Automatic control of simulated moving beds II: Nonlinear isotherm

Simulated moving bed (SMB) chromatography has become a widely used separation technology in the pharmaceutical and fine chemical industries. However, operation of SMBs at their economic optimum is still an open issue because of the absence of proper process control schemes. This work proposes an on-line optimization-based control concept to avoid the tradeoff between the robustness and productivity of the process and to accelerate the development of SMB separations. The control concept requires minimal information on the system, i.e., Henry's constants and the average porosity of the columns. This paper illustrates how a controller that is based only on the linear adsorption isotherm parameters can find the correct operating conditions for the SMB applied to a system characterized by a nonlinear competitive isotherm in order first to fulfill the product specifications and then to optimize the economics of the operation. The performance of the controller is assessed for several scenarios addressing the main challenges in SMB operation.