Ok, time for another post on my experiences with the ACR. My ACR has been running fine since my last post. I have not had to purge even one time. No gas build up, no decrease in effulent strength, just a model citizen of a calcium reactor.
Then 2 days ago I decided to test my theoretical venting procedure, even though the reactor did not need it, just to confirm the expected steps required, manually. I am not going to go through all the steps here, but the end result was that I vented all gas from the reactor until it was venting only effluent (to waste) and then recreated the CO2 bubble.
With in 24 hours, the CO2 bubble overshot the float switch and the circulation pump began sucking CO2. Essentially the same situation I originally mistook for air incursion. I vented the excess CO2 to put the water level back within the float switch range, and started to monitor the CO2 bubble level more actively. Then it occurred again, and again and again.
This really had me scratching my head. The reactor had been running perfectly for 3+ weeks straight, why could I not get it to stabilize? Then I remembered that I had inserted the newly constructed check valve into the feed line after I had restarted the reactor last time. Could it be that the presence of the check valve made it near impossible to get the gas bubble and water level stable in relation to the float switch?
Only one way to find out, I created a bypass around the check valve that I can toggle on and off. I restarted the reactor and manually adjusted the water level / CO2 bubble to be fairly close to where I though it should be and enabled the normal operation. The solenoid went through it's normal period of gradual declining on and off fast toggles and as of now is again completely stable. Meaning no more excess CO2 build up overshooting the float valve. I have the check valve bypass open currently, but I am pretty sure I could close it and things would remain stable.
What I concluded from this is that the ACR has a very narrow boundary where the pressure of the CO2 bubble is close to the head pressure of the feed pump. Upon startup, when the pressure of the CO2 bubble approaches the head pressure of the pump, it simply pushed the excess water from the ACR back into the feed line once it approached and started to exceed the head pressure of the feed pump. This is the critical condition that is required for the gas bubble to sync up to the float valve. Equalizing the gas bubble pressure to the head pressure. Having a check valve inline during this stage, prevents the syncing and stabilization. It should be noted, that when I was establishing the gas bubble, a fair bit of effluent can get pushed out, so I have a drain valve on the effluent line to prevent all of this from back feeding. For the final portion of the process I close that and allow the 'normal' back feeding to occur when it is close to the correct level for the float valve to disable the CO2.
Going forward, I could just turn on the bypass for the check valve, get the ACR running and then turn the bypass off to gain the protection the check valve affords. That approach leaves too much uncertainty for my comfort. I think I am going to look to change the flow through the ACR, moving my Masterflex to the feed line and positioning the effluent line high enough above the top of the ACR, so the effluent is pushed out of the reactor and will not flow out on its own. The rate will be controlled by the Masterflex, no needle valve need apply. This will remove the need for a check valve and the gas bubble will then be at atmospheric pressure. The DKH will probably decline, but my effluent is around 100 dkh, so a decline will be of no concern. I will update with feedback once I get around to making this change.
Dennis
