chemical engineering: March 2010

Monday, March 29, 2010

Determine the Characteristic Curve of an Installed Control Valve

The performance of a control valve is defined by its inherent and installed characteristic curves. The inherent characteristic curve is a plot of the percent of valve opening vs. the percent of maximum flow coefficient (CV). The inherent characteristic curve is determined by measuring the flow rate at various positions of valve travel with a fixed differential pressure across the valve (typically 1 psid) and calculating the CV at each position using a form of the generalized Control Valve CV equation

Thanks to Jeff Sines

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Saturday, March 27, 2010

Brief About NACE MR 0175

Sulfide -stress cracking is basically a hydrogen-embrittlement phenomenon .Atomic hydrogen enters the steel to cause cracking. The hydrogen is generated on the surface of the steel because of a corrosion reaction. Iron reacts with h2s to form iron sulfide and hydrogen .This hydrogen is generated in atomic form on the steel surface ,where it can either combine to form molecular hydrogen and leave the surface as bubbles or diffuse into steel .This latter process may result in hydrogen embrittlement .Hydrogen sulfide prevents hydrogen recombination & thus promote entry of atomic hydrogen into steel .It is important to note that water must be present for this mechanism to occur ;without it SSC will not be observed ,because the ionization of the hydrogen sulfide is required.

Following is a lecture presentation on NACE Standard MR0175 - Petroleum and Natural Gas Industries – Materials for use in H2S-containing Environments in Oil and Gas Production.

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Tedious & Simple Method In Determining Specific volume For Isentropic Nozzle Flow Mass Flux

Earlier post "API Std 520 Part 1 Dec 2008 is Released" highlighted one of the main changes was to use of isentropic nozzle flow method and/or ideal gas specific heat ratio for vapor/gas relief flow calculation.

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Isentropic nozzle flow method is considering one dimensional homogeneous flow is limiting in Pressure Relief Valve (PRV) nozzle with isentropic (adiabatic and reversible) expansion across the PRV nozzle. Maximum mass flux across the PRV nozzle will be determined follow by mass flow passing the PRV. In determining the maximum mass flux, an integration of specific volume (v) time differential pressure (dP) is required. This integration involve substantial derivation of specific volume (v) which change with pressure (P). If the system can be modelled in HYSYS, you may consider the following tedious and simplified method in determining the specific volume (v) with varies pressure (P).

Tedious method

The detailed method involve the fluid expanded isentropically across multiple expander with fix differential pressure (dP). Entire model is simulated using HYSYS with Isentropic expansion using Expanders. Stream 1 is the feed to PRV nozzle. Stream 1 is expanded isentropically (polytropic efficiency =100%) to stream 2 with fix differential pressure. Stream 2 is further expanded isentropically to stream 3, Stream 4 is further expanded isentropically to stream 4,.............

Mass density is extracted from each stream in order to use for integration of specific volume (v) time differential pressure (dP). Following is the example of specific volume (Inverse of Mass density).

Simple Method

A simple method is proposed hereafter. It basically utilize the capability of Property Table.

Step 1 : Enter stream 1 and open the Property Table Utility in Attachment tab.

Step 2 :From the Connections tab, select Variable 1 as Pressure with Incremental pressure from Outlet (e.g. 1 barg) to Inlet pressure (e.g. 12 barg).

Step 3 :From the Connections tab, select Variable 2 as Entropy with State mode. Enter the Entropy of Stream 1 here.

Step 4 : In Dep. Prop. tab, Add Mass Density. Now the system is ready for calculation. Click the Calculate button.

Now Mass density change according to pressure (with isentropic expansion) is ready.

Above method can be easily adopted for subcooled flashing, two phase flashing flow across the PRV nozzle.

Do you have better idea ?

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Let's do it together !

Earth Hour 2010 will drop on March 27th, 2010, 8.30pm Local time. The effort is simple for everyone :

TURN OFF ALL NON-ESSENTIAL ELECTRICAL APPLIANCE FOR 60 MINUTES from 8.30pm to 9.30pm Local time

We in Chemical & Process, Oil and Gas industries known as one of the major "contributor" in global warming is encourage to take this opportunity to take some effort...

