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Nov
01

Biggest Opportunities for Process Control Improvement – Concentrations

The process variable of greatest interest in a process stream is generally concentration. If the final concentration is not right, not much else matters. Yet online analyzers are few and far between. Plant analyzer groups have been cut back or allowed to disappear through attrition. While I think the staffing of these groups would be more than justified, given the current situation analyzers are needed more than ever that can be maintained and supported without special expertise.

Coriolis mass flow meters offer exceptionally accurate mass flow and density measurement with minimal maintenance when properly selected and installed. Many compositions can be better controlled by a more accurate mass flow ratio and the stream density can be used to provide an inference of changes in the stream composition. For specialty chemical and pharmaceutical, the potential number of Coriolis flow meters is quite large because the pipe sizes are small and the value of the product is high.

We loose sight figuratively and literally that the concentration in any stream does not usually match what is listed on the process flow diagram. The concentrations are quite variable due to fluctuations or unknowns in the raw materials and in the unit operations and from cycling introduced by poor controller tuning and final element resolution. The effect of most of these disturbances is typically unmeasured. Often not considered is the capability offered by the Coriolis meter to track down a disturbance. For example, if the temperature corrected density of a feed has changed, it probably means the concentration of a raw material or intermediate has changed.

The extended use of Coriolis meters on feed, recycle, and product streams in any industry with reasonable pipe sizes for both continuous and batch operations seems to me to be one of the biggest straightforward opportunities.