Recharging desiccant on a QSI

[swag72]

I've decided that it's probably a good time to recharge my desiccant on my QSI683..... Easily done according to page 79 of the following ... http://www.qsimaging.com/docs/QSI User Guide 3.1.pdf ... but ....... It says 4-5 hours at 500 degrees Fahrenheit. That equates to 260 degrees Celsius...... For starters my oven doesn't go above 250 degrees!! But an oven on full blast for 4-5 hours? Really? Will be cheaper to buy a new QSI with electric costs out here

Has anyone recharged QSI desiccant and did it really need this heat for this long?

[ChrisLX200]

That must be wrong!  Silica gel only needs 100deg for about 30-60min to regenerate. Maybe it's not silica gel but even so...

[swag72]

I couldn't believe it Chris, which is why I asked!! You've even made me go back and check the paper ..... here it is, clear as day on Pg 80..... It will drive out the water molecules I'm sure as well as my husband when I get the electricity bill  

 

[SkyBound]

Can't you just replace the desiccant.....? Are they not in tablet form ?

[swag72]

I don't know @SkyBound I've not looked!

[hughgilhespie]

Hi Sara,

The dessicant is probably a type called Molecular Sieve. It is a very effective dessicant but it does need fairly high temperatures to regenerate.

I quote

'

Molecular Sieves are synthetic crystalline zeolites in which the atoms are arranged in a definite pattern. Internally, the structure has many cavities inter-connected by smaller pores of a uniform size. These pores are only able to accept and pass to the cavities molecules of the same and smaller size, hence the name molecular sieve.

The water vapour adsorption characteristics are very different from those of silica gel. Molecular sieves can adsorb up to approximately 20% by weight of water before the relative humidity of the surrounding air increases significantly. Any further increase causes a large rise in relative humidity.

These characteristics enable molecular sieves to maintain very low dewpoints (-50°C for 10% by weight of adsorbed water). The material also has the ability to rapidly adsorb water vapour and is capable of maintaining high adsorption efficiency at high temperatures of up to 90°C.

Molecular Sieves are available in four primary generic forms, 3A, 4A, 5A and 13X. Each form has its own specific properties and applications, and all retain a polar preference for adsorption of water.

• 3A is the preferred Molecular Sieves adsorbent for the commercial dehydration of unsaturated hydrocarbon streams.

• 4A is the preferred Molecular Sieves adsorbent for the static dehydration in a closed gas or liquid drying system.

• 5A is the preferred Molecular Sieves adsorbent for the separation of normal paraffin's from hydrocarbons.

• 13X is used commercially for general gas drying, air plant feed purification and liquid hydrocarbon and natural gas sweetening.'

The regeneration temperature for 4A grade is 200 - 315 C so 250 is about right.

Regards, Hugh

[Whirlwind]

On ‎03‎/‎12‎/‎2016 at 13:00, SkyBound said:

Can't you just replace the desiccant.....? Are they not in tablet form ?

The desiccant is held in a small brass(?) container that is sealed in place with a rubber o-ring inside a small covered chamber in the ccd.  You put the whole brass container in the oven (without the o-ring obviously  )

[swag72]

Just in case anyone wants to do this ...... I have a follow up from a QSI dealer in the US who spoke directly to QSI on my request.

As per the instructions, unscrew the plate, but ensure that the camera is upright as Argon is heavier than air (the gas that is in the chamber) and so the minimal amount will escape. Remove the canister and close the cover right away. Then the desiccant can be recharged in a lower temperature oven (not a raging inferno as per the instructions!!) for 8 hours. 

[r3i]

On 12/13/2016 at 08:08, swag72 said:

Just in case anyone wants to do this ...... I have a follow up from a QSI dealer in the US who spoke directly to QSI on my request.

As per the instructions, unscrew the plate, but ensure that the camera is upright as Argon is heavier than air (the gas that is in the chamber) and so the minimal amount will escape. Remove the canister and close the cover right away. Then the desiccant can be recharged in a lower temperature oven (not a raging inferno as per the instructions!!) for 8 hours. 

Sounds like you're still going to get through a lot of electricity if you're increasing the time by an additional 3 hours even if it is at a lower temperature.  How often do you need to go through this process?

[swag72]

13 minutes ago, r3i said:

Sounds like you're still going to get through a lot of electricity if you're increasing the time by an additional 3 hours even if it is at a lower temperature.  How often do you need to go through this process?

Not often I wouldn't think........