Showing papers in "Clean Products and Processes in 2001"

A life cycle assessment of biomass cofiring in a coal-fired power plant

Abstract: The generation of electricity, and the consumption of energy in general, often result in adverse effects on the environment. Coal-fired power plants generate over half of the electricity used in the U.S., and therefore play a significant role in any discussion of energy and the environment. By cofiring biomass, currently operating coal plants have an opportunity to reduce the impact they have, but to what degree, and with what trade-offs? A life cycle assessment has been conducted on a coal-fired power system that cofires wood residue. The assessment was conducted in a cradle-to-grave manner to cover all processes necessary for the operation of the power plant, including raw material extraction, feed preparation, transportation, and waste disposal and recycling. Cofiring was found to significantly reduce the environmental footprint of the average coal-fired power plant. At rates of 5% and 15% by heat input, cofiring reduces greenhouse gas emissions on a CO2-equivalent basis by 5.4% and 18.2%, respectively. Emissions of SO2, NOx, non-methane hydrocarbons, particulates, and carbon monoxide are also reduced with cofiring. Additionally, total system energy consumption is lowered by 3.5% and 12.4% for the 5% and 15% cofiring cases, respectively. Finally, resource consumption and solid waste generation were found to be much less for systems that cofire.

Adsorptive cooling: a clean technology

Abstract: As a consequence of the Kyoto Protocol and its predecessor, the Montreal Protocol, environmental considerations will play an important role in the choice of a refrigeration or heat pump system. Accordingly, sorption technology is expected to develop for cooling as well as for heat pump applications because it uses benign fluids. At the moment, liquid absorption technology is the leading technology in that field; however, adsorption offers advantages that cannot be achieved by liquid absorption technology. This article addresses the measures to reduce halocarbon emissions and the possibilities of adsorption technology. Not only are the direct emissions taken into account but also the indirect ones due to energy consumption. Several cases that show that adsorption cooling is very promising, from the global warming point of view, are considered in this article. They are: waste heat adsorption chilling, natural gas adsorption chilling, trigeneration and natural gas reversible heat pump. Adsorption air conditioning for automobiles is also discussed as a very challenging possibility for adsorption cooling.

Process integration design methods for water conservation and wastewater reduction in industry

Abstract: This paper is part 2 of a three-part series of papers addressing operational techniques for applying mass integration design in industry with special focus on water conservation and wastewater reduction. This paper presents a design technique for any number of wastewater streams containing multiple contaminants. The technique comprises a single non-linear optimization program to minimize the wastewater discharged (or maximize the amount of recycled wastewater). This program is developed based on general water allocation principles and uses the transshipment model theory to allow the "shipment" of wastewater (referred to as "sources" or "warehouses") to process water users (referred to as "sinks", "demands" or "customers"). A detailed case study of industrial significance, highlighting land treatment technology, is included to illustrate the proposed methodology and various process scenarios are evaluated within this case study to demonstrate the general applicability of the proposed optimization program.

Environmental issues for polymer matrix composites and structural adhesives

Abstract: The U.S. Department of Defense (DoD) has been utilizing polymer matrix composite (PMC) and structural adhesive materials in military equipment for over 20 years. However, the volume of PMCs in fielded systems has remained relatively low. Currently, however, the DoD has established strategic goals that will necessitate the use of lightweight composites in order to meet performance requirements. Therefore, the volume of composites used in DoD systems is expected to see an unprecedented 100-fold increase over the next 30 years. As production volumes increase, the need to address environmental impact increases. The major contributions to environmental degradation from composites are generation of hazardous air pollutants (HAPs) and generation of hazardous (HW) and solid wastes. HAPs result primarily during the curing of the composite. HWs arise from expiration of stockpiled resin materials and from soiled support media used during manufacturing and clean up. Due to the wide range of applications and materials systems, as well as manufacturing and repair requirements, a family of environmentally benign solutions is needed to reduce and eliminate environmental impacts from PMC manufacturing. Solutions are proposed involving use of new technologies and materials to reduce pollutants from composite manufacturing. The technologies proposed include alternative curing of thermoset composites using electron beam (E-beam) irradiation and materials substitution employing thermoplastics processed using electromagnetic irradiation.

