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Q: Ammonium Persulfate Shelf Life ( Answered 5 out of 5 stars,   1 Comment )
Subject: Ammonium Persulfate Shelf Life
Category: Science > Chemistry
Asked by: rs7-ga
List Price: $100.00
Posted: 26 Dec 2003 08:25 PST
Expires: 25 Jan 2004 08:25 PST
Question ID: 290398
I have set up a pilot plant to manufacture ammonium persulfate. The
problem is that the shelf life is limited (the assay drops) and it
forms a very hard cake within weeks of keeping in sealed 25 kg bags.
Of course moisture and surface impurities are factors. But the APS
centrifuged cake is washed and dried well in a fluid bed dryer at 50
deg C. before packing. Question: How do I improve the shelf life of
ammonium persulfate?

Request for Question Clarification by pafalafa-ga on 26 Dec 2003 09:27 PST
A few questions, if I may:

1.  What material is it packed in, i.e., what are the bags made of?

2.  What is the purity of the ammonium persulfate?

3.  What are the storage conditions, especially regarding temperature and humidity?

4.  Persulfates don't like most metals, other than good quality
stainless steel (it especially dislikes aluminum).  Might there be any
metal as a contaminant, or metal in contact with the finished product
at any time?

Clarification of Question by rs7-ga on 26 Dec 2003 18:35 PST
Thank you for your interest.

The APS (25 Kg) is packed in a polyethylene inner bag which is then
placed in a laminated HDPE woven bag. The inner bag is sealed. Yhis
is, I beleive, the industry norm.

When packed, the APS purity is about 99.4% to 99.6%. The balance is
water (0.15%) and ammonium sulfate. pH of 3% soln. a4-6.5. However,
within a few weeks the purity starts dropping to 97-98, pH of 3% soln.
to 3 and the 25 kg forms one big hard rock.

The bags are stored < 35 deg.C, RH could be high (upto 90%) but the
bags are sealed, away from sunlight.

Stainless steel and PVC equipments are used in the manufacturing
process. The impurity level in the APS of Fe, Pb, Cu are all <10ppm.

There was an article presented at some Powders symposium in 2001
which, I beleive discussed persulfates caking (hence shelf life, I
suppose). Can't find this.

Appreciate any help you could give. Thanks.

Request for Question Clarification by pafalafa-ga on 26 Dec 2003 19:39 PST
Everything I've seen about storing APS recommends cool, dry storage
conditions.  This may not be feasible for your facility...but this
also may be the root of the problem.  The humidity, in particular, is
a concern.

Your initial specs seem pretty conventional, except for the water
content which -- at 0.15% -- is quite a bit higher than the 0.02% I've
seen in other commercial-grade APS.  Is it possible to tweak the
production to produce a drier material?

Lastly, are you using dedicated equipment?  APS appears to be very
susceptible to even small amounts of contamination leading to rapid

I'll try looking through some of the industrial literature to see if
anything pops up that could constitute an answer to your question. 
But for the moment, I don't have anything more to offer than what I've
mentioned here.

If I find anything more, I'll be sure to let you know.  Meanwhile, best of luck.  


Clarification of Question by rs7-ga on 28 Dec 2003 05:21 PST
Thank you for your efforts, Pafalafa. Perhaps the industrial
literature could throw something up. Thanks again.

Request for Question Clarification by pafalafa-ga on 29 Dec 2003 12:14 PST
I looked...but no luck.  There was nothing I saw that was specific to
the shelf life of APS.

Do you happen to remember anything more about the Powders symposium --
date, place, sponsor, speaker? -- anything that might help pinning it

If you can provide a few more details, I might be able to find it.  


P.S.  Have you been in touch with FMC?  They *might* be willing to
offer some technical advice, even though they're the
competition...just a thought.

Clarification of Question by rs7-ga on 02 Jan 2004 06:00 PST
It was: "Solids Handling & Processing Symposium" held by AICHe
(American Institute of Chemical Engg.) in Nov. 2000. The paper was:
Advances in Characterizing Caking Propensity of Powders, presented by
Bryan J. Ennis, E&G Associates, Leipers Fork, Nashville, TN.

The Abstract is posted on the Net. The paper should be available with
L XXXXXX (I forget)Library but is not.

Thank you and have a great 2004.

