Dahn, CJ
1989
Measurement and Interpretation of Explosion Bomb Tests for Low Rank Coal
Cannon, J.N.; Kramer, S.K.; Smoot, L.D. and Dahn, C.J.
Western States Section, The Combustion Institute, Pullman, Washington, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates) and US Department of Energy.
Twenty-liter bomb tests have become a common method to evaluate safety implications involving pulverized coal (p.c.) in coalmines, coal power plant pulverizers and other equipment. However, only limited data are available for low rank coals. Further, some published bomb test results show more variation than is acceptable to many researchers which clouds credibility of the data. Often, significant variables are not controlled or reported adequately. The objective of this paper is to provide new data for low rank coals and illuminate the variables and effects that are significant.
Subbituminous coal from the Decker, Montana open pit mine was obtained from the mine face and immediately sealed in double-wall, plastic bags under nitrogen. Fifteen sets of 20-liter bomb tests with this coal were conducted to determine the effects of particle size, moisture, oxidation age and dust concentration on explosion characteristics. Mean particle size ranged from 3 to 50 mm; moisture ranged from 3 to 21%; low temperature oxidation age varied from mine-face fresh to 10 days. Dust concentrations ranged from 0.025 to 0.875 gm/liter. The test samples were obtained, stored, ground, classified and analyzed at this laboratory. The bomb tests were conducted by Safety Consulting Engineers Inc., of Chicago and included 20-liter bomb pressure-time traces. Maximum pressure varied between 95 and 135 psi and maximum pressure rise rate ranged from 2000 to 7000 psi/sec. The influence of coal sample storage length was examined through duplicate tests. Multivariate statistical regressions are used to extract information from the noted tests, clarifying the estimates of error for the data. Concentration and particle size have greater influence than moisture while oxidation age has very little influence.
The transient combustion processes during bomb tests are identified and the effects of the test variables are interpreted in light of these processes. Burning velocities are also estimated from various available theories and compared. Analytical methods show that the maximum pressure in the bomb is related to fuel concentration, fuel heating value and molecular weight of the product gases. Experimental results indicate that convective and radiant heat losses to the container wall and incomplete combustion significantly lower maximum pressure compared to predictions. In addition, initial turbulence in the bomb prior to ignition has a significant influence on observations. Requirements for controlling these variables in order to obtain consistent and repeatable test data from standard bomb tests are noted. The implication of the laboratory test results to full-scale explosions is also noted.
Dahn, CJ
1989
Measurement and Interpretation of Explosion Bomb Tests for Low Rank Coal
Cannon, J.N.; Kramer, S.K.; Smoot, L.D. and Dahn, C.J.
Western States Section, The Combustion Institute, Pullman, Washington, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates) and US Department of Energy.
Twenty-liter bomb tests have become a common method to evaluate safety implications involving pulverized coal (p.c.) in coalmines, coal power plant pulverizers and other equipment. However, only limited data are available for low rank coals. Further, some published bomb test results show more variation than is acceptable to many researchers which clouds credibility of the data. Often, significant variables are not controlled or reported adequately. The objective of this paper is to provide new data for low rank coals and illuminate the variables and effects that are significant.
Subbituminous coal from the Decker, Montana open pit mine was obtained from the mine face and immediately sealed in double-wall, plastic bags under nitrogen. Fifteen sets of 20-liter bomb tests with this coal were conducted to determine the effects of particle size, moisture, oxidation age and dust concentration on explosion characteristics. Mean particle size ranged from 3 to 50 mm; moisture ranged from 3 to 21%; low temperature oxidation age varied from mine-face fresh to 10 days. Dust concentrations ranged from 0.025 to 0.875 gm/liter. The test samples were obtained, stored, ground, classified and analyzed at this laboratory. The bomb tests were conducted by Safety Consulting Engineers Inc., of Chicago and included 20-liter bomb pressure-time traces. Maximum pressure varied between 95 and 135 psi and maximum pressure rise rate ranged from 2000 to 7000 psi/sec. The influence of coal sample storage length was examined through duplicate tests. Multivariate statistical regressions are used to extract information from the noted tests, clarifying the estimates of error for the data. Concentration and particle size have greater influence than moisture while oxidation age has very little influence.
The transient combustion processes during bomb tests are identified and the effects of the test variables are interpreted in light of these processes. Burning velocities are also estimated from various available theories and compared. Analytical methods show that the maximum pressure in the bomb is related to fuel concentration, fuel heating value and molecular weight of the product gases. Experimental results indicate that convective and radiant heat losses to the container wall and incomplete combustion significantly lower maximum pressure compared to predictions. In addition, initial turbulence in the bomb prior to ignition has a significant influence on observations. Requirements for controlling these variables in order to obtain consistent and repeatable test data from standard bomb tests are noted. The implication of the laboratory test results to full-scale explosions is also noted.