Single-component balancing

Interval 1 No solid flow and only liquid flow implies a single-component balance problem. The total material balance becomes ... 

The resulting flowsheet whose complexness is just sufficient for the purpose of the balance is finally redrawn in the graph form. The graph representation of the flowsheet for the single-component balance shown in Fig. 2-1 is in Fig. 2-5. The graph consists of nodes (circles) and streams (arrows). Every stream is incident either with two nodes or with one node and the environment (which can te viewed also as one of the nodes). 

This section deals with classification of variables which has close relation to solvability of the balancing problem. Let s start with some simple examples of single-component balance shown in Fig. 2-7. 

In the previous chapter, we have dealt with single-component balances, thus with the case when only one quantity is balanced around each node. A multicomponent balance is a set of several component balances. In chemical process networks, the components are certain chemical species present in the streams as the components of a mixture. Generally, the species can be transformed into one another by chemical reactions so their quantities may not be conserved individually. The individual balances are then not independent, as they must obey stoichiometric laws. This chapter deals mainly with steady-state chemical species balancing where chemical reactions are admitted the wording steady state is explained below. Formally precise unsteady-state balancing brings some problems, mainly because the holdup (accumulation) of a component in a unit is difficult to identify, due to spatial variability of the concentrations. See Section 4.7. 

An example of using the method for single-component balancing is given in Madron (1992), Subsection 6.3.3. For a system containing 16 units and 49 streams, the calculation performed on a WANG 2200 computer took 30 seconds. 

The optimal selection of measuring points in the case of a single-component balance by the method of finding the maximum spanning tree is applicable even when we are not able to assign costs to streams exactly. Sometimes it is possible to arrange the streams in accordance with our wish to measure them directly. The order in such a series (number one is ascribed to the stream that can be measured in the easiest way) is so-called priority of... 

One of the most important areas of balancing is the single-component balancing as a basis for mass and utilities accounting. Results of this kind of balancing are invaluable in good housekeeping in process plants. Typical applications are... 

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