Evaluation of LNG Production Technologies

Outline LNG Background Objective Simulation Specifications Liquefaction Techniques Heat Exchanger Types Simulation Method Results

Flow Diagram for a Typical LNG Plant

LNG (Liquefied Natural Gas) Basics

Combustible mixture of hydrocarbonsDry VS. Wet

NGL Extraction Dehydration/Scrubbing Liquefied Natural Gas

Target temperature for Natural gas:-260°FReduces volume by a factor 600

Objective

Main Objectives Simulate Processes Optimize Processes

Minimize compressor work Compare Processes based on

Capital cost Energy cost Total cost per capacity(Ton)

* Italicized processes signify Patent searched processes.* Bolded processes signify processes not included in scope of project.

Liquefaction Processes

Mixed Refrigerants Pure Refrigerants Both Other

Linde Process CoP Simple Cascade APCI C3 MRBP Self refrigerated

process

Axens Liquefin ProcessCoP Enhanced

CascadeAPCI AP-X

ABB Randall Turbo-Expander

Dual Mixed Refrigerant Linde 2006Williams Field

Services co.

Technip-TEALARCMustang Group

ExxonMobilDual Multi-component

Black and Veatch Prico Process

Technip- Snamprogetti

Flow diagrams

Black and Veatch’s PRICO Process

Axens Liquefin Process

ExxonMobil Dual Multi-Component Cycle

C3MR: Air Products and Chemical Inc

AP-X: Air Products and Chemical Inc.

DMR- Dual Mixed Refrigerant

Technip- TEALARC System

BP- Self Refrigerated Process

Linde/Statoil -Mixed Fluid Cascade Process Linde- CO2 MFCP

ConocoPhilips Simple Cascade

Simulation Specifications Natural Gas composition

Methane: 0.98 Ethane: 0.01 Propane: 0.01

Inlet conditions Pressure: 750 psia Temperature: 1000F

Outlet conditions Pressure: 14.7 psia Temperature: -260oF

Capacity: Common min. to max. capacity of process Common min. Capacity: 200,000 lbs/hr

Beihai City, China

Liquefaction Techniques Different Liquefaction techniques include:

Single Refrigeration cycle Multiple Refrigeration cycles Self Refrigerated cycles Cascade Processes

The cooling of natural gas involves the use of refrigerants which could either be pure component refrigerants or mixed component refrigerants.

Liquefaction TechniquesSchematic of a Simple Refrigeration Cycle

Compressor

Heat Exchanger

Expander

Liquefaction Techniques

Mixed refrigerants are mainly composed of hydrocarbons ranging from methane to pentane, Nitrogen and CO2.

Pure component Refrigerants Specific operating ranges for each component

Mixed Refrigerants Modified to meet specific cooling demands. Helps improve the process efficiency

Liquefaction Techniques

Natural gas cooling curve

Area between curves represents work done by the system

T-Q Diagrams

Liquefaction TechniquesSingle Refrigeration Cycle

One refrigeration loop that cools the natural gas to its required temperature range.

Usually requires fewer equipment and can only handle small base loads.

Lower capital costs and a higher operating efficiency

Black and Veatch:PRICO Process

Single mixed refrigerant loop and single compression system

Limited capacity (1.3 MTPA)

Low capital cost Great Pilot Process

Inlet Gas

LNG

Cold Box

Compressor Condenser

Expander

Residue

100oC

-260oC

Inlet Gas

LNG

Cold Box

Compressor

Simple Refrigeration Cycle

Refrigeration Cycles and Natural Gas Liquefaction

Black and Veatch- PRICO Process

Liquefaction Techniques Multiple Refrigeration cycles

Contains two or more refrigeration cycles. Refrigerants involved could be a combination of mixed or pure component refrigerants.

Some cycles are setup primarily to supplement cooling of the other refrigerants before cooling the natural gas.

More equipment usually involved to handle larger base loads.

Air Products and Chemical Inc: C3-MR

APCI processes are used in almost 90% of the industry

Good standard by which to judge the other processes

Capacity of about 5 MTPA Utilizes Propane (C3) and

Mixed Refrigerants (MR)

Inlet Gas

LNG

Mixed Refrigerant

Liquefaction TechniquesSelf Refrigerated Cycles

Takes advantage of the cooling ability of hydrocarbons available in the natural gas to help in the liquefaction process.

