Improved operating scenarios for the production of acrylonitrile‐butadiene emulsions

Abstract

This article focuses on important aspects related to the production of acrylonitrile‐butadiene rubber (nitrile rubber or NBR) emulsions using a train of eight continuously stirred tank reactors. The first aspect we discuss concerns miscellaneous operating procedures, targeted toward achieving desired properties of the NBR emulsion and at the same time reducing the amount of off‐spec material during the transient period. In one of the operating procedures discussed, the first reactor is started full of “batch recipe,” whereas the remaining reactors in the train are half full with all reaction ingredients. In another case, we discuss an alternative design scenario, where the first reactor in the train is of a much smaller volume compared with the following reactors. The benefits of these two operating (production) scenarios are illustrated by comparison of different polymer and latex properties obtained with the commonly used procedures. Second, we discuss a novel criterion that can quantitatively distinguish between Cases I and II kinetics emulsion polymerization behavior with respect to continuous reactor stability (oscillatory behavior). Finally, additional feed policies are addressed, such as splitting the more reactive monomer and/or other reaction ingredients among the reactors of the train for better control of certain desired properties. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Surrogate Models for Online Monitoring and Process Troubleshooting of NBR Emulsion Copolymerization

“…The builtin function, trainlm.m, in MATLAB is based on this algorithm and is used in the simulations for the NBR system. The desired output, Y, is obtained from the mechanistic model, which gives good predictions when compared with the experimental data, as established in previous work [4,5]. The original mechanistic model is highly nonlinear with 32 multiscale state variables.…”

“…This method of obtaining the estimates (for initial reaction ingredients) is easier and less time consuming compared to using the fully mechanistic model. Using the mechanistic model (which is very useful in its own right, as we have shown in previous publications, e.g., Madhuranthakam and Penlidis [4,5]), a trial and error approach has to be used for initial reaction ingredients. During the operation of the reactor train, for any slight discrepancies in the desired properties of the products, it is always possible to fine-tune the estimates obtained using the ANN-based inverse modeling.…”

“…In general, the inflows to the last few reactors are manipulated rather than manipulating the inflows to the first few reactors, due to the fact that the monomer droplets are absent in the last few reactors. For example, in a reactor train started up full of recipe, the monomer droplets will disappear in the sixth reactor of the train [5]. Especially for grade changes involving MW w , the corresponding manipulated variable is the flow rate of CTA added to the reactors with monomer droplets present.…”

“…This model is capable of simulating the emulsion polymerisation of NBR in batch and in a train of CSTRs, with add-on options, such as choosing the type of reactor start-up, different modes of monomer partitioning, and the effect of impurities. More detailed information regarding the traits and attributes of this model can be obtained elsewhere [4,5]. The mechanistic model developed by our group is complete and comprehensive and has been used for more than just obtaining the simulated dynamic behavior of commercial trains of CSTRs corresponding to different operating conditions.…”

A Closed‐Loop Control Strategy for Producing Nitrile Rubber of Uniform Chemical Composition in a Semibatch Reactor: A Simulation Study

“…Also, a practical procedure for minimizing the off‐spec generated during changes of grade (from AJLT to BJLT, and vice versa) was proposed and successfully evaluated through simulations . Different operation scenarios of a train of eight reactors utilized for the NBR production were discussed by Madhuranthakam and Penlidis . Washington et al presented a complete mathematical model that is useful to simulate the NBR polymerization in batch or continuous reactors, as well as in a train of CSTRs.…”