You might try thermal sprayed tungsten carbide-cobalt compositions. Pure ceramic coatings are also available, but these may hold up better under thermal cycling. Over that big an area, you might also try sheets of quartz. I assume you need a cheap solution?

I worked with similar type towers, where we were trying to maintain high temperatures and hold up time for a reaction to take place. The towers were in series.  We injected water to control the inlet temperature to the base of the 1st tower to lower the temperature of the inlet gas from 3100̊ F to 2100̊F.  We used radial nozzles to inject water instead of a single spray head.  You will have to keep the water off the refractory.  The ceramic lining was made and applied by Plibrico Refractory Technology using a monolithic gunnited material.  Our tower linings were originally brick.

Their website is: www.plibrico.com

Dale Johnson in their Florida office would be the one most familiar with towers with conditions similar to your situation.  

Operating in you temperature range is not cheap. I could write a book on trials and tribulations in operating this  equipment.