Hi all.

Most chemical/physical industrial processes end dumping wastes/ores that have no applications. Besides the gases burned in refinery stacks, what hydrocarbons do petrochemicals yield and how are they disposed of ?

Beyond lazy humans disposing plastics into oceans and everywhere else ☹️...

2 hours ago, Externet said:

Hi all.

Most chemical/physical industrial processes end dumping wastes/ores that have no applications. Besides the gases burned in refinery stacks, what hydrocarbons do petrochemicals yield and how are they disposed of ?

Beyond lazy humans disposing plastics into oceans and everywhere else ☹️...

With hydrocarbons, none. The residue from distillation is sold either as residual fuel oil for ships or processed into bitumen, or via further vacuum-distillation to produce lubricating base oils. The sulphur removed from distillate fuels is also sold. In some cat cracking processes surplus carbon is generated as petroleum coke. This can also be sold for a number of purposes.

When I first joined Shell and went on the induction course, we were introduced to the "carcass of beef analogy". The butcher buys a whole carcass and divides it up into valuable and less valuable cuts of meat, plus bones and offal. All of these can be sold for some kind of price, though many of the cheaper cuts command a price that is actually less per kg than was paid for the whole carcass. But even though these may look at first glance as if they are sold "at a loss", it make sense to sell them for whatever you can get. They can be seen as "byproducts", with some value though not very much.

So it is with crude oil. It gets converted into multiple products and byproducts but all have a price and can be sold.

Edited April 5Apr 5 by exchemist

By pure chance I happened to be watching a YT video about the difference between gasoline and kerosene, and why jet aeroplane engines are designed to run on the latter.

https://www.youtube.com/watch?v=vKl7Gva_ums

At just over 1m elapsed you will find this handy illustration of a fractional distillation tower, and what all the different distillation products are used for.

19 minutes ago, toucana said:

By pure chance I happened to be watching a YT video about the difference between gasoline and kerosene, and why jet aeroplane engines are designed to run on the latter.

https://www.youtube.com/watch?v=vKl7Gva_ums

At just over 1m elapsed you will find this handy illustration of a fractional distillation tower, and what all the different distillation products are used for.

One minor error is that wax for candles comes not from fuel oil but from the dewaxing of lubricating oil fractions.

The residue from the primary distillation depicted can undergo vacuum distillation to produce lubricating oil feedstocks. The vacuum distillates undergo either solvent extraction to remove aromatic compounds (Shell uses, or used, furfural) or hydrotreatment (to convert the aromatics to paraffins), which leaves a highly paraffinic material. This is then dewaxed to produce lubricating base oils with an acceptable "pour point" (i.e. so they don't set solid at low temperature because of the presence of paraffin wax). The residue from vacuum distillation undergoes an additional process known as de-asphalting, to get rid of "asphaltenes", which are high molecular weight, fused-ring aromatics. This residue becomes "bright stock", the most viscous grade of lubricating base oil.

Actually, wax is generated from the older solvent dewaxing process, which uses a solvent such as methyl ethyl ketone (MEK) to precipitate the wax, after which the solvent is boiled off again for re-use. There is also a more modern alternative known as catalytic dewaxing, which uses hydrotreatment to break up the long chains of paraffin wax into shorter paraffins with a lower pour point. So that doesn't produce wax as a byproduct.

Residual fuel oil (RFO), which is produced by simpler refineries without a luboil train, is the stuff burnt by large marine and power plant diesel engines. This is quite challenging to use as fuel, as it needs to be hot in order to flow, is often full of sulphur which forms sulphuric acid when burnt, corroding the cylinders, and asphaltenes, which are tarry substances that can gum up parts and block filters. It also can have vanadium in it, which erodes the valves in an engine. But it is cheap, which is why big ships and power stations use it. Engine designers and luboil manufacturers go to great lengths to overcome the challenges of burning this stuff without damaging the engines. Turbines are unable to burn it. They need distillate fuel or gas. But of course a steam turbine can be fed from a boiler burning RFO.

Edited April 6Apr 6 by exchemist