chemical engineering

Saturday, July 16, 2011

what is Chemical Engineering

Chemical engineers use math, physics, and economics to solve practical problems. The difference between chemical engineers and other types of engineers is that they apply a knowledge of chemistry in addition to other engineering disciplines. Chemical engineers may be called 'universal engineers' because their scientific and technical mastery is so extensive.

Reference websites:
http://en.wikipedia.org/wiki/Chemical_engineering
http://cheme.stanford.edu/prospective_students/whatis_cheme.html

Saturday, November 13, 2010

How much can be done in Six days ?

What you can do with Six days ? Many things... Have you ever thought of a 15-story building erected within Six days ?

It took six days to build a level 9 Earthquake-resistant, sound-proofed, thermal-insulated 15-story hotel in Changsha, complete with everything, from the cabling to three-pane windows. This of course excludes the prefabrication of components and modules, earthing and foundation preparation. But believe it is sufficiently impress many peoples. This is the Ark Hotel in Changsha, HuNan county, China. May check Changsha using Google map.

Following video clip (Youtube) shows how a building is erected within 6 days.

This believe is another record... Nevertheless many out there still questioning on safety of this building. What do you think ?

The way Chinese do things, in particular this case, possibly may trigger another revolution in business...

Related Post

Saturday, October 9, 2010

CE Oct 2010

Chemical Engineering Digital Issue for Oct 2010...

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Rare-earth metals for the future
Issues revolving around economics, workforce and technological innovation will be crucial as rare-earth metal production diversifies and demand for these critical technology metals grows

FAYF - MSMPR crystallization
This one-page reference guide describes examples of mixed-suspension, mixed-product removal crystallizers

Industrial Insulation Systems : Material Selection Factors
To provide the desired functions while beingexposed to harsh environments, insulation material should be carefully selected and specified to meet the design goals

Improving control valve performance
Control valves have a major impact on control-loop performance, so improvements in valve performance can have significant economic benefits. This article shows how poor control-valve performance can be identified and corrected to achieve these benefits

Crossover applications for the ASME-Bioprocessing Equipment Standard
The ASME-BPE Standard was created for the pharmaceutical industry, but can be very useful in the biofuel and chemical industries as well

Lessons in feedstock changes
Switching to renewable feedstocks can offer financial and environmental benefits, but can also compound challenges associated with processing solids

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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".

Related Post

Friday, October 8, 2010

HP Oct 2010

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

Click here to view the complete October issue

Articles from the October Issue in HP main focus on Advance control.

How to have a successful data reconciliation software implementation
Follow these guidelines to ensure success

Improve exploration, production and refining with 'add-at-will' wireless automation
After the technology was validated, a wireless infrastructure was installed blanketing 80% of a US refinery

Building and installing a reliable industrial Ethernet infrastructure
Here are six practical guidelines to consider

Increase your margin by 25%
Here's how to make sure that the planning LPs always match the plant

Advanced process control in the plant engineering and construction phases
Testing MVC performance using a dynamic model offers several benefits

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

Quick Way To Find Altitude of a Plant

Atmospheric pressure change with altitude and this will have impacts to facilities design. Do not Under-estimate The Impact of Altitude Change. Sometime you may want to find altitude of specific location in particular you are conducting feasibility study and identifying plant location. This post will provide a quick way to find altitude of a plant using Google Map.

Simple Steps
Following are some steps to find altitude of a specific location using Google Map :
Step 1 : Execute a "Find_Altitude.htm" by clicking here.
Step 2 : You may choose to Open the file using Internet Explorer or Save the file and execute later.
Step 3 : Google Map will shows map of Singapore island. You may zoom out the map by clicking "-" (in pull bar), left hand side of map
Step 4 : Zoom to the plant location you wish to find the altitude.
Step 5 : Double click the location. Altitude will be displaced in a box.

Example

Find altitude of "Nature Reserve" and "Sentosa Island Beach" in Singapore island.

