Research On Efficient Dust Suppression Mechanism Of Grab Unloading Under Air Curtain Barrier And Negative Pressure Guidance

Grab is widely used in ports,thermal power plants,grain depots and other places to load and unload and transfer ore,coal,grain and other bulk materials,due to the inherent powder and fine particles in the bulk material,it is easy to diffuse into the air to form aggregation diffusion dust,which brings the problem of dust pollution and resource waste,affecting the service life of the grab.Even caused dust explosion caused major losses.The existing researches mainly focus on the free fall of bulk materials,rather than the variable flow rate and crosssection characteristics of grab bucket discharge.Moreover,the diversity and variability of dust generation environment are related to the characteristics of bulk materials,air flow field in discharge area,discharge equipment and other factors,and belong to the complex flow field under multi-variable working conditions.At present,there is a lack of effective dust suppression methods and related research mechanisms,and the treatment effect is not obvious.Therefore,this paper studies the dust control problem during the unloading of the grab.Based on the study of the characteristics of the dust flow field caused by the induced air flow in the open space,the coupling of the air curtain barrier flow field and the dust flow field is constructed,and a limited dust separation space is formed with the hopper to prevent dust spillover.On this basis,the negative pressure guided flow field is constructed,and finally the pressure gradient guided dust suppression flow field coupled with multiple flow fields is formed,so as to achieve the goal of efficiently controlling dust and guiding the orderly settlement of dust.This is a typical comprehensive theoretical study of gas-solid two-phase flow combining turbulence dynamics and particle kinematics.The main research results are as follows:The flow field characteristics of dust dispersing from grab unloading in open space are obtained.Firstly,by deducing the microscopic force and motion equations of dust particles,the theoretical models of dust suspension velocity and induced air flow were established.Moreover,the influencing factors of dust production during discharge were analyzed by orthogonal test method,and the influencing magnitude and changing trend of dust production were obtained.Then,by constructing the experimental model and measuring system of bucket unloading,the dust diffusion range,diffusion speed and direction,settling time,dust concentration and induced wind speed are compared during unloading.Finally,by using CFD-DEM coupling modeling and simulation method,the DPM model of dust is established,the distribution and diffusion law of induced airflow and dust are further obtained,which lays a foundation for controlling and guiding the orderly settlement of dust.This paper designs a space air curtain jet barrier system in the process of grab unloading.Firstly,by studying the theory of air curtain jet and the mechanism of dust isolation,the space air curtain jet barrier system is designed for the unloading condition of grab bucket.The closed space is formed by connecting air curtain jet from end to end,and the air curtain barrier flow field is constructed.Then,experiments and CFD numerical simulation are used to analyze the barrier performance of the air curtain under different air curtain jet modes,jet port widths,air curtain jet velocity and induced wind velocity.Finally,the key component of the space air curtain jet barrier system,the air curtain generator,is designed to study the influence mechanism of air column diameter,guide vane spacing,supply groove length and guide vane deflection Angle on the uniformity,dispersion and skew of air curtain jet,and to explore the barrier performance of air curtain under different transverse interference wind speeds.Design the negative pressure guide dust removal system in the unloading process of grab.On the basis of the air curtain blocking flow field,in order to form the pressure gradient guided dust suppression flow field,it is necessary to construct the negative pressure guided flow field,so that the strength of the flow field is greater than that of the dust complex flow field.Combining the structure and performance characteristics of the hopper and the space air curtain,the form and position of the suction hood are rationally arranged,and the flow ratio method is used to obtain the relationship between the negative pressure suction capacity and time during the discharge process.Combined with the distribution law of the dust flow,the appropriate suction capacity can be selected for different bulk materials,so as to obtain the design method of the negative pressure guided dust removal system.A comprehensive experimental dust suppression system with air curtain barrier and negative pressure guidance was established.Firstly,the model of air curtain barrier and negative pressure guidance system is established,the experimental measurement system and control system are designed,and the comprehensive experimental system of air curtain barrier and negative pressure guidance is built.Then,the dust suppression performance under different air curtain jet Angle,arc deflector,air curtain jet velocity and air curtain arrangement is analyzed under the two conditions of air curtain barrier alone and air curtain barrier and negative pressure guidance together.Finally,combining with the flow field characteristics of the open-space grab discharge condition,the dust diffusion quantity under three different working conditions is compared,and the optimal dust suppression structure and design parameters suitable for different bulk materials are obtained,which proves that the dust suppression system can effectively suppress dust.In this paper,the formation and mechanism of dust flow field in open space,air curtain barrier flow field,negative pressure guided flow field and pressure gradient guided dust suppression field are deeply studied,and the dust suppression problem in the loading and unloading of bulk materials,which is widely used,is explored,so as to build an efficient dust suppression system scheme and promote the development and improvement of the dust suppression theory and technology of grab unloading.