Journal of Energy Engineering

The nation's inland waterway system affords a means of transporting large objects limited only by channel depth, size of locks and bridge clearances. The concept of prefabricating standardized, hydroelectric powerhouses at shipyards, transporting them along the inland waterways and installing them at navigation dams without powerhouses was examined for the McClellan‐Kerr Arkansas River Navigation system. It was found that construction costs for the float‐in design was very close to those of conventional sitebuilt design. Experience at Greenup Dam on the Ohio River where a float‐in powerhouse has been installed indicated that construction time could be reduced if the float‐in design was used. This time saving, use of standardized designs and construction of the float‐in module at a shipyard may offer advantages that should be examined in more detail when the power potential of the nation's low navigation dams is assessed.

The development and testing of the concept of pulsed‐flow air classification for waste‐to‐energy production are discussed. Air classifiers, a potentially valuable unit operation in waste‐to‐energy production facilities, currently do not meet expectations. Standard designs generally lose large amounts of combustible material as well as produce a fuel that is high in metal and glass contaminants. Pulsed‐flow classification is presented as a concept which can avoid both pitfalls. Municipal solid waste (MSW) is composed of particles which can be cataloged as combustible and non‐combustible fractions by defining a density split between aluminum and plastic: generally all other non‐combustibles are more dense than aluminum, while all other combustibles are less dense than plastic. However, current designs for classifiers tend to separate by aerodynamic characteristics which do not always produce a split based on density alone. Pulsed‐flow classifiers are seen to offer a unique solution to this puzzle. In this paper, each aspect of theory and laboratory testing is presented, including: (1) Preliminary determination; (2) particle characteristics; (3) theory of pulsed‐flow classification; (4) experimental equipment; (5) laboratory testing; and (6) pulsed‐flow air classification for energy production. Conclusions from the research are summarized in the final section of the paper.

The impact of feed composition on the stability of air classification in waste‐to‐energy production facilities is analyzed. Vertical air classification is one means of separating combustible organic matter from non‐combustible inorganics typically found in municipal solid waste. Aerodynamically light organics ideally exit upward with air flow, while heavy inorganics ideally exit downward against the current. Problems develop in practice as organic matter is lost downward and inorganic matter exits upward to contaminate the fuel product. Utilizing a lab‐scale vertical classifier, the overall efficiency and the sensitivity of the efficiency to air velocity is determined for several feed compositions. Particle‐to‐particle interaction is observed for a variety of feed compositions, and the effect this interaction has on the quality of the fuel product is documented. Results suggest modification to the design and operation of waste‐to‐energy fuel production facilities. Feed material to the classifier that is high in organic matter is seen to be not necessarily useful in producing a clean fuel product. Pre‐processing techniques are suggested to polish this feed prior to air classification.

A general numerical model for the analysis of coupled fluid flow, thermal and mass transport in porous media was applied to assess feasibility of simultaneous cooling water supply and effluent disposal by wells. Hydraulic conductivities were calibrated using groundwater heads and flux data. Existing conditions, a Ghyben‐Herzberg lens in dynamic equilibrium, were modeled, and served as initial conditions for subsequent analysis. Various injection and supply well configurations were modeled and feasible configurations were identified. A number of conclusions were developed regarding flow velocities, cross‐circulation flow, hydraulic interchange with the adjacent ocean, heat removal mechanisms, effects on the fresh water lens, and ocean bottom heating.

A method has been identified for controlling acid production and subsequent dissolution of toxic pollutants in drainage from coal storage piles. Results of laboratory and field experiments indicate that it may be possible to prevent, rather than treat, acid drainage by periodically applying an environmentally safe detergent formulation to the coal. These experiments showed that a mild solution of sodium lauryl sulfate (SLS) effectively blocks the activity of the bacteria that promote acid formation and chemical leaching. Drainage from coal treated once with 50 mg/L of SLS remained neutral for 60 days, about three times longer than the untreated control sample. An extrapolation of results to an industrial‐scale application revealed that the cost of the SLS needed for a single application would likely be no more than $200 per acre of coal storage area ($500 per hectare) or, expressed per unit weight of coal, $4,000 per million metric tons.

Fluidized bed combustion in industrial applications offers many advantages from the resource utilization and the air quality points of view. A cash flow model is developed to predict the economic consequences of an investment in an industrial coal‐fired atmospheric fluidized bed combustion boiler. The return on investment is calculated for boilers in the range of 50,000 to 500,000 lb/hr. The investment costs range from $3.8 to $28.8 million, with calculated returns on investment from 8.4% to 14.2%. These returns are not adequate to justify the investment decision. A sensitivity analysis shows that the most influential variables are the costs of the fossil fuels—the net difference between the displaced natural gas and residual fuel oil vs. the coal used in the fluidized bed boiler.