Improved Manual Method for Settle Out Condition Estimation

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In earlier discussion "Simple Manual Method for Settle Out Condition Estimation", a manual method has been can be considered without using any Process Simulator. This method basically utilising universal gas law (PV=znRT) with the following basis and assumption :

• Vapor only system
• No condensation during the process
  
• Compressibility factor assumed same for condition before and after settle-out and assumed (z=1)
  
• Limited fluid with molecular weight is similar range. Higher the different, higher the deviation

In this method (T x n method), the settle out temperature is calculated using this equation :

T_s = Sum (n₁ x T₁ + n₂ x T₂ + n₃ x T₃ +...) / n_s

This method (T x n method) has a particular known issue where it does not considered the impact of Molecular Weight (MW). In the event molecular weight of each sections are different, the calculated settle temperature will not change with molecular weight. In this post, an improved method is introduced to use same derivation per T x n method, however it includes MW as part the calculation. It basically use mass (m) to replace mole (n) which simply name as T x m method.

Derivation
A system consists of n-section with pressure (P_i, kPag), temperature (Ti, K), Molecular weight (MW_i), physical volume (V_i, m3) for i-section.

Number of mass in each i-section (before settle-out),

m_i = (P_i x V_i x MW_i) / (z_i x R x T_i).....[1]

Total mass (after settle-out),

m_s = Sum (m₁ + m₂ + m₃...).....[2]

Total volume (after settle-out),

V_s = Sum (V₁ + V₂ + V₃...).....[3]

Volume at normal condition (P_i,n = 1.01325 bar & Ti,_n = 273.15 K) for each i-section (before settle-out)

V_i,n = (P_i x V_i / T_i) /(P_i,n / T_i,n)......[4]

Total volume at normal condition (after settle-out)

V_s,n = Sum (V_1,n + V_2,n + V_3,n...).....[5]

m_i x T_i for each i-section (before settle-out),

m_i x T_i = (P_i x V_i x MW_i) / (z_i x R).....[6]

Total m_s x T_s (after settle-out),

m_s x T_s = Sum (m₁ x T₁ + m₂ x T₂ + m₃ x T₃ +...).....[7]

Thus, From [7] and [2],
Settle-out temperature (T_s),

T_s = Sum (m₁ x T₁ + m₂ x T₂ + m₃ x T₃ +...) / m_s .....[8]

Settle-out pressure (P_s),

P_s = (1.01325) x (V_s,n / V_s) x (T_s / 273.15)......[9]

Case Study
There are five sets of system with each system has 3 section will be settled-out. The five set of fluid will have same pressure and temperature prior to settle out, however the composition of each section will be difference as follow :

Composition Set 1 :
Section 1 : Methane : 100%
Section 2 : Methane : 100%
Section 3 : Methane : 100%

Composition Set 2 :
Section 1 : Ethane : 100%
Section 2 : Methane : 100%
Section 3 : Methane : 100%

Composition Set 3 :
Section 1 : Ethane : 100%
Section 2 : Methane : 100%
Section 3 : Methane : 50%, Ethane : 20%, Propane : 30%

Composition Set 4 :
Section 1 : Propane : 100%
Section 2 : Propane : 100%
Section 3 : Methane : 50%, Ethane : 20%, Propane : 30%

Composition Set 5 :
Section 1 : Propane : 100%
Section 2 : Propane : 100%
Section 3 : Ethane : 40%, Propane : 60%

Image below display the results of HYSYS Settle-out using method in "Simple Method For Compressor Settle Out (Vapor Only) Using HYSYS", T x n and T x m methods.

Above results show
i) Settle-out pressure and temperature will not change with composition.
ii) if the composition are close between each sections, both T x n and T x m may be used.
iii) Accuracy for T x m are typically higher than T x n methods.

Related Topic

• Simple Manual Method for Settle Out Condition Estimation
• Adjusted Method For Compressor Settle Out (with Vapor & Liquid) Using HYSYS
• Simple Method For Compressor Settle Out (Vapor only) Using HYSYS
• Combine Anti-surge control (ASC) & Capacity Control (CC) Functions ?
• Saturate Dry Gas With Water in HYSYS
• Saturate Dry Gas With Water in HYSYS Using SATURATE Extension
• Useful Documentation for HYSYS ...

