WABT of Diesel Hydrotreating is normally changed keeping in view the Diesel product Sulfur results. There is no fix method/rate of increase or decrease the WABT. Normally, we increase ~2 degree C WABT with 1 % unit load. Again, we can not fix the WABT rate with feed rate because the specifications of feeds and catalyst activity are not always the same. With fresh catalyst sometimes at low WABT you can achieve the desired desulfurization reactions.
After operation and WABT adjustment, practice you can tentatively fix the WABT rate with feed rate. We normally increase 2 degree C WABT with 1 % unit load increase and 2 degree decrease with 5 % unit load decrease.
But always keep in mind this practice for safety of Hydrotreating catalyst: First take the step of unit rate increase then go for WABT rise. In the same way, first decrease the WABT then go for unit rate decrease”.
Further, once the WABT has been adjusted according 2 degree C for 1 % unit load, final adjustment can be done according to the product Sulfur results.
In addition, the the temperature rising rate can be different according to your unit conditions. Means, your rate can be 1~4 degree C according to your plant condition.
Unit, product sulfur online analyser will also help you to optimize the temperature rising rate.