What is the maximum height of a charge gas compressor deck. 1

[CaracasEC]

Hi All,
What would be the maximum height of the Charge Gas Compressor deck for Ethylene Cracker Plant?

 

[zdas04]

I hope that someone knows what a "Charge Gas Compressor deck" is because it is foreign to me. If you want to expand on what it does, what suction and discharge pressure and temperature are expected/required then maybe someone who's never worked in a refinery or chemical plant might be able to help you.

David

 

[CaracasEC]

This compressor was used on Ethylene Cracker Downstream of the Quench Tower. This is a three stage compressor with x suction pressure, y discharge pressure and a z flow. However, the EPC contractor design the compressor structure/top of concrete to be 11 meters. Since this is driven by a condensing steam turbine on which below the expansion bellow is the surface condenser. From the nozzle end of the condenser, the height was 4 meters because of the NPSH requirement of the OH2 pump. Is there someone, working on an ethylene cracker with the same design?

 

[zdas04]

That clears everything up nicely. With x suction, y discharge, and z flow, your answer is obviously [β]. Have a nice life.

David

 

[CaracasEC]

Hi David,
For the detailed data sheet, suction pressure 1st/2nd/3rd to be 0.43/2.53/7.25barg. Discharge pressure to be 2.75/8.39/21.76barg. Rated Capacity 151837 x 1.05/ 135429 x 1.05/ 117514 x1.05 kg/hr respectively. Absorbed Power est 12926 x 1.05 kw. Thanks...

 

[JJPellin]

I cannot imagine why it would be a problem to set this compressor deck so high. The height was set to accommodate the turbine, condenser and condensate pumps. A few extra meters of head in the gas stream should have no significant impact on compressor performance. The only problem I would expect if this machine was installed in our plant would be from the operators. If they had to climb 35 feet of stairs to get up to the compressor to perform their rounds, they would not be happy. They might not make it up there as often as they would if it was closer to the ground. But, if it is their job to check it, they will check it. We have one set of blowers on the top of the CCR structure that require 144 steps to reach (maybe 35 meters).

I would rather have a high compressor deck than a set of condensate pumps continuously failing from cavitation. We have compressors with condensing steam turbine drivers on platforms 10 meters high (FCC main air compressor) and others on platforms only 2 meters high (hydrogen recycle). I prefer the taller deck with bottom exhaust turbine and accessible surface condenser.


Johnny Pellin

 

[CaracasEC]

The problem with this high compressor deck would a cost impact on the construction of the structure. If i can reduce it even to 2 meters then i can reduce the compressor structure cost and the compressor structure would be more stiff that will lessen the probability of resonance of the structure. I have once a visit on one of the Ethylene Cracker somewhere in Asia and the height from the grade to the bottom nozzle of the surface condenser is only about 1 meter compare to ours which will be 4 meters. What i found out is that the NPSH requirement of the condensate pump is about 2.6 meters (API OH2 Pump). When i suggest that a vertical pump should be used to reduce the NPSH requirements, it was too late that the compressor vendor have already bought these pumps and a cost impact in changing from horizontal to vertical will be charge.