Process for preparing isocyanates by phosgenation of amines, wherein phosgene and amine are brought into contact in at least 2 mixing chambers connected in parallel.

Process for preparing isocyanates

Modeling and simulation are established techniques for solving design problems in a wide range of engineering disciplines today. Dedicated computer languages, such as Modelica, and efficient software tools are available. In this thesis, an extension of Modelica, Optimica, targeted at dynamic optimization of Modelica models is proposed. In order to demonstrate the Optimica extension, supporting software has been developed. This includes a modularly extensible Modelica compiler, the JModelica compiler, and an extension that supports also Optimica.

A Modelica library for paper machine dryer section modeling, DryLib, has been developed. The classes in the library enable structured and hierarchical modeling of dryer sections at the application user level, while offering extensibility for the expert user. Based on DryLib, a parameter optimization problem, a model reduction problem, and an optimization-based control problem have been formulated and solved.

A start-up optimization problem for a plate reactor has been formulated in Optimica, and solved by means of the Optimica compiler. In addition, the robustness properties of the start-up trajectories have been evaluated by means of Monte-Carlo simulation.

In many control systems, it is necessary to consider interaction with a user. In this thesis, a manual control scheme for an unstable inverted pendulum system, where the inputs are bounded, is presented. The proposed controller is based on the notion of reachability sets and guarantees semi global stability for all references.

An inverted pendulum on a two wheels robot has been developed. A distributed control system, including sensor processing algorithms and a stabilizing control scheme has been implemented on three on-board embedded processors.

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Languages and Tools for Optimization of Large-Scale Systems

Process transitions (grade changeovers, startups, and restarts) are very frequent in industry, and usually lead to the loss of production time, the production of off-grade materials, and to inconsistent reproducibility of product grades. Two aspects of using multivariate statistical methods based on PCA and PLS to improve process transition performance using historical records of transition data are discussed. First, multivariate SPC approaches are proposed to determine if the process conditions for the commencement of a transition (“startup readiness”) are correct and to assess the successful completion of a transition (“production readiness for the new grade”). The latter is illustrated using a simulated fluidized-bed process for the production of different grades of linear low-density polyethylene. Second, analysis tools are suggested for diagnosing the reasons for past transition problems and for monitoring new transitions to ensure repeatable high quality transitions. The latter methods are aimed at reducing the amount of off-specification materials and reducing transition time, as illustrated on industrial data from restarts of a polymerization process.

Multivariate SPC for startups and grade transitions

An ontology based approach for operational process modeling

https://estudogeral.sib.uc.pt/bitstream/10316/3831/1/file5c4684ef4de24e54b05f944ed52530d4.pdf

Start-up and wrong-way behavior in a tubular reactor: dilution effect of the catalytic bed

Rules are presented for the startup of an adiabatic tubular reactor, based on a qualitative analysis of the dynamic behavior of continuously-operated vapor- and liquid-phase processes. The relationships between the process dynamics, operating criteria, and operating constraints are investigated, since a reactor startup cannot be isolated from an entire plant startup. Composition control of the process material is critical to speed up plant startup operations and to minimize the amount of offgrade materials. The initial reactor conditions are normally critical for a successful startup. For process conditioning, a plant should have an operating mode at which the reactor can be included in a recycle loop together with its feed system and downstream process section. Experimental data of an adiabatic tubular reactor startup and thermal runaway demonstrate some operational problems when such an intermediate operating stage is missing. The derived rules are applied to an industrial, highly heat-integrated reactor section, and the resulting startup strategy is summarized in an elementary-step diagram.

/pdf/reactor-operating-procedures-for-startup-of-continuously-52ow9cyeqv.pdf

Reactor Operating Procedures for Startup of Continuously-Operated Chemical Plants

The safeguarding methodology of chemical plants is usually based on controlling the instantaneous values of process state variables within a certain operating window, the process being brought to shutdown when operating constraints are exceeded. This method does not necessarily prevent chemical reactors suffering from a runaway during dynamic operations because (a) excessive amounts of unreacted chemicals can still accumulate in the process, and (b) no means are provided to the operating personnel to identify hazardous process deviations. A model-based startup and safeguarding procedure is developed for an industrial adiabatic tubular reactor to improve process safety during startup. The trajectories of manipulated variables are calculated by minimizing the amount of one of the main reactants in the reactor effuent. It is concluded that proper control of the initial reactor temperature profile is critical for a safe startup while the impact of other manipulated variables is relatively smaller than that of the initial reactor temperature profile.

/pdf/startup-strategy-design-and-safeguarding-of-industrial-3uc7g85fej.pdf

Startup strategy design and safeguarding of industrial adiabatic tubular reactor systems

The dynamic behaviour of an adiabatic tubular plant reactor during the startup is demonstrated, together with the impact of a feed-pump failure of one of the reactants. A dynamic model of the reactor system is presented, and the system response is calculated as a function of experimentally-determined, time-dependent, manipulated variables. The values of model parameters are estimated by using the SimuSolv (1991) computer program. The data set collected during the reactor start-up is used for the parameter estimation procedure. An excellent agreement is obtained between the experimental and the calculated system response. Many continuously-operated commercial reactors require a complete conversion of one of the main reactants at the reactor exit. It is shown that for an industrial tubular reactor a much higher initial reactor temperature is required during the startup, compared to the reactor inlet temperature during normal steady-state operation, to ensure a complete reactant conversion. Much more research is necessary to determine whether this is a generally valid rule.

/pdf/startup-of-an-industrial-adiabatic-tubular-reactor-4bv0znx45b.pdf

Startup of an industrial adiabatic tubular reactor

https://ris.utwente.nl/ws/files/6438734/Verwijs94start.pdf

J. W. Verwijs

Papers

Reactor Operating Procedures for Startup of Continuously-Operated Chemical Plants

Startup strategy design and safeguarding of industrial adiabatic tubular reactor systems

Startup of an industrial adiabatic tubular reactor

Start-up and safeguarding of an industrial adiabatic tubular reactor