Dehydration methods

(Absorption & Adsorption)

Done by:
Ahmed Osama Amin (Bn:1)
Ahmed Samir Abd Elmonaem (Bn:5)
Hossam Mohamed Abd Elmageed (Bn:12)
Mohamed Salah Elshazly (Bn:20)
Muhamed Mahmoud Mahmoud (Bn:21)
4th Year-Petroleum Engineering
 Table of contents
I. Introduction …………………………………………………………………..... 3
A. Brief overview of gas dehydration ……………………………………………………… 3
B. Significance of effective gas dehydration in the industry ………………………...…… 3

II. Absorption Method …………………………………………………………… 5

A. Explanation of absorption in gas dehydration ………………………………………… 5
B. Overview of different absorption agents ……………...…………………………...…… 6
C. Process description and key equipment ………………………………………………... 8
D. Advantages and disadvantages of absorption ………………………………………….. 9

III. Adsorption Method ……………………………………………………….... 11

A. Explanation of adsorption in gas dehydration ……………………………………….. 11
B. Overview of adsorbents ………………………………………………………………… 12
C. Process description and key equipment ………………………………………………. 15
D. Advantages and disadvantages of adsorption ……………………………………….... 16

IV. Summary ……………………………………………………………………………………..…………. 18

V. Comparison between Absorption and Adsorption ………………………... 20

VI. Conclusion …………………………………………………………………... 20

VII. References ………………………………………………………………….. 21

Introduction
Brief overview of gas dehydration
Gas dehydration is a crucial process in the field of petroleum engineering, essential for maintaining the quality
and integrity of natural gas. This procedure revolves around the removal of water content from natural gas
streams, addressing various issues associated with water vapor.

Key Points
Significance: Water in natural gas can lead to corrosion, hydrate formation, and reduced pipeline efficiency.
Dehydration is indispensable for preventing these issues and ensuring the overall reliability of the gas
transportation system.

Objectives: The primary goals of gas dehydration include compliance with pipeline specifications and
enhancing the efficiency of downstream processes. Removing moisture from the gas stream is essential to meet
specific quality standards for safe and effective transportation.

Methods: Common methods for gas dehydration include absorption and adsorption. Absorption employs
absorbents like glycols to capture and remove water, while adsorption relies on adsorbents such as molecular
sieves to attract and trap water molecules.

Technological Advancements: Advances in gas dehydration technologies have led to more efficient and
environmentally friendly methods over the years. These advancements contribute to the sustainability of the
petroleum industry.

Significance of effective gas dehydration in the industry

The significance of effective gas dehydration in the petroleum industry cannot be overstated, playing a crucial
role in ensuring the integrity, safety, and efficiency of gas processing. Here are key points highlighting its
importance:

Corrosion Prevention: Water vapor in natural gas can lead to corrosion of pipelines and associated equipment.
Corrosion poses a serious threat to the infrastructure's structural integrity, potentially leading to leaks, ruptures,
and safety hazards.
Hydrate Formation Avoidance: Water in natural gas can form hydrates, especially under certain temperature
and pressure conditions. Hydrates are solid crystalline structures that can block pipelines, impeding the flow of
gas and causing operational disruptions.

Pipeline Integrity: Dehydrating gas is essential for maintaining the integrity of pipelines. Water-related issues
can compromise the structural strength of pipelines, leading to increased maintenance costs and reducing the
overall lifespan of the infrastructure.

Efficiency of Downstream Processes: Downstream processes, such as gas compression and liquefaction,
operate more efficiently with dehydrated gas. Removing moisture ensures that these processes can function
optimally, contributing to overall operational efficiency.

Compliance with Pipeline Specifications: Gas transported through pipelines must meet specific quality
standards, including moisture content. Effective gas dehydration ensures that the gas complies with these
specifications, meeting regulatory requirements and industry standards.

Environmental and Safety Considerations: Gas dehydration contributes to environmental and safety aspects
by reducing the risk of gas leaks, explosions, and other accidents associated with water-related issues. This is
particularly crucial in maintaining a safe working environment and minimizing environmental impact.

