Explain sampling of mine air behind seal of area
Answers
Answer:A second method of analysis included was a time series analysis to relate leakage rates to changes in barometric pressure that may not be site specific. Two accepted methods of time series analysis are the rescaled range technique [9,10] and the ARIMA approach, commonly referred to as the Box–Jenkins method [11,12].
Experimental design and study site
Mine study site
Field monitoring was conducted through a cooperative research agreement between Signal Peak Energy Bull Mountain No. 1 Mine operator and NIOSH. The monitored study site is shown in Figure 1, where the study panel is the one Right longwall panel measuring 380 by 4900 m (1250 by 16,000 ft). The mine operator had completed the first longwall panel and was mining the second when the study was performed. As with many western US coal mines, the mined coal seam has a relatively high spontaneous combustion potential. The mine began one Right longwall panel using a bleeder system but switched to bleederless system.
Figure 1
Figure 1
Map of the Signal Peak Energy Bull Mountain #1 mine (modified from Zipf et al., 2013) [14].
Ventilation description
An unusual feature of this mine is the application of an Australian Safety in Mines Testing and Research Station (SIMTARS) atmospheric monitoring system. The mine operator is working the thick Mammoth seam of relatively low-rank coal in the four corners region of Montana that is either of high-volatile bituminous C or sub bituminous coal rank. Due to the low rank of the mined coal, no methane is emitted from the coal bed with mining. Gas emissions from the mined seam consist entirely of carbon dioxide, although the gas present in the ventilation system may not be a ‘seam gas’ but could be a product of adjacent strata rock reactions or oxidation.
The underground monitoring site is shown in Figure 2. Entries are numbered from right to left in the figure. Instrument arrays were installed in entries 1 and 7 to produce data from the upwind and downwind sides of the seal line. Monitoring instrumentation consisted of a 0–25% oxygen sensor, a 0–5% methane sensor, a 0–3% carbon dioxide sensor, a digital flow metre, a digital barometer and a differential pressure monitor. With the exception of the differential pressure sensor and the barometer, an instrument array was installed on either end of the seal line. The differential pressure metre was installed on the number seven seal sampling line. The air sweeping the seal line was classified as intake air. Barometric pressure was measured at Entry 1 and differential pressure was measured at Entry 7.
Figure 2
Figure 2
Monitoring site for measurement of mine seal leakage rate.
Ventilation data analysis
Raw data consisted of measurements of data which were recorded every five minutes from 2:00 pm on 1 February through 12:20 pm on 17 May. In all but the final stage of analysis, data for the months of February and March, and for the months of April and May, respectively, were treated as two separate data-sets since it was thought that there could be some difference in the findings due to the change of season. Analysis of the monitoring data was conducted using two methods. The first is the Atkinson equation. The equation related leakage or flow quantity to head pressure, resistance and flow turbulence [13]. The Atkinson equation form used in the study is shown by the equation given below:
Hl = RQn
where Hl = head loss, R = resistance, Q = air quantity, n = exponent for quantity where n = 1 indicates laminar flow.
In fluid mechanics, Hl is shown to be proportional to Q2 [8].
A second method of analysis used is a time series analysis. A time series is made up of observations of a variable made over time. The time interval between observations must remain constant throughout the series. Time units may be as small as minutes or as large as years. The purpose of time series analysis is to recognise the process or model underlying the observed data; identification of the model then makes it possible to forecast future observations.
After working with both statistical approaches, the classical method of time series analysis – the Box–Jenkins method – was chosen for this study [11,12] over the rescaled range technique [15]. The method uses four possible components of a time series: trend, seasonal cycles within a year, larger cycles over a period of one or more years and random error. One or more of these components is assumed to be present in every series. If only random error is present, then the observation at any given time point is considered to be independent of observations at previous time points, and no model can be identified. If in addition to random error, one or more of the other components is present, then the observation at any given time point is considered to be related to or influenced by observations at previous time point(s). The correlations between observations at a given time point and observations at an earlier time point are known as an ‘autocorrelations’.
Answer:
Explanation:
Firedamp is flammable gas found in coal mines. It is the name given to a number of flammable gases, especially methane. It is particularly found in areas where the coal is bituminous. The gas accumulates in pockets in the coal and adjacent strata, and when they are penetrated, the release can trigger explosions.