Industrial simulation experience since 1997

Solid-Liquid flash calculations : Determination of the identity and amounts of solid phases at equilibium, in a mixture containing water and several dissolved ionic species, involves complex thermodynamic calculations. The possible existance of a large number of solid phases (all combinations of anions and cations, mixed salts, and hydrated single/mixed salts) adds to this complexity. Standard approaches based on free energy minimization often face numerical pitfalls such as landing into negative concentrations. A dynamic simulation approach was formulated, based on novel rate equations, which guaranteed convergence to the correct solution from any starting mixture. A software package based on this approach was developed.

Simulation of a particle former : In a particle former, a melt is deposited on a moving metal belt in the form of droplets, which solidify as the belt moves along, and are taken off at the end of the belt as solid particles. A simulation package was developed for a commercial plant, which calculates profiles of melt temperature and belt temperature along and across the belt. It accounts for heat transfer between the belt, melt and the gas phase, heat conduction across the belt, cooling by radiant heat transfer, heat of solidification and crystallization, heat generation by internal heaters (if any), and heat loss to atmosphere.

Solid-state polymerization (SSP) of PET : Dynamic simulation of a crucial commercial reactor was conducted to pinpoint the previously unknown cause of start-up problems which made the reactor inoperable. A customized dynamic simulation software package was developed which was used successfully to examine various plant start-up scenarios, and identify acceptable start up procedures. Other reactors in this process, including precrystallizer, crystallizers and the main SSP reactor, were also simulated. The simulation software is being used for predicting plant performance and also for plant improvements.

Continuous process for guanidine nitrate : A batch process used earlier was developed into a continuous process, using laboratory kinetic experiments, earlier plant data and simulation techniques. This made the process safer (because of lower inventories), without compromising on process efficiency, and also improved the control aspects.

Extraction of lactam from nylon chips : The extraction column in a commercial plant was simulated, taking into account the internal diffusion within chips. The software package was used for determining the performance under higher capacity, and for designing a new column under space restrictions.

Melt spinning of filaments : Simulation software was developed for the complex process of melt spinning of polymer melts using several quench geometries (crossflow, radial out, radial in) and spinerette cross-sections (solid circular, hollow). This has been sold to several multinational clients so far for PET/PP spinning. It can also handle nylon spinning.

Simulation of PET reactors : Simulation software was developed for several reactors including prepolymeriser, loop esterifier, and finisher in a commercial PET plant. The software was used for plant improvements.

Drawing of filaments : The process of drawing of spun filaments (cold as well as high temperature processes) was simulated for commercial operating plants.

Hydrogenation in a high pressure slurry reactor : This simulation package was developed for an Italian university as a teaching aid. It demonstrates the effect of various operating conditions on reactor performance.

Sintering of polytetrafluoroethylene (PTFE) billets : This simulation package helps billet manufacturers in designing appropriate sintering temperature cycles for products of different sizes, compositions and properties.

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