Why Drying? Hydrates………….

Hydrates• The compounds formed by the interaction of water and

hydrocarbons at certain pressures and temperatures.They are crystalline substances

• Reaction with water

• Propane or Butane react with water and form hydrates

• block lines filters, pumps re-liquifaction plants.

• Can be prevented by inhibitors

.

Hydrates Filter of Viking Grace

Hydrates Filter

Hamworthy design

Drying of Cargo Tanks

Why to Dry Tanks?

How can you dry Tanks?

Moisture/condensation will freeze

For Invar Membrane, corrosion may be caused by IG

Use of IG Generator delivering dry air

R22 Compressor

FWCondenser

Air Blower

Drying Tanks

Inert Gas Generator

MAIB Tanker Awareness by WMA

Inert Gas Generator, can be used to deliver dry air (burner not used)

Dry Tanks later Inert Tanks

Water Content at Dew Point TemperatureDP Temp +40 = 52 g/m3

DP Temp +4 = 7 g/m345 g/m3 Removed

DP Temp -40 = 0.1 g/m3

6.9 g/m3 Removed

Methane Hydrates

Lighter

Heavier

N

A

I

L

itrogen

ir

nert Gas

PG

Methane

Changing Atmospheres - Displacement

Methane @ -100°C = Air

Inerting Tanks then Pipelines

Why?

How?

To prevent formation of a flammable atmosphere (anywhere in the system) IGC Code Ch. 9

With IG Generator (typical - 14,000 m3/hr)

In line cooler/dryer

Oxygen < 2.0% by vol.

Dew Point < - 40°C

Always by Displacement (layer or piston method) in parallel

Inerting• By displacement method

• low speed of inert gas

• 135,000 m³

• IGG 11,000 m³/hr

• 1.25 atmosphere changes = 168,750 m³

• Total time 15hrs 20mins

• Gas oil consumption about 16 tonnes

• 1.5 atmosphere changes = 202,500 m³

• Total time 18hrs 25mins

• Gas oil consumption about 18 tonnes

• entering of IG on top or bottom of tank (depending of specific density)

Dilution Method

• By mixing of inert gas and gas residues

• high speed of IG entering (mixing)