Frontiers in Chemical Engineering Research Needs and Opportunities (1988) / Chapter Skim
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7 Environmental Protection, Process Safety, and Hazardous Waste Mangement
7 Environmental Protection, Process Safety, and Hazardous Waste Mangement
Pages 105-134
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From page 106... ...
. Chemical engineers are involved in all aspects of chemical manufacture and processing; therefore, it should be their responsibility to safely manage chemicals in the environment.
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From page 107... ...
to the global and regional impacts associated with energy utilization (e.g., carbon dioxide, acid rain, and photochemical oxidants) , the improper disposal of chemical waste (e.g., Love Canal and Times Beach)
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From page 108... ...
Airborne lead from automobile exhausts Carbon monoxide from automobile exhausts Photochemical oxidants, particularly ozone (Los Angeles) Sulfur oxides (SOx)
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From page 109... ...
Large-scale air quality problems arising from combustion-generated emissions, such as acid rain (Figure 7.4) , regional hazes, and volatile toxic compounds, have also assumed prominence and will likely be the targets of future legislation.
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From page 110... ...
This geographic pattern of acid rain correlates with the emission and transport of sulfur dioxide from coal-burning plants. From U.S./Canada Work Group #2, Atmospheric Science and Analysis, U.S.
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From page 111... ...
After a few years of pursuing such methods, it is clear that they do not provide a solution to the problem of containment of waste in existing landfills; slurry walls leak and clay caps crack. It is also becoming increasingly clear that it will require decades to accomplish an adequate cleanup of hazardous waste sites nationwide.
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From page 112... ...
Tree graphs could be particularly helpful in evaluating the process safety implications of highly selective synthesis routes. Near the apex of the chemical synthesis tree graph materials that might be used in chemical reactions are of highest value.
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From page 113... ...
Most accidents in chemical plants occur when the plant is not operating at a steady state for example, when it is starting up or shutting down or when a transient of temperature, pressure, or reactant concentration occurs. Fundamental research in non-steady-state process control and the management of process transients is therefore warranted.
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From page 114... ...
Nitrogen oxide emissions from furnaces and boilers come mostly from oxidation of the nitrogen atoms in the fuel, whereas in internal combustion engines these emissions are derived largely from oxidation of atmospheric nitrogen. Burners of advanced design currently reduce the emissions of nitrogen oxides by a factor of 2 from uncontrolled combustion systems by staging the addition of oxygen to produce an initial fuel-rich regime in which the bound nitrogen is partially converted to N2 (Figure 7.71.
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From page 115... ...
In addition, the sooting tendency of aromatic compounds is higher than that of aliphatics, and the i: aromatic content of fuels is ex ~pected to increase in the future my> as petroleum resource availabil Fluoranthene ity forces refiners to use fuel feedstocks with lower ratios of hydrogen to carbon. Soot is objectionable not only because of its opacity but also because soot particles are car riers of toxic compounds.
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From page 116... ...
Although significant progress has been made in simulating the dynamics of multicomponent aerosols, basic information on the fundamental chemistry and physics of soot formation and growth is needed to enable researchers to predict the size and chemical composition of soot particles as a function of fuel type and combustion conditions. Ash The United States uses a disproportionate amount of gas and oil compared to coal (Figure 7.11~.
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From page 117... ...
The volatilized suboxides and elemental metals are then reoxidized in the boundary layer around the burning particle, where they subsequently nucleate to form a submicron aerosol. There is a general understanding that the size of ash particles produced during coal combustion decreases with decreasing coal particle size and with decreasing mineral content of the parent coal particles.
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From page 118... ...
Buildings now contain many synthetic polymeric materials that can burn to yield such toxic compounds as hydrogen cyanide and hydrogen chloride in addition to common combustion products such as carbon monoxide. For this reason, consideration is being given to banning certain materials, at least in public buildings.
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From page 119... ...
remediation of old, abandoned waste disposal sites. The problems of handling and disposing of radioactive waste are largely the concern of nuclear engineers, often working with chemical engineers to develop separation and encapsulation technologies for radioactive nuclides, and are not discussed here.
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From page 120... ...
A major effort must be mounted to conduct advanced research and to educate engineers to solve the problems associated with the disposal and environmental behavior of toxic chemicals. Detoxification of Currently Generated Waste Many technologies have been proposed for detoxifying waste by processes that destroy chemical bonds: pyrolytic; biological; and catalyzed and uncatalyzed reactions with oxygen, hydrogen, and ozone.
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From page 121... ...
· What new organic compounds can be synthesized during the incineration process? Factors that influence the destruction effi cogency In Incineration Include · local temperatures and gas composition · residence time, · extent of atomization of liquid wastes, · dispersion of solid wastes, · fluctuations in the waste stream compos lion and heating value, · combustion aerodynamics, and · turbulent mixing rates.
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From page 122... ...
