See also there:
http://www.jetro.go.jp/mexico/topics/20071017878-topics/Kawasaki_Waste_Heat_Recovery_Cement_Plant.pdf
http://www.energymanagertraining.com/Presentations/3L_CHP/05NewDelhi/01Cogenerationofpower-NCCBM.pdf
To evaluate the power, simple thermodynamics can be used assuming a cold source at 100°C (boiling water at 1 atm). However, the actual efficiency is much lower than the Carnot efficiency, between 30% and 40% of the Carbot efficiency. This gives typically:
P = G Cg (T-To) * (1-To/T) * 35%
where G is the gas flowrate, Cg its specific heat, T the absolute temperature, To the cold source temperature.
Waste Heat Power Generation in the cement industry started in Japan in the 70's. In the 90's, the Chinese government heavily promoted this technology. As a result, th Chinese suppliers now have a mature technology (more than 100 units intalled) and are the cheapest in the world.
You can find a lot of interesting info from Chines suppliers here:
http://www.china-power-contractor.cn/china-waste-heat-recovery-power-plant-cement.html
Best regards