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When working on design of intensified processes or develop of a new technology it is very important to have the necessary tools and criteria to select the best option. In this work the environmental impact and occupational health of twelve intensified reactive distillations processes to produce diphenyl carbonate are evaluated and studied, diphenyl carbonate is an important precursor of polycarbonate by a green route. These designs were selected due to their different attributes as low cost and bad controllability, high cost and good controllability and the intermediate case that has in balance the cost and controllability. These intensified processes are grouped in four different schemes: Conventional Reactive Distillation (CRD); Thermally Coupled Reactive Distillation (TCRD); Reactive Distillation with heat Integration (RDHI) and Reactive Distillation with Thermally Coupled and Heat Integration (THRD). The results show that all intensified processes presented important reductions of around 30% in environmental impact and 60% less occupational health risk. However, TCRD processes are the options that have the best balance between cost, controllability, environmental impact and occupational health.

Combustion of residual (waste) biomass represents an environmental hazard and a lost economic opportunity. The production of specialty chemicals provides a more attractive pathway to dispose of residual biomass; however, a problem that arises in recovering products from waste is that there are currently no well-established markets that bring together all stakeholders involved (e.g., biomass production, collection, transportation, and processing). In this context, coordination is essential as all the stakeholders in the supply chain (SC) depend on the revenue generated from the derived products. In this work, we propose a market coordination framework for the production of levulinic acid and furfural from lignocellulosic biomass (obtained from agricultural residues). Coordination brings a number of important economic benefits that would be difficult to achieve under existing markets (which are uncoordinated and based on peer-to-peer transactions). We demonstrate insights provided by our framework by using a case study for the State of Guanajuato in Mexico. Our results indicate that production of 330,000 tonnes per year of levulinic acid and 394,000 tonnes per year of furfural can be achieved. This constitutes 3% of the annual global demand for methyltetrahydrofuran. The SC is designed around a single biorefinery and the SC creates a total value of 3.57 billion USD per year and draws 64.65% of the available biomass supply. Our results also indicate that this market would avoid the generation of 850,000 tonnes of CO2 annually (corresponding to a 34% reduction in emissions from the combustion of agricultural residues). As such, the deployment of such a market can bring both economic and environmental benefits.

Polycarbonate has a very extensive commercial application thanks to its multiple physical properties. The environmental problems associated with the conventional process to obtain polycarbonate by the phosgene route has stimulated the research of intensified schemes as is the case of the reactive distillation for the synthesis of Diphenyl Carbonate (DPC). These intensified processes are complex in their structure because of the several degrees of freedom and are subject to be optimized in terms of crucial criteria such as the cost and the control properties. This work presents the multi-objective optimization involving cost and control properties of four intensified systems configurations to produce DPC: a conventional reactive distillation (CRD), a thermally coupled reactive distillation (TCRD), and two novel configurations which uses vapor recompression technology, a reactive distillation with heat integration (RDHI) through vapor recompression, and a reactive distillation with thermally coupling and heat integration (THRD) through vapor recompression. The results of the multi-objective optimization show that the tray holdups and diameter values of the columns strongly influence the control properties; thus, for large values of the tray holdups and diameters, the control properties were better. The control properties also were influenced by the presence of the interlinking streams in the reactive and separation columns, in particular, the presence of one interlinking stream tend to favor the control properties of a configuration. To close it is important to remark that the TCRD configuration was the most attractive arrangement to be implemented to produce DPC, mainly because the optimized designs showed the best control properties, and also the optimized designs achieved significant energy savings because they did not require electric power.

Silane has found recent applications in the manufacture of solar photovoltaic cells, which provide solar power economically. One method for the production of silane takes trichlorosilane as a starting molecule, with a reaction mechanism that involves two other intermediate valuable products, dichlorosilane and monochlorsilane. The production system involves a series of reactors and separation steps that can be intensified via reactive distillation. In this work, optimal designs of reactive distillation systems for the production of trichlorosilane, dichlorosilane and silane are developed. Furthermore, a multi-product reactive distillation system for the production of any of these types of silane products is designed. It is shown that an intensified design can be obtained for the production of the three silane products using the same column. The operating conditions at which the columns should be adjusted for the production of each product are reported.

A hybrid polycrystalline silicon production route is optimized following a two-step procedure. First, surrogate models for the main units are developed following different techniques which depend on the available information. Secondly, the optimization of the entire process flowsheet allows determining the optimal tradeoff between yield and energy consumption. A base production capacity of 2000 t/y of polycrystalline silicon is considered, with an equipment cost of 9.97 M$. Three scenarios are evaluated: maximum silicon production, minimum operating costs and maximum total profit. The maximization of the total profit is the most promising scenario, obtaining a selling price of 8.93 $/kgPoly, below the commercial price, 10 $/kgPoly. The revenue obtained is 10 M$/y, with an operating cost of 6.48 M$/y. Furthermore, a plant scale-up study was performed. If the production capacity is increased by a factor of 10, it results in a reduction of 1.03 $/kgSiPoly.

This paper presents a new optimization approach for the simultaneous structural optimization of process flowsheets with the operating conditions through combining process simulators with metaheuristic techniques. The proposed approach allows optimization of a superstructure in process simulators and reduce the computation time. A superstructure for different configurations for producing solar-grade silicon is considered, which includes three different configurations for solar-grade silicon production (Siemens Process, Intensified FBR Union Carbide Process, and Hybrid Process). The operating conditions with major impact in the performance of each of the proposed configuration were considered as decision variables. The improved multi-objective differential evolution (I-MODE) algorithm was selected as search method from others metaheuristic techniques because its efficiency to solve multi-objective problems in a short central process unit (CPU) time. The optimization algorithm consists in linking the process simulator software Aspen PlusTM with the metaheuristic technique. The results offered attractive options for the considered objective functions in the addressed case study.

