Gas Geochemistry of Combustion Gases
Report of the project:
Gas Geochemistry 2004
During the project extensive compositional and flow measurements of gas emanations have been performed by different working groups (BGR, DMT) at two fire zones in the Wuda area. It could be shown, that portable gas detection instruments - equipped with up to five gas sensors - are a rapid, cost-effective and reliable method for on-site analysis of combustion gases.
Component specific flow measurements have been performed by means of emission chamber measurements for low flow areas and matrix flow (applied by BGR), differential pressure measurements (Pitot-static tube) were used by DMT in high temperature fractures (total flow only). The Flow measurements have proven that not only open vents and cracks emanate combustion gases but also significant gas flows occur through the undisturbed ground.
Gasflow-Measurements at Fire Zone 3.2
Source: BGR
Potential Combustion Processes in Coal Fires
Source: BGR
The fire zones among themselves are very inhomogeneous in terms of temperature and gas composition and fire zones compared to others are different. No clear relationship between gas composition and temperature could be established. In addition it has been demonstrated that non-combustion products like explosive hydrocarbons & hydrogen were detectable, clearly indicating that more than a simple combustion process is involved.
Permanent Monitoring Station 2005
Data from Monitoring Station (June 15th to June 30th)
Source: BGR
In June 2005 the installation of the permanent gas monitoring station has been completed. Several combustion gases and temperatures at two localities as well as ambient pressure, temperature and wind direction were measured.
Data of the continous monitoring (30 second intervalls) of chemical composition, temperatures, differental pressure and weather information (wind speed & direction, barometric pressure, ambient temperature) were downloaded on a daily basis.
During October 2005 the monitoring station was removed and evaluation of the gathered data is under the way. These data will provide more insides in the dynamic of the combustion process and maybe tied to dynamic or static modeling.
A long version of the intermediate report (state of June, 2005) can be downloaded here (Measurements of flue gas compositions from subsurface coal fires (PDF, 4 MB)).