Pellet Diameter Research Articles

Combustion characteristics of low-concentration coal mine methane in ceramic foam burner with embedded alumina pellets

Ceramic foam as a rigid matrix is difficult to be embedded with various shapes of heat exchange tubes. In this paper, a ceramic foam burner with embedded alumina pellets was designed, which can set different shapes of tubes by taking advantage of the discrete pellets. An experimental system was built to study the effects of the pellet diameter and pellet location on the combustion of low-concentration coal mine methane (LCM). Results indicate that the heat transfer features of 13-mm pellets are more similar to those of 10-PPI ceramic foam compared with 6-mm pellets and 9-mm pellets. When arranged in upper section of the burner, the 13-mm pellets preserve the combustion heat, which helps to move the flame stabilization position to the upstream of the burner. In addition, the start-up time in the burner with the upper 13-mm pellets is longer than that with the intermediate 13-mm pellets. The total NOx emissions of the studied burners are improved with the increasing inlet velocity, while the CO emissions first decrease and then increase. The HC emissions of the ceramic foam burner with embedded pellets are between those of the pellet burner and the ceramic foam burner.

Catalytic combustion of premixed methane/air in a two-zone perovskite-based alumina pileup-pellets burner with different pellet diameters

In this study, methane/air combustion in a two-zone catalytic alumina pileup-pellets burner with equivalence ratios varying from 0.55 to 0.70 was researched. The catalytic alumina pileup-pellets were designed by directly depositing perovskite LaMn0.4Co0.6O3 on inert alumina pileup-pellets supports. Flame stability limits, pressure drops, flame temperatures, flue gas temperatures, and pollutants emissions of both catalytic and inert burners with different pellet diameters were investigated. The flame stability limits expanded as equivalence ratio or pellet diameter increased. The flame stability limits were also increased by depositing the perovskite catalyst. The pressure drops of catalytic burners were lower than those inert burners in both reaction and cold flows. More uniform axial temperature distributions were obtained for catalytic burners than for inert burners. Flame temperatures and flue gas temperatures were significantly reduced for catalytic burners compared with inert burners, as were pollutants emissions for unburned hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxides (NOX). The HC emissions reduced as either pellet diameter or inlet velocity increased. The HC emissions of catalytic burners (less than 550ppm) were significantly lower than those inert burners (ranging from 900 to 2750ppm). The CO emissions of catalytic burners reduced significantly at lower velocities (S<35cm/s) and were almost unchanged at a level below 50ppm, at higher velocities (S>35cm/s). The CO emissions of catalytic burners were sensitive to changes in pellet diameters at lower velocities (S<20cm/s). The NOX emissions of catalytic burners (less than 2ppm) were significantly lower than those inert burners (ranging from 4 to 13ppm).

Numerical study of diffusion filtration combustion characteristics in a plane-parallel packed bed

Abstract Numerical investigations on characteristics of diffusion filtration combustion are conducted in a plane-parallel packed bed. A detailed gas-phase reaction mechanism is used, and mass dispersion in packed bed is also taken into account. Attention is mainly focused on the combustion characteristics and the influencing factors, such as the gas and solid temperature profiles in the burner, the influences of solid thermal conductivity, mass dispersion and convective heat transfer between the gas and solid phases on the flame shape. The predicted results are compared with the available experimental and analytical data. For different gas mixture velocities and pellet diameters, the numerical model can successfully predict the flame shape. The predictions show that the diffusion combustion in packed bed remains the essential characteristics of normal diffusion combustion, although the solid properties can affect the flame structure. Compared with premixed combustion in porous media, there are two high temperature zones, which belong to gas and solid separately. These two high temperature zones locate at different positions in the burner. Results show that, the flame height remains almost the same with the increasing of thermal conductivity of solid but almost does not depend on the convective heat transfer between the solid and gas phases. In contrast, mass dispersion imposes significant influence on the flame structure. Higher mass dispersion will lead to the reduction of flame height but the increase of flame width.

