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Effects of solid feed rate and level of overflow solid outlet on pressure drop of bubbling fluidized-bed. • Pressure drop of fluidized-bed over level of solid outlet (L) grows with L. • Power of bubble (POB) lifting solid per L decreased with increasing L. • POB is invariant for fixed flow rates of bubble and solid and fixed L. The effect of level of the overflow outlet for continuous flow of solid particles on the pressure drop of a bubbling fluidized-bed that employed an in-bed inlet for solid feed was investigated with changing solid properties, solid feed rate, gas velocity, and level of the overflow outlet. The pressure drop of fluidized-bed (Δp bed,f) decreased with increasing gas velocity, but increased with either solid feed rate or level of the overflow solid outlet (L). The Δp bed,f /L increased with L. Irrespective of particle size and density, bed height converted for minimum fluidization condition (pressure head by bed weight, H mf,f) decreased with increasing the volume flow rate of bubble but increased with either the solid feed rate or the level of the overflow solid outlet. The nominal vertical height, height between the H mf,f and the level of the overflow outlet, that bubbles transported particles while drawing the solid particles out of the fluidized-bed increased as either the volume flow rate of bubble or level of the overflow outlet increased. However, it decreased as the solid feed rate increased. It appeared that the power of bubble for lifting solid to be discharged through the overflow outlet was same at the fixed volume flow rate of bubble, solid feed rate, and level of the overflow solid exit. The power of bubble increased with the level of the overflow outlet but not linearly. The correlation proposed for the pressure drop across the bubbling fluidized-bed was useful to predict the pressure drop across the recycle chamber of the loop seal and the external solid circulation rate in the circulating fluidized-bed system. [ABSTRACT FROM AUTHOR]

Graphical abstract Archimedes number versus absolute slope at transport velocity. Highlights • This model determined the transport velocity from the correlation of entrainment rate. • The criterion for locating the transport velocity was proposed. • The criterion increased with Archimedes number. • A correlation for the criterion was successful in predicting the transport velocity. Abstract This study improved the model that used the correlation of the particle entrainment rate to determine the transport velocity. It proposed the new absolute value of the local slope as the criterion of the model for locating the transport velocity in the relationship between dimensionless velocity (U/U t) and the reciprocal of the entrainment rate (1/K i ∗+). It indicated that the criterion depended on properties of fluidized particles and increased with Archemedes number. The Archemedes number was modified by substituting the critical diameter, the maximum particle diameter at which the sum of the interparticle adhesion forces gave a dominant influence to the particle entrainment rate, for the diameter of particles in case that the mean diameter of particles was smaller than the critical diameter. A correlation was suggested to calculate the absolute value of the local slope at the transport velocity. The new model was successful covering the effect of particle properties in predicting the transport velocity. [ABSTRACT FROM AUTHOR]

Correlations for solids flow rate through recycle chamber G s , r : G s , r = G s , b b g , r when. G s , b b g , r ≤ G s , r t r G s , r = G s , b b g , r - G s , b b g , r r A r i s A r when G s , b b g , r > G s , r t r and. G s , r ≥ G s , r t r G s , r = G s , r t r when G s , b b g , r > G s , r t r and. G s , r < G s , r t r [Display omitted] • Correlations for solids flow rate (SFR) through recycle chamber (RC) were proposed. • SFR through RC increased with gauge pressure (GP) at base of RC. • SFR through RC decreased with increasing GP at base of riser of fast bed. This study investigated the flow rate of solids through the recycle chamber of a loop seal in a circulating fluidized bed (CFB) at atmospheric pressure and temperature. Flow characteristics of alumina particles were measured in the downcomer, horizontal passage, recycle chamber, and riser (0.05 m i.d., 2.7 m high). As the gas velocity in the riser increased, the pressure drop in the downcomer decreased, and thus, the aeration rate required at the bottom of the supply chamber to attain the minimum fluidization state for the bed of the downcomer increased. Based on experimental data, relationships that could predict the flow rate of solids through the recycle chamber G s , r were derived by extending the correlation for the solids flow rate through the bubbling fluidized bed that discharged solids via overflow exit. G s , r increased in proportion to the gauge pressure at the base of the recycle chamber. When the riser was under the fast bed condition, the back pressure against the flow of solids coming from the recycle chamber to the riser appeared significantly, and G s , r was inversely proportional to the gauge pressure at the base of the riser. The derived relationships for G s , r were in good agreement with measured data. [ABSTRACT FROM AUTHOR]

• Silica alumina (Kaolin) catalyst enhances pyrolysis oil yield by 4.4% instead of gas yield reduction. • The optimum temp. for LDPE catalytic(Kaolin) pyrolysis is 520 °C lower than 560 °C at sand pyrolysis. • Light oil fractions increased to 11.9% (2.58 time more) over kaolin LDPE pyrolysis in FB reactor. • Kaolin has the potential to serve as a reliable substitute for sand. Low-density polyethylene (LDPE) is the second most prevalent waste plastic globally, followed by polypropylene. The pyrolytic conditions required to obtain light oil(≤C12) from LDPE are more stringent than those for polypropylene, water plastics, acrylonitrile, butadiene, styrene, and other materials. Consequently, numerous researchers have underscored the necessity of employing catalysts in LDPE pyrolysis. This study explored the pyrolysis characteristics of LDPE at various temperatures in a non-catalytic fluidized bed reactor. The experiments employed a mixture of sand + kaolin, one of the Si-Al catalysts, to investigate the pyrolysis of LDPE in a fluidized bed reactor at different temperatures. The findings demonstrated that using sand + kaolin as a fluidized bed material significantly enhances the yield of pyrolysis oil while concurrently reducing the gas yield compared to using sand alone. Moreover, a higher light oil fraction was obtained using kaolin (16.67 wt%) at 560 °C compared with 8.6 wt%. In addition, the study revealed that elevated temperatures (520 °C, 560 °C, and 600 °C) led to a reduction in olefins and paraffin, coupled with an increase in the formation of naphthenes, aromatics, and ketones in the pyrolysis oil. Overall, the findings underscore the promising potential of kaolin as an alternative to sand, facilitating the enhanced production of valuable light oil fractions. The insights garnered from this study are invaluable for devising effective waste management strategies. [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]