TurboSonic and Dow Chemical Offer SO₂-Removal Technology

Dow Chemical, a longtime vendor of its Gas/Spec technology using regenerable amines for sulfur removal in gas processing, has teamed up with TurboSonic Technologies, Inc. (Waterloo, Ontario) to produce the TurboTak SO₂ system. The twist: a regenerable amine absorbent that allows SO₂ to be removed without generating the lime sludge that conventional gas scrubbing uses. In addition, unlike the front-end gas purification that Gas/Spec is known for, TurboTak will be geared more for fluegas cleanup in combustion or vent gas disposal. Several applications in pulp and papermaking are already in the works.

The new GAS/SPEC 1 TurboSox Amine will be used exclusively in the TurboTak sulfur dioxide systems by TurboSonic, like the one shown. (1)GAS/SPEC is a registered trademark and service mark of The Dow Chemical Company.

TurboSonic has been marketing its advanced scrubbing system, TurboTak, since the late 1970s. The heart of the system is a gas- and liquid-phase nozzle that atomizes absorbent highly efficiently. The atomized spray contacts the gas stream to be scrubbed; no packings or trays are needed in the contacting column. About 150 units are in use worldwide in a variety of scrubbing applications, according to Egbert van Everdingen, sales manager at TurboSonic.

"Our amine technology was developed about a decade ago for possible application in coal-fired power plants," explained Shelby Oostwouder, marketing manager for the Gas/Spec Technology Group (Houston, Texas). "It was successfully tested for coal-burning plants, but ultimately we decided not to market it until TurboSonic came along." Dow would only characterize the amine as a proprietary, patented material.

Like most absorption strippers, TurboTak contacts fluegas with the absorbent liquid, generally in the 120-140°F range. SO₂ preferentially binds with the amine. In a regeneration step running above 150°F, the absorbent is heated, releasing the SO₂. A minimal amount of amine is lost on each cycle. Van Everdingen said that the process has been used on gas streams ranging up to 7 percent SO₂ (70,000 ppm).

"Around that level, it become more economical just to use the gas stream as a feed to something like an acid plant," he said. "TurboTak SO₂ will really excel at levels below that percentage, where it is not economical to use the gas as a feedstream, and where it is difficult to remove all the SO₂." The process can reduce SO₂ concentrations to below detectable limits.

TurboSonic will be marketing the system. Contact them at:

TurboSonic Inc., 550 Parkside Drive, Suite A-14, Waterloo, Ontario, Canada N2L 5V4. Tel: 519- 885-5513. Fax: 519-885-6992.

Once the SO₂ is concentrated, it can be used as a feed for an acid plant, ammonium bisulfite fertilizer, or for sulfite pulping processes. Alternatively, the stream can be stored and sold as a merchant product.

Economics remain to be worked out in detail, but van Everdingen says that the capital cost can be half that of conventional multistage absorbers. Compared to lime or limestone scrubbing, TurboTak SO₂ does not produce large volumes of waste sludge, and requires less plant space. A demonstration project is underway at a paper mill.

By Nick Basta