Group 37 Take Home Quiz

8/10/2019 Group 37 Take Home Quiz

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School of Chemical and Biomedical Engineering

Division of Chemical and Biomolecular Engineering Plant Safety Take Home Quiz

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Nanyang Technological University

SCHOOL OF CHEMICAL AND BIOMEDICAL ENGINEERING

Division of Chemical & Biomolecular Engineering

CH 4101 Chemical, Biological and Plant Safety

Take Home Quiz

Name: : Amanda Oh U1120828

Goh Jun Xian U1121414A

Lim Jun Jie U1121458C

Liu Jia Wei U1121611C

Ng Yi Jun U1122180G

Group: 37


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(a)Calculate the mass discharge rate of ETO for the following release incidents:

(i) The pipeline is sheared off completely very close to T501

Assumptions:

Pipeline is sheared off at orifice

Orifice is well-rounded, hence C0= 1

Temperature and vapour does not change when passing through orifice

Pipeline is at ground level

Raw Data:

Ratio of heat capacities,

at 566 R

Conversion factor, gc= 32.174 lbm-ft/lbf-sec2

Ideal gas constant, Rg = 1545 ft lbf R-1

lb-mol-1

Molar mass of ETO, M = 44.05 lb/lb-mol

Upstream temperature, T0= 566 R

Upstream pressure, P0= 20 psia

Ambient pressure, P = 14.7 psia

Calculation:

To determine whether flow through the orifice is choked or not, we use equation 4-49

Hence flow is not choked.


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We then use equation 4-48 to calculate the mass discharge rate of ETO for a non-choked

pipe:

(ii) The pipeline is sheared off completely at the position of valve V503 while C502 is

operating.

Assumptions:

Since the fluid path length through the release is greater than 10 cm(through a pipe),

equilibrium flashing conditions are achieved and the flow is choked.

Pressure of liquid (200psia) is greater than the saturation vapor pressure(25psia).

At T501: At C502 discharge:

To determine whether flow through the orifice is choked or not, we use equation 4-49


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Hence flow is choked.

At C502 discharge, the density and viscosity are obtained from the graphs provided

(b)For the larger of the two discharge rates in part (a) and a 1-hour incident time, what is

the maximum downwind distance from the release point at which a potential life-

threatening hazardous condition could exist at ground level for wind-weather

conditions corresponding to 1.5m/s and stability class F?

Assumptions:

Pipe is at ground level, z = 0

Wind is one-directional, y = 0

Continuous release of material from pipe, hence gas release is in plume form

Assume heat of vapourisation does not change over the temperature range

Raw data:

Wind speed, u = 1.5 m/s

Depressurized boiling temperature, Tb= 283.8 K

Upstream temperature, T0= 358.9 K

Standard molar heat capacity of ETO, Cp = 48.19 J/(mol.K)

Heat of vapourisation, Hv= 23671.13 J/mol


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Pasquill-Gifford stability

classy(m) z(m)

Rural conditions

F 0.04x(1 + 0.0001x)

-1/2

0.016x(1 + 0.0003x)

-1

Urban Conditions

E-F 0.11x(1 + 0.0004x)-1/2

0.08x(1 + 0.0015x)-1/2

Table 1. Values of Sigma at different conditions

To determine the life-threatening hazardous concentration, we refer to the emergency

response planning guidelines (ERPG).

Classification of ERPG:

ERPG-1 is the maximum airborne concentration below which it is believed nearly allindividuals could be exposed for up to 1 hr without experiencing effects other than

mild transient adverse health effects or perceiving a clearly defined objectionable

odor.

ERPG-2 is the maximum airborne concentration below which it is believed nearly all

individuals could be exposed for up to 1 hr without experiencing or developing

irreversible or other serious health effects or symptoms that could impair their

abilities to take protective action.

ERPG-3 is the maximum airborne concentration below which it is believed nearly allindividuals could be exposed for up to 1 hr without experiencing or developing life-

threatening health effects

Chemical ERPG-1 ERPG-2 ERPG-3

Ethylene oxide NA 50 ppm 500 ppm

Table 2. Different ERPG values of ethylene oxide

We determine ERPG-3 to be the life-threatening hazardous condition and hence the

concentration is 500 ppm.

Concentration, = 500 ppm = 915 mg/m3

Amount of liquid vapourised,


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We use equation 5-48 to calculate for plume with continuous steady-state source at ground

level and wind moving in x direction at constant velocity u.

For rural condition,

Using excel solver, x = 11.02 km for rural conditions.

For urban condition,

Using excel solver, x = 1.927 km for urban conditions.

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Group 37 Take Home Quiz