freeze-drying (lyophilization),

[gwapa]

Does anybody know of freeze-drying (lyophilization)?
How does the refrigeration system work?
What kind of refigerant does the system use?
what are the operation paramentres?
Any coments about the controls?
Appreciate your thoughts
Regards
Gwapa

[absrbrtek]

I have serviced the Hull America lyphilyzers. Basicaly its a vacuum chamber that they pull down to between -75C and -100C. They had (2) 35 HP 2 stage recip compressors feeding a 3/4 ton txv for the evap. The cold plates used (1) 35 HP 2 stage compressor. Real easy to go down the wrong path when servicing them.

I cant remember what the vacuum in the chamber was pulled to as we only did the refrigeration side of the equipment. The ones we serviced were running on R502 and we converted them to R507.

[Plank!]

About 7 years ago i was involved in the installation of the freeze dry plant for nescafe coffee. It used a NH3/CO2 cascade system, reportedly 2.7MW but good for a whole lot more, the CO2 operated very close to its triple point for a room temperature of -48C again i'm not sure what the vacuum pressure was, but at a guess, from the sheer size of the chamber the vacuum may not have been very deep.

The plant we replaced was 22 years old (at that time) and used R22 evaporating at -52C. Craziest set up i've ever seen, the refrigerant was full of coffee and air, even had automatic air purgers fitted on the R22 condensors, each vented every two minutes or so.

[smpsmp45]

There are few Danish companies who were involved in this. Recently York has taken over this company. There are few plants in India , though the recent one in Coffee is very succesful. So also used in Fisheries . Others used in veg / fruit etc did not do well commercially. I have some details on that. I shall see if I can scan those details & post them here.

[absrbrtek]

The ones we serviced were for pharmacutical use. The dehydrated raw blood with them to produce Rogam. An anti rejection drug given to woman after pregnacy.

[Josip]

Hi, gwapa :)

I was in India to do some other job in a coffee freeze drying plant...all ammonia, Sabroe SAB 202 screws 2+2 in 2 stage system, cold room temp -40*C/-50*C=-40*F/-58*F....complete design done by Danish firms...link for one is here:

http://www.niroinc.com/index.asp

a lot of material to read;) in library...

Best regards, Josip :)

[gwapa]

Hi all
The theorical aspects of lyofilizacion are clear. However I am very courios about the refrigeration itself

What kind of evaporator does it use?It should support vacuon outside.
How big could you build a lyophilizacion room?
What does it happen during vacuon time .there are very little air in the room
The low stage evaporator is overfeeded,or DX

[Plank!]

1. The vacuum makes a difference of less than 1 bar to the eveporator - therefore almost any type will do.
2. How much money do you have? First system i worked on was 2.7MW and 4 storeys high, how big do you want?
3. In the system i mentioned the vacuum chamber was below the blast freezer - evaporators in pods with airtight doors off each side wall (13 in total)
4. In this case all the lowstage evaporators are overfed with pumped CO2

BTW system mentioned is for coffee

[norseman]

Hi Gwapa.

The systems works by sublimation which means that you pull the solid like frozen water from the products without having a liquid state. Most freeze driers of professional type use a chamber who holds shelfs with a controlled temperature where the products should be situated. The shelfs are cooled or heated by a liquid flowing through them. Low temperature units use a special silicone oil. The shelf temperature can be +60c to -70c normally. The fluid used is passing a heat exchanger from the single or cascade cooling system and a heater. The condenser has to be colder and seen down to -110c. The vacuum is either pulled as low as possible, but many use it at a level. Often 100mbar is used. The shelf temperature try to rise the product temperature since the low vacuum pull the product temperature down and make then a reduced sublimation. You can try to look at SP industries or Virtis who make a lot of such units.

Regards Pedro

[gwapa]

Thanks everybody
I got a lot of information from you all I appreciate it.

Everyday one lern something new
Regards
Gwapa

[Ponca Dave]

When frozen things are heated in a vacuum
(at least .06 atmoshere) they sublime into a vapor
bypassing the liquid state. This is a deep vacuum
but the vacuum is the key. The heat is just what it takes to bring to melting plus the latent heat of fusion.