Detection of glycol loss and utilizing new molecular seive in the glycol dehydration plant

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Detection of glycol loss and utilizing new
molecular seive in the glycol dehydration plant
Presented by Student Name Student ID
number Sultan Rashed 200213414 Saoud
Ahmed 200213431 Omar Al-Akbari 200101711 Saleh
Al Jabri 200235602 Rashed Al
Hakmani 200204495 Supervised by Dr. Nayef
Gasem
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Outlines

• Introduction
• Adsorption process
• Adsorption dehydration
• Glycol dehydration unit design
• Molecular sieve unit design
• Estimation cost
• Conclusion

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Introduction

• (GP1) In order to solve Abu Hasa Plant problem
  (losses of glycol) we
• studied the natural gas composition and
  properties.
• studied the problem of water in natural gas and
  its affect.
• studied two methods of dehydration which is
  liquid desiccant and solid desiccant
• studied the systems equipments
• did material balances for the glycol regeneration
  cycle
• did energy balances
• used chemical engineering simulation programs
  HYSYS
• did HAZOP study.
• (GP2) In order to compare between glycol system
  and solid desiccant we
• do design for equipments of glycol and solid
  desiccant systems
• calculate the total capital and operating costs
• determine possible locations of glycol losses
• compare between the two systems depending on
  advantages and disadvantages of each system.

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Adsorption of water by a solid desiccant

• Adsorption is purely a surface phenomenon
• molecules from the gas are held on the surface of
  a solid by surface forces
• function of operating temperature (?as T?) and
  pressure (? as P?)
• In NG industry a solid desiccant is used to
  remove water vapor from a gas stream

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Properties of physical adsorbents in NG
dehydration

• 1. Large surface area to 500-800 m2/g.
• 2. Good "activity and retention" for the
  components to be removed.
• 3. High mass transfer rate rate of removal.
• 4. Easy, economic regeneration.
• 5. Small resistance to gas flow small ?P
• 6. High mechanical strength resist crushing and
  dust formation.
• 7. Cheap, non-corrosive, non-toxic, and
  chemically inert

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Typical types of adsorbents
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Solid-desiccant dehydration process

• two or more adsorption towers are filled with a
  solid desiccant (on, stand-by)
• wet NG is passed through from top to bottom
• high-temperature dry gas stream is used to
  regenerate solids
• There are two mechanisms
• Chemisorption uncommon
• Physical adsorption common in gas dehydration

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Design of separator

• Separation units are engineered to meet the needs
  and requirements for
• Volume
• Gravity
• Pressure
• Foaming
• Paraffin
• Hydrates
• Impurities
• Corrosion
• The design standard of separation units must meet
  quality and reliability.
• sufficient instrumentation and control devices
  are necessary to ensure safe and continuous
  operation
• Horizontal separators are used
• in handling high to medium gas-oil ratios
• for large volumes of gas and liquids
• as 3-phase separators.

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Info. needed for design

• The separator used before absorption tower in
  Abu-Hassa Natural gas plant is used to separate
  condensed liquid from gas feed to absorber.
• After doing our GP1 mass balance we found all
  information needed to design this separator.

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Info. needed for design

• The information needed are
• P, Pressure in separator 387.3psia
• T, Temperature in separator 64.4F
• Mwav, Average molecular weight 29.68lb/lbmole
• ?L, density of liquid _at_STP 26.92lb/ft3
• z, compressibility factor 0.88
• q, Gas flow rate _at_STP 200.6MMSCFD
• Area for liquid 0.25 Area for gas
• F, volumetric flow rate to separator 6612m3/d
• Residence time 10min

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Design An Absorption Dehydration

• Information Required to Design an Absorption
  Dehydration Plant
• The number of stages needed in the absorber
  tower.
• Determine the column diameter.
• Overall height of the column.

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Design An Absorption Dehydration

• Natural gas information

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Design An Absorption Dehydration
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Design An Absorption Dehydration

• The Equilibrium data for TEG water system

(86,47)
(99.6,2)
Equilibrium Data Curve
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Design An Absorption Dehydration

• Determine the column diameter
• Diameter may be estimated by cross-section area
• Superficial velocity is estimated
• The density of vapor and liquid

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Design An Absorption Dehydration
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Design An Absorption Dehydration

• Gas volumetric flow rate of 162.3 MMscfd
• Diameter may be estimated by cross-section area
• Absorber diameter

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Design An Absorption Dehydration

• The height of absorber tower
• There is relationship between the height and
  number of trays.

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Heat Exchanger Design

• Objectives sought in H.E. design
• Heat load.
• Define the area or size (dimensions) and length
  of tube. of the H.E.
• Number of tube.
• Velocity.
• Drop in pressure.

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Shell and tube heat exchangers

• Fig. Shell and tube heat exchangers

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Where the symbols in the equations refer to the
following parameters

• Rate of heat transfer
• Reynolds number
• Density of TEG
• Viscosity of TEG
• Velocity
• Different in temperature
• Log mean temperature difference
• Friction factor

• Overall heat transfer coefficient
• Area of heat transfer
• Length of tube
• Diameter of tube
• Number of tubes
• Pressure drop inside tube

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Step1 Calculate heat transfer rate

• Step2 Calculate the log mean temperature
  difference

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Step 3 Choose the tube length and diameter

• Tube length 6 m , Tube diameter 0.0254 m
• Step 4 Calculate the area and number of tube

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• Step 5 Calculate the velocity
• Step 6 Calculate the pressure drop inside the
  tube

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Reboiler design
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• Step1 Required heat load
• Step2 Heat to vaporize water picked up in
  absorber
• Step3 Heat to vaporize reflux water in still.
  25 is returned
• Step4 Heat losses from still

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• Total heat load
• Using rule of thumb equation
• Regenerator duty

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Mole sieve

• Calculate the vessel diameter, weight of
  desiccant, vessel height, pressure drop,
  thickness of the vessel and weight of the vessel.
  