Automated measurement of sintering degree in optical microscopy through image analysis of particle joins

In general terms, sintering describes the bonding of particles into a more coherent structure, where joins form between packed particles, usually as a result of heating. Characterization of sintering is an important topic in the fields of metallurgy, steel, iron ore pellets, ceramics, and snow for understanding material properties and material strength. Characterization using image analysis has been applied in a number of these fields but is either semi-automatic, requiring human interaction in the analysis, or based on statistical sampling and stereology to characterize the sample. This paper presents a novel fully automatic image analysis algorithm to analyze and determine the degree of sintering based on analysis of the particle joins and structure. Quantitative image analysis of the sintering degree is demonstrated for samples of iron ore pellets but could be readily applied to other packed particle materials. Microscope images of polished cross-sections of iron ore pellets have been imaged in their entirety and automated analysis of hundreds of images has been performed. Joins between particles have been identified based on morphological image processing and features have been calculated based on the geometric properties and curvature of these joins. The features have been analyzed and determined to hold discriminative power by displaying properties consistent with sintering theory and results from traditional pellet diameter measurements on the heated samples, and a statistical evaluation using the Welch t-test.

English

A study was conducted to examine the nutritional and economic effects of using pellet diets at various pellet diameters of 2, 4 and 6 mm pellet for broiler finisher birds in an experiment using Arbor Acre broilers chickens. Two hundred and forty Arbor Acre birds at the finisher phase (28-56 days) of broiler production were used in a 2 x 4 factorial experiment using completely randomized design. Diets in this study had same quantities of ingredients with identical nutrients composition. The study was conducted under similar environmental conditions and management practices. Data on growth performance, nitrogen utilization, carcass and visceral organs characteristics, haematology and serum biochemistry were collected and evaluated. Economic analyses were carried out. Birds on 4 mm pellet diameter diet had the highest body weight gain of 59.11&plusmn;0.54 g/bird/day and the lowest feed conversion ratio (FCR) of 2.11&plusmn;0.03. Measured carcass and visceral organs were higher (P&lt;0.05) for birds on the pellet diets. Most heamatogical parameters were higher for birds on the pellet diets. Birds on balanced 4 mm pellet diets had better feed intake, increased growth rate and better feed efficiency when fed with broiler finisher birds. The 4 mm pellet diets also enhanced most carcass and organs characteristics. Heamatological and blood biochemistry indices of experimental birds on 4 mm pellet diets were not adversely affected and were better in some cases than values obtained from existing literature. There was an overall better net return per bird for birds on 4 mm pellet diameter diets in broiler finisher diets.&nbsp; &nbsp; Key words: Nutritional benefit, cost and benefit analyses, feed pelleting. &nbsp

Effects of Creep Feed Pellet Diameter on Suckling and Nursery Pig Performance

A total of 26 litters of pigs (PIC 327 × 1050; initially 7.1 lb and 10 d of age) were used in a 31-d growth trial to evaluate the effects of creep feed pellet diameter on suckling pig and subsequent nursery pig growth performance. On d 10 of the suckling phase, sows and their litters were allotted to one of two dietary treatments by parity and pig weight in a completely randomized design with 13 replications per treatment. Starting on d 10, pigs were fed the same creep feed formulation, but pelleted using either a 1/8 in. (small) or 1/2 in. (large) die. Chromic oxide was included in the diets as a fecal marker, and fecal swabs were taken twice a day on d 14, 17, and 21 to determine the percentage of pigs that were consuming creep feed. On d 21, pigs were weaned, re-allotted to nursery treatments for 21 d, and fed in two phases. Phase 1 (d 0 to 7 postweaning) treatment diets were the same diets as fed during the suckling period, with 50% of the pigs remaining on their previously allotted pellet diameter treatment. The other 50% of pigs were re-allotted to the opposite pellet diameter treatment in the nursery, creating a 2 × 2 factorial with the main effects of pellet diameter during suckling and pellet diameter during the nursery phase. A common meal Phase 2 diet (d 7 to 21) was fed to all pigs. During the suckling phase (d 10 to 21), litters of pigs fed the large creep feed pellet had decreased (P < 0.03) pre-weaning mortality and tended (P < 0.06) to have greater litter BW gain and litter ADG. There were no significant differences observed in pig BW, pig BW gain, litter CV, or pigs identified as creep feed eaters. From d 17 to 21 of suckling, pigs fed the large creep feed pellet had increased (P < 0.05) average daily creep feed intake. During the nursery phase, no interactions were observed for Phase 1 (d 0 to 7) when experimental diets were fed. Feeding a large pellet during the nursery phase, regardless of previous creep feed treatment, increased (P < 0.05) ADFI from d 0 to 4, 4 to 7, and 0 to 7. Pigs fed the large pellet in the suckling phase, regardless of pellet diameter fed during the nursery phase, had improved (P < 0.01) ADG from d 0 to 7 after weaning. Results from this study indicate that feeding a large creep feed pellet may be correlated with reduced preweaning mortality. However, there is no improvement on individual suckling pig growth performance or percentage of pigs eating creep feed between feeding either a small or large diameter pellet. Feeding a large creep feed pellet improved F/G for the entire nursery phase, and feeding a large nursery pellet increased ADFI during the first week in the nursery.

