Ion Exchange / DM plant calculations

A. Hi Yuva. I can't understand your question ... can you re-word it with a little more length?

I am probably misunderstanding you, but although you can use sodium chloride for removing water hardness (the sodium replaces calcium and magnesium), you can't regenerate dual bed (cation and anion), or mixed bed ion exchangers with sodium chloride. You must use a hydroxide (like the sodium hydroxide you mentioned) to provide OH- ions, and an acid (like the hydrochloric acid you mentioned) to provide the H+ ions. Good luck.

Regards,

A. For on-site regenerated systems, 4% HCl and 4% NaOH are typically used at a dosage of approximately 4 pounds (100% basis) of chemical per cubic foot (for counter-current systems).

For off-site regenerated cation and anion resins or co-currently regenerated systems, the strength is the same but the dosage is higher, typically about 6 pounds of chemical per cubic foot of resin.

One other note about softeners. 16% brine is more concentrated than needed. 8-10% brine at the correct dosage would be more efficient and save some salt. The dosage required depends upon whether the softener is regenerated in a co-current or counter-current manner.

A. Hi Sachin. Lyle Kirman's answer to Yuva Raj is immediately before your question. If Lyle's response is not what you were looking for, please try to phrase your question in terms of what you have done and are trying to do, and write a few paragraphs describing it so we can understand why Lyle's response doesn't already answer your question. I can't tell if you are looking for an analysis method for acid & alkali, or for conversions from one scale to another, or if you're asking what is the standard concentration of acid & alkali to use for regeneration, or what. Readers: PLEASE POST YOUR SITUATION -- NOT ABSTRACT QUESTIONS. Thanks!

Regards,

A. It is extremely difficult to get accurate pH measurements on high purity water. Resistivity is the best assurance that the pH is within a narrow range close to 7.0. If the resistivity of your water is > 10 Meg-Ohm, then the pH is probably > 6.5.

A. Hi Debdas,

15 BV/Hr looks a bit high to me. Usually my experience is 2 to 6BV/Hr (0.25 to 0.75 gpm/ft3). You may consult your resin supplier a suitable flow rate.

Regards,
David

A. It depends upon several factors. In residential applications, where there is a brief, but relatively high peak flow and long periods of no flow, rates of 40 BV per hour are common. This rate would not be suitable for a continuous flow. For a continuous flow rates of 5-15 BV/hour are not uncommon.

A. Hello Anand,

Your IX resin supplier should be happy to do this for you. For the quantity of resin needed, you will also need to tell them the flow rate that you want to operate at.

? Hi Satish. That's a question that I hope one of our knowledgeable readers will address. But I have a question for you: Why are you interested in that approach? What's the deal?

Luck and Regards,

A. Satish,

If there is hardness in the water, then it will foul the anion resin and the system will not work. On the other hand if the water is completely soft, then the system will work and should make better water quality than a Cation-anion configuration, since there will be less sodium leakage.

Hi Swapnil. I think you have to start with the ionic load. Lyle Kirman has told us above the long way to do the calculation and the quick way to estimate it as a check. Why not take a shot at the calculation here, or explain why you can't do the calculation he instructed. That way we'll all learn something.

Also, since you are using FFIP resin, maybe you can try to answer Kishor's query please? Thanks.

Regards,

? Hi Manish. Sorry, I don't know what DRO means. And are you saying that the infeed water contains 10 ppm TDS?

Regards,

? Hi, Samikannu. I'm trying to understand your message and have posted it as I understand it. And you are saying that the incoming water has hardness which results from 200 ppm of some sort of TDS (presumably Ca and Mg and carbonates)? 200 ppm is very hard water. Please clarify. Thanks.

Regards,

A. The D. M. Plant performance does not depend only on the ionic concentration of feed water. There are several factors which control the performance like regenerant concentration, contact time, water used for displacement of regenerant, quality of regenerant, faulty valves in the line, power water pressure during regeneration injection. In short, it is difficult to answer this question without knowing the problem in detail.

 Hi Dinesh. Anyone is welcome to try. But I suspect that the design of an ion exchange resin and the calculation of its ion exchange capacity is partially empirical, and involves far more than can be covered in the paragraph length responses usually offered in forums of this type. I think you'll probably have to read a book about the design of resins. But good luck.

Please try your best to describe your situation. Thanks.

Regards,

A. All resin manufacturers test their resins and publish their minimum capacity. However, the total capacity usually exceeds the operating capacity by a significant amount, sometimes by as much as 30%.

A. Ion exchange is limited, resin is good.
total resin required for 1000 l/day = approx. 3 ltr.
Salt required for re-generation: 0.5 kg/day
OBR: 1000 ltr.
OBR may increase or decrease on the basis of resin quantity.

A. For 1000 ltr daily use for 7 days reg., you need 28 ltr resin and approx. 4.5 kg salt weekly.

A. Hi kuppatgiri,
Apologies, but abstract questions rarely get any response from the readers; and if they have to pull teeth as well ... :-)

I don't understand your brief question :-(
What do you mean by 'region', do you mean how much plant area (real estate) is required for typical installation of that capacity? Or maybe was this an auto-correct, and you meant how much 'regenerant' (acid & caustic) rather than 'region'? And what do you mean by 'how much chemical required'? For one regeneration, or what?

Please get back to us with 2 or 3 paragraphs introducing yourself and describing the situation which prompts your question, and then I'm fairly confident you will get some help! Thanks! Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey