO 2 capture process is to produce highly concentrated CO 2 during the sorbent regeneration in the conditions of CO 2 rich with a presence of H 2 O, which thermodynamically reduces the sorbent regeneration efficiency at low temperature. This could be overcome by increasing the regeneration temperature although the sorbent regeneration energy increases. The dry sorbent performance in the carbonator was evaluated by changing the temperature, CO 2 and H 2 O concentration in the regenerator, which showed about 88% CO 2 removal efficiency and 5.6 wt% dynamic sorption capacity. The dry sorbent was sampled at each operating condition to confirm the dry sorbent performance, evaluated over CO 2 concentration. The optimal regeneration condition was obtained by considering CO 2 removal efficiency, dynamic sorption capacity and regeneration energy. Finally, the optimal regenerator temperature was determined to be approximately 468 K where the CO 2 capture process in the circulated fluidized bed reactor showed 95% for CO 2 purity. Image 1 • Highest CO 2 removal efficiency was obtained as 88% in a CFB reactor. • Effect of H 2 O during regeneration was negligible on sorbent performance. • Comparable sorbent performance observed even at high concentration CO 2 condition. • Optimal regenerator temperature was determined to be around 468 K. [ABSTRACT FROM AUTHOR]

Dry sorbent CO 2 capture process is a proven technology to remove CO 2 efficiently from flue gas. The current system was used to understand the effect of solid inlet height (H in) and horizontal heat transfer tubes on solid hydrodynamics in the fast fluidized bed (FFB). Also, the ranges of stable hydrodynamic conditions were visually confirmed at the varied H in , gas velocity (U g) and solid circulation rate (G s). The changes in the suspension density (ρ sus) during CO 2 carbonation reaction was experimentally measured and matched to the ρ sus at the specific gas velocity under no reaction bed. It showed that the ρ sus at the initial U g = 1.4 m/s under the reaction mode increased to that at 1.04 m/s along the bed due to the carbonation reaction. Heat transfer coefficients (HTC) were obtained during CO 2 carbonation operation over 80 h, which resulted in CO 2 removal efficiency (85%) and CO 2 purity (96%). Finally, the effect of ρ sus was determined to be the most significant factor on HTCs, ranged from 135 to 215 W/m2∙oC during the carbonation reaction. It indicated that the different local HTCs at different bed heights were observed at the carbonation or no reaction modes due to the exothermic reaction heat. Image 1 • Hydrodynamics in FB reactor during CO 2 carbonation reaction was investigated. • Over 80 h of carbonation reaction was conducted. • Above 84% average CO 2 removal efficiency with 95% CO 2 purity was achieved. • Suspension density and T cw in FB reactor were important factors determining HTC. • Higher HTC was ranged from 135 to 215 W/m2-oC at different conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The working capacity and stability of absorbent were studied for CO 2 capture. • MPS-supported epoxide-functionalization of PEHA absorbent was synthesized. • PO-PEHA/MPS adsorbent exhibited the working capacity of 1.8 mmol g−1 in 20 cycle. • When the adsorption time was reduced, the regeneration heat was 2.86 GJ tCO 2 -1. • Adsorbent that is regenerated in 100% CO 2 , not inert (N 2 , He) conditions was developed. N -functionalized solid adsorbents have been studied for post-combustion CO 2 capture. Most studies have focused only on the adsorption condition of the adsorbents. Few studies have focused on the regeneration condition of adsorbents. Regeneration is required under the condition of 100 % CO 2 for high-purity CO 2 separation. Regeneration under inert conditions such as N 2 or He, not under the condition of 100 % CO 2 regeneration are required additional cost for high-purity CO 2 separation. In this study, a macroporous silica (MPS) support, which combined a high surface area, large porosity and large pore volume, was selected as the support to achieve high CO 2 capture performance. Pentaethylenehexamine (PEHA) was selected because of its high amine content, high adsorption capacity, high thermal stability, and low cost. The epoxide functionalization of PEHA was used to suppress the urea formation under regeneration conditions. The working capacity and cyclic stability of epoxide functionalization of MPS-based PEHA adsorbents were investigated. A working capacity of 1.8 mmol g−1 was maintained by repeating adsorption and desorption experiments 20 times under an adsorption condition of 15 % CO 2 and a desorption condition of 100 % CO 2. Additionally, the stability of the adsorbent under a 100 % CO 2 regeneration condition was confirmed by maintaining the working capacity constant during 20 repeated adsorption and desorption cycle experiments. When the adsorption time was reduced to minimize H 2 O adsorption, the regeneration heat of the adsorbent was 2.86 GJ tCO 2 -1. These results demonstrated that the regeneration ability was excellent under the condition of 100 % CO 2 , which is the actual process application condition. This approach is promising for industrial applications of CO 2 capture technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comprehensive physical and chemical properties of plastic pyrolysis fuel studied. • Relationship between boiling point and vapor temperature during separation was found. • Best HHV was 44.6 MJ/kg with 3.6 cSt for viscosity and 12 mg/g for TAN. • Above 40% of olefins included in lighter fractions (<300 °C b.p.). • CO 2 reduction potential for plastic pyrolysis was determined to be 0.26 tCO 2 /ton. Pyrolysis is a waste conversion technology to solve an increasing plastic waste issue worldwide. Waste plastic pyrolysis fuel from a commercial-scale pyrolysis plant (10 ton/day) was comprehensively investigated using distillation methods by separating the crude pyrolysis fuel to isolate the diesel-like pyrolysis fuel fraction (C 9 –C 25 for fraction 2 + fraction 3, middle distillate). Other fractions were C 5 –C 10 for the light distillate (fraction 1), and >C 25 for the heavy distillate (fraction 4). The relationship between the fuel boiling point and liquid vapor temperature were found for designing a scaled-up oil separation process. The diesel grade pyrolysis fuel fraction comprised approximately 70–80% of the crude pyrolysis fuel, wherein it had values of 43–45 MJ/kg, 1–6 cSt, and 12–42 mg KOH /g oil. Meanwhile, the elemental ratios of the crude pyrolysis oil improved to 0.1 for O/C and 1.9 for H/C after separation, close to petroleum fuels (0.0 O/C and 1.95 H/C). The highest relative chemical composition was the olefins (46% in fraction 1 and 41% in fraction 2), whereas the paraffin was approximately 15–20% in the light fraction. Finally, the potential CO 2 reduction for the plastic waste-to-energy process was evaluated, revealing that a total of 0.26 tCO 2 /ton waste of emissions could be avoided during the waste plastic pyrolysis process. [ABSTRACT FROM AUTHOR]

