Dividing-wall Column Technology Research Articles

Operation, validation and model comparison for a reactive dividing wall column

The reactive dividing wall column (RDWC) is a highly integrated apparatus that combines the features of reactive distillation and dividing wall column technology. The high degree of integration results in complex interactions between vapour-liquid equilibrium, chemical reaction and component distribution. This leads to a considerably more complex column design and operation than for conventional distillation columns. Therefore, precise simulation models are a prerequisite for a successful implementation and operation of this technology. A newly developed rate-based (NEQ) RDWC model for packed columns is presented and a detailed investigation on the influence of separation modeling was carried out. Comprehensive experimental RDWC data are presented for the reference system of the butyl acetate transesterification with hexanol and employed for a model validation. The validation results for the NEQ model are compared to the well-known equilibrium stage (EQ) approach. The rate-based model is shown to predict the inner flows and concentrations of the column with higher precision. Furthermore, an analysis of the validation results enhances the understanding of the interactions between separation, chemical reaction and reactant conversion.

Eco-efficient butanol separation in the ABE fermentation process

Abstract Butanol is considered a superior biofuel, as it is more energy dense and less hygroscopic than the more popular ethanol, resulting in higher possible blending ratios with gasoline. However, the production cost of the acetone-butanol-ethanol (ABE) fermentation process is still high, mainly due to the low butanol titer, yield and productivity in bioprocesses. The conventional recovery by distillation is an energy-intensive process that has largely restricted the economic production of biobutanol. Other methods based on gas stripping, liquid-liquid extraction, adsorption, and membranes are also energy intensive due to the bulk removal of water. This work proposes a new process for the butanol recovery by enhanced distillation (e.g. dividing-wall column technology) using only few operating units in an optimized sequence to reduce overall costs. A plant capacity of 40 ktpy butanol is considered and purities of 99.4 wt% butanol, 99.4 wt% acetone and 91.4 wt% ethanol. The complete downstream processing was rigorously simulated and optimized using Aspen Plus. The enhanced process is effective in terms of eco-efficiency (1.24 kWh/kg butanol, significant lower costs and emissions) and can be readily employed at large scale to improve the economics of biobutanol production.

Novel applications of dividing‐wall column technology to biofuel production processes

AbstractBiofuels enjoy nowadays increased public and scientific attention, driven by key factors such as volatile oil price, the need for increased energy security, and concerns over greenhouse gas emissions from fossil fuels. However, in order to make biofuels a competitive alternative, the cost of production has to be significantly reduced by using enhanced process technologies. Distillation is heavily involved in the production processes of biofuels—taking the blame for the high energy requirements that have a negative impact on the operating costs. Dividing‐wall column (DWC) is one of the best examples of proven industrial process intensification technology in distillation, as it allows significantly lower investment and operating costs while also reducing the number of equipment units and the carbon footprint.This work presents an overview of novel applications using the DWC technology in the production of the most important biofuels, by employing multi‐component separations, azeotropic, extractive or reactive distillation in a DWC: enhanced methanol recovery and glycerol separation in biodiesel production, synthesis of fatty acid methyl esters and dimethyl ether (DME) by reactive distillation, integrated DME purification and methanol or CO2 recovery in the dimethyl ether process, as well as bioethanol concentration and dehydration. The industrially relevant case studies presented here show that significant energy savings are possible (ranging from ∼20 to 60%) while simplifying the processes by using less equipment that requires a lower plant footprint. Remarkably, in most cases there is also the possibility of revamping existing plants producing biofuels, and thus reusing the already available equipment. © 2013 Society of Chemical Industry