“Without knowing the force of words, it is impossible to know more.” (Confucius)

 

PTOA Segment 67: All Together Now ... Soup's On!

PTOA Segment 67 focussed on how the three methods of heat transfer ... Radiation, Conduction, and Convection ... work together to heat up a can of soup in a saucepan.

No additional jargon was introduced in this PTOA Segment 67.

 

PTOA Segment 68: All Together Now ... Raise Process Temps!

PTOA Segment 68 focussed on how the three methods of heat transfer ... Radiation, Conduction, and Convection ... work together to achieve target process temperatures in process industries.

The concept of "linear thermal expansion" was introduced and will be featured in a future PTOA Static Equipment Focus Study Area.

No other additional jargon was introduced in this PTOA Segment 68.

 

PTOA Segment 69: Playing With Fire

Burner (in Fired Heater, Package Boiler, or Reaction Furnace): The hardware component in a firebox that is designed to combine the combustion air, fuel source, and ignition source needed to create and sustain the combustion reaction.

(Combustion) Air Register: A vent in the burner assembly that can be adjusted by Process Operators to determine how much air will be drafted into the firebox; the oxygen in the air supplies the oxygen needed for the combustion reaction.

Flameout: The dangerous loss of flame at a burner tip while fuel and combustion oxygen and purge gas are still being charged into the firebox.

Flame Impingement: Elongated flames that extend from the burner to touch the refractory walls or heater tubes.

Low-NOx burners (aka Lo-NOx burners) : Burners designed to diminish the emission of nitrogen oxides by improved combustion at the burner tip.

Pilot Gas: A gas that is ignited to provide the ignition source for the combustion reaction that takes place in the burner. Natural gas (aka Methane, aka CH₄) is often used as pilot gas.

Purge Gas (in a Firebox): An inert gas (usually nitrogen) that is used to snuff out the combustion reaction and therefore insure a non-reactive, non-explosive condition exists in the firebox.

The verb "purge" in process industry means:

"to displace an atmosphere with a different atmosphere by using pressure to push and dilute the non-desired atmosphere out of the equipment that is being purged."

Nitrogen can be used to flood the firebox and snuff out the combustion reaction, aka "purge the firebox with nitrogen."

Once an inert atmosphere is confirmed, the nitrogen will then be purged out of the non-ignited firebox by opening up on air registers and the damper.

Once an air atmosphere is confirmed to exist in the (20% oxygen, 78% nitrogen), the burners can be ignited again.

 

PTOA Segment 70: Flame Management 101

Damper: An adjustable plate in the stack of the heater that can be adjusted as needed to create draft.

Draft: The upward flow of gaseous combustion products and flue gases through a firebox and up its chimney which is only possible by creating a vacuum (see definition of vacuum below).

Excess O2 (aka Excess Oxygen): Once the amount of carbon in the combustion fuel is known, the amount of oxygen required to burn the carbon to completion is also known.

The amount of oxygen over and above what is necessary to complete the combustion reaction is the 'excess oxygen' which is easily detectable by an oxygen analyzer located in the stack of a fired heater, package boiler, or reaction furnace.

Excess Oxygen is an analytical reading used by Control Board Operators to optimize the combustion reaction.

Oxygen-to-Fuel Ratio: Literally, the ratio of combustion oxygen to the amount (which will also hint at type) of fuel:

Too little combustion oxygen causes flameout and flame impingement but too much combustion oxygen causes significant heater inefficiencies as well as contributes to global warming, ozone-depleting smog,and airborne health hazards.

Vacuum: A negative-pressure area that must be created to make a fluid flow when the surrounding environment is at atmospheric pressure.

Everyday examples of creating a vacuum:

The process of causing lemonade in a glass to flow into the mouth through a straw is an example of creating a vacuum.

The household appliance called a vacuum cleaner sucks up dirt from a carpet by creating a vacuum within the device.

Examples of creating vacuums in process industries include:

• Creating draft through chimneys.
• Use of vacuum trucks to suck up the muck in sewers so that the processing of dirty water does not get backed up.
• Steam jet ejectors use steam and a modified-venturi device to entrain fluids to flow without need of a power source or any moving parts.

 

PTOA Segment 71: Your Mission: Find Hot Spots and Coke

Coke: Deposits made mostly of carbon with a very little bit of hydrogen that are caused by "thermally degrading" (=burning) process streams which flow through heater pipes at too low of a flowrate compared to burner firing rates.

PTOA Readers and Students can Imagine the chemical composition of coke as a sheet of carbon atoms (C) connected to each other and ever so often there is a hydrogen also attached to a carbon.

In real life, coke presents itself as something like a deposit made of pencil lead.

Flux of Heat (through a firebox): The expected, designed flow of heat through a firebox that begins with the continuous supply of radiated heat from the burners which is then continuously transferred by conduction through firebox tube walls and thence continuously transferred by convection into the process fluid that is being heated as it continuously flows inside the tubes and eventually exits the firebox... ergo removing heat from the firebox at an expected, constant rate.

Any impediment to the designed interface of radiant, conduction, or convection heat transfer will result in the inefficient operation of the firebox at a minimum and a potentially dangerous situation if unnoticed by Process Operators and Control Board Operators.

Hot Spots: Glowing spots in the light orange-yellow-white color spectrum that are the outcome of built up coke deposits interrupting the flux of heat through a firebox.

Outside Operators can detect hot spots with the help of hand held instruments that use pyrometry.

©2015 PTOA Segment 00091
PTOA Process Industry Jargon Recap 3-3

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