Pellet Bulk Research Articles

Comparison of the physical properties of cotton and sesame stalk pellets produced at different moisture contents and combustion of the finest pellets

ABSTRACT In this study, cotton and sesame stalks that are grown regionally and burned in coarse form as a source of heat energy form in the current application are used as pellet raw materials. Although these residues are used as biomass raw materials in different forms, there is limited information about their use as pellets. In order to compare the production efficiency and physical properties of the pellets obtained, production capacity, specific energy consumption, bulk density, particle density, durability, compression resistance, specific compression resistance, and tensile strength tests have been applied. In the moisture content ranges pellet durability, bulk density, particle density and tensile strength were achieved as 89–98%, 430–695 kg/m3, 921–1367 kg/m3, 2.83–7.28 Mpa for cotton stalk pellets, and 93–97%, 510–660 kg/m3, 4.26–5.85 Mpa for sesame stalk pellets, respectively. 20% pelletizing moisture for both stalks increased pellet production capacity, reduced energy consumption, but affected negatively their physical structures. It was concluded that the ideal pelleting moisture values for cotton stalks and sesame stalks were 10% and 15%, respectively. During combustion experiments, O2, CO2, CO, and NOx emissions, flue gas temperature, and combustion efficiency were observed. According to the results of combustion experiments, CO and NOx emissions were found to be 1646 ppm and 50 ppm for cotton stalks, 2862 ppm and 134 ppm for sesame stalks, respectively. High O2 emission values (18–19%) were observed for both pellets.

Influence of blending proportions of Teak Sawdust and Cajuput leaves on characteristics of biomass pellets

Fuel pellets made from biomass is considered as a solid fuel that is also an alternative fuel which can substitute for the current fuels and can be considered as a fuel that has sustainable production. This research is the study of the production of fuel pellets from Teak sawdust blends with Cajuput leaves at five proportions by weight of Teak sawdust 100%, Cajuput leaves 100%, Teak sawdust 75% +Cajuput leaves 25%, Teak sawdust 50% +Cajuput leaves 50%, Teak sawdust 25% +Cajuput leaves 75% . The pellets were produced by a grinding and pelleting machine at three different speeds of 200, 250, and 300 rpm. After that, the quality of fuel pellets was evaluated by the physical properties as pellet dimensions, particles and bulk density, as well as moisture content and durability. The results show that blending proportion of Teak sawdust 75% and Cajuput leaves 25% provided the appropriate fuel pellet properties.

Combustion of Straw Pellets in an Agitated Fuel Bed: Experiments and DEM/CFD Simulations

ABSTRACT The influence of bed agitation during the combustion of biomass pellets was investigated experimentally and numerically. In the experiments, a bulk of straw pellets was burnt in a batch-operated reactor. The reactor allows for air staging and mixing of the fuel bed by vertically moveable mixing elements. The primary to secondary air ratio was varied and the reactor was operated either in the agitated (moving mixing elements) or the static mode (mixing elements at rest). The overall mass of the bulk was measured continuously during the combustion process. The results show a significant increase of the mass loss rate by almost 60% when the bed was agitated compared to the static case. Samples of the residual material of the pellets reveal a totally different amount of molten and agglomerated ash particles for the different operational conditions. Decreased primary to secondary air ratios as well as agitation of the fuel bed did lead to less agglomeration of the ash. The Discrete Element Method (DEM) was coupled with a Computational Fluid Dynamics (CFD) simulation. Coupled DEM/CFD simulations of the batch reactor were performed to get access to bulk internal data of the solid material and the fluid phase. Simulations identified that a reduced amount of ash exposed to the volatile flame through agitation of the fuel bed was the main reason for minimized ash agglomeration.

Characterization of the relocated and dispersed fuel in the Halden reactor project LOCA tests based on gamma scan data

The on-going Loss-of-Coolant Accident (LOCA) test program at the OECD Halden Reactor Project (HRP) conducts in-house gamma scanning as standard post-irradiation examination (PIE) procedure on Light Water Reactor (LWR) fuel rods. One of the primary objectives of the program is to investigate fuel relocation into the balloon region and fuel dispersal through the cladding rupture opening after burst. A simple model called Gamma Transport Model was formulated for the purpose of interpretation of fuel relocation based on the gamma scan data. Fuel relocation may have a strong effect on the linear heat generation rate at the balloon due to, firstly, increase in linear fuel density, and secondly due to differences in burn-up and local heat generation rate at the periphery and bulk of the pellet. For this analysis, a pair of short-lived isotopes with very different fission product yields for 235U and 239Pu is selected from the gamma scan spectrum. The intention is to use the difference in the ratio of their concentrations in the balloon region to qualitatively make conclusion on the fuel relocation. As a separate outcome, the same analysis can be applied to the dispersed fuel region and to draw conclusion on its origin (pellet rim or bulk). The Gamma Transport Model is validated against a special (non-destructive) case from the Halden LOCA test program and then applied for the analysis of selected tests. In addition, a methodology is presented for estimation of the amount of dispersed fuel from the LOCA tests based on the gamma scan data. Currently, at Halden there is no possibility to measure the dispersed fuel and hence an alternative is needed. Such information can be used for code validation and for inferring additional information based on other test parameters such as cladding rupture opening.

