Emerson Exchange 365

It’s great to see presentations from Emerson Exchange become articles published in industry magazines. Here’s one from EMRex 2016 that was one of the finalists for a best presentation award, and it reminds us why so many people come to this event every year.

In this article in Processing, Ariana Cornwell (She was still Ariana Buckley last October) and James Simon from Chemours, working with Brian Cleary from Emerson Automation Solutions, recount the complex process of trying to solve a seemingly simple accounting problem: getting an accurate handle on feedstock usage and inventory. The feedstock in this case is a dry powder, which makes the situation a bit more complex.

Feedstocks delivered as solids are different because they can present a wide range of characteristics. Many different particle sizes can exist – they can be granular or sticky – and they can respond differently to changing atmospheric conditions, which causes them to behave unpredictably in a storage environment. One of the most difficult tasks with solids is measuring inventory on a continuous basis. The experiences at The Chemours Company’s facility in LaPorte, Texas shows how complicated such applications can be, and how the right measuring technology can solve several problems simultaneously.

The product in this case is “spar,” a form of calcium fluoride. It is used in this facility to make hydrofluoric acid, and it is one of the two main feedstocks. Once spar gets delivered to the plant, it is processed and then transferred to one of two storage silos. The problem for the team was to determine how much spar was being used, and how much was on hand in the two silos.

For many years, the only practical way to measure level in the silos was by sending an operator to the tank roof twice a week. The procedure called for opening a specific nozzle on the roof and lowering a tape measure to the product surface. This manual rodding procedure provided a usable reading of the level directly below the nozzle, however, this by itself was insufficient for several reasons:

• The accuracy and consistency of the reading depended on the technician inserting and reading the tape measure. Different people did it in slightly different ways.
• It was a single spot reading and did not correct for the contour of the product in the silo. It was impossible to tell if the reading was the high or low spot for the surface overall.
• Sending a person to the top of the high tank, even with railings and appropriate protective measures and equipment, was not a desirable approach in terms of personnel safety and productivity.

The article goes into more detail describing the approaches the plant tried to solve the problem, but they all shared the same deficiency: they only provided a spot measurement and did not consider the contour of the dry material in the silo. One by one these approaches were abandoned, and manual measuring remained the only practical approach, until someone in the plant spotted an interesting article in an industrial publication.

Chemours discovered Emerson Automation Solutions’ Rosemount 5708 3D Solids Scanner – Acoustic Phased-Array that had been developed specifically for applications in dusty environments with solids. The solids scanner uses three acoustic antennas combined so that it only requires one vessel opening. The three antennas each send and receive acoustic signals from different angles, which allows the device to take a group of overlapping “pictures” of the product surface. Since the pictures are taken from slightly different positions, it is possible to map the distance and direction over the full surface and measure all the contours, calculating a true average level or total volume of the product, regardless of the contour of the surface.

The plant installed one of these 5708 scanners but continued to perform manual measurements in parallel with the new technique. Before long, the accuracy of the scanner was proven and both silos were fully outfitted. The tape measure was retired.

Once Chemours understood the accuracy of the measurements, company management began using the data for accounting purposes to monitor spar usage after the drying stage. Because this feedstock typically costs more than $50 million annually and is the highest cost element of the process, there was a strong push to use this new data to get a more accurate handle on usage. Even a 0.5 percent error in the measurement over a year’s time amounts to more than $250,000, so more accurate inventory has the potential to produce considerable savings.

There are dozens of stories like this every year at Emerson Exchange where your peers and experts talk about problems solved. There are also discussions here at Emerson Exchange365 every day. Come and join our Level Group for new ideas to solve your process problems.