Weight feed flow rate/product distribution

The steady-state model used in RTO typically is obtained either from fundamental knowledge of the plant or from experimental data. It utilizes the plant operating conditions for each unit such as temperature, pressure, and feed flow rates to predict properties such as product yields (or distributions), production rates, and measurable product characteristics (e.g., purity, viscosity, and molecular weight). The economic model involves the costs of raw materials, values of products, and costs of production as functions of operating conditions, projected sales figures, and so on. An objective function is specified in terms of these quantities in particular, operating profit over some specific period of time can be expressed as... 

The first three columns of Table 10.5 show sieve data for a 100-cc slurry sample containing 21.0 g of solids taken from a 20,000-gal (75-m3) mixed suspension-mixed product removal crystallizer (MSMPR) producing cubic ammonium sulfate crystals. Solids density is 1.77 g/cm3, and the density of the clear liquor leaving the crystallizer is 1.18 g/cm3. The hot feed flows to the crystallizer at 374,000 lb/h (47 kg/s). Calculate the residence time r, the crystal size distribution function n, the growth rate G, the nucleation density n°, the nucleation birth rate B°, and the area-weighted average crystal size L3 2 for the product crystals. 

For an open circuit ball mill 5 liters in volume operating at a flow rate of 1 liter per hr the product is a Z1O2 suspension with a Ros-lin-Rammler size distribution with a weight mean size of 0.5 jam and a volume to surface mean diameter of 0.7 jam. Determine the feed distribution to the mill assuming the value of j3 the grinding selectivity factor is 1.0 and k is 0.5 (hr/jam) . ... 

More detailed product information was provided by Uemichi et al. who used a fixed bed flow reactor to examine the decomposition of polypropylene in the presence of silica-alumina.Detailed product analysis was carried out for compounds with 16 or fewer carbon atoms, resolving the products into normal alkanes, isoalkanes, alkenes and aromatics. For a reaction temperature of 750 K, a catalyst weight of 3.0 g and a polypropylene feed rate of 0.150 g min , the polymer was converted over 95% to low molecular weight products, forming C4 and C5 isoalkanes and alkenes in the highest yields. The overall carbon number distribution for reaction over SA is summarized in Figure 4, in which thermal degradation results for even more severe conditions of 799 K and a feed rate of 0.116 g min are included for comparison. The increased rate of conversion and the shift of the product distribution to lower carbon numbers are apparent from this plot. 

If maximum product size is desired, the process stream flow is parallel, with a fresh feed and slurry discharge to product recovery equipment from each crystallizer. Cascaded product flow is avoided because flow through a series of tanks narrows the residence time distribution and the CSD and reduces the mass mean size by reducing the number of larger crystals in the distribution tail. This tail represents the major mass-weighted fraction. Population models have been solved to verify this effect, assuming an equal nucleation rate in each stage (Randolph and Larson 1988). The actual mean in industrial practice is lower because transfer of... 

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