Since the late 1970s, the number of design projects focusing on the solution of environmental problems has increased significantly. These, in turn, are closely related to environ- mental regulations, which have become increasingly strict. Although it is beyond the scope of this book to provide a comprehensive treatment of the many kinds of designs that have been completed, it is important that the reader gain a brief introduction to typical design problems. This is accom- plished through the design projects listed in Table 1.1. As can be seen, a large fraction of the design projects are concerned with air quality; others involve water treatment; two involve soil treatment; one involves the conversion of waste fuel to chemicals; one proposes the use of a biochemical conversion to consume solid waste and produce ethanol fuel; and several involve the production of fuels and chemicals from renew- able resources. The problem statements for these design projects, as they were presented to student groups, are reproduced in the file, Supplement_to_Appendix_II.pdf, in the PDF Files folder, which can be downloaded from the Wiley Web site associated with this book. Keep in mind that, as the designs proceeded, the design teams often upgraded the information provided, and in some cases created varia- tions that were not anticipated by the originator of the problem statement.
A closer look at Table 1.1 shows that the projects address many aspects of air-quality control. Two alternative approaches to sulfur removal from fuels are proposed, one involving desulfurization of the fuel, the other the recovery of sulfur from its combustion products. One is concerned with NOx removal from combustion products, and three
involve the recovery of hydrocarbons from effluent gases. One explores the interesting possibility of growing algae by the photosynthesis of CO2 from combustion gases as a
vehicle for reducing the rate at which CO2 is introduced
into the atmosphere. Under water treatment, the projects involve the recovery of organic and inorganic chemicals from aqueous waste streams. Two alternative approaches to soil treatment are proposed, including the use of phytoremedia- tion; that is, using plants to absorb lead and other heavy metals. All of the projects involve chemical reactions, and consequently, the design teams are comprised of chemical engineers, chemists, and biochemists. In this respect, it seems clear that chemistry and biology are the key ingredients that qualify chemical engineers to tackle these more challenging environmental problems.
1.5
SAFETY CONSIDERATIONS
A principal objective in the design and operation of chemical processes is to maintain safe conditions for operating personnel and inhabitants who live in the vicinity of the plants. Unfortu- nately, the importance of meeting this objective is driven home periodically by accidents, especially accidents in which lives are lost and extensive damage occurs. To avoid this, all companies have extensive safety policies and procedures to administer them. In recent years, these have been augmented through cooperative efforts coordinated by technical societies, for example, the Center for Chemical Plant Safety of the American Institute of Chemical Engineers, which was formed in 1985, shortly after the accident in Bhopal, India, on December 3, 1984. In this accident, which took place in a plant partially
owned by Union Carbide and partially owned locally, water (or some other substance—the cause is still uncertain) accidentally flowed into a tank in which the highly reactive intermediate, methyl iso- cyanate (MIC) was stored, leading to a rapid
increase in temperature accompanied by boiling, which caused toxic MIC vapors to escape from the tank. The vapors passed through a pressure-relief system and into a scrubber and flare system that had been installed to consume the MIC in the event of an accidental release. Unfortunately, these systems were not operating, and approximately 25 tons of toxic MIC vapor were released, causing a dense vapor cloud that escaped and drifted over the surrounding community, killing more than 3,800 civilians and seriously injuring an estimated 30,000 more.
