Balanced Control Scheme for Reactor/Separator Processes with Material Recycle

Abstract

The simple reactor/separator process with recycle has recently been used as a benchmark case to gain insights into the problem of plantwide control structure selection. This paper explores the use of a balanced control scheme aimed at improving the disturbance rejection capabilities of the controlled process. The idea is to change the operating conditions in both the reactor and the separator so that the composition control effort in the presence of production rate changes is distributed. To this end, a parallel control structure is proposed where the product composition is regulated by means of simultaneous feedback manipulations of the vapor boilup rate and the reactor temperature. In this way, the use of the reactor temperature as a secondary control input reduces the snowball effects reflected in large vapor boilup rate changes in response to relatively small production rate changes. Nonlinear simulations show that effective composition control can be obtained with moderate vapor boilup control efforts.

Trajectory tracking in a nonlinear CSTR. Controller design based on a linear algebra approach

“…In comparison with others previous published, our controller does not present the disadvantage of the controller proposed by [8,32,33] where among other things, you must factorize the transfer function of the plant and solve optimization problems to obtain final control inputs to implement. The main advantage over the designed controller by [19,22,23] is that, knowing the system model only needs C aref to calculate the control action.…”

Optimizing Control of CSTR/Distillation Column Processes with One Material Recycle

“…Hence, manipulation of the reactor holdup and temperature must be considered for processes with a small Da value, to alleviate the snowball effect. 2,3,6 However, manipulation of the reactor holdup and temperature for bounded chemistry is necessarily accompanied by economical losses: increased separation cost and increased production of undesired species at lower production rates. Note that the operation with the maximum reactor holdup and temperature minimizes the recycle flow rate and undesired product.…”

“…12 Configuration C1, with the reactor holdup and temperature being held constant, suffers from the snowball effect when the perpass conversion is small, such that a balanced control structure that manipulates the reactor holdup and temperature has been proposed. 2,4,6 In terms of the process chemistries, the process should be designed and operated for large per-pass conversions when the chemistry is bounded, to minimize the production of undesired species, whereas the process should be designed and operated for small per-pass conversions when the chemistry is nonbounded. In this regard, configuration C1 may be applicable only to processes with bounded chemistry, whereas configuration C2 is applicable to both of the chemistries.…”

“…In addition to the conventional control configuration, they proposed using the reactor temperature to control reactor composition. Monroy-Loperena et al 6 also suggested using the reactor temperature to effectively handle disturbances.…”

Quantitative Feedback Control of Multiple Input Single Output Systems

“…Such systems are common in process industry [5], where the MISO control sometimes pursues the management of the global production system [6], whereas other times it governs low-level process variables (typical examples are two pumps or a pump and a valve, used as actuators in pressure or flow control [7][8][9]). In other cases the MISO control attends certain subsystems in a process, such as chemical reactors [10][11][12] or biological reactors [13][14][15]. More specific usages can be found in drying sections of paper machines [7,16] or in aerobic digesters of waste water treatment plants [17].…”