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Odd Effect Using a Bromine Donor with Chlorine in Cooling Water

10/11/2017 4:22 PM

I have been summarizing some of my recent data, where I am using ORP and total chlorine (responds to oxidizing bromine species in solution also) where I am pretty sure that most of the time all the chlorine gets converted to active bromine. It still reports as active total chlorine. ORP as measured is recorded, along with chloride concentration, pH, and temperature, and about 20-30 mV is added to correct the ORP to "normal" or "standard" conditions. There is a definite sigmoid shaped curve (also known as the logistic or growth curve. Is this correlated with residual algae growing in my system? I don't know for sure, but I always see at least a bit of green, just not slimy green, and I can see clearly to the bottom of the cooling water in the cooling tower. I think we are "titrating" the algal growth curve, maybe. Sorry for the picture of the chart, it is poor, also note considerable data is off the curve.

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#1

Re: Odd effect using a bromine donor with chlorine in cooling water

10/11/2017 5:36 PM

From engineered, artificial girlfriends to this???? Dude, you have too much time on your hands.

You need a nice hobby, like fishing, building flagstone walk ways, or goat herding!

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#6
In reply to #1

Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 8:39 AM

We don't herd goats in West Texas, we make cabrito out of them!

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#2

Re: Odd effect using a bromine donor with chlorine in cooling water

10/11/2017 7:06 PM

It's definitely not my area of expertise, but I'm thinking that if the Oxidation-Reduction Potential (ORP) is a function not only of free chlorine but free bromine and pH, that that might account for the scatter. (The other parameters are uncontrolled).

Just my uneducated guess...

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#7
In reply to #2

Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 8:47 AM

True there are many, many more variables at play. Which cells of the cooling tower circulation were online, how many, what was the fan speed, ratio of chlorine gas to "B3500" liquid injection in the concentrated (inducted) stream. I am modeling in the temperature dependence, although this is virtually never done for ORP, and the changes are minimal, basically just a spectrum offset of the ORP values. The pH and the chloride activity neither vary a great deal.

Perhaps the scatter is as much related to peaking utilization of the plant as is anything. It seems that tags (dispatches) that start earlier will have better correlation to the line.

From other studies I have done, virtually all the injected bromide in the form of N-dibromo sulfamic acid is converted to active bromine in the concentrated induction stream, usually the ratio of free chlorine to total chlorine (could contain contributions from chloramine and bromine) is about 0.3, sometimes more some less.

We have a possible base-load dispatch coming up for a couple of weeks, maybe I will see a clear picture of that.

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#3

Re: Odd effect using a bromine donor with chlorine in cooling water

10/11/2017 8:54 PM

Can you get intoxicated by ingesting too much chlorine, buddy?

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#8
In reply to #3

Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 9:10 AM

Surely intoxication is the result of intimate contact with toxic chemicals. You don't get inebriated with chlorine, just dead.

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#4

Re: Odd effect using a bromine donor with chlorine in cooling water

10/11/2017 9:13 PM

Some of these may help.

Choose the Right Cooling Tower Chemicals - Power Engineering

Chlorine and Chlorine Alternatives | GE Water

Bromine Chemistry CTI 1986

This "titrating" sounds obscene, like something from your thread on building sex toys?

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#9
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Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 9:12 AM

You mean you do not know what a titration is? BTW, I have never posted a thread on a sex toy, that was your evil imaginings at work. I was talking about AI, human engineering, and a lassie with orange hair and green skin.

I have seen those links before, and I appreciate you took the time to put them up.

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#12
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Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 11:18 AM

He said titration. Heh, heh, heh.

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#18
In reply to #12

Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 2:45 PM

titration - means you only get 2.

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#20
In reply to #18

Re: Odd effect using a bromine donor with chlorine in cooling water

10/13/2017 8:51 AM

2 what? guesses?

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#21
In reply to #20

Re: Odd effect using a bromine donor with chlorine in cooling water

10/13/2017 12:45 PM

Guess.

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#13
In reply to #9

Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 11:31 AM

BTW, do you have an analysis of chemical species present? I would assume that it is a closed loop system with makeup feed. Any possibility the departures from the curve are a result of chemical input from the makeup feed?

I did a masters in contaminant hydrology at one point and it is surprising what you find in water sometimes. Our local water system occasionally switches back and forth from surface water to well water and the changes are often spectacular.

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#14
In reply to #13

Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 12:46 PM

The makeup (BTW this is open-cycle cooling water, i.e.- cooling tower), is potable city water. We are a really small plant, daily intake is about 0.1-0.15 MMGD.

Water supply these days is majority well water from the extreme north of Texas, with varying amounts surface water (treated well for potability), from Lake Alan Henry, SE and downhill from Lubbock (who ever thought up that dumb idea?)

City of Lubbock chloraminates the water to about 2.7 (max?) total chlorine, mostly monochloramine. The chemistry of bromine by reacting with chlorine species is such that chloramine goes away in the concentrated loop, and any residual is fugitive emitted to atmosphere.

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#15
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Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 1:16 PM

So the cooling tower just cools it enough to meet a discharge temperature permit?

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#16
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Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 1:51 PM

No, it cools off our steam condenser, oil coolers, etc. We might bleed the tower just a bit on unit startups to cool something like flash tank effluent off.

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#17
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Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 2:32 PM

So it is a recirculating system with potentially variable chemical input. Your data point scatter doesn't seem that bad.

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#19
In reply to #17

Re: Odd effect using a bromine donor with chlorine in cooling water

10/13/2017 8:47 AM

No, not too bad, considering there are variable such as air flow I have not built into the model. The cooling tower HMI does put fan speed up, I think, so it should be in the historian, but first I have to identify the correct tags for those.

It would appear the total chlorine numbers that don't fall on the line are higher than the function calculated from ORP. This may be an indication of variable and high bleed-off during unit start up, where we use cooling tower bleed off to control final wastewater temperature, since the HRSG flash tank will run us out of specs.

Or it could be samples that were pulled on some really cool or humid days soon after dispatchable load was reached, where the fans have only just started, or were not started yet. (Not a natural draft cooling tower in sight).

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#11
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Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 9:33 AM

The third link above is recommended reading, especially if anyone out there listening is planning to use treated effluent wastewater for cooling system makeup.

Bromine is just more effective at higher pH values, the side-reaction compounds decay much, much faster in the environment, and these days, the economy of using bromine compounds whether sodium bromide, or some N-substituted bromine compound converted by high concentration of chlorine is attractive.

There are also new ways of making chlorine dioxide where the explosion risk has been eliminated for all practical purposes. ClO2 is also a very effective oxidizing biocide that penetrates into extracellular material, and is quite environmentally friendly compared to stand-alone chlorine systems.

It also has been said and tested that ozone (if economical for the unit in question), is also efficacious in preventing biological fouling (slime and the like) and algal blooms in cooling water.

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#5

Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 5:07 AM

Who does the chemical testing and treatment of your cooling tower water?

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#10
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Re: Odd effect using a bromine donor with chlorine in cooling water

10/12/2017 9:12 AM

Me. Is that a problem, after all it is my job.

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