2 replies to this topic

[scottsilvi]

Hi all -

Let me start by saying I wasn't entirely sure if this was the correct forum for this type of inquiry, so I apologize if I'm posting in the wrong location. I'm certainly not a ChemE professional, but I am in the learning phase, so student seemed most appropriate. I'm a software engineer by trade, having spent about 8 years in the industry. I've been moving into the open-hardware space (tinker / maker) and have prototyped a system that currently utilizes an electrochemical sensor.

 

I'm looking for a sensor that can detect a difference between diesel & petrol vapors. I don't particularly care what property I'm differentiating (and, to be frank, I'm fine with saying "diesel" / "not diesel" or "unleaded" / "not unleaded" ... it's not necessary to have true detection of both, e.g. "diesel" / "unleaded" explicitly). 

 

I've prototyped this with an electrochemical sensor, despite documentation stating "not made for fuel vapors"... I absolutely get distinct voltages between diesel & gasoline. I'm not sure if they say don't use them with vapors because of the highly combustible nature of these vapors, or if they're not reliable, or what ... but hoping to get confirmation one way or another (it turns out causing huge explosions is frowned upon).

 

The prototype used a basic MQ5 sensor (datasheet here). So my first question, which shows my naivety, is whether or not an electrochemical sensor (even a more robust one) is a viable option, given the conditions.

 

I've also been looking into photoionization detectors, oscillating tuning fork sensors, catalytic bead sensors, infrared sensors...

 

A lot of these sensors end up being remarkably expensive, and I'm wondering if I'm overlooking something simple, or if this truly is a really expensive problem to solve.

 

Many thanks,

 

Scott

Edited by scottsilvi, 05 July 2014 - 11:47 AM.

[Pilesar]

Consider the specifications for diesel and how the specs differ from the other streams you are comparing. One likely difference is the temperature range where the material boils. Review the ASTM lab procedures that already exist to characterize diesel for buyers and sellers. Some of these detailed procedures are really fairly simple. Because you have flammable vapors, you may need an inherently safe instrument rated for OSHA Div I hazardous areas which will add to costs.

[Pilesar]

You specify "diesel vapors". This may be different from "vaporized diesel". What do you get if you condense the vapors into a separate container? If this is just the first fumes weathering off of liquid diesel, then the condensed product will be lighter than diesel. The light ends of petroleum streams are not necessarily very similar to the bulk liquid and may have a great range of characteristics depending upon their source.