• Regeneration design
• Estimate heat required for regeneration
• Total regeneration cooling
• Estimation time of regeneration

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Mole sieve
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Calculate the viscosity, density and pressure drop

• from GPSA figure 23-26
• Density
• Pressure drop

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Estimate vessel internal diameter

• Gases volumetric flow
• V max 34 ft/min (fig.9-11)
• Vessel area
• Vessel ID 2.12m

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• Estimate water loading for 8 hr cycle

Inlet gas contains 42.5 lbH2O /MMscf from figure
4.4
Estimate weight of desiccant required in vessel
md Dynamic capacity at 65 F dynamic capacity at
75 F CTCss 65 F 130.981 12.74
lbH2O / 100 lb sieve

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Vessel height
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Regeneration design

• Estimate heat required for regeneration
• heating of water to 250 F
• Vaporizing water
• Heating of water from 250 F to 550 F
• heating vessel

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Regeneration design

• Estimate heat required for regeneration
• heat desiccant bed to 500 F
• Total regeneration heat

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Cost Estimation

• Cost plays an active role for the engineering
  life
• Design engineer needs to be able to make quick
  cost estimates to decide between alternative
  designs and for the project evaluation.

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Estimating the total capital cost of a plant

• Direct project expenses include
• equipment cost
• materials required for installation
• labor to install equipment and material
• Indirect cost
• freight, insurance, and taxes
• construction overhead
• contractor engineering expenses
• contingency

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Factors affecting the costs associated with
Capital Cost evaluation of chemical plants

• (1) Direct Project Expenses
• Equipment free on board cost
• Materials required for installation
• Labor to install equipment and material
• (2) Indirect Project Expenses
• Transportation costs, insurance, and taxes
• Construction overhead (vacation, sick leave and
  salaries)
• Contractor engineering expenses (salaries and
  project management)
• (3) Contingency and Fee
• Contingency (loss of time due to storms, strikes,
  and small changes in the design).
• Contractor fee (depend on type of plant)
• (4) Auxiliary Facilities
• Site development (civil engineering work)
• Auxiliary Buildings
• Off-sites and Utilities

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Lang Factor Technique
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Estimating the manufacturing (operating) cost of
a plant

• Direct Manufacturing Costs
• Variable costs
• Operating and labor
• Row materials
• Pollution control (air, water, and solid waste)
• Utilities
• Electricity
• Fuels
• Water
• Semi-variable costs
• Laboratory charges
• Maintenance
• Overhead (plant and salaries)
• Fixed Manufacturing Costs
• General Expenses
• Management
• Sales
• Financing

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Estimated Operating labor Cost

• Where NOL is the number of operators per shift, P
  is the number of processing steps involving the
  handling of particulate solids

Operating Labor
Labor Costs
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For new plant
Operating Labor
Labor Costs

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Estimated utility cost for mole sieve plant

• The utility cost for fan
• Duty
• Cost of electricity 0.06/kW.hr. And the
  efficiency of electricity 0.9.
• calculate the electricity power
• Yearly Cost

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The utility cost for heater

• Duty
• Cost of noncreative process 6.0/GJ with the
  efficiency 0.9.
• Yearly Cost

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The utility cost for Pump (Original plant)

• The shaft Power is 5.92 kW. The efficiency of an
  electric drive is about 85.
• Electric power
• The Cost of Electric is 0.06/kWh
• Yearly Cost

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The utility cost for fan (original plant)

• Duty
• Cost of electricity 0.06/kW.hr. And the
  efficiency of electricity 0.9.
• calculate the electricity power
• Yearly Cost

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The utility cost for heater (Original plant)

• Duty
• Cost of noncreative process 6.0/GJ with the
  efficiency 0.9.
• Yearly Cost

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The Estimated Cost of EquipmentAbsorption tower
cost
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Calculate the purchased cost

• Absorption tower
• For the Tower

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• For the Tray

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• Total cost of absorption tower is

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Purchased Cost for other equipment
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Conclusion

• Natural gas processing is an essential part of
  chemical engineering.
• Natural gas dehydration is an important process
  due to
• the pipe line specifications
• water problems in natural gas transportation and
  processing
• requirements of the users

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Conclusion

• The possible places of glycol losses are located
  in
• accumulator-reboiler system
• flash drum
• Advantages of Glycol dehydration
• Lower installed cost
• It is a continuous process.
• Low pressure drop (5-10 psi)
• Require less regeneration heat per pound of water
  vapor removed (low operating cost).
• Disadvantages of Glycol dehydration
• Water dew-point temperature is limited to
  temperature value higher then -25 oF
• For lower temperature than -25 oF, a stripping
  gas is required with very high concentrated lean
  glycol solution.
• Glycols are corrosive when decomposed or
  contaminated.

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Conclusion

• Advantages of molecular sieves
• Very low dew point and water content can be
  obtained
• Best suited for large volumes of gas under very
  high pressure
• Dehydration of very small quantities of natural
  gas at low cost
• insensitive to moderate changes in gas
  temperature, flow rate, and pressure.
• They are relatively free from problems of
  corrosion, foaming, etc.
• Some types can be used for simultaneous
  dehydration and sweetening
• Molecular Sieves disadvantages
• The most expansive adsorbents
• The regeneration temperature is very high
  (operating cost).
• Pressure drop is too high
• High space and weight required
• Mechanical breaking and contamination of liquid,
  oil and glycol are possible