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Exothermic Reaction with Activated Carbon

Exothermic Reaction with Activated Carbon

Exothermic Reaction with Activated Carbon

(OP)
Hi,

Does anyone have experience of substances which can react exothermically with Activated Carbon? For example, when scrubbing a multicomponent gas through an AC filter at ambient temp, the temp of the carbon bed starts to rise rapidly.

Regards
PR

The scientist describes what is; the engineer creates what never was.

RE: Exothermic Reaction with Activated Carbon

Organic sulphur compounds such as mercaptans,aldehydes , ketones and some organic acids can generate heat when being absorbed by activated carbon.

Oxidisers and activated carbon may cause spontaneous combustion.


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: Exothermic Reaction with Activated Carbon

There is almost always energy released when something is adsorbed onto activated carbon. That is why it gets absorbed. It is a lower energy state than not being adsorbed.

https://www.ncbi.nlm.nih.gov/pubmed/15666466.

There are also many materials that react with air, such as alkyd paints and linseed oil. These can spontaneously combust when on cotton rags or on activated carbon.

RE: Exothermic Reaction with Activated Carbon

In chloralkali Activated Carbon is used for dechlorination of brine (which is to be resaturated). The carbon completely removes about 30-40ppm dissolved Cl2 & the reaction is exothermic. Too much high Cl2 in feed >200ppm caused thermal degradation of activated carbon

RE: Exothermic Reaction with Activated Carbon

All carbon adsorption processes are exothermal, which means energy is released into the bed during adsorption. Further, the activated carbon or the metals in or on the activated carbon can lead to catalytic oxidation of VOC’s in the bed. This can lead to intense local heating or even spontaneous combustion in the bed, thus destroying part or all of the bed. If the entire bed is not destroyed, the properties of the activated carbon in the rest of the bed will change as a result of the high temperatures (change in pore size).

One process consists of a bed of activated carbon bed with which the odor or solvent is first adsorbed and then desorbed, after which the cycle can start again. See the upload.

RE: Exothermic Reaction with Activated Carbon

bimr, well if a bed is in service with liquids/electrolytes like brine or waste water I highly doubt 'burning' of bed (even partially)

RE: Exothermic Reaction with Activated Carbon

The OP asked for examples where exothermic reactions were possible. The example posted was for the removal of VOC's from a gas stream using activated carbon.

Don't recall anyone requesting an example of liquid phase "burning".

RE: Exothermic Reaction with Activated Carbon

(OP)
Thanks for the advice all. Yes it was VOC adsorption exothermic process. Problem was that the gas flow was too low and thus it overheated. Solution was to maintain a high enough gas flow to cool / remove the heat of adsorption by the mass of gas itself.

The scientist describes what is; the engineer creates what never was.

RE: Exothermic Reaction with Activated Carbon

An interesting and logical detail ProcessRookie!

Keith Cress
kcress - http://www.flaminsystems.com

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