Energy-saving design and optimization of pressure-swing-assisted ternary heterogenous azeotropic distillations

A huge amount of energy is always consumed to separate the ternary azeotropic mixtures by distilla-tions.The heterogeneous azeotropic distillation and the pressure-swing distillation are two kinds of effective technologies to separate heterogeneous azeotropes without entrainer addition.To give better play to the synergistic energy-saving effect of these two processes,a novel pressure-swing-assisted ternary heterogeneous azeotropic distillation(THAD)process is proposed firstly.In this process,the ternary heterogeneous azeotrope is decanted into two liquid phases before being refluxed into the azeotropic distillation column to avoid the aqueous phase remixing,and three columns'pressures are modified to decrease the flowrates of the recycle streams.Then the dividing wall column and heat integration technologies are introduced to further reduce its energy consumption,and the pressure-swing-assisted ternary heterogeneous azeotropic dividing-wall column and its heat integration structure are achieved.A genetic algorithm procedure is used to optimize the proposed processes.The design results show that the proposed processes have higher energy efficiencies and lower CO2 emissions than the published THAD process.     

Ceramic Membranes for Water Separation from Organic Solvents

Novel hydrophilic SiO_x modified alumina membranes with high separation factors and flux rates have been prepared for the separation of water from organic solvents. For the preparation of the membranes, SiO_x networks are deposited inside the γ‐Al₂O₃ layer of a commercial ultrafiltration membrane by hydrolysis of tetraethylorthosilicate in autoclaves at 250 °C. The transport resistances of the individual membrane layers for the permeation flux are described by a model. The membranes are stable towards solvents to temperatures of at least 150 °C. Pervaporation studies show that water can be separated from solvents such as acetonitrile, tetrahydrofurane, 2‐propanol, ethyl alcohol, dimethylsulfoxide, N, N‐dimethylformamide, and phenol. The separation performance of the membranes allows their use in technical separation processes, especially for the removal of water.     

Unified targeting algorithm for diverse process integration problems of resource conservation networks

A single algorithm is developed to establish minimum resource targets for diverse process integration problems including those of heat/mass exchange, water, hydrogen, carbon emission and material reuse networks. Previous algorithms such as the problem table algorithm for heat exchange networks and the composite table algorithm for resource allocation networks are special cases of the newly proposed unified targeting algorithm (UTA). The conversion of streams to equivalent inlet-outlet (demand-source) pairs is shown to be a key basis for the unified approach. The tabular data from the UTA may be plotted to obtain the grand composite curve (GCC) or the limiting composite curve (LCC). These provide graphical representations of the net load deficit/surplus at various levels for resource targeting and pinch identification. For allocation networks with system loss/gain, the UTA with increasing level sort order yields the Deficit LCC to target the minimum resource, whereas the UTA with decreasing level sort order provides the Surplus LCC to target the minimum waste/excess. A single UTA calculation along with the use of fundamental overall system balance equations is sufficient to establish complete targets for a problem. Six practical case studies from diverse domains are presented to illustrate the detailed steps of the UTA.     

Small Electrocyclone Performance

Cyclone Separators and Electrostatic Precipitators (ESPs) are both effective particle separators. The former are more efficient at removing the larger particles, while the latter more suited to removing the smaller size classes. We explore the performance of an “Electrocyclone”, constructed by simply retrofitting an electrode coaxially to a small existing “Whitby” cyclone. Tests were performed with respect to particle size, resitivity, loading and various other operating parameters. Non‐electrical separation efficiencies ranged from 71 to 75 % and with the application of additional electrical forces the increase in separation efficiency was between 17 and 21 % at a cyclone Reynolds number of 19000, with the most conductive particle most easily separated. Further parametric testing correlated the effects of dust loading, electrocyclone Reynolds Number and particle cut upon separation efficiency. In particular we show that the separation of the smallest size cuts (D < 38 μm) of the dust sample almost doubled upon application of the corona. We conclude, based on this initial study of small devices, the range of use of cyclones may be extended significantly by the application of additional electrophoretic separation.     

Liberation and Separation of Valuables from Building Material Waste

In general a recycling process starting with development, planning, production, utilization and disposal of a product, e.g., of a building, during its lifetime may be regarded as a system of material cycles. The main object is to minimize the input of raw materials and the output of waste for every stage of a building. These material cycles may be designed by reprocessing the building material waste to valuables of high quality. To approach this aim a joint research project dealt with the liberation and separation of aggregates (d = 2–16 mm) from concrete waste. The liberation is accomplished by a pneumatic cannon to simulate the stressing in impact crushers. With this cannon spherical concrete samples (d = 150 mm) are comminuted. The comminution is evaluated by the liberation grade. Fully liberated, partially liberated and non‐liberated particles are distinguished. The experiments show an unexpectedly high liberation grade of up to 95% with a comparably small specific energy consumption of about 1 kWh/t. For separating both fully liberated and partially liberated aggregate, a pilot scale zigzag apparatus consisting of a zigzag channel, an air cyclone, a blower, a filter and a feeding system was used. If the diameter of the particles is kept nearly constant (e.g., by sieving) a multi‐stage density separation in a turbulent cross‐flow channel can be carried out. The separation performance may be evaluated by means of the separation function or grade efficiency curve, respectively. For the partially liberated aggregate a comparably good grade sharpness of about 0.74–0.84 is obtained for a 15‐stage zigzag apparatus with different particle size fractions and particle contents in air.