Accordingly, such reactions as the biological reduction of a heavy metal ion can be carried out at relatively fast rates, although at millimolar concentrations. There are significant research opportunities for chemical engineers in the design and opti TABLE 7.2 Examples of Biodegradation for Waste Management Industry Effluent Stream Major Contaminants Removed by Biodegradation Ammonia, sulfides, cyanides, phenols Sludges containing hydrocarbons Phenols, halogenated hydrocarbons, polymers, tars, cyanide, sulfated hydrocarbons, ammonium compounds Alcohols, ketones, benzene, xylene, toluene, organic residues Phenols, organic sulfur compounds, oils, lignins, cellulose Dyes, surfactants, solvents Steel Petroleum refining Organic chemical manufacture Pharmaceutical manufacture Pulp and paper Textile Coke-oven gas scrubbing operation Primary distillation process Intermediate organic chemicals and by-products Recovery and purification solvent streams Washing operations Wash waters, deep discharges SOURCE: Office of Technology Assessment:.~4
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From page 123... ...
Separation Processes A large fraction of the hazardous waste generated in industry is in the form of dilute aqueous solutions. The special challenges of separation in highly dilute solutions may be met by the development of new, possibly liquid-filled, membranes; by processes involving selective concentration of toxic chemicals on the surfaces of particles; or by the use of reversed micelles.
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From page 124... ...
The high charge-to-surface ratio of the valuable heavy metal ions suggests that they too should be extractable from dilute aqueous solutions. The potential of reversed micelles needs to be evaluated by theoretical analysis of the metal ion distribution within micelles, by evaluation of the free energy of the solvated ions in the reversed micelle organic solution and the bulk aqueous water, and by the experimental char acterization of reversed micelles by small-angle neutron and x-ray scattering.
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From page 125... ...
The Atmospheric Environment Over the last two decades, significant progress has been made in understanding the mechanisms of transport and transformation of pollutants in the atmosphere. Mathematical models have been developed to describe the spatial and temporal distributions of sulfur dioxide, carbon monoxide, nitrogen oxides, hydrocarbons, and ozone.
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From page 126... ...
Chemical engineers can assist in developing such systems, including · home heating and cooking burners that minimize the generation of oxides of nitrogen; ~ improved heat transfer devices that will allow for air exchange with the outside environment while avoiding excessive loss of heat; and ~ resins, binders, coatings, and glues for building materials that do not emit hazardous compounds, such as formaldehyde. Finally, there is a need for simple instrumentation that can be used to quantify occupant exposure to air pollution.
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From page 127... ...
Gaseous and particulate contaminants frequently found in indoor air pollution affect different parts of the respiratory system. Some, such as carbon monoxide and nitrogen dioxide, move from the lungs into the bloodstream.
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From page 128... ...
Chemical engineers have been at the forefront in using advanced mathematical tools and instrumentation to characterize the size and extent of petroleum reservoirs. This technology should be transferred to the groundwater problem and, in particular, to the task of designing cost-effective sampling strategies.
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From page 129... ...
'| ll'Current laws and programs fo 1111lllIlllllcus on the removal of pollutants from the medium-air, water, or land in which they are found, often with little regard for chem ical management of the environ ment as a whole. Because mod ern analytical techniques have revealed trace amounts of many toxic chemicals throughout the environment, however, the me dium-specific approach to pol lution control is now questiona ble.15 The diverse effects of acid rain and of leachates from haz ardous waste sites illustrate the mobility of chemicals in the en vironment ([Figure 7.19~.
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From page 130... ...
Chemical engineers have the theoretical tools to make important contributions to modeling the trans port and transformation of chemical species in the body from the entry of species into the body to their action at the ultimate site where they exert their toxic effect. Chemical engineers are also more likely than life scientists to ap
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From page 131... ...
While the techniques and governing rules for risk assessment are generally straightforward, much creative work needs to be done before the methodology can be used efficiently and effectively to anticipate and correct safety problems or to analyze operating abnormalities for precursors of danger. New techniques employing expert systems for analysis of complex chemical processes can be used to anticipate safety problems associated with various design decisions.
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From page 132... ...
IMPLICATIONS OF RESEARCH FRONTIERS This chapter has made clear the challenges to chemical engineers in research related to environmental protection, process safety, and hazardous waste management. Chemical engineering education must become strongly oriented to these topics, as well.
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From page 133... ...
Because of the critical importance of maintaining our environmental quality and improving process safety and hazardous waste management, the committee recommends that these federal agencies undertake new initiatives in chemical engineering research. The details of proposed initiatives for EPA and NSF are spelled out in more detail in Chapter 10 and Appendix A of this report.
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From page 134... ...
Simpler, Cheaper Plants or Wealth and Safety at Work Notes on Inherently Safer and Simpler Plants. London: Institution of Chemical Engineers, 1984.
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