System and method for mixing recirculating combustion ash with hydrated lime and water

A method for mixing recirculating ash from solid fuel combustion with hydrated lime and water and to feed a mixture thereof into a desulfurization reactor, the method comprising:

• directing the recirculating ash, the hydrated lime, and the water to a mixer having a housing via a feed chute, the housing having a front wall, two outer vertical sidewalls, a rear wall, a top, and a bottom, and the front wall includes an opening for the mixture to exit the mixer;
• rotating, at a first selected speed, in a first direction, a first rotatable vertical shaft having a first impeller, the first impeller comprising a first plurality of blades disposed on the first vertical shaft in the same horizontal plane, the first plurality of blades of the first impeller distributed about the circumference of the first vertical shaft, the blades having a shear contact with the mixture to add shear forces and avoid agglomeration and pellet formation in the mixture when exhibiting a selected moisture content;
• increasing a residence time of the mixture in a mixing region formed by a vertical wall disposed within the housing, the mixing region including the first rotatable vertical shaft(s);
• forming a feeding region within the housing with the vertical wall, the feeding region operably connected to the opening of the front wall, and providing an opening beneath the vertical wall between the vertical wall and the bottom of the mixer;
• fluidizing the mixture with a fluidization mechanism in at least the feeding region to increase flowability of the mixture, the fluidizing including directing gases or air into the mixture from the bottom of the housing;
• and
• directing the mixture to the opening.

A system for treating flue gases and mixing recirculating ash from solid fuel combustion with hydrated lime and water and to feed the mixture into a desulfurization reactor, the system comprising:

• a plant system including a boiler having a combustion system that combusts fuel to form flue gases and ash;
• a flue gas treatment system operable to provide a semi-dry flue gas desulphurization of heated acid-rich flue gases, the flue gas treatment system including;
• a reactor for reacting acidic flue gasses with hydrated lime under humidified conditions,
• a particulate collector operable to separate gaseous pollutants from particulate matter yielding captured dust while flue gases are directed to a stack for disposal, and
• a mixer for recirculating ash from solid fuel combustion with hydrated lime and water and to feed the mixture into a desulfurization reactor, the mixer comprising:
• a housing including a front wall, two outer vertical sidewalls, a rear wall, a top, and a bottom,
• wherein, the top includes a feed chute configured for the entry and addition of product to the mixer, and the front wall includes an opening for mixed product to exit the mixer,
• one or more rotatable vertical shafts having at least one an impeller, the at least one impeller comprising a first plurality of blades disposed on the vertical shaft in the same horizontal plane, the first plurality of blades of the at least one impeller distributed equidistantly about the circumference of the vertical shaft, the blades having a shear contact with the mixture to add shear forces and avoid agglomeration and pellet formation in the mixture when exhibiting a selected moisture content,
• a vertical wall disposed within the housing forming a mixing region with the one or more vertical shaft(s) and a feeding region that is operably connected to the opening of the front wall, the internal vertical wall operable to increase a residence time of the mixture in the mixing region and to prevent bypassing, the vertical wall including an opening, beneath the vertical wall between the vertical wall and the bottom of the mixer;
• and
• a fluidization mechanism in at least the feeding region to increase flowability of the mixture, the fluidizing mechanism directing gases or air into the mixture from the bottom of the housing.