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The detail of this research can be found
in;
Master Thesis titiled "Development of the
Environmental Fate and Risk Assessment Tool (EFRAT) and Application to
Solvent Recovery from a Gaseous Waste Stream", Michigan Technological University,
Houghton, MI, August 1998.
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Paper published in the Environmental Science
and Technology (Journal) titled "Comparative Environemtnal Assessments
of VOC Recovery and Recycle Design Alternative for a Gaseous Waste Stream.",
Vol. 34, No. 24, 2000, pp.5222-5228.
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The waste generated from the chemical and allied
products industries have significant negative impacts on human and biotic
health, severely degrade the quality of the air, water, and soil in the
environment, and costs billions of dollars each year to manage, treat,
and dispose. The aim of process design for pollution prevention is to create
chemical processes which reduce the generation of waste, and its hazardous
characteristics at the source (i.e. within the process). Modern chemical
process designs utilize commercial process simulators or other process
models to improve energy and mass efficiency, and account for environmental
impacts at the source of waste generation and at all levels of the product's
life cycle.
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In this research, a new methodology and software
was developed and applied to environmental assessment of chemical process
designs. The Environmental Fate and Risk Assessment Tool (EFRAT) is able
to evaluate chemical processes in terms of human health effects (carcinogenic
and non-carcinogenic effects on both ingestion and inhalation routes),
toxic effects to biota (fish toxicity) and damage to environmental systems
(global warming, ozone depletion, smog formation and acid rain). Using
the software, the process designer computes environmental partitioning,
relative risk indexes and emission rates for each process pollutant with
input from process simulator results (chemicals used, equipment type and
throughput). EFRAT has been developed in conjunction with other software
tools developed in the Department of Chemical Engineering and the Department
of Environmental Engineering at MTU which evaluate economic and safety
aspects of chemical process designs, and a tool which performs process
rankings based on multicriteria assessments.
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The EFRAT software was used to evaluate a case
study involving solvent recovery from a gaseous waste stream (0.5 vol.
% of VOCs) containing toluene and ethyl acetate (50/50-wt. % each). This
case study involved absorption and adsorption technologies where the environmental
impacts from these processes were quantified using the EFRAT software and
then compared. In addition to that, EFRAT was used in "Environmental Optimization
of Chemical Processes", to find the minimum environmental impacts by varying
designs/operating conditions. Different absorption oil flow rates (10 to
800 kgmole/hr) were used to demonstrate this capability. Process composite
indexes (average, local, regional, and global process composite indexes)
were used to determine the optimum operating flow rate with different weightings
on all the 9 normalized relative risk indexes. When the regional or global
scale impacts are the priority, the absorption oil flow rate should be
approximately 50 kgmole/hr (56.9 gpm) to reach the minimum impacts. At
flow rate of 300 kgmole/hr, the local scale impacts will be minimized while
at 200 kgmole/hr, the average process composite index will reach its minimum.
A general methodology/software was developed
for the multi-criteria environmental impacts assessment for chemical process
designs. This software has demonstrated its ability to prioritize different
technologies, configurations, and operating conditions in terms of environmental
impacts in the solvent recovery case study. In the future, more case studies
should be evaluated using the EFRAT methodology/software, including all
of the life cycle stages of goods/chemicals.
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