Study on Energy Requirement of Wood Chip Compaction

In order to utilize waste products such as sawdust and chips in the wood industry, pellets are made using compaction pressures in the range of 100 MPa or higher. During the compaction process, the density and the modulus of elasticity of the material rapidly increase. Wood materials generally show non-linear viscoelasticplastic behavior and, therefore, the pressure-deformation relationship is dependent on the loading velocity and on the time during which the material is subjected to constant deformation or load. The energy requirement of pellet production depends on many infl uencing factors and in such cases the use of dimensionless numbers in the form of similarity equation facilitates the processing of experimental results and the obtained similarity relationship has a more general validity for the users. Various fractions of different wood species were used in these experiments, and the pressure, pellet diameter, temperature were also varied. The proposed similarity equation shows a good correlation with the experimental results.

Bioleaching of copper from tailings by fermentation broths of Aspergillus niger in pellet form

Owing to the substantial amounts of metals embodied in tailings, they are potential viable sources of metals. This work aims at developing a technique to microbially recover copper present in tailings. Based on orthogonal design, the effects of different variables, such as temperature, fermentation time, inoculum size and medium components, on pellet morphology of A. niger were investigated in shake flasks. Leaching of copper from its tailings was conducted using fermentation broths of Aspergillus niger with different pellet morphology. Copper extraction gradually increased with reduction in pellet diameter of A. niger. A large amount of compact smooth pellets with a diameter of 0.96 mm were obtained under the optimum fermentation conditions of 30°C , 0.8% inoculum size(OD600=0.1), 30% potato-sucrose contents, 65 h fermentation time. After 3 days of leaching, copper extraction reached 83.25% with the fermentation broths aforementioned at 30°C, 180 r·min.

Numerical simulation and parameters optimisation of direct reduction process of iron ore–carbon composite pellet

A mathematical model considering heat transfer, mass transfer, porosity change, stepwise reductions of iron oxides and carbon gasification has been developed to investigate the direct reduction process of iron ore–carbon composite pellet. The governing equations were discretised in fully implicit form based on control volume method and numerically solved using tri-diagonal matrix algorithm. The model has been validated by comparison with experimental data from the literature. The effects of some operational parameters have been investigated, and the optimal combination of these parameters is determined by orthogonal test. The results show that the reduction rate increases with the decrease of pellet diameter initially. However, the final degree of reduction increases with the increase of pellet diameter ranging from 5 to 15 mm. Chemical reaction rates increase significantly with the increase of furnace temperature. The degree of reduction for pellet with C/O ratio of 0·8 is lower than pellets with C/O ratio of 1·0 and 1·2 after reduction for 900 s. The degree of reduction is 95·84%, which is high enough in engineering, when furnace temperature, reduction time, C/O mole ratio, and pellet diameter are 1473 K, 10 min, 1·2, and 20 mm, respectively.

Effect of feed form, pellet diameter and enzymes supplementation on carcass characteristics, meat quality, blood plasma constituents and stress indicators of broilers

Abstract. Four hundred-twenty broilers were used in a factorial design (4×3) in which four feed forms (mash vs. pellet diet with diameter of 2 mm, 3 mm and 3.5 mm, respectively) and three enzymes treatments (unsupplemented, phytase, phytase+multi-enzyme) were used. Each treatment was replicated five times (7 broiler/replicate). Feed form had no effects on most of carcass traits and physical characteristics of meat, but pellet diets decreased the relative weight of gizzard and caecum length. Feeding 3.5 mm pellet diets increased abdominal fat compared to that of broilers fed mash diets. Pellet with 3 mm diameter increased and decreased respectively meat fat and moisture. Pellets with 3.5 mm diameter increased meat ash compared to broilers fed mash diet. Levels of plasma glucose and alanine aminotransferase of broilers fed 2 mm pellet, cholesterol of broilers fed 3 mm pellet and albumin/globulin ratio, monocytes and red blood cells of broilers fed 3.5 mm pellet were significantly higher than those of broilers fed mash diet. Haemoglobin, phagocytic activity, heterophils and heterophils/lymphocyte ratio were higher in groups fed mash diets and 2 mm pellet. Packed cell volume and phagocytic index were the highest in group fed mash diets. Phytase or multi-enzyme+phytase increased carcass yield, total edible parts and decreased inedible parts compared to broilers fed diet without enzyme supplementation. Enzyme supplementations significantly and similarly increased plasma glucose, total protein, triglycerides, red blood cells and phagocytic activity and decreased phagocytic index in comparison to the control group. However, phytase alone decreased cholesterol and increased monocytes by contrast with the control group. Multi-enzymes+phytase induced greater effect on white blood cells than phytase alone.

