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The hydrogen in the vent gas stream of the hydrocracker (used to produce bio-jet fuel) cannot be reused since it has many impurities. The metal membrane can be a potential candidate for recovering hydrogen from this vent gas. In this work, the authors report the development of a composite palladium membrane and its application, for the first time, in the recovery of hydrogen from a simulated vent gas environment. A dense thin film (thickness ~3 µm) of Pd metal was coated on a ceramic support tube by the sputter deposition technique. The hydrogen permeance of the Pd membrane was found to be 18.75 × 10-6 mol·m-2·h-1·Pa-1, which was reduced to 3.25 × 10-6 mol·m-2·h-1·Pa-1, with an exposure of 100 h in the simulated bio-jet fuel environment. To avoid the loss of permeability, a thin layer of Pt can be coated over the Pd membrane. The present study used MATLAB software to simulate the Pt-coated Pd composite membrane performance in the bio-jet fuel production environment. Simulation studies confirmed that a membrane area of ~95 cm² (250 mm length and 12 mm OD) is sufficient for the complete recovery of hydrogen from the vent gas stream of hydrocracker at a feed velocity of 0.075 m/s. [ABSTRACT FROM AUTHOR]

A Ranque-Hilsch Vortex Tube (RHVT) is a device that can cause simultaneous thermal and species separation in a compressible fluid mixture. The binary mixture is compressed and tangentially introduced into the vortex chamber of the RHVT, and two streams are withdrawn at opposite ends of the device. The RHVT acts as a centrifugal separator that separates the mixture into two streams, one enriched and the other depleted of the component with higher molecular weight. The extent of separation depends on the magnitude of swirl velocity of gas mixture inside the RHVT. Now a new combined heat and mass transfer model using heat and mass transfer analogy has been proposed by the authors to predict the species separation in a RHVT. The aim of this paper is to use this model to estimate the magnitude of swirl velocity of gas mixture inside the RHVT. The estimated values have been compared with range of experimentally as well as numerically obtained values reported in the literature. For a given configuration in published literature and values of cold mass fraction the average swirl velocity inside the RHVT was found to vary between 90 m/s and 130 m/s. It is found that for a fixed value of inlet pressure, average swirl velocity is a function of cold mass fraction. The value of average swirl velocity minimizes near cold mass fraction = 0.3 and maximizes near cold mass fraction = 0.8. Parametric studies have been carried out to understand the effect of important RHVT parameters on swirl velocity. Also relation between swirl velocity and species separation has been explored. [ABSTRACT FROM AUTHOR]