submarines atmosphere control and air treatment

Submarines’ Atmosphere Control and Air Treatment

Mohammed Dayraki104357965

Underwater Intervention Systems06-88-590-38/92-590-64 F15

Instructor:Dr. Graham Reader

Leading Teaching Assistants:Marko JefticKelvin Xie

Department of Electrical Engineering, Faculty of EngineeringUniversity of Windsor

401 Sunset Avenue, Windsor, ON N9B 3P4

SUBMARINES’ ATMOSPHERE CONTROL AND AIR TREATMENT

Abstract

This project looks at Submarines’ Atmosphere Control and Air Treatment. Its goal is to

focus on the systems used in underwater vehicles to supply oxygen, remove carbon

dioxide, and to purify the atmosphere in the vehicle. It also includes emergency air

systems in case of accidents. The project gives a general view about the need of

oxygen for a human and the statistics of oxygen level in a human and in seawater. One

the 2 types of equations used in the paper shows how the studies where done and the

other type shows how every system work. The best climate a crewman should be in so

there’s no psychological or physical effects is highlighted in the paper and a general

view about the USS Pennsylvania Submarine is used. As a conclusion, food resupply is

the only thing preventing a submarine from staying forever underwater.

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List of Contents

ABSTRACT……………………………………………………………………………..……….2

INTRODUCTION………………………………………………………………......……………4

AIM…………………………………………………………………………………….………….5

THE NEED OF OXYGEN……………………………………………………………...……….6

OXYGEN BLOOD LEVELS…………………………………………………………….………6

CONCENTRATION OF OXYGEN IN SEAWATER…………………………….……………6

DETERMINATION OF HENRY COEFFICIENT……………………………………..………7

CARBON DIOXIDE LEVELS IN THE AIR……………………………………………………9

CLIMATE OF THE ATMOSPHERE ………………………………………..…………………9

USS PENNSYLVANIA SUBMARINE…………………………………………………………9

ATMOSPHERE CONTROL AND AIR TREATMENT SYSTEMS…………………...……10

OXYGEN SUPPLY SYSTEMS……………………………………………………….………10

CARBON DIOXIDE REMOVAL………………………………………………………………12

AIR PURIFICATION………………………………………………………………...…………13

EMERGENCY AIR………………………………………………………………….…………14

HOW LONG CAN A SUBMARINE STAY UNDERWATER? …………………….………15

CONCLUSION…………………………………………………………………………………15

APPENDIX A…………………………………………………………………….…..…………16

APPENDIX B………………………………………………………………………...…………17

LIST OF REFERNCES…………………………………………………….….………………18

LIST OF DEFINITIONS, SYMBOLS AND ABBREVIATION………………………………19

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Introduction

Submarines’ Atmosphere Control and Air Treatment goes deep into a submarine’s air

control systems which include electrochemical oxygen generators, solid polymer oxygen

generators, oxygen candle furnace, LiOH absorbers, CO2 scrubbers, CO−H2 burners,

activated carbon, emergency air breathing systems, oxygen breathing apparatus, and

Scott air packs. This paper explains how a submarine can stay underwater for 20 years

theoretically and 90 days in reality. The report reviews studies in human’s oxygen need,

seawater oxygen level, and chemical reactions and combines them so that submarines’

climate will be similar to the normal climate on land.

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Aim

The purpose of the project is to highlight the systems used in a submarine to supply O2

to the crew and remove the CO2 from the air inside.

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The Need of Oxygen:

A human’s body uses many ways to extract energy from the surroundings so it can

survive. A major way is food which is is used as raw materials to make and heal body

cells. Another way is oxygen where our body use it to enrich all the organs a human

has. Upon inhaling, our lungs are filled up with air and alveoli absorb the oxygen into

our bloodstream. Hemoglobin then picks the oxygen to any organ in the body.

Cytochrome C then takes the oxygen molecules, mix them with water and, harvests the

released energy. The cell after that uses the energy for everyday function [1].

Oxygen Blood Levels:

The body of a human needs a very specific oxygen level in the blood. The normal

oxygen saturation in humans are considered 95-100 percent. Mayo clinic [2] defines

that hypoxemia is a result of oxygen level below 90 percent. If oxygen blood level is

under 80 percent, some organs will start malfunctioning including the brain and the

heart and continued low oxygen levels may lead to failure in respiratory or cardiac

systems.