LNG and Supply Chain

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Natural gas is used in industry and household to provide heating energy. It is explored from gas well, treated, transported to customer via large and long pipeline. It is become non-cost effective once the pipeline length is exceeded 3000 - 3500 km. Thus, another mode of transportation, Liquefied Natural Gas (LNG) is considered cost effective.

Liquefied Natural gas (LNG) is a process of cooling down the natural gas to form liquid for easy storage and transportation. A LNG is normally contains of Methane (CH4) which is more than 90% and other light hydrocarbon such as Ethane (C2H6), Propane (C3H8), Butane (C4H10) and Nitrogen (N2) inert gas. LNG is non-corrosive, non-toxic, non-carcinogenic, odorless and colorless. However, it is flammable and explosive and create greenhouse effect to environment.

Natural gas may contains of other contaminants such as Carbon Dioxide (CO2), Hydrogen Sulfide (H2S), Water (H2O), Mercury (Hg), Nitrogen (N2), Helium (He), BTEX, etc. These contaminants potentially cause corrosion, cracking and freezing problem in the natural gas liquefaction process. and drop in Higher Heating Value (HHV). Thus they shall be removed prior to liquefaction process. Read more in "Typical Gas Processing Flow Scheme" and "Gas Processing, NGL Extraction & LPG Fractionation".



Entire LNG supply chain consist of LNG production, transportation and regassification process. Natural gas produced from gas well will be treated in order to remove contaminants as mentioned above prior feed to cryogenic section for liquefaction. In the liquefaction process, Natural gas is chilled down to about -160 degC. Ethane (C2), Propane (C3) and Butane (C4) will be recovered as Ethylene feedstock and production of Liquefied Petroleum Gas (LPG). Heavy hydrocarbon (C5+) will be removed from natural gas and sale as stablised condensate. In the process of liquefaction, the natural gas volume will reduce roughly about 600 times and this ease for LNG storage and transportation. Once the LNG is produced, it will store in LNG tank at atmospheric pressure prior pumped to LNG tanker for transportation.

LNG pumped into LNG tanker via LNG loading station will be send to customer. Good insulation is one of the key factor in keep LNG in liquid form during the transportation process. Any vaporized LNG will be compressed and used as fuel to generate power and drive all equipment in LNG tanker.

Once the LNG tanker arrived at LNG terminal, it is unloaded from the LNG tanker to the LNG storage tank. From the LNG storage, LNG is pumped and regassified using seawater or closed loop heated water. Vaporized natural gas is then injected into natural gas grid and deliver to customer.

Following are few video clips for the LNG supply chain, LNG liquefaction and terminal.

LNG supply chain



LNG Liquefaction Plant



LNG Terminal

Related Topics

• Gas Processing, NGL Extraction & LPG Fractionation
• Typical Gas Processing Flow Scheme
• Typical Refinery Flow Scheme
• Floating Gas Refinery Unit

Obtain HYSYS Worldwide Support Information Instantly

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Some time you may experience problem or technical issue with HYSYS operation, or you may found some bugs in the HYSYS, it is common that you can make necessary report to Aspen HYSYS support center to looks for solution. Aspen HYSYS has a team operate world wide to support all Aspen HYSYS registered users.

Aspen HYSYS has many support centers i.e. U.S., Canada, Mexican, Venezuela, France, UK, Egypt, South Africa, Malaysia, Singapore, Australia, etc. You may sometime would like quick information for the contact. HYSYS has one unique support email address : esupport@aspentech.com

However, you may like to obtain other information i.e contact number, fax number, etc for a particular nearest support center. This is especially important when you are outstation. One of the quickest way is from the HYSYS software itself. HYSYS has built-in these information in the HYSYS itself. See below image.

(Click to view larger image)

To launch this utility, just simply open the Help | About HYSYS..., pop-up display will show the HYSYS version/build. Then click the Technical Support at the bottom. You can obtain information for phone number, fax number, email address, toll free number, international toll free number, website address and support website address for all latest support centers.


Related Topic

• Useful Documentation for HYSYS ...
• HYSYS Version & Build number

HYSYS Version & Build number

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HYSYS release is normally follow it build number. i.e version 3.2, the build number is 5029. For some of the HYSYS version i.e. 2004, there are several builds released for the same versions. Following is a simple listing of build for references.