See more video clip in "Earth Hour 2010 - You can Help Our Friend... Environment..."

Visit Earth Hour website : http://www.earthhour.org/

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Saturday, March 20, 2010

NACE MR0103 versus MR0175

NACE MR0103 "Materials Resistant to Sulfide Stress Cracking in Corrosive Petroleum Refining Environments" was developed by Task Group 231 to provide a standard set of requirements for materials used in sour petroleum refinery equipment. In the past, NACE MR01752, "Sulfide Stress Cracking Resistant Metallic Materials for Oilfield Equipment", was frequently referenced for this equipment, even though refinery applications were outside the scope of MR0175. The process used to develop MR0103 is described, followed by a review of the requirements in the standard accompanied by highlights of the differences between MR0103 and the previous and current versions of MR0175.

An Overview of NACE International Standard MR0103 and Comparison with MR0175

Click here to download the article

Download #1

Download #2

A presentation has been prepared by the author which further summary the differences. You may download via the following link : Download Presentation Handout

Thanks to Don BUSH, Jeff BROWN & Keith LEWIS

Earth Hour 2010 - You can Help Our Friend... Environment...

Earth hour is an effort by WWF (World Wide Fund for Nature/World Wildlife Fund) to create awareness on global warming and the need to take action on climate change. All of us can participate in this annual event. Last year 2009, Chemical & Process Technology has participate as well..."Earth Hour - Simple Effort Minimise Global Warming".

In 2009 hundreds of millions of people around the world showed their support by turning off their lights for one hour. You may see the following video clips showing what happened in 2009.

Earth Hour 2010 will drop on March 27th, 2010, 8.30pm Local time. The effort is simple for everyone. It is simple :

TURN OFF ALL NON-ESSENTIAL ELECTRICAL APPLIANCE FOR 60 MINUTES from 8.30pm to 9.30pm Local time

We in Chemical & Process, Oil and Gas industries known as one of the major "contributor" in global warming is encourage to take this opportunity to take some effort...

Visit Earth Hour website : http://www.earthhour.org/

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Thursday, March 18, 2010

Tank Normal Venting Rate (API Std 2000) - Spreadsheet is ready

Atmospheric storage tank normal venting based on API Std 2000 6th edition, Nov 2009 has been discussed in "Tank Normal Venting Rate Estimation Using Latest Method As in API Std 2000". Ankur, an experience engineer in Chemical industry, actively involved in CheResource Forum, has take his effort and time to program it in Microsoft Excel spreadsheet. Thanks to Ankur.

As reminder, the information and methods included within this spreadsheet are presented for common sharing and intended to be used by technically skilled persons at their own discretion. We do not warrant the suitability or accuracy of these methods.

Insulation type and recommended thermal conductivity have also been included in the spreadsheet for easy reference. The insulation type and thermal conductivity as follow :

Common Insulation Materials	Average Thermal Conductivity, W/m-K
Cellular glass	0.05
Mineral Fiber	0.04
Calcium Silicate	0.06
Perlite	0.07

Products contain volatile components or dissolved gases or flashing products may result adddtional volatile component / gases / vapor. This amount will increase the outbreathing rate.

Products stored at temperature above 40 degC or its vapor pressure higher than 5.0 kPa, products evaporation rate shall be added into outbreathing rate.

Read and download spreadsheet in "Tank Normal Venting Rate Estimation Using Latest Method As in API Std 2000".

* If you find any error or improvement, please inform us.
**If you have any useful program and would like to share within our community, please send to me.

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Wednesday, March 17, 2010

Quick Estimate Evaporation Rate From Spilled Liquid

Liquid in tank truck or storage tank may spill on the ground. Wind blowing, solar and ground surface heating will results evaporation of spilled liquid. The evaporation rate is one of the key information required during design phase for consequence analysis and preparation of emergency handling measures. What is the quick way to estimate evaporation rate ?

