Salt slippage 1

[bethw]

We have a water softening system here in our plant that consists of 3 tanks. They are sold by Braswell. This system is about a year old and has run well until about 3 months ago when each of the tanks started to slip sodium. It has been cycling up in the boilers. The amount of slippage in each tank is the same, the public water supply is in the 7 ppm range and the units are giving us 15-20 ppm. Each one tests this level. We changed salt supplier from the "yellow bags" to the "white bags", I'm not sure if this has anything to do with it, but it's the only thing different we've found that was done. Could this be the cause of it? We have extended the rinse times, but to no avail. What can you chem guys tell me about what is happening?

 

[bimr]

It is normal to have a higher concentration of sodium on the discharge side of a softener. Basically, the water softener is exchanging sodium for hardness.

What is important for your boiler is that the hardness is zero, not that the concentration of sodium is higher.

Here is a typical water analysis before and after water softener treatment:

Softener Influent..................Softener Effluent
50 mg/l Calcium as CaCO3...........1 mg/l Calcium as CaCO3
10 mg/l Magnesium as CaCO3.........1 mg/l Magnesium as CaCO3
20 mg/l Sodium as CaCO3............78 mg/l Sodium as CaCO3

As you can see, the sodium will increase after water softening treatment.

Perhaps you could state the water analysis?

 

[bethw]

The chloride level in city water supply 7 ppm. Softener effluent 20 ppm. Our boilers have 250-300 ppm in them, would like 150 or so. The hardness from each tank is 1 or less ppm measured as CaC03. I'll have to get the boiler water hardness tomorrow when I get back to work. Our water treatments main concern is the chloride levels at this point, up until recently it was much lower.

 

[GarySCWSVI]

Increased chlorides in the soft water is typically due to insufficient rinsing of the resin bed during the regeneration cycle. I suggest that you either increase the length of the slow rinse or the fast rinse time. Try increasing slow rinse time first. You can also do a Brine Elution Study to determine the correct rinse time. I do not believe it has anything to do with changing the type of salt used for regeneration.

Gary Schreiber, CWS VI
The Purolite Co.

 

[bethw]

We increased the rinse time from 30 to 45 minutes but have seen no change in the chloride level of the effluent. It seems to "bottom out" at the 20ppm level. These units regen a litle differently than other softeners: There are only 3 steps in the regen cycle. The first is the brine draw which is counterflow to the normal flow, it's upwards in the tank. This seems to combine a brine flow and a backwash in one step. It's 18 minutes long. The unit will run out of brine and draw in air after 3 minutes of draw. This is also a concern, will the air affect the regen? After the 18 minute step the "rinse" is run. this also is counterflow to the normal flow but at a higher rate. This is the one we have extended. After this step, the unit goes through the purge and refill of the brine tank, which runs normal flow direction, downward, and packs the bed. It's 6 minutes long. By adjusting the refill time of the brine tank (and the final rinse)together, we can adjust the length of the first brine draw and first rinse, get it? Do you suppose we might be putting to much water back into the brine tank and consequently having a too long brine draw?

 

[786392]

Dear
just a wild thought;Is wash water OK w.r.t.Chlorides level?

Best Regards
Qalander(Chem)

 

[bethw]

Wash water is the inlet water to the tanks. It's the same for all three, they are on a common header. 7ppm

 

[786392]

Drain-out after first step and air 's quick backing in;

Is there any possibility of softener resins channelisation in such a way that active surface area availability is hampered?

Have you checked /Established no loss of any resins?

The problem you refferred is apparently on all the three sets!If I am not mistaken or

At one particular train?

Best Regards
Qalander(Chem)

 

[bimr]

The chloride concentration will not increase through a water softener unless the operator fails to complete the rinse cycle that occurs after water softener regeneration.

You have stated that you have rinsed down the water softener so that this is not possible.

You may have some brine trapped in the regeneration distributor after regeneration has occurred.

However, it is more likely that you have a leaking valve that is allowing brine to enter.

 

[bethw]

The problem is common to all three tanks and each has the same CL residual reading after each is regened with the extended rinse time and the small amount of hardness that is coming through. That is what pointed me in this direction. Each unit is isolated when the sample is taken to insure that the sample is from that tank and not backfed from the others, and it started at what seems the same time from all three. My primary concern was if the change in salt from one kind to another had any impact on the regen cycle. Further investigation is ongoing..

 

[mxmaciek]

I wolud agree with bimr in this case. If your rinsing time is long enough to eliminater dosed salt out of vessel, considering that you have no dead zone inside of the vessel itself, the source can be leaking valve or regenerant remained in the system after regen only.

 

[bimr]

Drawing in air during the regeneration process is not considered to be good practice. If iron is present, the air will oxidize the iron and foul the resin bed.

Is it possible that you have some anion resin mixed into the water softening resin? Anion resin is sometimes used to remove nitrates. The anion resin is regenerated with sodium chloride and will exchange chloride for nitrate.

Is it possible that used resin instead of new was used?

Have you measured the chloride concentration in the raw water and in the effluent at the same time? Is the water analysis for the raw water current? The chloride concentration the raw water is not constant and will change. Sometimes a City will change from Well #1 to Well #2 which results in a change in the chlorided concnetration. Sometimes there is a seasonal change.

It would be helpful if you would post some pertinent information such as:

Complete water analysis
Water source
Equipment of Age
Equipment New/Used
Resin New/Used
Capacity of system
Automatic or Manual
Boiler Pressure
Industry
Etc.

Otherwise you should expect call-and-response answers.

 

[bethw]

I'll post complete information tomorrow when I get back to work. For now: the system is less than two years old, it was new when installed likewise the resin. There are three tanks 13X54. Our boiler pressure is 90 lbs. and we average 90%+ returns. Daily usage right now of 4,000 gallons or so make up. Hospital service. Capacity of each tank is about 30,000 gallons double check tomorrow, they run in paralell and usage is monitored from one tank. When it reaches 10,000 gallons , it regens the next tank in line, thus when it reaches 10,000, the oldest tank is regened, it has 30,000 on it. Tank 2 has 20,000, and tank 1 has 10,000. And it continues to advance etc. System worked well until several months ago when we noticed the chloride levels starting to cycle up in the boilers. It had to be coming from the softener, condensate CL levels were 0, and here we are. Our water comes from a huge lake, city water for 100,000+ people. It doesn't change that much. I'm begining to agree with the leaking valve idea, I regened a tank today and the brine tank was empty of brine. It had to have gone somwhere.

 

[mxmaciek]

Have you sorted it out now?

 

[bethw]

I am going to have the resin tested to eliminate it from the equation. All three vessels have the same results after each one is regenerated. We just can't seem to pinpoint what the problem is so we will check this first. They seem to be passing more hardness after each regeneration as time goes on.

 

[786392]

Correct approach,
It is useful to check internal distribution system while reloading and
Do ensure system in-place for avoiding the major disturbance beyond plans in resin's bulk formation and contacting surface inside vessels (containment) during/after any of the regeneration steps.

Best Regards
Qalander(Chem)