Build	Version
7020	V7.0
6924	2006.5 with CP3
	2006.5 with CP2
	2006.5 with CP1
	2006.5
6729	2006 with CP2
	2006 with CP1
6728	2006
6612	2004.2 with CP5 + Patch 6
	2004.2 with CP5
	2004.2 with CP4
	2004.2 with CP3
	2004.2 with CP2
	2004.2 with CP1
	2004.2
6510	2004.1 with CP1
	2004.1
6150	2004
5029	3.2
4815	3.1
4602	3.0.1
3874	2.4.2
3870	2.4.1
3806	2.2.2
3797	2.2
3216	2.1.3
3198	2.1.1

This post is sort of follow-up post from earlier post "Incompatibility HYSYS Version & Its File...What to do ?", which has discussed the way to identify HYSYS version/build. One of the important information is the cumulative patches should match with the correct version. If you have version 2006.5, you should ensure you have installed CP3 to ensure proper operation of HYSYS 2006.5.

Related Topic

• Incompatibility HYSYS Version & Its File...What to do ?
• Mass Heat of Vaporization in HYSYS only for Pure Component
• Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS
• Useful Documentation for HYSYS ...
• Extend of Pool Fire...
• How Fluid Characteristic affect 2 phase Relief via PSV on Liquid filled Vessel Exposing to External Fire

Why Restriction Orifice is some distance from Blowdown valve ? - Clarif #01

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A reader MT (abbre.) has read "Why Restriction Orifice is some distance from Blowdown valve ?" and drop me a note. The question are more-or-less as follow :

i) For cases where huge pressure drop is not foreseen or low temperature is not expected downstream of restriction orifice (RO), is it still necessary to provide the minimum distance ?

ii) If the Flare header is Stainless steel (SS), and the process piping is Carbon steel (CS), the Spec break between CS and SS will be shown at the blowdown valve (BDV), i.e. BDV is designed for the most conservative material - SS. In this case, i do not seen the reason of the minimum distance.

Original Intention

The intention of the proposed arrangement in "Why Restriction Orifice is some distance from Blowdown valve ?" is to avoid the BDV stem stuck at position in case the depressured fluid temperature is dropped to sub-zero (below zero degree Celcious).

Responses

i) In case low pressure drop and the depressured temperature is still higher than sub-zero, this requirement is NOT necessary. As long as there is NO risk of fluid temperature drop below zero degree Celcious, then this arrangement is not required.

ii) The process piping upto BDV (excluded BDV) is CS and from BDV onwards is SS. This is a good arrangement with good spec break. The 600mm requirement is mainly related to frozen of moisture content (below zero degree Celcious), it has no/less relationship with the material. Thus, as long as the depressured temperature can drop below zero degree Celcious, regardless what the material of construction (MOC) is, the 600 mm arrangement still applicable.

Related Post

• Few Recommendation on Manual Blowdown Line
• A refresh to Process Engineer on few phenomenons in restriction orifice
• Bug in ASPENTECH HYSYS 2006 Dynamic Depressuring Fisher Valve model
• Controlled and Non-controlled Type Depressuring
• How to apply valve equation in HYSYS Depressuring ?
• Why Restriction Orifice is some distance from Blowdown valve ?

Simple Manual Method for Settle Out Condition Estimation

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Compression system shutdown, block-in, settle out follow by system blowdown is common in any oil and gas, refinery and LNG production facilities. A methodology using HYSYS simulation software has been presented in "Simple Method For Compressor Settle Out (Vapor Only) Using HYSYS" and this method is particularly applicable to vapor only system. In order to handle system contains vapor and liquid, the method has been extended "Adjusted Method For Compressor Settle Out (with Vapor & Liquid) Using HYSYS". Some engineers asked a question, this method is applicable during detailed design. Nevertheless, is there any simpler and manual method that may be used for quick estimation during proposal and/or conceptual stage ? Yes... Following is a simple manual method may be considered.

This method is utilising universal gas law (PV=znRT) with the following basis and assumption :

• Vapor only system
• No condensation during the process
  
• Compressibility factor assumed same for condition before and after settle-out and assumed (z=1)
  
• Limited fluid with molecular weight is similar range. Higher the different, higher the deviation

A system consists of n-section with pressure (P_i, kPag), temperature (Ti, K), Molecular weight (MW_i), physical volume (V_i, m3) for i-section.

