Page 17
| Title | Control of Pollutant Emissions from Coal and Wood Combustion in Spreader-Stoker Systems |
| Creator | Munro, J. M.; Bradshaw, F. W.; Pershing, D. W. |
| Publisher | Digitized by J. Willard Marriott Library, University of Utah |
| Date | 1982 |
| Spatial Coverage | presented at Newport Beach, California |
| Abstract | Stoker-fired boilers and furnaces are significant in terms of both solid fuel utilization and environmental impact; however, they have received relatively little research attention. The purpose of this investigation was to study the formation and control of nitrogen oxides and particulates in spreader-stoker combustion of bituminous coal and hogged wood. The study focused on optimizing the combustion conditions in each of the two distinct combustion zones, the bed phase and the suspension phase. The experimental work was carried out in a 750,000 Btu/hr laboratoryscale model stoker furnace. Local oxygen availability was found to be the controlling parameter for nitric oxide (NO) formation in each stage. Minimum NO emissions were found when local stoichiometric ratios were held at 0.70 - 0.85; reductions in NO emissions under these conditions were as much as 39 and 55 percent for wood and coal firing, respectively. Two control technologies for reducing pollutant emissions were investigated: Removal of the fines in the stoker feed, and optimizing the interaction between the bed and suspension phases through stoichiometry control. Fines removal during coal firing with, an excess-air bed resulted in a 20 percent reduction in NO emissions and an 81 percent reduction in particulate emissions. Stoichiometry optimization produced reductions in NO emissions of 4Q percent and 60 percent for excess-air beds and fuel-rich beds, respectively. Particulate emissions were reduced by 60 percent when the fuel bed was staged due to lower suspension-zone velocities. |
| Type | Text |
| Format | application/pdf |
| Language | eng |
| Rights | This material may be protected by copyright. Permission required for use in any form. For further information please contact the American Flame Research Committee. |
| Conversion Specifications | Original scanned with Canon EOS-1Ds Mark II, 16.7 megapixel digital camera and saved as 400 ppi uncompressed TIFF, 16 bit depth. |
| Scanning Technician | Cliodhna Davis |
| ARK | ark:/87278/s6mw2kq8 |
| Setname | uu_afrc |
| ID | 3467 |
| Reference URL | https://collections.lib.utah.edu/ark:/87278/s6mw2kq8 |
Page Metadata
| Title | Page 17 |
| Format | application/pdf |
| OCR Text | ideal gas density. The particulate loadings did not correlate well with gas velocity at the spreader; however, Figure 7 shows the total particulate loadings as a function of superficial bed off-gas velocity. The two lines represent the data obtained at the two levels of overfire-air height. While the particulate loadings were somewhat dependent upon both the stoichiometry distribution and the overfire-air height, the primary parameter appeared to be superficial velocity above the fuel bed. Increasing the vertical velocity significantly increased the particulate loadings. Decreasing the overfire-air height to 20 inches (below the spreader) increased the particulate carry-over, due to the higher vertical velocity at the spreader. The influence of increasing excess oxygen was somewhat complex because the higher oxygen partial pressure enhanced the carbon burnout and somewhat mitigated the increased entrainment due to the higher volumetric flow rates of the exhaust gases. The particle size results indicated that the loadings of the two smallest particle size ranges remained relatively constant and accounted for less than 0.5 lb/10 Btu. The loadings of particles larger than 0.094 inches showed the largest deviations among the experimental runs. Thus, total particulate loadings increased primarily due to increased carry-over of large particles, while small particle emissions remained approximately constant . In order to evaluate the extent of carbon utilization in the suspension phase, several samples were characterized in terms of their chemical constituents. The analyses indicate that hydrogen evolution is essentially complete in all the particulates, a result identical to that found with coal-firing. Carbon contents were low in the smallest particulate-size range relative to the larger particulates. Higher heating rates in the small particles outweighed the shorter combustion-zone residence times which they would have experienced. The particulate composition data showed no discernible differences due to other furnace parameters. Utah Bituminous Coal Figure 8A illustrates the particulate emissions data obtained during experiments which simulated current field practice in terms of air 25-17 |
| Setname | uu_afrc |
| ID | 3462 |
| Reference URL | https://collections.lib.utah.edu/ark:/87278/s6mw2kq8/3462 |