OCR Text |
Show Moreover, the boiler is base loaded at 120 kpph during routine production. However, in winter months when demands for space heat are high, operation at loads up to 140 kpph would be desirable. However, operation at this higher load was not possible because of excessive opacity at loads above 120 kpph even with the F G R system. Morton looked to cofire to address these problems. Dual Coen CoFyr burners with combined firing capacity of 80 MMBtu/hr were retrofit to the boiler in October 1998. This system was tested in June 1998. The primary incentives for cofire at Morton were: • The ability to operate at typical loads with acceptable opacity without the need for FGR • The ability to achieve smokeless startup • The ability to operate at a boiler load of as low as 50 kpph • The ability to operate at loads up to 140 kpph with acceptable opacity • The ability to achieve improved boiler efficiency The testing to establish these benefits, again, included continuous monitoring for 02, CO, NOx, and S02, EPA Method 5 for particulate, Andersen impactors for particle sizing, and grab sampling of fuel and ash, along with the collection of boiler operating data. Figure 13 show the effect of cofire on the Morton boiler opacity. The figure shows that, at 120 kpph load, stack gas opacity decreased from 13 percent with no cofire to 9 percent with 7 percent cofire. While this reduction seems modest, as opacity increases above 15 percent, small excursions in operation can readily cause exceedance of the 20 percent per limit. Moreover, the figure shows that operation at an increased load of 145 kpph with 9 percent gas cofiring was shown possible with average opacity of 13 to 16 percent. Thus, with gas cofiring, increased steam demand can be satisfied in an operating mode comparable to that formerly experience at typical load with the F G R system running. Figure 14 shows the boiler load, gas flowrate, and stack opacity for a simulated boiler startup during which the boiler was taken from a boiler load of 54 kpph firing gas only to a load of 85 kpph with coal and 7 percent gas cofire. The figure clearly shows that smokeless startup was achieved with maximum opacity of 10 percent. Figure 15 shows the effect of gas cofire on boiler efficiency. The figure shows that 7 percent gas cofire at 120 kpph load increased boiler efficiency by 1.6 percentage points from 80.8 to 82.4 percent. This efficiency increase resulted from decreased bottom ash and economizer hopper ash carbon content, as well as decreased stack gas 02. ACKNOWLEDGEMENTS The cofiring field evaluations discussed in this paper were cofunded by GRI, the host sites, and the local natural gas distribution and/or transmission company. In addition to cofunding, the host sites played a key role in the design and implementation of the cofire systems and supporting the start-up, optimization, and performance testing. The expertise and cooperation of both the engineering and boiler operation teams at Ford Cleveland Engine Plant, Capitol Heating Plant, Eli Lilly Tippecanoe Laboratories, Purdue University, and Morton International Manistee plant were essential in the success of the cofiring modifications. The gas companies developed the projects and maintained a sustained role throughout in project integration and site liaison. The efforts of East Ohio Gas, Washington Gas, Indiana Gas, and Michigan Consolidated Gas were essential in ensuring that the benefits of cofiring were identified and fully realized. 14 |