Ammonia Plant vs Chiler units

[samiam]

Hi,

I need the opinions and experience of the masses:

I require glycol spplied at -10C and 0C for air coolers loacted in various rooms.

With classical industrial refrigeration, I can achived this using Ammonia, LP veesels, compressors, condensers, pumps etc..
However, chiller units to can produce chiled glycol (even at -10C, so the manufacturer said). These chiller units also have pumps as pert of teh packakge. Redunday wrt compressors would be easy to achieved.


My refrigeration heat load is quite low;
a) -10C glycol supply for 300KW.
b) 0C glycol supply for 600KW.

Additionally - would screws or recips be better??

Maybea similar excesie had been carried out by you. What are the opinions.

[US Iceman]

My preference would be to use a small ammonia central system operating at two evaporating temperatures. Each temperature level could have at least two compressors, plus an additional compressor connected to operate off of either temperature level (as a swing compressor).

So you would have 2 compressors for the -10°C load & 2 compressors for the 0°C load, with one compressor capable of operating off of either temperature level.

I like recip. compressors. Their part load efficiency is much better than screws and they are easier to work on.

I think I would look at some flooded plate heat exchangers and an evaporative condenser which sufficient reserve capacity for low condensing temperatures.

The refrigeration system is the easy part. How are you planning on defrosting the glycol coils when required?

[samiam]

Hi - thanks for the reply

I agree with your thoughts on the Ammonia plant - what I need to perform is a Cost Benefit Analysis of the 2 options, and a plantroom comparison. The chiller is a complete unit, no plantroom required, using possibly R134a (They dont make them in R22 - the site is in a developing country)

My thoughts on the defrost were Electric (I could use Hot Gas - however, the number of coils will be low and I wuld have to add anothe PHe and a set of pumps)

So much work - so little time...

[HallsEngineer]

Halls have started doing chillers on ammonia with either air cooled or Evap condensers, as have grenco. Everything is on inverters. Bit pricey but they are very efficent.

[samiam]

Thanks - I could not find anny brochures on the website. Do you know where I can get some.

[Josip]

Hi, Samiam :)

I have to agree with US Iceman..in all.



Hi - thanks for the reply

I agree with your thoughts on the Ammonia plant - what I need to perform is a Cost Benefit Analysis of the 2 options, and a plantroom comparison. The chiller is a complete unit, no plantroom required, using possibly R134a (They dont make them in R22 - the site is in a developing country)

My thoughts on the defrost were Electric (I could use Hot Gas - however, the number of coils will be low and I wuld have to add anothe PHe and a set of pumps)

So much work - so little time...

If you want low first installation costs then you should go with chillers...as you said: it is in one "developing country" why not "help them to save some money" and install cheap crap;)

If you want low running cost and long time (20-30years) running plant then...install industrial ammonia plant, to leave something worth behind you...

No need any "Cost Benefit Analysis"....believe me.

Best regards, Josip :)

[Core4 Guy]

First your USA loads are:

85 tons and 170 tons but I didn't see any actual room temps...

I definitely would look at a built up system rather than a "chiller" package of any type.

Advantages: (if designed right)

Defrost heat is free on built-up systems
No parasitic loads of glycol pumps
Less things to go wrong
No secondary heat exchange increasing efficiency
Ease of multiple evap temps
Best ROI (again if designed properly, built for your facility, in your geographical location, with your energy costs)

As far as ammonia vs a halocarbon. Either is a preference. Contreary to most thought you can have a more efficient R-22 system than an NH3 system depending on design...

Never go with a packaged system. Chillers are by name inefficent they are designed to Chill water not your load.