Number of mole in each i-section (before settle-out),

n_i = (P_i x V_i) / (z_i x R x T_i).....[1]

Total mole (after settle-out),

n_s = Sum (n₁ + n₂ + n₃...).....[2]

Total volume (after settle-out),

V_s = Sum (V₁ + V₂ + V₃...).....[3]

Volume at normal condition (P_i,n = 1.01325 bar & Ti,_n = 273.15 K) for each i-section (before settle-out)

V_i,n = (P_i x V_i / T_i) /(P_i,n / T_i,n)......[4]

Total volume at normal condition (after settle-out)

V_s,n = Sum (V_1,n + V_2,n + V_3,n...).....[5]

n_i x T_i for each i-section (before settle-out),

n_i x T_i = (P_i x V_i) / (z_i x R).....[6]

Total n_s x T_s (after settle-out),

n_s x T_s = Sum (n₁ x T₁ + n₂ x T₂ + n₃ x T₃ +...).....[7]

Thus, From [7] and [2],
Settle-out temperature (T_s),

T_s = Sum (n₁ x T₁ + n₂ x T₂ + n₃ x T₃ +...) / n_s .....[8]

Settle-out pressure (P_s),

P_s = (1.01325) x (V_s,n / V_s) x (T_s / 273.15)......[9]

Case Study
A methane compression system with the following conditions.

Suction :
Pressure, P₁ = 5 barg
Temperature, T₁ = 50 degC
Molecular weight, MW = 16.0429
Physical Volume, V₁ = 1 m³

Compressor discharge (Hot) :
Pressure, P₂ = 15 barg
Temperature, T₂ = 150 degC
Molecular weight, MW = 16.0429
Physical Volume, V₂ = 1 m³

Cooler discharge (Cool) :
Pressure, P₃ = 15 barg
Temperature, T₃ = 50 degC
Molecular weight, MW = 16.0429
Physical Volume, V₃ = 1 m³

Using method as proposed in "Simple Method For Compressor Settle Out (Vapor Only) Using HYSYS", the settle out pressure and temperature are 11.73 barg and 86.3 degC. (see below image).

Using manual method as proposed above (program in Excel), the settle out pressure and temperature are 11.67 barg and 85.7 degC. (see below image).

The percentage error are 0.5% and 0.7% for pressure and temperature respectively.
This shown the method is reasonable.

Related Topic

• Adjusted Method For Compressor Settle Out (with Vapor & Liquid) Using HYSYS
• Simple Method For Compressor Settle Out (Vapor only) Using HYSYS
• Combine Anti-surge control (ASC) & Capacity Control (CC) Functions ?
• Saturate Dry Gas With Water in HYSYS
• Saturate Dry Gas With Water in HYSYS Using SATURATE Extension
• Useful Documentation for HYSYS ...

Incompatibility HYSYS Version & Its File...What to do ?

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Some time you received an HYSYS file (ABC.hsc) from contractor or client, you open the file using a particular version (i.e. HYSYS 3.2), you may experience the HYSYS failed to open the file. Reason being you are using older version/build of HYSYS (i.e 3.2 ) to open a newer version/build of HYSYS (i.e 2006).

There are several questions may be raised :

i) How to know which version/build of HYSYS that you are using ?
ii) How can you know which version/build of HYSYS a case was created ?
iii) How to open a newer version/build of HYSYS with older version/build of HYSYS ?

HYSYS version
To know which version of HYSYS you are using, just simply open the Help | About HYSYS..., pop-up display will show the HYSYS version/build. The following image shows it is HYSYS version 3.2 (Build 5029).

HYSYS Version of Created File
To know which version the file was created, first you need to make small changes in HYSYS Preferences. Click Tools | Preferences, the Session Preferences pop-up will be displayed. Click Files tab and select HYPROTECH file Picker on the top, then click the Save Preferences Set. See

Now click the File | Open | Case, the file open pop-up is displayed. You will notice the version / build of the file created in HYSYS.

(Click to view large image)

You may also get similar information when you click the File | Save As. See below image.

(Click to view large image)

Open File Created in Newer Version with Older Version of HYSYS
The topic has been discussed in earlier post "Open HYSYS File in Older Version of HYSYS".

To get more tutorial and information related to HYSYS, check out "Useful Documentation for HYSYS ...".