Request for Question Clarification by pafalafa-ga on 07 Jan 2004 20:19 PST
Hello again, and a very Happy New Year.

I haven't had any luck with the conference might be
obtainable, but it would be a heck of a lot of effort to track it
down, as it's pretty much disappeared into the ether.

However, I might have a better solution.  I've heard from an expert on
persulfate manufacture who used to work for FMC, and is now a private
consultant.  He wrote:


I have solved this [caking] problem for FMC already.  Since I am currently
also a consultant.....I am sure we...can help your
client with information, tests, methods, etc. already proven to have
significantly improved the shelf life, or reduce the caking tendency, for
ammonium persulfate.  I just can not divulge any ...proprietary
information, but that should not be necessary to help with the solution.


Should I post his contact information as an answer to your question? 
You could then proceed to contact him directly and hopefully work out
a mutually satisfactory arrangement.

Let me know what you think.


Request for Question Clarification by pafalafa-ga on 14 Jan 2004 09:14 PST

Are you still interested in an answer to this question?

As I said earlier, I can put you in touch with an expert in solving
persulfate caking problems if you would like to consider having him do
some consulting work for you.

Clarification of Question by rs7-ga on 14 Jan 2004 18:55 PST
Please do post the contact details of the Consultant as an Answer,
Pafalafa-ga. And thank you. It could be a person I had tried to
contact (Mr. L... , I forget) but my e-mails to him were unanswered.
Perhaps I had the wrong contact co-ords.
Many thanks and cheers.
Subject: Re: Ammonium Persulfate Shelf Life
Answered By: pafalafa-ga on 14 Jan 2004 19:13 PST
Rated:5 out of 5 stars
Hello again,

I'm glad we were able to come to closure on this question.  I've done
a fair amount of work in the chemical process industries, and I was
particularly eager to try and run down a solution to your problem for

And I think the solution lies in the expertise of this one fellow who
has tons of experience with solving persulfate caking problems.  You
can have a look at his resume here: 6470/6470_Info_Douglas_Lenz.pdf

but I can't resist excerpting a few key items from his experience:

--As a former Senior Research Process Engineer and Process Group
Leader with FMC Corporation's Active Oxidants Division, Dr. Lenz is a highly
recognized professional with an extensive background in leading professionals,
technology piloting, scale-up and optimization as well as
modeling/simulation and project management.

--He led the systematic development from lab to complete design of
several technologies, including a 40-million pounds/year solid
percarbonate plant and a 25-million pounds/year thermally stable
persulfate process.

--Led teams involved in developing and using cutting edge modeling and
simulations involving powder technology, storage safety, process
control & optimization.

--Led program incorporating statistical process control (SPC) tools,
which increased persulfate production by 35%, ?on-stream plant run
time? by 8% and overall efficiency by 5%.


...and so on.  I'm sure you get the idea.

Dr. Lenz's contact information is as follows:

DHLenz & Associates
6248 Cloverleaf Drive 
East Amherst, New York 14051
(716) 868-9869


I have been in touch with him already, and he expressed confidence
that he could, indeed, assist you with your problem.  I will contact
him again to let him know he can expect to hear from you.


I hope this answers leads to a swift and effective solution to your
caking problems.

If anything here is unclear -- or if you need additional information
-- just let me know by posting a Request for Clarification and I'll be
happy to assist you further.


search strategy:  Google search on:  persulfate caking

Request for Answer Clarification by rs7-ga on 16 Jan 2004 07:54 PST
Thank you pafalafa-ga. Actually I had sent an e-mail to Dr. Lenz on
Dec. 6th but received no response. Have again sent (same address) but
yet no response. Hope I hear from him soon. Wonder if he receives the
Thank you again. Rating follows.

Clarification of Answer by pafalafa-ga on 16 Jan 2004 11:46 PST
Dr. Lenz and I have been in communication, and he is expecting your email.  

If for any reason, you have not heard from him after a reasonable
amount of time, let me know, and I will find out what the situation

Thanks again.

rs7-ga rated this answer:5 out of 5 stars
Many thanks. Great effort. No news as yet from Dr.L.

Subject: Re: Ammonium Persulfate Shelf Life
From: pafalafa-ga on 16 Jan 2004 20:15 PST
Thanks so much for the kind words and generous rating.  Please let me
know how things work out when you have a chance.


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