Table 1.1 Environmental Design Projects
Project Location in Booky
Environmental—Air Quality
R134a Refrigerant (2001) App. IIS—Design Problem A-IIS.9.1
Biocatalytic Desulfurization of Diesel Oil (1994) App. IIS—Design Problem A-IIS.9.2
Sulfur Recovery Using Oxygen-Enriched Air (1993) App. IIS—Design Problem A-IIS.9.3
California Smog Control (1995) App. IIS—Design Problem A-IIS.9.4
Zero Emissions (1991) App. IIS—Design Problem A-IIS.9.5
Volatile Organic Compound Abatement (1994) App. IIS—Design Problem A-IIS.9.6
Recovery and Purification of HFC by Distillation (1997) App. IIS—Design Problem A-IIS.9.7
Carbon Dioxide Fixation by Microalgae for Mitigating the Greenhouse Effect (1993)
App. IIS—Design Problem A-IIS.9.8
Hydrogen Generation for Reformulated Gasoline (1994) App. IIS—Design Problem A-IIS.9.9
R125 Refrigerant Manufacture (2004) App. IIS—Design Problem A-IIS.9.10
Zero-Emissions Solar Power Plant (2008) App. IIS—Design Problem A-IIS.9.11
Removing CO2from Stack Gas and Sequestration Technologies (2008) App. IIS—Design Problem A-IIS.9.12
Environmental–Water Treatment
Effluent Remediation from Wafer Fabrication (1993) App. IIS—Design Problem A-IIS.10.1
Recovery of Germanium from Optical Fiber Manufacturing Effluents (1991) App. IIS—Design Problem A-IIS.10.2
Solvent Waste Recovery (1997) App. IIS—Design Problem A-IIS.10.3
Environmental–Soil Treatment
Phytoremediation of Lead-Contaminated Sites (1995) App. IIS—Design Problem A-IIS.11.1
Soil Remediation and Reclamation (1993) App. IIS—Design Problem A-IIS.11.2
Environmental–Renewable Fuels and Chemicals
Fuel Processor for 5 KW PEM Fuel Cell Unit (2002) App. IIS—Design Problem A-IIS.12.1
Production of Low-Sulfur Diesel Fuel (2000) App. IIS—Design Problem A-IIS.12.2
Waste Fuel Upgrading to Acetone and Isopropanol (1997) App. IIS—Design Problem A-IIS.12.3
Conversion of Cheese Whey (Solid Waste) to Lactic Acid (1993) App. IIS—Design Problem A-IIS.12.4
Ethanol for Gasoline from Corn Syrup (1990) App. IIS—Design Problem A-IIS.12.5
Furfural and Methyl-tetrahydrofuran-based Biorefinery (2008) App. IIS—Design Problem A-IIS.12.6
Furfural and THF in China – Corn to Clothes (2008) App. IIS—Design Problem A-IIS.12.7
Diethyl Succinate Manufacture within a Biorefinery (2008) App. IIS—Design Problem A-IIS.12.8
1-3 Propanediol from Corn Syrup (2008) App. IIS—Design Problem A-IIS.12.9
Biobutanol as Fuel (2008) App. IIS—Design Problem A-IIS.12.10
Green Diesel Fuel – A Biofuel Process (2008) App. IIS—Design Problem A-IIS.12.11
Environmental–Miscellaneous
Combined Cycle Power Generation (2001) App. IIS—Design Problem A-IIS.13.1
ww w .w ile y.com/colle g e / se id er 1.5 Safety Considerations 21
Like Section 1.4 on environmental issues, this section begins with a review of two safety issues that are considered by many design teams, followed by an introduction to many of the design approaches for dealing with these issues. For more comprehensive coverage of these areas, the reader is referred to Chemical Process Safety: Fundamentals with Applications (Crowl and Louvar, 1990); Plant Design for Safety—A User- Friendly Approach (Kletz, 1991); a collection of student problems, Safety, Health, and Loss Prevention in Chemical Processes: Problems for Undergraduate Engineering Curricula—Student Problems (American Institute of Chem- ical Engineers, 1990); and Guidelines for Engineering Design for Process Safety, CCPS, AIChE (1993).
The U.S. Chemical Safety and Hazard Investigation Board (CSB), established by the Clean Air Act Amendments of 1990, is an independent federal agency with the mission of ensuring the safety of workers and the public by preventing or minimizing the effects of chemical incidents. They attempt to determine the root and contributing causes of chemical accidents. Their Web site at http://www.csb.gov is a very useful source of brief and detailed accident reports.