Effect of feed form, pellet diameter and enzymes supplementation on growth performance and nutrient digestibility of broiler during days 21-37 of age

Abstract. A total of 420 21-day-old broilers were wing banded and randomly distributed among 60 cages of 7 birds per cage during days 21-37 of age. A factorial design (4×3) was used in which there were four feed forms (mash vs. pellet diet with diameter 2-2 mm, 2-3 mm and 3-3.5 mm, respectively) and three enzyme treatments (unsupplemented, phytase, phytase plus multi-enzyme). Each treatment was replicated 5 times with 7 broilers per replicate. Body weight gain of broilers fed 2-3 mm-diet was significantly greater than that of those fed mash diet and 2-2 mm or 3-3.5 mm pellet-diet. Feed conversion ratio was the best in broilers fed 2-3 mm and 3-3.5 mm pellet-diets. However, feed intake was significantly lower in broilers fed pellet-diets than that of those fed the mash diet. The production index and economic efficiency were significantly higher in groups fed 2-3 mm pellet diameter compared to those fed 2-2 mm and 3-3.5 mm pellet diets. Digestibility of crude protein, ether extract, crude fibre and crude ash were significantly and similarly greater in groups fed pellet diets in comparison with those fed mash diet. Enzyme supplementations significantly and similarly increased growth and production index whereas improved feed conversion ratio and economic efficiency than the control group and this concurred with greater digestibility of crude protein, ether extract and crude ash. However, multi-enzymes plus phytase induced greater effect on the production and economic traits than phytase alone showing synergetic effects. Pellet diet at 2-3 mm supplemented with multi-enzyme plus phytase resulted in the highest performance and nutrient digestibility of broilers during day 20-37 d of age.

A novel preparation method for “small” eggshell Co/γ-Al2O3 catalysts: A promising catalytic system for compact Fischer–Tropsch reactors

Due to the need of limiting pressure drop, and the consequent necessity of adopting “big” catalyst pellets, low-temperature Fischer–Tropsch synthesis in industrial fixed-bed reactors may suffer of strong intra-particle mass transport limitations, which are known to result in decreased CO conversion rate and C5+ selectivity. Upon decoupling the pellet diameter and the diffusive length, eggshell catalysts represent an engineering solution for the intensification of the Fischer–Tropsch reactors. In this work, preparation, characterization and testing of impregnated Co/γ-Al2O3 eggshell catalysts with sharply defined outer shell regions are reported. The method developed to impregnate the active phase only on the outer layer of the support is based on the “protection” of the inner pores of the support with an organic liquid and on the control of the contact time between the impregnating solution and the protected support. The method is particularly suitable to prepare “small” eggshell pellets, with diameters below 1mm, to be used in compact FT reactors. It is shown that 600μm pellets, with catalytically active layers 75μm thick, grant a remarkable combination of high CO conversion rate and high C5+ selectivity, thus resulting extremely interesting for operations in reactors 3–6m long.

Effects of pellet characteristics on L-lactic acid fermentation by R. oryzae: pellet morphology, diameter, density, and interior structure.

