This manual is not intended as a recommendation of any particular technology, process, or method. Mention of trade names, vendors, or commercial products do not constitute endorsement or recommendation for use. It is offered for educational and informational purposes.
This material is copyrighted by the authors. Permission to copy all or in part with appropriate credit noted is freely given. It is being provided on the Internet with the consent of the authors. Questions should be directed to the authors:
Russell F. Dunn
Vydyne Technology
Monsanto Chemical Company
Gonzalez, FL 32560
(904) 968-8216
Mahmoud M. El-Halwagi
Chemical Engineering Department
Auburn University
Auburn, Alabama 36849
(334) 844-2064
Several institutions and individuals have helped make this work possible. We would like to acknowledge the funding provided by the State of Alabama through its program of Alabama Universities/TVA Research Consortium (contract # AUTRC 95-04-AUB). We are also grateful to the TVA for managing this program. In particular, we are indebted to Mr. Joseph Phillips of the TVA for technically managing this project and for providing insightful suggestions. The support of Auburn University and the National Science Foundation (contract # NSF-NYI-CTS-9457013) are also gratefully acknowledged. Thanks are also due to Dr. B. K. Srinivas of General Electric's Corporate Research and Development for reviewing the document and providing useful suggestions. Finally, we are grateful to the continued support, patience and encouragement that we have received from our two families.
Volatile Organic Compounds "VOC's" are among the most important chemicals used in and emitted from the process industries. Due to the significant economic and environmental implications of disposing of VOC's, much attention has been recently directed towards pollution-prevention techniques aimed at reducing VOC emissions from industrial facilities in a cost-effective manner. This document presents some of the latest developments in the area of systematically addressing VOC pollution prevention. Chapter I provides an overview of pollution-prevention approaches. Chapters II - III discuss the VOC separation technologies for aqueous and gaseous wastes, respectively. Chapter IV introduces a design philosophy aimed at identifying the most cost-effective technology(s) for a given VOC separation task. Chapters V - VIII present systematic tools for the design of cost-effective VOC recovery systems for aqueous and gaseous wastes.
Recently, several environmental regulations have been enacted that require industries to limit gaseous and aqueous emissions containing volatile organic compounds "VOC's." These new laws have greatly increased the number of regulated VOC's and expanded the categories of emissions from industrial facilities, which has greatly increased the number of companies required to reduce emissions. For example, reduction of VOC gasesous emissions is mandated under Title I of the Clean Air Act Amendment of 1990 which calls for the reduction of VOC emissions in areas exceeding the current National Ambient Air Quality Standard for ozone of 0.12 ppm. VOC's have also been regulated under Title III of the Amendments which requires a reduction of the emission of 189 hazardous air pollutants (HAP's), many of which are VOC's. Similarly, NESHAP's (National Emission Standards for Hazardous Air Pollutants), regulate the levels of VOC's in both air emissions and wastewater. This regulation also requires the control of "fugitive" VOC's from processing units. Another regulation, known as the VOHAP (Volatile Hazardous Air Pollutant) and VVHAP (Very Volatile Hazardous Air Pollutant) applies to a large number of VOC's. A significant number of VOC's have also been added to the TC (Toxicity Characteristic) Rule, which is part of the hazardous waste regulations under RCRA (Resource Conservation and Recovery Act). In addition, chemical-specific effluent limitations are being added to wastewater standards under the NPDES (National Pollutant Discharge Elimination System). These are extremely stringent and apply to a large number of VOC's. Some specific examples of VOC's that are regulated are included in Attachment 1-I.
In response to the need to find cost-effective ways of reducing VOC's emissions, many industrial initiatives have occurred. These initiatives have led to the realization that pollution prevention provides the most comprehensive and efficient strategy for reducing VOC's emissions. Furthermore, it has been realized that any succesful pollution prevention strategy should address management and technical concerns. For example, management concerns addressed within a corporate pollution strategy are reduced liability, improved corporate image within the community, and reduced uncertainty relative to waste shipments from the company to some disposal party. Examples of technical concerns are waste reduction process efficiency, economics of recovery and recycle of wastes, and energy efficiency.
Within the past decade, significant academic efforts have been devoted to the development of systematic tools and robust design methodologies that could be incorporated within a corporate pollution strategy to allow the systematic development of environmentally acceptable process designs. These tools and methodologies are designed to address the technical and, in many cases, the management concerns of a company with respect to their corporate pollution strategy. Prior to presenting the systematic tools and design methodologies that have been developed for use in designing VOC separation systems, several pollution prevention terms should be defined. Additional information on these definitions can be found in Noyes (1993) and Freeman (1990). The following is a brief discsussion of these terms. In addition, Figure 1.1 is included as a hierarchical representation of these definitions.
Pollution Prevention Definitions as Used by the Environmental Protection Agency
Waste - Nonproduct outputs of processes and discarded products, regardless of the environmental medium impacted.
Pollution Prevention - "Industrial pollution prevention" and pollution prevention refer to the combination of source reduction and toxic chemical use substitution. It does not include any recycling or treatment of pollutants. It also does not include substituting a nontoxic product made with nontoxic chemicals for a nontoxic product made with toxic chemicals.
Waste Minimization - Current RCRA definition indicates that waste minimization refers to source reduction and recycling activities, but does not include treatment and energy recovery activities.
Recycling - Recycling techniques are categorized as use, reuse and reclamation techniques. These techniques allow potential waste materials to be put to a beneficial use rather than going to treatment, storage or disposal.
Use or Reuse - Use and reuse involves the return of a potential waste material either to the originating process as a substitute for an input material, or to another process as an input material.
Reclamation - The recovery of a useful or valuable material from a waste stream is referred to as reclamation.
Source Reduction - Source reduction is any practice that:
This term also includes:
- Equipment or technology modifications
- Process or procedure modifications
- Reformulation or Redesign of products
- Substitution of raw materials
- Improvements in housekeeping, maintenance, training or inventory control
Toxic Chemical Use Substitution - This term refers to the replacement of toxic chemicals with less harmful chemicals.
Toxic Use Reduction - Source reduction activities whose intent is to reduce, avoid or eliminate the use of toxic substances in processes and/or products.
The design methodologies discussed in this manual are used to promote the attractive economics associated with cost-effective recovery technologies. The ability to determine the most cost-effective recovery technology often shifts the emphasis from regulatory drivers to economic drivers for waste minimization as illustrated in Figure 1.2.
Freeman, Harry. Hazardous Waste Minimization, McGraw-Hill , Inc. New York, 2-4, 1990.
Noyes, Robert. Pollution Prevention Technology Handbook, Noyes Publications, Park Ridge, NJ, 2-6, 1993.
Phillips, J. W., Tennessee Valley Authority, Muscle Shoals, Alabama, Personal Communication, 1995.
|
|
|