United Arab Emirates University

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United Arab
Emirates University
College of Engineering Training and
Graduation Projects Unit Graduation
Project II
Liquefied Natural Gas
Advisor Dr. Marcelo Castier Done by Basma
Ali 200211743  Fatima Rashid 200212000  Latifa
Obaid 200203237  Sheikh AL thahry 200202742
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Outline

• Back ground Gp1
• Introduction to Liquefied Natural Gas project
• Main objectives challenges
• Process Descriptions of the co production plant
• Equipments sizing Design parameters
• HAZOP study Process Modifications
• Economic evaluation
• Site layout location
• Conclusions

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Background GPI

• Process Selection
• Material Balance Calculation.
• Energy Balance Calculation.

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Process of Liquefaction of Natural Gas
Co-production.
Hybrid cycle.
Double Mixed Refrigerant
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HYSIS simulation
Compression Loop
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HYSIS simulation
Compression Loop
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Project description

• Project objective
• The main technical challenge of this project is
  to cool natural gas into very
• low temperature (approximately -163 0C), what
  requires several interlinked refrigeration
  cycles.
• Raw Feed Materials Specifications
• Tools and Methods

Conditions Stream Temperature (oC) Pressure (kPa) Mass flow rate (kg/sec)
Natural gas 31 8860 129.515
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Project challenge

• Setup the process model in a commercial simulator
  (HYSYS) and obtain numerical convergence.
• Design a unusual distillation column with
  multiple feeds and products and, more
  importantly, with a liquid recycle structure at
  the top of the column that does not occur via a
  conventional condenser.
• Design a liquid expander, which exists in the
  plant to recover mechanical work from liquid
  expansion.

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Process Description
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Introduction to NGL
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Important definitions

• Natural gas is a mixture of hydrocarbon gases and
  acid gases with varying molecules and amount of
  impurities.
• NGL is removal of certain components, such as
  dust, helium, water, and heavy hydrocarbons and
  then condensed into a liquid at close to
  atmospheric pressure.

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Equipment sizing Design parameters
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Introduction to equipment design

• Design mean is to formulate a plan for devise
  designed.
• Important of equipment design-
• Checking new process designs
• Providing equipment size and performance
  estimates
• Helping to troubleshoot problems with operating
  systems
• Verifying the reasonableness of results of
  computer calculations and simulations
• Obtaining approximate costs for process units

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Equipment Design
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High-Pressure Phase Separator

• From heuristics of separator-
• Rule 1 ? Vertical Vessel Rule 1 ? L/D between
  2.5 and 5 with optimum at 3.0 Rule 3 ? liquid
  hold-up time is 5 min based on ½ volume of vessel
  Rule 4 ? Gas velocity u (m/s) is given by
• where k 0.0305 for vessels without mesh
  entrainers
• Data provided from HYSYS-Vapor flow, Liquid
  flow, ?v and ?l

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Heat Exchanger Design

• Heat exchanger is device that is used to transfer
  thermal energy from one fluid to another without
  mixing the two fluids.
• Main parameter of designing heat exchanger
• determining its type, area and duty.
• The type of heat exchangers in the LNG plant are
  shell and tube heat exchangers.

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Expander Design

• Liquid expanders offer the potential to improve
  process efficiency by recovering otherwise unused
  energy.
• Type of Liquid Expander
• Cryogenic Liquid Expander
• Joule Thompson (JT) Valve
• Hydraulic turbine.
• Flashing liquid expander.

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Expander Design

• Assumptions
• Adiabatic.
• Reversible.
• ?S 0, isentropic process.
• Ideal gas.
• Equations
• dH T ds V dP
• ? H V dP.
• Rackett equation Vsat Vc Zc (1-Tr) 0.2857

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Compressor

• Mechanical device that increases the pressure of
  a gas by reducing its volume. Compression of a
  gas naturally increases its temperature.

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Compressors design

• Determination of
• Type of compressor.
• V. m./?
• CR Pout/Pin lt3
• Poptimum Pout vPin/Pout
• Efficiency.
• Power actual power.
• R.A.P n. Z. R. T. (Pout/Pin)a - 1)/a,
• a Cp/Cv, A (k-1)k
• Actual power R.A.P / ?
• Outlet temperature.

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Determination of compressibility factor
Tr T/Tc Pr P/Pc

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Valves design

• A device that regulates the flow of substances
  like gases, fluidized solids, slurries or
  liquids, by opening or closing.
• Valves applications
• Used for safety purposes.
• Used for controlling applications.

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Valves design parameter

• a)  The process requirements (pressure and flow)
  downstream.
• b)  The service (regular flow line,
  intermittent, blow-down, depressurizing).
• c)  The variations in the flow and pressure with
  time.
• d)  Fluid characteristics (composition, solids,
  Newtonian or non-Newtonian).
• e)  Phase behavior (single phase, two phase,
  water contain).
• f) The suitable diameter for the suitable pipe
  with stand
• the range of velocity between 5 10 ft.

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Distillation Column Design

• Distillation is a process in which a liquid or
  vapor mixture of two or more substances is
  separated into its component.
• Determination of relative volatility
• Raults Law

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Cont Relative Volatility

• Minimum number of stages by using Fenske equation
  
• Nmin
• Log (XLD/XHD)(XHW/XLW) /Log (aavg.)
• Actual Reflux Ratio
• (R-Rmin)/(R1)

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Diameter Height of tower
?vap ( avg.Mw P) / (R/T)
Volume flow rate (Top flow Mwav.)/(vap.?
3600)

Velocity (1.35)/(top ?) 0.5
Diameter (m) ((4Volume flow rate)/(pv))0.5

Refer to recommended tray table Hmin (NAS
1)plate spacing Hmax (NAS 1)plate
spacing(13)
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HAZOP study and Process modification
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Definition of HAZOP

• An analysis of the hazards which could occur at
  step in the process, and a description and
  implementation of the measures to be taken for
  their control.
• Invented by the BCI "British chemical industry"
  in the United Kingdom.
• Officially adopted in 1974 after flixborough
  explosion.
• This chemical plant explosion killed twenty eight
  people and injured scores of others
• the public living nearby
• Lack of a systematic review of the qualified
  personnel.