In summary, the significance of effective gas dehydration lies in its role as a preventative measure against
corrosion, hydrate formation, and other water-related challenges. It safeguards pipeline integrity, enhances
operational efficiency, and contributes to the overall safety and compliance of the gas processing industry.
Absorption Method
Explanation of absorption in gas dehydration
Principle of Absorption: Absorption is a process where one substance, known as the absorbent, selectively
captures and retains another substance, in this case, water vapor from natural gas. The principle relies on the
fact that certain absorbents, such as glycols, have a strong affinity for water molecules.

Absorbents Used: In gas dehydration, liquid absorbents like Tri ethylene glycol (TEG) or diethylene glycol
(DEG) are commonly employed. These glycols have a high affinity for water, allowing them to effectively
capture and remove water from the natural gas stream.

Absorption Process Steps:

Contact: Wet natural gas comes into contact with the liquid absorbent. Water molecules present in the gas are
absorbed by the liquid absorbent.
Separation: The absorbent, now containing the absorbed water, is separated from the dehydrated gas.

Key Equipment:
Absorber Tower: This is where the absorption takes place. The tower is designed to facilitate contact between
the wet gas and the absorbent.
Rich-Glycol Regenerator: The absorbent, now referred to as rich glycol (containing water), is processed in a
regenerator to release the absorbed water and regenerate the glycol for reuse.

Regeneration Process: After absorbing water, the absorbent needs to be regenerated to maintain its
effectiveness. Regeneration typically involves heating the rich glycol to release the captured water vapor,
leaving the absorbent in a state ready for the next absorption cycle.

Efficiency and Limitations:

Absorption is known for its efficiency in removing water from natural gas, especially in applications where low
moisture levels are required. However, the process consumes energy for regeneration, and the choice of
absorbent depends on factors such as temperature and pressure conditions.

Applications: Absorption is widely applied in various industries, especially in natural gas processing, where
stringent moisture content specifications must be met.
Overview of different absorption agents

1. Tri ethylene Glycol (TEG):

Description: TEG is a widely used liquid absorbent in gas dehydration. It belongs to the glycol family and
has excellent water absorption properties.
Advantages:
• High affinity for water molecules.
• Efficient at low temperatures.
• Considerations:
• Requires regeneration to maintain effectiveness.
• Energy-intensive regeneration process.

2. Diethylene Glycol (DEG):

Description: Similar to TEG, DEG is another glycol-based absorbent used in gas dehydration.
Advantages:
• Effective in capturing water vapor.
• Operates at lower temperatures.
• Considerations:
• Regeneration process needed.
• Energy consumption during regeneration.

3. Methyl diethanolamine (MDEA):

Description: MDEA is an amine-based absorbent used for natural gas sweetening and dehydration.
Advantages:
• Selective for acid gases and water removal.
• Lower energy consumption during regeneration compared to glycols.
• Considerations:
• May require additional equipment for efficient operation.
• Potential for amine degradation.
4. Di isopropanol amine (DIPA):
Description: DIPA is another amine-based absorbent commonly used in gas sweetening and dehydration
processes.
Advantages:
• Effective for both acid gas removal and dehydration.
• Relatively low energy requirements for regeneration.
Considerations:
• Potential for foaming issues.
• Consideration needed for corrosion issues.

5. Potassium Carbonate (K2CO3):

Description: In certain applications, potassium carbonate is used as an absorbent for acid gases and water
removal.
Advantages:
• High capacity for acid gas removal.
• Can operate at higher temperatures.
Considerations:
• Limited use in specific conditions.
• May require additional treatment for water removal.

6. Sodium Hydroxide (NaOH):

Description: Sodium hydroxide, or caustic soda, is used in some industrial applications for acid gas and
water removal.
Advantages:
• Effective in removing acidic components.
• Can be economical for certain applications.
Considerations:
• Corrosive nature.
• Limited application in gas dehydration.
 Considerations for Selection: Temperature and Pressure Conditions: Different absorbents have
optimal performance under specific temperature and pressure conditions.

Regeneration Requirements: Energy consumption during regeneration varies among absorbents.