Related Topic

• Mass Heat of Vaporization in HYSYS only for Pure Component
• Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS
• Useful Documentation for HYSYS ...
• Extend of Pool Fire...
• How Fluid Characteristic affect 2 phase Relief via PSV on Liquid filled Vessel Exposing to External Fire
• Definition of Terms Related to PRESSURE

Power in Human Cell Size Micro Battery

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Team led by associate director, Shuguang Zhang managed to use the energy generated by trees to power a network of wireless sensors (-Tree Power-), Professor Zhong Lin, Wang research group managed to generate power from Fabric (-Fabric Generate Power Caught Global Interests...-), and now MIT engineers led by professors Yet-Ming Chiang have developed a way to create and install tiny microbatteries, about half the size of a human cell and built with viruses which could one day power a range of miniature devices, from labs-on-a-chip to implantable medical sensors -- by stamping them onto a variety of surfaces.

In the Proceedings of the National Academy of Sciences (PNAS) the week of Aug. 18, the team describes assembling and successfully testing two of the three key components of a battery. A complete battery is on its way.

"To our knowledge, this is the first instance in which microcontact printing has been used to fabricate and position microbattery electrodes and the first use of virus-based assembly in such a process," wrote MIT professors Paula T. Hammond, Angela M. Belcher, Yet-Ming Chiang and colleagues. Read more in MIT Tech Talk.

Related Topic

• Tree Power
• Nanowire battery... High Potential of Replacing Lithium Battery
• Fabric Generate Power Caught Global Interests...
• "Power shirt"
• Own Your Fuel Filling Station in Your Garage
• Euro 6 Million Supporting Nanotechnology
• Nanowerk - NanoTech News & Database Center
• Nano Technology - Revolution in Material Selection

How to Merge Several FLARENET Models into Single Model ?

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Nowadays Oil & gas, LNG, Petrochemical, Refinery plant capacity are large and some time a few design centers are working together to manage the project during design phase. The project may splits into several large units and each design center will design their own units. The design include flare system modeling using FLARENET.

Several design center will generate their own FLARENET models and upto one point of time, all models may required to merge in order to check the overall flare system performance. Some steps presented in thmay be used to merge several FLARENET models into single model using built in utility in FLARENET.

Download

If you aware of any other method, please share with us.

Related Topic

• Guideline on Quick Determination of Flare Stack Support Type
• Must Read Flare Handbook
• Why not bury flare pipe header ?
• Use Ultra-Sonic Flowmeter in FLARE Gas Header for emission monitoring
• FLARE combustion efficiency
• Factors and Criteria for Vent Stack Design

Tree Power

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A group of researchers with team member Andreas Mershin, a postdoctoral associate at the CBE and Christopher Love, an MIT senior in chemistry, led by Shuguang Zhang, the associate director of the MIT's Center for Biomedical Engineering (CBE) from the Massachusetts Institute of Technology (MIT) has managed to use the energy generated by trees to power a network of wireless sensors to prevent spreading forest fires. These sensors are powered by off-the-shelf batteries which is rechargeable by electricity generated by the trees.

Although the power generated by tree is small, it sufficient to produces enough electricity to enable four time signals emission a day from the system. This obviously a break through in power industrial where human being is still struggling with. It is believed the tree power may be adopted to be utilized in other wireless applications. Read more in "Using tree power to prevent forest fires?"

Related Topic

• Nanowire battery... High Potential of Replacing Lithium Battery
• Fabric Generate Power Caught Global Interests...
• "Power shirt"
• Own Your Fuel Filling Station in Your Garage
• Euro 6 Million Supporting Nanotechnology
• Nanowerk - NanoTech News & Database Center
• Nano Technology - Revolution in Material Selection

Check Valve Types and Selection

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Check valves or Non-return valves (NRV) are normally installed in piping to avoid back flow. Rotating equipment such as pump, compressor, etc will always be equipped with NRV(s) on the discharge to avoid back flow when rotating equipment is shut. Back flow creates severe surging to the rotating equipment and potentially damage the equipment. In certain process system, NRV will be employed to avoid contamination, overheating, etc due to back flow.

Check valves or Non-return valves (NRV) is basically an automatic valve open to allow forward flow and close to against reverse flow. In principle, it split into four basic types. There are swing, dual-plate, tilting disc and lifting type. Wrong selection of check valve type can leads to operability problem, leakage and continual maintenance issue.

