Boilers, furnaces, metals and ceramics manufacture, and similar processes produce waste off-gases containing acidic species that, if released uncontrolled, are harmful to human health and the environment. The acid gases of primary concern are oxides of sulfur (SOx) and hydrogen halides (HX). Gas scrubbing with alkaline solutions and solids is employed to reduce emissions of these acid gases. Different scrubbing technologies have been practised for decades but least expensive to implement and simplest to operate are usually "dry scrubbing" or dry sorbent injection (DSI) systems. In DSI systems, a dry powdered alkaline material is injected into the hot gas stream to neutralize the acidic species, and the resulting solid salts and remaining excess alkaline material is collected by a downstream particulate capture device. These systems are capable of high levels of acid gas reduction. Various alkaline materials, both chemically processed and naturally occurring, have seen application in dry scrubbing. Dry hydrated lime, a calcium based alkaline sorbent, is in wide use in dry scrubbing, largely because of its moderate cost and availability. However, a sodium based alkaline sorbent such as sodium bicarbonate, macholite, and trona can provide particular advantages that make them a superior choice in certain applications. A mechanically refined trona in both a powder and granular form is being used throughout these industries for SOx mitigation and recently at a few glass production plants with good success and having economic advantages over other sorbents. This paper will discuss the application process, important variables to insure optimal sorbent usage, the chemistry of the operation and data collected under various conditions including glass production. This paper summarises the advantages of DSI systems and of dry injection of sodium based alkaline sorbents in particular.
