In an earlier blending applications post, I mentioned some of the advantages of online/inline blending over traditional, batch-based blending. It’s a process which crosses many industries including refining, pulp and paper, chemicals/specialty chemicals and food and beverage to name a few.
I came across an article, Optimizing blending operations by Julie Valentine, a refining specialist in Emerson’s Micro Motion division. Julie notes that for refiners, the motivation for changes to the blend process are in improved control, improved measurement, improved analyzers and improved optimization techniques. One of the keys is high performance flow measurements of the raw materials to precisely control their flow rate as they are blended together. The Micro Motion Coriolis flow meters are extensively used for both the raw material and final blending product flow measurement. Their 0.1% accuracy couple embedded advanced control in control systems like the DeltaV system, enable blend optimization to be done within the control system.
In the article, Julie describes a U.K. lube blending plant which switched from a sequential measurement system to a flow measurement based system. This switch enabled the raw materials to simultaneously flow into the mixing tanks, increasing the throughput of the operation. The accurate measurement of the raw materials meant that the blend would be on-spec as it was filling in the mix tank, and shortened the overall mix cycle, again increasing throughput.
The Coriolis meters also provide high accuracy density measurements, which was important since blend component pipe headers are cross connected and this density measurement can quickly spot and notify operators of cross contamination which can affect the quality of the blend.
One other example Julie cites is where the blending optimization for the blend of gasoline allows refineries to make use of the blend components available from production and choose the blend which will produce the required specification at the lowest cost, while also managing inventory levels.
The accuracy of the flow measurement is critical to the blend optimizer. Julie cites a study where poor flow measurement with 0.3% accuracy translates into lost profitability of up to $200,000 per year for a 100,000BPD facility. This is caused by the blend optimizer making the wrong optimization decisions based upon the inaccurate data it receives.