Lift Check valves
- higher pressure drop is expected.
- equipped with small return spring to facilitate valve closure on reverse flow
- two type of seat. hard seat for for high differential pressure sealing and resilient seat for low differential pressure sealing
- shortest travel length. Fastest response.
- excellent performance for low and/or pulsating flows
- not good for fluid with particles
- Body install horizontal with disc / piston vertically
- Small check valve range from 1/2" to 2" lift piston type check valve
- Prefer operate in full open position

Minimum Recommended Line Velocity, Vmin (ft/s) = 12 SQRT (v)

where
v = Specific Volume of the Fluid (ft3/lb)

Lift Check Valve

Swing Check Valve
- Tight sealing / shut-off
- Low pressure drop
- Susceptible to water hammer
- Not good for low flow and/or pulsating flow
- Vertical (upward flow) & horizontal installation
- Easiest check valve to maintain
- Prefer operate in full open position

Swing check valves should be sized such that the flow velocity in the line is sufficient to hold the disc in the fully open position.

Minimum Recommended Line Velocity, Vmin (ft/s) = 75 SQRT(v)

where
v = Specific Volume of the Fluid (ft3/lb)

Swing Check Valve

Dual plate Check valve
The characteristic of dual plate check valve is pretty same as swing check valve.
- low pressure drop
- Not good for low flow and/or pulsating flow
- Vertical (upward flow) & horizontal installation
- Faster opening and closure compare to swing check valve
- Susceptible to water hammer (lesser than Swing check valve)
- Prefer operate in full open position

Dual Plate Check Valve

Tilting Disc Check Valves
- Fast opening and closing without damage to disc and seat
- Stable at low and pulsating flows
- Moderate pressure drop. Lower than lifting check valve but higher than swing check valve
- Vertical (upward) & horizontal installation
- Moderate tight sealing
- Prefer operate in full open position

Minimum Recommended Line Velocity, Vmin (ft/s) = 24 sqrt (v)

where
v = Specific Volume of the Fluid (ft3/lb)

Tilting Disc Check Valve

Selection Consideration
There are four (4) main criteria shall be considered for the selection of check valve type :

• non-slam characteristic
• pressure loss
• cost
• application

Comparative rating for each type of check valve have been provided for these criteria (specifically first two technical criteria). These rating will be plotted on a Check Valve Comparative Selection Chart and together budget for final selection. Read more in "Design and Selection of Check Valve".

Related Post

• Several Strategies To Minimize Relief Capacity in Back-Flow Scenario
• How to predict Check Valve Slam ?
• How to Select a Check Valve (NRV) Quantitatively ?
• Why Redundant NRV in Series within a Line ?
• Why bypass Non-Return Valve (NRV) ?
• Potential Problem associate with Double NRV in Series within a Line
• Basis & Tips on Setting Centrifugal Pump "Warming" Recycle Flow

Mass Heat of Vaporization in HYSYS only for Pure Component

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Since the released of this article "Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS", a few young engineers raised a question. The proposed method does not work for pure component i.e. pure propane. How shall i obtain the latent heat of pure component using HYSYS ?

The proposed method in "Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS" is typically use to handle system with multi-component with large ranging of boiling point. It is typical useful for crude, naphtha, gasoline, condensate, etc. However, the propose method can not be used for pure component as it has only single boiling point at one pressure i.e. 152.4 Btu/lb at 100 psia for pure propane.

To obtain the latent heat of vaporization for pure component from HYSYS, it is pretty simple. From stream properties tab, latent heat of vaporization (Hvap) will be the Vapor Mass Enthalpy (Hv) minus Liquid Mass Enthalpy (Hl). Refer to above image. Hv = - 1032.6 Btu/lb, Hl = -1185 Btu/lb, thus Hvap = -1032.6 - (-1185) = 152.4 Btu/lb at 100 psia.

Another way is to read the Latent heat of Vaporization (Hvap) directly from properties tab. See above image. Mass Heat of Vap (Btu/lb) = 152.4 Btu/lb.

Important Note :
For pure component, latent heat of vaporization can be obtained by Vapor Mass Enthalpy (Hv) minus Liquid Mass Enthalpy (Hl).

For multi-component, latent heat of vaporization is NOT advisable to obtain by Vapor Mass Enthalpy (Hv) minus Liquid Mass Enthalpy (Hl). Rigorous method proposed in "Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS" can be used.

