Radioisotope Techniques for Process Investigations

In all chemical plants and refineries there generally is not enough instrumentation in the right places in

our processes. During the design phase, decisions were made between knowing more about the process,

which means buying more instruments, and saving capital funds. When a problem appears with the

operation of a vessel, there are always gaps in the knowledge of what is happening due to a lack of

instruments in the places where knowledge is not routinely required. Process engineers and operations

personnel need to know what is happening so they can take corrective action. When knowledge is

missing, they often take actions that make matters worse.

For distillation and separation processes Chemical Engineers have historically relied upon plant process

measurements such as flow rates, temperatures, and pressures and model or simulation results for data

with which to solve troubleshooting or re-design problems. An array of on-line diagnostic services are

available that can provide additional data offering real-time information on how pieces of process

equipment are actually operating. The most common application is Gamma Scanning. This test is

primarily applied, but not necessarily limited to, distillation or separation columns. Gamma scans

provide a density profile of the internal process of operating distillation columns and other process

vessels. The density profile can be used to diagnose the hydraulic operating conditions of mass transfer

devices such as damage to internals, flooding, degree of entrainment or weeping, liquid levels on trays

and distributors, liquid distribution through packed beds, etc. The presenter will show case studies

where scanning revealed vital process information that helped solve an operating problem, or helped

make a revamp/re-design successful. Additional derivatives from gamma scanning of detecting flow

distribution patterns will be demonstrated. The ThruVision Scan technique is a specialized horizontal

gamma scan used to generate a topographic profile of the internal cross-sectional density of process

equipment. This profile is useful for the detailed study of liquid flow distribution through packed

columns as well as having applications beyond distillation columns. A hybrid application involving tracers

and scanning on fixed bed catalytic reactors will also be discussed.