Effect of low and high storage temperatures on headspace gas concentrations and physical properties of wood pellets

Headspace gas concentrations and wood pellet properties were studied in sealed glass canisters at 5–40°C storage temperatures. CO2 and CO concentrations at 5, 10, 20 and 40°C at the end of 23–28 days of storage were 1600 and 200, 4700 and 1200, and 31 200 and 15 800 parts per million by volume (ppmv) respectively. Corresponding O2 concentration was about 19·49, 19·20, 18·0 and 2·07% respectively. Non-linear regression equations adequately described the gas concentrations in the storage container as a function of time. Safe level estimation functions developed were linear for O2 and logarithmic for CO and CO2 concentrations. Measured pellet properties moisture, length, diameter, unit, bulk and tapped density, durability, calorific value, ash content and percent fines were in the range of 4·6–5·02%, 14–15 mm, 6·4–6·5 mm, 1125–1175 kg m−3, 750–770 kg m−3, 825–840 kg m−3, 73–74%, 18·32–18·78 MJ kg−1, 0·65–0·74% and 0·13–0·15%. Durability values of pellets decreased by 13% at 40°C storage temperature and other properties changed marginally.

Mathematical Description of a Heterogeneous Catalytic Process on the Basis of the Dendrite Model of a Catalyst Pellet

A mathematical model is suggested for a heterogeneous catalytic process. The model is based on the assumption that the spherical surface of a catalyst pellet has a layer in which there are many dendrites that are formed by interconnected macrochannels and microchannels and have a single inlet at the surface. The depth of penetration of fine microchannels into the pellet bulk is assumed to depend on the diameter of the inlet channel. The model is applied to the regeneration of a carburized catalyst.

Processing technique for fabrication of advanced YBCO bulk materials for industrial applications

We present a processing technique for fabrication of advanced semi-finished parts and products based on the high-temperature superconductor (HTSC) YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO). High-quality YBCO bulk components are produced powder metallurgically by sintering and partial melting of precursor powders. Depending on size, shape, tolerances and levitation requirements, parts are either die-pressed or precision machined from isostatically pressed blocks. The oxygenation process can be monitored in-situ by a macro-thermogravimetric analyzer. The texture of the bulk of full-size pellets was verified by elastic neutron scattering. Levitation properties under static and dynamic load levels were analyzed using a test bench with a three dimensional force sensor unit. Flux mapping was used to verify the homogeneity of the material, to evaluate macroscopic critical currents and to investigate the field trapping capability. Several HTSC frictionless bearing modules have been built. They are manufactured in various sizes, ranging from O 40 mm to O 140 mm. Lifting forces are up to 200 N per bearing module. Applications for the bearings are seen for mechanical components in high speed rotating machinery, in cryogenic systems, gyroscopes, transportation systems and vibration isolation.

Mechanical properties of steel pellets in particulate fluidized bed fixtures

Abstract Experiments were designed, built, and used to measure the stress-strain profiles of steel pellets when confined under pressure. The principles of the mechanics of granular media were used to compute the pellet's bulk mechanical properties. Spherical steel pellets were used in the tests. Shear tests of the granular material were performed for different compaction pressures. Shear tests produced the angle of internal friction that is characteristic of granules. Simple uniaxial compression tests produced information that led to the computation of Poisson's ratio, Young's modulus, and the modulus of rigidity of the compacted granular steel pellets. The results reflect the variation in these material properties with compaction loads and depth of the material. These results make up a database that is essential for the modeling, design, synthesis, and analysis of flexible fluidized bed fixtures in which steel pellets make up the fixturing medium.

Notes on Hawk and Owl Pellet Formation and Identification

This paper records the progress to date (March 15, 1940) of attempts made to establish a basis for the identification of the pellets of certain raptorial birds found in western Kansas. The fundamental purpose of this study is to show that the accurate identification and interpretation of pellets, which have been formed under natural conditions in the field, may increase their value as food habits data when carefully studied. The birds dealt with in this study are the barn owl, short-eared owl, longeared owl, great horned owl, and the marsh hawk. In conducting studies on these birds repeated field observations were made over a period of six months. With the exception of two weeks in December, there were but few times during this period when more than 24 hours elapsed between visits to the areas frequented by these birds. Although it was not expected that birds would be sighted on every visit, regularity was considered necessary in order to gather all obtainable facts on fresh pellet deposits. This periodic collecting of pellets made it possible to gain information on the nocturnal feeding habits of the owls, though the birds were seldom seen. Before beginning this study, pellets that had accumulated in the areas under observation were collected and retained for analysis. However, only those pellets which were observed to appear from day to day were considered important as field data. As field data, each ensuing pellet carried a particular value that is not found in pellets comprising mass accumulations. For example, it was possible to estimate the frequency with which owls dropped pellets in one particular place. As described elsewhere in this paper, it was found that an owl might disgorge pellets a.t one roost daily for a week or more, and then not return to that roost for several days. How much this may have been due to pressure from other species was only partially determined. However, these habits may have an important bearing on pellet analysis when used in predation studies. Thus, when a bulk of pellets is gathered from an owl roost, an attempt should be made to determine how many birds of the same or different species have visited the area; also, the length of time the pellets have been accumulating under the roost. In this way it can be estimated whether or not every pellet the owl or owls have dropped during a certain period is represented in the accumulation.