A new energy-integrated pervaporation distillation approach

Hybrid-pervaporation-distillation processes have been intensely studied in the last years and considered as a good alternative in the separation of homogeneous azeotropic mixtures. Compared with the techniques in use in the chemical industry, they can reduce the energy consumption and avoid the use of entrainers. However, due to the evaporation enthalpy, a temperature drop is presented along the membrane and external heat exchangers are required between two consecutive pervaporation steps. In the present paper, a process approach has been developed in order to avoid the external energy support and the temperature drop along the module. The novel energy integration concept utilizes the distillate vapor stream of a distillation column as heating medium in the membrane. The vapor condenses partially and energy is released directly into the module. For the study of the new energy integrated process, a novel membrane configuration is developed and a mathematical model is built. Simulation results show that the new process can yield to higher permeation fluxes and smaller temperature drop in the membrane, what also means a reduction in the required membrane area, if a constant purity in the product is considered. Due to the energy integration concept, there is no need of external heat supply in the pervaporation and the permeate flux rises, which can reduce the operation and investment costs.

In the present paper, a novel heat integration concept for a hybrid distillation pervaporation process has been developed and two membrane module designs have been presented. Simulation results show that using heat integration obtains increase of product purity (up to 30% in the present case study) and significant membrane surface reduction if desired product purity is fixed. With the new process design an increase in the turbulence and a decrease in the temperature and concentration polarization phenomena (problems of the pervaporation performance) are solved. It has to be pointed out that no additional external energy supply is needed in the pervaporation process because the condensation energy of the distillate stream is sufficient for heating the membrane module.