A Model of Attrition in the Jetting Region of Fluidised                    Beds

Ghadiri, Mojtaba; Boerefijn, R.

doi:10.14356/kona.1996006

Cited by 18 publications

(6 citation statements)

References 10 publications

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“…Attrition by abrasion depends on the resistance of the bed particles to surface wear. Secondary fragmentation should rather be related to the resistance of the particles to the impacts on the walls and the internals of the bed or in the jetting region of fluidized beds (Ghadiri et al, 1995). Percolative fragmentation is associated with the loss of connectivity of the solid porous structure that occurs whenever particle voidage increases, by chemical reaction, beyond a threshold (Kerstein and Niksa, 1984).…”

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confidence: 99%

Comminution of limestone during batch fluidized‐bed calcination and sulfation

et al. 1997

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Batchwise fluidized-bed calcination and sulfation of a limestone were done to investigate particle comminution phenomena and their relation with parallel occurrence of reactions. Operating conditions of the bed were those typical of atmospheric bubbling fluidized-bed combustors. A general framework of comminution phenomena is outlined, which includes different types of fragmentations as well as attrition by abrasion. Comminution processes were characterized by following the modifications of bed sorbent particle-size distribution and the elutriation rates of fines throughout conversion. Mutual interactions between comminution processes and the progress of chemical reactions are assessed

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confidence: 99%

Comminution of limestone during batch fluidized‐bed calcination and sulfation

et al. 1997

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“…Abanades et al 127,132 demonstrated that the reactivity decrease of the CaO-based sorbent with cycling would be the combined consequences of the conversion associated with the filling up of the micropores existing in the calcine and that associated with the formation of a product layer in the walls of the large pores present in the calcine. 133,134 The limiting factor for further carbonation reaction was strongly related to the gas diffusion resistance through this product layer, as proposed by Mess et al 135 The abovementioned phenomenon has also been found in metal oxides at high temperatures, which resulted in a decrease in surface area and deactivation of particles. 136−138 It is reported that migration of metal cations and their subsequent enrichment on the particle surface resulted in the sintering, 139 which was more significant after several redox cycles.…”

Section: Resultsmentioning

confidence: 90%

“…These results are consistent with those reported in the literature. Abanades et al , demonstrated that the reactivity decrease of the CaO-based sorbent with cycling would be the combined consequences of the conversion associated with the filling up of the micropores existing in the calcine and that associated with the formation of a product layer in the walls of the large pores present in the calcine. , The limiting factor for further carbonation reaction was strongly related to the gas diffusion resistance through this product layer, as proposed by Mess et al…”

Section: Resultsmentioning

confidence: 96%

CO₂ Capture from Biomass Gasification Producer Gas Using a Novel Calcium and Iron-Based Sorbent through Carbonation–Calcination Looping

Dashtestani

Nusheh²,

Siriwongrungson

et al. 2020

Ind. Eng. Chem. Res.

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In this study, a novel sorbent material based on CaO and Fe2O3 was investigated for its performance in CO2 capture from simulated biomass gasification producer gas. Experiments were conducted in a fixed bed reactor and each run of the experiments included three major stages of sorbent material reduction, CO2 capture (carbonation), and CO2 release (calcination). The operation temperature in the CO2 capture stage was controlled at 590, 620, 650, and 680 °C, while the temperature for the CO2 release was maintained at 850 °C. The duration of the CO2 capture stage was 3 h and that of the CO2 release stage was 2 h. The effect of cycles of carbonation–calcination looping of the sorbent material was also investigated at the carbonation temperature of 650 °C. The experimental results show that effective CO2 capture by the sorbent material occurred in the initial 20 min during the carbonation. In the calcination stage, the rate of CO2 release reached the peak in 30–40 min from the start of the calcination. The carbonation temperature has a significant effect on CO2 capture and the optimum carbonation temperature was found to be 620 °C, at which CO2 capture efficiency was 94% for the first cycle and 90.4% as average for the first three cycles. It was also found that the CO2 capture efficiency was reduced with cycling. Mechanisms of the CO2 capture and the effect of cycling were also examined.