Ultraviolet disinfection application to a wastewater treatment plant

Abstract: Considering most benefits of using ultraviolet (UV) radiation, the Lacey, Olympia, Tumwater and Thurston County (LOTT) wastewater treatment plant located in the City of Olympia was the first major POTW on the U.S. West Coast to install and successfully operate a UV disinfection system that processes about 22 MGD of wastewater. The LOTT's secondary treatment process is a biological nutrients removal system, and has the capabilities of removing more than 90% total suspended solids (TSS), biological oxygen demand, and nutrients (including phosphorus). This high quality effluent with low TSS contributes to achieving a highly efficient UV disinfection system with monthly geometric mean values in the range of 4–48 fecal coliform per 100 ml, well below the NPDES permit limit set to 200 counts per 100 ml. This paper summarizes the results and conclusion from the pilot study conducted at LOTT prior to installing a full-scale UV system, with references to other updated work reported elsewhere.

Cleaner energy production with integrated gasification combined cycle systems and use of metal oxide sorbents for H2S cleanup from coal gas

Abstract: World primary energy demand increases with increases in population and economic development. Within the last 25 years, total energy consumption has almost doubled. In order to meet this demand, research into new sources of energy as well as improving the efficiency of energy production technologies is being carried out. In both cases, the production of clean energy is very important because of environmental concerns and regulations. Integrated gasification combined cycle (IGCC) technology seems to be one of the most promising technologies for production of energy by using fossil fuels, especially coal. Hot gas desulfurization is a crucial issue in the development of the IGCC system. This paper reviews the importance of clean energy production, the IGCC technology and focuses on the development of several metal oxide-based sorbents used for desulfurization of the hot coal gas in the IGCC system.

How do you select the “greenest” technology? Development of guidance for the pharmaceutical industry

Abstract: There is widespread interest in government and industry in green chemistry and green technology. For truly “green” processes to be developed, scientists must take a concurrent, integrated approach that considers chemistry and technology. While it is vital to understand those things traditionally considered in technology selection such as operational, quality, and cost differences, it is equally vital to understand the associated environmental and safety issues that are inherent to the chosen technology. This is a major challenge and there is a clear need for guidance in this area. This paper proposes the concept of a “Clean/Green Technology Guide” as an expert system that would provide scientists and engineers with comparative environmental and safety performance information on available technologies for commonly performed unit operations in the pharmaceutical industry. At this stage, the framework has been developed to demonstrate the concept, using a metric set based on the concepts of sustainable development. This framework is used to evaluate the alternatives on a case-scenario basis, and will compare traditional and emerging technologies. A life-cycle approach is also used in the evaluation of the alternatives. This approach is illustrated by comparing batch, mini-, and microreactors.

Determination of total volatile organic compound emissions from furniture polishes

Abstract: In this study, an environmental test chamber with controlled temperature, relative humidity, and airflow rate was developed to evaluate emissions of total volatile organic compounds (TVOCs) from three different kinds of furniture polish. The time dependence of TVOC concentrations produced from the emissions of furniture polish products in the chamber was tested. TVOC emissions from each furniture polish were compared. The main volatile organic compounds emitted from each polish were identified by gas chromatography/mass spectrometry. A double-exponential equation was developed to evaluate the characteristics of emissions of TVOCs from these furniture polish products. With this double-exponential model, the physical processes of TVOC emissions can be explained. A variety of emission parameters can be calculated. These emission parameters could be used to estimate real indoor TVOC concentrations.

A screening methodology for improved solvent selection using economic and environmental assessments

Abstract: Solvents are used in many applications in chemical manufacturing. An ideal solvent exhibits superior solubility, economic, and environmental impact characteristics. There are many approaches developed for identifying the best solvents, including the use of the Hansen solubility parameters, activity coefficients, toxicity properties, flammability characteristics, and methods based on structure–activity relationships.

