Process Modules or Blocks

Lin (100) suggested breaking the process flowsheet into one or more blocks of modules. Each block of modules contains one or more modules and all of the modules in the same block are solved simultaneously. The whole process flowsheet is then solved by conventional sequential modular approach by treating each block as a module. 

The first step in setting up a process for the sequential modular approach is to reconstruct the process flowchart in terms of blocks or modules (process units or operations) and streams connecting them. Several types of blocks and names that might be given to them are as follows ... 

We will examine in detail enzymes and enzyme inhibitors, enzymes being the proteinaceous substances that catalyze the myriad biochemical reactions or processes that occur in the body. Almost without exception, there is one enzyme specific to each biochemical reaction. (What may be called supporting reactions, side reactions, or simultaneous reactions may also be involved and, in fact, may be a necessity.) In turn, there are other proteinaceous substances, or still other chemical substances, that will inhibit, block, modulate, or control the action of enzymes, and on rare occasion, even accelerate or promote the action. Known as enzyme inhibitors, such substances may affect more than one enzyme, or many different enzymes that is, they may have side effects, or in other words, are nonselective. These inhibitors may be generated internally, or more likely may originate from external sources. That is, they may be designated as medicines. In fact, modem medicine is more and more viewed as encompassing enzymes and enzyme inhibitors. Broadly, this may be viewed as the utilization of biologically active or biochemically active substances, that is, bioactive substances, either natural or synthetic. 

By metabolism or primary metabolism is meant the biochanical processes, sequences, or pathways by which cells grow and proliferate, and are sustained. The various steps involved are each selectively catalyzed by a particular enzyme, which may in turn be inhibited, blocked, controlled, or modulated by other substances called enzyme inhibitors. As had been noted the latter may be internally generated or may be administered from external sources. The action can therefore be described as biochemical, both of the enzymes and of the inhibitors. 

Transcription factors are proteins involved in the regulation of gene expression that bind to the promoter elements upstream of genes and either promote or block transcription. Through this process they modulate gene expression. Transcription factors... 

Process simulation units (that is, blocks, modules, or subroutines) are mapped into more descriptive models of process equipment (e.g., mapping a HEATX simulation unit into a floating-head, shell-and-tube heat exchanger mapping a RADFRAC simulation unit into a tray tower, complete with reboiler, condenser, reflux accumulator, etc.) and associated plant bulks, which include installation items, such as piping, instrumentation, insulation, paint, etc. 

A process plant can be represented as a network of units (nodes, modules, clusters of modules) and links (connections) between them. This is shown in Figure 1, where the blocks represent the nodes (modules, or a set of closely-coupled modules) and the lines the connections. 

It is very important to remove suspended solid particles ahead of membrane processes, especially those using hollow fibre or spiral wound modules, or the particles are likely to block the narrow flow passages. For large flow rates, a suitable filter for this purpose would be a deep bed filter, whereas for smaller flows, polishing cartridges with pleated or thick media can be used. 

The most successful and user-friendly approach, which is now adopted by virtually all commercial systems, is the fill-in-the-forms or table-driven process control languages (PCLs). The core of these languages is a number of basic functional blocks or software modules. AU modules are defined as database points. Using a module is analogous to calhng a subroutine in conventional programs. 

In an information flow diagram, such as that shown in Figure 4.5b, each block represents a calculation module that is, the set of equations that relate the outlet stream component flows to the inlet flows. The basic function of most chemical processing units (unit operations) is to divide the inlet flow of a component between two or more outlet... 

---