Process description and key equipment

Process Description:
Contact with Absorbent: Wet natural gas enters the absorption unit or absorber tower, where it comes into
contact with the liquid absorbent, such as Tri ethylene Glycol (TEG) or Diethylene Glycol (DEG). Water
molecules in the gas are selectively absorbed by the liquid absorbent.

Separation of Dehydrated Gas: The dehydrated gas, now with reduced moisture content, separates from the
liquid absorbent. This separation is typically done in a separator or demister, allowing the dehydrated gas to
proceed for further processing or transportation.

Regeneration of Absorbent: The liquid absorbent, now loaded with absorbed water, is sent to the regeneration
unit. In the regeneration unit, the absorbent is heated to release the captured water vapor, restoring the
absorbent's effectiveness.

Cooling and Reuse: After regeneration, the absorbent is cooled before being returned to the absorption unit for
the next cycle. This cooling step is crucial to ensure the absorbent is at the right temperature for effective
absorption.

Key Equipment:
Absorber Tower: The absorber tower is a vertical vessel where the absorption process takes place. It is
designed to facilitate contact between the wet gas and the liquid absorbent.

Separator or Demister: After absorption, the dehydrated gas and liquid absorbent need to be separated. A
separator or demister accomplishes this by allowing the gas to pass through while capturing any liquid droplets.

Rich-Glycol Regenerator: The rich glycol, laden with absorbed water, is sent to the regenerator for the
regeneration process. In the regenerator, the absorbent is heated to release the captured water vapor.
Heat Exchangers: Heat exchangers are essential for controlling temperatures in various stages of the process.
They facilitate the exchange of heat between the hot regenerated absorbent and the incoming cool absorbent.

Pumps: Pumps are used to circulate the liquid absorbent through the absorption and regeneration units. They
ensure a continuous and controlled flow of absorbent in the system.

Cooling System: A cooling system is employed to cool the absorbent after regeneration, preparing it for the
absorption process. This can involve air coolers or water-based cooling systems.

Instrumentation and Controls: Monitoring and control systems are critical for maintaining optimal conditions
throughout the process. Sensors and controllers help regulate temperatures, pressures, and flow rates.
Understanding the intricacies of these components is crucial for the efficient operation of the gas dehydration
unit using the absorption method.

Advantages and disadvantages of absorption

Advantages:

• High Efficiency in Water Removal: Absorption is highly effective in removing water vapor from
natural gas, ensuring that the gas meets stringent moisture content specifications.

• Selective Water Absorption: The choice of absorbents, such as glycols, allows for selective water
absorption, reducing the likelihood of other gas components being absorbed.

• Applicability to Various Conditions: Absorption is applicable under a range of temperature and

pressure conditions, making it versatile for different gas processing scenarios.

• Proven Technology: Absorption has been a well-established and proven technology in the gas
processing industry, with a track record of successful implementation.

• Suitability for Low Moisture Levels: Absorption is particularly suitable for applications where
extremely low moisture levels in natural gas are required.
Disadvantages:

• Energy Intensive: The regeneration process in absorption is energy intensive. Heating the absorbent
to release the absorbed water requires significant energy input.

• Large Footprint: Absorption units, especially those designed for high-capacity applications, can
have a large physical footprint, impacting the overall space requirements of the facility.

• Chemical Management: Managing and maintaining the liquid absorbent, often chemical solutions
like glycols, requires careful attention. Regular monitoring and replenishment are necessary for
efficient operation.

• Potential for Foaming: Certain absorbents, especially glycols, may tend to foam under certain
conditions. Foaming can reduce the efficiency of the absorption process and may require additional
anti-foaming agents.

• Corrosion Considerations: Absorption units can be susceptible to corrosion due to the presence of
chemical solutions. Corrosion-resistant materials and proper maintenance are crucial to mitigate this
risk.

• Environmental Impact: The use of certain absorbents, especially glycols, can have environmental
implications. Proper disposal and treatment of spent absorbents are essential to minimize
environmental impact.

• Limited Capacity for Deep Dehydration: While absorption is highly efficient, it may have
limitations in achieving extremely low moisture levels in comparison to other dehydration methods
like adsorption.

