Emerson Exchange 365

For chemical plants, reducing process variability can make a substantial impact on the bottom line. The results of such a project, carried out in a northern region of the Czech Republic, were presented at the 2014 Emerson Global Users Exchange in Orlando, Florida.

Lovochemie is a KD5 nitric acid plant in Lovosice. Built more than 20 years ago, the plant faces tightening, local environmental regulations. To modernize, improve yield and meet new requirements, management decided to upgrade with the DeltaV distributed control system. Emerson Process Management’s work on the project included an advanced control study by Mark Brewer, a senior consultant at Emerson.

Brewer noted how difficult it can be to optimize control processes manually. “Relying on traditional solutions,” he explained, “operators faced a complicated set of individual control loops, operating constraints, disturbances and variability, and other conditions forced them to operate within a comfort zone that was manageable, yet inefficient. Profits were lost as a result.”

In addition to those issues, Brewer said lab results were not continuously measured online. There were interactions between one valve and many other loops, and economic drivers came into play. Overall, the manual process was complicated and continually changing, making it very difficult to optimize.

“Multivariable Predictive Control (MPC) is the key to reducing process variability,” Brewer continued. “DeltaV embedded MPC allows a process to operate closer to optimal constraints, so that the safe operating window moves closer to the optimum operating point.”

“The benefits of tighter process control typically include higher product yield, increased quality and consistency, reduced giveaway, and lower energy consumption. These key performance indicators are typically where profits are made.”

“Specific to the nitric acid control process at Lovochemie, a primary objective was to optimize natural gas usage while reducing the possibility of excess emissions. If NOx is too low, it indicates too much natural gas is being used. If NOx is too high, environmental limits may be breached.”

Brewer designed and deployed DeltaV MPC at Lovochemie in less than three months, and the results were immediate. Within just one week, variability of O₂, NOx and temperature were markedly reduced, bringing the operation closer to safe optimum constraints.

With the nitric acid process at Lovochemie under automatic control for the first time, Brewer and the Lovochemie team couldn’t be more pleased. “The project demonstrated that DeltaV embedded MPC is easy to use, responsive, and effective,” said Brewer. “That’s what it’s all about.”