Case History: Alabama Pulp & Paper Mill

SITUATION
The existing burner at an Alabama pulp and paper mill exhibited limited flame-shaping capability - causing flame impingement on the burner and the front 25-35 feet of refractory in their lime recovery kiln. To minimize costly burner and refractory repairs, the mill limited the highly radiant petroleum coke firing to less than 40% of total heat input. With natural gas prices rising, the mill contacted Coen for a solution to increase coke firing.

The mill sought to increase coke firing to 80% when cofired with either natural gas or a waste fuel oil with particulates. Additionally, the product quality needed to be maintained while eliminating flame impingement on the kiln refractory when firing any combination of fuels.

SOLUTION
Coen, utilizing the latest Computational Fluid Dynamics (CFD) software, provided a 3D combustion model that replicated the existing burner's shortcomings. It modeled temperature contours, coke firing mass flow, and most important, flame shape and radiation heat flux to the refractory lining.

The CFD modeling persuaded the customer that a properly designed burner system could eliminate flame impingement, increase coke firing, and meet their production requirements. (See Figures 1, 2 & 3).

Within 16 weeks, Coen delivered a multi-fuel dual air zone kiln burner, which successfully started up in a week. The new burner conveyed the coke in an outer air zone while an inner air zone spinner created a strong recirculation zone to stabilize the difficult to burn coke fuel. For precise flame shape control, CFD modeling created unique drillings for the gas and oil firing nozzles. Coen's Super Non-Clog (SNC) oil atomizer easily handled the waste oil with particulates.

RESULTS
The start-up produced results predicted by the engineering study and CFD modeling. The new burner eliminated flame impingement on the kiln refractory and fired over 80% petroleum coke at maximum heat load (See Figure 4). The new Coen burner handled gas and oil in combination with petroleum coke and could switch fuels on the fly. Product quality remained high and fuel cost savings approached $2 MM per year by replacing natural gas with coke firing.

Coen Company, Inc., 1510 Rollins Road, Burlingame, CA 94010. Tel: 650-697-0440; Fax: 650-686-5655.