Reactor controller: Specialized device regulates difficult exothermic reactions

By Control Engineering Staff October 4, 2006

Controller performance is demonstrated and compared in this trend chart.

Although reactors are major operating units in many chemical plants, keeping close control of temperatures in exothermic reactors is still a common problem. Many plants use poorly performing PID loops or do it manually and simply deal with resulting problems. CyboSoft has now developed a model-free adaptive controller, the MFA XRT, to regulate the temperature of an exothermic reactor.

Since heat and reaction speed are directly related in exothermic processes, the process can run away if the controller cannot respond quickly enough to stop it. “Typically, a non-self-regulating or run-away process like this could be controlled by using a P-controller,” says Steve Mulkey, engineering director. “However, when the process also includes a large time delay, it becomes extremely difficult to control. A run-away process requires rapid control action to search for a new balance point and yet a process with a large time delay requires a patient control action. These two requirements are in conflict.”

CyboSoft claims the MFA XRT controller solves this dilemma by providing a “smart” control signal. Its performance is demonstrated against a PID controller in a real-time simulation system that is included in the CyboCon MFA control software-Professional Edition. It shows how the controller on the top makes rapid and decisive adjustments to bring the reaction into balance, while the PID controller cannot get the operation in hand (see illustration). The patented model-free adaptive control approach is said to be key to these difficult applications.

For more about how the model-free approach works, click here to read an article from Control Engineering Europe on its complex operations.

— Daily News Desk, Peter Welander ,process industries editor , Control Engineering