Industrial ecology approach to management of fly ash from fluidized bed combustion: Production of slow-release fertilizer and soil conditioner.

摘要

Coal has been a major energy source since the Industrial Revolution. Despite its environmental problems, coal consumption is still growing because of the lack of alternatives such as natural gas and petroleum resources. As a result, more than 50 million metric tons of fly ash are generated by the electric utilities in the United States yearly, almost one-third of which is used in a number of applications. Alternatives for the reuse of fly ash in the United States and Puerto Rico previously considered are mostly for low-technology uses and they have had limited success. Thus, many attempts to utilize the fly ash are currently underway, focusing on the high-technology and high-value areas.; An alternative for management and final disposal of the fly ash generated at a fluidized bed (FBC) coal-fired power plant which is in harmony with the principles of industrial ecology was thoroughly studied. It was demonstrated that the ash can be pelletized by reacting it with a proper binder (KOH or KC1 solutions) and sintering the pellets at temperatures between 400 and 600°C for periods of time ranging from 30 to 120 min, producing in the process a potassium fertilizer and soil conditioner. The product, containing about 10% by weight slow-release K2O, was found to be of great potential value for agricultural purposes, especially for, but not limited to, tropical areas. The product was also found to be safe from the points of view of health and the environment. The transport of certain trace elements leached from the pellets through the soil was simulated using the software package Hydrus-1D.