This paper proposed a sustainable strategy for converting plastic waste into energy over pyrolysis to address the dual crises of environment and energy. A fluidized-bed reactor was designed for processing three different plastic waste (PP, LDPE and ABS). A product yield and properties from a fluidized bed system were comprehensively analyzed and compared with those from a fixed-bed system. The fluidized-bed reactor well converted ABS and PP wastes into pyrolysis fuel, exhibiting higher medium and low fraction (C 5 ∼ C 22 of 89.17 % for ABS) as compared to the amount from a fixed bed reactor (84.7 %) whereas LDPE and PP resulted in the similar product yields in the range of C 5 ∼ C 22 from both reactors. In case of LDPE, the given pyrolysis temperature (520 °C) was not feasible to properly process them into fuels so that dominant heavy oil (∼67.4 %) were produced regardless of the reactor type. GCMS analysis indicated that ABS pyrolysis oil is mainly composed of aromatics, aromatic-N and olefins whereas PP pyrolysis oil mainly includes olefins, paraffins and oxygenated compounds. From the current study, a potential use of a fluidized-bed reactor for pyrolysis was evaluated to overcome the major limitations of conventional pyrolysis process. [Display omitted] • Pyrolysis with fluidized bed and fixed bed reactors were carried out for plastic waste. • Fluidized-bed reactor produces 26–38 % more light chemicals (C5–C10) than fixed-bed. • LDPE requires severer pyrolysis conditions (>520 °C) for a complete pyrolysis reaction. • ABS oil is mainly composed of aromatics (72 %) whereas PP includes paraffins and olefins. • Fluidized-bed reactor enhances C1–C2 gas yield (8.6–38.1 % more) over fixed-bed. [ABSTRACT FROM AUTHOR]

3 MWth scale chemical looping combustion (CLC) system using circulating fluidized bed (CFB) is being developed as a liquidized natural gas power generation technology to reduce CO 2 emissions. Dipleg, considered a blood vessel of CFB, conveys solids captured by cyclone to the fluidized bed while preventing gas mixing. This vertical passage plays key role in solids circulation and cyclone performance in thousands of CFB systems, yet only a limited information is available on its design and operation. This study experimentally investigated the flow characteristics in dipleg to verify design and operating conditions for smooth solid flow while predicting the amount of gas mixing. When solid circulation rate increased, both upward and downward gas flowrates in dipleg increased. It was found that the sum of two flowrates were equal to the volumetric flowrate of solids in the dipleg. Unstable operation occurred when 1) the gas-solid relative velocity in the dipleg became higher than the minimum slugging velocity, and 2) bubble diameter in bubbling bed became larger than the dipleg diameter. Finally, models for operation range and the amount of gas mixing in dipleg were proposed, and the design and operation range of the dipleg in 3 MWth scale CLC was suggested. Gas flows and design range of a dipleg in 3 MWth chemical looping combustor derived in this study. [Display omitted] • Applicability of dipleg in CFB was investigated and design factors were confirmed. • The amount of up- and down-stream gas was measured within dipleg. • Almost same amount of gas was exchanged with the down-stream particles. • Slugging in dipleg interfered the solid flow. • Bubble, larger than dipleg diameter, prevents the solid flow within dipleg. [ABSTRACT FROM AUTHOR]

