Extracting heat from recip. compressor through jacket water 1

[dimeivan]

From a practical point of view, I need to know how much heat can/should be extracted from a reciprocating compression stage through its jacket water. As far as I know, jacket water in compressor cylinders only serve to keep metal temperatures in an acceptable range, not to cool process gas.
i.e. I need to withdraw 100 Btu/h from the gas stream, how much of that should be extracted by jacket water, and how much by post-stage cooling means?

PD: I know that API recommends water entering 10F above suction temp. of the gas, and exiting 30F above the entering temp., maximum.

many thanks!

 

[dcasto]

100 btu\hour from a 1 lb\hour gas stream is not possible from a 1000000 lb\hour is

 

[dimeivan]

By saying 100 Btu/h I meant an example, say, if you had to remove 100 use-the-units-you-like, how much of that (in 100percent) could be removed by jacket water and how by afterstage coolers.

 

[JJPellin]

The jacket cooling is designed to remove heat generated by the mechanical operation of the piston in the cylinder. It should not be used to remove any of the heat of compression in the gas stream. Any gas cooling should be accomplished with a process cooler downstream of the compressor stage. If you attempt to cool the gas with the jacket cooling, you would create a risk of condensing liquid in the cylinder. And, I have been told that liquid in a positive displacement compressor is a bad thing.

Johnny Pellin

 

[pmover]

You should submit your question to the compressor mfg. They can tell you the quantity of heat removal by the compressor jacket water cooling system based on a set of operating or design process conditions.

good luck!
-pmover

 

[dcasto]

There are very few water cooled cylinders any more. In the 1980s we removed water circulating pumps on compressor cylinders and just filled the jacket with 50 50 EG water. Ariel led the way in the 1970s with gas cooled cylinders.

Uneven temps in cyliders caused valves to not seat well and cylinder walls to warp that was a major reason for cooling water. Newer materials could handle warping and valve seating.


I suppose you could circulate enough coolant to remove huge amounts of heat but you could also Condense liquids which would destroy valves at a minimum cylinders at the worst

If you need some free heat cool the compressed gas

 

[dimeivan]

I´m currently working on a 35-year old Dresser-Clark compressor, so eliminating jacket water is not feasible. This compressor has suffered from moderate efficiency loss, and the owner is not willing to replace it or even touch it. As a result from this eff loss, high temperatures are being recorded in 1st and 2nd stage discharges. The owner has asked to evaluate the posibility of increasing jacket water flow, in order to decrease, at least a few degrees, the exiting temperatures.
I know that feeding cold water would lead to condensation, I´m not planning to do that, but to increase water flow.
My point is if increasing water flow will yield any improvement at all.
Thank you!

 

[dcasto]

You can not extract enough heat. You need to run the conditions on the unit and see if the higher temperature is normal. You say it has inefficiencies how do you know that. If the gas composition changes or pressures change the hotter temps could be normal. Changing valve design and rings could help too.

 

[dimeivan]

dcasto,
The gas composition has not been altered, it compresses a mixture of H2 and N2 feeding a reactor. Running at the same compression ratio as the original datasheet, the unit delivers higher discharge temperatures than design, operating at the same suction temperature.
Nevertheless, I aprecciate your assistance. I have now a clearer picture of how to find a practical solution.