Separating petrol and diesel via SG 2

[v8landy]

Hi

New project just been dumped on me! Need budget costs and proposal by next week!

Will be dealing with 70 million L per year of petrol / diesel mix.

This comes about at the interface following product changes in line trasfers.

We currently on site do not have that capacity so are looking into upgrading what we have or building new.

We currently batch distil, but could modify one of the stills (hot oil) to allow a mid point insertion into the column and take of tops and bottoms as required.

Just a thought, could a centrifuge be used to separate via sg? Petrol being about 700 and diesel being about 820 to 950???

 

[mbeychok]

Petrol and diesel are mutually soluble in each other. Centrifuging would not separate them ... might even mix them better.

You will have to re-distill the mixture.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[v8landy]

Thanks for fast reply.

On now with major (for us) disltilation project.

 

[25362]

Although I tend to agree with mbeychok, here is one site that hints to the contrary:

http://arxiv.org/abs/0707.2266v1"

then press PDF to read the article.

 

[v8landy]

I knew I was not that mad with my idea;-)

 

[djack77494]

I have never seen or heard of (until now) the concept of separating miscible hydrocarbons via centrifuges. While it may not be totally impossible, I do not think it to be at all commercially practical. My suggestion is to proceed with your distillation project - that will work.
Doug

 

[v8landy]

Yes I agree with you djack, i think the centrifuge way is a while off yet!

SO on with my distillation project.

We will be looking at boil-ups of approx 7 t per hour.

Many things to thing around like.

Can our hot oil supply this and the other stills?
Batch or continueous?
Modify current or start from scratch?

Do anyone have any very rough ball park figures (I am in the UK) for a plant such as this?

I am guessing so far for the following

- reboiler ~ £80 -90K
- 1m x 20m column 30 theroy plates £120K
- COndensor £60K
- Steel structure - £90K
-£60K misc

~ already £0.5 million.GBP +/- 60%

 

[dcasto]

Feed pumps, reflux pumps, hot oil circulation pumps, controls, safety system.

We just did a 24 inch by 40 foot stabilizer for $1.5MM US.

 

[mbeychok]

Shalom, 25362:

The article you pointed us to involves a binary mixture of liquids. A mixture of petrol and diesel involves 30 or more mutually miscible liquids, if not more.

I find it most difficult to believe that centrifuging two miscible liquids will separate them. As for separating 30 or more miscible hydrocarbon liquids into the original petrol and diesel, that would be a pipe dream!!

With all due respect to Messrs. Yoav Tsori and Ludwik Leibler.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[unclesyd]

mbeychok,
Way out of the box.
I don't know how easy diesel will emulsify compared to gasoline but if it is easy to emulsify there may be a possibility of mechanical separation.

I don't know the exact details but we have a process where we have two mutually soluble liquids where the solvent is very easy to emulsify. Once the solvent is emulsified the stream is fed into a Podbielniak Centrifugal Extractor. The Pods separate the two, product and solvent, and if I recall the solvent emulsion is then broken and the solvent is recycled. The seperation is extremely good.

Information on Pods.

http://www.chemicalonline.com/Conte...851-c50c-11d3-9a82-00a0c9c83afb&VNETCOOKIE=NO

http://www.bpprocess.com/products/centrifugals/pods/

 

[mbeychok]

unclesyd:

Have you ever worked in an oil refinery lab? Have you ever mixed petrol and diesel? Have you ever looked at a componenent-by-component analysis of gasoline and of diesel oil? One that includes the specific gravity of each of the omponents? Do you realize that each of them is a mixture of about 15 or more separate hydrocarbon liquids? And all of them are mutually soluble?

Once you have mixed gasoline and diesel, there is no interface. They are each soluble in the other. Do you understand that?

... we have a process where we have two mutually soluble liquids where the solvent is very easy to emulsify ...

Referring to the above quote from your posting, these are not two mutually soluble liquids!! There are about 30 mutually soluble liquids in the mixture. Neither the gasoline nor the diesel is the "solvent". There is no solvent or solute when you mix them. All 30 hydrocarbons are mutually soluble.

Depending on how well they were separated by distillation in their source refinery, the lightest specific gravity components of the diesel oil may actually be lighter than than the heaviest specific gravity component of the petrol. In other words, it is possible to have overlapping components in the petrol and the diesel oil. (Again, dependent upon how well or how poorly they were separated by distillation in the source refinery.)

Sure, a centrifuge may possibly separate an emulsion of oil and water ... but we are not dealing with a water-oil emusion. Sure, a centrifuge may separate two insoluble liquids with even a very, very small difference in specific gravity ... but we are not dealing with two insoluble liquids.

I repeat what I said earlier: It is a pipedream to think that a centrifuge will separate the gasoline from the diesel oil.

And don't forget that the original post was talking about 70,000,000 liters per year ... or roughly 200,000 liters per day!!!


Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[25362]

I'd add to mbeychok's message that molecules aren't just attached to one another by dispersion forces but are also entangled like noodles because of their length and complexity. Therefore, forces to separate them just by using high g's wouldn't be practical.

 

[unclesyd]

I apologise if I have affronted or profaned anyone in the oil patch.

No I haven't worked in an oil refinery lab but have worked in Metallurgical, Physical Chemistry, Electrochemical, Physical Properties, Analytical, not petroleum, and Organic Chemistry Labs. I do know that every petroleum product we purchase is a mixture.
Having some knowledge about gasoline and diesel which is probably more dangerous than knowing nothing I made in what some people may call a irrational statement. My post was made with some local knowledge that I have experienced with some higher boiling organic chemicals that we process, the byproducts of our high (5500 psig) and low (450 psig) hydrogenation process. These high boilers with boiling points above 225C @ 760 mm all tend to emulsify very easily. This was just a statement/question as to whether diesel may act in similar manner. It was also asked in light that not too many people are familiar with PODs and their capability and also realizing that the most PODs that I've seen running in parallel is 6.

 

[enzyme76]

Dcasto

Feed pumps, reflux pumps, hot oil circulation pumps, controls, safety system.

We just did a 24 inch by 40 foot stabilizer for $1.5MM US.

Do you have a break-down of this cost. i.e anything you can attatch?

V8

 

[dcasto]

no, sorry. $850K was a bid by the unit packager Thomas Russel in Tulsa, OK. The rest was install and some truck loading facilities.

 

[djack77494]

Rather than 30 or so separate compounds, both diesel and gasoline/petrol actually have at least hundreds of individual compounds making up these complex mixtures. Furthermore, many of the compounds found in gasoline are also found in diesel, and vice versa; it's just a matter of relative concentrations. Note that even distillation just (in a sense) "reassembles" mixtures that are similar to the originals.
Doug