“Words are, of course, the most powerful drug used by mankind.”    (Rudyard Kipling)

 

U JUST CRACK ME UP!

Catalyst:  A substance that:

•  Lowers the reaction energy needed to get a reaction to happen.
• Selectively attracts reactants to engage with it while...
• Providing a surface area for the reactants to get ripped up and changed into something else.

The catalyst is not changed in the reaction. However bits of matter left over from incompleted reactions do build up and clog up the surface of the catalyst. Additionally, repeated pressuring and depressuring of the reactor pulverizes some of the catalyst into dust.

Therefore the catalyst in a fixed-bed reactor needs to be dumped and refilled or regenerated while it sits in the reactor. Catalyst run lengths vary but can be six months to 2 years before having to regenerate or refill.

There is only one known chemical reaction that takes place in nature and that is rust forming on a nail or other metal. All other chemical reactions require catalyst.

Catalyst bed: The volume of catalyst loaded in a reactor.

"Volume" is a measurement of length (how long across) times width (how far back) times height (how deep).

The vertical height of a catalyst bed, the condition of the catalyst, and the reactant flowrate determine how much time the reaction has to be completed.

Quench (Gas): A gas that is piped into a reactor to cool down exothermic reactions that take place in the catalyst beds.

When cooling is not sufficient to stop a runaway temperature, inert gas (more than likely nitrogen) can be brought in to snuff the reaction out; however the catalyst may be permanently damaged with inerting.

Temperature Runaway: An uncontrolled exothermic reaction that keeps reacting and generating heat.

 

THE REASONS WHY IT'S HOT IN HERE

No additional process industry jargon appeared in this PTOA segment which reviewed temperature-increasing process industry equipment.

 

I HEAT UP.... I COOL DOWN

(Vertical) Baffles: The hardware attached to the outside of a tube bundle that is inserted into the shell of a shell and tube heat exchanger.

The baffles cause the shell side process fluid to swirl around and around the bundle which enhances heat transfer.

Channel Head: The hardware that directs the tube side flow through a 2-pass U-bundle shell and tube heat exchanger.

The tube side inlet, diverter plate, and tube side outlet are fabricated into the channel head body.

Diverter Plate: The horizontal plate in a 2 pass shell and tube heat exchanger that separates the tube side inlet flow from the tube side outlet flow in the channel head.

Shell: The pipe that accommodates the shell side flow of a shell and tube heat exchanger.

The shell is a section of pipe with a diameter that is just large enough to accommodate a tube bundle with its attached baffles.

The shell side inlet and shell side outlet are fabricated into the shell.

Shell and Tube Heat Exchanger: A temperature-changing piece of process industry equipment that conserves thermal energy by transferring the heat out of a process stream that must be cooled down into a process stream that must be heated up.

Shell Side Flow: The process flow that enters the shell side inlet of a shell and tube heat exchanger, is swirled around by the baffles on the tube bundle to enhance intimate contact with the tubes in the bundle, and then exits the exchanger via the shell side outlet at a significantly different process temperature.

Shell Side Inlet: The shell side inlet is the opening that allows a process stream to flow into the shell of a shell and tube heat exchanger.

The shell side inlet is typically on the top of a typical 2-pass exchanger but is typically on the bottom of a reboiler.

Shell Side Outlet: The shell side outlet is the opening that allows a process stream to exit the shell of a shell and tube heat exchanger.

The shell side outlet will typically be on the bottom of a typical 2-pass exchanger. A reboiler has a liquid stream outlet on the bottom and a vapor stream outlet on the top.

Tube Bundle: Multiple small diameter tubes in a sideways-U shape.

The 'lower leg' of each U shaped tube is attached to the lower part of a tube sheet and the 'upper leg' of each U shaped tube is attached to the upper part of the tube sheet.

Tube Side Flow: The process flow that enters the shell and tube heat exchanger via the tube side flow inlet on the channel head.

The process flow then abruptly smacks into the diverter plate and is thus directed to flow through the tube sheet and enter the many tubes of the tube bundle.

The tube side process flow continues through the tube bundle and exits the tube sheet outlet side at a significantly different temperature.

After exiting the tube sheet, the tube side flow is once again aggregated and flows out the tube side outlet on the channel head as a single process stream.

Tube Side Inlet: The tube side inlet is an opening fabricated into the channel head of a shell and tube heat exchanger that allows a process stream to enter the tube side flow path of the exchanger.

Tube Side Outlet: The tube side outlet  is an opening fabricated into the channel head of a shell and tube heat exchanger that allows the tube side process stream to exit the  exchanger.

Tube Sheet: A circular plate of metal to which both ends of the multiple U-shaped tubes that comprise the tube bundle are attached.

 

OH SAY CAN YOU SEE?  (NOPE!)

CW: The abbreviation for "Cooling Water" that is written on PFDs to alert the Reader that cooling water is in use as the cooling media for a shell and tube heat exchanger.

ISA Symbol for Generic Shell and Tube Heat Exchanger: A circle with a zig zag line through it at the horizontal diameter.

The circle represents the shell side process flow.

The zig-zag line represents the tube side process flow.

PFD Label Key: Written words that appear on top of a PFD that inform the Reader of the tag name and hint at the processing function of the equipment found on the PFD.

The PFD creator will locate the labels at the top of the PFD and above the equipment that the tag identifies.

This intentional placement of label keys facilitates decoding the schematic; the schematic Reader follows the flow path of a process stream and then glances up to catch the tag name of the equipment that the process stream enters.

 

DIY! (DO IT YOURSELF!)

Service Duty (of a Shell and Tube Heat Exchanger): The functional role of the shell and tube heat exchanger (e.g.,  preheating, condensing, reboiling,etc.) and also which process streams are being heated up or cooled down and which process streams enter shell side or tube side.

Service Duty Guidelines(for Shell and Tube Heat Exchangers):

Tube side flow is favored for corrosive, gooky, and/or high pressure streams.

Shell side flow is favored for low pressure process streams and process streams that are mixed phase (gas and liquid) and/or in which condensing is taking place in the exchanger.

 

©2015 PTOA Segment 00053
PTOA Process Industry Jargon Recap 2-3

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