Toluene/xylene Vent Condenser

[TBP]

OK, chemical-types, I'm not getting much response to this question over at the "Heat Transfer & Thermodynamics" forum, so I'll try here.

I need to select a heat exchanger for a vent condenser, and the plant people have very little information. Depending upon what they're doing, they clean a process vessel with either one of these chemicals. The temp during the cleaning is 158*F. There is a 2" vent, and this is where they need the condenser. On the cold side of the condenser, there's cooling water with an inlet temp of 85*F.

Does anyone know where I can find data on the vapours from these two gases? I can find a little info for them in the liquid state. Any help will be greatly appreciated.

 

[TD2K]

CRC handbook of chemistry and physics and Perry's both have information on vapor pressure.

the following is the temperature that the compound has a vapor pressure of:

1 mmHg, 10 mmHG, 40 mmHg,100 mmHg, 400 mmHg and 760 mmHg

toluene, the values are:

-26.7, 6.4, 31.8, 51.9, 89.5, 110.6 (all in deg C)

xylene (2, 3 and 4 xylene in order)

-3.8, 32.1, 59.5, 81.3, 121.7, 144.4
-6.9, 28.3, 55.3, 76.8, 116.7, 139.1
-8.1, 27.3, 54.4, 75.9, 115.9, 138.3

Heat capacities at 27 deg C are:

toluene: 24.94 cal/gmoleK
xylene: 32.1, 30.66 and 30.49 cal/gmmoleK for 2, 3 and 4 xylene in that order.

didn't have much luck finding any data on the thermal conductivity for either component.

 

u can find some relevent matter in the petroleum refinery journals..
if u look at the years of 180-1985 u will find more info..
bye
santy

 

[handee]

TBP, I don't really know how I came across this post, but I've also got a condenser sizing project ongoing, and it has not been an easy matter. I'm wondering how you made out, if it was a success, and where was your best source of information. Obviously, the hard part is estimating the vapor load and the condensing efficiency and thus the condensing duty...

-Fran

Fran McConville
author of the Pilot Plant Real Book

http://www.pprbook.com

 

[TBP]

I was only involved in the selection process for the heat exchanger for a third party, and as far as I know, the project never got off the ground. We never did get enough data to properly size the condenser. I suspect that "lack of data" issue dominoed through the other aspects of the project and it just quietly drifted to the bottom of the project pile and on ito limbo.

 

[DickRussell]

For physical properties, everything you need is available in the DIPPR database. This can be licensed or accessed online through various providers.

It sounds like your first problem is definition of the vent stream from which to condense organics. If the fluid just sits in the vessel, what is it that moves anything out the 2-inch vent pipe? I am guessing that during the period when solvent is introduced to the vessel there is displacement of some of whatever vapor is present there at the start. Then at some time later presumably the vessel is drained, then purged with an inert gas, such as nitrogen, to effect drying. Worst-case scenario then would be the solvent exerting its partial pressure in the purge gas, and rate is whatever the rate of purge gas is. Use of a vent condenser cooled with just 85 F cooling water will get you to within a few degrees of 85 F, but you also need to consider the environmental aspects of release of whatever solvent is left in the cooled gas. You may need a refrigerated vent condenser or carbon adsorption step after that.

But all of this is just a guess at your situation. If you can lay out in detail the whole cleaning process and vent gas cleanup specifications for forum readers, you are sure to get some good advice, as well as more questions to be asked.

 

[25362]

DickRussell is so right !... Not only environmental considerations, but also safety aspects must be contemplated, such as flammability limits and static electricity.

The dew point of the mix of a non condensable (ie nitrogen) with either of the solvents will come down as condensation progresses. At 32 deg C (~90 deg F) the VP of toluene would be 40 mm Hg (from the data brought by TD2K) ie more than 5% in the emitted gas. If the gas were air, it would mean the mix would be just inside the flammable envelope (1.2<=>7.1).

Speaking of static electricity, the relaxation time required for a charge to dissipate by leakage from o-xylene:

(2.54)[&times;](8.85[&times;]10^-14)[&divide;](1[&times;]10^-15) = 225 s = almost 4 min !

The factors use in the estimate are, respectively: xylene's dielectric constant, the permittivity constant, and xylene's specific conductivity.

Good luck.

 

[roker]

hello,
a vent condenser for organic solvents is very common in the industry like food and pharma, more data are needed for the process like: sizes of the vessel, is it jacketed, is it stirred, vacuum etc.
many times you use a condenser with cooling water and a vent condenser on top of it with chilled water.

regards