矿山蓄热/储能充填体的热-力性能与传热过程

Thermal-mechanical properties and heat transfer process of heat storage/energy storage backfill body in mine

我国地下矿山储存着丰富的地热资源,深部矿井资源的开采为地热资源的开发提供了有利条件。将充填采矿与地热资源开采相结合,利用蓄热/储能功能性充填体提取地热,借助深部矿井开采已有条件为地热开发的动力供应和管路布设提供保障,可有效节约地热资源开发所需的钻探和开采成本,促进矿区的长期可持续发展。蓄热/储能功能性充填的总体实施方案包括充填材料制备、采热管路布置、充填体蓄热/释热3个阶段,本研究在材料制备方面提出了适宜于矿山蓄热/储能功能性充填的材料特性及优化目标,并测试了使用石蜡作为相变材料替代部分骨料(如尾矿)的充填材料热力学性能,结果表明随着灰砂比或料浆质量浓度的增加,充填体的抗压强度增大,同时相变材料的加入会使充填体的抗压强度、导热系数下降,而比热容明显增大。采用实验测试的方法对不同管路布置及不同换热工况下采热系统的性能展开研究,并基于热平衡计算了系统的总能效系数,得到了最优的采热管路布置方式及设计参数,当采用蛇形管路布置,载热流体入口速度为0.7 m/s,围岩温度为35℃时,采热系统具有更高的总能效系数,其值为0.48。采用数值模拟的方法对添加石蜡的充填体蓄热/释热行为展开研究,结果表明:蓄热/释热过程中(20 h),添加质量分数10%石蜡的充填体比不添加石蜡的充填体多蓄存55.5%的热量,但释热量大幅减少,总能效系数降低。

There are abundant geothermal resources in underground mines in China,and the exploitation of mineral resources in deep mines provides some favourable conditions for the exploitation of geothermal resources.Combining backfill mining with geothermal resource exploitation,utilizing heat storage/energy storage functional backfill body to extract geothermal resource and providing guarantee for power supply and pipeline layout of geothermal resource exploitation with the aid of existing conditions of deep mining,can effectively save some drilling and mining costs required for geothermal resource exploitation and promote the long-term sustainable development of mining areas.The overall implementation plan of heat storage/energy storage functional backfill consists of three stages,which are backfill material preparation,pipe arrangement and heat storage/heat release of backfill body.In this study,the aspect of material preparation,the material characteristics and optimization objectives suitable for heat storage/energy storage functional backfill are put forward.The thermophysical properties of backfill material,which the part aggregate(such as tailings)was instead by using the paraffin as phase change material,were tested.The results show that the compressive strength of backfill body increases with the increase of cement-tailing ratio or slurry mass concentration.Meanwhile,the addition of paraffin will reduce the compressive strength and thermal conductivity of backfill body,while the specific heat capacity increases significantly.The characteristics of heat extraction system for different pipe arrangement and different heat transfer conditions were studied by experimental test.The total energy efficiency coefficient of the system was calculated based on the heat balance and the optimal layout and design parameters of the pipe were obtained,when the serpentine pipe arrangement is adopted,the inlet velocity of heat transfer fluid is 0.7 m/s and the surrounding rock temperature is 35℃,the energy efficiency coefficient is the highest,which is 0.48.The heat storage/heat release behavior of backfill body added with paraffin was studied by numerical simulation,the results show that:in the process of heat storage/heat release,the backfill body with 10%mass fraction paraffin can store 55.5%more heat capacity than the backfill body without paraffin,however,the heat release capacity is greatly reduced and the total energy efficiency coefficient is reduced.