Cristhian Almeida-Rivera

Designing reactive distillation processes: present and future

The potential benefits of applying reactive distillation (RD) processes are taxed by significant complexities in process development and design. The design problem is formulated in the wider context of process development and engineering. From that perspective design methods for RD units developed over the last decades are classified and described. A fingerprint of the most representative work in the three categories, graphical, optimisation- and heuristic-based, is presented and deficiencies are identified. In response to a need for a more integrated design methodology, a conceptual model is offered which uses a hierarchy of embedded design spaces of increasing refinement and conjugates the strengths of both the graphical- and optimisation-based methods.

Product driven process synthesis methodology

Abstract In the last ten years much more processes are being reported to be designed through a process synthesis approach. It has been recognized during those years that (i) processes for structured products are more difficult to design through process synthesis; (ii) process synthesis is disconnected from product development. In a response to those shortfalls a number of authors have described that the gaps need to be filled, however no methodology extension has been proposed. In this work, we will present extensions to the conceptual process synthesis methodology to include (structured) product design. The whole design methodology spans from how the new product can enlighten the consumer, financial and supply chain boundary conditions, through an optimal flowsheet able to produce the desired product cost effectively. A real case study will be used to illustrate the applicability and scope of the proposed methodology

Feasibility of equilibrium-controlled reactive distillation process: application of residue curve mapping

Abstract The residue curve mapping technique (RCM) has been considered a powerful tool for the flow-sheet development and preliminary design of conventional multi-component separation processes. It does not only represent a good approximation to actual equilibrium behavior, but also it allows performing feasibility analysis of separation processes where non-ideal and azeotropic mixtures are involved. Applications of RCM to reactive distillation processes have recently been reported, but a generalized and systematic approach is still missing for the case of reactive feeds outside the conventional composition ranges and represents the aim of this contribution. An RCM-based feasibility analysis has been applied to the homogeneous reactive distillation synthesis of methyl tert-butyl ether (MTBE) at 11 atm from isobutene (IB) and methanol (MeOH) and in the presence of n-Butane (nC4). The reaction space, defined in terms of transformed composition variables, has been divided into sub-regions characterized by separation boundaries. A feasibility analysis of the reactive distillation process has been performed based upon the location of the reacting mixture, defined by [xMeOHF, xIBF, xnC4]∈[0, 1], and initial separation sequences have been generated according to the feed transformed-composition. In all the cases, high purity MTBE has been obtained.

Modelling and experimental validation of emulsification processes in continuous rotor–stator units

Despite the wide range of industrial applications of structured emulsions, current approaches toward process design and scale-up are commonly based on trial-and-error experimentation. As this design approach is foreseen to deliver most likely suboptimal process solutions, we propose in this contribution a model-based approach as the way forward to designing manufacturing processes of structured emulsions. In this context, process modelling and simulation techniques are applied to predict production rates and equipment sizing. Moreover, sensitivity analysis of the process model provides insight about potential bottlenecks in the process.

Dynamic modelling of the margarine production process

Abstract A mathematical model of the margarine production process was developed by considering the votator barrel as a series of well mixed stages and employing heat and mass transfer equations. The model was solved using a commercial simulation package to give predictions of product temperature, mechanical dissipation and heat transfer rate. These predictions were found to agree closely with experimental measurements. The process model has the potential to predict local temperature and shear conditions within an ice cream freezer and therefore represents an important first step towards systematic freezer design, and performance optimisation and scale-up based on product quality considerations.

