Research On Efficient Dust Control Technology With Arc Foam Jet

The existing foam spray equipment is rather rough and spray process is moreextensive, resulted in a serious waste of foam, which not only increases the cost anddecrease efficiency of dust removal, but also influences the operating environment.Based on the existing foam dust control technologies and the mechanism of dustcontrol with foam, the paper proposes the idea of arc foam jet with considering thereality of mining machinery in our country. In this paper, through theoretic analysis,numerical simulation, laboratory experiments and field tests, it analyzes the formingand developing mechanism of arc foam jet. It also develops efficient foam sprayequipment consisting of arc foam nozzle and adjustable installation device, discusshow wind field affects the foam spray and weaken its efficiency. As a result, we get anefficient foam dust control technology with efficient foam spray as the core deviceand ventilation duct with Coanda effect (VDCE) as the important part.The interaction process of dust particle with foam was captured based onhigh-speed photography technology in this research. Depending on superficialphysical chemistry and mechanics and so on, it analyzes the mechanism of dustcontrol with foam. The results revealed that the foam film is the physical barrierblocking dust. The deformation, rupture and vibration of foam films are the majormodes to alleviate the impact of dust particles. Three distinct regimes of the dustremoval with foam were identified, namely, the impact between particle and foam(collision-rupture-collision), the attachment of the particle and foam, and thesedimentation of particle-foam agglomerates. Contact efficiency, adhesion efficiencyand deposition efficiency are three keys to foam dust control, and the contactefficiency is the most important thing. The current study suggests that one of the keyfoam dust control technologies is improving the state of foam spray, which canachieve efficient foam spray and increase the contact efficiency. Finally improve theeffect of foam.Through the researching on mining machinery and analyzing on thecharacteristics of dust arising from mining equipment, the paper proposes the standardfor optimum spray pattern to get fine foam spray. Take vertical-axis roadheader asapplication background, it analyses three kinds of foam jet shapes: the full cone jet,flat jet and arc jet. Theoretical comparison is made on the minimum volume of foamwhen using the full cone jet, flat jet and arc jet. The results show that the arc jet is the better choice for achieving the efficient foam dedusting. In the same condition ofenwrapped dust source, the arc jet requires the least amount of foam. Based onnon-newtonian fluid mechanics and other related theories and the manufacturingtechnology of nozzle, it proposes the formation scheme of arc spray pattern andpreliminary design for the critical size of jet nozzle. Combined with jet mechanics andother relevant theories, high-speed photography technology and numerical simulationmethod, this dissertation studies the formation and the development process of thefoam arc spray, establishes center velocity and pressure dimensionless equations ofarc jet spray and elaborates the characteristics of arc jet spray.Experiment platform for design of efficient dust control technology with foam isdevised and constructed. Base on this platform, it analyzes the fabric parameters ofnozzle which can affect the enwrapping performance of the foam spray. Based onexperimental results, it comes to a design method which can confirm the fabricparameter of nozzle and optimize the structure of nozzle; it also designs the rectifierwing to eliminate wing current phenomenon. The adjustable installation support ofnozzle is designed to make sure the foam jet wrap the dust source efficiently. Inaddition, the experiment analyzes the relationship between the operation conditionand performance of arc foam nozzle, and gets the optimal working condition range ofthe nozzle.In order to reveal the influence of airflow on the dispersion of foam ejected fromroadheader-mounted external nozzle, the paper studies the arc foam jet distributionunder the condition of gentle breeze and normal forced ventilation in heading face.The results show that airflow can significantly affect the trajectory of foam jet. Inorder to mitigate the effect of airflow on foam jet, it brings forward a method as“change the wind speed distribution with the same amount of wind”, which canalleviate the impact of airflow, and design a VDCE. Numerical simulation andexperimental results show that the application of VDCE can effectively mitigate theinfluence of airflow on the foam jet.The field experiment carried out in3下412heading face of Fucun coal mine. Theresult shows that the efficient dust control technology with arc foam jet can reducetotal dust and respiratory dust to92.6%and92.5%respectively, which consists with aarc foam nozzle as the core device and VDCE as the important part. Its total dustsuppression efficiency is5.6%and10.4%higher than the flat nozzle and full conenozzle. Its respirable dust suppression efficiency is5.6%and11.7%higher than the flat nozzle and full cone nozzle. The dust suppression efficiency when using VDCEaveragely increase2.7%, whatever the nozzle is arc, flat or full cone. It proves that theefficient foam dust control technology with arc foam jet can weaken the influence ofairflow on foam dispersion. The results prove that efficient foam dust controltechnology with arc foam jet makes the foam highly used, and improve the efficiencyof the foam dust control. On the one hand, the technology puts forward a brand newconcept for foam dust control, on the other hand, it gives a reference to design dustremoval device of mining equipment.