Volumetric solid loading

Effect of Downcomer Aeration. When only the central gas flows (No. 7 and No. 8 flows) were employed without downcomer aeration, the solids circulation rate depended primarily on the entrainment rate of the jets. The linear relationship for both bed materials (hollow epoxy and polyethylene) in Fig. 8 shows that the volumetric concentration of the solids inside the draft tube after acceleration (or the gas voidage) is approximately constant, independent of particle density. This can be readily realized by expressing the volumetric solid loading in the draft tube as follows ... 

A straight line relationship between LJpr and Gr as shown in Fig. 8 implies that the volumetric solid loading (j) is approximately constant because Ar is constant and er can be assumed to be approximately constant when the downcomer is not fluidized. More than 85% of the gas supplied through the central No. 7 and No. 8 flows in those experiments ends up in the draft tube as can be seen from the gas bypassing data presented in Fig. 7. 

Reactor volumetric solids loading 3 to 12% heat usage 25 to 60 kW/m of kiln volume solids capacity for cement 0.4 to 1.1 Mg/d m kiln volume solids capacity pigments, dolomite 0.1 to 2 Mg/d-m kiln volume. 

Increasing the solids loading leads to a decrease in gas holdup and gas-liquid volumetric mass-transfer coefficient at the same power/volume [e.g., Inga and Morsi, Can. J. Chem. Eng. 75 872 (1997)]. 

Rotating microscreen batch, fluid loading 3 to 6 L/s m of submerged area usually 66% area submerged solids loading 0.05 to 0.1 g/s m headless 7 to 14 cm to max. of 45 cm. Clean by backwash at 2 to 5 % volumetric throughput capacity. Screen pack downstream of extruders screen pack area directly proportional to rate of extrusion. Cycle time for the screen to blind > time between shutdowns. For example, screen pack area 0.17 m s/kg and screen pack diameter 20 cm s/kg but must be custom selected for the polymer. 

Solids loading ratio, 4>, as mentioned earlier, is the dimensionless ratio of the mass flow rate of the material conveyed divided by the mass flow rate of the air used to convey the material. Air flow rate is almost exclusively expressed in terms of a volumetric flow rate and so air mass flow rate is most conveniently derived from the conveying line inlet air conditions. A further re-arrangement of the above equations gives ... 

Figure 3 displays the effect of solids loading on the particle fluctuating velocities at the centerline. As stated previously, the solids loading was increased by applying a pressure head to the hopper while maintaining a constant volumetric flow of air (5scfm). The r.m.s. values of both the axial and radial fluctuations, Up and Vp, respectively, decrease initially for... 

One manner in which size may be computed, for estimating purposes, is by employing a volumetric heat-transfer concept as used for rotary diyers. It it is assumed that contacting efficiency is in the same order as that provided by efficient lifters in a rotaiy dryer and that the velocity difference between gas and solids controls, Eq. (12-52) may be employed to estimate a volumetric heat-transfer coefficient. By assuming a duct diameter of 0.3 m (D) and a gas velocity of 23 m/s, if the solids velocity is taken as 80 percent of this speed, the velocity difference between the two would be 4.6 m/s. If the exit gas has a density of 1 kg/m, the relative mass flow rate of the gas G becomes 4.8 kg/(s m the volumetric heat-transfer coefficient is 2235 J/(m s K). This is not far different from many coefficients found in commercial installations however, it is usually not possible to predict accurately the acdual difference in velocity between gas and soRds. Furthermore, the coefficient is influenced by the sohds-to-gas loading and particle size, which control the total solids surface exposed to the gas. Therefore, the figure given is only an approximation. 

The reactor volume is calculated from Mj and the bulk density of the catalyst material, (-r ) depends not only on composition and temperature, but also on the nature and size of the catalyst pellets and the flow velocity of the mixture. In a heterogeneous reaction where a solid catalyst is used, the reactor load is often determined by the term space velocity, SV. This is defined as the volumetric flow at the inlet of the reactor divided by the reaction volume (or the total mass of catalyst), that is... 

The proposed catalyst loading, that is the ratio by volume of catalyst to aniline, is to be 0.03. Under the conditions of agitation to be used, it is estimated that the gas volume fraction in the three-phase system will be 0.15 and that the volumetric gas-liquid mass transfer coefficient (also with respect to unit volume of the whole three-phase system) kLa, 0.20 s-1. The liquid-solid mass transfer coefficient is estimated to be 2.2 x 10-3 m/s and the Henry s law coefficient M = PA/CA for hydrogen in aniline at 403 K (130°C) = 2240 barm3/kmol where PA is the partial pressure in the gas phase and CA is the equilibrium concentration in the liquid. 

Anaerobic Filter. An anaerobic filter consists of packed support media that traps biomass as well as facilitates attached growth of biomass as a biofilm (Fig. 8). Such a reactor configuration helps in the retention of suspended biomass as well as gas-liquid-solid separation. The flow of liquid can be upward or downward, and treatment occurs due to attached and suspended biomass. Treated effluent is collected at the bottom or top of the reactor for discharge and recycling. Gas produced in the media is collected underneath the bioreactor cover and transported for storage or use. Volumetric loading rates vary from 5 to 20 kg COD/m day with HRT values of 0.5-4 days. 

In general, solid solutes should be weighed on weighing paper or plastic weighing boats, using an analytical or top-loading balance. Liquids are more conveniently dispensed by volumetric techniques however, this assumes that the density is known. If a small amount of a liquid is to be weighed, it should be added to a tared flask by means of a disposable Pasteur pipet with a latex bulb. The hazardous properties of all materials should be known before use and the proper safety precautions obeyed. 

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