Flow-sheet presentation examples

The process flow sheet presented in Figure 32.10 provides the minimum information that should be given. Very often, additional information is implemented in the form of a rectangle with four different values, for example, pressure, enthalpy, mass flow, and temperature. The orientation, together with the units used, should also be shown in the diagram. As an example, the conflguration with the highest... 

Various techniques are available to separate the different types of particles that may be present in a sohd mixture. The choice depends on the physicochemical nature of the sohds and on site-specific considerations (for example, wet versus diy methods). A key consideration is the extent of the liberation of the individual particles to be separated. Particles attached to each other obviously cannot be separated by direct mechanical means except after the attachment has been broken. In ore processing, the mineral values are generally liberated by size reduction (see Sec. 20). Rarely is liberation complete at any one size, and a physical-separation flow sheet wih incorporate a sequence of operations that often are designed first to rejec t as much... 

Complex Flow Sheets Operating plants do not consist of single flashes, neat exchangers, distilfation towers, or reac tors. As the number of pieces of eqmpment increases within the unit under study, the reconciliation becomes more difficult. For example. Fig. 30-21 presents a more comphcated, three-module unit. 

The material balance is presented on a block flow sheet so that the reader can graphically visualize what is happening. An example is given in Figure 4E- 1. Each major operation appears as a block. No attempt is made to identify the specific pieces of equipment or to size them. The blocks are interconnected with flow lines, which indicate for each substance where it enters the process, what path it follows, and where it is eventually discharged. These flow lines are keyed to a chart that gives the composition and amount of each stream in the form of a unit ratio material balance. A material balance should be given for each product made by a multipurpose plant. 

Many flow-sheeting programs perform the partitioning, solution ordering, and tearing functions discussed above and present the user with one or more choices of solution sequence and tear variables. FLOWTRAN, however, does not do this. The user must identify the recycle loops, the calculation sequence, and the tear streams. The preceding example illustrated their identification and selection. 

A flow sheet can be quite complicated especially in the case of complex ores containing wolframite and scheelite besides other valuable minerals. As an example, ore dressing at Xihuashan Mine is presented in Fig. 5.4. 

The project team must detail all past costs that the project has incurred since its inception (start of EvP) on an annual basis. In addition, an annual project financial information table (ProFIT) data sheet should be presented. This sheet contains the revenue and cost forecasts for the upcoming ten-year period. It computes net present value (NPV) of future cash flows and return on capital employed (ROCE) automatically. At this stage, the team is expected to include detailed production costs data as well as estimates of plant costs (based on an engineering estimate, for example). The ten-year projection should be provided for three scenarios base, optimistic, and pessimistic. These cases are not meant to be simple percentage changes of the sales projections. Instead, the team should try to identify the drivers of the project s success and construct alternatives for the future that lead to different results for the project. The base case should be the most likely case. The optimistic scenario should be based on the positive development of some (not all) key success factors. The pessimistic scenario is usually the minimum feasible case, meaning a situation where the organization would still prusue the project, but some factors do not develop in a positive way. 

Steady-state flow reactors, with a constant supply of reactants and continuous removal of products, can be operated as both a continuous stirred-tank bioreactor (CSTB) and as a plug flow bioreactor (PFB). It is possible to have different configurations of the membrane bioreactor where the biocatalyst is immobilized in the fractionated membrane support (Katoh and Yoshida, 2010). In Fig. 1.6 the scheme of a CSMB in which the biocatalyst is immobilized on the surface of the membrane beads is presented. The biocatalyst immobilized in the porous structure of a fractioned membrane can also be operated in CSMB. For example, two configurations are shown in Fig. 1.7 (a) for flat-sheet and (b) for spherical porous structures, respectively. Such structures could also be adopted for PFB, where a bed of membrane support with the immobilized biocatalyst could be utilized, in either a fixed or fluid configuration. 

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