Change NH3 to CO2

[gwapa]

Dear Friends
I am almost ready with the enginering project for a refrigeration system for an Ice Cream Plant. The design is a convetional two stage ammonia system. Two low temperature level -35C and -45C intercooler at -10C and condensing at 35C.
So we will have load at all diferents sucction temperature.
The owner call me up asking which will be the impact to change the project from Nh3 to CO2.
The question look to me very interesting and I would like to chear with you all.
Best regards
Gwapa

[US Iceman]

Some observations for your consideration....

1) the CO2 compressors will be smaller because of the higher vapor density of CO2.

2) A CO2 cascade system is a lot more complex than a simple two-stage NH3 system, i.e., fade-out drums or emergency power and cooling of CO2 during main power outage.

3) I have heard some speculation that CO2 power input is not much better (if at all) than NH3 power input.

4) Hot gas defrosting is more complicated with CO2 rather than the relatively simple system commonly used for NH3.

Just some quick points for your review gwapa.

[nh3 sweden]

Like the iceman says, during longer powerfailures it dosent take long before the safetyvalves blows. I have watched it a couple of times. Defrosting type is electric or with some kind of brine.

[Josip]

Hi, qwapa

Dear Friends
I am almost ready with the enginering project for a refrigeration system for an Ice Cream Plant. The design is a convetional two stage ammonia system. Two low temperature level -35C and -45C intercooler at -10C and condensing at 35C.
So we will have load at all diferents sucction temperature.
The owner call me up asking which will be the impact to change the project from Nh3 to CO2.
The question look to me very interesting and I would like to chear with you all.
Best regards
Gwapa

... stay with 2 stage ammonia .... don't make a headache to the owner and to yourself too ... ... down to -40C evaporating temp ammonia has a better COP then CO2 ...... definitely....

.... need to use ammonia only for hardening tunnel at -45C... design plant with only 2 systems -10C intercooler and -45C with a back pressure valve on -35C connected to the -45C system...

...you can save more money

.....if calculate condensing temp down to +30C ... we discussed that couple of times here on RE forums ....

spent some more money...

.... if using temper at -30C for cold rooms ...but less ammonia more safe... gravity feeding PHE with temper for cold rooms ....

... then again save some money ..... if install PHE as oil coolers oil/temper and use that heat for sanitary water or for heating/defrosting...

.... bigger investment but you are building a factory to last many years ...

...of course this is only one of idea ... not the best one, but for sure enough good to think about....

Best regards, Josip

[t0nz06]

We have a ice cream plant just like you want to design. We have -45 for the hardening tunnel & 35 for our warehouse and freezer barrels at low stage. we used frick compressors 3 pcsw 250hp at low stage at high stge we have -12ckt with 2pcs 600hp & 350hp frick compressors. we used intercooler at high side