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Sunday, December 18, 2011


Pipe Tools is a handy simple tool available free for Iphone user to retrieve pipe and/or tubing data. Steel Pipe charts and Casing/Tubing charts that fit in your Iphone is really a handy tool helps engineer to obtain pipe information such as wall thickness, mass per unit length, etc. You can have quick conversion between feet, metres, net tons, metric tonnes for any pipe size. By entering unit Compare pipe costs $/ft, $/m, $/net ton, $/metric tonne. Plus more tools for the pipe industry!



Steel pipe charts are provided in the Pipe Tools summarize the Imperial wall thickness and pipe mass data from ASME B36.10M, and casing and tubing data from API 5CT.

Pipe Tools has a handy tool to present the metric equivalents of the pipe chart data. Navigation of this data is by tapable and movable tables and by picker selections.


This app has a conversion feature for comparing pipe prices., to calculate the carbon equivalents of your pipes, find out yield strength (YS) on your MTR is in Metric and the spec is in Imperial.

You may easily download from Iphone's APP STORE. Read more information in ITune.

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posted by Webworm, 1:44 AM | link | 9 Comments |



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Optimize capacity for large ethylene oxide reactors
Many factors must be considered in fine-tuning unit design

Selecting the right steam methane reformer: Can vs. box design
Simulating various configurations and cost estimates aids in the selection of a steam methane reformer for hydrogen production

Investment roadmap: Planning for carbon capture and storage
Reducing emissions can be approached the same way as any other new capital project

Knowledge transfer: A primer for major capital projects
Improve transfer strategy across the project supply chain to achieve smooth end-user takeover

Manage risks with dividing-wall column installations
A simple auxiliary configuration and an extensive modeling study can mitigate the implementation risks of DWCs

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posted by Webworm, 1:42 AM | link | 0 Comments |

Thursday, December 15, 2011

Earlier post "Mal-Distribution of Phases at T-Junction Phenomenon" and "Stagnant Liquid In Inclined Parallel Pipe Downstream of T-Junction" have shown two phase flow mal-distribution and stagnant liquid phenomenon at T-junction or splitting tee.



The flow distribution from a manifold to parallel channels is becoming of interest in predicting the heat transfer performance of heat exchangers. As discussed, due to maldistribution of two phase flow at T-junction, flow rates through the channels to each heat exchanger are not uniform. In the extreme case, there is almost no flow through some of them (i.e. stagnant liquid phenomenon). As of today, there is still no general way to predict the distribution of two-phase mixtures at header–channel junctions (T-junction).



Simulation studies by Bernoux et al. (2001) with two-phase distribution at the inlet manifold of compact heat exchangers, results showed that the vapor distribution to the channels became uniform with the increase of the mass quality (Xv), but the liquid distribution still remained unbalanced. Besides, the liquid distribution through the channels was not much sensitive to the mass flux (MFlux).

Flow behavior studies (by Osakabe et al, 1999) in a horizontal square header (with each side being 40 mm) connected to four parallel vertical tubes (10 mm in diameter) for the bubbly and slug flows at the inlet, largest amount of the liquid flow into the first tube for a low mass quality (Xv) flow in the header; however, the tendency of mal-distribution is reduced with the increase of the mass quality (Xv) inside the header.

Flow behavior at one junction has no influence on that at the next junction. On the other hand, for the most of the compact heat exchangers, the distance between the channels is comparable to or even smaller than the header size (hydraulic diameter), flow interaction between the junctions has to be taken into account.

Infact, behavior of flow separation in small T-junctions appeared different from that in the large T-junctions. There are strong interaction between each T-junctions. The flow behavior at one T-junction is strongly influenced by other T-junction especially when the distance between the T-junction is equivalent to or smaller than the hydraulic diameter of the header (as reported by Lee & Lee, 2004).


Further investigation on two-phase flow behavior at the upward header co-current flow and horizontal rectangular parallel channels and simulating the corresponding parts of compact heat exchangers shown that intrusion depth of the channels into header affects flow distribution of the liquid-phase. Less amount of liquid was separated out through the channels at the rear part except near the end-partition with the zero intrusion depth, Reversed trend observed for deeper intrusion. This indicated that a uniform distribution could be obtained by adjusting the intrusion depth. Deeper intrusion channel promote mixing effect and hence the uniform distribution to each outlet.