Step 1 : Execute a "Find_Altitude.htm" by clicking here.
Step 2 : Open the file using Internet Explorer. Google Map will shows map of Singapore island.

Step 3 : Double click the "Nature Reserve". The altitude of "Nature Reserve" in Singapore is approximately 60.64 m. See below image.

Step 4 : Double click the "Sentosa Island Beach". The altitude of "Sentosa Island Beach" in Singapore is approximately 0.0 m. See below image.

Shall take note that this is just for reference only.
Do you have better idea ?

Wednesday, October 6, 2010

Do not Under-estimate The Impact of Altitude Change

Many LNG plants are built at the seaside to ease transportation, product loading and unloading. The atmospheric pressure with plant near seaside is 101325 Pa and all facilities are designed to the atmospheric pressure of 101325 Pa. However, if this plant is built in inland at high altitude, atmospheric pressure can seriously affect the design and operation of a LNG plant. Prior to discuss how the design and operation is impacted, lets step back to look at definition of pressure.

Operating pressure is commonly written as gauge pressure e.g. kPag, barg, etc in engineering whilst absolute pressure e.g kPaa, bara, etc. Absolute pressure equal to gauge pressure plus atmospheric pressure.

Example :
5 bar abs = 5 barg + 1.01325 bar = 6.01325 bara

The standard atmosphere pressure is pressure defined as being equal to 101,325 Pa or 101.325 kPa and normally refer to mean sea level (h=0 m). Atmospheric pressure is decreased with altitude (elevation from mean sea level or earth surface) with following relation.

where
P_b = Static pressure (Pa)
T_b = Standard temperature (K)
L_b = Standard temperature lapse rate -0.0065 (K/m) in ISA
h = Height above sea level (meters)
h_b = Height at bottom of layer b (meters; e.g., h1 = 11,000 meters)
R = Universal gas constant for air: 8.31432 N.m /(mol.K)
g₀ = Gravitational acceleration (9.80665 m/s2)
M = Molar mass of Earth's air (0.0289644 kg/mol)

Altitude = 0 – 11000m, T_b = 288.15 K, L_b = -0.0065 K/m, P_b = 101325 Pa
Altitude = 11000 – 20000m, T_b = 216.65 K, L_b = -1 x 10E-30 K/m, P_b = 22632.1 Pa
Altitude = 20000 – 32000m, T_b = 216.65 K, L_b = 0.001 K/m, P_b = 5474.89 Pa

By inclusion of specific parameters, for altitude = 0 – 11000m, atmospheric pressure is

Example
At altitude of 500m above mean sea level, atmospheric pressure is approximately 95460.84 Pa.
At altitude of 1000m above mean sea level, atmospheric pressure is approximately 89874.57 Pa.

How altitude impacting LNG production rate ?
Let compare LNG production rate change with a plant built at seaside (h = 0) and another LNG plant built at a site with altitude of 1000m. For both plant, LNG store at same gauge pressure (e.g. 50 mbarg), same LNG rundown temperature (e.g. -163 degC), same LNG tank dimension with same in-leak heat (normally higher altitude is with lower ambient temperature, lower in-leak heat is expected. However, the impact is negligible).

LNG from Main Cryogenic Heat Exchanger (MCHE) outlet is set at 50 barg and negative 164.8 degC. A JT valve is letting down pressure to LNG storage tank operating pressure of 50 mbarg. MCHE outlet mass flow set at 50000 kg/h. LNG is pure Methane (C1). Assumed same in-leak heat of 300 kW.

Case : Seaside
Altitude, h = 0m
Atmospheric pressure = 101.325 kPa abs
LNG operating pressure = 50 mbarg = 5 + 101.325 kPa abs = 106.325 kPa abs
From simulation (see below image), BOG flow = 1374 kg/h,
LNG production rate = 48626 kg/h

Case : Inland
Altitude, h = 1000m
Atmospheric pressure = 101325 (1 - 2.25577E-05 x 1000)^5.25588 = 89.8746 kPa abs
LNG operating pressure = 50 mbarg = 5 + 89.8746 kPa abs = 94.8746 kPa abs
From simulation (see below image), BOG flow = 1863 kg/h,
LNG production rate = 48137 kg/h

Same facilities and operating condition, the LNG production in Inland (at 1000m) reduced by 1%.

