2PBE April 2016

Control ConceptsCase History

MAJOR ELECTRIC UTILITY SOLVES DSI MATERIAL FLOWPROBLEMA major electric utility’s coal-fired plant in theMidwest needed to meet Federal emissions standardswhile keeping power output maximized. This 2600MW plant contains a pair of the largest coal-firedgenerators in the U.S. To meet current Federalemission standards, the plant recently installed a DrySorbent Injection (DSI) system designed to mitigateHCI and SO2 flue gas emissions. DSI technology relies on bulk solid materials thatexhibit poor flow properties, such as Hydrated Lime,Trona, Soda Ash and Sodium Bicarbonate. At thisgenerating station, the process feeding the powderedmaterial to the DSI system consists of a 5-footdiameter mixer, connected to three legs of parallelscrew conveyors dropping materials three stories viaan array of rotary valves, screw conveyors andhoppers, then on to a final dilute-phase pneumaticconveyor that supplies theDSI system. There are atotal of two of these DSIsystems (one per each1300 MW generator), sothe opportunities for flowproblems were doubled,given the amount oftwists, turns and distancethe powder needs toreliably travel in order tokeep the system runningproperly. The utility couldface significant penaltiesand fines of millions ofdollars if emissionsfrom the plant are notup to compliancestandards.The utility contactedControl Concepts,Inc., manufacturer ofthe Airsweep®

Material FlowSystem. TheAirsweep System hasbecome the defaultflow aid choiceamong manymanufacturers ofproprietary DSIsystems, as well asmajor manufacturersof the DSI materials used in those systems. Thesemanufacturers know that the Airsweep System can

provide on-demand flow of a wide variety of DSImaterials, including Hydrated Lime, Trona, Soda Ash,Calcium Carbonate, Sodium Bicarbonate and others.Each Airsweep nozzle delivers a powerful pulse of airor inert gas, knifing between the material and the innercontact surface of the vessel, chute, duct, etc., to breakfriction and immediately restore flow. One of ControlConcept’s key Midwest distributors worked closelywith the company’s engineers and plant personnel todesign and install an Airsweep System consisting ofboth large (model VA-51) nozzles mounted on thevessels and small (model VA-06) nozzles mounted inthe numerous possible chokepoints in the ducts,screws and elbows. All nozzles installed wereconstructed of 316 stainless steel to resist corrosion.Local controllers were provided, tying into the plant’sDSL system to start and stop the system depending

upon the need for DSI material.Since system start-up in autumn, 2015,the generating plant has been runningcontinuously and at capacity, with noemission compliance issues, thanks tothe DSI system and on-demand materialflow delivered by the Airsweep®

Material Flow System.

VA-51 and VA-06 Airsweeps prior to installation on chute

For more information, visitwww.ControlConceptsUSA.com or call 800-662-4762.

Air manifold and flex hoses distributecompressed air to VA-06 Airsweeps onductwork.

VA-51 Airsweep mounted onscrew conveyor trough.