Above shown that mal-distribution of two phase flow at T-junctions affects by many factors i.e. vapor mass quality, flow pattern, distance of T-junction, size of T-junction and header size, penetration of T-junction into header, etc. Infact, above only several factors affecting mal-distribution, there are many more factors affecting it. In a compact heat exchanger i.e. Plate Fin Heat Exchanger (PFHE), Brazed Aluminum Heat Exchanger (BAHX), gas & liquid fraction flow from header to each channel may be different from tube to tube. This could seriously affects the heat transfer performance of the heat exchanger. Not only that performance varies at each channel would lead to change in temperature profile, and hence thermal stress profile of heat exchanger which increase the fatigue cracking tendency and life span of the heat exchanger.


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posted by Webworm, 8:51 AM | link | 2 Comments |

Wednesday, December 14, 2011

In earlier post "Mal-Distribution of Phases at T-Junction Phenomenon", there were several mal-distribution phenomenon shown. In this post there is another phenomenon where engineer may not see or feel it and it may not has any consequence. It is flow preferential and stagnant liquid phenomenon in a inclined splitting tee.


Taitel et al (1999 & 2003) has investigated two phase flow with common inlet, split at impacting T-junction, flow in inclined parallel pipes and merge at common outlet. Flow splitting of gas and liquid in four (4) parallel pips was investigated. Experimental results were obtained for 0°, 5°, 10° and 15° inclinations.

For the horizontal case (0°) the flow takes place in all of the 4 pipes, usually with an "approximately" even splitting. For the inclined pipes various flow configuration could take place. For low liquid and gas flow rates the two-phase mixture prefers to flow in a single pipe while stagnant liquid fills part of the other three (3) pipes. As the flow rates of liquid and gas increase, flow in two, three and eventually in four pipes takes place.


This has provided some insight and idea to the designer and operator, there is a minimum flow for two phase flow in parallel pipes. Under turndown operation, there is possible flow in single pipe while liquid column stagnant in the other pipe. Whenever increase production, it shall be gradually increase to avoid large liquid volume feed to the downstream equipment and pipe failure due to slugging flow in downstream pipe.

Another potential issue is present of heavy sand in the two phase flow. Heavy sand will tend to stays and accumulates in the stagnant liquid and potentially partially block the pipes. Therefore, this stagnant liquid phenomenon should be checked and taken care during design and operation phase.

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posted by Webworm, 7:25 AM | link | 2 Comments |

Monday, December 12, 2011

Multiphase flow, primarily gas-liquid flow, exists in chemical, power, oil/gas production and refining plants. Multiphase flow is very complex phenomena. Most application has considered that fluid split at T-junction, all phases will be evenly split between the run and branch. In reality, maldistribution of phase occurred at T-junction. Each phase has their preference route. This maldistribution phenomenon has been experienced in many industrial applications.


Mal-Distribution of Phases at T-Junction Phenomenon
In the Oil and gas, refinery, petrochemical and chemical plant, pipes has been widely used to transfer product from equipment to equipment for further processing. Starting from offshore platform, oil & gas produce from reservoir via wellheads, partially stabilized in production separators (sometime produced water knocked-out in the production separator and further re-inject back to reservoir or treated and disposed locally), separated gas and condensate/oil will be transport to onshore via separate long pipelines. Along the pipeline, external cooling by ambient and seawater couple with pressure drop in the pipeline, condensation will occur in some places in the pipeline and two phase flow initiated. Gas with condensate arrived onshore will be dumped into a multi-fingers slugcatcher. Impacting Tee will be used to split the flow between the fingers. Gas-condensate is then separated in the slugcatcher via slight-inclined horizontal pipe with vertical Tee. At the impacting Tee, maldistribution of gas & condensate between the branches are observed in reality. These ended-up some fingers are over capacity and some under capacity.

Production from several wellhead platforms will be send to central processing platform (CEP) for partial separation and stabilization via long subsea pipeline. Due to geographical arrangement of wellhead platforms and well develop at different phases, those pipelines could be mixed at topside or subsea using Tee.

Gaslift used to enhance oil productivity will be supplied from central processing platform via long gaslift pipeline. The gaslift pipeline will be delivered from one platform to another platform. Tee will be used to split the gas flow. In order to avoid condensation, generally the gaslift dew point will be depressed to avoid condensation along the gaslift pipeline. Inefficient performance and mal-operation of topside gaslift dew point control will result saturated gas feed into the gaslift pipeline. Similar to above gas pipeline, condensation occurred in the long pipeline due to external cooling and pressure drop and affect the proper split.

