Years come and go...But today is just a little bit special...
~ 20072007 ~
Double Match...
It happens only once in a lifetime ..
I wish you a very Wonderful Day !
Friday, July 20, 2007
Just realize...
Years come and go...But today is just a little bit special...
It happens only once in a lifetime ..
I wish you a very Wonderful Day !
Wednesday, July 18, 2007
How does Supercritical fluid looks like ?
As discussed in previous post, Carbon Dioxide (CO2) is known as one of industrial waste gas causing global warming...there are number of measures are implemented to reduce global warming. CO2 reduction measures are CO2 capturing, reinjection into aquifer, injection into reservior for well maintenance, gas injection for enhanced oil recovery (EOR), etc.
Co2 being captured will be injected in the reservior. The injection can be as high as 300-400 atm which is higher than the critical pressure of Co2.
How does Co2 in Supercritical looks like ?
The following image (running in sequence) shows liquid Co2 under pressure boiled and transform itself to supercritical fluid (SCF).
CLICK IMAGE...
Source : Nottingham University
Further Reading
Tuesday, July 17, 2007
"Cooking a Vessel" in Process Engineering...
"Cooking a Vessel"
Have you ever heart of this term in Process Engineering ???
This term probably mean heat up (and circulate when possible) a solution inside a dirty or impure vessel for the sake of dissolving or simply rinsing out the internals prior to sweeping it with a semi-pure fluid and conditioning the vessel for production service.
This is a necessity when you done internal work inside a distillation column, for example, during an annual turn-around and there are traces of grease, oils, and gasket adhesive and other "goodies" inside the assembled and repaired internal parts. In order to ensure that all these impurities are not mixed in with the finished product, the column, reboiler, condenser, associated vessels and all their internals are "cooked" with a hot fluid - usually a solvent or a hot caustic solution - in order to rinse and sweep out all undesired impurities left in the vessels after human entry.Other Forum members may have the same terminology for other techniques used in their plants.
Source : Art Montermayor
During precommissioning / commisioning phase, some system may required acid cleaning in order to remove grease, oil, corrosion stuff, welded slag, etc. Through acid cleaning, it may oxidize metal surface layer so that it form a strong and corrosion resistance layer for vessel protection. Sometime, it called passivation and "cooking a vessel" in layman term.
Monday, July 16, 2007
How to design Shell and Tube Heat Exchanger...
Let's some interesting articles from Dr.R. Shankar Subramanian, University of Clarkson
How to Design a Shell-and-Tube Heat Exchanger
A lot has been written about designing heat exchangers, and specifically, shell-and-tube heat exchangers. For example, the book by Kern (1) published in 1950 details basic design procedures for a variety of heat exchangers. Since the publication of that book, with the advent of computers, design procedures have become sophisticated even though the basic goals of design remain the same. Because it is possible to specify an infinite number of different heat exchangers that would perform the given service (heat load), we have to identify the specific heat exchanger that would do it subject to certain constraints. These constraints can be based on allowable pressure drop considerations either on the shell-side or on the tube-side or both, and usually include that of minimizing the overall cost. An article in 1979 by Taborek (2) outlines how heat exchanger design techniques evolved over the years since the appearance of the book by Kern. More recent developments are discussed in numerous articles in the magazine “Chemical Engineering.”
Here is a step-by-step approach to specifying a new shell-and-tube heat exchanger. We shall focus on sensible heat transfer, and make extensive use of Chapter 11 in Perry’s Handbook (3). From hereon, references to page numbers, table numbers, and equation numbers are from Perry’s Handbook.
R. Shankar Subramanian, University of Clarkson
Sunday, July 15, 2007
Heat Transfer - Internal and External Flow
Wanna to share some findings today...some notes from Dr. Shankar Subramanian, University of Clarkson.
Heat Transfer to or from a Fluid Flowing Through a Tube
A common situation encountered by the chemical engineer is heat transfer to fluid flowing through a tube. This can occur in heat exchangers, boilers, condensers, evaporators, and a host of other process equipment. Therefore, it is useful to know how to estimate heat transfer coefficients in this situation.
We can classify the flow of a fluid in a straight circular tube into either laminar or turbulent flow. It is assumed from hereon that we assume fully developed incompressible, Newtonian, steady flow conditions. Fully developed flow implies that the tube is long compared with the entrance length in which the velocity distribution at the inlet adjusts itself to the geometry and no longer changes with distance along the tube.
R. Shankar Subramanian, University of Clarkson
External flows occur when the fluid is confined in such a large channel or container such that it can be considered practically unbounded in extent when considering heat transfer to a stationary solid surface. The ideal starting point for this is flow over a flat plate that is long and wide. We know that in this situation, for flow at large values of a suitably defined Reynolds number, a boundary layer forms on the surface in which the velocity varies from zero (no slip) at the solid surface to the value in the free stream. Outside the boundary layer, viscous forces are entirely negligible, and potential flow can be assumed to prevail. Potential flow means flow in which the vorticity is zero and viscous forces are neglected.
R. Shankar Subramanian, University of Clarkson
R. Shankar Subramanian, University of Clarkson
Thursday, July 12, 2007
Wednesday, July 11, 2007
Factors and Criteria for Vent Stack Design
Vent and flare stack are used dispose waste gas in safe and enviroment friendly manner. Flare stack is probably preferred as compare to vent stack if the release fluid contain HC from environmental point of view e.g. impact to greenhouse effect for 1 mole of C1 is about 20 times of 1 mole of CO2. However, flare stack may be costly.
For a vent stack, at least 3 main criteria shall be met :
i) Toxic / flammable component well dispersed and meeting health and safe level during Normal operation (Nor. Op.) and emergency situation (Emer. Op.). very much subject to components / species in vent gas. Local regulations will probably indicate the limits of various components. In additional, Material Safety Datasheet (MSDS) will probably indicate the limits. PHAST, FRED, etc can be used for dispersion study.
ii) Radiation due to ignition of lightning (Emer. Op.). In the event, vent gas is HC and potentially ignited by lightning, radiation study shall be conducted to ensure radiation at the receptor (human) point is meeting criteria e.g. 6.31 kW/m2. In addition to the radiation level, the temperature of receptor (equipment) shall not damage the equipment. FLARESIM, FRED, etc can be used for radiation study.
iii) Noise level at receptor meeting noise criteria during Normal operation (Nor. Op.) and emergency situation (Emer. Op.). Noise level at receptor (human) is meeting criteria e.g. 115 dBA with background noise. Keeping in mind, some plant owner may impose more stringent requirement i.e. 90 dBA @ receptor (human). FLARESIM, FRED, etc can be used for noise study.
If some spill over control PCV tie to vent header and release continuously into vent stack, fluid exit temperature may be a concern in some environment sensitive area.
API 521 has recommended Mach = 0.5 and this value is probably a good start for vent diameter determination. Vent stack height will subject to above criteria, location of vent stack, plant layout, wind speed, wind direction, etc. Modeling vent stack with inclusion of vent diameter and height using software as mentioned will be conducted in order to ensure meeting all criteria as mentioned earlier.
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