Concentration of Oxygen in Seawater:

To calculate the standard atmospheric concentrations (USAC) in seawater, the equation

of henry coefficient as a function of temperature and salinity is used at a total pressure

of 1 atmosphere.

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Determination of the Henry Coefficient:

In system of standard composition saturated with water vapor at total pressure P,

Henry’s Law is:

f o=ko , sno , d

nw+ns+no , d+nr ,d(1)

where f o(atm) and k o ,s(atm) are the vapor phase fugacity and the Henry coefficient for

oxygen, and no ,d, nw, ns, and nr ,dare the numbers of moles of dissolved oxygen, pure

water, sea salt, and the number of moles of all other gases especially nitrogen dissolved

in the volume V.

The concentration, by mass, of dissolved oxygen in mol . kg−1 is:

Cop≡

no , dpsV s

(2)

where Cop is the standard atmospheric concentration of dissolved oxygen and no ,d, ps,

and V s are the number of moles of dissolved oxygen, pressure of the system, and the

volume of it relatively.

t

( C❑o )

SP

(atm*)

k o ,0

(atm)

k o ,s

(atm)

%dev of

k o ,s ¿ fit

0.231 20.172 0.7754 25427 29332 0.054

0.228 31.634 0.7769 25425 31793 0.032

0.218 48.667 0.7842 25418 35806 -0.071

5.010 20.204 0.7950 28863 33097 0.069

5.023 31.703 0.7987 28873 35762 0.031

10.017 20.209 0.8131 32536 37095 0.091

10.029 31.639 0.8219 32545 49830 -0.186

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15.009 20.098 0.8408 36221 40977 -0.077

15.009 20.459 0.8399 36221 41155 0.134

15.011 31.750 0.8468 36222 44082 0.026

15.008 48.514 0.8546 36220 48917 0.085

25.038 20.089 0.9104 43488 48758 -0.056

25.033 31.894 0.9171 43484 52139 -0.07

29.993 31.894 0.9402 46922 55957 0.035

35.092 20.228 0.9710 50288 56054 0.016

35.081 31.856 0.9749 50287 59633 -0.026

35.006 49.478 0.9733 50239 65518 0.026

45.007 31.912 1.0464 56258 66167 0.075

Table.1: The variation of the Henry Coefficient k o ,0 for oxygen depending on the

variation of temperature, Salinity, and Pressure

18 samples were taken with variable temperatures, salinity, and pressure as shown in

table.1 to experience the difference of Oxygen concentration in the seawater. In the

experiment, “the salinity sample was taken after the vapor phase and liquid phase

samples had been isolated. The seawater used in these measurements was taken from

Buzzards Bay, off Massachusetts, filtered, and stored in the dark. The pH was

determined with a Corning model 10 meter and was constant within 8.2 ± 0.1” [3]. The

results for k o ,s from 18 experiments on seawater samples with salinities up to 50 and at

temperatures between 0 and 45 C❑o are in the table.

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Carbon Dioxide Levels in the Air:

“The air we breathe contains about about 0.03% of carbon dioxide (equivalent to a

partial pressure of about 30Pa) (Haux, 1981)” [4]. It will be hard to uphold such level in

an underwater vehicle. Once the CO2 reaches 4%, the atmosphere in the vehicle will be

lethal to humans. As a result, air treatment systems should maintain the carbon dioxide

level so the crew will stay have good mental and physical performance. For such

performance, a maximum partial pressure for carbon dioxide should be 1500Pa or 1.5%

CO2.

Climate of the Atmosphere:

The climate of a the vehicle is very important for which it define the physical and the

psychological stresses of the crew. In normal atmospheres, the temperature should be

between 18 and 22 C❑o . Humidity should stay between 50% and 65% for best

performance. The problem is that heat is generated by all the process equipment so air

conditioning systems should be applied in the submarine.