Attrition rate versus static bed height. [Display omitted] • The rate of attrition (RA) by bubbles related with RA by gas jets. • An equation on top size of particles (TSP) formed by attrition was proposed. • Bed heights existed for minimum RA and TSP formed by attrition. Particle attrition induced by bubbles in a bubbling fluidized bed was investigated with CO 2 adsorbent particles (0.128 mm in diameter, 1770 kg/m3 in apparent density). The theoretical relationship between the rate of attrition by gas jets on the perforated plate distributor (R a,j) and the rate of attrition by bubbles (R a,b) in the bed was revealed that the rate constant of attrition by bubbles (K a,b) was the product of the rate constant of attrition by gas jets (C a) and dimensionless particle diameter (d pbc). An attrition tube (0.035 m-i.d.) using the perforated-plate distributor designed for reducing the attrition by gas jets was employed as the fluidized bed, and the air as the fluidizing gas. The mode of attrition by bubbles was identified as abrasion. The rate of attrition by bubbles (R a,b) was linearly proportional to the power given to the bed solids by bubbles. The top size of the fine particles formed by attrition (d pm,ab) increased exponentially with an increase of bed mass and gas velocity. The effects of temperature, pressure, and area of internal surface contacting particle bed on the R a,b and d pm,ab were negligible under the tested condition. Empirical relationships on R a,b and d pm,ab were proposed based on the experimental data. When both jet and bubble attrition were significant, there existed the static bed heights that gave respectively the minimum attrition rate and the minimum of the top size of fine particles formed by attrition. Each optimal static bed heights increased with an increase of the orifice jet velocity of the perforated plate distributor. [ABSTRACT FROM AUTHOR]

• Pyrolysis oil separator was available for upgrading and separating more diesel grade fuels. • Ni-based catalyst showed the highest deoxygenation due to its high strong acid sites. • MDC-7 led to more light oil production whereas Ni-based favored more middle oil. • Catalytic reactions and coke formation occurred on the strong acid sites. The catalytic upgrading of plastic pyrolysis oil was conducted in a 2-kg-scale pyrolysis oil separation system with or without zeolite 4A, Cu-based (MDC-7) and Ni-based catalysts to produce light (F1), middle (F2) and heavy (F3) oil fractions. From the preliminary separation tests without a catalyst, the separation vapor temperature for diesel-like middle fraction (C 11 - C 22) was determined to be in the range of 107–305 °C. After the pyrolysis oil separation with catalysts, the heavy carbon range (>C 23) sharply decreased from 22.1 wt% in the crude plastic pyrolysis oil to 0.1–1.6 wt% and 7.3–8.4 wt% in the F1 and F2, respectively. Among three catalysts, Ni-based catalyst exhibited the highest deoxygenation capacity (1.23% O in F1 and 0.3% O in F2) owing to its strong acid sites concentration (1.115 mmol/g). Accordingly, the order of the deoxygenation capacity was Ni-based > MDC-7 > zeolite 4A > no catalyst. Moreover, the catalytic reactions (deoxygenation) and coke formation mainly occurred on the strong acid sites. MDC-7 catalyst contributed to more production of C 6 –C 10 range (15.8 %) with aromatic and naphthenic compounds. In contrast, the major catalytic mechanisms of Ni-based catalyst were dehydration, decarboxylation and decarbonylation reactions. In addition, the physical properties of catalytically upgraded pyrolysis oil were close to those of the petroleum-based fuels. Finally, the current study suggested that Ni-based catalyst was a suitable catalyst for the production of diesel-like fraction (C 11 -C 12) with the lowest contents of oxygen from the plastic pyrolysis oil. [ABSTRACT FROM AUTHOR]

CO 2 methanation, as a power-to-gas technology, is considered to be an important method to secure energy supply by utilizing CO 2 and H 2 gases. In this study, a 0.2 kW CH 4 bench-scale fluidized bed reactor was used for CO 2 methanation using approximately 13 kg nickel-based catalyst to investigate the effect of temperature, gas velocity, and H 2 /CO 2 ratio on CO 2 conversion, CH 4 purity, and CH 4 selectivity. Response surface methodology (RSM) was employed to design the experimental conditions to statistically evaluate the effect of operating variables. Reduced quadratic model equations for CO 2 conversion and CH 4 purity were derived, which determined the optimal conditions within the experimental conditions. The suggested conditions for the highest CO 2 conversion were 297 °C, 4.66H 2 /CO 2 , and 4.0 U g /U mf (velocity ratio), whereas different conditions were determined for the highest CH 4 purity. Among the operating variables, temperature was the most influential factor, followed by the gas ratio. The highest CO 2 conversion and CH 4 purity were 98% and 81.6%, respectively. Additionally, the heat transfer coefficient (h o) was found to be 115 W/m2∙°C during a 10-h continuous CO 2 methanation experiment, which is an important design factor for the further scale-up of the process. • CO 2 methanation was performed in a fluidized bed reactor using nickel beads. • CO 2 conversion and CH 4 purity were 98% and 81%, respectively. • Optimal conditions for CO 2 conversion were 297 °C, 4.6H 2 /CO 2 and 4 U g /U mf. • Heat transfer coefficient during CO 2 methanation was 115 W/m2/oC. [ABSTRACT FROM AUTHOR]