Evaporation rate from spilled liquid subjects to several factors such as :

spilled liquid volatility
spilled liquid properties
spilled liquid surface area expose to wind blowing
spilled liquid temperature
wind speed

Evaporation Rate
Evaporation rate of spilled liquid can be estimated using following equation

E = (0.284 U^0.78.MW^2/3.A.VP) / (82.05 T)

where
E = Evaporation rate (lb / min)
U = Wind speed above spilled liquid surface (m/s)
MW = Spilled liquid molecular weight
A = Spilled liquid surface area (ft²)
VP = Spilled liquid vapor pressure at liquid temperature (mmHg)
T = Spilled liquid temperature (K)

Spilled Liquid Surface Area

Spilled liquid surface area is normally fix by the containment itself. Liquid spilled from tank into diked area, the spilled liquid surface area will be the diked area itself unless the spilled quantity is so small where it will not covers entire diked area. To estimate spilled liquid surface area without any containment, it is assumed that the spilled liquid will have 10mm (or 0.033 ft) thickness. Therefore,

Spilled liquid surface area (ft²)

A = V / 0.033

where
V = Spilled liquid volume (ft³)

Example

Methanol with vapor pressure (VP) of 125 mmHg and MW of 32.04 stored at 25 degC in a 25,000 US gal tank (10 ft diameter). Overfilled methanol results spillage of 1,000 US gal of methanol spread in the diked area (100ft x 40 ft) which contain 8 identical tanks. Assuming wind speed is 1.5 m/s, estimate evaporation rate.

Spilled volume,

V = 1000 US gal

V = 1000 / 7.48051948 ft³

[1 ft³ = 7.48051948 US gallons]

Spilled area (without containment),

A_wc = V / 0.033

A_wc = (1000 / 7.48051948) / 0.033

A_wc = 4,050 ft²

Diked area,

A_dike = Total dike area - tank area

A_dike = 100x40 - 8 x (PI x 10^2)/4

A_dike = 3371.7 ft²

Since A_wc is larger than A_dike, entire dike area will be occupied by spilled liquid.

Inputs

U =1.5 m/s
MW =32.04
A =3371.7 ft²
VP =125 mmHg
T =25 + 273.15 = 298.15 K

Evaporation rate

E = (0.284 U^0.78.MW^2/3.A.VP) / (82.05 T)

E = (0.284x1.5^0.78.(32.04)^2/3.3371.7.125) / (82.05x298.15)

E = 67.7 lb / min

Above method is a quick method in determining evaporation rate.

Ref : "Risk management program guidance for offsite Consequence Analysis", US EPA, Apr 1999

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Monday, March 15, 2010

Another Quick Way to Find Latitude Using GOOGLE MAP

Latitude of a plant is one of the parameter in determining C-factor and Y-factor of Tank normal inbreathing and outbreathing as discussed in "Tank Normal Venting Rate Estimation Using Latest Method As in API Std 2000". Simple method to find latitude is using Google Map.

Another Method

Lately Google Map has introduced new features. You can view the Latitude and Longitude directly and immediately as you move you mouse along the Google Map. Following are the steps to configure it.

Step 1 : Goes to Google map (http://maps.google.com/)
Step 2 : Click "New!" at top right and find . (See below image). Or you can click http://maps.google.com/maps?ftr=0.

Step 3 : Scroll down and find "LatLng Tooltip" and Click "Enable"

Step 4 : Click Save Changes at the bottom of page. Now configuration is done.

Try to find "Ras Laffan, Qatar" again in Google Map. You will get the latitude and longitude immediately from the Google Map. You may also move the mouse and see the effect of latitude and longitude changes...

Simple ? Let us know if you have even better method...

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FREE HP March 2010

FREE Hydrocarbon Processing for March 2010 is available now...


Welcome to the March Issue!