Featured Resources:
LNG Industry
Provides global coverage of the entire LNG value chain.... >>

Oil production system producing high viscosity oil, steam will be injected to enhance oil recovery. Multiple steam injection is implemented to ensure proper distribution of steam and increase the oil recovery efficiency. Steam supply from main header will be distributed to all injection points via tees. In some cases, steam is supplied from central utility production unit which is far away from the users, cooling by external (imperfect insulation) and pressure drop along header will lead to two phase flow. Maldistribution of steam-condensate at each split will result oil recovery performance dropped.

The LPG or natural gas will be supplied to users such as factory, household, etc. A lot of pipeline and tees will be used for transfer and splitting the flow. Similar to above gas pipeline, condensation could occur in the pipeline and distribution network, malditribution at the splitting tee and could result some users received large amount of condensate.

In the chemical plant, there are two phase flow gas (with low liquid loading) feeding to condenser. In order to increase operability and turndown, multiple condensers will be installed. When the plant is operate under partial capacity, some condensers will be put in operation. Maldistribution occurred at splitting tee result some condenser over capacity (fed with high liquid loading) and the some condenser under capacity (fed with low liquid loading).

Phase maldistribution has been reported from offshore platforms in the UK North Sea. Two main (phase) vessel separators has been installed in parallel in order to enable production to continue albeit at a reduced level if there was a need for maintenance or modification of a separator. To ensure an even split of the phases, an impacting T-junction was employed. When the system was started up it was found that one separator received most of the gas whilst the other got most of the liquid. Inspection of the pipework upstream of the junction showed that bend located upstream result centrifuging of the phases and presenting each outlet with substantially one phase

There are others phase maldistribution observed on T-junction. For example, phase separation in main coolant piping of light water nuclear reactor (LWR) can play significant role in the effectiveness of emergency core cooling (ECC) system during analysis of Loss-of-coolant-accident (LOCA).

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posted by Webworm, 6:58 AM | link | 0 Comments |

Sunday, December 11, 2011



Nowadays Smart phone has been commonly used by most engineers. A lot of handy application has been created to ease engineers like you for daily activities. Similarly DNV has created and released a "LNG Conversion Calculator" for Iphone user. It is FREE.


Above is snapshot of the DNV's LNG Conversion Calculator.

This LNG Conversion Calculator cover several important units :
  • m3 NG
  • ft3 NG
  • tonnes oil eq
  • tonnes LNG
  • BTU
  • barrels oil eq
  • m3 LNG
You may easily download from Iphone's APP STORE. Read more information in ITune.

Following are some typical results :
  • 1 x 106 tonnes LNG = 52 x 1012 BTU 
  • 1 x 106 tonnes LNG = 8.68 x 106 barrels oil eq
  • 1 x 106 tonnes LNG = 1.23 x 106 tonnes oil eq
  • 1 x 106 tonnes LNG = 2255.822 x 103 m3 LNG 
  • 1 x 106 tonnes LNG = 1.38 x 109 m3 NG 
  • 1 x 106 tonnes LNG = 48.7 x 109 ft3 NG
Featured Resources:
LNG Industry
Provides global coverage of the entire LNG value chain.... >>


Comments :
  1. Exact conversion subjects to molecular weight. Above is only approximation.
  2. Finding shows above was based on "BP Statistical Review of US, Energy" as source.
  3. Present version is 1.1. Only cover mass-volume conversion. Wish develop can expand it to cover flowrate to ease users.
  4. There is no clear definition of volumetric flow at condition i.e. at Standard or Normal condition, etc.

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posted by Webworm, 1:20 AM | link | 0 Comments |

Saturday, December 10, 2011

Liquefied Natural gas (LNG) contains of majority 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), Heavy Hydrocarbon, BTEX, CO2, S, etc. These component need to be extracted from natural gas to an acceptable, practical and economic level when it is liquefied and transported. The following are general reasons why these contaminants need to be extracted :
  • solidify / freezing results cryogenic heat exchanger blockage (contaminants such as CO2, H2O,  C5+, BTEX, etc)
  • corrosion & cracking of cryogenic heat exchanger made of aluminum material (contaminant such as Hg)
  • affecting product heating value (component such as N2, C2, C3, C4, etc)
  • extraction highly valuable / important component (such as N2, He, etc)
  • product toxicity (such as H2S, mercaptans i.e. methanethiol (CH3SH) and ethanethiol (C2H5SH), etc)
  • stratification results roller (such as N2)
Freeze & Blockage
Component in natural gas potentially freeze and blocking cryogenic heat exchanger need to be reduced to level at or below it freezing point. The following table list out the solubility of several components in LNG :


