Study On The Crane Scheduling System In The Steelmaking-Continuous Casting Section

For the optimization of the crane scheduling in the steelmaking shop and the foundation of the intelligent crane scheduling system,the crane scheduling problem was studied which was derived from the molten steel refining span and the receiving span in the steelmaking shop of Shougang Jingtang Iron&Steel Co.Ltd.The scheduling hierarchy in the steelmaking shop is complex where is filled with many uncertain elements,leading to the dynamic arriving of the jobs,the vast rescheduling processes and the diverse initial conditions at each rescheduling.Moreover,the one ladle capacity of the station and the multiple cranes situation make it necessary to consider the station capacity constraint and the crane non-conflict constraint in the scheduling.Therefore,the statue and objective of the crane scheduling problem were analyzed in the view of the metallurgical process engineering.The strategies of the crane scheduling in the complex steelmaking shop and their applicability was analyzed.The mathematical model of crane scheduling model was built.The objective of the model considered the maintenance of the crane scheduling on the process schedule and the balance of workloads between cranes.The constraints of the model considered the non-conflict constraint,the job logic order constraint,the station capacity constraint and the constraints caused by the initial condition at each rescheduling.The model was solved by a heuristic method under the predictive-reactive strategy and a rule scheduling method under the completely reactive scheduling strategy.The target steelmaking shop taken as a prototype,a crane scheduling simulation platform was established,which included the job generation scheme based on different scheduling strategies,the ladle turret rotation control scheme,the crane operation scheme based on an active/passive evasion mode and different ways to determine the crane priorities,and the crane scheduling evaluation system.Meanwhile,a crane operation demonstration platform was established,which received the data from the crane scheduling simulation platform and then re-demonstrated the real-time operations and moving trajectories of the cranes,evaluation indexes and job statuses.Finally,based on the completely reactive scheduling strategy,a ladle-crane scheduling management system was developed and applied.The modules and communication solution of this system,the crane and ladle-car positioning solution were introduced and the application performance of the system was presented.On the crane scheduling simulation platform,the contrastive analyses of different dynamic scheduling strategies,rescheduling modes,algorithms and crane operation schemes were conducted.The real performance of the ladle-crane scheduling management system was analyzed.The following results and conclusions were obtained:1)Under the predictive-reactive scheduling strategy,the proposed real-time heuristic method was compared with the exhaustive method.The former method could reach 94.2%of the optimization performance of the latter in the refining span,and 97.1%in the receiving span,which showed the proposed real-time heuristic method could obtain high-quality near-optimal solution.2)Both using the heuristic method,the predictive-reactive scheduling strategy was compared with the completely reactive scheduling strategy.In the refining span,the former declined 17.8%in the total punishment index and both the strategies were 0 in the job-assignment changing ratio index.In the receiving span,the former declined 15.3%in the total punishment index,but was 6.7 times as large as the latter in the job-assignment changing ratio index.In the receiving span,the rule scheduling method under the completely reactive scheduling was compared with the heuristic method under the predictive-reactive scheduling strategy,the former was 2.6 times as larger as the latter in the total punishment index.In the job-assignment changing ratio index,the former was 0 and the latter was 6.4%.The result showed that the predictive-reactive scheduling strategy performed better to gain an optimized solution than the completely reactive strategy;however,the latter never changed the crane a job assigned,which performed better that the former.3)The crane scheduling result under an assumed abnormal ladle routes was compared with the result under the normal ladle routes,the former was 2.9 times as large as the latter in the total punishment index and 64.1%in the executing efficiency index,which identified that the ladle routes had a direct and obvious effect upon the crane scheduling.The optimization of the ladle route should be prior to the crane scheduling.4)The optimal number of cranes under different work intensities was verified:When two continuous casters were working at the same time and in different regions,two crane were competent for the work intensities;when they were in the same region,three cranes were needed.When three continuous casters were working at the same time,three cranes were competent for this work intensity.5)When the cranes were permitted to move towards the start point ahead of the job release time,the total punishment index declined 10.4%in the refining span and a maximum number of 4.2%in the receiving span.In the rule scheduling under the completely reactive strategy,the crane priority was ordered by the job type,the job release time and the crane status,respectively.The latter two ways was 2.2 times and 4.6 times as large as the former one respectively,which showed that the crane scheduling result could be improved by the designed crane operation solution.6)When the ladle-crane management system was successfully put on line,the average time of ladle transporting from the converter to the refining decreased from 12.23 minutes to 10.01 minutes,a decrease of 18.2%;the time from the refining to the continuous casting decreased from 9.37 minutes to 8.36 minutes,a decrease of 10.7%.The ratio of ladle cross routes decreased from 22.5%to 19.2%,a decrease of 3.3 percentage.The average ladle turnover period decreased from 227.85 minutesto 224.92 minutes,causing that the ladle turnover rate increased from 6.75 to 6.85 heats/(ladle·day).With the application of this system and other energy-saving technologies and measures,the average value of the BOF tapping temperature in 2019 declined from 1655.0? of Jan.to Jun.to 1653.3? of Jul.to Dec.,a decrease of 1.7?.These results showed that this system performed well in the steelmaking shop.