Understanding these advantages and disadvantages is essential for making informed decisions
regarding the selection of gas dehydration methods based on specific application requirements.
Adsorption method
Explanation of adsorption in gas dehydration
Principle of Adsorption: Adsorption is a process in which molecules of a gas or liquid adhere to the
surface of a solid material, known as an adsorbent. In gas dehydration, the focus is on removing water vapor
from the gas stream.

Adsorbents Used: Common adsorbents in gas dehydration include molecular sieves, silica gel, and
activated alumina. These materials have a porous structure that provides a large surface area for the adsorption
of water molecules.

Selective Water Adsorption: The porous nature of adsorbents allows them to selectively attract and trap
water molecules while letting the dry gas pass through.

Adsorption Process Steps:

Contact with Adsorbent: Wet natural gas passes through a bed or vessel filled with the adsorbent material.
Adsorption of Water: Water molecules in the gas are adsorbed onto the surface of the adsorbent, effectively
removing moisture from the gas stream.
Dehydrated Gas Output: The dehydrated gas, with reduced moisture content, exits the adsorption unit for
further processing or transportation.

Regeneration of Adsorbent: After reaching saturation, the adsorbent needs regeneration to release the
captured water molecules and restore its adsorption capacity. Regeneration typically involves heating the
adsorbent bed to release the trapped water vapor.

Cooling and Reuse: After regeneration, the adsorbent is cooled before being returned to the adsorption unit
for the next cycle. Cooling is essential to ensure the adsorbent is at the right temperature for effective water
adsorption.

Key Aspects of Adsorption:

Pore Size and Selectivity: The pore size of the adsorbent material determines its selectivity for specific
molecules. Molecular sieves, for example, can be tailored to selectively adsorb water molecules.

Capacity for Deep Dehydration: Adsorption methods, especially with advanced materials like molecular
sieves, have the capability to achieve deep dehydration, making them suitable for applications requiring
extremely low moisture levels.
Energy Efficiency: Adsorption methods are often considered more energy-efficient than absorption methods,
especially during the regeneration process.

Variety of Adsorbents: Different adsorbents are available to accommodate various operating conditions and
gas compositions. The choice of adsorbent depends on factors such as temperature, pressure, and the specific
components in the gas stream.

Applications: Adsorption is widely used in natural gas processing, petrochemical, and industrial applications
where achieving low moisture levels is crucial.

Overview of adsorbents
1. Molecular Sieves:
Description: Molecular sieves are crystalline, porous materials with uniform-sized pores. They are highly
effective in adsorbing water molecules while allowing dry gases to pass through.
Advantages:

• High selectivity for water.

• Excellent capacity for deep dehydration.
Considerations:

• Regeneration by heating is a standard process.

• Different types (3A, 4A, 5A, 13X) are available for specific applications.

2. Silica Gel:
Description: Silica gel is a porous, granular form of silica that adsorbs water vapor.
Advantages:

• Cost-effective.
• Stable and non-reactive.
Considerations:

• Limited capacity compared to molecular sieves.

• Requires regeneration.
3. Activated Alumina:
Description: Activated alumina is a porous, granular substance made from aluminum oxide. It has a large
surface area and is effective in adsorbing water.
Advantages:

• High surface area.

• Regenerable for reuse.
Considerations:

• Temperature and dew point limitations.

• Susceptible to dusting.

4. Zeolites:
Description: Zeolites are microporous aluminosilicate minerals with a three-dimensional structure. They
are used as adsorbents in gas dehydration.
Advantages:

• Selective adsorption properties.

• Regenerable.
Considerations:

• Variability in performance based on the type of zeolite.

• Limited capacity for certain gases.

5. Porous Ceramic Beads:

Description: Porous ceramic beads are solid, inert materials with a high porosity that allows for effective
water adsorption.
Advantages:

• Chemically stable.
• Regenerable.
Considerations:

• May have lower capacity compared to some other adsorbents.

• Requires proper sizing for optimal performance.
 6. Calcium Oxide (Lime):
Description: Calcium oxide, commonly known as lime, is used for adsorbing acidic gases and water vapor.
Advantages:

• Effectively removes acidic components.

