I am looking for information on oilfield production of diesel fuel. If you know of places on the internet where I could find some theory on diesel topping or manufacturers of skid-mounted topping units, please advise.
A company in Shreveport, LA USA now called Beaird Industries (called Riley-Beaird at the time) about 30 years ago developed a topping unit which made a perfect cut of #2 distillate. The design was finalized too late for use on the Alaska Pipeline, as a provider of fuel for the prime movers, which was its intended purpose. Several were sold as "mini" refineries, and only a handfull were produced.
The diesel product that the first pilot plant produced was tested successfully in the companies own over the road transport trucks as they delivered the companies products across the nation. The unit made #2 distillate, however, not the blended diesel that one can buy at the truck stop.
There is no reason why they could not scale the design up or down if you had an application that would be financially attractive for them to manufacture. The pilot plant used electric heat, and Dowtherm as the heat transfer fluid, but could use other combinations.
You might guess that I was the project/design engineer on that products development. Ask for Bill in the evaporator sales group, and refer to it as the DFS. Tell him someone from Monroe sent you.