Coalbed Methane Dewatering Pump Engines



Coalbed Methane Dewatering Pump EnginesCoalbed methane (CBM) dewatering pump engines refer specifically to engines located at CBM wells that provide lift to bring the water in the well up to the wellhead. Removing water from CBM wells allows the methane to flow freely through the fissures in the coal seam to the well. Generally, CBM dewatering pump engines are small natural gas or diesel-fired engines. Where electricity is available, CBM dewatering pump engines may be powered by electric motors or electric-powered submersible pumps may be used for removing water. For CBM dewatering pumps powered by electricity, emissions are assumed to be zero. Figure 1 shows a CBM dewatering pump.Figure 1. Coalbed Methane Dewatering PumpThe basic methodology for estimating emissions from a single non-electrified CBM dewatering pump engine is shown below:Equation 1) where:Eengine are emissions from a CBM dewatering pump engine [ton/year/engine] EFi is the emissions factor of pollutant i [g/hp-hr]HP is the horsepower of the engine [hp]LF is the load factor of the enginetannual is the annual number of hours the engine is used [hr/yr]907,185 is the unit conversion factor g/tonExtrapolation to county-level emissionsCBM dewatering pump engine emissions have been scaled up to the county level on the basis of CBM well counts. The methodology for scaling up CBM dewatering pump engine emissions is shown below:Equation 2) where:Eengine,TOTAL is the total emissions from CBM dewatering pump engines in a county [ton/yr]n is the total number of CBM dewatering pump engines per well, generally equal to 1 (n=1) [engine/well]Eengine is the total emissions from a CBM dewatering pump engine (as shown in Equation 1) [ton/yr/engine]fpump is the fraction of CBM wells with dewatering pump enginesFE is the fraction of CBM dewatering pump engines that are electricWCBM,TOTAL is the total number of CBM wells in a county [wells]Example Calculation for CBM dewatering pump engines:Using the equations provided above, NOx emissions from CBM dewatering pump engines in Calhoun County, Arkansas may be calculated as follows:where:E engine = emissions from a CBM dewatering pump engine [ton/yr/engine]EF = 8.24 [g/hp-hr] HP = 77.5 [hp]LF = 0.85 (load factor for the engine)tannual = 8,000 [hr/yr]907,185 [g/ton] Therefore:E engine = 4.79 [ton/yr/engine]Total NOx emissions from all CBM dewatering pump engines in Calhoun County can be evaluated as follows:where:Eengine,TOTAL is the total emissions from CBM dewatering pump engines in a county [ton/yr]n = 1 [engine/well]Eengine = 4.79 [ton/yr/engine]fpump = 0.95 (fraction of CBM wells with CBM dewatering pump engines)FE = 0.965 (fraction of CBM dewatering pump engines that are electrified)WCBM,TOTAL = 18 [wells]Therefore: E engine, TOTAL = 2.86 [ton/yr][Note – the example above is for illustrative purposes only, there are currently no default factors available to estimate emissions from CBM dewatering pump engines.] ................
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