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“…There is also extensive literature on the breakage and attrition of particles in high velocity air jets in which particle-particle collisions are the main mechanisms of particle breakage, e.g. Forsythe and Hertwig (1949), Gwyn (1969), Ghadiri et al (1994), Ghadiri and Boerefijn (1996), Boerefijn et al (2000), Bentham et al (2004), Dumas et al (2011), Xiao et al (2012 and Zhang et al (2012). Chen and Lloyd (1994) studied the breakage of agglomerated milk powders in the dry powder dispersion unit of the Malvern Mastersizer 2600c.…”

Section: Introductionmentioning

confidence: 99%

A method for grindability testing using the Scirocco disperser

Bonakdar

Ali

Dogbe

et al. 2016

International Journal of Pharmaceutics

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In the early stages of development of a new Active Pharmaceutical Ingredient (API), insufficient material quantity is available for addressing processing issues, and it is highly desirable to be able to assess processability issues using the smallest possible powder sample quantity. A good example is milling of new active pharmaceutical ingredients. For particle breakage that is sensitive to strain rate, impact testing is the most appropriate method. However, there is no commercially available single particle impact tester for fine particulate solids. In contrast, dry powder dispersers, such as the Scirocco disperser of the Malvern Mastersizer 2000, are widely available, and can be used for this purpose, provided particle impact velocity is known. However, the distance within which the particles can accelerate before impacting on the bend is very short and different particle sizes accelerate to different velocities before impact. As the breakage is proportional to the square of impact velocity, the interpretation of breakage data is not straightforward and requires an analysis of particle velocity as a function of size, density and shape. We report our work using an integrated experimental and CFD modelling approach to 2 evaluate the suitability of this device as a grindability testing device, with the particle sizing being done immediately following dispersion by laser diffraction. Aspirin, sucrose and -lactose monohydrate are tested using narrow sieve cuts in order to minimise variations in impact velocity. The tests are carried out at eight different air nozzle pressures. As intuitively expected, smaller particles accelerate faster and impact the wall at a higher velocity compared to the larger particles. However, for a given velocity the extent of breakage of larger particles is larger. Using a numerical simulation based on CFD, the relationship between impact velocity and particle size and density has been established assuming a spherical shape, and using one-way coupling, as the particle concentration is very low. Taking account of these dependencies, a clear unification of the change in the specific surface area as a function of particle size, density and impact velocity is observed, and the slope of the fitted line gives a measure of grindability for each material. The trend of data obtained here matches the one obtained by single particle impact testing. Hence aerodynamic dispersion of solids by the Scirocco disperser can be used to evaluate the ease of grindability of different materials.

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A Model of Attrition in the Jetting Region of Fluidised Beds

Cited by 18 publications

References 10 publications

Comminution of limestone during batch fluidized‐bed calcination and sulfation

Comminution of limestone during batch fluidized‐bed calcination and sulfation

CO₂ Capture from Biomass Gasification Producer Gas Using a Novel Calcium and Iron-Based Sorbent through Carbonation–Calcination Looping

A method for grindability testing using the Scirocco disperser

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A Model of Attrition in the Jetting Region of Fluidised Beds

Cited by 18 publications

References 10 publications

Comminution of limestone during batch fluidized‐bed calcination and sulfation

Comminution of limestone during batch fluidized‐bed calcination and sulfation

CO2 Capture from Biomass Gasification Producer Gas Using a Novel Calcium and Iron-Based Sorbent through Carbonation–Calcination Looping

A method for grindability testing using the Scirocco disperser

Contact Info

Product

Resources

About

CO₂ Capture from Biomass Gasification Producer Gas Using a Novel Calcium and Iron-Based Sorbent through Carbonation–Calcination Looping