• Cost-effective.
Considerations:

• Limited capacity for water adsorption.

• Reactivity with certain gases.

7. Zeolite-Imidazolate Frameworks (ZIFs):

Description: ZIFs are a class of metal-organic frameworks with tunable pore sizes and high surface areas.
Advantages:
• Tailor-made for specific applications.
• High capacity for gas adsorption.
Considerations:
• May require careful engineering for stability.
• Relatively recent introduction in comparison to traditional adsorbents.

Considerations for Selection:

Pore Size and Selectivity: Different adsorbents have varying pore sizes and selectivity for specific gases.

Regeneration Requirements: Regeneration methods differ among adsorbents and impact the overall
energy efficiency.

Operating Conditions: Consider temperature, pressure, and gas composition to choose the most suitable
adsorbent for a given application.
Process description and key equipment
Process Description:
Contact with Adsorbent: Wet natural gas flows through a bed or vessel containing the adsorbent material,
such as molecular sieves or silica gel. The porous structure of the adsorbent allows it to selectively adsorb water
molecules from the gas stream.
Adsorption of Water: Water molecules in the gas are attracted to and trapped by the surface of the adsorbent.
The adsorption process reduces the moisture content of the gas.

Dehydrated Gas Output: The gas, now with reduced moisture content, exits the adsorption unit for further
processing or transportation.

Saturation and Switching to Another Bed: As the adsorbent reaches saturation, the adsorption bed needs
regeneration. Some systems employ multiple adsorption beds, allowing for a cyclic operation. When one bed is
in adsorption mode, the other is in regeneration mode.

Regeneration of Adsorbent: The saturated adsorbent bed undergoes a regeneration process to release the
trapped water molecules. Regeneration is typically achieved by heating the adsorbent bed, and the released
water vapor is vented.

Cooling and Reuse: After regeneration, the adsorbent is cooled before being returned to the adsorption mode
for the next cycle. Cooling is crucial to prepare the adsorbent for effective water adsorption in the next cycle.

Key Equipment:
Adsorption Vessel: The adsorption vessel or bed is the main component where the gas comes into contact with
the adsorbent material. It is designed to allow efficient adsorption of water molecules.

Adsorbent Material: The choice of adsorbent material (e.g., molecular sieves, silica gel) is critical and
depends on factors such as gas composition, operating conditions, and required moisture levels.

Valves and Manifolds: Valves control the flow of gas and direct it between different stages of the adsorption
and regeneration cycles. Manifolds help distribute and collect gas within the system.

Heaters: Heaters are used during the regeneration phase to heat the adsorbent bed and release the trapped water
vapor. The heating process varies based on the adsorbent material and system design.
Coolers: Coolers are employed to cool the adsorbent after regeneration, ensuring it is at an optimal temperature
for effective water adsorption in the next cycle.

Pressure Swing Adsorption (PSA) or Temperature Swing Adsorption (TSA) Systems: Some systems
operate based on pressure swing or temperature swing principles, where changing pressure or temperature helps
in desorbing water from the adsorbent.

Instrumentation and Controls: Sensors, controllers, and monitoring systems play a crucial role in maintaining
optimal conditions during the adsorption and regeneration cycles.

Desorption Vent: In systems with multiple adsorption beds, a desorption vent releases the water vapor during
the regeneration phase.

Understanding the functions of these components is essential for designing and operating
efficient adsorption units for gas dehydration.

Advantages and disadvantages of adsorption

Advantages:

• High Efficiency in Energy Efficiency: Adsorption is often considered more energy-efficient than
absorption during the regeneration process. It can be particularly advantageous in applications where
minimizing energy consumption is a priority.

• Suitability for Deep Dehydration: Adsorption methods, especially with advanced adsorbents like
molecular sieves, have the capability to achieve deep dehydration, making them suitable for
applications requiring extremely low moisture levels.

• Regenerability: Adsorbents used in gas dehydration, such as molecular sieves and activated
alumina, are regenerable. This allows for the reuse of the adsorbent material, contributing to the
overall cost-effectiveness of the process.

