Single‐Point Intrinsic Viscosity and Density Measurements for In‐Line MIMO Control Purposes of a Lumped‐Distributed Polymeric System

Vega, Márcia Peixoto; Bellumat, Ernanda; Lima, Enrique Luis; Pinto, José Carlos

doi:10.1002/mren.201200041

Cited by 3 publications

(5 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Vega et al used periodic manual measurements of intrinsic viscosity on reaction aliquots together with densitometer measurements for conversion to achieve a closed loop controller via an experimentally determined Mark−Houwink relation. 25 Figure 8 shows η r and instantaneous η r,inst computed by the general eq 3 for the reaction of Figures 5 and 6. The two curves are reminiscent of M w,e and M w,inst,e in Figure 6, and an η r controller can be constructed by retracing the steps in the above M w controller.…”

Section: W Controller and Resultsmentioning

confidence: 99%

“…Since it is related to molecular weight, often by a Mark–Houwink relationship, it can serve as a useful replacement for direct measurements of M w . Vega et al used periodic manual measurements of intrinsic viscosity on reaction aliquots together with densitometer measurements for conversion to achieve a closed loop controller via an experimentally determined Mark–Houwink relation …”

Section: Implementation Of the Automatic Acomp M W Controller And Res...mentioning

confidence: 99%

“…Furthermore, observability and convergence are not guaranteed due to the nonlinearity of polymerization processes. , The model utilized must balance the need for high accuracy and precision with the quick response time required for active control , while maintaining desired quality. , The most commonly used method for state estimation is calorimetry, and much literature has been devoted to the refinement of this technique to estimate the conversion. ,, Lack of convergences or even observability over the entire reaction and time severely limits this technique for dynamic control throughout an entire reaction. Vega et al proposed an alternative to calorimetry and typical state estimation techniques using aliquot measurements of viscosity and density correlated to molecular weight and conversion, combined with a simplified process model. The use of conversion and molecular weight as the optimized variables shows how refined online process characterization eases the burden for process control and optimization …”

Section: Introductionmentioning

confidence: 99%

“…11,22,23 Lack of convergences or even observability over the entire reaction 24 and time severely limits this technique for dynamic control throughout an entire reaction. Vega et al 25 proposed an alternative to calorimetry and typical state estimation techniques using aliquot measurements of viscosity and density correlated to molecular weight and conversion, combined with a simplified process model. The use of conversion and molecular weight as the optimized variables shows how refined online process characterization eases the burden for process control and optimization.…”

Section: ■ Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Automatic Control of Polymer Molecular Weight during Synthesis

McAfee

Leonardi²,

Montgomery³

et al. 2016

Macromolecules

View full text Add to dashboard Cite

The continuous record of monomer and polymer concentrations, C m and C p , and cumulative weight-average mass, M w , furnished by automatic continuous online monitoring of polymerization reactions (ACOMP) has been harnessed to provide feedback to control reactor monomer flow in order to follow a target trajectory M w,t (t) during linear chain growth free radical polymerization. This was achieved without a detailed kinetic model. Two proportionality parameters to pilot the controller, α and p, result from (i) reaction rate = αC m and (ii) M w,inst = pC m , where M w,inst is instantaneous M w . Using Ansatz values for α and p, the controller periodically recomputes these, based on the ACOMP data stream, in order to follow M w,t (t). A histogram of concentration vs M w,inst estimates the molecular weight distribution width. Invoking an instantaneous distribution provides polydispersities. Results are compared to GPC analysis on end products. The concept of "isomorphic reaction pair" is introduced: two reactions that follow the same trajectory under different reaction variables, e.g., varying T at constant [initiator] and varying [initiator] at T = constant. The controller can be used, as is, for high solids reactions, and extended to copolymerization, including for possible control of composition gradients in controlled radical polymerization.

show abstract

Section: W Controller and Resultsmentioning

confidence: 99%

Section: Implementation Of the Automatic Acomp M W Controller And Res...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Automatic Control of Polymer Molecular Weight during Synthesis

McAfee

Leonardi²,

Montgomery³

et al. 2016

Macromolecules

View full text Add to dashboard Cite

show abstract

“…Vega et al used periodic manual measurements of intrinsic viscosity on reaction aliquots, together with densitometer measurements for conversion to achieve a closed-loop controller via an experimentally determined Mark Houwink relation. [44] In the current ACOMP system the concentration of polymer and shear rate are low enough that the approximation is used that η r ≅ [η]. This approximation is usually made for viscosity measurements made in GPC characterization.…”

Section: Cta Batch Reactions For Validation Of Methodology and Determmentioning

confidence: 99%

Automatic Synthesis of Multimodal Polymers

Leonardi¹,

Montgomery²,

Siqueira

et al. 2017

Macro Reaction Engineering

View full text Add to dashboard Cite

An automatic molecular weight controller is used in semi‐batch reactions to produce final polymers that contain distinct subpopulations with different molecular weight distributions (MWD). While blending polymers with different MWD is frequently used to make multimodal polymer products, a method is introduced here allowing the multimodal product to be made in successive, automatically controlled stages in the same reactor. The method is demonstrated using free radical polymerization of acrylamide to produce widely separated multimodal MWD. Automatic Continuous Online Monitoring of Polymerization reactions with a Control Interface (ACOMP/CI) was used. Weight average molecular weight (Mw) in the ACOMP/CI was continuously measured with multi‐angle light scattering and ultra‐violet absorption. The controller used two principles: both polymerization rate and instantaneous molecular weight are proportional to monomer concentration. By controlling monomer flow rate into the reactor, the controller produced a targeted amount of polymer with a desired first Mw and then automatically introduced chain transfer agent (CTA) into the reactor to produce a second population of polymers with much lower Mw. Subsequently, reactions were performed to produce trimodal populations. This approach is kindred to multi‐stage synthesis of polymers where distinctly different processes are carried out in succeeding stages to produce polymers with highly specific properties.

show abstract

Design of Nonlinear Model‐Based Control Using Bifurcation Analysis for Solution Polymerizations Carried Out in Lumped‐Distributed Reactors

Vega

Oliveira

Lima

et al. 2017

Macro Reaction Engineering

Self Cite

View full text Add to dashboard Cite

In order to implement nonlinear control, nonlinear system identification must be performed, however, there are open questions concerning this field of process control, for example, experimental planning, model structure selection, parameter estimation, and validation. Therefore, the study of nonlinear model identification is a relevant unsolved problem that needs to be handled for nonlinear control synthesis. This paper presents the use of bifurcation theory, dynamic and stability analysis for nonlinear identification, and control of polymerization reactors. Peroxide‐initiated styrene‐solution polymerization reactors (lumped‐distributed) are investigated: batch, continuous stirred‐tank reactor (CSTR), and tubular reactors. Open and closed loop analyses are carried out using jacket temperature and weight average molecular weight setpoints as the bifurcation parameters. Phenomenological mathematical models, neural network nonlinear models, and an experimental data from a polymerization unit are employed for validating the proposed methodology in order to implement confident nonlinear controllers.

show abstract

Single‐Point Intrinsic Viscosity and Density Measurements for In‐Line MIMO Control Purposes of a Lumped‐Distributed Polymeric System

Cited by 3 publications

References 22 publications

Automatic Control of Polymer Molecular Weight during Synthesis

Automatic Control of Polymer Molecular Weight during Synthesis

Automatic Synthesis of Multimodal Polymers

Design of Nonlinear Model‐Based Control Using Bifurcation Analysis for Solution Polymerizations Carried Out in Lumped‐Distributed Reactors

Contact Info

Product

Resources

About