Kalk slurry viscosity temp. dependent?

[AcroporAddict]

Guys,
I use an Avast Marine K2 kalk stirrer, which is a slow stir 24/7 type reactor that uses a stir bar at the bottom of the reactor driven by a slow electric motor. I just emptied and refilled my reactor, and it looked an operated as before, but the next day I found the kalk slurry all clumped up a the bottom of the reactor, so thick that it made it hard for the stir bar to turn. One big difference is the temperature of my equipment room with the recent big freeze, and lows in Atlanta of 7 degrees, etc. My sump and all operating equipment are in an unheated area of my basement, and the room temp has been much cooler than normal, say from the upper 60s normally down to the lower 50s or something similar.

I just opened a new 5 gallon bucket of BRS Kalk powder, which is what I have always used, and mix with 0 TDS RODI. Main variable I can see is the temperature the stirrer is sitting at. The kalk powder seems the same as always.

Can a lower temperature cause kalk slurry to clump up like that? I always completely empty the old kalk out and replace with new every two weeks.

Thanks for any help.

[bertoni]

Lower temperature should improve solubility, actually. If the reactor froze, though, that might cause problems.

[AcroporAddict]

Strange thing it happening. First time in 10 months use. Possible it could be a bad batch of kalk powder as well. I always stir it up very well when I replace the kalk. I just changed it out again, so we'll see if this was a fluke or if it happens again.

[tmz]

As noted the cooler tempearture should increase solubility. The motor may be running hot for some reason contributing to localized clumping from precipitation. I'm not familiar with the unit so that's just a consideration to check.

[AcroporAddict]

Originally Posted by tmz

As noted the cooler tempearture should increase solubility. The motor may be running hot for some reason contributing to localized clumping from precipitation. I'm not familiar with the unit so that's just a consideration to check.

Thanks Tom. Sounds from your and Jonathan's response it is not the cooler room temps. The motor is on top of the reactor lid, so no direct contact and no heat transfer. The only part of the reactor that is in contact with the slurry is the all plastic stir bar. Strange. I typically replace the kalk every two weeks, and completely clean out the reactor of any unused material when I do change it out.

Guess I'll just observe and see if the incident repeats itself. Thanks again.

[bertoni]

Hmm, strange. I don't know what happened.

[tmz]

You are welcome,
It's puzzling. Reaching now.The only other thing I thought of is that CO2 equilibration from the air might increase with the cooler limewater in the reactor due to overall increased solubility . If more CO2 got into the limewater than usual it might outweigh the increased max sturation level and cause precipitation. But if the reactor is sealed to the air , I don't see how that could happen.

[AcroporAddict]

Originally Posted by tmz

You are welcome,
It's puzzling. Reaching now.The only other thing I thought of is that CO2 equilibration from the air might increase with the cooler limewater in the reactor due to overall increased solubility . If more CO2 got into the limewater than usual it might outweigh the increased max sturation level and cause precipitation. But if the reactor is sealed to the air , I don't see how that could happen.

The reactor is not sealed. It has a lid, but the lid just has a machined groove that fits the top of the reactor. The reactor typically gets a skin on the top of the water. Water from the ATO reservoir is injected at the bottom of the reactor where the stir bar turns, and the kalk water gravity feeds out a bulkhead at the top of the reactor. A pvc elbow (with vent hole in it) attached to the exit bulkhead inside the reactor keeps the caco3 skin from interfering with the clear water leaving the reactor.

Thanks again for your ideas. I am lost.

[dkeller_nc]

Originally Posted by tmz

You are welcome,
It's puzzling. Reaching now.The only other thing I thought of is that CO2 equilibration from the air might increase with the cooler limewater in the reactor due to overall increased solubility . If more CO2 got into the limewater than usual it might outweigh the increased max sturation level and cause precipitation. But if the reactor is sealed to the air , I don't see how that could happen.

This was my thought. Here's a possible explanation - with extremely cold temperatures, one's heating system runs much more often. If it's a combustion system (i.e., natural gas or heating oil), and your Kalk stirrer/ATO is in the same room as the furnace, you could have had an increase in the CO2 concentration in the room's air. An increase in CO2 in the air will cause a concomitant rise in the CO2 concentration in the ATO water.

The lime particles in a reactor eventually get coated with calcium carbonate from reacting with the CO2 in the make-up RODI, necessitating cleaning out the reactor and replacing the solid lime long before all of the original charge dissolves. It might be that you had this happen a whole lot more quickly than if the CO2 concentration in the ATO/kalk reactor room was normal.

If you do have a combustion furnace, and given the possible consequences, I'd get an HVAC technician check things out.

[AcroporAddict]

Originally Posted by dkeller_nc

This was my thought. Here's a possible explanation - with extremely cold temperatures, one's heating system runs much more often. If it's a combustion system (i.e., natural gas or heating oil), and your Kalk stirrer/ATO is in the same room as the furnace, you could have had an increase in the CO2 concentration in the room's air. An increase in CO2 in the air will cause a concomitant rise in the CO2 concentration in the ATO water.

The lime particles in a reactor eventually get coated with calcium carbonate from reacting with the CO2 in the make-up RODI, necessitating cleaning out the reactor and replacing the solid lime long before all of the original charge dissolves. It might be that you had this happen a whole lot more quickly than if the CO2 concentration in the ATO/kalk reactor room was normal.

If you do have a combustion furnace, and given the possible consequences, I'd get an HVAC technician check things out.

Thank you for the suggestion. At first I thought you were referring to carbon monoxide, but you are suggesting maybe the furnace gases are not venting off like they should after combustion (CO2 and water vapor mainly)? I think my furnaces are functioning normally, though, and I maintain a CO monitor/alarm in the room. I have my HVAC systems serviced twice yearly.

The Kalk stirrer seems to be back to normal after I changed the kalk out again.

It may have been an equipment issue, now that I look back on it. The K2 stirrer motor is in the lid, and it connects to the stir bar via a coupler that uses a top and bottom set screw. I played with the connection a bit, and what I saw was that the bottom set screw connecting the collar to the stir bar was a bit loose, while the upper set screw connecting the collar to the motor was tight.

So in other words, when you looked at the full of water/kalk slurry reactor, you saw the collar/motor turning at the top, but the collar set screw apparently wasn't tight enough on the stir bar, so the stir bar was not turning, even though the motor and collar were. The kalk slurry probably clumped up because it wasn't being turned, is what I am now thinking. I snugged up the set screw on the stir bar, and it seems back to normal.

[dkeller_nc]

Originally Posted by AcroporAddict

Thank you for the suggestion. At first I thought you were referring to carbon monoxide, but you are suggesting maybe the furnace gases are not venting off like they should after combustion (CO2 and water vapor mainly)?

Yes, I was referring to CO2 rather than CO. A well-functioning gas furnace shouldn't be generating any carbon monoxide, but it's possible to have excess CO2 build-up within a room or even a whole house if the heat exchanger has corroded or is cracked.

But it sounds like you found a simpler explanation, which is always preferred.