Representation-of-Methane liquefication plant (Autosaved).PPTX

Starting Point:

Project Timeline: June-July 2026

Responsible:

Rana (BAU, MECH 4th year), June 2026

Nagham Harmouch (BAU, MECH 4th year), June 2026

Alaa (LU, MECH 3rd year), July 2026

Yasmin (LU, MECH 3rd year), July 2026

Background:

Methane is the simplest hydrocarbon found in small quantities in Earth’s atmosphere. It is a potent greenhouse gas. Methane is flammable and is used as fuel worldwide. It is a principal component of natural gas. Natural gas consists almost entirely of methane (CH4). Typically, LNG is 85 to 95-plus per cent methane, along with a few per cent ethane, even less propaneand butane, and trace amounts of nitrogen. Liquefied natural gas (LNG) is 600 times smaller
than natural gas when the latter is in its gaseous form, and it can be quickly shipped overseas. LNG is converted back to a gaseous state for use as an energy source upon reaching its destination. LNG is also used directly as a transportation fuel for ships and cars. Commercial uses for natural gas include heating, generating electricity, manufacturing products like fertilizers, paints and medicines, and occasionally fueling commercial vehicles. Liquefied naturalgas (LNG) is predominantly methane (CH4) converted into liquid form for storage or transport.

LNG utilization has grown significantly over the next 10 years, and it is highly likely that LNG will play a very important role in the world. Today there are numerous import and export terminals in operation and on the drawing boards, and the present fleet of worldwide LNG tankers is increasing at a rapid pace. This growth in the LNG industry will require a significant increase in the skilled workforce necessary to operate and maintain this production, processing, export, receiving, distributing, and vaporizing facilities. 

To better respond to anomalies during plant operation, engineers need some understanding of thermodynamics.The cases studied are mostly steady-state (the properties of the fluid at any point do not change with time) and steady-flow (the flow rate does not change with time) type problems.

1.    How the Methane Liquefaction System Works:

The methane liquefaction system operates on the same fundamental cryogenic principle used in industrial gas liquefaction systems. Methane is compressed, cooled through refrigeration and cryogenic heat exchange, expanded through a Joule–Thomson (JT) valve, and partially liquefied. The liquid methane is separated from the vapor phase, while the cold vapor is recycled through the heat exchanger to recover refrigeration energy and improve efficiency.

2.    Process Steps

a)    Natural gas pretreatment:

Before entering the liquefaction unit, natural gas must be purified by removing:

·      Water (H₂O)

·      Carbon dioxide (CO₂)

·      Hydrogen sulfide (H₂S)

·      Heavy hydrocarbons

Purpose

·      Prevent ice formation

·      Prevent CO₂ freezing

·      Avoid blockage in cryogenic equipment

·      Protect compressors and heat exchangers

b)   Compression

Methane is compressed to high pressure using a multistage compressor train.

Compression occurs in multiple stages with intercooling to reduce power consumption and compressor discharge temperature. This approach is commonly used in cryogenic liquefaction systems.

c) Intercooling

After each compression stage, methane is cooled back to approximately 280 K.

Benefits

·      Reduces compressor work

·      Improves overall efficiency

·      Prevents overheating

·      Protects compressor components

d) Cryogenic Cooling

After compression, methane enters the Main Cryogenic Heat Exchanger (MCHX).

Cooling Process:

The compressed methane is cooled: 280 K → 210 K using:

·      Mixed refrigerant cycle

·      Recovered cold vapor from the separator

The ICPT design highlights the importance of heat exchange and cold-energy recovery. Without sufficient heat exchange, reaching liquefaction temperature becomes difficult.

e) Joule–Thomson Expansion

The cooled methane expands through a JT valve.

Pressure Drop: 100 bar → 1 bar

Effect

·      Isenthalpic expansion

·      Significant temperature reduction

·      Partial liquefaction of methane

The JT valve is the key component that produces the final temperature drop required for LNG formation.

f) Phase Separation

The expanded methane enters a cryogenic separator.

Separator Outputs:

Liquid Stream:   LNG product

Vapor Stream:   Cold methane vapor

The separator separates the liquid methane from the vapor phase.

g) Vapor Recycle

The unliquefied methane vapor leaving the separator is returned to the cryogenic heat exchanger. There it absorbs heat from the incoming high-pressure methane stream and acts as a cooling medium before being recompressed and recycled through the process. This cold-energy recovery significantly improves system efficiency and reduces refrigeration requirements.

3.    Methane Liquefaction Temperature

 LNG production requires cooling methane to approximately:

T~ -160°C Or T~113 K

This is the typical liquefaction temperature of methane at near atmospheric pressure. The liquefied methane is then stored in insulated cryogenic tanks.

4.   Compressor Specifications

Why Multiple Compressors?

A compression ratio of : 100/1=100 is too high for a single compressor.

Therefore :

·      Compressor 1: 1à5 bar

·      Compressor 2: 5à25 bar

·      Compressor 3 : 25à100 bar

With cooling between stages .

5.    Heat Exchanger Specifications :

Main Cryogenic Heat Exchanger (MCHX) or Multi-stream Heat Exchanger (MSHX)

Main Characteristics:

·      Cryogenic service

·      Multiple hot and cold streams

·      Very small temperature approach

·      Highly insulated

·      Large heat-transfer surface area

·      H andles phase change (gasàliquid)

         Common Types

·      Plate-Fin Heat Exchanger (PHX)

·      Spiral-Wound Heat Exchanger (SWHX)

       These are the most common LNG heat exchangers

Function of the Heat Exchanger:

The cryogenic heat exchanger:

·      Cools methane from ambient conditions to cryogenic temperatures

·      Transfers heat between hot and cold process streams

·      Recovers cold energy from recycled vapor

·      Reduces refrigeration duty

·      Improves overall liquefaction efficiency

The cold methane vapor returning from the separator serves as an internal refrigeration source, similar to the recycle stream used in the ICPT cryogenic liquefaction concept.

6.    Design Notes

·      Several operating cycles are usually required before the system reaches steady cryogenic temperatures.

·      Cryogenic equipment must be highly insulated to minimize heat leakage.

·      Pressure-relief devices are required for safety.

·      Cryogenic temperatures and high pressures can cause thermal stresses and material cracking if unsuitable materials are used.

According to the methane physical properties: the liquifecation temperature is -160 degree C(around 113 Kelvin)

Inlet pressure=1 bar

Final Pressure = 100 bar because in a linde-Hampson liquification cycle gas is highly compressed and cooled.

Software used for building the cycle : DWSIM

References:

[1] Chapters concerning LOX Project in ICPT Final Report 2021 - Apr 2025 (pdf)

[2] Modelling and optimisation of a natural gas liquefaction
process, Master Thesis

[3] Liquefication of Oxygen System Concept/Design

[4] Liquefication of Oxygen Prototype (ICPT-LOX) and Air Distillation

[5]