Production of Nitric AcidProduction of Nitric AcidEnvironmental Impact Environmental Impact

AssessmentAssessment

Erik Tolonen Nick Poulin

Environmental Engineering

Environmental Planning and Decision Making

ENVE4104

Contents

Introduction

Risk Assessment

Fault Tree

Event Tree

IntroductionChemicals of Interest

• Ammonia (NH3)

• Nitric Acid (HNO3)

• Nitric Oxide (NO)

• Nitrogen Dioxide (NO2)

• Nitrous Oxide (N2O)Ammonia was determined to be the most hazardous chemical present in the process

Hazard Identification

All chemicals are non-carcinogenic

Chemical RfC Toxicity Score

Ammonia 0.3 ppm (IRIS) 0.00027

Nitric Acid n/a n/a

Nitric Oxide n/a n/a

Nitrogen Dioxide 0.037 mg/m3 (NAAQS) n/a

Nitrous Oxide n/a n/a

Human Health Effects• Causes irritation of the eyes, skin and respiratory system• No Observed Adverse Effect Level (NOAEL) – 6.4 mg/m3

• Lowest Observed Adverse Effect Level (LOAEL) – 17.4 mg/m3

– Respiratory lesions increase the severity of pneumonia and rhinitis

Environmental Effects• Impact on certain types of plants and trees (reduced ability to retain

water)

Hazard IdentificationNH3

Ammonia is considered to be toxic by the Canadian Environmental Protection Act

Exposure Assessment

Nitric Acid Plant

Wind

Rain

Groundwater

Ingestion,AbsorptionInhalation

NH3

Release of Ammonia

Air River Ground Water

Advection/Dispersion Advection Advection/Dispersion

Inhalation Ingestion, Absorption

Transport Media

Transport Mechanism

Exposure Mechanism

Adults/Children Adults/Children Population at Risk

Ingestion, Absorption

Adults

Air Transport Model:

Assumptions:

- Transport by advection and dispersion only

- Ammonia is released from a 20 m height stack with a 10 m plumb rise

- Wind direction is directly towards the city (Worst Case Scenario)

- No density or buoyancy effects

Gaussian Model Parameters:

- Atmosphere Stability Class D

- Rate of Emission: 0.062 kg/s (223.2 kg/hr) over 30 hours

- Total Amount of Ammonia Released: 6696 kg

- Inhalation Reference Exposure Level: 0.3 ppm

25

20

0

37

5

55

0

72

5

90

0

10

75

12

50

14

25

16

00

17

75

19

50

21

25

S1 S

9 S1

7 S2

5 S3

3 S4

1 S4

9 S5

7

S6

5S

73

S8

1

0.00E+00

1.00E-05

2.00E-05

3.00E-05

4.00E-05

5.00E-05

6.00E-05

7.00E-05

8.00E-05

Concentration: (ppm)

Distance x: (m)Distance y: (m)

Air Dispersion Model7.00E-05-8.00E-05

6.00E-05-7.00E-05

5.00E-05-6.00E-05

4.00E-05-5.00E-05

3.00E-05-4.00E-05

2.00E-05-3.00E-05

1.00E-05-2.00E-05

0.00E+00-1.00E-05

25

12

5

22

5

32

5

42

5

52

5

62

5

72

5

82

5

92

5

10

25

11

25

12

25

13

25

14

25

15

25

16

25

17

25

18

25

19

25

20

25

21

25

22

25

S1

S5

S9

S13

S17

S21

S25

S29

S33

S37

S41

S45

S49

S53

S57

S61

S65

S69

S73

S77

S81

0.00

0.00

0.00

0.00

0.00

Concentration: (ppm)

Distance x: (m)

Distance y: (m)

Air Dispersion Model

6.00E-05-8.00E-05

4.00E-05-6.00E-05

2.00E-05-4.00E-05

0.00E+00-2.00E-05

City

Air Transport Model:

Results:

- Ammonia levels in the city will reach 0.3 ppm when emission rate reaches 80311.7 kg/s (80.3 tonnes/s).

- Amount required is much greater then current release at plant

Water/Ground Water Transport Model:

Assumptions:

-Transport by advection only

-Thoroughly mixed with river water

-No retardation or attenuation present in soil

Advection:

-Flow time to reach city: 84.3 yrs

-Flow time to reach river: 28.2 yrs

Solubility:- 42.8 wt % at 0 OC

- Amount of Ammonia entering groundwater insignificant

Intake DoseI = [CxCRxEFxED]/[BWxAT]

C = Conc. at exposure point = 0.00008 ppm (0.00011mg/m3)

CR = Contact Rate = 289.5 m3/hr = 6947 m3/dayEF = Exposure Frequency = 1.25 days/yearED = Exposure Duration = 30 hrs = 0.003 yearBW = Body Weight = 70 kgAT = 1.25 days

I = 0.00003 mg/kg-day

Exposure Assessment

Toxicity Assessment

Case Studies(1) Soda Ash Facility Workers Exposed to Ammonia

• No Observed Adverse Effect Level (NOAEL) – 9.2 ppm (6.4 mg/m3)

(2) 344 Rats Exposed to Ammonia

• Lowest Observed Adverse Effect Level (LOAEL) – 17.4 mg/m3

Risk Characterization

Hazard Index for AmmoniaHI = CDI/RfC

CDI = chronic daily intake =

RfC = reference dose = 0.3 ppm

Fault TreeRelease of Ammonia

to Environment

AND

Faulty equipment

OR

Excessive concentration of NH3

in process

OR

Broken pipesLoose pipe connections

Insufficient oxidation of ammonia

Excess ammonia inputted into system by plant operators

OR OR

Insufficient air supplied to ammonia converter

Improper operating temperature or pressure

OR

Miscalculation of required ammonia

Improperly calibrated measuring instruments

Improper upkeep or maintenance by plant operators

OR

Loose connection at ammonia input port

Improper upkeep or maintenance by plant operators

Excess pressure within pipes

Event Tree

Source Transport Media Transfer Mech Exposure Mech Receptors Exposure Route

Nitric Acid Production Process

Air-Critical

Water

Soil

Washout by rain

Volatilization

Uptake by plants

Ambient air

Drinking water wells

Consumption of food

Anyone breathing the air

Users of well water

Humans, animals that eat the plants

Inhalation

Ingestion,Absorption

Ingestion

Conclusions

Conclusions