Developments In Thermal Treatment Technologies

A 2007 WTERT survey (1) showed that the
global waste-to-energy capacity (WTE)
increased in the period 2001-2007 by about 4
million metric tons per annum. By far, the
principal technology used globally for energy
recovery from municipal solid wastes is
combustion of “as received” MSW on moving
grates (“mass burn” or stocker technology). The
three dominant grate technologies, by Martin,
Von Roll, and Keppel-Seghers, represent about
75% of the total growth in capacity. In the same
period, Japan and China built several plants that
were based either on the direct smelting or on
fluid bed combustion of solid wastes. In China,
there have been some mass-burn new plants and
also over forty circulating fluid bed WTEs, using
technologies developed by the Institute of
Thermal Power Engineering of Zhejiang
University and by the Institute of Engineering
Thermophysics of the Chinese Academy of
Sciences. WTE technologies in China are
actively supported by the national and local
governments and many more plants are projected
as sprawling cities are running out of landfill
space. Japan is the largest user of thermal
treatment of MSW in the world (40 million
tonnes) and some of the newest plants use stoker
technology, such as the Hiroshima WTE
designed by the famous architect Taniguchi and
the Sendai WTE that uses advanced oxygen
enrichment technology. However, there are also
over 100 thermal treatment plants based on
relatively novel processes. The Direct Smelting
and the Ebara fluid bed technologies developed
in Japan require pre-processing of the MSW,
combust the resulting syngas to generate steam,
and produce a vitrified residue. The
Thermoselect Gasification and Melting
technology, originally developed in Europe, has
been adopted successfully in seven Japanese
facilities by JFE, a company with extensive
experience both in high temperature metal
processing and with various MSW thermal
treatment technologies, including mass burn.
This paper also includes a brief report on the
results of a study by WTERT on ways to increase
beneficial uses of WTE ash in the U.S.