USS Pennsylvania Submarine:

“You can’t see her, she can dive over 250 meters and stay down for 6 months. You

can’t hear her; she can run for 20 years without refueling. She is the most lethal weapon

ever designed.” [5] The USS Pennsylvania is an Ohio Class Submarine. It’s controlled

by a captain on deck and 165 men. The petrol that this submarine undergoes is about

72 days where the submarine stays underwater hiding. Once the hatch is closed, the

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crew are sealed inside the Pennsylvania for the time of their mission. To stay alive,

every man needs oxygen and food. To produce oxygen, the USS submarine uses

Electrolysis in a very big scale using Oxygen Generators type H.P Serial no. 2139.

Atmosphere Control and Air Treatment Systems:

Nowadays, all Navy submarines are equipped with oxygen supply systems to maintain

proper atmospheric conditions and to remove contaminants. Controlling the source of

the materials is the most effective way of reducing and eliminating toxic contaminant.

Oxygen Supply Systems:

By using electrolysis oxygen generators (EDGs), stored oxygen, or oxygen candle

furnaces, oxygen may be refilled in an underwater vehicle. Nuclear submarines in

general are equipped with EOG systems but carry other systems as back up. One

specialty about EOG is that it can supply oxygen forever while other are limited by

storage capacity.

-Electrochemical Oxygen Generator:

Through electrolysis of water, oxygen is produced. By passing direct current through a

KOH solution, the water is electrolyzed to H 2 and O2. Sixteen electrolytic cells at about

1000 amps are required to produce 120 SCFH of O2 which is sufficient for 120 men in

the submarine at a pressure up to 3000 psig. After that, gases are removed from all the

cells and O2is distributed while H 2 is discharged.

-Solid Polymer Oxygen Generator:

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These type of generators are advanced technology oxygen generator where they

provide safe and reliable oxygen production. By using Solid Polymer Electrolyte (SPE)

cell, the oxygen generating Plant (OGP) produces breathing oxygen through electrolysis

which requires no free acids or caustic liquids. The pros of OGP are:

- It eliminates caustic electrolyte (KOH) and asbestos which is used as an

insulator.

- It’s controlled by a Microprocessor and requires only 15 minutes to shutdown and

restart to full operation.

- It can be operated at low pressure that can be 500-600 psi once oxygen banks

are charged.

- It has reduced inventory of combustible gases such as hydrogen

- It has a maximum output of O2 which is 225 SCFH. This will permits providing the

entire crew with oxygen using only one OGP

- Produces pure oxygen products without any H 2contamination

-Oxygen Candle Furnace:

The chlorate candle is a mixture of sodium chlorate, iron, a small amount of barium

peroxide, and a fibrous binding material. Burning the “Candle” is the basic process

where decomposition of the chlorate is applied:

NaClO3(s)+Fe( s )→NaCl(s)+O2 (g)+Fe( x )O( y)(s) (3)

Iron is combined with some oxygen and produces heat to support the reaction. To

remove unwanted chlorine products, barium peroxide is added:

BaO2 ( x )+Cl2(g )→BaCl2( s )+O2 (g) (4)

2BaO2 (x)+4 HOCl2 ( g)→2 BaCl2(s )+3O2 (g)+2H 2O(l ) (5)

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Each candle burns about 400 F for 45- 60 minutes, and yields 115 of O2 at 0.5 psig. By

filtration, smoke and salt are also produced.

Carbon Dioxide Removal:

CO2 is removed from the submarine by regenerative or non regenerative classes

depending on if the absorbent can be recycled at sea.

-LiOH Absorbers:

It’s one of the non regenerative means to remove Carbon Dioxide from the gas torrent

that will pass through containers holding the LiOH . Each 31.5 lb. container can absorb

29 lbs. of CO2 theoretically where it operates below 2% at 1 atm. total pressure and

requires no power even if it is sued with a fan when possible.

2 LiOH+CO2→Li2CO3+H2O (6)

-CO2 Scrubbers:

CO2 scrubbers are regenerative systems that use aqueous solutions of 25 – 30 wt. %

(4-5 M) monoethanolamine (MEA), NH2CH2CH2OH. Lewis acid-base reaction is the

process:

H−O−CH 2−NH2+O=O→H−O−CH 2−CH 2−NH−CO−OH (7)

Equation (7) will be stopped by heat or by low pressure atmosphere. Air treated should

enter the exchange tower at 80°F and 75% relative humidity CO2 (RH). It’s driven

through woven stainless steel which the MEA solution is flowing. At this phase, 70 to

90% of the Carbon Dioxide is removed. After that, the air is filtered to entrap droplets of

the MEA solution and then it’s returned to the submarine at about 75°F and 100%.

