OCR Text |
Show - 2 - unreliable, extremely site specific, or very limited in the ranges of tested operating conditions. Inconsistencies or limitations in the data will be negatively reflected in the predictive accuracy of the correlations developed from this information. A wide variety of simple relationships for predicting slagging and fouling behavior based only on coal physical/chemical properties already exists (as summarized adequately in the open literature.(2-5)) Numerous detailed studies examining individual aspects of the ash deposition process have also been presented including studies of specific deposition mechanisms as well as evaluations of the importance of chemical and morphological changes of coal ash constituents.(2, 6-9} To date, however, few investigations have adequately addressed the relative dependence in practical terms of slagging and fouling on both operating conditions and coal physical/chemical characteristics. Yeakel and Finkelman recently discussed the important relationship between process complexity and correlative complexity in their examination of fouling behavior.(10) It was determined that the inclusion of five coal characteristic terms in a non-linear empirical model resulted in the ability to accurately predict deposit buildup rates in a pilot-scale combustor. Barrett et al., collected and analyzed slagging and fouling data from utility boilers.(l) The results indicated that substantial improvements in the predictive accuracy of empirical indices could be achieved by including boiler parameters (e.g., steam flow/boiler plan area). These two recent studies provide additional incentive for engaging in this type of correlative effort. COMBUSTOR DESCRIPTION In order to aid current and future customers, Consolidation Coal Company, in the early 1980s, constructed a pilot-scale combustion furnace designed to simulate corranercial boiler operating conditions. The combustor, shown in Figure 1, is a nominal 1.5 MM Btu/hr furnace and may be configured in the most common firing methods found in the United States - wall, opposed-wall, tangential, and cyclone. Several attempts at comparing pilot combustor ash deposition data with limited commercial-scale investigations have proven quite successful.(ll, 12) A more detailed description of the facility has been reported elsewhere.(13) Several methods were consistently used over the past five years for investigating ash deposition behavior during fuel evaluation testing. Slagging behavior was investigated utilizing a 1.6 sq.ft. water-wall panel located 2-ft above the burners in the first radiant section of the furnace. The pane 1 was coo 1 ed wi th a n organ i c fl u i d of known therma 1 properties with hot-side wall temperatures ranging between 400-500°F. Fouling behavior was simulated using two 1.5-in. 0.0., air-cooled tubes (1000° F sk in tempera tures) 1 oca ted a t the entrance to the convect ion section above the nose. Easy access permitted acquisition of deposit samples for subsequent chemical analyses. |