PTQ Q4 2025 Issue

Central role of diagnostics in distillation energy transition: Part 1

Acquire capital and utilities savings when pursuing the huge potential for reducing CO 2 emissions by troubleshooting, diagnosing, and solving plant problems

Henry Z Kister Fluor Corp ., Norman P Lieberman Process Improvement Engineering

T he refining and petrochemical industry has been focusing on developing new technologies for the energy transition and reducing carbon dioxide (CO₂) emissions, such as reprocessing cooking and soybean oils, carbon capture, and hydrogen generation. However, one simple technology often gets overlooked: improving exist - ing processes and troubleshooting, diagnosing, and solving plant problems. Unlike new technologies that come at a cost, troubleshooting, diagnosing, and solving plant prob - lems can lead to capital and utilities savings. Inspection and good measurement A classic example of eliminating an unnecessary carbon footprint is described in Reference 1. Following a turna - round, all the tray manways in the atmospheric crude tower (see Figure 1 ) were reinstalled, except for those on Trays 21-24, which separate diesel from the atmospheric tower bottoms (ATB). The reason why they were not reinstalled is unknown; perhaps the contractor was in a rush or lost

of 114 Btu/lb. Therefore, the total heat duty for vapouris - ing the diesel was 170 Btu/lb x 120,000 = 20 MM Btu/h. In addition, the rest of the ATB required heating from the reduced ATB temperature of 640ºF (due to the presence of the diesel) to the normal 670ºF, with a specific heat of 0.67 Btu/lb ºF. This heating duty was 1,000,000 x 0.67 x 30 = 20 MM Btu/h. So, the additional heater duty needed was 40 MM Btu/h. All this because of four uninstalled manways. There is more. The vacuum heater was limited by com - bustion airflow at 140 MM Btu/h, and the extra 40 MM Btu/h increased its duty to 180 MM Btu/h. To provide this duty, a new 200 MM Btu/h heater was ordered and built. In addition, the vapourised diesel increased the vapour traf - fic in the vacuum tower beyond the flood limit, promoting entrainment of resid into the heavy vacuum gas oil (HVGO) product, contaminating it. Process Improvement Engineering (led by Lieberman) was called in to consult on the vacuum tower capacity limitation, beginning with troubleshooting the towers.

the required hardware. Upon restart, the vapour channelled through the open manways and separation was lost. As the diesel product needed to be kept on specification, the refinery had to run Trays 21-24 at a lower temper - ature, which meant a large loss of diesel to the ATB. The ATB contained 12% diesel by weight. The lighter die - sel reduced the ATB boiling point from the normal 670ºF to 640ºF. The ATB was heated to 720ºF before entering the vacuum tower. The total ATB rate was 1,000,000 lb/h. The diesel increased this rate by 12%. This diesel needed to be heated from 640ºF to 720ºF at a sensible heat of 56 Btu/lb and vapourised at a latent heat

To vacuum

Kero

LVGO

Vacuum tower

Atmospheric crude tower

Diesel

HVGO

Hot crude feed

Vacuum heater

720˚F

640˚F

ATB 12% diesel

Fuel gas

Resid

Figure 1 Crude tower with uninstalled manways and vacuum tower

PTQ Q4 2025