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Benefits of using HAZOP techniques

• easy to learn.
• can be easily adapted to almost all industrial
  operations
• No special level of academic qualification is
  required. 
• The HAZOP Study is an opportunity to correct
  these before such changes become too expensive,
  or 'impossible' to accomplish.
• HAZOP methodology is perhaps the most widely used
  aid to loss prevention.

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Procedure setup
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HAZOP Analysis
3. Subdivide the system or activity and develop
deviations
2. Define the problems of interest for the
analysis
1. Define the system or activity
2.0 Define the problems of interest for the
analysis
1.0 Define the system or activity
5. Use the results in decision making
4. Conduct HAZOP reviews
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Process Modification

• Studying the special concern of these conditions
  are important to provide conditions that allow
  effective process performance.

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Special Concern Area of Equipments
Conditions Type of Equipments
High temperature (Tgt250OC) or pressure (Pgt10 bar)Low temperature (Tlt40OC) or pressure (Plt1 bar) Separators
Pout/Pin gt 3High Temperature inlet gas Compressors
?TIngt100oC Heat exchangers
Large ?P across valve Valves
Streams of greatly differing temperatures mixStreams of greatly differing composition mix Mixers
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Special Concern areas

• Distillation Column
• There are a special concern.
• Heat Exchanger
• ? TIn 105.9 oC -30 oC
• 75.9 oC lt100 oC

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Economic evaluation
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Introduction to equipments cost

• Cost Estimation
• Cost estimation models are mathematical
  algorithms or parametric equations used to
  determine the costs of plant.
• The results of the models are typically necessary
  to measure approval to proceed, and are factored
  into business plans, budgets, and other financial
  planning and tracking mechanisms.

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Total module and Grass root cost

• Total module cost can be evaluated from
• And Grass root cost can be evaluated from

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Cost Estimation for Coolers
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Estimation Costs
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Cost estimation for distillation column

• Cost equations for tower and trays.
• Volume p D2 L / 4
• Area for trays V / L

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Raw material Cost

• The cost of raw materials can be estimated by
  using the current price listed in such
  publications as the Chemical Market Reporter
  (CMR).

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Labor Operating Cost
The technique used to estimate operating labor
requirements is based on data obtained from five
chemical companies and correlated by Alkayat and
Gerrard.
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Equipment Type Number of Equipment Nnp
Exchangers 9 9
Compressors 4 4
Expanders 3 3
Tower 1 1
Vessel 1 -
Total   17
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Utilities Cost (CuT)

• Specific difficulties emerge when estimating the
  cost of fuel like electricity, stream and thermal
  fluid.
• Costs of utility streams required by process
  includes
• Fuel gas, oil and coal.
• Electric power.
• Stream.
• Cooling water.
• Process water.
• Boiler feed water.
• Instrument air.
• Inert gas.
• Refrigeration.

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Changes in Fuel prices
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Compression between coal and NG
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Plant Layout

• It is necessary to make a preliminary study on
  the layout of the plant equipments.

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Layout depending factor

• Main rooms as control room and offices should sit
  away from areas that have high accident risk and
  upstream of the current winds.
• Reactors, boilers, etc., Should build up
• away from the chemical storage tanks.
• Storage tanks should be easy access and choice on
  whether all tanks (of raw materials and products)
  should be located together or dispersed
  throughout the site

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• Availability of plant requirement.
• Minimizing plant piping systems.
• Suitable access to equipment that usual require
  maintenance or repair and keep a space between
  equbments.
• Access to the plant in the case of an accident.
• Availability of source of cooling place for
  equipments need cooling water close.

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The aim of minimizing the layout of plant
equipment

• avoid damage to persons and property due to fire
  or explosion.
• decrease Maintenance costs.
• reduce number of worker in the plant.
• decrease operating costs.
• reduce construction costs.
• Reduce cost of expansion or modifications on
  plant.

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Piping and Instrumental Diagram (PID) Designs

• The piping and instrumentation diagram (PID)
  provides information need by engineers to begin
  planning for the construction of the plant.
• Mechanical engineers and civil engineers will
  design and install pieces of equipment.
• Instrument engineers will specify, install and
  check control system.
• Piping engineers will develop plant layout and
  elevation drawings.
• Project engineers will develop plant and
  construction schedules.

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Conventions in constructing PD diagram

• For equipments, show every piece including spare
  units, parallel units and summary details of each
  unit.
• For piping, include all lines including drains,
  sample connections and specify size, schedule,
  materials of construction and insulation.
• For instruments, identify indicators, recorders,
  controllers and show instrument line.
• For utilities, identify entrance utilities, exist
  utilities and exist to waste treatment
  facilities.

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Conclusion

• Total Module Cost and Grass Roots Cost
• Cost of operating labor (COL)
• Utility costs (CUT)
• Total utilities cost 4.685107
  /yr
• Raw materials costs (CRM)
• Capital Cost of Manufacturing (COMd)

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Qatar Conference of LNG
Important Dates Full Paper Submission June 16,
2008         Paper Acceptance  August 8, 2008
        Final Submission August 24, 2008