The European project F 3 Factory aims at designing small to medium scale plants consisting of standardized container assemblies for delocalized production of various chemicals. Within the framework of the F 3 Factory project, the design of a modular, multiproduct, and continuous plant for manufacturing water-soluble polymers is addressed. Free radical polymerization in aqueous solution is examined through two industrial cases: polymerization of acrylic acid (AA) in the presence of chain transfer agent (CTA) and copolymerization of AA with one comonomer. A methodology for performing the transition from batch recipes to continuous operations is proposed. Offl ine and inline monitoring of monomer consumption is achieved using Raman spectroscopy combined with chemometrics. A modular pilot plant meeting the requirements of F 3 Factory project is designed and demonstrated at INVITE (Bayer, Leverkusen). The two polymerization processes are successively operated in the same pilot plant separated by an intermediate extensive washing. For each process, several polymer grades are produced by modifi cation of reaction conditions (inlet fl ow of CTA or reactor temperature). Transition dynamics are characterized using inline monitoring. The fl exibility of the modular plant is demonstrated.
reactors by continuous ones. The reactor system which is investigated here comprises several inputs and due to the near plug fl ow characteristics between the inputs and the outputs, reacts to the changes of the infl ows with large time delays. Model-based optimizing control is the obvious candidate to control such a multi-input plants with significant delays. While the standard implementations of model predictive control penalize the deviations of the states or outputs from reference values and the control moves in the cost function, in this work the controller is formulated to account directly for the economics of the reactor system while the product quality parameters are imposed as constraints. [ 1 ] Some applications of optimizing control can be found in refs. [ 27 -30 ] . Limited computation power and lack of effi cient optimization algorithms have caused thatIn this contribution, a nonlinear model-based optimizing control for continuous polymerization of acrylic acid in tubular reactors with multiple side injections of monomer is developed. The background of this work is to transfer the production of polymers from semibatch to continuous operations. The confi guration of the tubular reactor, which imposes long delays between the inputs and the measurements, and the lack of intermediate measurements as well as the nonlinear reaction kinetics and sharp moving fronts of concentrations when the infl ows are changed, make the application of the optimizing control very challenging. In order to simulate the sharp fronts of the reactor system faithfully and fast, the spatial domain of the partial differential equations model of the tubular reactor is discretized by applying the weighted essentially non-oscillatory scheme. We formulate the controller such that it optimizes the productivity of the reactor directly, while the product quality parameters are imposed as constraints. A particle fi lter is implemented to estimate the states of the reactor system and to initialize the process model. The simulation results show that the controller can increase the product throughput considerably compared to an initial operating point and has a robust performance against the measurement noise. Furthermore, the effect of formulating the quality constraints as hard or soft constraints as well as a changeover scenario between the different grades of a polymer are studied.
The transfer of copolymerization processes from discontinuous plants to continuous plants has become a topic of industrial interest in the recent years. The motivations for such a transfer are better product consistency, smaller capital investment, and smaller footprint of the plants. However the experiences of the F3 project show that some copolymerization processes cannot be transferred to continuous production if the product quality must remain the same because in a continuous reactor, feeds can be added only at certain points along the reactor. This paper discusses the transferability of semibatch polymerization processes to a continuous plug-fl ow reactor with side injections in a generic fashion. Transferability of a semibatch recipe here means the possibility of the production of the same product in both modes of operation (semibatch and continuous). To determine the limits of the transferability from semibatch to continuous production, a model-based analysis has been performed based on a simplifi ed kinetic model and realistic kinetic para meters. The ranges of product qualities that can be produced in both modes of operation and the minimum changes in the product qualities, if no 1:1 transfer is possible are determined by means of model-based optimization. Besides the numerical results, also an analytical treatment is presented. This provides a sound basis for an analysis of the transferability from a kinetic and an economic point of view.
In this work, the operation of modular flexible continuous polymerization plants is investigated. For a benchmark problem (six products with an overall yearly demand of 20,000 t, two continuous production lines with modules that can be moved between the lines) that is defined by industrial speciality polymer producers, the optimal campaign planning problem is solved, minimizing the cost of cleaning and waste production. The results are compared to the production of the same portfolio of products in a batch plant. The results show that the changeovers between different products and production parameters lead to a loss of production capacity and additional costs. For long production campaigns (demand satisfaction on a monthly basis), these costs and losses are comparatively small, whereas for short demand satisfaction periods (one week) they are significant. On the other hand, longer demand satisfaction periods require a significant amount of product inventory and hence storage facilities.
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