Abstract: A refractory brick and system of bricks for constructing flue walls of a ring furnace. The brick and the bricks of the system have opposed sides and upper and lower surfaces when disposed in a vertical wall structure, with one of the surfaces having at least one crosswise groove while the other surface has a corresponding crosswise tongue for seating in the groove of an adjacent brick, the tongues and grooves terminating short of the ends or sides of the brick when the bricks are disposed in a vertical wall structure. The crosswise tongues and grooves have rounded configurations sized to mate with bricks having the same tongue and groove configurations when a plurality of such bricks are stacked one upon the other in constructing a vertical wall.

Abstract: The invention includes process and apparatus for removing pollutants from a gas including fluidizing a bed of particles in a container, introducing a gas containing pollutant into the bed, removing the pollutant through deposition on the particles, controlling temperatures in the container by injecting coolant fluid through a coolant nozzle, and reducing clogging or fouling on the coolant nozzle. The process and apparatus includes controlling temperatures in the container within narrowly specified ranges of temperatures and providing a constant pressure of coolant fluid and constant pressure of purge gas to the coolant nozzle such that interchangeable selection made between the coolant fluid and purge gas in a time period sufficiently short provides accurate temperature control and reduces clogging or fouling on the coolant nozzle.