Select Articles from the March Issue

Fieldbus diagnostics: latest advancements optimize plant asset management
New field diagnostic profiles will benefit a wide range of automation stakeholders

Breaking down the silos between energy and asset management
Having them share a common platform offers several advantages

Improving data reconciliation and yield accounting
Here’s how the Mathura Refinery’s data reconciliation and yield accounting project was implemented

Ensuring safe operations when fulfilling action item requirements
Consider implementing this criteria to accurately document the process

Iron sulfides—effect on amine plants
Amine plants treating gas containing H2S will have iron sulfides in the system. Here’s where they help and hinder plant operation

Consider new methods for bottom of the barrel processing—Part 2
New principles of molecule management dictate the best economics when upgrading residuum

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BUKU TEKS KIMIA ANORGANIK ONLINE

Taro Saito,

diterjemahkan dari versi Bahasa Inggrisnya oleh Ismunandar
MUKI KAGAKU by Taro Saito
© 1996 by Taro Saito
Reproduced by permission of Iwanami Shoten, Publishers, Tokyo

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© 2006 by Yashito Takeuchi

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BUKU TEKS KIMIA KUANTUM ONLINE

Koichi Ohno,

diterjemahkan dari versi Bahasa Inggrisnya oleh Bambang Prijamboedi

Quantum Chemistry by Koichi Ohno
© 2004 by Koichi Ohno
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Professor Emeritus of Chemical Engineering,
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Thursday, March 11, 2010

Find Latitude & Longitude Using GOOGLE MAP

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Tank Normal Venting Rate Estimation Using Latest Method As in API Std 2000 has included a parameter C factor thermal inbreathing calculation and Y-factor in thermal outbreathing calculation. These parameters subject latitude of plant site.This post will introduce a simple method in find Latitude and Longitude of your plant site using Google Map.

Latitude is line appear horizontal on earth with varying curvature from equator which divides the planet into a Northern Hemisphere, a Southern Hemisphere and has a latitude of 0°. Latitude is ranging from 0° at the equator to +90° at the North poles and -90° at the South Pole.

Methodology
Google map is widely used by many engineer to locate longitude and latitude of plant. site Following is simple steps to find longitude and latitude of a plant site.

Step 1 : Goes to Google map (http://maps.google.com/)
Step 2 : Type location of your plant site (example Ras Laffan in Qatar)

(Click image to view larger picture)

Step 3 : Move mouse and point to A.
Step 4 : Right click and select "Whats here ?"

Latitude and longitude of location A will appear in Search Box. (see below)
Lattitude = 25.924887
Longitude = 51.575317

(Click image to view larger picture)

Simple ? Let us know if you have even better method...

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Wednesday, March 10, 2010

CE March 2010

FREE Chemical Engineering Digital Issue for March 2010...

Saving Energy In Regenerative Oxidizers

Regenerative thermal oxidizers (RTOs) can be retrofitted with catalyst beds to help reduce consumption of auxiliary energy during oxidation of VOCs. Energy savings after such a retrofit can quickly justify the costs of catalysts and installation. Here’s the how-to

Greenhouse Gases: U.S. Starts Counting

On January 1, 2010, nearly 10,000 facilities became subject to EPA rules on collecting data on greenhouse gas emissions. This article looks at the rules and how they might impact the CPI’s demand for mitigation solutions

FAYF - Steam Traps and Tracer Lines

This one-page guide discusses the selection of steam traps for steam tracer lines

Agglomeration Technology: Mechanisms
This review focuses on the mechanisms of agitation (wet granulation) and compression (compaction) methods

Purifying Coke cooling Wastewater
A new method for treating coke-cooling wastewater in a delayed coking unit

Water Solubility in Benzene Derivatives
Solubility and Henry’s Law constants for water in benzene derivatives

Would You Use a Safety PLC for Process Control ?
Ensure unambiguous independence of the control and safety layers of protection

***********************

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Tuesday, March 9, 2010

Green Calculator - How Much Energy Could Your Company Save ?

Earlier post "Is Your Company "Green" Enough ?", an Green Assessment using radar chart is introduced by Infor . The Green Assessment tool will allows you to assess how far your company's efforts in achieving a Green organization. This Green Assessment is benchmarked with many other companies and other industries.

Again Infor introduce another Green Calculator to estimate the potential of energy and costs saving that you can achieve using the EAM Asset Sustainability method. The Infor Energy Savings Calculator is designed to analyze your company’s current power usage and policies, and provide recommendations to help reduce energy costs and drive green initiatives.

Check out Green Calculator...

