Good question JohnE,
In a refinery we actually do not MAKE any one product called Gasoline or Diesel or Kerosine. We use different series of towers to distill, more to crack in the presence of catalysts, towers that are strictly strippers, DEA (diethanolamine) clean ups, ammonia clean ups, sour water clean ups, and dozens of other methods to end up with each unit's products. These products are things like light coker gas oil, heavy hydrocrackate, light gas oil, heavy gas oil, C2-C4 products, heavy cat naptha, medium cycle oil, de-eth gas, slurry, heavy cycle oil along with many others coming off diffent towers. I can't think of a single product that has come from our different units that hasn't been cracked. Since they are all cracked, they contain benzene, ammonia, sulfur, and the other baddies that must be removed. Most of the remaining processes in the plant are simply cleaning up what has been cracked or selectively putting hydrogen molecules where we want them on the products.
My unit takes the medium cycle oil and hhc up to about 2200 psi, and runs it through a catalyst bed (three huge reactors). We inject pure hydrogen heated to about 900 degrees and under about 2000 pounds at this point to selectively add hydrogen molecules to the feed stocks. This is called hydrocracking, or if it isn't really active because of dead catalyst it is called hydrofining. Both do about the same thing. All traces possible of sulfur have been removed from the feed stock first, then before it comes to the hydrogen plant, and again in my unit using both the DEA and sour water washes. When the product leaves my unit it can actually be used as pure diesel. I take a quart sample of it to the lab every night for analysis.
The gasoline products are actually blends of many of the different product streams. Obviously I cannot give out what consitutes a blend make-up but it has more butane in it during the winter for cold weather starts. These blends vary according to orders, like Seattle may want 8 million gallons of a certain blend. We blend this from our tankage and then pipeline it to the Seattle market, who handles a very big part of our inventory. You guys in that area are burning our products and don't even know it. Same for down the Salt Lake way, everything between MT and Washington, Wyoming, and several other states in the NW down into the northen part of CA. Gasoline in a Holiday station may be selling their blend of our gasoline while the Exxon station across the street may be selling a slightly different blend. The diesel is pretty well the same everywhere. Its the lowest we can get it as far as sulfur goes.
Most of our pumps up here are marked #1 diesel, #2 diesel, or winter blend. Winter blend will be about 50/50. During hard winters, I run straight #1 and suffer the small mpg loss and power loss with the much lower cloud and pour points in the #1. If your truck is louder here on #2, it will also be louder from diesel in Wyoming using #2 and in Seattle and everywhere in between using the same #2 because it all comes from the Billings Refinery, and the diesel is the same for everyone.
The process of producing gasoline and diesel is quite a study, it takes years to get to the position I now hold. This explanation is very elementary but gives some of the basics that should be pretty easy to understand. I have used our products for 21 years and have not even had to clean any injectors, so I think the processes work pretty good and keep a good clean product for the public. _ didn't say perfect cause I know we aren't_ but I believe we are certainly the best the Northwest has available.
Thanks for putting up with the lengthy post. E-mail if you would like something explained that I did not do such a good job of explaining. Hope this helps clarify the "red dye" myth of it being something it isn't. Take one tank of diesel and half it. Put red dye in one half, leave the other alone. Compositions are exactly the same, one is just prettier red.
Thanks for the patience from all of you. Hope this helped.
Steve H
Steve H