Last data update: Sep 23, 2024. (Total: 47723 publications since 2009)
Records 1-3 (of 3 Records) |
Query Trace: Krog RB [original query] |
---|
Methane emissions and airflow patterns on a longwall face: Potential influences from longwall gob permeability distributions on a bleederless longwall panel
Schatzel SJ , Krog RB , Dougherty H . Trans Soc Min Metall Explor Inc 2017 342 (1) 51-61 Longwall face ventilation is an important component of the overall coal mine ventilation system. Increased production rates due to higher-capacity mining equipment tend to also increase methane emission rates from the coal face, which must be diluted by the face ventilation. Increases in panel length, with some mines exceeding 6,100 m (20,000 ft), and panel width provide additional challenges to face ventilation designs. To assess the effectiveness of current face ventilation practices at a study site, a face monitoring study with continuous monitoring of methane concentrations and automated recording of longwall shearer activity was combined with a tracer gas test on a longwall face. The study was conducted at a U.S. longwall mine operating in a thick, bituminous coal seam and using a U-type, bleederless ventilation system. Multiple gob gas ventholes were located near the longwall face. These boreholes had some unusual design concepts, including a system of manifolds to modify borehole vacuum and flow and completion depths close to the horizon of the mined coalbed that enabled direct communication with the mine atmosphere. The mine operator also had the capacity to inject nitrogen into the longwall gob, which occurred during the monitoring study. The results show that emission rates on the longwall face showed a very limited increase in methane concentrations from headgate to tailgate despite the occurrence of methane delays during monitoring. Average face air velocities were 3.03 m/s (596 fpm) at shield 57 and 2.20 m/s (433 fpm) at shield 165. The time required for the sulfur hexafluoride (SF(6)) peak to occur at each monitoring location has been interpreted as being representative of the movement of the tracer slug. The rate of movement of the slug was much slower in reaching the first monitoring location at shield 57 compared with the other face locations. This lower rate of movement, compared with the main face ventilation, is thought to be the product of a flow path within and behind the shields that is moving in the general direction of the headgate to the tailgate. Barometric pressure variations were pronounced over the course of the study and varied on a diurnal basis. |
A study of leakage rates through mine seals in underground coal mines
Schatzel SJ , Krog RB , Mazzella A , Hollerich C , Rubinstein E . Int J Min Reclam Environ 2015 2015 (2) 165-169 The National Institute for Occupational Safety and Health conducted a study on leakage rates through underground coal mine seals. Leakage rates of coal bed gas into active workings have not been well established. New seal construction standards have exacerbated the knowledge gap in our understanding of how well these seals isolate active workings near a seal line. At a western US underground coal mine, we determined seal leakage rates ranged from about 0 to 0.036m3/s for seven 340 kPa seals. The seal leakage rate varied in essentially a linear manner with variations in head pressure at the mine seals. |
Methane emissions and airflow patterns along longwall faces and through bleeder ventilation systems
Krog RB , Schatzel SJ , Dougherty HN . Int J Min Miner Eng 2014 5 (4) 328-349 The National Institute for Occupational Safety and Health (NIOSH) conducted an investigation of longwall face and bleeder ventilation systems using tracer gas experiments and computer network ventilation. The condition of gateroad entries, along with the caved material's permeability and porosity changes as the longwall face advances, determine the resistance of the airflow pathways within the longwall's worked-out area of the bleeder system. A series of field evaluations were conducted on a four-panel longwall district. Tracer gas was released at the mouth of the longwall section or on the longwall face and sampled at various locations in the gateroads inby the shield line. Measurements of arrival times and concentrations defined airflow/gas movements for the active/completed panels and the bleeder system, providing real field data to delineate these pathways. Results showed a sustained ability of the bleeder system to ventilate the longwall tailgate corner as the panels retreated. |
- Page last reviewed:Feb 1, 2024
- Page last updated:Sep 23, 2024
- Content source:
- Powered by CDC PHGKB Infrastructure