The effects of pellet morphology, diameter, density, and interior structure on L-lactic acid fermentation by Rhizopus oryzae were characterized for different inoculum sizes and concentrations of peptone and CaCO3. Inoculum size was the most important factor determining pellet formation and diameter. The diameter decreased with increasing inoculum size, and larger pellets were observed for lower inoculum sizes. Peptone concentration had the greatest effect on pellet density, which increased with increasing peptone concentration. L-lactic acid production depended heavily on pellet density but not on pellet diameter. Low-density pellets formed easily under conditions of low peptone concentration and often had a relatively hollow structure, with a thin condensed layer surrounding the pellet and an extraordinarily loose biomass or hollow center. As expected, this structure greatly decreased production. The production of L-lactic acid increased until the density reached a certain level (50-60 kg/m(3)), in which the compact part was distributed homogeneously in the thick outer layer of the pellet and loose in the central layer. Homogeneously structured, denser pellets had limited mass transfer, causing a lower overall turnover rate. However, the interior structure remained nearly constant throughout all fermentation phases for pellets with the same density. CaCO3 concentration only had a slight influence on pellet diameter and density, probably because it increases spore germination and filamentous hypha extension. This work also provides a new analysis method to quantify the interior structure of pellets, thus giving insight into pellet structure and its relationship with productivity.

Effects of pellet diameter during and after lactation on feed intake of piglets pre and post weaning

Effects of pellet diameter during and after lactation on feed intake of piglets pre and post weaning

Preparation of solid self-emulsifying drug delivery systems using magnesium aluminometasilicates and fluid-bed coating process

Solid lipid-based drug delivery systems combine the advantages of solid dosage forms and the solubilizing potential of lipophilic vehicles. In spite of the fact that many methods were proposed for the solidification of liquid lipid formulations, there is no data on the application of the fluid-bed coating technique to impregnate porous pellets, containing magnesium aluminometasilicates with liquid self-emulsifying formulations. Moreover, the functionality of magnesium aluminometasilicates to form porous pellets by the extrusion/spheronization process has not been studied so far.Therefore, the aim of the present work was to determine if magnesium aluminometasilicates could be incorporated into pellets in the extrusion/spheronization process and then to examine if such pellets may be used as solid cores for the conversion of liquid SEDDS into solid SEDDS (S-SEDDS) in the fluid-bed coating process. To achieve these goals, three grades of Neusilin namely SG2, US2 and NS2N were combined with MCC in three wt.% ratios i.e.: 30+70, 50+50, or 70+30. The results showed that the pellets whose matrix was composed of Neusilin SG2 had the highest porosity and the best mechanical resistance. The fluid-bed coating method was found suitable for the impregnation of the placebo pellets with liquid SEDDS, containing ibuprofen as an insoluble model drug. The amount of SEDDS adsorbed on the surface of pellets with silicates was from eight to fourteen times higher as compared to pellets without silicates. The morphology, diameter and circularity of pellets before and after the fluid-bed coating process was examined by scanning electron microscopy (SEM) and the automated particle characterization system (Morphologi G3). The pellets containing Neusilin SG2 had twice as high mechanical resistance as the pellets with Neusilin US2 or Neusilin NS2N, and they were suitable for fluid-bed processing. Dissolution studies showed that from the formulation composed of 70wt.% of Neusilin SG2 after 45min, more than 75% of ibuprofen was dissolved in water and after 30min, more than 80% of ibuprofen was dissolved in the phosphate buffer. Similar results were obtained for S-SEDDS containing 70wt.% of Neusilin US2. The sustained release of ibuprofen was found if 30wt.% of Neusilin US2, 30–50% of Neusilin SG2, or 50–70wt.% of Neusilin NS2N was incorporated into the matrix of pellets.

Experimental study on temperature variation in a porous inert media burner for premixed methane air combustion

The detailed axial temperature variations of the porous media burner during startup and switch-off processes were experimentally measured and analyzed for the premixed methane air combustion. A tubular burner filled by alumina pellets with diameters of 10 mm and 4.3 mm, respectively, was used as the porous media burner to study the effect of the burner inlet gas flow rate, equivalence ratio, and diameter of alumina pellets on the combustion temperature distribution along the burner axis and the combustion wave velocity. The results showed that the superadiabatic combustion could be achieved for the combustion wave velocity greater than zero, and the critical equivalence ratio corresponding to the superadiabatic combustion was bigger for the smaller pellet diameter or higher inlet air flow rate. This study can provide the useful information for the design and operation of the porous media burner, and is significant to understand the combustion phenomena in the porous media burner.

