Solid Bulk Density Research Articles

Effects of Pyrolysis on Biogas Production during Anaerobic Co-digestion of Corn Stover

The effects of pyrolysis pretreatment on biogas production during anaerobic co-digestion of corn stover were studied. The corn stover characteristics were investigated by performing thermogravimetric analysis using a heating rate of 10.0°C/min and an air atmosphere at atmospheric pressure. Corn stover aliquots pretreated in an electric furnace at 100°C for 360 min, 200°C for 15 min, and 300°C for 5 min were used. Untreated and pretreated corn stover samples were analyzed by scanning electron microscopy and other methods, and the bulk densities and component ratios were compared to identify changes caused by the pretreatments. The amounts of total solids, volatile solids, volatile fatty acids, and total ammonia nitrogen produced when the stover samples were anaerobically digested were measured. The biogas production rate and the methane concentration in the biogas were determined. The substrate-specific methane yields were determined, and the relationships between the yields and pretreatment conditions were assessed. The sample pretreated at 300°C for 5 min produced the most biogas. The corn stover total solid bulk density was directly related to the substrate-specific methane yield, the substratespecific methane yield decreasing as the total solid bulk density increased.

On the specific surface area of nanoporous materials

A proper quantification of the specific surface area of nanoporous materials is necessary for a better understanding of the properties that are affected by the high surface-area-to-volume ratio of nanoporous metals, nanoporous polymers and nanoporous ceramics. In this paper we derive an analytical expression that relates the specific surface area of arbitrary nanoporous materials to their solid bulk density and ligament size. Computed specific surface areas of porous materials with regular nanopores are in good agreement with the expression derived. These regular void geometries include single and double gyroid structures, as well as materials with spherical and cylindrical nanopores. Validation of the expression for disordered nanoporous materials is performed by investigation of the specific surface areas of various nanoporous gold electrodes in the double-layer charging regime.

Polymorphic Generation through Solvent Selection: Ranitidine Hydrochloride

The fundamental processes of crystal nucleation and growth are strongly dependent on the solvents used in the crystallization process. Consequently, the product quality is also affected by the choice of solvent used in the process. In this study, several solvents were used, and their impact on the polymorphic generation of ranitidine hydrochloride (RAN-HCl) was studied using two different recrystallization modes. The solid-state FTIR and UV spectrophotometer were used for characterization and quantification of two polymorphic forms of RAN-HCl. It was found that methanol concentration greater than 10 wt % at nucleation onset favored formation of Form 2. The best results with respect to the solid bulk density were achieved with acetonitrile as an antisolvent.

Control of Product Quality in Batch Crystallization of Pharmaceuticals and Fine Chemicals. Part 1: Design of the Crystallization Process and the Effect of Solvent

The product quality in a crystallization process refers to the crystal size distribution (CSD), crystal morphology, polymorphic outcome and the degree of crystallinity, and purity. In addition, the product yield is also important. Properties such as the filterability and solid bulk density are directly related to the CSD. To obtain the desired product quality, attention should be paid to the various operating conditions such as the local and average levels of supersaturation, the type of the solvent, the operating temperature and pressure, the type and concentration of impurities and tailor-made additives, degree of mixedness, geometry and the mode of operation of the crystallizer, and seeding and feeding policies. In addition to these variables, the implementation of external control either in the form of a feedback controller or an optimal control policy can further improve the product quality. In Part 1 of the present communication, an attempt is made to present a systematic approach to investigate the effect of various operating conditions, i.e., the design of the crystallization processes, on the product quality. In particular the effect of the solvent in terms of the solubility and its ability to participate in forming hydrogen bonds with the solute molecules will be studied. The effect of mixing, the seeding policy, and the design of the feed system on the product quality will also be discussed. Experimental results are presented to demonstrate the effect of the operating conditions in improving the filterability and solid bulk density of ranitidine hydrochloride and another pharmaceutical compound. In Part 2, the effect of the “external control” on the product quality will be discussed.

