Energy efficient concentration

With the increasing fuel prices, it becomes more and more important to find energy efficient concentration methods for industrial effluents. Hyperfiltration (HF).also called reverse osmosis is in several cases the most favorable method. 

Kita et al. (2003) reported on a tubular-type PV and vapor permeation module with zeolite membranes for fuel EtOH production. They used two types of zeolite membranes (i) NaA-type zeolite membrane, which was grown on the surface of a porous cylindrical mullite support and (ii) T-type zeolite membrane, which was also grown hydrothermally on the mullite support. Both membranes were studied for the flux and the separation factor of PV and vapor permeation for water-alcohol mixtures at 50°C and 75°C. The membranes were selective for permeating water preferentially with the high permeation flux. The separation factor of the T-type zeolite membrane was slightly smaller than the NaA zeolite membrane. They also claimed that this can provide more energy-efficient concentration of the EtOH to fuel grade EtOH. 

J. Douglas and A. Amamath, Free Concentration an Energy-Efficient Separation Process, EPRI Journal, p. 17,1989. 

The carbons are broadly comparable in terms of their maximum concentration and implied energy efficiency but the two monolithic forms offer the advantage of smaller pressure vessel sizes and improved heat transfer. 

Flue gas recirculation (FGR) is the rerouting of some of the flue gases back to the furnace. By using the flue gas from the economizer outlet, both the furnace air temperature and the furnace oxygen concentration can be reduced. However, in retrofits FGR can be very expensive. Flue gas recirculation is typically applied to oil- and gas-fired boilers and reduces NO, emissions by 20 to 50%. Modifications to the boiler in the form of ducting and an energy efficiency loss due to the power requirements of the recirculation fans can make the cost of this option higher. 

A process is inherently safe in a rigorous sense, when no fluctuation or disturbance can cause an accident. To search for synthetic routes that avoid hazardous reactants, intermediates, and reaction mixtures, is an impetus to be seriously considered by chemists and process designers. Nevertheless, there will always be a need to cope with potentially hazardous materials and reaction mixtures in future process design work, the more so because process streams are expected to become potentially more dangerous in the future. The process streams will be more concentrated to increase energy efficiency, to ease purification, and to decrease the load of wastewater and spent acids. More concentrated process streams have a higher specific content of latent energy and are hence less stable. 

Energy-efficient houses have been shown to have higher radon concentrations than others. In the Netherlands, for example, rooms with double-glazed windows were found to have radon concentrations twice as high as those in rooms with single-pane windows (Wolfs et al, 1984). New York energy-efficient houses with heat storage masses had radon concentrations 1.6 times those for conventional homes (Fleischer and Turner, 1984) and in Sweden the same enhancement in radon concentration is found (Nyblom, 1980). 

Nero, A.V., M.L. Baegel, C.D. Hollowell, J.G. Ingersoll, and W.W. Nazaroff, Radon Concentrations and Infiltration Rates Measured in Conventional and Energy-efficient Houses, Health Phys. 45 401 (1983). 

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