Effect of Trona on the Leaching of Trace Elements from Coal Fly Ash

Status

Complete                                      View Final Report: PDF

Sequential Number

Identification Number

Matching Research Agency

 Electric Power Research Institute (EPRI)

Principal Investigator

Student Involvement

One graduate student

Project Objective

To perform standard laboratory leaching tests on fly ash samples collected at different trona and hydrated lime injection rates, and to develop fundamental understanding regarding the leaching behavior of As and Se from trona ashes.

Project Abstract

Trona has been tested or used to control SO2 and SO3 emissions from coal fired power plants. Due to its alkaline nature, trona is also effective to remove other acid gases such as hydrochloric acid (HCl), and hydrofluoric acid (HF) from flue gas emissions. EPA has proposed to have tighter control on emissions of both SOx and HCl, and trona injection method could be an option to meet these new EPA requirements. However, trona injection could result in some issues with the fly ash. Recent study indicated that trona injection for SO2 control significantly increased the leaching of anionic trace elements such as As and Se. Fly ash, in some cases, has been used as a construction material for highway, so that this otherwise wasted material can be beneficially used. While this practice improves the quality of the construction and offers environmental benefit by reducing the cement use therefore reduce greenhouse gas production, the use of trona ash could also pollute groundwater if the metal leaching is high. The objectives of this research are to perform standard laboratory leaching tests on fly ash samples collected at different trona and hydrated lime injection rates, and to develop fundamental understanding regarding the leaching behavior of As and Se from trona ashes. In addition, one fly ash will be used to develop a pozzolanic cement sample with portland cement. This sample will be taken out to measure the mechanical properties to ensure the structural stability of the cement. The metal leaching performance of the pozzolanic cement will also be tested. This research is important when determining what type of ash should be used or should not be used for highway construction, to prevent environment pollution.

Anticipated Benefits

After the research is completed, we can know how trona inject method impacts the fly ash leaching characteristics, therefore we can determine the environmental impact when the ash is used for road construction, or if the fly ash is still usable for road construction. This research is very important for sustainable road construction.

Milestones

Project Deliverables

A draft manuscript will serve as the project deliverable.

Technology Transfer Activities

A journal manuscript and a conference presentation will be prepared to disseminate the project results.

Transportation Research Board Keywords

Fly ash, leaching, heavy metals