Geotechnical/geochemical characterization of advanced coal process waste streams

摘要

Thirteen solid wastes, six coals and one unreacted sorbent produced from seven211u001eadvanced coal utilization processes were characterized for task three of this 211u001eproject. The advanced processes from which samples were obtained included a gas-211u001ereburning sorbent injection process, a pressurized fluidized-bed coal combustion 211u001eprocess, a coal-reburning process, a SO(sub x), NO(sub x), RO(sub x), BOX 211u001eprocess, an advanced flue desulfurization process, and an advanced coal cleaning 211u001eprocess. The waste samples ranged from coarse materials, such as bottom ashes and 211u001espent bed materials, to fine materials such as fly ashes and cyclone ashes. Based 211u001eon the results of the waste characterizations, an analysis of appropriate waste 211u001emanagement practices for the advanced process wastes was done. The analysis 211u001eindicated that using conventional waste management technology should be possible 211u001efor disposal of all the advanced process wastes studied for task three. However, 211u001esome wastes did possess properties that could present special problems for 211u001econventional waste management systems. Several task three wastes were self-211u001ehardening materials and one was self-heating. Self-hardening is caused by 211u001ecementitious and pozzolanic reactions that occur when water is added to the 211u001ewaste. All of the self-hardening wastes setup slowly (in a matter of hours or 211u001edays rather than minutes). Thus these wastes can still be handled with 211u001econventional management systems if care is taken not to allow them to setup in 211u001estorage bins or transport vehicles. Waste self-heating is caused by the 211u001eexothermic hydration of lime when the waste is mixed with conditioning water. If 211u001eenough lime is present, the temperature of the waste will rise until steam is 211u001eproduced. It is recommended that self-heating wastes be conditioned in a 211u001econtrolled manner so that the heat will be safely dissipated before the material 211u001eis transported to an ultimate disposal site. Waste utilization is important 211u001ebecause an advanced process waste will not require ultimate disposal when it is 211u001eput to use. Each task three waste was evaluated for utilization potential based 211u001eon its physical properties, bulk chemical composition, and mineral composition. 211u001eOnly one of the thirteen materials studied might be suitable for use as a 211u001epozzolanic concrete additive. However, many wastes appeared to be suitable for 211u001eother high-volume uses such as blasting grit, fine aggregate for asphalt 211u001econcrete, road deicer, structural fill material, soil stabilization additives, 211u001ewaste stabilization additives, landfill cover material, and pavement base course 211u001econstruction.