ComponentEstimated
Solubility
Concentration
(ppmV)
Practical
Acceptable
Concentration
(ppmV)
Remark
n-C58,9001,000
neo-C5-5
C6217150
C77050
C80.50.5
C90.10.1
C100.0000010
Cyclo-C6115100
M-Cyclo-C5575550
M-Cyclo-C6335300
Benzene1.530.5
Toluene / M-Benzene24.920
O-Xylene0.220.1
M-Xylene1.541.0
P-Xylene120100
CO24050 - 100Practical experience shown higher CO2 concentration is acceptable / practical.
H2O0.00011.0Practical experience shown higher H2O concentration is acceptable / practical.


Corrosion & Cracking
Mercury (Hg) present in natural gas can cause corrosion & cracking of cryogenic heat exchanger made of aluminum material. Typically Hg concentration shall be limited to 0.01 microgram / Nm3.

Featured Resources:
LNG Industry
Provides global coverage of the entire LNG value chain.... >>

Stratification & Rollover
At LNG storage condition, Nitrogen will have lower dew point compare to Methane. Nitrogen in LNG tends to vaporize first compare to Methane. As Nitrogen is heavier than Methane, top layer of LNG tank would tends to rollover and generate excessive vapor which can cause overpressure and relieve BOG to atmosphere. Through experience, Nitrogen content in LNG is normally limited to maximum 1 mol%.

Toxicity
Present of H2S, COS and merceptants in LNG would results high toxicity LNG. The following list out typical level in LNG :

ComponentPractical
Acceptable
Concentration
(ppmV)
Remark
H2S4                                                
COS0.5
Total Sulfur      10 - 200Subject to country
Merceptants Sulfur   6 - 15Subject to country




Above are typical value for quick reference. Figures may change according to LNG composition, liquefaction temperature, etc and will varies from case to case. Shall be used as reference only.



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posted by Webworm, 10:17 AM | link | 1 Comments |

Thursday, December 8, 2011

Chemical Engineering Digital Issue for Dec 2011 


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Thermal Fluid Systems
Design Considerations Single-fluid heat-transfer systems require specific design
considerations for troublefree operation

Troubleshooting Heat-Transfer Fluid SystemsReal cases illustrate how to analyze problems in heattransfer systems — sometimes symptoms can

Transporting Energy Through Time
A portfolio of new energy-storage technologies is poised to tackle applications on the next-generation power grid

Simulation Spreads its Wings
Simulation software is not just for designing plant layouts anymore. Enhancements and integration capabilities
allow it to help out in any number of ways around the facility

The Fractionation Column Lessons Learned in R&D
R&D projects should be undertaken thoughtfully, with involvement from marketing staff and with
cognizance of profit motive

Facts at Your Fingertips - Using Rupture Disks with Pressure Relief Valves
This one-page reference guide outlines considerations for using rupture disks in conjunction with pressure safety relief valves

Turnarounds : Shorter, Safer, Simpler
Wireless networks are easily justified in a turnaround budget, and keep paying off after startup

Solubility of Water in Benzenes as a Function of Temperature
Accurately determining the solubility of water in hydrocarbons is important for several reasons, including
product quality. A new correlation is compared to experimental data

Preventing Tank Corrosion
Why a tank’s coatingapplication process makes all the difference


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TIPS
If you are subscriber, you may access previous digital releases. Learn more in "How to Access Previous Chemical Engineering Digital Issue".

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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posted by Webworm, 8:31 AM | link | 2 Comments |

Wednesday, December 7, 2011

Plate fin heat exchangers (PFHE) is compact, low weight and high effectiveness are widely used in cryogenic applications. Normally PFHE is made of a stack of corrugated fins alternating with nearly equal number of flat separators known as parting sheets, bonded together to form a monolithic block. Feed and exit headers are welded to provide the necessary interface with the inlet and the exit streams. While aluminum is the most commonly used material, stainless steel construction is employed in high pressure and high temperature applications.


This following thesis "Design of Compact Plate Fin Heat Exchanger" by JAINENDER DEWATWAL is rather interesting for those who would like to have brief idea about PFHE and methodology for PFHE calculation. Several correlations such as MANGAHANIC, WIETING, JOSHI &WEB, DEEPAK & MAITY have been used in the calculation. For those who are new in PFHE design, this may be good source to start...

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posted by Webworm, 5:09 AM | link | 2 Comments |