Improving the filterability and solid density of ranitidine hydrochloride form 1

Ranitidine hydrochloride Form 1 produced by the original method (Price et al., 1978 US patent) has poor filtration and drying characteristics, which make it less desirable commercially in comparison with Form 2. This article shows that the operating parameters have significant influence on the final properties of Form 1. In terms of filterability and solid bulk density, it was found that at a higher temperature (∼48°C), the viscosity of the slurry decreased and improved product quality as compared with operating at room temperature (∼25°C). It was found that the rapid addition of acid to the ranitidine base increased product density but led to higher residual solvent inclusion. The presence of excess ranitidine base in the solution and also the manner of reactant addition had a significant influence on the onset of nucleation and the rate of crystallization. The best results in terms of filterability and bulk solid density were obtained using an initial pH of 5.3 and then increasing it to 6.3–6.4 after the onset of nucleation. © 2004 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1692–1700, 2004

Empirical correlation for prediction of the elutriation rate constant

In vessels containing fluidized solids, the gas leaving carries some suspended particles. This flux of solids is called entrainment, E or carryover and the bulk density of solids on this leaving gas stream is called the holdup. For design we need to know the rate of this entrainment and the size distribution of these entrained particles Rim in relation to the size distribution in the bed, Rib, as well as the variation of both these quantities with gas and solids properties, gas flow rate, bed geometry and location of the leaving gas stream. Steady-state elutriation experiments have been done in a fluidized bed 0,2 m diameter by 2,94 m high freeboard with superficial gas velocities up to 1 m/s using solids ranging in mean size from 0,15 to 0,58 mm and with particle density 2660 kg/m3. When the fine and coarse particles were mixed, the total entrainment flux above the freeboard was increased. None of the published correlations for estimating the elutriation rate constant were useful. A new simple equation, which is developed on the base of experimental results and theory of dimensional analyses, is presented.

EFFECT OF DRYING METHOD ON SHRINKAGE AND POROSITY

ABSTRACT The effect of drying method on bulk density, particle density, specific volume and porosity of banana, apple, carrot and potato at various moisture contents was investigated, using a large set of experimental measurements. Samples were dehydrated with five different drying methods: conventional, vacuum, microwave, freeze and osmotic drying. A simple mathematical model was used In order to correlate the above properties with the material moisture content. Four parameters with physical meaning were incorporated in the model: the enclosed water density pw, the dry solid density ps, the dry solid bulk density pbo and the volume shrinkage coefficient β'. The effect of drying method on the examined properties was taken into account through its effect on the corresponding parameters. Only, dry solid bulk density was dependent on both material and drying method. Freeze dried materials developed the highest porosity, whereas the lowest one was obtained using conventional air drying.

Bulk-Density Distributions of Solids in the Freeboard of a Gas-Solid Fluidized Bed

The freeboard region above the bubbling zone of a gas-solid fluidized bed provides the space not only for the disengagement of particles but also for additional contact and reaction between the particles and gas. The flow pattern and behavior of particles as well as their bulk-density distribution in the freeboard have a significant impact on the efficiency of fluidization. The results of numerous previous experimental studies indicate that the bulk density of solids essentially decreases exponentially as a function of the height of the freeboard. In the present work, this distribution has been obtained by first derived the Fokker-Planck equation from the linearized equation of motion of a single particle and then transforming this Fokker-Planck equation into that for the bulk-density distribution of solids. Its simplification to the one-dimensional case readily gives rise to an exponential distribution and agrees well with the available experimental data.

Entrainment of solids from fluidized beds I. Hold-up of solids in the freeboard II. Operation of fast fluidized beds

Part I: Kunii and Levenspiel proposed a flow model to represent the complex phenomena occurring in the freeboard above a fluidized bed. A somewhat more The key parameter emerging from this model is the decay constant for the fall off of bulk density of solids with height in the freeboard. Values for th Part II: Viewing the fast fluidized column as having a lower region of approximately constant bulk density and an upper region wherein the bulk density An example of a design calculation shows how the fast fluidized system responds to changes in operating variables. More importantly, it makes clear wha

Bulk density of solid polymer resins as a function of temperature and pressure

AbstractIn a plasticating extruder, solid polymers are heated and are subjected to high pressures before they are melted and delivered to a die. In both the solids conveying and melting sections, these temperature and pressure increases will compact the unmelted polymer bed as it moves down the screw channel. Performance of the extruder depends in part on how well the screw design matches the compaction behavior of the resin for a given set of process conditions. The design of these screw sections, however, is often done based on past experience and with little knowledge of the resin compaction behavior. A much improved design would include screw performance prediction using variable bulk density and computer simulations. Computer simulations, however, are often performed using constant solid bulk density because of the lack of reliable density data as a function of both pressure and temperature. An instrument was developed for studying the compaction behavior of pellet and powder resins. Bulk densities and storage friction coefficients are reported for several important thermoplastic resins as a function of temperature and pressure. The bulk density data were fitted to a semi‐empirical model.