Current and emerging technologies for extending the lifetime of electroless nickel plating baths

Abstract: The waste treatment and rejuvenation of spent electroless nickel baths has attracted a considerable amount of interest from electroplating shops, electroless nickel suppliers, universities and regulatory agencies due to the finite life of the baths and the associated waste that the process generates. It is generally accepted that the recycling of electroless nickel solutions is one of the most important challenges facing the electroless nickel-plating industry today. This review presents an overview of the existing and emerging technologies for extending the life of electroless nickel baths. The electroless nickel bath regenerative technologies are appraised from the standpoint of removal of harmful bath components, loss of valuable bath components, cost-effectiveness, secondary waste generation and ease of implementation. The review draws upon an array of academic papers, industrial/company reports, conference proceedings and patents in order to allow the reader to evaluate and compare the different technologies and options for extending the life of electroless nickel-plating solutions.

Screening of organomercurial-volatilizing bacteria in the mercury-polluted sediments and seawater of Minamata Bay in Japan

Abstract: The special organomercurial-volatilizing bacteria found in the seawater and sediments of Minamata Bay were screened to develop a method for the removal of mercury to produce clean products. A total of 104 mercury-resistant bacteria that could grow on an agar plate containing 40 µg/ml of HgCl2 were isolated from Minamata Bay. Almost all strains were Gram-negative rods. Eight of the 104 strains volatilized only mercuric chloride, while 21 of the 104 strains volatilized all of the organomercurials used in this study. Four strains isolated from the seawater were most resistant to methyl mercuric chloride, ethyl mercuric chloride, thimerosal, and fluorescein mercuric acetate as well as HgCl2, and volatilized all of the organomercurials used in this study. We were able to screen the most mercury-resistant bacteria and organomercurial-volatilizing bacteria, which contained an organomercurial lyase with a particularly wide range of substrate specificity.

An integrated approach to the retrofitting of mass exchange networks

Abstract: The synthesis of optimal mass exchange networks (MENs) deals with the identification of a cost-effective network of mass exchangers that preferentially transfer certain species from rich streams to lean streams. To date, MEN synthesis has dealt with grass-root design where the emphasis is on the maximization of process lean streams usage and the minimization of operating cost. Another important class of problems is the retrofit of MENs in which mass-exchange units already exist in the plant and the focus is to maximize the usage of the process units so as to minimize capital cost of newly added units and trade it off with operating cost. In this paper, we develop a systematic procedure for the retrofitting of MENs. First, we identify alternative structural configurations of interest through heuristics. Series and parallel structures are addressed. Next, we focus on two primary retrofitting strategies: those restricted by no capital constraints and those involving capital expenditure. The no-capital alternatives include enhancing performance of a current system as well as solvent substitution. The capital-based alternatives include the addition of new equipment. A new type of mass-pinch analysis is developed to maximize the utilization of existing capital while reconciling added capital with operating cost. The main concept in this novel pinch diagram is identifying maximum performance as dictated not only by thermodynamic limitations but also by physical size limitations. Different process alternatives are considered and screened to attain the optimum design. A case study is presented to demonstrate the broad applicability and potential benefits of the novel approach.

Synthesis of a novel water-soluble copolymer composed of 2-methylene-1,3,6-trioxocane and N-vinyl 2-pyrrolidone and its enzymatic degradation

Abstract: 2-Methylene-1,3,6-trioxocane (MTC) was copolymerized with N-vinyl-2-pyrroridone (NVP) at 60 °C to give enzymatic degradability to water-soluble poly-NVP (PNVP) and thus prepare a water-soluble PNVP containing an ester–ether moiety in the backbone of PNVP. The copolymer of MTC and NVP (poly-MTC–NVP) was hydrolyzed by Rhizopus arrhizus lipase. Using gel permeation chromatography, it was found that the molecular weight of poly-MTC–NVP after the lipase acted on it decreased compared with that of the original copolymer. In the case of poly-MTC–NVP with a small ester–ether moiety, the enzymatic degradability was particularly high.