How altitude impacting Air Compressor / Blower power requirement ?

Air compressor at seaside is sucking air at atmospheric pressure of 101.325 kPa abs. If this air compressor is located at altitude of 1000m, air compressor is sucking air at atmospheric pressure of 89.8746 kPa abs. With same discharge pressure, higher head is expected at high altitude and higher power is required. Normally the head is rather large for air compressor, therefore the additional power may not be so significant. However, it could be significant for an air blower sent air to process with fix pressure. One shall remember, it may have no significant impact to an air blower sucking air from atmosphere and discharging air to atmosphere again.

Concluding Remark
Atmospheric pressure change with altitude and this will have impacts to facilities design. Do not under-estimate this impact.

Wednesday, September 29, 2010

Quick Way to Estimate Insulation for Cold Services

Earlier post "How Boil-Off-Gas (BOG) is Generated" and "Quick Way to Estimate BOG" discussed several ways result Boil-Off-Gas (BOG) generation and simple way to estimate BOG. Heat leak into piping wrapped with Cold insulation is one of the way possibly result significant BOG generation, in particular in large base load plant where product is loaded into ship. Long rundown and loading line from production plant and from storage tank to ship can generate significant BOG. Proper selection and determination of insulation thickness can minimize BOG generation economically.

Key Rule

Rule of thumb for economic heat flux for heat in-leaks range from 25 to 35 W/m². This is the key rule to derive an economic insulation for cold service whilst minimizing BOG generation.

Insulation Material & Thermal Conductivity

Common insulation material used in cold services (sometime called cryogenic service in extremely low temperature case e.g. LNG with operating temperature of approximately -162 degC) are typically Polyurethane and Polyisocyanurate Foam (PIR). These insulation material have very low conductivity minimizing heat from ambient entering cold fluid. Typical thermal conductivity for these material is approximately 0.023 W/mK @ 20 degC.

Insulated Piping In-Leak Heat

Estimation of piping in-leak heat from ambient starts with estimation of heat transfer coefficient using Nusselt number which is a function of Prandtle and Reynolds number.

Overall heat transfer cooefficient estimate from Nusselt number :

where Prandtle number

and Reynolds number

Piping in-leak heat can be estimated with following equation

with heat flux

Case study

Piping nominal size = 6"
Piping external diameter = 152.4 mm
Piping length = 100 m
Insulation material = Polyisocyanurate
Insulation thermal conductivity = 0.023 W/mK
Assumed Insulation thickness = 60 mm
Piping external diameter (including insulation) = 152.4 + 2x60 = 272.4mm

Air :
Air Velocity = 5 m/s
Air Thermal Conductivity = 0.029 W/mK
Air specific heat = 1009 J/kgK
Air density = 1.038 kg/m3
Air viscosity = 0.02 cP

Calculation :
Air Prandtle Number = 0.6959

Air Reynolds Number =70687.8
Overall Heat transfer Coefficienct = 18.096 W/m2K
Piping In-leak heat = 2125.72 W
Piping surface area = 85.58 m2
Average heat flux = 24.8 W/mK < 25 W/mK...OK

Similar calculation applied to 1" to 28"
1" - 50mm insulation thickness
2" - 50mm insulation thickness
3" - 60mm insulation thickness
4" - 60mm insulation thickness
6" - 60mm insulation thickness
8" - 70mm insulation thickness
10" - 70mm insulation thickness
12" - 70mm insulation thickness
16" - 70mm insulation thickness
20" - 70mm insulation thickness
24" - 70mm insulation thickness
28" - 70mm insulation thickness