Date: Fri, 9 Jul 2010 11:21:44 -0400
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: Don Abramowitz <dabramow**At_Symbol_Here**BRYNMAWR.EDU>
Subject: Re: Sol-gel drying process
In-Reply-To: <1106557761.8528.1278688870233.JavaMail.root**At_Symbol_Here**>
< div style='font-family: Times New Roman; font-size: 12pt; color: #000000' >Barring other specifics, sounds like you had enough residual flammable vap or in the oven to form a flammable atmosphere.  The oven could easily have provided the ignition source.  Even though the oven was set to 13 0 C (not hot enough in itself to cause ignition), the surface of the heatin g elements in the oven were much hotter, and could have exceeded the autoig nition temperature of the flammable vapor/air mix.  (The autoignition temperature of isopropanol is about 400 C; a glowing heating element is muc h hotter.)  Other potential ignition sources:  a spark from the t hermostat for oven temp control, the fan motor (convection oven) and any in ternal switches. 

In addition to the 2-propanol, when you hydr olyze the aluminum sec-butoxide with water, I think you get butano l as a byproduct.   The damp "cake" could have contained enough f uel for the door-bending explosion, with enough left over for a little fire that would have self extinguished when the fuel ran out.

This is th e sort of thing where you can get away with it sometimes but not others, as the fuel/vapor mix has to fall withing a certain range.

As previous ly mentioned by others, the evaporation of the 1.5 l of 2-propanol is also a bit worrisome, as the only thing keeping the flammable vapors from igniti ng on the hot plate is the fume hood's continuous sweeping away and dilutin g of the vapors.  If the fan belt breaks, the vapors would engulf the hot plate and possibly light up.

       ;                          ;                          ;                          ;     Don

Donald Abramowitz, CIH
Environmental Health & Safety Officer< /span>
Bryn Mawr College
Bryn Mawr, PA

----- "Per ry Cooper" <pcooper2**At_Symbol_Here**JHMI.EDU> wrote:


Sharing an i ncident. Anyone want to chip in on recommendations? J< span style="font-size: 11pt; font-family: "Calibri","sans- serif"; color: rgb(31, 73, 125);">


General lab exhaust through the fume hood. Some equipment exhausted with localized flex duct but not the oven.

Adjacent are as complained of strong alcohol odor.



"=E2=80=A6.. intent to prepare a batch of fi ne particulate size aluminum oxide via the sol gel process. The components wer e an organometallic (aluminum sec- butoxide), a solvent (2-propanol) and water.& nbsp; 1.5l of 2-propanol was placed in a porcelain-lined steel container. 4.5kg o f aluminum sec-butoxide was added to the solvent while mixing. After these components were thoroughly mixed, 1.1l of water was added resulting in the formation of AlOH particles from the organic precursor.  At this point , the composition was a viscous slurry. In order to reduce the solvent content, t he container was placed on a hot plate inside the fume hood. The composition w as heated (temperature unknown but estimated to be 70-80=C2=B0C) for approxima tely 4 hours.  At the end of this period, most of the solvent had evaporated, leaving a slightly moist "cake=". In order to remove the remaining s olvent, the container was taken to room xxxxx and placed in a convection oven. I partially covered the container with a lid to allow venting and to prevent any swirling debris from contaminating the material. Oven temperature was set a t 130=C2=B0C and the general exhaust in this room was turned on. My intent wa s to let the material dry overnight and I left for the day. When I returned the following day, I checked the oven and it was apparent that there had been a n accident at some point after I left.  I later learned that there had b een a small explosion and fire. I believe the fire was confined to the oven and w as extinguished by covering the container with the lid.  The oven door wa s bent when it swung open and contacted the control enclosure but no other damage is apparent. In the past, I have used these same procedures and equipment to m ake similar compositions without incident=E2=80=A6.="







> Perry D. Cooper, MS, HEM, CCHO
> Manager - HSE - JHU
> The Johns Hopkins University
> Health, Safety & Environment
> www.hopkin
> Homewood Campus Safety Office
> 3400 N. Charles Street

G04 Wyman Park Bldg
> Baltimore, MD 21218
> Office: 410-516-2345
> Fax: 410-516-4314
>< /a>
> _______________________________
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