question about HCl compressor bypass cooler installation

[knapee]

Dear Sir

I have a HCL recipricating compressor, which suction temperature is -30 and discharge temperature is 70, and there is a bypass line back to suction line.

I wonder if this process is continuous proess / or non-continuous process will affect the bypass cooler set up or not.


Thank you so much.

 

[Montemayor]

Knapee:

Before you can generate a useful response to this query, you need to:

1. State what degrees you are referring to in the suction and discharge values; are they Fahrenheit of Celsius?
2. What is the purpose of what you call the “bypass line back to suction”? Surely you must have an operating manual for this compressor. This line could be a capacity control line – or a line to start up and shut down in an unloaded condition. We don’t know and can’t deduce from what little information you give.
3. State the make, horsepower, construction, and number of stages of the compressor;
4. State the capacity and all suction and discharge temperatures and pressures.

There may be more data required after the above is received.

 

[knapee]

Dear Sir

Thank you very much for your reply.
1.The suction line is -35 degree C, 8kg/cm2g and discharge is 60 degree C, 21kg/cm2g.
2. The bypass line is a capacity control or spillback control line/ and also for start up and shut down in unloading situation. and I don't have operating manual in this stage.
3. This is two stage of this compressor and 460V 60Hz 6kW
4. The normal capacity is about 550 kg/hr.
And, my question is the cooler located in the bypass line is
only for continuous operation or not?

thank you so much.

 

[Montemayor]

Knapee:

You didn't make the specific statement that you have a cooler installed in the recycle capacity control line that leads from the discharge of the 2nd stage back to the suction of the 1st stage. I have to assume that is what you mean. (I hate it when engineers expect detailed, specific help from others when they don't have the courtesy of furnishing ALL the detailed basic data required in order to allow us to respond in a specific manner with accurate and safe advice)

If my assumption is correct: then YES, you need to have the hot (60 oC) HCL recycled gas cooled (I presume close to -35 oC) before it enters the suction drum of the 1st stage. You do this because - as you admit - you are using this recycle as a capacity control. In other words, you are having to control the suction pressure of the 1st stage in order to control the density of the suction gas (by maintaining constant suction conditions) in the event the HCL gas supply to the 1st stage is too low.

You fail to tell us how (or with what) you are cooling the recycle gas - and I guess that is asking for too much.

I hope this helps you to make a safe operational decision with regards to this compressor.

 

[knapee]

Dear Sir

Thank you for your reply.

I am sorry I have to correct the last statement I made.
The power for this compressor is 16kw and 1 stage compressor.

The question in my mind is that I always here
other said the VFD(variable speed driver) control is for this kind reciprocating compressor
in continuous operation. But in our case, we use pressure sensor on the
discharge line from the compressor for this capactiy control, and
on-off valve (for non-continuous operation ) used on recycle line
or pressure control valve or flow control valve (for continuous operation)
used on recycle line. And, the interstage cooler only will be provide in the continuos operation.
Also unloading valve should be used in inlet line


I am not sure my point is right or not.

thank you so much.