Dry sorbent injection using sodium sorbent is a low-cost alternative to a semi-wet or wet scrubbing system for the removal of HCl and SO₂.

The dry sorbent injection process requires no slurry equipment or reactor vessel because the sorbent is stored and injected dry into the flue duct where it reacts with the acid gas. The spent sorbent is collected dry, either through a baghouse or electrostatic precipitator (ESP). It also can be collected through an existing wet scrubber vessel should DSI be used for trim scrubbing of acid mist, as is often the case when scrubbing SO₃.

SOLVAir products are the most effective for use in DSI systems. Both undergo rapid calcinations of contained sodium bicarbonate to sodium carbonate when heated at or above 275°F. The decomposition brings unreacted sodium carbonate to the particle surface, allowing HCl and SO₂ to be neutralized. Byproducts are sodium chloride and sodium sulfate, which are collected with fly ash.