Improving the capacity of mine degassing pipelines

Abstract

Purpose. To identify features of methane-air mixture flow within the steel degassing pipelines as well as within those ones made of composite materials, to develop engineering solutions improving their reliability for actual use. Methodology. To solve the problem of increasing the capacity of mine degassing pipelines, an analysis of fundamental studies on the physical and mechanical properties of mine methane and the processes of its recovery in a mine environment is conducted. Schemes of operating gas-transmission systems and peculiarities of functioning of zonal vacuum gas pipelines in the conditions of intensive removal of rocks of the bottom of underground workings and deformations of the massif are considered. Based on the results of expert assessment of production situations, potential reserves for enhancing the efficiency of in-mine gas pipelines have been determined. Reliability indicators of traditionally applied steel pipes and their analogues from composite materials used abroad are established, innovative technological and technical solutions for their construction at Ukrainian mines are recommended. Findings. According to the expert evaluation of the operation modes of mine degassing lines and analysis of the world practices to apply pipes made of composite materials for mining industry, an engineering solution concerning the improvement of operating degassing systems as well as their capacity has been substantiated. Originality. Innovative engineering solutions as for the modernization of the underground degassing systems, which allow increasing the capacity of mine pipelines, and provide maintaining of the quality the captured methane-air mixture in the process of its transportation from wells to vacuum pump stations, have been substantiated. Practical value. Implementation of the research results to decrease hydraulic resistance within the degassing mains as well as introduction of innovative engineering solutions for the construction of main degassing pipelines from long links of composite pipes with a minimum number of butt joints has been scheduled for Ukrainian mines dealing with the development of gassy coal seams.

The methods to calculate expediency of composite degassing pipelines

“…Generally, the degassing pipelines are mounted on small supports located within the fl oor of underground mine workings; another way is to suspend them to clamping devices. During operation, the degassing pipelines are infl uenced by aggressive mine environment resulting in corrosion of the pipes [1]. Moreover, the pipelines demonstrate linear deformations depending upon changes in spatial arrangement of mine workings under the eff ect of rock mass.…”

“…Globally, long composite pipes are applied for degassing systems. Research [1] has determined that such composite pipelines, being a part of degassing systems in coal mines, are quite promising from the engineering and economic viewpoints. To compare with traditional steel pipelines, composite ones have much lower hydraulic resistance coeffi cient and a smaller number of joints.…”

“…where P is pressure losses within a pipeline section, Pa; V р is analytical gas consumption, m 3 /h; d is internal gas line diameter, cm;  о is gas density if conditions are standard, kg/m 3 ; v is coeffi cient of kinematic gas viscosity, m 2 /s; L р is analytical length of a pipeline section, m. Some experiments [1] have helped understand that analytical roughness for new steel pipes (involving local blowouts within joints) is 0.02 and 0.10 mm. It excesses signifi cantly the roughness of a composite pipeline.…”

“…Nevertheless, light weight of polymeric pipes, ability to transport them in coils, and their simple operation help reduce the costs for delivery and installation of pipe links (Fig. 1) [1].…”

“…High plasticity is the advantage of composites providing their transportation in coils with up to 1,000 m total length depending upon the diameter [1]. Plastic properties of composite pipes as well as their physical and mechanical characteristics make it possible to use long-chain gas line construction in the curvilinear mine workings; in addition, the minimal joint number will be involved.…”