Transitions - Sustainable Design: The Science of Sustainability and Green Engineering - page 108

Scrubber and flare

N 2 gas N 2 gas

Coolant out Coolant out

Normal
vent

Normal
vent

Cooler Cooler

Pressure
release
device

Pressure
release
device

Coolant in Coolant in

Circulation Circulation

To auxiliary tank To auxiliary tank

2 pressure
monitors

2 pressure
monitors

Performance Performance

Monitor

To process
distribution

To process
distribution

monitor

Temperature
monitor

Performance
Monitor

Performance
monitor

Ground surface Ground surface

Cycle pump

Feed pump

2 tank
inventory
monitors

2 tank
inventory
monitors

Pressure
Monitor

Pressure
monitor

Normal vent Normal vent

N 2 gas N 2 gas

Pressure
release
device

Pressure
release
device

Pressure
release
device

Pressure
release
device

Emergency vent Emergency vent

Unit
product

Unit
product

Sevin Sevin

3 storage tanks 3 storage tanks

Methyl
carbamates

Methyl
carbamates

3 MIC unit tanks 3 MIC unit tanks

Scrubber Scrubber

(See cutaway detail) (See cutaway detail)

N 2 gas N 2 gas

Normal vent Normal vent

Normal vent Normal vent

N 2 gas N 2 gas

Pressure
release
device

Pressure
release
device

Pressure
release
device

Pressure
release
device

Flare Flare

Emergency
vent

Emergency
vent

Emergency
vent

Emergency
vent

Flare Flare

Scrubbers Scrubbers

Scrubber Scrubber

Methomyl unit tank Methomyl unit tank 2 distribution tanks 2 distribution tanks

Figure 3.5 Methyl isocyanate
processes at the Bhopal, India,
plant circa 1984.
Adapted from W. Worthy, 1985,
“Methyl isocyanate: the chemistry of a
hazard,” Chemical Engineering News ,
63(66), 29.

was highly cost-effective, involving only a single reaction step. A schematic of the
MIC process in shown in Figure 3.5. MIC is highly water reactive (see Table 3.1);
that is, it reacts violently with water, generating a very strong exothermic reaction
that produces carbon dioxide. When MIC vaporizes, it becomes a highly toxic
gas that, when concentrated, is highly caustic and burns tissues. This can lead to
scalding nasal and throat passages, blinding, and loss of limbs, as well as death.
An important point can be made about the information in Table 3.1. The
safety limits are based on workplace and workday scenarios (i.e., 8-hr days and
40-hr weeks). This is different, yet informative for residential building design.
For example, contaminant levels should be even more protective for residential
structure's indoor occupants, since they will be potentially exposed for larger
times (sometimes 24 hours per day for an entire lifetime).