Separation Technologies for the Industries of the Future (1998)

Separation processes, or processes that use physical, chemical, or electrical forces to isolate or concentrate selected constituents of a mixture, are essential to the chemical, petroleum refining, and materials processing industries. In addition to the important process roles separation technologies play in each of these industries, separation technologies present opportunities for reducing waste and using energy and raw materials more efficiently. New developments in separation technologies are, therefore, critical for the productivity and global competitiveness of U.S. industries.

Since 1993, the U.S. Department of Energy's Office of Industrial Technology (OIT) has managed its research program according to a ''market pull'' strategy, in other words, basing its project selection on industry-identified technology needs and priorities. The purpose of this strategy is to increase and document the commercial impact of OIT's programs. To determine industry's needs and priorities, OIT has developed partnerships with a number of energy-intensive and waste-intensive industries, called the "Industries of the Future" (IOF).

Several IOF industries identified separation technologies as an important area for research. The National Research Council Panel on Separation Technology for Industrial Recycling and Reuse was established to identify the most important needs for separation processes in the IOF; to identify separation technologies that can meet these needs, especially technologies that are applicable to two or more IOF industries; and to suggest criteria for identifying and coordinating research and development in separation technologies.

The panel included in its analysis the seven IOF industries that were involved in the program at the beginning of this study: chemicals (Chapter 2), petroleum refining

(Chapter 3), aluminum (Chapter 5), steel (Chapter 6), metal casting (Chapter 7), glass (Chapter 8), and forest products (Chapter 9). The separation needs of each of these industries are identified in the appropriate chapters and summarized in Chapters 4 and 10. Although a number of separation issues that affect more than one IOF industry were identified, the panel concluded that the needs of these industries are highly diverse and warrant individual treatment. In fact, the panel found that many important separation problems were unique to one industry.

Although separation technologies are essential to all seven IOF industries, only a few represent opportunities for cross-cutting research, i.e., research likely to benefit the majority of them. Because of the diversity of raw materials, product forms, and processing conditions in these industries, most research opportunities are industry-specific. The panel, therefore, does not believe that OIT's program would be significantly more efficient if a single cross-cutting research program in separation technology were established.

Nevertheless, relatively well developed separation technologies in one industry might be transferable to another industry. In addition, a few technology areas are relevant to more than one, in some cases all, of the IOF industries. The panel, therefore, recommends that the technical program managers at OIT coordinate separation research among the IOF industries, and monitor and disseminate the results. The panel identified five opportunities for coordinated programs: separation processes for the chemical and petroleum refining industries; bulk sorting technologies for the materials processing industries (especially aluminum, steel, metal casting, glass, and the polymer-recycling sector of the chemical industry); separation technologies for dilute gaseous and aqueous waste streams; drying and dewatering technologies; and lower cost oxygen production processes.

A number of issues are common to the chemical and petroleum refining industries. In addition to general improvements in process efficiency, the panel identified two separation technology areas with the potential to meet a number of needs in these industries:

• separation methods using multiple driving forces, including processes in which a naturally occurring driving force for a specific operation is enhanced by an intervention that changes the system thermodynamics or in which two or more separation techniques are combined (e.g., membrane

• separation and distillation; affinity-based adsorbent separation; and electrically aided separation)
• separation associated with chemical reaction, in other words, methods that combine reaction and separation in one process step (e.g., reactive metal complex sorbents and chemically facilitated transport membranes; combined chemical synthesis and separation processes; membrane reactors; and electrochemical methods of separation)

A number of the materials processing industries (aluminum, steel, metal casting, glass, and the polymer-recycling sector of the chemical industry) identified separation needs that can be classified as materials handling and sorting, specifically, the high-speed separation of scrap. Research and development in this area should focus on bring down the cost of these processes. Improved high-speed sorting technologies, such as air jet and conveyer belt technology systems, would facilitate this. Research and development should include:

• on-line sensors for high-speed analysis of the composition of streams and the makeup of individual objects in these streams
• physical separation techniques, including gravity separation (e.g., air jet and flowing film separation), froth flotation, magnetic separation, and electrical separation (e.g., electrostatic separation and tribo-electrification)
• high-speed sorting technologies, including the fundamental mechanics of high-speed conveying, techniques to position individual scrap pieces in sequential arrays before analysis, and methods for physically diverting analyzed pieces by material type

All of the IOF industries identified the separation of components from dilute gaseous streams, dilute aqueous streams, or both as important needs for their industries. Potential areas for cross-cutting research include:

• methods of separating components from dilute gaseous streams, such as adsorption, high-selectivity membranes, inorganic membranes, and advanced-particle-capture technologies for the removal of micron-sized particles
• methods of separating components from dilute aqueous streams, such as reactive metal complex sorbents, reducing agents, air oxidation combined with absorption, membranes, steam and air stripping, electrically facilitated

• separation, destructive-oxidation techniques, electrodialysis, ion exchange, and crystallization

Several industries identified needs that could be met by improvements in drying and dewatering technologies. Examples include: the removal of solvents from polymers (devolatilization) in the chemical industry; the removal of entrained water from crude oil and the drying of natural gas in the petroleum refining industry; the drying of ceramic casting materials and reclamation sand in the metal casting industry; the drying of paper in the forest products industry; and the drying of sludges from waste gas scrubbing and wastewater treatment.

The chemical, petroleum refining, aluminum, steel, and glass industries have stated that lower cost oxygen would be beneficial to them in combustion and other processes. The advantages of oxygen over air as a fuel or reactant are greater thermal efficiency; lower production rate of nitrogen oxides; lower volume, which can make the recovery of products or contaminants easier; and, in some cases, higher chemical efficiencies. Oxy-fuel is more energy efficient because there is no need to heat the nitrogen component of air. Currently, the relatively high cost of oxygen is a significant barrier to its widespread use in several emerging technologies.

The panel identified five enabling technologies that, although they are not separation processes, would promote improvements in industrial separation. Research areas include new membrane materials, sorbent materials for specific applications, on-line diagnostics and sensors, an improved understanding of thermodynamics, and particle characterization. The panel recommends that OIT focus its long-term, fundamental research in these areas.

Based on the research opportunities identified by the panel for each industry and the maturity of separation technologies, the panel identified four general criteria for selecting research and development projects:

• Time Scale. Research in this area should focus on high-impact technologies that have been demonstrated in the laboratory and will be ready for commercial application in five to seven years.
• Cross-cutting Criteria. OIT should only support cross-cutting research in separation technologies that are either (1) embryonic technologies that could lead to major advances in several industries or (2) improvements in mature, high-use technologies where incremental improvements could have a substantial effect.
• Impact on Existing Processes and Equipment. Proposed projects should be evaluated for the potential economic impact of a new separation method and for the potential effect of that new method on existing processes and equipment. OIT should consider funding the development of fundamental data when knowledge of such data can produce substantial improvements in existing separation processes.
• New Technologies. Projects for the development of new separation technologies should be multidisciplinary and should be potentially scaleable to production volume, both in technical and economic terms.