How to size DM plant and minimize regeneration waste

A. Generally, one speaks of the number of bed volumes of water that may be processed in a given service cycle. This depends on the type of regeneration used (countercurrent is always more efficient than co-current) and also on the capacity of the resin.

I'd suggest speaking to your resin supplier. And, read up a little on ion exchange, there's plenty of information out there.

A. Will need the analysis of water that you need to deionize. After that if you are familiar with ion exchange technology, the rest is simple maths.

A. There are several good references on this subject. Most of these come from the manufacturers of the IX resins. Most resin suppliers also have excellent computer programs that will calculate all of the information that you are requesting from the flow and water analysis data. You can usually get these as a free download, but if you are not familiar with the program, they can be frustrating. They may also run the program for you and give you the results.

I suggest that you contact some of the larger IX resin manufacturers and ask if they can provide these services to you.

Hi Ajeesh. Although Lyle has offered good advice, I think your need is immediate & imperative. I hope you can take this in the proper spirit, rather than as criticism: as an essential part of proper product stewardship, the world expects you to have a reasonable knowledge of the product line you are offering. It is one thing for a purchaser to lack expertise on a technology that they will purchase once in a lifetime; but it is not acceptable for a vendor to not clearly understand the essentials. If you cannot find an instructional course on IX technology to sign up for immediately, please get to the library for several books on IX, and drop everything else for 2 or 3 days to peruse them :-)

Good luck and regards,

A. I hope I am reading your question correctly in that you used to regenerate at 30 now you have to regenerate at 20 and you are wondering what effect this will have?

I would say very little; it will reduce the volume produced by a small amount but not too much. This is because de-ionisers only have a small area of the resin in the column that is working, the rest is exhausted or clean. Thus if water flows from top to bottom in a column that has just regenerated, only the top 5 cm or so of resin will be working, the rest does not work as it has clean water flowing over it.

As time passes and the top resin gets exhausted (filled with ions), the slice that is working moves down. It is only as the working slice gets near the end that the conductivity starts to rise and it rises fast.

Example: our one deioniser on the rinse system flows 278 L/minute. The conductivity stays around the 0 to 1 mark for about 4 days, then from 1 to 5 in one day, and from 5 to over 30 in about 12 hours. So it goes 5 days to get to 5 then 12 hours to get to over 30.

So a change of 20 to 30 will not have a lot of effect.

Q. Thanks to Mr. Martin Trigg for his views on regeneration of resins. To throw more light on this doubt I would like to quote a claim from an expert in ion exchange who says: "cation and anion units when regenerated before the resin gets completely exhausted, will on long run lead to spoiling of resins and resultant water output will be of poorer quality."

Regarding the above I would like to know whether it is true; if so what is the mechanism behind the theory?

Thanks,

A. The one thing that springs to mind at once is that the units are of a co-current regeneration type where the bed is not physically packed but held in place by the pressure of water flowing through it. When these units are regenerated the first step is a backwash where the bed is unpacked and this can cause the breakdown of the resin as it is washed around and the beads bang into each other.

We use counter current regeneration with a packed bed. As the bed is firmly packed in the vessels it does not move when regenerated thus it will not break down.

Counter current regeneration is where the chemicals to regenerate the unit flow in the opposite direction to the flow of water when in service. This is the newer type of unit and gives higher quality water and takes less time, the downside is they often need a supply of deionised water to regenerate.

Getting back to the point, if the units are co-current they will suffer a shorter resin life if regenerated more often but going back to the first reply the effect will be not the 2/3rds you would expect from the quick comparison between 20 and 30 micro S. You find out how much shorter by measuring the volume produced since regeneration, and the two different points, and doing some calculations.