using ammonia effectively overcoming obstacles and maximising benefits

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Using Ammonia Effectively Overcoming Obstacles and Maximising Benefits

Dr Andy Pearson

Star Refrigeration

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Introduction – Ammonia: the paradoxes

• The Paradoxes– Natural or not?– Good or evil?– Safe or dangerous?

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Using Ammonia Effectively – Presentation Contents

• Introduction– Reasons for wanting to use ammonia– Range of possible applications– Scope of potential advantages

• Overcoming Obstacles– Toxicity– Flammability– Public Image

• Strategy for Success– Design considerations– Legislative Framework

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Using Ammonia Effectively – Presentation Contents

• Introduction– Reasons for wanting to use ammonia– Range of possible applications– Scope of potential advantages

• Overcoming Obstacles– Toxicity– Flammability– Public Image

• Strategy for Success– Design considerations– Legislative Framework

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Reasons for wanting to use ammonia

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Reasons for wanting to use ammonia

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• High Temp Heat Pump• District Heating• Process Heating• Air cooled chiller• Water cooled chiller• Process chiller• Ice rink• Cold Store• Air Blast Freezer• Spiral Freezer

Reasons for wanting to use ammonia

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A = subcooling

A B

B = condensing

C

C = desuperheating

D

D = oil cooling

E = more subcool

E

Ammonia as a heat pump fluid

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A = subcooling

A B

B = condensing

C

C = desuperheating

D

D = oil cooling

E = more subcool

E

R-134a as a heat pump fluid

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IPLV =3.7

4.0 for 45%

3.4 for 42%

2.6 for 1%

3.7 for 12%

R-134a as a chiller fluid

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Ammonia as a chiller fluid

IPLV =4.6

5.0 for 45%

4.1 for 42%

3.0 for 1%

4.8 for 12%

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• Factory tested• Guaranteed

performance• Plug and play• Good turndown• Compact Design• Low charge• Low noise levels• Efficient fans• Long-life package

Ammonia as a chiller fluid

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Using Ammonia Effectively – Presentation Contents

• Introduction– Reasons for wanting to use ammonia– Range of possible applications– Scope of potential advantages

• Overcoming Obstacles– Toxicity– Flammability– Public Image

• Strategy for Success– Design considerations– Legislative Framework

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Overcoming Obstacles - Toxicity

• Toxic effect is related to dose• Dose for ammonia exposure is a combination:• Concentration of ammonia in the atmosphere….• ….and length of time the exposure lasts

• In the short term high doses can be tolerated:• For example a dose of 5000ppm would likely be fatal

after two hours exposure….• ….but it is not likely to cause any injury whatsoever if

the exposure lasts for less than one minute

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?

Overcoming Obstacles - Toxicity

8 hour TLV

300ppmIDLH

700ppm IDLH?1000ppm IDLH?

15 min TLV

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* Henderson and Haggard (1943) cited in AIHA “Hygienic Guide Series” (1971)

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Overcoming Obstacles - Toxicity

• Accidents occur when the rules are not followed, so….

• ….make the rules easier to follow• Do not impose excessive constraints or

restrictions;• ….too much PPE can cause accidents!• Have a canister respirator to

hand when opening a system• Wear the respirator when the

ammonia smell is “strong”• If in doubt, retreat! • Only experts should use

SCBA

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Flammability: detonation, explosion or conflagration?

• There are two main considerations when discussing flammability:– How easy is the gas to ignite?– How much damage does it do when it burns?

• These are assessed in EN378 by considering:– Lower flammable limit– Heat of Combustion

0 5 10 15 20 25 300MJ/kg

20MJ/kg

Class 2

LFL > 3.5 v/v

HOC < 19MJ/kg

LFL (ppm v/v)

HO

C (

MJ/

kg)

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Flammability: detonation, explosion or conflagration?

• Some new factors are being considered:– Burning velocity– Minimum Ignition Energy

• These are not currently assessed in EN378• MIE is an alternative to LFL (how easy…?)

• BV is an alternative to HOC (how damaging…?)

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Flammability: detonation, explosion or conflagration?

Key Questions:• Does this change do anything to make systems safer?• Are these new parameters easier to measure?• Do we need more than 2 classes:

– Non-flammable– Flammable

• Do we need more than 3 classes:– Non-flammable– Mildly flammable– Highly flammable

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Overcoming Obstacles - Public Image (1)

• 10 August: Fatal accident on Malaysian trawler kills six workers, five injured. Ammonia in refrigeration system is blamed in the press

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Overcoming Obstacles - Public Image (1)

• 10 August: Fatal accident on Malaysian trawler kills six workers, five injured. Ammonia in refrigeration system is blamed in the press

• 18 August: Further investigation suggests that ammonia was not to blame, but the workers were overcome by hydrogen sulphide

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Overcoming Obstacles - Public Image (1)

• 10 August: Fatal accident on Malaysian trawler kills six workers, five injured. Ammonia in refrigeration system is blamed in the press

• 18 August: Further investigation suggests that ammonia was not to blame, but the workers were overcome by hydrogen sulphide

• 25 August: It later transpires that the refrigeration system used R22, not ammonia

• Questions: how far did the original news spread? How far did the later correction spread?

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Overcoming Obstacles - Public Image (1)

• 10 August: Fatal accident on Malaysian trawler kills six workers, five injured. Ammonia in refrigeration system is blamed in the press

• 18 August: Further investigation suggests that ammonia was not to blame, but the workers were overcome by hydrogen sulphide

• 25 August: It later transpires that the refrigeration system used R22, not ammonia

• 1 October: ACR News – “An ammonia leak on a refrigeration system at a fish plant in Malaysia claimed six lives last month. The victims all died from ammonia inhalation”

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Overcoming Obstacles - Public Image (2)

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Overcoming Obstacles - Public Image (2)

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Using Ammonia Effectively – Presentation Contents

• Introduction– Reasons for wanting to use ammonia– Range of possible applications– Scope of potential advantages

• Overcoming Obstacles– Toxicity– Flammability– Public Image

• Strategy for Success– Design considerations– Legislative Framework

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Design Considerations: Recommendations

• Purchaser:– Specify EN378 as minimum design– Mandate detectors and alarms in unoccupied areas– Prohibit automatic plant room ventilation

• Designer/Installer:– Ensure compliance with EN378 parts 2 and 3– Design for minimum charge– Design for lifetime operation and efficiency

• Operator:– Ensure that the plant is designed for maintenance– Conduct a HAZOP before the design is finished

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Legislative Framework: Recommendations

• Toxicity:– Raise the IDLH to 1000ppm– Mandate detectors and alarms in unoccupied areas– Prohibit automatic plant room ventilation

• Flammability:– Stick with 3 classes (non-f, mildly-f and highly-f )– Use other metrics if appropriate but apply them simply

and consistently– Make the metric easy to measure and easy to validate

• Public Image:– Don’t believe everything you read in the papers

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Conclusions

• Ammonia is safe if it is used correctly• It is easy to use, and reliable in operation• It offers exceptionally good efficiency• The two key drivers for increased adoption are:

– Reduced charge systems– Enlightened regulation

• Incentive will come from:– Training and familiarity– Technical Development– Economies of Scale