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Tank Normal Venting Rate Estimation Using Latest Method As in API Std 2000

Liquid product like Chemical, condensate, etc is commonly stored in fixed roof vertical cylindrical tank. Inert gas blanketing system is provided to avoid air and moisture contact and contaminate liquid product. Liquid movement by content filling (pump-in) or emptying (pump out) and weather changes (ambient heating or cooling) will results internal pressure increase (overpressure) or decrease (vacuum) in the tank. Thus, a protecting system providing inbreathing or outbreathing gas is provided to maintain a constant pressure in the tank.

Inbreathing

Emptying (pump-out) and ambient cooling will lead to normal inbreathing. General equation to determine inbreathing flow :

V_in,air = V_pe + CV_tk^0.7 R_i

where

V_in,air = Total inbreathing in Nm3/h (Air)

V_pe = Pump-out or emptying in m3/h

V_tk = Tank capacity in m3

R_i = Insulation reduction factor
C = Factor subject to vapor pressure, average temperature and latitude (see Table 1)

Table 1 : C-factor for Inbreathing
Latitude	Vapor Pressure
	Hexane or similar		Higher than hexane or unknown
	Average Storage Temperature (^oC)
	< 25	>=25	< 25	>=25
Below 42^o	4	6.5	6.5	6.5
42^o to 58^o	3	5	5	5
Above 58^o	2.5	4	4	4

Find Latitude & Longitute Using GOOGLE MAP

Outbreathing

Filling (pump-out) and ambient heating will lead to normal outbreathing. General equation to determine outbreathing flow :

V_out,air = V_pf + YV_tk^0.9 R_i

where

V_out,air = Total Outbreathing in Nm3/h (Air)

V_pf = Pump-out or filling in m3/h

V_tk = Tank capacity in m3
R_i = Insulation reduction factor

Y = Factor subject to latitude (see Table 2)

Table 2 : Y-factor for Outbreathing
Latitude	Y-factor
Below 42^o	0.32
42^o to 58^o	0.25
Above 58^o	0.2

Special notes :
i) If products contain volatile components or dissolved gases or flashing products, perform flashing calculation to estimate quantity of volatile component / gases / vapor. This amount shall be added into outbreathing rate.

ii) If products stored temperature above 40 degC or its vapor pressure higher than 5.0 kPa, products evaporation rate shall be added into outbreathing rate.

iii) Quick check on plant latitude, check out in "Find Latitude & Longitute Using GOOGLE MAP"

Determination of R_i = Insulation reduction factor

If no insulation,

R_i = 1

If fully insulated including Shell and roof,

R_i = R_in = (1 + h x L_in / Lamda_in)^-1

If partial insulated,

R_i = R_inp

R_i = (A_inp / A_TTS).R_in + [1-(A_inp / A_TTS)]

L_in = Insulation thickness in m
Lamda_in = Insulation thermal conductivity in w/mK

h =Inside heat transfer coefficient in w/m2K [4 w/m2K is commonly assumed]

A_inp = Insulated surface area of tank in m2

A_TTS = Total tank surface area (shell + roof) in m2

Concluding remarks

The following method is the latest method used in API Std 2000, ISO 28300 & EN 14015. Nevertheless, API Std 2000 (6th edition) still maintaining the old method in ANNEX A as an alternative approach in determining normal venting rate. Comparison and recommendation can be found in "Tank Venting - API Std 2000 (Nov 2009) - Revised method and Old Method in ANNEX A".

In determining normal tank venting rate per ANNEX A, designer can estimate tank venting rate from a table. Siddhartha has presented an equation to predict tank venting based on simple correlation, as discussed in " Tank Normal Venting Rate Estimation Using Siddhartha Equation". JoeWong has further proposed a new correlation as discussed in "Tank Thermal Breathing - Proposed Equation Correlate API Std 2000 Data" with better accuracy.

Ref :
i) API Std 2000 "Venting Atmospheric and Low-Pressure Storage Tanks", 6th Edition, Nov. 2009
ii) ISO 28300 "Petroleum. petrochemical and natural gas industries - Venting Atmospheric and Low-Pressure Storage Tanks"
iii) EN 14015 "Specification for the design and manufacture of site built, vertical, cylindrical, flat-bottomed, above ground, welded, steel tanks for the storage of liquids at ambient temperature and above "

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