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Why CO2 is not desired in natural gas?
Because it reduces the heating value of the gas and has acidic characteristics causing corrosion
Two types of gas sweetening methods
- 1) regenerative: Liquid and solid sweetening
- Solid: activated carbon, activated alumina, iron, silica
- Liquid: Amine
- 2) non-regenerative: used in removal of small quantities of acid gas
- operated in conjunction of regenerated process
- used for final clean up of trace of toxic gas
- used caustic soda and lime carbonate
Occupational exposure limit
Block Flow Diagram
- introduction of Condensate gas
- Liquid separation
- Gas sweetening
- recovery of natural gas
Types of amine
- MEA (monoethanol amine): high capacity of absorbing toxic gas
- used when high degree of gas purification is required
- forms undesired salts when contacted with gases other than H2S and CO2
- DEA ( Diethanol amine)
- reduced degradation effect : lower operating losses
- less HC contamination of the acid gases results in better sulphur plant performance and improved sulfur quality
- TEA ( Triethanol amine)
- used when selective H2S removal is required
What is degradation effect?
is the result of chemical combination of amines with some sulfurous compounds from which the solution cannot be recovered during regeneration
The lean amine enters ---------- of the tower while sour gas enters at the ----------. This promotes ---------- flow
the sour gas reacts with amine and form----------- which stay in the solution
water soluble salt
The absorber tower is under ---- P and ------ T (Why) ; the regenerate is under -------- P and ------- T (Why)
- High, Low
- The reason is so the two compounds ( gas and liquid) are forced to see each other; this enhances the contact and separation
- Low, High
- The reason is we want to evaporate the H2S and CO2, but at the same time we do not want to send the water vapor which might have been evaporated and carried over with gas stream to escape ( this is done through locating an partial over head condenser at the top of the regenerate, so the water goes back into the regenerator )
Contactor and scrubber are other names for __________ and still and stripper or reactivator are other names for ________
Three types of heat exchange in sweetening process
- Partial over head condenser ( cooler)
- Amine-amine heat exchange
- Reboiler ( which is located at the bottom of the regenerator)
When the hot lean amine leaves the regenerator it has to go through steps. what are they and what is the purpose of each?
- When the hot lean amine leaves the regenerator from the bottom, it goes through a amine-amine heat exchange. This heat exchanges is the place where the heat from hot lean amine is being used to heat the rich amine that is on its way to the regenerator.
- Than it goes to the pump, because we are moving from low P to high P.
- Lastly, it goes through a cooler for further cooling because it is coming from the regenerator that has a high T and going to an Absorber that has a low T. So the purpose of the cooler is to cool down the lean amine to atm. T
What is the purpose of the liquid at the bottom of the absorber?
- To make sure the absorber is not running dry
- most importantly is to avoid the gas from moving down word of the tower.
The level is control by a valve that is located on the way of rich amine towards the heat exchanger
What is the purpose of rich amine flash drum?
To remove HC that is driven off with gas stream and rich amine.
it is located before the stripper
What is flashing?
Decreasing the pressure super fast to go from liquid to vapor, high P to low P, and low V to high V
- Temperature recording controller
- Flow Indicator
- Level Control
- Differential Pressure controller
What is the purpose of reclaimer and where is it located?
- It is an amine purifier
- it is used to remove degradation products in the solution
- it is located near the bottom of the stripper