1、翻 译部分Processing of coal mine gas with low methane concentrations for use in high-temperature fuel cellsTorsten Brinkmann, Carsten Scholles, Jan Wind, Thorsten Wolffa, Andreas Dengel, Wulf ClemensInstitute of Polymer Research, GKSS Research Centre Geesthacht GmbH,Max-Planck-Strae 1, 21502 Geesthacht,
2、 GermanyTel. +49 (0) 4752 872400; Fax: +49 (0)4752 872444; email: torsten.brinkmanngkss.deSTEAG Saar Energie AG, Technische Innovation, St. Johanner Strae 103, 66115 Saarbrcken, GermanyOTS Ingenieurgesellschaft mbH, Lessingstrae 28, 66121 Saarbrcken, GermanyReceived 15 January 2007; Accepted 20 Febr
3、uary 2007AbstractCoal mines are emitting off-gases containing methane of varying content. For environmental as well as economical reasons the gas should be collected and put to further use, i.e., as a feed stock for gas engines or fuel cells. Certain concentration ranges of the coal mine gas require
4、 an adjustment of the methane content due to safety related and technical constraints. The application of gas permeation is one possibility to increase the methane content to the desired levels. Employing methane selective, silicone-based, high-flux membranes is currently being investigated by a Ger
5、man project consortium. Experimental results as well as simulation studies showed that selectivity and flux of the membrane are sufficient to increase the methane content to the desired value at a reasonable recovery.Keywords: Gas permeation, methane recovery1. IntroductionCoal mines are emitting of
6、f-gases containing methane. The methane concentrations range from 20 vol.% for coal seam methane (CSM) from active mines to 80 vol.% for coal mine methane(CMM) from closed-down mines. As such it can be considered as an energy-rich resource and is collected by suction systems to be fed into pipelines
7、 for domestic and industrial consumption as well as to decentralised power generation units as gas engines or high-temperature fuel cells. Within Germany an additional benefit is that methane emitted from coal mines counts as a renewable energy and hence falls under the renewable energy legislation
8、with the associated economical benefits.Another important reason for drawing off the emitted methane is its ecological impact when vented to the atmosphere: methane is 20 times more harmful a greenhouse gas compared to carbon dioxide. However, methane contents below 35 vol.% cannot be used in gas en
9、gines and fuel cells. An additional aspect is safety: depending on methane and oxygen concentrations, the coal mine gas might form an explosive mixture. In these cases suction and/or compression of the gas is prohibited by safety regulations and the gas is vented to the atmosphere for operating mine
10、s whilst the recovery is simply being stopped for closed down mines. One possibility to increase the methane content and hence prevent venting of the gas is to apply a gas permeation process using methane selective membranes. Steag Saar Ener-gie, an operator of coal mine gas pipeline networks and po
11、wer plants in the German Federal State Saarland, the engineering consultant OTS and the GKSS Research Centre Geesthacht GmbH formed a consortium to investigate this technology. In a second stage of the project, the E&C Company Borsig Membrane Technology is also involved. The project is funded by the
12、 German Ministry of Economics and Technology.2. Process description and process designFeeding the gas into a pipeline at a pressure of 9 bar is conducted in a two-stage process. In the first stage gas is drawn from the coal mines by blowers. Subsequently compressors provide the pipeline pressure. Th
13、e oxygen content of the gas defines concentration ranges for which certain compression stages are allowed. Hence there are several possible options for integrating a membrane unit into the process. It was decided to design a pilot process possessing the flexibility to be employed at different pressu
14、re levels. Furthermore, two membrane modules can be installed so that two-stage operation is possible. Fig. 1 shows a simplified flowsheet of the pilot plant.The feed gas can be directed to either of the two membrane modules by means of valves. The driving force for the high pressure stage is genera
15、ted by compressors. The permeate is at a pressure of 1.3 bar and either forms the methane enriched product gas or, in case the required methane content cannot be achieved by one-stage operation, is fed to a second low-pressure stage. For this stage a vacuum pump operating at a pressure of 150 mbar s
16、upplies the driving force. A recycle compressor can be employed to feed the retentate of the low-pressure stage back to the feed side of the high-pressure stage. If only operation of the blowers is allowed, the low-pressure stage on its own can be employed to upgrade the coal mine gas.The membranes employed are silicone based high-flux membranes. The methane/nitrogen selectivity of this material is limited, but still allows for an increase in
