Transcript Glycol Pumps - WYCO Pump Repair & Sales

September 26, 2006
NATURAL GAS DEHYDRATION
GAS DEHYDRATION
WHAT IS GAS DEHYDRATION?
The removal of particulate water and water
vapor from a produced gas stream.
Why Dehydrate
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Water in pipelines causes corrosion
Water reduces pipeline efficiency
Water reduces accuracy in measurement
Water can form hydrates and cause
plugging
Types of Dehydration
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Calcium Chloride
Branded desiccants
Molecular Sieve
Membrane Units
Glycol
– Diethylene
– Triethylene
Glycol
Glycol is a hygroscopic liquid.
Which simply means GLYCOL has the ability to absorb water.
Diethylene Glycol
• Diethylene Glycol
– Lower Cost
– 328° Thermal Decomposition
– 474° Boiling Point
– 92% - 94% Regeneration
– Higher Operating Cost
– Higher Capital Cost
Triethylene Glycol
• Triethylene Glycol
– Higher Cost
– 404° Thermal Decomposition
– 550° Boiling Point
– 928% - 99.5% Regeneration
– Lower Operating Cost
– Lower Capital Cost
Parameters of a Dehy
• Fixed
• Minimum and Maximum gas capacity at a given
pressure and temperature
• Gas composition
• Minimum and Maximum heat input into the
regenerator
• Fire Tube surface area
• Vapor capacity of the still column
• Liquid and gas capacity of the inlet scrubber
Parameters of a Dehy
• Variable
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Gas flow into the absorber
Water content of the dehydrated gas
Glycol circulation rate
Glycol concentration
Dehydrator Sizing
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Gas Flow Rate
Gas Temperature
Gas Pressure
Pipeline Specifications
Utilities Available
Pad Size and Location
Dehydrator Sizing
Water Content of Natural Gas
Temperature Differences
Dehydrator Sizing
Water Content of Natural Gas
Pressure Differences
Dehydrator Sizing
Water Removal
Natural Gas Dehydrator
Contactor Tower
Glycol Cooler
Reboiler
Dry Gas
Outlet
Inlet Scrubber
Surge Tank
Wet Gas Inlet
High Pressure
Filter
Excess Separated
Gas Outlet
Condensate Outlet
Three Phase Gas, Glycol &
Condensate Separator
Condensate Outlet
Wet Glycol from Absorber (High Pressure)
Wet Glycol to Reboiler (Low Pressure)
Dry Glycol from Reboiler (Low Pressure)
Dry Glycol to Absorber (High Pressure)
Inlet Scrubber
• First stage of liquid removal
for the dehydration process
• Eliminates free liquids from
gas stream
• Requires liquid level
controller and high
pressure dump valve
• Used with pre-contactor
• Mist Eliminator
Absorber with Integral Scrubber
• Lower capital cost than separate
scrubber.
• Requires liquid level controller and
high pressure dump valve
• Reduces footprint of dehydrator
• Can not be used with pre-contactor
• Mist eliminator
Natural Gas Dehydrator
Dry Gas Out
Dry glycol
Reboiler
Absorber
(Contactor)
Wet
Gas
In
Wet glycol
Pump
Dry glycol
Wet glycol
Heat exchanger
surge tank
Absorber or Contact Tower
• Vessel where glycol
and natural gas make
contact
• Concurrent flow
– Gas flows up
– Glycol flows down
• Packed type
– Structured Packing
– Pall Ring Packing
• Tray type
– Bubble Cap
– Nutter Valve
Absorber with Scrubber
• Gas temp 60°-135° F
• Pressure 100 – 2600 psi
• Inlet glycol should be 10° F higher
than inlet gas
– Lower temp than gas will cause
foaming
– Higher temp might increase glycol
loss
• 5 psig maximum pressure drop
between inlet and outlet
• Liquid seal must be established
– Glycol circulation established on
tray type tower
– Gas flow should be gradually
increased
Absorber with Scrubber
• pH of Glycol should be 7.0 – 7.5
• Absorber must have an adequate
glycol/gas heat exchanger
• Gas flow must be kept in turn
down range or “channeling” may
occur
• Mist pad or mist extractor should
be used
• Glycol loss should be .1 gal per
MMSCF
• Tower should be level and secure
Surge or Storage Tank
• Holding tank for the dry or lean
glycol before it goes to the glycol
pump
• Level must be maintained for pump
head pressure
• Can be separate vessel or integral
to the reboiler.
– Individual surge tanks may have
glycol/glycol heat exchanger internally
– Integral surge tanks have panel or tube
type glycol/glycol exchangers
Reboiler
• Vessel where water is “cooked” out of
the glycol
• Temp range 375°- 400° for TEG
• Fire tube heat flux
– 6000-8000 BTU/Hr. per Sq./Ft
• Fire tube must be free of deposits
– salt
– tar or coke
• Stripping Gas
– sparger style
– spillover style
– Stahl column
• Temperature Control deadband should
be as small as possible
• Pressure should be at a minimum
Still Column
• Still Column (where wet or
“rich” glycol is injected for water
removal)
• Packed with ceramic saddles
• 225°F Ideal Temperature
• Temperatures below 218°F will
cause reboiler to flood
• Temperatures above 250°F will
cause excess glycol loss out
vent.
Glycol Pump
• Pump piping should be
correctly sized
• A High pressure filter MUST
be used and maintained
• Charcoal filters used for high
condensate wells
• Inlet strainer MUST be
installed and maintained
• Pump should be secured on
a level surface
3 Phase Glycol/Gas/Condensate
Separator
• Separates any liquids that
might get carried over with the
glycol such as condensate or
compressor oils
• Used to reclaim some of the
gas that would ordinarily lost
through the still column
• Flash separator pressure
should be kept as low as
possible to prevent pump
stalling