Numerous expansion stages are required to achieve desired temperatures.

Considered as a safer method because there are no external refrigerants needing storage.

BP Self Refrigerated Process

Neither refrigerants, compressor, nor expanders present in setup.

Cost include mainly capital costs and electricity.

Low Production rate (51%) Capacities of over 1.3MTPA

attainable .

Inlet gasLNG

Residue Gas

Liquefaction TechniquesCascade Processes

A series of heat exchangers with each stage using a different refrigerant.

Tailored to take advantage of different thermodynamic properties of the refrigerants to be used.

Usually have high capital costs and can handle very large base loads.

ConocoPhilips Simple Cascade

3 stage pure refrigerant process Propane Ethylene Methane

5 MTPA Capacity

Pre- Cooling

Sub-Cooling

Liquefaction

Inlet Gas

LNG

Residue Gas

Propane

EthyleneMethane

Equipment

Plate Fin Heat Exchanger

Spiral Wound Heat Exchanger

Spiral Wound Heat Exchanger

Equipment Comparison   Plate-Fin-Heat-Exchangers Coil-Wound-Heat-Exchangers

Characteristics Extremely compact Compact

Multiple streams Multiple streams

Single and two-phase streams Single and two-phase streams

Fluid Very clean Clean

Flow-types Counter-flow Cross counter-flow

Cross-flow

Heating-surface 300 - 1400 m²/m³ 20 - 300 m²/m³

Materials Aluminum Aluminum

Stainless steel (SS)

Carbon steel (CS)

Special alloys

Temperatures -269°C to +65 °C (150 °F) All

Pressures Up to 115 bar (1660 psi) Up to 250 bar (3625 psi)

Applications Cryogenic plants Also for corrosive fluids

Non-corrosive fluids Also for thermal shocks

Very limited installation space Also for higher temperatures

Our Evaluation Methods

Data on operating conditions (Temperatures, Pressures, Flowrates, etc) for all these processes is not widely available (Only some is reported).

We decided to perform simulations using our best estimates.

We used minimum compression work as guide.

We identified non-improvable points

Details of methodology Conditions after each stage of refrigeration were noted After making simple simulations mimic real process,

variables were transferred to real process simulation Optimization- Refrigerant composition Optimization- Compressor work Restriction needed- Heat transfer area

All cells in LNG HX must have equal area Restriction needed- Second law of thermodynamics

Check temperature of streams Utilities

Obtain cooling water flow rate

Pre- Cooling

Sub-Cooling

Liquefaction

High Pressure

Low Pressure

CO2 Pre-cooled Linde Process

Modification of the Mixed Fluid Cascade Process

Three distinct stages using 3 mixed refrigerants with different compositions

Carbon dioxide is sole refrigerant in pre-cooling stage

Separate cycles and mixed refrigerants help in the flexibility and thermodynamic efficiency

Process is safer because hydrocarbon inventory is less

8 MTPA Capacity

Inlet Gas

LNG

100oC

-70oC

-140oC

-260oC

Results

Economic Life of 20 years New train required at the documented

maximum capacity of each specific process. Average cost of electricity and cooling water

throughout the US used in analysis. Energy cost evaluated at a minimum capacity

of 1.2 MTPA

Cost Basis

Results

10

10

Results

Results

Process Cost per ton ($) Max capacity (MTPA) Prico 5.12 1.20 Liquefin 3.41 6.00 ExxonMobil 4.83 4.80 DMR 12.58 4.80 APX 19.20 7.80 MFCP 31.73 7.20 MFCP(CO2) 24.77 7.20 TEALARC 25.35 6.00 C3MR 12.93 4.80 Conoco 20.15 5.00

Analysis

Our results may not match market trendsOperating temperature and pressure range

as well as flowrate information unavailablePrecedents to compare results unavailable Information on cost to use process

unavailable (licensing, proprietary production fees, etc.)

Analysis We may be trapped in local minima and failed

to identify better conditions

Work

Temperature

Global Minimum

Local Minimum

Conclusions We successfully simulated several LNG

production plants We obtained capital and operating costs and

determined a ranking Some connection with existing trends were

identified, but other results do not coincide with market trends

We discussed why discrepancies may arise.

Questions?