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Stainless steel screens are used to recycle the MEA solution. The material is passed

through a column packed with glass rings and is heated to drive off the carbon dioxide

under pressure. When the solution is clean, it’s returned to the absorption cycle and the

CO2 is cooled and thrown overboard.

Carry-over of MEA and ammonia are problems in this systems. They are created when

the MEA slowly breaks down during the stripping phase to the submarine’s atmosphere

with the cleaned air. The decomposition of MEA is also catalyzed by the presence of

metal ions so chelating agents are added to limit this degradation. Materials escapes

into the submarine even after filtering.

Air Purification:

CO−H2 Burner:

Burners are used to oxidize CO, H2, and hydrocarbons into to CO2 and H2O. It’s done

by drawing preheated air through CuO/MnO2 catalyst bed at about 600° F. When these

gases cool down, they are passed through a layer of Li2CO3 so acidic gases like HCI

will be eliminated. The last stage is done when air is passed through activated charcoal,

a simple absorber. Charcoal can be used forever and it does not need additional fuel

once it has reached operating temperature.

Activated Carbon:

To prepare charcoal, you can use any carbonaceous material and it can be activated by

the use of controlled heating. Through heating the capillaries, which can’t be

carbonized, are removed. When the charcoal is activated, increase in the vapor

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adsorption is noticed. In submarines, the activated coconut shell charcoal is referred to

as activated carbon. Removing contaminant gases is a difficult phenomenon involving

capillary attraction and adsorption. Activated carbon is basically used for odor removal

in washroom, water closet, sand sanitary tanks.

Emergency Air:

Emergency Air Breathing (EAB) System:

The EAB system is used in case of fire with development of smoke, CO, CO2, or in

case of toxic component detection. This system provides full-face masks for each crew

member into the ship’s clean, high pressure air banks and hoses and pressure

reduction gear are part of the EAB system.

Oxygen Breathing Apparatus (OBA):

It’s a self-contained unit that is worn by each person and can generate to 60 minutes

supply of oxygen and removes exhaled carbon dioxide. It functions by decomposing

potassium superoxide KO2.

4 KO2 (s)+2H 2O(g)→KOH (s)+3O2(g ) (8)

Equation (8) is initiated by water vapor exhaled by the wearer of the system. KOH

produced will interact by K2O and removes the CO2 from the air as Eq. (9) shows.

CO2(g)+2KOH (g)→K 2CO3(g)+H 2O( g) (9)

Rebreathing is allowed in this system since it uses only a fraction of Oxygen.

SCBA – Scott Air Packs:

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Scott Air Packs are the same system used for SCUBA but it’s created for the air

environment. It’s rechargeable, portable, and it’s used sometimes as a replacement for

OBAs.

How long can a Submarine stay Underwater?

Nuclear- powered submarines stay underwater for long periods which can last for

several months and that’s because of the oxygen generating and atmosphere control

systems for breathing and nuclear power for the submarine itself. Food and supplies are

the only reasons for the submarine to come back to the base. A normal submarine

carries 90-day supply of food.

Conclusion

As a conclusion, Submarines and especially nuclear- powered ones are stealthy

monsters that have the ability to stay underwater forever if it wasn’t for the crew inside

it. “You can’t see her, she can dive over 250 meters and stay down for 6 months. You

can’t hear her; she can run for 20 years without refueling. She is the most lethal weapon

ever designed.” [5] One of the solutions for this problem is treating crewmen like

astronauts so they’ll have more space for more food supplies.

