DSI systems use dilute phase conveying to move hydrated lime from the storage silo into the flue gas. Hydrated lime conveying lines can be split into multiple injection points, with each injection location having multiple injection lances for hydrated lime. Equipment typically consists of a hydrated lime storage silo with a cone bottom, a rotary valve feeder, a variable speed conveying air blower, feed splitters, and injection lances.
The Mississippi Lime R&D group has studied dry sorbent hydrated lime conveying systems very closely. The main priority is to keep hydrated lime suspended in the conveying air without the material depositing in the line. While doing this, the system designer and operator should control the conveying air velocity and temperature to avoid formation of a hard scale a calcium carbonate than can occur from the reaction of hydrated lime and carbon dioxide in the conveying air. Based upon our studies and field experience, Mississippi Lime recommends the following for hydrated lime DSI conveying systems:
• Variable speed feed blower
• Use of air coolers between the feed blower and rotary feed valve
• Air sweep bin activation on cone of fee bin
• Shallow Pocket Drop Through Rotary Valve
• Hydrate:Air > 0.6 lbs hyd:lb air
– Pickup velocity 2800 - 3300 ft/min
• Minimal bends; smooth unions
• Piping/Lance diameter > 1.25”
Mississippi Lime has a portable silo and blower system to use for hydrated lime demonstrations. This hydrated lime injection equipment has state of the art controls and is optimized for feeding hydrated lime for DSI projects.