Separation Technologies for the Industries of the Future (1998) / Chapter Skim
Currently Skimming:
4 Cross-Cutting Issues for the Chemical and Petroleum Refining Industries
4 Cross-Cutting Issues for the Chemical and Petroleum Refining Industries
Pages 36-50
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 36... ...
The petroleum refining industry requires improved methods for removing acid gases from natural gas and process streams, for recovering hydrogen from gaseous waste streams that are currently burned for fuel, and 36
|
From page 37... ...
The separation and recovery of valuable components, such as metal ions, and the removal of contaminants, such as VOCs or particulates, from dilute gaseous and aqueous waste streams presents important problems for both industries. Technologies of interest include reactive metal complex sorbents/chemically facilitated transport membranes, reducing agents, electrically aided membrane separation, continuous adsorption processes, air oxidation combined with absorption, highselectivity gas separation membranes, and pervaporation.
|
From page 38... ...
The high specificity of metal coordination complexes is exploited in chemically facilitated transport membranes, which allow for continuous, noncyclical, separation processes (O'Hare and Bohrer, 1989~. In a chemically facilitated transport membrane, a reversible coordination complex or other reversibly binding species essentially acts as a highly specific mobile "carrier" for the desired component of the mixture.
|
From page 39... ...
For each of these hybrid systems, however, significant challenges will have to be overcome to achieve selectivity with the individual catalytic synthesis, distillation, sorption, or membrane separation steps. Membrane Reactors The most intimate combination of a separation process with chemical synthesis occurs in a membrane reactor, in which the membrane and catalyst are one and the same.
|
From page 40... ...
For a membrane to work in the reactor configuration shown in Figure 4-1, it must be stable in the reaction environment, selectively transport desired species at high rates, and be easily incorporated into modules. Separation Methods with Multiple Driving Forces The driving force in a separation process can be enhanced by coupling different physical and chemical phenomena.
|
From page 41... ...
After the undesired species have been purged, conditions in the column are altered, for example by adjusting pH, to release the desired species from the receptor. This highly selective process should be investigated for use with separation techniques other than chromatography.
|
From page 42... ...
Electrode material could be applied to either side of the membrane. The promise of electrochemical synthesis/separation methods is that they will be able to synthesize pure products under moderate conditions and with high energy efficiency, while simultaneously performing separation processes.
|
From page 43... ...
Emerging applications include the use of thin, nanostructured, dense metal membranes for the separation of gases, such as hydrogen. Other applications include the use of molecular sieve membranes, such as zeolite and carbon molecular sieve materials, for the separation of isomers and dense, perovskite-type oxide membranes to produce high-purity oxygen.
|
From page 44... ...
So-called hydrophobic sorbents, such as activated carbon, silicalite, and various resins, tend to be selective for less polar components and tend to select among hydrophobic species based roughly on boiling points. Hydrophilic absorbents (e.g., activated alumina, silica gel, and zeolite molecular sieves)
|
From page 45... ...
Note that the slope of the plot increases as purity increases, meaning that the incremental energy cost associated with increasing purity by a fixed amount increases as the base value increases. The figure also shows the effect on energy costs of high and low process variability for the same mean operating value of product purity.
|
From page 46... ...
In most separation processes, the thermodynamic description of equilibrium between two phases is an indispensable tool in understanding driving forces. Research in phase equilibrium is hardly new, and extensive information is available.
|
From page 47... ...
Supplying the critical thermodynamic information for separation processes in the areas described above will require combining advanced analytical-chemistry technology with phase-equilibrium equipment and deriving correlations that accurately describe and generalize the experimental data.
|
From page 48... ...
page blank
|
From page 49... ...
1 1 II SEPARATION IN THE MATERIALS PROCESSING INDUSTRIES page 49
|
From page 50... ...
1 page blank
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.