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Appendix A: Normal Amount of Substances in the Atmosphere

Substance 8-h weighted

Average Limit

(ppm)

Ceiling

concentration

Ammonia 50

Carbon Dioxide 5000

Carbon Monoxide 50

Freon-12 1000

Hydrogen Chloride 5

Hydrogen Fluoride 3

Mercury 0.1 mg/m3

Nitric Acid 25

Nitrogen Dioxide 5

Oil Mist 5 mg/m3

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Ozone 0.1

Phosgene 0.1

Stibene 0.1

Appendix B: Line Drawing of an Ohio Class in its original SSBN configuration

1-Sonar Dome

2- Main Ballast Tanks

3- Computer Room

4-Integrated Radio Room

5-Sonar Room

6-Command and Control Center

7-Navigation Center

8-Missle Control Center

9-Engine Room

10-Reactor Compartment

11-Auxillairy Machinery Room no.1

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12-Crew’s Berthing

13-Auxiliary Machinery Room no.2

14-Torpedo room

15-Wardroom

16-Chief Petty Quarters

17-Missle Compartment

List of References

[1] Why do we need to breathe oxygen? (1996, January 31). Retrieved November 26,

2015, from http://www.pa.msu.edu/sciencet/ask_st/013196.html

[2] Hypoxemia (low blood oxygen). (n.d.). Retrieved November 26, 2015, from

http://www.mayoclinic.org/symptoms/hypoxemia/basics/definition/sym-20050930

[3] Benson, B. B., & Krause Jr, D. (1984). The concentration and isotopic fractionation

of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere.

Limnology and oceanography, 29(3), 620-632.

[4] Ross, C. T. (2006). A conceptual design of an underwater vehicle. Ocean

Engineering, 33(16), 2087-2104

[5] Largest Dams, L. (2013, September 28). The largest submarine in the U.S. Navy

[Video file]. Retrieved from

https://www.youtube.com/watch?v=UxB11eAl-YE

[6] Massachusetts Institute of Technology. (September 12, 2001). Revision Paper about

Submarine Air Treatment. Retrieved from

http://web.mit.edu/12.000/www/m2005/a2/8/pdf1.pdf

[7] Herbich, J. B. (1998). Developments in Offshore Engineering: Wave Phenomena

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and Offshore Topics: Wave Phenomena and Offshore Topics. Chapter 10, Diving

and Underwater Life Support. Gulf Professional Publishing.

[8] List of Ohio-class submarines. (2015, November 25). In Wikipedia, The Free

Encyclopedia. Retrieved 21:57, November 26, 2015, from

https://en.wikipedia.org/w/index.php?title=List_of_Ohio-

class_submarines&oldid=692455881

[9] Powers, R. (n.d.). U.S. Navy Submarines Frequently Asked Questions. Retrieved

November 26, 2015, from http://usmilitary.about.com/od/navy/l/blsubfaq.htm

List of definitions, Symbols and Abbreviation

Alveoli: Alveoli are lungs sacs which allow oxygen and carbon dioxide to move between

the lungs and blood stream.

Hemoglobin: Hemoglobin is a protein molecule in red blood cells that carries oxygen

from the lungs to the body’s tissues and return carbon dioxide from the tissues back to

the lungs.

Cytochrome C: Cytochrome C is the electron transport chain in mitochondria.

Oxygen saturation: Oxygen saturation is the level of oxygen needed in a human blood

to be healthy

Hypoxemia: Hypoxemia is the abnormally low concentration of oxygen in the blood.

Vapor phase fugacity: Fugacity is the effective pressure which replaces the true

pressure in chemical calculations.

Corning model: Coring model Is a meter used to calculate the pH (Acid or Basic) of the

material

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Ohio Class Submarine: is a class of nuclear-powered submarine currently used by the

US navy. It has 18 submarines.

Electrolysis: Electrolysis is a technique used to separate oxygen and hydrogen through

a direct electric current.

Microprocessor: The microprocessor is a computer processor that controls the

computer’s central processing unit (CPU)

NaClO3(s): The S in the equation represents that it’s Solid

monoethanolamine: Monoethanolamine is also called Ethanolamine and it’s an organic

chemical compound.

aqueous: Aqueous solutions are solutions in which the water is the solvent.

SCUBA: Scuba diving is a mode of underwater diving where a diver uses a self-

contained underwater breathing apparatus to breathe underwater.

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submarines atmosphere control and air treatment

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