Product Driven Process Design Method

Abstract In the last ten years much more processes are being reported to be designed through a process synthesis approach. It has been recognized during those years that (i) processes for structured products are more difficult to design through process synthesis; (ii) process synthesis is disconnected from product development. In a response to those shortfalls a number of authors have described that the gaps need to be filled, however no methodology extension has been proposed. In this work, we will present extensions to the conceptual process synthesis methodology to include (structured) product design. The whole design methodology spans from how the new product can enlighten the consumer, financial and supply chain boundary conditions, through an optimal flowsheet able to produce the desired product cost effectively. A real case study will be used to illustrate the applicability and scope of the proposed methodology

Prediction of Supercritical Carbon Dioxide Drying of Food Products in Packed Beds

Drying assisted by supercritical carbon dioxide is foreseen to become a promising technology for sensitive food products. In this contribution, a mathematical model is derived to describe the changes in water concentration in both a solid food matrix and a fluid carrier during drying. Finite different element method is used to solve the set of mass balance equations. A remarkable agreement between simulated and experimental data was obtained. Moreover, the simulated changes in water concentration in the solid and fluid carrier gave a coherent description of the process. This model can be used as a tool for optimizing the operating conditions and process scale-up in supercritical carbon dioxide assisted drying.

Modelling and simulation of extensional-flow units in emulsion formation

Here we studied the emulsification process carried out in an extensional-flow unit. By means of rigorous population and momentum balances we captured the phenomenological description of the first principles occurring in such unit. The strong feature of our model approach resides in the fully mechanistic description of the governing phenomena. A population balance equation was formulated and solved to account for the disappearance and appearance of droplets at each size class. Coalescence mechanism was included to account for the instability of newly created droplets. We validated the accuracy of the results obtained from our equation-based model with experimental data obtained at pilot-plant scale. The results obtained by simulation showed that at a given set of operational conditions and pre-emulsion properties the product obtained was within the desired and narrow specifications space. As a concluding remark we suggest further exploring the design and development of extensional-flow units for structured emulsions.

Mathematical Model for Simulating the Springback Effect of Gel Matrixes During Drying Processes and Its Experimental Validation

Volume change is one a fundamental aspect in characterization of drying processes. Several attempts to simulate the volume change during drying have been reported in the open literature. However, so far no theoretical approach has been used to support these simulations, especially when it comes to dealing with the springback effect. In this contribution, a theoretical model was built to predict the volume change including the springback phenomenon. The theory behind the present model is based on three physical mechanisms, which are represented by the shrinkage, collapse, and swelling functions. The resulting set of equations was implemented and solved in MATLAB(Mathworks, Inc., Natick, MA) by formulating the model as a constrained optimization problem. Data for three gels reported by an independent group and characterized by different profiles in terms of the springback effect were used to validate the model. This validation showed excellent agreement between the predictions obtained by this model and the experimental data. The average error lies somewhere between 1.6 and 4.4% depending on the gel. The information extracted from the parameters included in this theoretical model should assist in understanding the mechanisms that occur during processes involving moisture/solvent changes. Hence, the present model can be used as a reliable tool to predict volume changes and to understand the dynamic mechanisms involved in pore formation/disappearance during drying processes.

Mathematical description of mass transfer in supercritical-carbon-dioxide-drying processes

For thermo-sensitive food products, supercritical-carbon-dioxide (SC-CO2) drying process could be a promising technology. The process takes place in three steps: (i) removal of water from the food matrixes, (ii) adsorption of the water removed in the adsorber bed, and (iii) regeneration of the adsorber with hot air. In this investigation, a mathematical model is derived to describe the changes of water concentration in SCCO2, in the solid food matrix and in the adsober bed during the entire drying processes. The mass balance equations of the model involve several parameters such as the geometry of the autoclave and the adsorber bed, mass transfer coefficients, diffusion coefficients, equilibrium constants between the solids and the fluids, the specific interfacial area of the solid matrixes, the porosities of the packed beds, the SC-CO2 flowrate and the particle size. Preliminary results obtained with the model suggest that each parameter may contribute differently to the drying kinetics. This finding allows the identification of the bottlenecks encountered in drying processes and offer leads and strategies to overcome them. The present model could eventually be used as a tool for optimizing the operating conditions and process scale-up in SC-CO2 drying.