Design of multi-phase and catalytic chemical reactors: a simulation tool for pollution prevention

Abstract: A comprehensive chemical reactor analysis tool was required to complete a project to develop an advanced on-line process optimization analysis system for pollution prevention. The advanced process analysis system integrates programs (reactors, on-line optimization, pinch analysis, and process flow-sheeting) to analyze and modify chemical processes for waste minimization. The reactor analysis program is to be used to evaluate and analyze multi-phase and catalytic reactors to suggest to the plant and process engineers the best reactor type and operating conditions. A multi-phase catalytic reactor design and analysis tool, ReaCat, has been developed. ReaCat incorporates models to design the following reactor types: plug flow, CSTR, batch, catalytic fixed-bed, catalytic fluidized-bed, gas–liquid stirred tank, trickle-bed, three-phase fixed bubble-bed, bubble slurry column, CSTR slurry, and three-phase fluidized-bed. This paper gives a summary of the multi-phase and catalytic reactors: classifications, theory and design models, numerical methods, and solution algorithms. A description of the reactor analysis tool including comparison cases with experimental data is presented.

Contrasting approaches to the generation of environmental improvement options for production systems

Abstract: This article reviews two common types of improvement tools presently used in industry to identify opportunities to prevent or at least to reduce the environmental impacts of production systems and processes. Despite their proven ability to result in appropriate environmental improvement options in different industry sectors, their successful application is hampered by the fact that these tools do not take the specific causes of the environmental impacts of the production process into account, i.e. the question of which process features cause the environmental impacts of the production process is not raised nor is the flexibility for change of the production system taken into consideration. This paper sets the stage for a new generation of improvement tools, based on an environmental diagnosis of the production system. The diagnosis aims to result in a thorough understanding of the production system to guide and drive the identification of environmental improvement options that specifically target process-, product-, and site-specific environmental conditions. Alternative ways to develop such a diagnostic approach on the basis of presently used tools are being explored, and a synthesis thereof is proposed to achieve synergy between these contrasting approaches.

Controlled-release system for the insect growth regulator cyromazine

Abstract: An encapsulation system designed to give long-lasting effectiveness of the insect growth regulator (IGR) cyromazine (Neporex) against Culex pipiens (Culicidae) mosquito larvae was developed. The main thrust of the research was to develop a simple method for preparing controlled-release formulations by means of an extrusion technique in combination with a supplementary coating and to study the release characteristics and effectiveness of the formulations. A series of formulations were prepared with low-density polyethylene (LDPE 600) for the matrix and with polyurea or one of four types of polyurethane for the coating. The rate of release of the active material from the controlled-release formulations was determined in an in vitro dissolution system. The biological activity of the controlled-release formulations was tested in vivo against C. pipiens larvae.

Low VOC latex paints from a precipitation polymerization process

Abstract: Even though paints and coatings have been very useful in protecting various substrates, their use has been accompanied by a heavy environmental price. There is a need to minimize the use of volatile organic compounds (VOCs) in the formulation of these materials. In the latex paint area, we have implemented a conventional precipitation process in emulsions to form binder particles that contain block copolymers and have softer blocks on the particle surface. The softer surface provides the binder film-forming properties without the need for the use of solvents or VOCs. The covalent connections between the soft blocks and the hard blocks are expected to impart good performance in the resulting dry coatings. Indeed, we have shown that our test coating from these binder particles containing block copolymer have similar properties in most performance categories to those of a semi-gloss control paint that has been formulated with typical amounts of VOCs.

Picklex® as a non-polluting metal surface finishing pretreatment and pretreatment/conversion coating

Abstract: Picklex (International Chemical Products, Huntsville, Alabama), a proprietary formulation, is an alternative to conventional metal surface pretreatments and is claimed not to produce waste or to lower production with no loss in performance. A laboratory program was designed to evaluate Picklex in common, large scale, polluting surface finishing operations against conventional processes, using steel and aluminum panels, measuring product coating properties, process operability, and costs. Twenty-one surface finishing combinations were tested under both "contaminated" and "noncontaminated" conditions with respect to finish adhesion, bending, impact, hardness, and corrosion resistance. Results indicate that Picklex-pretreated panels performed as well as panels that were conventionally pretreated, and with a simpler process. Picklex is particularly acceptable for powder coated steel or aluminum, but may not be suitable for certain metal plates. The results are interpreted in terms of the surface film produced by Picklex. A rate of use of 5,400 ft2/gal was estimated. Picklex did not generate by-product waste solids, was effective at room temperature, used short processing times, and was easy to use. An engineering assessment indicated that Picklex can have cost advantages as well. The economics of Picklex depend on minimizing dragout. These results suggest that Picklex is a promising alternative in some metal surface pretreatments.