Resource Recovery and Conservation最新文献

The burning of municipal waste as a means of waste removal has been carried out on a commercial scale in Western Europe for more than a hundred years. The development of incineration processes designed to utilize the energy contained in the waste was slow, but has gained considerable impetus in recent times because of current shortages of energy.

The following objectives are particularly important as regards the improvement and further development of waste incineration facilities: raising the level of energy efficiency; reducing harmful emissions; and increasing plant reliability essentially through the reduction of corrosion problems. It should be examined whether flue gas recirculation represents a suitable means for optimizing waste incineration. This involves ascertaining how flue gas recirculation, i.e. the return of a part of the flow of flue gases from the boiler outlet back into the combustion chamber, affects the energy balance of the entire process, the formation of harmful material, and the degree of damage caused by corrosion and erosion.

This first article reviews general recirculation experiences to date and their special application to municipal waste incineration. It also shows the possible effects of flue gas recirculation on waste incineration but without detailed data. Data will be published later.

An outline of laboratory-scale investigations of pyrolysis is followed by a description of pilot-scale experiments designed to exploit the raw material content of polymeric substances rather than their heating value merely as fuels. Dependent on the feed material, gaseous products (40–60 wt.%, e.g. hydrogen, methane, ethylene, ethane) as well as liquid products (40–60 wt.%, mainly simple aromatics) are obtained. The gas is sufficient to heat the process.

Fluid sand beds are surprisingly insensitive to the unit size of the feed material, so that scrap tyres can be pyrolyzed as a whole to avoid the cost of size reduction. Carbon soot and fillers are separated in a cyclone and metal pieces can be removed from the inclined bottom of the reactor. Results for a 2 Mg/day pilot plant are presented and a preview of a 4000 Mg/year plant is given, for which cost—benefit calculations are compared with those of some other scrap tyre pyrolysis processes.

A fluidization test system was designed and constructed for measurement of fluidization parameters for fly ashes and fly-ash—charcoal mixtures as part of continuing research on aluminum recovery from power plant fly ash by the HiChlor process. Bituminous and sub-bituminous coal fly ashes were tested and significant differences in fluidization characteristics were observed. Fly ashes which had been mechanically collected fluidized uniformly at low air flow-rates. Electrostatically precipitated fly ashes exhibited channeling tendencies and did not fluidize.

Fluidization characteristics of electrostatically collected ashes improved when pulverized charcoal was added. Fluidization of the mixtures was aided initially by a mechanical stirrer. Once fluidized, the mixtures would refluidize without stirring. Smooth fluidization and large bed expansion were observed. A fly-ash—coal mixture fluidized only after being oven-dried.

This paper presents one year's (June 1976–May 1977) operational and economic information in the refuse-derived fuel pneumatic transport and storage subsystems of the Ames, Iowa, solid waste recovery system. A review of the system design is also included. Resultant average cost per unit mass is $8.60/Mg, of which 63% is capital, 16% is labor and the remainder is electrical energy and repair.

Decisions must be made soon in the Netherlands in regard to the new Waste Disposal Act with respect to future waste treatment methods. For this reason, there is a need for data related to the specific waste composition in the Netherlands. Three research projects in the field of thermal treatment have been started recently: fluid-bed combustion, cocurrent gasification, and spouted-fluid-bed pyrolysis. A brief description of the basic research program and the processes involved is presented. The final evaluation of the three processes is expected to be completed in about two years.