Study And Application Of Separation Technology In CBM Gathering And Transportation System

With the advance of CBM development technology,the production of CBM in China has increased dramatically in recent years.For the specail production process of the CBM,the well production usually contains water.When the pressure and temperature changed in the gathering pipeline,free water was formed in the pipeline.With the extension of production,the coal dust in the coal seam will go into the pipeline following the gas flow.In this paper,the high efficient separation technology of dust and water in the process of coal bed gas gathering and transportation is studied.The cyclone separation technology and coalescence filtration technology are studied for different particle sizes.Cyclone separation technology is studied to seperate the particle with size of 10 ?m above.By numerical simulation and experimental test,the separation performance and flow field distribution of the traditional parallel cyclone separator and counter-flow cyclone separator are systematically analyzed and studied.A new type of reflux pipe is invented to conbime the traditional parallel cyclone separator and counter-flow cyclone separator together,then fluid velocity can be effectively used,and two stage cyclone separation was achieved in a single stage cyclone pressure drop.The experimental test shows that the separation efficiency of parallel & counter-flow bipolar cyclone separator is up to 97% for 10 ?m particle.Focus on the special situation of low pressure and flow rate of CBM well,the rotary impeller and return pipe are arranged in the conventional cyclone separator.Using the numerical simulation method,the internal structure of the separator is redesigned,and an inner recirculation type dynamic cyclone separator is proposed,and then the laboratory separation performance test was carried out.Base on the analysis of inner recirculation type dynamic cyclone separator,the internal structure of the separator is optimized and improved,a second separation was achieved in the same separator,and then an external reflux type bipolar cyclone separator is proposed.The high speed rotating impeller is used to accelerate the gas,then the extremely strong centrifugal force is produced,and the separation efficiency of the fine dust is improved.The rotation of the impeller makes the separator has a certain self suction,which meets the requirement of large flow fluctuation and low pressure drop of CBM gathering.Coalescence filtration technology is studied when the particle size is above 2 ?m.Through testing various materials and specifications of the filter,the influencing factors of filter performance is analyzed,and the size effect and heterogeneity of liquid droplet distribution in the filtration process is discovered.And on the basis of this finding,the elements and the size of the filter is optimized improved,and the fast disassembly and assembly structure is introduced,and then,a filter structure with porosity gradient distribution is proposed.The experimental test result shows that the filtration efficiency of up to 99.99% for 2 ?m particle.Laboratory tests show that,with the achievements of parallel & counter-flow bipolar cyclone separator,inner recirculation type dynamic cyclone separator,external reflux type bipolar cyclone separator and filter structure with porosity gradient distribution,the problem of separation in CBM gathering system can be well solved.But,it still needs to be further verified in actual production,which should be continue to complement and improve.