Multiple products

Column products other than the distillate and bottoms may be taken out as liquid or vapor side draws from any tray. Multiple product columns are used in certain applications as a one-step process for separating multi-component streams into a number of products with different compositions. A multi-product column could, therefore, perform the equivalent task of several columns. In many situations the separation realized in the multi-product column is only a crude separation to be followed by further downstream processing. 

The compositions of the side products depend on their location in the column, in accordance with the composition profile that exists along the column. A small liquid product taken from a column tray has the same composition as the undisturbed liquid on that tray. As the product rate varies, the column L/V ratio and other column parameters also vary. New steady-state conditions are re-established with a new column composition profile. The side product composition is therefore also dependent on its flow rate. 

Multi-product columns consist of the basic modules column sections, equilib- 

Each side product provides one additional independent column variable. To define the column performance, the flow rate of each side product must be known. Alternatively, a side product flow rate may be allowed to vary in order to meet a performance specification such as the concentration of a component in that product. The side product flow rate becomes a dependent variable which must be calculated to satisfy the performance specification. It has been established in Chapter 7 that a fixed-feed, fixed-configuration, fixed-pressure column with a partial condenser (having only a vapor distillate) and a reboiler has two degrees of freedom. Two variables, such as the condenser and reboiler duties, may be varied independently. Each side product adds to the column one degree of freedom. Hence, a column as defined above with S side products has 2 + S degrees of freedom. The duties and side product flow rates can each be varied independently, allowing 2 -i- S performance specifications. This conclusion can be reached by applying the description rule since each additional product rate can be controlled independently by external means. 

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Plasma fractionation is unusual in pharmaceutical manufacturing because it involves the processing of proteins and the preparation of multiple products from a single feedstock. A wide range of unit operations are utilized to accompHsh these tasks. They are Hsted in Table 3 some are common to a number of products and all must be closely integrated. The overall manufacturing operation can be represented as a set of individual product streams, each based on the processing of an intermediate product derived from a mainstream fractionation process (Fig. 1). 

Hydrothermal Synthesis Systems. Of the unit operations depicted in Figure 1, the pressurized sections from reactor inlet to pressure letdown ate key to hydrothermal process design. In consideration of scale-up of a hydrothermal process for high performance materials, several criteria must be considered. First, the mode of operation, which can be either continuous, semicontinuous, or batch, must be determined. Factors to consider ate the operating conditions, the manufacturing demand, the composition of the product mix (single or multiple products), the amount of waste that can be tolerated, and the materials of constmction requirements. Criteria for the selection of hydrothermal reactor design maybe summarized as... 

Fig. 12. Open-cycle compressors (a) simple and (b) multiple product schematic.

Distillation appHcations can be characterized by the type of materials separated, such as petroleum appHcations, gas separations, electrolyte separations, etc. These appHcations have specific characteristics in terms of the way or the correlations by which the physical properties are deterrnined or estimated the special configurations of the process equipment such as having side strippers, multiple product withdrawals, and internal pump arounds the presence of reactions or two Hquid phases etc. Various distillation programs can model these special characteristics of the appHcations to varying degrees and with more or less accuracy and efficiency. 

Multiple Products. If each component of a multicomponent distillation is to be essentially pure when recovered, the number of columns required for the distillation system is N — 1, where AJ is the number of components. Thus, ia a five-component system, recovery of all five components as essentially pure products requires four separate columns. However, those four columns can be arranged ia 14 different ways (43). 

All but the very simplest equipment suites contain multiple process units. The minimum number of process units is one for each type of processing equipment required to make a batch of product. However, many equipment suites contain multiple process units of each type. In such equipment suites, multiple batches and multiple production runs can be in progress at a given time. 

Timing issues due to scheduling multiple products or batches Timing issues due to a more complex supply chain... 

Your general aim should be to improve product quality, increase productivity, and reduce the cost of development and manufacture. However, productivity is not easy to measure with multiple products on multiple lines, each at a different stage of maturity. This makes comparisons to detect changes in productivity difficult, if not impossible. However there may be factors common to all product lines, such as labor costs. Merely outsourcing manufacture to developing countries may not improve your productivity. The labor costs may reduce but rework and warranty claims increase. Productivity is only improved if product quality has been maintained. Certain processes may also be common to more than one product line and hence improving productivity of common processes can have wide-ranging impact. 

It is also hypothesized that formation of 2-benzyl-2-hydroxydihydrobenzofuran-3-ones 6 and 2-arylbenzofuran-3-carboxylic acids 7 are derived from an intramolecular attack of the phenoxide at the P-position. Despite the complex mechanism and multiple products, general trends have emerged through experimental results. If the chalcone lacks a 6 -methoxy group but has a hydroxyl group at the C2 or C4 positions, flavonols are favored. However, if the 6 -methoxy group is present and no hydroxyl substituent is present at C2 or C4 aurones and flavonols are formed. Others have also shown that pH and temperature influence the product distribution. 

Consolidation Even though blow molding provides the capability of providing multiple products combined into one, by including hinges the designer has an added feature. The ability to produce many articulated products in one shot has always opened new design... 

Polymer and coating chemists use computer models to predict the properties of formulated products from the characteristics of the raw materials and processing conditions (1, 2). Usually, the chemist supplies the identification and amounts of the materials. The software retrieves raw material property data needed for the modelling calculations from a raw material database. However, the chemist often works with groups of materials that are used as a unit. For instance, intermediates used in multiple products or premixes are themselves formulated products, not raw materials in the sense of being purchased or basic chemical species. Also, some ingredients are often used in constant ratio. In these cases, experimentation and calculation are simplified if the chemist can refer to these sets of materials as a unit, even though the unit may not be part of the raw material database. 

In this case, there are two winners Don t fall into the trap of thinking that there must always be one clear winner. Sometimes there is, bnt sometimes, there are multiple products (perhaps even more than two). The goal is to predict all of the products, and to predict which products are major and which are minor. To accomplish this goal, you will need to perform the following three steps ... 

For a linear plan the pseudo-overall yield as defined above is numerically close to the multiplicative product of the reaction yields. The difference between the two values diminishes as the reaction yields approach 1 as would be expected. However, for complex plans with several converging branches this alternative definition becomes less useful. For the triclosan branch equation (4.16) yields 0.405 (40.5%) for the pseudo-overall yield. 

It is clear that the use of batch reactors has some serious drawbacks. For the production of larger quantities, mnltiple batch mns have to be performed and this often leads to batch to batch variation in prodnct qnahty and performance. Furthermore, the productivity is often lower than for dedicated continnons reactors and fixed costs are higher cansed by high operator efforts. Therefore, switching to continuons processes holds great appeal, if we can find a device that is snitable for multiple products. 

Figure 26, shown earlier, is a simple form of input mapping called table lookup. A more complicated inference mechanism is illustrated in Fig. 30. Here we see a simple example from a fluidized catalytic cracking unit in which multiple product quality attributes can be explained by multiple operating parameters (Ramesh et al., 1992).

So far plants have been considered involving a single product. However, batch processes often produce multiple products in the same equipment. Here two broad types of process can be distinguished. In flowshop or multiproduct plants, all products produced require all steps in the process and follow the same sequence of operations. In jobshop or multipurpose processes, not all products require all steps and/or might follow a different sequence of steps9. 

Production schedules for batch processes can be sequential, overlapping, parallel, use intermediate storage, or use a combination of these. Such schedules can be analyzed using Gantt charts. Batch processes often produce multiple products in the same equipment and can be distinguished as flowshop or multiproduct plants. Equipment cleaning and material transfer policy have a significant effect on the production schedule. 

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