TABLE OF CONTENTS The previous chapter dealt primarily with mass integration. A common feature of mass-integration techniques is that they are chemo-centric ; namely they are based on tracking individual chemical species. Nonetheless, many material reuse problems are driven and governed by properties or functionalities of the streams and not by their chemical constituency. The following are some examples of property-based problems:
The usage of material utilities (e.g., solvents) relies on their characteristics, such as equilibrium distribution coefficients, viscosity, and volatility without the need to chemically characterize these materials.
Constraints on process units that can accept recycled/reused process streams and wastes are not limited to compositions of components but are also based on the properties of the feeds to processing units.
The performance of process units depends on properties. For instance, a heat exchanger performs based on the heat capacities and heat transfer coefficients of the matched streams. The chemical identity of the components is only useful to the extent of determining the values of heat capacities and heat-transfer coefficients. Similar examples can be given for many other units (e.g., vapor pressure in condensers, specific gravity in decantation, relative volatility in distillation, Henry s coefficient in absorption, density and head in pumps, density, pressure ratio, and heat-capacity ratio in compressors, etc.).
Quantities of emission are dependent on properties of the pollutants (e.g., volatility, solubility, etc.).
The environmental regulations involve limits on properties (e.g., pH, color, toxicity, TOC, BOD, ozone-depleting ability).
Tracking numerous chemical pollutants is prohibitively...