Related Topic

• Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS
• Useful Documentation for HYSYS ...
• Extend of Pool Fire...
• How Fluid Characteristic affect 2 phase Relief via PSV on Liquid filled Vessel Exposing to External Fire
• Definition of Terms Related to PRESSURE

Definition of Terms Related to PRESSURE

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A simple question always asked and debated by many engineers. What is the different between the following terms ?

• Maximum Allowable Working Pressure (MAWP)
• Design Pressure (P_D)
• Maximum Allowable Operating Pressure (MAOP)
• Maximum Operating Pressure (P_O,Max)
• Normal Operating Pressure (P_O)
• Minimum Operating Pressure (P_O,Min)
• Minimum Allowable Operating Pressure (MinAOP)
  

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A mechanical engineer may have different understanding than a process engineer. A process engineer from an organization may have slightly different understanding than a process engineer from another organization. A process engineer educated and/or practising engineering in a country i.e China may have different interpretation than another process engineer educated and / or practising engineering in another country i.e. USA, UK, etc. This always creates a lot of confusion, unnecessary argument and rework. In worst event could lead to hazard. Thus, first far most important thing is to define correctly the meaning of each terms so that everyone have same understanding.

Following are the simple definition of above mentioned terms. Whenever a post contains one or more of these terms, the following shall be referred.

Normal Operating Pressure (P_O) - System pressure as expected to be operated at during normal operation throughout the design life of the system.

Maximum Operating Pressure (P_{O, Max}) - Maximum system pressure as expected during normal operation, may occur in some process transient period or different operating mode or campaigns and it built into the design to cater for any uncertainties due to start-up, fouled, decayed, etc. It provides some level of flexibility for a proper operation of the system throughout the entire life of the system.

Minimum Operating Pressure (P_{O, Min}) - Minimum system pressure as expected during normal operation, may occur in some process transient period or different operating mode or campaigns and it built into the design to cater for any uncertainties due to start-up, fouled, decayed, etc. It provides some level of flexibility for a proper operation of the system throughout the entire life of the system.

Maximum Allowable Operating Pressure (MAOP) - Maximum system pressure that can be allowed to ensure a proper operation of an a device or system.

Minimum Allowable Operating Pressure (MinAOP) - Minimum system pressure that can be allowed to ensure a proper operation of an a device or system.

Design Pressure (P_D) - A pressure chosen / specified (normally chosen by process engineer) to have certain margin (i.e. 10%) above the P_O,Max (or MAOP). It is a maximum pressure in the system that :

- is NOT expected during normal operation
- may only occur during emergency situation such as fire, loss of utilities, valve failure, any abnormal operation corresponding to a short duration, mal-operation, etc

Design pressure becomes MINIMUM pressure that can be hold by any components within the system without mechanical failure. It is used to define the minimum MAWP of components within the system. For example, design pressure is used to calculate minimum vessel wall thickness.

Maximum Allowable Working Pressure (MAWP) - A maximum gauge pressure permissible by a equipment / device (at coincident temperature specified for that pressure) and is governed by code i.e. ASME, JIS, GB, etc

In many cases...

MinAOP <= P_O,Min <= P_O <= P_O,Max < MAOP < P_D <= MAWP

Example :

A pressure vessel contains instrument air is normally operate between 6 - 8 barg. The system would trip under Low-Low pressure of 5 barg to allow sufficient instrument air volume for safe operation of some critical valve during shutdown. The system is designed for 11 barg as specified by the process designer. A conventional spring loaded pressure relief valve (PRV) is provided to protect the vessel from overpressure. The minimum wall thickness required for 11 barg is 6.27 mm, plus 1.5 mm corrosion allowance as specified by process engineer, the total required wall thickness is 7.77 mm. Mechanical engineer has decided to provide 8.0 mm as wall thickness which correspondence to 12 barg.

(Note : all parameters have been selected arbitrary. Just for illustration only.)

• Maximum Allowable Working Pressure (MAWP) = 12 barg
  
• Design Pressure (P_D) = 11 barg
  
• Maximum Allowable Operating Pressure (MAOP) = 10 barg (~90% of 11 barg)
  
• Maximum Operating Pressure (P_O,Max) = 8 barg
  
• Normal Operating Pressure (P_O) = 7 barg
  
• Minimum Operating Pressure (P_O,Min) = 6 barg
  
• Minimum Allowable Operating Pressure (MinAOP) = 5 barg

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Chemical Engineering Digital Issue for November 2008

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FREE Chemical Engineering Digital Issue for November 2008 has just been released !
Chemical Engineering magazine has just released November 2008 issue. If you are the subscriber of Chemical Engineering, you shall received similar notification.