Characterizing fundamental parameter-based analysis for soil–ceramic matrices in polarized energy-dispersive X-ray fluorescence (PEDXRF) spectrometry

Analytical polarized energy-dispersive X-ray fluorescence (PEDXRF) spectrometry (PEDXRFS) represents a substantial advancement over conventional XRF. The higher signal-to-noise commensurate with background lowering and better energy resolution, permits trace analysis for elements with Z ≥ 11. Concomitantly, improvements in analytical software based on the fundamental parameters (FP) approach have improved accuracies and precisions for standard-less analysis (SLA). Two ceramic and soil standard reference materials (SRMs), 98a-Plastic Clay and GSS-1 powders, differed in their intrinsic matrix properties of grain size, bulk, and surface monolayer densities as well as the elemental concentrations. The SRMs were analyzed as powder and as pellets compacted under the same pressure conditions to double the bulk density. Different geometries represented by the sample cup (10, 15, and 24 mm) and pellet (10, 15, and 25 mm) diameters with the same sample thickness (with differing masses and aspect ratios), as well as (for powder samples only) identical low masses (0.5 g) but with varying thicknesses, were analyzed. PEDXRFS combined with TURBOQUANT® (TQ) as SLA-FP enables good quantitative analysis for powders (Z ≥ 13) even for masses significantly lower than recommended, for soil–ceramic samples. Pellets (Z ≥ 12) yielded the best accuracy factor (AF) at high aspect ratio and thicknesses of the matrix analytical depth. Binder in pellets depreciates the AF. TQ needs to adequately quantitate matrix interferences effects, to improve accuracy in the analysis of low atomic numbers, e.g. Na and Mg.

A numerical study of the effectiveness factors of nickel catalyst pellets used in steam methane reforming for residential fuel cell applications

A numerical study is performed to evaluate the effectiveness factors of commercial nickel catalyst pellets commonly used in small-scale steam methane reformers for residential fuel cell applications. Based on the intrinsic reaction kinetics of the steam reforming process, the standard composition of the partially reformed gas mixture is determined as a function of the methane conversion. The heterogeneous reforming reactions inside the spherical catalyst pellets are then modeled by considering the distributed reaction, multi-component diffusion and permeation, and conductive and convective heat transfer in the porous media. Various operating conditions, including the reforming temperature, steam-to-carbon (S/C) ratio, operating pressure, and geometrical parameters, such as the pellet diameter and mean pore size, are simulated. The effectiveness factors calculated for each condition are presented as a function of the methane conversion. Finally, simple correlations for the effectiveness factors are presented, and their accuracies are assessed.

Multi-recycling of transuranic elements in a PWR assembly with reduced fuel rod diameter

This paper examines the multi-recycling of transuranic (TRU) elements (Pu-Np-Am-Cm) in standard Pressurized Water Reactor (PWR) assemblies. The original feed of TRU comes from legacy spent UOX fuel. For all subsequent recycling passes, TRU elements from the previous generation are employed, supplemented by TRU from legacy UOX fuel, as needed. The design criteria include: 235U enrichment requirements to remain below 5 w/o, TRU loading limits to avoid return to criticality under voided conditions, and assembly power peaking factors. In order to carry out multiple recycling passes within the design envelope, additional neutron moderation is required and achieved by reducing the fuel pellet diameter by about 13%, thus keeping the assembly design compatible with current PWR core internals. TRU transmutation rates and long-term ingestion radiotoxicity results are presented for 15 recycling passes and compared to standard UOX and MOX once-through cycles. The results also show that TRU fuel isotopics and radiotoxicity tend towards an equilibrium, enabling further additional recycling passes.

Dependence of Pellet Shape and Size on Pressure Drop in Thrusters

The most important parameters influencing the pressure drop over a reacting catalyst bed are analyzed using a multiphase multicomponent flow model. The model, in which the gas and liquid phases are treated as separate fluids, simulates the flow of highly concentrated hydrogen peroxide from a tank, through the injector, into the catalyst bed to the nozzle. It contains submodels to describe the interphase mass, momentum, and energy transfer occurring in the catalyst bed, in which it is assumed there is a pellet-based catalyst structure. The main purpose is to investigate the influence of pellet shape and dimensions on the pressure drop over the bed and the required bed length. The model has been verified and validated against experimental data and shows improved predictions of the pressure drop compared with traditionally employed pressure drop models. It is shown that cylindrical pellets with a diameter to length ratio larger than two give a lower pressure drop for a given bed length than spherical pellets. It is furthermore shown that this result is independent of the inlet mass flux and liquid volume fraction distribution and is reliable for high bed to pellet diameter ratios.