Dry injection of sodium bicarbonate or trona is a low-cost solution for HCl mitigation. In a DSI system, sodium bicarbonate or trona is injected directly into hot flue gas. After injection, the sorbent is calcined into porous sodium carbonate. Its high surface area enables fast gas-solid reactions between acid gases (mainly HCl and SO2) and Na2CO3 to form NaCl and Na2SO4 which are collected by either electrostatic precipitators (ESP) or fabric filters. DSI systems using sodium bicarbonate in Europe have shown that over 99% of HCl and 95% of SO2 removal have been achieved.
This paper describes the concept of a DSI system with sodium bicarbonate or trona, performance data at several plants, and system design guidelines.