If I had to do the same again
I would, my friend, Fernando
Yes, if I had to do the same again
I would, my friend, Fernando...

("Fernando," by ABBA, 1976)

PTOA Segment 26:  HOUSTON ... YOU FIXED THE PROBLEM

This PTOA segment clarified the difference between producing saturated and superheated steam in a package boiler.

PTOA Readers and Students learned that the only way to create superheated steam is to first remove it from the liquid/saturated steam interface above the liquid level in a steam drum. Then heat can be added to the steam to raise its temperature above the boiling point temperature.

A key learning concept reiterated in this PTOA segment is how the Heat of Vaporization hides considerable heat that is not sensed nor displayed by a boiler TI.

Because of the 'hidden heat,' Process Operators must use the feedback from 3-Element Control (BFW flowrate, steam production flowrate, and steam drum level) to understand the actual processing situation in a package boiler.

The featured Systran Houston's animated you-tube clip showed :

• How saturated steam is generated in the steam drum of a package boiler. Any steam in contact with a liquid level is saturated steam.
• How superheated steam is subsequently generated by removing the saturated steam from the liquid level in the steam drum and running it through a superheater coil that is located in the chimney of the boiler stack.The heat generated by combustion indirectly transfers heat into the steam that flows through the superheater coil.

The Systran Houston you tube also showed:

• BFW flowing into the bottom of the liquid level in a boiler steam drum.
• The BFW flows downward through downcomers into a mud drum.
• Hot BFW and steam rise back into the steam drum via risers and D Tubes.

 

PTOA Segment 27: THE HEAT IS ON!

This PTOA Segment introduced exothermic chemical reactions as another way process stream temperatures can be increased.

PTOA Readers and Students had recently focussed on physical/phase changes that can directly change process temperatures. In comparison, exothermic chemical reactions use the heat generated from changes in chemical structure to directly heat up process streams.

Exothermic chemical reactions release energy that is stored in chemical bonds when those bonds are broken. The released thermal energy increases process stream temperatures.

PTOA Readers and Students who never thought the basics of high school chemistry would ever apply to them thought otherwise after reading this PTOA Segment.

The fundamentals of understanding and interpreting written chemical reactions were featured in this segment:

Reactants are on the left side of the chemical equation and Products are on the right side of the chemical reaction.

The chemical reaction arrow points to the desired Products.

Some chemical reactions have an arrow pointing both ways which indicates that the chemical reaction can go in either direction, depending upon the environment.

In the real world of industrial processing, the reactants in a written chemical equation are feedstocks that flow into a reactor. The products in a written chemical equation are the reactor products that flow out of the reactor.

Process Operators must maintain process temperature, process pressures, and feedstock/reactant flowrates that optimize production of desired products and limit production of less valuable by-products.

The structure of the Steam Methane Reforming (SMR), Water gas shift (aka Hydrogen Shift), and Combustion reactions were reviewed as an example of real-world chemical reactions used to make Hydrogen gas.

 

PTOA Segment 28: U JUST CRACK ME UP!

This PTOA Segment used a popular industrial process to demonstrate how a process temperature can be increased from the heat evolved during an exothermic chemical reaction.

The chemical reaction known as "hydrocracking" and the "Hydrocracking Reactor" were featured.

An exothermic reaction is easy to identify:

• The process temperature of the exiting reactor effluent process stream will always be greater than the process temperature of the feedstocks/reactants that enter the reactor.
• A method of sending cooling quench gas into the reactor that can stop a temperature runaway if/when needed will be included in the reactor design.

The hydrocracking reaction changes big, complex hydrocarbons into smaller hydrocarbons that have more commercial value.

The chemical energy stored in the bonds of the large hydrocarbons is released as thermal energy when the bonds are broken.

Hydrogen gas is needed as a reactant to replace broken carbon-carbon bonds and make carbon-hydrogen bonds. The bonds that are created make totally different molecules than the bonds of the chemicals that once existed.

The reactor/reaction products are chemically different than the reactor feedstock/reactants that entered the reactor. Otherwise stated, the products are permanently different than the reactants.

PTOA Readers and Students began to realize how the various plants in a processing complex are integrated:

The hydrogen used as a reactant in the hydrocracking reactor was made in a Hydrogen Plant using the SMR and Hydrogen Shift reactions that PTOA Readers and Students had focussed on in earlier segments.

No chemical reactions would occur without catalysts.

Catalysts provide amenable conditions and a surface area for the chemical reaction to take place. Catalysts are selected for their ability to favor production of desired products.

The flow through a fixed tubular reactor was focussed on.

The feedstock/reactants enter the reactor inlet and keep flowing downward.

The success of making desired products depends upon the vertical length of the catalyst bed, the condition of the catalyst, and the flowrate of the feedstocks/reactants.

Process Operators are responsible for operating reactors optimally to preserve the condition of the catalyst while maintaining reactant flowrates that favor making desired products instead of less valuable by-products.

 

PTOA Segment #29: THE REASONS WHY IT'S HOT IN HERE

This PTOA Segment summarized Temperature-Increasing Process Industry Equipment and exothermic chemical reactions.

Fired Heaters and Package Boilers indirectly heat up process streams by generating heat via combusting fuel gas/natural gas and oxygen in burners. The heat from combustion indirectly heats the process fluids that are flowing through tubes in the firebox.

Fired Heaters are installed where it is absolutely necessary to attain a target temperature.

Package Boilers make steam and superheated steam which can be used to indirectly heat process streams in reboilers and steam tracing.

Exothermic chemical reactions are a chemical means by which a process temperature will be signficantly increased.

Physical processes that release heat into the surrounding atmosphere include the Heat of Condensation and the Heat of Freezing. The process stream and solid that respectively remain will be sensed as cooler and the heat that is released will be absorbed into the surroundings.

Process Operators must understand the sources that increase process temperatures. When a process temperature appears to be too high, the first place to start troubleshooting is the Process Industry Temperature-Increasing Equipment.

 

©2015 PTOA Segment 00047
PTOA Deja Vu Review 2-2

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