Effects of Sorbent Injection on Particulate Properties: Part II. High-Temperature Sorbent Injection

Abstract

This article is the second part of a two-part series dealing with the effects of sorbent injection processes on particulate properties. Part II (this article) reviews the effects on particulate properties of high-temperature sorbent injection processes (those processes that involve sorbent injection into the combustion or economizer sections of a boiler). Part I of this series (December 1992 pp: 1592) reviewed the effects on particulate properties of low-temperature sorbent injection processes (processes that involve sorbent injection into flue gas at temperatures near 300°F). In this article, we review information that is known about the effects of high-temperature sorbent injection on electrical resistivity, particulate mass loading, particulate size distribution, particulate morphology and cohesivity.

When a high-temperature sorbent injection process is applied to a boiler burning medium- to high-sulfur coal, the electrical resistivity of the particulate matter is increased substantially and the performance of the electrostatic precipitator is degraded accordingly. The resistivity may be brought back to an acceptable level by the use of flue gas humidification or conditioning with SO₃. Certain mixtures of ash and highly reactive sorbent do not appear to respond to SO₃ conditioning.

Compared to ordinary fly ash, the ash and sorbent mixtures produced by high-temperature sorbent injection contain more rough, angular particles and tend to be more cohesive. High-temperature sorbent injection processes tend to shift the particle size distribution toward finer particles.