This work presents a reactive distillation column for the catalytic disproportionation of trichlorosilane to silane which includes three consecutive reversible reactions. This reaction system is however characterized by a large distinction in the boiling points of the components, which make the reactive distillation extremely favored. Nevertheless, the normal reactive distillation column possesses the shortage of high refrigeration requirement. By removing heat at temperature higher than that at the condenser a superstructure representation, rigorous simulations, and optimization problems were combined to derive optimal reactive distillation columns which can realize heat integration between stages and utilities at several refrigeration conditions. An iterative simulation-optimization procedure was proposed to consider temperature changes in stages due to heat integration. The results showed that the installation of two inter-condensers results in the best option with economic savings up to 56%.

a b s t r a c t Recently, a two-step biodiesel production process which uses short-chain alcohols at supercritical con- ditions has been proposed. In addition, literature reports suggest that the COSMO-SAC thermodynamic model is a suitable alternative for the prediction of VLE for supercritical methanol/methyl esters mix- tures. Thus, in this work a simulation study of the two-step supercritical method for the production of biodiesel is performed by using the COSMO-SAC model. Further, alternative system configurations for biodiesel production based on reactive distillation are proposed and their total emissions are compared to those corresponding to the conventional catalytic method. The study demonstrates the benefits of using reactive distillation for the esterification step and discusses the environmental impact of the supercritical production process. It has been found that the intensified alternatives reduce the emissions considerably and, through the reuse of the excess methanol, the emissions level of the supercritical process can be compared to those of the catalytic method.

The design and optimization of a coupled multicomponent distillation system is a non-linear and multivariable problem. The complexity of this kind of problem results in high solving difficulty. This paper addresses the application of genetic algorithms to the optimization of intensified distillation systems for quaternary distillations. We used a multiobjective genetic algorithm with restrictions coupled to the Aspen Plus™ process simulator for the evaluation of the objective function. Several mixtures to test the effect of relative volatilities of feed mixtures on energy consumption, second law efficiency, total annual cost and theoretical control properties have been studied. Numerical performance shows that this design tool is robust and suitable for the design of coupled multicomponent distillation sequences.

Thermally coupled distillation systems (TCDS) have been proposed to perform distillation separation tasks with the incentive of achieving lower energy consumption levels with respect to conventional distillation sequences. In particular, the presence of recycle streams for TCDS schemes has influenced the notion that control problems might be expected during the operation of those systems with respect to the rather well-known behavior of conventional distillation sequences. That has been one of the main reasons for the lack of industrial implementation of thermally coupled distillation schemes. Recently, some alternatives to thermally coupled distillation arrangements that might provide better operational properties than the complex columns have been proposed. In this work, we analyze the control properties of two alternatives to the coupled systems. The results indicate that a reduction in the number of interconnections in alternate configurations does not necessarily provide an improvement of controllability properties.

The understanding of the dynamic behavior of distillation columns has received considerable attention due to the fact that distillation is one of the most widely used unit operations in chemical process industries. Thermally coupled distillation sequences (TCDS) can provide significant energy savings with respect to the operation of sequences based on conventional distillation columns. TCDS exhibit a complex structure, with recycle streams, that appear to affect their controllability properties. One potential solution to this problem has been suggested through the operation of TCDS under conditions that do not provide minimum energy consumption. The basic idea is that if one changes the operation point, the control properties might change as well. In this work, we analyze the dynamic behavior of two TCDS structures under different operating points, including the one with minimum energy consumption. The control analysis properties are analyzed with the application of the singular value decomposition technique at zero frequency and closed-loop dynamic responses using standard PI controllers. The results show that the controllability properties of distillation sequences may change significantly depending on the selected operation point.

The Petlyuk distillation configuration has received considerable attention because of its efficiency to reduce the energy required for the separation of ternary mixtures. The structure of the Petlyuk system offers some control challenges arising from the transfer of vapor streams back and forth between the columns. This means that neither of the columns can have a uniform lower nor higher pressure. Recently, some alternate Petlyuk-like schemes that might provide better operational properties than the Petlyuk column have been proposed. In this work, we analyze the control properties of six alternative thermally coupled distillation schemes to the Petlyuk system. The theoretical control properties are analyzed with the application of the singular value decomposition technique. Rigorous closed loop simulations are used to supplement the theoretical analysis. The results indicate that a reduction in the number of interconnections of the Petlyuk configuration does not necessarily provide an improvement of its controllability properties.

A comparative analysis of the feedback control responses to set point changes of three thermally coupled distillation schemes and two conventional distillation sequences for the separation of ternary mixtures is presented. Designs for the thermally coupled schemes were obtained and optimized for energy consumption to link their energy characteristics to their dynamic behavior. For the comparison of the dynamic behavior, responses to set point changes under closed loop operation with proportional-integral (PI) controllers were obtained. For each separation scheme, the parameters of the PI controllers of the three composition control loops were optimized using the integral of the absolute error criterion. The effects of feed composition and of the ease of separability index were considered. The dynamic tests showed that in many cases the thermally coupled distillation schemes outperformed the dynamic responses of the conventional distillation sequences. The results indicate that there exist cases in which the energy savings provided by the thermally coupled systems do not conflict with their dynamic properties.