Journal of Energy Engineering

Field experience with air classifiers in waste‐to‐energy has indicated the need for redesign. Previous work indicates a heed to achieve separation based more on density and less on aerodynamic characteristics than is possible with current classifier technology. The development of the concept and theory of pulsed‐flow air classification are summarized. Methodology and equipment for testing various air classifiers are described. Laboratory experimentation shows that pulsed‐flow air classification is capable of superior separations by density than conventional classifiers. Comparisons with other types of air classifiers, including passive pulsing classifiers, show the active pulsed‐flow air classifier to be superior. Continuous‐feed comparison testing with a conventional zigzag classifier shows the superiority of the active pulsed‐flow system both in terms of separation efficiency and operational considerations, which are extensively discussed.

In 1980, the Department of Energy's Laramie Energy Technology Center conducted a steam‐driven tar sand recovery experiment near Vernal, UT. This experiment yielded 1,150 barrels of bitumen and 6,250 barrels of process water, which was highly contaminated with emulsified oils and dissolved organics. The process waters were successfully treated by bench‐scale, continuous‐flow air flotation (AF), but significant amounts of very dilute sludge were generated. The present study investigated the effects of adding a second flotation stage to the AF system to thicken stage I sludge, produce a clean effluent suitable for recycling, and thereby increase the hydraulic efficiency of the system. Key stage II operating variables were polymer dose, air flowrate, and liquid residence time. These were optimized to minimize sludge volume and maximize effluent quality and volume. Total organic carbon and total suspended solids removals in the stage II system were 96 and 99%, respectively. Overall sludge production equalled about 2% of the total influent flow.

The performances of two pulsing air classifiers are compared to the performances of two nonpulsing classifiers in a waste‐to‐energy application. Four laboratory scale classifiers are constructed and the air flow regimes are documented. Particle separation data is obtained and evaluated. Performances of the respective classifiers are compared and conclusions are drawn that indicate the relatively large advantages of the passive pulsing classifiers under consideration. Four laboratory scale classifiers are constructed with varying wall configurations: pulsing stacked triangle and zag‐zag, and nonpulsing straight and zig‐zag. Documented flow regimes illustrate pulsing actions that are suggested to be responsible for the observed superior performances of the pulsing classifiers. The two pulsing classifiers are seen to exhibit greater maximum efficiencies and to maintain those relatively greater efficiencies over a much wider range of air flows through the classifier throats. The potential thus exists for a less contaminated waste‐to‐energy fuel as well as reduced loss of valuable combustible organic materials in the process.

A fully reversible axial machine in a tidal power plant has to perform turbining and pumping in both normal and reversed directions of flow. Runner blades having “S” cambered profile are found to be suitable for all four modes of operation. Cascade characteristics of four “S” blade profiles are presented and compared in this paper. “S” profiles with maximum camber of about 5% of chord length is found to be suitable.

A joint effort between the Department of Energy and private industry through the Electric Power Research Institute combined various subsystems at the Central Receiver Test Facility (CRTF) in Albuquerque, NM, with a steam generator and a turbine/generator to produce electric power. This effort demonstrates the feasibility of using molten salt as the primary medium for energy transfer from a central tower solar receiver through thermal storage to a steam generator. A conventional steam turbine converts the energy by means of the electric generator for delivery of electrical power to the utility grid. The Molten Salt Electric Experiment (MSEE) uses a 5 megawatt thermal $\left(5{\mathrm{MW}}_t\right)$ solar receiver, which was successfully tested in 1980, to produce 566 °C (1,050 °F) liquid sodium nitrate‐potassium nitrate (60/40) from a 310 °C (590 °F) feed supply at the rate of 43,900 kg/h (97,000 lbs/hr). (${\mathrm{MW}}_t=\mathrm{electrical}$ equivalent of Btu/hr of thermal energy absorbed by a soiar receiver.) The hot molten salt then flows into a storage subsystem which was tested successfully in 1981. Checkout of the integrated molten salt system has been underway since the later part of 1983. Design considerations for handling molten salt and precautions required to maintain the liquid phase [melting point 221 °C (430 °F)] will be examined.

A simple approximate calculation is presented for the evaporated volume from a reservoir forced by a heat load rejected to that reservoir. The method explicitly incorporates the effect of meteorology through the parameters of natural (unloaded) water temperature and wind speed, and is therefore more accurate than the traditional volume/unit-energy relations.