| Coal was the most important disposable energy and has played very important role during the human development history.Although it has been replaced step by step by diversified energy because of environment issues,resource exhausted and cost of utilization,etc.,coal is still over half of Chinese energy structure which is up to 60%.Especially in China,after ten years ’golden age’ high speed development of coal industry,along with the economic transition and economic structure adjustment of the whole country,the coal industry is also experiencing supply-side reform.The large scale mining is not a technical problem anymore,however the massive machine mining causes serious pressure on environmental problems,which is proven to be the most important reason of utility of this energy.Due to the special occurrence condition,the current mining process inevitably interfuses coal gangue inside coal layers or part of roof and floor rock.After the mixed coal is transported onto the surface,not only the additional wash process is needed to separate them,but the discharge of gangue is the biggest resource of solid waste pollution.Therefore,China has clarified in ’twelfth five years plan’ that the new coal mines are not allowed to have new waste dump and the current ones need to be treated environment friendly or eliminated.The modern mining technic uses mostly shearer working with roof supports and scraper conveyor to finish the mining cycles.Large scale machine mining inevitably produces parting of coal seams or rocks of roof and floor together.Especially for the top coal caving,the rear coal caving is fully rely on human manipulate.The working face conditions are impossible for accurate operation,so it is normal to have gangue in the coal.Eliminating the gangue inside lump raw coal(granularity above 35mm or 50mm)is the first step for coal washing normally,also named raw coal preparation,because it is relative easy to intensively treat the gangue in lump raw coal while more than 60%coal gangue can be discharged directly.So,to implement separating gangue from lump raw coal underground,not only the technic is feasible,but the economic and social benefits are significant.Based on above reasons,the German company,KI-ID raised the idea of separating gangue from lump raw coal underground firstly.Chinese started researching such solutions just in recent 10 years.However,the working conditions are much worse underground than it on the surface,the mature separation technics cannot be applied underground directly.We have to identify and solve many detail problems during the application.This project concluded the development and different solutions of separating gangue from lump raw coal underground,then pointed out the most applicable and meaningful solution is the underground raw coal preparation system with the core machine of underground mechanical moving sieve jig.This system includes raw coal screening,sub-carries,mechanical moving sieve jig separating,dewatering and coal slurry treatment.The moving sieve jig machine on ground is already the mature equipment,but because of its dimension and matching equipment,it cannot be used directly underground or in the roadway.Therefore,to design and develop a new moving sieve jig which is suitable for underground transportation,assembly and usage is the key of this solution.Mechanical moving sieve jig has been existing for more than 20 years.Although it is mature equipment in respect of separation effect,the structure and some technical data still has big optimization space for lack of moving sieve theory especially the optimization of moving sieve kinematics characteristics.Some basic kinematics parameters are still from practice.Troditional scientific research and theory can not find proper regularity to describe and optimize those parameters from the complex interaction of fluid and solid.From the analysis of ground application experience of mechanical moving sieve jig,it has the disadvantages of huge size,large contruction scale,complex installation process and difficult control of installation precision.The huge size of discharge system is particularly not able to meet the underground coal mine installing and operating conditions.Therefore,to develop new type of separating machine for underground application and to innovate by modern design and optimization methods based on current quipments and relative experience is the key of this project.The above problems are effectively solved through the redesign and optimization of main driving system,container structure and discharging system,etc.The new design and optimization is innovatory work to the mechanical moving sieve jig not only for the total new structure that can easily fit the underground tunnel,but also for the significant improvement of performance and reliability.Meantime,this research also optimize the quick-return characteristic of the moving sieve by kinematic simulation and parameter optimization in ADAMS of the new driving system.Through analyzing the kinematic parameters of the moving sieve,this paper also did some foundation work to further study the jigging law in fluid dynamics.Jigging process is a very complex dynamic process of liquid solid two-phase flow,which is affected by many factors.The hierarchical mechanism is too complex,and there are many variables are at work,coupling and influencing at the same time.Currently the state of the layered detecting methods and the technology are not available,meanwhile there are environmental interference factors of uncertainty.Due to above reasons,it is too hard to use traditional mathematic model to describe the relationship between the production process operation parameters and the system goal needed to achieve.Therefore,the classical control method based on precise mathematical model is not sophisticated enough for the jigging process.However,in the process of moving sieve jigging hierarchy,the bed stabilization by controlling the gangue volume is critical for the system separating accuracy and treatment capacity.Since the birth of moving sieve jig machine,it has been using kinds of sensors to collect data change to reflect change of gangue bed thickness,then according to the simple specific linear model to control the discharging speed and to realize automatic discharge gangue.This method is the simplest but has the shortage of slow responding speed.Aim at the nonlinear,time-varying uncertainties and pure lag features of discharging system,the fuzzy logic control was creatively developed which realizes the discharging motor fuzzy and logic control.During the industrial test in Tangshan mine,the curves between the amounts of gangue and discharge motor output frequency in three types working conditions were monitored,which show that the fuzzy logic control makes the gangue bed more stable,improves the separating efficiency and gets better response than before.At last,on the background of underground raw coal preparation system in Tangshan coal mine,based on the analysis of coal nature,production and transportation conditions,the process flow and system layout design of raw coal preparation system was designed.After one and a half years period of equipment development,roadway construction,and installation and debugging etc.,the industrial test was carried out.This project adopts centralized control system,including safety inspection system and production monitoring system,which improves the automation level.The entire project was successful.By analyzing the system product,the results show that the system effectively implemented separation of the lump coal and gangue above 50 mm size,corresponding ash index accords with the feature of coal and waste rock floating and sunken,and the system operation has reached the design target.Till now,this system is still operating well and became the necessary production link.The application of this system creates net profit 11.65 million Yuan by saving transportation and backfilling of gangue;saves coal washing fees about 5 million Yuan;at same time,it reduces coal gangue on surface transfer treatment and discharge by 60%.All of these generated huge economic and social benefits.Green technique in coal mining is the inevitable developing direction.To realize coal mine underground raw coal preparation,and to improve the raw coal separation efficiency further,there are still much theoretical analysis and field test to be done.The underground moving sieve jig is still incomplete.With the increasing focus on environmental protection globally,to realize the coordinated development of the coal resources exploitation and environmental protection,there are still much work to do.Underground raw coal preparation technology is one of the key technologies to realize green mining of coal mine.Through this project research,the moving sieve jig technology and the underground raw coal preparation system with the main equipment of underground mechanical moving sieve jig were successfully applied industrially,which laid a foundation for further green mining of underground coal mines. |
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