Interesting articles for this month:

2008 Salary Report Ch.E.s
Wonder when the CPI will feel the hit of the weakening world economy

Process Modeling Moves Center-Stage
A model solution for the CPI: Reducing risk while increasing profit

When Size Matters
Particle sizing equipment gets updated to meet the changing needs of the CPI

Biodiesel Production
This one-page guide illustrates the process of biodiesel production by basecatalyzed transesterification of vegetable oil

Condition-Based Maintenance Management Enhances Reliability
Understand reliability, condition monitoring and maintenance management to keep rotating equipment in top form

Get More From Vertical Thermosiphon Reboilers
The effects of three different heat-transfer-enhancement devices are outlined here

Temperature and Pressure Measurement
Calibrate high-quality thermometers with this instrument; A pressure transducer for hazardous applications is introduced; Ultra-compact pressure transmitters offer

If you yet to be subscriber of Chemical Engineering, requested your FREE subscription via this link (click HERE). Prior to fill-up the form, read "Tips on Succession in FREE Subscription".

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• Non - Technical Quick References for a Chemical & Process Engineers
• R&D engineer, Academician and Student...Don't miss this !
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Adjusted Method For Compressor Settle Out (with Vapor & Liquid) Using HYSYS

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Since the release of "Simple Method For Compressor Settle Out Using HYSYS", some readers of Chemical & Process Technology raised a question. The proposed method has considered all in VAPOR, how shall this method apply in case of present of VAPOR and LIQUID in Compressor Suction drum and Air Cooler Downstream ?

It is correct that the simple method is simplified version for VAPOR only Settle out condition. Nevertheless, minimum adjustment to the method enable the method to be used for condition with VAPOR and LIQUID. First refer to following image.

Step 1 : Compressor Suction. Estimate physical volume of vapor (Vv1) and liquid (Vl1).

Step 2a : Compressor Suction. Separate Compressor Suction Inlet (stream 1) with 2-phases (vapor & Liquid) with Separator unit operation.

Step 2b : Copy Compressor Suction Inlet Vapor (stream 2) condition and composition to a new stream Actual Compressor Suction Inlet Vapor ((stream 4). Adjust Mass flow of this stream until the Actual Volumetric Flow equal to Vv1.

Step 2c : Copy Compressor Suction Inlet Liquid (stream 3) condition and composition to a new stream Actual Compressor Suction Inlet Liquid (stream 5). Adjust Mass flow of this stream until the Actual Volumetric Flow equal to Vl1.

Step 2d : Mix Actual Compressor Suction Inlet Vapor (stream 4) and Actual Compressor Suction Inlet Liquid (stream 5) to form Compressor Suction (stream 6).

Normally the Compressor Discharge stream is superheated and no liquid is expected.

Step 3 : Air Cooler Downstream. Estimate physical volume of vapor (Vv3) and liquid (Vl3).

Step 4a : Air Cooler Downstream. Separate Air Cooler Downstream Outlet (stream 7) with 2-phases (vapor & Liquid) with Separator unit operation.

Step 4b : Copy Air Cooler Downstream Outlet Vapor (stream 8) condition and composition to a new stream Actual Air Cooler Downstream Outlet Vapor (stream 9) . Adjust Mass flow of this stream until the Actual Volumetric Flow equal to Vv3.

Step 4c : Copy Air Cooler Downstream Outlet Liquid (stream 10) condition and composition to a new stream Actual Air Cooler Downstream Outlet Liquid (stream 11). Adjust Mass flow of this stream until the Actual Volumetric Flow equal to Vl3.

Step 4d : Mix Actual Air Cooler Downstream Outlet Vapor (stream 9) and Actual Air Cooler Downstream Outlet Liquid (stream 11) to form Air Cooler Downstream (stream 12).

The remaining steps are same as "Simple Method For Compressor Settle Out Using HYSYS" by adjusting Settle Out Cond Actual Volumetric Flow same as Vv1+Vl1+V2+Vv3+Vl3.

Related Topic

• Simple Manual Method for Settle Out Condition Estimation
• Simple Method For Compressor Settle Out Using HYSYS
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• Saturate Dry Gas With Water in HYSYS Using SATURATE Extension
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