• Variety of Adsorbents: Different adsorbents are available to accommodate various operating

conditions and gas compositions. The choice of adsorbent depends on factors such as temperature,
pressure, and the specific components in the gas stream.
 • Selective Adsorption: Adsorption methods can be designed to selectively adsorb specific
molecules, providing flexibility in addressing the unique challenges of different gas streams.

• Compact Design: Adsorption units can be designed with a relatively compact footprint, making
them suitable for applications where space is limited.

Disadvantages:

• Limited Capacity: Adsorption units may have a limited capacity for water removal compared to
absorption methods. This limitation may necessitate larger adsorption units or more frequent
regeneration cycles.

• Complexity in Design: The design and operation of adsorption units, especially those using pressure
swing adsorption (PSA) or temperature swing adsorption (TSA), can be more complex than simpler
absorption systems.

• Equipment Sensitivity: Some adsorbents, particularly those with smaller pore sizes like molecular
sieves, can be sensitive to impurities or contaminants in the gas stream, affecting their performance.

• Regeneration Time: The regeneration process in adsorption can take time, impacting the overall
cycle duration. This may influence the efficiency of the entire gas processing system.

• Initial Capital Cost: The upfront capital cost of installing adsorption units, especially those with
sophisticated designs, can be higher than simpler absorption systems.

• Maintenance Challenges: Adsorption units may require careful maintenance to ensure the
adsorbent material's longevity and optimal performance. Contaminants or deterioration of the
adsorbent can affect efficiency.

Understanding these advantages and disadvantages is essential for making informed decisions
regarding the selection of gas dehydration methods based on specific application requirements.
Summary
Absorption Method:
Overview:
Principle: Involves using liquid absorbents (e.g., glycols) to capture and remove water from natural gas.

Process Description: Wet natural gas contacts the liquid absorbent in an absorber tower, and water is absorbed
by the liquid. The absorbent is then regenerated for reuse.

Key Equipment: Absorber tower, regenerator, pumps, heat exchangers.

Advantages:
• High efficiency in water removal.
• Selective absorption.
• Applicable to various conditions.
• Proven technology with a track record.
• Suitable for low moisture levels.

Disadvantages:
• Energy-intensive regeneration.
• Large physical footprint.
• Chemical management required.
• Potential for foaming
• Corrosion considerations.
• Limited capacity for deep dehydration.
Adsorption Method:
Overview:
Principle: Involves using solid adsorbents (e.g., molecular sieves, silica gel) to attract and trap water molecules
from natural gas.

Process Description: Wet natural gas passes through a bed of adsorbent material, where water is adsorbed.
Regeneration involves heating the adsorbent to release trapped water vapor.

Key Equipment: Adsorption vessel, adsorbent material, valves, heaters, coolers, PSA/TSA systems.

Advantages:
• Energy-efficient regeneration.
• Suitability for deep dehydration.
• Regenerable adsorbents.
• Variety of adsorbent options.
• Selective adsorption.
• Compact design.

Disadvantages:
• Limited capacity compared to
absorption.
• Complexity in design.
• Equipment sensitivity to impurities.
• Regeneration time.
• Initial capital cost.
• Maintenance challenges.
Comparison:
POC Absorption Adsorption

Energy Efficiency Energy-intensive regeneration. Generally more energy-efficient

during regeneration.

Capacity Higher capacity for water removal. Limited capacity compared to

absorption.

Regenerability Requires regeneration for absorbent Adsorbents are regenerable.

reuse.

Complexity Generally simpler in design. Can be more complex, especially

with PSA/TSA systems.

Space Requirements Larger physical footprint. Generally more compact.

Sensitivity Less sensitive to impurities. Adsorbents can be sensitive to

contaminants.

Initial Capital Cost Potentially lower initial cost. Higher upfront capital cost.

In conclusion, the choice between absorption and adsorption methods depends on specific
application requirements, considering factors such as energy efficiency, capacity needs,
space constraints, and sensitivity to impurities. Both methods have their advantages and
disadvantages, and the selection should align with the goals and constraints of the gas
dehydration process.
Reference

https://www.gpaglobal.org/